Chemical bath deposition ͑CBD͒ is an advantageous thin film deposition technique for depositing compound semiconductors at low temperature. In this paper, nickel oxide thin films were prepared by CBD from an aqueous solution composed of nickel sulfate, potassium persulfate, and ammonia at room temperature. Thin film growth mechanisms were studied by using quartz crystal microbalance, UV-vis absorption, and photon correlation spectroscopy. The data indicate that film growth is strongly dependent upon mixing conditions and competes with homogeneous particle formation. No film formation was observed without the addition of persulfate. A growth mechanism based on the combination of particle sticking and molecule level heterogeneous growth is proposed. The as-deposited film contained ␣-Ni͑OH͒ 2 and 4Ni͑OH͒ 2 ·NiOOH·xH 2 O and was converted to nickel oxide ͑NiO͒ by thermal annealing according to thermogravimetric, X-ray diffraction and X-ray photoelectron spectroscopy measurements.NiO is a transition metal oxide that has several potential applications, such as smart window, 1 solar thermal absorber, 2 electrodes for batteries, 3 and photoelectrocatalysts. NiO thin films have been prepared by various techniques, including thermal evaporation, 4 sputtering, 5 spray pyrolysis, 6 sol-gel, 7 chemical vapor deposition, 8 electrochemical deposition, 9 and chemical solution deposition. 10 Chemical solution deposition, also called chemical bath deposition ͑CBD͒, is an advantageous technique because of its low cost and low-temperature operating conditions. There are a few reports on the deposition of NiO thin films by chemical bath deposition. Pramanik and Bhattacharya 11 deposited NiO thin films using nickel sulfate, ammonia, and persulfate aqueous solution at room temperature. The obtained films were polycrystalline NiO with a black appearance. Varkey and Fort 12 deposited nickel oxide thin films using nickel sulfate and ammonia solution over the temperature range 60-80°C. Pejova et al. 13 used a bath containing nickel nitrate and urea at a temperature of 100°C. The as-deposited films were Ni͑OH͒ 2 ·H 2 O with a green appearance and were transformed into nickel oxide films after thermal annealing.In this study, the growth mechanism of NiO thin film by the chemical bath deposition following Pramanik's chemistry was studied in real time by using quartz crystal microbalance, UV-vis absorption, and photon correlation spectroscopy ͑PCS͒. The resulting thin films and particles were characterized by scanning electron microscopy ͑SEM͒, X-ray diffraction ͑XRD͒, UV-vis absorption, X-ray photoelectron spectroscopy ͑XPS͒, and thermogravimetric analysis ͑TGA͒. ExperimentalSolution for CBD was prepared by mixing 40 mL of 1 M nickel sulfate ͑Alfa Aesar͒, 30 mL of 0.25 M potassium persulfate ͑Ald-rich͒, 10 mL of aqueous ammonia ͑28-30% NH 3 , EM Science͒, and 20 mL of deionized water in a 250 mL Pyrex beaker at room temperature ͑recipe A͒. The mixing was carried out by a 5 cm magnetic stir bar with 200 rpm. Substrates used for depositions inc...

Modification of conventional zinc titanate (ZT) sorbents to increase their reactivity and stability during multiple cycles of sulfidation/regeneration at high and middle temperatures was pursued by addition of Co 3 O 4 . Moreover, evaluation of the modified zinc titanates (ZTC) was conducted using several instruments such as an X-ray diffractometer, Fourier transform infrared spectrometer, scanning electron microscope, and so on. The ZTC sorbents prepared by the physical mixing of the ZT sorbent with 25 wt % of Co 3 O 4 showed an excellent sulfur-removing capacity and no deactivation even after multiple cycles of sulfidation/regeneration in both high-and middle-temperature conditions. The cobalt permeated the Zn 2 TiO 4 lattice, leading to a new spinel phase, ZnCoTiO 4 . It worked not only as an active site during the sulfidation process but also as a support to prevent zinc migration to the outside of the sorbents and to minimize volume expansion/contraction. Under middle-temperature conditions, the phase separation of the ZTC sorbent including a cobalt oxide intermediate in addition to the ZnCoTiO 4 spinel structure was observed. Also, the cobalt additive increased the regeneration capacity of Zn-based sorbents because it played an important role as the catalyst for oxidation.

Rate coefficients for the reaction CH3 + O2 = CH3O + O were measured behind reflected shock waves in a series of lean CH4−O2−Ar mixtures using hydroxyl and methyl radical diagnostics. The rate coefficients are well represented by an Arrhenius expression given as k = (1.6 ) × 1013 exp(−15813 ± 587 K/T) cm3 mol-1 s-1. This expression, which is valid in the temperature range 1575−1822 K, supports the downward trend in the rate coefficients that has been reported in recent determinations. All measurements to date, including the present study, have been to some extent affected by secondary reactions. The complications due to secondary reactions, choice of thermochemical data, and shock−boundary layer interactions that affect the determination of the rate coefficients are examined.