• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1991년도 추계학술대회 논문집
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• pp.37-39
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• 1991

This paper is studies the effects of additives on the magnetic properties of Sr-ferrite. The specimens have been composed of SrO and Fe$_2$O$_3$with ratio of 1:5.9. As 1st additives, it is mixed to 0.2wt%, 0.7wt% and 1wt% of CaCo$_3$with 0.3wt% SiO$_2$. As 2nd addition, it is mixed to 0.5wt%, 1wt% of Na$_2$SiO$_3$, 0.5wt%, 1wt% of Cr$_2$O$_3$and 0.5wt%, 1wt% of Al$_2$O$_3$and sintering conditions was carried out at 1210$^{\circ}C$, 1230$^{\circ}C$ and 1250$^{\circ}C$. From experiments on the magnetic properties of specimen, the results were shown follows; (1) In case of additive SiO$_2$and CaO, it is stable magnetoplumbite structure for liquid phase grown, enhances mignetic propertics. (2) In case of basic compositions + 0.5wt% Al$_2$O$_3$, it is confirmed better properties by increasing of the coercivity than 0.5wt% Cr$_2$O$_3$additives. (3) In case of mixed additives of Cr$_2$O$_3$and Al$_2$O$_3$, magnetic propeties decrease with sintering density.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 춘계학술발표회 초록집
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• pp.3-3
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• 2001

Recently TiN, TiAlN, CrN hardcoatings have adapted many industrial application such as die, mold and cutting tools because of good wear resistant and thermal stability. However, in terms of high speed process, general hard coatings have been limited by oxidation and thermal hardness drop. Especially in the case of PCB drill, high speed cutting and without lubricant process condition have not adapted these coatings until now. Therefore more recently, superhard nanocomposite coating which have superhard and good thermal stability have developed. In previous works, WC-TiAlN new nanocomposite film was investigated by cathodic arc ion plating system. Control of AI concentration, WC-TiAlN multi layer composite coating with controlled microstructure was carried out and provides additional enhancement of mechanical properties as well as oxidation resistance at elevated temperature. It is noted that microhardness ofWC-TiA1N multi layer composite coating increased up to 50 Gpa and got thermal stability about $900^{\circ}C$. In this study WC-TiAlN nanocomposite coating was deposited on PCB drill for enhancement of life time. The parameter was A1 concentration and plasma cleaning time for edge sharpness maintaining. The characteristic of WC-TiAlN film formation and wear behaviors are discussed with data from AlES, XRD, EDS and SEM analysis. Through field test, enhancement of life time for PCB drill was measured.

• 한국분말재료학회지
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• 제19권6호
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• pp.435-441
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• 2012

A new manufacturing process of Fe-Cr-Al powder porous metal was attempted. First, ultra-fine fecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid (0.05~0.5% powders) was dispersed on PU (Polyurethane) foam through the electrospray process. And then degreasing and sintering processes were conduced. In order to examine the effect of sintering temperature in process, pre-samples were sintered for two hours at temperatures of $1350^{\circ}C$, $1400^{\circ}C$, $1450^{\circ}C$, and $1500^{\circ}C$, respectively, in $H_2$ atmospheres. A 24-hour TGA (thermo gravimetric analysis) test was conducted at $1000^{\circ}C$ in a 79% $N_2$+21% $O_2$ to investigate the high temperature oxidation behavior of powder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased with increasing sintering temperature (2.57% oxidation weight gain at $1500^{\circ}C$ sintered specimen). The high temperature oxidation mechanism of newly manufactured Fe-Cr-Al powder porous metal was also discussed.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.35-50
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• 2012

