• Korean Journal of Materials Research
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• v.22 no.12
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• pp.701-705
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• 2012

The effects of clay, aluminum hydroxide, and carbon powder on the sintering of a Si/SiC mixture from photovoltaic silicon-wafer production were investigated. Sintering temperature was fixed at $1,350^{\circ}C$ and the sintered bodies were characterized by SEM and XRD to analyze the microstructure and to measure the apparent porosity, absorptivity, and apparent density. The XRD peak intensity of SiC in the sintered body was increased by adding 5% carbon to the Si/SiC mixture. From this result, it is confirmed that Si in the Si/SiC mixture had reacted with the added carbon. Addition of aluminum hydroxide decreased the cristobalite phase and increased the stable mullite phase. The measurement of the physical properties indicates that adding carbon to the Si/SiC mixture enables us to obtain a dense sintered body that has high apparent density and low absorptivity. The sintered body produced from the Si/SiC mixture with aluminum hydroxide and carbon powder as sintering additives can be applied to diesel particulate filters or to heat storage materials, etc., since it possesses high thermal conductivity, and anticorrosion and antioxidation properties.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.611-619
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• 2018

Basalt powder sludge (abbreviated BPS) is an inevitable industry by product resulted from the stone processing. Recently, demands for natural materials have been increasing in the construction and landscaping fields, therefore, amounts of BPS have been also increasing. Since most of BPS are used as landfill and earth soil, it is necessary to figure out to expedite their utilization. In this study, by considering the characteristics of precipitation of Jeju, effectiveness of BPS as a filler for asphalt compounds mixed with cement were analyzed. As a result, BPS satisfies quality criterion required in KS F 3501. Marshall mixing designs were performed to determine the optimal asphalt content for the Modified recycling asphalt mixture (27% recycling aggregate) and the Normal asphalt mixture. Effectiveness of BPS were identified by the Marshall Stability Test with the mixing ratio (level 3) of two asphalt compounds and composition ration (level 3) of BPS and cement. Performance of asphalt compounds shown appropriate effect of mixing and composition ratios of the filler were assessed. Test results show that two types of asphalt compounds satisfy the quality standards of the MLIT (2015). Therefore, BPS could be used as filler for asphalt compounds.

• Journal of Physiology & Pathology in Korean Medicine
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• v.33 no.2
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• pp.131-140
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• 2019

The objective of present study is to evaluate concentration-dependent in vitro anti-osteoarthritic (OA) effects of synergic mixed formula consisted of dried pomegranate juice concentrate powder, Eucommiae Cortex aqueous extract and Achyranthis Radix aqueous extract 5:4:1 (g/g) mixture on the primary cultured rat articular chondrocytes. First, any cytotoxic effect of mixture was observed using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium Bromide) assay. Next, cyto-protective effect of test substances was evaluated by using the recombinant human interleukin $(rhIL)-1{\alpha}$ induced chondrocytes. In addition, anti-inflammatory effects were also observed on the lipopolysaccaride (LPS) treated chondrocytes through prostaglandin $E_2(PGE_2)$ productions and 5-lipoxygenase (LPO) activities, and inhibitory effects on matrix metalloproteinase (MMP)-2 and MMP-9 activities were observed on $rhIL-1{\alpha}$ treated chondrocytes with their extracellular matrix (ECM) related mRNA expressions. No obvious cytotoxic effects of mixture were demonstrated. Inflammatory damages of chondrocytes and related ECM degradations induced by treatment of LPS or $rhIL-1{\alpha}$ were significantly and concentration-dependently inhibited by pretreatment of mixture from a concentration level of 0.001 mg/ml to 1 mg/ml. In addition, mixture showed $IC_{50}$ for $rhIL-1{\alpha}-induced$ MMP-2 and MMP-9 activities as 44.01 and $162.47{\mu}g/ml$, and also showed $EC_{50}$ for $rhIL-1{\alpha}-induced$ inhibition of collagen type II, SOX9 and aggrecan mRNA expression as 8.61, 10.79 and $4.47{\mu}g/ml$, respectively. It is observed that mixture showed concentration-dependent anti-inflammatory and cytoprotective ECM preserved effects on the primary cultured rat articular chondrocytes without cytotoxicity.

