Morphology of Electrospun Non-Woven Membranes of Poly(vinylidene fluoride-co-hexafluoropropylene): Porous and Fibers

Guilherme Dognani,Flávio Camargo Cabrera,Aldo Eloizo Job,Deuber Lincon da Silva Agostini 한국섬유공학회 2019 Fibers and polymers Vol.20 No.3

In this paper, poly(vinylidene fluoride-co-hexafluoropropylene) nanofibers membranes were fabricated by facilesingle-capillary electrospinning at different times of production. The materials were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle (CA), mercury porosity intrusion (MIP), Tensile tests, capillary flow porosity (CFP) and, BET surface by nitrogen adsorption-desorption. The membranes were fabricated varying the fibers density, the thickness and the morphology. The samples presented a good fiber diameter distribution and an average diameter of 321 nm. AFM results showed high porosity (82.7-87.5 %), a high contact angle of 159.2 o, mean pore size of 0.637 μm and hydrophobicity of the membranes. A low value of permeate pure water flux, 5.2 %, was observed for the densest fabricated membrane. The porosity of fibers diameters was similar for all samples, which is an important parameter as they can be potential materials for membrane distillation process.

미세기공함유 유리의 제조 및 특성

채수진(Chae, Soo-Jin),박만규(Park, Man-Gyu),강원호(Kang, Won-Ho) 한국산학기술학회 2009 한국산학기술학회논문지 Vol.10 No.3

판유리 폐기물과 hydroxyapatite를 사용하여 미세기공 함유 다공성유리를 제조하여 미세기공의 형태와 기계적 강도를 평가하였다. 발포제의 함량은 7%이상 함유시 기공이 조대하여지고 불균질하게 형성되었으며, 3~5% 함유시발포 열처리온도 830~840℃에서 10㎛전후의 균일한 기공크기를 생성하였다. 기공성유리의 압축강도 및 곡강도는 각각 18㎏/㎠, 8㎏/㎠를 나타내었다. The waste sheet glass cullet and hydroxyapatite is applied to make the fine porous glass. It’s mechanical strength is examined, and the structure of porous glass is observed. The pore size and shapes were not homogeneous and bigger pore size when HAp was over 7%. In the sintering temperature range of 830~840℃, and 3~5% of HAp were showed about 10㎛ pore size and homogenous morphology. The compressive strength and bending strength were appeared about 18㎏/㎠, 8㎏/㎠ respectively.

Preparation of a Porous Chitosan/Fibroin-Hydroxyapatite Composite Matrix for Tissue Engineering

Kim, Hong-Sung,Kim, Jong-Tae,Jung, Young-Jin,Ryu, Su-Chak,Son, Hong-Joo,Kim, Yong-Gyun The Polymer Society of Korea 2007 Macromolecular Research Vol.15 No.1

Chitosan, fibroin, and hydroxyapatite are natural biopolymers and bioceramics that are biocompatible, biodegradable, and resorb able for biomedical applications. The highly porous, chitosan-based, bioceramic hybrid composite, chitosanlfibroin-hydroxyapatite composite, was prepared by a novel method using thermally induced phase separation. The composite had a porosity of more than 94% and exhibited two continuous and different morphologies: an irregularly isotropic pore structure on the surface and a regularly anisotropic multilayered structure in the interior. In addition, the composite was composed of an interconnected open pore structure with a pore size below a few hundred microns. The chemical composition, pore morphology, microstructure, fluid absorptivity, protein permeability, and mechanical strength were investigated according to the composition rate of bioceramics to biopolymers for use in tissue engineering. The incorporation of hydroxyapatite improved the fluid absorptivity, protein permeability, and tenacity of the composite while maintaining high porosity and a suitable microstructure.

Porous Nafion membranes

Joseph, Dickson,Bü,sselmann, Julian,Harms, Corinna,Henkensmeier, Dirk,Larsen, Mikkel Juul,Dyck, Alexander,Jang, Jong Hyun,Kim, Hyoung-Juhn,Nam, Suk Woo Elsevier 2016 Journal of membrane science Vol.520 No.-