$900^{\circ}C$이상 초고온 He-gas 분위기 또는 용융불화염 (molten salts, FLINAK) 환경에서 사용될 VHTR(Very High Temperature Reactor)의 IHX(Intermediate heat exchanger)용 열수송 구조재료로 가장 가능성이 높은 합금인 Inconel 617 및 Hastelloy X 상에 습식화학적, 물리적기상합성법(Vacuum arc-plasma과 RF magnetron sputtering) 및 pack cementation에 의한 표면개질 및 마이크로 초내열(refractory ceramics) 코팅층(TiN, TiCN, TiAlN, $Al_2O_3$, $TiO_2$)을 형성시켰다. 고온 장기사용 시 문제가 될 수 있는 고온에서의 조직변화, 미세구조와 상(phase)형성, 고온 부식 및 그에 따른 마모(wear resistance) 손상 등 이들 소재의 내열, 내식 및 내마모 물성을 개선하는 연구를 수행하였다. TiAlN 박막의 경우 공기분위기에서 N이 분해되나 치밀한 산화물($TiO_2/Al_2O_3$ layer)을 형성하여 내식성 있는 보호피막을 형성함으로 기판과의 열팽창 계수로 인한 박리가 발생하지 않아 보호피막으로 적합하였다. Pack cementation법에 의한 aluminiding(Al-Ni합금)도 He 및 공기분위기에서 고온물성의 저하를 가져오는 $Cr_2O_3$의 생성을 충분히 억제하고 있었으며 He 및 air 분위기에서 사용이 가능한 박막으로 여겨진다. 내열 및 내식성에 대한 실험을 종합한 결과, 공기분위기에서 사용할 수 없는 박막은 He-gas 및 FLINAK(LiF-NaF-KF) 용융염 분위기에서도 사용할 수 없었으며, He-gas, FLINAK 및 air 분위기에서 모두 사용이 가능한 박막으로는 Inconel 617에서는 $(TiO_2-)Al_2O_3$, TiAlN 및 Al-Ni이었고 Hastelloy에서는 Al-Ni 및 $Al_2O_3$가 가장 적당하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.213-213
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• 2014

$300^{\circ}C$와 $500^{\circ}C$에서 아크 이온 증착된 도포층의 조성은 각각 Fe : Al : Ti : Si : N = 1.31 : 36.52 : 31.31 : 0.48 : 30.38 [wt.%]와 Fe : Cr : Al : Ti : Si : N = 1.24 : 0.56 : 36.82 : 32.72 : 0.59 : 28.07 [wt.%] 이었다. 0.1N $H_2SO_4$ 수용액과 인공해수 (ASTM D1141-98) 분위기에서 $300^{\circ}C$, $500^{\circ}C$에서 증착된 도포층의 부식전압과 부식속도는 각각 $-0.2787V_{SHE}$, $0.002A/cm^2$, $-2.764V_{SHE}$, $0.002A/cm^2$ 와 $-0.2799V_{SHE}$, $0.002A/cm^2$, $-0.0394V_{SHE}$, $0.002A/cm^2$이었다. 나노 경도값은 각각 23.6, 25.8 GPa 이었다. 이는 각각 2208.2, $2434.2H_V$에 해당되었다.

• 대한수학회논문집
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• 제34권4호
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• pp.1303-1313
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• 2019

Recently Hui et al. ([8,9]) studied contact CR-warped product submanifolds and also warped product pseudo-slant submanifolds of a $(LCS)_n$-manifold $\bar{M}$. The characterization for both these classes of warped product submanifolds have been studied here. It is also shown that there do not exists any proper warped product bi-slant submanifold of a $(LCS)_n$-manifold. Although the existence of a bi-slant submanifold of $(LCS)_n$-manifold is ensured by an example.

• Asian Pacific Journal of Cancer Prevention
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• 제17권10호
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• pp.4761-4767
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• 2016

Objective: The use of Shamma (smokeless tobacco) by certain groups is giving rise to health problems, including cancer, in parts of Saudi Arabia. Our objective was to determine metals levels in Shamma using inductively coupled plasma mass spectrometry (ICP-MS). Methods: Thirty-three samples of Shamma (smokeless tobacco) were collected, comprising four types: brown Shamma (n = 14.0), red Shamma (n = 9.0), white Shamma (n = 4.0), and yellow Shamma (n = 6.0). All samples were collected randomly from Shamma users in the city of Najran. Levels of 11 elements (Al, As, Cd, Co, Cr, Cu, Li, Mn, Ni, Pb, and Zn) were determined by ICP-MS. Results: A mixed standard (20 ppb) of all elements was used for quality control, and average recoveries ranged from 74.7% to 112.2%. The highest average concentrations were found in the following order: Al ($598.8-812.2{\mu}g/g$), Mn ($51.0-80.6{\mu}g/g$), and Ni ($23.2-53.3{\mu}g/g$) in all four Shamma types. The lowest concentrations were for As ($0.7-1.0{\mu}g/g$) and Cd ($0.0-0.06{\mu}g/g$). Conclusions: The colour of each Shamma type reflects additives mixed into the tobacco. Cr and Cu were showed significant differences (P < 0.05) among Shamma types. Moreover, Pb levels are higher in red and yellow Shamma, which could be due to use (PbCrO4) as yellow colouring agent and lead tetroxide, Pb3O4 as a red colouring agent. The findings from this study can be used to raise public awareness about the safety and health effects of Shamma, which is clearly a source of oral exposure to metals.

