Yoshinori Yamada

X-Ray Photoelectron Spectroscopy of Fluorocarbon Films Deposited by RF Sputtering

Fluorocarbon films are deposited by rf sputtering of poly(tetrafluoroethylene) targets under conditions of various power and pressure levels in pure argon in order to examine the effect of discharge conditions on the deposition rate and molecular structure of the deposited films. The molecular structures of the films are investigated by means of X-ray photoelectron spectroscopy. The films deposited under conditions favoring high deposition rate, such as higher power at a constant pressure or lower pressure at a constant power, contain higher concentrations of cross-links. Heating the deposited films results in an increase in the component of the C1s spectrum assigned to the cross-linked structure.

Friction and damage of coatings formed by sputtering polytetrafluoroethylene and polyimide

Abstract To investigate the tribological performance of coating films formed by sputtering, polytetrafluoroethylene (PTFE) and polymide (PI) films were prepared on glass substrates. A sapphire ball 5 mm in diameter was slid on the films at a slow speed. The friction coefficients of these films did not depend on the load and film thickness. When the sliding was repeated on the same track, the friction of PTFE films increased as the number of passes increased. A large fluctuation in the friction was observed as the film wore away from the track. With PI films the friction coefficient was almost constant during the experiment. Using a pin-on-disk apparatus, the life of the films was estimated as the number of passes when the friction coefficient exceeded 0.5. Although almost all films were worn away from the track in relatively small passes, thin films left on the track were effective in suppressing the friction increase. PI film exhibited a much longer life than PTFE, although PI film exhibited a brittle fracture in contrast to PTFE film. Heat treating the films effectively increased the PTFE film life but decreased the PI film life.

Single crystalline In?Ga?Zn oxide films grown from c-axis aligned crystalline materials and their transistor characteristics

In this study, we analyzed the crystallinity of c-axis aligned crystalline In?Ga?Zn oxide (CAAC-IGZO) and single crystalline (sc) IGZO films. CAAC-IGZO films were formed on (111)-oriented yttria-stabilized-zirconia substrates by magnetron sputtering using a target. Sc-IGZO films were obtained by annealing CAAC-IGZO films at 1200 ?C. The proportion of Zn in the composition changed during growth of the films, and as a result, sc-InGaO3(ZnO)3 films were obtained. By using CAAC-IGZO films as the starting material, sc-IGZO films were formed even without a ZnO layer. This is presumably because the CAAC-IGZO film originally exhibits c-axis orientation. In addition, the characteristics of transistors fabricated using sc-IGZO and CAAC-IGZO films were compared, and no significant difference in current drivability, i.e., field-effect mobility, was observed between the different transistors. In this sense, CAAC-IGZO films that require no high temperature annealing are favorable for industrialization.

Effect of the degree of crystallinity on the friction and wear of poly(ethylene terephthalate) under water lubrication

Abstract By means of a pin-on-disk type of wear-testing apparatus, coefficients of friction and wear depths of various poly(ethylene terephthalate) (PET) specimens with different degrees of crystallinity were measured at sliding speeds of 0.01 and 0.1 m s −1 under a constant load of 10 N with water lubrication. The coefficients of friction with lubrication were lower than those for unlubricated conditions and there was little dependence on the degree of crystallinity. However, the wear rates with lubrication were higher than those obtained under dry conditions and decreased with increasing degree of crystallinity, in contrast with the unlubricated wear rates. These results are discussed on the basis of the plasticization of worn polymer surfaces by water. The worn surfaces and frictional tracks were observed by optical and electron microscopy. The frictional tracks for low crystallinity PET were smooth with many fine scratches and characteristic of transfer wear. For high crystallinity, frictional tracks were somewhat different from those for low crystallinity PET.

Investigation of transfer phenomenon by X-ray photoelectron spectroscopy and tribological properties of polymers sliding against polymers

Abstract Tribological properties of polymeric materials were investigated with various polymer-polymer combinations by means of a pin-on-disk wear testing apparatus. The specific wear rate was related to the cohesive energy density of the polymeric materials, but hat of a given polymer slider was dependent on the mated polymeric materials, and a high wear rate was observed in the sliding against a polymer counterface with higher cohesive energy than that of the slider. By means of X-ray photoelectron spectroscopy it was confirmed that the polymer transfer did occur on the mated polymer, and the degree of covering of the track with transfer films could be estimated. The covering ratio with transfer films was dependent on the polymer-polymer combinations. Poly(tetrafluoroethylene) (PTFE) transfer film on various polymers was very effective in reducing friction irrespective of the covering with the transfer films. With the other polymers, high density poly(ethylene) (HDPE), poly(propylene) (PP), and polyacetal (PAc), the transfer film was less effective in reducing friction than PTFE transfers and friction in the steady state dependent on the polymer-polymer combinations.

