Computed Radiography에서 Additional Filtration Material에 따른 Radiation Dose와 Image Quality의 변화

권순무(Soon-Mu Kwon),조형욱(Hyung-Wook Cho),강영한(Yeong-Han Kang),김부순(Boo-Soon Kim),김정수(Jung-Su Kim) 대한방사선과학회(구 대한방사선기술학회) 2014 방사선기술과학 Vol.37 No.4

필터는 저에너지 X선을 흡수함으로써 평균에너지를 증가시키고, 환자의 피폭선량을 감소시키는 작용을 한다. 본 연구는 Mo과 W 등의 재질이 디지털 방사선영상장치인 CR에서도 사용이 가능한지 SNR, FOM, histogram 등의 영상평가와 선량 측정을 통해 확인하였다. 또한 필터의 재질에 따른 선질측정과 함께 관전압의 변화에 따른 적합한 필터 조합을 찾아보았다. 피부입사선량은 Mo필터가 Cu필터에 비해 42~56%까지 선량 경감효과가 있었고, 투과선량도 Mo필터가 Cu필터보다 1.5배 정도 높게 나타났다. 영상 평가에서 W은 필터로 사용함에 부적절하였으나, Mo은 80 kVp 이상의 관전압에서 영상의 질을 저하시키지 않으면서 선량을 감소시킬 수 있는 필터로 충분히 사용할 수 있음을 확인하였다. 2.0 mmAl+0.1 mmMo은 관전압이 높아질수 록 2.0 mmAl + 0.2 mmCu와 histogram width가 거의 같아서, 비교적 높은 관전압인 80, 100, 120 kVp에서는 Mo필터의 사용이 가능하다. 2.0 mmAl + 0.1 mmMo의 SNR은 2.0 mmAl + 0.2 mmCu와 2.0 mmAl+0.1 mmCu 의 SNR과도 큰 차이가 나지 않았다. 따라서 디지털 방사선 영상 중 80 kVp 이상을 이용하는 일반촬영에서 Cu를 대신하여 Mo을 필터로 사용하면 Cu에 비해 영상의 질을 저하시키지 않으면서 환자의 피폭선량을 크게 감소시킬 수 있으므로, 실제 임상의 흉부 촬영 및 고관전압 촬영 등에 충분히 적용할 수 있다고 본다. Filter absorbs low-energy X-ray to increase the average energy and reduces patient exposure dose. This study investigates if the materials of Mo and W could be used for the digital imaging device CR by con-ducting image assessment and dose measurement of SNR, FOM and histogram. In addition, measurement of beam quality was conducted depending on the material of the filter, and at the same time, a proper combination of filters was examined depending on the change in tube voltage (kVp). In regard to en-trance skin dose, Mo filter showed the dose reduction by 42∼56%, compared to Cu filter. Moreover, Mo filter showed higher transmission dose by around 1.5 times than that of Cu filter. In image assessment, it was found that W was unsuitable to be used as a filter, whereas Mo could be used as a filter to reduce dose without decline in image quality at the tube voltage of 80 kVp or higher. As tube voltage increased, 2.0 mm Al+0.1 mm Mo almost had a similar histogram width to that of 2.0 mm Al+0.2 mm Cu. Therefore, Mo filter can be used at relatively high tube voltage of 80 kVp, 100 kVp and 120 kVp. The SNR of 2.0 mm Al+0.1 mm Mo did not show any significant difference from those of 2.0 mm Al+0.2 mm Cu and 2.0 mm Al+0.1 mm Cu. As a result, if Mo filter is used to replace Cu filter in general radiography, where 80 kVp or higher is used for digital radiation image, patient exposure dose can be reduced significantly with-out decline in image quality, compared to Cu filter. Therefore, it is believed that Mo filter can be applied to chest X-ray and high tube voltage X-ray in actual clinical practice.

