69 reads in the past 30 days
Material selection and manufacturing for high‐temperature heat exchangers: Review of state‐of‐the‐art development, opportunities, and challengesJuly 2024
·
389 Reads
·
2 Citations
Published by Wiley and American Ceramic Society
Online ISSN: 2578-3270
Disciplines: Ceramics
69 reads in the past 30 days
Material selection and manufacturing for high‐temperature heat exchangers: Review of state‐of‐the‐art development, opportunities, and challengesJuly 2024
·
389 Reads
·
2 Citations
46 reads in the past 30 days
Radiation heat transfer during hypersonic flight: A review of emissivity measurement and enhancement approaches of ultra‐high temperature ceramicsFebruary 2023
·
669 Reads
·
12 Citations
41 reads in the past 30 days
An overview of dental glass–ceramics: From material design to the manufacturing processMay 2024
·
313 Reads
40 reads in the past 30 days
Rapid and low‐temperature synthesis of MoAlB MAB phase by using stress‐induced Al‐particlesJanuary 2025
·
40 Reads
38 reads in the past 30 days
Characterization of soda–lime silicate glass bottles to support recycling effortsApril 2024
·
273 Reads
·
1 Citation
International Journal of Ceramic Engineering & Science is ACerS’ open access journal for ceramic science and ceramic engineering research at all levels. This ceramics journal is broad in scope and publishes peer-reviewed sound papers across all aspects of ceramic and glass materials, including regular research articles, preliminary work, opinion/perspective papers (invited), and reviews.
January 2025
·
40 Reads
Currently, MoAlB particles are produced at 1000°C and higher temperatures. In this manuscript, we report the rapid synthesis of MoAlB by altering the stress of Al particles to affect Al reactivity. The Al particles were purposefully stress‐altered to reduce their threshold for reaction. The stress‐altering process consisted of annealing followed by quenching of the aluminum powder. The combined process caused a reaction at a lower temperature between Mo, B, and Al to form MoAlB. The stress‐altering of Al particles (i.e., Al [TT‐treated]) was effective in producing >95 wt.% MoAlB after reaction at only 700°C for 10 min, a significant reduction in temperature. Based on these results, we can further project that this process can be used for manufacturing Al‐based compositions at significantly lower temperatures.
January 2025
·
36 Reads
Foamed concrete, a lightweight, cement slurry‐based cellular material, presents a promising solution to economic and environmental challenges in the construction industry. Its versatility spans from structural applications to thermal insulation and soundproofing, offering benefits such as low density, energy efficiency, and affordability. The study explored the feasibility of using locally sourced materials, specifically by utilizing three different powder detergents (K, M, and S) as foaming agents. These detergents were evaluated for their composition, density, and stability and then combined with two cement grades 32.5R and 42.5R. A total of 12 sample foamed concrete groups were manufactured and checked for compressive strength, density, and water absorption. The results demonstrated that all detergents in specific formulations successfully produced foamed concrete that met or exceeded the ASTM requirements of 1.4 MPa. Samples from Detergent K achieved a dry density range of 1.32–1.539 g/cm³ with 28‐day compressive strength ranges of 0.64–14.25 MPa. Samples from Detergent M produced dry densities in the range of 1.255–1.559 g/cm³ with a compressive strength range of 0.41–12.26 MPa and those from Detergent S produced dry density range of 1.061–1.394 g/cm³ with compressive strength range of 1.03–7. 75 MPa. Notably, there were correlations between the detergent's pH, the relevant oxide quantities and the foam's density and stability which together influenced the overall performance of the foamed concrete.
January 2025
·
51 Reads
Pure and different percentages (0.25, 0.5, 1.0, and 2.5%) of silver (Ag) doped hydroxyapatites (Hap) were synthesized employing the wet chemical precipitation method. The samples were characterized with the aid of X‐ray diffraction (phase analysis, crystallographic characterization, and crystal size calculation using Scherrer equation and different models), scanning electron microscopy, and optical bandgap energy. The Hap containing 0.25% Ag showed better photocatalytic activity in various dye concentrations, catalyst doses, and pH. At a very low catalyst dose (0.375 g/L) and 20 ppm pollutant concentration, reaction rate, and rate constant were evaluated for the Congo Red dye, ciprofloxacin, amoxicillin, and levofloxacin. The maximum rate constant (0.0028 min⁻¹) and reaction rate (9.657 × 10⁻⁸ mole L⁻¹·min⁻¹) were found for Congo Red dye and ciprofloxacin, respectively, using 0.25_Ag‐Hap (0.25% Ag‐doped Hap). The energies of the valance band (3.14 eV) and conduction band (−0.36 eV) were lower in the case of 0.25_Ag‐Hap than the other samples. Simplified reaction mechanisms were proposed for the photocatalytic degradation of Congo Red dye, ciprofloxacin, amoxicillin, and levofloxacin.
