Papers by Keyword: Chemical Synthesis

Abstract: Y is used as a dopant for the first time in preparing conductive powders to improve its performance. Y and Sb doped SnO₂ conductive particles are prepared by the complexation-coprecipi-tation method with Sn, Sb₂O₃ and Y₂O₃ as the raw materials. The crystal phase and structure of the prepared conductive particles are characterized by FTIR and XRD techniques respectively. The resistivity of the prepared conductive powders are measured with four-point measurement method. The resistivity of Y and Sb doped SnO₂ conductive particles is 0.22 Ωcm. FTIR spectrum of Y and Sb doped SnO₂ conductive particles shows that the vibration peak are wide peak in 570 cm^-1 ~ 400 cm^-1, and have intense absorption in 4000 cm^-1 ~ 2500 cm^-1, respectively.Y and Sb doped SnO₂ conductive powders have a structure of tetragonal rutile. The complex doping is achieved well by complexation-coprecipitation method and is recognized as replacement doping or caulking doping.

Abstract: Investigation on polycrystalline electroceramics involves the synthesis, the consolidation and the analysis of the electrical behavior, along with careful evaluation of the final microstructure. The synthesis of ceramic powders with controlled characteristics is crucial in the study of materials with optimized properties. Distinct properties may be found in ceramic materials prepared by the several existing methods, due to chemical and phase homogeneities, and to the particle size distribution or medium particle size. In this work, yttrium-doped barium zirconate proton conductor was synthesized by spray pyrolysis, and characterized by several techniques aiming identifying the influence of some parameters of this method of synthesis with particle characteristics. Nanocrystalline powders synthesized at 600-700oC were found to be cubic and single phase. Moreover, depending on the gas flow and furnace temperature, spheroid and porous or cubic and solid particles may be obtained.

Abstract: A facile one-step solvothermal route was developed to synthesize NiO nanoflowers (200-300 nm in diameter) with the introduction of poly(vinyl-pyrrolidone)/stearic acid (PVP/SA) mixture. The product was characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopes (FESEM), Fourier transform infrared spectrometry (FT-IR), Thermal gravimetric analyze (TGA), and Brunauer-Emmett-Teller (BET). The mesoporous NiO nanoflowers showed an excellent adsorption capacity for organic pollutants (Congo red) from waste water (about 56 mg Congo red per g NiO).

Abstract: Pr doped SnO₂ particles as negative electrode material of lithium-ion battery are synthesized by the coprecipitation method with SnCl₄·5H₂O and Pr₂O₃ as raw materials. The structure of the SnO₂ particles and Pr doped SnO₂ particles are investigated respectively by XRD analysis. Doping is achieved well by coprecipitation method and is recognized as replacement doping or caulking doping. Electrochemical properties of the SnO₂ particles and Pr doped SnO₂ particles are tested by charge-discharge and cycle voltammogram experimentation, respectively. The initial specific discharge capacity of Pr doped SnO₂ the negative electrode materials is 676.3mAh/g. After 20 cycles, the capacity retention ratio is 90.5%. The reversible capacity of Pr doped SnO₂ negative electrode material higher than the reversible capacity of SnO₂ negative electrode material. Pr doped SnO₂ particles has good lithiumion intercalation/deintercalation performance.

Abstract: In this work, soft combustion technique was used to study the effect of lanthanum (La) doping on the properties of Bi_0.5Na_0.5TiO₃ (BNT). The amount of La dopant investigated for (Bi_0.5Na_0.5)_(1-1.5x)La_xTiO₃ (BNLT) pellets were x = 0, 0.01, 0.02, 0.05 and 0.10 (0, 1, 2, 5 and 10 mol% La). The addition of La dopant into the BNT structure caused lattice distortion and altered the crystal symmetry of the BNT from hexagonal to tetragonal symmetry for BNLT. BNT and BNLT pellets were sintered at 1100°C for 3 hours and pure perovskite phase BNT was obtained with the addition of La up to 5 mol%. A secondary phase of Bi₂(Ti₂O₇) appeared when the pellet was doped with 10 mol% of La dopant. Increasing of La dopant in the pellet resulted in the increasing of dielectric constant and decreasing of dielectric loss. An optimum property was obtained by 5 mol% BNLT with dielectric constant of 753 and dielectric loss of 0.0377. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Abstract: Cobalt-boron nanoparticles have been synthesized by a chemical reaction between NaBH₄ and CoCl₂.₆H₂O through manipulating pH value of the reaction mixture. The morphology, structure, phase composition, and thermal behavior have been examined via FESEM, TEM, XRD, EDS, and DSC techniques, respectively. It is demonstrated that the morphology and structure of ultimate nanoparticles completely depends on the pH value of reaction mixture. While the neutral pH value favors the smallest nanoparticles with a mean particle size of 50 nm and complete amorphous structure, the acidic condition promotes the growth process and the crystal structure. Furthermore, these nanoparticles transform into cobalt nanocrystallites after heated at 600°C, and retained the discrepancies in the morphology and the structure of the parent cobalt-boron nanoparticles. A detailed characterization of the nanoparticulates, discussions on the synthesis mechanism, and subsequent formation transformation have been provided.

