In this study, crystallization was effectively suppressed in Al-based metallic glasses (Al-MGs) during pulverization by cryo-milling by applying an extremely low processing temperature and using a surfactant. Before Al-MGs can be used as an additive in Ag paste for solar cells, the particle sizes of the Al-MGs must be reduced by milling. However, during the ball milling process crystallization of the Al-MG is a problem. Once the Al-MG is crystallized, they no longer exhibit glass-like behavior, such as thermoplastic deformation, which is critical to decrease the electrical resistance of the Ag electrode. The main reason for crystallization during the ball milling process is the heat generated by collisions between the particles and the balls, or between the particles. Once the heat reaches the crystallization temperature of the Al-MGs, they start crystallization. Another reason for the crystallization is agglomeration of the particles. If the initially fed particles become severely agglomerated, they coalesce instead of being pulverized during the milling. The coalesced particles experience more collisions and finally crystallize. In this study, the heat generated during milling was suppressed by using cryo-milling with liquid-nitrogen, which was regularly fed into the milling jar. Also, the MG powders were dispersed using a surfactant before milling, so that the problem of agglomeration was resolved. Cryo-milling with the surfactant led to D50 = 10 um after 6 h milling, and we finally achieved a specific contact resistance of 0.22 mΩcm2 and electrical resistivity of 2.81 μΩcm using the milled MG particles.

시몽동의 기술철학의 “개체화”(individualization)의 기초모델은 “결정화”(crystalization)라는 물리화학적 현상에서 시작된다. 결정화 과정은 결정종(결정씨앗: germe/seed)과 모액(母液: mother liquid)이라는 주위환경(milieu) 사이에서 일어난다. 결정씨앗은 주위환경(milieu) 안에서 자신의 현실적 구조를 형성하며 확장해나간다. 한편 결정씨앗이 자라기 이전에는 잠재력(potential)으로만 남아 있던 주위환경은 결정씨앗이 자라기 시작하면서부터 발동하여, 그 잠재력이 에너지로 전환되고 역동성으로 가득 찬 주위환경이 되어 씨앗의 숙성과 구조화를 가능하게 하여 씨앗의 잠재성을 현실화한다. 시몽동의 결정화와 변환의 시각에서 세이머스 히니(Seamus Heaney)의 전 시집과 시론의 핵심적인 내용을 파악한 조감도를 그려보는 작업은 성장과정에 있는 젊은 시인의 “개체이전의 존재”와 “앞선 미래”를 내다보는 비전을 선험적(apriori)으로 제시해준다. 시몽동의 변환과정은 이질적인 힘을 임시적으로 집결하여 통합을 생성할 뿐 아니라, 존재나 실체를 둘러싸고 있는 것을 구조화하는 것을 설명하여, 개체이전의 존재의 과거와 현재로부터 미지의 미래로 창의적인 도약을 생성한다. 또한 주위환경 내에서 그리고 주위환경으로서 존재를 에워싸고 또 존재를 가능하게 하는 영역을 생성한다. 시몽동의 변환의 시학의 문맥에서 보면 히니의 시론과 시를 새로이 자리매김할 수 있다.

Phosphorus is a vital resource for sustaining agriculture and nutrition, but a limited non-renewable resource. Thus, the recovery of phosphorus from waste activated sludge(WAS) was attempted by microwave heating and magnesium ammonium phosphorus(MAP) crystallization. Polyphosphate-accumulating organisms(PAOs) in WAS release phosphate from the cell when they are exposed to high temperature environments. Microwave heating caused phosphorus and ammonia to release from WAS. The amount was increased with increasing temperature, showing that 88.5% of polyphosphate present in the cells were released in the form of phosphate at 80oC. A similar result was also observed in the release of ammonia. On the other hand, both phosphorus and ammonia were crystallized with magnesium, and then was harvested as MAP. Phosphorus recovery rate reached almost 97.8%, but the ammonia was about 13.4%. These results cleary indicate that phosphorus could be recovered from WAS using a physiological trait of PAOs. Heavy metal analyses also show that the MAP crystal is useful and safe as a phosphorus fertilizer.

과거 모자이크 기법은 바닥에 천을 깔고 타일을 수작업으로 붙여 제작하였다. 하지만 최근 기술의 발달로 데이터 저장 방식이 아날로그에서 디지털로 발전하여 컴퓨터를 통한 이미지 표현과 변환이 가능해지며 모자이크의 표현 기법 또한 다양하게 발전하고, 디지털로의 예술표현 방식으로도 사용 되어지며 공학 분야에서도 그 제작 과정에 대한 연구들이 다양하다. 본 논문에서 제안하는 기법은 나선형으로 실시간 퍼져나가는 결정화(Crystallization)모자이크로 타일요소는 3D석영(Crystal)을 사용 한다. 기존 연구들은 대체로 이미지를 좀 더 세밀하게 묘사하기 위함이 연구 목적의 주를 이루고 있지만 본 기법은 시도되지 않았던 나선 드로잉과 결정화를 접목하고 3D 공간에서의 새로운 모자이크 방식을 시도 한다. 또한 제안하는 기법의 대한 검증과 이를 기반으로 게임으로의 발전방향에 대해 모색한다. 본 기법을 바탕으로 제작된 작품 ‘Spiral Crystallization Photo’ 는 MWU Award`18에 서 Top27에 선정되었으며 Unite Seoul 2018에서 전시 되었다.

