The electrical conductivity and dielectric relaxation of glasses in the system MnO-Fe₂O₃-P₂O₅ were studied over the temperature range 20-16°C. This system contains MnO and Fe₂O₃, both of them confer an electronic conduction. The samples used in the experiment were prepared under following conditions, i.e.
1) melting in the air, being kept for about 2h at 350°C, and then gradually cooling (normally cooled glass),
2) melting with a reducing agent, being kept for about 2hrs. at 350°C, and then gradually cooling (reduced glass),
3) melting in the air and then annealing at a temperature above 100°C than T_g (annealing glass or crystallized glass).
The ratio (Fe²⁺/Fe²⁺+Fe³⁺) in the system was analyzed chemically and the effects of the ratio on the electrical properties were determined in connection with the composition of the glass. The conductivity in the (50-x)MnO-xFe₂O₃-50P₂O₅ glasses increased linearly by replacing MnO with Fe₂O₃. The conductivities of the reduced iron-containing glasses was about one order of magnitude higher than those of the normally cooled glasses. The conductivity of crystallized glass having composition 50MnO-50P₂O₅ was greater than about 5.5 order of magnitude over those of the normally cooled glass, and the straight line representing the relation between log σ and 1/T was found to break at about 80°C. These facts suggest that the preferential segregation of transition metal, consisting of a particular oxidation state, would be assumed to explain the large change in conductivity observed in this crystallized glass. The dielectric constant ε' and dielectric lossε'' increased with the increase of the amount of Fe₂O₃. In the reduced glass containing MnO and Fe₂O₃, the dielectric loss ε'' increased with the increase of the amount of Fe²⁺ion. The value of ε'' _max decreased with increasing the annealing temperature.
Relaxation losses in these glasses containing transition elements are considered to be related to the electron transition between the two different valences of the elements and the manner of distribution of the elements in the glass.

View full abstract

Single crystals of willemite have been grown by the slow cooling flux merhod using Na₂MoO₄ and Na₂WO₄ as solvents. The main experiments on crystal growth were carried out at soaking temperatures of 1215-1405°C and cooling rates of 3.3-5.7°C/h with Na₂MoO₄ flux which was the most promising flux, and mixtures of ZnO and SiO₂ with molar ratio of 2:1 and Zn₂SiO₄ powders prepared by solid-state reaction at 1400°C were used as starting materials. The needle-shaped willemite crystals as large as 0.36mm in diameter and 6.0mm long were grown from spontaneous nuclei on a wall of a Pt crucible at the soaking temperature of 1390°C. It is inferred that a precipitate of fine crystals of willemite and ZnO in glass matrix which was resulted by reaction of unsolved Zn₂SiO₄ powder excess to its solubility with the flux had scarcely acted as effective nuclei. The willemite crystals were generally colorless and transparent and often contained several columnar cavities and/or flux inclusions. An external shape of the crystal was generally hexagonal prismatic column with c-axis orientation, being bounded by a (1120) and r (1011) faces. Mn-doped willemite crystals were larger than pure ones, the largest having dimensions of 0.5×0.5×6.2mm. However, they contained more imperfections. When exposed to an ultraviolet light, they fluoresced a light green color.

View full abstract

This paper describes the method for the determination of Sr in television tube glass by atomic absorption spectrometry.
The interference of the glass components to the Sr determination is as follows:
(i) Ba, Ca, Mg, Sb, As and Fe do not interfere.
(ii) Na and K increase the absorbance of Sr, but up to 500ppm the absorbance of Sr is nearly saturated.
(iii) Ti, Al, Zr and Si decrease the absorbance of Sr, but by the addition of La, the absorbance is appreciably restored.
In case that 10ppm Sr and 1000ppm La are in the solution, 1.5ppm Ti, 10ppm Al, 20ppm Zr and 5ppm Si are allowable.
The method of determination is as follows.
0.5g of powdered glass sample is decomposed by HF and HClO₄, and Si is completely eliminated as SiF₄.
The residue is dissolved by dilute HCl.
The contents of Ti, Al and Zr are within the limit, an aliquot of the sample solution, La and K solution are transferred to the volumetric flask so that the final concentration of analyte will be about 15ppm Sr, 1000ppm La and 500ppm K, and then Sr is determined by atomic absorption spectrometry.
But in case that the contents of Ti, Al and Zr are over the limit, it is necessary to remove them by the hydroxide precipitation method.
And then Sr is determined as mentioned above.
The average relative difference is about ±3% and reasonably good results are obtained in the range of about 9.5 to 11.5% SrO in the television tube glass.

View full abstract

CaO⋅Al₂O₃ solid solution synthesized by substituting Fe and Si for Al crystallizes as the aggregation of distorted small crystals. This distortion was qualitatively estimated by measuring the heat of wetting and observing the chatacter of Laue patterns. The heat of wetting was lowered in proportion to the distortion of inner crystal, thus the high value of 2110erg/cm² for pure CA lowered to 1760, 1550 and 1340erg/cm² for each Fe-, Si- and Fe-Si substituted CA. The pH value of the solution increased immediately after mixing of sample and water in proportion to the heat of wetting corresponding to the activity of surface, but the hydration velocity of them corresponded to the distortion of inner crystals. By the general conception on the hydration of CA, CAH₁₀ is formed at first and converts to C₂AH₈ but in the hydration of CA solid solution containing Fe₂O₃, C₂AH₈ was formed frmed from early curing time with small pH increase. This yields an increase of compressive strength though initial hardening was delayed. The crystals with Fe and Si have great lattice distortion thus more great strengths of hydrates can be expected than the others. The hydration of pure CA was more slow than those of CA solid solutions with Fe, Si and Fe plus Si. The CAH₁₀ crystallized with a great hydration heat and next C₂AH₈ was formed slowly with a great pH increase. The high strength was not expected. In the Si-substituted series the early hardening were accelerated but also with less increase of strength.

