Decomposition of Nitrogen Trifluoride Using Low Power Arc Plasma

The low power arc plasma is characterized by extremely high enthalpy and temperature and it is easy to generate and control,and thus thermal decomposition process based on the plasma torch is receiving a great attention for decomposing non-degradable greenhouse gases.In order to elevate the economic feasibility,the efects of input power,waste gas flow rate and additive gases on the destruction and removal efciency(DRE) of NF3 are examined.Specific energy density(SED) deceases as the flow rate increases,and accordingly,the DRE is reduced.The DRE is basically determined by the specific energy density.The highest DRE of NF3 was 97% for the waste gas flow rate of 100 L/min at a low input power level of 2 kW with the help of hydrogen additional gas.The inlet and outlet concentration of NF3 was analyzed using Fourier transform infrared spectroscopy(FT-IR) for DRE of NF3 evaluation.As a result,large amount of NF3 can be efciently decomposed by low power arc plasma systems.     

Experimental Study of Material Removal Process of Fused Silica Glass Using MR Jet Polishing System

Recently,there has been an investigation of polishing processes that has considered new ultra-precision polishing technology for micro parts and optical parts such as those with aspheric and complex shapes.One suitable means of polishing complex shapes is to use a jet of abrasive fluid.However,aerodynamic disturbances and radial spreading are generated by the unstable polishing process of the jet on the surface of the workpiece when it is being polished.A method of jet stabilization has been proposed in which the original nozzle form of a jet of magnetorheological(MR)fluid contains abrasive particles that are magnetized using a magnetic.This paper details the design of an MR jet polishing system that uses an electromagnet,a nozzle,and a hydraulic unit to stabilize a slurry jet based on MR fluid,Second,for silica glass,the polishing spot and section profile are analyzed and the effect of the MR fluid jet polishing process is evaluated.The results of the experiment show that the removal profile is W-shaped and that,in this case,a stable can be proof of a distance of several tens of millimeters from the nozzle.Such results show the possibility of applying the proposed polishing method using MR fluids in ultra-precision micro and optical parts production processes.MR jet polishing shows great potential for use as a new type of precision surface polishing technology.In particular,this is a highly valuable process for the polishing of complex shapes such as micro parts,concaves parts,and cavities.     

Formation of unidirectional nanoporous structures in thickly anodized aluminum oxide layer

A series of anodic aluminum oxide(AAO) was grown on the commercially pure 1050 aluminum sheet by controlling electrolyte temperature (2–15 °C) and an odizing time (0.5–6 h), using a fixed applied current density of 3 A/dm² in diluted sulfuric acid electrolyte. A crack-free thick AAO with the thickness of 105–120 μm and containing unidirectional nano sized pores (average pore diameter of 5–7 nm) is successfully achieved in the specimens anodized for 2 h, irrespective of electrolyte temperature. When anodizing time reaches 6 h, very thick AAO with the thickness of 230–284 μm is grown, and average diameter of unidirectional pores is in the range of 6–24 nm. The higher values in both the AAO thickness and pore diameter are attained for the specimens anodized at higher temperatures of 10–15 °C. A crack is observed to exist in the AAO after anodizing up to 4 h and more. A higher fraction (more than 9%) of the crack is shown in the specimens anodized at higher temperatures of 10–15 °C for 6 h and a considerable amount of giant cracks are contained.     

Formation behavior of anodic TiO2 nanombes in fluoride containing electrolytes

TiO₂ nanotube layers can be formed with titanium in the electrolytes containing fluoride by electrochemical method. The role of fluoride ion, the crystallinity of the anodic oxide, and the chemical state were investigated. The results show the anodic film is composed of oxide and a little amount of hydroxide. The presence of F⁻ ions leads to chemical dissolution of Ti oxide layer and prevents hydroxide precipitation. Consequently, chemical dissolution rate increases with increasing the fluoride content in the range of 0–2% (in mass fraction) because F⁻ ions in electrolyte attack the interface and allow the ions of the electrolyte to easily penetrate into the interface. The as-anodized TiO₂ nanotubes exhibit an amorphous structure. Thermally treated nanotubes are composed of mixtures of the anatase and rutile phases.     

