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ZIRCONIUM BORIDE/BORON CARBIDE COMPOSITE AND METHOD FOR MANUFACTURING SAME

Foreign code F210010284
File No. (S2019-0386-N0)
Posted date Jan 28, 2021
Country WIPO
International application number 2020JP006751
International publication number WO 2020202878
Date of international filing Feb 20, 2020
Date of international publication Oct 8, 2020
Priority data
  • P2019-070753 (Apr 2, 2019) JP
  • P2019-154503 (Aug 27, 2019) JP
Title ZIRCONIUM BORIDE/BORON CARBIDE COMPOSITE AND METHOD FOR MANUFACTURING SAME
Abstract To provide: a high-density zirconium boride/boron carbide composite having a Vickers hardness Hv of 23 GPa or more and a fracture toughness value KIC of 9.0 MPa•m1/2 or more, said zirconium boride/boron carbide being represented by ZrB2/B4C; and a method for manufacturing the same. The method according to the present invention comprises: a step for preparing a starting material by mixing an amorphous boron powder with an amorphous carbon powder to give a molar ratio B:C of (3.6-6.5):1; a step for weighing a ZrB2 powder in such an amount as to give a theoretical ratio by volume to B4C, which is synthesized from the starting material, ZrB2/B4C of 10/90-60/40 vol% and mixing with the starting material to give a mixed powder; and a step for molding the mixed powder using a die to give a molded article and then sintering the obtained molded article to thereby simultaneously synthesize and sinter the ZrB2/B4C composite.
Outline of related art and contending technology BACKGROUND ART
Zirconium boride (ZrB2), which is an ultra-high temperature heat-resistant ceramic (UHTC) recently attracting attention in the field of engineering ceramics, is a covalent material having a high melting point of Tm = 3200 °C. and is expected to be UHTC for space aircraft at present, but it is difficult to produce dense and high-density sintered compact because of being a difficult-to-sinter material. For example, Patent Document 1 below discloses a method for producing tungsten-added ZrB2 by wet-mixing a predetermined amount of Zr powder, a predetermined amount of tungsten (W) powder, and a predetermined amount of B powder, press-molding the mixture to form a compact, and subjecting the compact to discharge plasma sintering (another name: pulse energization press-sintering). However, the Vickers hardness (Hv) of the sintered compact obtained by using such a manufacturing method is 20.7 GPa at the maximum, and it is desirable to further improve the mechanical properties, and particularly to further improve the strength at high temperatures.
For UHTC which can be used in the atmosphere, the preparation of composites of ZrB2/SiC, ZrB2/B4C, ZrB2/LaB6 based mainly on ZrB2 of metal boride has been studied, however, high melting point compounds are difficult to sinter due to covalent bonding, It is difficult to produce a high-density sintered compact, and it is difficult to produce a high-density sintered compact even if a pulse energization pressure sintering method (Pulsed Electric-current Pressure Sintering: PECPS) suitable for producing a high-density sintered compact of a hard-to-sinter material is used.
Boron carbide (B4C) is known as a material having a light weight (theoretical density Dx = 2.515 Mg · m-3) and a high melting point (Tm = 2450 °C), Since the cubic boron nitride (c-BN) has a hardness (Vickers hardness Hv: 29 ~ 33 GPa) next to cubic boron nitride (c-BN), a composite composed of both ZrB2 and B4C is also one of the possible materials for use as UHTC. However, since B4C is also a covalent hard sintering material, a high temperature and high pressure of 2050 ~ 2150 °C./30 ~ 50 MPa is required for the preparation of ZrB2/B4C composite added to ZrB2, resulting in a high cost production, and there are few reports on the preparation.
Scope of claims (In Japanese)[請求項1]
 ビッカース硬度H vが23GPa以上で、破壊靭性値K ICが9.0MPa・m 1/2以上であり、ホウ化ジルコニウム/炭化ホウ素の理論上の体積比率が10/90~60/40vol%であることを特徴とするホウ化ジルコニウム/炭化ホウ素コンポジット。

[請求項2]
 前記ホウ化ジルコニウム/炭化ホウ素の理論上の体積比率が40/60~60/40vol%であり、1000~1600℃における曲げ強度σ bが500MPa以上であることを特徴とする請求項1に記載のホウ化ジルコニウム/炭化ホウ素コンポジット。

[請求項3]
 ビッカース硬度H vが29GPa以上で、破壊靭性値K ICが9.3MPa・m 1/2以上であり、ホウ化ジルコニウム/炭化ホウ素の理論上の体積比率が20/80~50/50vol%であることを特徴とするホウ化ジルコニウム/炭化ホウ素コンポジット。

[請求項4]
 ホウ化ジルコニウム/炭化ホウ素コンポジットを製造するための方法であって、
 非晶質ホウ素粉体と非晶質炭素粉体をB:C=(3.6~6.5):1のモル比となるように混合を行ない、非晶質ホウ素と非晶質炭素とから成る出発原料を調製する工程と、
 ホウ化ジルコニウム粉体を、前記出発原料から合成される炭化ホウ素との理論上の体積比率がZrB 2/B 4C=10/90~60/40vol%となるように秤量し、前記出発原料と混合して、混合粉を得る工程と、
 前記混合粉を用いて金型成形を行い、所望の形状を有した成形体を得、得られた成形体を焼結してホウ化ジルコニウム/炭化ホウ素コンポジットを合成同時焼結する工程
を含むことを特徴とするホウ化ジルコニウム/炭化ホウ素コンポジットの製造方法。

[請求項5]
 前記焼結が、10Pa以下の真空中、1800~2000℃の焼結温度、10~100MPaの加圧力および5~30分の保持時間の条件でのパルス通電加圧焼結であることを特徴とする請求項4に記載のホウ化ジルコニウム/炭化ホウ素コンポジットの製造方法。

[請求項6]
 前記ZrB 2とB 4Cの理論上の体積比率が20/80~50/50vol%の範囲であることを特徴とする請求項4又は5に記載のホウ化ジルコニウム/炭化ホウ素コンポジットの製造方法。
  • Applicant
  • ※All designated countries except for US in the data before July 2012
  • THE DOSHISHA
  • Inventor
  • HIROTA Ken
  • KATO Masaki
  • MIYAMOTO Hiroyuki
  • Tung Duy Le
IPC(International Patent Classification)
Specified countries National States: AE AG AL AM AO AT AU AZ BA BB BG BH BN BR BW BY BZ CA CH CL CN CO CR CU CZ DE DJ DK DM DO DZ EC EE EG ES FI GB GD GE GH GM GT HN HR HU ID IL IN IR IS JO JP KE KG KH KN KP KR KW KZ LA LC LK LR LS LU LY MA MD ME MG MK MN MW MX MY MZ NA NG NI NO NZ OM PA PE PG PH PL PT QA RO RS RU RW SA SC SD SE SG SK SL ST SV SY TH TJ TM TN TR TT TZ UA UG US UZ VC VN WS ZA ZM ZW
ARIPO: BW GH GM KE LR LS MW MZ NA RW SD SL SZ TZ UG ZM ZW
EAPO: AM AZ BY KG KZ RU TJ TM
EPO: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR
OAPI: BF BJ CF CG CI CM GA GN GQ GW KM ML MR NE SN ST TD TG

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