Mo Sheet Research Articles

Photocatalyst Sheets Composed of Particulate LaMg1/3Ta2/3O2N and Mo-Doped BiVO4 for Z-Scheme Water Splitting under Visible Light

Z-Scheme water splitting by photocatalyst sheets is a promising approach for efficient and scalable H2 production. One of the most important challenges in developing such photocatalyst sheets is the application of photocatalysts with long absorption edges. In this study, RhCrOx-loaded LaMg1/3Ta2/3O2N (RhCrOx/LaMg1/3Ta2/3O2N) and Mo-doped BiVO4 (BiVO4:Mo), with absorption edges at 600 and 540 nm, are investigated as the hydrogen evolution photocatalyst and oxygen evolution photocatalyst in photocatalyst sheets, respectively. The (RhCrOx/LaMg1/3Ta2/3O2N)/Au/BiVO4:Mo sheet exhibits water splitting activity that is ∼5 times higher than that of corresponding powder suspensions. Stable water splitting is achieved under visible light using the (RhCrOx/LaMg1/3Ta2/3O2N)/Au/BiVO4:Mo sheet coated with an amorphous TiO2 protective layer. However, the results show the low H2 evolution activity of the RhCrOx/LaMg1/3Ta2/3O2N imposes a ceiling on the activity of the photocatalyst sheet. The surface modification of LaMg1/...

Metal Free Hybrid Capacitor Using Intercalation of 1-Butyl-3-Methylimidazolium Cation to Acetylene Black, Ketjen Black and Graphite

1. Introduction Lithium ion capacitor (LIC) is one of the most promising hybrid capacitors (HCs) with the negative electrode for lithium ion battery (LIB) and activated carbon (AC) positive electrode. Recent progress of LIC realized its high energy density over 80 Wh kg-1 and LIC is already commercially available for several applications like backup power supply, load leveling for natural power sources, energy regeneration etc. 1 Moreover, LIC has better cyclic performance and power density than LIB so high performance LIC is considered as next generation power sources for mobile electric devices and electric vehicles. However, the charging mechanism of the carbon negative electrode is insertion of Li+ ion and its potential is 0.01 V vs. Li/Li+ which is quite similar to the Li metal precipitating potential (0V vs. Li/Li+). It is well known that the precipitation of Li metal causes internal short circuiting and deadly explosion. To avoid such risk, Li free HC is one of the most promising idea. In this work, we realized the Li+ free HC with ionic liquid for safe and high energy density power sources. Recent study suggested the large cation like 1-Butyl-3-methylimidazolium (BMI+) can be inserted/deserted into carbon electrode. So we used the ionic liquid (1-Butyl-3-methylimidazolium tetrafluoroborate (BMIBF4)) as electrolyte and insertion/desertion of BMI+ into carbon electrode was used as negative electrode reaction. AC was used as positive electrode. Three different carbon materials (acetylene black (AB), ketjen black (KB) and graphite) were investigated as negative electrode materials. 2. Experimental Mo sheet was used as current collector. AB, KB and graphite powder was dispersed into N-methyl-2-pyrrolidon with polyvinylidene difluoride which is used as binder. The slurry was sonicated for 15 min and casted onto Mo current collector. AC was mixed with polytetrafluoroethylene in mortar and cold pressed with 30 MPa for 5 min, which was used as positive electrode. BMIBF4 was dried under vacuum for 24 h at 85 °C. The homemade glass cell was used for HC. Ag wire was used as pseudo reference electrode. 3. Results and discussion Fig. 1 shows the charge/discharge curves of HCs with the KB, AB and graphite negative electrodes. HCs with AB and graphite negative electrode was charged to 3.7 V but the cell voltage was limited below 3.2 V in the case of the HC with KB negative electrode because decomposition of the electrolyte was started below 3.5 V. Excepting the charge voltage, three HCs showed almost the same features. Fig. 2 shows the changes in the potential of KB, AB and graphite negative electrode and AC positive electrode. Each negative electrode showed plateaus during charge/discharge process around -2 V vs Ag and -1 V vs Ag, respectively. On the other hand, AC positive electrode showed triangular charge/discharge curves which is typical for the electrochemical double layer capacitor. These phenomena suggests the charge/discharge process of negative electrode in HCs is insertion/desertion of BMI+ and the positive electrode worked as electrochemical double layer capacitor. Fig. 3 shows the change in discharge capacitance with cycle number for the HCs. The discharge capacitance of HC with AB and graphite negative electrode rapidly decreased. However, the HC with KB electrode showed long life cycle durability over 1500 cycles. This might be due to the property of KB, which has shell like carbon layers and it prevented collapse of the negative electrode materials. References 1) K. Naoi et. al. Energy Environ. Sci., 5, 9363 (2012) Figure 1