PMOS에 적합한 Mo 전극의 전기적 화학적 안정성

노영진,이충근,홍신남 대한전자공학회 2004 電子工學會論文誌-SD (Semiconductor and devices) Vol.41 No.4

본 논문에서는 Mo을 PMOS의 금속 게이트로 사용하였을 때의 Mo의 특성에 대해서 연구 하였다. Mo을 게이트 물질로 사용한 MOS 커패시터를 제작하였고, 소자의 C-V 특성 곡선으로부터 일함수를 추출하였다. 그 결과 Mo 게이트는 PMOS에 적합한 일함수를 나타내는 것을 알 수 있었다. Mo의 전기적/화학적 안정성을 검증하기 위해서 600, 700, 800 그리고 900℃에서 급속 열처리를 수행하였으며 열처리 이후 유효 산화막의 두께와 일함수의 변화를 살펴보았다. 또한 900℃ 열처리 이후의 XRD 분석을 통해서 Mo 금속 게이트가 SiO₂에 대해서 안정하다는 것을 확인하였다. 4점 탐침기로 측정한 Mo 금속 게이트의 면저항은 10Ω/□ 미만으로 폴리 실리콘에 비해서 매우 작은 값을 나타냈다. In this paper, the properties of Mo as PMOS gate electrodes were studied. The work-function of Mo extracted from C-V characteristic curves was appropriate for PMOS. To identify the electrical and chemical stability of Mo metal gate, the changes of work-function and EOT(Effective Oxide Thickness) values were investigated after 600, 700, 800 and 90$0^{\circ}C$ RTA(Rapid Thermal Annealing). Also it was found that Mo metal gate was stable up to 90$0^{\circ}C$ with underlying SiO$_2$through X-ray diffraction measurement. Sheet resistances of Mo metal gate obtained from 4-point probe were less than 10$\Omega$/$\square$ that was much lower than those of polysilicon.

Mo-MoO₃-graphene nanocomposites as anode materials for lithium-ion batteries: scalable, facile preparation and characterization

Lee, Hack-Jun,Shim, Hyun-Woo,Kim, Jae-Chan,Kim, Dong-Wan Elsevier 2017 ELECTROCHIMICA ACTA Vol.251 No.-

<P><B>Abstract</B></P> <P>The development of high-performance anode materials, along with simple synthesis processes, is of main issues to replace the commercial graphite anode and to achieve practical applications of Li-ion batteries (LIBs). Herein, we report a facile, scalable preparation of multiple Mo-MoO<SUB>3</SUB>-graphene nanocomposites using a simple wire-explosion process, followed by heat treatment in air, and their electrochemical performance as anode materials of LIBs. In this process, Mo wire is electrically exploded in methanol containing graphene at room temperature, resulting in well-dispersed Mo nanoparticles anchored on graphene. Subsequently, partial oxidation of Mo nanoparticles to MoO<SUB>3</SUB> is achieved at 300°C in air, forming Mo-MoO<SUB>3</SUB>-graphene nanocomposites. For comparison, Mo-MoO<SUB>3</SUB> nanocomposites are also prepared under the same conditions, without using graphene. Systematic phase and microstructural characterizations of both nanocomposites, as well as the as-synthesized Mo nanoparticles, are investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and Raman spectroscopy. Their Li-storage performances are also evaluated and compared. Since graphene acts as a mechanical support to prevent Mo nanoparticle aggregation, and both Mo nanoparticles and graphene play an important role in providing effective electron pathways between active MoO<SUB>3</SUB> nanoparticles, Mo-MoO<SUB>3</SUB>-graphene nanocomposites exhibit the conductivity and Li<SUP>+</SUP> diffusivity enhancements (3.35×10<SUP>−14</SUP> cm<SUP>2</SUP> s<SUP>−1</SUP>), and structural stability, resulting in not only enhanced cycling performance, with a reversible capacity of 611mA h g<SUP>−1</SUP> after 50 cycles at a constant current rate of 0.1C, but also a better rate performance than Mo-MoO<SUB>3</SUB> nanocomposites. These synergistic functions are responsible for the better Li-storage performance of Mo-MoO<SUB>3</SUB>-graphene nanocomposite, which can lead to the promising candidates for LIB anode materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Wire-explosion in liquid media is of effective way to make complex nanostructures. </LI> <LI> Mo-MoO<SUB>3</SUB>-graphene nanocomposites (MG-300) are prepared via simple two-step process. </LI> <LI> The structural features and electrochemical evaluations are systematically studied. </LI> <LI> A fast Li<SUP>+</SUP> diffusivity (3.35×10<SUP>−14</SUP> cm<SUP>2</SUP> s<SUP>−1</SUP>) and structural stability of MG-300. </LI> <LI> Synergistic functions of MG-300 anode lead to the enhanced Li-storage performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

