Porous HAp with three-dimensional network channels was prepared in a polymer foam process using a in-situ formation. HAp/polyol with various HAp solid contents was formed with an addition of isocyanate. Under all conditions, the obtained porous HAp had pore sizes ranging 50 μm to 250 μm. The influence of the HAp content on the physical and mechanical properties of porous HAp scaffolds was investigated. As the solid content increased, the porosity of the porous HAp decreased from 79.3% to 77.9%. On the other hand, the compressive strength of the porous HAp increased from 0.7 MPa to 3.7 MPa. With a HAp solid content of 15 g, the obtained porous HAp had physical properties that were more suitable for scaffolds compared to other conditions.
In this paper, a novel non-vacuum technique is described for the fabrication of a CuInSe2 (CIS) absorber layer for thin film solar cells using a low-cost precursor solution. A solution containing Cu- and Inrelated chemicals was coated onto a Mo/glass substrate using the Doctor blade method and the precursor layer was then selenized in an evaporation chamber. The precursor layer was found to be composed of CuCl crystals and amorphous In compound, which were completely converted to chalcopyrite CIS phase by the selenization process. Morphological, crystallographic and compositional analyses were performed at each step of the fabrication process by SEM, XRD and EDS, respectively.
A preparation of NixMn1-xFe2O4 nanoparticles produced via the reduction of Nickel nitrate hexahydrate, Manganese (II) nitrate hexahydrate and Iron nitrate nonahydrate with hydrazine in Igepal CO-520/cyclohexane reverse micelle solutions was investigated. Transmission Electron Microscope (TEM), X-ray Diffraction (XRD) and Vibration Sample Magnetometer (VSM) analyses showed that the resultant nanoparticles increased the molar ration of water to Igepal CO-520 as the concentrations of Nickel nitrate hexahyrate, Manganese (II) nitrate hexahydrate and Iron nitrate nonahydrate increased. The average size of the synthesized particles calcined at 600˚C for 2hrs was in the range of 20 nm to 30 nm, and the particle distribution was broadened. The phase of the synthesized particles was crystalline, and the magnetic behavior of the synthesized particles was superparamagnetism. The effect of the synthesis parameters of the molar ratio of water to surfactant and the calcination temperature was discussed.
Polycrystalline germanium (Ge) thin films were grown by metal organic chemical vapor deposition (MOCVD) using tetra-allyl germanium [Ge(allyl)4], and germane (GeH4) as precursors. Ge thin films were grown on a TiN(50nm)/SiO2/Si substrate by varying the growth conditions of the reactive gas (H2), temperature (300-700˚C) and pressure (1-760Torr). H2 gas helps to remove carbon from Ge film for a Ge(allyl)4 precursor but not for a GeH4 precursor. Ge(allyl)4 exhibits island growth (VW mode) characteristics under conditions of 760Torr at 400-700˚C, whereas GeH4 shows a layer growth pattern (FM mode) under conditions of 5Torr at 400-700˚C. The activation energies of the two precursors under optimized deposition conditions were 13.4 KJ/mol and 31.0 KJ/mol, respectively.
In this study, a new cleaning process with a low cost of ownership (CoO) was developed with ozonated DI water (DIO3). An ozone concentration of 40 ppm at room temperature was used to remove organic wax film and particles. Wax residues thicker than 200 Å remained after only a commercial dewaxer treatment. A DIO3 treatment in place of a dewaxer showed a low removal rate on a thick wax layer of 8000 Å due to the diffusion-limited reaction of ozone. A dewaxer was combined with a DIO3 rinse to reduce the wax removal time and remove wax residue completely. Replacing DI rinse with the DIO3 rinse resulted in a surface with a contact angle of less than 5˚, which indicates no further cleaning steps would be required. The particle removal efficiency (PRE) was further improved by combining a SC-1 cleaning step with the DIO3 rinsing process. A reduction in the process time was obtained by introducing DIO3 cleaning with a dewaxing process.
LaFeO3 powders were synthesized using a method involving solution combustion, and the surfaceproperties of these powders were examined by x-ray photoelectron spectroscopy. As the amount of fuelincreased during the synthesis, the LaFeO3 powders became amorphous with a large plate-like shape. It wasfound that the O 1s spectra were composed of two types of photoelectrons by deconvolutioning the spectra.Photoelectrons with higher binding energy come from adsorbed oxygen (O−) whereas those with lower energycome from lattice oxygen (O2−). The ratio of adsorbed and lattice oxygen increased as the ratio of the fuel andnitrate (Φ) increased. The binding energy of both types of oxygen increased as Φ increased due to the formationof carbonates.