The Effects of Grain Size and Texture on Dynamic Abnormal Grain Growth in Mo

This is the first report of abnormal grain morphologies specific to a Mo sheet material produced from a commercial-purity arc-melted ingot. Abnormal grains initiated and grew during plastic deformation of this material at temperatures of 1793 K and 1813 K (1520 °C and 1540 °C). This abnormal grain growth during high-temperature plastic deformation is termed dynamic abnormal grain growth, DAGG. DAGG in this material readily consumes nearly all grains near the sheet center while leaving many grains near the sheet surface unconsumed. Crystallographic texture, grain size, and other microstructural features are characterized. After recrystallization, a significant through-thickness variation in crystallographic texture exists in this material but does not appear to directly influence DAGG propagation. Instead, dynamic normal grain growth, which may be influenced by texture, preferentially occurs near the sheet surface prior to DAGG. The large grains thus produced near the sheet surface inhibit the subsequent growth of the abnormal grains produced by DAGG, which preferentially consume the finer grains near the sheet center. This produces abnormal grains that span the sheet center but leave unconsumed polycrystalline microstructure near the sheet surface. Abnormal grains are preferentially oriented with the $$\left\langle 110\right\rangle $$ approximately along the tensile axis. These results provide additional new evidence that boundary curvature is the primary driving force for DAGG in Mo.

Preparation and properties of high-strength molybdenum alloy sheets doped with Al2O3 particles

The pure molybdenum sheet and the Al2O3-doped molybdenum alloy sheets were prepared by the hydrothermal method and a subsequent powder metallurgy process. The effects of Al2O3 particles addition on the recrystallization temperature, microstructures and properties of the Mo sheets were investigated as the focus. The Al2O3-doped Mo sheets have greater strength than the pure Mo sheet, and the 0.50 wt% Al2O3-doped Mo sheet has the best performance. For the unannealed specimens, the strength increases with the increase in Al2O3 content. Compared with that of pure Mo sheet, the strength of 0.50 wt% Al2O3-doped Mo sheet increases by 72 %, 54 %, 73 % and 76 %, respectively, when annealed at 1000, 1100, 1200 and 1300 °C, which is a very obvious reinforcement effect. When lower than 1100 °C, the elongation of the pure Mo sheet is the best. However, when the annealing temperature is equal to or greater than 1100 °C, the 0.50 wt% Al2O3-doped Mo sheet obtains the best elongation. Moreover, the Al2O3 addition can greatly improve the recrystallization temperature of molybdenum sheets; for example, the recrystallization temperature of the 0.50 wt% Al2O3-doped Mo sheet increases by 200 °C at least than that of the pure Mo sheet. Lastly, the strengthening mechanism was discussed.

Characterization of Al2O3 in High-Strength Mo Alloy Sheets by High-Resolution Transmission Electron Microscopy.

A novel type of alumina (Al2O3)-doped molybdenum (Mo) alloy sheet was prepared by a hydrothermal method and a subsequent powder metallurgy process. Then the characterization of α-Al2O3 was investigated using high-resolution transmission electron microscopy as the research focus. The tensile strength of the Al2O3-doped Mo sheet is 43-85% higher than that of the pure Mo sheet, a very obvious reinforcement effect. The sub-micron and nanometer-scale Al2O3 particles can increase the recrystallization temperature by hindering grain boundary migration and improve the tensile strength by effectively blocking the motion of the dislocations. The Al2O3 particles have a good bond with the Mo matrix and there exists an amorphous transition layer at the interface between Al2O3 particles and the Mo matrix in the as-rolled sheet. The sub-structure of α-Al2O3 is characterized by a number of nanograins in the $\left[ {2\bar{2}1} \right]$ direction. Lastly, a new computer-based method for indexing diffraction patterns of the hexagonal system is introduced, with 16 types of diffraction patterns of α-Al2O3 indexed.

