• 한국응용과학기술학회지
• /
• 제20권2호
• /
• pp.141-147
• /
• 2003

Oxidized polyethylene wax is obtained by oxidation of polyethylene wax and it is composed of various chemicals, e.g., fatty acid, alcohol, ketone and ester. The application of oxidized polyethylene wax is determined by the composition of these chemical substances. In this basic study we observed the basic reaction parameters of time, temperature, oxygen concentration and catalysts on the oxidation reaction of low molecular weight polyethylene(PE wax) by analyzing the acid value, physical and chemical properties of oxidized PE wax to develop a new oxidation process. Acid values are increased with temperature increase in the rage of $150^{\circ}C^{\sim}180^{\circ}C$ but decreased beyond 190$^{\circ}C$. Acid values are also increased with oxygen concentration. As the oxidation reaction proceeds the molecular weight and softening points of oxidation products are decreased by cracking reaction, but the viscosities are increased. To observe the crystallinity of oxidation products SEM experiment was performed. To obtain a high acid-value product in a mild condition, we adopted free radical catalysts and the acid value of the product using catalyst was higher than the product obtained without catalyst in the same reaction condition. The effective initiators were dicumyl peroxide(DCPO), t-butylperoxy-2-ethyl hexanoate(HOPO) and benzoyl peroxide(BPO) having long half-life.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.570-574
• /
• 1999

In this paper, by using the electrophoresis, preparation of YBCO superconducting wire deposited on metal Ag base wire was studied with its Properties. YBCO Powder could be prepared by solid state reactions with calcining and sintering processes. Superconducting wire prepared on metal Ag wire used as cathode of deposition base could be also fabricated in the YBCO/acetone-dispersed solution to obtain several tens of re thick films. And then it could be used as superconducting wire for measurement after calcination, sintering and oxygen absorption processes. In the process of film deposition, a catalyst I$_2$added into the suspension solution was very useful for preparing thick film of YBCO, and BaF$_2$ of additive material was also necessary for preparing crack-free wire of YBCO superconductor. As a result, YBCO superconducting wire added 2~3wt.% of BaF$_2$\ulcorner with catalyst, 12 had better deposition condition for uniform and dense YBCO wires, and critical current density, Jc was calculated at the value of 1,458A/$\textrm{cm}^2$(more than 10$^{3}$A/$\textrm{cm}^2$ ,77K, o[T]) of 30${\mu}{\textrm}{m}$ thick sample by 4 point prove method.

• 한국표면공학회지
• /
• 제51권5호
• /
• pp.332-336
• /
• 2018

Alkaline oxygen electrocatalysis, targeting anion exchange membrane alkaline-based metal-air batteries has become a subject of intensive investigation because of its advantages compared to its acidic counterparts in reaction kinetics and materials stability. However, significant breakthroughs in the design and synthesis of efficient oxygen reduction catalysts from earth-abundant elements instead of precious metals in alkaline media still remain in high demand. One of the most inexpensive alternatives is carbonaceous materials, which have attracted extensive attention either as catalyst supports or as metal-free cathode catalysts for oxygen reduction. Also, carbon composite materials have been recognized as the most promising because of their reasonable balance between catalytic activity, durability, and cost. In particular, heteroatom (e.g., N, B, S or P) doping on carbon materials can tune the electronic and geometric properties of carbon, providing more active sites and enhancing the interaction between carbon structure and active sites. Here, we focused on boron and nitrogen doped nanocarbon composit (BNC nanocarbon) catalysts synthesized by a solution plasma process using the simple precursor of pyridine and boric acid without further annealing process. Additionally, guidance for rational design and synthesis of alkaline ORR catalysts with improved activity is also presented.

• Journal of Electrochemical Science and Technology
• /
• 제13권3호
• /
• pp.354-361
• /
• 2022

In a direct methanol fuel cell system (DMFC), one of the drawbacks is methanol crossover. Methanol from the anode passes through the membrane and enters the cathode, causing mixed potential in the cell. Only Pt-based catalysts are capable of operating as cathode for oxygen reduction reaction (ORR) in a harsh acidic condition of DMFC. However, it causes mixed potential due to high activity toward methanol oxidation reaction of Pt. To overcome this situation, developing Pt-based catalyst that has methanol tolerance is significant, by controlling reactant adsorption or reaction kinetics. Pt/C decorated with phosphate ion was prepared by modified polyol method as cathode catalyst in DMFC. Phosphate ions, bonded to the carbon of Pt/C, surround free Pt surface and block only methanol adsorption on Pt, not oxygen. It leads to the suppression of methanol oxidation in an oxygen atmosphere, resulting in high DMFC performance compared to pristine Pt/C.

• 한국염색가공학회지
• /
• 제33권4호
• /
• pp.238-249
• /
• 2021

In this study, the effect on flame retardancy and various physical properties when TiO₂ was added with a citric acid/phosphate complex acid catalyst together with Pyrovatex CP new (N-methylol dimethylphosphonopropionamide), a phosphorus-based flame retardant, was studied on cotton fibers. SEM-EDS analysis was performed to confirm the surface characteristics and surface element analysis of the flame-retardant treated cotton fibers, and a vertical carbonization test was performed to confirm the char formation capability and flame retardancy according to the phosphoric acid ratio. By comparing the LOI index before and after washing 10 times, the washing durability of the flame retardant solution containing the phosphoric acid catalyst and TiO₂ was tested by LOI index after ten washing cycles. In addition, the influence of the flame-retardant processing on the physical properties were compared including thermogravimetric analysis (TGA), tear strength and whiteness.

