Sinterability of Silicon Nitride Powder Produced by the CRN Process

2009 ◽  
Vol 147-149 ◽  
pp. 896-901
Author(s):  
Ahmet Atasoy ◽  
M. Tümer
Keyword(s):  
Liquid Phase ◽  
Laboratory Experiments ◽  
Graphite Crucible ◽  
Nitride Powder ◽  
Sintering Process ◽  
Sintering Aids ◽  
X Ray ◽  
Liquid Phases ◽  
Linear Relationships ◽  
Silicon Nitride Powder

In the present work, laboratory experiments were carried out on the sintering of silicone nitride powder without any sintering additives. Silicone nitride powder was produced at own laboratory conditions by carbothermal reduction-nitriding of silica of which was presented elsewhere. It consists of mainly -Si3N4 (83%) and -Si3N4 (17%) phases with a small amount of minor constituents. Before compaction procedure, the powder was ball milled for 2 h and then 2 gr. of the sample was compacted uniaxially at a pressure of 25 MPa. The green compact was placed into furnace in a graphite crucible. The sintering process was carried out in a programmable muffle furnace at 1700 °C and held for 1 h. with a 20 °C/min. heating rate. The sintered compacts were analyzed using X-ray, SEM, SEM-EDS techniques. The results showed that the formation of liquid phase can accelerate the densification of the compact. The densification of the pure SIALON can be increased by adding of sintering aids that accelerates the formation of liquid phases in the sample. The densified sialons give better hardness and thermal properties of the sample. It was well demonstrated that for the densification of sialons large amount of liquid phase forming oxides are needed to add to initial composition. It is also suggested that there is linear relationships between densification and amount of liquid phase formed in the compact.

Effect of WC Addition on Phase Formation and Microstructure of TiC-Ni Composites

2008 ◽  
Vol 55-57 ◽  
pp. 353-356
Author(s):  
Nawarat Wora-uaychai ◽  
Nuchthana Poolthong ◽  
Ruangdaj Tongsri
Keyword(s):  
Liquid Phase ◽  
Tungsten Carbide ◽  
Phase Formation ◽  
Liquid Phase Sintering ◽  
Precipitation Process ◽  
Solid Solution Phase ◽  
Binder Phase ◽  
Sintering Process ◽  
X Ray Diffraction ◽  
X Ray

In this research, titanium carbide-nickel (TiC-Ni) composites, with tungsten carbide addition, were fabricated by using a powder metallurgy technique. The TiC-Ni mixtures containing between 0-15 wt. % tungsten carbide (WC), were compacted and then sintered at 1300°C and 1400°C, respectively. The phase formation and microstructure of the WC-added TiC-Ni composites have been investigated by X-ray diffraction and scanning electron microscopy techniques. Mechanical properties of these composites were assessed by an indentation technique. The X-ray diffraction patterns showed no evidence of tungsten rich phases in the sintered WC-added cermets. This indicates that during the sintering process, tungsten carbide particles were dissolved in metallic binder phase (Ni phase) via dissolution/re-precipitation process during liquid phase sintering. The liquid phase formed during sintering process could improve sinterability of TiC-based cermets i.e., it could lower sintering temperatures. The TiC-Ni composites typically exhibited a core-rim structure. The cores consisted of undissolved TiC particles enveloped by rims of (Ti, W)C solid solution phase. Hardness of TiC-Ni composites increased with WC content. Sintering temperature also had a slight effect on hardness values.

