The decoupling statuses of the consumption of 22 kinds of metal with economic growth were analyzed. Metals were Fe, Al, Cu, Cr, Zn, Mn, Pb, Ni, Co, Sn, Sb, Si, Mo, W, Li, In, Ga, Ag, Au, Pt, Pd and rare earths. The relations of the annual consumption per capita of each metal to GDP per capita were approximated into two steps of liner formulas; yM=aM, 1X (X<cM) and yM=aM, 2X+bM, 2 (X>cM), where yM is the annual consumption of the metal M per capita, X is GDP per capita. The metal which has only single relation of yM=aM, 1X was judged to stay in the state of coupling. When aM, 1>aM ,2, the state was judged to be decoupling. Furthermore, it was judged to be the status of an absolute decoupling when aM, 2<0. The metals which have attend to absolute decoupling are Au, Sn, Zn and W. Cu and Pb are at the border of the absolute decoupling. While Fe, Al, Ni, Mo, Sb, Ag, Pd are decoupling to GDP per capita, Si and Pt are still in the status of the coupling with economic growth. In the case of Co, Li, In, Ga and rare earth, new coupling relation with economic growth have developed in these several years.
Forecasting are made regarding the consumption up to 2050 of following metals: Fe, Al, Cu, Mn, Zn, Cr, Pb, Ni, Si, Sn, rare earths, Mo, Li, Sb, W, Ag, Co, In, Au, Ga, Pt and Pd. The forecasts are based on the liniar decoupling model of the relation between per capita metal consumption and per capita GDP. The models of each metal are applied to the economic development model of BRICs and G6 countries. According these forecasts, the overall consumption of metals in 2050 will be five times greater than the current levels, and demand for metals, such as Au, Ag, Cu, Ni, Sn, Zn, Pb, and Sb, is expected to be several times greater than the amount of their respective reserves. Demand for iron and platinum, which is considered to be optimistic about the resource exhaustion, will also exceed the current reserves. Urgent measures are needed to find alternatives from common resources and to shift into materials circulation society.
Nano-sized metal particles (Pt and Pd) can be fabricated under UV-light irradiation using a photo-assisted deposition (PAD-SP) method on the single-site photocatalyst. The nano-sized metals were deposited directly on the photo-excited tetrahedrally coordinated titanium oxide moieties within the frameworks. Characterization by X-Ray Absorption Fine Structure (XAFS) and Transmission Electron Microscope (TEM) analysis revealed that the size of metal particles depends on the preparation methods and that the metal particles with the smaller size were formed on the photo-deposited catalysts compared to the conventionally prepared impregnated catalysts. These nano-sized metal catalysts are useful as efficient catalysts for the various reactions such as the oxidation of CO and the direct synthesis of H2O2 from H2 and O2 under an aqueous condition. The direct interaction between the precusor species of the nano-sized metal and the photo-excited tetra-titanium-oxide realized by the PAD-SP method has possibility to design the unique and active nano-sized metal catalysts.
Palladium (Pd) and its alloys are industrially used for separation and purification of hydrogen gas. However, Pd is too expensive and a rare natural resource, so that the development of non-Pd based hydrogen permeation alloys is strongly desired. The present authors have found out that high hydrogen permeability (Φ) is compatible with resistance against the hydrogen embrittlement in the Nb-TiNi alloys consisting of the bcc-(Nb, Ti) and the B2-TiNi phases. The value of Φ for Nb40Ti30Ni30 alloy, for example, is slightly higher than that of pure Pd. Then, in this paper, the possibility of substitution of these alloys for the Pd based hydrogen permeation alloys is discussed based on the experimental data, the prices of the metals and so on.
After the development of Nd-Fe-B magnets, rare earth magnets are now essential components in many fields of technology. In the industry of Nd-Fe-B sintered magnets in Japan, the total amount of production has increased about 20% from year to year. Especially, the use for the motors in hybrid cars is considered as one of the most attractive applications in Japan. Because of usage environment of hybrid cars, in which temperature increases up to 200°C, high coerecivity and high heat resistance are required to Nd-Fe-B sintered magnets. It is well known that Dy addition is effective for increase in coerecivity. However, the natural abundance of Dy is quite smaller than that of Nd and the resource locality is limited in the world, which leads to the escalating price of Dy. Therefore, the decrease of Dy content in Nd-Fe-B magnets is strongly demanded. This article reviews the status and trend in the research for saving Dy in Nd-Fe-B sintered magnets.
Tungsten carbide (WC) based hard metal is known for its excellent combination of hardness and fracture toughness and has been widely used in a wide range of industrial applications such as various kinds of cutting tools and wear resistant components. Recently, it is becoming great concern to save the amounts of WC due to the increase of global demands and the national strategy of the producing countries of the raw materials. High velocity oxy-fuel (HVOF) has been widely used to deposit coatings of WC-Co. However, fracture toughness of HVOF sprayed WC-Co coatings is much lower than its sintered bodies, due to the formations of the detrimental phases such as W2C and η phase during deposition. In other words, if the toughness of the coatings can be improved, there is a great possibility to substitute a part of sintered bulk applications, and hence to lead to resource savings of tungsten. In the present paper, we investigated the possibility to fabricate degradation free WC-Co coatings by Warm Spray deposition which is a new spray technique and has the capability to control sprayed particle temperature. The microstructure and mechanical properties of those coatings were evaluated and compared with the ones by conventional HVOF deposition and the sintered bulk WC-Co. WC-Co coatings without detrimental phases were successfully deposited by Warm Sprayings but the fracture toughness was lower than HVOF coatings. The reasons of this poor fracture properties were discussed.
