The undercooling of the single micro-sized droplet of Sn-3.0Ag-0.5Cu(wt%)alloy has been studied via the newly developed fast calorimetric scanning technique,by which the fast heating and cooling treatment for a single...The undercooling of the single micro-sized droplet of Sn-3.0Ag-0.5Cu(wt%)alloy has been studied via the newly developed fast calorimetric scanning technique,by which the fast heating and cooling treatment for a single droplet can be realized,with the maximum heating or cooling rate being 1×104K/s.Owing to the nearly spherical shape of the single droplet upon heating and cooling and the resul-tant geometric stability,the influence of the droplet size on the solidification process could be elimi-nated.As a result,the puzzled issue on how to separate the mutual effects of droplet size and cooling rate in the field of rapid solidification has been primarily solved,making it possible to study separately the effect of droplet size and cooling rate.Meanwhile,the in-situ observation on deep undercooling could be actualized in this condition,differing from that obtained only by theoretical calculation.The results showed that the undercooling was increased with the increasing cooling rate,and the maximum in-situ measured undercooling reached 116.9K.The undercooling of the single droplet,however,was increased abruptly when cooled at the rate of 2×103K/s.The undercooling increased slightly as the cooling rate was increased continuously to 1×104K/s,implying the infeasibility for gaining large undercooling only by increasing the cooling rate.展开更多
The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differentia...The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differential scanning calorimetry(DSC). The βphase of PVDF was observed after quenching from the melt and further annealing above the glass transition temperature over a composition range. The PVDF/PEMA blend with weight ratio of 3:2 has formed higher content of PVDF β crystals than others. By taking advantage of fast cooling rate of ultrafast differential scanning calorimeter(UFDSC), the quenching process of blends was modeled and tested simultaneously, and the melting behavior of β crystals in all blends was investigated. Three types of crystallization behavior of βphase PVDF in blends were found after quenching-annealing at different temperatures.展开更多
基金Supported by the Robert Bosch Foundation(Grant No.32.5.8003.0025.0/MA01)the National Natural Science Foundation of China(Grant No.50571057)+1 种基金the National High-Tech Research and Development Program of China("863" Project)(Grant No. 2006AA03Z339)the Shanghai Rising-Star Program(Grant No.06QA14020)
文摘The undercooling of the single micro-sized droplet of Sn-3.0Ag-0.5Cu(wt%)alloy has been studied via the newly developed fast calorimetric scanning technique,by which the fast heating and cooling treatment for a single droplet can be realized,with the maximum heating or cooling rate being 1×104K/s.Owing to the nearly spherical shape of the single droplet upon heating and cooling and the resul-tant geometric stability,the influence of the droplet size on the solidification process could be elimi-nated.As a result,the puzzled issue on how to separate the mutual effects of droplet size and cooling rate in the field of rapid solidification has been primarily solved,making it possible to study separately the effect of droplet size and cooling rate.Meanwhile,the in-situ observation on deep undercooling could be actualized in this condition,differing from that obtained only by theoretical calculation.The results showed that the undercooling was increased with the increasing cooling rate,and the maximum in-situ measured undercooling reached 116.9K.The undercooling of the single droplet,however,was increased abruptly when cooled at the rate of 2×103K/s.The undercooling increased slightly as the cooling rate was increased continuously to 1×104K/s,implying the infeasibility for gaining large undercooling only by increasing the cooling rate.
基金financially supported by the National Natural Science Foundation of China (Nos. 21474049, 51673094 and 21404055)Tianshan Scholars Program by Yili Normal Universitythe Shenzhen Science and Technology Innovation Committee (Nos. JCYJ20160608140827794, JCYJ20160531151102203 and JCYJ20170818110206085)
文摘The nature of the crystalline phase of poly(vinylidene fluoride)(PVDF) in compatible blends with poly(ethyl methacrylate)(PEMA) was investigated by using X-ray diffraction(XRD), infrared microscopy(IR) and differential scanning calorimetry(DSC). The βphase of PVDF was observed after quenching from the melt and further annealing above the glass transition temperature over a composition range. The PVDF/PEMA blend with weight ratio of 3:2 has formed higher content of PVDF β crystals than others. By taking advantage of fast cooling rate of ultrafast differential scanning calorimeter(UFDSC), the quenching process of blends was modeled and tested simultaneously, and the melting behavior of β crystals in all blends was investigated. Three types of crystallization behavior of βphase PVDF in blends were found after quenching-annealing at different temperatures.