$Al_2O_3/Mo/MnO_2$ 복합재료의 기계적 특성

박현,김경남,Park, Hyun,Kim, Kyung-Nam 한국결정성장학회 2006 韓國結晶成長學會誌 Vol.16 No.4

When $Al_2O_3-MoO_3$ mixture is reduced, $MoO_3$ is only reduced to Mo at $900^{\circ}C$. But a compound between $Al_2O_3$ and Mo is not formed up to $1300^{\circ}C$. In the case of $Al_2O_3-MoO_3-MnO_2$ mixture, an intermediate compound $Mn_2Mo_3O_8$ is firstly formed at $900^{\circ}C$ and changes to $MnAl_2O_4$ at $1100^{\circ}C{\sim}1300^{\circ}C$. $Al_2O_3/Mo/MnO_2$ composite are manufactured by a selective reduction process in which Mo is only reduced in the powder mixture of $Al_2O_3,\;MoO_3\;and\;MnO_2$ oxide. For $Al_2O_3/Mo$ composite, the average grain size was not changed with increasing Mo content because of inhibition of grain growth of $Al_2O_3$ matrix in the presence of Mo particles. Fracture strength increased with increasing Mo content due to phenomenon of grain growth inhibition of $Al_2O_3$ matrix. Hardness decreased because of a lower hardness value of Mo, whereas fracture toughness increased. For $Al_2O_3,\;Mo\;and\;MnO_2$ composite, grain growth was facilitated by MnOB and it showed a lower fracture strength because of grain growth effect with increasing Mo and $MnO_2$ content. Hardness decreased because of the grain growth of matrix and coalesced Mo particles to be located in grain boundary, whereas fracture toughness increased. [ $Al_2O_3-MoO_3$ ]의 혼합물을 환원소성하면 $MoO_3$만 $900^{\circ}C$에서 Mo로 환원되고 $1300^{\circ}C$까지 $Al_2O_3$와 Mo간의 화합물은 형성되지 않았다. $Al_2O_3-MoO_3-MnO_2$, 혼합물의 경우, $900^{\circ}C$에서 먼저 $MnO_2$가 $MoO_3$와 반응하여 중간화합물 $Mn_2Mo_3O_8$를 형성하였다가. $1100^{\circ}C$와 $1300^{\circ}C$에서 $Mn_2Mo_3O_8$ 화합물은 사라지고 새로운 화합물 $MnAl_2O_4$가 생성되었다. $Al_2O_3$와 $MoO_3,\;MnO_2$의 혼합분말 중 Mo만이 선택적으로 환원되는 selective reduction process에 의해 $Al_2O_3/Mo/MnO_2$ 복합재를 제조하였다. $Al_2O_3/Mo$ 복합재의 경우 Mo의 함량이 증가함에도 불구하고 Mo입자가 $Al_2O_3$ matrix의 입성장을 억제하여 평균입경의 변화는 거의 없었다. 파괴강도는 $Al_2O_3$ matrix의 입성장 억제 현상 때문에 Mo의 함량이 증가함에 따라 증가하였다. 경도는 Mo의 낮은 경도값 때문에 약간 감소하였으나 반면에 파괴인성은 증가하였다. $Al_2O_3/Mo/MnO_2$ 복합재의 경우 $MnO_2$는 matrix의 입성장을 촉진시켰고, Mo와 $MnO_2$의 함량이 증가함에 따라 $MnO_2$의 입성장효과 때문에 오히려 낮은 파괴강도를 보였다. 경도는 입계에 존재하는 coalesced Mo 입자들과 matrix의 입성장 때문에 더욱 감소하였으나 반면에 파괴인성은 더욱 증가하는 경 향을 보였다.

