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Surface modification of ultrafine precipitated silica with 3-methacryloxypropyltrimethoxysilane in carbonization process
Abstract
Ultrafine precipitated silica was obtained from Na2SiO3 solutions and simulative lime kiln gas by carbonization process. The surface modification of ultrafine precipitated silica using 3-methacryloxypropyltrmethoxysilane (KH570) at the rear stage of carbonization process was investigated. The optimum synthesis condition of precipitated silica was obtained from the orthogonal tests: reaction temperature of 80 °C, limekiln gas flow rate of 1.2 L/min, sodium silicate concentration of 40 g/L and polyethylene glycol 6000 (PEG6000) concentration of 4 g/L. The modification degree and basic physicochemical properties of precipitated silica were analyzed by Fourier transformation infrared spectroscopy (FT-IR), thermogravimetry (TG) and X-ray diffraction (XRD). The result demonstrates that KH570 is mainly grafted to the silica surface by chemical bond rather than physical adsorption. Average activation index of precipitated silica is nearly 90% for KH570 dosage of 1%. After modification, the BET (Brunauer–Emmett–Teller) specific surface area and DBP (dimethyl terephthalate) absorption value of precipitated silica become smaller, while the average pore diameter becomes larger.
... In the case of the modified SiCN, the weight of ceramic decreases obviously with the increasing of temperature and a sharper thermal loss occurred near 600 °C. The quality decreased by approximately 9.3 wt% due to the pyrolysis of the oxygen-containing functional groups on the H-SiCN surface [32,33]. FT-IR and TGA results suggest that a substantial number of hydroxyl groups are successfully grafted on the surface of SiCN by this straightforward method. ...
Dielectric capacitors have attracted considerable attention in recent years due to their safety, environmental friendliness, high power density, and long service life. However, constrained by the limitations of dielectric materials, the energy storage density of the dielectric capacitors remains suboptimal. Therefore, the development of novel high-performance dielectric materials is imperative. In this work, surface-hydroxylated SiCN ceramics (H-SiCN) were employed as fillers, and H-SiCN/PVDF composites displaying superior dielectric attributes and considerable energy storage density were attained via a hot-pressing technique. After the surface hydroxylation of SiCN, the permittivity of the H-SiCN/PVDF composites increases slightly, the dielectric loss decreases, and the breakdown strength enhances significantly. When the volume fraction of H-SiCN is 20 vol%, the H-SiCN/PVDF composite film achieves the maximum energy storage of 12.23 J cm⁻³, which is increased by 101.2% compared to that of the SiCN/PVDF composite film. Robust hydrogen bonds are formed between the F atoms of PVDF and the hydroxyl groups on the surface of SiCN, which strengthens the interfacial combination between them and promotes polarization intensity. This work may provide reference significance for the design of high-performance dielectric materials.
... HNT modifications have good hydrophobic properties, allowing for greater dispersion in the polymer to enhance the contact at the interface. HNTs' were combined with 3-(trimethoxy silyl) propyl methacrylate by Guo et al. to create a high strength nanocomposite (polyamide 6/halloysite) [67]. The results showed that the mechanical and thermal properties of the nanocomposites were significantly improved. ...
Polymer–clay nanocomposites are the most remarkable nanomaterials of the current decade with broad range of applications, because they attempt a great competence to impart outstanding properties when compared to pure polymers even at a very less percentage of nanofiller inclusion. Montmorillonite, vermiculite, halloysite, sepiolite, laponite, bentonite, and attapulgite are the dominant classes of clay used as reinforcement in polymer–clay nanocomposites. Clay is easily accessible, easily processed, inexpensive, and non-toxic, and clay nanocomposites have seen significant commercial interest due to improvements in processing. Clay nanocomposites show distinctive properties of outstanding thermal stability, enhanced flame retardancy, high dimensional stability, decreased gas permeability, and enhanced anticorrosive and improved mechanical properties. This review reveals the polymer-based nanocomposites reinforced with halloysite nanotubes, for high-performance promising applications. The qualities of the nanofiller can be changed by chemically modifying exterior surface and interior lumen. Chemical alteration of the halloysite nanotube surface, in particular, results in nanoarchitecture with targeted affinity through functionalization of the outer surface and potential for drug transport through functionalization of the nanotube lumen. The various functionalization techniques of altering the nanofillers to allow interaction with polymers are discussed. The significance of filler dispersion in the polymeric matrix is also featured. The consequences of functionalized nanofillers on the microstructure and morphology, mechanical strength, thermal stability, drug encapsulation and sustained release abilities, and flame retardancy as well as barrier properties can be summarized. Subsequently, the challenges, key problems, future prospects, and feasible mechanism for polymeric clay nanocomposites are also reviewed.
Graphical Abstract
... In the process of compounding with GPEs produced by in situ polymerizations, the hollow structure prevents the leakage of liquid electrolyte and greatly improves the mechanical properties of GPEs. On the other hand, the addition of inorganic fillers weakened the crystallinity of the polymer and improved the conductivity of GPEs [28][29][30]. Wang et al. [31] reported the effects of different appearances of BaTiO 3 nanoparticles on PEO-based CPEs. Among them, BaTiO 3 nanospheres with the highest specific surface area significantly improved the electrochemical performance of CPEs than nanocubes and nanowires. ...
Unlike conventional organic liquid electrolytes, which have uncontrollable lithium dendrite growth and serious safety concerns, gel polymer electrolytes (GPEs) are widely considered to be one of the best candidates for the next generation of high energy density lithium metal batteries (LMBs). However, the challenge of maintaining high mechanical strength and good electrochemical stability simultaneously has not yet been met by these materials. Therefore, in this paper, we designed bayberry silica nanoparticles (BSNPs) with ultra-high specific surface area and compounded them with polyvinylidene fluoride – hexafluoropropylene (PVDF-HFP) (BSNPs-CPE) to effectively solve these problems. The results show that compared with the blank sample and industrial silica nanoparticles (SNPs-CPE) composite electrolyte, BSNPs-CPE not only has higher absorption rate and ion conductivity but also has a higher lithium-ion migration. In addition, due to the good compatibility between BSNPs-CPE and lithium metal, a stable SEI layer can be generated. At the same time, lithium metal batteries of BSNPs-CPE exhibit good cycling performance and rate capacity. After 300 cycles, the excellent capacity of up to 147.2 mAh g− 1 remains at the current rate of 1.0 C. More encouragingly, the capacity of 119 mAh g− 1 was obtained at the current rate of 10 C, which keeps much higher than that of the blank sample (76.2 mAh g− 1). This kind of nanostructure with micropore and high specific surface area provides important significance for the design of high-performance lithium metal battery.
... The stretching vibration of -OH group at 3430 cm −1 can both be found and the unmodified LT powders surface have higher intensity. Compared with unmodified LT powders, new peaks appeared at 2922 cm −1 ,1717 cm −1 , 1634 cm −1 , and 1128 cm −1 on the FTIR of spectrum of KH570-LT, which indicated the vibration peak of C-H, C=O, C=C, and C-O respectively [18,21]. The results indicated that KH570 was chemically grafted on the surface of LT particles, which can improve the dispersion and hydrophobicity of LT powders. ...
Copper clad laminates (CCLs) with low dissipation factor (Df) are urgently needed in the fields of high-frequency communications devices. A novel resin matrix of modified poly (2,6-dimethyl-1,4-phenylene ether) (MPPE) and styrene-ethylene/butylene-styrene (SEBS) was employed in the fabrication of high-frequency copper clad laminates (CCLs). The composites were reinforced by E-glass fabrics, which were modified with phenyltriethoxysilane (PhTES). The composite laminates obtained exhibited impressive dielectric loss of 0.0027 at 10 GHz when the weight ratio of MPPE to SEBS was 5:1. In order to modify the dielectric constant (Dk), coefficient of thermal expansion (CTE) and other performances of laminates, Li2TiO3 (LT) ceramic powders were introduced into the resin matrix. The composite laminates showed low dielectric loss of 0.0026 at 10 GHz and relatively high flexural strength of 125 MPa when the mass ratio of LT fillers to resin is 0.4. Moreover, the composite laminates all maintain low water uptake (<0.5%). The microstructure and thermal properties of composite laminates filled with LT ceramic powders were also tested. These results show that copper clad laminates prepared with modified polyphenylene ether (MPPE)/SEBS and LT ceramic fillers have strong competitiveness to fabricate printed circuit boards (PCBs) for high-frequency and high-speed applications.
... The XRD patterns of pure silica (unmodified silica), E150-MS, and 150-MS are shown in Fig. 6(A). The typical dispersion peak with glass state characteristic at 23 � appears in XRD patterns of pure silica, E150-MS, and 150-MS, which demonstrates that pure silica and modified silica are amorphous silica [36]. The N 2 adsorption isotherms curves of pure silica, E150-MS, and 150-MS are shown in Fig. 6(B). ...
