• JSTS:Journal of Semiconductor Technology and Science
• /
• v.17 no.2
• /
• pp.204-209
• /
• 2017

We have investigated a Mo/Au gate scheme for use in AlGaN/GaN-on-Si HFETs. AlGaN/GaN-on-Si HFETs were fabricated with Ni/Au or Mo/Au gates and their electrical characteristics were compared after thermal stress tests. While insignificant difference was observed in DC characteristics, the Mo/Au gate device exhibited lower on-resistance with superior pulsed characteristics in comparison with the Ni/Au gate device.

• Journal of Korea Foundry Society
• /
• v.15 no.3
• /
• pp.252-261
• /
• 1995

The purposes of this study were to investigate the microstructural changes in alloy ribbons of Al-Fe-Mo-Si quarternary system at $450{\sim}500^{\circ}C$, and to study the coarsening mechanism of fine precipitates. Using the hot stage in TEM, in situ microstructural changes in Al-4Fe-0.5Mo-1.5Si alloy ribbon and Al-8Fe-2Mo-1.5Si alloy ribbon have been examined successively up to 60 hours at $450^{\circ}C$ and $500^{\circ}C$. Cell structure in zone B of Al-4Fe-0.5Mo-1.5Si alloy ribbon was observed to collapse even in 10 minutes by in-situ heating at $450^{\circ}C$ and the size of precipitates in zone B increased twice in 60 hours. The precipitates in zone A of Al-4Fe-0.5Mo-1.5Si alloy ribbon showed slower coarsening rate than those in zone B by in-situ heating at $450^{\circ}C$. The precipitates in zone A of Al-8Fe-2Mo-1.5Si alloy ribbon increased 50% by in-situ heating at $500^{\circ}C$ in 50 hours compared to the initial precipitates while any microstructual change in zone B was not observed by in-situ heating at $500^{\circ}C$ up to 50 hours. Only the precipitates in zone A of Al-4Fe-0.5Mo-1.5Si alloy ribbon satisfied $r^3{\propto}t$ relationship of coarsening mechanism.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2000.04a
• /
• pp.71.1-71.1
• /
• 2000

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2005.11a
• /
• pp.63-63
• /
• 2005

• Journal of the Korean Magnetics Society
• /
• v.1 no.2
• /
• pp.37-41
• /
• 1991

Amorphous $Fe_{68.5}Co_5M_3Cu_1Si_{13.5}B_9(M=Nb, Mo, Mn, Cr)$ alloys were prepared by using rapidly quenching techinque and were annealed above their crystallization temperatures. Coercive force, initial permeability and AC power loss of the annealed $Fe_{68.5}Co_5M_3Cu_1Si_{13.5}B_9(M=Nb, Mo, Mn, Cr)$ alloys have been studied systematically. Nanocrystallines are formed in the annealed alloys which include Mo and Nb. Remarkably improved soft magnetic properties are obtained in the alloys whose average grain size is around 10 nm. However, soft magnetic properties of the alloys are degraded when grain size is less than IOnm or larger than 15nm. It is considered that the degradation of soft magnetic properties in the alloys whose average grain size is less than 10 nm is due to the Fe-rich amorphous phase retained at grain boundary during the initial crystallization process.

• Nuclear Engineering and Technology
• /
• v.45 no.7
• /
• pp.827-838
• /
• 2013

Interaction layer growth between U-Mo alloy fuel particles and Al in a dispersion fuel is a concern due to the volume expansion and other unfavorable irradiation behavior of the interaction product. To reduce interaction layer (IL) growth, a small amount of Si is added to the Al. As a result, IL growth is affected by the Si content in the Al matrix. In order to predict IL growth during fabrication and irradiation, empirical models were developed. For IL growth prediction during fabrication and any follow-on heating process before irradiation, out-of-pile heating test data were used to develop kinetic correlations. Two out-of-pile correlations, one for the pure Al matrix and the other for the Al matrix with Si addition, respectively, were developed, which are Arrhenius equations that include temperature and time. For IL growth predictions during irradiation, the out-of-pile correlations were modified to include a fission-rate term to consider fission enhanced diffusion, and multiplication factors to incorporate the Si addition effect and the effect of the Mo content. The in-pile correlation is applicable for a pure Al matrix and an Al matrix with the Si content up to 8 wt%, for fuel temperatures up to $200^{\circ}C$, and for Mo content in the range of 6 - 10wt%. In order to cover these ranges, in-pile data were included in modeling from various tests, such as the US RERTR-4, -5, -6, -7 and -9 tests and Korea's KOMO-4 test, that were designed to systematically examine the effects of the fission rate, temperature, Si content in Al matrix, and Mo content in U-Mo particles. A model converting the IL thickness to the IL volume fraction in the meat was also developed.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1405-1407
• /
• 2001

