• Journal of the Korean Wood Science and Technology
• /
• v.43 no.6
• /
• pp.757-767
• /
• 2015

This study was conducted to investigate the effects of moisture content and particle size of sawdust on the fuel characteristics of wood pellets produced with Mongolian oak (Quercus mongolica, QUM), red pine (Pinus densiflora, PID) and larch (Larix kaempferi, LAK) sawdust using a flat-die pelletizer. Prior to produce wood pellets, the sawdust was controlled to the moisture content of 8, 11, 12% and was screened to the particle size of 2 and 4 mesh. In the analysis of its chemical composition, QUM had a high ash content, and PID and LAK contained large amount of lignin. In case of the fuel characteristics, PID pellets had the lowest moisture content of pellets (P-MC), and LAR pellets was found to have the highest bilk density (BD) and durability (DU). With the increase of moisture content of sawdust (S-MC), P-MC and DU of QUM, PID and LAK pellets increased, but BD of QUM and LAK pellets decreased. When size of sawdust used for the production of wood pellets decreased, P-MC and BD of LAK pellets and BD of QUM pellets increased. Decrease of particle size contributed to the increase of DU of QUM, PID and LAK pellets. In addition, BD and DU of QUM pellets produced with 12% S-MC sawdust increased as its particle size reduced. For LAK pellets, DU was not influence by particle size in the S-MCs of 10% and 12%, but increased with the decrease of particle size in the S-MC of 8%. Based on the results and economical aspects, 10% MC and 2 mesh paricle size for QUM sawdust and 12% MC and 2 mesh particle size for PID sawdust might be optimal conditions for pellets production, and fuel characteristics of wood pellets produced by the conditions greatly exceeded the minimum requirements for the $1^{st}$-grade wood pellets of the standard designated by Korea Forest Research Institute.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.4
• /
• pp.400-406
• /
• 2023

In this study, the relationship between the material properties and air permeability characteristics was examined, an experimental method to analyze the air permeability characteristics was presented, and experimental results were derived. The effects of compressive strength and apparent density of hardened concrete on air permeability characteristics were evaluated experimentally. Focusing on the mix proportions used in nuclear power plant concrete structures, concrete test specimens were manufactured and air permeability characteristics were measured according to changes in binder, maximum aggregate size, and water-binder ratio. The apparent density was over 2,400 kg/m³ for the OPC mix and the FA-35 mix, and the air permeability for both mixes were low, in the range of 0.1-0.2 L/min. On the other hand, in the case of the combination of FA-40, FA-45, and FA-M, the apparent density was measured to be less than 2,400 kg/m³ and the air permeability was measured to be more than 0.3 L/min, experimentally verifying that the apparent density is an important factor in air permeability characteristics.

• Resources Recycling
• /
• v.9 no.2
• /
• pp.40-45
• /
• 2000

Low density ceramic supporter was prepared by using fly ash as a starting mterial with borax or glass powders. Also the wheat powders were used by 30 wt% to increase the initial porosity of the supporter. The density of the supporter decreased as the amount of borax increased. The bulk density of $0.79g/\textrm{cm}^3$ and the apparent density of $1.10g/\textrm{cm}^3$ were obtained when the fly ash with 15% of borax was sintered at $1160^{\circ}C$ for 15 minutes. The density also decreased as the plate glass powders past through $212\mu\textrm{m}$ size were mixed. When the fly ash with 12% of glass powder was sintered at $1280^{\circ}C$ for 10 minutes, the bulk and apparent density were $0.90g/\textrm{cm}^3$ and $1.00g/\textrm{cm}^3$, respectively.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2003.11a
• /
• pp.50-50
• /
• 2003

용사 공정은 소재의 표면 특성을 개질하기 위한 가장 효과적인 공정의 하나로서, 최근 항공기용 엔진 부품을 포함하여 자동차, 및 각종 산업 분야에 폭 넓게 사용되고 있으나, 산업 환경의 고도화로 용사 코팅층의 다양한 분야에서의 고특성화가 요구되고 있다. 소재의 나노화는 이러 한 소재의 고 특성화 요구에 부응할 수 있는 새로운 기술로서, 현재 많은 분야에서 응용이 진행되고 있다. 특히 최근에는 나노기술을 용사 공정에 응용하기 위한 시도가 진행되고 있으나, 나노 분말 제조 기술이 아직 확립되어 있지 않고, 또한 나노 분말을 용사 공정에 응용하기 위한 기술의 부족으로 나노 용사공정에의 적용은 제한을 받고 있다. 이를 위해서는 나노분말 제조 기술의 개발이 이루어져야하고, 나노 분말 제조 기술과 용사 분말 제조 기술 그리고 용사 기술의 접목이 이루어 져야하는 어려움이 있다. 본 연구에서는 나노 용사용 분말을 제조하기 위 한 원료용 나노 분말을 화학적 공정에 의하여 제조 한 후, 이 분말의 유동도 및 밀도 제어를 위한 후 처리 공정을 개발하였다. 제조된 분말의 입자 크기는 약 150nm였으며, 용사 분말 제조후 분말의 겉보기 겉보기 밀도가 3.8g/cc로서 일반 용사용 분말에 비하여 우수하였다.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.11a
• /
• pp.185-186
• /
• 2023