The interfacial interaction between nano-silica and rubber matrix is very important for the preparation of high-performance rubber composites. In this paper, we first proposed the use of TWEEN-20 as a new silica modifier, it has four long arms consisting of three polyether chains with terminal hydroxyl group and a fatty chain. The oxygen on the polyether can form a hydrogen bond with the silanol groups on silica surface, and the terminal hydroxyl groups can chemically react with the silanol groups without any VOCs. Moreover, the long fatty chain can weaken silica polarity to obtain a better compatibility with rubber, so that silica modified by TWEEN-20 with chemical reaction and physical absorption can homogeneously disperses in rubber matrix. Nextly, we prepared high-performance natural rubber (NR) composites by adjusting the ratio of TWEEN-20 to TESPT to adjust the physical and chemical interaction between nano-silica and rubber molecular chains. The results indicated that the performances, including the filler dispersion, static mechanical properties, and dynamic heating (viscoelastic self-heating), were optimal when the ratio of TESPT to TWEEN-20 was 2:1. In addition, one-third of TESPT was replaced by TWEEN-20 to prepare silica/rubber composites, which can reduce one-third of VOCs, improve “scorchy”, and achieve high dispersion of silica.
... Chemical methods involve modification either by grafting polymers or modifiers [28,32e34]. The silane coupling agent 3methacryloxypropyltrimethoxysilane (MPS) is one of the most commonly used modifiers, which has hydrolyzable and organofunctional ends [35,36]. The hydrolysable methoxy groups react with the silanols on the SiO 2 surface, while the alkyl chains containing CC double bonds react with the polymer chains. ...
... a hydrophobic polymer, such as rubber [11]. However, the silica surface can be modified due to the numerous reactive hydroxyl groups [12,13]. Silica modification is an effective method for improving the compatibility between silica and rubber. ...
The study of preparing silica/rubber composites used in tires with low rolling resistance in an energy-saving method is fast-growing. In this study, a novel strategy is proposed, in which silica was modified by combing alcohol polyoxyethylene ether (AEO) and 3-mercaptopropyltriethoxysilane (K-MEPTS) for preparing silica/natural rubber (NR) master batches. A thermal gravimetric analyzer and Raman spectroscopy results indicated that both AEO and K-MEPTS could be grafted on to the silica surface, and AEO has a chance to shield the mercaptopropyl group on K-MEPTS. Silica modified by AEO and K-MEPTS together was completely co-coagulated with the rubber in preparing silica/NR composites using the latex compounding method with the help of the interaction between AEO and K-MEPTS. The performance of composites prepared by silica/NR master batches was investigated by a rubber process analyzer (RPA), transmission electron microscopy (TEM) and a tensile tester. These results demonstrate that AEO forms a physical interface between silica and rubber, resulting in good silica dispersion in the matrix. K-MEPTS forms a chemical interface between silica and rubber, enhancing the reinforcing effect of silica and reducing the mutual friction between silica particles. In summary, using a proper combination of AEO and K-MEPTS is a user-friendly approach for preparing silica/NR composites with excellent performance.
... In this research, ABS rubber particles containing nanosized silica particles were in situ synthesized. Firstly, hydrophobicity surface modification of colloidal silica nanoparticles (commercial silica colloid) was carried out in an emulsion system [19][20][21][22][23][24][25][26]. Thus obtained hydrophobic nanosilica powder was well dispersed in styrene monomer prior to graft copolymerization. ...
In this study, in situ synthesis of acrylonitrile-butadiene-styrene rubber particles containing hydrophobic silica nanoparticles (HDTMS-silica) was carried out. Firstly, three of HDTMS-silicas (HDTMS-silica1, HDTMS-silica2, and HDTMS-silica3) were prepared by silanization of SiO2 nanoparticle with hexadecyltrimethoxysilane (HDTMS : SiO2 wt ratios of 1 : 1, 2 : 1, and 3 : 1) in an emulsion system. Then, HDTMS-silica/styrene and acrylonitrile mixture was fed into a polybutadiene latex reactor. Following that, graft copolymerization was carried out using persulfate initiator at temperature of 65 °C for 3.5 h. Thus obtained Acrylonitrile-butadiene-styrene rubber containing HDTMS-silica was melt extruded with styrene-acrylonitrile (SAN) to prepare ABS nanocomposite compound. Mechanical properties of ABS nanocomposite compounds were evaluated. It was found that all of HDTMS : SiO2 wt ratios produced hydrophobic SiO2 nanoparticles exhibiting good dispersibility in toluene test. In fact, 3 : 1 HDTMS : SiO2 showed the complete hydrophobicity modification, judged by the absence of silanol absorption band. However, the optimum mechanical properties were achieved at 2 wt% loading of 2 : 1 HDTMS: SiO2. Below 2 : 1 ratio, the HDTMS ratio was not enough to obtain the fully hydrophobic surface modification. Above 2 : 1 ratio, the excessive HDTMS ratio led to a decrease in SiO2 content judged by Si EDX mapping, causing a gradual decrease in its energy absorption and reinforcement performance. In case of 2 : 1 HDTMS : SiO2, optimum mechanical properties were achievable at 2 wt% HDTMS-SiO2 loading, resulting from the optimum dispersibility of HDTMS-SiO2 nanoparticles. Further increase in HDTMS-SiO2 loading resulted in a reverse effect due to agglomeration problem.
Graphical Abstract
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... [31][32][33]35,36 Nevertheless, high ionic conductivity could be obtained only when a very low amount of filler was added. 36,37 In contrast, the better hardness of GPEs can normally be obtained with higher inorganic filler content. 38 This indicates that it is important to find the optimum content of inorganic filler. ...
A composite gel polymer electrolyte (CGPE) based on poly(vinylidenefluoride-hexafluoropropylene) (PVDF-HFP) polymer that includes Al-doped Li0.33La0.56TiO3 (A-LLTO) particles covered with a modified SiO2 (m-SiO2) layer was fabricated through a simple solution-casting method followed by activation in a liquid electrolyte. The obtained CGPE possessed high ionic conductivity, a large electrochemical stability window, and interfacial stability- all superior to that of the pure gel polymer electrolyte (GPE). In addition, under a highly polarized condition, the CGPE effectively suppressed the growth of Li dendrites due to the improved stiffness of the GPE by the addition of inorganic A- LLTO/m-SiO2 particles. Accordingly, the Li-ion polymer and Li-O2 cells employing the CGPE exhibited remarkably improved cyclability compared to cells without CGPE. In particular, the CGPE as a protection layer for the Li metal electrode in a Li-O2 cell was effective in blocking the contamination of the Li electrode by oxygen gas or impurities diffused from the cathode side, while suppressing the Li dendrites.
... On the one hand, the two Si-OH of DEDMS modifier reacted with the hydroxyl groups of quartz sand particles and formed the covalent bond. On the other hand, one Si-OH reacted with the hydroxyl groups of quartz sand particles and formed the covalent bond, and another Si-OH had condensation reaction with Si-OH of other DEDMS [36]. After almost all of the hydroxyl groups of quartz sand particles reacted with DEDMS, the superhydrophobic quartz sand particles were obtained. ...
In this study, we present a strategy to fabricate durable superhydrophobic materials by employing organosilane surface-functionalized quartz sand particles. The quartz sand particles are bonded intimately with diethoxydimethylsilane and triethoxymethylsilane to enhance the mechanical properties of the materials. The obtained materials possess superhydrophobicity with the water contact angle of 158 ± 1° and self-cleaning ability. Moreover, the materials can endure the 6H pencil hardness test and also can keep stable superhydrophobicity under extreme environment conditions of immersion test and mechanical force. Scanning electron microscopy and water contact angle measurement were used to describe the morphological features and explain the obtained surface wettability. The chemical compositions of the materials were confirmed by Fourier-transform infrared spectrophotometer and X-ray photoelectron spectrometer. The appearance of the successful durable superhydrophobic material could yield a prospective candidate for various practical applications.
... The molecular formula of silane coupling agent modifier and its chemical changes during hydrolysis are shown in Fig.1.During hydrolysis of the silane, the SiOC 2 H 5 group will transform into Si-OH.We hypothesize that the surface modification mechanism is carried through in the mode given in Fig.1. In general, one Si-OH of silane coupling agent reacts with the hydroxyl groups of quartz sand surface and forms the covalent bond, and two other Si-OH either have condensation reaction with Si-OH of other silane-coupling agent or being free state [5], thus there is possible to form the hydrogen bond in the interface simultaneously. Therefore, silane coupling agent was grafted on the quartz sand surface through chemical bond [7][8]. ...