C O2 velocity measurement and models for temperatures up to 200°C and pressures up to 100 MPa

Geophysics ◽  
2010 ◽  
Vol 75 (3) ◽  
pp. E123-E129 ◽  
Author(s):  
De-Hua Han ◽  
Min Sun ◽  
Micheal Batzle
Keyword(s):  
Liquid Phase ◽  
Critical Point ◽  
Velocity Measurement ◽  
Laboratory Experiments ◽  
Empirical Models ◽  
Measured Data ◽  
Seismic Properties ◽  
Liquid Phases ◽  
Temperature And Pressure ◽  
Text Component

Studies on how the velocity of [Formula: see text] is affected by temperature and pressure are important for understanding seismic properties of fluid and rock systems with a [Formula: see text] component. We carried out laboratory experiments to investigate velocity of [Formula: see text] in temperatures ranging from [Formula: see text] and pressures ranging from [Formula: see text], in which [Formula: see text] is in a liquid phase. The results show that under the above conditions, in general, the velocity of [Formula: see text] increases as pressure increases and temperature decreases. Near the critical point ([Formula: see text] and [Formula: see text]), the velocity of [Formula: see text] reaches a minimum and has a complicated behavior with temperature and pressure conditions due to the [Formula: see text] transition between gas and liquid phases. We also developed preliminary empirical models to calculate the velocity of [Formula: see text] based on newly measured data.

Influence of YAG-Based Composite Sintering Aids on Gas Pressure Sintered BNw/Si3N4 Composites

2015 ◽  
Vol 655 ◽  
pp. 53-57
Author(s):  
Xian Li Wang ◽  
Hong Yu Gong ◽  
Yu Jun Zhang ◽  
Song Wei Che
Keyword(s):  
Dielectric Properties ◽  
Bending Strength ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Gas Pressure ◽  
Apparent Porosity ◽  
Sintering Process ◽  
Sintering Aids ◽  
Liquid Phases ◽  
Gas Pressure Sintering

BNw/Si3N4composites were fabricated by gas pressure sintering process using α-Si3N4powder and self-made BN whisker as principal raw materials. The effects of different sintering additives such as YAG, MgO+YAG and RE2O3+YAG(RE=La, Sm, Dy) on the apparent porosity, microstructure, phase composition, mechanical performance and dielectric properties of the composites were analysed. The results revealed that composite sintering aids at certain ratio (MgO/RE2O3:YAG=1:5) was more conducive to ceramic densification than single YAG additive. The BNw/Si3N4sintered with La2O3+YAG acquired the highest density and the maximum bending strength (272.46 MPa) and fracture toughness(4.9 MPa·m1/2). It was speculated that ceramic densification process was related to formation of different eutectic liquid phases with different viscosity. Additionally, when the apparent porosity of BNw/Si3N4composites was 20% or less, dielectric properties of the material were mainly influenced by the porosity and the value of the permittivity and dielectric loss decreased with the increase of ceramic porosity.

Control of Microstructures in the YBA2CU3O7‐σ system: 1. Reaction with CO2

1989 ◽  
Vol 169 ◽  
Author(s):  
Angus I. Kingon ◽  
Cheryl D. Davis ◽  
Thomas M. Hare ◽  
Hayne Palmour III ◽  
Carl C. Koch ◽  
...  
Keyword(s):  
Melting Point ◽  
Liquid Phase ◽  
Low Temperature ◽  
Peritectic Reaction ◽  
Sintering Process ◽  
Reaction Products ◽  
Incongruent Melting ◽  
Liquid Phases ◽  
Temperature Liquid ◽  
System 1

AbstractControlled reactions have been undertaken between CO2 and polycrystalline YBa2Cu3O7‐σ in the temperature range 500°‐700°C. Typical reaction products are Y2BaCu05, BaC03 and CuO. Subsequent processing in O2 (e.g. sintering) results in the formation of liquid phases(s) by peritectic reaction at temperatures of 935‐975°C, well below the incongruent melting point of YBa2Cu3O7‐σ (∼1010°C). This “low temperature” liquid phase is shown to have a dramatic influence on the sintering process, and the resulting microstructures. The reactions are difficult to reverse even after extended times at temperatures >900°C. The results give an indication of the effect of adsorbed CO2 into YBa2Cu3O7‐σ powders, albeit on a more localized scale.

