Study of an argon–hydrogen RF inductive thermal plasma torch used for silicon deposition by optical emission spectroscopy

The hydrogenation of silicon deposited on a substrate for photovoltaic applications has been obtained by a plasma torch. This method shows a great advantage and leads to the improvement of the electronic properties of the material. The hydrogenation of silicon allows the crystallographic defects elimination (dislocations, dangling bonds) which leads to an increase of the diffusion length.In order to understand silicon hydrogenation by RF inductive thermal plasma spraying, a study of the discharge by optical emission spectroscopy (OES) has been undertaken. This study has been compared with the hydrogen content measured by the exodiffusion technique.The detection of highly excited species of atomic and molecular hydrogen proves the specificity of the inductive plasma. Hydrogen emission lines have been used to calculate the electronic density on the plasma axis. Furthermore, the ArI lines were used to calculate the electronic temperature in the plasma. With this information, the deviation from the local thermodynamic equilibrium (LTE) of the plasma has also been estimated.     

H2 production from methane pyrolysis over commercial carbon catalysts: Kinetic and deactivation study

Hydrogen production from catalytic methane decomposition (DeCH₄) is a simple process to produce high purity hydrogen with no formation of carbon oxides (CO or CO₂). However, to completely avoid those emissions, the catalyst must not be regenerated. Therefore, it is necessary to use inexpensive catalysts, which show low deactivation during the process. Use of carbon materials as catalysts fulfils these requirements.     

The effects of bimetallic Co–Ru nanoparticles on Co/RuO2/Al2O3 catalysts for the water gas shift and methanation

The effects of Co on RuO₂/Al₂O₃'s activities for water gas shift (WGS) and methanation were studied. Catalysts were characterized with BET, XRD, SEM/EDS, H₂-TPR and CO-TPR. The effects of various parameters, such as calcination temperature, Ru–Co loading, Ru/Co ratio, inlet CO concentration and H₂O/CO ratio on the activities of catalysts were investigated. There existed Co_I (strongly interact with RuO₂) and Co_II (weakly interact with RuO₂). For Co/RuO₂/Al₂O₃ (Ru/Co = 1, AT = 350), only Co_I existed as bimetallic Co–Ru nanoparticles. This unique structure led this catalyst to achieve the highest CO conversion of 98.6% exceeding WGS's theoretical thermodynamic equilibrium limit due to the co-occurrence of methanation. Co/RuO₂/Al₂O₃ was more favorable to catalyze CO methanation than CO₂ methanation. The apparent activation energies of forward and reverse WGS catalyzed by Co/RuO₂/Al₂O₃ were 37.8 and 74.6 kJ mol⁻¹, respectively. The difference was corresponding well to the enthalpy change (−41.1 kJ mol⁻¹) of WGS.     

Passive solar heating of a non-airconditioned building with movable insulation over the roof pond

This paper presents a simple mathematical model for solar space heating in a non-airconditioned building with movable insulation over the roof pond. The building room considered is of rectangular shape (6 m × 5 m × 4 m) based on the ground. The effects of heat conduction to the ground, heat transfers to furnishings and heat losses due to air ventilation/infiltration have been taken into account in the general heat transfer analysis. The day-to-night change of insulation over the roof pond has been represented by a rectangular step function variation of the heat transfer coefficient at the pond's surface. An increase of 3 to 4°C in the room air temperature is achieved by means of movable insulation over the roof pond on a mild winter's day (17th February, 1982) in New Delhi.     

Printed, flexible electrochromic displays using interdigitated electrodes

We describe herein some of our initial studies in pursuit of a simple, economical method of mass producing electrochromic displays. The approach we have taken is to print the display on polymer film utilizing commercially available conductive inks in an interdigitated electrode structure with a conductive metal oxide powder, dispersed in a polymer binder, as the electrode surface. A range of electrochromic materials suitable for use with an aqueous gel electrolyte have been explored and examples presented.     

The empirical relationship between global radiation and global ultraviolet (0.290–0.385) μm solar radiation components

Measurements of the monthly average daily global and global ultraviolet solar radiation over a period of three years (1985, 1986, 1987) in Kuwait are reported. Over the three years the computed yearly daily means for the above solar radiation components were 5.592 kW h/m² and 0.260 kW h/m². The effect of atmospheric dust on the measured solar radiation components is investigated. Employing the least-square linear regression analysis an estimated empirical function relating global radiation to ultraviolet radiation was proposed for the past three years' measurements.     

Study of the ice sublimation processEtude du processus de sublimation de la glaceUntersuchung des EissublimationsprozessesИccлeдoвaниe пpoцecca cyблимaции льдa

The basic transfer equations for evaporation of a solid body into vacuum are considered. Experimental results on ice sublimation with thermoradiative and conductive heat supply as well as on sublimation in drying processes and continuous sublimation process from a permeable plate are presented. These studies explain the peculiarities of the sublimation mechanism for different energy supplies and under periodic and continuous conditions of the process. With ice sublimation from a porous permeable plate near a surface, a stepwise change in temperature is observed at a distance of several lengths of the mean free path of vapour molecules.     

Mixed convective peristaltic flow of Eyring‐Prandtl fluid with chemical reaction and variable electrical conductivity in a tapered asymmetric channel

The influence of inconstant electrical conductivity and chemical reaction on the peristaltic motion of non‐Newtonian Eyring‐Prandtl fluid inside a tapered asymmetric channel is investigated. The system is concerned by a uniform external magnetic field. The heat and mass transfer are considered. The problem is controlled mathematically by a system of nonlinear partial differential equations which describe the velocity, temperature, and nanoparticle concentration of the fluid. By means of long wavelength and low Reynolds numbers, our system is simplified. It is explained by using the multi‐step differential transform method as a semi‐analytical technique. The distributions of velocity, temperature, nanoparticle concentration, as well as pressure gradient and pressure rise are obtained as a function of the physical parameters of the problem. The effects of these parameters on these distributions are deliberated numerically and illustrated graphically through a set of figures. The results indicate that the parameters play a significant role in controlling the velocity, temperature, nanoparticle concentration, pressure gradient, and pressure rise.     

Premixed hydrogen-air combustion system for fuel cell systems

The advance of efficient hydrogen-air combustion systems has increasingly become of interest in the framework of the development of fuel cell systems, especially for the automotive sector. Therefore, compact modulating systems are required, with the additional demand of low emissions, to be integrated in a fuel cell system. A modulating combustion system based on combustion within inert porous media and an integrated heat exchanger has been developed and investigated. The system is able to handle premixed combustion of lean H₂/air mixtures at a surface load range of 1075 kW/m²-2150 kW/m², and a global equivalence ratio of ?=0.5. The special hydrogen-air mixing concept eliminates the risk of flame flashback and enables operation with very low NO_x emissions.