• Journal of Powder Materials
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• v.17 no.2
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• pp.101-106
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• 2010

In this study, we successfully synthesized a nano-sized lanthanum-modified lead-titanate (PLT) powder with a perovskite structure using a high-energy mechanochemical process (MCP). In addition, the sintering behavior of synthesized PLT nanopowder was investigated and the sintering temperature that can make the full dense PLT specimen decreased to below $1050^{\circ}C$ by using $Bi_2O_3$ powder as sintering agent. The pure PLT phase of perovskite structure was formed after MCP was conducted for 4 h and the average size of the particles was approximately 20 nm. After sintered at 1050 and $1150^{\circ}C$, the relative density of PLT was about 93.84 and 95.78%, respectively. The density of PLT increased with adding $Bi_2O_3$ and the specimen with the relative densitiy over 96% were fabricated below $1050^{\circ}C$ when 2 wt% of $Bi_2O_3$ was added.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.37-38
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• 2013

The fine powder obtained from the manufacturing process of recycled coarse aggregate contains unhydareted cement particles on their surface. It is believed that the alkalinity of the powder (11.0-12.5) is enough to active the slag-based composites. In this paper, the obtained powder was sieved and divided into two sizes, i.e., 0.08 mm and 0.3 mm, and added to the slag-based mortar. Results showed that the fine powder had an effect on the slump and the compressive strength of slag-based composites. With the different pH values of the powder, it could be seen that the distance between the two level powders. And found the peak 28 days compressive strength as the replacement ratio of the recycled aggregate powder changed. The findings from this study provide an indication that with achieved compressive strength, the fine powder can be used in a light weight concrete.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.1
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• pp.138-144
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• 1998

$\alpha$-$Fe_2O_3$ fine powders with the sizes smaller than 0.5 $\mu \textrm{m}$ were prepared by the solvolysis and condensation reaction using iron(III) nitrate and ethanol as starting materials. The variation of pH and the change of FT-IR absorption peak were observed to study the reaction mechanism of iron(III) nitrate solution. In addition, the decomposition mechanism of the precipitated gel was investigated by differential scanning calorimeter, X-ray diffractometer and FT-IR spectrometer. Scanning electron microscope and BET method were performed to analyze the effects of Iron (III) nitrate concentration and reaction temperature on the particle size of $\alpha$-$Fe_2O_3$ powders.

• Korean Journal of Materials Research
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• v.17 no.1
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• pp.50-55
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• 2007

Ultra-fine Copper powder for a conductive paste in electric-electronic field have been synthesized by chemical reduction of aqueous $CuSO_4$ with hydrazine hydrate $(N_2H_4{\cdot}H_2O)$ as a reductor. The effect of reaction conditions such as dispersant and reaction temperature on the particle size and shape for the prepared Cu powders was investigated by means of XRD, SEM, TEM and TGA. Experiments showed that type of dispersant and reaction temperature were affected on the particle size and morphology of the copper powder. When the carboxymethyl cellulose (CMC) was added as a dispersant the relative mono-dispersed and spherical Cu powder was obtained. Cu powders with particle size of approximately 140nm and narrow particle size distribution were obtained from 0.3M $CuSO_4$ with adding of 0.03M CMC and 40ml $N_2H_4{\cdot}H_2O$ at a reaction temperature of $70^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.6
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• pp.538-544
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• 2000

The laser patterning of sputter-deposited CoNdZr/Cu/CoNbZr multi-layered films had been tried using Nd:YAG laser. However generally it is very difficult to remove metal films because of their high reflectance of the laser on the surfaces. As a counterproposal for this problem authors for the first time tried to deposit energy-absorbing layers on the metal films and then irradiated the laser on the surfaces of energy-absorbing layers. Here the energy-absorbing layers consisted of laser energy-absorbing fine powders and binding polymers. Three kinds of powders for the energy-absorbing layers had been used to see the difference in the pattern formation with the degree of laser energy absorption. They were electrically conductive silver powders insulating BaTiO$_3$powder and semiconducting carbon powder. Remarkable difference in width of the formed pattern and the roughness of pattern edge were observed with the characteristic of the powder for the energy-absorbing layer. The pattern width using carbon paste was about three times larger than that using BaTiO$_3$paste. It was observed that the energy-absorbing layer with carbon was the most effective on this micro-patterning.

• Journal of the Optical Society of Korea
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• v.16 no.1
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• pp.36-41
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• 2012

Polymethylmethacrylate powders are commonly used to improve the spreadability and blurring effects of powder foundation cosmetics. In this study, the opacity and haze effect of four types of polymethylmethacrylate powders and their 10wt% powder foundation formulation was evaluated. The distorted random hemispherical particulates with both concave and convex portions showed the highest haze and opacity value as a single powder substance. And as a formulated phase, the powder foundation formulation containing particulates with fine pores provided the highest haze and opacity value. We also examined the quantity of reflected light over the angular range $20-75^{\circ}$ by polarized light goniophotometry. The total reflected light intensity, surface-reflected light, and internally reflected light were characterized. These studies demonstrated that hemispherical PMMA powders produce natural brilliance by creating high internally reflected light which is similar to the total reflection profile of artificial skin.

