The sol/gel phase diagrams were studied for two systems: polyacrylamide/Cr (III) and polyacrylamide/glyoxal. Sol or gel phase could be distinguished according to the concentrations of polymer and crosslinker. The boun...The sol/gel phase diagrams were studied for two systems: polyacrylamide/Cr (III) and polyacrylamide/glyoxal. Sol or gel phase could be distinguished according to the concentrations of polymer and crosslinker. The boundary polymer concentration did not depend on the types of gelation and decreased with increasing polymer dimension (molecular weight and conformation). The gelation, which is basically interchain bonding, requires the occurrence of entanglement. The overlap concentration is thus considered as the minimum polymer concentration required for gelation.展开更多
The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La 3+ were studied by chemical p hase analysis, X-ray diffraction and infrared spectrometry an...The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La 3+ were studied by chemical p hase analysis, X-ray diffraction and infrared spectrometry analysis. The expe rimental results show that phase transformation reactions of FeCO 3, Fe 2O 3 and BaFe 2O 4, barium hexaferrite and γ-Fe 2O 3 take place in the heat tr eatment of gel. While the doping lanthanide ion replace barium ion, an equivalen t quantity of Fe 3+ are reduced to Fe 2+ to maintain the charge equili brium.展开更多
In this paper, a planar three layer quasisteady laminar flow model is proposed in a cough machine which simulates mucous gel transport in model trachea due to mild forced expiration. The flow is governed by the time d...In this paper, a planar three layer quasisteady laminar flow model is proposed in a cough machine which simulates mucous gel transport in model trachea due to mild forced expiration. The flow is governed by the time dependent pressure gradient generated in trachea due to mild forced expiration. Mucous gel is represented by a viscoelastic Voigt element whereas sol phase fluid and air are considered as Newtonian fluids. For fixed airflow rate, it is shown that when the viscosity of mucous gel is small, mucous gel transport decreases as the elastic modulus increases. However, elastic modulus has negligible effect on large gel viscosity. It is also shown that for fixed airflow rate and fixed airway dimension, mucous gel transport increases with the thickness of sol phase fluid and this increase is further enhanced as the viscosity of sol phase fluid decreases. The effect of surfactant is studied by considering sol phase as surfactant layer which causes slip at the wall and interface of sol phase and mucous gel. It is found that in the presence of surfactant mucous gel transport is enhanced.展开更多
YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some interm...YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.展开更多
In this study,the sol-gel method was introduced to prepare the composite phase change material (CPCM). The CPCM was added to fabric with coating techniques and the thermal activity of modified fabric was studied. In a...In this study,the sol-gel method was introduced to prepare the composite phase change material (CPCM). The CPCM was added to fabric with coating techniques and the thermal activity of modified fabric was studied. In addition,the thermal property and the microstructure of CPCM were also discussed in detail by means of polarization microscope and differential scanning calorimeter,respectively. According to the analysis of main influencial factors of the property of CPCM,the optimal preparing technique was determined. It was proved that CPCM could exhibit a good thermal property while phase transformation process took place,and a better appearance of the fabric modified with CPCM could be obtained due to the fact that in a warm circumstance,the liquid-state phase change material could be firmly enwrapped and embedded in the three-dimensional network all the time during the phase transformation. Besides,the fabric treated with CPCM had a high phase-transition enthalpy and an appropriate phase-transition temperature. As a result,a desirable temperature-adjustable function appeared.展开更多
The phase separation and gel formation behavior in an alkoxy-derived silica sol-gel system containing C16EO15 has been investigated. Various gel morphologies similar to other sol-gel systems containing organic additiv...The phase separation and gel formation behavior in an alkoxy-derived silica sol-gel system containing C16EO15 has been investigated. Various gel morphologies similar to other sol-gel systems containing organic additives were obtained by changing the preparation conditions. Micrometer-range interconnected porous gels were obtained by freezing transitional structures of phase separation in the sol-gel process. The dependence of the resulting gel morphology on several important reaction parameters such as the starting composition, reaction temperature and acid catalyst concentration was studied in detail. The experimental results indicate that the gel morphology is mainly determined by the time relation between the onset of phase separation and gel formation.展开更多
