Synthesis of high‐purity high‐entropy metal diboride powders by boro/carbothermal reduction

2019 ◽  
Vol 102 (12) ◽  
pp. 7071-7076 ◽  
Author(s):  
Da Liu ◽  
Honghua Liu ◽  
Shanshan Ning ◽  
Beilin Ye ◽  
Yanhui Chu
Keyword(s):  
High Purity ◽  
Carbothermal Reduction ◽  
High Entropy

Synthesis of β-Sialon/Ti(C,N) Composites Using Low and Middle Grade Bauxite and Ilmenite by Carbothermal Reduction-Nitridation

2012 ◽  
Vol 624 ◽  
pp. 112-116 ◽  
Author(s):  
De Xin Yang ◽  
Yan Gai Liu ◽  
Ding Yun Ye ◽  
Zhao Hui Huang ◽  
Ming Hao Fang ◽  
...  
Keyword(s):  
Reaction Temperature ◽  
High Purity ◽  
Carbothermal Reduction ◽  
Nitrogen Atmosphere ◽  
Reducing Agent ◽  
Raw Material ◽  
Reaction Products ◽  
Middle Grade ◽  
Rutile Tio2

β-Sialon/Ti(C,N) composites were prepared using low and middle grade bauxite and ilmenite as raw material,while coke as reducing agent in high purity nitrogen atmosphere through carbothermal reducrion-nitridation(CRN).The main phases of low and middle grade bauxite are kaolinire(Al2O3•2SiO2•2H2O) and (Al2O3•H2O)2 and ilmenite mainly contain ilmenite(FeTiO3) and rutile(TiO2).The reaction products of bauxite are the β-Sialon(Z=3,Si3Al3O3N5) while those of ilmenite are TiC and Fe.The results showed that the main phases are β-Sialon,Ti(C,N),Al2O3 and Fe when the reaction temperature is at 1400°C holding for 4 hours(10wt% ilmenite and 90wt% bauxite as raw material).However,β-Sialon decomposes into 21R at 1450°C and into 15R and AlN at 1500°C.So 1400°C is selected as the proper temperature to synthesize β-Sialon/Ti(C,N) composites.At 1400°C,the β-Sialon crystals with the largest quantity grow well and show long column in shape.With the increase of the reacrion temperature β-Sialon begin to decompose,the β-Sialon crystals change to short columnar,with the number decreasing quickly.

scholarly journals Optimal preparation of high-entropy boride-silicon carbide ceramics

2020 ◽  
Author(s):  
Yan Zhang ◽  
Shi-Kuan Sun ◽  
Wei-Ming Guo ◽  
Liang Xu ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Carbothermal Reduction ◽  
Powder Processing ◽  
Full Density ◽  
High Entropy ◽  
Sic Ceramics ◽  
Reduction Methods ◽  
Borothermal Reduction ◽  
Carbide Ceramics ◽  
Silicon Carbide Ceramics

Abstract High-entropy boride-silicon carbide (HEB-SiC) ceramics were fabricated by using boride-based powders prepared from borothermal and boro/carbothermal reduction methods. The effects of processing routes (borothermal reduction and boro/carbothermal reduction) of HEB powders were examined. HEB-SiC ceramics with nearly relatively full density (>98%) were prepared by spark plasma sintering at 2000oC. It was demonstrated that the addition of SiC led to slightly coarsening of the microstructure. The HEB-SiC ceramics prepared from boro/carbothermal reduction powders showed the fine-grained microstructure and higher Vickers’ hardness but lower fracture toughness values as compared with the same composition prepared from borothermal reduction powders. These results indicated that the selection of the powder processing method and the addition of SiC phase could contribute to the optimal preparation of high-entropy boride-based ceramics.

scholarly journals Synthesis of Silicon Carbide Powders from Methyl-Modified Silica Aerogels

2020 ◽  
Vol 10 (18) ◽  
pp. 6161
Author(s):  
Kyoung-Jin Lee ◽  
Yanggu Kang ◽  
Young Hun Kim ◽  
Se Won Baek ◽  
Haejin Hwang
Keyword(s):  
Silicon Carbide ◽  
High Purity ◽  
Silica Aerogel ◽  
Carbothermal Reduction ◽  
Single Phase ◽  
Phase Evolution ◽  
Silica Aerogels ◽  
Methyl Groups ◽  
Modified Silica ◽  
Lower Temperature

β-silicon carbide (SiC) powders were synthesized by the carbothermal reduction of methyl-modified silica aerogel/carbon mixtures. The correlations between the phase evolution and morphologies of the SiC powders and the C/SiO2 ratio were investigated. At a C/SiO2 ratio of 3, β-SiC formed at 1425 °C and single-phase SiC powders were obtained at 1525 °C. The methyl groups (-CH3) on the silica aerogel surfaces played important roles in the formation of SiC during the carbothermal reduction. SiC could be synthesized from the silica aerogel/carbon mixtures under lower temperature and C/SiO2 ratios than those needed for quartz or hydrophilic silica. The morphology of the SiC powder depended on the C/SiO2 ratio. A low C/SiO2 ratio resulted in β-SiC powder with spherical morphology, while agglomerates consisting of fine SiC particles were obtained at the C/SiO2 ratio of 3. High-purity SiC powder (99.95%) could be obtained with C/SiO2 = 0.5 and 3 at 1525 °C for 5 h.

scholarly journals Synthesis of high-entropy boride powders via boro/carbothermal reduction method

