Showing papers in "Bulletin of Materials Science in 2007"
TL;DR: Instrumental characterizations of the clay were performed by different techniques such as XRF, XRD and FTIR as discussed by the authors, which showed the presence of quartz, alumina, haematite and different mineral matters.
Abstract: Instrumental characterizations of the clay were performed by different techniques such as XRF, XRD and FTIR. XRF shows the chemical compositions of the clay where Al-oxide and silica oxide are present in major quantity whereas XRD confirms the presence of these minerals in clay. FTIR studies show the presence of quartz, alumina, haematite and different mineral matters.
394 citations
TL;DR: The physics of interactions between CNT and its surrounding matrix material in such nano-composites has yet to be elucidated and methods for determining the parameters controlling interfacial characteristics such as interfacial shear stress, is still challenging.
Abstract: Because of their high mechanical strength, carbon nanotubes (CNTs) are being considered as nanoscale fibres to enhance the performance of polymer composite materials. Novel CNT-based composites have been fabricated using different methods, expecting that the resulting composites would possess enhanced or completely new set of physical properties due to the addition of CNTs. However, the physics of interactions between CNT and its surrounding matrix material in such nano-composites has yet to be elucidated and methods for determining the parameters controlling interfacial characteristics such as interfacial shear stress, is still challenging. An improvement of the physical properties of polymer nanocomposites, based on carbon nanotubes (CNTs), is addicted to a good dispersion and strong interactions between the matrix and the filler.
248 citations
TL;DR: The physical properties of nanowires are influenced by the morphology of the nanowire, diameter dependent band gap, carrier density of states etc. as mentioned in this paper, which is different from that of their parent counterpart.
Abstract: Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap, carrier density of states etc. Nanowires hold lot of promises for different applications. Basic electronic devices like junction diodes, transistors, FETs and logic gates can be fabricated by using semiconductor and superlattice nanowires. Thermoelectric cooling system can be fabricated by using metallic nanowires. Semiconductor nanowire junctions can be used for different opto-electronic applications. Moreover, periodic arrays of magnetic nanowires hold high potential for recording media application. Nanowires are also potential candidates for sensor and bio-medical applications.
174 citations
TL;DR: In this article, the authors studied the thermogravimetric (TG) measurements of dolomite sample and found that activation energies vary between 97 and 147 kJ mol−1.
Abstract: Thermal decomposition behaviour of dolomite sample has been studied by thermogravimetric (TG) measurements. Differential thermal analysis (DTA) curve of dolomite shows two peaks at 777·8°C and 834°C. The two endothermic peaks observed in dolomite are essentially due to decarbonation of dolomite and calcite, respectively. The TG data of the decomposition steps have also been analysed using various differential, difference-differential and integral methods, viz. Freeman-Carroll, Horowitz-Metzger, Coats-Redfern methods. Values of activation entropy, Arrhenius factor, and order of reaction have been approximated and compared. Measured activation energies vary between 97 and 147 kJ mol−1. The large fluctuation in activation energy is attributed to the presence of impurities such as SiO2, Al2O3, Fe2O3, Cl− etc in the samples. FTIR and XRD analyses confirm the decomposition reaction. SEM observation of the heat-treated samples at 950°C shows cluster of grains, indicating the structural transformation.
166 citations
TL;DR: In this article, the photocatalytic degradation of indigo carmine dye was studied using hydrothermally prepared TiO2 impregnated activated carbon (TiO2: AC).
Abstract: The photocatalytic degradation of indigo carmine dye was studied using hydrothermally prepared TiO2 impregnated activated carbon (TiO2: AC). A comparison between the degradation of the indigo carmine dye using commercial TiO2 and TiO2: AC revealed the efficiency of the title compound. The degradation reaction was optimized with respect to the dye concentration and catalyst amount. The reduction in the chemical oxygen demand (COD) revealed the mineralization of dye along with colour removal. The active compound like TiO2 was impregnated onto the activated carbon surface under mild hydrothermal conditions (<250°C, P ∼ 40 bars). The impregnated activated carbon samples were characterized using powder X-ray diffraction (XRD) and scanning electron microscope (SEM).
147 citations
TL;DR: In this article, the authors evaluated the properties of MOC concrete and found that it has high compressive strength associated with high flexural strength and the ratio of compressive to flexuric strength varies between 6 and 8, while the elastic moduli of the compositions studied are found to be 23-85 GPa and the abrasion losses between 0·11 and 0·20%.