Silicon powder is a kind of important nonmetallic mineral. It not only reduce the cost of polymer materials, but also can improve the performance of materials. In order to make silicon powder play a better role, this paper shows that surface modification of silicon powder by using the silane coupling agents KH550 and KH560. Through hydrophobic property, infiltrating performance, activation index, infrared spectroscopy(FT-IR) and scanning electron microscopy (SEM).It can be find that the evaluation and characterization of silicon powder modification effect. Comprehensive analysis shows that the modification effect is best,when KH550 and KH560 is the ratio of 1:2.
The aramid fiber reinforced polyurethane composites (AF@PU), which exhibit high strength and lightweight characteristics, have attracted widespread concerns for advanced personal protective systems. However, the interface is essential to influence the stress transfer efficiency but frequently overlooked. In this work, polydopamine and γ-aminopropyltriethoxysilane modified SiO 2 (m-SiO 2 ) were utilized to strengthen the interface. Attributing to the strong bonding strength between fibers and polymer resins improved by m-SiO 2 at the interface, the tensile, flexural, and compressive strength of m-SiO 2 /AF@PU are maximally increased. The deposition of abundant m-SiO 2 enhances the interface roughness, the interfacial peeling strength of the m-SiO 2 /AF@PU is increased by 490.4%, and the interlaminar shear strength is increased by 51.1%. In addition, m-SiO 2 /AF@PU demonstrates the maximal energy absorption value; the ballistic limit velocity is improved from 449.8 m s ⁻¹ of AF@PU to 508.5 m s ⁻¹ of m-SiO 2 /AF@PU. This work highlights the interface strengthening and ballistic performance, thus providing an efficient guideline for the design of next-generation fiber reinforced polymer resin composites.
To maintain a comfortable and healthy indoor environment without large amounts of energy consumption is of great importance. The progress of multifunctional indoor coatings with formaldehyde photodegradation and humidity buffering capability is necessary. From the viewpoints of circular economy, the preparation of effective photocatalysts (denoted as sFCC/GCN-x and ESF/GCN-y) via the decoration of recycling industrial wastes (i.e., spent fluid catalytic cracking catalysts (sFCC) and enhancement silica fume (ESF)) onto graphitic carbon nitride (GCN) by using a simple route is reported. The obtained results show that the prepared sFCC/GCN-0.15 and ESF/GCN-0.15 photocatalysts have the rate constants of formaldehyde degradation of 0.0075 and 0.0082 min-1, respectively, which are superior to that of pristine GCN (0.0044 min-1) under visible-light irradiation. The enhanced transfer kinetics of photogenerated electrons and declined recombination of electron-hole pairs may account for the surpassing photocatalytic performance. Results obtained from electron paramagnetic resonance spectra and Mott-Schottky plots indicate that the formation of ･O2- via the reaction of O2 with electrons generated on the conduction band is the major reaction pathway to photodegrade formaldehyde under visible light. To further assess the real applications of prepared photocatalysts, the sFCC/GCN-0.15 and ESF/GCN-0.15 are used to fabricate the multifunctional coatings (denoted as s- and E-coatings) with sFCC and ESF as the main compositions. Experimentally, the E-coatings could reach the formaldehyde degradation efficiency of ca. 84.5% after 3 h of visible light irradiation and excellent humidity buffering ability (293.8 g m-2) which is at least 10-folds higher than commercial coatings (28.9 g m-2). This notable progress of humidity buffering capacity on E-coatings can be attributed to their surface textural properties. Most importantly, this study exemplifies the valorization of inorganic silica wastes to produce sustainable and multifunctional coatings which may offer the practical and cost-effective applications in the indoor living space.
In this paper, an accelerant with vulcanization‐promoting and silanization‐promoting effects, 1,3‐diphenylguanidine (DPG), is loaded on green filler silica by high‐energy ball milling technology. Meanwhile, DPG breaks the ionization equilibrium of latex and realizes the self‐flocculation. The DPG‐induced self‐flocculation technology promotes the dispersion of silica and the silanization reaction, forming more complete filler‐rubber network and three‐dimensional crosslinking network. X‐ray diffraction, Fourier‐transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and thermogravimetric analysis results show that the ball milling technology makes DPG strongly adsorbed on the surface of silica, and the loading rate is 14.4%. Compared with dry mixing, the ball milling‐self‐flocculation technology increase the silanization index, tensile strength and aging coefficient by 8%, 31%, and 19%, respectively. The curing rate is improved, and the rolling resistance is the lowest. This research provides a green flocculation technology of the raw materials in formula without other flocculants and acidic wastewater discharge, avoiding the serious dust pollution and high energy consumption in the dry mixing process, as well as the poor aging resistance of rubber in the acid flocculation process of latex.
CaO–B2O3–La2O3 (CBL) glass is widely used in high-frequency packaging and co-firing with highly conductive metal electrodes as a new lead-free glass/ceramic system in low-temperature co-fired ceramic (LTCC) materials due to its multiple advantages, such as low softening point, controllable crystallisation properties, and chemical stability. The silane coupling agent, KH-570, was used as a surface modifier for preparing modified CBL glass powder to obtain a tape-casting slurry with low viscosity and excellent stability in a polymethyl methacrylate binder system; this system achieved better co-firing compatibility between the composite and Ag electrodes. In this study, the modification mechanism of the silane coupling agent with the powder is elucidated. The effects of the modified powder on the kinetic stability and rheological properties of the slurries were investigated. A slurry with a solid content of 39.6 vol.% and lowest viscosity of 1500 mPa s could be obtained with the addition of 2 wt.% KH-570. In particular, the uniformity of tape-casting slurry was observed during tape casting, leading to a difference in the density of green tapes, which increased from 2.45 (without KH-570) to 2.61 g/cm³ (with 2 wt.% KH-570), and the tensile strength increased to 5.11 MPa. Simultaneously, the micromorphology and surface roughness of the green tapes and substrate were analysed by scanning electron microscopy and atomic force microscopy. The results showed an improvement in densification and a decrease in Ra after modification, resulting in the sintered substrate obtaining a higher density of 3.06 g/cm³ and a lower dielectric loss of 9.8 × 10⁻⁴ (12 GHz). The excellent co-firing compatibility between green tapes and silver paste at 850 °C was confirmed by energy-dispersive X-ray spectroscopy. In this study, high-quality LTCC materials were manufactured by coupling modification, with their stable performance ensuring their wide application.
The surface of reactive nano‐silica coated with a silage coupling agent containing the epoxy group (denoted as E‐SiO2) and dimer fatty acids (DFA) were allowed to participate in the in‐situ polycondensation reaction of unsaturated polyester resin (UPR), thus obtaining E‐SiO2/DFA/UPR hybrid material. Fourier transform infrared spectrometer, scanning electron microscope, and X‐ray energy dispersive spectrometer were used to analyze the structure of the material, morphology of tensile section, and the element composition of the section. It was found that E‐SiO2 grafted onto the DFA/UPR backbone by chemical bonds, and the material exhibited ductile fracture with Si element on the fracture surface. Thermogravimetric analysis, differential scanning calorimetry, stress–strain test, tensile test, bending test, hardness test, and water resistance test, the influence of the content of E‐SiO2 on the thermal stability, mechanical properties, and water resistance of the materials was studied. The results show that E‐SiO2 has a good reinforcing and toughening effect for the in‐situ polymerized E‐SiO2/DFA/UPR composite due to the chemical reaction between the epoxy group of E‐SiO2 and the hydroxyl group (carboxyl group) of DFA/UPR. A heterogeneous network structure was formed in the cured E‐SiO2/DFA/UPR composites. The mechanical properties and thermal properties of E‐SiO2 nanocomposites were improved. When 0.8 wt% E‐SiO2 was added, the tensile strength, Young's modulus, flexural strength, flexural stress, elongation at break, and Shore A hardness increased by 37.03%, 69.18%, 86.81%, 86.80%, 14.0%, and 14.71%, respectively, compared to DFA/UPR. At the same time, the addition of E‐SiO2 also improved the water resistance of hybrid materials.
In this study, transparent powder (TP) with a refractive index similar to that of poly(vinyl chloride) (PVC) was used as inorganic filler to prepare PVC composite film with high transparency. TP was modified with γ‐methylacryloxypropyl trimethoxy silane (KH570) and characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, and Zeta potential analysis. Then, KH570 modified TP was incorporated into PVC, and its effects on the mechanical, transparent, and thermal properties of soft PVC composite film were investigated by tensile test, transmittance measurement and thermogravimetric analysis. The results show that the optimum loading of modified TP is 7.5 phr (mass), at which the breaking strength (18.5 MPa) and elongation at break (669.5%) of the composite film are 60.9% and 54.0% higher than that of pure PVC film, respectively. The highest light transmittance is 85.6% at a filler loading of 5 phr. Thus, TP filled PVC composite film has excellent mechanical transparent properties and high transparency.
