The microgravity environment offers considerable advantages for the measurement of thermophysical properties, in particular for hightemperature metallic melts. The absence of convection and the possibility for containerless processing are the two major benefits. This paper reviews past microgravity experiments dealing with thermophysical property measurements and discusses the methods used. The trend for future microgravity experiments will also be addressed.

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Isothermal oxidation behavior of in situ synthesized TiB/Ti composites has been investigated. Samples of titanium matrix composites reinforced with 0, 5 and 8 vol% TiB particulates were oxidized at 823, 873, and 923 K for 300 h in atmospheric air. Scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry, and transmission electron microscopy (TEM) were used to identify oxidation products and characterize oxide scale morphology. Oxidation was observed to follow parabolic kinetics. Rate of oxidation decreased with the increase of TiB reinforcements. The oxide scale formed on TiB/Ti composites was rutile-type TiO₂. No other oxides were observed within the oxide scale. The increased oxidation resistance due to the addition of the in situ synthesized TiB reinforcement was attributed to the improved tendency for the formation of thin and dense oxide avoiding crack and spallation, the strong enough interfacial cohesion and the clean interfacial microstructure between the reinforcements and the titanium matrix alloy.

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It is well known that a sharp Cube texture is developed for the producing process of a pure aluminum foil for capacitors. The orientation analysis using scanning electron microscopy/electron backscattered diffraction pattern (SEM/EBSP) method has been performed on the transverse direction (TD) sections of partially annealed (PAed) and additionally rolled (ARed) foils through the thickness in order to reveal how Cube-oriented grains have advantages for growth in comparison with the other grains with orientation components of rolling texture. Samples were annealed repeatedly with increasing the temperature in a vacuum. The Cube grains were distributed throughout foil thickness homogeneously in the PAed and ARed foils. The main mechanism of preferential growth of the Cube grains in the PAed foils was driven by grain boundary energy. However, the growth for ARed foils was caused by strain induced grain boundary migration (SIBM) driven by the difference in stored energy between the Cube and the other grains, because the former store less strain energy than the latter after the additional rolling. Furthermore, the grown-up Cube grains having similar orientations met each other and made a cluster in both the foils. Since the clusters develop to reach the foil surfaces and become stable, the Cube grains are easy to cover all of the foil in the final stage of annealing.

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The age-hardening response in Al-Mg alloys, with and without trace additions of Ag, aged isothermally at 160°C, 200°C and 240°C was investigated. Additionally, the effects on ageing response of cold work introduced after solution treatment, water quenching and prior to the ageing treatments were clarified for the Al-Mg-(Ag) alloy. The dislocation populations in the as-quenched microstructures of Al-10 mass% Mg alloys with and without trace additions of Ag were characterised. Trace additions (0.5 mass%) of Ag to Al-Mg alloys with low solute Mg contents (<5 mass%) promote an age-hardening response, while similar additions to Al-Mg alloys with higher solute Mg contents (e.g. 10 mass%) enhance significantly the age-hardening response. The age-hardening response in an Al-10Mg-0.5Ag (mass%) alloy is significantly enhanced by the introduction of 7% cold work, post solution treatment and prior to ageing at 160°C and 200°C. The identity of the dislocations in as-quenched Ag-free and Ag-modified Al-10 mass% Mg alloys has been confirmed as unit perfect a/2‹110› type. The addition of Ag does not appear to modify the form of the dislocations and no dissociation of these dislocations was observed. The density of dislocations in the solution treated and quenched condition in the Al-10 mass% Mg alloy was higher by a factor of ∼2 compared to that in the Al-10Mg-0.5Ag (mass%) alloy subjected to similar treatment.

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Design of two-phase alloys consisting of niobium solid solution (A2) and α-Nb₅Si₃ (D8_l) phases in the Nb-Ti-Si ternary system is pursued for ultra-high temperature structural applications. Compositional and annealing conditions are determined for the formation of A2/D8_l lamellar microstructure via eutectoid decomposition of Nb₃Si (tP32) phase in the Nb-Si binary and Nb-Ti-Si ternary system. Addition of titanium is found to result in increased room temperature toughness, but decreased high temperature strength. Enhancement of mechanical properties is achieved by applying the directional solidification technique. Mechanical properties of the alloys are discussed from microstructural point of view.

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The time-temperature-transformation (TTT) diagram within the medium temperature range of medium carbon steel has been determined. A single type of C-curve is found within the bainite temperature range for the studied steel. Distinct reaction C-curves were not observed for both types of microstructure, upper bainite and lower bainite in the TTT diagram. Experimental results on the kinetics of the isothermal formation of bainite at different temperature have demonstrated that both type of microstructure, upper and lower bainite, possesses similar overall transformation kinetics. Some applications of phase transformation theory towards the formation of bainitic microstructures are discussed, with particular emphasis on the bainite start temperature, transition temperature from upper to lower bainite, martensite start temperature and the thickness of bainitic plates.

