Kinds Of Ceramics Research Articles

Ａｌ‐ＭｇおよびＡｌ‐Ｓｉ合金を溶融インサート材に用いたセラミックスとアルミニウムの接合

Joining of aluminum (A1100) and four kinds of ceramics, Si3N4, SiC, Al2O3 and PS-ZrO2 (partially stabilized), was attempted by using Al-Mg and Al-Si alloys as fusible insert. Effects of insert composition and joining parameters, such as temperature, time, pressure, cooling rate and amount of insert, on the bond strength were investigated. The results obtained are as follows: (1) Both aluminum alloys worked successfully on the joining, and relatively high bond strength was obtained at the compositions, 5-20wt%Mg and 5-10wt%Si. (2) Joining at temperatures below 878K using the Al-Mg alloy insert, however, gave rise to high thermal stress, which decreased the bond strengths of Al2O3 and SiC remarkably. (3) A use of Al-Si alloy insert can be recommended when thermal stress becomes a serious problem. (4) Al-10wt%Mg alloy can be recommended as suitable insert for Si3N4 and SiC, and Al-5wt%Si alloy for PS-ZrO2 and Al2O3. (5) The following measures are effective to reduce the thermal stress in use of the Al-Mg alloy insert; i) to minimize the amount of the insert, ii) to increase joining temperature and/or time, and iii) to decrease the rate of cooling after joining.

Study on the semiconducting mechanism of BaTiO3 and SrTiO3 ceramics

Abstract The effects of sintering temperature, cooling condition and of doping amount of Nb 2 O 5 on the semiconducting behavior of BaTiO 3 and SrTiO 3 ceramics have been investigated. The results show that the variations of conductivity with the amount of Nb 2 O 5 for the two kinds of ceramics are not exactly identical. For doped SrTiO 3 ceramics the semiconduction is attributed to the loss of oxygen. For doped BaTiO 3 ceramics the semiconducting process is controlled by two principles, valency compensation semiconduction and oxygen loss semiconduction. These results were proven by Raman spectroscopy.

Ceramic material processing by electrical discharge in electrolyte

New ceramic materials receive a great deal of attention as machine components, but they are hard to work. So a hybrid processing which combines electrical discharge processing with grinding is proposed. In this study, in order to examine the possibility of this hybrid processing, the electrical discharge processing on four kinds of ceramics was carried out with a needle electrode. The ceramic materials were alumina and three kinds of silicon nitride series to which are added alumina (ASN), magnesia (MSN), yttria and alumina (YASN). The results obtained showed that a pit can be formed on any ceramic and the pit depth apparently varies with the ceramic material. The removal rates of ASN, alumina, YASN and MSN become low in turn, and are independent of their mechanical properties. In the case of the silicon nitride series, the removal rates depended on their sintering additives, and the higher the applied voltage, the greater was the volume removed. High removal rate and low electrode loss are obtained when the needle electrode is negative. The ceramic materials are mainly removed by etching the grain boundary in a high-temperature electrolyte during the discharging process.

セラミックスの精密重畳振動ねじ立て

In this report, it is analayzed theoretically that female precision threading of ceramics can be realized by a new precision ultrasonic super position vibration tapping. And this analytical results can be confirmed by the experiments using a newly developed precision ultrasonic super position vibration tapping machine with the electric stepping motor and 28 kHz ultrasonic torsional vibration mode diamond tap (M 5 pitch 0.8 mm). The main results are as follows : (1) It has been verified that precise female screw threading of WA wheel (φ15×5) can be machined by a new ultrasonic super position vibration tapping machine with diamond tap in one stroke and more efficient. (2) Female thread with precise screw thread shape can be machined more efficient and unusual cutting noise and tap failures scarcely occurred of appliance of earthenware and glass of daily use. (3) By this study, it is believed that this new tapping machine has the possibility of precision machining in female screw threading of various kinds of ceramics.

セラミックスの常温における繰返し疲労挙動

The cyclic fatigue behavior of different kinds of ceramics was investigated at room temperature. Flexural specimens, with an indentation induced flaw at the center of the reduced gage section, were tested under a cyclic load applied by four-point bending. All ceramics tested were shown to be susceptible to cyclic fatigue failure. The cyclic fatigue degradation compared to its flexural strength increased in this order: hot-pressed AlN, sintered SiC, hot-pressed Si3N4, sintered Si3N4, and sintered Al2O3. The apparent fatigue limit was about 80% of the average flexural strength for AlN, and about 60% for sintered Al2O3. There existed a correlation between the scatter in fatigue and flexural strength. The scatter in fatigue strength was smaller than the scatter in flexural strength. SEM fractography revealed a dominant intergranular fracture in Al2O3 and Si3N4, which suggests a possible stress corrosion cracking mechanism in the grain boundary glassy phase. On the other hand, hot-pressed AlN showed a mixed mode fracture of intergranular and transgranular cracking, and SiC exhibited transgranular cracking only.

