• Journal of the Korean Wood Science and Technology
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• 제44권6호
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• pp.842-851
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• 2016

The objective of this study was to improve physical and mechanical properties of soft-inner part of oil palm trunk (S-OPT) after impregnation with phenol formaldehyde (PF) resin and densification by close system compression (CSC) method. Effect of different methods of PF resin impregnation (i.e., no vacuum-pressure, vacuum, and vacuum-pressure) was evaluated. The results showed that PF resin impregnation and CSC significantly improved the physical and mechanical properties of S-OPT up to: (1) 176% in density; (2) 309% in modulus of rupture (MOR); (3) 287% modulus of elasticity (MOE); and (4) 191% in the compressive strength. Physical and mechanical properties of S-OPT showed their best performances when PF resin impregnated with vacuum-pressure method as shown by higher weight gain, density, MOR, MOE, compressive strength, and lower recovery of set due to better penetration of PF resin into S-OPT. Combining PF resin impregnation and densification by CSC method could be a good method to improve physical and mechanical properties of S-OPT.

• 한국세라믹학회지
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• 제30권10호
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• pp.852-858
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• 1993

The effect of coal tar ptch-impregnated carbon materials which were made from petroleum coke was investigated at various pressure time and impregnation-sintering cycle. As a result, density and bending strength of the carbon materials were remarkably increased in the condition of pressure times of 5hrs and of the cycle of 3rd times. And the value of d002 and Lc of the graphitic carbon sintered at 230$0^{\circ}C$ shwoed 3.387$\AA$ and 167$\AA$, respectively.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.240-244
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• 1998

The analytical method was developed to calculate efficiency of densifying carbon/carbon (C/C) composites using coal tar pitch as a matrix precursor at each cyle. Three factors were defined in analyzing the densification process: impregnation efficiency, retention efficiency, and overall densification efficiency. The relationships developed were applied to the experimental results for three densification cycles of C/C composites with pitches as an impregnant to evaluate the factors which may depend on the impregnant and on the route of carbonization. The impregnation efficiency increased with the repeated process cycles whereas the retention efficiency decreased irrespective of the impregnant and carbonization route. Carbonization route P+A+G, in which pressure carbonizationl (P) and graphitization (G) were done before after atmospheric pressure carboniztion (A) respectively, using impregnant of high carbon yields was the most effective method in densifying C/C composites.

• 한국세라믹학회지
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• 제35권9호
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• pp.974-980
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• 1998

This study is concerned with the production of carbon fiber reinforced carbon(C/C) with polyaromatic mesophase pitch as matrix precursor and with the investigation of friction-wear characteristics in ambient air using a constant speed type of friction tester. The main problem in using the polyaromatic mesophase as the matrix precursor is the high viscosity which may limit the complete impregnation of the fiber preform in the vacuum. To solve these problems two dimensional carbon fiber fabrics were infiltrated with meso-phase pitch in the pitch impregnator. After the impregnation and the heat treatment process. C/C com-posites were characterized by density porosity to monitor the influence of high pressure and temperature. It showed that the bulk density was increased and the apparent porosity and the density increasing rate was reduced as repeating the impregnation the carbonization and the heat treatment. The friction-wear charac-teristics of C/C composites were investigated by measuring the average friction coefficient and the specific wear rate as functions friction speed and friction pressure using a constant speed type of friction tester. C/C composite4s showed the average friction coefficient to be reduced as increasing the friction speed and the friction pressure.

• 한국화재소방학회논문지
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• 제26권4호
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• pp.18-23
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• 2012

이산화탄소 주조법에서 사용되고 있는 방법을 응용하여 목질내에 규산겔과 탄산소다, 이산화규소가 석출된 목재를 제조한 후 외부 복사열원(20, 25, 35 및 50 $kW/m^2$)에 따른 점화시간, 점화온도, 질량감소속도, 임계열유속을 측정하였다. 연구결과, 물유리와 이산화탄소를 이용한 가압함침 처리된 목재는 Pre-Flashover 단계에서의 복사열원(20 $kW/m^2$ 이하)에서 난연성능이 있음을 확인할 수 있었다. 향후 지속적인 연구를 통해 우수한 배합비율을 찾는다면 난연목재로서의 활용가능성이 있다고 판단된다.

