Tin Oxide Gel Research Articles

Bio-inspired hierarchical nanofibrous SnS/C composite with enhanced anodic performances in lithium-ion batteries

Tin sulfide-based anodic materials with high specific capacities for lithium storage have attracted some attentions. Whereas, their poor cycling stability caused by the sever volume variation upon the repeated charge/discharge processes and their intrinsic poor electrical conductivity still need to be solved urgently. Herein, a bio-inspired hierarchical nanofibrous SnS/C composite was synthesized by employing natural cellulose substance as both scaffold and carbon source. Tin oxide gel film was firstly deposited on each cellulose nanofiber through layer-by-layer self-assembly processes, and then the composite was sulfided by hydrothermal treatment followed by carbonization and reduction in Ar atmosphere. The resultant nanocomposite manifests a unique three-dimensional (3D) porous structure composed of interlaced carbon nanofibers anchored with SnS nanoflakes. Used as the anodic material in lithium-ion batteries, the SnS/C composite exhibits remarkable electrochemical performances with a high specific capacity (1396 mAh g−1 in the 1st cycle at 100 mA g−1), long cycle life (612 mAh g−1 after 70 cycles) and good rate capacity (298 mAh g−1 at 1000 mA g−1), which are superior to the nanofibrous SnS2. The superior anodic performances of the SnS/C composite are mainly due to the 3D hierarchical porous nanostructure and the nanofibrous carbon conductive matrix together with the ultrathin carbon-coating layer, promoting the electrode-electrolyte contact, accommodating the drastic volume changes of SnS, inhibiting the active SnS particles from aggregation and facilitating the electron transfer and lithium-ion diffusion during the charge/discharge processes.

A Hierarchical, Nanofibrous, Tin‐Oxide/Silicon Composite Derived from Cellulose as a High‐Performance Anode Material for Lithium‐Ion Batteries

AbstractA hierarchical nanofibrous tin‐oxide/silicon composite with tin oxide nanoparticles anchored on the silicon nanofiber surface is fabricated employing natural cellulose substance (ordinary filter paper) as structural template. Tin oxide gel is deposited uniformly onto the surface of the silicon nanofibers that prepared by magnesiothermic reduction of the silica replica of the filter paper, and thereafter, the as‐prepared tin‐oxide−gel/silicon nanocomposite is calcined in argon atmosphere to yield the tin‐oxide/silicon nanocomposite. The resulted tin‐oxide/silicon nanocomposite possesses a hierarchical network structure that inherited from the initial cellulose substance. When the nanocomposite is evaluated as an anode material in lithium‐ion batteries, it exhibits superior lithium storage properties compared with the pure silicon nanofiber and tin oxide powder matters. For such a nanocomposite with 58.8 wt% tin oxide content delivers a specific reversible capacity of 547.8 mAh g−1 after 150 discharge/charge cycles at 100 mA g−1. The improved lithium storage performances are attributed to the unique three‐dimensional hierarchical porous network structure of the nanocomposite, high dispersed fine tin oxide nanoparticles on the silicon nanofiber surface, as well as the synergistic effects between the silicon nanofibers and the tin oxide nanoparticles on the lithium storage.

Evaluating the state of indium–tin oxide gels via estimation of their cohesive energy

In the fabrication of metal oxide films by the solution process, it is very important to know the state of a gel. In this report, the type of for indium–tin oxide (ITO) gel was determined according to the cohesive energy for agglutinating a gel. We developed the new method of determining a gel’s state to elucidate the total cohesive energy of an ITO gel film and its components. We employed an optical method based on the Lifshitz–van der Waals theory and a contact angle measurement method based on the van Oss theory to estimate components of cohesive energy. The result showed that the van der Waals interaction was the dominant interaction in the agglutination of the ITO gel. This indicated that the ITO gel is a physical gel. This result coincided well with these obtained by conventional methods such as thermogravimetric–differential thermal analysis and resolvability tests. The new method will be very useful for evaluating the gel state nondestructively.

