• Title/Summary/Keyword: $B_4C$

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Effect of TiB2 Coating on the Mechanical Properties of B4C/Al Composites Prepared by Infiltration Process (TiB2코팅이 함침법으로 제조되는 B4C/Al 복합체의 기계적 특성에 미치는 영향)

  • 김선혜;임경란;심광보;김창삼
    • Journal of the Korean Ceramic Society
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    • v.40 no.8
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    • pp.777-783
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    • 2003
  • The mechanical properties of B$_4$C/Al composites normally depend on the species and quantity of reaction products between B$_4$C and Al and then the control of reaction products is necessary to make desirable composites for lightweight advanced or armor materials. TiB$_2$ is chemically inert with aluminum and has a lower contact angle (85$^{\circ}$ at 100$0^{\circ}C$) to liquid aluminum than B$_4$C. Thus, TiB$_2$ coating on B$_4$C may lower infiltration temperature of aluminum when the B$_4$C/Al composites is fabricated by infiltration process. In this study, the effects of TiB$_2$ on the microstructure and mechanical properties of the B$_4$C/Al composites have been investigated. TiB$_2$ coated B$_4$C powder was prepared using the sol-gel technique. It was found that the B$_4$C surface is homogeneously covered with TiB$_2$ having a particles size of 20-50 nm. While the B$_4$C/Al composites prepared by infiltration after TiB$_2$ coating had 17 wt% of unreacted Al, on the other hand, the B$_4$C/Al composites without coating included 14 wt% of Al. As a result, the composites infiltrated after the coating showed higher fracture toughness and lower hardness. This strongly suggests that TiB$_2$ not only lowers the infiltration temperature, but also inhibits the reaction between B$_4$C and Al.

Reaction Synthesis and Mechanical Properties of $B_4C$-based Ceramic Composites

  • Han, Jae-Ho;Park, Sang-Whan;Kim, Young-Do
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.1080-1081
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    • 2006
  • In this investigation, $B_4C$ based ceramic composites were fabricated by in-situ reaction hot pressing using $B_4C$, TiC SiC powder as starting materials. The reaction synthesized composites by hot pressing at $1950^{\circ}C$ was found to posses very high relative density. The reaction synthesized $B_4C$ composites comprise $B_4C$, $TiB_2$, SiC and graphite by the reaction between TiC and $B_4C$. The newly formed $TiB_2$ and graphite was embedded both inside grain and at grain boundary $B_4C$. The mechanical properties of reaction synthesized $B_4C-TiB_2-SiC$-graphite composites were more enhanced compared to those of monolithic $B_4C$.

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Pressureless Infiltration Processing of B4C/Al Composite by Surface Modification (표면 개질에 의한 상압에서의 B4C/Al복합체 제조 방법)

  • 임경란;강덕일;김창삼
    • Journal of the Korean Ceramic Society
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    • v.40 no.2
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    • pp.128-131
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    • 2003
  • Formation of$B_4C/Al$composite by pressureless infiltration was investigated by lowering wetting angle via surface modification of $B_4C$powder with alumina precursor. Surface modification was confirmed by zeta potential analysis. The$B_4C/Al$composite was prepared by placing an Al 6061 disk on the$B_4C$preform and heating at $1030{\circ}C$/20 min under a flowing argon, but no infiltration took place for a bare $B_4C$ preform even at$1250{\circ}C$/30 min. Analysis of XRD and SEM showed the $Al_3BC$phase besides$B_4C$and Al, but no trace of deteriorative$A1_4C_3$.

Improvement of Impact Resistance of B4C Tile Inserted B4Cp/Al7075 Hybrid Composites Through Interface Control (B4C tile 삽입 B4Cp/Al7075 하이브리드 복합재의 계면 제어를 통한 내충격 특성의 향상)

  • Park, Jongbok;Lee, Taegyu;Lee, Donghyun;Cho, Seungchan;Lee, Sang-Kwan;Hong, Soon Hyung;Ryu, Ho Jin
    • Composites Research
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    • v.33 no.5
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    • pp.235-240
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    • 2020
  • In this study, in order to improve the impact resistance of the B4C tile-inserted B4Cp/Al7075 hybrid composite, a control method of the B4C/Al7075 interface was developed and the characteristics of the controlled interface were analyzed. B2O3, Ni, and Si were coated on the B4C tile surface using additional thermal oxidation, electroless plating, and plasma spraying. The coated B4C tile is inserted into the B4Cp/Al7075 composite material using the liquid pressurization method. Interfacial energy, bonding strength, and impact resistance were measured to analyze the effect of the coating. All coatings enhanced interfacial energy, bonding strength, and impact resistance, and in particular, it was confirmed that the impact resistance increased by 86.8% when B2O3 coating was used. This study is significant in developing and analyzing a core surface treatment method that improves the performance of B4C/Al series composites, which are attracting attention as next-generation lightweight amour and bulletproof materials.

