We studied thin Ni-Cr films deposited by Tripole Magnetron Sputtering (TMS) developed to provide enable composition control of deposited films. Ni-Cr films deposited at a substrate temperature of 200°C showed that their resistivity is influenced by their microstructure, reflected by sputtering conditions, whereas their composition is predominant in their temperature coefficient of resistivity.
We developed cemented carbide cutting tools coated with a layer of TiN, moderate temperature-Ti (C, N), bonding, and α-Al2O3 by chemical vapor deposition (CVD). Tool life is about twice that of ordinary TiN-Ti (C, N) -TiC-κ-Al2O3 coating in cutting tests on a cast metal FC 250 due to improved α-Al2O3 layer adherence. CVD coatings of cutting tools were studied using X-ray diffraction, SEM, EPMA, TEM, and TEM-EDX, with the following results: (1) Bonding layer grains consisted of Ti, C, N, and O, or of Ti, C, and O. (2) The crystal structure of the bonding layer phase was face-centered cubic with a lattice parameter of 0.431nm. (3) Bonding layer grains grew epitaxially on moderate temperature-Ti (C, N) layer grains. (4) No disorder of lattice fringes in interfaces between bonding layer grains and α-Al2O3 layer grains was seen. (3) and (4) are considered to be the reason for improved tool life and α-Al2O3 layer adherence.
The temperature dependence of metal nitride thermal stress was measured up to 500°C using a high-temperature thin film stress system (Tencor F2400), and primary results for TiN, CrN, Cr2N, and AlTiN were presented. A series of metal nitrides-TiN, CrN, Cr2N and AlTiN -were deposited by cathodic arc-ion plating onto Ti-6Al-4V and SUS304 substrate. The temperature dependence of the thermal expansion coefficient and the bi-axial modulus of these coatings were calculated from the temperature-stress relationship for coating deposited onto substrates having different thermal expansion coefficients. Results showed that thermal expansion coefficients of these coatings were monotonically increased as temperature increased up to about 500°C. Of these, Cr2N and AlTiN are largest at about 9.5×10-6/°C at room temperature. The biaxial modulus showed slight temperature dependence for all coatings, but different for each coating. The room-temperature biaxial moduluses of TiN, CrN, Cr2N, and AlTiN are 420, 320, 290 and 500GPa. Using there results, the stress-temperature relationship of TiN, CrN, and Cr2N which were deposited onto SKD61 and Ti-6Al-4V substrate were calculated.
Reaction-bonded silicon carbide (Si-SiC) is potentially promising as a ceramic for use in large-scale structural components in very aggressive corrosion environments. Protective silica scale consisting of amorphous and crystalline layers, se-called bilayer scale, formes on Si-SiC in thermal oxide environments. Thermal cycling may induce severe cracking in crystalline but not amorphous layers due to thermal expansion mismatch between the two layers and the Si-SiC substrate. The amorphous layer is desirable as stable protective scale. Si-SiC samples with silica bilayer scale were heat-treated to study scale thermomechanical stability, then analyzed using SEM and EDX. The mechanical properties on scale Young's modulus and hardness, were measured using depth-sensing microindentation technique. The 1300°C heat-treatment up to 50hr did not affect the bilayer silica scale structure, i.e., no transformation occurred between crystalline and amorphous layers. The Young's modulus and hardness of scale increased with heat-treatment. Change is related to impurity content of Al and K in scale, which was decreased by heat treatment and corresponds to the dependence of silica bulk mechanical properties in the chemical composition.
Several amines used as complexing agents for electroless palladium-nickel plating baths do not ensure bath stability and only a fixed ratio of a 9: 1 (palladium: nickel) alloy is obtained in such baths. We studied bath composition, focusing on complexing agent selection and conditions for improving bath stability and changing the alloy ratio. Bath stability is greatly improved by the addition of carboxylic acid as a secondary complexing agent beside the addition of amines. The alloy ratio can be changed from 9: 1 to 7: 3 (Pd/Ni ratio) by changing the carboxylic acid concentration. The bath construction sequence greatly influences bath stability. Palladium and nickel ions are preliminarily complexed with ethylene diamine and carboxylic acid, then each solution is mixed to construct the bath, yielding a stable electroless palladium-nickel plating bath.
