• 대한금속재료학회지
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• 제50권1호
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• pp.52-58
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• 2012

Hydrogen-delayed fracture (HDF) was analyzed from the deposited weld metals of 600-MPa and 800-MPa flux-cored arc (FCA) welding wires, and then from the diffusible hydrogen behavior of the weld zone. Two types of deposited weld metal, that is, rutile weld metal and alkali weld metal, were used for each strength level. Constant loading test (CLT) and thermal desorption spectrometry (TDS) analysis were conducted on the hydrogen pre-charged specimens electrochemically for 72 h. The effects of microstructures such as acicular ferrite, grain-boundary ferrite, and low-temperature-transformation phase on the time-to-failure and amount of diffusible hydrogen were analyzed. The fracture time for hydrogen-purged specimens in the constant loading tests decreased as the grain size of acicular ferrite decreased. The major trapping site for diffusible hydrogen was the grain boundary, as determined by calculating the activation energies for hydrogen detrapping. As the strength was increased and alkali weld metal was used, the resistance to HDF decreased.

• 한국분말재료학회지
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• 제29권1호
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• pp.47-55
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• 2022

Tungsten carbide is widely used in carbide tools. However, its production process generates a significant number of end-of-life products and by-products. Therefore, it is necessary to develop efficient recycling methods and investigate the remanufacturing of tungsten carbide using recycled materials. Herein, we have recovered 99.9% of the tungsten in cemented carbide hard scrap as tungsten oxide via an alkali leaching process. Subsequently, using the recovered tungsten oxide as a starting material, tungsten carbide has been produced by employing a self-propagating high-temperature synthesis (SHS) method. SHS is advantageous as it reduces the reaction time and is energy-efficient. Tungsten carbide with a carbon content of 6.18 wt % and a particle size of 116 nm has been successfully synthesized by optimizing the SHS process parameters, pulverization, and mixing. In this study, a series of processes for the high-efficiency recycling and quality improvement of tungsten-based materials have been developed.

• Korean Chemical Engineering Research
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• 제54권5호
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• pp.671-677
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• 2016

대나무를 원료로 탄화 및 활성화온도 $900^{\circ}C$에서 대나무 활성탄을 만들고, 이 대나무 활성탄에 알칼리 금속(Na, K)과 알칼리토금속(Ca, Mg)을 담지 시켜 알칼리 담지 대나무활성탄을 제조하였다. 제조된 알칼리 담지 활성탄의 비표면적 및 세공분포 등의 물리적 특성을 분석하였다. 또한 폐 대나무활성탄의 재활용을 위하여 알칼리 담지 대나무활성탄과 NO 기체의 반응 특성 실험을 열중량분석기를 사용하여 비등온반응(반응온도 $20{\sim}850^{\circ}C$, NO 농도 0.1 kPa)과 등온반응(반응온도 600, 650, 700, 750, 800, $850^{\circ}C$, NO 농도 0.1~1.8 kPa) 조건에서 하였다. 실험 결과, 대나무 활성탄 특성 분석에서 알칼리 담지 대나무 활성탄에서는 알칼리 담지량이 증가할수록 세공 부피와 표면적이 감소하였다. 비등온과 등온 NO 반응에서는 전체적으로 Ca금속담지 대나무활성탄[BA(Ca)]과 Na금속담지 대나무활성탄[BA(Na)], K금속담지 대나무활성탄[BA(K)], Mg금속담지 대나무활성탄[BA(Mg)]이 대나무활성탄[BA]에 비하여 반응속도가 향상되는 것을 볼 수 있다. BA(Ca)> BA(Na)> BA(K)> BA(Mg)> BA 순으로 촉매 활성이 유효하였다. NO 반응에서의 활성화에너지는 82.87 kJ/mol[BA], 37.85 kJ/mol[BA(Na)], 69.98 kJ/mol[BA(K)], 33.43 kJ/mol[BA(Ca)], 88.90 kJ/mol[BA(Mg)]로 나타났고, NO 분압에 대한 반응차수는 0.76[BA], 0.63[BA(Na)], 0.77[BA(K)], 0.42[BA(Ca)], 0.30[BA(Mg)]이었다.

• 공업화학
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• 제31권5호
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• pp.560-567
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• 2020

본 연구는 다양한 산업공정의 배가스 중 대표적인 활성저하 물질로 알려진 알칼리 금속[Na(Sodium)과 K(Potassium)]이 V/W/TiO₂ 촉매의 NH₃-SCR 반응에 미치는 영향을 확인 하였다. 이에 따른 활성 저하 원인을 규명하고자 NO, NH₃-TPD, DRIFT, H₂-TPR 분석을 수행 하였다. 그 결과, 각 알칼리 금속은 촉매 피독으로 작용하여 NH₃ 흡착양이 저하되고, Na과 K은 촉매의 반응 활성에 기여하는 L산점과 B산점을 감소시켜 SCR 반응을 저하시킨다. H₂-TPR 분석을 통하여 알칼리 금속은 V-O-V (bridge oxygen bond)와 V=O (terminal bond)의 환원 온도에 영향을 끼쳐, 환원 온도가 고온으로 올라가기 때문에 활성 저하 원인으로 판단된다.

