Boron Oxide를 添加한 炭素/炭素 複合材의 酸化擧動

金敬原 충남대학교 1999 국내석사

The effects of boron oxide as an oxidation inhibitor on C/C composites and structural characteristics of boron-implanted C/C composites were investigated. In order to understand the oxidation properties of the C/C composites, four different preparation methods were employed by varying the B_2O_3 introduction time. The first was an unmodified C/C composite (XX), which had no boron component. The second was a modified C/C composite where the carbon fiber preform was infiltrated by boron oxide solution (OX). The third was a C/C composite prepared with carbon precursor which contained boron oxide during the carbonization process (XO). The fourth was a C/C composite both the second and the third method were employed together (OO). The preparation conditions for all the specimens were the same, except for the introduction time of boron oxide into the carbon precursor. Also, the influence of HTT on the carbon/carbon composites was observed at 2300˚C and 2800˚C, respectively. After severe HTT, most amount of boron oxide was evaporated only to have less than 0.4B/C% in all specimens. The higher the HTT, the less the content of boron. At the temperature of 2300˚C, relatively large amount of B_2O_3 was detected while significant amount of B_2O_3 were converted into substituted boron and B_4C at 2800˚C. Small amount of boron increased not only the graphitization efficiency but also the oxidation resistance. Thus, boron containing carbon material need not to be treated as high temperatures as non-containing materials to get enough graphitization. In the latter, the heat treatment temperature played very significant roll in the graphitization procedure. If boron existed in the composites, ultra high temperature was of no use in order to obtain highly graphitized composites. During the preparation of composites, the introduction time of boron oxide was not important in terms of oxidation behavior. In other words, in both specimens that boron oxide was added on carbon fiber preform and that boron oxide added during carbonization process showed almost the same oxidation behavior. However, the former was slightly better than the latter as the time went by. Thus, boron oxide should be treated on carbon preform so as to get longer lasting oxidation resistance. At the early stage of oxidation reaction, boron-implanted material seems to promote its reactivity on oxygen according to activation energy. However, boron oxide increased the activation energy of oxidation reaction as the reaction proceeds. Boron atoms on the graphite layer plane catalyzed oxidation at first stage of reaction then boron oxide barrier was formed by reacting with oxygen, which blocked the active sites of C/C composites. Enough carbon atoms surrounding boron atom must be gasified by reactant gas in order to form boron oxide film at the active sites of carbon surface.

Pressure-induced structural evolutions of boron-bearing rhyolitic glasses and origins of deep boron cycle in the upper mantle : Insights from high-resolution multi-nuclear solid-state NMR spectroscopy