January 2025
·
25 Reads
This study aims to enhance the self‐cleaning properties of clay roof tiles by incorporating red mud as an industrial waste. This approach contributes to a sustainable environment by upcycling waste and developing an improved building material. Various analyses were conducted to compare the physical, structural, morphological, elemental, and optical properties of clay tiles with varying amounts of red mud. The characterization results indicated that the addition of red mud to clay roof tiles resulted in homogeneous and uniform tiles with enhanced physical properties. The red mud‐mixed clay roof tiles exhibited photocatalytic activity for the oxidation of methylene blue dye. Notably, while adding more than 5% red mud improved the physical properties, the optimal photocatalytic activity was observed in clay roof tiles with a 5% red mud addition. This study underscores the dual benefits of this approach: improving the functional properties of clay roof tiles and promoting the valorization of industrial waste.
January 2025
·
36 Reads
This study delves into the impact of different potassium‐waterglass (K‐WG) compositions on the early reaction dynamics and strength evolution in metakaolin‐based geopolymers (GP). By maintaining a constant SiO2/Al2O3 ratio of 4, the study explores the influence of varying H2O/K2O and K2O/Al2O3 ratios on GP properties under both dry and saturated curing conditions. Early reaction kinetics are examined using isothermal calorimetry at room temperature (21°C), and pH measurements provide insights into alkali leaching. A strong correlation was found between total heat release and strength gain, as evidenced by ultrasonic cement analyzer (UCA) readings. The study further identifies that increased H2O/K2O ratios prolong setting times and delay the geopolymerization peaks, while a higher K2O/Al2O3 ratio enhances the geopolymerization process. Vicat tests confirmed the results obtained by calorimetry and UCA: only the GP4 formulation (H2O/K2O = 8.7 and K2O/Al2O3 = 1.3) hardened in less than 7 days. Additionally, it was found that saturated curing conditions decelerate strength development, with an initial notable decline in compressive strength at 24 h compared with dry curing. However, this difference diminishes to a negligible 7.6% after 3 days. Optimal ratios of H2O/K2O = 8.7 and K2O/Al2O3 = 1.3 were determined to be critical for achieving reliable strength measurements at 1 day of curing. pH assessments indicated strong water resistance in all GP formulations, with leaching primarily governed by diffusion mechanisms. Specifically, the K‐WG composition with SiO2/K2O = 1.53 and H2O/K2O = 8.69 showcased minimal leachability. These fundamental findings are crucial for the later design of GP materials that require rapid strength development, especially crucial for applications necessitating cementing under extreme conditions, such as deep‐sea drilling, geothermal energy production, and high‐temperature industrial processes.
December 2024
·
8 Reads
Bismuth oxide and bismuth complexes with organic ligands, particularly Schiff bases, have received much attention due to their non‐toxicity, antibacterial, and photocatalytic properties in removing water and environmental contaminants by oxidative degradation. This work investigates the synthesis of bismuth complexes with the salicylidine Schiff base ligand of H2L through hydrothermal and solvothermal methods, the preparation of bismuth oxide nanoparticles from these complexes, and the synthesis of bismuth oxide nanoparticles from bismuth nitrate. To characterize the products, several techniques including infrared, UV–vis, X‐ray diffraction (XRD), energy‐dispersive X‐ray analysis, and scanning electron microscopy (SEM) have been used. Hydrothermally and solvothermally produced bismuth(III) complexes with H2L had particle sizes of about 46 and 15 nm, respectively, while oxide nanoparticles made from them had sizes of about 42 and 52 nm, respectively. The study also investigates the usage of complexes and oxide nanoparticles as photocatalysts under an ultraviolet (UV) lamp (30 W) irradiation to remove contaminants such as methyl orange, acid red 14, orange acid 7, and malachite green from water. The results showed that the bismuth complexes and oxide nanoparticles effectively remove these dyes from contaminated water samples.