The surface alteration of silica clay by a silane coupling agent was done to improve the compatibility with epoxy polymer matrix. It can be attained with ethoxy based silanes namely (3-mercaptopropyl) triethoxysilane (MPTES), propyltriethoxysilane (PTES) and 3-aminopropyl(diethoxy)methylsilane (APDES) in order to enhance the anticorrosion potential of epoxy coatings on mild steel. The structural and thermal properties of the functionalized clay nanoparticles are studied by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The morphological features of the functional nanoclay were also described by employing field emission scanning electron microscopy with energy dispersive x-ray analysis (FE-SEM/ EDX) and TEM (Transmission electron microscopy) analysis. These analyses showed the well functionalization of nanoclay by silanes. The well dispersion of functionalized nanoclay in the epoxy resin produces better nanocomposites which are coated on the mild steel. The coated steel samples were analyzed in terms of microstructure and corrosion resistant properties in 3.5% NaCl solution. Electrochemical impedance spectroscopy (EIS), scanning electrochemical microscopy (SECM), salt spray analysis, and analysis of oxygen and water permeability were applied to assess the barrier properties against water permeation, oxygen penetration and protectiveness of silane-modified epoxy coatings. It was found that all the modified coatings showed higher barrier resistance and superior corrosion resistance than pure epoxy coating, which were described by higher charge transfer resistance (Rct) 6815.36 kΩcm² and lower double-layer capacitance (Cdl) 405.51 µF at the electrolyte/metal interface. The tensile strength was found to be 113 MPa for EP-MPTES/clay nanocomposite while the value of pure epoxy coated specimen was 41 MPa. Therefore, the silane grafted clay nanoparticles results in slower diffusion processes, which specifically slow down the anodic reaction, thus blocking the overall corrosion path. Modified clay-epoxy nanocomposite displays good thermostability, better dispersion, outstanding mechanical property and superior water resistance property. Among the examined silanes, MPTES shows an effective functionalization of nanoclay, followed by the APDES and PTES. A possible mechanism has also been proposed.
SiC is a promising functional ceramic material with many great properties. High concentrated SiC slurry with excellent rheology and stability is required in some processes of ceramic forming. In this work, the dispersion of SiC powders was obviously improved by ternary modifiers: KH560, sodium humate and SDS. Modified SiC slurry showed the lowest viscosity of 0.168 Pa·s at a solid content of 50 vol%. The maximum absolute value of zeta potential of SiC increased from 47.3 to 61.6 mV by modification. Sedimentation experiments showed that a highly stable suspension of modified SiC was obtained at pH 10. SiC green body with high density of 2.643 g/cm³ was prepared with modified powders by slip casting. X-ray photoelectron spectra (XPS) and thermogravimetry (TG) measurements indicated the adsorption of modifiers on SiC surface. Therefore, modified SiC powders could stably disperse in aqueous media due to the increase of electrosteric repulsion between particles. The novel strategy used in this study could further improve the dispersion of SiC powders.
Preparation of hydrophobic precipitated silica nanoparticles by carbonation reaction using CO2 greenhouse gas instead of inorganic acid with the Na2SiO3 solutions has attracted widespread concern. Polymer surface modifiers may become inactive owing to the pH value of the reaction system changes constantly during the carbonation and In-situ surface modification process. Therefore, the effects of the position of adding 3-methacryloxypropyltrmethoxysilane (KH570) modifier on physicochemical performance and surface chemistry structure of precipitated silica nanoparticles were investigated during carbonation, and the in-situ modification process parameters were researched in the optimal modification position. The result demonstrates that the optimum in-situ modification position is the rear stage of carbonation process, and KH570 is mainly grafted to the surface of silica by chemical bond rather than physical adsorption. The optimum in-situ modification condition was obtained from the single factor tests: modification temperature of 80° C, modifier dosage of 2%, modification time of 40 min and pH value of 7 – 8. The average activation index of precipitated silica nanoparticles is nearly 100% under optimum in-situ modification condition. These hydrophobic precipitated silica nanoparticles are promising in hydrophobic filler materials.
Structural supercapacitors are energy storage devices that can function as structural materials. We synthesized composite solid polymer electrolytes (CSPEs) from 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm][OTF]), poly (ethylene glycol) monomethyl ether acrylate (PEGA) and functionalized silica filler. Two types of fumed silica were used: one had an unmodified surface, and the other an organically modified surface. The CSPEs were prepared by adding ionic liquids (IL) to the PEGA and the ratios between PEGA and IL were 7: 3 and 5: 5, respectively. The functionalized silica was synthesized by the sol-gel method under acidic conditions using methacryloxypropyl trimethoxysilane (MAPTMS), whereas the effects of silica filler on the electrochemical and thermal properties of CSPEs were investigated using electrochemical impedance spectroscopy, cyclic voltammetry, and differential scanning calorimetry. The ionic conductivity of CSPEs based on PEGA/[OTF]_SiO2 at various concentrations of [EMIm][OTF] was 5.7×10−4 and 4.8×10−4S/cm, and their specific capacitance was 10.0 and 9.5 F/g, respectively. With the addition of silica filler, the ionic conductivity and specific capacitance of the synthesized CSPEs were lower than those of the neat CSPEs.
Mercapto as an effective functional group for immobilizing heavy metal ions is usually grafted into various materials. However, mercapto is easily oxidized, which limits its practical application to a great extent. Therefore, mercapto iron complex functionalized nanosilica (RNS−SF) was prepared to improve the stability of amendments and the immobilization efficiencies in Pb/Cd-contaminated soil. RNS−SF was characterized with SEM, TEM, FTIR. The long-term stability and immobilization governing factors of RNS−SF were investigated. The results showed that the immobilization efficiencies of Pb and Cd in contaminated soil via RNS−SF were 98.7% and 97.9% with the dosage of 3% (w/w), respectively. Moreover, its immobilization efficiencies remains unchanged from -20°C to 50°C. And after 360 days storage at room temperature, the immobilization efficiencies of Pb and Cd were all about 90%. RNS−SF had the best passivation effect on Pb and Cd when the soil moisture maintained at 60% after 6 days aging. Sequential extraction experiments demonstrated that the fractions of EXC species and Carb species of Pb and Cd in the contaminated soil before and after RNS−SF immobilization declined from 22.62% and 43.12% to 0.321% and 0.94%, resulting in substantially reduced environmental risk of Pb and Cd.
Rock asphalt can be used feasibly to toughen oil-well cements. However, the interface between non-hydrophilic rock asphalt and cement is poor, which reduces the overall mechanical properties of the composites. Therefore, in this study, the sol–gel method was used to synthesise dicalcium silicate (C2S), which was applied as a coating on the surface of rock asphalt to improve its interfacial bonding with cement. Our analysis indicated that the formed C2S consisted of β crystals with an average particle size of 13.622 µm. Infrared testing showed the presence of O–Si–O, Si–OH, and Si–O bonds in C2S-coated rock asphalt. Scanning electron microscopy and energy-dispersive X-ray analysis indicated that C2S has been grafted on the surface of rock asphalt. Compared to untreated rock asphalt, the surface free energy of C2S-coated rock asphalt increased from 12.71 to 35.83 mJ/m² while the interfacial binding energy with cement increased from 45.61 (untreated rock asphalt) to 84.76 (C2S-coated rock asphalt) mJ/m². In addition, mechanical testing showed that the tensile strength and toughness of C2S-coated rock asphalt-containing cement composites were very high. This is because C2S-coated rock asphalt formed an excellent transition zone at the interface with the cement matrix, resulting in a strong and durable interface.
To realize a wide range of applications using three-dimensional (3D) printing, it is urgent to develop 3D printing resins with exceptional features such as enhanced mechanical properties. Herein, we developed a series of photocurable elastomers incorporating a cross-linkable SiO2 nanofiller for digital light processing (DLP) 3D printing. Methacrylate-functionalized polyether polyol was synthesized for the photocurable elastomers. To enhance the mechanical properties, surface-modified SiO2 nanoparticles (NPs) were incorporated into photocurable elastomers; this led to the generation of interfacial cross-links between the polymer matrix and the NPs surface. The effect of SiO2 NPs on the photocuring behavior of the elastomers was monitored using a photocuring depth test. Due to the small size and exceptional dispersibility of surface-modified SiO2 NPs, suppressed severe light scattering, photocuring process, and 3D printing with a large amount of SiO2 NPs (up to 20 wt %) were evenly conducted. Furthermore, tensile testing and hardness measurements were performed to reveal the effect of SiO2 NPs on the mechanical properties of 3D-printed structures. The elastomer containing 20 wt % of cross-linkable SiO2 NPs was observed to enhance the tensile strength and hardness by 87 and 52%, respectively, overcoming the limitation of conventional composites. To evaluate the resilience of the various photocurable elastomers containing SiO2 NPs, continuous tensile loading–unloading tests were conducted. Furthermore, 3D printing of various structures was carried out using a DLP printer, and their compression and bending deformation was monitored in terms of the amount of SiO2 NPs. Under high pressure, 3D-printed structures containing cross-linkable SiO2 NPs were observed to exhibit mechanical durability without defects. Therefore, this study proposes a promising method for the development of photocurable elastomers, which can be utilized in practical 3D printing applications.