이아침 서울대학교 대학원 2022 국내박사

The pressure-induced structural evolutions of hydrous boron-bearing model rhyolitic melts under high pressures enable to infer the detailed geochemical processes (melting and fluid-rock-melt interactions) occurring in Earth’s interiors and to control the melt properties (sound wave velocity, melt viscosity, and the boron isotope composition, δ11B) of complex magmatic melts, providing insights into the boron cycle toward the deeper part of the upper mantle (~10 GPa). Considering the formation depth of mantle melts under high pressure and the supply of boron and water into deep mantle in the subducting slab of 300 km (~10 GPa), it is necessary to explore the detailed boron coordination number in multicomponent boron-bearing silicate melts under compression to better understand the deep boron and water cycle. Despite the geochemical-geophysical importance, the structures of hydrous multicomponent boron-bearing silicate melts and glasses above 3 GPa are currently unavailable. This dissertation is for a systematic exploration of pressure-induced coordination transformation of framework cations (including boron) and network connectivity in boron-bearing rhyolitic glasses with varying composition upon compression up to 9 GPa using multi-nuclear (11B, 23Na, 27Al, 29Si, and 17O) solid-state nuclear magnetic resonance (NMR). The main objective of this thesis is probing the pressure-induced structural evolution and their effect on macroscopic properties (including boron isotope composition) in multi-component boron-bearing rhyolitic glasses with varying composition (e.g., Si/B ratio and water content). The compositional effect on the structures (particularly, topological evolution of boron species and their spatial proximity) and the NMR parameters of B, Al, and O configurations in binary sodium borate and sodium aluminoborosilicate glasses in NaBSiO4–NaAlSiO4 and NaBSi3O8–NaAlSi3O8 joins at 1 atm were investigated in detail. Novel structural findings include the two distinct [4]B species in sodium borate glasses with low alkali content and the presence of Na–O–B peak in NaAl0.25B0.75SiO4 glasses. The proximity between [3]B and [4]B in NaAlSiO4-NaBSiO4 glasses was revealed via 11B double quantum magic angle spinning (MAS) NMR. The changes in quadrupolar coupling constants and isotropic chemical shift for diverse coordination B and Al environments and oxygen clusters provide the improved insights in the effect of composition on the changes in the 2nd nearest neighbors environments and the extent of topological distortion. The effects of B/Al and Si/B ratios on the local configurations around cations and the degree of network polymerization of Na2O-Al2O3-B2O3-SiO2 glasses in nepheline (NaAlSiO4) - malinkoite (NaBSiO4) and albite (NaAlSi3O8) - reedmergnerite (NaBSi3O8) joins were explored using NMR. An increase in the B coordination numbers from 3 ([3]B) to 4 ([4]B) was confirmed as B/Al and Si/B ratios increase. The Al is mainly four coordinated, except in NaAl0.25B0.75SiO4 glasses, with a minor amount of [5]Al species, revealing a more prominent control of Si over that of B on the Al coordination environments. The fractions of B-O-B and Na-NBO increase as B/Al ratio increases, accounting for a drastic enhancement in the dissolution rate of glasses. A dramatic increase also indicates an enhanced connectivity of relatively weaker bonds such as B-O-B and Na-O-Si as composition reached a certain boron content. This is linked to a decrease in the melt viscosity with increasing B2O3 component. Based on the measured fractions of [3,4]B with varying composition, the trend of the evolution of boron isotope composition in sodium aluminoborosilicate melts was estimated, confirming the preferential enrichment of 10B into rhyolitic melts with increasing boron content. The decreased fraction of [3]B species with increasing Si/B may partly explain the reduction in δ11B in boron-bearing volcanic rocks at deeper depths in the subduction zone. The structures, particularly the coordination transformation of constituent elements, were also explored in boron-bearing nepheline and albite glasses – a model rhyolitic melts - upon compression to a depth of ~270 km (~9.2 GPa) in the mantle using multi-nuclear solid-state NMR spectroscopy. The results showed that the conversion of [3]B into [4]B is prominent upon compression up to 6 GPa. In contrast, the formation of [5,6]Al is accompanied by the formation of oxygen tricluster above 6 GPa where all the non-bridging oxygens are consumed. The increase in the [4]B population tends to be larger for the glasses with low Si content as pressure increases to 9.2 GPa. Considering a preferential partitioning of 10B to [4]B, an increase in [4]B population in the melts leads to an pressure-induced enrichment of 10B. As the increase in Si/B ratio in the melts tends to decrease the pressure-induced increase in [4]B fraction, the contribution of boron coordination transformation on the 11B/10B ratios in silicate melt would be somewhat minor in deep mantle melts with increasing Si content. The detailed boron environments in rhyolitic melts at high pressure yield useful constraints for the isotope composition (11B/10B) of dense mantle melts, thereby enabling quantification of deep boron cycle. The effect of water on the cation coordination transformation (B, Al, and Na) in hydrous boron-bearing rhyolitic glasses at high pressure was explored up to 8 GPa (corresponding to a depth of ~240 km in the mantle) using multi-nuclear solid-state NMR. At the same water content of 4 wt%, the formation of [4]B was promoted in hydrous glasses than in dry glasses while the formation of [5,6]Al was suppressed up to 8 GPa. With the addition of water of 1 wt%, more boron tends to become highly