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Directionally solidified NbSi₂/Nb₅Si₃ in-situ composites have been prepared. Scanning Electron Microscopes (SEM) and X-ray diffraction (XRD) have been used to investigate phase constitution and microstructure. It was found that microstructure and phase stability of directionally solidified alloys depended on growth rate, heat-treatment and alloying element. Compression strength was tested in the temperature range from 1473 to 1773 K and compression axes parallel to growth direction was chosen. High-temperature strength of NbSi₂/Nb₅Si₃ composites increased from 222.9 to 593.77 MPa at 1773 K due to Mo addition.

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Steelmaking is well known to be one of the highest energy-consuming industries, where high temperature molten slag is discharged without any heat recovery. This paper describes the hot experiments where a Rotary Cup Atomizer (RCA) is used to produce dry glassy slag without water impingement. In this, the properties for granulated slag were chiefly investigated. Molten slag was first poured onto the center of the rotating cup at various rotating speeds. Slag granulation was then observed using a video camera, and finally, the particles were collected for physical and chemical analyses. The results of XRD and DSC analyses demonstrate that all slag drops obtained by the RCA method are undoubtedly glassy. The particle size of the granulated slag is strongly controlled by both the diameter of the cup and the speed of rotation. The relationship between the particle size and the two parameters is expressed as D_p = 16.86/rω. Smaller particles that produced at a higher rotating speed seem to be more transparent or glassy and have compression strength twice higher in comparison with water granulated slag. The data obtained will provide valuable information not only for producing glassy slag, but also for exchanging energy between gas and molten slag efficiently.

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Microstructural analyses by field emission-type scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were performed on a ferritic heat-resisting steel that contained 12 mass% chromium and 2 mass% tungsten to characterize its multi-scale structure, consisting of prior austenite grains, packets, blocks, subgrains and precipitates. The size distributions of the blocks, subgrains and precipitates were quantitatively evaluated before and after a creep-fatigue test to relate them to their creep-fatigue property. Our results showed that the occupancy of precipitates on prior austenite grain boundaries increased markedly and subgrains became coarse during the creep-fatigue test, while the block size did not change. It is suggested that the growth of grain boundary precipitates and coarse subgrains plays an important role in the intergranular fracture mechanism caused by creep-fatigue.

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A Mg—Zn—Y—Zr alloy sheet containing icosahedral quasicrystalline particles and Zr-rich particles has been developed by the thermomechanical processes, i.e. hot extrusion and hot rolling. The grain size is found to be 5 μm. The superplastic deformation behavior of the alloy has been investigated. Under the test condition in the strain rate range of 5 × 10⁻⁴ to 5 × 10⁻² s⁻¹ and the temperature range between 300°C and 450°C, large elongation to failures are observed, especially around 600% at 450°C (5 × 10⁻⁴ s⁻¹). During superplastic deformation, the concurrent grain growth rate is significantly retarded by the presence of I-phase particles, thermally stable at the temperature up to around 500°C. In addition, the formation of cavities is found to be negligible because of interfacial coherency between icosahedral quasicrystalline particles and the α-Mg matrix. Although superplastic deformation could be relatively prevented by the pinning effect of the distributed particles, microstructure stability can provide large elongation to failure in such an alloy.

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Silicon nitride (Si₃N₄) is one of the attractive ceramics in respect of its excellent properties both in wear and thermal shock resistance. In this research, Si₃N₄ thick coatings were fabricated by reactive RF (Radio Frequency) plasma spray process, and a reactive plasma spraying, in which metal element reacts with surrounding active species in plasma, has been considered to be an useful way for the formation of non-oxide ceramics coatings. Spraying with Ar/N₂ mixed gas was not effective for the fabrication of Si₃N₄ coatings. Hydrogen addition as a reactive plasma gas improved the nitridation significantly. Si₃N₄ content in the coatings could be controlled by changing N₂ and/or H₂ fraction in plasma gas. Hardness of the coatings obtained increased with increasing Si₃N₄ content in the coating. Nitriding reaction of Si in reactive RF plasma spraying was promoted in the liquid phase of Si after deposited onto the substrate.