• 한국가구학회지
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• 제18권2호
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• pp.111-119
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• 2007

An experiment was conducted to know the safranine impregnation distance from surface to inward using 6 different hardwood species. During impregnation, 3 parameters were applied-vacuum, pressure and soaking time. Only vacuum treatment did not increase the permeability of wood. Vacuum followed by pressure increased the penetration depth of safranine in radial, tangential and longitudinal direction. Longitudinal penetration was found easy to impregnate. Comparing with radial and tangential direction, radial penetration was found easy. There was a striking difference among sapwood and heartwood permeability. Safranine input depth was found highest in diffused porous wood rather than in ring porous wood. At increased vacuum and pressure, safranine penetration was found easy.

• 공업화학
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• 제32권5호
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• pp.569-573
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• 2021

본 연구에서는 코크스, 바인더 피치 및 함침 피치를 사용하여 고밀도 탄소 블록을 제조하고, 함침 공정 시 피치의 유동성이 탄소 블록의 고밀도화에 미치는 영향을 고찰하였다. 코크스와 바인더 피치의 고압 성형을 통해 그린블록을 제조하고 열처리 공정을 통하여 탄소 블록을 얻었다. 열처리 공정 시 바인더 피치의 휘발에 의해 생성된 기공을 제거하고자 함침 공정을 진행하였다. 함침 공정은 함침 피치를 용융하는 전처리 단계와 피치를 탄소 블록에 함침하는 고압 반응 단계로 나누어 진행하였다. 함침 피치의 용융은 140~200 ℃에서 진행하였으며, 열처리 온도가 증가할수록 함침 피치의 점도가 감소하였다. 함침 피치의 점도 감소는 유동성을 향상시켜 탄소 블록 내부 기공을 효율적으로 함침하여 탄소 블록의 기공률을 83% 감소시켰고 겉보기 밀도를 5% 상승시켰다.

• Carbon letters
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• 제16권1호
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• pp.25-33
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• 2015

The prime objective of this research was to study the influence of hot-pressing pressure and matrix-to-reinforcement ratio on the densification of short-carbon-fiber-reinforced, randomly oriented carbon/carbon-composite. Secondary objectives included determination of the physical and mechanical properties of the resulting composite. The 'hybrid carbon-fiber-reinforced mesophase-pitch-derived carbon-matrix' composite was fabricated by hot pressing. During hot pressing, pressure was varied from 5 to 20 MPa, and reinforcement wt% from 30 to 70. Densification of all the compacts was carried at low impregnation pressure with phenolic resin. The effect of the impregnation cycles was determined using measurements of microstructure and density. The results showed that effective densification strongly depended on the hot-pressing pressure and reinforcement wt%. Furthermore, results showed that compacts processed at lower hot-pressing pressure, and at higher reinforcement wt%, gained density gradually during three densification cycles and showed the symptoms of further gains with additional densification cycles. In contrast, samples that were hot-pressed at moderate pressure and at moderate reinforcement wt%, achieved maximum density within three densification cycles. Furthermore, examination of microstructure revealed the formation of cracks in samples processed at lower pressure and with low reinforcement wt%.

• Journal of the Korean Wood Science and Technology
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• 제43권3호
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• pp.327-333
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• 2015

진공가압 수지함침 처리에 의한 목재의 치수안정화 정도를 측정하기 위하여 침엽수 3수종에 수용성 멜라민 수지를 수지농도와 처리시간별로 처리한 후, 수지함침 열압축목재(compreg)를 제조한 다음 치수안정성 개선효과를 검토하였다. 수지농도가 높고 처리시간이 길수록 용적 수축률과 항용적 팽윤율은 증가하였으나, 용적 팽윤율, 항용적 수축률 및 흡수성은 감소하였다. 또한 중량 증가율은 수지의 농도가 높을수록 현저히 증가하였으나 처리시간과는 일정한 관계가 없었다.

• KEPCO Journal on Electric Power and Energy
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• 제3권2호
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• pp.113-117
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• 2017

As the competition in the manufacturing market for small and medium sized generators is intensifying, there is increasing pressure to reduce production cost. Manufacturing the generator stator windings with global vacuum pressure impregnation (GVPI) is a very effective way to reduce costs. However, the stator winding has a fatal disadvantage in that the insulation wears due to vibration in the slot. KEPRI (KEPCO Research Institute) conducted insulation diagnosis for three generators in KOMIPO (Korea Midland Power Co., Ltd.) which were manufactured by GVPI and operated for about 17 years. Insulation diagnosis showed that deterioration of insulation has progressed significantly. Therefore, KEPRI recommended replacing the stator windings of all three generators. In this paper, the insulation properties of the generator stator winding with global GVPI are described by comparing and analyzing the insulation diagnosis results and visual inspection for stator windings.