Ching-Iuan Su

A study of hydrophobic electrospun membrane applied in seawater desalination by membrane distillation

In this study, two composite nanofibrous membranes of Polyvinylidenefluoride (PVDF) and [poly(vinylidenefluorideco-hexafluoropropylene)] (PVDF-co-HFP) prepared by the electrospinning process were employed in a direct contact membrane distillation (DCMD) system. We changed the pump flow rate and temperature difference to examine their effects on permeate flux and salt rejection. The SEM observations, porosity analyzer technique, and contact angle measurement indicated the nanobrous membrane with an average fiber diameter of 170 nm and maximum pore diameter distribution of 0.3 µm is the best membrane for the DCMD system. However, the ability of the hydrophobic membrane affects the filtration efficiency of the DCMD system. The contact angle of the PVDF-HFP electrospun membrane (128°) shows better hydrophobic than the PVDF electrospun membrane (125 °). From the experiment of 12 hours, the salt rejection of PVDFHFP (99.9901 %) was better than that of PVDF composite membrane (99.9888 %) and was almost the same as that of the PTFE commercial membrane (99.9951 %). In addition, the permeate flux of the PVDF-HFP composite membrane is 4.28 kg/ m2hr higher than the PTFE commercial membrane.

PAN-based carbon nanofiber absorbents prepared using electrospinning

This study takes polyacrylonitrile (PAN) as a raw material for PAN-based nanofiber nonwoven prepared using electrospinning. First we construct a thermal-stable process for the fabrication of oxidized nanofiber nonwovens as the precursor. A semi-open high-temperature erect furnace is then used with steam as the activator, through carbonization and activation processes to prepare carbon nanofiber absorbents continuously. The experiment varies the production rate and activator flow rate to prepare carbon nanofiber absorbents. Experimental results show that carbon nanofiber adsorbents are primarily made up of micropores and mesopores, averaging under 20 Å. Given a production rate of 10–20 cm/min with a matching activator feed rate of 120 ml/min, the specific surface area can reach about 1000 m2/g, producing an adsorption ratio of carbon tetrachloride over 200 %.

Yarn formation of nanofibers prepared using electrospinning

In this study, the process of electrospinning was used on nanofiber yarn formation. The parameters in the study were flow rate and twist multiplier, which were discussed their effect on yarn formation. Further, a normal yarn was used as the core yarn, which was wrapped with nanofibers to form a new type of composite yarn. In this part of the experiment, the parameters were flow rate and collector width, which were discussed in terms of their effect on the yarn quality of nanofibrous composite yarn. The experiment result showed the diameter of the nanofiber was between 220 nm to 260 nm. When the collector width was 5 mm, there was a high quality wrapping resulting in good yarn, with the nanofiber composite yarn having a strength of 3.25 (cN/dtex).

Optimum manufacturing conditions of activated carbon fiber absorbents. I. Effect of flame retardant reagent concentration

In this paper, viscose rayon-based knitted fabrics were utilized as the precursor to produce activated carbon fiber absorbents (ACFA). To obtain better pore characteristics and higher weight yield of ACFA, the effect of flame retardant reagent concentration was studied. Experimental results revealed that both BET surface area and micropore volume increased with increasing flame retardant reagent concentration. On the other hand, both weight yield and micropore volume ratio (Vmic/Vtot) decreased as the flame retardant reagent concentration increased. It was therefore concluded that controlling the flame retardant reagent concentration at 30% not only could obtain better absorption property of ACFA but also helped maintain its production efficiency.

Effect of temperature and activators on the characteristics of activated carbon fibers prepared from viscose-rayon knitted fabrics

This study used viscose rayon-based knitted fabric, pre-treated by a composite flame retardant, as the precursor. The fabric then underwent oxidation, carbonization and activation in a semi-open high-temperature erect furnace to produce Activated Carbon Fabrics (ACF). The microstructure and chemical properties of the ACF were obtained under carbonization temperatures of 600–1000 °C and by different activation sources. The results showed that the ACF produced was mainly of a microporous structure. When the carbonization temperature was increased, the production rate dropped while both the true density (DHe) and crystallization thickness increased. In addition, ACF prepared using steam, plus water as the activation source, has a larger specific surface area, greater crystallization thickness and a higher true density (DHe).