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Rapidly solidified bismuth-telluride based alloy foil; fabricated using the single roller melt spinning method exhibits a fine microstructure with unidirectional crystals. Meanwhile, a hot-pressing process, using rapidly solidified foils, was used to prepare the consolidated samples. The fine microstructure of this alloy is extremely effective in decreasing thermal conductivity because of the grain boundary scattering of the phonons, a key factor improving the thermoelectric properties of thermoelectric materials. Hot-pressed samples using these rapidly solidified foils display lower thermal conductivity values than the alloys made by the conventional hot-consolidating method using pulverized ingot powder. In this case, thermoelectric properties were investigated comparatively in terms of hot-pressed rapidly solidified foil specimens and pulverized powders of these foils under 53 μm in size, evaluating the dependence of the hot-pressing temperature and consequent pressure on the thermoelectric properties of these specimens. The maximum figure of merit (Z) obtained was 3.34 × 10⁻³ K⁻¹.

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To study the effects of electron beam (EB) irradiation on the bending stress-strain curves for soda glass, we measured these curves by a standard bending test. EB irradiation enhanced bending fracture stress and rigidity of the glass, and also extended the crack length of a homogeneously fractured sample. When the EB irradiation generated dangling bonds at the weaker-bonded metal-oxygen atomic pairs in the soda glass network structure, partial relaxation occurred at points of residual strain in the network structure. Evidently the increased rigidity was mainly due to an increase in the bonding energy for the silicon-oxygen atomic pairs in the atomic network structure. The irradiation also eliminated the crack origin points in the homogeneously fractured soda glass, thus inducing a high fracture stress.

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The aim of this study is to improve the sensitivity of alcohol sensors by combining the advantages of TiO₂ and SnO₂ films in a double layer device. In this study, an RF magnetron sputtering system was employed to fabricate SnO₂/TiO₂ double-layer and SnO₂ single-layer films for applications as alcohol sensors.
The TiO₂ layer of the SnO₂/TiO₂ double-layer thin film and the SnO₂ single-layer film were all deposited under various O₂/Ar ratios of 0.2, 0.4, 0.6, and 0.8. The SnO₂ layer, the top coating of SnO₂/TiO₂ double-layer, was deposited at a fixed O₂/Ar ratio of 0.2 with an argon flow rate of 50 sccm. The crystal structure and surface morphology of the films were examined by X-ray diffraction (XRD), Grazing Incident X-Ray Diffraction (GID) and Scanning Electron Microscopy (SEM). The sensitivity value of the film can be calculated from the change in the resistance of the film when exposed to alcohol.
The results show that SnO₂/TiO₂ double layer films have better sensitivity and quicker recovery time compared to those of single-layer SnO₂ films.

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In yttria-stabilized cubic zirconia, the addition of 0.15—5 mass% pure silica introduces a glass phase dispersing uniformly along grainboundary facets and at multiple junctions. For a grain size of 0.75 or 1.7 μm, the dispersion of the glass phase decreases the elastic modulus, the Vickers hardness and the elastic modulus-to-hardness ratio, whereas it affects little in the value of fracture toughness measured by an indentation method. The latter result arises because the decrease in the elastic modulus-to-hardness ratio is compensated by a decrease in the crack length for a given indentation load. Inspection of crack-propagation paths indicates that the glass phase with sizes smaller than those of the matrix grains is not a site for easy crack-propagation, but provides a site for a crack-deflection mechanism.

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The adhesion of electrodeposited Cu, Ni and Ag films on Cu, Ni and Ag substrates has been examined by the adhesion tape test. Different interfacial structures have been observed by SEM, GD-OES and TEM for the different film/substrate combinations and have been discussed in relation to the interface adhesion. Results show that the different combinations of the electrodeposited films and substrates reveal the different interface adhesive feature. Typically a strong adhesion presents in the interfaces of Ni film/Cu substrate, while a weak adhesion presents in the interfaces of Cu film/Ni substrate, Cu film/Ag substrates, Ni film/Ag substrate, Ag film/Ni substrate as well as Ag film/Cu substrate. The crystallographic coherency existing in the interface of Cu deposited film/Ni substrate suggests that the adhesion of electrodeposited films on various metal substrates is primarily determined by the crystallographic coherency rather than by the effect of voids in the interfaces.

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This study proposes a low-pressure control method for an arc-submerged nanoparticle synthesis system (ASNSS) developed for TiO₂ nanoparticle fabrication. The photocatalytic and surface adsorptive activity of TiO₂ nanofluid is examined via the decomposition of methylene blue. Experimental results show that the ASNSS can successfully prepare anatase TiO₂. The rate constant of photocatalytic reaction of TiO₂ nanoparticles for methylene blue is 0.0365 (min⁻¹), and the rate constant of surface adsorption of methylene blue on TiO₂ is 0.0437 (min⁻¹). Experimental results indicate that the TiO₂ nanofluid prepared by the ASNSS has excellent photocatalytic activity and surface adsorption property for degradation of methylene blue.