One of the major sources causing eutrophication and algal blooms of lakes or streams is phosphorus which comes from point and nonpoint pollution sources. HAP (hydroxyapatite) crystallization using granular alkaline materials can achieve the decrease of phosphorus load from wastewater treatment plants and nonpoint pollution control facilities. In order to induce HAP crystal formation, continuous supply of calcium and hydroxyl ions is required. In this research, considering HAP crystallization, several types of lime-based granular alkaline materials were prepared, and the elution characteristics of calcium and hydroxyl ions of each were analyzed. Also, column tests were performed to verify phosphorus removal efficiencies of granular alkaline materials. Material_1 (gypsum+cement mixed material) achieved the highest pH values in the column tests consistently, also, Material_2 (gypsum+slag mixed material) and Material_3 (calcined limestone material) achieved over pH 9.0 for 240 hours (10 days) and proved the efficiencies of long-term ion supplier for HAP crystallization. In the column tests using Material_3, considerable pH increase and phosphorus removal were carried out according to each linear velocity and filtration depth. T-P removal efficiencies were 87.0, 84.0, 68.0% and those of PO4-P 100.0, 97.0, 80.0% for linear velocity of 1.0, 2.5, 5.0 m/hr respectively. Based on the column test results, the applicability of phosphorus removal processes for small-scale wastewater treatment plants and nonpoint pollution control facilities was found out.

The recent development of electro-optic devices and anticorrosion media has led to the necessity to investigate infrared optical systems with solid-solid interfaces of materials that often have the characteristic of amorphousness. One of the most promising classes of materials for those purposes seems to be the chalcogenide glasses. Chalcogenide glasses, based on the Ge-Sb-Se system, have drawn a great deal of attention because of their use in preparing optical lenses and transparent fibers in the range of 3~12 um. In this study, amorphous Ge-Sb-Se chalcogenide for application in an infrared optical product design and manufacture was prepared by a standard melt-quenching technique. The results of the structural, optical and surface roughness analysis of high purity Ge-Sb-Se chalcogenide glasses are reported after various annealing processes.

Recently, pollution problem in coastal water has become more serious and pollution including red tide serves as a main reason for reduction of fishes resources. Particularly, nutrients such as nitrogen and phosphorus are the most serious pollutants. Normally, biological wastewater treatment process is used in removing such nutrients. However, it is difficult to adopt the biological wastewater treatment process to a small-scale fish processing factory in case of using seawater as wash water. Thus, removing nutrients through struvite crystallization is investigated in this study for treating shrimp processing wastewater. Experiments were conducted by varying molar ratio of Mg2+:NH4-N:PO4-P from 1:1:1 to 2:1:1. It can be concluded that optimum molar ratio is 1:1:1. Struvite crystallization process is compared with chemical coagulation process using PAC and struvite crystallization process is proven as the more effective process in removing nutrients from wastewater. In view of results obtained from these experiments, struvite crystallization process is a promising method in removing nitrogen and phosphorus from wastewater; however, not so good in removing organics. Thus, struvite crystallization process is suitable as the pre-treatment process in treating shrimp processing wastewater and additional biological process is needed to remove organics.

Ni(OH)2 hollow spheres have been prepared by solvent displacement crystallization using a micro-injection device, and the effect of process parameters such as concentration and the relative ratio of the injection speed of the precursor solution, which is an aqueous solution of NiSO4·6H2O, to isopropyl alcohol of displacement solvent have been investigated. The crystal phases after NaOH treatment are in the β-phase for all process parameters. A higher concentration of NiSO4·6H2O aqueous solution is injected by a micro-injection device and bigger Ni(OH)2 hollow spheres with a narrower particle size distribution are formed. The crystallinity and hardness of the as-obtained powder are so poor that hydrothermal treatment of the as-obtained Ni(OH)2 at 120oC for 24 h in distilled water is performed in order to greatly improve the crystallinity. It is thought that a relative ratio of the injection speed of NiSO4·6H2O to that of isopropyl alcohol of at least more than 1 is preferable to synthesize Ni(OH)2 hollow spheres. It is confirmed that this solution- based process is very effective in synthesizing ceramic hollow spheres by simple adjustment of the process parameters such as the concentration and the injection speed.

Silicoaluminophosphate (SAPO-34) zeolite membranes (pore diameter of 0.38nm) have shown high tendency in separation of light gas mixtures. In this work, SAPO-34 membranes were synthesized under various conditions such as different seed, the composition of coating gel and temperature. Membranes prepared by secondary growth method were analyzed using SEM and XRD for the morphology; and gas properties which were tested using a homemade single gas testing apparatus. The crystallinity was improved by the addition of dipropyl amine as an additional structure directing agent (SDA) and also the membrane show nitrogen selectivity in response. Nitrogen selective membranes show a high gas permeance (above 2000 GPU) and low selectivity (max 2.25).