Formula omitted]/SnO2 as a new electrode for electrochemical supercapacitors

The SO42−/SnO2 system has been investigated as a potential electrode material for supercapacitors. It is precipitated as a tin oxide gel by an alkaline hydrolysis of SnCl4, and subsequently impregnated with sulfuric acid and calcined. The SO42−/SnO2 is characterized by XRD, FT-IR and an electrochemical analyzer system. The specific capacitance of SO42−/SnO2 is 51.95Fg−1 at 5mV/s scan rate compared to the SnO2 value of only 15.61Fg−1. SO42−/SnO2 maintains 92.15% of its maximum capacitance after 2000 cycles.

A new way to prepare tin oxide precursor polymeric gels

Transparent tin oxide gels are elaborated in the isopropoxide/toluene/isopropanol system. The gelation occurs at room temperature without any acid or base additions. The formation of the SnO2 precursor gels polymeric network is evidenced by Fourier transform infrared spectroscopy. The gelation time is studied as a function of the complexing ratio R = [acac]/[Sn(OR)4], the hydrolysis ratio W = [H2O]/[Sn(OR)4], the concentration of tin oxide precursor C = [Sn(OR)4], and the volume fraction of toluene P = (toluene volume) / (total solvent volume).

Photodegradation enhancement of Congo red aqueous solution using a mixture of SnO 2· xH 2O gel/ZnO powder

The system tin oxide gel mixed with zinc oxide powder (SnO 2· xH 2O/ZnO powder) was investigated for Congo red removal from aqueous solution. The Congo red photodegradation increases when a gel of tin oxide is mixed with a small amount of zinc oxide powder (2.5% in mass). This activity increases more when tin oxide gel is mixed with smaller particles size of ZnO prepared by precipitation method. When the amount of zinc oxide is higher (25% in mass), Congo red is removed by adsorption process rather than by photodegradation. This adsorption is mainly due to zinc oxide powder. The adsorption reaction is more active when zinc oxide is mixed with tin oxide gel than when zinc oxide is used alone.

One step aqueous solution preparation of nanosize iron-doped tin oxide from SnO 2· xH 2O gel

Nanosized iron-doped tin oxide solid solution was prepared by mixing tin oxide gel SnO 2· xH 2O with a boiling solution of iron nitrate. The XRD data of the as-prepared and annealed sample at 773 K show that the patterns are indexed to the rutile phase without any trace of an extra phase. SEM and TEM results performed on different selected area of the samples reveal a homogeneous composition of 8 at.% of Fe content and a size of about 2 nm of the particles. The particles size was found to increase slightly with temperature; about 7 nm after 24 h at 773 K. Structural and magnetic results seem to indicate that Fe 3+ substitute for Sn 4+ on the as-prepared sample. The system presents some weak ferromagnetic character at room temperature.

Catalytic action of sulfated tin oxide for etherification and esterification in comparison with sulfated zirconia

Two highly active solid superacids of sulfated tin oxide were prepared, and their catalytic action was compared with that of sulfated zirconia. One was prepared from tin oxide gel, which was precipitated by the hydrolysis of SnCl 4 and washed with aqueous ammonium acetate solution, followed by exposure to aqueous sulfuric acid and calcination. The other was prepared from meta-stannic acid following the above procedures. The latter material was higher than the former in catalytic activities for the etherification of methanol and esterification of n-octanoic acid with methanol, and both showed activities higher than those of sulfated zirconia for the reactions. TPD measurements using ammonia and pyridine as probes showed that most of the acid sites on the surface of sulfated tin oxide have high strength of acidity with a narrow distribution, indicating the steady adsorption of both probes up to 673 K. On the other hand, the acidity on sulfated zirconia was shown to be heterogeneous, covering a wide range of strength, the temperature range of desorption of the probes being 473–823 K. The acid strength was estimated by the heat of Ar adsorption to be 29.7–31.0 and 24.3 kJ mol −1 for the sulfated tin and zirconium oxides, respectively. Differences in activities between the two Sn materials were explained on the basis of their IR spectra.

