Effect of Precursors on Transmittance and Microstructure of Mullite Ceramics

2009 ◽  
Vol 620-622 ◽  
pp. 429-432 ◽  
Author(s):  
Gui Min Zhang ◽  
Zheng Yi Fu ◽  
Yu Cheng Wang ◽  
Hao Wang ◽  
Wei Min Wang ◽  
...  
Keyword(s):  
Spray Drying ◽  
Ethanol Solution ◽  
Spherical Particles ◽  
Plasma Sintering ◽  
The Matrix ◽  
Conventional Drying ◽  
Spark Plasma ◽  
Mean Size ◽  
Dta Curves ◽  
Equiaxed Grains

Two different kinds of mullite precursors with composition 3Al2O3•2SiO2 (3:2) were prepared by conventional drying ethanol solution and spray-drying aqueous solution of aluminum nitrate nanohydrate and tetraethoxysilane, respectively. The results of scanning electron microscope (SEM) indicate that one powder consists of irregular particles with size of 1-10μm, the other powder is made of inhomogeneously sized hollow spherical particles with mean size of 0.5-5μm. The TG-DTA curves indicate the hollow spherical particles are unfavorable to eliminate the decomposed products. After the precursors were sintered by Spark Plasma Sintering at 1450°C for 10min, the microstructures of the former are made of fine equiaxed grains with sizes of around 0.5μm, the latter consist of elongated grains distributed in the matrix of fine grains with imhomogenous size of 0.5~10μm due to the liquid phase forming. The different microstructures lead to the former sintered body is transparent, while, the sample from spray-drying is opaque.

Spark Plasma Sintering of Titanium Spherical Particles

2016 ◽  
Vol 47 (5) ◽  
pp. 2725-2731 ◽  
Author(s):  
Mohammad Abedi ◽  
Dmitry O. Moskovskikh ◽  
Alexander S. Rogachev ◽  
Alexander S. Mukasyan
Keyword(s):  
Spark Plasma Sintering ◽  
Spherical Particles ◽  
Plasma Sintering ◽  
Spark Plasma

Formation of in-situ reinforced microstructure in α–sialon ceramics I: Stoichiometric oxygen-rich compositions

2002 ◽  
Vol 17 (2) ◽  
pp. 336-342 ◽  
Author(s):  
Zhijian Shen ◽  
Hong Peng ◽  
Mats Nygren
Keyword(s):  
Hot Pressing ◽  
Single Phase ◽  
Transient Liquid Phase ◽  
Precursor Powder ◽  
Temperature Dependent ◽  
Consolidation Process ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Equiaxed Grains

The abnormal grain growth in α–sialon ceramics was investigated. The preparations had stoichiometric compositions on the oxygen-rich phase boundary, and they were stabilized by Y, Nd, Sm, Dy, and Yb, respectively. Specimens were prepared from α–Si3N4 as precursor powder by applying conventional hot pressing and a novel rapid consolidation process, namely spark plasma sintering (SPS). Single-phase α–sialon ceramics with in situ reinforced bimodal microstructure, i.e., large elongated grains embedded in a matrix consisting of small equiaxed grains, were obtained above 1750 °C in all systems compacted by SPS and above 1800 °C in systems stabilized by Nd and Sm but not Dy, Y, or Yb by a two-step hot-pressing procedure. It was observed that the formation of abnormally grown α–sialon grains was strongly temperature-dependent, indicating that it was encouraged by the formation of a transient liquid phase that stimulated the dissolution of any remaining nitride precursors and early formed small α–sialon grains and sequentially facilitated supersaturation by the α–sialon constituents. The presence of elongated grains improves fracture resistance in the obtained materials.

The Influence of RuO2 Addition on the Thermoelectric Properties of BiSbTe Alloys

2012 ◽  
Vol 512-515 ◽  
pp. 1651-1654 ◽  
Author(s):  
Yu Kun Xiao ◽  
Zhi Xiang Li ◽  
Jun Jiang ◽  
Sheng Hui Yang ◽  
Ting Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Lattice Thermal Conductivity ◽  
Combined Process ◽  
Plasma Sintering ◽  
The Matrix ◽  
Spark Plasma ◽  
Xrd Patterns ◽  
Factor Α ◽  
P Type

P-type BiSbTe/RuO2 composite was fabricated using a combined process of melting and spark plasma sintering. The XRD patterns showed that RuO2 reacted with the matrix for the RuO2 content of 1.0 wt% and 4.0 wt% samples. The measured thermoelectric properties showed that the highest electrical conductivity was obtained for the sample with 2.0 wt% RuO2. The power factor (α2σ/κ) decreased with the increase of RuO2 below 450 K. The lattice thermal conductivity was lower than that of BiSbTe over the whole temperature range for BiSbTe/2.0 wt% RuO2.

