Etienne Frans. Vansant

Etienne Frans. Vansant
University of Antwerp | UA · Department of Chemistry

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391
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Publications

Publications (391)
Article
Full-text available
Purpose To evaluate urinary stones using small-angle X-ray scattering (SAXS) and nitrogen porosimetry (NP). Traditionally, stones are categorized as hard or soft based on their chemical composition. We hypothesized that stone hardness is associated not only with its chemical composition but also with its internal architecture. SAXS and NP are well-...
Article
Full-text available
With the evolution of the field of nanomaterials in the past number of years, it has become apparent that it will be key to future technological de- velopments. However, while there are unlimited re- search undertakings on nanomaterials, limited research results on nanomaterial costs exist; all in spite of the generous funding that nanotechnology p...
Article
Full-text available
Everett’s theorem-6 of the domain theory was examined by conducting adsorption in situ with small angle x-ray scattering (SAXS) supplemented by the contrast matching technique. The study focuses on the spectrum differences of a point to which the system arrives from different scanning paths. It is noted that according to this theorem at a common po...
Article
The statistical analysis of patents in specific areas can be an important tool for the evaluation of trends and advancements in specific research fields. Patenting is generally considered to be steered by commercial needs; hence it primarily concentrates on research results that are expected to have an important economic value. Patent data can be u...
Article
Background: Nanotechnology has been in the limelight since its emergence and its products affect everyday lives. Nanomaterials are characterized by features such as size and shape, thus rendering their possible number essentially unlimited, which in turn makes them difficult to study and categorize regarding possible dangers. This work suggests th...
Article
Herein, we report the formation of a series of nanocomposites composed of LDH structures and TiO2 with anatase crystal phase. The structure of the LDH clay was modulated by the insertion of different di-, tri- or tetravalent cations, such as Zn2+, Cu2+, Al3+, Fe3+ or Ti4+, within the brucite-like sheets. Afterwards, the anatase seeds were deposited...
Article
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Vycor porous glass has long served as a model mesoporous material. During the physical adsorption of halogenated hydrocarbon vapours, such as dibromomethane, the adsorption isotherm exhibits an hysteresis loop; a gradual ascent is observed at higher pressures during adsorption, and a sharp drop is observed at lower pressures during desorption. For...
Article
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The work reported involves a detailed characterization study on a series of nanocomposite systems comprising layered double hydroxides and TiO2 seeds with anatase crystal structure. The TiO2/LDH nanocomposite structural and textural features were varied by the isomorphous substitution within the LDH sheets network of the divalent cations (Zn2+ by C...
Article
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SBA-15 mesoporous silicas modified with rhodium were studied as catalysts for the N2O decomposition reaction. Rhodium was deposited on SBA-15 by the Molecular Designed Dispersion (MDD) method using Rh(acac)3 as a precursor of active phase. The same method was used for the deposition of Cu, Fe, Al and Ti. The SBA-15 support modified with metals were...
Article
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In this study we report the synthesis of a series of composite nanostructures comprising LDH and TiO2 phases. The materials characterization showed that the LDH crystallites are encapsulated inside the TiO2 matrix after the anatase seeds are deposited on MgxAl-LDHs. The structure in which LDH phase is embedded into anatase matrix is unique bringing...
Article
A simple solvothermal impregnation method was used to prepare ZnO nanoparticles supported on MCM-41 and SBA-15. X-ray powder diffraction, N2 adsorption–desorption, Electron Probe Micro Analysis (EPMA), and UV–vis spectroscopy were used to characterize the prepared materials. The influence of the ZnO loading of different supports on the structural c...
Article
Adsorption of CO and CO2 has been studied on zeolite Y in which Na+ ions have been partially exchanged for Ca2+ ions. Physisorption of CO and CO2 provides a sensitive method for the observation of the population of Na+ and Ca2+ ions in supercage positions. The results indicate that Ca2+ ions introduced into a NaY zeolite by aqueous ion exchange pre...
Article
To evaluate the interaction energy of molecules adsorbed in the Y and A zeolites, the electrostatic field has been calculated in the large cavities. The zeolites have been considered as crystals consisting of point charges, with the positive charges statistically localized at all cationic sites and the negative charges distributed equally among the...