Dynamic Abnormal Grain Growth in Refractory Metals

High-temperature plastic deformation of the body-centered cubic (BCC) refractory metals Mo and Ta can initiate and propagate abnormal grains at significantly lower temperatures and faster rates than is possible by static annealing alone. This discovery reveals a new and potentially important aspect of abnormal grain growth (AGG) phenomena. The process of AGG during plastic deformation at elevated temperatures, termed dynamic abnormal grain growth (DAGG), was observed at homologous temperatures between 0.52 and 0.72 in both Mo and Ta sheet materials; these temperatures are much lower than those for previous observations of AGG in these materials during static annealing. DAGG was used to repeatedly grow single crystals several centimeters in length. Investigations to date have produced a basic understanding of the conditions that lead to DAGG and how DAGG is affected by microstructure in BCC refractory metals. The current state of understanding for DAGG is reviewed in this paper. Attention is given to the roles of temperature, plastic strain, boundary mobility and preexisting microstructure. DAGG is considered for its potential useful applications in solid-state crystal growth and its possibly detrimental role in creating undesired abnormal grains during thermomechanical processing.

Texture evolution and mechanical anisotropy of biomedical hot-rolled Co–Cr–Mo alloy

Crystallographic textures and their effect on the mechanical anisotropy of a hot-rolled biomedical Co–Cr–Mo alloy were investigated. The hot-rolled Co–28Cr–6Mo–0.13N (mass%) alloy examined here exhibited a monotonic strength increment following hot-rolling reduction, eventually reaching a 0.2% proof stress of 1400MPa while maintaining acceptable ductility (>10%). The dominant hot-rolling texture was a brass-type component, which is characterized by the alloy’s peculiarly low stacking fault energy (SFE) even at hot rolling temperatures, although the minor peaks of the near copper component were also identified. However, because of the onset of dynamic recrystallization (DRX) during the hot rolling process, the texture intensity was relatively weak even after 90% hot rolling, although the grain refinement originating from the DRX was not significant (the “less active DRX” condition increased the strain accumulation during the process, resulting in high-strength samples). The weakened texture development resulted in negligible in-plane anisotropy for the hot-rolled specimen strength, when the specimens were tensile strained in the rolling direction (RD) and transverse direction (TD). The elongation-to-failure, however, exhibited a difference with respect to the tensile loading axis. It is suggested that the ductility anisotropy is closely related to a strain-induced γ (fcc)→ε (hcp) martensitic transformation during tensile loading, resulting in a difference in the proportion of quasi-cleavage fracture surfaces. The obtained results will be helpful in the development of high-strength Co–Cr–Mo alloy plates and sheets, and have implications regarding plastic deformation and texture evolution during the hot rolling of non-conventional metallic materials with low SFE at elevated temperatures, where planar dislocation slips of Shockley partial dislocations and thermally activated process interplay.

Oxidation Resistance of Diffusion Silicide Coatings on Mo and TZM Alloy

Characterization of microstructure of pack cemented silicide coatings based on MoSi2 phase was described in this article as well as a short term oxidation resistance of these types of coatings at temperature 1200oC. Silicide coatings were deposited on top surface of Mo and Mo alloys of TZM type by diffusional process of siliconizing in activated powders. Morphology of coatings was characterized by evaluation of chemical and phase’s composition of deposited coatings by EDS and XRD methods respectively. In the case of Mo sheet after diffusion process of siliconizing single layer of MoSi2 type was obtained, but in the case of TZM alloy, in the same conditions of process, double layered coating was generated. Thick outer layer was build form MoSi2 phase, but very thin internal layer consist Mo5Si3 phase. The thicknesses of coatings were ca. 45μm, and were uniform. Morphology of coatings was free from inclusion and contaminations in their cores. The isolated cracks were observed, but their volume was very small. The oxidation test was performed at temperature 1200oC. The specimens were tested at 25, 500 and 100 hours of test. After each period of test characterization of coatings top surface was made. Total destruction of specimens was observed in range between 50 and 100 h of test.

