• 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.

• Elastomers and Composites
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• v.40 no.3
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• pp.174-180
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• 2005

Sonochemical synthesis of fullerene oxides $[C_{70}O_n](n=1{\sim}2)$ by fullerene$[C_{70}]$ and metal hexacarbonyl complexes $M(CO)_6$(M=Cr, Mo, W) took place under air atmosphere. The reactivity of fullerene$[C_{70}]$ and several metal hexacarbonyl complexes $M(CO)_6$(M=Cr, Mo, W) under same ultrasonic condition increased in the order of $Mo(CO)_6$ > $W(CO)_6$ > $Cr(CO)_6$. The MALDI-TOF-MS, UV-visible spectra, and HPLC analysis confirmed that the products of sonochemical reaction were $[C_{70}O_n](n=1{\sim}2)$.

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.696-702
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• 1998

The effect of alkali metal salt on the activity of Co-Mo catalyst which has high resistance to sulfur poisoning for water gas shift reaction(WGSR) was studied. Two groups of catalysts were prepared to investigate the effects of anion and cation in alkali metal salts. For K-doped catalysts made with various potassium salts having different anion, the catalytic activity was explained to depend mainly on the BET surface area. Among the catalysts prepared by various nitrates of alkali metal as precursor, the Li-doped catalyst showed the best activity, and the others did not make significant differences giving relatively low activities. And the change of BET surface area by varying the loading of alkali metal showed a similar trend to that of activity. In this case, the activity was dependent on both BET surface area and the ratio of $Mo^{6+}$ with a tetrahedral coordination symmetry to $Mo^{6+}$ with an octahedral one, $Mo^6+[T]/Mo^{6+}[O]$ value.

• Applied Chemistry for Engineering
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• v.3 no.3
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• pp.407-411
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• 1992

The effects of phase transfer catalyst was studied on the substitution of CO ligand of $Mo(CO)_6$ [M=Cr, Mo, W] with two electron-pairs donating ligands, 2, 2'-bipyridine and 2, 2'-biquinoline. The change of product yield, $M(CO)_4(L)_2$, was discussed according to reaction time, mole composition of $M(CO)_6$, and type of ligand.

• Journal of the Korean Electrochemical Society
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• v.2 no.3
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• pp.150-155
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• 1999

The Electrochemical stabilities of the Brewer-Engel type intermetallic compounds of Co-Mo $(35 wt\%)$ and Ni-Mo$(35 wt\%)$ manufactured by the arc-melting method for the hydrogen electrode of $H_2-O_2$ alkaline fuel cell were investigated. Effects of temperature and concentration on the electrochemical behavior of the electrodes in the $80^{\circ}C$ 6 N KOH solution deaerated with $N_2$ gas were studied by electrochemical methods. The effect of overpotential on the electrochemical stabilities of Co-Mo and Ni-Mo intermetallic compounds was also discussed under the normal operation condition of AFC. It was shown that Co-Mo electrode had lower electrochemical stability as compared to Ni-Mo. In the case of Co-Mo electrode, a simultaneous dissolution of cobalt and molybdenum has occurred at low anodic overpotential form equilibrium hydrogen electrode potential, but the dissolution of cobalt was serious, and Co(OH)l layer on the electrode surface formed at the high anodic overpotential. In contrast the Ni-Mo electrode had high electrochemical stability because formation of the dense and thin protective $Ni(OH)_2$ layer prevented the dissolution of molybdenum.

• Journal of Korea Foundry Society
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• v.27 no.3
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• pp.120-125
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• 2007

The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.

• Bulletin of the Korean Chemical Society
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• v.21 no.10
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• pp.1044-1046
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• 2000

Catalytic copolymerization of diethyl dipropargylmalonate (DEDPM) and phenylacetylene (PA) by Mo(CO)6 and (toluene) Mo(CO)3/chloranil has resulted in the expected copolymer consiting of a polyene backbone with five-and/or six-membered rings and th e PPA structure. Both complexes exhibited not only varying degree of catalytic activity depending upon the relative mole ratio of two monomers but also characterize the types of coploymers. The former yields the polyene backbone containing only five-membered rings as well as PA while the latter produces the polymers consisting of both five-and six-membered ring structure. Comparative studies show that Mo(CO)6 exhibits reactivity toward DEDPM alone, thus catalyzing initially metathesis cyclopoly-merization of DEDPM followed by copolymerization with PA while the (toluene)Mo(CO)3/chloranil system shows affinity for both PA and DEDPM.

