Structure Analysis of Some Fused Materials by X-ray Diffraction : Part I. NaNO_3, NaNO_2 and PbO-B_2O_3 System

A new method of X-ray diffraction measurement widely applicable to fused materials including corrosive substances up to high temperature ranges has been described. By the Fourier Analysis of X-ray diffraction data, the atomic radial distribution curves of several fused materials have been obtained. Fused NaNO_3 and NaNO_2 contain Na^+ ions and NO_3^- or NO_2^- radicals, which are in thermal motion being restricted by their specific shapes and charge distributions. The structure of fused PbO-B_2O_3 system in the range of PbO/B_2O_3=4/1 to 1/3 in mol-ratio are, in general, considerably similar to their glass, but Pb-O bonds become more ionic by the fusion or by the increase of B_2O_3 content. Its abnormal glass-forming-limit (94 wt % in PbO) is also explained

The Structural Model of Monatomic Liquids Including Metallic Liquids near the Melting Points

Under criticism of the data of atomic radial distribution curves for monatomic liquids, a simple reduced-type structural model of liquids near their melting points having only one parameter is proposed, which is the residual molecular diameter subtracted twice the root-mean-square amplitude of molecular vibration from the mean intermolecular distance, therefore depending on the temperature. Combining this model with the free volume theory several molecular properties of monatomic van der Waals and metallic liquids including spherico-symmetrical molecular liquids are unitarily explained ; for example, at their melting points the shapes and positions of 1st and 2nd peaks in the radial distribution curves, the molar volumes, the self-diffusion coefficients, the viscosity coefficients and the entropies etc., It is also useful to interpret the apparent differences of properties between van der Waals and metallic liquids. And we get some suggestions from this model that the existence of the critical point between the solid and liquid (or fluid) may be possible

Statistico-Thermodynamical Studies on the Fundamental Reactions concerning Steel-Making. IV : The Oxidation and Reduction Equilibrium of Magnetite with Gas Phases

It is known that magnetite crystals can contain excess oxygen over the stoichiometric composition of Fe_3O_4 by high temperature oxidation, and the oxygen content depends on the oxygen pressure in atmosphere and on the temperature. The Fe_3O_4 crystal has a crystal structure of the inversed-spinel type, in which O^ ions occupy the closed packed cubic lattice points, and the tetrahedral lattice sites (8 f) of its unit cell are occupied by 8 Fe^ ions, and octahedral lattice sites (16 c) by 8 Fe^ and 8 Fe^ ions statistically. When the magnetite crystal contains excess oxygen under an oxidizing atmosphere, it can be assumed that a vacant site accompanying two electron defects which result in two Fe^ ions is found on the octahedral lattice points occupied by Fe^ ions. Under these circumstances we can calculate the partition function of magnetite phase, from which the equilibrium relation between the oxygen content in magnetite, the partial pressure of oxygen in atmosphere and the temperature is deduced theoretically. These results are in good agreement with observations by Greig et al. and Darken and Gurry

Statistico-Thermodynamical Studies on the Fundamental Reactions concerning Steel-Making. V : The Oxidation and Reduction Equilibrium of Mn-wustite (Fe, Mn) O with Gas Phase

It is known that Mn-wustite (Fe, Mn) O takes a from of solid solution over all compositions of Fe- and Mn-atoms, and its oxygen content varies with oxygen pressure in the thermal equilibrium and with temperature. So we examined the quantitative relation between the solid and gas phases in the above-mentioned system. Taking into consideration the previous papers in which wustite and magnetite solid solutions were discussed, a configurational model for the Mn-wustite was assumed as follows : (1) O^ and metal ions are arranged on the lattice of NaCl type, (2) in the negative ion lattice-sites O^ ions are perfectly packed, (3) in the positive ion sites Fe^, Mn^ and vacancies are randomly distributed, and (4) on some of Fe^ ions the electron-defects are trapped, producing Fe^ so that the total electrical charge of crystal is neutralized. Considering such a model, the partition function of Mn-wustite was formulated on the base of statistical thermodynamics, and the equilibrium relation between the solid composition and oxygen pressure in the gas phase was calculated. The calculated result was in agreement with the experimental values by Matoba and Gunji (1954) and our data obtained by repeated measurements of weight change using a spring balance

A Structural Model for Monatomic Liquids including Metallic Liquids

Under criticism of the data of atomic radial distribution curves for eighteen monatomic liquids, a simple reduced-type structural model of liquids near their melting points having only one parameter A, which is the residual molecular diameter subtracted twice the root-mean-square amplitude of molecular vibration from the mean intermolecular distance r_1 is proposed as follows : "Let V_0 be the volume at closest packing of spherical molecules of diameter A, then the volume of liquid at T_m is 1.5 V_0 for quasi face-centred cubic lattice. But about 10 per cent of the sites in this quasi-lattice are empty, and these spaces are distributed through all interstices explaining the second peak at 1.9 r_1 of the distribution curves. Thus the total volume is about 1.65 V_0." Combining this model with the free volume theory several molecular properties of monatomic van der Waals and metallic liquids including spherico-symmetrical molecular liquids are explained ; for example, the shapes and positions of 1st and 2nd peaks in the radial distribution curves, the entropies, the self-diffusion coefficients and the viscosity coefficients at their melting points

Statistico-Thermodynamical Studies on Fundamental Reactions concerning Steel-Making. VI : On the Configuration of Fe-O Molten Slag and its Interation with Gaseous Oxygen

The iron and oxygen atom-ratio of Fe-O melts is continuously variable by the change of oxygen pressure in the gaseous phase. It is very reasonable that we suppose Fe-O melts are constructed by ionic components Fe^, Fe^ and O^, thanks to the previous results on Fe-O solid-solution phases (ref. previous Reports II and IV) and the electro-conductivity of melts. We assume the following configurational model for Fe-O molten system : (1) Oxygen ions O^ are arranged on the face-centered cubic lattice (nearly close-packed), because they are very large compared with iron ions. (2) Fe^ ions are distributed on the tetrahedral and octahedral interstitial lattice points of the oxygen-ion lattice. (3) If any tetrahedral lattice point is occupied by a iron ion, its nearest octahedral lattice points are vacant, and it is the same for the nearest neighbors of octahedral iron ions. (4) Positive holes are randomly distributed on Fe^ ions, and thus Fe^ ions are formed. Using the above model the partition function of the Fe-O molten slag was formulated by the statistical thermodynamic method, and the equilibrium relation between the slag composition and the pressure of oxygen in gas phase was calculated. These theoretical results are in good agreement with the measured values of Darken and Gurry (1946) in the wide range of pressure, 10^ to 1 atm of O_2, and temperature 1400°to 1600℃