5, 11, 17, 23-tetra-tert-butyl-25, 27-diethoxy-26, 28-dihydroxycalix \ arene /hydroxy-terminated silicone oil coated fiber was first prepared and applied for solid-phase microextraction with sol-gel technology. The pr...5, 11, 17, 23-tetra-tert-butyl-25, 27-diethoxy-26, 28-dihydroxycalix \ arene /hydroxy-terminated silicone oil coated fiber was first prepared and applied for solid-phase microextraction with sol-gel technology. The properties of the new coating were investigated by analysis of benzene derivatives, polycyclic aromatic hydrocarbons and aromatic amines. The fiber is characterized by good sensitivity and selectivity to these aromatics. The fiber has stable performance at a high temperature of 380℃ and after a long solvent immersing, thus its lifetime is very long. It shows good fiber-to-fiber and batch-to-batch reproducibility. Furthermore, broad linear ranges and low detection limits are also its characteristics.展开更多
The sol-gel technology is applied for the preparation of solid-phase microextraction (SPME) fiber. The fiber demonstrates high thermal stability, efficient extraction rate and the selectivity for non-polar or low-pol...The sol-gel technology is applied for the preparation of solid-phase microextraction (SPME) fiber. The fiber demonstrates high thermal stability, efficient extraction rate and the selectivity for non-polar or low-polar analytes. Efficient SPME-GC-FID analyses of benzene- toluene-ethylbenzene-xylenes (BTEXs) and low-polar halocarbon were achieved by the sol-gel coated DSDA-DDBT-TiO2 fiber. Some parameters of the SPME fiber for the determination of halocarbon in aqueous sample were investigated.展开更多
The rare earth berate YBO3 synthesized by sol-gel technique was found to be in two phases. However, the low-svmmetry form of YBO3 which was found also in some other rare earth (Sm, Eu, Gd) berates has a much different...The rare earth berate YBO3 synthesized by sol-gel technique was found to be in two phases. However, the low-svmmetry form of YBO3 which was found also in some other rare earth (Sm, Eu, Gd) berates has a much different dependence on the preparing conditions, The photoluminescent spectra indicate that there are more than two sites for Eu3+ in the sol-gel prepared polycrystalline YBO3:Eu with low-symmetry.展开更多
This work mainly involved the preparation of a nano-scale form-stable phase change material（PCM） consisting of capric and myristic acid（CA-MA） binary eutectic acting as thermal absorbing material and nano silicon ...This work mainly involved the preparation of a nano-scale form-stable phase change material（PCM） consisting of capric and myristic acid（CA-MA） binary eutectic acting as thermal absorbing material and nano silicon dioxide（nano-SiO_2） serving as the supporting material. Industrial water glass for preparation of the nano silicon dioxide matrix and CA-MA eutectic mixture were compounded by single-step sol-gel method with the silane coupling agent. The morphology, chemical characterization and form stability property of the composite PCM were investigated by transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, Fourier-transform infrared（FT-IR） spectroscopy and polarizing microscopy（POM）. It was indicated that the average diameter of the composite PCM particle ranged from 30-100 nm. The CA-MA eutectic was immobilized in the network pores constructed by the Si-O bonds so that the composite PCM was allowed no liquid leakage above the melting temperature of the CA-MA eutectic. Differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA） measurement were conducted to investigate the thermal properties and stability of the composite PCM. From the measurement results, the mass fraction of the CA-MA eutectic in the composite PCM was about 40%. The phase change temperature and latent heat of the composite were determined to be 21.15 ℃ and 55.67 J/g, respectively. Meanwhile, thermal conductivity of the composite was measured to be 0.208 W·m^（-1）·K^（-1） by using the transient hot-wire method. The composite PCM was able to maintain the surrounding temperature close to its phase change temperature and behaved well in thermalregulated performance which was verified by the heat storage-release experiment. This kind of form-stable PCM was supposed to complete thermal insulation even temperature regulation by the dual effect of relatively low thermal conductivity and phase change thermal storage-release properties. So it can be formulated that the nanoscale CA-MA/SiO_2 composite PCM with the form-stable property, good thermal storage capacity and relatively low thermal conductivity can be applied for energy conservation as a kind of thermal functional material.展开更多
基金This work was supported by Polymer Physics Laboratory
文摘The sol/gel phase diagrams were studied for two systems: polyacrylamide/Cr (III) and polyacrylamide/glyoxal. Sol or gel phase could be distinguished according to the concentrations of polymer and crosslinker. The boundary polymer concentration did not depend on the types of gelation and decreased with increasing polymer dimension (molecular weight and conformation). The gelation, which is basically interchain bonding, requires the occurrence of entanglement. The overlap concentration is thus considered as the minimum polymer concentration required for gelation.