In this work, low density hollow glass beads (HGB)/silicon rubber (SR) composites were prepared by solution method and flocculation process. The prepared samples were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, tensile test, and friction test. The results show that the densities of SR composites decrease from 1.140 to 0.792 g/cm³ with the addition of HGB. By comparing theoretical density with true density, it can be estimated that the ratio of shattered HGB increase from 8.79% to 24.76%. Especially, the mechanical properties of SR composites were improved by surface modification of HGB. By adding surface‐modified HGB at 5 and 10 wt%, the tensile strengths of SR composites were enhanced by 17.8% and 28.2%, respectively. In addition, tear strength, shore A hardness, compression set, and friction property were significantly ameliorated. Furthermore, the mechanism of surface‐modified HGB in mechanical properties was analyzed.
An upgrade synthesis method of electroless copper plating was developed to prepare the copper-coated mesophase pitch-based carbon fibers (Cu@CF) with APTES (3-Aminopropyl triethoxysilane) grafting modification. The microstructure and properties of the fibers which were prepared by the APTES sensitization method were investigated and compared with those prepared by the conventional SnCl2 sensitization method. The results showed that as-coated fibers sensitized by APTES demonstrated to have better interfacial cohesion between the copper layer and the fiber surface than those sensitized by SnCl2 did. Moreover, the resistivity of Cu@CF-APTES declined to 2.3±0.9 µΩ·cm, while that of Cu@CF-SnCl2 was 9.3±3.7 µΩ·cm. Besides, not only the strength of Cu@CF-APTES increased, but the strength discreteness of them reduced due to the fact that no peeling phenomenon was observed between the copper layer and fiber during the stretch test.
Nano-silica is an important component for producing elastomer composites used for fabricating “green tires.” However, the poor dispersion of silica particles in the rubber matrix and the emission of volatile organic compounds (VOCs) during the silica modification limit the applications of the modifiers. Here, bis-epoxypropyl polysulfide (BEP), a novel epoxy-type coupling agent, was designed and synthesized for nano-silica modification to cause an interfacial interaction between nano-silica and the rubber matrix and avoid VOC emission. The thermogravimetric analysis result and the bound rubber content show that BEP effectively built a bridge between the nano-silica and the rubber, which led to a strong interfacial effect and promising mechanical performance characteristics. The silica dispersion in solution-polymerized styrene-butadiene rubber (SSBR) was studied using a transmission electron microscope and a rubber process analyzer, and the results demonstrate that BEP could significantly improve silica dispersion. The static and dynamic mechanical performance results indicate that BEP is a valid coupling agent that can achieve silica/SSBR composites with high moduli and reinforcement indices. Moreover, the combination of BEP and bis-(γ-triethoxysilylpropyl)-tetrasulfide (TESPT) was also found to demonstrate a synergistic effect, which resulted in excellent static and dynamic performances of silica/SSBR composites for preparing higher-energy-efficient “green tires.”
Drag reducers (DRs) have a significant effect on shale hydraulic fracturing. Hence, it is very essential to develop excellent DRs for engineering applications. In this work, a novel nanocomposite drag reducer (PASD-SiO2) was synthesized using acrylamide (AM), sodium 4-styrenesulfonate (SSS), dimethylhexadeylallylammonium bromide (DMAAB) and modified nanosilica by redox free radical copolymerization. Fourier transform infrared spectroscopy (FT-IR), ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), elemental analysis, dynamic light scattering spectrophotometer (DLS) and scanning electron microscopy (SEM) were utilized to characterize the copolymer. Then its solution properties were evaluated. The results showed that the nanocomposite exhibited better performances of temperature resistance, salt tolerance, shear resistance and viscoelasticity than those of a pure polymer. The indoor drag reduction measurements were carried out in a closed loop flow system. The maximum drag reduction efficiency of PASD-3%SiO2 was 59.2%, which was 9.7% higher than that of a neat polymer. These improvements in desirable properties were mainly attributed to the dispersion of silica nanoparticles in the polymer matrix. Nanosilica acted as a cross-linker and enhanced the strength of the network structures, which improved the structural stability. In addition, the polymer containing silica nanoparticles exhibited improved structural rigidity. Therefore, the polymer molecules showed more persistent and effective restriction towards vortices under turbulent flows. This novel drag reducer showed good potential for slickwater fracturing applications.
Combination of nanoparticles and polycarboxylate superplasticizers (PCE) is expected to synchronously improve the workability, mechanical properties and durability of the mortars and concretes. In this study, nanosilica (NS) has been introduced and grafted onto PCE molecular chains through radical polymerization. Nanosilica-doped polycarboxylate superplasticizer (NS/PCE) was thus obtained and used as the modified water reducer in cement pastes and mortars. The effect of NS/PCE on adsorption, dispersion and mechanical properties of cement pastes or mortars has also been investigated. Results showed that PCE had been chemically bonded to anchor onto the surface of NS by Si-O⁻. NS was uniformly dispersed in PCE due to the steric resistance and electrostatic repulsive force. The as-obtained NS/PCE had better dispersion and enhanced adsorption performance compared to that of the undoped PCE. NS/PCE can effectively reduce the amount and orientation coefficient of Ca(OH)2 crystals in cement-based materials, which is beneficial to the microstructure refinement and the mechanical properties improvement of cement matrix.
Nanoparticles (NPs) are able to improve the separation efficiency of proteins in SDS-polyacrylamide gel electrophoresis (SDS-PAGE) due to their capability in enhancing heat dissipation during electrophoresis. However, the intrinsic surface charges of NPs (at buffer pH or charge induced due to the SDS coating) make them acquire electrophoretic mobility and move in the gel. Such a movement leads to viscosity and temperature gradients in the gel and deteriorates the separation. In this work, we proposed a novel method by using tethered NPs in the gel. Silica NPs, as the model NPs, were prepared and their surfaces were modified by 3-[(Methacryloxy)propyl] trimethoxysilane (MPS) which locks the NPs in the gel via covalent bonds (M-SiO2/ PA (polyacrylamide)). SiO2 NPs were embedded into the gel (SiO2/PA) as the positive control while pure PA gel was chosen as the negative control. The results showed that at relatively high voltage of 250 V, although the Joule heat generated during electrophoresis disturbed the separation in the pure gel, the SiO2/PA and M-SiO2/PA nanocomposite gels showed better performances. In comparison with pure PA gel, the resolution increased by 3 and 32% for SiO2/PA and M-SiO2/PA, respectively, in a relatively short separation time of 35 min. The gel with tethered NPs presented more efficient separation in terms of band broadening and resolution compared with the gel with free NPs probably due to the movement of free charged particles in the gel. Of course, the migration speed of protein bands in the gels decreased especially for larger proteins in the presence of the NPs compared to the pristine gel due to the steric hindrance of the NPs. Finally, we separated E. coli proteins, as a real sample. Among three gels (pure PA, SiO2/PA, and M-SiO2/PA), the gel containing M-SiO2 showed the best performance.
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Soils contaminated with Pb and Cd greatly threaten the health of humans. With a view to decrease the environmental risk of Pb and Cd in the soil, we design and prepare a type of immobilization material possessing high stability and high immobilization efficiency towards Pb and Cd. Nanosilica which has good compatibility with soils is chosen as the matrix and functional groups (mercapto) are loaded on the nanosilica surface via the covalently bonding between 3-mercaptopropyl-trimethoxysilane (denoted as MPTS) and nanosilica. The as-prepared MPTS/nano-silica is characterized, and its immobilization efficiency towards Pb and Cd in contaminated soil as well as the stability of the immobilized Pb and Cd under acidic condition is evaluated. Results demonstrate that the as-prepared nanosilica has spherical or spheroidal shape and exhibits a diameter of 20–30 nm. In the meantime, MPTS/nano-silica selectively reacts with Pb and Cd to reduce the content of bioavailable-Pb and bioavailable-Cd from 1193.54 mg/kg and 12.46 mg/kg to 10.34 mg/kg and 0.22 mg/kg, respectively, providing an immobilization rate of 99.12% and 98.23% for Pb and Cd. The results of chemical species analysis of Pb/Cd indicate that the nanosilica can transform most Pb/Cd from unstable species into more stable species. More importantly, MPTS/nano-silica exhibits low impact on soil and the Pb- and Cd-species immobilized by MPTS/nano-silica exhibit greatly increased acid resistance, which could be significant for the long-term remediation of the heavy-metal-contaminated soils.