coordinated while aluminum coordination number slightly decreases. This indicates that a small amount of water preferentially affects the boron coordination number at high pressure. With high water content of 8 wt%, both [4]B and [5,6]Al fractions increase up to 8 GPa. Upon hydration, the 23Na isotropic chemical shift (δiso) increases. An increase in 23Na δiso is related with a decrease in average Na-O distance. There seems a threshold of water content when the water-induced suppression of the formation of [5,6]Al is terminated. Above the threshold water content, the formation of [5,6]Al is promoted in hydrous glasses than in dry glasses. Considering a preferential partitioning of 10B to [4]B, more 10B becomes to enrich in the hydrous silicate melts and glasses at high pressure. The systematic variation in the Na environment in sodium aluminoborosilicate glasses was investigated with varying composition and pressure using 23Na NMR spectroscopy. The 23Na NMR parameters including 23Na isotropic chemical shift (23Na δiso) and quadrupolar coupling constant (Cq) were obtained. With decreasing Si/(B+Al) ratio from 3 to 1, the 23Na δiso systematically increases by ~7 ppm with increasing pressure up to 9.2 GPa. For both boron-bearing nepheline and albite glasses, the 23Na δiso increases by ~ 2 ppm under compression up to 9.2 GPa. These indicate the contribution on 23Na δiso is prominent for the changes in Si content than for the pressurization up to 9.2 GPa. The Cq variations do not seem clear with varying composition and pressure. An increase in 23Na δiso indicates a reduction of average Na-O distance which could affect the Na diffusivity. The changes in the isotropic chemical shift for Na environment in sodium aluminoborosilicate glasses provide the improved insights into the changes in the electrical conductivity which Na ions dominantly contribute in the glasses. 화산 유리 또는 화산암의 붕소 농도 및 동위 원소 조성은 용융, 유체-암석 상호작용, 수화 광물의 탈수화 작용 등의 섭입대에서 나타나는 여러 지질학적 현상들을 이해하는 중요한 지구화학적 추적자로 이용된다. 뿐만 아니라 붕소는 소량으로도 용융체의 점성도 및 용해도와 같은 용융체의 이동 물성에도 영향을 준다. 붕소의 동위 원소 분배 정도는 온도 외에 붕소의 배위수와 밀접한 관련이 있으므로, 붕소를 함유한 함수 유문암질 용융체 및 유리의 압력에 따른 원자 구조 변화 규명은 지구 또는 행성 내부에서 일어나는 지구화학적 현상 이해에 도움을 준다. 온도가 낮고 물이 풍부할 것으로 예상되는 섭입대에서 약 300 km 깊이까지 맨틀이 녹고, 붕소가 섭입할 수 있으므로, 약 10 GPa에 해당하는 압력 범위까지의 붕소를 함유한 마그마 용융체의 고압 구조를 규명하는 것이 붕소 및 물의 순환을 이해하는 데 필수적이다. 이러한 중요성에도 불구하고, 3 GPa 이상의 압력에서 붕소를 함유한 함수 유문암질 용융체의 원자 구조는 밝혀진 바 없다. 본 학위 논문의 주된 목적은 고상 핵자기 공명 분광분석을 이용하여 붕소를 함유한 유문암질 유리의 압력에 따른 양이온의 배위수 변화와 네트워크 연결도를 통해 원자 구조 변화가 붕소 동위 원소를 포함한 여러 물성에 미치는 영향을 규명하는 데에 있다. 지구 내부 약 270 km에 해당하는 9.2 GPa까지의 압력 환경에서 붕소를 함유한 비정질 마그마의 원자 구조를 규명하였다. 상압 환경에서 이원계 비정질 소듐보레이트와 사성분계 비정질 소듐 알루미노보로실리케이트(NaBSiO4–NaAlSiO4 및 NaBSi3O8–NaAlSi3O8) 조성 변화에 따른 구조 변화가 규명되었다. 특히 붕소의 위상학적 구조와 각 배위 환경간의 공간적 친밀도 정보와 각 핵종(B, Al, 및 O)에 대한 NMR 매개 변수가 획득되었다. 알칼리 함량이 낮은 소듐보레이트 유리에서 처음으로 2개의 [4]B 피크가 분리되어 관찰되었다. 17O 이차원 3QMAS NMR 결과를 통해 NaAl0.25B0.75SiO4 유리에서 Na-O-B 피크의 존재를 처음으로 관찰하였다. 11B DQMAS NMR 기법을 이용하여 붕소를 함유한 네펠린 유리(NaAlSiO4-NaBSiO4)의 [3]B 및 [4]B 사이의 공간적 친화도가 B/Al 비율에 따라 규명되었다. 본 연구에서 획득한 사중극자 커플링 상수(quadrupolar coupling constant, Cq)와 등방성 화학적 차폐(isotropic chemical shift, δiso)의 조성에 따른 변화를 통해, 산소를 사이에 두고 결합된 2차 최근접 양이온(2nd nearest neighbors)의 환경과 위상학적 무질서도 변화에 대한 조성 효과에 원자 구조 단위의 실마리를 제공하였다. B/Al 및 Si/B 비율에 따른 양이온의 배위 환경 변화 및 네크워크 중합도의 변화를 규명하기 위해 네펠린(nepheline, NaAlSiO4)-말린코아이트(malinkoite, NaBSiO4), 알바이트(albite, NaAlSi3O8)-리드멀그너라이트(reedmergnerite, NaBSi3O8)의 유사이원계 유리의 원자 구조를 NMR을 이용하여 분석하였다. B/Al 및 Si/B의 비율이 증가함에 따라 붕소의 배위수가 3에서 4로 증가하는 것이 확인되었다. 특정 조성의 유리(NaAl0.25B0.75SiO4)에서는 소량의 [5]Al가 관찰되었으나 이를 제외한 모든 조성의 유리에서 대부분의 알루미늄의 배위수는 4였다. B/Al 비율이 증가함에 따라, B-O-B와 Na-NBO가 증가하는 것이 관찰되었고, 이는 유리의 급격한 용해도 증가에 실마리를 제공한다. B-O-B와 Na-O-Si는 상대적으로 약한 결합을 이루므로 이들의 증가는 용융체의 점성도 감소에 영향을 미칠 것이다. 본 연구에서 획득한 [3,4]B 분율을 통해 유문암질 용융체의 붕소 동위 원소 변화 경향을 추정하였고, 붕소의 함량이 증가함에 따라 마그마 용융체에 10B가 우선적으로 부화한다는 것을 확인하였다. Si/B 비율이 증가함에 따라 [3]B 분율이 감소하였고, 이는 섭입대에서 멀어질수록 감소하는 δ11B의 변화를 부분적으로 설명할 수 있다. Si/B 비율이 다른 붕소를 함유한 네펠린과 알바이트 유리의 9.2 GPa 압력까지 원자 구조 변화를 규명하였다. 6 GPa까지 압력이 증가함에 따라 붕소의 배위수 변화가 우세하였지만, 그 이상의 압력에서는 알루미늄의 배위수 변화가 우세하였다. 압력 영역에 따른 배위수 변화의 양상에 대해, 6 GPa까지는 NBO에 의해 붕소의 배위수가 증가하다가 NBO가 소진 된 후, 삼중산소의 형성과 더불어 알루미늄의 배위수가 증가하는 것으로 메커니즘을 제안하였다. 압력에 따른 [4]B의 증가는 실리콘의 함량이 낮은 네펠린 유리에서 두드러졌고, 이는 압력에 따른 [4]B의 생성으로 해당 마그마 용융체가 10B를 선호할 수 있다는 것을 보여준다. 깊은 맨틀에서 실리카 함량이 적을수록 규산염 용융체의 붕소 배위 환경 변화에 따른 동위 원소 선호 정도가 커질 것으로 예상된다. 붕소는 지각-맨틀의 물의 순환에 대한 간접적인 지시자로도 이용이 되므로 고압 환경에서 규산염 용융체에 물의 함량에 따른 붕소의 원자 환경 규명은 필수적이다. 지하 약 240 km 깊이에 해당하는 8 GPa까지의 압력 환경에서의 붕소를 함유한 함수 유문암질 유리의 양이온의 원자 환경에 물이 미치는 영향을 규명하였다. 물의 함량이 증가함에 따라 [4]B의 분율은 증가하였고, 고배위수 알루미늄([5,6]Al)의 함량은 감소하였다. 물의 함량이 약 1 wt% 첨가되었을 때, 붕소 배위수 변화가 우세하였고, 이는 OH-에 의한 것으로 추정된다. 물이 8 wt%까지 첨가되었을 때, 알루미늄 배위수가 증가하였고, 이는 특정 물의 함량 이상에서는 [5,6]Al 분율의 감소가 중단되고 다시 알루미늄 배위수가 증가한다는 것을 보여준다. [4]B에 10B가 부화하므로, 고압 환경에서 함수 규산염 용융체에 무수 환경보다 더 많은 10B가 부화하여 δ11B가 낮아지는 것을 선호할 것으로 예상된다. 붕소를 함유한 소듐 알루미노규산염 유리의 조성 및 압력에 따른 소듐 원자 환경 변화를 23Na NMR 분광 분석을 이용하여 규명하였다. 23Na δiso와 Cq를 이차원 3QMAS NMR 스펙트럼으로부터 획득하였다. 실리카 함량[Si/(B+Al)]이 3에서 1로 작아짐에 따라, 23Na δiso의 값이 압력에 관계 없이 약 7 ppm 증가하였다. 실리카 함량에 관계 없이, 상압 환경과 9.2 GPa 압력 환경을 비교하였을 때, 23Na δiso 값은 약 2 ppm 증가하였다. 압력 및 조성에 따른 23Na δiso 변화의 차이를 통해 본 연구에서의 조성 차이가 9.2 GPa의 압력 환경에서보다 소듐 원자 환경에 더 큰 영향을 미친다는 것을 알 수 있다. δiso의 변화 정도와는 달리 Cq의 변화는 조성 및 압력에 따라 유의미하게 관찰되지 않았다. 23Na 등방성 화학적 차폐의 증가는 평균 Na-O 결합 길이의 감소를 의미한다. Na-O 결합 길이는 소듐의 확산 및 이동에 영향을 준다. 유리의 전기 전도도에는 소듐과 같은 양이온 이동이 지배적으로 영향을 미치므로, 본 연구의 Na 환경의 조성 및 압력에 따른 등방성 화학적 차폐의 변화는 Na 이온의 이동에 대한 원자 단위의 기작 제공과 더불어 전기 전도도의 이해에 도움이 될 것이다. 본 학위 논문의 결과는 고압 맨틀 용융체의 붕소 동위 원소 조성에 대한 압력 및 조성에 따른 체계적인 원자 단위의 기작을 제공하며, 지구 내부 붕소 순환에 대한 정량화를 가능하게 한다. 압력 및 조성에 따른 붕소 배위 환경 변화는 붕소 동위 원소 조성 변화를 설명할 때, 규산염 용융체 내의 조성 및 용융 생성 당시의 압력 환경 또한 고려해야 한다는 것을 시사한다. 붕소를 함유한 규산염 유리는 핵폐기물 유리의 모델로, 조성에 따른 붕규산염 유리의 원자 구조 규명은 핵폐기물 유리와 지하수의 반응성 및 유리의 안정성 예측에 도움을 줄 것이다.