文摘The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La 3+ were studied by chemical p hase analysis, X-ray diffraction and infrared spectrometry analysis. The expe rimental results show that phase transformation reactions of FeCO 3, Fe 2O 3 and BaFe 2O 4, barium hexaferrite and γ-Fe 2O 3 take place in the heat tr eatment of gel. While the doping lanthanide ion replace barium ion, an equivalen t quantity of Fe 3+ are reduced to Fe 2+ to maintain the charge equili brium.
文摘In this paper, a planar three layer quasisteady laminar flow model is proposed in a cough machine which simulates mucous gel transport in model trachea due to mild forced expiration. The flow is governed by the time dependent pressure gradient generated in trachea due to mild forced expiration. Mucous gel is represented by a viscoelastic Voigt element whereas sol phase fluid and air are considered as Newtonian fluids. For fixed airflow rate, it is shown that when the viscosity of mucous gel is small, mucous gel transport decreases as the elastic modulus increases. However, elastic modulus has negligible effect on large gel viscosity. It is also shown that for fixed airflow rate and fixed airway dimension, mucous gel transport increases with the thickness of sol phase fluid and this increase is further enhanced as the viscosity of sol phase fluid decreases. The effect of surfactant is studied by considering sol phase as surfactant layer which causes slip at the wall and interface of sol phase and mucous gel. It is found that in the presence of surfactant mucous gel transport is enhanced.
文摘YAG： Ce^3 ＋ phosphor particles were prepared using polyacrylamide gel method. The structure evolution of powders during annealing process was followed by X-ray diffraction determination. It is found that some intermediate phases, including θ-Al2O3, YAM and YAP, are formed when calcining polyacrylamide gel, however, the pure YAG phase can be formed directly when calcining polyacrylamide gel with α-Al2O3 as seed crystal. These facts show that the existence of α- Al2O3 seed crystal can block the formation of θ-Al2O3, YAM and YAP, and accelerate its reaction with Y2O3 to form YAG phase directly at lower temperature. The emission peak of prepared YAG ： Ce^3 ＋ phosphor is wide with maximum at 550 nm and the exitation band has two peaks, the major one is around at 460 nm, which matches the blue emission of GaN LED and is suitable for the assemble of white LED. Some fluxes can enhance the photoluminescence intensity of phosphor particles, that can be attributed both to the improvement of crystallization processes of YAG and to the stabilization of trivalence cerium ion in YAG：Ce^3 ＋.
基金Fujian Province I mportant Science and Technology Development Fund,China (No.2005Z17)
文摘In this study,the sol-gel method was introduced to prepare the composite phase change material (CPCM). The CPCM was added to fabric with coating techniques and the thermal activity of modified fabric was studied. In addition,the thermal property and the microstructure of CPCM were also discussed in detail by means of polarization microscope and differential scanning calorimeter,respectively. According to the analysis of main influencial factors of the property of CPCM,the optimal preparing technique was determined. It was proved that CPCM could exhibit a good thermal property while phase transformation process took place,and a better appearance of the fabric modified with CPCM could be obtained due to the fact that in a warm circumstance,the liquid-state phase change material could be firmly enwrapped and embedded in the three-dimensional network all the time during the phase transformation. Besides,the fabric treated with CPCM had a high phase-transition enthalpy and an appropriate phase-transition temperature. As a result,a desirable temperature-adjustable function appeared.