Laser Remelting of Silicide Coatings on Mo and TZM Alloy

Characterization of top surface and microstructure of silicide coatings obtained during diffusion process of pack cementation type and laser remelting treatments was showed in this article. The basic materials were pure Mo sheet and TZM molybdenum alloy. The coatings were deposited in powder process and glazed by different types of lasers. In first step the phase’s compositions of coatings was described by XRD analysis in initial condition and after remelting process. The morphology of the coatings top surface was described as well. All types of coatings were characterized by network of cracks on top surface of the coatings. Laser treatment of the silicide top surface changed morphology of the top surface, especially their cracks network. LM and SEM analysis revealed that internal coatings morphology was very similar in all cases.

Microstructural Characterization of Silicide Coatings on Mo and TZM Alloy

Characterization of microstructure of silicide coatings obtained during diffusion process of pack cementation type was showed in this article. The basic materials were pure Mo sheet and TZM molybdenum alloys as well. The coatings were deposited in out of pack process with three different times of exposure. The temperature of deposition process was constant. In first step the phases compositions of coatings was described by XRD analysis. In each cases the MoSi2 phase was obtained on top surface of the coatings. The morphology of the coatings was very similar as well. All types of coatings were characterized by network of cracks on top surface of the coatings. There was no influence of depositions time on phases constituent and coatings topography. LM and SEM analysis revealed that internal coatings morphology was very similar in all cases. Basic differences was related to the thickness of coatings. All coatings were good quality without deep cracks. Microstructure was a columnar-like type without pores and voids.

Comparative study on graphene growth mechanism using Ni films, Ni/Mo sheets, and Pt substrates

We demonstrate a comparative study on graphene growth mechanism using various catalytic metal substrates such as Ni thin films, Ni-deposited Mo (Ni/Mo) sheets, and Pt sheets during chemical vapor deposition (CVD). Depending on the substrates, two kinds of graphene growth mechanisms that involve either precipitation or surface adsorption of carbon have been reported. We synthesized graphene, focusing especially on the initial growth stage during CVD, by varying synthesis parameters such as synthesis time, amount of feedstock, and cooling rate after synthesis. We concluded that precipitation-driven synthesis is dominant in the case of Ni substrates whereas adsorption-driven growth is dominant in the Ni/Mo system. In the case of the Pt substrate, which is generally believed to grow by carbon precipitation, graphene growth by adsorption was found to be dominant. We believe that our results will contribute to a clearer understanding of the graphene synthesis mechanism, and development of manufacturing routes for controllable synthesis of high-quality graphenes.

Mechanical properties of molybdenum products prepared by using molybdenum powders with different micro-morphologies

Using two kinds of molybdenum (Mo) powders with different micro-morphologies as raw materials, the Mo wires with a diameter of 0.18 mm and Mo sheets with thickness of 0.5 and 0.2 mm were prepared at the same process of pressing, sintering, drawing, or rolling, respectively. By comparative analysis on the microstructure and mechanical properties of Mo wires and Mo sheets, the effect of Mo powder micro-morphology on properties and quality of Mo products was studied. The results show that, compared with that prepared by traditional Mo powder with inhomogeneous particle size and aggregation, the Mo wires prepared by specific Mo powder with homogeneous particle sizes, less agglomeration, and better dispersion exhibit higher yield, higher tensile strength, and lower elongation at room temperature, and the Mo sheets also show excellent high-temperature performances and better isotropy. The essential reason for those is the difference of Mo powder micro-morphology. Inhomogeneous particle size and aggregation of Mo powder greatly influence the microstructure of Mo sintered compacts and mechanical properties of Mo products.

Recrystallization of BCC Metals: Distribution of Strain Hardening and Texture Formation

Data are presented on the x-ray line broadening distribution over the texture of cold-rolled Nb and Mo sheets. The method of generalized X-ray pole figures, which combine texture measurements with X-ray line profile analysis, is employed. The X-ray line broadening is considered as an indicator of residual deformation effects. It was revealed that these effects in cold-rolled BCC metals rise as the grain orientation shifts away from texture maxima towards texture minima. The intensity of X-ray reflections change during annealing at 200 – 500C and this change correlates with the line broadening. The recrystallization texture of BCC metals is dominated by orientations deflected from the peak maxima by 25 – 30 deg. These orientations in the deformed structure have relatively high stored energy. Their volume fraction is sufficient for them to be able to consume most of the deformed matrix.

