Some types of ZnO nanostructures with various shape and size, including tetrapod-like ZnO (T-ZnO) nanorods, nanowires and nanonbbons, have been obtained by controlled growth process. The nanostructures of ZnO have bee...Some types of ZnO nanostructures with various shape and size, including tetrapod-like ZnO (T-ZnO) nanorods, nanowires and nanonbbons, have been obtained by controlled growth process. The nanostructures of ZnO have been investigated by means of field-emission scanning electron microscope, transmission electron microscopy and high-resolution transmission electron microscopy. The growth mechanisms of various ZnO nanostructures were proposed and discussed.展开更多
为了探究气候变化背景下QTT(QiTai radio Telescope)台址长时间尺度的树木生长动态,明确树木生长的限制因素。研究以天山山区优势树种雪岭云杉Picea schrenkiana为研究对象,运用VS(Vaganov-Shashkin model)模型对其树轮年表(1950—2022...为了探究气候变化背景下QTT(QiTai radio Telescope)台址长时间尺度的树木生长动态,明确树木生长的限制因素。研究以天山山区优势树种雪岭云杉Picea schrenkiana为研究对象,运用VS(Vaganov-Shashkin model)模型对其树轮年表(1950—2022年)进行模拟,从而获取树木生长的限制性因素及其生长动态。研究结果表明:(1)树木生长呈现右偏单峰模式,且在生长旺盛期,水分是生长的主要限制因子;(2)过去73年间,生长季起始时间以1.5天每10年的速度提前,生长季结束时间没有显著变化,生长季长度以2.3天每10年速度延长;(3)树木生长与4—6月降水显著正相关,而与5—6月温度显著负相关。在气候变化背景下,水分限制将持续,随着生长季长度延长,水分限制的缓解将有效促进树木生长。研究结果将有助于台址区科学合理的开展森林经营管理,有效促进树木生长。展开更多
The effect of magnetic nanoparticles(mNPs) on the devitrification crystallization of typical vitrification solution Vs55 was systematically explored by differential scanning calorimetry(DSC) and cryomicroscope system....The effect of magnetic nanoparticles(mNPs) on the devitrification crystallization of typical vitrification solution Vs55 was systematically explored by differential scanning calorimetry(DSC) and cryomicroscope system. The results show tliat,(i) the mNPs coated by both carboxylic acid(CA) and polyethylene glycol(PEG) had little effect on the glass transition temperature(rg) of Vs55, but had significant effect on the devitrification transition temperature(7a) and devitrification enthalpy(Hrd),(ii) in the range of the devitrification area(-85- 0℃), the MNPs coated by CA can significantly accelerate the devitrification of Vs55 as the isothermal temperatures and the cooling rates increased, and the ice growth rate was 0.37 p.m/s at the isothermal temperature of-85 ℃, and was about 2.19 gm/s at -75℃. Also, the ice growth rates rose from 1.72 pm/s to 3.54 pm/s when the cooling rates were increased from 2 ℃/min to 100 ℃/min(at the isothennal temperature of -75℃),(iii) magnetic nanoparticles coated by both PEG and CA could promote the devitrification of Vs55, for instance, without any crystal growth inside Vs55 at the isothermal temperature of-80℃, but 1.04 and 2.31 gm/s for adding magnetic nanoparticles coated by CA and PEG, respectively. Compared with the samples coated by CA, PEG promoted the devitrification of Vs55 in a much more positive way, and the ice growth rates were 0.62 and 6.25 μm/s at the isothermal temperatures of -85 and -75 ℃, respectively. Tliese results indicate that the surface coating of MNPs could significantly affect tlie recrystallization of Vs55, and further work should be conducted in the future research.展开更多
Uniform ZnO toothed-nanobelts and nanocombs were fabricated respectively through pure zinc powder evaporation without catalyst at temperature of 600-650℃. Scanning electron microscopy （SEM） and high-resolution tran...Uniform ZnO toothed-nanobelts and nanocombs were fabricated respectively through pure zinc powder evaporation without catalyst at temperature of 600-650℃. Scanning electron microscopy （SEM） and high-resolution transmission electron microscopy （HRTEM） observations show that such ZnO nanostructures have several types in morphology, and all of them are single crystalline. The experimental results reveal that the growth of the ZnO nanostructures was controlled by vapor-solid mechanism. Room temperature photoluminescence spectra of the toothed-nanobelts show a UV emission at - 390 nm and a broad green emission with 4 subordinate peaks at 455-495 nm.展开更多
The aluminum nitride whiskers were synthesized by the nitridation of Al/AlN powders in a flowing nitrogen atmosphere. The whiskers were about 0. 5祄 in diameter and 10~20祄 in length, and they were straight and had sm...The aluminum nitride whiskers were synthesized by the nitridation of Al/AlN powders in a flowing nitrogen atmosphere. The whiskers were about 0. 5祄 in diameter and 10~20祄 in length, and they were straight and had smooth surfaces. The morphology of the whiskers were studied by means of SEM and TEM. The AlN whiskers were grown via vapor-solid (VS) mechanism.展开更多
Large quantity growth of ZnO nanorods is achieved by oxidation of Zn powders with catalyst free method.The products are characterized using X ray diffraction,scanning electron microscopy,transmission electron micro...Large quantity growth of ZnO nanorods is achieved by oxidation of Zn powders with catalyst free method.The products are characterized using X ray diffraction,scanning electron microscopy,transmission electron microscopy and photoluminescence spectroscopy.The as grown nanorods are structurally uniform with diameter ranging from 60 to 150nm and lengths of up to 5-8μm,and they are single crystalline in nature with growth direction parallel to .Room temperature photoluminescence spectrum of the nanorods shows a strong and sharp UV emission band at 385 nm and a weak and broad green emission band at 495 nm.The vapor solid model is also proposed to explain the growth behavior of ZnO nanorods in our synthesis process.展开更多
文摘Some types of ZnO nanostructures with various shape and size, including tetrapod-like ZnO (T-ZnO) nanorods, nanowires and nanonbbons, have been obtained by controlled growth process. The nanostructures of ZnO have been investigated by means of field-emission scanning electron microscope, transmission electron microscopy and high-resolution transmission electron microscopy. The growth mechanisms of various ZnO nanostructures were proposed and discussed.