Article
The adsorption properties of partially exchanged (Na,H) clinoptilolites and silanated H-clinoptilolites have been investigated as a function of the degree of modification. A different sorption behaviour of N2, Kr and Xe in (Na, H) clinoptilolites is observed in three exchange regions. In samples having a proton loading lower than 10%, adsorption of...
Article
A study has been made of the exchange properties of +H3N-CH2-NH+3, +H3N-(CH2-NH+3, +H3N-(CH2)3-NH+3, +H3N-CH2-CH(NH+3)-CH3, +H3N-(CH2)4-NH+3, +H3N-(CH2)5-NH+3 and +H3N-(CH2)6-NH+3 in the zeolites X and Y. For steric reasons, none of the organic cations could effect a complete replacement of the Na+ ions initially present in the zeolite. A linear de...
Article
The interaction energies of Ar, CO and CO2 molecules adsorbed in the large cavities of the zeolites NaY and CaY have been determined from the calculation of the dispersion, polarization, field-dipole, field gradient-quadrupole and repulsion components for different positions of the molecules. We have illustrated theoretically the non-cation specifi...
Article
The polarisability and the equivalent ionic conductance of the short-chain alkylammonium ions were determined by refractometric and conductometric measurements in aqueous solutions.
Article
New Zealand allophane and halloysite samples were investigated using sorption, DTA, infrared, crystallographic and Mössbauer techniques. The data support the hypotheses linking both minerals, although marked differences were detected, which are related to their structures and consequently, to their polarity.
Article
The EPR spectra of the cupric-ammonia complexes in the zeolites X and Y were studied. Ammonia adsorption in the copper(II)-X and -Y zeolites resulted in the formation of square planar Cu(II)-NH3 complexes. Desorption of ammonia produced in both zeolites a distorted tetrahedral complex.
Article
The physicochemical properties of the iron exchanged A-type zeolites are affected by the degree of dehydration of the samples. Mössbauer and adsorption techniques were used to investigate the cation distributions in these zeolites. At lower degrees of hydration, a significant number of iron ions are located inside the sodalite cavities. A systemati...
Article
The influence of 4 reaction parameters on the homogeneous saponification method is examined. Firstly, the use of xylene, cyclohexane and tetrachloromethane instead of toluene indicates some experimental complications. It could however be concluded that a changing solubility parameter had a minor effect on the VA conversion rate. Secondly, reactions...
Article
An attempt was made to clarify the adsorption mechanism of partially hydrated and ammoniated ferrierite. The adsorption of CO, CO2, N2, O2, Xe, Kr, Ar, CH4 on the H-ferrierite was investigated as a function of the adsorption temperature. Using equilibrium thermal analyses and adsorption techniques (N2 at 77 K) the dehydration and deammoniation of f...
Article
The adsorption of H2S, CH3SH and CS2 on Cu(II)Y zeolite reveals an affinity sequence CH3SH » CS2 > H2S. Very strong displacement effects of CS2 and H2S by SH were observed when binary mixtures of CS2/CH3SH and CS2/H2S were contacted with Cu(II)Y. In ternary mixtures H2S is displaced by both, CS2 and CH3SH while CS2 is displaced by CH3SH. The intera...
Article
Three high pressure ethylene vinylacetate (EVA) copolymers having a mol % VA between 0 and 20 are transformed into ethylene vinylalcohol vinylacetate (EVALVA) terpolymers by an homogeneous saponification method. The acetoxy-hydroxide conversion proved to be caused by two similtaneously occuring reactions, a saponification and a transesterification....
Article
SBA-15 mesoporous silica was modified with metal (Al, Ti, Cu, Fe) oxides by the molecular designed dispersion (MDD) method using acetylacetonate complexes of metals as precursors of the catalytically active components. The modified mesoporous silicas were characterized with respect to texture (BET), composition (EPMA), coordination and aggregation...
