Erbium boride composites with high ZT values at 800 K

2013 ◽  
Vol 1490 ◽  
pp. 41-44
Author(s):  
Frederick C. Stober ◽  
Barbara R. Albert
Keyword(s):  
High Temperature ◽  
Energy Conversion ◽  
Single Phase ◽  
Rietveld Analysis ◽  
Molar Ratio ◽  
Refractory Materials ◽  
Solid Reaction ◽  
Seebeck Coefficients ◽  
Electrical Conductivities ◽  
Multi Phase

ABSTRACTSingle phase erbium borides ErB2, ErB4, and ErB12 show Seebeck coefficients and power factors with absolute values that are significantly lower than those of a stable Er-B multi phase composite obtained through high temperature solid-solid reaction from the elements (molar ratio Er:B = 1:6). According to quantitative Rietveld analysis the composite consists of erbium diboride (1 %), tetraboride (83 %), and dodecaboride (16 %), and the measurement of the electrical conductivities, Seebeck coefficients, and thermal conductivities leads to ZT values as high as 0.53 at 830 K. Such refractory materials can be used for energy conversion in a range of high temperatures that are otherwise difficult to address.

scholarly journals Dielectric Properties of Rhombohedral PbNb2O6

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Kriti Ranjan Sahu ◽  
Udayan De
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
High Temperature ◽  
Single Phase ◽  
Rhombohedral Phase ◽  
Orthorhombic Phase ◽  
Dielectric Materials ◽  
Rietveld Analysis ◽  
Bulk Resistance ◽  
Relaxation Time Constant

Dielectric materials are needed in many electrical and electronic applications. So, basic characterizations need to be done for all dielectrics. PbNb2O6 (PN) is ferroelectric and piezoelectric only in its orthorhombic phase, with potential high temperature applications. So, its rhombohedral phase, frequently formed as an undesirable impurity in the preparation of orthorhombic PN, has been ignored with respect to possible dielectric characterizations. Here, essentially single phase rhombohedral PN has been prepared, checking structure from XRD Rietveld Analysis, and the real and imaginary parts of permittivity measured in an Impedance Spectrometer (IS) up to ~700∘C and over 20 Hz to 5.5 MHz range, for heating and some cooling runs. Variations, with temperature, of relaxation time constant (τ), AC and DC conductivity, bulk resistance, activation energy and capacitance have been explored from our IS data.

scholarly journals Refractory Materials For High-Temperature Thermoelectric Energy Conversion

1983 ◽  
Vol 24 ◽  
Author(s):  
Charles Wood ◽  
David Emin
Keyword(s):  
Rare Earth ◽  
High Temperature ◽  
Energy Conversion ◽  
Transport Properties ◽  
Refractory Material ◽  
High Temperatures ◽  
Refractory Materials ◽  
Efficient Energy ◽  
Thermoelectric Energy ◽  
Material Systems

ABSTRACTTwo refractory material systems show promise for efficient energy conversion at high temperatures (>1000 K): the rare-earth chalcogenides and the boron-rich borides. The electronic and thermal transport properties of these two systems are compared and discussed.

Measurements of the Thermal Conductivity of Individual α-Tetragonal Boron Nanoribbons

2011 ◽  
Author(s):  
Juekuan Yang ◽  
Scott W. Waltermire ◽  
Yang Yang ◽  
Deyu Li ◽  
Xiaoxia Wu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Silicon Nanowires ◽  
Complex Structures ◽  
One Dimensional ◽  
Seebeck Coefficients ◽  
Electrical Conductivities ◽  
Mechanical Devices ◽  
Property Characterization

Boron-based materials (i.e., boron and its borides) are mostly semiconductors with complex structures. These structures are characterized by an arrangement of an icosahedral cluster of B12 atoms [1]. The complexity of the crystal structure gives boron-based material a high melting point and low thermal conductivity at high temperature. On the other hand, the Seebeck coefficients and electrical conductivities of most bulk boron-based materials increase as temperature increases. Therefore, bulk boron-based materials are good candidates for high-temperature thermoelectric applications [2]. Due to the unique properties of bulk boron-based materials, one-dimensional nanostructures of boron-based materials have also attracted much attention, and various boron-based nanostructures have been synthesized recently [3]. These boron-based nanostructures are projected to be promising materials for novel nanoelectronic and nanoelectro-mechanical devices, as well as high temperature thermoelectric materials. However, compared to the extensive studies of carbon nanotubes and silicon nanowires, little has been done on the property characterization of boron and boride nanostructures.

COPPER ALLOY No. 230

Alloy Digest ◽  
1972 ◽  
Vol 21 (3) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
Shear Strength ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Copper Alloy ◽  
Single Phase ◽  
Heat Treating ◽  
Temperature Performance

Abstract COPPER ALLOY No. 230 is a single-phase brass containing 15% zinc which is the most widely used of the low zinc brasses. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear strength as well as fracture toughness and creep. It also includes information on low and high temperature performance, and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Cu-252. Producer or source: Brass mills.

scholarly journals Fabrication and Characterization of Quinary High Entropy-Ultra-High Temperature Diborides

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 108-120
Author(s):  
Simone Barbarossa ◽  
Roberto Orrù ◽  
Valeria Cannillo ◽  
Antonio Iacomini ◽  
Sebastiano Garroni ◽  
...  
Keyword(s):  
High Temperature ◽  
Single Phase ◽  
Nominal Composition ◽  
High Entropy ◽  
Chemical Complexity ◽  
Alternative Processing ◽  
Plasma Sintering ◽  
High Temperature Synthesis ◽  
Spark Plasma

Due to their inherent chemical complexity and their refractory nature, the obtainment of highly dense and single-phase high entropy (HE) diborides represents a very hard target to achieve. In this framework, homogeneous (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2, (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2, and (Hf0.2Zr0.2Nb0.2Mo0.2Ti0.2)B2 ceramics with high relative densities (97.4, 96.5, and 98.2%, respectively) were successfully produced by spark plasma sintering (SPS) using powders prepared by self-propagating high-temperature synthesis (SHS). Although the latter technique did not lead to the complete conversion of initial precursors into the prescribed HE phases, such a goal was fully reached after SPS (1950 °C/20 min/20 MPa). The three HE products showed similar and, in some cases, even better mechanical properties compared to ceramics with the same nominal composition attained using alternative processing methods. Superior Vickers hardness and elastic modulus values were found for the (Hf0.2Nb0.2Ta0.2Mo0.2Ti0.2)B2 and the (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2 systems, i.e., 28.1 GPa/538.5 GPa and 28.08 GPa/498.1 GPa, respectively, in spite of the correspondingly higher residual porosities (1.2 and 2.2 vol.%, respectively). In contrast, the third ceramic, not containing tantalum, displayed lower values of these two properties (25.1 GPa/404.5 GPa). However, the corresponding fracture toughness (8.84 MPa m1/2) was relatively higher. This fact can be likely ascribed to the smaller residual porosity (0.3 vol.%) of the sintered material.

Single-phase (Hf-Mo-Nb-Ta-Ti)C high-entropy ceramic: A potential high temperature anti-wear material

2021 ◽  
Vol 157 ◽  
pp. 106883
Author(s):  
Qichun Sun ◽  
Hui Tan ◽  
Shengyu Zhu ◽  
Zongxiao Zhu ◽  
Long Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Single Phase ◽  
High Entropy
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