Materials Science Forum Vols. 544-545

Abstract: Interests on the fabrication of microfluidic devices have increased in the fields of micro total analysis system (μ-TAS) and MEMS (Microelectromechanical systems) due to their chemical inertness and high thermal stability. The thermal characterization of the SiCN preceramic polymer, polyvinylsilazane, showed that the cured polymer has ceramic properties at heat treatment temperature of 600 oC or above. In the characterization of the mechanical properties, the characteristic values of the elastic modulus and hardness notably increased for the heat-treated SiCN. The present study describes the preparation of nano-sized patterns and microfluidic channels using a soft lithographic technique. The study shows that the fabrication of microchannels using the cured inorganic polymers holds tremendous potential in the field of microfluidics, where materials with high optical transparency, thermal stability and chemical inertness are in demand as niche between conventional microfluidics using glass and polymeric materials.

Abstract: The possible utilization of automobile shredder residue as a fuel in the cement kiln process was investigated. The detailed characteristics of the automobile shredder residues were investigated in terms of it’s chlorine content as a fuel feed and its circulation in cement kiln. For estimation of the chlorine content in the cement kiln system, the Weber model which is one of the circulation material’s forecast model was used. From the results, we estimated the chlorine by-pass rate should be 1 ~ 2 percent, for maintaining the present level of chlorine content’s on the hot-meal of the cement kiln system.

Abstract: Nano-rod ZnWO4 was solvothermally prepared by the reaction of Zn(CH3COO)2.2H2O with Na2(WO4).2H2O in water at 150-200 oC using the pH of 5.0, 7.0, 9.0 and 12.0 for 24, 48 and 72 h. N-cetyl pyridinium chloride was used as a surfactant. By using XRD, SAED, EDX and TEM, nano-rod ZnWO4 containing Zn, W and O was detected. The pH values can play a role in the length of the nano-rods and their crystallinities. FTIR revealed the presence of Zn-O-W, W-O and Zn-O stretching vibrations of the products. Their photoluminescent (PL) spectra are similar and the wavelengths at the highest intensities were detected over the range of 445-450 nm.

Abstract: ZnS thin films were grown by Atomic Layer Deposition (ALD) method with Diethyl- Zinc (DEZ) and hydrogen sulfide (H2S) for the application of a channel layer of OITFT (Organic-Inorganic Thin-Film Transistor). ZnS has many advantages such as high channel mobility, high deposition rate, transparency at room temperature due to the broad band gap (bandgap of ZnS : 3.7 eV), nontoxic characteristic, low resistivity, and less sensitive about oxidation than ZnO. The deposition rate of the ZnS films in our system was about 1.6 Å/cycle. ZnS film was characterized by AES, XRD, Hall-effect measurement.

Abstract: Characteristics of nucleation and crystal growth of aragonite precipitated calcium carbonate in Ca(OH)2 – MgCl2 – CO2 system via a carbonation process is investigated. Aragonite precipitated calcium carbonate with high aspect ratio was synthesized at high reaction temperature and concentration of Ca(OH)2 slurry. The increase in crystal size with decreased in CO2 gas flow rate can be explained by a decrease in the nucleation rate and an increase in the crystal growth rate caused by a decrease in the dissolution rate to CO3 2- ion. In this study, crystal growth of aragonite was investigated by adding aragonite seed. It was found that crystal growth of aragonite precipitated calcium carbonate could be controlled by three-step carbonation process using reactants as the Ca(OH)2. Aragonite with an aspect ratio from 5 to 27 and diameter from 3μm to 24μm was thereby grown at a reaction temperature of 80°C and a CO2 flow rate of 50ml/min. It was also found that MgCl2 aqueous solution can be used again in the carbonation process for the synthesis of aragonite precipitated calcium carbonate.

Abstract: By the solution-dropping method imitating the growth of stalagmite in nature, piezoelectric KNbO3 crystal was prepared onto a substrate by dropping metastable K2NbO3F aqueous solution. The transformation from K2NbO3F to KNbO3 was accelerated by separately dropping H2O2 solution at the same time. Under the conditions of K2NbO3F concentration of 4.2×10-2 mol/l, H2O2 concentration of 9mol/l, dropping rate of 1.7ml/min, dropping time of 2 h, and substrate temperature of 20°C, KNbO3 crystals of 2 to 5μm and polycrystalline film composed of KNbO3 crystals of < 1μm were grown at aqueous temperatures of 20°C and 60°C, respectively.

Abstract: The decomposition characteristics of CF4 with Argon or oxygen in 2.45GHz microwave has been investigated by using a Langmuir probe with variation of the microwave power and chamber pressure. For CF4/Ar and CF4/O2/Ar discharges, the ion density and the electron density decrease with increasing microwave power. The electron temperature was decreased by reducing the mean free path of electrons with increasing microwave power. Also with increasing pressure, the electron temperature increase, and ion and electron density decrease by increase of inelastic collision frequency and of collision with the walls in the chamber. The electron temperature is 13.6 ~ 5.9 [eV], the electron density is 4.4×1010 ~ 2.2×1010 [cm-3] and ion density is 5.2×1011 ~ 4×1010 [cm-3]. According as add oxygen, ion and electron density increased relatively comparing to CF4/Ar discharge. The electron temperature is 8.5 ~ 6.2 [eV], the electron and ion density is 5.1×1010 ~ 2.1×1010 [cm-3] and 3.7×1011 ~ 7.3×1010 [cm-3], respectively.

Abstract: The objective of this study is to investigate the efficient method to maximize both color and TOC removal of the azo dye solution by reduction and oxidation with a laboratory synthesized nano-sized zero valent iron (nZVI). The decolorization efficiency increased with the decrease of pH and increase of zero valent iron dosage. The optimum dosage of nano-sized zero-valent iron was 20mg/L at pH 3. The surface normalized constant of nZVI was higher than those reported for the discoloring of azo dye with other ZVIs. The sequential dose of nZVI/H2O2 remove color and TOC more effectively than the simultaneous dose. Pre-reduction by nZVI could convert azo dye to products whose oxidation is more degradable and therefore enhances the removal efficiency.

Abstract: As electronic devices are getting smaller and lighter, the density of copper lines on flexible printed circuit board (FPCB) is getting higher. Conventionally, subtractive method was used for copper line on a flexible films, however, as the line pitch is getting smaller, the lateral etching of copper cause serious problem. To replace the subtractive method, semi-additive method was used for fine pitch copper line fabrication. In semi additive process, sputtered layer for the electroplating copper was required. The feasibility of electroless plating to replace high cost sputtered copper seed layer was investigated. Electroless depositions of copper were conducted on different substrate to find optimum conditions of electroless copper plating. To find optimum conditions, the effects and selectivity of activation method on several substrates were also investigated. The adhesion strength between polyimide and copper was improved by treating the polyimide surface with butylamines. Pretreatment prior to electroless plating is very sensitive and surface dependent. Surface morphologies were investigated with FESEM.