Abstract: The scope of magnesium oxychloride (MOC) cement in concrete works has been evaluated. MOC cement concrete compositions of varying strengths having good placing and finishing characteristics were prepared and investigated for their compressive and flexural strengths, E-values, abrasion resistance etc. The durability of MOC concrete compositions against extreme environmental conditions viz. heating-cooling, freezing-thawing, wetting-drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ratio of compressive to flexural strength varies between 6 and 8. The elastic moduli of the compositions studied are found to be 23–85 GPa and the abrasion losses between 0·11 and 0·20%. While alternate heating-cooling cycles have no adverse effect on MOC concrete, it can be made durable against freezing-thawing and the excessive exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution of the same concentration.
96 citations
TL;DR: In this paper, the preparation of poly (methyl methacrylate) (PMMA), PMMA/SiO2, and PMMA-TiO2 nanocomposites are reported.
Abstract: Hybrid materials, which consist of organic-inorganic materials, are of profound interest owing to their unexpected synergistically derived properties. These hybrid materials replaced the pristine polymers due to their higher strength and stiffness in the recent years. In the present work, studies concerning the preparation of poly (methyl methacrylate) (PMMA), PMMA/SiO2, and PMMA/TiO2 nanocomposites are reported. These nanocomposite polymers were synthesized by means of free radical polymerization of methyl methacrylate using benzoyl peroxide as an initiator in a water medium. Further ‘sol-gel’ transformation based hydrolysis and condensation of Ti and Si alkoxides were used to prepare the inorganic phase during the polymerization process of MMA.
91 citations
TL;DR: In this article, the size of the copper nanoparticles as well as its ex- posed surface area is investigated for the condensation of iodobenzene to biphenyl in the presence of copper powder as catalyst.
Abstract: The condensation of iodobenzene to biphenyl is an industrially important reaction due to its sig- nificant role in organic synthesis as drug intermediates. The reaction takes place in the presence of copper powder as catalyst. We have shown in this paper that the size of the copper nanoparticles as well as its ex- posed surface area is responsible for the yield of chemical reaction. The uncapped copper powder showed a 43% conversion of iodobenzene to biphenyl in 5 h under our experimental conditions. Same amount of copper nanoparticles (size, ~ 66 nm diameter) prepared by citrate capping showed 88% conversion of iodobenzene to biphenyl, which increased to about 95% when 8 nm diameter capped copper nanoparticles are used. Surpris- ingly, 5 nm size copper nanoparticles showed no change in the yield of about 95%.
86 citations
TL;DR: In this article, the authors studied the thermal transition temperature as a function of copper concentration and showed a strong branching and steric effect in copper-doped PVA complexes, which indicated the presence of O-H, C-C, C=C and C-O groups.
Abstract: 5 mol% PVA: x mol% Cu2+ polymer films were prepared by casting process. Thermal transitions and thermal degradation of samples with respect to copper concentration were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Increase in glass transition temperature as a function of copper concentration shows a strong branching and steric effects in copper doped PVA complexes. Thermal degradation of films to an extent of 4–5% was found with an increase in copper content. FTIR spectrum of PVA doped Cu2+ ions indicate the presence of O-H, C-H, C=C and C-O groups.
83 citations
TL;DR: In this paper, amino acid L-arginine was doped in KDP and the results were discussed in terms of second harmonic generation (SHG) efficiency and thermal stability.
Abstract: Potassium dihydrogen phosphate (KDP) is a well known nonlinear optical (NLO) material with different applications. Since most of the amino acids exhibit NLO property, it is of interest to dope them in KDP. In the present study, amino acid L-arginine was doped in KDP. The doping of L-arginine was confirmed by FT-IR and paper chromatography. Thermogravimetry suggested that as the amount of doping increases the thermal stability decreases as well as the value of thermodynamic and kinetic parameters decreases. The second harmonic generation (SHG) efficiency of L-arginine doped KDP crystals was found to be increasing with doping concentration of L-arginine. The results are discussed here.
79 citations
TL;DR: In this paper, the structural and optical properties of CdSe films have been studied thoroughly in the present work, and the hexagonal structure with a preferred orientation along the (0 0 2) direction of films has been confirmed by the X-ray diffraction analysis.