December 2024
·
8 Reads
ZnO varistors doped with Y2O3, Bi2O3, and Co2O3 were analyzed for electrical performance, microstructure, phase composition, and elemental distribution using electrical performance testing, scanning electron microscopy, X‐ray diffraction, and energy dispersive spectroscopy tests. The best results were obtained with 0.5 mol% Y2O3, 2 mol% Bi2O3, and 3 mol% Co2O3, yielding a 356 V/mm voltage gradient, 0.9 μA\umu {\rm A} leakage current, and a nonlinear coefficient of 66.2. The Voronoi network model explained how Bi2O3 and Co2O3 enhance Y‐doped varistor performance. Grain size was identified as the primary factor affecting the voltage gradient, while the thick grain boundary phase impedance, the direct contact area ratio, surface state density, and donor density were key factors influencing the nonlinear coefficient and leakage current. The results indicate that doping with Bi2O3 and Co2O3 significantly enhances the electrical properties of Y‐doped varistors, and simulation methods effectively reveal the effect mechanisms of dopants on the varistors.
December 2024
·
41 Reads
In this study, the local‐scale structure of geopolymers shaped by extrusion or 3D printing was investigated and correlated to the reactivity of the raw materials. The reactivity of the different metakaolin mixtures was evaluated using zeta potential measurements with different alkali silicate solutions, followed by shaping via 3D printing; additionally, the different networks formed were identified via NMR spectroscopy. The results showed that in the presence of weakly reactive basic solutions, the Al(OH)4⁻ species were released in low amounts due to an increase in the polymerized silicate species in the solution, resulting in a low zeta potential in absolute value. Conversely, for more reactive solutions, the silicate species were more depolymerized, and the siliceous and aluminous metakaolin species were more easily released in solution, resulting in increasingly low zeta potential values. Some samples were 3D printed with metakaolin mixtures using different printers and silicate solutions (K, KNa) with alkaline cation concentrations of [M] > 2.8 M in the mixtures; here, the metakaolin zeta potential values were greater than −50 mV, and the local‐scale structure consisted of more than 50% geopolymer networks (Q⁴(3Al) + Q⁴(2Al)).
December 2024
·
49 Reads
The aim of this work is to study the influence of the palm fibers treated with soda hydroxide solution on the properties of the compressed earth bricks stabilized (CEBs) with alkali‐activated binder. The improvement in their mechanical parameters is attributable with 15 wt.% of alkali‐activated binder‐based natural pozzolan. To achieve this objective, mortars composed of treated fibers at different levels (0.1, 0.2, 0.3, 0.4, and 0.5 wt.%) of lengths of 4 and 16 cm have been developed. These different mortars with and without fibers were subjected to mechanical (dry and wet compressive test, flexural test), physical (water absorption), mineralogical (XRD, FTIR), and microstructural (SEM/EDS) characterizations after 7 and 90 days. The results revealed that in general the incorporation of fibers improves the mechanical and physical properties of CEBs stabilized with 15 wt.% of alkali‐activated binder. Furthermore, the X‐ray diffraction analysis indicated that certain mineralogical phases of the raw materials dissolve during alkaline activation. The Fourier transform infrared spectra revealed the effectiveness of the fibers in sorption water molecules. Moreover, optical examination reveals that the binder utilized completely wraps the fibers. This demonstrates that the treated fibers function flawlessly as a filler in the matrix. At 90 days with the addition of 0.4 wt.% fibers, the maximum dry compressive strength and flexural strength values were 8.08±0.40 and 5.8±0.19 MPa, respectively. The stabilized earth bricks reinforced with 0.4 wt.% of palm fibers exhibited the mechanical properties values fitting the requirements of the materials candidate for the building construction applications especially as masonry bricks.