Boronizing 및 Multi-boronizing 處理에 의한 鋼材의 表面物性 向上에 관한 硏究

조재현 昌原大學校 2003 국내박사

This paper has been investigated on the effects of surface properties with various boronizing techniques. Three kinds of boronizing processes were applied, such as the paste thermal diffusion boronizing, plasma aided paste boronizing, and multi-boronizing, and the various substrate alloys were used, such as carbon steels, stainless steels, Mar-M 247 superalloy. The boronizing behaviors and properties of the boride layers were examined in the various substrate alloys by analyzing the thickness of the boride layer, distribution of hardness, wear resistance, corrosion resistance, and high temperature oxidation etc. In the case of paste thermal diffusion boronizing treatment, the thickness of boride layer reduced with increasing the carbon content, and increased with the treatment temperature and time. The XRD results showed that the phase of the boride layer consisted of FeB and Fe_(2)B on carbon steels, and FeB, Fe_(2)B, and CrB on the 12Cr steel. The boronizing treatment improved the wear, erosion resistances and corrosion resistance under acidic solutions. The resistance of high temperature oxidation was also improved by the boronizing treatment. Plasma aided paste boronizing treatment was applied to overcome disadvantages of the thermal diffusion boronizing treatment which resulted in distortion of the sample. This process is useful method because the boronizing mechanism is combined with gas and liquid reaction. The experimental results showed that the boride layer by the plasma aided paste boronizing formed at lower temperatures and shorter treatment time and lower activation energy for boronizing than that by the thermal diffusion process. However, the properties of the boride layer were similar to those of thermal diffusion process. The XRD results showed that the FeB, Ni_(3)B, CrB phases were found in the STS 304 alloy. The corrosion resistance decreased in 1 mole sulpuric acid at 298°(K). The effect of multi-boronizing treatment on the surface properties was examined in the hot working tool steel (STD61) and the Mar-M247 superalloy by analyzing the boronizing behavior and boride layer. The boronizing behavior and properties of boride were similar to the results of the thermal diffusion boronizing and plasma boronizing. Ce was distributed ununiformly in the boride layer and a Cr-rich zone was observed in the FeB boride layer. The hot corrosion resistance of the Mar-M247 superalloy was examined in Na_(2)SO_(4)-NaCl molten salt. The XRD results showed that the Ni_2Al_3 phase formed between the aluminized layer and substrate when the surface modification temperature was below 1273°(K), however, the NiAl phase formed when the temperature was above 1273°(K). The intensity of the XRD peak in the NiAl phase increased after the post heat treatment, where the NiAl phase resulted in enhancing the hot corrosion resistance of the aluminized layer. The suitable mixed ratio of pack materials for aluminizing was 25 wt.% Al : 4 wt.% NH4Cl : 71 wt.% Al_(2)O_(3) powder. The 170μm thickness of aluminide layer was obtained at 1273^vK for 20 hours. The corrosion resistance of boro-aluminized Mar- M247 specimens decreased due to blocking outward diffusion of Cr by boron. It was also found that the cohesion between the oxide scale and aluminized layer decreased during thermal cycling in Na_(2)SO_(4)-NaCl molten salt.

Boron 添加에 따른 炭素材料의 機械的 物性變化 및 酸化擧動

盧伯男 충남대학교 1999 국내석사

This paper describes the mechanical properties and oxidation resistance of carbon fibers and 2D C/C composites with and without additions of boron additives(boron and boron oxide), and describes the changes in these properties resulting from increased HTT of the composites. In case of carbon fibers, for this experiment, were heat treated up to 1800℃, 2000℃, 2200℃, 2400℃, 2600℃ and 2800℃ each with and without boron coating on the surface of fibers. On the other hand, for invesgigation of 2D carbon/carbon composites, specimen were heat treated up to 1800℃, 2000℃, 2200℃, 2400℃ and 2600℃ with addition of boron in the matrix. and prepared references with same HTT condition without boron addition. The treatment of boron in carbon fibers below 2200℃ did not show the improvement of tensile strength and modulus except for the improvement of oxidation resistance. and B_2O_3 coating layer more contribute than that of crystallization of carbon fiber in terms of reducing the active sites from oxygenl attacks. In cases of boron-doped carbon fiber above 2600℃, carbon fibers are doped substitutionally with boron, which acceletate the graphitization of carbon fibers. The addition of boron in matrix showed the decrease of mechanical properties of 2D carbon/carbon composites. but 1% and 3% boron added specimen heat-treated up to 1700℃ and 2000℃ showed the slight increasement of ILSS. It is probably that boron particles bar from the propagation of cracks byt others heat-treated up to 2300℃ and 2600℃ showed no differences between boron added specimen and non-added specimen. Boron oxide implanted carbon fibers showed more resistant on oxygen attack but what heat-treated below 2200℃ showed almost trend of air oxidation. Although protection barrier B_2O_3 might be formed on the surface of carbon fibers and protect sxygen attack a little bit but boron oxide may not affect the graphitization which is the most important factor for oxidation resistance. These results described that Heat treatment above 2300℃ resulted in a reaction between the inhibitors and the carbonaceous components of the composites. These reaction affected both fibers and matrix, resulting in almost complete crystallization of the composite components. This crystallization transformed the microstructure of the carbon fibers and composites, weakening them and producing brittle failure behaviour.

