The CALPHAD (Calculations of Phase Diagrams) method has succeeded in obtaining multicomponent phase diagrams for technological applications in the last few decades. However, this approach is faced with some difficulties in calculating phase equilibria in the metastable region and thermodynamic properties of metastable phases, those are usually not accessible experimentally. Within the same time frame, first-principles calculations based on the electron theory have progressed extensively and have interacted with the CALPHAD method. In this paper, after a brief overview of the history and the basics of the CALPHAD method, we present our recent research results on the calculations of thermodynamic properties such as enthalpy of formation at finite temperatures using electron theory as well as lattice vibration and cluster expansion method, with special emphasis on making use of these theoretical values in the CALPHAD description of thermodynamic properties of alloys.
As one type of the CCS (Carbon Capture and Storage), “distributed CCS” (DCCS), conducted by injection facilities situated dispersively near CO2 emission sources, has recently attracted attention. This study estimates the storage potential of CO2 of the DCCS into the aquifer in Japan. This study assumes three cases of the storage depth of 50m∼400m, 400m∼750m, and 50m∼750m. The calculated CO2 storage potential ranges from 7.9Gt·CO2 to 33.6Gt·CO2, which indicates that the DCCS in Japan can stably control domestic emission of CO2 to achieve the reduction commitments under the Kyoto Protocol for decades of years. Under the DCCS, proportion of dissolved CO2 into formation water to injected CO2 is higher than that of traditional CCCS (Concentrated CCS). This indicates that, in DCCS, solubility trapping and subsequent mineral trapping of CO2 would efficiently occurs. Further study would be needed how fast the solubility trapping progresses to mineral trapping. In DCCS, regional distribution of geothermal gradient would be influential to the estimate of the storage potential of CO2 Investigation of the geothermal gradient around the injected area would improve accuracy of prediction of the storage potential of CO2.
In this study, we attempted to measure frost heave pressure, i.e., the pressure that develops in the heat-flow direction when rocks are subject to frost heave and ice lenses grow. We used two kinds of rock samples: one was Ohya tuff, whose frost heave was already known to be high, and the other was Kimachi sandstone, whose frost heave was lower than that of the former. Ohya tuff and Kimachi sandstone, in which the occurrence of frost heave has previously been confirmed, were used as specimens. To conduct the experiment, we made original frost heave experiment equipment that was combined with a reaction frame and a load cell. The test results clearly showed that the maximum frost heave pressure did not depend on the kind of rock and was proportional to the temperature gradient. In addition, we clarified that the speed of the increase in pressure was proportional to the frost heave rate — the growth rate of the ice lens.
The degree to which a rock abrades a cutting tool or a bit is called its “abrasivity”. Laboratory tests of abrasivity can be broadly divided into 4 kinds; drilling, rubbing, turning operation and tumbling tests. In the previous study, authors conducted drilling, rubbing and turning operation tests to examine rock abrasivity. Within the range of tests conducted, the turning operation test turned out to be superior to the other tests, albeit slightly, in terms of practicality. The present study was started to compare the results of the turning operation test with those of two scratch tests (Mohs and CERCHAR tests) . Mohs hardness created by Friedrich Mohs is widely known as hardness scale especially for minerals. CERCHAR test developed by Centre d’Études et Recherches des Charbonnages de France is also widely used to examine rock abrasivity especially in France in the coal mining industry. The results of two scratch tests have been investigated and compared with the results of the turning operation test. Comparatively, better correlation was observed between the Mohs hardness and the abrasivity index of the turning operation test. Reasonable correlation was found between the abrasivity indices of the CERCHAR and the turning operation tests. The correlations are applicable within the following range, 2.5 ≤ IMohs ≤ 6.
This paper describes study on evaluation method of particle size and penetrability of ultrafine cement grout. Proposed method to evaluate particle size (digital image method) provided larger particle size than the result obtained by the conventional granulometry. The results by digital image method well coincided with penetrability of grout into cracks indicating that the proposed digital image method was right measure to evaluate the particle size of ultra fine cement grout. The proposed method was applied to evaluate the difference between single and double mixings of grout. The result clearly indicated the difference and it can be said that the double mixing was superior for ultrafine cement grout.
This paper describes a fundamental examination of a quicklime (calcium oxide) mixing treatment combined with carbon dioxide ventilation for the remediation process of soils contaminated with volatile organic compounds (VOCs). The quicklime mixing treatment is widely applied to remove VOCs in soils using the heat of reaction with calcium oxide and pore water. To maintain a higher temperature and to ensure that most of the VOCs are volatilized, quicklime is usually mixed at a ratio of 10% with soils in this treatment. However, a surplus of quicklime addition results in higher (alkaline) soil pH and causes serious damage to the soil ecosystems. To solve this problem, the simultaneous ventilation of carbon dioxide during quicklime mixing with contaminated soil was examined. Under these conditions calcium hydroxide was generated by the reaction of quicklime with pore water; the calcium hydroxide then reacted with carbon dioxide to produce additional heat of reaction. It is expected that the heat from the second reaction can be used for the treatment, allowing the amount of quicklime addition for the treatment to be reduced. Laboratory experiments showed that more than half of the calcium hydroxide was changed to calcium carbonate when the mixed soil sample was ventilated by carbon dioxide, using mixing ratios of 5% quicklime and 5% water in the soil. The maximum soil temperature reached with this treatment was the same as that for the treatment using 10% quicklime. Pilot scale and operational scale experiments confirmed the effectiveness of using carbon dioxide ventilation coupled with quicklime mixing treatment.
In an attempt to recover tantalum from Printed Circuit board (PCB) , tantalum was concentrated by heat treatment and physical separation from mounted parts for PCB. Tantalum of PCBs is derived from tantalum capacitors. PCBs for personal computer (PC) and household appliance were crushed by water explosion to strip mounted parts from PCBs. More parts were stripped from PCB for PC composed of epoxy resin than from PCB for household appliance composed of phenol resin. Then, tantalum sintered bodies were separated from molded resins by heat treatment for tantalum capacitors at 723, 773K in the air and screening with 0.5mm sieve. 70% of tantalum grade was obtained after separation for tantalum capacitors. Tantalum recovery decreased under the condition of heat treatment at low oxygen concentration. Behavior of other parts by heat treatment was also investigated. While epoxy resin molding IC parts was powderized at over 723K, tantalum sintered body was powderized at over 823K. As a result, mounted parts of PCB for hard disk drive (HDD) were heated at 723K and the residue with size over 0.5mm was re-heated at 823K and screened. Material balances of tantalum, copper and precious metals were investigated on the process. 16% of tantalum grade and 71% of tantalum recovery was obtained. 13% of copper, 49% of gold, 12% of silver and 16% of palladium were distributed to the tantalum concentrated residue.