Abstract: Thin films of cadmium selenide (CdSe) as a semiconductor is well suited for opto-electronic applications such as photo detection or solar energy conversion, due to its optical and electrical properties, as well as its good chemical and mechanical stability. In order to explore the possibility of using this in optoelectronics, a preliminary and thorough study of optical and structural properties of the host material is an important step. Based on the above view, the structural and optical properties of CdSe films have been studied thoroughly in the present work. The host material, CdSe film, has been prepared by the physical vapour deposition method of electron beam evaporation (PVD: EBE) technique under a pressure of 5 × 10−5 mbar. The structural properties have been studied by XRD technique. The hexagonal structure with a preferred orientation along the (0 0 2) direction of films has been confirmed by the X-ray diffraction analysis. The films have been analysed for optical band gap and absorbed a direct intrinsic band gap of 1·92 eV.
TL;DR: In this paper, two coal samples collected from Makum coal field, Assam, India were studied by X-ray diffractogram and FT-IR techniques, and they were found to be lignite in nature.
Abstract: Two coal samples collected from Makum coal field, Assam, India were studied by XRD and FT-IR techniques. The X-ray diffractogram shows the existence of some crystalline carbons in Assam coals as proven by the appearance of peaks. The radial distribution functional (RDF) method was applied for the determination of structural aspects of the coals. The study indicates that the coals are lignite in type and there is no evidence of graphite-like structures. The maximum in the G(r) plots of function of radial distribution of atoms (FRDA) relates to different distances between carbon atoms of aliphatic chains. The first significant maximum relates to the C-C bond (type C-CH=CH-C), the second maximum relates to the distance between carbon atoms of aliphatic chains that are located across one carbon atom. The curve intensity profiles obtained from FRDA show quite regular molecular packets for this coal. The coals were found to be lignite in nature. FT-IR study shows the presence of aliphatic carbon, C=O and C-O stretching associated with -OH and -NH stretching vibrations. Kaolinite and quartz were also found to be major minerals in Assam coals by FTIR spectroscopy. The difference in intensities of carbonyl groups of the coal samples is likely to relate with the rank.
TL;DR: In this paper, the optical properties of cerium oxide (CeO2) thin films are studied in the wavelength range of 200-850 nm, and the optical band gap of the film is determined and is found to decrease with the increase of film thickness.
Abstract: Cerium oxide (CeO2) thin films have been prepared by electron beam evaporation technique onto glass substrate at a pressure of about 6 × 10−6 Torr. The thickness of CeO2 films ranges from 140–180 nm. The optical properties of cerium oxide films are studied in the wavelength range of 200–850 nm. The film is highly transparent in the visible region. It is also observed that the film has low reflectance in the ultra-violet region. The optical band gap of the film is determined and is found to decrease with the increase of film thickness. The values of absorption coefficient, extinction coefficient, refractive index, dielectric constant, phase angle and loss angle have been calculated from the optical measurements. The X-ray diffraction of the film showed that the film is crystalline in nature. The crystallite size of CeO2 films have been evaluated and found to be small. The experimental d-values of the film agreed closely with the standard values.
TL;DR: In this paper, colloidal zinc metallic nanoparticles are synthesized using pulsed laser ablation of metal plate in an aqueous solution of suitable surfactant to prevent aggregation.
Abstract: Colloidal zinc metallic nanoparticles are synthesized using pulsed laser ablation of metal plate in an aqueous solution of suitable surfactant to prevent aggregation. UV-visible absorption, TEM, small angle X-ray diffraction and wide-angle X-ray diffraction are used for the characterization of colloidal zinc metallic nanoparticles. Colloidal nanoparticles are found highly stable for a long time.
TL;DR: In this paper, the characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated, and the effects of microstructure and additive concentration on the gas response, selectivity, response time and recovery time of the sensor in the presence of ethanol vapours were studied and discussed.
Abstract: The characterization and ethanol gas sensing properties of pure and doped ZnO thick films were investigated. Thick films of pure zinc oxide were prepared by the screen printing technique. Pure zinc oxide was almost insensitive to ethanol. Thick films of Al2O3 (1 wt%) doped ZnO were observed to be highly sensitive to ethanol vapours at 300°C. Aluminium oxide grains dispersed around ZnO grains would result into the barrier height among the grains. Upon exposure of ethanol vapours, the barrier height would decrease greatly leading to drastic increase in conductance. It is reported that the surface misfits, calcination temperature and operating temperature can affect the microstructure and gas sensing performance of the sensor. The efforts are, therefore, made to create surface misfits by doping Al2O3 into zinc oxide and to study the sensing performance. The quick response and fast recovery are the main features of this sensor. The effects of microstructure and additive concentration on the gas response, selectivity, response time and recovery time of the sensor in the presence of ethanol vapours were studied and discussed.
