Fabrication of diamond/W – Cu functionally graded material by microwave sintering

Chenlong Wei,Jigui Cheng,Mei Zhang,Rui Zhou,Bangzheng Wei,Xinxi Yu,Laima Luo,Pengqi Chen 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.3

A four-layered W/Cu functionally graded material (FGM) (W90% þ Cu10%/W80% þ Cu20%/W70% þ Cu30%/W60% þ Cu40%, wt.% fraction) and a four-layered diamond/WeCu FGM (W90% þ Cu10%/W80% þ Cu20%/W70% þ Cu30%/W55% þ Cu40% þ diamond5%, wt.% fraction) were fabricated by microwavesintering. The thermal conductivity and thermal shock resistance of diamond/WeCu FGM andWeCu FGM were investigated. The morphologies of the diamond particles and different FGMs wereanalyzed using AFM, SEM, EDS, and TEM. The results show that a 200 nm rough tungsten coating wasformed on the surface of the diamond. The density of the tungsten-coated diamond/WeCu FGM, obtainedby microwave sintering at 1200 C for 30 min, was 94.66%. The thermal conductivity of the fourlayereddiamond/WeCu FGM was 220 W$m-1$K-1, which is higher than that of the four-layered W/CuFGM (209 Wm 1 K 1). This indicates that adding an appropriate amount of tungsten-coated diamond tothe high Cu layer W/Cu FGM improves the thermal conductivity of the composite. The diamond/WeCuFGM sintered at 1200 C for 10 min exhibited better thermal shock resistance than diamond/WeCu FGMsintered at 1100 C for 10 min

텅스텐의 지구화학적 거동에 미치는 미생물의 영향

한협조,이종운 한국자원공학회 2019 한국자원공학회지 Vol.56 No.1

64~113 mg/kg의 W를 함유하는 토양 및 퇴적물에서 외견상 집락이 구분되는 13종류의 토착 미생물을 분리한 후 이들이 혐기성 조건에서 용존 W(VI)의 거동에 미치는 영향을 실험적으로 조사하였다. 1,000 mg/L의 W(VI)를주입한 결과 8종류의 미생물이 무생물적 비교시료(94 mg/L)에 비하여 2배 이상의 W(192~378 mg/L)를 용액으로부터침전시켜 제거하였다. 이들 중 Klebsiella sp.와 Pantoea sp.로 동정된 두 종을 이용하여 추가 실험을 수행한 결과, 비교시료에 비하여 월등히 많은 양(210~309 mg/L)의 W(VI)를 W(IV)로 환원하였다. 이러한 미생물학적 W(VI) 환원은 발효에 의한 용액의 pH 감소가 주된 기제인 것으로 보이며 Klebsiella sp.의 경우 W의 해독성 환원기제도 일부 고려할수 있다. 이 결과는 W의 지구화학적 거동에 미치는 미생물의 영향에 관한 최초의 보고이며 지질 매체 내에서 W의 순환에 미생물이 영향을 미칠 수 있음을 나타낸다. The effects of 13 indigenous microorganisms with distinct colony forms isolated from soils and sediments containing W of 64~113 mg/kg on the behavior of dissolved W(VI) were experimentally investigated under anaerobic condition. Compared with abiotic control (94 mg/L), eight bacteria decreased more than twice the amount of dissolved W (192~378 mg/L) forming precipitates in response to 1,000 mg/L W(VI) supply. The consecutive experiments using Klebsiella sp. and Pantoea sp. among the isolated microorganisms also showed that they reduced greater amounts (210~309 mg/L) of W(VI) to W(IV) than abiotic control. Such microbial reduction of W(VI) might be due to pH decrease by fermentation. In addition, for Klebsiella sp., detoxification was likely one of the mechanisms of W(VI) reduction. The results, which are the first evidence to our knowledge of the effects of microorganisms on geochemical behavior of W, indicate that microorganisms may influence the cycle of W in geological media.

Application of Pulsed Chemical Vapor Deposited Tungsten Thin Film as a Nucleation Layer for Ultrahigh Aspect Ratio Tungsten-Plug Fill Process

Jang, Byeonghyeon,Kim, Soo-Hyun Materials Research Society of Korea 2016 한국재료학회지 Vol.26 No.9

Tungsten (W) thin film was deposited at $400^{\circ}C$ using pulsed chemical vapor deposition (pulsed CVD); film was then evaluated as a nucleation layer for W-plug deposition at the contact, with an ultrahigh aspect ratio of about 14~15 (top opening diameter: 240~250 nm, bottom diameter: 98~100 nm) for dynamic random access memory. The deposition stage of pulsed CVD has four steps resulting in one deposition cycle: (1) Reaction of $WF_6$ with $SiH_4$. (2) Inert gas purge. (3) $SiH_4$ exposure without $WF_6$ supply. (4) Inert gas purge while conventional CVD consists of the continuous reaction of $WF_6$ and $SiH_4$. The pulsed CVD-W film showed better conformality at contacts compared to that of conventional CVD-W nucleation layer. It was found that resistivities of films deposited by pulsed CVD were closely related with the phases formed and with the microstructure, as characterized by the grain size. A lower contact resistance was obtained by using pulsed CVD-W film as a nucleation layer compared to that of the conventional CVD-W nucleation layer, even though the former has a higher resistivity (${\sim}100{\mu}{\Omega}-cm$) than that of the latter (${\sim}25{\mu}{\Omega}-cm$). The plan-view scanning electron microscopy images after focused ion beam milling showed that the lower contact resistance of the pulsed CVD-W based W-plug fill scheme was mainly due to its better plug filling capability.

