• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.176-180
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• 2006

[ $(Na_{0.5}Bi_{0.5})TiO_3$ ][NBT] thin films were prepared on a highly (100) oriented $LaNiO_3[LNO]$ by sol-gel process. X-ray diffraction patterns of the NBT films annealed above $600^{\circ}C$ for 5 minutes have confirmed a highly (100) oriented growth and pseudocubic structure (a=3.884${\AA}$). The (l00) orientation factor increased from 90 to $99\%$ with increasing soaking time from 5 to 60 minutes at $600^{\circ}C$. The NBT films ($600^{\circ}C$/5 min,) have a flat and dense microstructure with large columnar grains, and their grain size are about 44 nm. The Au/NBT/LNO/Si hetero structure sample show a ferroelectric properties.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.3
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• pp.181-189
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• 2002

A series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22, and 0.30) alloys are prepared and their oystal structure and P-C-T curves are examined. The electrochemical properties of these allqys such as activation conditions, discharge capacity, cycling performance are also investigated. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22 and 0.30) have the C14 Laves phase hexagonal structure. The electrode was activated by the hot-charging treatment. The best activation conditions were the current density 120 mA/g and the hot-charging time 12h at $80^{\circ}C$ in the case of the alloy with x=0.00. The discharge capacity increased rapidly until the fourth cycle and then decreased. The discharge capacity increased again from the 13th cycle, arriving at 234 mAh/g at the 50th cycle. The discharge capacily just after activation decreases with the increase in the amount of the substituted Fe but the cycling performance is improved. The discharge capacity after activation of the alloy with x=0.00 is 157 mAh/g at the current density 120 mA/g. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Fe_{0.15}$ is a good composition with a medium quantity of discharge capacities and a good cycling performance. The ICP analysis of the electrolyte for these electrodes after 50 charge-discharge cycles shows that the concentrations of V and Zr are relatively high. Another series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}M_{0.15}$ (M = Fe, Co, Cu, Mo and Al) alloys are prepared. They also have the C14 Laves phase hexagonal structure. The alloys with M = Co and Fe have relatively larger hydrogen storage capacities. The discharge capacities just after activation are relatively large in the case of the alloys with M = Al and Cu. They are 212 and 170 mAh/g, respectivety, at the current density 120mA/g. The $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Co_{0.15}$ alloy is the best one with a relatively large discharge capacity and a good cycling performance.

• Journal of the KSME
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• v.34 no.5
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• pp.392-398
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• 1994

구조용 고온재료로서 표 2에 나타내듯이 지금까지 니켈과 티타늄 알루미나이드($Ni_3Al$, NiAl, $Ti_3Al$, TiAl에 관하여 집중적인 연구가 진행되어 왔으며 다른 금속간 화합물에 대해서도 광범위한 연구가 진행중이다. 그 예로서 $Co_3Ti$는 800.deg. C에서 최대강도를 보이며 저온에서는 온도가 감소하면서 강도가 다시 증가하면 연성이라는 장점을 지닌 관계로 $MoSi_2$는 높은 융점과 우수한 산화저항력 때문에 $Nb_2Al$은 높은 융점과 경량성 때 문에 복합재료의 matrix로서 최근 주목을 받고 있다. 끝으로 비록 금속간화합물이 취성이라는 단점 때문에 실용화에 많은 문제점이 있으며 본 재료에 관한 연구가 준비 제조공정과정에서 수 소취성화, 고용점온도 취성 등으로 인하여 사용해온 기존의 재료를 보다 좀더 극한 상황에서 가볍고 저렴하게 사용할 수 있는 우주항공 및 지상대체재료로서 개발할 수 있음을 고려할 때 본 재료에 대한 본격적인 연구가 국재 경쟁력강화를 위해 신소재 개발에 부심하는 우리나라에서도 이루어질 필요가 있다.

• Journal of the Korean Vacuum Society
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• v.7 no.2
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• pp.141-149
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• 1998

The W thin films were deposited on Si3N4 by a PECVD technique. The effects of substrate temperature and gas flow ratio on the properties of the W films were investigated. The deposition of W films were limited by surface reaction at the temperature range of 150>~$250^{\circ}C$, W films had the deposition rate of 150~530 $\AA$/min and stress of 0.85~$14.35\times10 ^9 \textrm {dynes/cm}^2}$ at various substrate temperatures and $SiH_4/WF_6$ flow ratios. $SiH_4/WF_6$ flow ratio affected the deposition rate and stress of the W films, expecially, excessive flow of SiH4 abruptly changed the structure, chemical bonding, and stress of the W films. Among the deposited W films on TiN, Ti, Mo, NiCr and Al adhesion layer, the one on the Al had the best adhesion property.

• 대한공업교육학회지
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• v.31 no.1
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• pp.200-210
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• 2006

This C-ring test, normally employed for evaluating susceptibility to stress-corrosion cracking, was determined to be a suitable small scale test to evaluate PWHT(Post-Weld Heat Treatment) cracking susceptibility. This test is possible to incorporate an actual weld, to introduce a notch into the coarse grained HAZ(Heat Affected Zone), to load the coarse grained HAZ any level of stress ad, most importantly, since the C-ring is an approximately constant strain type test, the stress decreases with time at temperature in a manner similar to that of an actual steel weldment. The procedure employed in making the C-ring was presented in the experimental procedure section, however, several points deserve further discussion. The walls of the weld groove are made along radial lines form the center of th var in order to obtain an HAZ which is oriented perpendicular to the walls of the machined C-ring. Therefore, the plane of maximum stress will be aligned through the HAZ and, therefore, crack propagation will not be forced to deviate form the plane of maximum stress in order to remain in the coarse grained HAZ as is the case with the Y groove test.

• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.129-137
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• 2009

Corrosion behaviors of TiN coated dental casting alloys have been researched by using various electrochemical methods. Three casting alloys (Alloy 1: 63Co-27Cr-5.5Mo, Alloy 2: 63Ni-16Cr-5Mo, Alloy 3: 63Co-30Cr-5Mo) were prepared for fabricating partial denture frameworks with various casting methods; centrifugal casting(CF), high frequency induction casting(HFI) and vacuum pressure casting(VP). The specimens were coated with TiN film by RF-magnetron sputtering method. The corrosion behaviors were investigated using potentiostat (EG&G Co, 263A. USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion morphologies were analyzed using FE-SEM and EDX. Alloy 1 and Alloy 2 showed the ${\alpha}-Co$ and ${\varepsilon}-Co$ phase on the matrix, and it was disappeared in case of TiN coated Alloy 1 and 2. In the Alloy 3, $Ni_2Cr$ second phases were appeared at matrix. Corrosion potentials of TiN coated alloy were higher than that of non-coated alloy, but current density at passive region of TiN coated alloy was lower than that of non-coated alloy. Pitting corrosion resistances were increased in the order of centrifugal casting, high frequency induction casting and vacuum pressure casting method from cyclic potentiodynamic polarization test.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.2
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• pp.14-19
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• 2011

We have fabricated GaN Schottky barrier diode (SBD) for high-voltage applications on Si substrate. The leakage current and the electrical characteristics of GaN SBD are investigated by annealing metal-semiconductor junctions. Ohmic junctions of Ti/Al/Mo/Au and Schottky junctions of Ni/Au are used in the fabrication. A test structure is proposed to measured buffer leakage current through a mesa structure. When annealing temperature is increased from $700^{\circ}C$ to $800^{\circ}C$, measured buffer leakage current is also increased from 87 nA to 780 nA at the width of 100 ${\mu}m$. The diffusion of Au, Ti, Mo, O into GaN buffer layer increases the leakage current and that is verified by Auger electron spectroscopy. Experimental results show that the low leakage current and the high breakdown voltage of GaN SBD are achieved by annealing metal-semiconductor junctions.

• Korean Journal of Materials Research
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• v.31 no.7
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• pp.392-396
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• 2021

Expensive PCBN or ceramic cutting tools are used for processing of difficult-to-cut materials such as Ti and Ni alloy materials. These tools have the problem of breaking easily due to their high hardness but low fracture toughness. To solve these problems, cutting tools that form various coating layers are used in low-cost WC-Co hard material tools, and research on various tool materials is being conducted. In this study, binderless-WC, WC-6 wt%Co, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are densified using horizontal ball milled WC-Co, WC-Co-Mo₂C powders, and spark plasma sintering process (SPS process). Each SPSed Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are almost completely dense, with relative density of up to 99.5 % after the simultaneous application of pressure of 60 MPa and almost no significant change in grain size. The average grain sizes of WC for Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are about 0.37, 0.6, 0.54, and 0.43 ㎛, respectively. Mechanical properties, microstructure, and phase analysis of SPSed Binderless-WC, WC-6 wt%Co-1 wt% Mo₂C, and WC-6 wt%Co-2.5 wt% Mo₂C hard materials are investigated.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.24-34
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• 1998

In this research, effects of the types and amounts of binders and additives on desulfurization and regeneration reactivities of zinc titanate were investigated. Bentonite and kaolinite were used as binders and Mo-based, Ni-based, and Cu-based compounds were used as additives. A thermogravimetric analyzer (TGA) was utilized to investigate reactivities of desulfurization and regeneration for each sorbent. Two-cycle reactions of desulfurization-regeneration were performed in the TGA reactor. Results of XRD analysis showed that all sorbents had the crystalline phases of $Zn_2TiO_2$ and $Zn_2Ti_3O_8$ irrespective of the type and amount of binder and additive. Kaolinite-bound sorbents gave higher surface areas than bentonite-bound ones and the surface areas and pore volumes of sorbents increased with amount of binder increased. It was found that the most suitable temperatures for desulfurization and regeneration were 680$^{\circ}$C and 730$^{\circ}$C, respectively, and the sorbent prepared by the addition of 3 mol% CuO showed the best performance in terms of desulfurization and regeneration. Nio-added sorbents had good regenerability whereas $MoO_3-based$ sorbents showed poor performance. In cycle experiments in a fixed bed reactor 3 mol% CuO-added sorbents showed high reactivity.

• Journal of Powder Materials
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• v.14 no.4
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• pp.230-237
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• 2007

The fabrication of Fe alloy-40 wt.%TiC composite materials using spark plasma sintering process after ball-milling was studied. Raw powders to fabricate Fe alloy-TiC composite were Fe alloy, $TiH_{2}$ and activated carbon. Fe alloy powder was Distaloy AE (4%Ni-1%Cu-0.5%Mo-0.01%C-bal.%Fe) made by Hoeganes company with better toughness and lower melting point. These powders were ball-milled in horizontal attrition ball mill at a ball-to-powder weight ratio of 30 : 1. After that, these mixture powders were sintered by using spark plasma sintering apparatus for 5 min at $1200-1275^{\circ}C$ in vacuum atmosphere under $10^{-3}$ torr. DistaloyAE-40 wt.%TiC composite was directly synthesized by dehydrogenation and carburization reaction during sintering process. The phase transformation of as-milled powders and sintered materials was confirmed using X-ray diffraction (XRD) and transmission electron microscope (TEM). The density and harness materials was measured in order to confirm the densification behavior. In case of DistaloyAE-40 wt.%TiC composite retained for 5 min at $1275^{\circ}C$, it has the relative density of about 96% through the influence of rapid densification and fine TiC particle reinforced Fe-based composites materials.