High Temperature Microstructural Stability of Si3N4 in TiAl Alloys

2007 ◽  
Vol 534-536 ◽  
pp. 1577-1580
Author(s):  
Jee Hoon Choi ◽  
Dong Bok Lee
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Mechanical Alloying ◽  
Spark Plasma Sintering ◽  
Reaction Layer ◽  
Microstructural Stability ◽  
Tial Alloys ◽  
Plasma Sintering ◽  
The Matrix ◽  
Spark Plasma

Alloys of Ti-50 at.% Al with (3 and 10)wt.% Si3N4 particles were prepared by a mechanical alloying-spark plasma sintering (MA-SPS) method. The matrix consisted primarily of TiAl, Ti2AlN, TiN. Si3N4 was unstable in the matrix and started to decompose forming a Ti5Si3 reaction layer on the surface of former Si3N4 particles during sintering and heat treatment at 1373 K.

Effect of Milling Time on the Properties of Nanocrystalline CuCr50 Alloys

2011 ◽  
Vol 299-300 ◽  
pp. 824-827
Author(s):  
Kun Yu Shi ◽  
Tao Shen ◽  
Li Hong Xue ◽  
Chun Hao Chen ◽  
You Wei Yan
Keyword(s):  
Electrical Conductivity ◽  
Crystallite Size ◽  
Milling Time ◽  
Micro Hardness ◽  
Uniform Microstructure ◽  
High Relative Density ◽  
Plasma Sintering ◽  
The Matrix ◽  
Spark Plasma ◽  
Bulk Nanocrystalline

Nanocrystalline CuCr50 alloys were fabricated by means of mechanical alloying and spark plasma sintering. The influence of milling time on the as-milled powders and properties of sintered compacts were investigated. The results show that crystallite size of powders decreases gradually with increase of milling time, while the micro-strain increases firstly then decreases correspondingly. The crystallite size is 22 nm at milling 100h.The micro-hardness of the compacts improves greatly with the increase of milling time, reaching 363HV at 150h which is about 3 times as high as that of the industrial standard (120HV), while the electrical conductivity improves gradually decline. The bulk nanocrystalline CuCr50 alloys sintered at 900°C for 5min exhibit high relative density of 96% and uniform microstructure: nanoparticles Cr with size of about 120nm are uniformly dispersed in the matrix.

Effects of Consolidation Process on the Microstructure and Mechanical Properties of ODS Ferritic Alloy

2013 ◽  
Vol 747-748 ◽  
pp. 507-512 ◽  
Author(s):  
Tong Liu ◽  
Hai Long Shen ◽  
Tong Wen Zhang ◽  
Mu Zhu ◽  
Cheng Gong Qin
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Hot Isostatic Pressing ◽  
Oxide Dispersion Strengthened ◽  
Consolidation Process ◽  
Ferritic Alloy ◽  
Plasma Sintering ◽  
The Matrix ◽  
Spark Plasma ◽  
Oxide Particles

The oxide-dispersion-strengthened (ODS) ferritic alloy powders (Fe-14Cr-3Al-2W-0.1Ti-0.35Y2O3) were prepared by mechanical alloying (MA) at a rotation speed of 720 rpm for 24 h. All the elements were mixed homogenously in the powder, and Cr and Al dissolved in α-Fe after MA. The bulk samples were produced by spark plasma sintering (SPS) at 950 and 50 MPa and by hot isostatic pressing (HIP) at 1150 and 130 MPa, respectively. The SPS sample showed a tensile strength of 730 MPa and a poor ductility due to the existence of pores in microsize. The HIP sample had a high tensile strength of 980 MPa, yield strength of 710 MPa and elongation of 10.3 %. The excellent mechanical properties of the HIP sample was due to the small grain size of the matrix of about 400 nm and the fine oxide particles of 5-40 nm.

scholarly journals Influence of molybdenum content on the microstructure of spark plasma sintered titanium alloys

2021 ◽  
Vol 1 (1) ◽  
pp. 41-47
Author(s):  
M. Saravana Kumar ◽  
S. Rashia Begum ◽  
M. Vasumathi ◽  
Chinh Chien Nguyen ◽  
Quyet Van Le
Keyword(s):  
Relative Density ◽  
Phase Evolution ◽  
Microstructural Development ◽  
Sintered Titanium ◽  
Sintering Process ◽  
Plasma Sintering ◽  
The Matrix ◽  
Molybdenum Addition ◽  
Spark Plasma ◽  
Mo Content

Five titanium-based alloys containing 4, 8, 12, 16, and 20 wt% molybdenum additive were fabricated by spark plasma sintering process at 1200 ˚C. The samples were scrutinized in terms of relative density, phase evolution, and microstructural development. The relative density reached 99.9% with the molybdenum addition up to 16 wt% but slightly dropped in the sample with 20 wt% additive. In the specimens with 4 wt% Mo, molybdenum solved completely in the matrix and three different phase morphologies were observed, namely continuous α-Ti, laminar α-Ti, and very thin laminar β-Ti. With increasing Mo content to 20 wt%, widespread single β-Ti appeared alongside remained Mo and α-Ti. Ductile fracture mode was dominant in the samples with low Mo contents whilst it changed to brittle in the specimens with higher content of molybdenum.