Bimetallic catalysts supported on mesoporous carbon for hydrogenation of succinic Acid to γ-butyrolactone and 1,4-butanediol

강기혁 서울대학교 대학원 2017 국내박사

1,4-Butanediol (BDO) is a versatile chemical that can be used in a wide range of industrial applications. BDO has been used as an organic solvent and a fine chemical for production of adhesives, fibers, and polyurethanes. Recently, BDO has received much attention as an important raw material for thermoplastic polymers such as polybutylene succinate (PBS) and polybutylene terephthalate (PBT). As the consumption of these polymers is growing faster in electronics and automobile industries, in particular, the global demand for BDO is expected to increase rapidly. BDO has been produced through several conventional routes; hydrogenation of maleic anhydride, isomerization of propylene oxide, and acetoxylation of butadiene. These processes rely on petrochemical feedstocks derived from fossil fuel. Due to the limited amount of fossil fuel, however, current research trend for BDO production moves toward the utilization of renewable energy sources such as biomass. In this respect, conversion of succinic acid to BDO by catalytic hydrogenation has attracted recent attraction as a promising process, because succinic acid can be obtained from bio-refinery process. Hydrogenation of succinic acid to BDO occurs via two-step hydrogenation reactions as shown in Fig. 1. Succinic acid is first transformed into -butyrolactone (GBL) by hydrogenation, and then BDO or tetrahydrofuran (THF) is formed through consecutive hydrogenation of GBL. For the catalytic conversion of succinic acid, various noble metal catalysts such as Pd, Pt, Rh, Ru, and Re have been investigated. Among these catalysts, rhenium has been considered as the most efficient monometallic catalyst for the selective formation of BDO. However, several studies have shown that rhenium alone was not sufficient to obtain high yield for BDO. In an attempt to improve BDO production by hydrogenation of succinic acid, Re-based bimetallic catalysts, including Re-Pt/C, Re-Pd/C, Re-Pd/TiO2, and Re-Ru/C, have been investigated. Nonetheless, the researches have rarely elucidated the effect of interaction between rhenium and other metal on the selective formation of BDO from succinic acid. This is because combination of rhenium and noble metal causes difficulty in structural and chemical analyses. For example, rhenium can be miscible with noble metals such as Pt, Pd, and Ru to form a solid-solution due to their similar atomic sizes and surface energies, which complicates characterization. Moreover, since rhenium does not cause dissociative hydrogen chemisorption at low temperature, either modified hydrogen chemisorption or CO chemisorption method is essential for determining metal dispersion of Re-based catalyst. In addition, only a few studies have focused on the modification of carbon support for hydrogenation of succinic acid to BDO. It has been reported that addition of non-metal elements such as sulfur, boron, and phosphorous into carbon affects physicochemical properties of carbon support [24-30]. In particular, boron can be easily substituted for carbon atom during carbon growth process, which significantly changes structural and electronic properties of carbon lattice. Thus, it is expected that boron-containing carbon effectively interacts with active metal species to enhance reducibility and hydrogen adsorption behavior of supported metal catalyst. To utilize transition metals for production of BDO, we have studied for a bifunctional metal catalyst supported on mesoporous carbon, which contained rhenium and copper. Interestingly, this catalyst showed a considerable catalytic activity in the hydrogenation of succinic acid to GBL and BDO via dimethyl succinate (DMS) in the presence of methanol. Although the catalyst contains transition metal, yield for GBL and BDO over the catalyst was comparable to that over noble metal-based catalysts, due to its bifunctional catalysis. Thus, a systematic investigation on the catalyst based on a combination of transition metal and noble metal for hydrogenation of succinic acid to GBL and BDO would be worthwhile. In this work, Re-based metal catalysts were supported on mesoporous carbon, and they were applied to the liquid-phase hydrogenation of succinic acid to BDO. First of all, A series of Re-Ru bimetallic catalysts supported on mesoporous carbon (denoted as (0.6-x)Re-xRu/MC) were prepared by a single-step surfactant-templating method and a subsequent incipient wetness impregnation method with a variation of ruthenium loading (x, mol%), and they were applied to the liquid-phase hydrogenation of succinic acid to 1,4-butanediol (BDO). The effect of metal content on the catalytic activities and physicochemical properties of (0.6-x)Re-xRu/MC catalysts was investigated. It was found that a Re-Ru miscible phase was formed in the catalysts during the reduction process, and it was responsible for strong interaction between rhenium and ruthenium. It was also revealed that reducibility, metal dispersion, and oxidation state of (0.6-x)Re-xRu/MC catalysts were affected by Re:Ru molar ratio. In particular, the oxidation state was closely related to the hydrogen adsorption behavior of the catalysts. The amount of weak hydrogen-binding sites increased with increasing the ratios of metallic rhenium (Re0) and ruthenium (Ru0) with respect to total metallic species in the reduced (0.6-x)Re-xRu/MC catalysts. Catalytic performance in the hydrogenation of succinic acid to BDO over (0.6-x)Re-xRu/MC showed a volcano-shaped trend with respect to Re:Ru molar ratio. This result was well correlated with the amount of weak hydrogen-binding sites of the catalysts. Among the catalysts tested, 0.3Re-0.3Ru/MC with the largest amount of weak hydrogen-binding sites showed the best catalytic performance in the BDO production by hydrogenation of succinic acid. A series of Re-Ru bimetallic catalysts supported on mesoporous boron-modified carbon (denoted as Re-Ru/xBMC, x = B/C molar ratio) were prepared by a single-step surfactant-templating method and a subsequent incipient wetness impregnation method, and they were used for liquid-phase hydrogenation of succinic acid to 1,4-butandiol (BDO). The effect of boron addition on the catalytic activities and physicochemical properties of Re-Ru/xBMC catalysts was investigated. It was found that the addition of boron into carbon support affected surface area, metal dispersion, and reducibility of rhenium and ruthenium species in the Re-Ru/xBMC catalysts. It was also observed that boron species in carbon framework existed in several different phases such as substituted boron, partial oxidized boron, and boron oxide. In particular, the amount of substituted boron species was closely related to the hydrogen adsorption behavior of Re-Ru/xBMC catalysts. The amount of weak hydrogen-binding sites increased with increasing the amount of substituted boron species of the catalysts. Yield for BDO in the hydrogenation of succinic acid showed a volcano-shaped trend with respect to B/C molar ratio. This result was in good agreement with the amount of weak hydrogen-binding sites of the catalysts. It was revealed that TOFBDO increased with increasing the amount of weak hydrogen-binding sites of Re-Ru/xBMC catalysts. Among the catalysts, Re-Ru/0.04BMC with the largest amount of weak hydrogen-binding sites served as an efficient catalyst in the selective formation of BDO by hydrogenation of succinic acid. A mesoporous rhenium-copper-carbon composite catalyst (Re-Cu-MC) was prepared by a facile single-step surfactant-templating method. For comparison, a series of mesoporous carbon-supported catalysts (Re/Cu-MC, Cu/Re-MC, and Re-Cu/MC) were also prepared. The catalysts were applied to the liquid-phase hydrogenation of succinic acid to -butyrolactone (GBL) and 1,4-butanediol (BDO). The effect of preparation method on the physicochemical properties and catalytic activities of the catalysts was investigated. It was found that the catalysts based on metal-carbon composite (Re-Cu-MC, Re/Cu-MC, and Cu/Re-MC) were favorable for enhancing textural properties and metal-support interaction of the catalysts. Surface atomic ratios of metal species (Re/C and Cu/C) on the catalyst surface increased with increasing metal-support interaction. Yield for GBL and BDO increased with decreasing average metal particle size of the catalysts. It was revealed that metal particle size of the catalysts served as a key factor determining the catalytic activity and stability in the reaction. Among the catalysts tested, Re-Cu-MC catalyst with the smallest average metal particle size showed the best catalytic performance in the hydrogenation of succinic acid to GBL and BDO. In summary, various Re-based metal catalysts supported on mesoporous carbon were prepared, and they were applied to the liquid-phase hydrogenation of succinic acid to BDO. The catalysts were characterized by nitrogen adsorption-desorption, TPR, XRD, CO chemisorption, TEM, STEM-EDX mapping, Raman, XPS, and H2-TPD analyses.