Article
Structural transformations induced in gamma and alpha globulins under influence of gamma irradiation using doses of 2.5 and 24 kGy were studied by differential scanning calorimetry (DSC) and thermogravimetry (TG, DTG). Thermal decomposition of the globulins irradiated in water suspensions occurs at higher temperatures, in comparison to the referenc...
Article
Detailed knowledge of the transport properties of nanoporous materials is a prerequisite for their complete characterization and optimum technological exploitation. One of the best ways to attain this information is provided by the “microscopic” techniques of diffusion measurement, in particular by the pulsed field gradient technique of NMR and by...
Article
A very large number of different synthesis approaches for the preparation of mesoporous materials has been reported in literature since the first development of ordered mesoporous materials in the 1990’s. Since then, the synthesis of advanced mesoporous materials has undergone an explosive growth. Moreover, this type of materials gains growing succ...
Article
Combined TiO2/SiO2 mesoporous materials were prepared by deposition of TiO2 nanoparticles synthesised via the acid-catalysed sol–gel method. In the first synthesis step a titania solution is prepared, by dissolving titaniumtetraisopropoxide in nitric acid. The influences of the initial titaniumtetraisopropoxide concentration and the temperature of...
Article
An aluminium-free Ti-Beta/SBA-15 composite material was prepared by the post-synthesis incipient wetness-deposition of different amounts of Ti-Beta nanoparticles solution on the SBA-15 matrix. The presence of crystalline nanoparticles in the solution, used for impregnation on SBA-15, was confirmed by HRTEM measurements. The hexagonal arrangement of...
Article
This report describes the synthesis and photocatalytic behavior of TiO2/SiO2 mesoporous materials prepared by acid catalyzed sol-gel method. The properties of ordered TiO2/Si-MCM-41 and TiO2/Si-SBA-15 materials were identified by XRD, N2 sorption measurements and chemical analysis. It has been shown that the photocatalytic degradation of rhodamine...
Article
Full-text available
Sn4+-containing LDH was prepared using the co-precipitation method at constant pH, and characterized using X-ray diffraction, UV–vis diffuse reflectance spectroscopy and TG/DTG methods. The obtained product was further exposed to different thermal treatments in order to obtain nano-sized coupled ZnO/SnO2 systems with enhanced photocatalytic perform...
Article
Sn4+-containing LDH was prepared using the co-precipitation method at constant pH, and characterized using X-ray diffraction, UV–vis diffuse reflectance spectroscopy and TG/DTG methods. The obtained product was further exposed to different thermal treatments in order to obtain nano-sized coupled ZnO/SnO2 systems with enhanced photocatalytic perform...
Article
Post-synthesis hydrothermal treatments have been used to improve the quality of MCM-41 materials. In our latest work, merging of surfactant-containing silica microspheres during the hydrothermal treatments was observed. Mechanistic insights and the different stages that are involved in the merging process can be summarized as follows. First, the su...
Article
Full-text available
Zn/Al- and Zn/Al/Sn-LDHs were prepared by the co-precipitation method at constant pH. The LDH structure and the local environment of the tin cations were investigated using XRD and UV-vis DR methods. Band component analysis of both infrared and Raman spectra has been used for the detailed characterization. Raman spectroscopy proved to be more usefu...
Article
Titania nanoparticles have been deposited on inert porous silica supports with high specific surface area. These materials have potential applications in paint and textile industry as the titania particles selectively deposited on the inner surface of the silica supports act as a photocatalyst. The inert external surface is necessary to avoid photo...
Article
Titanate nanotubes were prepared via a hydrothermal treatment of TiO2 powders (Riedel De Haen) in a basic solution. Morphology and structure of the prepared samples were characterized by high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), XRD, FT-Raman spectroscopy, nitrogen sorption and DSC. The pho...
Article
Zn/Al-LDHs with cationic ratio of 1–4 were prepared by the co-precipitation method at constant pH. The XRD patterns showed that additional phase is present in all samples due to the lattice strains created when more Zn2+ is added and the longer periods of hydrothermal treatment. The as-synthesized samples were calcined at different temperatures and...