In order to search stable intermetallic compounds in a broad composition area in ternary, quaternary and higher-order systems, it is effective to utilize the calculation of formation enthalpy for screening prior to the experimental study. As the number of candidates is tremendously large for ternary and quaternary alloys, an augmented-spherical-wave (ASW) method was employed for fast calculation. To evaluate the accuracy of the calculation, the formation enthalpy of B2, L10 and B19 structures of 99 equi-atomic compounds are estimated, and the most stable structure for each alloy is compared with the literature. It is found that 75% of the reported structures are predicted by the calculation results, and B19 structure tends to be evaluated less stable than L10 structure. The formation enthalpy of Heusler-like structure with Co-Fe-Ti-Zr equi-atomic quaternary composition is also estimated and this quaternary compound is unstable comparing with the estimated formation enthalpy of binary B2-CoFe, CoZr, FeTi and FeZr. An experimental study revealed there is a phase near the composition of the quaternary compound, but the structure is Laves-C14 Fe2Zr, neither the Heusler type nor bcc-based structure. It is concluded that the combination of ASW calculation and the experimental study is suitable for a broad search of compounds with relatively symmetric structure.
We have researched on an intrinsic semiconductor of β-FeSi2 from the viewpoint of function units constituting the β-FeSi2 lattice. The function units of Fe(I), Fe(II) and Si were clarified and their functions were reported. Both high Seebeck coefficient and high electrical conductivity were shown by doping control of both the Fe(II) and Si units. Thermal shock resistance was one figure heightened by decreasing the a-axis lattice constant of β-FeSi2 related to the Si unit. The Fe unit control was effective to change the band gap between 1 and 0.84 eV. Further understanding and utilizing the function units is a possible way to realize a practical thermoelectric material of β-FeSi2.
Research and development of 3d multinary alloys and compounds for functional materials in terms of substitution of materials containing rare and toxic elements have been carried out extensively. Fe2VAl Heusler alloy and its related alloys exhibit a large Seebeck coefficient, therefore, these alloys have a potential as a substitute of the Bi-Te system for room-temperature thermoelectric materials. Furthermore, Pb-Zn-Te electrostrictive and TbFe2-based magnetostrictive materials are probably replaced with Ni-based magnetic shape memory Heusler alloys, which exhibit a large magnetic-field induced strain. In addition, the control of a large negative thermal expansion of Mn3XN (X=Zn, Ga)anti-Perovskite compounds by partial substitution is useful way to overcome a usage of expensive W element and its compounds. Finally, we focus on magnetic refrigerants which are keenly desired in utilization of magnetic refrigeration. The existing candidates for magnetic refrigerants are limited to compounds containing elements such as As, Gd and Sb. On the other hand, La(FexSi1-x)13 compounds offer advantages on account of environmental safety, low-prices, and a large magnetocaloric effects. To utilize these 3d-based functional materials by taking advantage of the ability to control the electronic state in multinary system, the material designs based on electronic structures and supports of computer-aided phase diagrams are highly useful.
In order to promote the recycling of copper alloy scrap, we developed a new technique for removing Pb from copper alloy scrap containing 2-6 mass% Pb. However, we must evaluate quantitatively the level of environmental impact reduction that can be obtained using this new technology. In this study, a manufacturing system that produces Pb-free copper alloy products from copper alloy scrap containing Pb was assessed by means of life cycle assessment (LCA). The superiority of the new manufacturing system that uses copper alloy scrap containing Pb over the conventional one that uses virgin materials was investigated from the viewpoint of environmental impact. LCA software (JEMAI-LCA) was used to assess environmental impacts such as global warming, acidification, energy consumption and resource consumption. We assessed the raw material acquisition and casting process of Pb-free copper alloy products. The subsequent processes such as machining, assembling, transportation, use and recycling/waste processing are not taken into account in the environmental impact assessment. The results show that the conversion of the conventional system that uses virgin materials into the new one that uses copper alloy scrap containing Pb decreases the environmental impact, significantly. This is attributed to the non-utilization of virgin materials and the decrease in energy consumption during the casting process.