Etch-back 공정을 통한 고효율 N-type 태양전지의 보론 에미터 프로파일 형성

심경배 성균관대학교 일반대학원 2017 국내석사

P-type 결정질 실리콘 웨이퍼를 이용하여 제작하는 태양전지는 현재까지도 태양광 발전 분야에서 높은 점유율을 차지하고 있다. 하지만 p-type 웨이퍼에 존재하는 최대 1×1018개의 oxygen이 boron dopant와 결합하여 boron-oxygen complex를 형성하게 되고, 이는 light-induced degradation (LID)을 야기하게 되어 minority carrier lifetime (MCLT)의 감소와 더불어 모듈에서는 1-3%의 효율 감소를 보이며 태양전지에서는 0.2-0.5% 효율을 저하시키는 원인이 된다. 그러나 N-type 태양전지의 경우 기판에 phosphorus가 존재하기 때문에 B-O complex에 의한 LID 현상이 생기지 않을 뿐만 아니라 metal impurity에 의한 불안정성이 없어 높은 lifetime을 가지고 있다. 하지만 boron emitter 형성시의 boron rich layer (BRL)의 형성으로 인한 MCLT (Minority Carrier Lifetime)의 감소 및 효율저하의 문제가 있으며 BRL 형성을 최소화하고 etch-back 공정을 통해 MCLT를 극대화 하는 고면저항 boron emitter 형성 공정 최적화 연구를 진행하였다. boron emitter의 BRL이 잔존하는 상태에서의 etch-back 공정에서는 균일도에 문제가 있다. 따라서 BRL 제거를 위해 in-situ oxidation을 Ramp-down 구간에서 진행하였으며, in-situ Oxidation의 N2와 O2 ratio 변화에 따른 BSG 에칭공정 후 10% HF에서의 Hydrophobic한 표면이 확인하였다. MCLT의 결과는 O2 flow 200 sccm에서 가장 높은 MCLT인 대략 120 μs 및 균일도 5.42 % 확인하였다. 이후 deep junction depth와 낮은 표면 농도를 갖는 boron doping profile을 형성 후 etch-back 공정을 통해 고면저항의 emitter 형성 하였다. 면저항이 증가함에 따라 boron emitter에서의 내부의 misfit dislocation과 금속 불순물과 같은 SRV 증가요소의 감소로 인해 MCLT의 증가가 되는 것으로 판단되며 boron depletion layer (BDL)를 제거되는 100 Ω/sq.에서 SiOx passivation 후 MCLT 360 μs를 확보 하였다. 먼저 태양전지 제작 전 TCAD를 통해 etch-back 공정에 따른 doping profile 변화에 대한 물리적 효과를 분석하였고 그 후 면저항에 따른 태양전지를 제작하여 특성을 분석하였다. 실험 결과 boron emitter 면저항이 100 Ω/sq.에서 효율 19.48%, Voc 636.9 mV, Jsc 39.3 mA/cm2, FF 77.56%으로 다른 면저항 대비 가장 높은 Voc, FF 및 효율을 얻었다. Jsc는 면저항이 증가하면서 재결합의 감소로 150 Ω/sq.에서 39.33 mA/cm2으로 가장 높았으며 200 Ω/sq.에서는 다소 감소하는 경향을 보였다. FF는 BDL이 제거되는 100 Ω/sq.에서 평균적으로 가장 높은 값을 얻었으며 BDL만 제거된 100 Ω/sq.에서 표면 농도가 가장 높으며 접촉 저항이 낮아 FF가 가장 높은 것이라 판단된다. 본 연구를 통해 selective emitter와 같은 복잡한 구조가 아닌 일반적인 구조의 고효율 n-type 결정질 태양전지의 고효율 양산공정 개발이 가능할 것으로 기대된다.

