scholarly journals Densification of ultra-refractory transition metal diboride ceramics

2020 ◽  
Vol 52 (1) ◽  
pp. 1-14
Author(s):  
W.G. Fahrenholtz ◽  
G.E. Hilmas ◽  
Ruixing Li
Keyword(s):  
Transition Metal ◽  
Hot Pressing ◽  
Full Density ◽  
Oxygen Impurity ◽  
Self Diffusion ◽  
Melting Temperatures ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Metal Diborides ◽  
Transition Metal Diborides

The densification behavior of transition metal diboride compounds was reviewed with emphasis on ZrB2 and HfB2. These compounds are considered ultra-high temperature ceramics because they have melting temperatures above 3000?C. Densification of transition metal diborides is difficult due to their strong covalent bonding, which results in extremely high melting temperatures and low self-diffusion coefficients. In addition, oxide impurities present on the surface of powder particles promotes coarsening, which further inhibits densification. Studies prior to the 1990s predominantly used hot pressing for densification. Those reports revealed densification mechanisms and identified that oxygen impurity contents below about 0.5 wt% were required for effective densification. Subsequent studies have employed advanced sintering methods such as spark plasma sintering and reactive hot pressing to produce materials with nearly full density and higher metallic purity. Further studies are needed to identify fundamental densification mechanisms and further improve the elevated temperature properties of transition metal diborides.

High-entropy transition metal diborides by reactive and non-reactive spark plasma sintering: A comparative investigation

2020 ◽  
Vol 40 (4) ◽  
pp. 942-952 ◽  
Author(s):  
Giovanna Tallarita ◽  
Roberta Licheri ◽  
Sebastiano Garroni ◽  
Simone Barbarossa ◽  
Roberto Orrù ◽  
...  
Keyword(s):  
Transition Metal ◽  
Spark Plasma Sintering ◽  
Comparative Investigation ◽  
High Entropy ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Metal Diborides ◽  
Transition Metal Diborides

Ultra-Fine Grained Ti-15Mo Alloy Prepared by Powder Metallurgy

2018 ◽  
Vol 941 ◽  
pp. 1276-1281
Author(s):  
Anna Terynková ◽  
Jiří Kozlík ◽  
Kristína Bartha ◽  
Tomáš Chráska ◽  
Josef Stráský
Keyword(s):  
Powder Metallurgy ◽  
Bulk Material ◽  
Alpha Phase ◽  
Full Density ◽  
Fine Grained ◽  
Cryogenic Milling ◽  
Aircraft Manufacturing ◽  
Plasma Sintering ◽  
Beta Matrix ◽  
Spark Plasma

Ti-15Mo alloy belongs to metastable β-Ti alloys that are currently used in aircraft manufacturing and Ti15Mo alloy is a perspective candidate for the use in medicine thanks to its biotolerant composition. In this study, Ti15Mo alloy was prepared by advanced techniques of powder metallurgy. The powder of gas atomized Ti-15Mo alloy was subjected to cryogenic milling to achieve ultra-fine grained microstructure within the powder particles. Powder was subsequently compacted using spark plasma sintering (SPS). The effect of cryogenic milling on the microstructure and phase composition of final bulk material after SPS was studied by scanning electron microscopy. Sintering at 750°C was not sufficient for achieving full density in gas atomized powder, while milled material could be successfully sintered at this temperature. Alpha phase particles precipitated during sintering and their size, as well as the size of beta matrix grains, was strongly affected by the sintering temperature.

Spark Plasma Sintering and Hot Pressing Sintering of Nanocrystalline WC-10CO-0.8VC

2007 ◽  
Vol 534-536 ◽  
pp. 1229-1232
Author(s):  
Li Hui Zhu ◽  
Guang Jie Shao ◽  
Yi Xiong Liu ◽  
Dave Siddle
Keyword(s):  
Relative Density ◽  
Spark Plasma Sintering ◽  
Hot Pressing ◽  
Nanocrystalline Powders ◽  
Microstructure And Properties ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Hot Pressing Sintering

WC-10Co-0.8VC nanocrystalline powders were sintered by spark plasma sintering (SPS) and hot pressing sintering (HPS), and the microstructure and properties were compared. Results show that, sintered at 1300°C, the sample prepared by SPS for only 3 minutes has higher density than that prepared by HPS for 60 minutes. SEM and SPM observation shows SPS at 1200°C has a more uniform and finer microstructure, and most of the WC grains are smaller than 100nm. It has a relative density of 95.1%, HV30 of 1887, and KIC of 11.5 MPam1/2. If a suitable sintering parameter is chosen, SPS is a promising consolidation technique to prepare nanocrystalline WC-10Co-0.8VC with improved properties.

