Geopolymer, also known as alkali aluminum silicate, is used as a substitute for Portland cement, and it is also used as a binder because of its good adhesive properties and heat resistance. Since Davidovits developed Geopolymer matrix composites (GMCs) based on the binder properties of geopolymer, they have been utilized as flame exhaust ducts and aircraft fire protection materials. Geopolymer structures are formed through hydrolysis and dehydration reactions, and their physical properties can be influenced by reaction conditions such as concentration, reaction time, and temperature. The aim of this study is to examine the effects of silica size and aging time on the mechanical properties of composites. Commercial water glass and kaolin were used to synthesize geopolymers, and two types of silica powder were added to increase the silicon content. Using carbon fiber mats, a fiber-reinforced composite material was fabricated using the hand lay-up method. Spectroscopy was used to confirm polymerization, aging effects, and heat treatment, and composite materials were used to measure flexural strength. As a result, it was confirmed that the longer time aging and use of nano-sized silica particles were helpful in improving the mechanical properties of the geopolymer matrix composite.

The Ag/WC electrical contacts were prepared via powder metallurgy using 60 wt% Ag, 40 wt% WC, and small amounts of Co3O4 with varying WC particle sizes. After the fabrication of the contact materials, microstructure observations confirmed that WC-1 had an average grain size (AGS) of 0.27 μm, and WC-2 had an AGS of 0.35 μm. The Ag matrix in WC-1 formed fine grains, whereas a significantly larger and continuous growth of the Ag matrix was observed in WC-2. This indicates the different flow behaviors of liquid Ag during the sintering process owing to the different WC sizes. The electrical conductivities of WC-1 and WC-2 were 47.8% and 60.4%, respectively, and had a significant influence on the Ag matrix. In particular, WC-2 exhibited extremely high electrical conductivity owing to its large and continuous Ag-grain matrix. The yield strengths of WC-1 and WC-2 after compression tests were 349.9 MPa and 280.7 MPa, respectively. The high yield strength of WC-1 can be attributed to the Hall–Petch effect, whereas the low yield strength of WC-2 can be explained by the high fraction of high-angle boundaries (HAB) between the WC grains. Furthermore, the relationships between the microstructure, electrical/mechanical properties, and deformation mechanisms were evaluated.

This study examined the effects of micro- (crystallinity) and macro (orientation)-crystalline properties of graphite on the initial efficiency, discharge capacity, and rate performance of anodic materials. Needle coke and regular coke were selected as raw materials and pulverized to 2–25 μm to determine the effects of crystalline properties on particle shape after pulverization. Needle coke with outstanding crystallinity had high initial efficiency, and smaller particles with larger specific surface areas saw increased irreversible capacity due to the formation of SEI layers. Because of cavities existing between crystals, the poorer the crystalline properties were, the greater the capacity of the lithium ions increased. As such, regular coke had a 30 mAh/g higher discharge capacity than that of needle coke. Rate performance was more affected by particle size than by crystalline structure, and was the highest at a particle distribution of 10–15 μm.

Recycled cenosphere, which is a hollow shaped particle from fly ash, has become attractive as a building material due to its light weight and excellent heat insulation and soundproof properties. In this paper, we investigated the effect of cenosphere size on the physical and optical properties. High brightness of cenosphere as raw material is required for a wide range of ceramics applications, particularly in fields of building materials and industrial ceramic tiles. Cenospheres were sorted by particle size; the microstructure was analyzed according to the cenosphere size distribution. Cenospheres were generally composed of quartz, mullite, and amorphous phase. Colour measurement corresponding to chemical composition revealed that the contents of iron oxide and carbon in the cenospheres were the major factors determining the brightness of the cenospheres.

The red ginseng is known to have effects on antioxidativity and cytotoxicity. Nanoscale active substances have various advantages such as improved bioavailability and permeation ability into the cell. However, few studies conducted with the nanoparticles of red ginseng due to its low yield rate and difficulty of manufacturing the product in pilot scale. This study, therefore, investigated the size effects of ultra-fine powder of red ginseng on antioxidativity and cytotoxicity. Red ginseng powder (6, 8, or 158 μm) prepared using a pilot scale was provided by a local company. Antioxidativity was measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assays, and cytotoxicity was tested by methylthiazolyl tetrazolium (MTT) assay. The results of DPPH and ABTS radical electron donating ability IC50 of red ginseng were ranged from 2.27 to 3.34 mg/ml and 2.94 to 3.09 mg/ml, respectively, which were not significantly different between all samples. However, the results of cytotoxicity clearly showed a pattern of decreased toxicity in 6 and 8 μm power compared to 158 μm powder. Unexpectedly, particle sizes of red ginseng did not significantly affect antioxidativity. It is believed that these were related to the process of pilot scale production. These phenomena are also believed to be caused by aggregation of low size power particle that increases water holding capacity. From our result, it is concluded that this range of particle size of red ginseng affected the reduction of cytotoxicity.