文摘The phase separation and gel formation behavior in an alkoxy-derived silica sol-gel system containing C16EO15 has been investigated. Various gel morphologies similar to other sol-gel systems containing organic additives were obtained by changing the preparation conditions. Micrometer-range interconnected porous gels were obtained by freezing transitional structures of phase separation in the sol-gel process. The dependence of the resulting gel morphology on several important reaction parameters such as the starting composition, reaction temperature and acid catalyst concentration was studied in detail. The experimental results indicate that the gel morphology is mainly determined by the time relation between the onset of phase separation and gel formation.
文摘5, 11, 17, 23-tetra-tert-butyl-25, 27-diethoxy-26, 28-dihydroxycalix \ arene /hydroxy-terminated silicone oil coated fiber was first prepared and applied for solid-phase microextraction with sol-gel technology. The properties of the new coating were investigated by analysis of benzene derivatives, polycyclic aromatic hydrocarbons and aromatic amines. The fiber is characterized by good sensitivity and selectivity to these aromatics. The fiber has stable performance at a high temperature of 380℃ and after a long solvent immersing, thus its lifetime is very long. It shows good fiber-to-fiber and batch-to-batch reproducibility. Furthermore, broad linear ranges and low detection limits are also its characteristics.
文摘The sol-gel technology is applied for the preparation of solid-phase microextraction (SPME) fiber. The fiber demonstrates high thermal stability, efficient extraction rate and the selectivity for non-polar or low-polar analytes. Efficient SPME-GC-FID analyses of benzene- toluene-ethylbenzene-xylenes (BTEXs) and low-polar halocarbon were achieved by the sol-gel coated DSDA-DDBT-TiO2 fiber. Some parameters of the SPME fiber for the determination of halocarbon in aqueous sample were investigated.
文摘The rare earth berate YBO3 synthesized by sol-gel technique was found to be in two phases. However, the low-svmmetry form of YBO3 which was found also in some other rare earth (Sm, Eu, Gd) berates has a much different dependence on the preparing conditions, The photoluminescent spectra indicate that there are more than two sites for Eu3+ in the sol-gel prepared polycrystalline YBO3:Eu with low-symmetry.
基金Funded by the National Natural Science Foundation of China(No.51308275)Natural Science Foundation of Liaoning Province(No.SY2016004)the Colleges and Universities Excellent Talents Supporting Plan Program of Liaoning Province(No.LJQ2015049)
文摘This work mainly involved the preparation of a nano-scale form-stable phase change material（PCM） consisting of capric and myristic acid（CA-MA） binary eutectic acting as thermal absorbing material and nano silicon dioxide（nano-SiO_2） serving as the supporting material. Industrial water glass for preparation of the nano silicon dioxide matrix and CA-MA eutectic mixture were compounded by single-step sol-gel method with the silane coupling agent. The morphology, chemical characterization and form stability property of the composite PCM were investigated by transmission electron microscopy（TEM）, scanning electron microscopy（SEM）, Fourier-transform infrared（FT-IR） spectroscopy and polarizing microscopy（POM）. It was indicated that the average diameter of the composite PCM particle ranged from 30-100 nm. The CA-MA eutectic was immobilized in the network pores constructed by the Si-O bonds so that the composite PCM was allowed no liquid leakage above the melting temperature of the CA-MA eutectic. Differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA） measurement were conducted to investigate the thermal properties and stability of the composite PCM. From the measurement results, the mass fraction of the CA-MA eutectic in the composite PCM was about 40%. The phase change temperature and latent heat of the composite were determined to be 21.15 ℃ and 55.67 J/g, respectively. Meanwhile, thermal conductivity of the composite was measured to be 0.208 W·m^（-1）·K^（-1） by using the transient hot-wire method. The composite PCM was able to maintain the surrounding temperature close to its phase change temperature and behaved well in thermalregulated performance which was verified by the heat storage-release experiment. This kind of form-stable PCM was supposed to complete thermal insulation even temperature regulation by the dual effect of relatively low thermal conductivity and phase change thermal storage-release properties. So it can be formulated that the nanoscale CA-MA/SiO_2 composite PCM with the form-stable property, good thermal storage capacity and relatively low thermal conductivity can be applied for energy conservation as a kind of thermal functional material.