High Speed Slurry Flow Finishing of the Inner Wall of a Stainless Steel Pipe

Recently, a high speed slurry flow finishing method has been developed for capillary with very fine holes of less than 1 mm inner diameter in our laboratory. In the present work, this finishing method has been tested to finish the inner walls of pipes. The hole diameter is only several millimeters larger than that of the capillaries. In the experiment, a stainless steel mandrel is inserted into the pipe. Such a setup makes it possible for the slurry to flow at high flow rates through the narrow clearance between the inner wall of the pipe and the mandrel under a relatively low slurry injection pressure. It is found that the surface roughness of the inner wall decreases with an increasing number of slurry passes, which proves that by such a modification of the setup, the inner wall of the pipe having a relatively large hole can be finished. The raising of the flow pressure exhibits a rapid decrease in surface roughness in the early stage and a low roughness level. Introduction There are many engineering parts having holes, such as capillaries, pipes, ferrule and so on. In the case of fine holes, it is difficult to finish the inner wall of the hole by ordinary polishing method. In our previous reports [1,2], a new polishing method for inner wall of a fine hole, in which polishing is performed by the high speed slurry flowing through the hole has been developed. In the present study, the high speed slurry flow finishing method is applied to the finishing of the inner wall of pipes having a hole in relatively large diameter. Experimental Tests Polishing apparatus. An schematic view of a slurry flow finishing machine is shown in Fig.1. It has a symmetrical structure composed of an air compressor, a set of plungers, cartridges A and cartridges B. The cartridges A and B are filled with ion exchanged distilled water, where abrasive grains have settled in advance on the bottom of one of the cartridges A. In the present work, because hole diameter is 4.35 mm, that is about ten times larger than that of capillary, slurry injection pressure should be raised to get the high flow rate of the slurry. Raising the slurry injection pressure demands the reconstruction of the apparatus, that is, reinforcing the flow line and the sealing of the connecting parts. In avoiding such a substantial reconstruction, a device was made in setting the pipe on the machine. A pipe is installed into a work holder with fixing ferrules as shown in Fig.1. In addition, a stainless steel mandrel whose diameter and length are 4mm and 200mm respectively, is inserted into the pipe and their ends were fixed with the support tools. Such a setup makes it possible that slurry flows at high flow rate through the narrow clearance between the inner wall of the pipe and the mandrel without raising the slurry injection pressure. Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 345-348 doi:10.4028/www.scientific.net/KEM.238-239.345

Development of high speed slurry flow finishing of the inner wall of stainless steel capillary: Polishing and gas flow characteristics of various size of capillaries

Abstract A new finishing method for inner wall of capillaries has been developed, in which the polishing is performed by letting the slurry flow through the capillary at high speed. With the increasing number of slurry passes, the surface roughness of as-received capillaries decreases rapidly in the early stage of the low number of slurry passes, and then tends to saturate to a certain level depending on the diameter of the capillaries. It is also found that the decreasing surface roughness of the inner wall results in the increasing conductance of gas flow through the capillary. Accounting for the effect of the capillary diameter D on the differential pressure which is measured in nitrogen gas flow through the capillary at a constant flow rate, an empirical equation is found between the differential pressure P and the surface roughness Ra, logP · D4 = 0.362 + logRa1/6.

Application of high speed slurry flow finishing method for finishing of inner wall of fine hole die: Effects of the hardness of die material on the polishing characteristics

In order to warrant the quality of drawn metal wires, the inner wall of the hole die which has been used in the drawing of metal wire, has been usually finished by hand work for a long time using a bar daubed the kneaded paste containing diamond powder. High speed slurry flow finishing method which has been recently developed for the finishing of inner wall of capillary has been applied to the finishing of the hole die. It is found that the surface roughness of inner wall of the hole decreases with the increasing number of slurry flow pass in a relatively short finishing time, and that surface roughness reduction rate depends on the hardness of die materials. Experiments show that the bell mouth shape is spontaneously formed in the high speed slurry flow finishing.

Development of polishing pad with self generating porosity

The pad with self generating porosity has newly been developed, which is made of the petroleum pitch and the salt grains. Polishing of a silicon wafer is conducted using a new pad which is immersed into the slurry of the ultra-dispersed super fine diamonds. It is found that the surface roughness of silicon wafer decreases drastically with the polishing time, in which the slurry of polycrystalline diamonds yields a rapid decrease of surface roughness rather than that of singlecrystalline diamonds. Experiments show that the developed pad has an excellent performance for polishing of the silicon wafer rather than the conventional vesicant polyurethane pad.

Finishing of Tiny Nozzles by a Gyration Flow Finishing Method

A gyration flow finishing method has been recently developed, in which polishing is performed by gyrating a polishing fluid through a tiny nozzle. In the polishing method, the polishing fluid is a mixture of suspended powder of peach seeds and grains fed into olive oil. Adding the peach seeds to the slurry, the surface texture of the inner wall of the tiny nozzle drilled by electric discharge machining is eliminated in a short time. The present study focuses on the effect of the polishing fluid supplied from the back of the workpiece. It is found that sucking the polishing fluid out of the back of the workpiece is very effective for deburring and chamfering the tiny nozzles. Introduction Tiny nozzles are progressively used in industrial applications such as a fuel injection nozzle of an engine, spinneret, water jet cleaner nozzle, and so on. It is necessary that the inner wall is very smooth on the tiny nozzles used for fluid exhaust nozzles and the edge in a fluid inflow side is chamfered. The smooth inner wall of the nozzle and chamfered nozzle cause that the fluid flow resistance is reduced. For example, in a case of the water jet cleaner nozzle as shown in Fig. 1, the water flows from the upper in the hole which is closed unilaterally and it is jetted from the injection bore which is perpendicular to the hole. The inner texture and edge profile of the bore influence the water jet power. Polishing the inner nozzle and chamfering the back of the nozzle are very difficult by ordinary finishing methods. A new polishing method, called gyration flow finishing method, has been developed, in which the polishing is performed by gyrating the polishing fluid in a tiny nozzle [1]. This paper is intended to report the results of deburring and chamfering the tiny nozzle in the back of workpiece by the gyration flow finishing method. Water injection bore nozzzle (a) Aspect of jetting water Fig.1 Water jet cleaner nozzzle (b) Schematic view of water jet nozzle Key Engineering Materials Online: 2003-04-15 ISSN: 1662-9795, Vols. 238-239, pp 341-344 doi:10.4028/www.scientific.net/KEM.238-239.341