Rh-Mn/tungsten carbides for direct synthesis of mixed alcohols from syngas: Effects of tungsten carbide phases

Won, Ba Da,Jeong, Min Hye,Kim, Myeong Hun,Chung, Chan-Hwa,Moon, Dong Ju,Suh, Young-Woong,Baik, Joon Hyun,Bae, Jong Wook Elsevier 2018 Microporous and mesoporous materials Vol.255 No.-

<P><B>Abstract</B></P> <P>Effects of the crystalline tungsten carbide (WxC) phases on an ordered mesoporous bimetallic Rh-Mn/WxC, which were prepared by changing carbon source to tungsten (C/W) ratios of the WxC support using a hard-template of an ordered mesoporous SBA-15, were investigated for a direct synthesis of mixed alcohols by CO hydrogenation from syngas. The C/W ratios on the mesoporous Rh-Mn/WxC showed a significantly different catalytic activity, especially on the C<SUB>1</SUB> - C<SUB>3</SUB> alcohol productivity. The Rh-Mn/WxC prepared at C/W molar ratio of 10 having a metastable W<SUB>2</SUB>C main phase (Rh-Mn/WxC(10)) revealed a higher CO conversion of 8.1% and selectivity to higher alcohols of 54.4% compared to other catalysts having a main crystalline phases of WO<SUB>3</SUB> or WC. The enhanced catalytic activity and selectivity to mixed alcohols on the Rh-Mn/WxC(10) were attributed to the largely exposed smaller active Rh nanoparticles with its stronger interactions with the metastable W<SUB>2</SUB>C phases. The superior activity was originated from the intimate interactions of Rh nanoparticles with Mn promoter by maintaining proper oxidation states confirmed by surface ratios of the metallic Rh to oxidized Rh<SUP> <B>n+</B> </SUP> species. The stable preservation of the ordered mesoporous structures of the W<SUB>2</SUB>C phase in the amorphous carbon matrixes significantly altered the chemical states of the small Rh nanoparticles below 2 nm in size by preferentially existing on the outer surfaces of the W<SUB>2</SUB>C support, which resulted in showing an enhanced productivity of higher C<SUB>1</SUB> –C<SUB>3</SUB> alcohols with 171.8 g/(kg<SUB>cat</SUB>·h).</P> <P><B>Highlights</B></P> <P> <UL> <LI> WxC phases on mesoporous Rh-Mn/WxC changed C<SUB>1</SUB>-C<SUB>3</SUB> alcohol selectivity from direct CO hydrogenation. </LI> <LI> Metastable W<SUB>2</SUB>C phase is beneficial for a higher productivity of mixed alcohols. </LI> <LI> Different oxidation states of strongly interacted small Rh nanoparticles are well correlated with catalytic activity. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

W-WC의 Spark Plasma Sintering에 의한 W₂C의 합성 및 식각특성

오규상,이성민,류성수,Oh, Gyu-Sang,Lee, Sung-Min,Ryu, Sung-Soo 한국분말야금학회 2020 한국분말재료학회지 (KPMI) Vol.27 No.4

W₂C is synthesized through a reaction-sintering process from an ultrafine-W and WC powder mixture using spark plasma sintering (SPS). The effect of various parameters, such as W:WC molar ratio, sintering temperature, and sintering time, on the synthesis behavior of W₂C is investigated through X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) analysis of the microstructure, and final sintered density. Further, the etching properties of a W₂C specimen are analyzed. A W₂C sintered specimen with a particle size of 2.0 ㎛ and a relative density over 98% could be obtained from a W-WC powder mixture with 55 mol%, after SPS at 1700℃ for 20 min under a pressure of 50 MPa. The sample etching rate is similar to that of SiC. Based on X-ray photoelectron spectroscopy (XPS) analysis, it is confirmed that fluorocarbon-based layers such as C-F and C-F2 with lower etch rates are also formed.

