ROOM TEMPERATURE PHOTOLUMINESCENCE OF POLYCRYSTALLINE SIC PREPARED FROM CARBON-SATURATED SI MELT

2002 ◽  
Vol 16 (06n07) ◽  
pp. 1047-1051
Author(s):  
JIANPING MA ◽  
ZHIMING CHEN ◽  
GANG LU ◽  
MINGBIN YU ◽  
LIANMAO HANG ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Uv Light ◽  
X Ray Diffraction ◽  
X Ray ◽  
Room Temperature Photoluminescence ◽  
Composition And Structure ◽  
Light Excitation ◽  
Scanning Electron

Intense photoluminescence (PL) has been observed at room temperature from the polycrystalline SiC samples prepared from carbon-saturated Si melt at a temperature ranging from 1500 to 1650°C. Composition and structure of the samples have been confirmed by means of X-ray photoelectron spectroscopy, X-ray diffraction and scanning electron microscopy. PL measurements with 325 nm UV light excitation revealed that the room temperature PL spectrum of the samples consists of 3 luminescent bands, the peak energies of which are 2.38 eV, 2.77 eV and 3.06 eV, respectively. The 2.38 eV band is much stronger than the others. It is suggested that some extrinsic PL mechanisms associated with defect or interface states would be responsible to the intensive PL observed at room temperature.

PREPARATION OF LUMINESCENT PbWO4 MICROCRYSTALS WITH HIERARCHICAL STRUCTURES BY USING MICROWAVE IRRADIATION HEATING METHOD

2010 ◽  
Vol 24 (32) ◽  
pp. 3081-3087 ◽  
Author(s):  
GENGPING WAN ◽  
GUIZHEN WANG
Keyword(s):  
Electron Microscopy ◽  
Microwave Irradiation ◽  
Room Temperature ◽  
Hierarchical Structures ◽  
X Ray Diffraction ◽  
Lead Tungstate ◽  
Heating Method ◽  
X Ray ◽  
Room Temperature Photoluminescence ◽  
Scanning Electron

Lead tungstate ( PbWO 4) microcrystals with hierarchical structures have been successfully synthesized via a facile microwave irradiation heating method. The cetyltrimethylammonium bromine (CTAB) and microwave-heated power were found to play an important role in the morphological control of resulting PbWO 4 mirocrystals. The products were characterized by the techniques of powder X-ray diffraction and field-emission scanning electron microscopy. A growth mechanism of PbWO 4 microstructures was proposed. The luminescence properties of the final products were investigated and the as-prepared PbWO 4 microcrystals displayed a very unique room-temperature photoluminescence compared to the reported results.

Platinum Reduction Study on Pt/C Electro-catalysts for PEMFC

2013 ◽  
Vol 16 (3) ◽  
pp. 141-145
Author(s):  
M.L. Hernandez-Pichardo ◽  
R. Gonzalez-Huerta ◽  
P. del Angel ◽  
E. Palacios-Gonzalez ◽  
M. Tufiño-Velazquez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Uv Light ◽  
Reducing Agents ◽  
Impregnation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthesis Conditions ◽  
Platinum Species ◽  
Scanning Electron

Platinum reduction on Pt/C catalysts was studied on samples prepared by the impregnation method using different Pt precursors and reducing agents such as ethanol, sodium borohydride and ethanol-UV light (photo-assisted reduction), in order to compare the efficiency of the different reducing agents. The influence of the reduction level of the platinum species on the electrochemical behavior of these catalysts has been determined. The catalysts were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and linear and cyclic voltammetry. The results show that the reduction level depends mainly on the platinum precursor. Moreover, it was found that the higher electrochemical activity was found using catalysts reduced with ethanol, whereas by using NaBH4 as the reducing agent, the total reduction of the platinum precursor is very difficult in same synthesis conditions. The analysis of the XPS results shows that samples reduced with ethanol presented the lower PtOx/Pt reduction ratio.

