• Title/Summary/Keyword: aluminum nitride

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Optimization of chemical mechanical polishing for bulk AlN single crystal surface (화학적 기계적 연마 공정을 통한 bulk AlN 단결정의 표면 가공)

  • Lee, Jung Hun;Park, Cheol Woo;Park, Jae Hwa;Kang, Hyo Sang;Kang, Suk Hyun;Lee, Hee Ae;Lee, Joo Hyung;In, Jun Hyeong;Kang, Seung Min;Shim, Kwang Bo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.28 no.1
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    • pp.51-56
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    • 2018
  • To evaluate surface characteristics of AlN single crystal grown by physical vapor transport (PVT) method, chemical mechanical polishing (CMP) were performed with diamond slurry and $SiO_2$ slurry after mechanical polishing (MP), then the surface morphology and analysis of polishing characteristics of the slurry types were analyzed. To estimate how pH of slurry effects polishing process, pH of $SiO_2$ slurry was controlled, the results from estimating the effect of zeta potential and MRR (material removal rate) were compared in accordance with each pH via zeta potential analyzer. Eventually, surface roughness RMS (0.2 nm) could be derived with atomic force microscope (AFM).

Microstructure and thermal conductivity of AIN ceramics with ${Y_2}{O_3}$ fabricated by pressureless sintering (상압 소결법으로 제조된 이트리아 첨가 질화 알루미늄 세라믹스의 미세 구조 및 열전도도)

  • Chae, Jae-Hong;Park, Joo-Seok;Ahn, Jong-Pil;Kim, Kyoung-Hun
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.19 no.1
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    • pp.33-38
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    • 2009
  • The effect of ${Y_2}{O_3}$ as a sintering additive on thermal conductivity and microstructure of pressureless sintered AIN ceramics was investigated at sintering temperature range from 1,700 to $1,900^{\circ}C$. ${Y_2}{O_3}$ added AIN specimens showed higher densification rate than pure AIN because of the formation of the yttrium aluminates secondary phase by reaction of ${Y_2}{O_3}$ and ${Al_2}{O_3}$ of AIN surface. The thermal conductivity of AIN specimens was promoted by the addition of ${Y_2}{O_3}$ in spite of the formation of secondary phase in AIN gram boundaries and grain boundary triple junction, because ${Y_2}{O_3}$ addition could reduced the oxygen contents in AIN lattice which is primary factor of thermal conductivity. The them1al conductivity of AIN specimens was promoted by increasing sintering time because the increases of average grain size and the elimination of secondary phases from the grain boundary due to the evaporation. Particularly. the thermal conductivity of AIN specimen sintered at $1,900^{\circ}C$ for 5 hours improved over 20 %. $141\;Wm^{-1}K^{-1}$, compared with the specimen sintered at $1,900^{\circ}C$ for 1 hour.

The study of evaluating surface characteristics and effect of thermal annealing process for AlN single crystal grown by PVT method (PVT법으로 성장된 AlN 단결정의 표면 특성 평가 및 고온 어닐링 공정의 효과에 대한 연구)

  • Kang, Hyo Sang;Kang, Suk Hyun;Park, Cheol Woo;Park, Jae Hwa;Kim, Hyun Mi;Lee, Jung Hun;Lee, Hee Ae;Lee, Joo Hyung;Kang, Seung Min;Shim, Kwang Bo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.27 no.3
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    • pp.143-147
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    • 2017
  • To evaluate surface characteristics and improve crystalline quality of AlN single crystal grown by physical vapor transport (PVT) method, wet chemical etching process using $KOH/H_2O_2$ mixture in a low temperature condition and thermal annealing process was proceeded respectively. Conventional etching process using strong base etchant at a high temperature (above $300^{\circ}C$) had formed over etching phenomenon according to crystalline quality of materials. When it occurred to over etching phenomenon, it had a low reliability of dislocation density because it cannot show correct number of etch pits per estimated area. Therefore, it was proceeded to etching process in a low temperature (below $100^{\circ}C$) using $H_2O_2$ as an oxidizer in KOH aqueous solution and to be determined optimum etching condition and dislocation density via scanning electron microscope (SEM). For improving crystalline quality of AlN single crystal, thermal annealing process was proceeded. When compared with specimens as-prepared and as-annealed, full width at half maximum (FWHM) of the specimen as-annealed was decreased exponentially, and we analyzed the mechanism of this process via double crystal X-ray diffraction (DC-XRD).

A Scale-Up Test for Preparation of AlN by Carbon Reduction and Subsequent Nitridation Method (탄소환원질화법에 의한 AlN 제조 규모확대 시험결과)

  • Park, Hyung-Kyu;Kim, Sung-Don;Nam, Chul-Woo;Kim, Dae-Woong;Kang, Moon-Soo;Shin, Gwang-Hee
    • Resources Recycling
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    • v.25 no.5
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    • pp.75-83
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    • 2016
  • AlN powder was prepared by carbon reduction and subsequent nitridation method through the scale-up experiments of 0.7 ~ 1.5 kg per batch. AlN powder was synthesized using the mixture of $Al_2O_3$ powder and carbon black at $1,550{\sim}1,750^{\circ}C$ for 0.5 ~ 4 hours under nitrogen atmosphere (flow rate of nitrogen gas: $10{\sim}40{\ell}/min$) at $2.0{\times}10^{-1}Torr$. Experimental results showed that $1,700{\sim}1,750^{\circ}C$ for the reaction temperature, 3 hr for reaction time, and $40{\ell}/min$ for the flow rate of nitrogen gas were the optimal conditions. Also, in order to remove carbon in the synthesized AlN, the remained carbon was removed at $650{\sim}750^{\circ}C$ for 1 ~ 2 hr using horizontal tube furnace. The results showed that 1 : 3.2 mol ratio of $Al_2O_3$ to carbon black, reaction temperature of $750^{\circ}C$, reaction time of 2 hours, rotating speed of 1.5 rpm under atmosphere condition were the optimal conditions. Under these conditions, high-purity AlN powder over 99% could be prepared: carbon and oxygen contents of the AlN powder were 835 ppm and 0.77%, respectively.

Improving Thermal Conductivity of Neutron Absorbing B4C/Al Composites by Introducing cBN Reinforcement (cBN 입자상 강화재 첨가에 따른 중성자 흡수용 B4C/Al 복합재의 열전도도 변화 연구)

  • Minwoo Kang;Donghyun Lee;Tae Gyu Lee;Junghwan Kim;Sang-Bok Lee;Hansang Kwon;Seungchan Cho
    • Composites Research
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    • v.36 no.6
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    • pp.435-440
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    • 2023
  • This study aimed to enhance the thermal conductivity of B4C/Al composite materials, commonly used in transport/storage containers for spent nuclear fuel, by incorporating both boron carbide (B4C) and cubic boron nitride(cBN) as reinforcing agents in an aluminum (Al) matrix. The composite materials were successfully manufactured through a stir casting process and practical neutron-absorbing materials were obtained by rolling the fabricated composite ingot. The evaluation of the thermal conductivity of the fabricated composites was carried out because thermal conductivity is critical for neutron absorbing materials. The thermal conductivity measurement results indicated an approximately 3% increase in thermal conductivity under the same volume fraction when compared to composite materials using only B4C particles. Through neutron absorption cross-sectional area calculations, it was confirmed that the neutron absorption capability decreased to a negligible level. Based on the findings of this study, new design approaches for neutron absorption materials are proposed, contributing to the development of high-performance transport/storage containers.