Optimum manufacturing conditions of activated carbon fiber absorbents. II. Effect of carbonization and activation conditions

In this paper, viscose rayon-based knitted fabrics were utilized as the precursor to produce activated carbon fiber absorbents (ACFA). The effects of carbonization and activation conditions on characteristics (ACFA) were examined. Experimental results revealed that increasing the flow rate of environmental gas N2 and steam activator used in conjunction and decreasing the production rate of ACFA can obtain better pore properties. However, higher flow rate of steam activator and lower production rate of ACFA reduced the weight yield. According to our findings, to maintain good absorption property of ACFA, the optimum manufacturing conditions are flow rate of gas N2 at 80 cc/min, flow rate of steam activator at 60 ml/min, and production rate of ACFA at 30 cm/min, with flame retardant reagent concentration maintained at 30%. Under these conditions, the weight yield can be up to 40.85% and the BET surface area can exceed 1500 g/m2.

Evaluation of activated carbon fiber applied in supercapacitor electrodes

This study uses rayon woven fabrics as the raw material for activated carbon fabrics (ACFs), which were manufactured by oxidation, carbonization and activation engineering in a continuous semi-open high-temperature furnace. First, the activated carbon fabrics are prepared under two specific manufacturing conditions with different production rates and flow rates of steam activation at 1000 °C. Then the electrochemical prosperities of the ACFs are evaluated by a three-electrode device. The experimental results show that the BET specific surface area and electrical capacitance are higher with a lower production rate. Moreover, the steam activator higher flow rate under the proposed approach. ACFs with a 2332.1 m2/g specific surface area and 78.7 % mesopore ratio result in a higher electronic conductivity of 430.4 F/g at the low rate charge (5 mV/s) and with 60 % capacitance retention during the high-speed charging-discharging process (100 mV/s).

Effect of Activator on Characteristics of Carbon Fiber Absorbents

This study utilized viscose–based nonwoven to produce carbon fiber absorbent continuously through a semi-opened erect oven with different kinds and levels of activator. The experiment results showed when air was used as an activator, the pore is in the form of split-shape, and the BET specific surface area increased with the increase of air amounts. Steam was used as an activator, the pore is accumulated by the micropore, and the mesopores are generated by incomplete evaporation of the water molecule.

Optimum heat treatment conditions for PAN-based oxidized electrospun nonwovens

In this study, the polyacrylonitrile (PAN)-based precursor was produced by electrospinning for the fabrication of oxidized nanofiber nonwovens. The parameters adopted for the oxidation process were chosen from the thermal analysis results obtained using DSC and TGA. The oxidation temperatures of 270, 300, and 330 oC were selected for heating times of 30, 50, and 70 min at three levels of tension. The variations in yield rate, breaking strength, shrinkage and stiffness of the oxidized PAN-based electrospun nonwovens were examined in this article. The results indicate that the physical properties of electrospun nonwovens were affected by the oxidation conditions. In addition, the limit oxygen index (LOI) was found to increase with increasing heat treatment temperature and time. In addition, the optimum oxidation condition was found to be heating temperature of 300 °C for a duration of 70 min. Under this condition, high-quality PAN-based oxidized electrospun nonwovens were produced with aromatization index (AI) of 62 % and LOI of 44 %.

Optimum parameters of the continuous process of electrospun nanofibrous yarn

The study uses the Taguchi method, analysis of variance (ANOVA), and principal component analysis (PCA) to design the optimal parameters of different quality characteristics on the continuous process of electrospun nanofibrous yarn. In recent years, the development of nanofibrous yarn has focused on the technique of electrospinning. In the study, the experiment is designed by a Taguchi L9(34) orthogonal array. Taguchi method is a unique statistical method which can efficiently evaluate optimal parameters and the effects of factor on quality characteristics. The experimental results obtained by the method are more accurate and objective than one-factor-at-a-time experiments. The discussed control factors are the concentration of the solution, nozzle size, flow rate, and take-up velocity. The considered quality characteristics are fiber diameter, fiber uniformity, and fiber arrangement. The optimum parameters of different quality characteristics are obtained through the main effect plot of signal-to-noise ratios (S/N ratios), then ANOVA and confidence intervals (CI) are applied to prove the results are reasonable. The multiple quality characteristics are analyzed by PCA through the normalized S/N ratios and principal component score. According to the experiments and analysis results, the optimum parameters for multiple quality characteristics are a concentration of 6 wt.%, nozzle number of 26G, flow rate of 3 ml/hr, take-up velocity of 100 cm/min.