The hydrolysis and condensation of Vinyltriethoxysilane (VTES) in a preliminary treatment solution, consisting of VTES, ethanol, and water acidified with acetic acid was investigated using gel permeation chromatography (GPC). This was done to determine the variation in water content over time to obtain information about the useful treatment of TiO2 with a silane coupling agent. The main results obtained are as follows: 1) VTES sedimented onto TiO2 treated with VTES does not necessarily demonstrate the hydrophobicity of TiO2. 2) An increase in the pH of the aqueous solution results in a delay in the condensation reaction to dimer or higher order polymers. In contrast, an increase in the water content leads to a remarkable acceleration of the hydrolysis and condensation polymerization of VTES. 3) For effective preliminary treatment of TiO2, conditions must be selected, under which the monomer disappears rapidly and polymers of polymerization numbering 2-4 are stable for a long period. 4) The induction period detected from the rate curve of the variation in water content corresponds to the hydrolysis reaction of the ethoxy group and water content variation cannot be determined by the Karl Fischer method. Thus, the average degree of polymerization can be calculated from the equation for the condensation reaction. 5) The M value that indicates the degree of hydrophobicity increases with a slight increase in the degree of polymerization, reaching M=30% at an average degree of polymerization of 1.1 (corresponding to a 0.5mass% decrease in water content). However, it is necessary to select a suitable preliminary treatment solution and stable conditions for an average degree of polymerization of 2-4 must be selected in order to reach M=35%.
To easily characterize the state of real metal surfaces in ambient environments, we have developed an extremely sensitive technique for the surface analysis using photoelectron emission phenomena depending on temperature. We call this method temperature programmed photoelectron emission (TPPE). The emitted electrons were detected by a gas-flow Geiger counter with Q gas. A PE spectrum representing the curve of the PE intensity vs. wavelength was obtained at different temperatures in the temperature-increase and subsequent temperature-decrease process between 25 and 350°C. The number of emitted electrons in a PE spectrum (PE total count) as a function of the measurement temperature was investigated for 17 kinds of rolled metal sheets that were cleaned in acetone. The metals were distinctly classified into five groups A-I (Al, Pt, Pb), A-II (Ag, Cu, Au, Ni), B-III (Ta), B-IV (Pd, W, Ti, Mo), and B-V (Nb, Fe, Zn, Co, Sn). The A groups indicated a temperature dependent PE total count, while the B groups indicated a virtually temperature independent PE total count. With the A groups a greater amount of the adsorbed oxygen that was present on the initial surface was found by XPS to change to oxide oxygen after TPPE measurement, with the exception of Al. This chemical change is suggested to play a substantial role in the temperature dependence of the PE total count. With the B groups oxide oxygen existed predominantly on the initial surface, resulting in little change in the chemical state of the oxygen. It is suggested that the ability of the metals in gas chemisorption is closely related to the TPPE behavior.
Bonding of nickel alloys (Hastelloy B, Inconel 600 and Monel) was performed by means of the powder-pack method using the bonding powder which contains no SiC. The boride layer was analyzed using X-ray diffraction and EPMA. The high-temperature microhardness and friction and wear characteristics of bonded nickel alloys were investigated. The obtained results are as follows: (1) Thick boride layers could be obtained without flaking in this study. The thickness of the layers was about 65∼75μm under the bonding conditions for 7.2ks at 1173K. (2) The Knoop hardness of bonded Hastelloy B, Inconel 600 and Monel were 1650HK, 1580HK and 600HK, respesctively. The boride layers of nickel alloys mainly consisted of Ni2B. Ni3B and Cu were also detected in the boride layers of Hastelloy B and Monel, respectively. (3) The high-temperature microhardness of Hastelloy B and Inconel 600 were greatly improved by bonding. But bonding was ineffective for the high-temperature microhardness of Monel. (4) The friction coefficients of bonded Hastelloy B and Inconel 600 against SUJ2 and SUS 304 indicated lower values than those of untreated materials, but a reduction in the friction coefficients was not recognized in Monel. This result was considered to be attributable to the precipitation of copper in the boride layer of Monel. (5) The wear resistance of nickel alloys against SUJ2 and SUS 304 was improved by bonding. (6) Bonding was effective for reduction of wear loss of the mating materials of Hastelloy B and Inconel 600, but it was ineffective for those of Monel.
The deterioration behavior of pigmented epoxy (EP-P), clear epoxy (EP-C) and clear polyvinyl chloride (PVC-C) coated steel in an aqueous 3% NaCl solution was investigated by scanning acoustic microscope (SAM). Results of experiments showed that SAM can be used to identify and determine the extent of disbonding due to blisters on any kind of coatings applied on steel. For clear coating film, the characteristics and the nature of blisters on the coating film were substantially observed by the SAM than by visual inspection. As for the analysis of SAM imaging, the disbonded area increased linearly with increasing immersion time in an aqueous 3% NaCl solution. The percentage of disbonded area was found higher on pigmented coating films than on clear coating films. The linear relationship between the percentage of disbonded area by the SAM and the coating film resistance (Rf) by electrochemical impedance spectroscopy (EIS) might or might not be unequivocally shown. The relation was due to a mode of deterioration of coating film, a mode of under-corrosion of coating film, etc.
Conversion coating on zinc plating film using Cr (III) compound as main constituent were investigated. Corrosion resistance of the film were evaluated by salt spray test and measuring polarization resistance, Rp. Surface analysis were made to determine the elements on the film and depth profile by Auger electron spectroscopy (AES). Corrosion resistance of the passive film composed of both Cr (III) and silicate was better than those film consisting of each own component. With addition of phosphate and by post-treatment with dipping in colloidal silica sol solution, the corrosion resistance of the film was improved more. The evaluations of the film by measurement of polarization resistance were almost same results. The results of surface analysis using AES indicated that Cr (III) in the film was increased with addition of silicate, and that the thickness of the film was increased with addition of phosphate. These were thought to be responsible for improving the corrosion resistance of those Cr (III) film composed of silicate and phosphate.
The work functions (WFs) of Al, Zn, Cd, Mo, Fe, Ni and Cu exposed to air were continuously measured in air using a contact potential difference method (CPD). Here, a gold plate was used as a reference material whose WF was measured precisely using an “electron spectroscopy in air” (ESA) method. The WFs of Al, Zn and Cd increased by approximately 0.1eV within 10 minutes after exposing the fresh surface of these metals to air. However, the WFs of Mo, Fe, Ni and Cu remained unchanged even after prolonged exposure to air. This can be explained by the influence of the stress in oxide films, which is induced by lattice misfit between the oxide films and bulk metals. The WFs measured by ESA and CPD were fundamentally the same for all these metals when they were exposed to air for 10 minutes or more.
Reaction of hydrogensulfite ion (HSO3-) by the dissolved oxygen (O2) in aqueous solution was remarkably enhanced under the freezing process, in which hydrogensulfite ion was changed to sulfuric ion (SO42-). When the concentration of hydrogensulfite ion was fixed at 2.0×10-4moldm-3, the time profile of pH value was reduced 6.0 to 4.5 under the freezing process, in which the change of acidity was accelerated to the later stage in freezing.