• Journal of the Korean Wood Science and Technology
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• 제45권6호
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• pp.872-882
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• 2017

The objective of this study was to evaluate the properties of bamboo oriented strand board (B-OSB) from andong (Gigantochloa psedoarundinacea) and betung (Dendrocalamus asper) with and without steam treatment. Strands were steam-treated at $126^{\circ}C$ for 1 h under 0.14 MPa pressure. The extractive content of bamboo strands before and after steam treatment were determined according to a standard (TAPPI T 204 om-88). Three-layer B-OSB with the core layer perpendicular to the surface and back layers were formed and binded with 8% of phenol formaldehyde (PF) resin with the addition of 1% of wax. The evaluation of physical and mechanical properties of the boards were conducted in accordance with the JIS A 5908:2003 standard. The results showed that steam treatment of bamboo strands significantly reduced the extractive content. Steam treatment tended to increase the dimensional stability and mechanical properties of B-OSB from andong and betung. The results showed that the dimensional stability and bending strength of B-OSB from betung was higher than those of andong. The internal bond strength of B-OSB from andong was higher than betung owing to a greater amount of extractives dissolved during the steam treatment.

• Korean Chemical Engineering Research
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• 제56권3호
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• pp.303-308
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• 2018

본 연구에서는 리튬이차전지 음극활물질인 Silicon/Carbon (Si/C) 복합소재를 제조하여 바인더 및 첨가제가 전지성능에 미치는 영향을 조사하였다. Si/C 합성물은 마그네슘의 열 환원 반응을 통해 SBA-15 (Santa Barbara Amorphous material No. 15)를 제조한 후 페놀 수지의 탄화 과정을 통해 합성하였다. Si/C 음극소재는 충 방전, 순환전압전류, 임피던스 테스트를 통해 전기화학적 성능을 분석하였다. PAA 바인더를 이용한 Si/C 전지의 용량은 1,899 mAh/g으로 다른 바인더를 사용한 합성물보다 우수하였으며, 40 사이클 동안 92%에 달하는 높은 용량 보존율을 나타내었다. 또한, VC 첨가제를 사용한 전지의 경우 3,049 mAh/g의 높은 초기용량을 나타내며, 실리콘 표면에 보호막을 형성해 초기 비가역용량을 감소시켜줌을 알 수 있었다.

• Journal of the Korean Wood Science and Technology
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• 제39권5호
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• pp.451-458
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• 2011

Adhesives derived from renewable resources allow wood panel producers to make lower cost alternatives to formaldehyde-based adhesive resins. Among them, adhesive components extracted from industrial by-products or wastes are the most important research fields in the efficient utilization of waste and cost reduction. In our study, the rapeseed flour, which is a by product from the production of biodiesel extracted from rapeseed, was introduced to develop alternative adhesives for the production of wood flooring. The rapeseed flour was hydrolyzed with 1% sodium hydroxide solution and PF prepolymers were prepared with 3-molar ratios, 1.8, 2.1 and 2.4. The linear fracture mechanics was introduced to evaluate the glue bond quality in wood flooring composed of fancy-veneered and plywood, and the formaldehyde emission and adhesive penetration were also investigated. The formaldehyde emissions of wood flooring met the requirement of the standard of $SE_0$ specified in the KS standard. The rapeseed flour adhesive penetrated sufficiently into the vessel elements and lumens in fancy veneer and plywood and gave strong bond quality to the wood flooring. The fracture mechanics was introduced to evaluate the adhesive joint between fancy veneer and plywood. The critical stress intensity factor ($K_{IC}$) of boliva overlayed wood flooring was increased with increasing molar ratio and this was the same tendency in oak overlayed wood flooring. From the results, the formulated adhesives were efficiently used to bond fancy veneer onto the plywood to make wood flooring and showed a potential to be used as a component of environmentally friendly adhesive resin systems for production of flooring.

• Tribology and Lubricants
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• 제33권1호
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• pp.15-22
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• 2017

Because the running speed of vehicles is increasing and a shorter braking distance is required, high heat-resistant brake pads are needed to satisfy the requirements of customers and car makers. In the near future, hazardous materials such as Cu, Cr, Zn, and Sb will be restricted from use in friction materials. Ceramic composites reinforced by carbon fibers are good candidates for eco-friendly friction materials. In this study, we develop ceramic composite friction materials. The friction materials are composed of carbon fibers, Si, SiC, graphite, and phenol resin and are prepared by hot forming and heat treatment at high temperatures. The density, void ratio, and compressive strength are $1.59-1.66g/cm^3$, 16.6-20, and 70-90 MPa, respectively. Friction and wear tests are performed using a pin-on-plate-type reciprocating friction tester at 25, 100, and $200^{\circ}C$. The counterpart material is a CrMoV steel extracted from a KTX brake disc. Friction coefficient, wear amount, and wear mechanism are measured and examined. We determine that the friction coefficients depend on the temperature and the fluctuation of the friction coefficients is larger at higher temperatures. The amount of wear increases with the surface temperatures of the specimens. The tribological properties of the developed composites are similar to those of a Cu-based sintered friction material. Through this study, it is confirmed that ceramic composite materials can be used as friction materials.