• 한국진공학회지
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• 제15권1호
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• pp.110-116
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• 2006

본 연구에서는 나노 두께를 갖는 두 층을 반복적으로 증착하여 나노 다층 구조를 갖는 질화 물이 코팅된 절삭공구의 기계적 성능과 절삭성능의 향상에 대해 고찰하였다. 이러한 질화물계 나노 다층막에 대한 재료는 격자상수와 결정구조에 따라 $Ti_{0.54}Al_{0.46}N-CrN$계와 $Ti_{0.84}Al_{0.16}N-NlN$계를 선택하여, UBM sputtering 증착법을 이용하여 초경(WC-Co) 인서트(insert)위에 증착하였다. 공정 변수들인 증착온도, 압력. 기판 바이어스 전압, 기판회전 속도 등을 조절하여 다른 주기 값을 갖는 일정한 두께의 다층막들을 증착 시켰고, 주기에 따른 초격자 형성, 경도 값과 절삭성능을 관찰하였다. 증착된 다층막들은 그 주기 값에 따라 경도 값이 다르게 나타났으며. 경도 값이 상대적으로 높았던 특정 주기의 다층막이 코팅된 절삭 공구의 경우, 기존의 상용화된 제품에 비해 frank wear로 비교한 절삭 성능이 $20\%$이상 향상됨을 관찰하였다

• 전자공학회논문지D
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• 제36D권7호
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• pp.17-25
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• 1999

PECVD 법을 이용하여 Tungsten Nitride($WN_x$) 박막을 $WSi_3N_4$ 기판위에 형성하였다. $WN_x$ 박막은 기관온도, 가스의 유량, rf power 등의 공정변수를 변화시키면서 형성되었고, 서로 다른 질소원으로 $NH_3$와 $N_2$를 각각 사용하여 박막의 특성을 조사하였다. $WN_x$ 막 내의 질소함량은 $NH_3$와 $N_2$의 유량에 따라 0~45% 정도로 변화하였으며, $NH_3$를 사용하였을 때, 최고 160nm/min의 높은 성장률을 나타내었다. $WSi_3N_4$ 기판 위에서는 TiN이나 Si 위에서보다 높은 성장률을 나타내었다. $WN_x$ 박막의 순도를 AES로 측정해 본 결과 $NH_3$를 사용했을 때 고순도의 박막을 얻을 수 있었다. XRD 분석으로 순수한 다결정의 W가 비정질의 $WN_x$로 변화되는 것을 알 수 있었으며, 이것은 $WN_x$가 식각 공정시 미세 패턴 형성이 W보다 유리할 것이라는 것을 보여준다. TiN, NiCr, Al 등의 다양한 기판 위에 형성해 본 결과 Al 위에서 최대 $1.6 {\mu}m$의 두꺼운 막이 형성되었다.

• The Journal of Advanced Prosthodontics
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• 제11권1호
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• pp.23-31
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• 2019

PURPOSE. To investigate and compare the surface roughness (SR), weight and height of monolithic zirconia (MZ), ceramometal (CM), lithium disilicate glass ceramic (LD), composite resin (CR), and their antagonistic human teeth enamel. MATERIALS AND METHODS. 32 disc shaped specimens for the four test materials (n=8) and 32 premolars were prepared and randomly divided. SR, weight and height of the materials and the antagonist enamel were recorded before and after subjecting the specimens to 240,000 wear-cycles ($49N/0.8Hz/5^{\circ}C/50^{\circ}C$). SR, height, weight, and digital microscopic qualitative evaluation were measured. RESULTS. CM ($0.23+0.08{\mu}m$) and LD ($0.68+0.16{\mu}m$) exhibited the least and highest mean difference in the SR, respectively. ANOVA revealed significance (P=.001) between the materials for the SR. Paired T-Test showed significance (P<.05) for the pre- and post- SR for all the materials. For the antagonistic enamel, no significance (P=.987) was found between the groups. However, the pre- and post- SR values of all the enamel groups were significant (P<.05). Wear cycles had significant effect on enamel weight loss against all the materials (P<.05). CR and MZ showed the lowest and highest height loss of 0.14 mm and 0.46 mm, respectively. CONCLUSION. MZ and CM are more resistant to SR against the enamel than LD and CR. Enamel worn against test materials showed similar SR. Significant variations in SR values for the tested materials (MZ, LD, CM, and CR) against the enamel were found. Wear simulation significantly affected the enamel weight loss against all the materials, and enamel antagonist against MZ and CM showed more height loss.