We have investigated the crystallization mechanism of the lithium disilicate (Li2O-2SiO2, LSO) glass particles with different sizes by isothermal and non-isothermal processes. The LSO glass was fabricated by rapid quenching of melt. X-ray diffraction and differential scanning calorimetry measurements were performed. Different crystallization models of Johnson- Mehl-Avrami, modified Ozawa and Arrhenius were adopted to analyze the thermal measurements. The activation energy E and the Avrami exponent n, which describe a crystallization mechanism, were obtained for three different glass particle sizes. Values of E and n for the glass particle with size under 45 μm, 75~106 μm, and 125~150 μm, were 2.28 eV, 2.21 eV, 2.19 eV, and ~1.5 for the isothermal process, respectively. Those values for the non-isothermal process were 2.4 eV, 2.3 eV, 2.2 eV, and ~1.3, for the isothermal process, respectively. The obtained values of the crystallization parameters indicate that the crystallization occurs through the decreasing nucleation rate with a diffusion controlled growth, irrespective to the particle sizes. It is also concluded that the smaller glass particles require the higher heat absorption to be crystallized.

γ-Aminobutyric acid (GABA)-containing salt was prepared by crystallization of a mixture of salt water from deep sea and fermentation broth by lactic acid bacteria that contained GABA converted from glutamic acid. Salt from deep sea water has a lower sodium content but higher calcium, potassium and magnesium contents than commercial salt. Instead of monosodium glutamate (MSG), glutamic acid was used for solving the residual MSG problem. Fermentation by a lactic acid bacterium converted 90% of added glutamic acid (5%, w/v) to GABA, and continuous production of colorless fermentation broth containing more than 3% (w/v) GABA was achieved by using an activated carbon. Mixtures of salt water and fermentation broths with various GABA concentrations were co-crystallized and the GABA content was analyzed. This analysis showed that more than 90% of GABA from broth was adsorbed to salt. The appearance and surface of this prepared GABA-containing salt were examined with an image analyzer and scanning electron microscope. No difference was found with commercial sun-dried salt and no separated particles were detected, which indicates that the co-crystallization process used is suitable for the production of GABAcontaining salt.

The crystallization effects of boron (B) powder on the phase, full width at half maximum (FWHM) values, and critical properties were investigated for in-situ reacted MgB2 bulk superconductors. The semi-crystalline B powder was heat-treated at different temperatures of 1000, 1300 and 1500˚C for 5 hours in an Ar atmosphere. Then, using as-received and heat-treated B powders, the MgB2 samples were prepared at 600˚C for 40 hours in an Ar atmosphere. As the heat-treatment temperature of the B powder increased, both the particle size of the B powder and crystalline phase increased. In the case of MgB2 samples using B powders heat-treated at above 1300˚C, unreacted magnesium (Mg) and B remained due to the improved crystallinity of the B powder. As the heat-treatment temperature of B powder increased, the critical current density of MgB2 decreased continuously due to the reduction of grain boundary density and superconducting volume caused by unreacted Mg and B.

Wastewater containing heavy metals such as copper (Cu) and nickel (Ni) is harmful to humans and the environment due to its high toxicity. Crystallization in a fluidized bed reactor (FBR) has recently received significant attention for heavy metal removal and recovery. It is necessary to find optimum reaction conditions to enhance crystallization efficacy. In this study, the effects of crystallization reagent and pH were investigated to maximize crystallization efficacy of Cu-S and Ni-S in a FBR. CaS and Na2S·9H2O were used as crystallization reagent, and pH were varied in the range of 1 to 7. Additionally, each optimum crystallization condition for Cu and Ni were sequentially employed in two FBRs for their selective removal from the mixture of Cu and Ni. As major results, the crystallization of Cu was most effective in the range of pH 1-2 for both CaS and Na2S·9H2O reagents. At pH 1, Cu was completely removed within five minutes. Ni showed a superior reactivity with S in Na2S·9H2O compared to that in CaS at pH 7. When applying each optimum crystallization condition sequentially, only Cu was firstly crystallized at pH 1 with CaS, and then, in the second FBR, the residual Ni was completely removed at pH 7 with Na2S·9H2O. Each crystal recovered from two different FBRs was mainly composed of CuxSy and NiS, respectively. Our results revealed that Cu and Ni can be selectively recovered as reusable resources from the mixture by controlling pH and choosing crystallization reagent accordingly.

The crystallization of polypropylene (PP) particles in PP/decalin solution was conducted using the thermally induced phase separation(TIPS). During the control of particles sizes followed by the cooling of PP/decalin solution, particles were formed controllably, the concentrated PP resulted in an increase in the average diameter of PP particles. The effects of surfactants changes on particles sizes were investigated by using a field emission scanning electron microscope (FE-SEM). The PP crystals showed spherical shapes with a diameter 5∼18 μm. Additionally, as an effect of concentration of PP, the size distribution of the PP particles became broad with higher concentration of PP in the solution.