• Journal of the Korean Wood Science and Technology
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• 제42권6호
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• pp.723-731
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• 2014

공진주파수 모드를 이용하는 비파괴 평가기술법을 거대억새 파티클 보드를 페놀수지로 함침한 후 탄화온도별(600, 800, 1000, $1200^{\circ}C$)로 제조한 세라믹에 적용하였다. 동적 탄성계수와 정적 휨 탄성계수는 탄화온도가 증가할수록 증가하였다. 휨 강도에 대한 동적 탄성계수 및 정적 휨 탄성계수는 밀접한 상관관계를 나타내었다. 그러나 휨 강도에 대한 상관관계에서 정적 탄성계수 보다 동적 탄성계수가 더 밀접한 상관관계를 나타내었다. 따라서 공진 주파수 모드를 사용하는 동적 탄성계수측정법으로 소성온도에 따라 제조된 거대억대 파티클보드의 휨 강도를 예측하는 비파괴 평가 방법으로 유용할 것으로 판단된다.

• 한국가구학회지
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• 제11권2호
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• pp.7-12
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• 2000

This paper describes the bending strength properties of laminated woods which had three kinds of specimens according to finger length-12, 4.5 mm and butt joint and the acoustic emissions (AEs) generated during the test. 3-ply laminated wood beams were tension side layers (lower layers) composed of one middle lamina and two side-jointed laminae, with one butt joint ($_1BJ$), one finger joint (12mm, $_1FJ_{12}$) or one finger joint (4.5mm, $_1FJ_{4.5}$) in the middle lamina of tension side layer. And 3-ply laminated wood beams were tension side layers (lower layers) also composed of one lamina, with one butt joint (BJ), one finger joint (12mm, $FJ_{12}$) or one finger joint (4.5mm, $FJ_{4.5}$/) in tension side layer. Cryptomelia pieces were cut for butt and two finger types and glued with resorcinol-phenol resin adhesive. The results were as follows It was not effective in the bending modulus of elasicity (MOE) with IFJL type and had no difference from finger length. The bending modulus of rupture (MOR) of laminated wood beams including finger joint was the same values as that including butt feint and had no difference from finger length. It was effective in MOE with FJL type and had no difference from finger length. The effect of finger joint on MOR was much higher than that of butt joint but had no difference from finger length. The AE generation time of IFJL type was earlier than that of the control wood and the number of AE count was much more than that of the control wood. However, the AE generation time of FJL type was earlier than that of the control wood and the number of U count was much fewer than that of the control wood.

• 한국세라믹학회지
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• 제50권6호
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• pp.402-409
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• 2013

The objective of this study was to develop a synthesis process for ${\beta}$-SiC powders to reduce the synthesis temperature and to control the particle size and to prevent particle agglomeration of the synthesized ${\beta}$-SiC powders. A phenol resin and TEOS were used as the starting materials for the carbon and Si sources, respectively. $SiO_2$-C hybrid precursors with various C/Si mole ratios were fabricated using a conventional sol-gel process. ${\beta}$-SiC powders were synthesized by a carbothermal reduction process using $SiO_2$-C hybrid precursors with various C/Si mole ratios (1.6 ~ 2.5) fabricated using a sol-gel process. In this study, the effects of excess carbon and the addition of Si powders to the $SiO_2$-C hybrid precursor on the synthesis temperature and particle size of ${\beta}$-SiC were examined. It was found that the addition of metallic Si powders to the $SiO_2$/C hybrid precursor with excess carbon reduced the synthesis temperature of the ${\beta}$-SiC powders to as low as $1300^{\circ}C$. The synthesis temperature for ${\beta}$-SiC appeared to be reduced with an increase of the C/Si mole ratio in the $SiO_2$-C hybrid precursor by a direct carburization reaction between Si and excess carbon.