Sucrose, boron, calcium이 장미의 花粉發芽와 花粉管伸長에 미치는 影響

김일섭 建國大學校 大學院 1989 국내석사

花木類인 Rosa hybrida의 育種 및 生殖生理 硏究에 必要한 基礎資料를 얻기 위하여 몇가지 品種을 選擇하여 花粉의 形態的 特性을 살펴보고, Sucrose, Boron, Calcium 等 몇가지 要因이 장미의 花粉發芽와 花粉管伸長에 미치는 影響을 調査한 것으로 그 結果를 要約하면 다음과 같다. 1. Rosa species 들의 Polar length , Equatorial dianleter 測定 結果 5品種 모두 有意性이 없었으며 P/E Ratio도 거의 1에 가까웠다. 2. Sucrose 添加培地에서는 대부분 15-20% 濃度에서 가장 높은 發芽率을 보였으며 R. H.T Madelon이 다른 4品種보다 뛰어난 發芽率을 나타내었다. 3. Sucrose 濃度別 花粉管 길이는 R. H.T Athena를 除外한 4品種에 있어 20%濃度에서 가장 優秀하였고 R. H.T Madelon이 가장 좋은 伸長率을 나타내었다. 4. Boron 添加培地에서의 發芽率은 Sucrose 單用培地에서보다 약2倍정도의 增加를 보였고 品種間에는 R. H.T Madelon이 가장 優秀하였다. Calcium 添加培地에서는 Sucrose 單用培地보다는 優秀하지만 Boron 및 Boron + Calcium 添加培地보다는 發芽率이 낮은 傾向이 있었다. 5. Boron 添加培地에서의 花粉管 길이는 R. H.T Super를 除外한 나머지 品種에서 가장 效果的이었고 品種間에 있어서는 R. H.T Sonia가 가장 길게 伸長하였으며 Boron + Calcium 添加培地에 있어서는 R. H.T Veronica가 가장 긴 花粉管伸長을 나타내었다. This study was carried out to obtain basic data about horticultural plant breeding and vegetative physiology. Effect of several factors such as sucrose, boron, calcium on the pollen germination and pollen tube growth in Rose hybrida was investigated and results are summarized as follows. 1. In the Rosa species, there was no significance on the Polar length, Equatorial diameter and P/E Ratio was nearly just the 1. 2. It was found that the germination rate was very excellent at medium of sucrose 15-20%. Especially, Rosa H.T Madelon showed great pollen germination than other species. 3. The pollen tube growth was excellent at 20% medium in 4 species except Rosa H.T Athena and among other things Rosa H.T Madelon was remarkable. 4. Pollen germination rate at boron was about twice than at medium of sucrose alone. Rosa H.T Madelon was very good one of the 5 species. In calcium medium, pollen germination was higher than at medium of sucrose alone but had a low tendency to than boron or boron+calcium medium. 5. At-boron medium, the pollen tube growth was excellent in 4 species except for Rosa H.T Super and among other things Rosa H.T Sonia was outstanding. At boron+calcium medium, Rosa H.T Veronica was very effective.

Effect of boron content on atomic structure of boron-bearing multicomponent oxide glasses : a view from the solid-state NMR

이아침 서울대학교 대학원 2017 국내석사

Understanding the effect of boron content on atomic structures of boron-bearing multicomponent silicate melts is essential to reveal the atomistic origins of diverse geochemical processes involving silica-rich magmas, such as explosive volcanic eruption and the reaction of magma in contact with aqueous solutions. It is also considered crucial in environmental science because a nuclear waste glasses contain B2O3. Despite the importance, the detailed atomic structure of boron-bearing multicomponent silicate glasses remains unsolved. We report experimental results on the effect of boron content on the atomic structures of sodium borate glasses and boron-bearing multicomponent silicate melts [nepheline (NaAlSiO4)- malinkoite (NaBSiO4) and albite (NaAlSi3O8)- reedmergnerite (NaBSi3O8) pseudo-binary glasses] using the high-resolution solid-state NMR (11B, 27Al, and 17O). The 11B NMR spectra of Na2O-B2O3 glasses show that four-coordinated boron ([4]B) increases at the expense of ring (three-coordinated boron, [3]B) not of non-ring ([3]B) with increasing sodium content based on the new interpretation from the results of quantum chemical calculations that 11B NMR chemical shift of non-ring ([3]B) increases with increasing sodium content. The two topological species of [4]B are firstly observed in 11B 3QMAS NMR spectra for Na2O-B2O3 glasses. The 11B NMR spectra of NaAlSiO4-NaBSiO4 and NaAlSi3O8-NaBSi3O8 glasses show that [4]B increases as boron content increases while non-ring ([3]B) decreases. 27Al MAS NMR spectra for NaAlSiO4-NaBSiO4 glasses confirm that four-coordinated aluminum ([4]Al) is dominant. It is also observed that a drastic decrease in the peak widths (full-width at half-maximum, FWHM) of [4]Al with an addition of boron into nepheline glasses, indicating a decrease in structural and topological disorder around [4]Al. The quantitative atomic environments around boron of multicomponent glasses are estimated from the simulation results of 11B MAS NMR spectra, revealing complex-nonlinear variation of boron topology with varying composition. 17O MAS and 3QMAS NMR spectra for NaAlSiO4-NaBSiO4 glasses show that Na-O-Si, B-O-B, and B-O-Si increase with increasing boron content, indicating that a drastic increase in dissolution rate might be due to an increase in B-O-B and B-O-Si which are relatively weaker bridging oxygen (BOs). An increase in non-bridging oxygen (NBO), Na-O-Si, implying a decrease in the degree of polymerization can explain the low viscosity of boron-bearing silicate melts. Na-O-B is firstly observed in 17O 3QMAS NMR spectra for NaAl0.25B0.75SiO4 glasses. The current experimental results with the changes in coordination environment, topological structure, and network connectivity in the nepheline-malinkoite and albite-reedmergnerite glasses can improve understanding of the structure-property relationships including dissolution and viscosity of multicomponent boron-bearing silicate melts.

