In order to study the influence of feed particle size on energy efficiency for production of fine particles, autogenous grinding tests were carried out using a stirred mill. The mill used was made of stainless steel and its volume was about 5.5 liters. The impellers were always run at a rotational speed of 69 rev/min. The sample used was limestone. The material was charged 5 kg and the feed size were 2.0-1.3, 1.3-1.O and1.0-0.67cm, respectively. The ground products were sieved in the size range from the feed size to 3μm.
As a result, it was found that the energy consumption to produce the particles finer than 3μm decreased with increase in the feed size and it became minimum when the feed size was closer to the distance between the top edge of the impeller and the wall of mill.

View full abstract

Permeation of hydrogen through natural zeolite was studied to obtain the fundamental data for the separation of hydrogen. The following results are obtained.
The membrane made of natural zeolite, which is yieled from Itaya of Yonezawa city of Yamagata prefecture, has the excellent heat-resistance and the complicated porous structure like a maze. The pore sizes of the membrane are found to be distributed from 80 to 10, 000 Å. It is also found that Itaya natural zeolite has many suitable pore sizes from 80 to 300 Å for the separation of hydrogen by Knudsen flow.
The rate of gas permeation increased as the operational pressure difference increased. The separation factor of hydrogen is affected by the ratio of the pressure of permeated gas P₂ to the pressure of feed gas P₁, and increases with an increase in the pressure difference. The pressure reduction of permeated gas was found to be very effective to increase the hydrogen separation factor of the membrane. It was also found that the rate of gas permeation was reduced in some degree as the operational temperature increased up to 523K, but that the separation of hydrogen by the membrane was improved.
These experimental results mentioned above reveal that Itaya natural zeolite can be utilized for the hydrogen separation from gas mixture under the wide range of opertional conditions of temperature and pressure.

View full abstract

Fabrication process and mechanical properties of uniaxially oriented SiC whisker reinforced AA 7001 aluminum alloy composites (FRM) with oriented whisker preform by electrostatic method is described.
In the electrostatic method of fabricating a uniaxially oriented SiC whisker preform, whiskers suspended in an insulating liquid (freon R-113) are oriented in the field direction. To investigate this phenomena, the experimental observation of whisker motion is made using a cell with 3-mm electrode gap, which viewed through a microscope. SiC whiskers are polarized and oriented in both dc and ac (f=12500 Hz) field, showing the time constant of polarization is sufficiently smaller than that of mechanical orientation. SiC whiskers form long agglomerates in the ac field. In the frequency range of 1 to 10 Hz, oriented whisker agglomerates with better orientation are observed.
A fabricated uniaxially oriented preform is incorpolated into an aluminum alloy by squeeze casting. This uniaxially oriented FRM has higher bending strength and fatigue strength than FRM with 3-dimensionally random oriented whiskers. Ratios of the matrix to the uniaxially oriented FRM in the bending strength and the fatigue strength are 2.1 and 4.2 respectively.

View full abstract

The structural changes of the merocyanine LB (Langmuir-Blodgett) films were investigated and then were compared with the typical changes of the molecular structures of merocyanine solutions. The photoisomerization of the as-deposited LB films was not attained. The structural changes of quinoid/benzenoid were attained by changing atmosphere gases (HCl gas, NH₃ gas). After treatments in the HCl gas atmosphere, the cis/trans photoisomerization characteristics of the LB films were obtained in the similar manner with the characteristics of the solutions.

View full abstract

Crushed fragments of window glass were treated by two typical machines, a ball mill and a disc crusher, and they were size-sorted and analyzed in terms of shapeand size-classifications with a sieving apparatus and an image analyzer, iteratively.
The size reduction by the disc-crusher revealed that both characteristics of particle elongation and shape irregularity, increased once to the certain maximum values and then reduced to the smaller fragments, stepwisely. On the contrary, the mill produced the smaller fragments, keeping same elongation and similar irregularity, little by little from the large lumps.
However the smaller particles such as 150-270 mesh resembled each other in shape characteristics, such as elongation, asymmetricity or irregularity which might be caused the property of the crushing materials.

View full abstract

In the ceramics production process composed of unit operations such as weighing, mixing, drying, crushing, granulation, forming, firing and so on, to control the homogeneity of materials is one of the most important problems because the properties of ceramics are strongly effected by the homogeneous degree.
In this paper, thin powder layer forming process is selected to be discussed, and doctor blade method is used, which is one of the thin powder layer forming processings. This method will give a thin powder layer. However, the thermophysical mechanism of the forming process has not yet been discussed. Then, the bulk density distributions are observed by its X-ray radiograph using the image processing system, and are thermophysically discussed.
The following findings are obtained. When electric field is applied to the powder layer, the homogeneity increases enormously. And the stronger electric field applies, the higher homogeneity of powder layer is obtained. Beacuse the electric field produces the corresponding negative free energy to the field in powder, it results in the increase of the entropy of powder laver.

View full abstract

In general, the integrated circuit (IC) is molded by epoxy resin. The molding in the package of IC includes both heating and cooling processes. Basically, substances expand when raised their temperature and contract when cooled. Thermal stresses occur when any portion of the thermal expansion or contraction in the plastic molded IC is constrained. In particular, these are induced during the cooling process (thermal contraction). It has been reported that, the thermal stresses have a variety of bad influence for the molded IC.
We have been analyzed in a part of the molding material by the photoelastic method. In the photoelastic method, mold resin must be transparent, but real mold resin is opaque to contain filler and so on. Therefore it is impossible to measure thermal stresses. Consequently, in this study, the finite element method was used as one of computer simulation methods, and the thermal stress disrtibution was analyzed in a molded IC section by this method. As the result, a part of maximum stress distribution values nearly agree with any portion of IC failures, and thermal stress values of opaque resin have approximately twice as much as those of transparent resin.

View full abstract

This investigation aimed at the characterization of monosized ulta high purity Al₂O₃, observing the microstructural evolution with the measurement of pore elimination during sintering. The small particle size of 0.39μm Al
2_O3 powder with a most frequent pore size of 0.12μm in the green stage gave almost full density Al₂O₃ at the low sintering temperature of 1400°C. Brook's diagram predicted the pore-grain boundary separation, however, no separation was observed. The experimental result of pore elimination agreed with Kingery and Francois' study of pore growth/separation by the parameter of equilibrium dihedral angle. The reduction of the coordination number of grains surrounding a pore is also of importance to obtain high density Al₂O₃.

View full abstract