Article
The incorporation of the tetravalent Ti4+ cations into layered double hydroxide (LDH) type materials was studied as a function of the cationic ratio in the brucite-like sheets. Therefore, Zn–Ti-LDHs with different cationic ratio were prepared by the coprecipitation method at constant pH. The X-ray diffraction patterns revealed that only for the cat...
Article
The photocatalytic activity of commercial P25 and mesoporous titania, synthesized following the Evaporation Induced Self Assembly procedure (EISA), is studied in aqueous and gaseous environment. In aqueous environment, the activity of mesoporous titania is inferior to the activity of P25 due to retarded diffusion kinetics. On the other hand, in gas...
Article
Hollow silica spheres were quickly synthesized by an octylamine (OA) templating method using tetraethyl orthosilicate (TEOS) as the silica source. N2-sorption results indicate that the hollow spheres have high surface areas and pore volumes. XRD and TEM measurements reveal that the structure of the hollow spheres depends on the amount of TEOS used...
Article
Ti–SBA-15 mesoporous molecular sieves were prepared following an in situ method. Titania was therefore added during the synthesis of SBA-15. The influence of the silica source, the titania source, the synthesis temperature and the ageing temperature are investigated. These influences are discussed towards structural features, porous characteristics...
Article
Ti–SBA-15 mesoporous molecular sieves were prepared following an in situ method. Titania was therefore added during the synthesis of SBA-15. The influence of the silica source, the titania source, the synthesis temperature and the ageing temperature are investigated. These influences are discussed towards structural features, porous characteristics...
Article
Silicalite-1 precursor nanoparticle solutions are prepared from a mixture of TPAOH, H 2 O and TEOS. Acidification of the clear nanoparticle solution and a consequent hydrothermal treatment results in the formation of a large pore mesoporous material. The use of meso-templates for the formation of the mesopores is no longer required. These materials...
Article
The dispersion and the loading of metals on support materials have great importance in the design of catalysts. Two MCM-41 supports having similar morphology, porosity characteristics and different OH/nm2 values were synthesized, in order to study the influence of silanol number on vanadia deposition. VOx supported MCM-41 catalysts were prepared th...
Article
The unique pore structure combined with its high pore volume and large pore size make MCF material attractive as a catalyst support related to reactions with large molecules or as a capsule for storing and controlled release of organic guest substances. By varying the amount of TEOS, or the stirring temperature or the aging conditions in the synthe...
Article
Since the first discovery of microporous zeolites, the field of porous materials has become a fast growing field with progress in a wide variety of different types of materials. Zeolites are among the best known examples. However, since the increasing interest for the processing of larger, bulky molecules, a lot of research is focused on mesoporous...
Article
A multistep deposition of anatase nanoparticles was employed to incorporate high amounts of titania into the mesopores of SBA-15. Anatase nanoparticles were synthesized and deposited following the Acid Catalyzed Sol Gel method. With this method, the size of the anatase nanoparticles can be controlled and therefore, the titania loading into the meso...
Article
Mesoporous titania was synthesised following the Evaporation-Induced Self-Assembly method. The structures had to be thermally stabilised in order to possess photocatalytic activity, since the photocatalytic active anatase phase needs to be accessible. The photocatalytic activity of the materials was tested by the photodegradation of rhodamine 6G. T...
Article
This paper reports the applicability of hydrothermal synthesis in alkaline medium for preparation of Ti-containing mesoporous MCM-41 materials. The influence of different parameters was investigated, such as the Ti source, the molar ratio between Si and Ti and also the synthesis temperature. Structural analysis shows that the high specific surface...
Article
Properties of SBA-15 materials modified by the impregnation of vanadium silicalite-1 zeolite-like nanoparticles (SBA-VS) have been studied. The influence of the amount and concentration of impregnated nanoparticles on the structural characteristics were studied by N2-sorption measurements, TEM and HRSTEM. Increasing the amount of nanoparticles on t...
Article
Porous clay heterostructures (PCH), obtained on the basis of synthetic saponite, were modified with copper and iron ions by an ion-exchange method and tested as catalysts for the selective reduction of NO with ammonia (NH3-SCR). Transition metal ions were introduced into H+ and NH4+ forms of PCH. The catalysts were characterized with respect to the...