실리콘 내 Boron 정량 분석

이상원 한서대학교 대학원 화학공학과 2010 국내석사

본 연구는 실리콘 내 boron 정량 분석을 하기 위한 전처리 과정을 수행하였다. 실리콘은 태양전지 및 태양광 모듈 부품 소재로써 현재 부각되고 있는 그린 에너지 산업의 주축이 되고 있으며, 실리콘에 포함된 boron 정량 분석의 중요성이 부각되고 있다. boron은 P형 실리콘 dopant 물질로써 life time 및 모듈 효율에 큰 영향을 미치고 있다. ICP-AES 분석 과정 중 전처리 공정을 통하여 boron 정량 분석 방법에 관해 연구를 수행하였다. 실리콘 내 boron 분석을 위한 전처리 과정에서 실리콘이 과다 포함된 경우 ICP-AES의 boron 파장 249.678nm, 249.773nm에서 matrix에 영향을 주어 실제 boron 측정 값 보다 높게 측정되는 결과를 얻었으며, 실리콘을 제거하여 분석을 진행 할 경우 boron의 휘발 특성으로 인해 boron이 소실되는 것을 확인하였다. Boron의 경우 상온 및 가열 상태에서 휘발되는 특성을 제어하기 위하여 마니톨(manitol)을 사용하였다. 마니톨은 boron을 흡착하여 산 용액 상태에서 녹아 ICP-AES 분석 중 boron 정량 분석에 중요한 첨가제로써 사용이 가능했으며, 마니톨에 대한 1차 오염이 boron 정량 분석에 영향을 미치지 않는 것을 확인하였다. boron 분석 과정 중 파장의 영향을 주는 실리콘을 SiF₄형태로 제거하고 휘발되는 boron을 제어하여 정량 분석이 가능하다는 결론을 얻었다. 실제 측정 데이터에서도 95%이상의 회수율을 보였으며 실험내용을 기반으로 실리콘 내 boron 정량 분석 방법을 확립하고 고찰하였다. This study was focused on the pre-treatment of silicon which was a basic major material for the solar cells and solar modulus to analyzer quantitative precise analysis of boron in silicon with the ICP-AES. Boron in silicon is a dopant material for making P type silicon and strongly influences solar module efficiency. when the pretreated sample for ICP-AES analysis contained silicon, 249.678nm, 249.773nm of boron wavelength in the ICP-AES affected matrix so that boron analysis value of the ICP-AES was measured higher than real boron measurement. And in the processing of pre-treatment for the complete removing silicon in the sample, it was found that boron also disappeared due to its volatility. It was found that it was very important to keep a boron without silicon in the processing of sample pre-treatment for precise analysis of boron. Therefore we tried to use manitol to control boron volatility not only at room temperature but also in the heating state. It was found that manitol played important role for the quantitative precise analysis of ICP-AES, because it adsorbed boron and was melted in the pre-treatment solution of strong acid and didn't affect boron analysis of ICP-AES. In this study, it was made the conclusion that it is possible quantitative precise analysis of boron was established by removing silicon that affected wavelength as the SiF₄ and by controlling volatile boron with the manitol.

Formation Mechanism of Screen Printed Ag in Boron Emitter

김찬석 Graduate School, Korea University 2015 국내박사

N-type wafer has advantages to achieve high efficiency solar cells. Metal impurities are more detrimental to n-type silicon, and it leads higher minority carrier lifetime. Fabrication of n-type crystalline silicon solar cells requires the formation of p-type emitter on n-type based wafer. Thus far, several methods, such as thermal diffusion, implantation, and spin coating have been adopted for the emitter formation. Thermal boron diffusion is one of the widely used methods for emitter formation due to its simplicity and productivity. Boron emitter using in n-type silicon solar cells has contact problems in screen printing technique. After firing process with silver paste has relatively high ρc over 100 mΩ?cm2. A lot of research has been studied to solve the contact problem. Aluminum added silver (Ag/Al) paste is the most powerful method to answer the solution so far. However, it still has problems like shunting behaviour, high line resistance. During firing process with silver paste, inverted pyramids of emitter are formed by silicon etching reaction. However, in boron emitter, it would be nearly progressed. When silicon is etched in a solution such as potassium hydroxide (KOH), hydroxide ion (OH-) etches silicon surface. The ions are created due to decomposition of water molecules (H2O) by electrons contained in silicon surface. In high boron doped emitter, the etching reaction is hardly occurred on account of little electrons. This study suggests that electron injection during firing is one of the candidates contributing to lowering contact resistance. More silver precipitates would formed by the injection of electrons into the boron emitter. This is confirmed by observing the silver crystallite or dendrite structures on boron emitter by using field emission scanning electron microscopy, and measuring the contact resistance between the boron emitter and screen-printed silver by using the transfer length method. The electron-injected sample has ~10,000 times lower contact resistance than normal samples. The contact resistance of the electron-injected sample is 0.021 mΩ?cm2 in optimized conditions and is lower than that of conventional p-type silicon solar cells. Thus, electron injection is a potential method to using silver paste in n-type silicon solar cells. Moreover, during the cooling-down stage, silver causes dendrite formation by electrochemical migration under electron injection condition; then, silver grows as a crystallite by silicon etching reaction if silver and oxygen are sufficiently dissolved in glass layer.