In the production of high-strength concrete of 80 MPa or more, silica fume is widely used as a binder to ensure the strength safety and pumpability of concrete. The bulk density of silica fume is an important physical property that can have a significant impact on the performance of concrete. Therefore, Understanding the effect of silica fume density on the physical properties of concrete and selecting the appropriate material with the correct density is crucial to ensuring optimal performance in construction projects.

• Clean Technology
• /
• v.29 no.4
• /
• pp.249-254
• /
• 2023

In this study, porosity estimation was conducted by the physical properties of zeolite. Because of the difficulty of directly measuring the porosity of particulate matter, the porosity was calculated by applying the measured physical properties of zeolite to the calculation formula presented in various literature. For this purpose, the average particle size, particle size distribution, specific surface area, and pore characteristics of three types of zeolite - zeolite beta, zeolite Y, and ZSM-5 - were measured. In addition, the true density using gas and liquid phases, and two types apparent density (tap and untapped density) were measured. We calculated the porosity using these results, compare and analyzed the results, and evaluated main factors that determine the porosity.

• Resources Recycling
• /
• v.25 no.6
• /
• pp.92-97
• /
• 2016

Spray dried $Cr_2O_3$ powder having an agglomerated structure of particles was twice treated into a plasma flame to increase its apparent density. The powder subjected to the first densification treatment did not show the entirely melted state keeping inner particle hollows, and it was fully melted after the second processing only. The powder size as a result of the second treatment decreased, and the apparent density as well as flowability were increased due to melting and surface smoothing effects. But a part of particles after the second densified treatment showed the hollow structure, especially those which were above $30{\mu}m$ in size. This densification behavior of the powder has been qualitatively discussed in terms of the thermal conductivity and inner gas pressure within aggregates exposed to the plasma flame.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2015.11a
• /
• pp.327-328
• /
• 2015

본 연구에서는 전기도금법을 이용하여 수지상(Dendrite) 구리 분말을 제조할 때 첨가제 유무를 비교하였다. 인가전위, 첨가제의 종류(JGB, PEG) 및 농도에 따른 수지상의 형상적인 특성이 비교되었으며, 겉보기 밀도와 비표면적(BET)이 측정되었다. 형상적 특성은 수지상의 2차 가지와 추축의 두께 비(ratio)로 비교한 결과 JGB 첨가(10ppm) 도금욕에서 30.67로 가장 큰값을 가지며, 겉보기 밀도는 JGB 첨가(80ppm)에서 $1.115g/cm^3fh$ 가장 낮은값을 보였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2015.05a
• /
• pp.148-149
• /
• 2015

본 연구에서는 전기 도금법을 이용하여 수 마이크로미터(${\mu}m$)에서 수십 마이크로미터 크기의 수지상(dendrite) 구리분말을 제조하였다. 구리 도금욕의 종류($Cu_2P_2O_7$, $CuSO_4$, $CuCl_2$), 인가 전위(E, Volt) 및 기판에 따른 수지상(Dendrite)의 형상적인 특성이 비교되었으며, 형상에 따른 겉보기밀도와 비표면적 측정(BET)이 진행되었다. 수지상의 2차 가지길이와 주축길이의 비(ratio)를 형상의 차이로 분류한 결과 염화구리 도금욕에서 0.14 로서 가장 큰 값을 가지며 겉보기 밀도는 $1.04g/cm^3$로 가장 낮은 값을 보였다.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.4 no.4
• /
• pp.363-370
• /
• 2016

Lightweight geopolymers are more readily produced and give higher fire resistant performance than foam cement concrete. Lowering the density of solid geopolymers can be achieved by inducing chemical reactions that entrain gases to foam the geopolymer structure. This paper reports on the effects of adding different concentrations of aluminum powder on the properties of cellular structured geopolymers. The apparent density of lightweight geopolymers has a range from 0.7 to $1.2g/m^3$ with 0.025, 0.05 and 0.10 wt% of a foaming agent concentration, which corresponds to about 37~60 % of the apparent density, $1.96g/cm^3$, of solid geopolymers. The compressive strength of cellular structured geopolymers decreased to 6~18 % of the compressive strength, 45 MPa of solid geopolymers. The microstructure of geopolymers gel was equivalent for both solid and cellular structured geopolymers. The workability of geopolymers with polyprophylene fibers needs to be improved as in fiber-reinforced cement concrete. The lightweight geopolymers could be used as indoor wall tile or board due to fire resistance and incombustibility of geopolymers.