November 2024
·
52 Reads
Handling the massive quantities of by‐products from metallurgical processes has become a major concern in recent decades. Efforts to develop sustainable alternatives for these secondary resources are ongoing to achieve the transition to climate neutrality. This study has investigated the potential of employing vanadium‐bearing slag as a new value‐added binder in refractories, aiming to replace virgin raw materials. Two types of vanadium‐bearing slags from BOF, each containing <2 wt.% vanadium were studied. Low‐cement vanadium slag‐based castables were prepared by gradually substituting 0, 2.5, and 5 wt.% of the commercial calcium aluminate cements (Secar71 and CMA72) by the slags. The flow values of the mixes containing 5 wt.% of slag decrease significantly from about 90% to 30% after 30 min, showing poor ability to flow and thus are not considered as self‐flow castables. Castables containing 2.5 wt.% of slag present a cold crushing strength value, in the range of 71–116 MPa while values for castables containing 5 wt.% of slag fall into the range of 53–68 MPa due to the lower packing properties leading to higher porosity and reduce in strength. Similar observation was concluded for cold modulus of rupture. The micrographs of the samples containing both slag and cement show promising compatibility between the binder and aggregates after sintering at 1500°C. Overall, characteristics obtained with the samples containing slag show promising alternatives as a refractory lining.
November 2024
·
26 Reads
The silver‐exchanged zeolites were created using a solid‐state ion exchange method with silver sulfate and silver nitrate salts. Various techniques, including X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy, were employed to examine the structure, morphology, and physical‐chemical properties of the samples. The antimicrobial effectiveness of the zeolites was tested against gram‐negative Escherichia coli and gram‐positive Staphylococcus aureus, common bacteria found in wastewater. Before the silver exchange, the original zeolite exhibited small clustered particles, but after the exchange, its shape underwent significant transformation. The original clinoptilolite did not contain any silver, whereas the silver‐exchanged samples AgSSE6% and AgNSE6% had silver contents of 2.29% and 3.80%, respectively. The XRD analysis confirmed the presence of Ag and AgO within the structure of the exchanged clinoptilolite. BET analysis indicated that the incorporation of Ag ions into the zeolite structure through ion exchange led to a reduction in surface area and micropores volume. The research findings revealed that zeolites exchanged with silver were more effective in inhibiting the growth of S. aureus, compared to E. coli. Additionally, zeolites treated with AgSO4 exhibited a wider inhibition zone against both bacteria compared to zeolites treated with AgNO3.
October 2024
·
5 Reads
To investigate the relationship between the electrical properties of Y–Al doped ZnO varistors and sintering temperature, in this study, we measured the voltage–current characteristics and electrical performance parameters of samples sintered at 1100∘C–1300∘C. Scanning electron microscopy observations revealed that as the sintering temperature increased, the grain size grew significantly, leading to a reduction in voltage gradient. Through C--V characteristic testing, X‐ray diffraction and energy dispersive X‐ray spectroscopy analysis, it was found that the increase in sintering temperature promoted the formation of interface negative charge and defect reactions by Y3+, increasing Ni and Nd; Al3+ tends to aggregate in the grain area, further increasing Nd; the volatilization of Bi3+ gradually increases, causing a decrease in Ni; the Φb first increases and then decreases with the changes in Ni and Nd, resulting in a U‐shaped variation characteristic of the nonlinear coefficient and leakage current density. At a sintering temperature of 1200∘C, the performance of ZnO varistors is optimal.
October 2024
·
75 Reads
The present study deals with two kaolins from Eseka and Dibamba‐Cameroon to determine their potential suitability as additive of CEM I 42.5R and to optimize the properties of cement in the sense to promote low‐carbon cement. X‐ray diffractometry was used to establish the mineralogical composition of two kaolins. X‐ray fluorescence was carried out to determine the chemical composition of kaolins and cement. Fine metakaolin powders obtained at 700°C were used as additive in CEM I 42.5R. Furthermore, consistency, setting time, water absorption, compressive and flexural test, and shrinkage test were evaluated. Scanning electron microscopy analysis was carried out to evaluate the microstructure variation. The substitution of CEM I with metakaolin resulted in a considerable increase in compressive and flexural strength from days 7 to 28 at optimum value. The compressive and flexural strengths at 28 days at optimum value of metakaolin increase to 52% and 44%, respectively, explaining the equilibrium oxides in the cement. The maximum values of strength with 20 wt.% MK1 and 30 wt.% MK2 at 7, 14, and 28 days appear in both cases when the ratio of SiO2/Al2O3 is between 2.8 and 2.9. The silica modulus and alumina modulus of cement–metakaolin improved when metakaolin was added. The properties of cement were optimized with a 52% increase in compressive strength at 28 days.