2021 ◽  
pp. 1-7
Author(s):  
Zhigang Yang ◽  
Yubo Gong ◽  
Shaolei Song ◽  
Gang Yu ◽  
Shiqing Ma
Keyword(s):  
Carbothermal Reduction ◽  
Reduction Method ◽  
High Entropy ◽  
Carbothermal Reduction Method

Catalyst-free growth of high purity 3C-SiC nanowires film on a graphite paper by sol-gel and ICVI carbothermal reduction

2018 ◽  
Vol 212 ◽  
pp. 86-89 ◽  
Author(s):  
Hongjiao Lin ◽  
Hejun Li ◽  
Qingliang Shen ◽  
Xiaohong Shi ◽  
Xinfa Tian ◽  
...  
Keyword(s):  
High Purity ◽  
Carbothermal Reduction ◽  
Sol Gel ◽  
Catalyst Free ◽  
Sic Nanowires ◽  
Free Growth

scholarly journals Fine-grained dual-phase high-entropy ceramics derived from boro/carbothermal reduction

2020 ◽  
Author(s):  
Si-Chun Luo ◽  
Wei-Ming Guo ◽  
Kevin Plucknett ◽  
Hua-Tay Lin
Keyword(s):  
Mechanical Properties ◽  
Carbothermal Reduction ◽  
Dual Phase ◽  
Boride Phase ◽  
High Entropy ◽  
Fine Grained ◽  
Grain Sizes ◽  
Pinning Effect ◽  
Precursor Powders ◽  
Reduction Approach

Abstract In the current work fine-grained dual-phase, high-entropy ceramics (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2-(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C with different phase ratios are prepared from powders synthesized via a boro/carbothermal reduction approach, by adjusting the content of B4C and C in the precursor powders. Phase compositions, densification, microstructure, and mechanical properties have been investigated. Due to the combination of pinning effect and the boro/carbothermal reduction approach, the average grain sizes (0.5–1.5 µm) of the dual-phase high-entropy ceramics, were much smaller as compared with previously reported values. The dual-phase high-entropy ceramics with 15 mol% boride phase exhibit the highest Vickers hardness (24.21 GPa) and fracture toughness (3.2 MPa•m1/2).

scholarly journals Synthesis of the superfine high-entropy zirconate nanopowders by polymerized complex method

2021 ◽  
Vol 11 (1) ◽  
pp. 136-144
Author(s):  
Yangjie Han ◽  
Renwang Yu ◽  
Honghua Liu ◽  
Yanhui Chu
Keyword(s):  
Particle Size ◽  
High Purity ◽  
Phase Evolution ◽  
Synthesis Temperature ◽  
Fluorite Phase ◽  
Complex Method ◽  
Crystallinity Degree ◽  
High Entropy ◽  
Polymerized Complex Method ◽  
Compositional Uniformity

AbstractThe high-purity and superfine high-entropy zirconate nanopowders, namely (Y0.25La0.25Sm0.25Eu0.25)2Zr2O7 nanopowders, without agglomeration, were successfully synthesized via polymerized complex method at low temperatures for the first time. The results showed that the crystallinity degree, lattice strain, and particle size of the as-synthesized powders were gradually enhanced with the increase of the synthesis temperature from 800 to 1300 °C. The as-synthesized powders involved fluorite phase in the range of 800–1200 °C while they underwent the phase evolution from fluorite to pyrochlore at 1300 °C. It is worth mentioning that the as-synthesized powders at 900 °C are of the highest quality among all the as-synthesized powders, which is due to the fact that they not only possess the particle size of 11 nm without agglomeration, but also show high purity and good compositional uniformity.

Dense and pure high-entropy metal diboride ceramics sintered from self-synthesized powders via boro/carbothermal reduction approach

2019 ◽  
Vol 62 (12) ◽  
pp. 1898-1909 ◽  
Author(s):  
Junfeng Gu ◽  
Ji Zou ◽  
Shi-Kuan Sun ◽  
Hao Wang ◽  
Su-Yang Yu ◽  
...  
Keyword(s):  
Carbothermal Reduction ◽  
High Entropy ◽  
Reduction Approach

scholarly journals Optimal preparation of high-entropy boride-silicon carbide ceramics

2020 ◽  
Author(s):  
Yan Zhang ◽  
Shi-Kuan Sun ◽  
Wei-Ming Guo ◽  
Liang Xu ◽  
Wei Zhang ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Carbothermal Reduction ◽  
Powder Processing ◽  
High Entropy ◽  
Fine Grained ◽  
Sic Ceramics ◽  
Reduction Methods ◽  
Borothermal Reduction ◽  
Carbide Ceramics ◽  
Silicon Carbide Ceramics

Abstract High-entropy boride-silicon carbide (HEB-SiC) ceramics were fabricated using boride-based powders prepared from borothermal and boro/carbothermal reduction methods. The effects of processing routes (borothermal reduction and boro/carbothermal reduction) on the HEB powders were examined. HEB-SiC ceramics with > 98% theoretical density were prepared by spark plasma sintering at 2000 °C. It was demonstrated that the addition of SiC led to slight coarsening of the microstructure. The HEB-SiC ceramics prepared from boro/carbothermal reduction powders showed a fine-grained microstructure and higher Vickers’ hardness but lower fracture toughness value as compared with the same composition prepared from borothermal reduction powders. These results indicated that the selection of the powder processing method and the addition of SiC phase could contribute to the optimal preparation of high-entropy boride-based ceramics.

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