Self-propagation high-temperature synthesis of half-Heusler thermoelectric materials: reaction mechanism and applicability

2018 ◽  
Vol 6 (40) ◽  
pp. 19470-19478 ◽  
Author(s):  
Yunfei Xing ◽  
Ruiheng Liu ◽  
Yi-Yang Sun ◽  
Fan Chen ◽  
Kunpeng Zhao ◽  
...  
Keyword(s):  
High Temperature ◽  
Reaction Mechanism ◽  
Thermoelectric Property ◽  
Thermoelectric Materials ◽  
Formation Enthalpy ◽  
Laboratory Scale ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Shs Method

By revealing reaction mechanism associated with formation enthalpy and reaction binaries, various HH thermoelectric materials are prepared by self-propagation high-temperature synthesis (SHS) method. The thermoelectric property and stability of the samples are comparable to those prepared by other laboratory-scale methods.

Preparation and Microwave Permittivity of SiC-AlN Solid Solution Powders

2007 ◽  
Vol 336-338 ◽  
pp. 310-312
Author(s):  
Xiao Kui Liu ◽  
Wan Cheng Zhou ◽  
Fa Luo ◽  
Dong Mei Zhu
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Carbon Black ◽  
Atomic Ratio ◽  
Nitrogen Atmosphere ◽  
Argon Atmosphere ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Microwave Permittivity ◽  
Shs Method

SiC-AlN solid solution powders were prepared from the mixtures of aluminum, silicon and carbon black in a nitrogen atmosphere with preheating self-propagating high temperature synthesis (SHS) method. The powders synthesized with different ratios of Al/Si were mixed with paraffin wax and the microwave permittivity of the mixtures was measured at the frequency of 8.2~12.4GHz. The results were contrasted with that of SiC powders synthesized by preheating SHS in argon and nitrogen atmosphere respectively. The ε′, ε″, and the tgδ (ε″/ε′) of the mixture of SiC prepared in a nitrogen atmosphere are highest, followed with those of the SiC-AlN solid solution powders and the SiC powders prepared in an argon atmosphere. Along with the increase of atomic ratio of Al/Si, the ε′, ε″, and tgδ of SiC-AlN solid solution decrease. We believe that, with the increase of AlN dissolved, the concentration of carriers and the effect of dielectric relaxation will decrease because of the two contrary dopants.

Immobilization of Radioactive Wastes into Perovskite Synrock by the SHS Method

2005 ◽  
Vol 475-479 ◽  
pp. 1627-1630 ◽  
Author(s):  
Rui Zhu Zhang ◽  
Zhi Meng Guo ◽  
Cheng Chang Jia ◽  
Guangfeng Lu
Keyword(s):  
High Temperature ◽  
Synthesis Process ◽  
Temperature Synthesis ◽  
Geological Disposal ◽  
Major Phase ◽  
Leach Rate ◽  
High Temperature Synthesis ◽  
Waste Loading ◽  
Shs Method

This paper researched the fabrication of perovskite synrock by self-propagating high temperature synthesis (SHS) and the characterization of the products. This synthesis process is simpler, the fabricated synrock can immobilize waste loading up to 35wt% SrO with satisfied physical properties (density>4.2g•cm-3, open porosity<0.2%, Leach rate<1.0 g•m-2•d-1). The structure analyses by XRD and SEM/EDS show that the major phase is perovskite which well agrees with the design. It proves that SHS offer a suitable Sr-waste synroc which is favorable for geological disposal.

Reaction mechanism of self-propagating high-temperature synthesis reaction in the Ni–Ti–B4C system

2008 ◽  
Vol 23 (9) ◽  
pp. 2519-2527 ◽  
Author(s):  
Y.F. Yang ◽  
H.Y. Wang ◽  
R.Y. Zhao ◽  
Y.H. Liang ◽  
Q.C. Jiang
Keyword(s):  
High Temperature ◽  
Reaction Mechanism ◽  
Intermetallic Compounds ◽  
Eutectic Point ◽  
The Self ◽  
Mutual Diffusion ◽  
Synthesis Reaction ◽  
Temperature Synthesis ◽  
Early Appearance ◽  
High Temperature Synthesis

