• Journal of Powder Materials
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• v.7 no.1
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• pp.35-41
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• 2000

Al2O3$.$SiC particle was prepared was prepared by the self-propagting high temperature sYthesis(SHS) process from a mixture of SiO2, Al and C powders, The fabricated Al2O3$.$SiC particle was applied to 2024Al/(Al2O3$.$SiC)pcomposite as a reinforcement. Aluminum matix composites were fabricares by the powder extrusion method using the synthesized Al2O3$.$SiC particle and commercial 2024Al powder. Theoptimum preparation conditions for Al2O3$.$SiC partticle by SHS process were described. The influence of the Al2O3$.$SiC voiume fraction on the mechanical was composite was also discussed. Despite adiabatic temperature was about 2367K, SHs reaction was completed not by itself, but by using pre-heating. Mean particle size of final particle synthesized was 0.73 ${\mu}$m and most of the particle was smaller than 2${\mu}$m. Elastic modulus and tensile strength of the composite increased with increase the volume fraction of reinforcement but, tensile strength depreciated at 30 vol% of reinforcement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.247-252
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• 2003

In this paper, we made four types of metal particle $Al_2$O$_3$ barrier reactors with and without dielectric of BaTiO$_3$ between metal particle and $Al_2$O$_3$ barrier to investigate NOx removal characteristic and the effect of dielectric on Nox removal. And Nox removal rate is measured when sludge pellets are put at down stream of plasma reactor. Nox removal rate in the reactor with $Al_2$O$_3$ barrier is much better than that in the reactor without $Al_2$O$_3$ barrier, Nox removal rate is not so good in metal particle-Al$_2$O$_3$ barrier reactor with BaTiO$_3$ between metal particle and $Al_2$O$_3$ barrier, however, Nox removal rate is about 40% in metal particle-Al$_2$O$_3$ barrier reactor with TiO$_2$. The most of NO is conversed to NO$_2$ in these kind of reactor. When sludge pellets are put at down stream of plasma reactor, Nox removal rate is greatly improved up to 90%. It indicates that sludge pellets have great effect on the NO$_2$ removal and the improvement of Nox removal rate, however, dielectric materials between metal particle and $Al_2$O$_3$ barrier have not effect. Organic materials included in sludge may react with NO$_2$ and ozone so that Nox removal rate is greatly improved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.917-921
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• 2002

In this paper, we made different types of non-thermal plasma reactors such as Metal-particle reactor with $Al_2O_3$ to measure NOx removal characteristic and the dielectric effect for NOx removal. NOx removal rate is not so good when we use just dielectric of $Al_2O_3$ at the Metal-particle reactor, also we just put sludge pellets(100%) without Metal-particle reactor with $Al_2O_3$ and dielectric such as $TiO_2$, $BaTiO_3$ to measure the effect of sludge for NOx removal so that NOx removal rate is almost the same. However NOx removal rate is more than 90% in case of the reactor of composition shape used both dielectric of $Al_2O_3$ and sludge pellets at the same time. In case of the shape of plasma reactor with dielectric, the Metal-particle reactor with $Al_2O_3$, and the metal-particle reactor with both $Al_2O_3$ and dielectric such as $TiO_2$, $BaTiO_3$ at the same time, they are almost the same effect for NOx removal, so we made MNPR(Metal-particle Non-thermal Plasma Reactor with $Al_2O_3$) to reduce these kinds of demerits. Finally, we think MNPR should be much better than other reactors for NOx removal.

• Journal of the Korean Ceramic Society
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• v.29 no.9
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• pp.711-718
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• 1992

Pb(Fe1/2Nb1/2)O3 was prepared by the molten salt synthesis method using an equimolar mixture of NaCl-KCl. Initial particle size could be controlled by varying the weight ratio of the NaCl-KCl to raw materials from 0.1 to 1.0, and the initial particle size effects on the sintering and dielectric properties of Pb(Fe1/2Nb1/2)O3 were investigated at the sintering temperature range from 90$0^{\circ}C$ to 105$0^{\circ}C$. As the weight ratio of salt increased, the average particle size decreased and the particle size distributions tended to narrow. As the initial particle size decreased, the linear shrinkage and density increased due to the promotion of densification. Dielectric constant increased with decreasing the initial particle size resulting from the increase of density and grain size.

• Journal of the Korean Society of Clothing and Textiles
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• v.17 no.3
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• pp.380-390
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• 1993

Effect of interfacial electrical conditions on adhesion of ${\alpha}-Fe_2O_3$ particles to PET fabric and the removal of ${\alpha}-Fe_2O_3$ particles from PET fabric, were investigated as functions of pH, electrolyte and ionic strength. The ${\zeta}$ potential of PET fiber and ${\alpha}-Fe_2O_3$ particles in the electrolyte solution were measured by streaming potential and microelectrophoresis methods respectively. The potential energy of interaction between ${\alpha}-Fe_2O_3$ particles and PET fabric were calculated by using the heterocoagulation theory for a sphere-plate model. The negative ${\zeta}$ potential of ${\alpha}-Fe_2O_3$ particle and PET fiber increased with pH, and then decreased certain pH and isoelectric points of ${\alpha}-Fe_2O_3$ particles and PET fiber were pH 6.5 and pH 3.5, respectively. The negative ${\zeta}$ potential of ${\alpha}-Fe_2O_3$ particle and PET fiber affected by electrolytes, were relatively high with polyanion electrolytes in solutions and were low with neutral salts. However, at surfactant solution, ${\zeta}$ potential was levelled off. The influence of the ionic strength on the ${\zeta}$ potential of ${\alpha}-Fe_2O_3$ particle was small but the negative ${\zeta}$ potential of PET fiber increased with the ionic strength. In the presence of anionic surfactant, the ${\zeta}$ potential of ${\alpha}-Fe_2O_3$ particle and PET fiber increased regardless of solution conditions. The interaction energy between ${\alpha}-Fe_2O_3$ particle and PET fabric increased with pH. The interaction energy was relatively high with polyanion electrolytes in solution, and the influence of ionic strength on the interaction energy was small, and the effective thickness of electrical double layer increased with decreasing the ionic strength.