The instrumented pulse electric discharge consolidation method is used to provide a way of in process nanocrystalline control densification of the amorphous ZrO2-20 mol%Al2O3 powder as prepared by rotating-arm reaction ball milling. The cylindrical compact height (hf) of the amorphous ZrO2-20 mol%Al2O3 powder is found to be a dominant process variable; at 1 mm, it leads to the densification prior to major crystallization after a high relative density of roughly 0.86 at 800 K, and significant decreases down to 1284 K in temperature necessary to obtain the full densification under 100 MPa. The rapid densification for amorphous and nanocrystalline supersaturated cubic ZrO2-20 mol%Al2O3 is fairly well expressed by an Arrhenius-type equation of Newtonian viscous flow: ηp=ηpo exp (Q/kT) having a greatly decreasing apparent activation energy Q from 300 to 72 kJ mol-1 and the process viscosity ηp at 1200 K with decreasing hf from 14.6 to 1 mm. The Berkovich indentation testing permits us to derive a relatively low level of 4.4 GPa for the value of the yield stress at room temperature in the full-density nanocrystalline ZrO2-20 mol%Al2O3 sample having the Vickers hardness number of approximately 800 DPN.
A lotus-type porous iron (AISI 1018) that is fabricated by unidirectional solidification using the continuous zone melting technique in a nitrogen atmosphere under a pressure of 2.5 MPa, was welded by a Nd: YAG laser. The melting property of lotus-type porous iron was investigated to evaluate its melting characteristics at different laser powers and welding speeds. The weld bead surface of the lotus-type porous iron was rough with pits and dents irrespective of the pore growth direction. The remarkable effect of the pore growth direction on the penetration depth of the weld bead was not observed. This was due to the unstable weld bead formation caused by the relatively large-sized pores and the blowing of the remaining gas from the closed pores as well as the smaller anisotropy of the thermal diffusivity as compared to the copper and magnesium cases.
The thermoelectric properties of SiC have been investigated. SiC specimens were prepared from α-SiC powder by sintering at 2100°C with addition of B4C, C and Al2O3. The maximum value of power factor, 9.43×10-4 W/mK2, at 800°C can be obtained for the specimens sintered with 3 mass% of Al2O3 in addition to B4C and C. This value is 30 times larger than that of non-addition specimen. As the reason, the electrical conductivity for the specimen sintered with addition of B4C, C and 3 mass%Al2O3 increased more than 50 times in comparison with that of non-addition specimen. On the other hand, the Seebeck coefficient decreased with the addition of Al2O3. This result suggests that the effect of the additives is very important to increase the value of power factor. The role of the addition of B4C, C and Al2O3 on the electrical conductivity and the Seebeck coefficients is discussed in this paper.
The structure of the rust formed on Al bearing steel was analyzed by EPMA and FIB-TEM, and the electrochemical behavior of the rust was investigated by the electrochemical impedance spectroscopy (EIS) method after the exposure test. The 0.8 mass% Al bearing steel showed high corrosion resistance compared to carbon steel (SM) and conventional weathering steel (SMA) in the exposure test. EIS measurement was taken to estimate the rust resistance (Rrust) of the rusted steel. It was found that Rrust of Al bearing steel was much larger than that of SMA or SM. EXEFS(Extended X-ray Emission Fine Structure)and the X-ray analysis by EPMA and TEM-EELS showed that Al existed in Al3+ oxidized state in the inner iron rust layer for Al bearing steel. TEM showed that nano-scale complex iron oxides containing Al were formed in the inner rust of the Al bearing steel. Finally, it was found that the corrosion resistance of Al bearing steel could be increased by the formation of the nano-scale complex oxide containing Al in inner rust to prevent the penetration of Cl ions.
We have demonstrated in our previous report that the excess energy created during mechanical alloying (MA) yielded alloying of elemental couples with even negative mixing enthalpy and that a formation of new ternary bcc phase. It was noticed that a structural correlation exists between the Laves and bcc structures. The aim of this study is to synthesize CaMg2 based bcc alloys in relation to the Laves phase structure with additive bcc vanadium, and to clarify the above issue on the structure and hydrogenation properties. The parent materials used in this study were CaMg2 and metallic element powder. The MA was performed under Ar gas atmosphere and the rotation speed is 710 rpm. The weight ratio of powder to ball is 1:40. With increasing MA time, the lattice parameter of bcc alloy increases. After 60 hours of MA, single bcc phase was formed. The TEM observations show that the alloy made after 60 hours of MA was composed of nano-structured bcc grains without deviation from the nominal composition. The TDS was used to measure the hydride properties of the synthesized bcc alloys. The result showed that 3 mass% of hydrogen was absorbed. A new phase appeared after the desorption of hydrogen. The reason can be explained by electronegativity argument of alloy elements relative to hydrogen. This result could encourage us to have a chance of formation of new alloy phases during hydrogenation.
The microstructures of red lead (minium) pigment and the behavior of the Pb species used in the wood-block-printed book Kodouzuroku published in the late Edo period have been investigated. A copper refining technique of the late Edo period is described in this book. Although the red lead pigment was used for the color of the flames in the illustration of the refining process, the color has long changed from red to black. A very small specimen is taken from the picture and then thinned by the focused-ion-beam method. The microstructures are observed using a transmission electron microscope. The Pb3O4 crystals exhibiting the red-color are detected in the pigment layer. The crystal diameter is 6~17 nm. Pb species that diffused from the pigment layer into the glue, which was used as a binding medium, are detected. The diffused Pb species are also detected in the paper fiber. Furthermore, nanosize αPbO particles have precipitated in the paper fiber. The Pb species diffused into the glue and paper fiber cause the blackening of the pigment layer and the paper fiber.