Spontaneously Adsorbed Mo Layers on Pt(111) and Pt(100) Single Crystal Electrode Surfaces

Han, Yoon-gu,Jung, Chang-hoon,Rhee, Choong-Kyun Korean Chemical Society 2002 Bulletin of the Korean Chemical Society Vol.23 No.3

The voltammetric behavior of spontaneously adsorbing Mo layers on Pt(111) and Pt(100) electrodes has been studied to estimate the number of electrons involved in the electrochemical processes of spontaneously adsorbed Mo and the number of the bloc ked Pt sites for hydrogen adsorption. On Pt(111) and Pt(100) surfaces, the spontaneously adsorbed Mo layers showed redox peaks at 0.10 V and 0.15 V, respectively, and continuous current-potential waves in the conventional hydrogen region. Since the potential range of the Mo redox processes on both surfaces overlapped partially with the potential range of hydrogen adsorption, the variation in the ratio of the total charge of Mo and H ($Q_H$ +$Q_{MO}$) to the hydrogen charge of clean Pt electrode ($Q_H^0$) was analyzed. From the analysis, six electrons were estimated to be involved in the electrochemical processes of the spontaneously adsorbed Mo, and four Pt sites for hydrogen adsorption were calculated to be blocked by one adsorbed Mo atom. Based on these figures and the pH dependence of the Mo redox processes, we have proposed an electrochemical equation for the spontaneously adsorbed Mo. This electrochemical equation led us to conclude that the saturation coverage of the spontaneously adsorbed Mo is 0.25. The coverage of Mo less than 0.25, however, could not be determined voltammetrically due to the convolution of the charges of Mo and H.

폐 인코넬계(Inconel 713C)내열합금 모의 침출액으로부터 액-액 추출법에 의한 Mo의 회수 및 Mo 화합물 제조

안종관(Jong-Gwan Ahn),김다영(Da-young Kim),인용현(Yong-Hyeon In) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.8

고온 부품 소재로 사용하는 니켈계 내열합금인 Inconel 713C에는 Ni 70 %, Cr 12 %, Al 6 % 및 Mo 4% 등의 유가금속을 함유되어 있다. 이중 유가금속에서 경제적 가치를 가지는 원소는 Mo이므로 회수하여 재활용하여야 한다. 본 연구는 폐 인코넬계(Inconel 713C) 모의 내열합금 침출액으로부터 액-액 추출법(용매추출법 및 역추출법)을 이용하여 Mo을 분리 회수하였다. 회수된 수상을 증발 건조 및 열처리법을 이용하여 Mo 화합물을 제조하였다. 수상은 NaMoO₄ · 2H₂O을 증류수에 용해하여 사용하였으며, 추출제로는 음이온추출제인 Alamine 336과 양이온추출제인 Cyanex 272, 희석제로는 등유(Kerosene) 사용하였고, 음이온추출제인 Alamine 336 1 %이상에서 99 % 이상의 추출률을 확인하였다. 역추출제로는 황산, 염산 및 질산을 사용하였고, 각각 농도가 증가할수록 탈거율이 증가하였으며, 질산의 경우 4 M에서 96 %의 탈거율을 나타냈었다. 용매추출과 역추출에서 얻은 Mo 함유 수상을 증발 건조하여 순도 97.5 %의 MoO₃를 제조하였다. 본 연구를 통해 Mo이 함유된 순환자원으로부터 Mo을 효율적으로 회수하면 국내의 자원효율성과 자원수요의 공급경쟁력을 향상시킬 수 있다. Inconel 713C which of a commercial Ni super alloy have the composition of 70 % Ni, 12 % Cr, 6 % Al and 4 % Mo. Mo is very expensive and have some economic value to recover in the alloy. In this study, liquid-liquid exraction(solvent extraction and stripping) has been performed to separate Mo from the synthetic leaching solution of spent Inconel 713C alloy and prepare to Mo powder by dying, evaporation and heat treatment. The experiments were conducted by using synthetic leaching solution which was prepared NaMoO₄·2H₂O by dissolved in distilled water. Alamine336 and Cyanex272 dissolved in kerosene were used as extractants. The extraction percentage of Mo by Alamine336 is 99 % in the condition of the range of pH 1 to 4 and 1 % of concentration of Alamine336. The stripping solutions are used by HCl, H₂SO₄ and HNO₃ solutions and the concentrations were controlled by distilled water. The concentrations of HCl, H₂SO₄ and HNO₃ as stripping solutions are increased, the stripping percentages of Mo are increased and the stripping percentage of Mo by HNO₃ is higher than other stripping solutions. After liquid-liquid extraction and heat treatment, MoO₃ powder which of the purity of 97.5 % was prepared.