View full abstract

The authors propose a new model which shows the mechanical behaviors of the plastic clay body. In the present paper the authors discuss about the spontaneous elastic deformation which arises at the moment when the external force is applied to the clay specimen. The mechanical model which contributes to this spontaneous deformation is composed of many spring elements arranged in a row. At the moment when the stress is applied, this part (I) deforms reversibly after Hooke's law. But if the stress τ exceeds the limited value (lst yiedl value), some of the spring elements are decayed, and then the residual elements support the stress. Consequently the elastic modulus of the part (I), G_I, will be estimated as follows,
G_I=G_I0e^-ατ
where τ is the stress, α is the constant, and G_I0 is the elastic modulus before the stress is applied.
As the plastic clay materials, we used the green body for electric porcelain and Kibushiclay mixed with alumina powder as non-plastic material. The specimens were formed into thin cylindrical tubes, 20mmφ-10mmφ×100mm, by extruding the raw materials above mentioned. Using the torsional test method, the strain arised in the specimen was measured at the moment, when the torque was applied to it. Then in some cases the recovery of deformation was also measured.
The experimental results agree well with the theoretical expectations from our mechanical model.
(1) The elasticity of the part (I) is inversely proportional to the exponential function of the stress.
(2) The elasticity before the stress is applied, G_I0, is inversely proportional to the exponential function of the moisture content (dry basis).
(3) When the stress beyond which the specimen initiates to flow is applied, most of the spring elements are decayed in the part (I), and the ratio of the residual elements becomes only 5% of the initial state.
(4) On the recovery of the elastic deformation some of the strain is remained, and therefore some residual stress arises.

View full abstract

The formation of fine titanium-nitride powders by the vapor phase reaction of TiCl₄-NH₃-H₂-N₂ system was investigated between 700° and 1500°C with emphasis on the effects of reaction conditions on the properties of the nitride powders. The following results were obtained.
1) Mixing temperature of TiCl₄ and NH₃ gave a remarkable influence on the properties of the titanium nitride powders produced. When the mixing temperature was about 250°C (method (A)), the nitride powders produced had a wide distribution of particle size from 0.01 to 0.4μ. BET surface area (S_BET) of the nitride powders by method (A) was larger than the surface area estimated from the particle size distribution based on the electron micrographs (S_EM). On the other hand, when the mixing temperature was above 700°C (method (B)), the nitride powders produced were finer than those by method (A) and had a narrow distribution of particle size from 0.03 to 0.2μ. In the case of method (B), the particle size can be controlled with reaction conditions (mainly with reaction temperature); it decreased with the increase of reaction temperature. S_BET of the nitridepowders by method (B) was nearly equal to S_EM.
2) These titanium nitrides showed a wide range of nonstoichiometry with an excess nitrogen; atomic ratio N/Ti=1.1-1.4. The N/Ti ratio decreased with the elevation of reaction temperature. X-ray diffraction patterns of all nitride samples showed NaCl-structure. It was found that these titanium nitrides contained Ti vacancies equivalent to the excess nitrogen.
3) For the formation process of titanium nitride particles, it was proposed that the process in method (A) consisted of the formation of TiCl₄-NH₃ adduct powders and the subsequent thermal decomposition into nitride, and that the process in method (B) consisted of the formation of TiN nuclei and its growth into nitride particles.

View full abstract

The internal friction in glasses of Na₂O-H₂O-P₂O₅ system was measured with the torsion pendulum technique at a frequency of 0.4Hz. The peaks in the internal friction exhibited similar behaviour to that of mixed alkali silicate glasses or to that of single alkali silicate glasses containing water. It was indicated that the hydrogen ions in the glasses caused the mixed alkali effect. It was proposed that the low temperature peak was due to the sodium ions or the hydrogen ions and the high temperature peak had close connection with the nonbridging oxygen ions owing to the occurrence of the two peaks in P₂O₅ glass containing none of alkali.
The compositional dependence for temperature and height of the high temperature peak was investigated, It was found that the mixed alkali effect greatly occurred in the compositional range of rich sodium ions because of the large disparity in size between the sodium ions and the hydrogen ions.

View full abstract

A precise but convenient method was developed for the determination of nitrogen and silicon in silicon nitride.
As for nitrogen, sample was decomposed with sodium hydroxide at about 320°C and the resulting ammonia was collected in boric acid solution with an aid of steam vapor as a carrier. The collected solution was then titrated with a standard acid solution against methyl red and the nitrogen content was obtained.
As for silicon, it was determined by a conventional gravimetric method after the disintegration of the sample with sodium potassium carbonate at about 800°C followed by dissolution in hydrochloric acid. Correction for silicon escaped into the solution, when it had been determined by the gravimetric method, was made by determining it with a spectrophotometric method as a heteropoly blue complex.
The method was applied to the determination of nitrogen and silicon in high purity silicon nitride, and they could be determined with satisfactory results.

View full abstract