• Journal of the Korean Ceramic Society
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• v.37 no.4
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• pp.368-375
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• 2000

Fracture toughness of particulate composites of Al2O3/SiC, Al2O3/ZrO2 and Al2O3/ZrO2/SiC was analysed theoretically. According to the suggested particle bridging model for obtaining the R-curve height, the crack extension resistance for the long crack was linearly proportional to the residual calmping stress at the interface between the second phase and the matrix. It was also a function of the particle size and the content. It was confirmed that the rising R-curve behavior of Al2O3 containing 30 vol% SiC particles of 3${\mu}{\textrm}{m}$ was owing to the strong crack bridging by SiC particles. For Al2O3/ZrO2/SiC composites, the tensional stress from the 3${\mu}{\textrm}{m}$ SiC particles was large enough to activate the spontaneous transformation of the ZrO2. The crack extension resistance due to the particle bridging mechanism did not seem to be affected much by the coupled toughening, but its resultant toughness increase could be significantly smaller due to the dependency on the matrix toughness.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.3
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• pp.219-224
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• 2020

Al₂O₃ powders with particle sizes of 0.35 ㎛, 0.5 ㎛, 1.5 ㎛, and 2.5 ㎛ are deposited onto glass and Cu substrates using the aerosol deposition (AD) process. The deposition characteristics of Al₂O₃ films using those four types of Al₂O₃ powders are investigated to determine the influence of the particle size on the films. To observe detailed micro-structures of the films, the cross-section and surface morphology are observed. Then, the crystalline size and internal strain are calculated from X-ray diffraction peaks in order to confirm the hammering effect as well as the micro-strain during the AD deposition. From the above results, deposition mechanisms related to the particle size are studied. The results of this study indicate the optimal particle size and formation mechanisms for dense Al₂O₃ film with a smooth surface roughness as well as for a porous Al₂O₃ film with a rough surface roughness.

• Journal of Powder Materials
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• v.9 no.5
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• pp.341-345
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• 2002

Nanoparticles of $Fe_2O_3$ with a mean particle size of 4-30 nm have been prepared by a pulsed wire evaporation method, and its structural and magnetic properties were studied by SQUID magnetometer and Mossbauer spectroscopy. From the main peak intensity of XRD and absorption rate of Mossbauer spectrum, the amounts of $\gamma-Fe_2O_3$ and $\alpha-Fe_2O_3$ in as-prepared sample are about 70% and 30%, respectively. The coercivity (53 Oe) and the saturation magnetization (14 emu/g) are about 20% of those of the bulk $\gamma-Fe_2O_3$. The low value of coercivity and saturation magnetization indicate that the $\gamma-Fe_2O_3$ phase nearly shows the spin glass-like behavior. Analysis of the set of Mossbauer spectrum indicates a distribution of magnetic hyperfine fields due to the particle size distribution yielding 20 nm of average particle size. The magnetic hyperfine parameters are consistent with values reported of bulk $\gamma-Fe_2O_3$ and $alpha-Fe_2O_3$. A quadrupole line on the center of spectrum represents of superparamagnetic phase of $\gamma-Fe_2O_3$ with a mean particle size of 7 nm or below.

• Fashion & Textile Research Journal
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• v.4 no.1
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• pp.86-91
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• 2002

To estimate dispersion stability of particles, suspending power and particle size were examined as functions of pHs, surfactants, electrolytes and ionic strengths using ${\alpha}-Fe_2O_3$ particle as the model of particulate soil. Suspending power and particle size were determined by UV-Vis spectrumeter and by light scattering using the polarization ratio method, respectively. The suspending power was relatively high with polyanion electrolytes and was low with neutral salts. The suspending power was biphasis, minimum pH 6~7, and the effect of surfactant on the suspending power was insignificant. Generally suspending power increased with decreasing the particle size governed aggregation of dispersed particles regardless of solution conditions. Hence the suspending power was inversely related to the particle size.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.162-165
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• 2006

In this study, Liquid Phase Sintered SiC (LPS-SiC) was fabricated by hot pressing method with $\beta$-SiC powder whose a particle size is 30nm and less on the average in argon condition at 1780 and $1800^{\circ}C$ under 20MPa. Alumina ($Al_2O_3$), yttria ($Y_2O_3$) and silica ($SiO_2$) were used for sintering additives. To investigate effects of particle-size and temperature on $SiO_2$, LPS-SiC was fixed $Al_2O_3$, $Y_2O_3$ and then particle-size of $SiO_2$ were changed as two kinds. The system of particle-size and temperature on sintering additives which affects a property of sintering os well os the influence depending on particle-size and temperature of sintering additives were investigated by measurement of sintering properties. Such as measurement of sintering density, vikers hardness and observing of microstructure were investigated to make sure of the optimum condition which is about matrix of $SiC_f/SiC$ composites. Base on the composition of sintering additives, microstructure and sintering property correlation, the effect of particle-size of sintering additives are discussed. An experimental method to investigate the dynamic characteristics of bums in extreme environmental condition is established.