TL;DR: In this paper, the effect of film thickness on the optical and structural properties of thin ZnS thin films was studied using chemical bath deposition using thiourea and zinc acetate as S2− and Zn2+ source.
Abstract: ZnS thin films of different thicknesses were prepared by chemical bath deposition using thiourea and zinc acetate as S2− and Zn2+ source. The effect of film thickness on the optical and structural properties was studied. The optical absorption studies in the wavelength range 250–750 nm show that band gap energy of ZnS increases from 3·68–4·10 eV as thickness varied from 332–76 nm. The structural estimation shows variation in grain size from 6·9–17·8 nm with thickness. The thermoemf measurement indicates that films prepared by this method are of n-type.
TL;DR: In this paper, a broadening of X-ray diffraction lines was used to determine the size of the nanocrystalline thin films of CdS and the band gap was determined from the UV spectrograph.
Abstract: Nanocrystalline thin films of CdS are deposited on glass substrates by chemical bath deposition technique using polyvinyl alcohol (PVA) matrix solution. Crystallite sizes of the nanocrystalline films are determined from broadening of X-ray diffraction lines and are found to vary from 5·4–10·2 nm. The band gap of the nanocrystalline material is determined from the UV spectrograph. The absorption edge is shifted towards the lower wave length side (i.e. blue shift) and are found to be within the range from 2·48–2·8 eV as grain sizes decrease from 10·2–5·4 nm. This is also supported by the spectral response curves. An increase of molarity decreases the grain size which in turn increases the band gap.
TL;DR: In this article, the suitability of tricalcium phosphate (TCP) for thermoluminescence dosimetry (TLD) applications is investigated, owing to their equivalence to bone mineral.
Abstract: The suitability of calcium phosphate crystals for thermoluminescence dosimetry (TLD) applications is investigated, owing to their equivalence to bone mineral. The α and β phases of tricalcium phosphate (TCP) were synthesized through wet precipitation and high temperature solid state routes and doped with Dy and Eu. The photoluminescence and thermoluminescence studies of the phosphors have been carried out. The TL properties were found to be highly dependent on the method of preparation of the material. Eu doping gave good PL emission, whereas Dy doping was more efficient in TL emission. β-TCP was found to be less TL sensitive than α-TCP, yet it was identified as a better phosphor material owing to its better fading characteristics. The dependence of TL of β-TCP: Dy on the energy and dose of radiation, and on the doping concentration were studied. The TL intensity was observed to fade exponentially during a storage period of 20 days, but it stabilized at 70% of the initial value after 30 days. The optimum doping concentration was found to be 0.5 mol%.
TL;DR: For the first time, sputtered zinc oxide (ZnO) thin films have been used as a CO2 gas sensor as mentioned in this paper, in the deposition temperature range from 130-153°C at a chamber pressure of 8·5 mbar for 18 h Argon and oxygen gases were used as sputtering and reactive gases, respectively ZnO phase could be crystallized using a pure metal target of zinc.
Abstract: For the first time, sputtered zinc oxide (ZnO) thin films have been used as a CO2 gas sensor Zinc oxide thin films have been synthesized using reactive dc sputtering method for gas sensor applications, in the deposition temperature range from 130–153°C at a chamber pressure of 8·5 mbar for 18 h Argon and oxygen gases were used as sputtering and reactive gases, respectively ZnO phase could be crystallized using a pure metal target of zinc The structure of the films determined by means of X-ray diffraction method indicates that the zinc oxide single phase can be fabricated in this substrate temperature range The sensitivity of the film synthesized at substrate temperature of 130°C is 2·17 in the presence of CO2 gas at a measuring temperature of 100°C
TL;DR: In this article, the optimal pyrolysis temperature of B4C synthesis is investigated and the electron micrographs and particle size analyser reveal the generation of fine B4Cs particles.
Abstract: Boron carbide (B4C) powder has been produced by carbothermal reduction of boric acid-citric acid gel. Initially a gel of boric acid-citric acid is prepared in an oven at 100°C. This gel is pyrolyzed in a high temperature furnace over a temperature range of 1000–1800 °C. The reaction initiation temperature range for B4C formation is determined by thermal analysis. The optimal pyrolysis temperature of B4C synthesis is investigated. During pyrolysis, the evaporation of boron-rich phases results in presence of free carbon in B4C powder. The electron micrographs and particle size analyser reveal the generation of fine B4C particles.