• 한국건설순환자원학회논문집
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• 제5권1호
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• pp.111-116
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• 2010

각종 중금속을 흡착하는 알칼리 용해성 아크릴계 수분산 중합체의 특성을 활용하여 광산 폐기물 및 도시폐기물의 소각재 등에서 용출되는 중금속의 처리 방법에 대하여 실험 하였으며 그 결과를 고찰하였다. 실험결과, 수은, 납, 카드뮴, 구리 이온 등에 대한 킬레이트 반응에 의한 알칼리 용해성 아크릴계 수분산 중합체의 효과적인 흡착 효과가 확인되었다. 수중에서 불분리성이고 각종 중금속의 용출을 방지하는 친환경성 가소성 그라우트의 특성을 활용하여 광산 폐기물 및 도시폐기물의 소각재 등에서 용출되는 중금속의 처리를 위한 기초적 용출실험을 실시하였으며 그 결과를 고찰하였다. 실험결과, 알칼리 용해성 수분산 중합체를 첨가한 친환경성 가소성 그라우트의 $Cr^{6+}$ 이온에 대한 효과적인 중금속 흡착 효과가 확인되었다.

• 한국응용과학기술학회지
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• 제30권3호
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• pp.494-503
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• 2013

In this study, $CO_2$ adsorbent was produced for minimizing energy loss due to ventilation within the building. For improved selectivity about low concentration of $CO_2$ in multiple-use facilities, the ball type adsorbent was modified from a commercial zeolite, alumina, alkali metals and activated carbon with mixing LiOH, binder, and $H_2O$. We measured specific surface area, pore characteristic, and crystal structure of the modified adsorbent. Effects of alkalization on the absorptive properties of the adsorbents were investigated. Continuous column tests (2,000 ppm) and batch chamber tests ($4m^3$, 5,000ppm) showed that the modified adsorbent indicated about the selectivity of $CO_2$ more than 9.7% (0.613 mmol/g) compared with ordinary adsorbents and $CO_2$ removal efficiency of 88.8% within l hour, respectively. It was estimated that the modified adsorbent was applicable to indoor environments.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1719-1721
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• 2012

We have investigated the $H_2$ adsorption structures and binding energies of the metal (M)-doped (M = Li, Na, K, Mg, and Al) silicon complexes, $M-Si_{19}H_{11}$ and $M-Si_{24}H_{12}$, using density functional calculations. Alkali metals are preferred as doping elements because the Mg-Si and Al-$H_2$ interactions are weak. The maximum numbers of $H_2$ molecules that can be adsorbed are four and five for M=Li and K, respectively. We propose that the K-decorated silicon material might be an effective hydrogen storage material with high hydrogen capacity and high reversibility.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.332-335
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• 2007

Electron injection improvement in OLED organic layers can be obtained by their doping or using alkaline-earth or alkali metals as electron injection layers (EIL). Common handling problems can be solved by an innovative metal dispensing technology to ensure controlled and reliable metal layers for OLED. Thickness and deposition rate of EIL during the process have been explored to optimize device performances.

• 분석과학
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• 제7권4호
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• pp.555-561
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• 1994

A method was described for the graphite furnace atomic absorption spectrophotometric determination of trace cadmium, copper, chromium and lead in urine samples. The elements were directly determined without any other treatments. The ash temperature was intensively optimized to improve the large background by the removal of organic materials and alkali and alkali earth metals in urine samples. Two kinds of standard solutions were used to plot calibration curves. From the recovery data, it could be confirmed that the analytical results with the synthetic urine matrix similar to real urine were more accurate than with a deionized water matrix.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.155-155
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• 2000

Adsorption of alkali metals on a silicon surface has attracted much attention due to its importance in metal-semiconductor interface technology, In particular, the bonding nature of alkali metal to silicon substrate has been a focus of fundamental research efforts. We examined the adsorbed layer of Cs on a Si(111)-(7$\times$) surface by reactive ion scattering (RIS) of hyperthermal Cs+ beams. RIS from a Cs-adsorbed surface gives rise to Cs, representing pickup of surface Cs by Cs projectile. The Cs intensity is proportional to surface coverage of Cs at a high substrate temperature (473 K), while it varies anomalously with Cs coverage at low temperatures (130-170 K). This observation indicates that RIS selectively detects metallic Cs on surface, but discriminates ionic Cs. Transition from ionic to metallic Cs adlayer is driven by thermal diffusion of Cs and their clustering process.