An Investigation on Structural and Electrical Properties of RF-Sputtered Molybdenum Thin Film Deposited on Different Substrates

Molybdenum (Mo) is the prominent choice as the back contact for various thin film solar cells such as CIGS, CZTS and CdTe. Physical vapour deposition (PVD) technique especially sputtering process has been chosen as the foremost method to deposit Mo thin film on top of desired substrate due to ease of parametric control of growth conditions. In this paper, we reported the effect of various RF power, operating pressure as well as temperature on Mo films on top of Mo sheet and soda lime glass (SLG) deposited using RF magnetron sputtering. Uniform surface morphology was obtained as RF power, operating pressure and deposition temperature were optimised. However, at higher deposition temperature less uniform surface was observed. XRD pattern of Mo films showed two different peak of <200> and <211> in case of Mo sheet and single peak <110> in case of SLG. While peak intensity varies as deposition condition varies in case of Mo films deposited on Mo sheet. Electrical properties of Mo films on both Mo sheet and SLG were improved as RF power and deposition temperature are optimised. On the other hand, electrical properties are affected as operating pressure increased. Lower resistivity of 1.2x10-9Ω.m and 6.65x10-6Ω.m were found in case of Mo films deposited on Mo sheet and SLG. Surface roughness of 0.017 nm-19.32nm were found in case of Mo films deposited on Mo sheet and 0.002 nm-5.04nm were found in case of SLG. Roughness increased as RF power and deposition temperature increased. However, roughness decreased as operating pressure increased.

Liquid-Phase Pulsed Laser Ablation and Electrophoretic Deposition for Chalcopyrite Thin-Film Solar Cell Application

We report ligand-free synthesis of colloidal metallic nanoparticles using liquid-phase pulsed laser ablation, and electrophoretic deposition of the nanoparticles for fabrication of Cu(In,Ga)Se(2) (CIGS) thin film solar cells. First, colloidal metallic nanoparticles of Cu-In and Cu-Ga alloys are produced by pulsed laser ablation in common organic solvents without using stabilizing ligands. The nanoparticles are examined for phase, composition, and electrical surface charging and charge modulation mechanisms. Metallic precursor thin films with high purity and precise composition are produced by electrophoretic deposition of the colloids without transferring to another solvent and without using binders. Finally, we demonstrate fabrication of CIGS solar cells on Mo sheet substrates with an (active area) energy conversion efficiency up to 7.37%.

Shot Peening Characteristics of Cold-Rolled Mo Sheet

The commercial pure Mo sheet was shot peened to increase high-temperature mechanical and thermal resistance. Shot peenining was conducted on the surface of cold-rolled Mo sheet with 0.4MPa of shot pressure. The hardness of bcc Mo sheet was increased with increase of shot peening time. Surface hardenss is gradually increased to 120s at the 0.4MPa pressure, but the profiles become almost flat at the prolonged time. The grains were deformed and work hardened in the surface layer. The surface roughness was also increased with peening time. The grain size of shot-peened Mo sheet was smaller than that of cold-rolled Mo sheet in the all recrystallization temperature range. The reason for this could be a larger density of nucleation sites caused by the higher surface deformation of shot-peened Mo sheet. Mo2C carbide phase was analyzed on the surface of recrystallized Mo sheet at the secondary recrystallization temperature range. It was considered that molybdenum carbide was formed due to the evaporation of graphite heating element in the hot-zone furnace. From this study, shot peening of Mo sheet could be a good cold work hardening method to improve high-temperature mechanical and thermal resistance properties.

