• 한국재료학회지
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• 제24권12호
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• pp.704-709
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• 2014

In this study, we fabricated a novel micro porous hybrid scaffold of biphasic calcium phosphate (BCP) and a polylectrolyte complex (PEC) of chitosan (CS) and hyaluronic acid (HA). The fabrication process included loading of CS-HA PEC in a bare BCP scaffold followed by lypophilization. SEM observation and porosimetry revealed that the scaffold was full of micro and macro pores with total porosity of more than 60 % and pore size in the range of $20{\sim}200{\mu}m$. The composite scaffold was mechanically stronger than the bare BCP scaffold and was significantly stronger than the CS-HA PEC polymer scaffold. Bone morphogenetic growth factor (BMP-2) was immobilized in CS-HA PEC in order to integrate the osteoinductive potentiality required for osteogenesis. The BCP frame, prepared by sponge replica, worked as a physical barrier that prolonged the BMP-2 release significantly. The preliminary biocompatibility data show improved biological performance of the BMP-2 immobilized hybrid scaffold in the presence of rabbit bone marrow stem cells (rBMSC).

• Carbon letters
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• 제4권2호
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• pp.57-63
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• 2003

In polymer precursor based activated carbon, the structure of starting material is likely to have profound effect on the surface properties of end product. To investigate this aspect phenolic resins of different types were prepared using phenol, mcresol and formaldehyde as reactants and $Et_3N$ and $NH_4OH$ as catalyst. Out of these resins two resol resins PFR1 and CFR1 (prepared in excess of formaldehyde using $Et_3N$ as catalyst in the basic pH range) were used as raw materials for the preparation of activated carbons by both chemical and physical activation methods. In chemical activation process both the resins gave activated carbons with high surface areas i.e. 2384 and 2895 $m^2/g$, but pore size distribution in PFR1 resin calculated from Horvath-Kawazoe method, contributes mainly in micropore range i.e. 84.1~88.7 volume percent of pores was covered by micropores. Whereas CFR1 resin when activated with KOH for 2h time, a considerable amount (32.8%) of mesopores was introduced in activated carbon prepared. Physical activation with $CO_2$ leads to the formation of activated carbon with a wide range of surface area (503~1119 $m^2/g$) with both of these resins. The maximum pore volume percentage was obtained in 3-20 ${\AA}$ region by physical activation method.

• 대한의용생체공학회:의공학회지
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• 제26권5호
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• pp.319-330
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• 2005

Over the past few decades, much effort has been made to improve the mechanical and biological performance of HA, in order to extend its range of applications. As a major inorganic component of human hard tissues, hydroxyapatite bioceramic is regarded as being one of the most biocompatible materials. Numerous in vitro and in vivo studies have confirmed its excellent bioactivity, osteoconductivity and bone forming ability. However, because of its poor mechanical properties, its use in hard tissue applications has been restricted to those areas in which it can be used in the form of small sized powders/granules or in the non-load bearing sites. A number of researchers have focused on improving the mechanical and biological performance of HA, as well as on the formulation of hybrid and composite systems in order to extend its range of applications. In this article, we reviewed our recent works on HA-based biomaterials; i) the strengthening of HA with ceramic oxides, ii) HA-based bioactive coatings on metallic implants, iii) HA-based porous scaffolds and iv) HA-polymer hybrids/composites.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1101-1108
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• 2009

The ocean contains around eighty elements of the periodic table and uranium is also one among them, with a uniform concentration of 3.3 ppb and a relative abundance factor of 23. With a large coastline, India has a large stake in exploiting the 4 billion tonnes of uranium locked in seawater. The development of radiation grafting techniques, which are useful in incorporating the required functional groups, has led to more efficient adsorbent preparations in various geometrical configurations. Separation based on a polymeric adsorbent is becoming an increasingly popular technique for the extraction of trace heavy metals from seawater. Radiation grafting has provided definite advantages over chemical grafting. Studies related to thermally bonded non woven porous polypropylene fiber sheet substrate characterization and parameters to incorporate specific groups such as acrylonitrile (AN) into polymer back bones have been investigated. The grafted polyacrylonitrile chains were chemically modified to convert acrylonitrile group into an amidoxime group, a chelating group responsible for heavy metal uptake from seawater/brine. The present work has been undertaken to concentrate heavy metal ions from lean solutions from constant potential sources only. A scheme was designed and developed for investigation of the recovery of heavy metal ions such as uranium and vanadium from seawater.

• 멤브레인
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• 제10권3호
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• pp.121-129
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• 2000

높은 선택도와 투과도를 가진 분리막이 요구되지만 선택도가 높은 막은 투과도가 낮은 것이 일반적이다. 본 연구에서는 적절한 선택도를 유지하면서 높은 투과도를 갖는 분리막을 제조하기 위하여 다공성 알루미나막을 실란커플링제로 코팅하였다. 코팅된막에 대한 물의 접촉각은 90$^{\circ}$ 이상이었으며, 큰 소수성을 가짐을 의미하기 때문에 에탄올, 이소프로판올, 부탄을 수용액의 농축을 위한 증기투과실험을 수행하였다. 공급액중의 알코을 농도가 증가함에 따라 투과도가 증가하였으며, 이는 물에 비하여 코팅된 막에 대한 에탄올, 이소프로판올, 부탄올의 친화도가 크기 때문으로 판단된다. 코팅된 알루미나막의 투과도는 고분자막의 투과도에 비하여 20~1000배로 크게 나타났다.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1784-1788
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• 2014