Mo/Mo-Na 후면전극에 의한 전해증착 CuInSe2 박막으로의 Na 첨가

장명제 ( Myeong Je Jang ),김명한 ( Myung Han Kim ) 충북대학교 산업과학기술연구소 2014 산업과학기술연구 논문집 Vol.28 No.2

Na in CuInSe2(CIS) absorber is well known to improve the solar cell performance. In the present study, Na was added into the electro-deposited CIS absorber with Mo / Mo-Na bilayer back contact, deposited on the Na-free Corning glass. The thickness of Mo-Na layer was varied between 0 and 500 nm. After heat-treating the Mo-Na / Mo / CIS layer at 500 °C for 30 min in Ar atmosphere, the AES depth profile analysis represented that Na was diffused from the Mo-Na layer to Mo layer and then diffused into the CIS layer. The XRD measurements showed the decreased peaks of the preferred orientation(110) of Mo with increasing Na concentration. The peaks of preferred orientation (112) of CIS orientation increased with the increase of Mo-Na layer thickness up to 200 nm, and then decreased as the Mo-Na layer thickness increased. The CIS grains, grown vertically to the Corning glass, showed the columnar dendrites and the grain sizes increased with the increase of Mo-Na layer thickness up to 200 nm. However, beyond that thickness, the CIS grains did not change so much in sizes and grew irregularly, especially at the Mo-Na layer thickness of 500 nm. The results represent that Na concentration in the CIS absorber can be controlled with varying the Mo-Na layer thickness of back contact and the excessive amount of Na in CIS absorber can be detrimental to the photovoltaic property.

Formation of a Mo₂N skin layer in columnar-structural Mo films using NH₃ plasma nitridation as the Se diffusion-barrier layer

Kim, H.T.,Kim, C.,Kim, C.d.,Park, C. Elsevier Sequoia 2016 Surface & Coatings Technology Vol.302 No.-

Mo<SUB>2</SUB>N skin layers were formed on columnar-structural Mo films by simple NH<SUB>3</SUB> plasma nitridation. The plasma-nitrided Mo (n-Mo) films contained the (111) preferred phase of γ-Mo<SUB>2</SUB>N phase and (112) preferred phase of β-Mo<SUB>2</SUB>N. The thickness of n-Mo films slightly increased without structural morphology change compared to that of pure-Mo films, and seldom changed after selenization. The electrical properties of the n-Mo films changed slightly compared to the Mo films after nitridation and the resistivity of the n-Mo films exhibited a slight increase after selenization. N-element was found widely along the z-axis of n-Mo films, and the concentration of N decreased gradually from the surface to bottom of Mo films. These results imply that the diffusion of N element occurred simultaneously along the lattice and grain boundaries (GB), which followed B-kinetics of Harrison's classification (GB width@?nitridation depth@?grain size). The n-Mo films exhibited the strong chemical stability under Se-environment, and the method developed in this study was an easy and effective technique for forming a Mo<SUB>2</SUB>N skin layer. Therefore, it is expected that this method can not only extend the process margin for selenization, but also reduce the resistive components in solar cell devices.