<P><B>Abstract</B></P> <P>By varying the amount of porogene (<I>ortho</I>-dichlorobenzene, ODB), and optimization of the dispersion process, two types of solvent cast Nafion membranes with an equivalent weight of 1100g/mol sulfonic acid can be obtained reproducibly. One type is a dense membrane with a porous layer on one surface. The other membrane type shows a novel structure, consisting of small closed pores throughout the membrane and a single layer of large open pores on one side. In addition, some membranes showed a structural morphology between these two types, a membrane with a dense part and a porous part on top of each other. The latter membrane structure was not fully reproducible yet, but probably could be by carefully adjusting the formulation of the casting solution. Also the effect of the casting temperature on the morphology is shown. Fully porous membranes were characterized for their water permeability, ion conductivity, mechanical properties, their performance in the fuel cell and the hydrogen crossover. While the fully porous membranes are not expected to be part of a real fuel cell, we expect that the new morphologies will inspire applied research, e.g. in which the pores are filled with electrolyte or material or a catalyst is blended into the polymer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nafion membranes with three different morphologies were prepared. </LI> <LI> a) dense Nafion membranes with a porous surface, based on EW 1100. </LI> <LI> b) mixed dense/porous membranes. </LI> <LI> c) fully porous membranes with closed pores and larger open pores on the surface. </LI> <LI> Membranes were prepared in a single step (solution casting). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Controlled synthesis of porous Co₃O₄ micro/nanostructures and their photocatalysis property

Huang, J.,Ren, H.,Chen, K.,Shim, J.J. Academic Press 2014 Superlattices and microstructures Vol.75 No.-

Porous nanoflower-like, micropancake-like and microflower-like Co<SUB>3</SUB>O<SUB>4</SUB> micro/nanostructures were synthesized by a template-free aqueous solution route combined with subsequent thermal treatment. Techniques of X-ray diffraction, scanning electron microscopy, thermogravimetric-differential thermal analysis, and transmission electron microscopy were used to characterize the structure and morphology of the products. The experimental results show that three kinds of morphologies of cobalt precursors can be achieved by addition of ammonia at different temperatures. The corresponding Co<SUB>3</SUB>O<SUB>4</SUB> hierarchical micro/nanostructures were obtained after 500<SUP>o</SUP>C calcinations. In addition, the obtained porous Co<SUB>3</SUB>O<SUB>4</SUB> hierarchical micro/nanostructures were used as catalyst to photodegrade Rhodamine B, methylene blue, p-nitrophenol, eosin B, and methyl orange. Compared with porous Co<SUB>3</SUB>O<SUB>4</SUB> micropancakes, the as-prepared porous Co<SUB>3</SUB>O<SUB>4</SUB> nanoflowers and microflowers exhibit higher catalytic activities due to their large surface areas and porous hierarchical structures. The photocatalytic reaction rate constant of the porous Co<SUB>3</SUB>O<SUB>4</SUB> nanoflowers in photocatalytic decomposition of Rhodamine B under UV light is calculated as 0.0828min<SUP>-1</SUP>.

Effects of Etching Time on the Bottom Surface Morphology of Ultrathin Porous Alumina Membranes for Use as Masks

양선아,최용찬,부상돈 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.10

We investigated the effect of etching time on bottom surface morphologies of ultrathin porous alumina membranes (UT-PAMs) anodized in oxalic and phosphoric acid. The morphology of the bottom surface was clearly changed and the unique surface undulation was observed during the etching process. Such an undulation regarding the bottom surface is attributed to the different etching rates between the dome shaped barrier layer and the hexagonal cell walls. The results suggested that the bottom morphology of UT-PAMs formed after the barrier layer is opened significantly affects the contact area of their bottom side with the substrate. During the initial stage of the opening process for the barrier layer, the porous section will contact with the substrate rather than the walls. However, as the etching time increases, the height of the porous section becomes considerably lower than that of the walls, which means that the walls will contact with the substrates with a gap between the pores and the substrates. Based on our experimental results, we propose a possible schematic diagram describing the effects of the UT-PAMs with different shaped bottom surfaces on the shape of fabricated nanodots when the UT-PAMs are used as a mask.

Controlling Morphology of Polymer Microspheres by Shirasu Porous Glass (SPG) Membrane Emulsification and Subsequent Polymerization: from Solid to Hollow

이정우,황덕율,심상은,임영목 한국고분자학회 2010 Macromolecular Research Vol.18 No.12

In this study, the solid, porous, and hollow polymer microspheres were prepared using a simple and novel production method based on Shirasu porous glass (SPG) membrane emulsification and suspension polymerization. With the SPG membrane, uniform-sized emulsion monomer droplets containing divinyl benzene (DVD), styrene (St),hexadecane (HD), and an initiator were prepared in an aqueous phase using a membrane emulsification technique. The aqueous phase contained hydroquinone (HQ) as a water-soluble inhibitor and polyvinylpyrrolidone (PVP) as a stabilizer. The morphology of the particles was affected by the stabilizer, St/DVB ratio, hexadecane amount, and initiator amount. Through this study, the porous polymer microspheres were achieved when the HD content was 30wt% relative to the monomer and the hollow polymer microspheres was achieved when the HD content was more than 62.5 wt% relative to the monomer. These results highlight the phase separation speed between polystyrene (PSt)and HD.

