Addition Of In2O3 Research Articles

Effects of In2O3 doping on the microstructure and electrical properties of ZnO–V2O5–Nb2O5 varistor ceramics

To understand the effects of In2O3 on the microstructure, grain size dispersion, density and nonlinear electrical characteristics, ZnO–V2O5–Nb2O5 varistor ceramics with 0.02, 0.05 and 0.1 mol.% In2O3 were fabricated via sintering at 950–975 °C for 1 h. The sintered samples were evaluated by x-ray diffraction, scanning electron microscopy, density measurements and electrical measurements through a voltage source meter. In2O3 addition improves relative density to ≥99 % and acts as an efficient grain growth inhibitor, resulting in a narrower grain dispersion and finer ZnO grains due to the formation of In–V–O intergranular phases. The breakdown potential (E1mA) increases sharply to 7.49 ± 0.3 kV/cm (from 1.66 ± 0.1 kV/cm) as a result of grain size reduction to 2.1 ± 0.1 μm (from 3.89 ± 0.2 μm) with In concentration of 0.1 mol.% (from 0.02 mol.%). Doping of In2O3 improves the nonlinear exponent and reduces the leakage current density as a direct consequence of enhanced Schottky barrier height.

Arc erosion behaviors of the densified Ag-SnO2 contact materials containing sub-micron and nano In2O3 additives

The effects of In2O3 additive size on the physical properties and arc erosion behaviors of the densified Ag-SnO2 materials were investigated. Arc resistance mechanism was analyzed based on the microscopic morphology characterization. Results revealed that the physical properties of the Ag-SnO2(In2O3) materials were significantly improved after densification. Relative density and electrical conductivity of the materials reached above 99.5% and 71%IACS, respectively. The densified Ag-SnO2 material containing sub-micron In2O3 showed the low and stable break arc energy. The mass loss of the cathode was dramatically decreased by 65.4%. Importantly, the generation of pores and micro-cracks on the surface of electrodes were significantly restrained and the contact resistance became more stable. By comparison, the nano In2O3 additive less than 100 nm effectively suppressed not only the splash of molten Ag on the surface of cathode but also the aggregation of SnO2 particles on anode. The arc erosion products were obviously decreased, resulting in an enhancement of arc-erosion resistance of Ag-SnO2(nano In2O3) materials. Compared with that without additive, the mass loss of the Ag-SnO2 material which contains nano In2O3 obviously decreased from 2.3 to 1.4 mg. The optimal mass fraction of nano In2O3 in the Ag-SnO2 contact materials was 1 wt%.

Facile Synthesis, Characterization, and Photocatalytic Evaluation of In2O3/SnO2 Microsphere Photocatalyst for Efficient Degradation of Rhodamine B.

The tin dioxide (SnO2) photocatalyst has a broad application prospect in the degradation of toxic organic pollutants. In this study, micron-sized spherical SnO2 and flower indium oxide (In2O3) structures were prepared by a simple hydrothermal method, and the In2O3/SnO2 composite samples were prepared by a “two-step method”. Using Rhodamine B (RhB) as a model organic pollutant, the photocatalytic performance of the In2O3/SnO2 composites was studied. The photocurrent density of 1.0 wt.% In2O3/SnO2 was twice that of pure SnO2 or In2O3, and the degradation rate was as high as 97% after 240 min irradiation (87% after 120 min irradiation). The reaction rate was five times that of SnO2 and nine times that of In2O3. Combined with the trapping experiment, the transient photocurrent response, and the corresponding characterization of active substances, the possible degradation mechanism was that the addition of In2O3 inhibited the efficiency of electron–hole pair recombination, accelerated the electron transfer and enhanced the photocatalytic activity.