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This study presents a rapid continuous process for grain refinement in metallic materials through severe plastic deformation (SPD). The principle is described and the process is applied to an Al-5056 alloy and an S45C carbon steel. The new process, designated in this study the severe torsion straining process (STSP), consists of producing a local heated zone in a rod and introducing torsion strain into the zone by rotating one end with the other. The process is continuous because the straining is achieved while the rod is moved so that the heated zone is shifted along the rod. The STSP does not require the use of any die and can be applicable to pipes or wires. Fine-grained structures produced with the STSP are confirmed using optical microscopy and transmission electron microscopy. Tensile properties are measured and compared with the unstrained fully annealed samples. The feasibility of the STSP is discussed with respect to the rotation speed and moving speed.

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Three kinds of microstructures with different grain boundary morphologies and their creep properties of a Ti-47Al-2Nb-2Mn+0.8 vol%TiB₂ alloy are investigated. Tensile creep tests and microstructural examinations indicate that a stabilized fine-grained fully lamellar (FGFL) microstructure with relatively smooth grain boundaries shows inferior creep resistance. A stabilized fully lamellar (FL) microstructure with well-interlocked grain boundaries and wider lamellar spacing yields reduced minimum strain rate and extended creep rupture life. Furthermore, a nearly lamellar microstructure (NL) with well-interlocked grain boundaries exhibits better creep resistance than the stabilized FGFL microstructure though it has four times wider lamellar spacing and 15 vol% equiaxed γ grains at the grain boundaries, but worse creep resistance than the stabilized FL microstructure. Examinations to the deformed microstructures show that grain boundary instability involving spheroidization of the lamellae is a major microstructural degradation process, resulting in fine globular regions at the grain boundaries. Voids develop along the grain boundaries, particularly in the fine globular regions, leading to intergranual fracture. It is suggested that grain boundary sliding (GBS) is operating in the stabilized FGFL microstructure, and promotes mutually with the grain boundary instability during subsequent creep deformation, resulting in increased minimum strain rate and shortened tertiary stage. The well-interlocked grain boundary inhibits the onset of GBS and enhances the grain boundary stability effectively. These results demonstrated that the grain boundary stability has a great effect on creep behavior of TiAl Alloys.

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Cathodic protection has been applied widely to steel reinforcement in concrete. However, it is generally very difficult to establish optimal corrosion protection for such steel and to precisely evaluate the corrosion protection effect. We evaluate the effects of various factors on the distribution of the protective current, and summarize the information for optimal corrosion protection. For this purpose we refined a numerical analysis technique using FEM to optimize the cathodic protection of the reinforcing steel in concrete. We have constructed a precise method to calculate the potential and current distribution in the concrete, which can account for ion migration, ion diffusion, and the polarization phenomena involving the anode and reinforcing steel. We have estimated the effect of anode shape on corrosion protection. The polarization properties derived from electrochemical measurements were used as boundary conditions for the FEM calculation. This calculation technique incorporates polarization behavior and variations of ion concentration due to ionic migration and diffusion, giving a precise estimate of the actual corrosion protection effect of a system. We have shown the typical effect of various factors on the current distribution for corrosion protection systems in concrete, as given by FEM.

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Cl K-edge XANES measurements of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys in chloride pollution have been performed using synchrotron radiation in order to clarify roles of anticorrosive alloying elements and of Cl in the corrosion resistance of weathering steel. The spectra of binary alloys show a shoulder structure near the absorption edge. The intensity of the shoulder peak depends on the kind and amount of the alloying element, whereas the energy position is invariant. This indicates that Cl is not combined directly with alloying elements in the rust.

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Hydrogen permeability (φ) of eutectic Nb-Zr-Ni alloy membranes containing the primary phases ZrNi or bcc-(Nb, Zr) was measured using a gas flow meter. φ of the Nb₁₀Zr₄₅Ni₄₅ alloy containing the primary ZrNi phase (16 vol%) was 2.35 × 10⁻⁸ [mol H₂ m⁻¹ s⁻¹ Pa^−0.5] at 673 K, while φ of the Nb₂₀Zr₄₀Ni₄₀ alloy containing the primary bcc-(Nb, Zr) phase (18 vol%) was 2.73 × 10⁻⁸ [mol H₂ m⁻¹ s⁻¹ Pa^−0.5] at 673 K. These values were higher than that of pure Pd and of the Nb₃₉Ti₃₁Ni₃₀ alloy that shows the highest φ value in the Nb-Ti-Ni system. The present work strongly supported our previous proposal that multiphase alloys containing eutectic structures, which suppress a hydrogen embrittlement, are promising as novel hydrogen permeation membranes.

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