The purpose of this study is to find out the effect of particle size of sediment on adsorption of fluoride. Particle size is classified as sand, silt and clay. Adsorption equilibrium time, adsorption isotherms and the effect of pH were investigated through batch tests. The pHpzc of sand, silt, clay was respectively 6, 8, 4.5 and AEC (anion exchange capacity) was highest in silt, respectively 0.0095, 0.0224, 0.014 meq g-1. Adsorption of fluoride on the sediment was in equilibrium within 300 minutes from all particle size. The experimental data of isotherms at various pH were well explained by Freundlich equation. As the experimental results of the effect of pH, the adsorption efficiency of sand and silt were reduced after the pHpzc. However, the adsorption efficiency of clay was maintained after the pHpzc, and decreased rapidly higher than pH 12.

This study investigates the thermal shock property of a polycrystalline diamond compact (PDC) produced by a high-pressure, high-temperature (HPHT) sintering process. Three kinds of PDCs are manufactured by the HPHT sintering process using different particle sizes of the initial diamond powders: 8-16 μm (D50 = 4.3 μm), 10-20 μm (D50 = 6.92 μm), and 12-22 μm (D50 = 8.94 μm). The microstructure observation results for the manufactured PDCs reveal that elemental Co and W are present along the interface of the diamond particles. The fractions of Co and WC in the PDC increase as the initial particle size decreases. The manufactured PDCs are subjected to thermal shock tests at two temperatures of 780oC and 830oC. The results reveal that the PDC with a smaller particle size of diamond easily produces microscale thermal cracks. This is mainly because of the abundant presence of Co and WC phases along the diamond interface and the easy formation of Co-based (CoO, Co3O4) and W-based (WO2) oxides in the PDC using smaller diamond particles. The microstructural factors for controlling the thermal shock property of PDC material are also discussed.

본 연구에서는 입자크기가 다른 3가지 α-알루미나 분체로부터 주입성형법과 소결법을 혼용하여 튜브형 α-알루 미나 지지체를 제조하여 초기 α-알루미나 분체의 입자크기와 소결 온도가 지지체의 기공구조와 기체투과 특성에 미치는 영 향을 고찰하였다. 평균입경이 0.2, 0.5, 1.7 μm인 α-알루미나 분체를 사용했을 시 제조된 α-알루미나 지지체는 각각 약 80, 130, 200 nm의 평균 기공경을 가졌으며 평균 기공경은 소결 온도 보다는 초기 알루미나 분체의 입자크기에 의존하였다. 모 든 시편에서 소결 온도가 증가할수록 지지체의 부피 밀도는 증가하였고 겉보기 기공률은 감소하였다. He, N2, O2, CO2에 대 하여 30°C에서 단일기체 투과 특성을 평가한 결과, 기체 투과도는 기공경 제곱에 비례하여 증가하였고 기공률이 증가함에 따 라서 직선적으로 증가하였다. 이를 토대로 제조된 α-알루미나 지지체의 기체 투과는 점성유동(viscous flow)에 의하여 이루 어지며, α-알루미나 지지체의 기체 투과 특성은 초기 α-알루미나 분체의 입자크기와 소결온도를 제어함으로써 조절될 수 있 음을 확인할 수 있었다.