Hydrogen production over highly active Pt based catalyst coatings by steam reforming of methanol: Effect of support and co-support

The effect of metal oxide (CeO2, Al2O3 and ZrO2) support and In2O3 co-supported Pt catalysts has been investigated on steam reforming of methanol in microreactors. CeO2, Al2O3 and ZrO2 were prepared by the sol-gel method and they were used as a support, which was impregnated with In2O3 as co-support followed by the introduction of Pt species via the wet impregnation method. The size and dispersion of the Pt nanoparticles on In2O3/support have been examined by transmission electron microscopy. From these TEM and XPS results, it was found that the addition of In2O3 supports the formation of a high concentration of metallic Pt nanoparticles with enhanced dispersion and controlled particle size on the surface. The activity and stability of all the developed catalysts were tested for the steam reforming of methanol in microreactors at different temperatures. Under reforming conditions without prior reduction, a Pt/CeO2 catalyst containing 15 wt % of Pt exhibited complete methanol conversion and high selectivity towards hydrogen at 350 °C. However, the CO formation was found to be very high (7.0 vol %) for this catalyst. Upon addition of In2O3 as a co-support to this formulation the formation of CO decreased considerably. Pt/In2O3/CeO2 catalyst containing 15 wt % of Pt and 15 wt % of In2O3 showed excellent catalytic performance at much lower concentration of CO. This change could be closely associated with the formation of metallic Pt nanoparticles with smaller size, higher dispersion with strong interaction between Pt, In2O3 and support, which creates more oxygen vacancies to activate the water molecule which then react with methanol to produce H2 and CO2 suppressing the CO formation. Moreover, CeO2 supported Pt/In2O3 catalyst displayed higher stability with lowest CO formation under continuous steam reforming operation of 100 h. The superior performance of this catalyst is thought to be due to the relative abundance of redox sites on the CeO2 surface, which is able to create an oxygen vacancy as it possesses higher oxygen storage capacity and oxygen exchange capacity. This work demonstrates that the nature of support plays a crucial role for the continuous activation of reactants and determines the catalytic stability during methanol steam reforming.

Domain evolution and corresponding piezoelectricity of lead-free In2O3-doped K0.5Na0.5NbO3 ceramics together with improved fatigue resistance and temperature stability

In this paper, (1-x)K0.5Na0.5NbO3-x mol% In2O3 (abbreviated as KNN-xIn) lead-free piezoelectric ceramics were prepared using conventional solid sintering method. The effects of In2O3 on the phase structure, microstructure, domain evolution, electrical properties, fatigue behavior and thermal stability of KNN ceramic matrix were systematically studied. XRD results show that all the ceramics possess the orthorhombic phase with domain architectures presented in the PFM. The addition of In2O3 improved the fatigue resistance owing to the enhanced density. The temperature stability of the 1.0 mol% In2O3 doped sample was significantly improved. It was found that the KNN ceramics with 1.0 mol% In2O3 addition exhibited good electrical properties (d33* = 179 pm/V, d33 = 103 pC/N, TC = 388 °C, Pr = 31.52 μC/cm2, εr = 327, tanδ = 3.28%). The results suggested that this material should be an attractive lead-free material for piezoelectric applications.

In2O3 sensitized disordered porous SnO2 aerogel with remarkable gas-sensing properties at room temperature

This study aimed at the preparation of In2O3 sensitized disordered porous SnO2 aerogel (In2O3/SnO2) gas-sensing material by a sol-gel hard template method, and tested its gas-sensing properties to NOx gas at room temperature. The remarkable gas-sensing material was achieved by doped In2O3 into disordered porous SnO2 aerogel. The SiO2 could catalyze the SnCl2·2H2O to form the sol-gel system when the Sn, In and Si sources were mixed in alcohol and water, the silicon templates were formed during the reaction, and the disordered porous In2O3/SnO2 aerogel composite was obtained when the silicon templates were removed. When the doped concentration of In2O3 was 0.1%, the composite exhibited the highest sensitivity and selectivity. For doping 0.1% In2O3 sample, when the NOx concentration was 100 ppm, the response reached 80.3%, the response time was only 2.0 s. The detection limit to NOx gas reached 0.08 ppm. The response of sample to NOx was much higher than the same concentration other gases (NH3, H2, O2 and N2). The gas sensing mechanism was proposed that the addition of In2O3 into SnO2 enhanced the catalytic activity for the reaction. In addition, the morphology and unique structure were helpful to the gas reaction on the surface of the sensing materials. The prepared In2O3/SnO2 composite immensely reduced the dosage of the much expensive In element, and had the much higher response, which would have a great development space in the gas sensor field.