The present study suggests a novel method to produce raspberry-like microparticles containing diverse functional materials inside. The raspberry-like microparticles were produced from a random assembly of uniformly-sized poly(methyl methacrylate) (PMMA) nanoparticles via electrospraying. The solution containing the PMMA nanoparticles were supplied through the inner nozzle and compressed air was emitted through the outer nozzle. The air supply helped fast evaporation of acetone, so it enabled copious amount of microparticles as dry powder. The microparticles were highly porous both on the surface and interiors, hence various materials with a function of UV-blocking ($TiO_2$ nanoparticles and methoxyphenyl triazine) or anti-aging (ethyl(4-(2,3-dihydro-1H-indene-5-carboxyamido) benzoate)) were loaded in large amount (17 wt % versus PMMA). The surface and interior structures of the microparticles were dependent on the characteristics of functional materials. The results clearly suggest that the process to prepare the raspberry-like microparticles can be an excellent approach to generate functional microstructures.

• Journal of Periodontal and Implant Science
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• 제43권6호
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• pp.251-261
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• 2013

A paradigm shift is taking place in medicine and dentistry from using synthetic implants and tissue grafts to a tissue engineering approach that uses degradable porous three-dimensional (3D) material hydrogels integrated with cells and bioactive factors to regenerate tissues such as dental bone and other oral tissues. Hydrogels have been established as a biomaterial of choice for many years, as they offer diverse properties that make them ideal in regenerative medicine, including dental applications. Being highly biocompatible and similar to native extracellular matrix, hydrogels have emerged as ideal candidates in the design of 3D scaffolds for tissue regeneration and drug delivery applications. However, precise control over hydrogel properties, such as porosity, pore size, and pore interconnectivity, remains a challenge. Traditional techniques for creating conventional crosslinked polymers have demonstrated limited success in the formation of hydrogels with large pore size, thus limiting cellular infiltration, tissue ingrowth, vascularization, and matrix mineralization (in the case of bone) of tissue-engineered constructs. Emerging technologies have demonstrated the ability to control microarchitectural features in hydrogels such as the creation of large pore size, porosity, and pore interconnectivity, thus allowing the creation of engineered hydrogel scaffolds with a structure and function closely mimicking native tissues. In this review, we explore the various technologies available for the preparation of macroporous scaffolds and their potential applications.

• 공업화학
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• 제5권6호
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• pp.1009-1015
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• 1994

분산중합으로 합성한 폴리스티렌 seed를 사용하여 seed 중합방법으로 단분산성인 다공성 스티렌-디비닐벤젠(St-DVB) 겔과 아크릴로니트릴-에틸렌 디메타크릴레이트(AN-EDMA) 겔을 제조하였다. 합성한 St-DVB 겔과 AN-EDMA 겔은 HPLC용 충진제로 적합한 좁은 입도분포와 다공성을 갖고 있으며, 이들 겔을 충진한 GPC 또는 HPLC용 column은 비교적 높은 효율을 나타내었다, 또한 AN-EDMA 겔을 아미드옥심화한 AAN-EDMA 겔에 대한 $Cu^{2+}$, $Cd^{2+}$ 및 ${UO_2}^{2+}$ 이온의 흡착특성을 시험하였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제18권4호
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• pp.8-18
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• 2013

Biocarrier beads with dead biomass, Bacillus drentensis, immobilized in polymer polysulfone were synthesized to remove heavy metals from wastewater. To identify the sorption mechanisms and theoretical nature of underlying processes, a series of batch experiments were carried out and a mathematical model was developed to quantify the biosorption of Pb(II) by the biocarrier beads. A series of mass balance equations for representing mass transfer of metal sorbents in biocarrier beads and surrounding solution were established. Major model parameters such as external mass transfer coefficient and maximum sorption capacity, etc. were determined from pseudo-first-order kinetic models and Langmuir isotherm model based on kinetic and equilibrium experimental measurements. The model simulation displays reasonable representations of experimental data and implied that the proposed model can be applied to quantitative analysis on biosorption mechanisms by porous granular beads. The simulation results also confirms that the biosorption of heavy metal by the biocarrier beads largely depended on surface adsorption.

• Carbon letters
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• 제9권4호
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• pp.298-302
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• 2008

Carbon blacks could be used as the filler for the electromagnetic interference (EMI) shielding. The poly vinyl alcohol (PVA) and polyvinylidene fluoride (PVDF) were used as the matrix for the carbon black fillers. Porous carbon blacks were prepared by $CO_2$ activation. The activation was performed by treating the carbon blacks in $CO_2$ to different degrees of burnoff. During the activation, the enlargement of pore diameters, and development of microporous and mesoporous structures were introduced in the carbon blacks, resulting in an increase of extremely large specific surface areas. The porosity of carbon blacks was an increasing function of the degree of burn-off. The surface area increased from $80\;m^2/g$ to $1142\;m^2/g$ and the total pore volume increased from $0.14073\;cc{\cdot}g^{-1}$ to $0.9343\;cc{\cdot}g^{-1}$. Also, the C=O functional group characterized by aldehydes, ketones, carboxylic acids and esters was enhanced during the activation process. The EMI shielding effectiveness (SE) of raw N330 carbon blacks filled with PVA was about 1 dB and those of the activated carbon blacks increased to the values between 6 and 9 dB. The EMI SE of raw N330 carbon blacks filled with PVDF was about 7 dB and the EMI SE increased to the range from 11 to 15 dB by the activation.