Crystal structure and thermoelectric properties of β-MoSi 2

A powder sample of a metastable phase β-MoSi 2 having the C40-type crystal structure was prepared by heating Mo sheets with a Na–Si melt at 858 K for 12 h to determine details of the crystal structure. The lattice constants ( a = 4.6016(3) Å and c = 6.5700(3) Å) and Si atom coordinate ( y = 0.1658(2)) of β-MoSi 2 were determined by Rietveld analysis of the X-ray powder diffraction. The thermoelectric properties were refined for a bulk sample prepared by sintering the β-MoSi 2 powder at 773 K and 600 MPa. The electrical resistivity of the sintered β-MoSi 2 sample with a relative density of 65% of the theoretical one was 2.5 mΩ cm at 300 K, and slightly increased with increasing temperature from 300 to 725 K. The Seebeck coefficients changed from +60 to +89 μV/K in the temperature range from 330 to 725 K. The maximum thermoelectric power factor was 2.2 × 10 −6 W cm −1 K −2 at 725 K.

ChemInform Abstract: Structure of LaMo2O5 Containing Both Isolated Mo6O18 Clusters and Sheets of Fused Triangular Mo3 Clusters.

The structure of the disordered lanthanum molybdate, LaMo{sub 2}O{sub 5}, has been solved and refined using powder neutron diffraction data collected at 300 K. The compound contains two types of Mo-Mo bonded units: isolated octahedral Mo{sub 6}O{sub 18} clusters, and infinite molybdenum oxide sheets, formed from condensed triangular Mo{sub 3}O{sub 13} clusters jointed together to give a total of four Mo-Mo bonds for each molybdenum. The Mo{sub 6}O{sub 18} clusters have 16 electrons available for metal-metal bonding. Disorder in this layered structure occurs because of interchange of layers of Mo sheets with layers of lanthanum ions. The Bragg scattering is accounted for by including layers occupied with a 50% probability by each of these structural elements and their associated oxygen atoms. A model showing how ordered subunits are stacked together to produce the average structure is presented. Extended X-ray absorption fine structure spectroscopy (EXAFS) at the Mo K-edge was used to give information on the local structure around molybdenum and to confirm that the final structural model gives a good description of Mo-O and Mo-Mo bonding.

Improvements in Fabrication Process for Nb-Based Single Flux Quantum Circuits in Japan

We developed an Nb-based fabrication process for single flux quantum (SFQ) circuits in a Japanese government project that began in September 2002 and ended in March 2007. Our conventional process, called the Standard Process (SDP), was improved by overhauling all the process steps and routine process checks for all wafers. Wafer yield with the improved SDP dramatically increased from 50% to over 90%. We also developed a new fabrication process for SFQ circuits, called the Advanced Process (ADP). The specifications for ADP are nine planarized Nb layers, a minimum Josephson junction (JJ) size of 1×1μm, a line width of 0.8μm, a JJ critical current density of 10kA/cm2, a 2.4Ω Mo sheet resistance, and vertically stacked superconductive contact holes. We fabricated an eight-bit SFQ shift register, a one million SQUID array and a 16-kbit RAM by using the ADP. The shift register was operated up to 120GHz and no short or open circuits were detected in the one million SQUID array. We confirmed correct memory operations by the 16-kbit RAM and a 5.7 times greater integration level compared to that possible with the SDP.

積層クラッドを用いたMoおよびNbに対するアルミナイド被膜の作製

In order to improve the oxidation resistances of Mo and Nb alloys, aluminide coatings were developed by lamination cladding. Mo, Nb, and Al sheets with a purity of 99.99 wt% and dimensions of 15 mm×10 mm×0.5 mm were prepared by cutting, followed by the development of a specimen piece by holding the Al sheet between two sheets of Mo or Nb. The specimen wrapped with a Ta foil to prevent oxidation was heated at temperatures of the order of the melting point of Al in a pure Ar atmosphere. On the basis of the elemental analysis by characteristic X-rays, the laminated layers formed on the Mo substrates were found to be composed of MoAl5, MoAl4, and Mo3Al8. It was also found that the main phase constituting the laminated layers changed from MoAl5 to Mo3Al8 on increasing the temperature from 973 K to 1473 K. In contrast, NbAl3 was singly formed on the Nb substrate, irrespective of the heating temperatures. However, since NbAl3 grains have a spherical shape, the NbAl3 layer was not formed on the Nb substrate.