Microstructure and Magnetic Properties of Hot-Pressed and Hot-Deformed Composite Magnets Produced by Spark Plasma Sintering Method

2011 ◽  
Vol 686 ◽  
pp. 740-744 ◽  
Author(s):  
Yi Long Ma ◽  
Deng Ming Chen ◽  
Qian Shen ◽  
Peng Jun Cao
Keyword(s):  
Magnetic Properties ◽  
Spark Plasma Sintering ◽  
Hot Pressing ◽  
Magnetic Energy ◽  
Pressing Temperature ◽  
Energy Product ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Energy Products ◽  
Fe Addition

Bulk isotropic and anisotropic Nd13.5Fe80.4Ga0.5B5.6 and Nd13.5Fe80.4Ga0.5B5.6/Fe magnets were synthesized by applying spark plasma sintering (SPS) technique. The effect of hot-pressing temperature on the magnetic properties of hot-pressed (HP) and hot-deformed (HD) magnets without additive and with 5% Fe addition was investigated. With increasing sintering temperature for HP magnets, the grain grew gradually. For HD magnets, the optimal magnetic properties could be obtained at hot-pressing temperature 680°C due to the development of desired c-axis texture and uniform microstructure, which resulted from the appropriate and uniform grain size in HP magnets. Fe addition could enhance remanence (Br) and magnetic energy products ((BH)m) of HP and HD magnets. However, the maximum magnetic energy product of HD magnets decreased when hot-pressing temperature was higher than 650°C.

scholarly journals Enabling highly efficient and broadband electromagnetic wave absorption by tuning impedance match in high-entropy transition metal diborides (HE TMB2)

2021 ◽  
Author(s):  
Weiming Zhang ◽  
Fu-Zhi Dai ◽  
Huimin Xiang ◽  
Biao Zhao ◽  
Xiaohui Wang ◽  
...  
Keyword(s):  
Electromagnetic Wave ◽  
Transition Metal ◽  
Impedance Match ◽  
Magnetic Losses ◽  
High Entropy ◽  
Wave Absorption ◽  
Highly Efficient ◽  
Absorbing Materials ◽  
Metal Diborides ◽  
Transition Metal Diborides

AbstractThe advance in communication technology has triggered worldwide concern on electromagnetic wave pollution. To cope with this challenge, exploring high-performance electromagnetic (EM) wave absorbing materials with dielectric and magnetic losses coupling is urgently required. Of the EM wave absorbers, transition metal diborides (TMB2) possess excellent dielectric loss capability. However, akin to other single dielectric materials, poor impedance match leads to inferior performance. High-entropy engineering is expected to be effective in tailoring the balance between dielectric and magnetic losses through compositional design. Herein, three HE TMB2 powders with nominal equimolar TM including HE TMB2-1 (TM = Zr, Hf, Nb, Ta), HE TMB2-2 (TM = Ti, Zr, Hf, Nb, Ta), and HE TMB2-3 (TM = Cr, Zr, Hf, Nb, Ta) have been designed and prepared by one-step boro/carbothermal reduction. As a result of synergistic effects of strong attenuation capability and impedance match, HE TMB2-1 shows much improved performance with the optimal minimum reflection loss (RLmin) of −59.6 dB (8.48 GHz, 2.68 mm) and effective absorption bandwidth (EAB) of 7.6 GHz (2.3 mm). Most impressively, incorporating Cr in HE TMB2-3 greatly improves the impedance match over 1–18 GHz, thus achieving the RLmin of −56.2 dB (8.48 GHz, 2.63 mm) and the EAB of 11.0 GHz (2.2 mm), which is superior to most other EM wave absorbing materials. This work reveals that constructing high-entropy compounds, especially by incorporating magnetic elements, is effectual in tailoring the impedance match for highly conductive compounds, i.e., tuning electrical conductivity and boosting magnetic loss to realize highly efficient and broadband EM wave absorption with dielectric and magnetic coupling in single-phase materials.

scholarly journals Physical, mechanical properties and wear resistance of iron-base matrix materials for sintered diamond tools fabricated by HP and SPS

Mechanik ◽  
2018 ◽  
Vol 91 (10) ◽  
pp. 846-849
Author(s):  
Elżbieta Bączek
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Metal Matrix ◽  
Physical And Mechanical Properties ◽  
Full Density ◽  
Matrix Composites ◽  
Plasma Sintering ◽  
Base Matrix ◽  
Spark Plasma ◽  
Sintered Diamond

Metal matrix composites were prepared by hot pressing (HP) and spark plasma sintering (SPS) techniques. Ball-milled ironbase powders were consolidated to near full density by these methods at 900°C. The physical and mechanical properties of the resulting composites were investigated. The specimens were tested for resistance to both 3-body and 2-body abrasion. The composites obtained by HP method (at 900°C/35 MPa) had higher density, hardness and resistance to abrasion than those obtained by SPS method.

Production of UHTC Complex Shapes and Architectures

2013 ◽  
pp. 246-277 ◽  
Author(s):  
Valentina Medri ◽  
Diletta Sciti ◽  
Elena Landi
Keyword(s):  
High Ratio ◽  
Full Density ◽  
Mechanical And Thermal Properties ◽  
Solar Absorbers ◽  
Plasma Sintering ◽  
Fine Microstructure ◽  
Spark Plasma ◽  
Near Net Shaping ◽  
Net Shaping ◽  
Radiant Burners

In spite of the difficult sinterability of Zr and Hf borides and carbides, recent results highlight that these ceramics can be produced with full density, fine microstructure, and controlled mechanical and thermal properties, through different procedures: pressureless sintering and hot pressing with proper sintering aids, reactive synthesis/sintering procedures starting from precursors, and field assisted technologies like spark plasma sintering. More recently, the use of near net shaping techniques and the development of UHTC porous components open the way to further and innovative applications, where the performances, fixed the material, are linked to 2D or 3D architectures and the high ratio of specific surface area to volume of the component and to the features of the porosity itself. Structural lightweight parts, insulator panels, filters, radiant burners, and solar absorbers are some of the possible applications.

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