TL;DR: In this paper, the citrate sol-gel method was used to synthesize molybdenum oxide nanoparticles and charac- terized using scanning electron microscopy and X-ray diffraction techniques.
Abstract: Nanoparticles of molybdenum oxide were synthesized using the citrate sol-gel method and charac- terized using scanning electron microscopy and X-ray diffraction techniques. The sensitivity of the material to the presence of various gases was analysed and the particles showed higher sensitivity towards NO2 gas.
TL;DR: In this article, the most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L−1 sodium tungstate, potassium iodate, and 1 mol l−1 orthophosphoric acid to a q = 0.1 mol L − 1 zirconium(IV) oxychloride.
Abstract: Zirconium(IV) tungstoiodophosphate has been synthesized under a variety of conditions. The most chemically and thermally stable sample is prepared by adding a mixture of aqueous solutions of 0·5 mol L−1 sodium tungstate, potassium iodate and 1 mol L−1 orthophosphoric acid to aqueous solution of 0·1 mol L−1 zirconium(IV) oxychloride. Its ion exchange capacity for Na+ and K+ was found to be 2·20 and 2·35 meq g−1 dry exchanger, respectively. The material has been characterized on the basis of chemical composition, pH titration, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. The effect on the exchange capacity of drying the exchanger at different temperatures has been studied. The analytical importance of the material has been established by quantitative separation of Pb2+ from other metal ions.
TL;DR: In this paper, X-ray diffraction, optical absorption and photoelectrochemical (PEC) techniques were used to characterize CdSe thin films on different substrates such as stainless steel, titanium and fluorine tinoxide (FTO) coated glass using non-aqueous bath.
Abstract: Thin films of CdSe were deposited by potentiostatic mode on different substrates such as stainless steel, titanium and fluorine tin-oxide (FTO) coated glass using non-aqueous bath. The preparative parameters were optimized to get good quality CdSe thin films. These films were characterized by X-ray diffraction (XRD), optical absorption and photoelectrochemical (PEC) techniques. XRD study revealed that the films were polycrystalline in nature with hexagonal phase. Optical absorption study showed that CdSe films were of direct band gap type semiconductor with a band gap energy of 1·8 eV. PEC study revealed that CdSe film deposited on FTO coated glass exhibited maximum values of fill factor (FF) and efficiency (η) as compared to the films deposited on stainless steel and titanium substrate.
TL;DR: In this article, the influence of veratraldehyde (VRTD) and p-amino benzoic acid (PABA) on Zn-Ni alloy electrodeposited onto mild steel was studied in acidic sulphate solutions.
Abstract: The influence of a condensation product (CP) of veratraldehyde (VRTD) and p-amino benzoic acid (PABA) on Zn-Ni alloy electrodeposited onto mild steel was studied in acidic sulphate solutions. Ethylenediaminetetraaceticacid (EDTA) and cetyltrimethylammoniumbromide (CTAB) were used as complexing and wetting agents, respectively. The effect of bath constituents, pH, current density and temperature on nature of deposit were studied through Hull cell experiments. The bath constituents and operating parameters were optimized. Deposit properties and corrosion resistance were discussed. Throwing power, current efficiency and polarization studies were carried out. SEM photomicrographs of the deposit obtained from optimum bath revealed fine-grained deposit of the alloy in the presence of condensation product and hence modified the morphology of zinc-nickel alloy deposit. IR spectrum of the scrapped deposit showed inclusion of addition agent.
TL;DR: In this paper, the X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM) were used to characterize the ethanol vapour sensing properties of WO3 thick films.
Abstract: This paper presents ethanol vapour sensing properties of WO3 thick films. In this work, the WO3 thick films were prepared by standard screen-printing method. These films were characterized by X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM). The ethanol vapour sensing properties of these thick films were investigated at different operating temperatures and ethanol vapour concentrations. The WO3 thick films exhibit excellent ethanol vapour sensing properties with a maximum sensitivity of ∼1424.6% at 400°C in air atmosphere with fast response and recovery time.
TL;DR: In this article, the Schottky conduction mechanism is found to dominate the current conduction at a high temperature and the reliability and the leakage current characteristics of ZnO2 films have been studied both at room and high temperatures.