In general, the larvae of Protaetia brevitarsis is raised on fermented oakwood sawdust. Many attempts have been to changes components sawdust, such as using other tree instead of oakwood or adding another material. Like this some study exists, about 'component' of sawdust, however little is known of relation between larval growth and quality of sawdust. The phenomenon-big particle size sawdust flows up on excrement from the larvae-is occurring in used sawdust for raising the larvae. This study was conducted to observe the larvae and adult of Protaetia brevitarsis act according to each sawdust particle size. We conducted choice experiments with Protaetia brevitarsis, which were offered sawdust differing in particle size. Females preferred to lay their eggs on the fine particle sawdust. Also in the case of larvae, the more fine sawdust particle has the more high level of preference, and so is hatchability. Especially larvae tend to be slanted toward finer sawdust. Growth rate of the larvae was shown the highest level in the finest sawdust just as others do. These results show that fine sawdust particle size is advantage for larval development and oviposition.

본 실험은 초고압과 입자도 차이에 따른 더덕의 외피와 육질의 항산화 활성을 비교 진행하였다. 외피의 경우 입자도 크기에 따른 항산화 활성의 유의 차가 나타나지 않았지만, 육질의 경우에는 입자도 크기에 따른 항산화 활성의 유의 차가 나타났다. 초고압 하에서 실시한 더덕 외피에서는 입자도간 항산화 활성의 유의차가 나타나지 않았다. 반면 육질에서는 초고압 처리한 압력에 따라 또한 측정한 항산화 성분에 따라 입자도 간에 유의차가 나타났다. 이와 같은 현상은 시료를 구성하는 물질이 서로 다른 경도를 지니고 있어서 내부저항에 차이가 생기는 것에 기인하며 초고압 처리가 내부저항에 작용하는 정도에 따라 기인되었을 것으로 추론한다. 이 같은 결과로 더덕을 외피와 육질을 분리하지 않은 채 입자도 영향을 분석할 경우 입자의 크기가 큰 영역에 항산화도가 높은 외피가 많이 분포되어 오히려 항산화도가 높음을 관찰하였다.

건강기능성 물질을 함유하며 고유의 색과 향미를 가지는 유색감자 홍영 분말을 첨가한 반죽 및 면의 물리화학적 특성을 확인하였다. 홍영 미세 분말은 ball-milling을 통하여 제조하였으며, 매우 낮은 입자도로 인하여 감자의 세포 및 전분 구조가 파괴되어 손상 전분의 함량이 높았다. 이 같은 손상 전분은 낮은 온도에서 물을 흡수하고 팽창하는 성질이 높아 일반 분쇄를 통하여 얻은 분말로 제조한 반죽에 비하여 BM 분말을 반죽에 첨가하였을 때 탄성이 높고 자유수가 적은 반죽 및 면이 제조되었다. 입자 크기를 달리하여 분쇄한 홍영 분말의 경우 손상 전분이 아닌 첨가 분말의 표면적에 의하여 영향을 받으므로 입자 크기가 클수록 반죽 내의 자유수가 많아 열처리 시 더 많은 호화가 발생하였다. 홍영 분말을 첨가한 경우 홍영 특유의 붉은색이 증가함을 확인하였으며, 홍영 분말의 입자 크기가 커질수록 적색도가 감소하였다. 홍영 분말의 다양한 입자 크기에 따라 손상 전분의 발생 및 입자의 표면적에 의하여 서로 다른 호화 특성 및 면 반죽의 조직감을 나타내었다. 본 연구 결과를 통하여 미세 분말(BM)의 경우 손상 전분으로 인하여 생반죽의 탄성이 밀가루에 비하여 매우 높아 성형에 더 많은 힘이 필요함을 확인할 수 있었다. 따라서 미세 분말인 BM 분말과 다르게 생반죽의 성형이 용이하면서 홍영 특유의 붉은 색을 가장 잘 나타내며, 조리 이후 반죽의 탄성을 향상시키고 밀가루와 인장력에 유의차가 나타나지 않는 R1 및 R2 분말로 제조한 면이 우수한 품질을 나타냄을 확인하였다. 본 연구 결과는 전분을 함유하는 대체 분말을 이용한 제면 제품의 개발 시 입자 크기의 결정에 대한 기반이 될 수 있을 것으로 사료된다.