• Korean Journal of Materials Research
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• v.26 no.6
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• pp.337-341
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• 2016

Cu-30 vol% SiC composites with relatively densified microstructure and a sound interface between the Cu and SiC phases were obtained by pressureless sintering of PCS-coated SiC and Cu powders. The coated SiC powders were prepared by thermal curing and pyrolysis of PCS. Thermal curing at $200^{\circ}C$ was performed to fabricate infusible materials prior to pyrolysis. The cured powders were heated treated up to $1600^{\circ}C$ for the pyrolysis process and for the formation of SiC crystals on the surface of the SiC powders. XRD analysis revealed that the main peaks corresponded to the ${\alpha}$-SiC phase; peaks for ${\beta}$-SiC were newly appeared. The formation of ${\beta}$-SiC is explained by the transformation of thermally-cured PCS on the surface of the initial ${\alpha}$-SiC powders. Using powder mixtures of coated SiC powder, hydrogen-reduced Cu-nitrate, and elemental Cu powders, Cu-SiC composites were fabricated by pressureless sintering at $1000^{\circ}C$. Microstructural observation for the sintered composites showed that the powder mixture of PCS-coated SiC and Cu exhibited a relatively dense and homogeneous microstructure. Conversely, large pores and separated interfaces between Cu and SiC were observed in the sintered composite using uncoated SiC powders. These results suggest that Cu-SiC composites with sound microstructure can be prepared using a PCS coated SiC powder mixture.

• Korean Journal of Materials Research
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• v.8 no.7
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• pp.596-600
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• 1998

Reaction bonded $AI_2O_3$(RBAO)-SiC ceramics were prepared from the Al/$AI_2O_3$/SiC powder mixture. The calcined alumina and fused alumina were used as the raw $AI_2O_3$ powder. The same sized (3mm) and differently sized (3mm + Smm) $Zr0_2$ balls were used in attrition milling of starting powders. The effect of $AI_2O_3$ powder shapes on the milling efficiency and reaction sintering was investigated. After attrition milling, isopressed compacts were preheated to 1l00$^{\circ}$C with a heating rate l.5$^{\circ}C$/min and then sintered at the temperature range 1500 to 1$600^{\circ}C$ for S hours with a heating rate 5$^{\circ}C$/min. The powder mixture with fused alumina was effectively comminuted than the mixtures with calcined alumina. And the same sized balls milled more effctive than the differently sized balls. The reaction sintering behavior differed not depending on the shapes of $AI_2O_3$ powder.

• Journal of Powder Materials
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• v.22 no.4
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• pp.266-270
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• 2015

The synthesis of NiTi alloy powders by hydrogen reduction and dehydrogenation process of NiO and $TiH_2$ powder mixtures is investigated. Mixtures of NiO and $TiH_2$ powders are prepared by simple mixing for 1 h or ball milling for 24 h. Simple-mixed mixture shows that fine NiO particles are homogeneously coated on the surface of $TiH_2$ powders, whereas ball milled one exhibits the morphology with mixing of fine NiO and $TiH_2$ particles. Thermogravimetric analysis in hydrogen atmosphere reveals that the NiO and $TiH_2$ phase are changed to metallic Ni and Ti in the temperature range of 260 to $290^{\circ}C$ and 553 to $639^{\circ}C$, respectively. In the simple-mixed powders by heat-up to $700^{\circ}C$, agglomerates with solid particles and solidified liquid phase are observed, and the size of agglomerates is increased at $1000^{\circ}C$. From the XRD analysis, the presence of liquid phase is explained by the formation and melting of $NiTi_2$ inter-metallic compound due to an exothermic reaction between Ni and Ti. The simple-mixed powders, heated to $1000^{\circ}C$, lead to the formation of NiTi phase but additional Ni-, Ti-rich and Ti-oxide phases. In contrast, the microstructure of ball-milled powders is characterized by the neck-grown particles, forming $Ni_3Ti$, Ti-oxide and unreacted Ni phase.

