Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applicat...Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applications on substrate materials with low melting points.We report a new synthesis route for PDC coatings using initiated chemical vapor deposited poly(1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane)(pV_3D_3) as the precurs or.We investigated the changes in siloxane moieties and the network topology,and proposed a three-stage mechanism for the thermal annealing process.The rise of the connectivity number for the structures obtained at increased annealing temperatures was found with strong correlation to the enhanced mechanical properties and thermal conductivity.Our PDC films obtained via annealing at 850℃ exhibit at least 14.6% higher hardness than prior reports for PDCs synthesized below 1100℃.Furthermore,thermal conductivity up to 1.02 W(mK)^(-1) was achieved at the annealing temperature as low as 700℃,which is on the same order of magnitude as PDCs obtained above 1100℃.Using minimum thermal conductivity models,we found that the thermal transport is dominated by diffusons in the films below the percolation of rigidity,while ultra-short mean-free path phonons contribute to the thermal conductivity of the films above the percolation threshold.The findings of this work provide new insights for the development of wear-resistant and thermally conductive PDC thin films for durable protection coatings.展开更多
We present a controlled,stepwise formation of layered semiconductor Bi_(2)O_(2)Se thin films prepared via the vapour process by annealing topological insulator Bi_(2)Se3 thin films in low oxygen atmosphere for differe...We present a controlled,stepwise formation of layered semiconductor Bi_(2)O_(2)Se thin films prepared via the vapour process by annealing topological insulator Bi_(2)Se3 thin films in low oxygen atmosphere for different reactions.Photodetectors based on Bi_(2)O_(2)Se thin film show a responsivity of 1.7×10^(4) A/W at a wavelength of 980 nm.Field-effect transistors based on Bi_(2)O_(2)Se thin film exhibit n-type behavior and present a high electron mobility of 17 cm^(2)/V·s.In addition,the electrical properties of the devices after 4 months keeping in the air shows little change,implying outstanding air-stability of our Bi_(2)O_(2)Se thin films.From the obtained results,it is evident that low oxygen annealing is a surprisingly effective method to fabricate Bi_(2)O_(2)Se thin films for integrated optoelectronic applications.展开更多
基金funding from the National Natural Science Foundation of China (22178301,21938011,51876186and 52150410417)the funding from the Natural Science Foundation of Zhejiang Province (LR21B060003 and LZ19E060002)+1 种基金grant from Science Technology Department of Zhejiang Province (2023C01182)supported by Shanxi Institute of Zhejiang University for New Materials and Chemical Industry(2022SZ-TD005)。
文摘Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applications on substrate materials with low melting points.We report a new synthesis route for PDC coatings using initiated chemical vapor deposited poly(1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane)(pV_3D_3) as the precurs or.We investigated the changes in siloxane moieties and the network topology,and proposed a three-stage mechanism for the thermal annealing process.The rise of the connectivity number for the structures obtained at increased annealing temperatures was found with strong correlation to the enhanced mechanical properties and thermal conductivity.Our PDC films obtained via annealing at 850℃ exhibit at least 14.6% higher hardness than prior reports for PDCs synthesized below 1100℃.Furthermore,thermal conductivity up to 1.02 W(mK)^(-1) was achieved at the annealing temperature as low as 700℃,which is on the same order of magnitude as PDCs obtained above 1100℃.Using minimum thermal conductivity models,we found that the thermal transport is dominated by diffusons in the films below the percolation of rigidity,while ultra-short mean-free path phonons contribute to the thermal conductivity of the films above the percolation threshold.The findings of this work provide new insights for the development of wear-resistant and thermally conductive PDC thin films for durable protection coatings.
基金supported by the Hunan Provincial Natural Science Foundation of China(Grant No.2019JJ40032)。
文摘We present a controlled,stepwise formation of layered semiconductor Bi_(2)O_(2)Se thin films prepared via the vapour process by annealing topological insulator Bi_(2)Se3 thin films in low oxygen atmosphere for different reactions.Photodetectors based on Bi_(2)O_(2)Se thin film show a responsivity of 1.7×10^(4) A/W at a wavelength of 980 nm.Field-effect transistors based on Bi_(2)O_(2)Se thin film exhibit n-type behavior and present a high electron mobility of 17 cm^(2)/V·s.In addition,the electrical properties of the devices after 4 months keeping in the air shows little change,implying outstanding air-stability of our Bi_(2)O_(2)Se thin films.From the obtained results,it is evident that low oxygen annealing is a surprisingly effective method to fabricate Bi_(2)O_(2)Se thin films for integrated optoelectronic applications.