• 한국표면공학회지
• /
• 제56권6호
• /
• pp.427-436
• /
• 2023

In the industry, it is recognized that human activities significantly lead to a large amount of wastewater, mainly due to the increased use of water and energy. As a result, the growing field of wastewater resource technology is getting more attention. The common technology for hydrogen production, water electrolysis, requires purified water, leading to the need for desalination and reprocessing. However, producing hydrogen directly from wastewater could be a more cost-effective option compared to traditional methods. To achieve this, a series of first-principle computational simulations were conducted to assess how waste nutrient ions affect standard electrolysis catalysts. This study focused on understanding the adsorption mechanisms of byproducts related to the oxygen evolution reaction (OER) in anion exchange membrane (AEM) electrolysis, using Co₃O₄ as a typical non-precious metal catalyst. At the same time, efforts were made to develop a comprehensive free energy prediction model for more accurate predictions of OER results.

• 공업화학
• /
• 제8권5호
• /
• pp.837-843
• /
• 1997

산화형 폴리에틸렌 왁스 제조에 있어서 주요 반응인자인 사용 왁스의 물성, 산화시간, 산화온도, 공기의 주입량 등에 따른 산가의 변화와 산화에 따른 폴리머의 물성을 분석하였다. 실험결과 주어진 반응조건 하에서 산화온도에 대한 산가의 변화는 $160^{\circ}C$까지는 증가하였지만 $170^{\circ}C$에서는 오히려 산가가 감소하는 경향을 보였고, 공기 주입량에 비례하여 산가는 증가하였다. 또한 사용한 왁스의 분자량이 낮을수록 산가가 높았다. 분자량과 밀도차가 공존하는 시료의 산화반응에서는 가지의 길이, 수 등에 의한 밀도보다는 분자량에 의한 영향이 큰 것으로 생각되었다. 산화가 진행됨에 따라 분자량은 감소하고 분자량 분포는 넓어짐을 알 수 있었다. 온화한 조건 하에서 고산가를 얻기 위하여 자유라디칼 개시제를 촉매로 사용하였는데 같은 조건 하에서 무촉매인 경우에 비하여 고산가의 산화형 왁스를 얻을 수 있었다. 또한 DCPO(dicumylperoxide), HOPO(t-butyl peroxy 2-ethyl heaxanoate), BPO(butylperoxide) 순의로 반감기가 긴 촉매가 효율적이었다.

• Journal of Electrochemical Science and Technology
• /
• 제6권4호
• /
• pp.121-130
• /
• 2015

The micro emulsion method has been successfully used for preparing perovskite LaCoO₃ with uniform, fine-shaped nanoparticles showing high activity as electro catalysts in oxygen reduction reactions (ORRs). They are, therefore, promising candidates for the air-cathode in metal-air rechargeable batteries. Since the activity of a catalyst is highly dependent on its specific surface area, nanoparticles of the perovskite catalyst are desirable for catalyzing both oxygen reduction and evolution reactions. Herein, LaCoO₃ powder was also prepared by sol-gel method for comparison, with a broad particle distribution and high agglomeration. The electro catalytic properties of LaCoO₃ and LaCoO₃-carbon Super P mixture layers toward the ORR were studied comparatively using the rotating disk electrode technique in 0.1 M KOH electrolyte to elucidate the effect of carbon Super P. Koutecky-Levich theory was applied to acquire the overall electron transfer number (n) during the ORR, calculated to be ~3.74 for the LaCoO₃-Super P mixture, quite close to the theoretical value (4.0), and ~2.7 for carbon-free LaCoO₃. A synergistic effect toward the ORR is observed when carbon is present in the LaCoO₃ layer. Carbon is assumed to be more than an additive, enhancing the electronic conductivity of the oxide catalyst. It is suggested that ORRs, catalyzed by the LaCoO₃-Super P mixture, are dominated by a 2+2-electron transfer pathway to form the final, hydroxyl ion product.

• 한국결정성장학회지
• /
• 제18권2호
• /
• pp.91-95
• /
• 2008

코디어라이트를 원료로 하여 다공성 세라믹 필터를 제조하였고, 진공함침법으로 $V_2O_5$ 촉매를 코팅하였다. 제조된 세라믹 필터의 기공률은 58%, 압축강도는 10 MPa, 400$^{\circ}C$, 5 cm/sec의 유속에서 압력손실은 1,200 Pa이었다. $V_2O_5$ 촉매의 경우 $NO_x$에 대해 80% 이상의 처리효율을 나타내었고, 산처리에 의한 필터의 비표면적 증가를 통해 처리효율을 약 10%개선할 수 있었다. 이는 필터의 비표면적 증가를 통해 코팅된 촉매의 분산성을 향상시킴으로써 촉매의 활성점이 증대되었기 때문으로 판단된다.

• 한국수소및신에너지학회논문집
• /
• 제25권2호
• /
• pp.105-113
• /
• 2014

Performance tests on $Ni/Ce-ZrO_2/Al_2O_3$ catalysts with additives (MgO, $La_2O_3$) were investigated in the combined reforming processes (SCR, ATR, TRM) in order to produce hydrogen and carbon monoxide (it is called "syngas".). The catalyst characterization was conducted using the BET surface analyzer, X-ray diffraction (XRD), SEM, TPR and TGA. The combined reforming process was developed to adjust the syngas ratio depending on the synthetic fuel (methanol, DME and GTL) manufacturing processes. Ni-based catalysts supported on alumina has been generally recommended as a combined reforming reaction catalyst. It was found that both free NiO and complexed NiO species were responsible for the catalytic activity in the combined reforming of methane conversion, and the $Ce-ZrO_2$ binary support employed had improved the oxygen storage capacity and thermal stability. The additives, MgO and $La_2O_3$, also seemed to play an important role to prevent the formation of the carbon deposition over the catalysts. The experimental results were compared with the equilibrium data using a commercial simulation tool (PRO/II).