Photocatalytic activity and photoluminescence properties of TiO2, In2O3, TiO2/In2O3 thin films multilayer

This study evaluated the effect of crystallization temperature (300, 500 and 700 °C) on the photocatalytic and photoluminescent properties of the multilayer thin films of TiO2, In2O3 and TiO2/In2O3 which were prepared by the Complex Polymerization Method (CPM) and deposited on substrates of Si (100) by the spin coating method. The results of X-ray diffraction (XRD) revealed that there was no chemical interaction between the oxides (TiO2/In2O3) in crystalline films. The morphology was observed by atomic force microscopy (AFM) with a mean grain size of 15–35 nm. The result showed that the photocatalytic property is significantly increased by increasing the crystallization temperature. This is due to the agitation of the molecules which facilitates the transfer of charge between the electron and the catalyst bore. UV–vis light absorption spectra indicated that the addition of In2O3 in TiO2 films is an effective way of increasing the uptake of TiO2 in the visible region up to ~ 600 nm for photocatalytic applications, it was also possible to observe that these films could be easily Recycled for reuse. The samples were also characterized by photoluminescence, where it was possible to observe that the reduction of the PL intensity increased the photocatalytic activity of the thin films, with the increase of the crystallization temperature. In addition, the method used in this study is simple and economical compared to other methods.

NO2 Gas Sensing Properties of Nano-Sized In2O3 Doped WO3 Powders Prepared from Polymer Solution Route

In2O3 doped WO3 powders were prepared by a polymer solution route and their NO2 gas sensing properties were analyzed. The synthesized powders showed nano-sized particles with specific surface areas of 6.01~21.5 m2/g and the particle size and shape changed according to the content of In2O3. The gas sensors fabricated with the synthesized powders were tested at operating temperatures of 400~500 oC and 100~500 ppm concentrations of NO2 atmosphere. The particle size and In2O3 content affected on the initial sensor resistance in an air atmosphere. The highest sensitivity (8.57 at 500 oC), which was 1.77 higher than the sensor consisting of the pure WO3 sample, was measured in the 0.5 mol% In2O3 doping sample. In addition, the response time and recovery time were improved by the addition of In2O3.

Thin-Layer Indium Oxide and Cobalt Oxyhydroxide Cobalt-Modified BiVO4 Photoanode for Solar-Assisted Water Electrolysis

Fabrication of high-performance tandem cell for solar-assisted water cleavage requires an efficient photoanode with excellent bulk charge separation and surface injection. In light of that, we developed a hybrid photoanode using visible light absorber as main scaffold, a thin layer In2O3 middle layer to enhance charge separation in bulk and finally an active CoOOH catalyst as outer decoration for better surface charge injection. Bulk separation was mainly augmented by In2O3 addition, while the addition of CoOOH largely advanced photocurrent onset and elevated injection efficiency. The resultant photoanode delivered a high current density at low applied bias, showing promising prospect for incorporation into tandem cell for solar-assisted water electrolysis.

