Polyvinyl alcohol(PVA) physiological saline gel was prepared using physiological saline solution of the polymer by freezing and thawing method. The influences of the concentration of PVA, freezing and thawing cycle ti...Polyvinyl alcohol(PVA) physiological saline gel was prepared using physiological saline solution of the polymer by freezing and thawing method. The influences of the concentration of PVA, freezing and thawing cycle times and solvent swelling media on the swelling properties of PVA saline gel were investigated. The result show that the electrolytical ions have great effect on the swelling behavior of PVA saline gel. The equilibrium swelling ratio of PVA saline gel in aqueous swelling media is larger than that in saline swelling media. Also, the equilibrium swelling ratios of PVA saline gel in aqueous and in saline media decrease with the increase of gel concentration and the increase of freezing and thawing cycle times. The decreasing speed of equilibrium swelling ratio with the increase of freezing and thawing cycle times of PVA gel in distilled water is faster than that in physiological saline. The swelling kinetic equation can sufficiently describe the swelling behavior of PVA physiological saline gel.展开更多
Polyvinyl alcohol/polyacrylamide semi-interpenetrated hydrogels were prepared via freeze-thaw process. When a 20 V of DC was applied across the gels, the gels with lower polyacrylamide content underwent a contraction ...Polyvinyl alcohol/polyacrylamide semi-interpenetrated hydrogels were prepared via freeze-thaw process. When a 20 V of DC was applied across the gels, the gels with lower polyacrylamide content underwent a contraction or partly turned into solution, while for the gels. with higher polyacrylamide concentration, a complete gel-sol transition was observed in a short time.展开更多
Precursors of La_(1-x)Sr_xFeO_3(x=0.0,0.1,0.4 and 0.6)nanocrystalline materials were prepared by the mixed salts dissolved in an aqueous solution of polyvinyl alcohol(PVA).XRD,DTA and TEM were used to characterize the...Precursors of La_(1-x)Sr_xFeO_3(x=0.0,0.1,0.4 and 0.6)nanocrystalline materials were prepared by the mixed salts dissolved in an aqueous solution of polyvinyl alcohol(PVA).XRD,DTA and TEM were used to characterize the samples. Well-nanocrystalline perovskite-type La_(1_x)Sr_xFeO_3 could be synthesized at the temperatures as low as 400～550℃ for 2h by the calcination of these amorphous precursors,and the calcination of wet LaFeO_3 gel was investigated at 300℃ for lh and 700℃ for 0.5h.展开更多
Al<sub>2</sub>O<sub>3</sub>/PVFM/Al<sub>2</sub>O<sub>3</sub> trilayer membranes are prepared by means of simple coating of PVA-Al<sub>2</sub>O<sub>3<...Al<sub>2</sub>O<sub>3</sub>/PVFM/Al<sub>2</sub>O<sub>3</sub> trilayer membranes are prepared by means of simple coating of PVA-Al<sub>2</sub>O<sub>3</sub> solution onto both sides of PVFM thin membranes, which is prepared via phase inversion method. The characteristics of the trilayer membranes and gel polymer electrolytes are investigated using FESEM, tensile testing apparatus, thermal shrinkage test, EIS and charge-discharge test. When inorganic Al<sub>2</sub>O<sub>3</sub> particles are used to coat the PVFM membrane, drawbacks associated with gel-type membranes, namely, poor mechanical strength and thermal stability are greatly improved. Lithium ion cell with the Al<sub>2</sub>O<sub>3</sub>/PVFM/Al<sub>2</sub>O<sub>3</sub> based GPE matched with LiFePO<sub>4</sub> shows excellent electrochemical performance.展开更多
Replacement of phosphoric acid electrolyte by phosphosilicate gel based electrolytes is proposed for performance enhancement of phosphoric acid fuel cell(PAFC).Phosphosilicate gel in paste form and in powder form is s...Replacement of phosphoric acid electrolyte by phosphosilicate gel based electrolytes is proposed for performance enhancement of phosphoric acid fuel cell(PAFC).Phosphosilicate gel in paste form and in powder form is synthesized from tetraethoxysilane and orthophosphoric acid using sol-gel method for two different P/Si ratio of 5 and 1.5 respectively.Replacement of phosphoric acid electrolyte by phosphosilicate gel paste enhances the peak power generation of the fuel cell by 133% at 120 ℃ cell temperature;increases the voltage generation in the ohmic regime and extends the maximum possible load current.Polyinyl alcohol(PVA) is used to bind the phosphosilicate gel powder and to form the hybrid crosslinked gel polymer electrolyte membrane.Soaking the membrane with phosphoric acid solution,instead of that with water improves the proton conductivity of the membrane,enhances the voltage and power generation by the fuel cell and extends the maximum possible operating temperature.At lower operating temperature of 70 ℃,peak power produced by phosphosilicate gel polymer electrolyte membrane fuel cell(PGMFC) is increased by 40% compared to that generated by phosphoric acid fuel cell(PAFC).However,the performance of composite membrane diminishes as the cell temperature increases.Thus phosphosilicate gel in paste form is found to be a good alternative of phosphoric acid electrolyte at medium operating temperature range while phosphosilicate gel-PVA composite offers performance enhancement at low operating temperatures.展开更多
The hydrogel wound dressing based on polyvinyl alcohol （PVA） was prepared by the freezing-thawing cyclic method. The dehydration kinetics of prepared hydrogels was determined using the experimental method and mathem...The hydrogel wound dressing based on polyvinyl alcohol （PVA） was prepared by the freezing-thawing cyclic method. The dehydration kinetics of prepared hydrogels was determined using the experimental method and mathematical modeling based on diffusion mechanism. The results show that the dehydration rate of PVA hydrogel wound dressing inversely depends on the hydrogel thickness as well as water content of the wound. On the other hand, the initial water content of hydrogel and the atmospheric humidity have little direct effect on the dehydration rate. The good agreement between experimental and mathematical modeling results in early stages of dehydration process shows that the predominate factor determining the dehydration of these wound dressings is diffusion.展开更多
文摘Polyvinyl alcohol(PVA) physiological saline gel was prepared using physiological saline solution of the polymer by freezing and thawing method. The influences of the concentration of PVA, freezing and thawing cycle times and solvent swelling media on the swelling properties of PVA saline gel were investigated. The result show that the electrolytical ions have great effect on the swelling behavior of PVA saline gel. The equilibrium swelling ratio of PVA saline gel in aqueous swelling media is larger than that in saline swelling media. Also, the equilibrium swelling ratios of PVA saline gel in aqueous and in saline media decrease with the increase of gel concentration and the increase of freezing and thawing cycle times. The decreasing speed of equilibrium swelling ratio with the increase of freezing and thawing cycle times of PVA gel in distilled water is faster than that in physiological saline. The swelling kinetic equation can sufficiently describe the swelling behavior of PVA physiological saline gel.
