Junichi Iwasaki

Structure, magnetic susceptibility and heat capacity of ScMnO3

Abstract Structure refinement of the room temperature X-ray powder diffraction data of ScMnO3 was carried out by Rietveld technique, based on the most probable space group P63cm. The manganese and scandium atoms are surrounded by five and seven oxygen atoms respectively. Three manganese atoms make three kinds of triangles (two regular and an isosceles). A weak ferromagnetic behaviour with small hysteresis was observed below 130 K on the magnetization curve and ScMnO3 becomes completely paramagnetic above it. The heat capacity of ScMnO3 was measured from 77 to 800 K by two types of calorimeters (a.c. calorimeter and differential scanning calorimeter). At 129 K a λ-type anomaly was seen in the heat capacity curve which corresponds to the magnetic transition. The enthalpy change and entropy change that accompanied the magnetic transition were 178 J mol−1 and 1.40 J mol−1 K−1 respectively. The baseline of the heat capacity from 150 to 250 K yields a Debye temperature of 615 K.

High-temperature enthalpy and heat capacity of ErMnO3

Abstract The heat capacity of ErMnO 3 was measured by differential scanning calorimetry (DSC) from 300K to about 850K. The heat capacity value at 298K was determined to be 103.7J mol −1 K −1 . In order to obtain thermodynamic data at higher temperatures, the enthalpy change of ErMnO 3 , H 0 T -H 0 298 , was measured in the temperature range 673–1373 K by the drop method. The accuracy of the enthalpy measurement was checked by comparing the measured enthalpy changes of Er 2 O 3 and Mn 2 O 3 with literature values. The relative error was ± 2% for both compounds. However, for the heat capacity calculated from the enthalpy change, the maximum deviation of the heat capacity from the references was ± 3%. The equation for the heat capacity of ErMnO 3 derived by combining the two methods (DSC and drop methods) was C p = 111.9 + 26.4 × 10 −3 T − 1.33 × 10 6 T −2 from 298 to 1373K. The standard Gibbs free energy of formation for ErMnO 3 , − 1362.7 kJ mol −1 at 298K, was also calculated using the above data.

Optimum Pressure Control of Molten Metals for Casting Production Using a Novel Greensand Mold Press Casting Method

This paper presents a novel method of sand mold press casting. In this process, molten metal is poured into a drag mold, and then the cope mold is placed on top of the drag mold, and the two molds are matched. The mold design for casting, the pouring control and the velocity control of the press have been previously clarified as key factors in the manufacture of sound products. This paper presents methods for modeling and control of the molten metal’s pressure for novel sand press casting technique. Substituting detailed information for the complex mold shape, the poured volume and initial temperature into a developed control input generator, an optimum pressing velocity design and a robust design for defect-free production are proposed by the sequential control algorithm based on the construction of an inverse system comprised of a sequential switching from higher to lower speed. The effectiveness of adaptive press casting is demonstrated by using CFD model simulations.