• Korean Journal of Materials Research
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• v.6 no.4
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• pp.428-435
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• 1996

초미립 SiC분말과 SiC platelet을 2차성으로 Si3N4에 첨가하여 SiC/Si3N4 하이브리드 복합체를 가압소결로 제조한 후 2차상의 영향을 조사한 결과핫프레스법을 이용한 경우 SiC platelet은 Si3N4 기지 복합채의 치밀화를 저해하지 않고 초미립의 SiC 첨가는 Si3N4의 입성장을 효과적으로 억제하여 미세한 $\beta$-Si3N4의 grain을 형성함을 관찰하였다. 초미립 SiC첨가를 통한 복합체의 강도 증진은 상대적으로 $\beta$-Si3N4입자의 미세화에 의한 인성의 저하를 유도하나 SiC platelet을 첨가하여 급격한 강도 저하 없이 높은 인성을 갖는 하이브리드 복합체를 제조할 수 있었으며 SiC/Si3N4 하이브리드 복합체의 인성증진은 elongated $\beta$-Si3N4와 platelet SiC의 debonding에 의한 grain pull-out 영향임을 알 수 있었다.

• Korean Journal of Materials Research
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• v.27 no.11
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• pp.603-608
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• 2017

$Si_3N_4$ is a ceramic material attracting attention in many fields because of its excellent abrasion resistance. In addition, Ti and TiAl alloys are metals used in a variety of high temperature environments, and have attracted much attention because of their high strength and high melting points. Therefore, study of the interface reaction between $Si_3N_4/Ti$ and $Si_3N_4/TiAl$ can be a useful practice to identify phase selection and diffusion control. In this study, $Si_3N_4/Ti_5Si_3+TiN/TiN/Ti$ diffusing pairs were formed in the $Si_3N_4/Ti$ interfacial reaction and $Si_3N_4/TiN(Al)/Ti_3Al/TiAl$ diffusion pathway was identified in the $Si_3N_4/TiAl$ interfacial reaction. The diffusion layers of the interface reactions were identified and, to investigate the kinetics of the diffusion layer, the integrated diffusion coefficients were estimated.

• The Korean Journal of Ceramics
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• v.5 no.3
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• pp.211-216
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• 1999

Four different $\beta-Si_3N_4$ ceramics with silicon oxynitrides $[Y_10(SiO_4)_6N_2, Yb_4Si_2N_2O_7, Er_2Si_3N_4O_3, \;and La_{10}(SiO_4)_6N_2$, respectivley] as secondary phases have been fabricated by hot-pressing the $Si_3N_4-Re_4Si_2N_2O_7$ (Re=Y, Yb, Er, and La) compositions at $1820^{\circ}C$ for 2h under a pressure of 25 MPa. The high temperature strength and oxidation behavior of the hot-pressed ceramics were characterized and compared with those of the ceramics fabricated from $Si_3N_4-Si_2O_7$ compositions. The $Si_3N_4-Re_4Si_2N_2O_7$composition investigated herein showed comparable high temperature strength to those from $Si_3N_4-Re_2Si_2O_7$ compositions. Si3N4 ceramics from a $Si_3N_4-Y_4Si_2N_2O_7$ composition showed the highest strength of 877 MPa at $1200^{\circ}C$ among the compositions. All $Si_3N_4$ ceramics investigated herein showed a parabolic weight gain with oxidation time at $1400^{\circ}C$ and the oxidation products of the ceramics were $SiO_2$ and $Re_2Si_2O_7$. The $Si_3N_4-Re_4Si_2N_2O_7$ compositions showed inferior oxidation resistance to those from $Si_3n_4-Re_2Si_2O_7$ compositions, owing to the incompatibility of the secondary crystalline phases of those ceramics with $SiO_2$, the oxidation product of Si3N4.Si3N4 ceramics from a $Si_3N_4-Er_4Si_2N_2O_7$ composition showed the best oxidation resistance of 0.375mg/$\textrm{cm}^2$ after oxidation at $1400^{\circ}C$ for 102 h in air among the compositions.

• Journal of the Korean Ceramic Society
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• v.38 no.1
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• pp.22-27
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• 2001

$\beta$-Si$_3$N$_4$종자입자 첨가가 소결조제로 Y-Mg-Si-Al-O-N계 oxynitride glass를 사용하여 일축가압 소결을 행한 SiC-Si$_3$N$_4$복합재료의 미세구조와 기계적 특성에 미치는 영향을 고찰하였다. 길게 자란 $\beta$-Si$_3$N$_4$입자들과 등방성의 $\beta$-SiC 입자들이 균일하게 분포된 미세구조를 얻었다. $\beta$-Si$_3$N$_4$종자입자 함량이 증가함에 따라 SiC-Si$_3$N$_4$복합재료의 강도와 파괴인성이 증가하였고, 이는 복합화에 기인하는 결함크기의 감소와 길게 자란 $\beta$-Si$_3$N$_4$입자에 의한 균열가교 및 균열회절 등에 기인하였다. SiC-70 wt% Si$_3$N$_4$복합재료의 대표적인 강도와 파괴인성은 각각 770 MPa과 6.2 MPa.m$^{1}$2/ 이었다.