Catalytic action of sulfated tin oxide for etherification and esterification in comparison with sulfated zirconia

Two highly active solid superacids of sulfated tin oxide were prepared, and their catalytic action was compared with that of sulfated zirconia. One was prepared from tin oxide gel, which was precipitated by the hydrolysis of SnCl4 and washed with aqueous ammonium acetate solution, followed by exposure to aqueous sulfuric acid and calcination. The other was prepared from meta-stannic acid following the above procedures. The latter material was higher than the former in catalytic activities for the etherification of methanol and esterification of n-octanoic acid with methanol, and both showed activities higher than those of sulfated zirconia for the reactions. TPD measurements using ammonia and pyridine as probes showed that most of the acid sites on the surface of sulfated tin oxide have high strength of acidity with a narrow distribution, indicating the steady adsorption of both probes up to 673 K. On the other hand, the acidity on sulfated zirconia was shown to be heterogeneous, covering a wide range of strength, the temperature range of desorption of the probes being 473–823 K. The acid strength was estimated by the heat of Ar adsorption to be 29.7–31.0 and 24.3 kJ mol−1 for the sulfated tin and zirconium oxides, respectively. Differences in activities between the two Sn materials were explained on the basis of their IR spectra.

Development of tin oxide material by screen-printing technology for micro-machined gas sensors

Screen-printing technology is a low-cost production process that enables to deposit sensing elements for gas sensors, mainly on ceramic substrates. This study is focused on the optimization of inks composition in order to improve the performance of sensors regarding electrical and adhesion properties, on ceramic or smooth substrates like Si-based wafers. It has been demonstrated that it is possible to replace the inorganic vehicles and mineral binders contained in conventional inks by a tin oxide gel. New ink was developed by addition of a SnO 2 gel to a commercial SnO 2 powder. The gel allows to control the rheological properties for ink deposition. Its decomposition at low temperature (250–300 °C) to form SnO 2 during annealing reinforces the mechanical adhesion of the thick layer on the substrate. As there is no more glassy binder in the ink, the conductance strongly increases. Moreover, the annealing temperatures required for new inks can be lowered contrary to conventional inks, which enhances the compatibility with the microelectronics process regarding the maximum temperatures that wafers can withstand.

Preparation of a Solid Superacid of Sulfated Tin Oxide with Acidity Higher Than That of Sulfated Zirconia and Its Applications to Aldol Condensation and Benzoylation1

A highly active solid superacid of sulfated tin oxide was prepared from tin oxide gel, which was precipitated by the hydrolysis of SnCl4 and washed with aqueous ammonium acetate solution, followed by exposure to aqueous sulfuric acid and calcining. Differencial thermal analysis suggested that the acetate ion remaining on the surface was replaced with sulfate ion. The acid strength of the sulfated tin oxide estimated by temperature-programmed desorption using argon was higher than that of sulfated zirconia, a well-known solid superacid, the activation energy of Ar desorption by the former being 10.6 kJ mol-1 in comparison with 9.3 kJ mol-1 by the latter. The sulfated tin oxide showed activities much higher than those of the sulfated zirconia for the skeletal isomerization of n-pentane, the Mukaiyama aldol condensation of 1-trimethylsilyloxy-1-cyclohexene with benzaldehyde, and the benzoylation of toluene with benzoic anhydride.

The Preparation of Solid Superacid of Sulfated Tin Oxide with Acidity Higher Than Sulfated Zirconia

Abstract A highly active solid superacid of sulfated tin oxide was prepared from tin oxide gel which was precipitated from SnCl4 solution and washed with aqueous ammonium acetate solution. The sulfated tin oxide showed activity much higher than the sulfated zirconia, a well known solid superacid, for the skeletal isomerization of n-pentane, and its acid strength estimated by temperature-programmed desorption using argon was also higher than that of the latter.

Preparation of Stabilized Nanosized Tin Oxide Particles by Hydrothermal Treatment

Stable colloidal suspensions of tin oxide (content 0.9–6.1 wt%) were synthesized by subjecting conventionally prepared tin oxide gels to hydrothermal treatment with an ammonia solution (pH 10.5) at 200°C for 3 h in an autoclave. Based on X‐ray diffractometry analyses, the tin oxide crystallites after hydrothermal treatment were resistant to thermal growth at elevated temperatures, and this feature became more conspicuous as the tin oxide content of the colloidal suspension decreased. For the powder derived from a 1.8 wt% colloidal suspension, for example, the mean sizes of the tin oxide crystallites were 7.5 and 13 nm after calcination at 600° and 900°C, respectively, in comparison with corresponding values of 13.5 and 29 nm for the untreated gel‐derived powder. Thin film spin‐coated from the same suspension had good uniformity, packed with tin oxide grains (crystallites) of a mean size of 6 nm after calcination at 600°C. Optical determination of the tin oxide sol particle size, as well as gravimetric analysis of the dehydration from the powder samples, were conducted to determine effects of hydrothermal treatment.

