• Analytical Science and Technology
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• v.29 no.6
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• pp.283-292
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• 2016

Conventional fingerprint powders used during crime scene investigations pose potential health hazards. Thus, multiple natural replacement powders, including squid ink powder, indigo and rice powder were used to develop (visualize) latent fingerprints on non-porous surfaces (e.g., glass, plastic and tile). Fingerprints developed using the natural powders were compared using the Automatic Fingerprint Identification System (AFIS) with those developed with traditional black powder. The peak areas of ridges were also compared using densitometric image analyses. Collectively, objective and quantitative evaluation methods were developed. The effectiveness of natural powders varied depending on the surface but, in general, squid ink powder performed well on most surfaces. Indigo powder performed well on tile surfaces, while rice powder performed well on glass surfaces. Plastic was the most difficult surface from which to develop fingerprints. Image analysis using Field Emission Scanning Electron Microscopy (SEM) demonstrated the importance of the size and shape of natural powder particles to properly adhere to the ridges. Although densitometric image analyses did not correlate the number of minutiae and ridge peak areas, an unbiased, objective evaluation method would be possible using image analyses with a reference image. Additional experimentation will yield safe and cost-effective natural powders with which adequate fingerprint development can be performed.

• Journal of Powder Materials
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• v.18 no.1
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• pp.35-40
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• 2011

LAS-system ceramic powder, spodumene ($Li_2O{\cdot}Al_2O_3{\cdot}4SiO_2$), was successfully synthesized by a chemical solution technique employing PVA(polyvinyl alcohol) as an organic carrier. The PVA content affected the microstructure of porous precursor gels and the crystalline development. The optimum PVA content contributed to homogeneous distribution of metal ions in the precursor gel and it resulted in the synthesis of glass free $\beta$-spodumene powder having a specific surface area of $7.57\;m^2/g$. The agglomerated $\beta$-spodumene powders were also enough soft to grind to fine powders by a simple ball milling process. The microstructures of the densified powder compacts were strongly dependant on the minor phases of spodumene solid solution and amount of liquid phase, which were formed from the inhomogeneous precursors.

• Journal of Powder Materials
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• v.15 no.3
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• pp.214-220
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• 2008

In this study, consolidation behavior and hardness of commercially available molybdenum powder were investigated. In order to analyze compaction response of the powders, the elastoplastic constitutive equation based on the yield function by Shima and Oyane was applied to predict the compact density under uniaxial pressure from 100MPa to 700MPa. The compacts were sintered at $1400-1600^{\circ}C$ for 20-60 min. The sintered density and grain size of molybdenum were increased with increasing the compacting pressure and processing temperature and time. The constitutive equation, proposed by Kwon and Kim, was applied to simulate the creep densification rate and grain growth of molybdenum powder compacts. The calculated results were compared with experimental data for the powders. The effects of the porosity and grain size on the hardness of the specimens were explained based on the modified plasticity theory of porous material and Hall-Petch type equation.

• Journal of Powder Materials
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• v.11 no.4
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• pp.341-347
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• 2004

In the study, a hybrid constitutive model for densification of metallic powders was applied to cold isostatic pressing. The model is based on a pressure-dependent plasticity model for porous materials combined with a dislocation density-based viscoplastic constitutive model considering microstructural features such as grain size and inter-particle spacing. Comparison of experiment and calculated results of microscale and nanoscale Cu powders was made. This theoretical approach is useful for powder densification analysis of various powder sizes, deformation routes and powder processing methods.

• Journal of the Korean Ceramic Society
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• v.26 no.2
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• pp.242-248
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• 1989

The powder properties and sinterability of ZrO2-8m/o Y2O3 prepared by coprecipitation were investigated. The specific surface area and the total pore volume were increased with increasing pH of sediment and using of ethyl alcohol for washing. The powders of prepared by freeze drying method were showed the smallest particle size and lowest agglomerate rate, and the powders obtained from spray drying method were showed porous structure. At 130$0^{\circ}C$, their relative density were 94-96%, so these sintered bodies have revealed high sinterability in spite of low sintering temperature.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.495-497
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• 2013

SiC-$Y_2O_3$ porous composites were fabricated using $Y_2O_3$ powders synthesized by sol-gel process to control physical and thermo-chemical properties. $Y_2O_3$ powders were mixed with SiC powders by co-pressing with HPCS (hydridopolycarbosilane) binder at moderate temperature. The properties of membranes were characterized by XRD, FE-SEM, and BET surface analysis. Hydrogen permeability was performed at various temperatures.