Formation of Titanium Dioxide Containing Calcium Phosphate Crystallites: A New Process

1995 ◽  
Vol 414 ◽  
Author(s):  
Laurent-Dominique Piveteau ◽  
Louis Schlapbach ◽  
Beat Gasser
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Titanium Dioxide ◽  
Chemical Composition ◽  
Photoelectron Spectroscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Composition And Structure ◽  
New Process ◽  
Scanning Electron

AbstractA method for producing titanium dioxide (TiO2) containing hydroxyapatite (HA) crystallite isproposed. Solutions of CaCI2+H3PO4 and TiCL4+HCI combined with KOH are used to precipitatefirst the HA and then the TiO2.The precipitate is then sintered between 900°C and 1000°C for 18 to48 hours. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Energy DispersiveX-ray Analysis (EDX) and scanning electron microscopy (SEM) have been used to determine thecrystallinity, the chemical composition and structure of the samples.

Influence of Silicon Nitride on Properties of Corundum Based Castable

2013 ◽  
Vol 634-638 ◽  
pp. 2358-2361
Author(s):  
Jun Cong Wei ◽  
Li Rong Yang
Keyword(s):  
Electron Microscopy ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Cold Strength ◽  
X Ray ◽  
Refractory Castables ◽  
Shock Resistance ◽  
Scanning Electron

The effects of Si3N4 addition on the room temperature physical properties and thermal shock resistance properties of corundum based refractory castables were investigated using brown corundum, white corundum and alumina micropowder as the starting materials and pure calcium aluminate as a binder. The phase composition, microstructure, mechanical properties of corundum based castables were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that as the increase in Si3N4 addition, the bulk density decreased and apparent porosity increased, the cold strength deduced. However, the residual strength rate increased. That is, the thermal shock resistance was improved. This is because even though the introduction of Si3N4 inhibited the sintering of material and deduced the compactness, microcracks were produced in the materials due to a difference in thermal expansion coefficient. So the thermal shock resistance of corundum based castable was improved.

N-type Ba0.2Co4Sb11.5Te0.5: Optimization of thermoelectric properties by different pressures

2019 ◽  
Vol 33 (03) ◽  
pp. 1950027 ◽  
Author(s):  
Jiaxiang Chen ◽  
Xiaopeng Jia ◽  
Yuewen Zhang ◽  
Haiqiang Liu ◽  
Baomin Liu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Seebeck Coefficient ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Absolute Value ◽  
X Ray ◽  
Coefficient Increase ◽  
Maximum Power Factor ◽  
Scanning Electron

The polycrystalline skutterudite [Formula: see text] were successfully synthesized from 1.5 GPa to 3.5 GPa by the high pressure and high temperature (HPHT) method. Negative Seebeck coefficient confirmed the n-type conductivity of all samples. The phase compositions of samples were investigated by X-ray diffraction (XRD) and the microstructures were observed by scanning electron microscopy (SEM). It was found that the grains appeared smaller and the grain boundaries became more abundant when pressures were higher. We measured the electrical properties from room temperature to 723 K. Both the electrical resistivity and absolute value of Seebeck coefficient increase with the increasing synthetic pressure. At 723 K, the maximum power factor of [Formula: see text] was obtained for the sample synthesized under 3 GPa. The maximum ZT value of 0.61 was reached by [Formula: see text] synthesized under 3 GPa and measured at 723 K.

Synthesis and characterization of homogeneous lead-substituted tin oxide with the (110) face of rutile structure

2000 ◽  
Vol 15 (10) ◽  
pp. 2076-2079
Author(s):  
Chika Nozaki ◽  
Takashi Yamada ◽  
Kenji Tabata ◽  
Eiji Suzuki
Keyword(s):  
Electron Microscopy ◽  
Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
Rutile Structure ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Electron

Synthesis of a rutile-type lead-substituted tin oxide with (110) face was investigated. The characterization was performed by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, infrared spectroscopy, x-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller surface area measurements. The homogeneous rutile-type lead-substituted tin oxide was obtained until 4.1 mol% of tin was substituted with lead. The surface of obtained oxide had a homogeneously lead-substituted (110) face.

scholarly journals Reduced Graphene Oxide–Epoxy Grafted Poly(Styrene-Co-Acrylate) Composites for Corrosion Protection of Mild Steel