• Journal of the Korean Ceramic Society
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• v.32 no.6
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• pp.726-734
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• 1995

Pb(Zr0.53Ti0.47)O3 (PZT) ceramics having different microstructures were fabricated at low temperatures using calcined PZT powders with addition of excess PbO powder and/or ball milling. The effects of excess PbO and ball milling time on the microstructure, the sintering characteristic, and the mechanical properties of these ceramics were studied. Fine powders with average particle size of 0.38㎛ could be obtained by ball milling with 2.5 mm Ф zirconia balls for 120 hours. By the addition of 2mol% of excess PbO to these powders, it was possible to obtain well-densitified PZT ceramics at low sintering temperature of 980℃. Densification behavior of PZT was affected by the addition of excess PbO powder, while, grain growth was hardly affected by PbO addition. It was observed that Vicker's hardness decreased and fracture toughness increased with the increasing amount of PbO. At 1mol% excess PbO, it was shown that the minimum values of hardness and maximum fracture toughness were achieved. In addition, with increasing sintering time, the fracture toughness decreased and the hardness increased.

• Journal of Powder Materials
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• v.1 no.1
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• pp.42-51
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• 1994

6061Al-SiCP metal matrix composite materials(MMCs) were fabricated by injecting SiCP particles directly into the atomized spray. The main attraction of this technique is the rapid fabrication of semi-finished, composite products in a combined atomization, particulate injection(10 $\mu\textrm{m}$, 40 $\mu\textrm{m}$, SiCP) and deposition operation. Conclusions obtained are as follows; The microstructure of the unreinforced spray formed 6061Al alloy consisted of relatively fine(50 $\mu\textrm{m}$) equiaxed grains. By comparision, the microstructure of the I/M materials was segregated and consisted of relatively coarse(150 $\mu\textrm{m}$) grains. The probability of clustering of SiCP particles in co-sprayed metal matrix composites increased it ceramic particle size(SiCP) was reduced and the volume fraction was held constant. Analysis of overspray powders collected from the spray atomization and deposition experiments indicated that morphology of powders were nearly spherical and degree of powders sphercity was deviated due to composite with SiCp particles. Interfacial bonding between matrix and ceramics was improved by heat treatment and addition of alloying elements(Mg). Maximum hardness values [Hv: 165 kg/mm2 for Al-10 $\mu\textrm{m}$ SiCp Hv--159 kg/mm2 for Al-40 $\mu\textrm{m}$SiCp] were obtained through the solution heat treatment at $530^{\circ}C$ for 2 hrs and aging at $178^{\circ}C$, and there by the resistance were improved.

• Journal of Powder Materials
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• v.14 no.5
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• pp.287-291
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• 2007

Oxidation behavior and microstructural characteristics of nano-sized Sn powder were studied. DTA-TG analysis showed that the Sn powder exhibited an endothermic peak at $227^{\circ}C$ and exothermic peak at $560^{\circ}C$ with an increase in weight. Based on the phase diagram consideration of Sn-O system and XRD analysis, it was interpreted that the first peak was for the melting of Sn powder and the second peak resulted from the formation of $SnO_2$ phase. Microstructural observation revealed that the $SnO_2$ powder, heated to $1000^{\circ}C$ under air atmosphere, consisted of agglomerates with large particle size due to the melting of Sn powder during heat treatment. Finally, fine $SnO_2$ powders with an average size of 50nm can be fabricated by controlled heat treatment and ultrasonic milling process.

• Journal of Powder Materials
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• v.25 no.4
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• pp.309-315
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• 2018

In the present work, we synthesize nano-sized ZnO, $SnO_2$, and $TiO_2$ powders by hydrothermal reaction using metal chlorides. We also examine the energy-storage characteristics of the resulting materials to evaluate the potential application of these powders to dye-sensitized solar cells. The control of processing parameters such as pressure, temperature, and the concentration of aqueous solution results in the formation of a variety of powder morphologies with different sizes. Nano-rod, nano-flower, and spherical powders are easily formed with the present method. Heat treatment after the hydrothermal reaction usually increases the size of the powder. At temperatures above $1000^{\circ}C$, a complete collapse of the shape occurs. With regard to the capacity of DSSC materials, the hydrothermally synthesized $TiO_2$ results in the highest current density of $9.1mA/cm^2$ among the examined oxides. This is attributed to the fine particle size and morphology with large specific surface area.