The SHS reaction in the Ni–Ti–B4C system starts with the formation of Ni–Ti and Ni–B intermetallic compounds from the solid interacted reaction among the reactants and, subsequently, the formation of Ni–Ti and Ni–B liquid at the eutectic point. Meanwhile, some C atoms from the reaction between Ni and B4C can dissolve into Ni–Ti liquid to form TiC. The heat generated from these reactions can promote the mutual diffusion of Ni–Ti–C and Ni–B liquid and simultaneously accelerate the formation of Ni–Ti–C–B liquid. Finally the precipitation of TiC and TiB2 occur when the C and B atoms in the liquid become supersaturated. The addition of Ni not only promotes the occurrence of the self-propagating high temperature synthesis (SHS) reaction by forming Ni–Ti liquid, but also accelerates the SHS reaction by forming Ni–B liquid and dissociative C. The early appearance of dissociative C from the reaction between Ni and B4C causes the formation of TiC prior to that of TiB2.

Determination of Non-Stoichiometry of Tubular Titanium Carbide Formed by Self-Propagating High Temperature Synthesis

2007 ◽  
Vol 534-536 ◽  
pp. 1301-1304
Author(s):  
Y. Choi ◽  
Nam Ihn Cho
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
High Temperature ◽  
Titanium Carbide ◽  
Combustion Temperature ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Scanning Electron ◽  
Shs Method

Titinium carbide (TiCx) was produced by self-propagating high temperature synthesis (SHS) method. The morphology and non-stoichiometric number of the SHS product were observed by scanning electron microscopy and neutron diffractometry, respectively. Tubular titanium carbide with hole inside was formed with different non-stoichiometric number (x), which value increased with combustion temperature.

Preparation Research of CaB6 Powder by Self-Propagating High-Temperature Synthesis

2011 ◽  
Vol 284-286 ◽  
pp. 2106-2109 ◽  
Author(s):  
Yi Yong Wang ◽  
Hui Jin
Keyword(s):  
Sulfuric Acid ◽  
High Temperature ◽  
High Purity ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Vacuum Atmosphere ◽  
Reaction Atmosphere ◽  
Shs Method ◽  
Magnesium Addition

Self-propagating High-temperature Synthesis (SHS) method was adopted to synthesize powder containing CaB6, and the power was leaching by sulfuric acid. Effects of reaction atmosphere, magnesium addition, H2SO4acidity and leaching temperature on the performances of CaB6powderwas investigated, the microstructure of products were researched by SEM and XRD, the results show that the phases of products by SHS are CaB6、Mg3B2O6and Ca3B2O6, and high purity CaB6powders are obtained after the products by SHS was leaching by Sulfuric acid. The SHS conditions are the vacuum atmosphere and 30% excessive magnesium addition and the leaching conditions are 55% acidity of Sulfuric acid and 40°C leaching temperature, the perfect and uniform grain of CaB6powers are obtained at the above conditions.

Ignition mechanism of mechanically activated Me–Si(Me = Ti, Nb, Mo) mixtures

2004 ◽  
Vol 19 (5) ◽  
pp. 1558-1566 ◽  
Author(s):  
U. Anselmi-Tamburini ◽  
F. Maglia ◽  
S. Doppiu ◽  
M. Monagheddu ◽  
G. Cocco ◽  
...  
Keyword(s):  
High Temperature ◽  
Reaction Mechanism ◽  
Mechanical Activation ◽  
Ignition Temperature ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Ignition Mechanism ◽  
Ignition Characteristics ◽  
Different Response

The influence of mechanical activation on the characteristics and mechanism of ignition of self-propagating high-temperature synthesis processes of different silicides in the systems Me–Si (Me =Ti, Nb, Mo) was investigated. The results show that mechanical activation does not alter the mechanism involved but influences significantly the ignition characteristics. The influence, however, strongly depends on the stoichiometry of the mixtures. The composition Ti:Si = 1:2 shows the largest influence, with the ignition temperatures decreasing from 1400 °C for unmilled powders to about 600 °C for powders milled for several hours. The compositionsTi:Si = 5:3, Nb:Si = 1:2 show less pronounced decreases, while the compositionMo:Si = 1:2 shows no decrease. These differences are discussed in terms of the role of microstructure in the reaction mechanism and the different response of the systems to contamination, particularly from oxygen. The results suggest that for these systems self-ignition processes during milling cannot be explained only on the basis of the decrease in the ignition temperature.

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