• Bulletin of the Korean Chemical Society
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• v.11 no.1
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• pp.15-19
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• 1990

The crystal structure of $(C_{12}H_{24}O_6{\cdot}K)_2K[Co(OH)_6Mo_6O_{18}]{\cdot}12H_2O$ has been determined by X-ray diffraction. Crystal data as follows ; monoclinic, space group $C_2/m,\;a\;=\;22.512(4)\;{\AA},\;b\;=\;18.304(4)\;{\AA},\;c\;=\;7.641(1)\;{\AA},\;{\beta}\;=\;90.52(2)\;{\AA}$, and Z = 2. A final conventional R value of 0.044 was obtained by least-squares refinement of 4173 independent observed $[{\mid}Fo{\mid}{\geq}3{\sigma}({\mid}Fo{\mid})]$ reflections. The $[Co(OH)_6Mo_6O_}{18}]^{-3}$ polyanion shows the well-known Anderson-structure and has approximate 3m symmetry. A $[Co(OH)_6Mo_6O_{18}]^{-3}$ polyanion is located between two crown ether complexed cations forming a sandwich structure. One potassium ion interacts with the crown ether via electrostatic interactions. The other potassium ion only interacts with the water molecules and terminal oxygen atoms of the polyanion.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.252-252
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• 2013

최근 그래핀, hexagonal boron nitride (h-BN) 및 $MoS_2$ (molybdenum disulfide)와 같은 2차원 결정 물질들은 무어의 법칙(Moore's Law)를 뛰어넘어 계속적인 소자의 소형화를 가능케 하고 또한 대면적, 저비용 소자 개발을 가능케 하는 우수한 특성을 가진 차세대 반도체 트랜지스터 소재로 각광받고 있다. $MoS_2$는 bulk 상태일 때는 1.2 eV의 indirect 밴드갭을 가지지만 단층형태일 때는 1.8 eV의 direct 밴드갭을 가지며 dielectric screening 기법등을 통해 mobility를 향상시킬 수 있는 것으로 연구된 바 있다. 본 연구에서는 화학기상증착 (chemical vapor deposition)법을 이용하여 $MoS_2$ 박막을 형성하기 위한 기초연구인 Mo 전구체의 특성평가 및 적합한 공정조건 개발 연구를 수행하였다. 사용한 전구체는 $Mo(CO)_6$ (Molybdenum hexacarbonyl)이고, 온도 및 압력, 반응기체(H2 S, Hydrogen sulfide) 유량 등의 공정 조건 변화에 따른 거동을 Fourier transform infrared spectroscopy (FT-IR) 시스템을 사용하여 측정하였다. 또한 $Mo(CO)_6$의 분자구조를 상용 프로그램인 Gaussian으로 시뮬레이션 하여 실제 FT-IR 측정 결과값과 비교 분석하였다.

• Korean Journal of Materials Research
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• v.29 no.11
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• pp.715-719
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• 2019

Molybdenum is a low-resistivity transition metal that can be applied to silicon devices using Si-metal electrode structures and thin film solar cell electrodes. We investigate the deposition of metal Mo thin film by plasma-enhanced atomic layer deposition (PE-ALD). $Mo(CO)_6$ and $H_2$ plasma are used as precursor. $H_2$ plasma is induced between ALD cycles for reduction of $Mo(CO)_6$ and Mo film is deposited on Si substrate at $300^{\circ}C$. Through variation of PE-ALD conditions such as precursor pulse time, plasma pulse time and plasma power, we find that these conditions result in low resistivity. The resistivity is affected by Mo pulse time. We can find the reason through analyzing XPS data according to Mo pulse time. The thickness uniformity is affected by plasma power. The lowest resistivity is $176{\mu}{\Omega}{\cdot}cm$ at $Mo(CO)_6$ pulse time 3s. The thickness uniformity of metal Mo thin film deposited by PE-ALD shows a value of less than 3% below the plasma power of 200 W.