• Korean Chemical Engineering Research
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• 제45권6호
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• pp.611-618
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• 2007

아민기로 코팅된 단분산 폴리스티렌 입자를 제조한 뒤 톨루엔-물로 구성된 유중수 액적(oil-in-water emulsion) 내부에서 입자를 자기 조립(self-assembly)시켜 다양한 다면체(polyhedra) 구조의 콜로이드 클러스터(colloidal cluster)를 제조하였다. 콜로이드 클러스터의 표면에서 솔-젤(sol-gel) 반응을 유발한 뒤 표면이 실리카로 코팅된 복합(composite) 콜로이드 클러스터를 제조할 수 있었고 이를 주형(template)으로 활용하여 고온 소성에 의해 내부의 폴리스티렌 입자를 제거하고 마이크로미터 크기의 다양한 구조의 비구형상 공동 입자(hollow particle)를 제조하였다. 밀도구배원심분리법 (density gradient centrifugation)에 의해 폴리스티렌 구성 입자의 수와 구조가 균일한 콜로이드 클러스터를 제조할 수 있었으며 표면 솔-젤 반응에 의해 비구형상 구조의 공동 입자를 제조하였다.

• 접착 및 계면
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• 제25권2호
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• pp.56-62
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• 2024

본 연구에서는 서로 다른 환원제를 사용하여 라이다 센서에 인식 가능한 검은색 중 공구조 물질을 합성하고 라이다 인식률을 비교하였다. 먼저, 실리카/티타니아 코어/쉘(WST) 물질을 졸-겔법을 통해 제조한 후 아스코르브산(AA)과 수소화붕소나트륨(SB)을 사용하여 환원하였다. 이후, 실리카 코어를 제거하여 두 가지의 다른 검은색 중공구조(AA-BHT 및 SB-BHT) 물질을 제조하였다. AA-BHT의 명도(L^*)와 NIR 반사율(R%)은 각각 약 19.1과 34.5 R%로 측정되었고, SB-BHT는 약 11.5와 31.8 R%로 검출되었다. AA-BHT는 SB-BHT에 비해 NIR 반사율이 높았으나 색상은 명도가 높은 검은색으로 나타났다. AA-BHT와 SB-BHT는 중공구조로 제조되어 코어/쉘 물질 대비 높은 근적외선 반사율을 나타냈으며, 이는 공기와 검은색 티타니아의 계면 사이에서 발생하는 프레넬의 반사 원리에 기인하였다. 본 연구 결과를 통해 두 물질 모두 다양한 환원법을 통해 성공적으로 검은색으로 제조되었으며, 상용화된 라이다 센서에 효과적으로 인지되어 미래의 자율주행차량용 검은색 물질로의 적합성을 나타내었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.467-467
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• 2011

Reflecting the growing importance of nanomaterials in science and technology, controlling the porosity combined with well-defined structural properties has been an ever-demanding pursuit in the related fields of frontier researches. A number of reports have focused on the synthesis of various nanoporous materials so far and, recently, the nanomaterials with multimodal porosity are getting an emerging importance due to their improved material properties compared with the mono porous materials. However, most of those materials are obtained in bulk phases while the spherical nanoparticles are one of the most practical platforms in a great number of applications. Here, we report on the synthesis of the core-shell silica nanoparticles with double mesoporous shells (DMSs). The DMS nsnoparticles are spherical and monodispersive and have two different mesoporous shells, i.e., the bimodal porosity. It is the first example of the core-shell silica nanoparticles with the different mesopores coexisting in the individual nanoparticles. Furthermore, the carbon and silica hollow capsules were also fabricated via a serial replication process.