Microstructure and mechanical properties of B4C-SiC composites (탄화붕소-탄화규소 복합체의 미세구조와 기계적 특성)

  • So, Sung Min;Kim, Kyoung Hun;Park, Joo Seok;Kim, Min Suk;Kim, Hyung Sun
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.29 no.6
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    • pp.338-344
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    • 2019
  • B4C-SiC composites were fabricated using hot press sintering method without sintering additives at 1,900~2,000℃ under a pressure of 40 MPa. The crystal phase, relative density, microstructure, and mechanical properties of B4C-SiC composites were evaluated. When B4C and SiC were uniformly dispersed in the composite, grain growth was inhibited, and a sintered body with a fine and uniform microstructure, with improved mechanical properties, was fabricated. The relative density of B4C-SiC composites sintered under 2,000℃ of temperature and 40 MPa of pressure was over 99.8 %, and the bending strength and Vicker's hardness at 50 wt% of B4C were 645 MPa and 30.6 GPa, respectively.

Effect of Addition of Other Componene (B4C, Mn, TiB2, B) on TiC-Ni3Al Cermet (TiC-Ni3Al Cermet에 타성분(B4C, Mn, TiB2, B) 첨가의 영향)

  • 김지헌;이완재
    • Journal of Powder Materials
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    • v.9 no.5
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    • pp.352-358
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    • 2002
  • The effects of boron or manganese added as $B_4C$, Mn, $TiB_2$, B on TiC-30vo1.%$Ni_3Al$ cermet sintered at 1380 and $1400^{\circ}C$ for 1 hour, were examined in relation with shrinkage, relative density, microstructure, lattice parameter, hardness and fracture toughness ($K_{IC}$). The results are summarized as follows: 1) The highest shrink-age showed about 30.5% in the specimen added B$_4$C and the maximum relative density was about 99% in the specimen added $TiB_2$; 2) The grains of TiC were grown during sintering and made the surrounding structure by adding boron and manganese. The largest grain size showed about $2.8\mutextrm{m}$ in the specimen with boron sintered at $1400^{\circ}C$;3) The lattice parameter of TiC was about $4.325\AA$ and $Ni_3Al$ about $3.592\AA$ by adding other elements; 4) The highest hardness was about $1100kgf/\textrm{mm}^2$ in the specimen with B4C; 5) The fracture toughness ($K_{IC}$) showed about $15MNm^{-3/2}$ in the specimen added $TiB_2$.

Sintering Behavior of $B_4C-SiC$ Composite ($B_4C-SiC$ 복합체의 상압소결거동)

  • 김득중;강을손
    • Journal of the Korean Ceramic Society
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    • v.31 no.7
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    • pp.739-744
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    • 1994
  • The B4C-C system was investigated to gain an understanding of the sintering behaviors of B4C. In order to get sintered density of 97% TD, sintering temperature of 225$0^{\circ}C$ was necessary. Since such a high temperature operation is actually difficult on a commercial basis, our objective was to examine the possibility of decreasing the sintering temperature by adding SiC. The addition of SiC in B4C increases the sintering rate about at 210$0^{\circ}C$ and results in a fine microstructure with more than 98% relative density on 55 wt% B4C-40wt% SiC-5 wt% C composition. The probability of liquid phase sintering was investigated, but the evidences of liquid phase formation were not observed with XRD and TEM observation. It was proposed that the addition of SiC and carbon to B4C reduce interface energy during sintering, which results in enhanced grain-boundary diffusion. Thus, the enhanced grain-boundary diffusion and retarded grain growth by SiC improve densification.

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Purification and Characterization of Lactate Dehydrogenase Isozymes in Channa argus (가물치(Channa argus) 젖산탈수소효소 동위효소들의 정제 및 특성)