Immobilization of heavy metals from aqueous solutions using polyacrylamide grafted hydrous tin (IV) oxide gel having carboxylate functional groups

A new adsorbent containing a carboxylate group has been prepared by the surface modification of a polyacrylamide grafted hydrous tin (IV) oxide gel. The product exhibits a very high adsorption potential for Pb(II), Hg(II) and Cd(II). The effect of initial metal ion concentration, adsorbent dose, pH, concentration of light metal ions, and temperature on metal removal has been studied. The process follows a first-order rate kinetics. The intraparticle diffusion of metal ions through pores in the adsorbent was shown to be the main rate limiting step. The equilibrium data fit well with the Langmuir adsorption isotherm. The selectivity order of the adsorbent is Pb(II)>Hg(II)>Cd(II). Adsorption rate constants and thermodynamic parameters were also presented to predict the nature of adsorption. The method was applied on synthetic wastewaters. Acid regeneration has been tried for several cycles with a view to recover the adsorbed metal ions and also to restore the sorbent to its original state.

Hydrothermal treatment of tin oxide sol solution for preparation of thin-film sensor with enhanced thermal stability and gas sensitivity

The effects of treating tin oxide gel hydrothermally in an ammonia solution at 200°C for 3 h were studied. The size of sol particles increased with increasing concentration of the resulting sol solution, i.e., 5, 8, 10 and 32 nm for 1.8, 3.2, 6.1 and 8.6 wt.% tin oxide sol as determined by an optical analyzer, whereas the crystallite size of tin oxide determined by X-ray diffraction analysis remained to be about 5–7 nm for all the solutions. The tin oxide powder collected was found to be resistant to grain growth on calcination, depending on the concentration of the sol solution. This tendency was maintained in the thin-films spin-coated on an alumina substrate from the sol solutions. The grain size of the film derived from 1.8 wt.% tin oxide sol was smaller than 10 nm in diameter after calcination at 600°C. This particular film exhibited an outstanding by high sensitivity to 800 ppm H 2 at 350°C, compared with conventional tin oxide elements of a sintered block type.

Role of Copper in the Characterization of Copper(II)-Promoted Tin(IV) Oxide Catalysts for the Catalytic Oxidation of Carbon Monoxide

Cu(II)/SnO2 catalyst materials with Cu:Sn ratios in the range 0.02−0.30 have been prepared by three routes: coprecipitation from aqueous solutions containing Cu2+ and Sn4+ ions, sorption of Cu2+ ions on to tin(IV) oxide gel, and destabilization of choline-stabilized tin(IV) oxide colloidal sols by the addition of aqueous copper(II) nitrate solution, and their constitution after thermal treatment in the temperature range 333−1273 K has been investigated by powder X-ray diffraction and EXAFS. Materials obtained by coprecipitation or impregnation are similar in nature irrespective of the Cu:Sn ratio with particle sizes <5 nm even after calcination at 673 K. Calcination at 873 K results in larger particles, but at temperatures ≥1073 K sintering to give very large particles occurs. EXAFS data show that the initial Cu(II) species from the coprecipitation or impregnation routes are hexaaqua {Cu(H2O)6}2+ ions sorbed onto the surface of the tin(IV) oxide particles but calcination at temperatures of 873 K and above causes the phase separation of CuO. EPR shows that only surface copper(II) is readily reduced on exposure to carbon monoxide. Copper(II)-promoted tin(IV) oxide catalysts effect the catalytic oxidation of CO for stoichiometric CO/O2 mixtures under at 328 K. The mode of operation of the catalysts appears to be synergistic in nature with the principal role of Cu(II) being mainly in electron transfer, i.e., it abstracts the negative surface charges (formed in the oxygen vacancies following desorption of CO2) to form Cu(I), which is then oxidized back to Cu(II) by reaction with oxygen. The activity of catalysts deactivated by running under highly reducing conditions can be restored completely by heating in a flow of air at 355 K. Irreversible deactivation occurs on processing at very high temperatures due to sintering and the phase separation of copper(II) oxide.