Abstract: Wurtzite type Zn_1-xNi_xO (x=0-0.10) nanoparticles were synthesized by a chemical method via an amorphous polymer precursor. The precursors were derived by a novel process involving a reaction between aqueous solutions of metal ions (Zn²⁺and Ni²⁺) and a freshly prepared solution of poly-vinyl alcohol (PVA)-sucrose under constant stirring at 60-65°C. Structural and magnetic properties of the recrystallized Ni-doped ZnO nanoparticles, obtained after heat treating the corresponding precursors at selected temperatures, were studied in detail. X-ray diffraction (XRD) reveals an increment in the lattice parameters and lattice volume in the doped ZnO samples, confirming the incorporation of Ni²⁺ ions in the ZnO host lattice. All doped samples showed room-temperature ferromagnetism (RTFM) with an increasing saturation magnetization with the increase in Ni doping in the otherwise non-magnetic ZnO. The studies reveals that the observed ferromagnetism is purely intrinsic in nature and it occurs due to the hybridized p-d exchange interaction between magnetic polarons via vacancy mediated defect states inside the crystal lattice.

Abstract: Bi₃NbTiO₉ (BNTO) powders were synthesized by a sol-gel chemical method using niobium oxalates, bismuth nitrate and tetra-n-butyl-titanate as starting materials. In order to determine the influence of the molar ratio of the deionized water to ethylene glycol on the particle morphology and crystallization, different molar ratios, the deionized water/ethylene glycol, were chosen to prepare BNTO powders. Single phase BNTO powders could be obtained at a calcinations temperature of 600°C. Moreover, the possible formation mechanism of BNTO powders was also proposed in this paper. In the baking process, perovskite phase BNTO was formed via a reaction between oxides and bismuth niobium.

Abstract: We present the structural, surface and electrical properties of La_0.7Ca_0.3MnO₃ (LCMO) thin films of varying film thicknesses from 150 nm to 300 nm on single crystal LaAlO₃ (LAO) (h00) oriented substrate, prepared using Chemical Solution Deposition (CSD) technique. X-ray diffraction study shows that all LCMO films are epitaxial and (h00) oriented. With increasing film thickness all the films displayed excellent transport properties such as a low resistivity, very high metal-insulator transition temperature (T_P). All the LCMO films show T_P above 275 K. The sharp transition causes highest TCR ~6.10 %/K and FCR ~50 %/T at around room temperature in CSD grown LCMO thin films, which has not been reported so far. A strong dependence of the electrical resistivity and TCR on film thickness is attributed to the oxygen optimization and variation in lattice parameter caused by residual compressive strain of the LCMO films.

Abstract: Conductive polypyrrole (PPy) was synthesized using a chemical polymerization method in aqueous solution. A series of reactions were carried out with different reaction times of 240 mins and 20 mins. All results were compared to find the highest conductivity and yield. The formation of PPy was verified with Fourier transform infrared (FTIR) analysis which has detected the C-N and pyrrole stretching peaks at 1462 cm^-1 and 1169 cm^-1, respectively, while the x-ray diffraction (XRD) study has shown a broad halo pattern around 25 ̊ related to PPy. The PPy particles sizes of 5-20 microns were measured from the scanning electron microscope (SEM) image. It was found that in the presence of sodium dodecylbenzene sulfonate (DBSNa) as surfactant, the highest conductivity value of 3.18 S/cm and yield of 68% were achieved at 20 mins reaction time and temperature of 0 °C.