Coatings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 666
Author(s):  
Xinchuan Fan ◽  
Yue Hu ◽  
Yijun Zhang ◽  
Jiachen Lu ◽  
Xiaofeng Chen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Photoelectron Spectroscopy ◽  
X Ray Diffraction ◽  
Corrosion Properties ◽  
X Ray ◽  
Transmission Electron ◽  
Reduced Graphene ◽  
Scanning Electron

Reduced graphene oxide–epoxy grafted poly(styrene-co-acrylate) composites (GESA) were prepared by anchoring different amount of epoxy modified poly(styrene-co-acrylate) (EPSA) onto reduced graphene oxide (rGO) sheets through π–π electrostatic attraction. The GESA composites were characterized by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The anti-corrosion properties of rGO/EPSA composites were evaluated by electro-chemical impedance spectroscopy (EIS) in hydroxyl-polyacrylate coating, and the results revealed that the corrosion rate was decreased from 3.509 × 10−1 to 1.394 × 10−6 mm/a.

Oxidation Behavior of Steel and Pure Copper at 500-700°C

2013 ◽  
Vol 421 ◽  
pp. 401-405
Author(s):  
Sang An Ha ◽  
Jei Pil Wang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Oxidation Behavior ◽  
Pure Copper ◽  
Thermal Gravimetric ◽  
X Ray Diffraction ◽  
X Ray ◽  
Composition And Structure ◽  
Gravimetric Apparatus ◽  
Scanning Electron

The oxidation behavior of steel and pure copper has been investigated in the temperature range of 500-700°C at various oxygen pressures. The rate of oxidation was measured using thermal gravimetric apparatus (TGA). The morphology, composition and structure of the oxide scale were determined by scanning electron microscopy (SEM) and X-ray diffraction (XRD).

scholarly journals Properties of Nanostructure Bismuth Telluride Thin Films Using Thermal Evaporation

2017 ◽  
Vol 2017 ◽  
pp. 1-4 ◽  
Author(s):  
Swati Arora ◽  
Vivek Jaimini ◽  
Subodh Srivastava ◽  
Y. K. Vijay
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Bismuth Telluride ◽  
Room Temperature ◽  
Thermal Evaporation ◽  
Silicon Substrates ◽  
X Ray Diffraction ◽  
Thermal Evaporation Method ◽  
X Ray ◽  
Scanning Electron

Bismuth telluride has high thermoelectric performance at room temperature; in present work, various nanostructure thin films of bismuth telluride were fabricated on silicon substrates at room temperature using thermal evaporation method. Tellurium (Te) and bismuth (Bi) were deposited on silicon substrate in different ratio of thickness. These films were annealed at 50°C and 100°C. After heat treatment, the thin films attained the semiconductor nature. Samples were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to show granular growth.

scholarly journals Preparation of Cerium Dioxide Layers on Titanium by Electrodeposition with Organic Solution

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Vaijayanti Namdeo Nande ◽  
Diana Kostyukova ◽  
Jeonghee Choi ◽  
Yong Hee Chung
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Cerium Dioxide ◽  
Average Crystallite Size ◽  
X Ray Diffraction ◽  
Organic Solution ◽  
X Ray ◽  
Titanium Foils ◽  
Scanning Electron

Layers of cerium dioxide nanoparticles were prepared on titanium by electrodeposition with organic solution. Three concentrations of cerium ions were used at 31.6 V. The organic solution was isobutanol and titanium foils were used as anodes and cathodes. Currents were monitored during the electrodeposition. Deposition times ranged from 0.5 to 8 h. Deposited Deposited layers were calcined at 700 K for 30 min. The morphology and composition of the deposited layers were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). As-prepared and calcined deposition layers were assayed to be cerium dioxide. The average crystallite size increased from 4 to 7 nm through calcination at 700 K. Sizes of calcined cerium oxide agglomerates were ranging from 73 to 146 nm for 30 min deposition and 209 to 262 nm for 8 h deposition. The electrodeposition efficiencies of 0.5 h deposition at three concentrations were measured to be highest.

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