title: Temperature-driven directional coalescence of silver nanoparticles.
abstract: Silver nanoparticles were synthesized with a chemical reduction method in the presence of polyvinylpyrrolidone as stabilizing agent. The thermal stability behavior of the silver nanoparticles was studied in the temperature range from 25 to 700°C. Thermal gravimetric analysis was used to measure the weight loss of the silver nanoparticles. Scanning electron microscopy and high-resolution transmission electron microscopy were used to observe the morphology and the change in shape of the silver nanoparticles. In situ temperature-dependent small-angle X-ray scattering was used to detect the increase in particle size with temperature. In situ temperature-dependent X-ray diffraction was used to characterize the increase in nanocrystal size and the thermal expansion coefficient. The results demonstrate that sequential slow and fast Ostward ripening are the main methods of nanoparticle growth at lower temperatures (<500°C), whereas successive random and directional coalescences are the main methods of nanoparticle growth at higher temperatures (>500°C). A four-stage model can be used to describe the whole sintering process. The thermal expansion coefficient (2.8 × 10(-5) K(-1)) of silver nanoparticles is about 30% larger than that of bulk silver. To our knowledge, the temperature-driven directional coalescence of silver nanocrystals is reported for the first time. Two possible mechanisms of directional coalescence have been proposed. This study is of importance not only in terms of its fundamental academic interest but also in terms of the thermal stability of silver nanoparticles.
authors.affiliation: National Center for Materials Service Safety, University of Science and Technology, Beijing 100083, People's Republic of China.
authors.forename: Shi
authors.initials: S
authors.lastname: Yan
authors.affiliation: National Center for Materials Service Safety, University of Science and Technology, Beijing 100083, People's Republic of China.
authors.forename: Dongbai
authors.initials: D
authors.lastname: Sun
authors.affiliation: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Gong
authors.affiliation: National Center for Materials Service Safety, University of Science and Technology, Beijing 100083, People's Republic of China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Tan
authors.affiliation: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Xueqing
authors.initials: X
authors.lastname: Xing
authors.affiliation: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Guang
authors.initials: G
authors.lastname: Mo
authors.affiliation: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Zhongjun
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Cai
authors.affiliation: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Li
authors.affiliation: Corrosion and Protection Center, Laboratory for Corrosion-Erosion and Surface Technology, University of Science and Technology, Beijing 100083, People's Republic of China.
authors.forename: Hongying
authors.initials: H
authors.lastname: Yu
authors.affiliation: Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Wu
keywords: SAXS; XRD; coalescence; nanocrystal; silver nanoparticles