Fabrication of Porous MoS2 with Controllable Morphology and Specific Surface Area for Hydrodeoxygenation

Zhenwi Zhang,Chuanjun Yue,Jianhen Hu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.9

SiO2 nanoparticles modified with aminopropyl-triethoxysilane (APTES) were used as hard templates for preparing porous MoS2. The method offers the advantages of simple steps, convenient operation, controllable pore size, and a specific surface area. Two morphologies of MoS2 were obtained by using thiourea and L-cysteine as sulfur sources, respectively. Porous MoS2 prepared by using thiourea had a smooth surface, whereas the surface of porous MoS2 prepared with L-cysteine had many burrs. The MoS2 nanomaterials with the respective morphologies were used to catalyze the hydrodeoxygenation (HDO) reaction. The activity of MoS2 prepared with L-cysteine was lower than that prepared with thiourea. Transmission electron microscopy and X-ray diffraction analyses showed that MoS2 had a large sheet-shaped structure and high crystallinity, leading to high reaction activity and high selectivity for cyclohexane. The reaction temperature also influenced the HDO significantly. The mechanism of hydrogenation of phenol was discussed.

Facile synthesis of porous TiO₂ nanospheres and their photocatalytic properties

Huang, J.,Ren, H.,Liu, X.,Li, X.,Shim, J.J. Academic Press 2015 Superlattices and microstructures Vol.81 No.-

Uniform and monodisperse porous TiO<SUB>2</SUB> nanospheres were synthesized by a hydrothermal method. Techniques of X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption, UV-vis absorption spectroscopy, and transmission electron microscopy were used to characterize the structure and morphology of the products. The BET surface area of the porous TiO<SUB>2</SUB> nanospheres was calculated to be 26.1cm<SUP>2</SUP>g<SUP>-1</SUP>. In addition, the obtained porous TiO<SUB>2</SUB> nanospheres were used as catalyst to photodegrade methylene blue, Rhodamine B, methyl orange, p-nitrophenol, and eosin B. Compared to commercial TiO<SUB>2</SUB> powder, the as-prepared porous TiO<SUB>2</SUB> nanospheres exhibited higher catalytic activities due to their large surface areas and porous nanostructures. The photocatalytic reaction rate constant of the porous TiO<SUB>2</SUB> nanospheres in photocatalytic decomposition of methylene blue and Rhodamine B under simulated solar light were calculated as 0.0545min<SUP>-1</SUP> and 0.0579min<SUP>-1</SUP>, respectively. Moreover, the catalyst was demonstrated to have good stability and reusability.

Morphological Effects of Polytetrafluoroethylene Meniscus Formation on Microscopic Transport Properties of Inhomogeneous Random Porous Gas Diffusion Media for Electrochemical Applications

Jiawen Liu,정성재,Akbar Ali,엄석기 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.4

In this study, the microscopic transport properties of porous gas diffusion media (PGDMs) with capillary meniscus formation are evaluated using a statistical approach for electrochemical applications. The microscopic morphology of PGDM is stochastically modeled using randomly distributed carbon fibers and various meniscus formations. In particular, the meniscus formation of hydrophobic polytetrafl uorethylene (PTFE) agent enables the generation of highly elaborate microstructures in commercial PGDMs. A single-phase three-dimensional 19-velocity lattice Boltzmann method is applied to simulate the microscale mass transfer phenomena within the PGDMs. The mass transport characteristics (i.e., anisotropic permeability, tortuosity, and effective diffusion coefficient) of the PGDM samples with different PTFE content are statistically investigated as a function of untreated porosity (i.e., porosity before PTFE loading) of the PGDMs. The predicted results reveal an inverse relationship between anisotropic permeability and PTFE loading because the addition of PTFE decreases the bulk porosity of the PGDMs. In addition, the electrical and thermal conductivities of PGDMs are statistically estimated in both the in-plane and through-plane directions. The results show that the in-plane electrical and thermal conductivities are greater than those in the through-plane direction because of the carbon-fiber orientation. Moreover, the addition of PTFE has relatively larger effects on the through-plane electrical and thermal conductivities.