scholarly journals Mechanical and Electrical Characteristics of WB2 Synthesized at High Pressure and High Temperature

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1212 ◽  
Author(s):  
Changchun Wang ◽  
Lele Song ◽  
Yupeng Xie
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
Electrical Resistivity ◽  
High Temperature ◽  
Vickers Hardness ◽  
Single Phase ◽  
Hard Material ◽  
Experimental Conditions ◽  
Boundary Density ◽  
Grain Sizes

Single-phase tungsten diboride (WB2) was synthesized at high pressure and high temperature. The different grain sizes ranging from 300 nm to 3 µm were successfully obtained in WB2 by controlling the experimental conditions. The effects of grain size on hardness and resistivity properties were investigated. The Vickers hardness of WB2 was modulated with grain size. The maximum asymptotic Vickers hardness is 25.5 GPa for WB2 with a grain size of 300 nm which is a 10% increase compared to WB2 with a grain size of 3 µm. The optimal electrical resistivity of WB2 was 10−7 Ωm with the biggest grain size of 3 µm, which is ascribed to low grain boundary density. The superior properties of hardness and electrical resistivity demonstrate that WB2 should be a new functional hard material replacing WC which is widely used in industrial production.

The Processing of Ultrafine-Grained Materials Using High-Pressure Torsion

2007 ◽  
Vol 558-559 ◽  
pp. 1283-1294 ◽  
Author(s):  
Cheng Xu ◽  
Z. Horita ◽  
Terence G. Langdon
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
High Pressure ◽  
High Pressure Torsion ◽  
Metallic Materials ◽  
Grain Sizes ◽  
Ultrafine Grained ◽  
Wide Range ◽  
Ultrafine Grained Materials ◽  
Thin Disks

It is now well-established that processing through the application of severe plastic deformation (SPD) leads to a significant reduction in the grain size of a wide range of metallic materials. This paper examines the fabrication of ultrafine-grained materials using high-pressure torsion (HPT) where this process is attractive because it leads to exceptional grain refinement with grain sizes that often lie in the nanometer or submicrometer ranges. Two aspects of HPT are examined. First, processing by HPT is usually confined to samples in the form of very thin disks but recent experiments demonstrate the potential for extending HPT also to bulk samples. Second, since the strains imposed in HPT vary with the distance from the center of the disk, it is important to examine the development of inhomogeneities in disk samples processed by HPT.

High-pressure and high-temperature electrical resistivity studies on Nd-123

2005 ◽  
Vol 59 (14-15) ◽  
pp. 1764-1766 ◽  
Author(s):  
R. Selva Vennila ◽  
N. Victor Jaya ◽  
S. Natarajan
Keyword(s):  
High Pressure ◽  
Electrical Resistivity ◽  
High Temperature

scholarly journals High pressure synthesis of BN and BCN crystals and their functionalization

2014 ◽  
Vol 70 (a1) ◽  
pp. C751-C751
Author(s):  
Takashi Taniguchi
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
High Purity ◽  
Chemical Vapour ◽  
Attractive Potential ◽  
Luminescence Spectra ◽  
Hard Material ◽  
High Temperature Annealing ◽  
Electrical Insulator ◽  
Carbon Impurity

Hexagonal BN (hBN) and cubic BN (cBN) are known as the representative crystal structures of BN. The former is chemically and thermally stable, and has been widely used as an electrical insulator and heat-resistant materials. The latter, which is a high-density phase, is an ultra-hard material second only to diamond. Recently, some progresses in the synthesis of high purity BN crystals were achieved by using Ba-BN as a solvent material at high pressure crystal growth [1]. Band-edge natures (cBN Eg=6.2eV and hBN Eg=6eV) were characterized by their optical properties. The key issue to obtain high purity crystals is to reduce oxygen and carbon contamination in the growth circumstances. It should be emphasized that hBN exhibits attractive potential for deep ultraviolet (DUV) light emitter [2 ] and also superior properties as substrate of graphene devices [3]. In this study, the effect of carbon impurity in BN is investigated. Three types of experimental approaches were carried out; (1) synthesis of high purity hBN single crystals and its characterization with respect to residual carbon, (2) high temperature solid state diffusion of carbon into hBN and its characterization, and (3) high temperature annealing of turbostratic B-C-N(t-BCN) compound under high pressure. t-BCN flakes obtained by chemical vapour deposition process was annealed near 3000C and 2GPa so as to become well crystallized.At annealing near 3000C at 2GPa with graphite, carbon incorporation of 1E21/cm3 in hBN was achieved with exhibiting totally different Cathode Luminescence spectra feature with high purity hBN crystals. Since major carbon contribution may affect the crystal structure of the 2-D layers stacking in hBN system, phase stability of BCN ternary phase will be introduced by the experimental results of high temperature annealing. Furthermore, effect of carbon impurity upon the synthesis of wurtzite BN from highly crystalline hBN via martensitic phase transformation will also be introduced.

Thermoelectric properties of S-doped Cu2Se materials synthesized by high-pressure and high-temperature method

2019 ◽  
Vol 34 (01) ◽  
pp. 2050006
Author(s):  
Lisha Xue ◽  
Chao Fang ◽  
Weixia Shen ◽  
Manjie Shen ◽  
Wenting Ji ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Pressure ◽  
Electrical Resistivity ◽  
High Temperature ◽  
Thermoelectric Properties ◽  
Composition Change ◽  
Selenium Compounds ◽  
Competitive Effects ◽  
Temperature Method ◽  
Pressure Synthesis

High-pressure technique is an effective route to synthesize thermoelectric materials and tune transport properties simultaneously. In this work, S-doped copper–selenium compounds [Formula: see text], [Formula: see text] were successfully synthesized by high-pressure and high-temperature (HPHT) technology in just 30 min. [Formula: see text] samples show layered morphology composed of abundant pores and lattice defects. The appropriate S introduction ([Formula: see text] and 0.03) can effectively enhance Seebeck coefficient and reduce the thermal conductivity of [Formula: see text]. Compared with the pure [Formula: see text] sample, [Formula: see text] exhibits a 30% lower thermal conductivity, but the decline of power factor by the distinctly increased electrical resistivity at high temperature results in a smaller zT at temperature [Formula: see text] K. The variations of thermoelectric properties are resulted from the competitive effects between S-doping and actual composition change (Cu:S). It indicates that S-doping is not so effective in improving the zT value of [Formula: see text] materials by high-pressure synthesis.