• Journal of the Korean Wood Science and Technology
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• 제32권3호
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• pp.42-51
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• 2004

Wood veneer-bamboo zephyr composite board (WBCB) was manufactured to evaluate the properties of bamboo as alternative raw materials for the manufacture of composite panels. Bamboo zephyr was prepared using Moso bamboo (Phyllostachys pubesens Mazel. et Z), Giant timber bamboo (Phyllostachys bambusoides Sieb. et Zucc), and Hachiku bamboo (Phyllostachys nigra var. henosos Stapf). The effect of age and species of bamboo on zephyr production was investigated in terms of the pass number of bamboo split through the rollers, and the width increasing rate of bamboo split. Five-ply WBCBs were produced with Keruing veneers as face and back layers, leading to three layers of bamboo zephyr sheets as core layer. Each layer was placed so that its grain direction was at right angles to that of the adjacent layer and the layers were bonded together with phenol-formaldehyde (PF) resin.The pass number of bamboo split was increased with an increase of the thickness of culm wall. At the same thickness, Moso bamboo showed no effect of the age of bamboo on the pass number. The pass number of split of Giant timber bamboo was lower than that of Moso bamboo. No significant effect of bamboo species and age on the width of zephyr produced was observed. The width of zephyr obtained could be expressed as a function of diameter multiplied by thickness of culm wall. The physical and mechanical properties of WBCB manufactured in all given conditions did not show any significant differences, and they were above the requirement of Korean Standard (KS).

• Journal of the Korean Wood Science and Technology
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• 제51권1호
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• pp.38-48
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• 2023

Two important steps in utilizing technical kraft lignin (KL) from black liquor to synthesize lignin-phenol-formaldehyde (LPF) resin are its extraction via precipitation and fractionation. However, the effects of precipitation pH and acetone fractionation on the characteristics of hardwood KL have not been studied for LPF resins. Therefore, this paper reports the effects of the precipitation pH of black liquor and acetone fractionation on the characteristics of KL from mixed hardwood species for LPF resins. The precipitation was conducted at various pH levels from 3 to 9 of black liquor to obtain crude KL (C-KL), which was used in acetone fractionation to produce acetone-soluble KL (AS-KL) and acetone-insoluble KL (AI-KL). Precipitation at pH 3 and 9 produced the highest and lowest yields of C-KL, respectively. As expected, the C-KL infrared spectra were similar regardless of the precipitation pH levels. As the pH increased, the molecular weight of C-KL increased. However, the molecular weight of AS-KL and AI-KL after acetone fractionation increased to a maximum of 4,170 and 47,190 g/mol at pH 7, then decreased to 3,210 and 19,970 g/mol at pH 9, respectively. The smallest molecular weights of AS-KL and AI-KL were 3,210 and 15,480 g/mol and were found at pH 9 and 3, respectively. These results suggest that both AS-KL at pH 9 and AI-KL at pH 3 have good potential as starting lignins for synthesizing LPF resins that require cross-linking for polymerization.

• Composites Research
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• 제20권5호
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• pp.49-55
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• 2007

반도체 쿼츠 웨이퍼 다이싱용 블레이드는 마이크로/나노 디바이스와 부품을 제조하기 위해 고정밀도의 가공성을 요구한다. 따라서 균일한 마이크로/나노 선폭의 가공을 위해서는 블레이드의 제작 단계에서 균일한 두께와 밀도를 유지하는 것이 중요하다. 기존의 실리콘웨이퍼 가공을 위해서는 금속의 블레이드가 사용되고 있지만 쿼츠 웨이퍼 가공을 위해서는 고분자 복합재가 사용된다. 이러한 복합재는 가공성, 전기전도성, 그리고 적절한 강도와 연성 및 마모저항성이 있어야 한다. 그러나 기존의 건식성형 공정으로는 균일성을 유지하기 위해 많은 공정과 비용이 소비되고 있다. 본 연구에서는 도전성 나노 세라믹스 분말, 연마재 세라믹스 분말에 열경화성 수지, 전도성 고분자를 혼합한 복합재 분말을 습식성형 공정에 의해 제조, 평가하는 연구를 수행하였다. 먼저 복합재 분말을 액상과 혼합하여 블레이드를 제작하였으며, 액상의 종류, 액상 건조공정의 영향을 고찰하였다. 평가는 마이크로미터 측정기와 현미경을 이용하여 두께를 측정하였다. 두께편차와 기공률, 밀도, 경도, 등의 특성을 비교, 평가하였다. 그 결과 습식성형에 의해 블레이드의 두께편차를 감소시킬 수 있었으며, 경도 등의 특성을 향상시킬 수 있었다.