• Carbon letters
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• 제14권1호
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• pp.55-57
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• 2013

The development of hollow carbon balls by $CO_2$ oxidation of two types of carbon blacks was studied. Super P (SP) and Denka Black (DB) were used for this study. Specific surface area (SSA), structural parameters, and microstructures were examined using Brunauer, Emmett and Teller apparatus, X-ray diffraction spectroscopy, and transmission electron microscope (TEM), respectively. The SSAs of both oxidized carbon blacks increased after oxidation. The SSAs of raw DB and SP were 73 $m^2/g$ and 60 $m^2/g$, respectively. Maximum SSAs of oxidized DB and SP were 152 $m^2/g$ and 253 $m^2/g$, respectively. The $d_{002}$ of DB and SP showed almost no change after oxidation. The Lc of raw DB ($38{\AA}$) and SP ($19{\AA}$) increased with increasing weight loss. The $L_c$ of SP increased up to $254{\AA}$ at 96% weight loss. The SSA increased about twice in DB (148 $m^2/g$) and about four times in SP (254 $m^2/g$) after 3 h oxidation compared with the original carbon blacks. Through TEM observation the outer parts of the oxidized carbon blacks showed a rigid shell structure and the inner parts looked empty. Generally it looked like an angular soccer ball, so we named it 'hollow carbon ball'. It is expected that the hollow carbon ball can be used as catalyst supports.

• 한국재료학회지
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• 제19권10호
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• pp.517-521
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• 2009

Si-C composite with hollow spherical structure was synthesized using ultrasonic treatment of organosilica powder formed by hydrolysis of phenyltrimethoxysilane. The prepared powder was pyrolyzed at various temperatures ranging from 900 to 1300 $^{\circ}C$ under nitrogen atmosphere to obtain optimum conditions for Li-ion battery anode materials with high capacity and cyclability. The XRD and elemental analysis results show that the pyrolyzed Si/C composite at 1100 $^{\circ}C$ has low oxygen and nitrogen levels, which is desirable for increasing the electrochemical capacity and reducing the irreversible capacity of the first discharge. The solid Si-C composite electrode shows a first charge capacity of $\sim$500 mAhg$^{-1}$ and a capacity fade within 30 cycles of 0.93% per cycle. On the other hand, the electrochemical performance of the hollow Si-C composite electrode exhibits a reversible charge capacity of $\sim$540 mAhg$^{-1}$ with an excellent capacity retention of capacity loss 0.43% per cycle up to 30 cycles. The improved electrochemical properties are attributed to facile diffusion of Li ions into the hollow shell with nanoscale thickness. In addition, the empty core space provides a buffer zone to relieve the mechanical stresses incurred during Li insertion.

• Composites Research
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• 제14권6호
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• pp.16-23
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• 2001

인발 와인딩에 의한 섬유강화 복합재료 중공 봉의 기계적 거동해석을 수행하였다. 이 목적의 수행을 위해 새롭게 제작된 와인더를 전통적 인발 시스템에 부탁하여 시편을 제작하였다. 또한 인발-와인딩된 시편을 제작할 수 있는 새로운 공법을 개발하였다. 이 연구를 위해 유한요소 해석 프로그램 POSTII를 확장 개발하였다. 비선형유한요소 수식화에는 2차 피올라-키르히호프 응력 텐서와 그린 변형률 텐서에 기초한 업데이트된 라그란지언 표현법이 사용되었다. 복합재료 중공봉의 유한요소 모델링을 위해 8절점 응축쉘요소를 사용하였다. 파손평가를 위해 모든 유한요소의 각 단층에서의 평균응력을 최대음력 판정법에 대입하였다. 수치해석 예로서 불포화 섬유강화 복합재료 중공 봉의 기계적 거동을 초기 하중상태에서 최종 붕괴가지 조사하였다. 파손에 따른 강성저하와 응력제하를 고려한 유한요소해석 결과는 극만 하중과 파손 및 변형에서 실험치와 잘 일치하였다.