Promoting effect of In2O3 on CuO for the Rochow reaction: The formation of P–N junctions at the hetero-interfaces

Here we report the first work on the synthesis of a series of xIn-CuO model catalysts for the Rochow reaction with formed P–N junctions at interfaces and with different In/Cu molar ratios. These composites were prepared by a one-pot hydrothermal method using metal nitrate salts and K2CO3 as the precursors and precipitant, respectively. Scanning electron microscopy and transmission electron microscopy characterization revealed the formation of the P–N junctions at the hetero-interfaces between CuO and In2O3, and X-ray photoelectron spectroscopy and H2 temperature-programmed reduction demonstrated a strong interaction between the CuO and In2O3 phases. The addition of In2O3 increased the electron density in the Cu nucleus, causing Cu2+ and In3+ to become less and more positively charged, respectively. When used for the Rochow reaction, the catalyst 2In–CuO (2wt.% In on CuO) exhibited a significantly higher Si conversion and dimethyldichlorosilane ((CH3)2SiCl2, M2) selectivity than CuO, which is attributed to the formation of P–N junctions that can facilitate the charge transfer. In addition, the detailed characterizations of the fresh and spent contact masses indicated that the Rochow reaction occurred on the Si surface and probably in the areas between ultrathin two-dimensional Cu–Si species and Cu doping deposits. In2O3 species promote the outward spreading of Cu∗ (intermediate species) and improve the Cu∗ diffusion rate at the reactive interfaces. This work not only deepens the fundamental understanding of the Rochow reaction, but also provides a new approach for the design of more efficient Cu-based catalysts by adding promoters such as In2O3 and by engineering the interfaces.

Structural and magnetic properties of indium–gadolinium oxide as a function of temperature

The addition of In2O3 to Gd2O3 results in the formation of solid solutions having the high pressure monoclinic and hexagonal phases of gadolinium oxide. The thermal stability and their thermal expansion coefficients were investigated up to 1000 °C using in situ X‐ray diffraction. No phase transitions were observed in these samples up to 1000 °C. Volume thermal expansion coefficients for the hexagonal and monoclinic phases of bulk Gd2−xInxO3 for x = 0.5 and 1.0 showed increasing trend in comparison to the end compound of In2O3. The inverse susceptibility measurements between 300 and 5 K showed the linear relationship with temperature consistent with the Curie–Weiss law. The Weis constants were small and negative, indicating a slight degree of anti‐ferromagnetic exchange between cations and consistent with the absence of magnetic order down to 5 K.

Outstanding efficiency of indium in bimetallic catalysts for hydroconversion of bioacids to bioalcohols

Step by step reduction of acetic acid (AA) to ethanol was investigated over novel bimetallic catalysts (PtIn/Al2O3) for the processing of VFAs (volatile fatty acids) that can be produced simply by thermochemical or biological biomass degradation. A fixed bed flow-through reactor was applied with hydrogen stream at 21 bar total pressure in the temperature range of 220–380 °C. AA hydroconversion activity of the parent alumina supported Pt catalyst and the yield of selectively produced alcohol can be increased drastically by In2O3 addition. Appearance of metallic indium creating a bimetallic catalyst can direct the consecutive catalytic reduction to ethanol formation inhibiting hydrodecarbonylation. Comparing the In-containing bimetallic catalysts studied recently, NiIn-catalyst showing similar activity to that of the PtIn-catalyst can be a cheap substitute for the expensive Pt catalysts in the reduction carboxylic acids.

Microstructural Controls of a Titania Electrode for Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have been fabricated by employing TiO2 nanotubes (TNTs) with large specific surface area (SSA) and submicron-sized macroporous (mp-)TiO2 powders. The SSA of TNT obtained was much larger than that of commercial TiO2 nanoparticles (P25, AEROXIDE®) and the photovoltaic performance of the DSSC with the TNT electrode was larger than that with the P25 electrode. The addition of P25 to the TNT electrode was ineffective in improving the performance, and further addition of In2O3 to the TNT electrode containing P25 led to larger improvement in photoenergy-conversion efficiency to η = 5.73%. This improvement in η is considered to arise from the enhancement of the electronic conduction among TiO2 particles by the mixing of In2O3. On the other hand, the photovoltaic performance of DSSCs with the mp-TiO2 electrodes was low, but the stacking of the mp-TiO2 film onto the P25 electrode was quite effective in improving the photovoltaic performance, probably because of the excellent light scattering properties of the mp-TiO2 film.