We studied silver-hydantoin noncyanide silver plating solution to determine the effect of potassium chloride, potassium sulfite, and potassium thiosulfate on deposit appearance using SEM imaging, brightness, and X-ray diffraction. We also studied the effects of hydantoin, 1-methylhydantoin, and 5, 5-dimethylhydantoin on limiting current density using a potential-current curve. Adding potassium chloride yielded a white, homogenized rock-like appearance. Potassium sulfite and potassium thiosulfate yielded a semibright apearance. Hydantoin gave higher limiting current density than 5, 5-dimethylhydantoin when used as a silver complex. If the plating solution used hydantoin alone, the solution precipitated easily. Mixing 1-methylhydantoin with hydantoin prevented precipitation. Soluble silver anode can also be applied to this bath.
In response to growing needs for improved corrosion resistance in the steel parts of automobiles and aircraft, electroplating of zinc-nickel alloys is being applied in place of pure zinc plating Experiments were undertaken to determine the dependence of zinc-nickel alloy plating electrodeposition and surface morphology from sulfate solutions on surfactants Cathode current density, surfactant types, and amounts in the baths were found to strongly influence deposit composition, surface morphology, and crystal structure Despite identical plating conditions, dodecyltrimethylammonium chloride (DTAC) addition from 5×10-5 to 1×10-4mol/L decreases the deposit's nickel content, but polyoxyethylenelaurylamine (POELA) addition at 5×10-3mL/L increases the deposit's nickel content. Anomalous codeposition is greatly accelerated by adding DTAC, but adding POELA helps ameliorate anomalous codeposition
To codeposit metal with particles that are hydrophobic, such as PTFE, a surfactant is required to disperse particles in the bath. Excess surfactant may, however, cause trouble during plating such as hindering metal electrodeposition or inhibiting particle codeposition. We studied the relationship between pretreatment of PTFE and the morphology of the deposit from a CuSO4 bath containing PTFE particles. We clarified that the codeposition process is improved by modifying the PTFE surface using the surfactant, then rinsing off excess surfactant. Combining nonionic and cationic surfactants yields a good morphology and appearance.
To obtain fundamental findings on providing an inorganic substrate with hydrophobic properties using a silane coupling agent by the dry method, which is often limited by an uneven product, a fundamental study was performed using TiO2 and a vinyltriethoxysilane (VTES) system. The hydrophobicity afforded by VTES treatment were determined as a function of parameters such as the VTES/EtOH/Aq.CH3COOH ratio, pH of aqueous phase, duration of pretreatment with VTES solution, H2O/VTES ratio and heat treatment temperature of VTES treated product. It was found that the molar ratio of H2O/VTES, pH of aqueous phase, pretreatment duration of VTES solution, and heat treatment temperature are important parameter to determine coupling effect. The principal findings obtained are as follows. 1. Optimum treatment of TiO2 can be achieved using VTES solution containing a stoichiometric amount of H2O at aqueous phase pH 3.3 after storing for more than 36hrs. 2. The pH value in the aqueous phase is intimately related to hydrolysis and condensation reactions of VTES, and thus to the hydrophobic properties of TiO2 treated with VTES solution. 3. Heat treatment of TiO2 powders treated with VTES is essential to provide a hydrophobic property to TiO2. However an excessively high temperature causes evaporation of hydrolysis and condensation products of VTES, resulting in poor hydrophobicity. 4. The required amount of VTES can be calculated by applying a closed packing model of VTES to the TiO2 substrate.
The photoelectrochemical behavior of sol-gel formed TiO2 film was studied, to improve photocatalysis. TiO2 film baked at 773K was confirmed to be anatase, showing n-type semiconductivity under illumination. TiO2 photopotential was reduced to -400mV vs. Ag/AgCl under UV illumination; when the lamp turn off, it gradually increased to the initial potential over a day. Above phenomenon was found more effective in TiO2 coated on oxygen ion implanted stainless steel substrate.
ArF eximer-laser-induced chemical vapor deposition (CVD) of coordinated unsaturated species of ironpentacarbonyl on quartz glass was conducted using a supersonic molecular beam. Fabricated thin films turned from black to metallic silver based on the number of laser shots. Ultraviolet absorption spectra from 200 to 350 nm indicated that black thin films were due to induced plasma oscillation in which coordinatied unsaturated ironpentacarbonyl spacies changed to fine metallic particles. For metallic thin films, electron microscopy clarified a meshes structure in which thin films were fabricated proceed through a three-dimensional Volmer-Weber mechanism.
Adhesion strength between flat copper and epoxy resin was studied by forming sulfur codeposited copper films or sulfide films on the flat copper surface, with the following results: 1. Copper films from an electroless coper plating bath with sodium sulfide strongly adhered to epoxy resin. Adhesion strength was particularly improved by adding over 100ppm sodium sulfide tothe plating bath. 2. The formation of sulfide films on the copper surface using sodium sulfide solution also effectively improved adhesion. Triazine dithiole treatment also showed a similar effect.