• Korean Membrane Journal
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• 제8권1호
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• pp.1-12
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• 2006

In semiconductor industries, dissolved oxygen is one of the most undesirable contaminants of ultrapure water. A method for dissolved oxygen removal (DOR) consists in the use of polymeric hollow fibres, loaded with a catalyst and fed with a reducing agent such as hydrogen. In this work, PVDF hollow fibres loaded with Pd were characterized by means of perporometry, scanning electron microscopy (SEM), energy dispersive X-ray (EDX). The hollow fibre analyzed shows a five-layer structure with remarkable morphological differences. An estimation of pore diameters and their distribution was performed giving a mean pore diameter of 100 nm. The permeance and selectivity of the fibres were measured using $H_2,\;N_2,\;O_2$ as single gases, at different operating conditions. An $H_2$ permeance of $37 mmol/m^2s$ was measured and $H_2/O_2$ and $H_2/N_2$ selectivities of ca. 3 were obtained. $H_2$ permeance was 1/3 when a water stream flows in the shell side. Catalytic fibrebehaviour was simulated using a mathematical model for a loop membrane reactor, considering only $O_2$ and $H_2$ diffusive transport inside the membrane and their catalytic reaction. Dimensionless parameters such as the Thiele modulus are employed to describe the system behaviour. The model agrees well with the experimental reaction data.

• Steel and Composite Structures
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• 제46권6호
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• pp.793-804
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• 2023

In this study, cyclic loading tests were conducted to assess the seismic performance of cast-in-place (CIP) concrete-filled hollow core precast concrete columns (HPCC) constructed using steel ducts and rubber tubes. The outer shells of HPCC, with a hollow ratio of 47%, were fabricated using steel ducts and rubber tubes, respectively. Two combinations of shear studs & long threaded bars or cross-deformed bars & V-ties were employed to ensure the structural integrity of the old concrete (outer shell) and new CIP concrete. Up to a drift ratio of 3.8%, the hysteresis loop, yielding stiffness, dissipated energy, and equivalent damping ratio of the HPCC specimens were largely comparable to those of the solid columns. Besides the similarities in cyclic load-displacement responses, the strain history of the longitudinal bars and the transverse confinement of the three specimens also exhibited similar patterns. The measured maximum moment exceeded the predicted moment according to ACI 318 by more than 1.03 times. However, the load reduction of the HPCC specimen after reaching peak strength was marginally greater than that of the solid specimen. The energy dissipation and equivalent damping ratios of the HPCC specimens were 20% and 25% lower than those of the solid specimen, respectively. Taking into account the overall results, the structural behavior of HPCC specimens fabricated using steel ducts and rubber tubes is deemed comparable to that of solid columns. Furthermore, it was confirmed that the two combinations for securing structural integrity functioned as expected, and that rubber air-tubes can be effectively used to create well-shaped hollow sections.

• 상하수도학회지
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• 제25권4호
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• pp.503-510
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• 2011

Ammonia in water which is toxic to human, its concentration is regulated below 0.5 mg/L in drinking water. Current study aimed to develop appropriate models for ammonia stripping using hollow fiber membrane contactor. Two different models were developed during the study. Model 1 was assumed only free ammonia ($NH_3$) transfer in stripping process, whereas the Model 2 was assumed with total ammonia ($NH_3+{NH_4}^+$) transfer. Ammonium chloride ($NH_4CI$), sodium hydroxide(NaOH) were used to make ammonia solution, which was concentration of 25 mg as N/L at a pH of 10.5. The experimental conditions were such that, the liquid flow was in tube-side in upward direction and t he gas flow was on shell-side in downward direction a t room temperature. The experimental and modeling results showed that marginal difference were observed at low gas flux. However the difference between the both models and experimental value were increased when the gas flux was increased. The study concludes that the Model 1 with free ammonia is more appropriate when both models were compared and useful in ammonia stripping process at low gas flux.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
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• pp.297-300
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• 2000

Succinic acid was produced by Enterococcus faecalis RKY1 cells immobilized in hollow fiber bioreactor as an alternatively immobilized culture in bioconversion of fumaric acid to succinic acid. The feed was pumped through the shell side. As the flow rate of the feed was increased, the steady state was obtained more quickly. The steady state was reached after 24 hr cultivation in 0.25 ml/min, 12 hr in 0.5 ml/min, and 9 hr in 1.0 ml/min, respectively. The effect of medium pH on succinate production was also investigated. By changing the medium pH of 8.0, the succinic acid produced was increased about 16% than that of pH 7.0.