One-step dip-coating method for preparation of ceramic nanofiber membrane with high permeability and low cost
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Keywords:
Dip-coating
Ceramic membrane
Ceramic membrane
Dip-coating
Filtration (mathematics)
Membrane Fouling
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상온에서 polyimide 위에 증착한 Cu의 초기성장 과정과 Cu/polyimide의 계면의 형태에 관하여 XPS를 이용하여 관찰하였다. Polyimide 위에 Cu가 증착됨에 따라, 초기단계에는 강한 결합의 Cu-N-O complex가 주가 되어 Cu/polyimide 계면을 형성하고, Cu의 증착두께가 증가함에 따라, 약한 결합의 Cu 산화물에서 서서히 metallic Cu로서 성장하는 것을 볼 수 있었다. 이상의 결과들을 통해, Cu/polyimide의 계면은 Cu-N-O complex와 Cu 산화물이 혼합되어 있는 형태이며 polyimide 표면에 가까울수록 Cu-N-O complex가 주가 되고, Cu 쪽에 가까울수록 Cu 산화물이 주가 되는 형태를 이루고 있다는 것을 알 수 있었다.
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A number of polyimide films incorporated with different amounts of octa(aminopropylsilsesquioxane) (POSS-NH2) were prepared from 1,2,4,5-Benzenetetracarboxylic anhydride, 4,4′-Oxydianiline and POSS-NH2. The structure and properties of the hybrid polyimide films were characterized and evaluated. It is found that, compared with pure polyimide without POSS-NH2, the thermal stabilities and electrical capabilities of hybrid polyimide films are improved. Meanwhile, the incorporation of POSS-NH2 also brings improvement in the flexibility of polyimide films.
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Ceramic membrane
Ultrafiltration (renal)
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Abstract Electrical conduction characteristics in two different polyimide films prepared by the imidization of polyamic acid (PAA) and pre-imidized polyimide (PI) solution were investigated. It is found that the current density of the polyimide film from PAA was higher than that of the polyimide film from PI at the same electric field, even though the conduction mechanism in both polyimide films follows the ionic hopping model. The hopping distance was calculated to be 2.8 nm for PAA type and 3.2 nm for PI type polyimide film. It is also found that the decay rate of the residual electrostatic charges on the polyimide films becomes faster in the PAA type than in the PI type polyimide film.
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Zigzag
Deposition
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Abstract High‐performance polyimide fibre is well known for its outstanding thermal stability, fire resistance and chemical stability, and it has great potential for use in fire‐protective textiles. One major drawback of polyimide fibre is that it is difficult to dye under regular conditions. In this work, it was found that polyimide fibre could be dyed with disperse dyes with the assistance of N ‐methylformanilide. Thus, it was proposed that there might exist an interaction between polyimide fibre and N ‐methylformanilide that plays an important role in dyeing. Experimental results showed that N ‐methylformanilide penetrated into polyimide fibre, resulting in a slight swell in diameter and decrease in the breaking strength of polyimide fibre. X‐ray diffractometric data showed no apparent solvent‐introduced increase on the crystallinity of polyimide fibres but an orderly change on the interplanar spacing. When N ‐methylformanilide was removed from polyimide fibre by thermal treatment, the diameter, breaking strength and interplanar spacing of the polyimide fibres were all recovered to some extent. This indicated that the interactions between polyimide macromolecular chains were broken because of the penetration of N ‐methylformanilide, and new interactions occurred between polyimide macromolecular chains and N ‐methylformanilide that played a role in lubricating dye molecules to diffuse into polyimide fibres.
Thermal Stability
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In this study, highly cross-linked and completely imidized polyimide aerogels were prepared from polyimide containing trimethoxysilane side groups, which was obtained as the condensation product of polyimide containing acid chloride side groups and 3-aminopropyltrimethoxysilane. After adding water and acid catalyst, the trimethoxysilane side groups hydrolyzed and condensed one another, and a continuous increase in the complex viscosities of the polyimide solutions with time was observed. The formed polyimide gels were dried by freeze-drying from tert-butyl alcohol to obtain polyimide aerogels, which consisted of a three-dimensional network of polyimide fibers tangled together. By varying the solution concentration of the polyimide containing trimethoxysilane side groups, polyimide aerogels with different densities (ranging from 0.19 to 0.42 g/cm3) were obtained. The resulting polyimide aerogels had small pore diameter (ranging from 20.7 to 58.3 nm), high surface area (ranging from 310 to 344 m2/g), high 5% weight loss temperature in air (at about 440 °C), and an excellent mechanical property. In addition, the glass transition temperature (349 °C) of the polyimide aerogels was much higher than that (210 °C) of the corresponding linear polyimide. So, even after being heated at 300 °C for 30 min, the porous structure of the polyimide aerogels was not completely destroyed.
Characterization
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A two-step process for preparing polyimide nanofiber was used in this work, and the nanofibers of precursor polyamic acid (PAA) were prepared by electrospinning. The polyimide nanofibers were obtained through thermal imidization at different thermal imidization temperatures. The influences of different imidization temperatures on morphology, chemical structure, thermal stability, and mechanical properties of the polyimide nanofibers were investigated by Fourier Transform Infrared Spectroscope (FT-IR), Scanning Electronic Microscopy (SEM), thermal gravimetric analysis (TGA) and Electromechanical Universal Testing Machine. The experimental results show that the imidization of PAA nanofibers was not complete under 290°C but complete under 350°C. With the rise of imidization temperature from 290 °C to 350°C, the polyimide nanofibers became thinner, and the thermal stability of polyimide nanofibers was also improved. The breaking strength and elongation at break of the nanofiber membranes increased at higher imidization temperature.
Electrospinning
Thermal Stability
Thermogravimetric analysis
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α-Al_2O_3 membrane supported on α-Al_2O_3 porous substrate was formed by dip-coating and the formation process of the top layer was investigated based on experiments and theories of capillary filtration and film-coating. A model was developed to interpret quantitatively the formation process of the top layers on the porous substrate and all variables affecting top layer thickness were considered in the model.The results of theoretical analysis showed that the effects of six variables,namely the mass concentration of ceramic powder(W_s), the viscosity of suspension (η), the diameter of ceramic powder(r), the pure water permeability of support(Q),dipping time(t) and the withdrawal speed of the support(U),on the thickness of the top layer were highly significant. In order to validate the model developed,ZrO_2 membranes were prepared by dip-coating using the slurry with different mass concentrations of ZrO_2 powder. The experimental data of the thickness of the as-prepared ZrO_2 membranes showed good agreement with the model.
Dip-coating
Ceramic membrane
Suspension
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