October 2024
·
86 Reads
To investigate the dynamic interaction between refining refractory and low‐carbon low‐silicon Al‐killed steel, the “refractory‐molten steel‐inclusion” system was analyzed using dynamic erosion experiments and the FactSage database. This study discussed the formation of interfacial layers between various refining refractories and molten steel, as well as the transformation of nonmetallic inclusions in steel. The findings indicate that the interaction between refractories and molten steel produces a distinct interface layer. The influence of various refining refractories on inclusions varies significantly. MgO‐C refractory promotes the formation of MgO·Al2O3 inclusions in steel, while Al2O3‐MgO refractory leads to the formation of SiO2‐MnO‐Al2O3 inclusions. Both Al2O3‐SiC refractory and Al2O3‐MgO‐C refractory result in Al2O3 inclusions with trace levels of MgO. Steel refined with Al2O3‐MgO‐C refractory has increased MgO content within Al2O3 inclusions but still does not reach the stoichiometric ratio of MgO·Al2O3. As the initial Al content increases, the influence of MgO‐C refractory inclusions becomes increasingly noticeable. The average MgO content within the inclusions rises with the reaction duration, achieving as high as 62.9%. The transition path of Al2O3 inclusions in molten steel follows “Al2O3→MgO·Al2O3→MgO.”
September 2024
·
41 Reads
·
1 Citation
This study utilizes finite element analysis (FEA) to explore the effect of standardized notch shapes—triangular, circular, and rectangular on the tensile behavior of oxide–oxide (O–O) ceramic matrix composites (CMCs) across various temperature ranges. Findings reveal that unnotched samples exhibited a superior equivalent stress of ∼425 MPa, closely aligning with experimental values. However, under elevated temperatures of 1000°C and 1200°C, degradation occurs, reaching up to 54% decrease at 1200°C. Notched samples demonstrate similar behavior, with all notches acting as stress concentrators. Analysis of single and double notches highlights that circular notches have the most significant stress concentrators due to their smooth surfaces and lack of sharp edges, in contrast to rectangular and triangular notches. Although all notch types influence stress concentration, the absence of non‐sharp corners in circular notches limit stress dissipation, resulting in higher stress concentrations. This trend persists under high temperature as well. The study emphasizes the critical need for a thorough assessment of notch effects, considering their position, orientation, shape, and size, as they significantly affect the mechanical properties of O–O CMCs.
September 2024
·
23 Reads
In this study, the role of MgB2 in composite coatings is pivotal. Electroless Ni–B plating, a current‐free chemical reduction process, deposits nickel–boron coatings. Other than MgB2, reinforcements like SiC, B4C, and so forth are used with Ni–B coatings for improved properties. The research focuses on Ni–B/MgB2 coatings on AISI 4140 steel using electroless deposition and annealing at different temperatures. Initially, the coating appears dense and amorphous, transforming into worm‐like structures through crystallization with MgB2. Higher annealing temperatures lead to brush‐like, feathery, and oyster mushroom structures, forming crystalline nickel boron compounds and oxide phases due to synergy. Interestingly, the newly introduced phases disrupt friction patterns nonlinearly, which is linked to MgB2’s ceramic nature and reinforcement quantity. Conversely, incorporating MgB2 and annealing‐induced intermetallic phases notably enhances hardness (up to 6) and improves hydrophilicity and antibacterial traits in the coating.
