Silver nanoparticles with different morphologies were prepared in AgNO3 aqueous solution using nanocarbon as template medium and polymer surfactant as protecting agent in an ultrasonic field.The polymer surfactant pol...Silver nanoparticles with different morphologies were prepared in AgNO3 aqueous solution using nanocarbon as template medium and polymer surfactant as protecting agent in an ultrasonic field.The polymer surfactant polyvinylpyrrolidone(PVP)was self-prepared and used directly in aqueous solution form.The molecular weight of PVP was measured by viscosimeter.The crystalline phase,component,size,and morphology of the as-synthesized silver naoparticles were characterized by XRD,TEM,FTIR,and Laser Granularity Instrument.The results indicated that ultrasonic was the key factor to deoxidize Ag+ to be Ago,nanocarbon and polymer surfactants accelerated the deoxidization reaction course and controlled the agglomeration of freshly formed silver nanoparticles,the category of polymer surfactant had decisive effect on the morphology of as-synthesized nanoparticle.Well-defined dendrites silver nanoparticle could be attained when choosing PVP as surfactant in AgNO3 aqueous solution,while regular sphere silver nanoparticle could be synthesized in the presence of polyvinyl alcohol(PVA)surfactant.Moreover,the concentration of AgNO3 and ultrasonic action time also had obvious effect on the morphology of silver nanoparticle,low concentration of AgNO3 and long time of ultrasonic were not in favor of forming dendrite silver.展开更多
NT build 443, or profile fitting method, is often used to measure the diffusion coefficient of chloride in concrete. However, this method is quite laborious and needs special equipment. Colorimetric method is a quick ...NT build 443, or profile fitting method, is often used to measure the diffusion coefficient of chloride in concrete. However, this method is quite laborious and needs special equipment. Colorimetric method is a quick and simple method to measure the penetration depth of chloride by spraying 0.1 mol/L silver nitrate solution. The objective of this work is to study the possibility of the use of colorimetric method in the calculation of non-steady-state diffusion coefficient. Twelve concrete mixtures with different supplementary cementitious materials and water-to-cement ratios of 0.35, 0.48 and 0.6 were used for study. According to NT build 443, the concrete specimens were immersed in 165 g/L NaC1 （2.8 mol/L） solution for 42 d. Both water-soluble （convert to free chloride） chloride and acid-soluble chloride at different layers of specimens were measured. The results show that the mean value of free chloride concentration at the color change boundary Cd was 0.306 mol/L. The surface free chloride concentration cs was obtained by profile fitting method, which was 40% lower than the chloride concentration of exposure solution after an immersion period of 42 d. Chloride diffusion coefficients obtained by the colorimetric method was not well correlated with those obtained by profile fitting method.展开更多
文摘Silver nanoparticles with different morphologies were prepared in AgNO3 aqueous solution using nanocarbon as template medium and polymer surfactant as protecting agent in an ultrasonic field.The polymer surfactant polyvinylpyrrolidone(PVP)was self-prepared and used directly in aqueous solution form.The molecular weight of PVP was measured by viscosimeter.The crystalline phase,component,size,and morphology of the as-synthesized silver naoparticles were characterized by XRD,TEM,FTIR,and Laser Granularity Instrument.The results indicated that ultrasonic was the key factor to deoxidize Ag+ to be Ago,nanocarbon and polymer surfactants accelerated the deoxidization reaction course and controlled the agglomeration of freshly formed silver nanoparticles,the category of polymer surfactant had decisive effect on the morphology of as-synthesized nanoparticle.Well-defined dendrites silver nanoparticle could be attained when choosing PVP as surfactant in AgNO3 aqueous solution,while regular sphere silver nanoparticle could be synthesized in the presence of polyvinyl alcohol(PVA)surfactant.Moreover,the concentration of AgNO3 and ultrasonic action time also had obvious effect on the morphology of silver nanoparticle,low concentration of AgNO3 and long time of ultrasonic were not in favor of forming dendrite silver.
基金Project(2010QZZD018) supported by Central South Universtiy,China,and Ghent University,Belgium
文摘NT build 443, or profile fitting method, is often used to measure the diffusion coefficient of chloride in concrete. However, this method is quite laborious and needs special equipment. Colorimetric method is a quick and simple method to measure the penetration depth of chloride by spraying 0.1 mol/L silver nitrate solution. The objective of this work is to study the possibility of the use of colorimetric method in the calculation of non-steady-state diffusion coefficient. Twelve concrete mixtures with different supplementary cementitious materials and water-to-cement ratios of 0.35, 0.48 and 0.6 were used for study. According to NT build 443, the concrete specimens were immersed in 165 g/L NaC1 （2.8 mol/L） solution for 42 d. Both water-soluble （convert to free chloride） chloride and acid-soluble chloride at different layers of specimens were measured. The results show that the mean value of free chloride concentration at the color change boundary Cd was 0.306 mol/L. The surface free chloride concentration cs was obtained by profile fitting method, which was 40% lower than the chloride concentration of exposure solution after an immersion period of 42 d. Chloride diffusion coefficients obtained by the colorimetric method was not well correlated with those obtained by profile fitting method.