A core-shell surface-imprinted polymer was successfully synthesized on the surface of silica spheres by precipitation polymerization. The polymers were used to selectively identify dichlorophen in complex environmental system. The physical-chemical properties of the silica sphere molecularly imprinted polymers were analyzed by scanning electron microscopy and transmission electron microscopy scans characterization. The adsorption properties of core-shell polymers were examined by adsorption isotherms, kinetics and selectivity experiments. The Langmuir adsorption isotherm well fitted the adsorption experimental data, and an increase of temperature enhanced the adsorption capacity. The maximum binding capacity of imprinted polymers reached 72.46 mg g⁻¹ at 318 K. Meanwhile, the adsorption data of binding experiments were well-fitting by the pseudo-second-order equation. Compared with nonimprinted polymer, the imprinted polymer not only has specific selectivity towards dichlorophen but also has higher adsorption performance. Moreover, via the regeneration experiments, it has been demonstrated that the MIPs have certain stability to the adsorption for the target, which provides a good reference for the adsorption of dichlorophen by the imprinted polymer in water.
As an environmentally hazardous waste, silica fume was considered as a potential alternative for cement and SiO2 production. The structure of Si–O was highly relevant to the reactivity of Si conversion for efficient utilization. In this study, the characteristic and chemical structure of Si–O in silica fume were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR). Deconvolution of XPS and FTIR spectra into elementary profiles was carried out to analyze the structural components. As a result, the valence state, bonding structure and elementary unit in the Si–O network of silica fume were determined. Then, the reactivity silica fume with alkali solution was studied involving the effects of NaOH concentration and temperature. The staged kinetics behavior was associated with the structure of Si–O bonds, and the activation energies were determined. The results thus provided fundamental information for the utilization of silica fume for SiO2 production and geopolymer.
Realizing and manipulating a fine dispersion of silica nanoparticles (NPs) in the polymer matrix is always a great challenge. In this work, we firstly successfully synthesized N, N'-bis[3-(triethoxysilyl)propyl-isopropanol] -propane-1, 3-diamine (TSPD), which was a new interface modifier, aiming to promote the dispersion of silica NPs. Through the Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance analyses (NMR) and mass spectroscopy, we verified that the TSPD contains together six ethoxy groups at its two ends. Then, we used this TSPD to modify the pure silica NPs and this modified silica was abbreviated as D-MS, which is realized by the TGA examination, scanning electron microscopy (SEM) analyses and dynamic light scattering (DLS) results. It was clearly observed that D-MS NPs are connected to one another but are not conglutinated tightly, exhibiting a novel pre-dispersed structure with around 1-2 nm certain extent of inter-particle distance. Next, we fabricated the following four elastomer nanocomposites such as pure silica/natural rubber (NR) composite (PS-NR), D-MS/NR composite (DMS-NR), bis-(γ-triethoxysilylpropyl)-tetrasulfide (TESPT) modified silica/NR composite (TS-NR) and TESPT modified D-MS/NR composite (T&DMS-NR), and found that the Payne effect is the smallest for T&DMS-NR via the combination use of the D-MS and the traditional coupling agent TESPT, attributed to its best dispersion state evidenced by the TEM results. Moreover, by measuring a series of other important mechanical performances such as the stress-strain curve, the dynamic strain dependent of the loss factor and the heat build-up, the T&DMS-NR system greatly exceeds those of the three other rubber composites. In general, this new approach provides a good opportunity to prepare a silica/rubber composite with excellent properties in mechanics strength and dynamic behavior by tailoring the fine dispersion of NPs.
In order to improve the application values of Ce element, in this paper, rare earth chloride solution was used as raw material, the pH value was controlled by inorganic alkali, the ceria powders with special physical properties were prepared by carbon dioxide carbonization method. Ce(OH)3 prepared at pH=7.5 exhibits smaller particle size than that prepared at other conditions. CeO2 precursor obtained by direct carbonization of Ce(OH)3 shows smaller particle size and narrow size distribution. According to characterization of SEM, XRD, and TG-DSC, CeO2 precursor forms at first by carbonization of Ce(OH)3 with the continuous addition of CO2 gas, and the chemical component is indicated to be Ce2O(CO3)2·6H2O. Cubic phase CeO2 powders are obtained by calcined at 750 oC for 4 h. The mean particle size D50 is 0.941 μm, and particle size distribution is smaller than 1. The microscopic appearance is homogeneous, with a spherical-like shape and a grain size of 200–500 nm. The light quality characteristics of sedimentation volume and accumulation density are obviously better than those of carbonate precipitation products. The carbonization method can be used not only to obtain ultra-fine rare earth oxides with fine particle size, narrow distribution and high dispersion properties, but also to achieve the reuse of carbon dioxide greenhouse gas.
To improve the hydrophobicity and lipophilicity of a quartz sand filter medium, two coupling agents, DN101 and KH570, were employed. The filter medium surface wettability and oil removal efficiency before and after modification were investigated, and the characteristics are summarized. The test results show that, after modification by the grafting of an organic long-chain coupling agent to the filter medium surface, the lipophilic to hydrophilic ratio increased from 1.31 (UQS) to 12.09 (MQD-Ti) and 5.11 (MQD-Si), and the oil removal efficiencies of MQD-Ti and MQD-Si improved by 21.7% and 6.9%, respectively. The stronger hydrophobicity resulted in higher quality factor values of 0.668 m−1 and 0.548 m−1 for MQD-Ti and MQD-Si, respectively, compared to 0.533 m−1 for UQS. This means that improving the filter medium surface hydrophobicity and oil removal efficiency via filter medium surface modification is effective.
To increase the encapsulation efficiency of microcapsules composed of water-soluble salt cores and hydrophobic material shells, we herein reported a facile and versatile strategy to improve the hydrophobicity of water-soluble salts [i.e., ammonium persulfate (APS)] by surface modification of APS using oleic acid or silane coupling agent, respectively. The results confirmed that the hydrophobicity of the two modified APS had been successfully improved compared with that of non-modified APS. Moreover, the two modified APS could be effectively encapsulated into hydrophobic polystyrene and the encapsulation efficiency of the resulting microcapsules goes up significantly. This study was expected to drive progress in the preparation technology of microcapsules which comprise water-soluble salts as cores and hydrophobic polymer materials as shells in many industrial application fields. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45294.
In high-temperature and high-salinity oil reservoirs, the poor thermal stability and salinity tolerance of partially hydrolyzed polyacrylamides (HPAM) solution hinder its efficiency in enhanced oil recovery (EOR). Therefore, a series of dispersible nano-SiO2 (denoted as DNS) separately surface-modified by silane coupling agents hexamethyldisilazane (denoted as HMDS) and hexadecyltrimethoxysilane (denoted as HDTS) are prepared by in-situ surface-modification technique. The two types of surface-modified hydrophobic nano-SiO2, i.e., DNS-HM (modified by HMDS) and DNS-HD (modified by HDTS), are separately added into HPAM solution to obtain the HPAM-based suspensions used for EOR. The effects of DNS-HM and DNS-HD on the thermal stability, apparent viscosity, and flooding performance of HPAM are investigated. The results indicated that the HPAM/DNS-HM8 and HPAM/DNS-HD16 (see Table 1) suspensions exhibit better apparent viscosity, storage stability and thermal stability than the HPAM/DNS-0 suspensions. Moreover, HPAM/DNS-HM8 suspension show better flooding performance and has a higher oil recovery factor (about 10.54%) than other HPAM-based suspensions.
In the study potassium titanate whiskers (PTW, K2Ti6O13) coated with nanometer calcium carbonate (C-PTW) were firstly prepared by adding carbon dioxide into the solution of calcium chloride and PTW; then coupling agent KH550 was used to modify the surface of C-PTW. The surface properties of the modified PTW were characterized by methods of SEM, EDS, XRD, FTIR spectroscopy, UV-Vis absorption spectra, and surface contact angle measurement. The results indicated that the appropriate coating ratio of CaCO3 to PTW was 0.07: 1, and that the ideal ratio of KH550 to C-PTW was 0.035: 1 by maximum settlement time. The surface of the modified C-PTW (K-C-PTW) showed excellent lipotropic properties and mobility because the surface of PTW coated by calcium carbonate possessed more hydroxyl groups than that of PTW, so the reaction between C-PTW and KH550 proceeded easier. It could be expected that the simple method may contribute to solve the problem of agglomeration for PTW in the application of composite material.
In this paper, two kinds of silane coupling agents, namely 3-aminopropyl triethoxysilane (KH550) and 3-mercaptopropyl trimethoxysilane (KH590), were adopted as preliminary modifiers to improve the hydrophobic surface properties of silicon carbide (SiC) powder for the first step. The factors that influence the modification effects were investigated by measuring the contact angle. The results showed that KH590 has a better effect than KH550 for the hydrophobic modification of SiC, and the contact angle improved most after SiC powder was reacted with 0.3 g KH590 at 75 °C in aqueous/alcohol solution for 4 h. On account of further enhancement of hydrophobicity, the study was focused on utilizing nucleophilic substitution between KH590 and hexadecyl iodiele to extend the length of alkyl chain. Compared with using KH590 alone, SiC powder modified by KH590 and hexadecyl iodiele showed better water resistance with an increase of contact angle from 106.8° to 127.5°. The Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectra (XPS) as well as X-ray diffraction (XRD) analysis results showed that KH550/KH590 and hexadecyl iodiele can be covalently bonded to the surface of SiC powder without altering its crystal configuration. This methodology may provide a new way of the modification of inorganic materials in further.