August 2024
·
196 Reads
Binder jet additive manufacturing is well suited for fabricating large (order of cm) and geometrically complex ceramic preforms. However, the main challenge in producing ceramic oxide parts via binder jetting is the high‐temperature postprocess tasked with eliminating internal porosity to achieve full densities. In this work, we demonstrate the ability to produce oxide ceramic parts with desirable densities by sintering binder jetted preforms. We investigate the sintering behavior of binder jetted preforms composed of three oxide powders with distinct morphologies: ball‐milled alumina, gas‐atomized silica, and sintered‐agglomerated zirconia. We fabricate the preform samples using a commercial binder jetting system and a conventional die‐pressing technique to understand the effect of starting densities. Furthermore, we parametrize the heating profiles to understand the effect of sintering temperature, sintering duration, and heating rate on each powder's densification behavior, microstructure, and phase composition. Results show the relatively low starting densities within the binder jetted preforms caused the onset sintering temperature to be higher than what is documented in conventional sintering studies. As expected, we observed sintered densities increase with respect to sintering temperature and duration. These findings were utilized to downselect sintering parameters capable of achieving high densities (>96%). Herein, this study validates the sintering of binder jetted preforms as a suitable way to manufacture ceramic parts, regardless of powder morphologies, thereby increasing the robustness of the supply chain involved in additive manufacturing of ceramic oxides.
July 2024
·
65 Reads
·
2 Citations
This work focuses on the development of new ceramic membranes based on mixtures of low‐cost and locally available raw materials such as kaolinitic clay and additives such as palm kernel shells and mango seed shells, which are used as pore‐forming agents to increase pore size, and on their efficiencies in rejecting organic and inorganic pollutants from brewery wastewater. The physical and chemical properties of raw materials were characterized via X‐ray diffraction, scanning electron microscopy, differential thermal analysis/thermogravimetry, energy dispersive X‐ray, and Fourier transform infrared spectrophotometry. Sintering was performed at 1100°C, and the permeability and mechanical properties of circular membranes were determined. The membrane filtration operation was used to assess the physicochemical parameters of the wastewater. The membrane composed of 85% kaolinite and 15% mango seed shells showed the best performance. The effective treatment of the breweries wastewater reduced the level of contamination by organic pollutants in the discharge water, with a reduction in concentration from 700 to 14 mg O2 L‒1 of chemical oxygen demand and 250 to 06 mg O2 L‒1 of biological oxygen demand for 5 days, representing elimination rates of 98% and 97.6%, respectively. The treated water is alkaline, with a reduction in pH from 10.79 to 7.77. Suspended matter, turbidity, and electrical conductivity had removal rates of 88%, 90.6%, and 99.8%, respectively. A significant reduction in the salinity of this wastewater contributed to sodium and chloride ion rejection rates of 93% and 79%, respectively, which is an important result for good reuse of the treated water in agriculture and domestic work.
July 2024
·
389 Reads
·
2 Citations
Many energy systems demand heat transfer at high temperatures to keep up with high demand for power, so high‐temperature material that can perform and last under these harsh conditions is needed for heat exchangers. The engineering requirements for these high‐temperature heat exchanger material call for high thermal conductivity, high resistance to fracture, high resistance to creep deformation, environmental stability in environments associated with the application, and high modulus of elasticity while maintaining low cost to make and maintain. Naturally, ceramics are a good solution for this endeavor. In the past, high‐temperature heat exchangers made from ceramics have been used. We provide examples of ceramics in relevant heat exchange applications and provide motivation where additive manufacturing (AM) can improve efficiency. AM for the relevant material is under development, and we provide insight on the AM of ceramic materials and examples of AM heat exchangers keeping cost in mind. The motivation of the review paper is to provide a framework for material and manufacturing selection for high‐temperature heat exchangers for AM to keep up with the demand for better efficiency, better material, better manufacturing, and cost moving forward with AM technology in high‐temperature ceramic heat exchangers.
July 2024
·
14 Reads
·
2 Citations
As the core component of lightning arrester, the performance of ZnO varistor directly affects the protection level of lightning arrester. Under the action of long‐term AC voltage, the varistors are prone to AC aging, which leads to the deterioration of its performance parameters and microstructure, resulting in the failure of the varistors. In this paper, the effects of MnO2 doping on the voltammetry and double Schottky barrier characteristics of ZnO varistors under AC were studied by means of C--V, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy characteristic testing. The AC accelerated aging test was carried out for 168 h under 135 and 0.85 ratio of peak voltage. The results showed that the introduction of Mn4+ inhibited the migration of interstitial zinc ions to grain boundaries and decreased the AC aging rate. The aging rate was lowest when 1.5 mol% MnO2 was doped.