  • Park, Eun-Mi;Yum, Jung-Joo
    • Journal of Life Science
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    • v.20 no.2
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    • pp.260-268
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    • 2010
  • The lactate dehydrogenase (EC 1.1.1.27, LDH) isozymes in tissues from Channa argus were purified and characterized by biochemical, immunochemical and kinetic methods. The activity of LDH in skeletal muscle was the highest at 380.4 units and those in heart, eye and brain tissues were 13.4, 3,5 and 5.4 units, respectively. Citrate synthase (EC 4.1.3.7, CS) activity in heart tissue was the highest at 20.7 units. LDH/CS in skeletal muscle, heart, eye and brain tissues were 172.9, 0.6, 0.32 and 0.47. Protein concentration in skeletal muscle tissue was 14.7 mg/g and specific activities of LDH in skeletal muscle, heart, eye and brain tissues were 25.88, 0.79, 0.31 and 1.38 units/mg, respectively. Therefore, skeletal muscle tissue was anaerobic and heart tissue was aerobic. The LDH isozymes in tissues were identified by polyacrylamide gel electrophoresis, immunoprecipitation and Western blot with antiserum against $A_4$, $B_4$, and eye-specific $C_4$. LDH $A_4$, $A_3B$, $A_2B_2$. $AB_3$ and $B_4$ isozymes were detected in every tissue, $C_4$, $AC_3$, $A_2C_2$ and $A_3C$ were detected in eye tissue, and $A_3C$ was found in brain tissue. LDH $A_4$, $A_3B$, $A_2B_2$, $AB_3$, $B_4$, eye-specific $C_4$ isozymes were purified by affinity chromatography and Preparative PAGE Cells. The LDH $A_4$ isozyme was purified in the fraction from elution with $NAD^+$ containing buffer of affinity chromatography. Eye-specific $C_4$ isozyme was eluted right after $A_4$, after which $B_4$ isozyme was eluted with plain buffer. As a result, one part of molecular structures in $A_4$, $B_4$ and eye-specific $C_4$ were similar, but were different from each other in $B_4$ and $C_4$. Therefore the subunit A may be conservative in evolution, and the evolution of subunit B seems to be faster than that of subunit A. The activity of LDH $A_4$, $A_2B_2$, $B_4$, and eye-specific $C_4$ isozymes remained at 39.98, 21.28, 19.67 and 16.87% as a result of the inhibition by 10 mM of pyruvate, so the degree of inhibition was very high. The $Km^{PYR}$ values were 0.17, 0.27 and 0.133 mM in $A_4$, $B_4$ and eye-specific $C_4$ isozymes, respectively. The optimum pH of LDH $A_4$, $B_4$, eye-specific $C_4$, $A_2B_2$, $A_3B$, and $AB_3$ were pH 6.5, pH 8.5, pH 5.5, pH 6.0-6.5, pH 5.0 and pH 7.5. The $A_4$ and heterotetramer isozymes stabilized a broad range of pH. Especially, LDH activities in skeletal muscle tissue were high, resulting in a high degree of muscle activity.LDH metabolism in eye tissue seems to be converted faster from pyruvate to lactate by eye-specific $C_4$ isozyme as eye-specific $C_4$ have the highest affinity for pyruvate, and right after the conversion, oxidation of lactate was induced by $A_4$ isozyme. It was found that expression of Ldh-C, affinity to substrate and reaction time of $C_4$ isozyme were different according to the ecological environmental and feeding capturing patterns.

Effect of Addition of Boron Carbide on the Graphitization and Oxidation Resistance of Raw Cokes (Raw Cokes의 흑연화 및 내산화성에 미치는 $B_4C$첨가 효과)

  • 염희남;김경자;김인기;정윤중
    • Journal of the Korean Ceramic Society
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    • v.34 no.4
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    • pp.413-419
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    • 1997
  • The specimens which were prepared from cokes with additions of 0~25 wt% B4C were sintered in Ar atmosphere at 220$0^{\circ}C$. The effects of B4C content on graphitization and oxidation resistance of cokes were investigated. B4C accelerates the graphitization of cokes and at 220$0^{\circ}C$ the degree of graphitization increased from 0.33 which is the value of pure carbon to 0.56, which increased bluk density and porosity. Especially bending strength increased as th graphitization temperature increased. Oxidation resistance property was greatly improved when B4C was added more than 10wt% at 80$0^{\circ}C$ and when B4C was added more than 20wt% at 100$0^{\circ}C$. This was because that the thin layer of B2O3 glass phase on the surface of the composite could be identified to increase the oxidation resistance.

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Thermal Stability and Behavior of Isothermal Crystallization in Fe-P-C-B-(AI-Ge) Amorphous Alloys (Fe-P-C-B-(AI-Ge)계 비정질합금의 열적 안정성과 등온결정화 거동)

  • Jeon, U-Yong;Guk, Jin-Seon;Bae, In-Seong;Seol, Gyeong-Won
    • Korean Journal of Materials Research
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    • v.8 no.11
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    • pp.1026-1030
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    • 1998
  • Thermal properties of Fe- base amorpous alloys were investigated. $Fe_{80}P_6C_{12}B_{12}$ and $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloys were fabricated by melt spinning method and thermal analysis was done by differential scanning calorimeter. After isothermal crystallization. the Avrami exponents of $Fe_{80}P_6C_{12}B_{12}$ and $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloys were 1.8-2.2 and 2.5-4.0, respectively. It means the former alloy shows diffusion controlled growth and the latter one shows interface controlled growth. For $Fe_{80}P_6C_{12}B_{12}$ and $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloys. the activation energies of isothermal crystallization was 353 and 371kJlmol. Also the activation energies of nucleation and growth were 301, 324kJlmol and 273. 30lkJ/mol, respectively. Thus $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloy is considered to be more stable than $Fe_{73}P_{11}C_6B_4AI_4Ge_2$ amorphous alloy.

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