Synthesis and Characterization of α-Phase Silicon Nitride Powders by Direct Nitridation

2013 ◽  
Vol 631-632 ◽  
pp. 434-436
Author(s):  
Jiu Ming Liu ◽  
Jian Lei Wang ◽  
Shu Xia Ren
Keyword(s):  
Silicon Nitride ◽  
Raw Materials ◽  
X Ray Diffraction ◽  
Nitrogen Gas ◽  
Pure Nitrogen ◽  
X Ray ◽  
Α Phase ◽  
Heat Treated ◽  
Direct Nitridation

Using silicon powders as raw materials, adding nano-silicon nitride as a diluent and NH4Cl3 and FeCl3 as catalysts, α-phase silicon nitride powders were prepared by direct nitridation method. The silicon powders were first milled with 20% α-Si3N4 and 4% NH4Cl3 for 30 minutes. Then the mixture was heat-treated at 1300°C for 1 hour in the pure nitrogen gas. The phases and their content of the as-prepared product were detected by X-ray diffraction (XRD) and the microstructure was studied by scanning electron microscope (SEM). The results showed that the product mainly consisted ofα-Si3N4 with a mass fraction over 92% and were submicron-sized particles．

Preparation of β-Phase Silicon Nitride Powders

2013 ◽  
Vol 650 ◽  
pp. 58-60
Author(s):  
Jian Lei Wang ◽  
Jiu Ming Liu ◽  
Shu Xia Ren
Keyword(s):  
Electron Microscope ◽  
Silicon Nitride ◽  
Phase Content ◽  
X Ray Diffraction ◽  
Nitrogen Gas ◽  
Pure Nitrogen ◽  
X Ray ◽  
Β Phase ◽  
Heat Treated ◽  
Scanning Electron

Silicon nitride powders high in β-phase content have been prepared by direct nitriding method. The silicon powders were first milled with 30%α-Si3N4 and 4% FeCl3 for 30 minutes. Then the mixture was heat-treated at 1400°C for 2 hours in the pure nitrogen gas. The phase and the microstructure of the as-prepared product were detected by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed that the product mainly consisted of β-Si3N4, whose content is more than 92%, and a little amount of α-Si3N4, and no silicon were detected within the detection limit.

Mechanosynthesis of Silicon Nitride Nanowires

2010 ◽  
Vol 148-149 ◽  
pp. 1347-1350 ◽  
Author(s):  
Shu Xia Ren ◽  
Feng Qiu Ji ◽  
Xiao Lan He
Keyword(s):  
Silicon Nitride ◽  
X Ray Diffraction ◽  
Nitrogen Gas ◽  
Pure Nitrogen ◽  
Ammonia Gas ◽  
Transmission Electron ◽  
Heat Treated ◽  
Nanowires Growth ◽  
Vs Mechanism ◽  
Si3n4 Nanowires

Silicon nitride nanowires have been synthesized by mechanosynthesis method. The silicon powders were first milled for 160 hours under the presence of ammonia gas with 300kPa. And then they were heat-treated at 1250 for 2 hours in the pure nitrogen gas. The phase and the microstructure of the as-prepared product were detected by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The results showed that the product consisted of α-Si3N4 nanowires. The nanowires had the length of tens of millimeters and the diameters of 50～100nm. The vapor-solid (VS) mechanism was employed to interpret the nanowires growth.

Microstructure Characterization of the Reaction Interface between CBN Grain and Titanium-Deposited Film

2012 ◽  
Vol 538-541 ◽  
pp. 166-171
Author(s):  
Wen Feng Ding ◽  
Yang Min Liang ◽  
Jian He ◽  
Li Tang ◽  
Jie Yu ◽  
...  
Keyword(s):  
Heating Temperature ◽  
Cubic Boron Nitride ◽  
High Vacuum ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Energy Dispersion Spectrometer ◽  
Heat Treated ◽  
Deposited Film

Cubic boron nitride (CBN) abrasive grains with surface titanium-deposited film were heat-treated during 550-950°C for 60 min under high vacuum circumstance. Detailed interfacial compounds analysis by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersion spectrometer (EDS), differential thermal analysis (DTA) indicates that the interfacial reactions are much dependent on the heating temperature to some extents, and the reaction products, TiN, TiB2 and TiB chiefly form the network structure. In particular, at 950°C the transition layers with excellent performance, CBN/TiB2/TiB/(TiB+TiN)/TiN/CBN, is realized.