文摘为了探究气候变化背景下QTT(QiTai radio Telescope)台址长时间尺度的树木生长动态,明确树木生长的限制因素。研究以天山山区优势树种雪岭云杉Picea schrenkiana为研究对象,运用VS(Vaganov-Shashkin model)模型对其树轮年表(1950—2022年)进行模拟,从而获取树木生长的限制性因素及其生长动态。研究结果表明:(1)树木生长呈现右偏单峰模式,且在生长旺盛期,水分是生长的主要限制因子;(2)过去73年间,生长季起始时间以1.5天每10年的速度提前,生长季结束时间没有显著变化,生长季长度以2.3天每10年速度延长;(3)树木生长与4—6月降水显著正相关,而与5—6月温度显著负相关。在气候变化背景下,水分限制将持续,随着生长季长度延长,水分限制的缓解将有效促进树木生长。研究结果将有助于台址区科学合理的开展森林经营管理,有效促进树木生长。
基金the National Natural Science Foundation of China(No.51576132).
文摘The effect of magnetic nanoparticles(mNPs) on the devitrification crystallization of typical vitrification solution Vs55 was systematically explored by differential scanning calorimetry(DSC) and cryomicroscope system. The results show tliat,(i) the mNPs coated by both carboxylic acid(CA) and polyethylene glycol(PEG) had little effect on the glass transition temperature(rg) of Vs55, but had significant effect on the devitrification transition temperature(7a) and devitrification enthalpy(Hrd),(ii) in the range of the devitrification area(-85- 0℃), the MNPs coated by CA can significantly accelerate the devitrification of Vs55 as the isothermal temperatures and the cooling rates increased, and the ice growth rate was 0.37 p.m/s at the isothermal temperature of-85 ℃, and was about 2.19 gm/s at -75℃. Also, the ice growth rates rose from 1.72 pm/s to 3.54 pm/s when the cooling rates were increased from 2 ℃/min to 100 ℃/min(at the isothennal temperature of -75℃),(iii) magnetic nanoparticles coated by both PEG and CA could promote the devitrification of Vs55, for instance, without any crystal growth inside Vs55 at the isothermal temperature of-80℃, but 1.04 and 2.31 gm/s for adding magnetic nanoparticles coated by CA and PEG, respectively. Compared with the samples coated by CA, PEG promoted the devitrification of Vs55 in a much more positive way, and the ice growth rates were 0.62 and 6.25 μm/s at the isothermal temperatures of -85 and -75 ℃, respectively. Tliese results indicate that the surface coating of MNPs could significantly affect tlie recrystallization of Vs55, and further work should be conducted in the future research.
基金Funded by the National Science Fund for Distinguished Young Scholars (No.50325209) ,the National Natural Science Foundationof China ( No.50232030) , the Science and Technology Fund ofMinistry of Education of China (104022) andthe Fundfor ReturnedOverseas Scholar of Ministry of Education of China (01-498)
文摘Uniform ZnO toothed-nanobelts and nanocombs were fabricated respectively through pure zinc powder evaporation without catalyst at temperature of 600-650℃. Scanning electron microscopy （SEM） and high-resolution transmission electron microscopy （HRTEM） observations show that such ZnO nanostructures have several types in morphology, and all of them are single crystalline. The experimental results reveal that the growth of the ZnO nanostructures was controlled by vapor-solid mechanism. Room temperature photoluminescence spectra of the toothed-nanobelts show a UV emission at - 390 nm and a broad green emission with 4 subordinate peaks at 455-495 nm.
文摘The aluminum nitride whiskers were synthesized by the nitridation of Al/AlN powders in a flowing nitrogen atmosphere. The whiskers were about 0. 5祄 in diameter and 10~20祄 in length, and they were straight and had smooth surfaces. The morphology of the whiskers were studied by means of SEM and TEM. The AlN whiskers were grown via vapor-solid (VS) mechanism.
文摘Large quantity growth of ZnO nanorods is achieved by oxidation of Zn powders with catalyst free method.The products are characterized using X ray diffraction,scanning electron microscopy,transmission electron microscopy and photoluminescence spectroscopy.The as grown nanorods are structurally uniform with diameter ranging from 60 to 150nm and lengths of up to 5-8μm,and they are single crystalline in nature with growth direction parallel to .Room temperature photoluminescence spectrum of the nanorods shows a strong and sharp UV emission band at 385 nm and a weak and broad green emission band at 495 nm.The vapor solid model is also proposed to explain the growth behavior of ZnO nanorods in our synthesis process.