• Journal of Powder Materials
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• v.6 no.1
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• pp.18-35
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• 1999

Phase equilibria in the system Si3N4-TiC-TiCxN1-x-C-N were determined by thermodynamic calculations (CALPHAD-method). The reaction peaction paths for Si3N4-TiC and SiC-TiC composites in the Ti-Si-C-n system were simulated at I bar N2-pressure and varying terpreatures. At a temperature of 1923 K two tie-triangles (TiC0.34N0.66+SiC+C and TiC0.13N0.87+SiC+Si3N4) and two 2-phase fieds (TiCxN1-x+SiC; 0.13

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.3
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• pp.386-391
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• 1996

SiC particles (average size is 270 nm) of 0, 10, 20, 30, 40 vol% were dispersed in $Si_{3}N_{4}$, and $Si_{3}N_{4}/SiC$ nanocomposites were fabricated by hot press. After sintering, matrix phase, ${\alpha}-Si_{3}N_{4}$ was transformed to ${\beta}-Si_{3}N_{4}$, and second phase, ${\beta}-SiC$ was not changed. No grain boundary crystalline phase by adding of sintering additives was detected. Grain growth of $Si_{3}N_{4}$ was supressed with increasing of SiC contents, and then fine grain was occurred. The highest fracture strength was obtained at 10 vol% SiC, and fracture toughness was decreased, but hardness was linearly increased with SiC content.

• Journal of the Korean Ceramic Society
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• v.19 no.2
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• pp.121-126
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• 1982

This paper deals with the $Si_3N_4$-bonded SiC refractory in terms of its microstructure development during nitridation. When mixture of SiC grains and fine Si power is fired under nitrogen atmosphere, an interlocking network of $Si_3N_4$ whiskers is formed by nitridation of Si. It is found that the strength of $Si_3N_4$-bonded SiC refractory is soley due to the physical nature of this interlocking whiskers. At the initial stage of nitridation, $Si_3N_4$ whisker forms in very thin and long shape and, with further nitridation, it becomes thicker with diameters up to 0.35$\mu\textrm{m}$. It is found that the mechanical strength of $Si_3N_4$-bonded SiC refractory depends on the degree of nitridation and the development of microstructure.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.53-58
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• 2008

Purpose: To design and fabricate the small sputter coating system for the Ophthalmic lens. Methods: The design of sputter target was done using macleod program for AR coating and mirror coating of Ophthalmic lens with Si target and then the sputter system was fabricated. Results: The optimum condition of AR coating with Si target was [air|$SiO_2$(81.3)|$Si_3N_4$ (102)|$SiO_2$(19.21)|$Si_3N_4$(15.95)|$SiO_2$(102)|glass], for blue color mirror coating [air|$SiO_2$(56.61)|$Si_3N_4$(135.86)|$SiO_2$(67.64)|$Si_3N_4$(55.4)|$SiO_2$(53.53)|$Si_3N_4$(51.28)|glass], for green color coating [air|$SiO_2$(66.2)|$Si_3N_4$(22.76)|$SiO_2$(56.58)|$Si_3N_4$(140.35)|$SiO_2$(152.35)|$Si_3N_4$(70.16)|$SiO_2$(121.87)|glass], for gold color [air|$SiO_2$(83.59)|$Si_3N_4$(144.86)|$SiO_2$(11.82)|$Si_3N_4$(129.93)|$SiO_2$(90.01)|$Si_3N_4$(88.37)|glass]. Conclusions: In the fabrication of sputtering coating apparatus, Dual cathode with same Ti target were coated at the same time on both sides of Ophthalmic lens to lessen the time of coating on Ophthalmic Lens and save the cost of the lens. The distance of target-substrate of cathode was variable from 12.5 cm to 20 cm. Turbo pump was used to take the whole coating process about 15 min. instead of diffusion pump. The lens holder was made to coat 2 pairs lens every coating and was rotated to get the uniformity of thin film.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.799-804
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• 1999

Composites of SiC-Si3N4 consisted of uniformly distributed elongated $\beta$-Si3N4 grains and equiaxed $\beta$-SiC grains were fabricated with $\beta$-SiC,. $\alpha$-Si3N4 Al2O3 and Y2O3 powders. By hot-pressing and subsequent annelaing elongated $\beta$-Si3N4 grains were grown via$\alpha$longrightarrow$\beta$ phase transformation and equiaxed $\beta$-Si3N4 composites increased with increasing the Si3N4 content owing to the reduced defect size and enhanced crack deflection by elongated $\beta$-Si3N4 grains and the grain boundary strengthening by nitrogen incorporation. Typical flexural strength and fracture toughness of SiC-40 wt% Si3N4 composites were 783 MPa and 4.2 MPa.m1/2 respectively.

• Journal of the Korean Ceramic Society
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• v.43 no.9 s.292
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• pp.582-587
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• 2006

Decomposition behavior of $ferro-Si_3N_4$was investigated with varying temperature and holding time in mud components for high temperature refractory applications. Porosities gradually increased with increasing temperature and holding time due to the carbothermal reduction of $Si_3N_4\;and\;SiO_2$. Silicon monoxide (SiO) as a intermediate resulted from evaporation of $Si_3N_4\;and\;SiO_2$ reacted with C sources to generate needle-like ${\beta}-SiC$ and Fe in $Si_3N_4$ acted as a catalyst in order to enhance growth of SiC grain with the preferred orientation. SiC generation yield increased with increasing holding time, all of the $Si_3N_4\;and\;SiO_2$ affected on SiC formation up to 2h. However, SiC generation was only dependent on residual $SiO_2$ over 2h, because the carbothermal reduction reaction of $Si_3N_4$ was no longer possible at that time.