July 2024
·
30 Reads
·
2 Citations
The impact of phosphates on phase formation in low Ca alkali‐activated materials (AAMs) is investigated using a polymer‐assisted sol‐gel process to fabricate MgO‐Al2O3‐SiO2‐P2O5 cement precursors covering a broad range of compositions activated with sodium hydroxide. X‐ray diffraction and magic angle spinning‐nuclear magnetic resonance are used to examine the crystalline and amorphous phases that form over 470 days of curing (35°C, 90% relative humidity). The results confirm that Al is preferentially incorporated into hydrotalcite‐like layered double hydroxides (LDH) over zeolites. Zeolites form when more Al is present than can be incorporated into the LDH. Little evidence of phosphate incorporation into aluminosilicate networks (such as zeolites or disordered aluminosilicate hydrate) was observed. The phosphates present in the precursor favor reaction with sodium to form water‐soluble sodium phosphate phases. In most cases, the remainder of the phosphates become adsorbed to the surface of other phases and are not intercalated into the LDH, though at high phosphate concentrations (26.6 wt. % P2O5) and extended curing times (470 days), phosphates are observed to intercalate into LDH phases. These results provide preliminary evidence that phosphates are compatible with low Ca AAMs, which is consequential as there is a growing interest in both the use of AAM and phosphate‐based corrosion inhibiter in steel‐reinforced concrete.
July 2024
·
159 Reads
The spectral reflectance and transmittance of two free‐standing ytterbium disilicate (Yb2Si2O7)—based environmental barrier coatings (EBCs) were measured from 25°C up to 1270°C. The measurements were collected over the spectral range of approximately 2–20 µm. The spectral emittance was then determined through conservation of energy and Kirchhoff's law of thermal radiation. The spectral emittance measurements for the EBCs were then compared to previous measurements for a thermal barrier coating (TBC).
July 2024
·
29 Reads
·
1 Citation
Complex alumina parts were printed using vat photopolymerization (VPP), which is a stereolithography‐based additive manufacturing (AM) technique used to shape ceramic preforms, or green parts. The critical flaw size was determined using classical fracture mechanics techniques. The strength and fracture toughness were measured and compared to flaws detected in x‐ray computed tomography (XCT or CT) distributions as well as the fracture surfaces. The strength was lower compared traditionally made alumina, and that is due to layering effects, slurry defects, and printing defects. The critical flaw size from fracture mechanics was 206 µm. XCT has high enough resolution to detect the critical flaw size and much smaller features, where the average flaw size observed in CT scans was around 80–100 µm. The fracture surfaces indicate that flaws causing failure are larger than that of the critical flaw size (∼300 µm), but fracture surfaces do not show definitive features compared to traditionally made ceramics. Since XCT can observe flaws smaller than the critical flaw size, this method can be used as a screening technique.
July 2024
·
70 Reads
The sharp increase in waterborne diseases due to bacterial contamination is limiting the supply of safe water in developing countries. This study focuses on the development and optimization of a low‐cost ceramic membrane based on natural resources and local waste for eliminating bacteria from water. The augmented simplex centroïd mixture design (ASCD) was used. The obtained optimal formulation consisted of 65% Ebebda clay (EB) 18.64% Koutaba clay (KG), and 16.34% cassava peel (PM) with a holding temperature of 1 100°C. The raw materials and membrane were characterized by chemical analysis using X‐ray florescence, X‐ray diffractometry, Thermal Gravimetric/Differential Scanning Calorimetry (TG/DSC), FTIR, scanning electron microscopy, SBET, porosity and flexural strength. The optimal membrane has 43.26% of porosity, 7.46 MPa of strength, 0.55 m²/g of specific surface area, an average pore diameter of 1.31 µm and a water permeability of 4 345,87 L h⁻¹ m⁻² bar⁻¹. The ability of the membrane support to retain Pseudomonas aeruginosa, Klebsiella pneumoniae, Salmonella sp and Staphylococcus aureus bacteria present in contaminated water was finally assessed. Retention tests showed 100% of P. aeruginosa, 97.37% of K. pneumoniae, 93.69% of Salmonella sp, and 90% of S. aureus, making this new, less expensive ceramic membrane a potential candidate for the water treatment.
July 2024
·
11 Reads
Acceptance rate
CiteScore™
Submission to first decision
Article processing charge
Editor-in-Chief
University of California, Davis, USA