Characterizing high-pressure compressed C60 whiskers and C60 powder

2003 ◽  
Vol 18 (1) ◽  
pp. 166-172 ◽  
Author(s):  
Kun'ichi Miyazawa ◽  
Minoru Akaishi ◽  
Yusuke Kuwasaki ◽  
Tadatomo Suga
Keyword(s):  
High Pressure ◽  
Electrical Resistivity ◽  
Electrical Properties ◽  
Vickers Hardness ◽  
High Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Of Dislocations ◽  
Mechanical And Electrical Properties

Structural, mechanical, and electrical properties were examined for C60 whiskers, high-pressure sintered C60 whiskers, and C60 powder. A high density of dislocations was observed in the C60 whiskers, and the C60 whiskers with diameters of a few hundred nanometers were found to be flexible. Although both the specimens sintered under the same condition showed similar surface x-ray diffraction profiles with a strong accumulation of [110]tr orientation, the sintered C60 whiskers showed a higher micro-Vickers hardness and an electrical resistivity four orders of magnitude lower than that of the sintered C60 powder.

Gradation Process by Imbibition in WC-Co for Mining Tools Application

2009 ◽  
Vol 83-86 ◽  
pp. 810-817
Author(s):  
Elodie Lefort-Sorlier ◽  
Christophe Colin ◽  
Alfazazi Dourfaye
Keyword(s):  
Grain Size ◽  
High Pressure ◽  
High Temperature ◽  
Thermal Processing ◽  
Temperature Step ◽  
High Pressure High Temperature ◽  
One Step ◽  
Shock Resistance ◽  
Composition Gradients ◽  
Mining Tools

Continuous composition gradients of several millimetres were generated in commercial WC-Co cutters to improve their shock resistance. This important gradation was obtained in one-step by using the imbibition process. The effects of this thermal processing were analysed in terms of microhardness, cobalt concentration and WC grain size. A gradient of a 300 HV amplitude is measured in the 8 mm-height sample treated by the imbibition process in association with a boron-rich coating. This gradient was preserved after the HPHT (high pressure – high temperature) step used for the diamond table deposition on the WC-Co cutter. To our knowledge, such gradients have never before been reported and should certainly increase cutter service life.

A high pressure-high temperature cell for electrical resistivity studies

Pramana ◽  
1985 ◽  
Vol 24 (6) ◽  
pp. 825-835 ◽  
Author(s):  
Mohammad Yousuf ◽  
P Ch Sahu ◽  
K Govinda Rajan
Keyword(s):  
High Pressure ◽  
Electrical Resistivity ◽  
High Temperature ◽  
High Pressure High Temperature

scholarly journals Characteristics of Lake Sediment from Southwestern Mongolia and Comparison with Meteorological Data

Geosciences ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 7
Author(s):  
Uyangaa Udaanjargal ◽  
Noriko Hasebe ◽  
Davaadorj Davaasuren ◽  
Keisuke Fukushi ◽  
Yukiya Tanaka ◽  
...  
Keyword(s):  
Grain Size ◽  
Organic Matter ◽  
High Temperature ◽  
Amorphous Silica ◽  
Meteorological Data ◽  
Principal Component ◽  
Short Time Scale ◽  
Mineral Particle ◽  
Grain Sizes ◽  
Silica Concentration

To understand how the climate system works in the continental interior, sediment cores that are approximately 30-cm long were taken from Olgoy, Boontsagaan, and Orog lakes, Mongolia. These cores were analyzed and compared with meteorological data (air temperature, precipitation, and wind) from climate stations in the study area. Comparison of metrological data from four stations shows similar climate fluctuations. When the temperature was high, less precipitation occurred in general. The sedimentary features measured in this study were water content, organic matter, carbonate, amorphous silica contents, whole and mineral grain size, and grain density. Excess 210Pb measurements were used to estimate sedimentary ages. According to principal component analysis (PCA), temperature correlates well to sediment characteristics in Olgoy Lake. Whole and mineral grain sizes are coarser when the temperature is high, while the amorphous-silica concentration is lower. A coarse grain size is interpreted to reflect low lake levels due to evaporation under high temperature with less precipitation. Amorphous silica may be from surrounding plants and reflects less vegetation when the temperature is high. However, in the recent 30 years, after the social system changed and overgrazing became a problem, the amount of amorphous silica has positively correlated with temperature on a short time scale. In the past 30 years, with less vegetation, amorphous silica has mainly come from weathered mineral particles. High temperature caused a thick, weathered mantle for each mineral particle, resulting in high amorphous-silica concentration. In Boontsagaan Lake, whole and mineral grain sizes are coarser when the wind speed is increased. Low precipitation correlates with a decrease in organic matter and an increase in carbonate and amorphous silica. In Orog Lake, it is difficult to establish an age model due to dried-up events. Some fluctuations in sedimentary characteristics may correspond to extreme events, such as earthquakes, and natural hazards, such as dzuds (harsh winters).

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