Amorphous silica (white carbon black) has been prepared via a one-step hydrochloride acidification of fly ash with the assistance of cetyl-trimethylammonium bromide (CTAB) and polyethylene glycol (PEG). The effects of surfactant types and their concentration on the properties of amorphous silica have been investigated by X-ray diffraction (XRD), particle size analysis and dibutyl phthalate (DBP) absorption value measurement. The results show that both the dispersity and hydrophobicity of the prepared silica modified by the mixed surfactants of CTAB and PEG are better than those modified by either CTAB or PEG individually. The particle size and DBP absorption value of the silica products are 3.2 µm and 3.11 cm3 · g−1 at the optimized CTAB concentration of 9 × 10−4 mol · L−1 and PEG dosage of 0.5 wt%, respectively. Consequently, the filtration time for the obtained silica is shortened as little as 3 min. It is worth mentioning that the purity of the products has been improved with the aid of the mixed surfactants. Copyright © 2016 Curtin University of Technology and John Wiley & Sons, Ltd.
The carbonation method with carbon dioxide to prepare lanthanum oxide powder was studied. Using lanthanum chloride solution and carbon dioxide as raw materials, lanthanum carbonate was synthesized by varying pH and temperature of the reaction system, and then calcined to obtain lanthanum oxide with small particle size and narrow distribution. The results showed that lanthanum carbonate precursors with lamellar morphology prepared in pH 5 and 25°C was determined to be La2(CO3)3·3.2H2O by means of XRD, TG analysis and FT-IR spectroscopy. Well-crystallized lanthanum oxide with median size 4.75 μm and particle size distribution less than 1.00 was obtained by calcinations of La2(CO3)3·3.2H2O at 800°C for 1.5 h. The carbonation method for lanthanum oxide powder would provide significant benefits containing mild reaction conditions, low cost, and product with small particle size and narrow distribution, easy to achieve large-scale production. More important, carbon dioxide could be recycled from waste gas which was beneficial to reduce the greenhouse effect in the carbon dioxide carbonation method.
A thermochemical synthetic methodology for silicon carbide/silica (SiC/SiO2) powder modified by integrating γ-methacryloxypropyl trimethoxy silane (KH570) and octylphenol polyoxyethylene ether (7) (OP-7) with hydrophilic SiC/SiO2 particles is described. On account of weak hydrophobicity of SiC/SiO2 powder modified by KH570 (SiC/SiO2-KH570), the study focuses on the improvement of hydrophobicity utilizing alkylation reaction between OP-7 and KH570 at high temperature. Compared with using KH570 alone, SiC/SiO2 powder modified by KH570 and OP-7 (SiC/SiO2-KH570-OP-7) shows better water resistance, and also an increased contact angle from 73.8° to 136.4°, resulting thus an improved hydrophobicity. Fourier transform infrared spectroscopy (FTIR), as well as X-ray photoelectron spectroscopy (XPS), was utilized to characterize these surfaces, and the results indicated that KH570 and OP-7 can be covalently bonded on the surface of SiC/SiO2 powder. Furthermore, it has been deeply investigated in the paper not only the possible modes of non-oxidative thermal degradation of OP-7 and KH570, but also the formation mechanism of more hydrophobic SiC/SiO2-KH570-OP-7 powder, which probably will have a potential utility for other inorganic materials.
A method was proposed for the preparation of silica powders using inexpensive material of sodium silicate (Na2SiO3) and carbon dioxide (CO2) by pressured carbonation, in which carbon dioxide acted as a precipitating reagent. Microstructure and size analyses of the precipitated silica powders were carried out using transmission electron microscopy and dynamic light scattering. The average particle size, size distribution and yield of silica powders were affected by reaction time, temperature and concentrations of surfactant and sodium silicate solutions. The particle size of silica powders increased with reaction temperature and concentration of sodium silicate, and the yield of silica powders increased with increasing reaction time. The size distribution of silica powders was affected by concentration of surfactant PEG. The optimal preparation conditions were experimentally determined for obtaining the silica powders with nanometer size, narrow size distribution, spherical shape and high purity without sodium carbonate and surfactant.
White carbon black was prepared from limekiln gas and water glass by carbonization method with addition of the surfactants as modifiers such as polyethylene glycol (PEG6000), neopelex (SDBS) and carboxymethylcellulose which were used to modify the prepared product by organic wet method. Silicon-alcohol groups as surfactant of white carbon black are taken by organic groups to advance the affinity to polymer colloidal particles and the reactivity. The priority order of product characteristics (yield of white carbon black, specific surface area, sorption rate of DBF) in single matching of the modifiers is polyethylene glycol (PEG6000) > carboxymethylcellulose > neopelex (SDBS). The priority order of product characteristics in multi-matching of the modifiers is polyethylene glycol (PEG6000) > multi-modifiers > neopelex (SDBS). The product grain size distribution was examined with scanning electron microscope, and infra-red spectrogram in the single matching and multi-matching of the surface modifiers. The experimental results can provide basic data and technical guidance for preparing the white carbon black of surface with excellent features.
The ultrafine SiO2 wet cake produced by a hypergravity continuous precipitation apparatus was modified using the silane coupling agent γ-methacryloxypropyltrimethoxysilane (KH-570) to improve its compatibility with organic solvents. The resulting modified ultrafine silica was characterized by Fourier transform infrared spectroscopy (FT-IR), surface hydroxyl number measurements, transmission electron microscopy (TEM) and di-n-butyl phthalate (DBP) oil absorption measurements. The results showed that KH-570 is an effective modifier as the compatibility of the modified ultrafine silica powder with organic solvents was enhanced, and the DBP oil absorption value increased from 1.9mL/g to 3.1mL/g. The optimum reaction conditions were found to involve a modification time of 4h and a modifier content of 10% of the quantity of silica. The surface hydroxyl number per square nanometer of ultrafine SiO2 was reduced from 1.15 to 0.9nm-2 after modification under these conditions.
Silicas of high dispersion degree were obtained. The process included formation of silica particles and their aggregation. Glycerin solution was used in precipitation process, resulting in a partial blocking of the silica surface hydroxyl groups (silanol groups) and, thus, in a decreased hydrophilicity of silica. Studies on the surface modification of silicas using silane coupling agents are described. The best modifiers were selected, which induced a change of the silica surface from the hydrophilic to the hydrophobic one. Basic physicochemical analyses of the obtained silicas were performed. Near infrared spectroscopy (NIR) was used to determine the degree of condensation of silica surface silanol groups. The degree of hydrophobization of silica surface was determined by a calorimetric method. Moreover, zeta potential, size distribution of primary particles, aggregates and agglomerates structures were determined by ZetaPlus instrument using electrophorectic (ELS) and dynamic (DLS) light scattering techniques.
FeOx/SBA-15 catalysts with different iron contents were studied for the selective oxidation of methane by oxygen. The catalyst with an iron content of 0.05wt% exhibited the highest single-pass formaldehyde yield (∼2% at 898K). The selectivity to formaldehyde and the specific site rate for formaldehyde formation decreased with increasing iron content. The structure-performance correlation suggests that the isolated iron species account for the selective oxidation of methane to formaldehyde, whereas the FemOn clusters are less active and the crystalline Fe2O3 mainly catalyzes the complete oxidation of methane. Kinetic investigations over the 0.05wt% FeOx/SBA-15 catalyst reveal that formaldehyde is the major primary product, and the consecutive oxidation of formaldehyde produces carbon monoxide as the main by-product. The reaction orders with respect to methane and oxygen were 1.0 and 0.20, respectively, and the activation energy was 102kJmol−1, which was significantly lower than those reported for other catalysts such as MoOx/SBA-15. Pulse reaction studies clarify that methane can react with the lattice oxygen but the products are only CO and CO2. Thus, the lattice oxygen cannot be responsible for formaldehyde formation. It is proposed that the activation of molecular oxygen on the reduced iron sites generated by methane molecules produces active oxygen species for the selective oxidation of methane.