The effect of Mo addition on the microstructural evolution and mechanical properties of Zr-Cu-based metallic glass thin films

신정호,김두인,조홍백,김도형,Hisayuki Suematsu,김광호 한양대학교 세라믹연구소 2014 Journal of Ceramic Processing Research Vol.15 No.2

Ternary Zr-Cu-Mo metallic glass thin films (MGTFs) with various Mo contents were synthesized on Si (100) wafers and AISI 304 stainless steel substrates by a magnetron co-sputtering technique, using Zr64Cu36 and Mo targets in an Ar gas environment. The effects of Mo addition in a binary Zr64Cu36 MGTF were investigated, with regard to the microstructural evolution and mechanical properties of Zr-Cu-Mo thin films. Instrumental analyses, such as EPMA, XRD, and HR-TEM revealed that ZrCu-Mo films with an Mo content below 38 at.% maintained the monolithic amorphous phase structure. However, when Mo content is added above 46 at.%, the Zr-Cu-Mo films begin to have nanocomposite structures of well-distributed Mo2Zr and Mo crystallites embedded in an amorphous matrix. The hardness and elastic modulus of amorphous Zr-Cu-Mo films showed nearly constant values of 10 GPa and 166 GPa, respectively, regardless of their Mo content. As Zr-Cu-Mo films have nanocomposite structures at a Mo content of 52 at.%, their mechanical properties showed increased hardness and elastic moduli of 17 GPa and 240 GPa, respectively. The Mo addition generally reduced the average friction coefficient of the ternary Zr-Cu-Mo thin films regardless of phase structure, which can be attributed to the effect of the Mo addition.

Improved photoelectrochemical performance of molybdenum (Mo)-doped monoclinic bismuth vanadate with increasing donor concentration

Tayebi, Meysam,Tayyebi, Ahmad,Lee, Byeong-Kyu Elsevier Science Publishers 2019 Catalysis today Vol.328 No.-

<P><B>Abstract</B></P> <P>Molybdenum (Mo)-doped Monoclinic Bismuth Vanadate (Mo-BiVO<SUB>4</SUB>; BVO) catalysts were fabricated via a simple dip coating method. We systematically studied the effect of Mo-doping with various concentration (1–5%) in BVO electrode through photoelectrochemical (PEC), Mott-Schottky and impedance measurement. Intermediate heat treatment and number of successive dip coating deposition were utilized to control the monoclinic crystallization and thickness of Mo-BVO photoanodes. Furthermore, the effect of Mo-doping in morphology, structure, chemical states and optical properties of the obtained electrodes were characterized by different physico-chemical and morphological methods BVO with 2% Mo doping (2% Mo-BVO) showed the best PEC performance, of about 15 times higher than that of the pure BVO. Improved charge carrier transport and optimized light absorption obtained upon Mo doping into the BVO crystal lattice while the monoclinic scheelite structure with small band-gap was retained. To understand the effect of Mo-doping, Mott Schottky and Impedance measurement carried out, in order to evaluate the donor concentration and conductivity of pure BVO and Mo-BVO. Interestingly, 2% Mo-BVO showed the maximum donor concentration (5.7E + 27) and minimum flat band potential (V<SUB>fb</SUB> = −0.45) compared to other prepared electrodes. Furthermore, we attempt to discuss the improved PEC performance of Mo-BVO using high donor concentration, up-shifting of Fermi level and consequently facilitating electrons transport in Mo-BVO compared to pure BVO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mo-BVO electrodes were fabricated via a four dip-coating cycles method. </LI> <LI> Photocurrent density increased 15-fold for 2% Mo-BVO compared with pure BVO. </LI> <LI> Mott-Schottky results indicated 2% Mo-BVO has the maximum donor concentration. </LI> <LI> The PEC measurement showed shifting of onset potential to lower voltage for Mo-BVO. </LI> <LI> The Impedance data exhibited 2% Mo-BVO has the best PEC performance compared to other photoanodes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>