The shape memory alloys are fascinating materials with great potential for application as new functional materials. Fundamental aspects of the thermoelastic martensitic transformation, with which the shape memory effect and the superplasticity are associated, are briefly summarized. The mechanisms of the above two properties are also described. Among several tens of shape memory alloy, the Ti-Ni alloy is considered to be the best for practical applications because of its excellence in mechanical properties, corrosion resistance, etc. In the latter half of the present paper, recent applications of the Ti-Ni alloy in various fields are introduced.

View full abstract

Recently, and elastic analysis by three-dimensional boundary element method based on fictitious stress method, in which the numerical integrations have to be used to get the influence coefficients, is extensively applied and studied. However, to analyze three dimensional models of natural geological structure and artificial underground excavation or for a large scale computation of stress and displacement and stability evaluation using their combined model, exploitation of much more accurate and faster analytical solutions in order to avoid numerical integration is regarded as extremely valuable. Kuriyama and Mizuta have carried out the study in which, however, the elaborate integration results seem complicated. Furthermore, if some observed points were located at the elongated line of one side of a triangular element (these points are regards as special observed ones), their analytical integrations can not be applied. In other words, the singular point (the center of gravity) and the special points (on the elongation of three sides) have to be evaded when using the analytical codes developed by Kuriyama and Mizuta. This is usually not realistic in a huge model. Therefore, the corrected and much more concise analytical integrations for arbitrary boundary shapes, arbitrary divisions of triangular elements and arbitrary observed points (except the three sides of triangular) are deduced in this paper.

View full abstract

The automation of breaking task of huge rocks consists of 1) automatic detection of huge rocks, 2) automatic control to make the breaker tip move to the surface of the huge rocks, and 3) carrying out the breaking task. In the previous study, the image processing to detect the huge rocks and to measure the three dimensional information of huge rock position were investigated. In this study, the algorithm to judge the breaking is proposed by use of force sensors. The strain gauges were attached on the chisel of the hydraulic breaker, and signals from the strain gauges were measured. Through the experiments of rock breaking, it was found that large compressive or tensile strain were obtained at the moment of rock breaking. The utilization of the neural network was proposed in this study to construct the algorithm to judge the rock breaking. It was confirmed that this algorithm works well from the experiments.

View full abstract

Spilled heavy fuel oil on the sea increases its viscosity up to about several hundred times from the original value in the process of mixing with water. In the case of the spilled heavy fuel oil from the Russian tanker in 1997, almost all of recovering machines were useless, because the pipes and pumps in the machines were choked with highly viscous oil. The purpose of the present paper is to investigate an applicability of a core annular flow (CAF) to recover a highly viscous fuel oil on the sea. The CAF consists of a thin water film introduced between the oil and the pipe wall. This film gives a reduction of pressure-gradient. In this paper, two-dimensional simulations using k-ε turbulent model and height functions were conduced with 176～4, 000 mPa・s oils keeping constant interfacial tension. Some of main results are as follows: 1) Pressure drop of the core annular flow with highly viscous oil in the core is slightly higher than that of single-phase water flow. 2) The core annular flows with different oil viscosity showed little difference in pressure drop. This result indicated a high potential of the core annular flow to the recovery of highly viscous spilled oil. 3) In the case of lifting or sinking core, tha pressure difference between the upper surface and the lower surface was counter-balanced with the lifting or sinking force. 4) Simulation of a core annular flow with a height function did not work well when the surface of the core became steep and multiple-valued function of the position.

View full abstract

Flotation behavior of coal and pyrite was investigated by bubble pick-up tests and Hallimond tube flotation. Flotation recovery of coal and pyrite was high in the acidic region and decreased with increasing pH. In solutions containing iron species the recovery of pyrite decreased drastically at pHs where iron hydroxide was precipitated, but coal flotation was not influenced. Zeta potentials of pyrite and iron hydroxide precipitates were measured under various conditions and the formed precipitates were characterized by XRD, FTIR, and settling velocity measurements. The precipitates formed at the pH where depression of pyrite flotation occurred were very fine sized amorphous ferric hydroxides, which preferentially adhered on pyrite surfaces and rendered pyrite hydrophilic. Selective flotation of artificial high sulfur coal (mixture of coal and pyrite) was performed in the following three solutions containing ferric iron adjusted to pH 2.5 : a) prepared with ferric sulfate, b) prepared by oxidizing ferrous sulfate with iron-oxidizing bacteria (Thiobacillus ferrooxidans), and c) prepared by centrifuging the solution of b). In all solutions coal was selectively recovered as a froth product with high combustible recovery and high separation efficiency.

View full abstract

The comminution process is often an indispensable unit operation for mineral processing. The main purose of mineral processing is to separate the valuable minerals from the gangue ones. It necessitates mineral liberation by comminution. Most of the conventional comminution models however, represents only the size reduction phenomena excluding liberations ones. Different comminution matrices were applied for the free and the locked particles respectively. For the locked particles the liberation probability function was introduced in addition to the above matrix. This probability function was determined assuming completely random cutting off the spherical particles from the coarser primary particles. The degree of liberation caused by fracture of the locked particle can be obtained by an approximated equation involving the liberataion probability function and the content of the component concerned.

View full abstract

Liberation is very important for recycling. This paper describes a new separation process using a high voltage discharge impulse. High frequency heating and microwave heating were also shown to be of potential use in processing of the minerals granodiorite and taconite. A concrete disk sample was prepared using 6 mm and 10 mm diameter borosilicate glass beads as aggregate. The sample was placed between the ground electrode and a rod like electrode in water, to which a high voltage impulse was applied. The high voltage discharge impulse liberated the glass beads from the concrete. A needle like electrode was more effective for fragmentation of concrete. The concrete was mainly broken by exceeding its tensile strength due to thermal expansion of the heated portion from a large current flow of plasma. The energy consumption was greatly reduced compared to a conventional compression test. The liberation of iron bars from concrete and metal from ceramics were also possible by using this process. High-frequency heating was applied to wet granodiorite. The tensile strength was reduced and the boundaries of mineral grains were observed on the breakage surface. Microwave heating was applied to a taconite sample in Minnesota. As with high-frequency heating, the tensile strength was reduced and the boundaries of magnetite grains were observed on the surface. These two methods may be useful for mineral liberation in combination with general crushing methods.

