Functionality of element iron is reviewed from a view point of evolving earth and life. Energy conversion of oxidation-reduction reaction of iron (Fe2+/Fe3+) is important for life of some bacteria and this has been continued for more than 10 billion years. Furthermore, iron has been saving life on earth by geomagnetic properties by positioning on earth's core. This most abundant metal element iron has a lot of unique properties that can be not substituted by other elements. We have been utilizing iron-carbon materials as many kinds of tools because of those widely-controllable mechanical properties. Some of magnetic, mechanical, chemical and electric properties are well known but there may be a lot of unknown properties of element iron and iron materials. Further interdiciplinary studies are suggested.
Recent studies on the preparation of some Si containing materials and Si crystals by using Na were reviewed. Silicon carbide and beta-iron disilicide (β-FeSi2) were fabricated at 700-800°C with Na melt or Na vapor. A new compound, Ba3Si4C2, was synthesized with Na melt and SiC nano-powder. The phase diagram of Na-Si binary system was proposed based on the results of thermal analysis and observation of sample morphology. Polycrystals and single crystals of Si were obtained by evaporation of Na from Na-Si melt at 800-900°C.
Platinum group metals (PGMs) are used in a wide range of application fields such as catalysts, electrodes, medical and electrical devices, and high-temperature materials. The supply of platinum is only about 200t per year and its price drastically fluctuates depending on the economic situation. Even so, PGMs are used in industry because of their excellent properties which are difficult to obtain in alternative materials. Thus, an understanding of the mechanism that results in these properties is necessary in order to optimize the properties of PGMs, increase their lifetimes, and find alternative materials. In this paper, some attempts to increase the lifetimes of PGMs and to search for alternative materials for use as high-temperature materials, coating materials, catalyst materials, and electrode materials are reported.
The cost of titanium (Ti) and its alloys is still much higher than the costs of steels and aluminum alloys; this has inhibited their widespread usage. It is necessary to reduce their cost in order to make Ti and its alloys common metallic materials, namely, ubiquitous titanium and its alloys for their widespread usage. One of the main reasons for their high cost is that they contain a large amount of high-cost rare metals. Therefore, it is imperative to conduct research and development for producing Ti alloys that utilize low-cost common metal elements such as Si, Al, Fe, Cu, and Sn and interstitial elements such as O, N, H, and C. In this paper, the effects of ubiquitous alloying elements such as interstitial elements, O, N, C, and H, and substitutional elements, Fe and Si, which have been generally treated as impurities on functionalities of titanium alloys are discussed.
A small amount of alloying element added in steel play a key factor to promise the excellent strength performance of a structure steel product. As an example the understanding of the relationship between the alloying element and the migration of a dislocation is an important issue even in the modern steel research field. Progress in computational metallurgy will make it possible to help to find new design concepts for new steel performances on the view point of strength control. This is still a work in progress due to limit in computer memory and calculation speed and insufficient quantitative information on the microstructure of steels. Atomic level characterization techniques are just one kind of solution for comparing experimental data and calculation results such as the first-principle method. In this paper, it is emphasis that there are lots of important subjects which will be solved using advanced characterization techniques and computer science in steels. Some of examples are introduced in both fields of the low carbon steels and the chromium containing steels.
Effects of zinc concentration on the stretch formability of the rolled Mg-Zn-Ca alloys were investigated. The zinc addition more than 0.5 mass% effectively modified the basal plane texture, which was characterized by the splitting basal pole toward the TD. The intensity of basal plane texture decreased with the increase in zinc concentration. The rolled Mg-1.5 mass%Zn-0.1 mass%Ca alloy showed significant stretch formability corresponding to the rolled aluminum alloys. On the other hand, the zinc addition more than 1.5 mass% deteriorated the stretch formability of rolled Mg-Zn-Ca alloys. The deterioration of the stretch formability of rolled Mg-Zn-Ca alloys with high zinc concentration was suggested to be responsible for the solid solution hardening. It was suggested that not only the TD-split texture but also the solid solution softening played an important role in the enhanced stretch formability of the rolled Mg-Zn-Ca alloys.