Article
Tens of micrometer-sized hollow silica spheres with thermally stable nanoporous shells were synthesized within 5min, followed by a drying and a calcination step. Most of the nanopores could be retained up to 700°C, and the hollow spherical morphology was remained at least until 950°C. It is proposed that a fast hydrolysis and condensation of tetrae...
Article
Spherical, irregular and gyroidal MCM-41 were used for the deposition of VOx by the molecular designed dispersion method (MDD), in liquid phase, using vanadyl acetylacetonate. The molecular designed dispersion method using metal complexes on a highly porous support is a suitable method to prepare high quality catalysts. Deposition of VO(acac)2 was...
Article
The growth of titania nanoparticles within the mesopores of SBA-15 has been controlled by a post-synthesis deposition using the acid-catalyzed sol–gel method (ACSG). The crystal size, the location and the crystalline phase of the titania nanoparticles can be tuned by a careful adjustment of the preparation conditions. The influence of the initial t...
Article
Continuous Wave (CW) and pulsed Electron Paramagnetic Resonance (EPR) spectroscopy in conjunction with Raman spectroscopy are used to investigate the properties of Vanadium Silicalite-1 (VS-1) nanoparticles dispersed onto the mesoporous walls of SBA-15 silica. The properties of the deposited zeolite nanoparticles are found to be remarkably differen...
Article
Full-text available
The characteristics of new types of coated wire potentiometric sensors based on composite coatings were compared with classical potentiometric sensors. The composite sensors contained respectively the clay montmorillonite (MM) and the zeolite NaY as the ionically conducting components, embedded in PVC based rubber phase membranes. The behavior of 2...
Article
Using a quaternary mixture of surfactant F127, demineralized water, HCl and butanol, it is possible to form different sized spheres of SBA-16 only by controlling the amount of siliceous precursor (TEOS) used during the synthesis. These spheres are well ordered and show very high porosity. The size of the spheres can be explained by an agglomeration...
Article
W. Stböer synthesized silica spheres by hydrolyzing TEOS in mixed solutions of ammonia, alcohol and water in 1968. About 30 years later, Unger's group successfully prepared ordered mesoporous silica spheres in the same system by introducing cetyltrimethylammonium bromide (C16TAB) as a template. The later has been assigned as a “modified Stöber meth...
Article
Mesoporous SBA-16 and SBA-15 were studied in order to control their possible morphologies. SBA-16 is synthesized using a silicon source (tetraethoxysilane, TEOS) and a ternary system consisting of surfactant F127 (EO106PO70EO106), water, and butanol. The same ternary system, with higher butanol concentration, is used to form SBA-15 material as well...
Article
Porous clay heterostructures (PCH) obtained on the basis of the synthetic saponite was used as a catalytic support for the deposition of transition metal (Cu, Fe) oxides. Transition metal oxides were introduced into the parent as well as ammonia treated PCH support by the ion-exchange method. The obtained catalysts were characterized with respect t...
Article
We present an efficient method for the quantification of crystalline versus amorphous phase content in mesoporous materials, making use of electron energy loss spectroscopy. The method is based on fitting a superposition of core-loss edges using the maximum likelihood method with measured reference spectra. We apply the method to mesoporous TiO2 sa...
Article
The molecular designed dispersion (MDD) method was used for the modification of SBA-15 with vanadium oxide. Vanadyl acetylacetonate was grafted on the support surface at different VO(acac)2 concentrations in a toluene solution, and then converted into the VOx/SBA-15 catalysts at elevated temperatures. The thermal transformation of surface species w...
Article
A post-synthesis deposition of titania nanoparticles in the pores of SBA-15 results in highly ordered hexagonal templated materials with anatase plugs for photocatalytic applications.
Article
Mesoporous silicas (MCM-48, SBA-15, MCF), reflecting various porous structures, were modified with copper and iron oxides by two different methods. For a first series of the samples the molecular designed dispersion (MDD) method using acetylacetonate complexes of copper and iron was applied for the deposition of transition metal oxides on the silic...