The milling characteristics of rice using different milling methods (dry and wet) were investigated. Generally, average particle sizes of dry-milling flours were bigger than those of wet-milling flours due to low moisture content. Three theoretical models for milling, such as the Rittinger, Kick, and Bond model, were applied to characterize the milling process of rice. The wet-milling method showed higher value milling constants including Bond’s work index. Baeksulgi was used to study the effect of the milling method and particle size on rice flour’s physicochemical property (water content, color value, and texture). Moisture content and hardness of Baeksulgi were smaller as the particle size became smaller. L value of Baeksulgi was greater as the particle size became smaller. The energy requirement for the milling of grains to obtain a suitable size of particles was estimated by the grinding models. The results of our study might provide a systematic way to estimate the energy requirement to obtain a suitable particle size by milling

The purpose of this study was to investigate the microstructures and mechanical properties of zirconia toughened alumina (ZTA) ceramics prepared from two kinds of 3Y-TZP powders. ZTA composites were prepared by adding two kinds of 3Y-TZP powders, 3YEH (BET = 7m2/g) and 3YEM (BET = 16m2/g), to α-alumina in the range of 5-25 wt%. It was found that the microstructure photographs of the ZTA composites showed that the average grain size of alumina decreased as the content of zirconia increased. In our present study, specimens containing 3YEM zirconia exhibited smaller grain sizes compared to those of 3YEH zirconia. The Vickers hardness of the ZTA composites that were sintered at 1600˚C for 2 hrs was found to smoothly decrease with increasing zirconia content because of the low Young modulus in zirconia. The Vickers hardness of the ZTA containing 3YEH zirconia was greater than that of the 3YEM zirconia. In substance, the fracture toughness (K1c) of the ZTA composites increased as the content of zirconia increased. The fracture toughness (K1c) of ZTA containing 3YEM zirconia was greater than that of 3YEH zirconia.

This study is focused on investigating the relation between the particle size of silver flake powder and mechanical milling parameters. Mechanical milling parameters such as ball size, impeller rotation speed and milling time of the attrition ball-mill were controlled to produce silver flake powder. The particle size of the silver flake powder increased with increasing ball size and impeller rotation speed. The change of the particle size of the silver flake powder with mechanical milling parameters was analyzed based on balls motion in the mill container of the attrition ball-mill. The silver flake particles were formed at the elastic deformation area of the ball due to the collision between balls. The change of the particle size of the silver flake powder with mechanical milling parameters well consists with the change of the collision energy of ball with parameters mentioned above.

Fly ash is one of the aluminosilicate sources used for the synthesis of geopolymers. The particle size distribution of fly ash and the content of unburned carbon residue are known to affect the compressive strength of geopolymers. In this study, the effects of particle size and unburned carbon content of fly ash on the compressive strength of geopolymers have been studied over a compositional range in geopolymer gels. Unburned carbon was effectively separated in the -46μm fraction using an air classifier and the fixed carbon content declined from 3.04 wt% to 0.06 wt%. The mean particle size (d50) decreased from 22.17μm to 10.79μm. Size separation of fly ash by air classification resulted in reduced particle size and carbon residue content with a collateral increase in reactivity with alkali activators. Geopolymers produced from carbon-free ash, which was separated by air classification, developed up to 50 % higher compressive strength compared to geopolymers synthesized from raw ash. It was presumed that porous carbon particles hinder geopolymerization by trapping vitreous spheres in the pores of carbon particles and allowing them to remain intact in spite of alkaline attack. The microstructure of the geopolymers did not vary considerably with compressive strength, but the highest connectivity of the geopolymer gel network was achieved when the Si/Al ratio of the geopolymer gel was 5.0.

In this paper we have studied the effect of water droplet size on nano-particle size distribution using SMPS(Scanning Mobility Particle Sizer)system. It can be seen that the unknown peak at >100 nm was caused by water droplets which did not dry completely when DI water was used as a solvent in the SMPS system. Therefore, it is important to dry water droplets generated from atomizer in the SMPS system when measuring the particle size distribution using less than 100 nm nano-particles in diameter. From this study, It can be concluded that the napion was a useful material as dryer ones and using EAG(Electro Aerosol Generator) as a particle generator was the most effective in reducing the effect of water droplets.

In the current study, the effects of particle size on compaction behavior of water-atomized pure iron powders are investigated. The iron powders are assorted into three groups depending on the particle size; 20-45 , 75-106 , and 150-180 for the compaction experiments. The powder compaction procedures are processed with pressure of 200, 400, 600, and 800 MPa in a cylindrical die. After the compaction stage, the group having 150-180 of particle size distribution shows the best densification behavior and reaches the highest green density. The reason for these results can be explained by the largest average grain size in the largest particle group, due to the low plastic deformation resistance in large grain sized materials.