It was studied to prepare high temperature heating elements using molybdenum disilicide($MoSi_2$). Molybdenum disilicide is widely used as material for manufacturing high temperature heating elements. $MoSi_2$ heating elements could be used at 1700-1900$^{\circ}C$. However, it is relatively expensive, and its demand depends on import. $MoSi_2$ powders was mixed with 4-5wt% of montmorillonites type bentonite as plasticizer and a small amount of $Si_3N_4$, $ThO_2$, and B as additives to prepare specimen of heating elements. Then, it was extruded, dried, sintered and machined followed by heating test. Effects of sintering conditions and amount of additives were investigated, It was sintered effectively at 1,350$^{\circ}C$ for five hours. Electrical resistivity was decreased with increasing of sintering temperature and time, and related with apparent density of the specimens. It was linealy decreased with increasing of sintered density. The heating elements thus prepared was stable at 1700$^{\circ}C$ and the physical properties such as specific electrical resistivity, hardness, apparent density, thermal expansion coefficient, and bending strength were almost identical with those of commercial heating elements.

• Journal of Powder Materials
• /
• v.13 no.6 s.59
• /
• pp.408-414
• /
• 2006

[ $MoSi_2$ ] alloys with Al, B or Nb were prepared by an advanced consolidation process that combined mechanical alloying with pulse discharge sintering (complex forming) to improve the mechanical properties. Their microstructure and mechanical properties were investigated. The $MoSi_2$ alloys fabricated by complex forming method showed very fine microstructure when compared with the sample sintered from commercial $MoSi_2$ powders. Alloys made from powders milled in Ar gas had fewer silica or alumina phases as compared to their counterparts sintered from powders milled in air. In densification of the sintered body, addition of B was more effective than Al or Nb. Both Victors hardness and tensile test indicated that the alloy fabricated by the complex forming method showed better properties than the sample sintered from commercial $MoSi_2$ powders. The Al added alloy sintered from the powders milled in air had the superior mechanical properties due to the suppression of $SiO_2$ and formation of fine $Al_2O_3$ particles.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.10a
• /
• pp.40.1-40.1
• /
• 2011

TZM합금은 융점이 높은 Mo 기지에 미세한 (Zr,Ti)C의 석출물이 분산되어 있어 고온에서 다양한 부품에 응용가능하다. 하지만, TZM합금이 대기중 고온에 노출될 경우, 초기 산화물이며 약 $600^{\circ}C$부터 기화가 시작되는 $MoO_3$상이 형성됨으로써 물성에 치명적인 영향을 미친다. 이러한 산화거동을 막기 위하여 표면보호 코팅을 필요로 한다. 본 연구에서는 복잡한 형상과 대량생산이 가능하며 표면 코팅층과 모재의 접합성이 가장 강하다고 알려진 확산코팅법을 이용하여 Si을 TZM 합금에 코팅하였으며, 코팅층의 형성 속도론을 이해하기 위하여 온도별 및 시간별로 코팅을 수행하여 시간과 온도에 따른 코팅층의 형성 기구를 고찰하고자 하였다. Si의 확산코팅결과, $MoSi_2$층은 $1350^{\circ}C$에서 산화시에 두께가 감소하였으며, $Mo_5Si_3$상은 두께가 성장하였다. 코팅층의 확산거동을 속도론적 분석을 통하여 규명하고 논의하고자 한다.

• Journal of the Korean institute of surface engineering
• /
• v.32 no.3
• /
• pp.433-439
• /
• 1999

In this study, the diffusion barrier properties of $1000\AA$ thick molybdenum compounds (Mox=1-5 Si) were investigated using sheet resistance measurements, X-ray diffractometry (XRD), and Rutherford back scattering spectrometry (RBS). Each barrier material was deposited by the de and rf magnetron co-sputtering of Mo and Si, respectively, and annealed at $500-700^{\circ}C$ for 30 min in vacuum. Each barrier material was failed at low temperatures due to Cu diffusion through grain boundaries and defects of barrier thin films or through the reaction of Cu with Si within Mo-barrier thin films. It was found that Mo rich thin films were less effective than Si rich films to Cu penetration activating Cu reaction with the substrate at a temperature higher than $500^{\circ}C$.