View full abstract

Dissolution behavior of molybdenum concentrate by electro-oxidation has been investigated in acidic and alkaline condition at constant current density of 625 A/m² (1A) and temperature (313K). The experiments on electro-oxidation of molybdenum concentrate obtained from Erdenet mine from Mongolia were carried out in an laboratory scale electrolysis cell with 10 mass % NaCl electrolyte. The overall current efficiency for MoS₂ dissolution was 97 % in alkaline and 92 % in acidic solution after 6 hours electrolysis, respectively. The current effeciency decreased to 82 % when the electodes were not separated from the slurry. It has been shown that the dissolution of MoS₂ proceeds mainly by electrochemically produced oxychlorites in the solution. The residue obtained in acidic solution consisted of Si and Al, and that in alkaline solution consisted of Si, Al, Cu and Fe. In alkaline solution, Cu and Fe, which are main impurities of the concentrate, are separated by precipitation from leaching solution.

View full abstract

Hydrolysis reaction of aluminium sulphate solutions of various concentrations and hydrolysis reaction of ferric sulphate solutions of various concentrations with the addition of aluminium sulphate have been investigated in an autoclave at 185゜C and 200゜C. The results indicate that Al³⁺ ion concentration increases with an increase in the sulphuric acid concentration in the solutiions when the hydrolysis reaction of the aluminium sulphate solutions proceeds to completion. Al³⁺ ion concentration is higher at 185゜C than 200゜C at the same sulphuric acid concentration in the solutions. A plot of logarithmic value of Al³⁺ ion concentration against logarithmic value of the sulphuric acid concentration shows a linear relationship which can be expressed by an empirical formula. The H₂O corners of the equilibrium diagrams of Al²O₃ - SO₃-H₂O system at 185゜C and 200゜C are established from the experimental data. Fe₂O₃ precipitates at lower sulphuric acid concentration region and Fe (OH) SO₄ precipitates at higher sulphuric acid concentration region when the hydrolysis reaction of the ferric sulphate solutions proceeds to completion. However, the sulphuric acid concentration at which Fe₂O₃ begins to precipitate with the addition of aluminium sulphate is lower than without aluminium sulphate. Fe³⁺ ion concentration increases with an increse of the sulphuric acid concentration, and with an increase of the amount of aluminium sulphate at the same sulphuric acid concentration. Moreover, Fe³⁺ ion concentration is higher at 185゜C than 200゜C. A plot of logarithmic value of Fe³⁺ ion concentration against logarithmic value of the sulphuric acid concentration in the region where Fe₂O₃ precipitates, or in the region where Fe (OH) SO₄ precipitates can be expressed by an empirical formula. The H₂O corners of the equilibrium diagrams of Fe₂O₃-SO₃-H₂O system in the presence of aluminium sulphate at 185゜C and 200゜C are established from the experimental data.

View full abstract

The formation and decomposition of dioxins (PCDD/Fs) in combustion gas have been discussed by thermodynamic calculations for the C-O-H-Cl quaternary gas system. The effects of temperature and gas composition are briefly summarized by changing the conditions based on the following “reference gas”: O₂0.1 + CO 1.8 + H₂0.15 + HCl 0.9 + C₂H₃Cl 0.1 mol=O:2 + C:2 + H:1.5 + Cl: 1 mol The effects of various additions (inhibitors) on the decomposition of PCDD/Fs are evaluated by use of thermodynamic package HSC Chemistry. The changes of the reference gas composition are calculated at 300゜C by addition of inhibitors such as CaO, SO₂, NH₃, sodium salts, organic compounds, and metals. The amounts of PCDD/Fs decrease efficiently by the additions of these substances, but it is clarified that the decrements are always reproduced by change in basic quaternary C-O-H-Cl gas composition. Increase in O or H, and decrease in Cl result in decomposition of PCDD/Fs, and thus, the regulation of the quaternary gas composition is of primary importance to control PCDD/Fs. The derived amounts of PCDD/Fs by equilibrium calculation are much higher than those observed in practice because of kinetic reasons. Taking account of slow reaction rates of the formation of PCDD/Fs and solid carbon deposition, thermodynamic simulations for depression of the formation of PCDD/Fs are demonstrated.

View full abstract

Thermodynamic evaluation was carried out for the fuming process of electric are furnace dust. Dust containing 34 % Fe, 24 % Zn and 3 % Pb was chosen for equilibrium calculation. Effects of temperature and amounts of carbon, water vapor and participating air on the volatilization behavior of zinc, lead and halogens and on the composition of the resultant slag or clinker were examined. It was clarified that Pb and Zn remain mostly in the condensed phases under oxidizing conditions, whereas they vaporize as Pb (g), PbS (g), PbCl (g) and Zn (g) under reducing conditions. Judged from the results, the temperature higher than 1, 200゜C is required to realize a high recovery of zinc. By addition of water the decomposition of halides is enhanced, but no significant effect is observed for vaporization of Pb and Zn. The condition for metallic iron to precipitate was shown as a function of temperature and C addition. Matte-making to extract copper, nickel and valuable metals from the dust was discussed from thermodynamic point of view. Substantial recoveries of these metals are expected when the matte is produced just before metallic iron precipitation.

View full abstract