Masaya Miyake

Development of a QMS with a ceramic single-piece quadrupole

Abstract A novel quadrupole mass spectrometer (QMS) has been developed by using a ceramic single-piece quadrupole. The quadrupole was made of silicon nitride (Si3N4). The four hyperbolic surfaces were coated with metal thin films of about 10 μm to form electrodes. Mass spectra were successfully obtained by using the conditions of the second stable zone in the mathieu diagram. It seems that there are no differences in sensitivity and resolution between the two QMSs with a ceramic quadrupole and a conventional metal one of the same dimensions.

Development of a high-strength Si3N4 sintered body☆

Due to its heat-, wear- and corrosion-resistant properties, Si3N4 ceramic is a promising material for cutting tools and other wear-resistant products, and for automotive engines, gas turbines, and other structural items. Sumitomo Electric has successfully developed sintered bodies (σ1 = 130 to 150 kg/mm2 at room temperature) with high strength by controlling grain shapes grain diameter and aspect ratio. The high strength Si3N4 materials have fracture toughnesses of KIC = 5–7 MPa/m, thermal shock resistance of ΔT = 9000°C, good acid-resistant properties, and other properties all superior to those of conventional Si3N4 materials. Highly reliable Si3N4 materials with high Weibull modulus (m > 20) have also been developed by reducing metal inclusions that would cause defect factors leading to breakup. The high strength Si3N4 is already in practical use for plastic machining tools for non-ferrous metals (Al, Cu alloys), forging tools, and other wear-resistant products and structures of steel facilities. It is also being used for automotive parts and other items requiring high reliability. The high strength Si3N4 sintered bodies fully satisfy the requirements of these products.

Korngrößenänderung beim Carburieren von Wolfram und Sintern von Wolframcarbid

Die Korngrosenanderungen im Verlauf der Herstellung von Hartlegierungen wurden mikroskopisch, rontgenographisch und korngrosenanalytisch untersucht. Die Reaktion von Wolfram mit Kohlenstoff wurde an der Oberflache und im Inneren der Wolframpartikel verfolgt und erlaubt so, den Mechanismus der Carburierung und das Kornwachstum zu erklaren. Drei charakteristische WC-Sorten wurden mit Kobalt in einer Kugelmuhle gemahlen und die resultierende Korngrosenverteilung mit den Eigenschaften des Ausgangsmaterials in Beziehung gebracht. Bei diesen Versuchen zeigte sich, das die Teilchen durch Absplittern zerkleinert werden. Das Kornwachstum beim Sintern beginnt bereits als Festkorperreaktion betrachtlich unterhalb jener Temperatur, bei der flussige Phase auftritt. Schlieslich wurde darauf hingewiesen, das die Erforschung der Defektstellen eine Klarung der Wachstumsphanomene erleichtern mag.

The Development of Ceramic Injection Molding

The method of forming thin ZrO2 bodies by Injection molding process using acrylic binder was studied. Concerning reological characteristics and properties of thermal decomposition, acrylic binder was compared with the more generally used wax binder. The flowing characteristics of the mixture of acrylic binder indicated high viscosity and gradual change in relation between temperature and viscosity. The compacts using acrylic binder had high flexural strength compared with those using wax binder. As a result, it was observed that ZrO2 mixed with acrylic binder filled the mold without defects. A mechanism for removing acrylic binder from compact which is different from that of wax binder was found. This mechanism made it possible to remove, without defects, acrylic binder, and to control the quantity of gas which decomposes the binder in the inner part of compact. Mixture with 45vol% acrylic binder was the best composition for injection moldability and removing binder. Sintered ZrO2 compact was densified by HIP (Hot Isostatic Pressing), and its mechanical properties were equal to those of the conventional process.

Study on the Change of Grain Size of WC Powder during Ball Milling of Cemented Carbide

The mixing phenomena of WC and Co powders have not yet been made clear enough in spite of their importance in the Cemented Carbide industry. Therefore, in this paper the crushing of WC powders and the behaviour of their grain growth during sintering were examined using variousWC powders, i.e., coarse single crystal, coarse polycrystalline and medium single crystalline WC powders.The obtained results were as follows;(1) Coarse single crystal WC powders were crushed markedly by chipping in the early ball milling stage. There-after, average grain size of WC continued to decrease with the appearance of fine chipping powders. Therefore, the grain size distribution of the coarse single crystal WC powder grew wider with the increase of ball milling time.(2) Polycrystalline WC powders were crushed in the same way as the above mentioned (single crystal) in the early ball milling stage. However, the grain boundary destruction seemed to be caused after having been WC crushed into the definite size.(3) Single crystal WC powder of medium size were more difficult to be crushed with chipping than the coarse one.(4) The grain growth of coarse single crystal WC during sintering is more rapid than polycrystalline one because the size distribution of the former was wider than that of the latter. Moreover the average grain size of WC in alloys formed medium single crystal WC powders in coarser than that from coarse one, because the former was less crushed than the latter.(5) In sum, the crushbility of WC in ball milling and its grain growth in sintering did not only depend upon WC grain size, but also the manufacturing process.