For the application of high-surface-area nanoporous platinum (Pt) to catalytic device, electrodes and sensors, dealloying technique, which can synthesize nanoporous Pt, was combined with surface alloying technique. As a result, nanoporous structure with ligament and pore sizes below 10 nm was successfully fabricated on the Pt plate surface. Cyclic voltammetry in H2SO4 indicated that the nanoporous structure increases the true surface area by 170 times. The approximation by spherical pore model suggested that the nanoporous surface layer has a thickness of 200 nm.
The Fe72B14.4Si9.6Nb4 metallic glass and pure Fe particles were dispersed into the pure aluminum by the friction stir processing. The microstructure and mechanical properties of the stir zone were analyzed using XRD, SEM, TEM and micro-hardness. As a result, it was found that the Fe metallic glass and pure Fe particles can be uniformly dispersed into the pure aluminum by friction stir processing and the mechanical properties of the stir zone are improved due to the formation of precipitates.
Thermal conductivity of the in-situ type AlN-Al-AlB12 ternary composite, which was synthesized with the aid of the exothermic reaction between molten Al and BN powder, has been studied. Although the thermal conductivity of this composite is certainly raised with an increase in AlN concentration, it significantly degenerates due to the existence of voids. The compound AlB12, which is uncalled-for product to our composite, may also lower the composite thermal conductivity. The void volume fraction in the composite is fairly decreased by flowing the atmospheric fresh N2 gas into the reaction chamber. Negative effect of voids to the composite thermal conductivity has been discussed.
Electrodeposition behavior of Sn-Cu alloys was investigated potentiostatically at 0.3 to −0.7 V vs. NHE and 298 K in sulfate bath containing additives of cresol sulfonic acid, benzal acetone and nonionic alkyl polyethylene glycol ether surfactant, and the contact resistance of Sn-Cu alloys deposited on Cu connector was evaluated. Cu behaved as more noble metal than Sn, showing the typical feature of regular type codeposition. In solution containing additives, the difference of deposition potential between Cu and Sn became small because Cu deposition was suppressed by the additives. The Sn-Cu alloys deposited from solution containing additives showed smooth surface. The deposited Sn-Cu alloys were composed of Cu, Sn, Cu6Sn5 and Cu3Sn phases in accordance with the equilibrium phase diagram of binary Cu-Sn system. The contact resistance of deposited Sn-Cu alloys increased by heating at 433 K, showing no improvement of connecting reliability by plating the stable metallic compound of Cu6Sn5. The connecting reliability of connector after abrasion was better in deposited films of Sn-Cu alloys than in reflow Sn plating.
Surface oscillation behavior of electromagnetically levitated molten copper was investigated under a static magnetic field in the range from 0 T to 1.0 T. Although the frequencies of m=0 and ±1 oscillations were almost kept constant up to 0.2 T, they became negligibly small above 0.2 T. The frequency of m=±2 oscillation gradually decreased as the static magnetic was increased up to 1.0 T. This behavior was basically interpreted in the following way, i.e., the Lorentz force acting on the copper droplet causes a resistive force to the surface oscillation, which leads to decreases in frequencies of surface oscillation.
Electrochemical measurements have been carried out to clarify an effect of phosphorous pentaoxide on corrosion of copper tubes used in heat exchangers in a solution which contains potassium formate with addition of benzotriazole as corrosion inhibitor. It was experimentally found that boundary between phosphorous pentaoxide and tube was severely attacked in the solution after several hours. It was shown that the existence of phosphorous pentaoxide derived from a solder material is responsible for the occurrence of the attacks. It was considered that the pitting attacks took place after electrochemical arrangements of anodic reaction which is oxidation of copper to copper-phosphorous ions of Cu(P2O7)2 6− and cathodic reaction which is reduction reaction of formic acid to formaldehyde in acid solution.