基金supported by the National Natural Science Foundation of China(Nos.20736002,20706013)Program for Changjiang Scholars and Innovative Research Team in University(No.IRT0721)the 111 Project(No.B08021).
文摘Polyvinyl alcohol/polyacrylamide semi-interpenetrated hydrogels were prepared via freeze-thaw process. When a 20 V of DC was applied across the gels, the gels with lower polyacrylamide content underwent a contraction or partly turned into solution, while for the gels. with higher polyacrylamide concentration, a complete gel-sol transition was observed in a short time.
文摘Precursors of La_(1-x)Sr_xFeO_3(x=0.0,0.1,0.4 and 0.6)nanocrystalline materials were prepared by the mixed salts dissolved in an aqueous solution of polyvinyl alcohol(PVA).XRD,DTA and TEM were used to characterize the samples. Well-nanocrystalline perovskite-type La_(1_x)Sr_xFeO_3 could be synthesized at the temperatures as low as 400～550℃ for 2h by the calcination of these amorphous precursors,and the calcination of wet LaFeO_3 gel was investigated at 300℃ for lh and 700℃ for 0.5h.
文摘Al<sub>2</sub>O<sub>3</sub>/PVFM/Al<sub>2</sub>O<sub>3</sub> trilayer membranes are prepared by means of simple coating of PVA-Al<sub>2</sub>O<sub>3</sub> solution onto both sides of PVFM thin membranes, which is prepared via phase inversion method. The characteristics of the trilayer membranes and gel polymer electrolytes are investigated using FESEM, tensile testing apparatus, thermal shrinkage test, EIS and charge-discharge test. When inorganic Al<sub>2</sub>O<sub>3</sub> particles are used to coat the PVFM membrane, drawbacks associated with gel-type membranes, namely, poor mechanical strength and thermal stability are greatly improved. Lithium ion cell with the Al<sub>2</sub>O<sub>3</sub>/PVFM/Al<sub>2</sub>O<sub>3</sub> based GPE matched with LiFePO<sub>4</sub> shows excellent electrochemical performance.
基金support from Naval Materials Research Laboratory(NMRL),DRDO,Ambernath,and from Department of Science & Technology,Indiaare gratefully acknowledged
文摘Replacement of phosphoric acid electrolyte by phosphosilicate gel based electrolytes is proposed for performance enhancement of phosphoric acid fuel cell(PAFC).Phosphosilicate gel in paste form and in powder form is synthesized from tetraethoxysilane and orthophosphoric acid using sol-gel method for two different P/Si ratio of 5 and 1.5 respectively.Replacement of phosphoric acid electrolyte by phosphosilicate gel paste enhances the peak power generation of the fuel cell by 133% at 120 ℃ cell temperature;increases the voltage generation in the ohmic regime and extends the maximum possible load current.Polyinyl alcohol(PVA) is used to bind the phosphosilicate gel powder and to form the hybrid crosslinked gel polymer electrolyte membrane.Soaking the membrane with phosphoric acid solution,instead of that with water improves the proton conductivity of the membrane,enhances the voltage and power generation by the fuel cell and extends the maximum possible operating temperature.At lower operating temperature of 70 ℃,peak power produced by phosphosilicate gel polymer electrolyte membrane fuel cell(PGMFC) is increased by 40% compared to that generated by phosphoric acid fuel cell(PAFC).However,the performance of composite membrane diminishes as the cell temperature increases.Thus phosphosilicate gel in paste form is found to be a good alternative of phosphoric acid electrolyte at medium operating temperature range while phosphosilicate gel-PVA composite offers performance enhancement at low operating temperatures.
文摘The hydrogel wound dressing based on polyvinyl alcohol （PVA） was prepared by the freezing-thawing cyclic method. The dehydration kinetics of prepared hydrogels was determined using the experimental method and mathematical modeling based on diffusion mechanism. The results show that the dehydration rate of PVA hydrogel wound dressing inversely depends on the hydrogel thickness as well as water content of the wound. On the other hand, the initial water content of hydrogel and the atmospheric humidity have little direct effect on the dehydration rate. The good agreement between experimental and mathematical modeling results in early stages of dehydration process shows that the predominate factor determining the dehydration of these wound dressings is diffusion.