Single crystal ZnIn2S4 layers were grown on thoroughly etched semi-insulating GaAs(100) substrateat 450oC with hot wall epitaxy (HWE) system by evaporating ZnIn2S4 source at 610oC. The crystalline structureof the single crystal thin films was investigated by the photoluminescence (PL) and double crystal X-ray rockingcurve (DCRC). The temperature dependence of the energy band gap of the ZnIn2S4 obtained from theabsorption spectra was well described by the Varshni’s relation, Eg(T)=2.9514eV-(7.24×10−4eV/K)T2/(T+489K). After the as-grown ZnIn2S4 single crystal thin films were annealed in Zn-, S-, and In-atmospheres, theorigin of point defects of ZnIn2S4 single crystal thin films has been investigated by the photoluminescence (PL)at 10K. The native defects of VZn, VS, Znint, and Sint obtained by PL measurements were classified as a donorsor acceptors type. And we concluded that the heat-treatment in the S-atmosphere converted ZnIn2S4 singlecrystal thin films to an optical p-type. Also, we confirmed that In in ZnIn2S4/GaAs did not form the nativedefects because In in ZnIn2S4 single crystal thin films existed in the form of stable bonds.
Since the 1990s, the second generation of Zirconium alloys containing main alloy compositions of Nb, Sn and Fe have been used as a replacement of Zircaloy-4 (Zr-Sn-Fe-Cr), a first-generation Zirconium alloy, to meet severe and rigorous reactor operating conditions characterized by high-burn-up, high-power and high-pH operations. In this study, the mechanical properties and creep behaviors of Zr-Sn-Fe-Cr and Zr-Nb-Sn-Fe alloys were investigated in a temperature range of 450~500˚C and in a stress range of 80~150 MPa. The mechanical testing results indicate that the yield and tensile strengths of the Zr-Nb-Sn-Fe alloy are slightly higher compared to those of Zr-Sn-Fe-Cr. This can be explained by the second phase strengthening of the β-Nb precipitates. The creep test results indicate that the stress exponent for the steady-state creep rate decreases with the increase in the applied stress. However, the stress exponent of the Zr-Sn-Fe-Cr alloy is lower than that of the Zr-Nb-Sn-Fe alloy in a relatively high stress range, whereas the creep activation energy of the former is slightly higher than that of the latter. This can be explained by the dynamic deformation aging effect caused by the interaction of dislocations with Sn substitutional atoms. A higher Sn content leads to a lower stress exponent value and higher creep activation energy.
The purpose of this study is to characterize various electrolytes on electrochemical mechanical planarization (ECMP). The ECMP system was modified from conventional CMP system to measure the potentiodynamic curve and removal rate of Cu. The potentiodynamic curves were measured in static and dynamic states in investigated electrolytes using a potentiostat for the evaluation of the polishing behavior on ECMP. KOH (alkaline) and NaNO3 (salt) were selected as electrolytes which have high conductivity. In static and dynamic states, the corrosion potential decreased and the corrosion current increased as a function of the electrolyte concentration. But, the electrochemical reaction was prevented by mechanical polishing effect in the dynamic state. The static etch and removal rate were measured as functions of concentration and applied voltage. When NaNO3 was used, the dissolution was much faster than that of KOH. It was concluded that the removal rate was strongly depended on electrochemical dissolution. The removal rate increased up to 350 nm/min in NaNO3 based electrolyte.
High-energy mechanical milling (HEMM) and sintering into Al-Mg alloy melt were employed tofabricate an Al alloy matrix composite reinforced with submicron and micron sized Al2O3 particles. Al-basedmetal matrix composite (MMC) reinforced with submicron and micron sized Al2O3 particles was successfullyfabricated by sintering at 1000oC for 2h into Al-Mg alloy melt, which used high energy mechanical milled Al-SiO2-CuO-ZnO composite powders. Submicron/micron-sized Al2O3 particles and eutectic Si were formed by in situdisplacement reaction between Al, SiO2, CuO, and ZnO during sintering for 2h into Al-Mg alloy melt and werehomogeneously distributed in the Al-Si-(Zn, Cu) matrix. The refined grains and homogeneously distributedsubmicron/micron-sized Al2O3 particles had good interfacial adhesive, which gives good wear resistance withhigher hardness.