This study has been carried out to investigate the non-isothermal behaviors and kinetic parameter of calcium carbonate by different thermal analysis methods. At the heating rate of 10°C/min, the onset calcination temperature, the peak and final temperatures of calcium carbonate were 612°C, 748°C, and 890°C respectively. As the heating rate of the calcium carbonate increased from 5°C/min to 20°C/min, the peak temperature increased from 719°C to 782°C. The activation energies of the calcium carbonate calculated by the methods of Kissinger and Freeman-Carroll were 40.15 kcal/mol and 43.47 kcal/mol, respectively.
In the present study, Zr-base metallic glass(MG)/diamond composites are fabricated using a combination of gas-atomization and spark plasma sintering (SPS). The densification behaviors of mixtures of soft MG and hard diamond powders during consolidation process are investigated. The influence of mixture characteristics on the densification is discussed and several mechanism explaining the influence of diamond particles on consolidation behaviour are proposed. The experimental results show that consolidation is enhanced with increasing diamond/Metallic Glass(MG) size ratio, while the diamond fraction is fixed.
In this paper, the electrochemical non-enzyme immunosensor has been developed for the determination of salmonella antigen, using inverse voltammetry. For the estimation of salmonella antigen concentration, the Fe_3O_4 nanoparticles synthesized by microemulsion method were conjugated with salmonella antigen. Then, the immunocomplex between antibody immobilized on the transducer surface and antigen containing a magnetic nanoparticles was formed. From the linear relationship between the reduction peak current of Fe(III) and salmonella antigen concentration, it is suggested that the electrochemical non-enzyme biosensor is applicable to detect salmonella antigen in the concentration range of 101-105 CFU/ml.
Fe-Cr steels are the most promising candidate for interconnect in solid oxide fuel cells. In this study, an effective, dense and well adherent (LaSr)(CrCo)O_3 [LSCC] coating layer was produced onto 430 stainless steel (STS-430) by atmospheric plasma spraying and the oxidation behavior as well as electrical properties of the LSCC coated STS-430 were investigated. A significant oxidation of pristine STS-430 occurred at 800°C in air environment, leading to the formation of Cr_2O_3 and FeCr_2O_4 scale layer up to sim7µm after 1200h, and consequently increased an area specific resistance of 330;mOmegacdotcm2. Although the plasma sprayed LSCC coating contained the characteristic pore network, the coated samples presented apparent advantages in reducing oxidation growth of STS-430, resulting a decrease in oxide scale thickness of sim1µm at 800°C after 1200h. The area specific resistance of the LSCC coated STS-430 was much reduced to sim7;mOmegacdotcm2 after exposure at 800°C for 1200h, compared to that of the pristine STS-403.
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Coatings Properties and Efficiency Performance of Cr-DLC Films Deposited by Hybrid Linear Ion Source for Hydraulic Gear Pump Sun-Yong Cha, Wang-Ryeol Kim, Min-Suk Park, Se-Hun Kwon, Won-Sub Chung, Myung-Chang Kang Journal of Korean Powder Metallurgy Institute.2010; 17(6): 456. CrossRef
The calcination and hydrogen-reduction behavior of Fe- and Ni-nitrate have been investigated. Fe_2O_3/NiO composite powders were prepared by chemical solution mixing of Fe- and Ni-nitrate and calcination at 350°C for 2 h. The calcined powders were hydrogen-reduced at 350°C for 30 min. The calcination and hydrogen-reduction behavior of Fe- and Ni-nitrate were analyzed by TG in air and hydrogen atmosphere, respectively. TG and XRD analysis for hydrogen-reduced powders revealed that the Fe_2O_3/NiO phase transformed to FeNi_3 phase at the temperature of 350°. The activation energy for the hydrogen reduction, evaluated by Kissinger method, was measured as 83.0 kJ/mol.
A visible-light photoactive TiO_2-xN_x photocatalyst was synthesized successfully by means of cogrinding of anatase-TiO_2(a-TiO_2) in NH_3 ambient, followed by heat-treatment at 200°C in air environment. In general, it is well known that the grinding-operation induces phase transformation of a-TiO_2 to rutile TiO_2. This study investigates the influence of the amount of NH_3 gas on the phase transformation rate of a-TiO_2 and enhancement of visible-light photocatalytic activity, and also examines the relation between the photocatalytic activity and the period of grinding time. The phase transformation rate of a-TiO_2 to rutile is retarded with the amount of NH3 injected. And the visible-light photocatalytic activity of samples, was more closely related to the period of grinding time than NH_3 amount injected, which means that the doping amount of nitrogen into TiO_2 more effective to mechanical energy than NH_3 amount injected. XRD, XPS, FT-IR, UV-vis, Specific surface area (SSA), NOx decomposition techniques are employed to verify above results more clearly.
Y_2O_3:Eu red phosphor was prepared by microwave synthesis. The crystal phase, particle morphology, and luminescent properties were characterized by XRD, SEM, and spectrofluorometer, respectively. The prepared Y_2O_3:Eu particles had good crystallinity and strong red emission under ultravioletet excitation. The crystallite size increased with calcination temperature and satuarated at 1200°C. The primary particle size initially formed was varied from 30 to 450 nm with microwave-irradiation (MI) time. It was found that the emission intensity of Y_2O_3:Eu phosphor strongly depends on the MI time. In terms of the emission intensity, it was recommended that the MI time should be less than 15 min. The emission intensity of Y_2O_3:Eu phosphor prepared by microwave syntehsis strongly depended on the crystallite size of which an optimal size range was 50-60 nm.
A composite of rapidly solidified Al-6061 alloy powder with graphite particle reinforcements was prepared by ball milling and subsequent hot extrusion. The microstructure and mechanical properties of these composites were investigated as a function of milling time. With increasing milling time, the gas atomized initially and spherical powders became elongated with a maximum aspect ratio after milling for 30 h. Then, refinement and spheroidization were achieved by further milling to 70 h with a homogeneous and fine dispersion of graphite particles forming between the matrix alloy layers. The best compression and wear properties were obtained in the powder milled for 70 h, associated with the increased fine and homogeneous distribution of graphite particles in the aluminum alloy matrix.
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This paper presents a novel single-step method to prepare the Ag nanometallic particle dispersed fluid (nanofluid) by electrical explosion of wire in liquid, deionized water (DI water). X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transmission electron microscope (TEM) were used to investigate the characteristics of the Ag nanofluids. Zeta potential was also used to measure the dispersion properties of the as-prepared Ag nanofluid. Pure Ag phase was detected in the nanofluids using water. FE-SEM analysis shows that the size of the particles formed in DI water was about 88 nm and Zeta potential value was about -43.68 without any physical and chemical treatments. Thermal conductivity of the as-prepared Ag particle dispersed nanofluid shows much higher value than that of pure DI water.
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The compaction response of TiO_2 nano powders with an addition of Ti powders prepared by magnetic pulsed compaction and subsequent sintering processes was investigated. All kinds of different bulk exhibited an average shrinkage of about 12% for different MPCed pressure and sintering temperature, which were approximately 50% lower than those fabricated by general process (20%) and a maximum density of around 92.7% was obtained for 0.8GPa MPCed pressure and 1400°C sintering temperature. The addition of Ti powder induced an increase in the formability and hardness of the sintered TiO_2. But the lower densities were obtained on sintering with addition of over 10 (wt%) Ti powder due to generation of crack during sintering. Subsequently it was verified that the optimum compaction pressure in MPC and sintering temperature were 0.8GPa and 1400°C, respectively.
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