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Y 2 O 3 :Eu 3+ red phosphors were synthesized by laser irradiation of Eu-doped Y 2 O 3 sintered targets immersed in water. The photoluminescence (PL) of the nanoparticles (NPs) was significantly enhanced by adding hydrogen peroxide to the water. Targets were synthesized using three methods, namely, sol-gel (SG), homogeneous-precipitation (HP), and solid-state reaction (SSR) followed by sintering. The sintered SG target contained 8.6 wt% of hexagonal oxygen-deficient byproduct, while the other targets were composed of pure cubic phase. The amount of hexagonal oxygen-deficient and monoclinic by-products in the nanophosphors increased to 33 wt% and 27 wt% in irradiated SG-and HP-derived targets, respectively. The SSRderived NPs were almost pure cubic phase. Addition of H 2 O 2 to the water minimized the amount of hexagonal oxygen-deficient and monoclinic byproducts (5.7 wt% and 6.4 wt% for SG-and HP-derived NPs respectively). Moreover, the PL of the NPs was enhanced by the formation of a pure cubic phase, and the optimum amount of added H 2 O 2 for maximum luminescence was 5 wt%. J. McKittrick-contributing editor Manuscript No. 33665.

In the present work, effect of CO 2 +H 2 gas mixture inclusion on shrinkage of plasma was numerically investigated on high power Ar inductively coupled thermal plasmas at atmospheric pressure. The gas mixture of CO 2 +H 2 has many reactions in wide temperature range of 300-20000 K which may cause some performance in thermal plasmas. Simulation has been carried out solving a two-dimensional local thermodynamic equilibrium (LTE) code. The active plasma power and input fundamental frequency were fixed at 27 kW and 450 kHz respectively. The main variable parameter was the admixture ratio of secondary gas (CO 2 +H 2 gas mixture) and it has been found that the injection of excess dissociative molecular gases shrink the plasma in radius keeping the center temperature about 10,000 K by investigating the plasma radius having temperature beyond 5,000 K for each of the case. The result also shows that increasing the inclusion (admixture ratio) of CO 2 +H 2 molecular gas raises the plasma peak temperature. The result is also compared with that of Ar-CO 2 and Ar-H 2 thermal plasma and finally a comparative study and conclusions have been made.

Here the authors developed a two-dimensional two-temperature chemical nonequilibrium (2T-NCE) model of Ar-CO 2 -H 2 inductively coupled thermal plasmas (ICTP) around atmospheric pressure (760 torr). Assuming 22 different particles in this model and by solving mass conservation equations for each particle, considering diffusion, convection and net production terms resulting from 198 chemical reactions, chemical non-equilibrium effects were taken into account. Species density of each particle or simply particle composition was also derived from the mass conservation equation of each one taking the non chemical equilibrium effect into account. Transport and thermodynamic properties of Ar-CO 2 -H 2 thermal plasmas were self-consistently calculated using the first order approximation of the Chapman-Enskog method at each iteration point implementing the local particle composition and temperature. Calculations at reduced pressure (500 and 300 torr) were also done to investigate the effect of pressure on non-equilibrium condition. Results obtained by the present model were compared with results from one temperature chemical equilibrium (1T-CE) model, one-temperature chemically non equilibrium (1T-NCE) model and finally with 2T-NCE model of Ar-N 2 -H 2 plasmas. Investigation shows that consideration of non-chemical equilibrium causes the plasma volume radially wider than CE model due to particle diffusion. At low pressure with same input power, presence of diffusion is relatively stronger than at high pressure. Comparison of present reactive model with non-reactive Ar-N 2 -H 2 plasmas shows that maximum temperature reaches higher in reactive C-H-O molecular system than non-reactive plasmas due to extra contribution of reaction heat.