Abstract: Photoluminescence (PL) properties of undoped ZnO thin films grown by rf magnetron sputtering on silicon substrates have been investigated. ZnO/Si substrates are characterized by Rutherford backscattering (RBS), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). ZrO2 thin films have been deposited on ZnO using microwave plasma enhanced chemical vapour deposition at a low temperature (150°C). Using metal insulator semiconductor (MIS) capacitor structures, the reliability and the leakage current characteristics of ZrO2 films have been studied both at room and high temperatures. Schottky conduction mechanism is found to dominate the current conduction at a high temperature. Good electrical and reliability properties suggest the suitability of deposited ZrO2 thin films as an alternative as gate dielectric on ZnO/n-Si heterostructure for future device applications.
TL;DR: In this article, the electrical conductivity of polyaniline doped polyvinylchloride (PVC) and poly(methyl methacrylate) (PMMA) thin films has been measured by studying the I-V characteristics at various temperatures in the range 323-363 K. The analysis of these results suggests that Schottky and Richardson mechanisms are primarily responsible for the observed conduction.
Abstract: The electrical conductivity of polyaniline doped polyvinylchloride (PVC) and poly(methyl methacrylate) (PMMA) thin films has been measured by studying the I–V characteristics at various temperatures in the range 323–363 K. The results are presented in the form of I–V characteristics and analysis has been made by interpretation of Poole-Frenkel, Fowler-Nordheim, Schottky ln(J) vs T plots, Richardson and Arrhenius plots. The analysis of these results suggests that Schottky and Richardson mechanisms are primarily responsible for the observed conduction.
TL;DR: In this paper, the electrical conductivity of naphthalene doped polystyrene (PS) films (≈61·58 μm thick) was studied as a function of dopant concentration and temperature.
Abstract: The electrical conductivity of naphthalene doped polystyrene (PS) films (≈61·58 μm thick) was studied as a function of dopant concentration and temperature. The formation of charge transfer (CT) complexes and strong concentration dependence of carrier mobility point out that the current carriers are transported through doped polymer system via hopping among sites associated with the dopant molecules. The activation energy, Ea, was calculated from the graph of log σ vs 103/T plot within low and high temperature regions.
TL;DR: In this paper, the a.c. conductivity and dielectric properties of polyaniline/cobaltous oxide composites are studied by sandwiching the pellets of these composites between the silver electrodes.
Abstract: Conducting polyaniline/cobaltous oxide composites have been synthesized using in situ deposition technique by placing fine graded/cobaltous oxide in polymerization mixture of aniline. The a.c. conductivity and dielectric properties are studied by sandwiching the pellets of these composites between the silver electrodes. It is observed that the values of conductivities increase up to 30 wt% of cobaltous oxide in polyaniline and decrease thereafter. Initial increment in conductivity is due to extended chain length of polyaniline where polarons possess sufficient energy to hop between favourable sites. Beyond 30 wt% of cobaltous oxide in polyaniline, blocking of charge carriers takes place reducing the conductivity values. It can be noted that the value of dielectric constant increases up to 10 wt% of cobaltous oxide. Thereafter, it decreases up to 30 wt% of cobaltous oxide and again increases up to 40 wt% of cobaltous oxide and decreases thereafter. The observed behaviour is attributed to the variation of a.c. conductivity. And it is observed that the dielectric loss increases up to 10 wt% of cobaltous oxide in polyaniline, decreases to a lower value of 20 wt% of cobaltous oxide and increases to 35 wt% and thereafter decreases. These values go in accordance with the values of dielectric constant. The results obtained for these composites are of greater scientific and technological importance.
TL;DR: Barium strontium titanate ((Ba0·87Sr0·13)TiO3-BST) ceramic powder was prepared by mechanochemical process and the effect of film thickness on gas response was also studied as discussed by the authors.
Abstract: Barium strontium titanate ((Ba0·87Sr0·13)TiO3-BST) ceramic powder was prepared by mechanochemical process. The thick films of different thicknesses of BST were prepared by screen-printing technique and gas-sensing performance of these films was tested for various gases. The films showed highest response and selectivity to ammonia gas. The effect of film thickness on gas response was also studied. As prepared BST thick films were surface modified by dipping them into an aqueous solution of titanium chloride (TiCl3) for different intervals of time. Surface modification shifted response to H2S gas suppressing the responses to ammonia and other gases. The surface modification, using dipping process, altered the adsorbate-adsorbent interactions, which gave the unusual sensitivity and selectivity effect. Sensitivity, selectivity, thermal stability, response and recovery time of the sensor were measured and presented.