• Korean Journal of Materials Research
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• v.22 no.1
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• pp.1-7
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• 2012

Thin film electrode consisting purely of porous anodic tin oxide with well-defined nano-channeled structure was fabricated for the first time and its electrochemical properties were investigated for application to an anode in a rechargeable lithium battery. To prepare the thin film electrode, first, a bi-layer of porous anodic tin oxides with well-defined nano-channels and discrete nano-channels with lots of lateral micro-cracks was prepared by pulsed and continuous anodization processes, respectively. Subsequent to the Cu coating on the layer, well-defined nano-channeled tin oxide was mechanically separated from the specimen, leading to an electrode comprised of porous tin oxide and a Cu current collector. The porous tin oxide nearly maintained its initial nano-structured character in spite of there being a series of fabrication steps. The resulting tin oxide film electrode reacted reversibly with lithium as an anode in a rechargeable lithium battery. Moreover, the tin oxide showed far more enhanced cycling stability than that of powders obtained from anodic tin oxides, strongly indicating that this thin film electrode is mechanically more stable against cycling-induced internal stress. In spite of the enhanced cycling stability, however, the reduction in the initial irreversible capacity and additional improvement of cycling stability are still needed to allow for practical use.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.546-552
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• 2010

The achievement of high gas permeability is a key factor in the development of porous SiC ceramics for applications of hot gas filter, vacuum chuck, and air spindle. However, few reports on the gas permeability of porous SiC ceramics can be found in the literature. In this paper, porous SiC ceramics were fabricated at temperatures ranging from $1600^{\circ}C$ to $1800^{\circ}C$ using the mixing powders of SiC, silicon, carbon and boron as starting materials. In some samples, expanded hollow microspheres as a pore former were used to make a cellular pore structure. It was possible to produce Si bonded SiC ceramics with porosities ranging from 42% to 55%. The maximum bending strength was 58MPa for the carbon content of 0.2 wt% and sintering temperature of $1700^{\circ}C$. The increase of air permeability was accelerated by addition of hollow microsphere as a pore former.

• Korean Journal of Materials Research
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• v.18 no.5
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• pp.229-234
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• 2008

Porous Ti implant samples were fabricated by the sintering of spherical Ti powders in a high vacuum furnace. To increase their surface area and biocompatibility, anodic oxidation and a hydrothermal treatment were then applied. Electrolytes in a mixture of glycerophosphate and calcium acetate were used for the anodizing treatment. The resulting oxide layer was found to have precipitated in the phase form of anatase $TiO_2$ and nano-scaled hydroxyapatite on the porous Ti implant surface. The porous Ti implant can be modified via an anodic oxidation method and a hydrothermal treatment for the enhancement of the bioactivity, and current multi-surface treatments can be applied for use in a dental implant system.

• Bulletin of the Korean Chemical Society
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• v.27 no.3
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• pp.399-402
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• 2006

Porous organic-inorganic hybrids have been prepared from tetraethylorthosilicate (TEOS) and organosilane precursors by sol-gel method. Two organosilanes, 3-(2,4-dinitrophenylamino)propyltriethoxysilane (DNPTES) and N-[[(2-nitrophenyl)methoxy]carbonyl]-3-triethoxysilylpropylamine (NPTES) were used to incorporate electron-accepting (di)nitrophenyl groups into the hybrids. The hybrids were characterized by FT-IR spectroscopy and elemental analysis, and their pore characteristics were studied by nitrogen sorption porosimetry. Surface area of the hybrids ranged from 563 to 770 $m^2$/g, pore volume, 0.23-0.30 $cm^3$/g, and porosity, 35-41%. It was demonstrated by UV-vis spectroscopy that aniline, ethylenediamine, and 1-aminonaphthalene could be removed from their hexane solutions in the presence of the hybrid powders. The removal of amines is attributable to donor-acceptor interaction between the electron-donating amines and electron-accepting (di)nitrophenyl moiety.