The properties of the film obtained from nickel electroplating bath called a “Nickel citrate bath” using citric acid in place of boric acid were investigated. A Nickel citrate bath is composed of 1.07M nickel sulfate, 0.19M nickel chloride and 0.08M citric acid. The results were compared with those obtained from a Watts bath under the same conditions. The film obtained from a Nickel citrate bath was widely different from that of a Watts bath in surface morphology, hardness, microstructure of cross section, and X-ray diffraction pattern. The film obtained from a Nickel citrate bath is harder than that of a Watts bath. The microstructure and orientation of deposit obtained from a Nickel citrate bath exhibited a near random orientation. This is attributed to the finer-grained deposit obtained from a Nickel citrate bath. As a reason, nickel-citrate complexes in a Nickel citrate bath and a complex formed between boric acid and nickel ion in a Watts bath are adsorbed in the same way on the cathode, resulting in the inhibition of the hydrogen evolution reaction. But it is thought to be due to the adsorptive interaction of the former being stronger in comparison with the latter.
The kinetics of desorption of bovine serum albumin (BSA) from ozone-modified alumina (Al2O3) particles during caustic alkali cleaning was studied. Al2O3 particles were treated with gaseous ozone generated from pure oxygen at concentrations of 0.05 to 0.2 vol%. As a result of ozone treatment, the absolute values of the surface charge density of Al2O3 particles decreased, with slight shifts in the apparent points of zero charge to the points corresponding to more acidic pH values, and the amount of BSA adsorbed on Al2O3 also decreased. The desorption curve of BSA, which was obtained by plotting the logarithm of the amount of residual BSA versus cleaning time, could be analyzed by the integrated desorption kinetic model which describes two simultaneous first-order reactions. The desorption curves of BSA from non-ozone-treated and ozone-treated particles could apparently be reduced to the sum of two independent first-order reactions occurring simultaneously at different rates, suggesting that a faster-desorbing and slower-desorbing BSA species were present on Al2O3 surfaces. It was found that the effect of ozone modification of Al2O3 surfaces was reflected both by an increase in the desorption rate constant, by one order of magnitude, of a slower-desorbing BSA species and by a decrease in its relative abundance on Al2O3 surfaces.
Microstructures of Pt/Ti thin-films on SiO2/Al2O3 substrates and their relationship to the temperature coefficient of resistance (TCR) were investigated by means of X-ray diffraction analysis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and measurement of electrical resistance. We prepared four different specimens: one as-sputtered and three annealed in vacuum, argon gas and air, respectively. The TCRs were determined to be the largest for the air-annealed specimen and decrease in order of the as-sputtered, the argon-annealed and the vacuum-annealed ones. It is observed that, in the as-sputtered specimen, the Pt film with the preferred (111) orientation deposits on the ultra-thin Ti film with the (00·1) orientation. In the annealed specimens, Ti partly migrates into the Pt film and forms TiO2 precipitates with the rutile-type structure at the Pt/SiO2 interface and in the Pt film. The TiO2 precipitates in the Pt film are relatively small in size, and the amount is observed to be the largest in the air-annealed specimen and decreases in order of the argon-annealed and the vacuum-annealed ones. It is considered that the remaining Ti atoms construct Pt-Ti solid solution in the Pt film, and thereby decrease the TCR from that of the pure Pt film. From these observations, the formation of a large amount of TiO2 precipitates in the air-annealed specimen results in a substantial decrease of Pt-Ti solid solution, and thereby gives rise to a higher value of TCR. It is clarified from the present investigation that oxgen in air play an important role in the improvement of the TCR value by forming a sufficient amount of TiO2 precipitates.
Friction and Wear properties of electroless Ni-P-SiC/PTFE multilayer deposits prepared by double bath method were evaluated by using a horizontal reciprocating friction and wear test apparatus. The multilayer deposits, consisting of SiC and PTFE particles, were found to exhibit excellent self-lubricating and wear characteristics under dry condition.