Modified Tin(IV) Oxide (M/SnO2M=Cr, La, Pr, Nd, Sm, Gd) Catalysts for the Oxidation of Carbon Monoxide and Propane

Materials formed by the incorporation of rare earth cations (M=La, Pr, Nd, Sm, Gd) into tin(IV) oxide using coprecipitation methods show no significant enhancement of catalytic activity toward the oxidation of carbon monoxide or propane over that of tin(IV) oxide itself. For chromium-promoted tin(IV) oxide catalysts, the temperature by which complete conversion of carbon monoxide and propane occurs is dependent on both the Cr:Sn atom ratio in the catalyst and the preparative route by which the chromium is incorporated into the catalyst. As prepared all the materials are hydrous gels comprising very small (<10 nm) particles of tin(IV) oxide over which the modifying metal component appears to be dispersed uniformly. Chromium(VI) oxyanions of the types CrO42−, Cr2O72−, and Cr3O102− are sorbed on to the surface of the tin(IV) oxide particles in the freshly prepared material derived from aqueous CrO3 and tin(IV) oxide gel. Prior to calcination the materials are microporous, but significant changes in specific surface area, pore volume, and pore size occur at temperature >673 K. Powder X-ray diffraction and electron microscopy confirm the formation of Cr2O3 on calcination at 1273 K.

Sintering and Crystallite Growth of Nanocrystalline Copper Doped Tin Oxide

The effect of Cu2+ contents and of firing temperature on sintering and crystallite growth of nanocrystalline SnO2 xerogels was analyzed by thermoanalysis (mass loss (TG), linear shrinkage, and differential thermal analysis (DTA)), X-ray powder diffraction (XRPD), and EXAFS (extended X-ray absorption fine structures) measurements. Samples were prepared by two methods: (a) coprecipitation of a colloidal suspension from aqueous solution containing both Sn(IV) and Cu(II) ions and (b) grafting copper(II) species on the surface of tin oxide gel. The thermoanalysis has shown that the shrinkage associated with the mass loss decreases by increasing the amount of copper. The EXAFS measurements carried out at the Cu K edge have evidenced the presence of copper in substitutional solid solution for the dried xerogel prepared with 0.7 mol % of copper, while for higher concentration of doping, copper has been observed also at the external surface of crystallites. The solid solution is metastable and copper migrates towa...

99/00946 Drying of coals by using supercritical carbon dioxide : Iwai, Y. et al. Ind. Eng. Chem. Res., 1998, 37, (7), 2893–2896

Shrinking behavior of tin oxide gels during solvent exchange in CO2 supercritical drying was investigated. The drying process consisted of two solvent-exchanging steps, including a first replacement of water by acetone and a second of acetone by liquid CO2. Gels prepared from a basic sol with a ζ-potential of −75 mV exhibited extensive shrinkage during both steps, while those from an acidic hydrous precipitate of lower potential (|ζ-potential|<35 mV) shrank only during the second step. The shrinkage during the first step correlates with the ξ-potential reduction with increasing acetone concentration, while that during the second step for both gels can be attributed to osmotic compressive pressure that arises from an increase in the liquid–solid (gel skeleton) interfacial energy with increasing CO2 concentration. Dramatically different aerogel microstructures were obtained by controlling the gel surface potential in conjunction with different combinations of solvent-evaporating and supercritical drying.

Preparation of tin oxide gels with versatile pore structures

Hydrous tin oxide gels were subjected to consecutive solvent-evaporation (SE) and CO2 supercritical (CS) drying steps, followed by re-hydration at low (30%) humidity, and the effects on pore structure of the SE drying duration and particle surface potential of the gel were investigated. The difference in surface potential has been found to impose significant variations in initial pore size distribution, while the SE drying step tends to narrow such differences and simultaneously reduce the mean pore size. It is demonstrated that varieties of pore structures have thus been obtained by simply varying these two parameters.