Characterization of Ni Nanopowders Produced by Electrical Explosion of Wire Technique

2006 ◽  
Vol 510-511 ◽  
pp. 710-713
Author(s):  
Hwan Tae Kim ◽  
Won Sik Seo ◽  
Dae Hwan Kwon ◽  
Pyuck Pa Choi ◽  
Ji Soon Kim ◽  
...  
Keyword(s):  
Particle Size ◽  
Electrical Explosion ◽  
Nickel Wire ◽  
X Ray Diffraction ◽  
Nitrogen Gas ◽  
Argon Gas ◽  
X Ray ◽  
Nickel Powders ◽  
The Mean

Nanosize nickel powders were successfully produced by electrical explosion of wire (EEW). In EEW, the nickel wire was discharged in a chamber filled with nitrogen or argon gas, and the produced powders were subsequently stabilized by air-passivation at room temperature for 2 h. X-ray diffraction only showed the nickel phase of FCC crystal structure, whereas TEM and XPS analyses showed the formation of a very thin oxide layer of NiO on the surface of particles. Particles were spherical in shape, and the mean particle size calculated by specific surface area was about 100 nm. The particle size decreased with increasing charging voltage and with increasing ambient gas pressure. Argon gas was more effective in producing finer particles than nitrogen gas.

Carbothermal Reduction and Nitridation of Quartz Mineral for the Production of Alpha Silicon Nitride Powders

2007 ◽  
Vol 554 ◽  
pp. 163-168 ◽  
Author(s):  
Adem Demir ◽  
Zafer Tatli ◽  
F. Caliskan ◽  
A.O. Kurt
Keyword(s):  
Silicon Nitride ◽  
Carbothermal Reduction ◽  
Raw Materials ◽  
Nitrogen Flow ◽  
Alumina Tube ◽  
Quartz Powder ◽  
Nitrogen Gas ◽  
Sem Images ◽  
Xrd Pattern ◽  
Α Phase

In this study, α-Si3N4 powder was produced by carbothermal reduction and nitridation (CRN) of quartz from Can-Canakkale. Carbon with a specific surface area of 110 m2g−1 and quartz powders were mixed then the powder mix was placed in an alumina tube furnace and reacted in between 1300-1500°C for 4 hours under nitrogen flow. The quartz powder was carbothermally reduced and nitrided to form silicon nitride powders. XRD results showed that the reaction product was mainly α-Si3N4 and contained some β-Si3N4 and residual quartz. In order to reduce amount of unreacted quartz, the raw materials mixture was grinded either with carbon black or with no carbon. After CRN reactions of separate grinded quartz powders with carbon, residual quartz was disappeared, reaction temperature was decreased and α-Si3N4 rate was increased. Hence, a better mixing of carbon and fine silica enhanced the α phase formation. SEM images and XRD pattern showed that sub micron particles (0.6–0.87m), high α-phase content Si3N4 powders can be produced at 1450°C for 4 h in flowing nitrogen gas during the CRN process.

Preparation of Cerium Dioxide Film by Anodization in Na2C2O4-NH3∙H2O-H2O-(CH2OH)2 Electrolyte

2017 ◽  
Vol 748 ◽  
pp. 7-11
Author(s):  
Xiao Zhen Liu ◽  
Wei Ren Rong ◽  
Xiao Zhou Liu ◽  
Xiao Hui Ren ◽  
Jie Chen ◽  
...  
Keyword(s):  
Oxide Film ◽  
Ethylene Glycol ◽  
Cerium Oxide ◽  
Cerium Dioxide ◽  
Raw Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heat Treated ◽  
Scanning Electron Microcopy ◽  
Dioxide Film

The cerium dioxide films were prepared with cerium foils as raw materials by anodization in Na2C2O4-NH3∙H2O-H2O-(CH2OH)2 electrolyte. The anodic cerium oxide film was heat treated at 550°C. The cerium dioxide films were characterized with X-ray diffraction (XRD), energy-dispersive analyses of X-ray (EDAX), Fourier transform infrared (FTIR) techniques and scanning electron microcopy (SEM), respectively. The anodic cerium oxide film is semi crystalline film. The heat treated anodic cerium oxide film at 550°C is the fluorite-structured cerium dioxide film, and the crystal structure of the cerium dioxide film becomes more complete than that of the anodic cerium oxide film. The cerium dioxide film is porous film. The water, ethylene glycol and CO2 are adsorbed in the anodic cerium oxide film. The adsorbing water, ethylene glycol and CO2 in the anodic cerium oxide film are removed at 550°C. The cerium dioxide film has strong absorption in the range of 1400~4000cm-1.

Synthesis and Characterization of New Polyurethane Adhesives

2006 ◽  
Vol 514-516 ◽  
pp. 843-847 ◽  
Author(s):  
Cristina Borges Correia ◽  
João C. Bordado
Keyword(s):  
Raw Materials ◽  
Impact Resistance ◽  
Inert Atmosphere ◽  
Stray Field ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Polyurethane Adhesives ◽  
Dimer Acids

Polyurethane adhesives provide excellent flexibility, impact resistance and durability. Polyurethanes are formed through the reaction of an isocyanate component with polyether or polyester polyols or other active hydrogen compounds. This paper refers to polyurethane adhesives made from polyester polyols with long aliphatic chains (up to 36 carbon atoms) and MDI (diphenylmethane-4,4’-diisocyanate). The polyester polyols have been made from dimer acids obtained from renewable sources and short chain diols. The polyols that were used presented different degrees of unsaturation. The influence of the different raw materials in the adhesives performance is studied. The polyurethanes were produced by reaction between quasi-stoichiometric quantities of polyol and MDI, at several temperatures. The reaction was carried under inert atmosphere and at temperatures below 100°C. Performance of the adhesives was tested by carrying adhesion, hardness and water absorption tests. Characterization of both the polyester polyols and polyurethane adhesives was carried by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Magnetic Nuclear Resonance (NMR), X-Ray Diffraction (WAXD), Scanning RMN Imaging of 1H of Stray- Field b (MRI) and Brookfield viscometry.

