Changes in chemical bonds in porous silicon (PS) during 192 days of aging were studied using transmission Fourier transform infrared spectroscopy in combination with photoluminescence (PL) measurement. PS exhibits PL peaking at about 650nm, but the PL peak position does not change much. PL intensity increases with aging time, and the intensity of infrared absorption bands other than CHx(x=1-3) changes. Si-H and SiH2 bands decrease in intensity with aging time. The O3Si-H band intensity increases, then levels off. C=O and O-H bands increase in intensity with aging time, but not in correlation with PL intensity. The Si-O band increases with aging time and is closely correlated with PL intensity. These results suggest that some oxygenrelated effect participates in PS luminescence.
Iridium-oxide-coated titanium electrodes used for oxygen and chlorine evolution are usually prepared using a complicated thermal decomposition process. To simplify preparation iridium was plated on to a titanium substrate and the plated iridium oxidized by electrolysis or heating. The electrode's electrochemical behavior after electrolysis or heating to oxidize iridium was studied in H2SO4 and NaCl solutions. When the electrode was electrolyzed in NaCl solution for 500 cycles using a rectangular wave of ±75mA/cm2, the overpotential for oxygen or chlorine evolution was marked reduced, due perhaps to two reasons for this. One involves the formation of iridium hydroxide by electrolysis, which indicates catalytic activity. The other involves cracks formed on the electrode surface by electrolysis, which increases the electrode surface and decreases the real current density and overpotential.
We studied the effects of electrodeposition conditions on Sn-Ag alloy composition and current efficiency in Pb-free solder plating employing a new pyrophosphate-iodide bath. We also investigated the morphology, phase structure, thermal characteristics and solderability of electroplated Sn-Ag alloy films. Ag content in deposits decreased with increasing current density during both agitation and nonagitation, Sn-Ag electroplated films containing between 2.0 and 20.0 at% silver consisted of β-Sn and the ε phases, β-Sn phase orientation in electrodeposited Sn-Ag alloy films became random with increasing ε phase content. The melting point, i.e., the temperature at which melting first occurred, of electroplated Sn-Ag alloy films was 221°C. Wetting time of electroplated Sn-Ag alloy films became minimum at a near Sn-Ag eutectic composition and was not affected by thickness from 0.5 to 10μm.
Pd-Sn alloy plating was studied in agitated baths containing 1.0mol/LK4P2O7, 0.03mol/L Pd(NH3)2Cl2, 0.5mol/L K2SnO3, and 0.7mol/L KNO2 with and without 0.15mol/L diethylenetriaminepentaacetic acid (DTPA). Addition of DTPA as reflected in current density-potential curves suggests that Pd2+ forms a stable Pd(DTPA)3- complex, and Sn4+ coexists in the bath with DTPA as pyrophosphate complexes. Current efficiency and Sn content in deposits increases with pH and current density. Deposit morphology revealed a rough grain when pH was ≥11.0 and current density was >3.0A/dm2. A dense, smooth Pd-19mass%Sn alloy deposit forming a solid solution was obtained at 2.0A/dm2 from a bath containing DTPA.
I2 effects on silver deposition current efficiency were investigated using a potassium iodide bath. Cathodic polarization curves in the I2 bath and Pt electrode rest potential in the aged KI solution were measured to clarify the I2 reduction mechanism. The following results were obtained: (1) In the lower pH range, I2 concentration in the bath increases with time in the presense of air according to equation (i): 4H++4I-+O2_??_2I2+2H2O……(i) (2) Silver deposition current efficiency decreased as I2 increased in the bath. This suggests that I3- is reduced in agreement with equation (ii) as silver is deposited: I3-+2e-→3I-……(ii)
We studied platinum-zinc alloy plating by adding zinc to an alkaline platinum bath that used hexahydroxoplatinate. Hexachloroplatinate solution and potassium hydroxide were mixed to prepare a potassium hexahydroxoplatinate solution. Zinc oxide was dissolved into the potassium hydroxide solution. These solutions were then used to compose a platinum-zinc alloy plating bath. We then analyzed deposition efficiency, alloy composition, crystal structure, and the appearance of the precipitated deposit. Deposition efficiency increased as zinc was added. When up to 0.7g/L of zinc had been added, the deposit contained 90wt% of platinum and 10wt% of zinc. The ratio of zinc to platinum in the deposit was higher than that in the plating solution. A mirror-bright platinum-zinc alloy of 3μm was plated on copper panel and the substrate was dissolved in nitric acid to fabricate a foil. The foil, however, was destroyed by bending. Zinc codeposited at 5wt% yielded a mirror-bright deposit, but the ductility of the deposit was poor.