The preparation of piezoelectric ceramics withk p value of 15%

PbNb2O6 PbCrO4 PZT piezoelectric ceramics with low radial coupling coefficient has been developed. Its chemical equation is given. This kind of ceramics is characterized byk p =0.15,Q M =5000,f/f r =6×10−6. It has been used successfully to make low-frequency narrow-band ceramic filter.

Combined machining of hard and brittle materials (Combination of electric discharge machining and grinding)

Combination of two machining processes has possibility to increase the productivity. This kind of approach is worthy to be tried especially for the machining of so called difficult-to-machine materials. In this study, cutoff and groove grinding with diamond wheel is combined with electric discharge machining. The effect of this new machining process is experimentally investigated in grooving cutoff operations of cemented carbide, sendust, and several kinds of ceramics. Experimental results show that this process is effective for some materials to decrease grinding forces, which makes it possible to increase the workpiece speed. In addition, effect of the combination on the wheel wear, surface roughness, and geometrical accuracy of the workpiece is investigated.

Fine structure of crack in ceramics

Many kinds of ceramics have been developed providing enough insulation, heat conduction or shock resistance. For the characteristics of strong toughness of the ceramics, movements of cracks by applying a force are noteworthy, because most ceramics are hardly distorted.In the present works, behavior of cracks in ceramics is observed with high resolution electron microscopy. Silicon nitride (Si3N4) ceramics were made by sintering in nitrogen atmosphere at 1800°C. Some Y2O3 and AlN were added to assist the sintering. A piece of the ceramics was sliced and polished mechanically untill 20μm in thickness. The specimen was mounted on a single hole grid, and was thinned with an ion etching equipment to be thin enough to observe.

焼結ダイヤモンド工具の切削性能と摩耗解析(第1報)

New materials such as fine ceramics have attracted much attention as structural materials. The industrial needs of machining such materials will be emphasized more and more in the future. For this purpose sintered diamond will be a tool material of the highest probability or expectancy. Hard materials such as ceramics will clearly reveal the disadvantages of sintered diamond tool as well as its disadvantages. The objective of this study is to supply useful knowledges for development of new tool materials and improvement of tool engineering by analyzing the mechanism of tool deterioration of sintered diamond. This report treats with the experimental and theoretical analysis of dynamics and thermal stresses which will lead to the tool deterioration of sintered diamond tool in machining two kinds of ceramics.

The recycled pots and potsherds of Spain

The Romans and their cultural heirs, the Byzantines, devised a method for using discarded amphorae in vaulting large buildings, which they each followed in eastern and southern Spain as well as in Italy. In the same Iberian regions, Spanish medieval masons continued incorporating used earthenwares into some edifices, but the reasoning behind the practice, the way in which it was executed, and the kinds of ceramics greatly changed through time, due in part to different architectural styles. Through artifact and archival evidence, the method now has been confirmed also to have been current in Andalusia at the time the Spanish American colonies were being established and to have diffused overseas as Sevillian masons migrated to the Caribbean. There reused whole vessels and potsherds have been recovered from numerous 16th to 18th century vault haunches. Apparently Indian builders of colonial Mexico did not, however, adopt the procedure.

セラミックのラッピング特性

As a part of precision machining of ceramics used for communication, Forsterite, Alumina and Steatite are lapped under the same lapping conditions, where the relations between the lapping characteristics and the structural properties are studied. The main results obtained are as follows:(1) Forsterite has a shallow and uniform distribution of pores and a dense matrix. It is liable to be fractured, leading to the occurrence of a prominent influence of lapping pressure on lapping quantity.(2) Alumina has deep pores which increase their numbers along the underlayers. It shows the frictional behavior during the final period of lapping.(3) Steatite has both small porosity and water absorption, of which surface roughness is best among three kinds of ceramics.(4) The lapping energy per a unit lapping quantity well explains the lapping ability. Say, the difficulty of lapping Alumina is 3.5-23 times as great as that of lapping Forsterite.