Improved densification by nano-sized sintering aids for Si3N4

1999 ◽  
Vol 14 (12) ◽  
pp. 4562-4569 ◽  
Author(s):  
Liwu Wang ◽  
Wolfgang M. Sigmund ◽  
Sukumar Roy ◽  
Fritz Aldinger
Keyword(s):  
Liquid Phase ◽  
Ball Milling ◽  
Combustion Process ◽  
Liquid Phase Sintering ◽  
Densification Process ◽  
Sintering Aids ◽  
X Ray Diffraction ◽  
X Ray

The densification of Si3N4 with nano-sized sintering aids that were in situ incorporated by a combustion process was studied in comparison with that of sintering aids mixed by ball milling. The combustion process directly produces amorphous and nano-sized Y–Al oxides within the Si3N4 powder. X-ray diffraction results indicate that amorphous Y–Al oxides begin to crystallize into Y3Al5O12 at about 600 °C. Additionally the nano-sized sintering aids are more homogeneously distributed and thereby promote the formation of eutectic melts at lower temperatures during liquid-phase sintering. Therefore, the densification process of Si3N4 during liquid-phase sintering is strongly accelerated. The microstructure of as-sintered parts from combusted powder seems more dense and homogeneous.

Electron Microscopy/Diffraction Study of the Ternary Mn-Er-S System

1990 ◽  
Vol 48 (1) ◽  
pp. 76-77
Author(s):  
A. R. Landa Canovas ◽  
L.C. Otero Diaz ◽  
T. White ◽  
B.G. Hyde
Keyword(s):  
Electron Microscopy ◽  
Gas Flow ◽  
Graphite Crucible ◽  
Nominal Composition ◽  
X Ray Diffraction ◽  
Alumina Crucible ◽  
X Ray ◽  
Intermediate Phases ◽  
Twin Band ◽  
Ar Gas

X-Ray diffraction revealed two intermediate phases in the system MnS+Er2S3,:MnEr2S4= MnS.Er2S3, and MnEr4S7= MnS.2Er2S3. Their structures may be described as NaCl type, chemically twinned at the unit cell level, and isostructural with CaTi2O4, and Y5S7 respectively; i.e. {l13} NaCl twin band widths are (4,4) and (4,3).The present study was to search for structurally-related (twinned B.) structures and or possible disorder, using the more sensitive and appropiate technigue of electron microscopy/diffraction.A sample with nominal composition MnEr2S4 was made by heating Mn3O4 and Er2O3 in a graphite crucible and a 5% H2S in Ar gas flow at 1500°C for 4 hours. A small amount of this material was thenannealed, in an alumina crucible, contained in sealed evacuated silica tube, for 24 days at 1100°C. Both samples were studied by X-ray powder diffraction, and in JEOL 2000 FX and 4000 EX microscopes.

scholarly journals Synthesis and Na+ Ion Conductivity of Stoichiometric Na3Zr2Si2PO12 by Liquid-Phase Sintering with NaPO3 Glass

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3790
Author(s):  
Yongzheng Ji ◽  
Tsuyoshi Honma ◽  
Takayuki Komatsu
Keyword(s):  
Solid State ◽  
Liquid Phase ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
Ion Conductivity ◽  
X Ray Diffraction ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Sintering Time ◽  
Lower Activation

Sodium super ionic conductor (NASICON)-type Na3Zr2Si2PO12 (NZSP) with the advantages of the high ionic conductivity, stability and safety is one of the most famous solid-state electrolytes. NZSP, however, requires the high sintering temperature about 1200 °C and long sintering time in the conventional solid-state reaction (SSR) method. In this study, the liquid-phase sintering (LPS) method was applied to synthesize NZSP with the use of NaPO3 glass with a low glass transition temperature of 292 °C. The formation of NZSP was confirmed by X-ray diffraction analyses in the samples obtained by the LPS method for the mixture of Na2ZrSi2O7, ZrO2, and NaPO3 glass. The sample sintered at 1000 °C for 10 h exhibited a higher Na+ ion conductivity of 1.81 mS/cm at 100 °C and a lower activation energy of 0.18 eV compared with the samples prepared by the SSR method. It is proposed that a new LPE method is effective for the synthesis of NZSP and the NaPO3 glass has a great contribution to the Na+ diffusion at the grain boundaries.