scholarly journals Ceramic raw materials from the State of Maranhão, Brazil. Part 1: chemical and mineralogical characterization and technological properties of clays from São Luis, Rosário, Pinheiro and Mirinzal

2012 ◽  
Vol 65 (4) ◽  
pp. 513-521
Author(s):  
José Manuel Rivas Mercury ◽  
Gricirene Sousa Correia ◽  
Nazaré Socorro Lemos Silva Vasconcelos ◽  
Aluísio Alves Cabral Jr. ◽  
Rômulo Simões Angélica
Keyword(s):  
Raw Materials ◽  
Mineralogical Composition ◽  
Exchange Capacity ◽  
High Plasticity ◽  
X Ray Diffraction ◽  
Specific Mass ◽  
Mineralogical Characterization ◽  
Heat Treated ◽  
Heavy Clay

This work involved the characterization of clays collected in the municipalities of São Luis, Rosário, Pinheiro and Mirinzal (state of Maranhão, Brazil), based on specific mass, specific surface area, cation exchange capacity (CEC), particle size distribution, X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetric analysis (TG-DTA) and Atterberg limits. Technological tests for ceramic applications were also carried out on compacts pressed under 20 MPa and heat-treated at 850, 950, 1050, 1150 and 1250ºC. Our results indicated that two of the clays composed of kaolinite, quartz, and anatase with high plasticity limits, have excellent properties and can be used in the whiteware industry. The other ones are red-firing clays and have a mineralogical composition of quartz, kaolin, feldspar, montmorillonite, hematite and goethite. The latter showed low and moderate values of plasticity, which makes them suitable for the production of heavy clay products.

Characterization of Portuguese gypsums as raw materials for dermocosmetics

Clay Minerals ◽  
2019 ◽  
Vol 54 (3) ◽  
pp. 277-281 ◽  
Author(s):  
Cristiana Costa ◽  
António Fortes ◽  
Fernando Rocha ◽  
Angela Cerqueira ◽  
Delfim Santos ◽  
...  
Keyword(s):  
Calcium Sulfate ◽  
Raw Materials ◽  
Cement Industry ◽  
Oil Absorption ◽  
Chemical Quality ◽  
X Ray Diffraction ◽  
X Ray ◽  
White Cement ◽  
Wet Sieving

AbstractPortuguese gypsum deposits utilized by the cement industry were characterized mineralogically, chemically and technologically for possible application in dermocosmetics. The deposits studied (Loulé, Óbidos and Soure) correspond to small outcrops in diapiric anticline areas. In principle, they represent gypsites which are white, and generally of higher quality for traditional applications (e.g. white cement), or greyish, and generally not adequate for cements and mortars. The analytical methods used to characterize the materials were wet sieving and X-ray sedimentation, X-ray diffraction, X-ray fluorescence spectrometry and assessment of abrasiveness, plasticity, texturometrics (adhesivity and firmness), oil absorption and cooling rate. The Óbidos gypsum displayed greater mineralogical and chemical quality (almost pure calcium sulfate) and had a finer grain size (<63 μm), whereas Loulé and Soure gypsums contain mineralogical impurities (mainly quartz). The Óbidos gypsum shows good characteristics in general for application in dermocosmetics because of its absorption, plasticity, adhesivity, firmness and low abrasiveness.

scholarly journals Characterization of cordierite-mullite ceramics prepared from natural raw materials

2013 ◽  
Vol 6 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Abdulmula Ali Albhilil ◽  
Martin Palou ◽  
Jana Kozánková
Keyword(s):  
Thermal Shock Resistance ◽  
Raw Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mercury Intrusion ◽  
Before And After ◽  
Shock Resistance ◽  
Quenching Method ◽  
Mullite Ceramics

Abstract Series of six cordierite-mullite ceramics were synthesized via solid state reaction at various temperatures from 1250 °C for pure cordierite to 1500 °C for pure mullite. Then the samples were submitted to the test of thermal shock resistance based on cycling heating-quenching procedure. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Mercury intrusion porosimeter (MIP) have been used to characterize the samples before and after cycling heating-quenching method. Sample 6 was broken after 35 heating-quenching cycles, while the five other reminded stable. The refractoriness of samples is found to be higher than that of commercial ones. XRD shows that heating-quenching procedure has led to crystallization of cordierite and mullite phases. Apart from sample 6, the pore structure is stable with slight consolidation. The microstructure images confirm the results of XRD and MIP showing crack in sample 6 only, but compact and larger particles resulting from crystal growth in other samples due to the repeated action of heating.

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