Two techniques were used to modify the surface of a hydrated silica. The new, `wet' technique of silica surface modification involved a direct reaction of the modifying agent with the surface groups of the just-forming hydrated silica. Commercial silane coupling agents of Y(CH2)nSi(OR)3 type were used as modifying substances. For comparison, the classical `dry' modification of the silica, earlier precipitated from sodium metasilicate solution, was conducted in parallel. In order to compare effects of modification performed using either of the techniques, basic physicochemical analysis of products was conducted, supplemented by near infrared (NIR) spectroscopy, calorimetric analysis to estimate heats of immersion of silica surface, transmission electron microscopy (TEM) to evaluate surface morphology of the products and DLS technique to evaluate the presence of agglomerate and aggregate structures. The studies demonstrated that the newly developed `wet' modification technique was useful in production of modified precipitated silicas with hydrophobic surfaces.
In the past, the importance of the industrial mass production of high-quality products and specialty chemicals by precipitation increased rapidly. In the industry, usually larger aggregates are produced and in order to produce colloidal systems with the desired properties, a more or less intense dispersion of the precipitated particles is necessary. The micromechanical properties such as the maximum indentation force, the plastic and elastic deformation energy, and the strength can give information on the product and the efficiency of the dispersion process. Generally, the temperature, as one of the most important parameters of the semi-batch precipitation process of silica, was varied in order to change the structure, the primary particle size, the aggregate size, and the primary particle interactions in the aggregates. Dispersion of the precipitated silica in a stirred media mill and a dissolver show that the higher the precipitation temperature, the higher is the product fineness and, thus, the smaller is the strength of the aggregates. The reason for this effect is the increase of the primary particle size and the decrease of the solid bonds with increasing precipitation temperature. Because of higher stress intensities, the product fineness in a stirred media mill is considerably higher than in the dissolver. In principal, the maximum achievable product fineness and the energy efficiency of the dispersion process increase with decreasing particle strength and maximum indentation force. Besides the maximum indentation force, the maximum achievable product fineness and the energy efficiency of the dispersion process increase with increasing quotient of plastic and elastic deformation energy.
Commercial silicon dioxide nano-particles were modified by graft copolymerization macromolecular coupling agents (LMPB-g-MAH) of maleic anhydride (MAH) onto low-molecular-weight polybutadiene liquid rubber (LMPB) in dimethylbenzene. The hydroxyl groups on the surface of nano-SiO2 particles can interact with anhydride groups [–(CO)2–O–] of LMPB-g-MAH and an organic coating layer was formed. The covalent bands [–(CO)–O–,–(CO)–NH–] formed was testified by Fourier transform infrared spectra (FT-IR). Through transmission electron micrograph (TEM) observation, it was found that LMPB-g-MAH improved the dispersibility of nano-SiO2 particles in dimethylbenzene. By using the particle size analysis, it was confirmed that the optimum graft degree (GD%) and the optimum loading of LMPB-g-MAH is 9–11%, 10–12%, respectively. The dispersion stabilization of modified SiO2 nano-particles in dimethylbenzene was significantly improved due to the introduction of grafted polymers on the surface of nano-particles. Thermo gravimetric analysis (TGA) and contact angle measurement indicated that LMPB-g-MAH molecules were absorbed or anchored on the surface of nano-SiO2 particle and the using efficiency is 74.66%, which facilitated to hinder the aggregation of nano-SiO2 particles.
In this work, a simple and inexpensive route to synthesize porous silica microflowers has been developed. By adding supercritical CO2 into the sodium silicate aqueous solutions, the porous silica microflowers were obtained. The results of scanning electron microscopy, transmission electron microscopy and nitrogen adsorption isotherms show that through the easy control of CO2 pressure, the morphologies and porosity properties of the obtained silica can be tuned. During this process, supercritical CO2 works not only as a reactant but also as a modifier to the morphology and porosity of silica. Moreover, the growth of silica microflowers was investigated by changing the reaction time. The silica microflowers show optical properties in the wavelength range of 340–480 nm.
Attempts were made to obtain highly dispersed silica from sodium metasilicate solution and carbon dioxide. The aim was to obtain silicas of high or low paraffin oil absorbing capacity. The precipitation process was conducted in a reactor with constant mixing, to which modifying agents were added (electrolytes or surfactants). Optimum conditions were established for carrying out the precipitation process of active silicas. The basic physicochemical properties of the precipitated silicas have been established as well as their porosity, surface morphology, crystalline character, absorbing capacity, etc.
The states of water and OH groups on the surface of amorphous nanosilica with heat treatment at different temperature for hours were studied by thermogravimetry (TG), differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR) spectroscopy. The physically adsorbed water, OH groups on surface and OH groups below surface were removed mainly at 343, 709, and 1210 K, respectively. With the increasing temperature in DSC curves, the physically adsorbed water was removed firstly; secondly OH groups on surface were dehydrated; lastly were OH groups below the surface. In a wide temperature range, the dehydration of the three kinds of water took place at the same time. According to the surface area and TG results, the H2O density and OH group density on surface were obtained. For the sample without heat treatment, the physically adsorbed water and OH groups on surface were 9.80 and 8.20 nm−2, respectively. And the physically adsorbed water and OH groups of the sample with heat treatment at 1273 K were about 0 and 2.50 nm−2, respectively.
The surface of silica nanoparticle was modified with cationic surfactant cetyltrimethylammonium bromide (CTAB), and the different experiment conditions including the amount of surfactant as well as the modification temperature has been studied. Based on the zeta potential plot of unmodified silica, the optimal conditions and possible mechanism for the surface modification of silica nanoparticles was discussed. Thermo gravimetric analysis (TGA) was used for the quantitative measurement of the hydroxyl groups on the silica particles. Brunauer–Emmett–Teller procedure (BET) and Fourier transform-infrared (FT-IR) were also used to investigate the specific surface area and the functional groups on the silica nanoparticle, respectively. The scanning electron microscopy (SEM) results showed a better dispersed state of silica nanoparticles after modifying their surface.
A review article is presented of the research results obtained by the author on the properties of amorphous silica surface. It has been shown that in any description of the surface silica the hydroxylation of the surface is of critical importance. An analysis was made of the processes of dehydration (the removal of physically adsorbed water), dehydroxylation (the removal of silanol groups from the silica surface), and rehydroxylation (the restoration of the hydroxyl covering). For each of these processes a probable mechanism is suggested. The results of experimental and theoretical studies permitted to construct the original model (Zhuravlev model-1 and model-2) for describing the surface chemistry of amorphous silica. The main advantage of this physico-chemical model lies in the possibility to determine the concentration and the distribution of different types of silanol and siloxane groups and to characterize the energetic heterogeneity of the silica surface as a function of the pretreatment temperature of SiO2 samples. The model makes it possible to determine the kind of the chemisorption of water (rapid, weakly activated or slow, strongly activated) under the restoration of the hydroxyl covering and also to assess of OH groups inside the SiO2 skeleton. The magnitude of the silanol number, that is, the number of OH groups per unit surface area, αOH, when the surface is hydroxylated to the maximum degree, is considered to be a physico-chemical constant. This constant has a numerical value: αOH,AVER=4.6 (least-squares method) and αOH,AVER=4.9 OH nm−2 (arithmetical mean) and is known in literature as the Kiselev–Zhuravlev constant. It has been established that adsorption and other surface properties per unit surface area of silica are identical (except for very fine pores). On the basis of data published in the literature, this model has been found to be useful in solving various applied and theoretical problems in the field of adsorption, catalysis, chromatography, chemical modification, etc. It has been shown that the Brunauer–Emmett–Teller (BET) method is the correct method and gives the opportunity to measure the real physical magnitude of the specific surface area, SKr (by using low temperature adsorption of krypton), for silicas and other oxide dispersed solids.
Recent developments in silica research: preparation, surface modification and application
- L Y Zhou
- L S Yin
- K S Zhou
- Z W Hu
- D M Kong
- X W Zhao
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- X K Ma
- N H Lee
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- K S Park
- S J Kim
X.K. Ma, N.H. Lee, H.J. Oh, J.W. Kim, C.K. Rhee, K.S. Park, S.J. Kim, Surface modifi-cation and characterization of highly dispersed silica nanoparticles by a cationic surfactant, Colloid Surf. A 358 (2010) 172–176.
Preparation of nanosilica by precipitation
- Y F Chen
- Y W Tian
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J. Mater. Metall. 3 (2004) 199-201.
Study on preparation Fe3O4nanoparticles from waste iron mud by orthodoxy design
- Li
Y. Li, Z. Li, Study on preparation Fe3O4nanoparticles from waste iron mud by
orthodoxy design, J. Univ. Chem. Technol. S. 22 (2008) 304-307.
Study on hydrophobic nano-silica synthesized directly in water solution
- Q Zhang
- Y F Yang
- G S Hu
Q. Zhang, Y.F. Yang, G.S. Hu, Study on hydrophobic nano-silica synthesized
directly in water solution, New Chem. Mater. 37 (2009) 103-105.
Preparation of nanosilica by precipitation
- Chen
Recent developments in silica research: preparation, surface modification and application
- Zhou
Study on hydrophobic nano-silica synthesized directly in water solution
- Zhang