Influence of In<sub>2</sub>O<sub>3</sub> Addition On The Magnetic And Electrical Properties of Iron – Deficient Ni-Zn Ferrite

The influence of low melting In2O3 addition on the magnetic and electrical properties of irondeficient ferrites of composition. Ni0.65Zn0.35Fe1.96O4 + xIn2O3(x = 0, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03 and 0.035) was investigated. Single phase spinel structure of all sintered samples were confirmed by X-ray diffraction. The lattice parameter of the samples increased with the increment of In2O3. The effect of In2O3 (melting point 680°C) can be explained by the formation of liquid phase on the grain surface due to reaction of In2O3 with the spinel phase at 1250°C sintering temperature. Saturation magnetization decreased almost linearly and Curie temperature linearly with the increasing addition of In2O3. The decrease in magnetization was possibly due to diamagnetic In3+ ions occupy B-sublattice ( octahedral sites) and replace Fe3+ ions keeping the magnetization of A-sublattice (tetrahedral sites) unchanged. When indium ions occupy B-sites and replace Fe3+ ions, the magnetization of B-sublattice (MB) decreases keeping the magnetization of A-sublattice (MA) constant which in turn weakens A-B exchange interaction (M = MB-MA). The dc resistivity of the samples increased almost linearly with the addition of In2O3. With the increasing addition of In2O3, In3+ ions occupy B-sites which reduces Fe2+ to Fe3+ electron hoping conduction in octahedral sites and contributes to increase in resistivity. DOI: http://dx.doi.org/10.3329/jbas.v36i2.12957 Journal of Bangladesh Academy of Sciences, Vol. 36, No. 2, 153-158, 2012

Acetic acid hydroconversion to ethanol over novel InNi/Al2O3 catalysts

Abstract Consecutive reduction of acetic acid (AA) to ethanol was studied looking for an advantageous catalyst for the processing of VFAs (volatile fatty acids) that can be produced by thermochemical or biological biomass degradation. A fixed bed flow-through reactor was applied with hydrogen stream at 21 bar total pressure in the temperature range of 220–380 °C. AA hydroconversion activity of the parent alumina supported Ni catalyst and the yield of selectively produced alcohol can be increased drastically by In2O3 addition. Efficient catalysts, containing finely dispersed metal particles were obtained by reduction with H2 at 450 °C. In the catalysts modified with In2O3 additive formation of indium metal and/or an intermetallic compound (InNi2) was observed resulting in a different catalytic behavior as for pure nickel particles supported on alumina. Appearance of metallic indium can direct the step by step catalytic reduction to ethanol formation inhibiting decarbonylation, decarboxylation, and additional dehydration. On comparing the commercial, conventionally used catalysts with the bimetallic alumina supported composite (InNi/Al2O3) the novel catalyst proved to be much more active and selective for producing ethanol.

Sunflower oil to green diesel over Raney-type Ni-catalyst

There are intensive efforts for reforming triglycerides to fuels. A non-pyrophoric Raney nickel type catalyst was investigated in the hydroconversion of sunflower oil. The catalyst was also tested in the transformation of octanoic acid as a model compound at 21bar in temperature range of 280–340°C. It was found that alumina supported Ni catalysts (one of them is non-pyrophoric Raney type Ni) selectively catalyze the hydrodecarbonylation and decarboxylation of fatty acids being corrosive intermediates of trigliceride deoxygenation process. Beside the main hydrodecarbonylation reaction Ni-containing catalysts are active in disadvantageous side reactions such as CO methanization and hydrogenolysis of paraffins producing methane byproduct in high concentration with extensive hydrogen consumption. Non-pyrophoric Raney nickel catalyst is more active than Ni/Al2O3 samples especially in the side reactions. To eliminate the active sites responsible for the side reactions the catalyst was modified with tin and lead. It turned out that poisoning either with Sn or Pb did not improve selectivity. Finally addition of In2O3 proved to be effective by directing the transformation to a different deoxygenating reaction pathway resulting in high alcohol yields.

