Applications of wear-resistant thick films formed by physical vapor deposition processes

Several physical vapor deposition processes are being developed in Japan to obtain hard refractory carbide and nitride thick films. A good example is the process for producing TiC and/or TiN by (1) reactive evaporation, (2) reactive r.f. ion plating, (3) reactive sputtering, (4) activated reactive evaporation with a probe electrode and a grounded substrate or (5) activated reactive evaporation with a positive-biased or a.c. modulated substrate (low pressure plasma deposition, d.c. or a.c.). Thick films of chromium, chromium carbide and chromium nitride deposited on steel sheets by (6) a hollow cathode discharge process are being investigated for wear applications.This paper describes the examination of such films formed by processes (4)–(6). Wear resistance is correlated to microhardness, X-ray diffraction diagrams, scanning electron microscopy observations and scratch test results.TiC-coated WC-Co throw-away tool tips, for example, prepared in suitable deposition conditions show marked improvements: $\text{1}\text{20}$ to $\text{1}\text{30}$ on crater depth and $\text{1}\text{4}$ to $\text{1}\text{5}$ on flank wear compared with uncoated tips after 15 min of lathe machining a Ni-Cr-Mo steel SNCM-8 rod at a feed rate of 0.4 mm rev^-1, with a depth of cut of 0.5 mm and at a machining speed of 234-158 m min^-1. The hardness, color and crystal structure are reported for TiN-coated sheets.The features of chromium together with its carbide and nitride films deposited by a hollow cathode discharge process for wear applications are also described.     

Theoretical study on the nature of the hydrogen bonds in an α-helical polymer and its model systems

The semi-empirical CNDO/2 SCF (self-consistent field) MO (molecular orbital) method using the tight-binding approximation for polymers was applied to polyglycine. The CNDO/2 calculations were also performed on model systems of this polymer. From the calculated results, the characteristics of the hydrogen bond in the α-helix were derived by comparison with those in the model systems. It was found that the hydrogen bond in the α-helix is very stable against proton transfer whereas the hydrogen bond in the model system is not so stable; this characteristic difference between the two systems is due to the coupling of two π-electron systems through hydrogen bonding in the α-helix.     

Neural network techniques applied to predict flammability limits of organic compounds

The application of the neural networks to correlate lower and upper flammability limits with chemical structures or basic physical properties for 150 organic compounds of diverse structures and functionalities was investigated. The prediction results based on a three-layer neural network with a back-propagation algorithm were compared with those obtained by multiple regression analysis. The comparison showed showed that the neural networks gave better versatility (range of applicability) and reliability. The predictive ability of the methods developed were tested for a new set of 50 compounds not included in the training data set and good agreement with observed lower and upper flammability limits was confirmed. The required information for the calculation were six easily available properties: standard enthalpy of combustion, molecular weight, critical temperature, critical pressure, oxygen balance, and diffusion coefficient in air. By using these calculable properties from the molecular structure, the method could be used to predict flammability limits of new compounds containing C, H, O, N, S, Cl, F and Br atoms.     

Strategic planning for CIM to enhance the competitive ability

A method of developing strategic CIM is described. Relationship between CIM and firm's competitive power is clarified, and a fundamental planning procedure for CIM is developed for enhancing the competitiveness. In the procedure, the system configuration of CIM is analyzed using 0–1 goal programming techniques. A numerical example is also demonstrated to show the effectiveness of the procedure.     

Immobilization of enzymes by radiation-induced polymerization of glass-forming monomers: 2. Effects of cooling rate and solvent on porosity and activity of immobilized enzymes

The effect of cooling rate of a monomeric system on the porosity and activity of an immobilized enzyme prepared by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperatures has been studied. Slow cooling gave the same effect on porosity of the polymer as decreasing the monomer concentration. A glass-forming solvent such as diethylene glycol was added to water to study the effect of the supercooling tendency of the solvent. Addition of diethylene glycol decreased porosity and also enzymic activity. Water was replaced by the miscible solvent p-dioxane and the immiscible solvent n-decane in order to clarify the effect of solvent. p-Dioxane had a similar effect to water on the relation between the monomer concentration, porosity and activity. On the other hand, polymer prepared from the system containing n-decane showed different immobilization properties owing to the presence of independent pores in the matrix.     

Mechanical properties of thermoplastic polyurethanes containing aliphatic polycarbonate soft segments with different chemical structures

Mechanical properties of linear thermoplastic polyurethanes (TPUs) prepared by polyaddition reaction using a polycarbonate diol (PCD), 1,4‐butanediol (a chain extender) and 4,4'‐diphenylmethane diissocyanate were investigated. Chemical composition among these three components was kept constant. Primary attention was directed to how chain length of an alkylene group in the PCD affected the mechanical properties of the resultant TPU. To clarify this effect, the PCDs were synthesized using 1,6‐hexanediol and 1,12‐dodecanediol. In addition, the TPUs from copolycarbonate diols containing these two components were also produced, and then extensively examined and further compared to the ones from the corresponding blended PCDs. From a practical point of view, weatherability and solubility in a polar solvent were also evaluated.     

Thermal Stability and Acid Resistivity of Glasses Based on ZnO-Al2O3-SiO2

The glass-forming region in the ZnO-Al₂O_3-SiO₂ system was studied, and the acid resistivity of the glass stabilized by PbO addition was measured. Glass containing more than 50 at.% SiO2 had a markedly increased acid resistivity. At about 50 at.% SiO₂, the crystallization of the glass caused its resistivity to decrease.     

Structural characterization of 1,2-polybutadiene by 13C n.m.r. spectroscopy: 1. Signal assignment in hydrogenated polybutadienes

The configurational sequences of 1,2-unit in a series of hydrogenated syndiotactic 1,2-polybutadienes were investigated in relation to the sequence distribution of 1,2- and 1,4-units. The signals at 10.20–10.94 ppm were assigned to the methyl carbons in the isolated 1,2-unit, the 1,2-1,2 dyad sequence flanked by 1,4-unit, and the 1,2-1,2-1,2 triad sequence, in order of increasing magnetic field. The splittings due to the configurational sequences were observed in the signals, reflecting the dyad and triad sequences of the 1,2-unit, which were assigned by considering the relative intensity of the signals and also the chemical shifts of model polymers.