Fabrication of SiC_p/AA5083 composite via friction stir welding

Microstructure and mechanical properties of SiCp /AA5083 composite fabricated by friction stir welding (FSW) were investigated.The influence of the number of FSW passes on the distribution of SiC particles and mechanical properties in the joint was studied.After one pass,the SiC particles were entangled in the upper side of the stir zone (SZ).However,the particle distribution became more uniform after two passes due to the repeated stirring of the joint.As the SiC particles facilitate the grain refinement in the SZ by the pinning effect,the particle including region has much smaller grain size than the SZ without SiC particles.The SiCp /AA5083 composite region exhibits a Vickers hardness of HV90,which is much higher than the value of HV80 in the SZ produced by FSW without SiC particles.     

EFFECTS OF EXTRUSION CONDITIONS ON PHYSICOCHEMICAL PROPERTIES OF A MUTANT RICE CULTIVAR,GOAMI2 – HIGH IN NONDIGESTIBLE CARBOHYDRATES

ABSTRACT

A mutant rice Goami2, a cultivar high in nondigestible carbohydrates (NDCs), was extrusion‐cooked at feed moisture (20, 25%), screw speed (200, 300 rpm) and barrel temperature (110, 120 and 130C). Effects of extrusion conditions on the physical and functional properties were investigated. NDCs were determined by total dietary fiber (TDF) and resistant starch (RS) contents. Increasing moisture resulted in an increment of density, water absorption index (WAI) and hardness, and a decrement in expansion and water solubility index (WSI). A higher barrel temperature decreased the hardness and increased the WSI probably due to a higher proportion of gelatinized starch. Extrusion caused a reduction in TDF in the extrudates, as well as a significant decrease in RS contents. However, extrudates processed at moisture (%), screw speed (rpm) and barrel temperature (C) combinations of 25/200/110 and 25/200/120 showed no significant difference in TDF contents compared with its raw rice. Multiple regression models showed that feed moisture had the most pronounced effect on extrudate qualities, followed by barrel temperature and screw speed.

PRACTICAL APPLICATIONS

Rice, being one of the primary dietary sources of carbohydrates worldwide, is the major energy and nutritional sources. In recent years, demands have been increasing for rice with a wide range of value‐added properties, such as enhanced nutrient, aroma, color and rice kernel shape, including functional properties. Goami2 is a mutant rice of Ilpumbyeo, a high japonica rice cultivar, and has been revealed to have higher nondigestible fractions. However, Goami2 rice has unsuitable properties for traditional cooking because of the difficulty of gelatinization, which might result in a hard texture of cooked rice compared with that of ordinary rice. On the basis of its nutritional and functional benefits, exploiting the possible utilization of Goami2 for processed food products would increase the potential consumption of Goami2 for various food products.     

Grain‐oriented segmentation of images of porous structures using ray casting and curvature energy minimization

We segment an image of a porous structure by successively identifying individual grains, using a process that requires no manual initialization. Adaptive thresholding is used to extract an incomplete edge map from the image. Then, seed points are created on a rectangular grid. Rays are cast from each point to identify the local grain. The grain with the best shape is selected by energy minimization, and the grain is used to update the edge map. This is repeated until all the grains have been recognized. Tests on scanning electron microscope images of titanium oxide and aluminium oxide show that their process achieves better results than five other contour detection techniques.     

Densification process of TiCx–Ni composites formed by self-propagating high-temperature synthesis reaction

Densification behaviour of the TiC-Ni system formed by self-propagating high-temperature synthesis (SHS) were studied to develop the structural metal-matrix composites. The composites were prepared by two routes: (1) consolidation during the SHS reaction, and (2) consolidation process after the SHS reaction. The final phases of the stoichiometric reactant mixture of titanium and graphite with 50 wt% nickel produced by simultaneous combustion reactions, were titanium carbide in a nickel-rich solid solution containing carbon and titanium. The density of the products was relatively low, with a value of 90% theoretical density. In the second approach, liquid infiltration and liquid-phase sintering were applied for the titanium carbide-nickel mixture. Densification rates were reduced due to the excess carbon in the combustion products of titanium carbide. The densities of the liquid-phase sintered samples were more than 97% theoretical density. This revised version was published online in November 2006 with corrections to the Cover Date.