Metal Injection Molding 공정으로 제조된 W-7Ni-3Fe 텅스텐 중합금의 미세조직 및 기계적 특성에 미치는 열처리의 영향

윤성준,주연아,윤태식,이기안 대한금속·재료학회 2018 대한금속·재료학회지 Vol.56 No.10

This study investigated the microstructure and room temperature mechanical properties of W-7Ni- 3Fe (wt%) tungsten heavy alloy (as-fabricated) which was manufactured by metal injection molding (MIM). To identify the effect of heat treatment on the W-7Ni-3Fe alloy, its properties were compared after heattreatment (1,100 oC for 1 hour) in vacuum atmosphere. The initial microstructural observations confirmed that both the as-fabricated and heat-treated specimens were composed of W phase and γ(Ni, Fe) phase. Vickers hardness measurements were 363.7 Hv for the as-fabricated specimen and 387.2 Hv for the heat-treated specimen. Room temperature tensile strength was tested, and the yield strength of the as-fabricated and heattreated specimens were 698.3 and 714.0 MPa, and the ultimate tensile strengths were 760.8 and 960.0 MPa, respectively. The elongation of the two materials was 2.4% (as-fabricated) and 20.3% (heat-treated). It was found that additional heat treatment after MIM significantly improved the alloy’s mechanical properties. In addition, fracture surface observation results confirmed that the main crack propagated along the interface between the spherical W phase and γ(Ni, Fe) phase in the as-fabricated specimen, and traversed the W phase in the heat-treated specimen. Based on the above findings, this study also discusses the fracture mechanisms of tungsten heavy alloy manufactured with MIM.

Tungsten Carbide-Silicon Carbide Nanocomposite Fibers Prepared from Tungsten Nanoparticle Dispersed Polycarbosilane by Electrospinning

신동근,조광연,진은주,김영희,김수룡,권우택,이윤주,Jun-Sung Hong,류도형 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.4

W2C–SiC nanocomposite fibers were fabricated by electrospinning and pyrolysis using tungsten nanoparticle (nW; diameter, 3-5 nm) dispersed polycarbosilane solution. The nW was uniformly dispersed in the electrospun polycarbosilane fibers and transformed into α-W2C during pyrolysis at 1200 o C, where the polycarbosilane-derived SiC fibers acted as a source of carbon and as an effective support for the α-W2C nanoparticles, preventing them from converting into another phase at 1200 o C. A part of the nW dispersed on the fiber surface is considered to transform into α-W2C at the early stages of pyrolysis by carburization with the gases evolved during the pyrolytic decomposition of poly carbosilane, such as CH4.

Surface morphology and deuterium retention in W and W-HfC alloy exposed to high flux D plasma irradiation

Wang Yongkui,Huang Xiaochen,Zhou Jiafeng,Fang Jun,Gao Yan,Ge Jinlong,Miao Shu,Xie Zhuoming 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.2

In this work, pure W and W-0.5wt%HfC alloy (WHC05) were fabricated by sintering and hot-rolling following the same processing route. After exposing to a high flux deuterium plasma irradiation with the Dþ flux to three fluences of 6.00 1024, 2.70 1025 and 7.02 1025 D/m2, the evolution of surface morphology, deuterium retention and hardening behaviors in pureWand WHC05 has been studied. The SEM results show the formation of D blisters on the irradiated area, and with the increase of D implantation, the size of these blisters increases from 200 ~ 500 nm (2.70 1025 D/m2) to 1 ~ 2 mm (7.02 1025 D/m2) in WHC05 and from 1 ~ 2 mm (2.70 1025 D/m2) to > 3 mm (7.02 1025 D/m2) in pure W, respectively. A higher D retention and obvious hardening are observed in pure W than that of the WHC05 alloy, indicating an improve radiation resistance in WHC05 compared to pure W.

비구면 유리 렌즈 성형용 초경합금(WC) 표면에 이온 빔 보조 마그네트론 스퍼터가 적용된 이리듐-레늄 코팅 박막 특성에 관한 연구

정경서(K. S. Jung),김미선(M. S. Kim),이상원(S. W. Lee),최상경(S. K. Choi),이수경(S. K. Lee) 한국소성가공학회 2012 한국소성가공학회 학술대회 논문집 Vol.2012 No.10

Iridium-Rhenium(Ir-Re) thin films were deposited onto the tungsten carbide(WC) molding core by ion beam assist sputtering system. The Ir-Re films were prepared by compound-target sputtering with iridium, rhenium and chromium as the sources. Argon were inlet into the chamber to be the plasma and reactive gases. The Ir-Re thin films were prepared with targets having atomic percent of 7:3 and the Ir-Re thin films were formed with about 200 ㎚ thickness. The Ir-Re thin films on tungsten carbide molding core were analyzed by scanning electron microscope(SEM) and surface roughness. Also, adhesion strength and coefficient friction of Ir-Re thin film were examined. The Ir-Re coating technique has been intensive efforts in the field of coating process because the coating technique and process have been their feature, like hardness, high elasticity, abrasion resistance and mechanical stability and also have been applied widely the industrial and biomedical areas. In this report, tungsten carbide(WC) molding core was manufactures using high performance precision machining and the efforts of Ir-Re coating on the surface roughness.

텡스텐 플러그 CVD 공정에서 SiH₄ Soak의 영향

이우선,서용진,김상용,박진성 한국전기전자재료학회 2003 전기전자재료학회논문지 Vol.16 No.1

The SiH$_4$soak step is widely used to prevent the WF$_{6}$ attack to the underlayer metal using the chemical vapor deposition (CVD) method. Reduction or skipping of the SiH$_4$soak process time if lead to optimizing W-plug deposition process on via. The electrical characteristics including via resistance and the structure of W-film are affected by the time of SiH$_4$soak process. The possibility of elimination of SiH$_4$soak process is confirmed In the case of W- film grown on the stable Ti/TiN underlayer.