Cu and Cu2In nanoparticles supported on amorphized zeolites for the selective reduction of biomass derived carboxylic acids to alcohols

Octanoic acid (OA) was used as reactant with medium chain length to model the aliphatic carboxylic acids which can be produced by catalytic, thermochemical or biological degradation of biomass. A flow through reactor was applied at 21bar total pressure (in general at 20bar hydrogen and 1bar octanoic acid partial pressures) and 330–380°C. Cu A-, X- and Y-zeolite based catalysts were pretreated in hydrogen flow at 450°C. During reduction/dehydration A- and X-zeolite structures collapsed and aluminosilicate supported copper catalysts were formed, which contain copper nanoparticles in high dispersion. The catalyst samples were modified by In2O3 co-catalyst. Fatty acid conversion activity of amorphized zeolite supported Cu catalysts and the yield of selectively produced alcohol can be increased drastically by In2O3 addition. Appearance of metallic indium can effectively rein in the step by step catalytic reduction at alkanol formation previous to dehydration of alcohols to alkenes and ethers.

Major effect on electrical properties and aging behavior of ZnO–Pr6O11-based varistor ceramics with small In2O3 doping changes

The effect of In2O3 doping on microstructure, electrical properties, and DC-accelerated aging behavior of the ZnO–Pr6O11-based varistor ceramics was systematically investigated. The addition of In2O3 did not significantly alter the sintered density increasing in the small range of 5.60–5.63 g/cm3 and the average grain size decreasing in the small range of 3.4–2.9 μm. However, the incorporation of In2O3 pronouncedly increased the breakdown field from 6,023 to 14,822 V/cm. Furthermore, the incorporation of In2O3 markedly improved the nonlinear coefficient (45 at 0.005 mol% In2O3) and it saliently suppressed the leakage current density (7.3 µA/cm2 at 0.005 mol% In2O3). In2O3 acted like the role of acceptor due to the donor concentration, which decreases in the range of 1.02 × 1017–0.24 × 1017 cm−3 with an increase in the content of In2O3. The ceramics added with 0.005 mol% In2O3 exhibited an excellent stability, with %ΔE1mA = 0% and %Δα = −2.2% under DC-accelerated aging stress state of 0.85 E1mA/115°C/24 h.

Crystallization and Ability of Hydroxyapatite Formation in Some Trivalent Oxides Containing Na-Ca-Silicate Glass-Ceramics

The formation of glass-ceramics based on Na2O- CaO-silicates containing P2O5 with minor additives of some trivalent oxides (e.g. La, In, Ga, and Al), has been investigated. Different crystalline phases including sodium- orthosilicate containing lanthanum, or aluminum were formed together with Na2Ca2Si3O9 ,N aInSi 2O6 ,a nd Na3Ga2Si3O10. The nature and mechanism of HA formed in the glass-ceramics are considered. In general, the presence of trivalent oxides in the glass-ceramics progres- sively reduced the ability to form a calcium phosphate layer on the surfaces of the materials. The addition of In2O3 decreased the crystallization of the hydroxyapatite layer. However, in the presence of either Ga2O3 or Al2O3 only the amorphous calcium phosphate layer was formed after the immersion of the crystallized specimens in the SBF solution.

Microstructure and properties of silver based cadmium free electrical contact materials

The presented work covers part of experimental results of simultaneous study of microstructure, density, hardness and electrical conductivity of sintered electrical contact materials based of Ag- SnO2 with 8, 10 and 12 mass% SnO2. The mentioned characteristics were analyzed in the function of different sintering regimes and after additional mechanical treatment (forging and rolling). The influence of small addition of In2O3 (2.9 mass%) on the increase of dispersion of main oxide SnO2 in Ag matrix is observed and presented also.