scholarly journals Tuning π-Acceptor/σ-Donor Ratio of the 2-Isocyanoazulene Ligand: Non-Fluorinated Rival of Pentafluorophenyl Isocyanide and Trifluorovinyl Isocyanide Discovered

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 981
Author(s):  
Mason D. Hart ◽  
John J. Meyers ◽  
Zachary A. Wood ◽  
Toshinori Nakakita ◽  
Jason C. Applegate ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Coordination Chemistry ◽  
Single Crystal ◽  
13C Nmr ◽  
Quantitative Assessment ◽  
X Ray ◽  
New Class ◽  
Linear Relationships ◽  
Ligand Charge Transfer ◽  
Donor Characteristics

Isocyanoazulenes (CNAz) constitute a relatively new class of isocyanoarenes that offers rich structural and electronic diversification of the organic isocyanide ligand platform. This article considers a series of 2-isocyano-1,3-X2-azulene ligands (X = H, Me, CO2Et, Br, and CN) and the corresponding zero-valent complexes thereof, [(OC)5Cr(2-isocyano-1,3-X2-azulene)]. Air- and thermally stable, X-ray structurally characterized 2-isocyano-1,3-dimethylazulene may be viewed as a non-benzenoid aromatic congener of 2,6-dimethyphenyl isocyanide (2,6-xylyl isocyanide), a longtime “workhorse” aryl isocyanide ligand in coordination chemistry. Single crystal X-ray crystallographic {Cr–CNAz bond distances}, cyclic voltametric {E1/2(Cr0/1+)}, 13C NMR {δ(13CN), δ(13CO)}, UV-vis {dπ(Cr) → pπ*(CNAz) Metal-to-Ligand Charge Transfer}, and FTIR {νN≡C, νC≡O, kC≡O} analyses of the [(OC)5Cr(2-isocyano-1,3-X2-azulene)] complexes provided a multifaceted, quantitative assessment of the π-acceptor/σ-donor characteristics of the above five 2-isocyanoazulenes. In particular, the following inverse linear relationships were documented: δ(13COtrans) vs. δ(13CN), δ(13COcis) vs. δ(13CN), and δ(13COtrans) vs. kC≡O,trans force constant. Remarkably, the net electron withdrawing capability of the 2-isocyano-1,3-dicyanoazulene ligand rivals those of perfluorinated isocyanides CNC6F5 and CNC2F3.

Transient liquid phase bonding of Cu and Al using metallic particles interlayers

2021 ◽  
pp. 095440542098823
Author(s):  
Alireza Zaheri ◽  
Mohammadreza Farahani ◽  
Alireza Sadeghi ◽  
Naser Souri
Keyword(s):  
Liquid Phase ◽  
Mechanical Test ◽  
Transient Liquid Phase ◽  
Transient Liquid Phase Bonding ◽  
Joint Interface ◽  
Test Results ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metallic Particles ◽  
Powder Interlayer

The bonding strength, and microstructures of Cu and Al couples using metallic powders as interlayer during transient liquid phase bonding (TLP bonding) were investigated. The interfacial morphologies and microstructures were studied by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy, and X-ray diffraction. First, to explore the optimum bonding time and temperature, nine samples were bonded without interlayers in a vacuum condition. Mechanical test results indicated that bonding at 560°C in 20 min returns the highest bond strength (84% of Al). This bonding condition was used to join ten samples with powder interlayers. Powders were prepared by mixing different combinations of Cu, Al (+Fe nanoparticles) and Zn. In the bonding zone, different Cu9Al4, CuAl, and CuAl2 intermetallic co-precipitate. The strongest bonding is formed in the sample with the 70Al (+Fe)-30Cu powder interlayer. Powder interlayers present thinner and more uniform intermetallic layers at the joint interface.

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