scholarly journals NIOBIUM REINFORCED BY α-Al2O3 FIBERS Part 1. Two-Component Compositions

2021 ◽  
pp. 58-77
Author(s):  
E.N. Kablov ◽  
◽  
B.V. Shchetanov ◽  
A.N. Bolshakova ◽  
I.Yu. Efimochkin ◽  
...  
Keyword(s):  
High Temperature ◽  
Mechanical Alloying ◽  
Barrier Coatings ◽  
Ternary Diagrams ◽  
New Class ◽  
Plasma Sintering ◽  
Two Component ◽  
The Matrix ◽  
Spark Plasma ◽  
Α Al2o3

The paper reviews the results of development of a new class of high-temperature composites based on niobium and various types of reinforcers continuous monocrystalline fibers (MCF) α-Al2O3, with TiN, Mo, W barrier coatings, and with controlled (Si, Ti) and uncontrolled (O, C) impurities. The analysis of Nb–Si, Nb–C, Nb–O binary diagrams and Nb–Si–Ti, Nb–Fe–Ti ternary diagrams was performed, on the basis of which the matrix compositions were selected. The basis for the preparation of composites was the powder method of mechanical alloying of the mixture preparing, followed by its pressing together with α-Al2O3 MCF by spark plasma sintering (SPS) and further preparation of experimental samples. An analysis of the interaction of fibers with a matrix was carried out, where the matrix was Nb or system on the basis of the above mentioned binary or ternary diagrams.

scholarly journals Fabrication Process and Thermoelectric Properties of CNT/Bi2(Se,Te)3Composites

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Kyung Tae Kim ◽  
Yeong Seong Eom ◽  
Injoon Son
Keyword(s):  
Figure Of Merit ◽  
Reduction Process ◽  
Sintering Process ◽  
Composite Powders ◽  
Synergistic Enhancement ◽  
Dimensionless Figure Of Merit ◽  
Plasma Sintering ◽  
The Matrix ◽  
Spark Plasma ◽  
Matrix Modifications

Carbon nanotube/bismuth-selenium-tellurium composites were fabricated by consolidating CNT/Bi2(Se,Te)3composite powders prepared from a polyol-reduction process. The synthesized composite powders exhibit CNTs homogeneously dispersed among Bi2(Se,Te)3matrix nanopowders of 300 nm in size. The powders were densified into a CNT/Bi2(Se,Te)3composite in which CNTs were randomly dispersed in the matrix through spark plasma sintering process. The effect of an addition of Se on the dimensionless figure-of-merit (ZT) of the composite was clearly shown in 3 vol.% CNT/Bi2(Se,Te)3composite as compared to CNT/Bi2Te3composite throughout the temperature range of 298 to 473 K. These results imply that matrix modifications such as an addition of Se as well as the incorporation of CNTs into bismuth telluride thermoelectric materials is a promising means of achieving synergistic enhancement of the thermoelectric performance levels of these materials.

scholarly journals Microstructure and Properties of Copper–Graphite Composites Fabricated by Spark Plasma Sintering Based on Two-Step Mixing

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1506
Author(s):  
Jinping Liu ◽  
Ke Sun ◽  
Longfei Zeng ◽  
Jing Wang ◽  
Xiangpeng Xiao ◽  
...  
Keyword(s):  
Spark Plasma Sintering ◽  
Wet Milling ◽  
Fatigue Wear ◽  
Graphite Content ◽  
Microstructure And Properties ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Mean Size ◽  
Graphite Composites ◽  
Annealed Copper

The microstructure and properties of Copper-Graphite Composites (CGC) prepared by spark plasma sintering (SPS) based on two-step mixing and wet milling were investigated. The results showed that Cu powders were rolled into Cu flakes during milling, and their size significantly decreased from 23.2 to 10.9 μm when the graphite content increased from 1.0 wt.% to 2.5 wt.%. The oxidation of Cu powder was avoided during two-step mixing and wet milling. After spark plasma sintering, the graphite powders of the composites were mainly distributed at Cu grain boundaries in granular and flake shapes. The mean size of Cu grains was 9.4 um for 1.0 wt.% graphite content and reduced slightly with the increasing of graphite content. Compared with other conventional methods, the composite prepared by two-step mixing and SPS achieved higher relative density, electrical conductivity, and micro-hardness, which, respectively, reduced from 98.78%, 89.7% IACS (International annealed copper standard), and 64 HV (Vickers-hardness) to 96.56%, 81.3% IACS, and 55 HV when the graphite content increased from 1.0 wt.% to 2.5 wt.%. As the graphite content increases, the friction coefficient and wear rate of the composite decreases. When the graphite content of CGC is 1.0 wt.%, the main wear mechanism was plastic deformation, delamination, adhesive, and fatigue wear. The adhesive and fatigue wear disappeared gradually with the increasing of graphite content.

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