• Journal of Powder Materials
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• v.23 no.2
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• pp.108-111
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• 2016

$Y_2O_3-H_3BO_3:Eu^{3+}$ powders are synthesized using a mechanical alloying method, and their photoluminescence (PL) properties are investigated through luminescence spectrophotometry. For samples milled for 300 min, some $Y_2O_3$ peaks ([222], [440], and [622]) and amorphous formations are observed. The 300-min-milled mixture annealed at $800^{\circ}C$ for 1 h with Eu = 8 mol% has the strongest PL intensity at every temperature increase of $100^{\circ}C$ (increasing from 700 to $1200^{\circ}C$ in $100^{\circ}C$ increments). PL peaks of the powder mixture, as excited by a xenon discharge lamp (20 kW) at 240 nm, are detected at approximately 592 nm (orange light, $^5D_o{\rightarrow}^7F_1$), 613 nm, 628 nm (red light, $^5D_o{\rightarrow}^7F_2$), and 650 nm. The PL intensity of powder mixtures milled for 120 min is generally lower than that of powder mixtures milled for 300 min under the same conditions. PL peaks due to $YBO_3$ and $Y_2O_3$ are observed for 300-min-milled $Y_2O_3-H_3BO_3$ with Eu = 8 mol% after annealing at $800^{\circ}C$ for 1 h.

• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.31-42
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• 1984

The toxic effect of adhesive resins on the dog's pulp tissue was studied with 70 teeth from 5 dogs. The experimental materials were Clearfil, a mixture of Clearfil with calcium hydroxide powder, Panavia-EX, and a mixture of Panavia-EX with calcium hydroxide powder. As a control group, calcium hydroxide powder was used. Each material was placed on the pulpotomized tissue surface. After 3 days, 1, 2,4, and 6 weeks, the teeth and apical tissue were processed routinly and stained with hematoxylin and eosin. Pathological tissue changes due to the toxicity of adhesive resins were observed by light microscope, and the pH of Panavia-EX and the Bonding agent of Clearfil were measured. Following were the results; 1. In the group of calcium hydroxide powder, slight inflammatory change was observed in the pulpotomized surface and adjacent pulp tissue on 3 day. 1 week case showed incomplete dentin bridge. The remaining pulp tissue was normalized according to the days elapsed. 2. In the group of Clearfil, early inflammatory change revealed in the superificial portion of the remaining pulp tissue on 3 day. The inflammation spreaded over the total pulp tissue and partial necrosis was observed in 1 week and 2 week cases. Total necrosis of pulp tissue and moderate inflammatory change at the apical tissue was noticed in 4 week and 6 week cases. 3. In the group of Panavia-EX, moderate inflammatory change appeared in the superficial pulp tissue on 3 day, and severe inflammatory change over all pulp tissue found in 1 week case. Pulp necrosis was obvious in 2 week case. 4 week and 6 week cases were totally necrotized up to the periapical tissue. 4. In the groups of mixtures with calcium hydroxide powder, the pulp tissue destruction was retarded, compared with the groups of Clearfil and Panavia-EX. 5. Panavia-EX was more destructive than Clearfil. 6. The acidity of freshly mixed Bonding agent of Cleafil was pH 4.0, and that of Panavia-EX was pH 2.0.

• Resources Recycling
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• v.26 no.3
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• pp.39-46
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• 2017

AlN powder was prepared by carbon reduction and subsequent nitridation method through lab- scale experiments. AlN powder was synthesized using the mixture of high purity $Al_2O_3$ powder and carbon black at $1,600{\sim}1,700^{\circ}C$ for 0.5~6 hours under nitrogen atmosphere (flow rate of nitrogen gas: $4.7{\times}10^{-6}{\sim}20{\times}10^{-6}m^3/sec$) with variation of charged height of the mixture powder. Experimental results showed that size of the synthesized particles grows with increasing of temperature. The reaction activation energy was calculated as 382 kJ/mol at the temperature range, and it was considered that chemical reaction is the rate determining step. Content of oxygen and nitrogen of the prpared samples were 0.71~0.96 wt% and 30.7~35.1 wt%. The results was similar with those of the commercial AlN product.

• Resources Recycling
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• v.26 no.1
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• pp.59-68
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• 2017

This study has been conducted to evaluate the effects of a single stage anaerobic co-biogasification of food waste and primary sewage sludge mixture (1 : 5 V/V%) according to mixing ratio (0% : CAP0, 0.5% : CAP0.5, 1%: CAP1.0) in red pepper powder, which was reported as the material anti-bacterial and anti-fungi, under mesophilic condition ($35^{\circ}C$). during 31 days. It showed that red pepper powder effected anaerobic bacteria, Especially, Hydrolytic bacteria and methanogenic bacteria was inhibited much more than Acetogenic bacteria with red pepper powder. at CAP0, Experimental cumulative methane yield (ECMY) and Experimental bio-energy production (EBEP) were 0.17 L $CH_4/g$ $VS_{fed}$ and 1,465 cal/g $VS_{fed}$ individually as the highest value during 31 days.