X-ray photoelectron spectroscopic characterization of molybdenum nitride thin films

The elemental composition and chemical states of a series of Mo nitride thin films have been investigated using x-ray photoelectron spectroscopy (XPS). The chemical composition and stoichiometry of the films were also tracked as a function of the preparative parameters: the nitrogen ion dose, ion accelerating energy and substrate temperature. At the lowest ion dose, the Mo concentration increased to a depth of ∼300 ?. The nitrogen concentration in the film decreased with increasing the ion energy. An increase in the ion energy to 100 and 200 kV led to a lower N/Mo ratio as compared to that at 50 kV. The magnitude of the binding energy separation at room temperature was smaller than that at higher temperatures. This difference might be due to the presence of B1-MoN at higher temperatures and the existence of δ-MoN at lower temperatures.     

Reduction of supported cobalt catalysts by hydrogen

The reduction of cobalt catalysts supported on Al₂O₃, SiO₂, and TiO₂ was investigated using a closed system filled with hydrogen gas. Effects of support and metal loading on the rate of reduction were also discussed. The activation energy of reduction increased in the following order: Co/TiO₂2O₃2. For different metal loadings, it was found that the catalyst with the higher loading was more readily reducible than that with the lower metal loading. This was confirmed using the results from measurements of particle size, amount of CO adsorbed and activity.     

IR,TPR, and TPD study of supported cobalt catalysts

The surface properties of supported Co catalysts for different metal loading and support materials have been studied using Infrared Spectroscopy(lR), Temperature-Programmed Reduction(TPR), and Temperature-Programmed Desorption(TPD). Supported Co catalysts are more difficult to reduce than unsupported CoO powder, and the activation energy of reduction increases with reduced metal loading. This is because the highly dispersed, small metal particles interact strongly with the support material. The metal-support interaction varies with different support materials providing different activation energies of reduction and CO desorption properties. A strong compensation effect is observed for the catalyst reduction process.     

Large area pattern replication by nanoimprint lithography for LCD–TFT application

Nanoimprint lithography is a high-throughput, low-cost, non-conventional lithographic method for fabricating micro/nanoscale patterns. In this study, we will present recent achievement in developing nanoimprint lithography for LCD–TFT fabrication. We fabricated metal gate for LCD–TFT with imprinting process. First, mold is pressed into a thin resist cast on a Cr layer which is deposited on a glass substrate. And the pressed resin is exposed to UV for curing, followed by demolding process. To acquire metal gate for LCD–TFT, subsequent process such as RIE with O₂ Plasmas, wet etching of Cr and striping of remained resin is followed. Finally, the fabricated metal gate has 3.5 μm level width, 97% uniformity overall on 1G size in a single imprint. Herewith nanoimprint lithography can substitute conventional photolithography steps in LCD–TFT process. Also it is expected that large area fine pattering such as functional optical films and PCBs could be effectively produced by nanoimprint process.     

Synthesis and catalytic properties of porous Ta carbide crystallites for hydrogen production from the decomposition of ammonia

Synthesis and catalytic properties of porous tantalum carbide crystallites for hydrogen production from the decomposition of ammonia were investigated using eight different samples which have been synthesized via temperature-programmed reduction method of Ta₂O₅ with pure CH₄. The Ta carbide crystallites synthesized using two different heating rates and space velocity showed the different surface areas. These results indicated that the structural properties of these materials have been related to the preparative conditions:heating rate and space velocity employed. The O₂ uptake has a linear relation with the BET surface area of tantalum carbides. The slope of the straight line corresponds to a site density showing an oxygen capacity of 1.36 × 10¹³ O/cm². The tantalum carbide crystallites were very active for ammonia decomposition with catalytic properties that were superior to commercial Ta carbide catalysts (Aldrich). It was also observed that the tantalum carbide crystallites were as much as two orders of magnitude more active than Pt/C catalyst (Engelhard). The activity increased with the decrease of particle size, suggesting the presence of the structure-sensitivity. The highest activity in tantalum carbides was observed at an atomic ratio of C₁/Ta^δ+ = 0.85, suggesting the presence of electron transfer between Ta metals and carbon (C₁) in Ta carbide crystallites.     

Development of large area nano imprint technology by step and repeat process and pattern stitching technique

In order to apply cost effective and productive nano imprint technology to the TFT-LCD fabrication, problems owing to large patterning area have to be solved. In this works, large area UV nano imprint process was developed by using of collimated UV light and shadow masks. It was shown that complex patterns could be easily replicated on 300 mm × 400 mm substrate by a large mold which is fabricated by suggested step and repeat process. Because roll pressing and alignment technique are important steps in our process for large area nano imprint, these process steps were optimized. Also, as a key technology for enlargement of patterning area, the stitching technique was developed. The idea using a collimated UV light is used for pattern stitching in nano imprint process. Developed large area pattern fabrication technique could be applied to various applications such as TFT-LCD process or optical film fabrication extensively.     

Analysis and verification of power transmission characteristics of the hydromechanical transmission for agricultural tractors

In this study, we developed a network model of a Hydromechanical transmission (HMT) for tractors. We verified the developed network model using commercial software and analyzed the power transmission characteristics of an HMT-equipped tractor based on the verified network model. We developed a network model considering the power losses of the transmission elements to analyze the power transmission characteristics of the HMT’s main shift. Using this model, we analyzed the power transmission characteristics of the main shift and confirmed that the power of the main shift can be split and circulated depending on the stroke of the Hydrostatic unit (HSU). We then used the model to analyze the HSU stroke, the power transmission efficiency, and the wheel torque, all of which comprise the power transmission characteristics of an HMT-equipped tractor. As a result, the HMT changed the driving speed of the tractor by continuously varying the HSU stroke. The tractor efficiency increased with the driving speed at each mode and decreased after having reached its maximum efficiency. To verify the developed network model, we compared the analysis results of the tractor’s power transmission efficiency and wheel torque with those obtained from commercial software. From the comparative analysis, we confirmed that the power transmission efficiency and wheel torque of the two models coincided. Therefore, we conclude that the developed network model is highly suitable for analyzing the power transmission characteristics of the HMT.

     

Effect of heating rate on pyrolysis of low-grade pyrolytic oil

The low-grade pyrolytic oil produced from pyrolysis of municipal plastic waste in a commercial rotary kiln reaction system cannot be an acceptable fuel oil due to its low quality. Thus, the degradation of pyrolytic oil was conducted in a bench scale batch reactor, which was done by two experiment conditions of high heating rate (about 7 °C/min) and low heating rate (1.5–3.6 °C/min) up to 420 °C of reaction temperature. The characteristics of raw pyrolytic oil were examined and also the characteristics of products obtained by different heating rates were compared. Raw pyrolytic oil had higher H/C ratio and higher heating value than commercial oils, and also its peak range in GC analysis showed wide distribution including all the range of gasoline, kerosene and diesel. In the upgrading of pyrolytic oil, cumulative amount profile of product oil, as a function of reaction time, was similar in shape to the degradation temperature profile. All product oils obtained by different degradation temperature had higher H/C ratio and slightly higher heating value than those of raw pyrolytic oil. Also, the characteristics of product oils were influenced by heating rate and reaction temperature.