The SiC whiskers (SiCw) synthesized from rice hulls is studied in this paper. The properties of the application in the composite materials are tested, and also compared with the SiCw produced in US and Japan, the resu...The SiC whiskers (SiCw) synthesized from rice hulls is studied in this paper. The properties of the application in the composite materials are tested, and also compared with the SiCw produced in US and Japan, the results indicate that the SiCw produced by this method is mainly straight crystals with multi nodes on face, the main type is P-SiC. lt has many advantages such as high strength and excellent oxidation resistance to high temperature. The Si3N4 ceramic composite materials reinforced and toughened with the SiCw, δfRT of the material is (856±22)MPa, δf300℃ is approximately (418. 5±14. 2) MPa and Klc is approximately (11. 3±1. 0) MPa m1/2. Besides, the application of the SiCw in the engineering materials of mining is forecasted.展开更多
As the large single-crystalline silicon wafers have revolutionized many industries including electronics and solar cells, it is envisioned that the availability of large single-crystalline perovskite crystals and wafe...As the large single-crystalline silicon wafers have revolutionized many industries including electronics and solar cells, it is envisioned that the availability of large single-crystalline perovskite crystals and wafers will revolutionize its broad applications in photovoltaics, optoelectronics, lasers, photodetectors, light emitting diodes(LEDs), etc. Here we report a method to grow large single-crystalline perovskites including single-halide crystals: CH3NH3PbX3(X=I, Br, Cl), and dual-halide ones:CH3NH3Pb(ClxBr1.x)3 and CH3NH3Pb(BrxI1.x)3, with the largest crystal being 120 mm in length. Meanwhile, we have advanced a process to slice the large perovskite crystals into thin wafers. It is found that the wafers exhibit remarkable features:(1)its trap-state density is a million times smaller than that in the microcrystalline perovskite thin films(MPTF);(2) its carrier mobility is 410 times higher than its most popular organic counterpart P3HT;(3) its optical absorption is expanded to as high as910 nm comparing to 797 nm for the MPTF;(4) while MPTF decomposes at 150 °C, the wafer is stable at high temperature up to270 °C;(5) when exposed to high humidity(75% RH), MPTF decomposes in 5 h while the wafer shows no change for overnight;(6) its photocurrent response is 250 times higher than its MPTF counterpart. A few electronic devices have been fabricated using the crystalline wafers. Among them, the Hall test gives low carrier concentration with high mobility. The trap-state density is measured much lower than common semiconductors. Moreover, the large SC-wafer is found particularly useful for mass production of integrated circuits. By adjusting the halide composition, both the optical absorption and the light emission can be fine-tuned across the entire visible spectrum from 400 nm to 800 nm. It is envisioned that a range of visible lasers and LEDs may be developed using the dual-halide perovskites. With fewer trap states, high mobility, broader absorption, and humidity resistance, it is expected that solar cells with high stable efficiency maybe attainable using the crystalline wafers.展开更多
文摘The SiC whiskers (SiCw) synthesized from rice hulls is studied in this paper. The properties of the application in the composite materials are tested, and also compared with the SiCw produced in US and Japan, the results indicate that the SiCw produced by this method is mainly straight crystals with multi nodes on face, the main type is P-SiC. lt has many advantages such as high strength and excellent oxidation resistance to high temperature. The Si3N4 ceramic composite materials reinforced and toughened with the SiCw, δfRT of the material is (856±22)MPa, δf300℃ is approximately (418. 5±14. 2) MPa and Klc is approximately (11. 3±1. 0) MPa m1/2. Besides, the application of the SiCw in the engineering materials of mining is forecasted.
基金supported by the National Key Research Project MOST (2016YFA0202400)the National Natural Science Foundation of China (61604090, 61604091, 61674098)+4 种基金National University Research Fund (GK261001009, GK201603107)the Changjiang Scholar and Innovative Research Team (IRT_14R33)the 111 Project (B14041)the Chinese National 1000-talent-plan Program (1110010341)the Innovation Funds of Graduate Programs, SNNU (2015CXS047)
文摘As the large single-crystalline silicon wafers have revolutionized many industries including electronics and solar cells, it is envisioned that the availability of large single-crystalline perovskite crystals and wafers will revolutionize its broad applications in photovoltaics, optoelectronics, lasers, photodetectors, light emitting diodes(LEDs), etc. Here we report a method to grow large single-crystalline perovskites including single-halide crystals: CH3NH3PbX3(X=I, Br, Cl), and dual-halide ones:CH3NH3Pb(ClxBr1.x)3 and CH3NH3Pb(BrxI1.x)3, with the largest crystal being 120 mm in length. Meanwhile, we have advanced a process to slice the large perovskite crystals into thin wafers. It is found that the wafers exhibit remarkable features:(1)its trap-state density is a million times smaller than that in the microcrystalline perovskite thin films(MPTF);(2) its carrier mobility is 410 times higher than its most popular organic counterpart P3HT;(3) its optical absorption is expanded to as high as910 nm comparing to 797 nm for the MPTF;(4) while MPTF decomposes at 150 °C, the wafer is stable at high temperature up to270 °C;(5) when exposed to high humidity(75% RH), MPTF decomposes in 5 h while the wafer shows no change for overnight;(6) its photocurrent response is 250 times higher than its MPTF counterpart. A few electronic devices have been fabricated using the crystalline wafers. Among them, the Hall test gives low carrier concentration with high mobility. The trap-state density is measured much lower than common semiconductors. Moreover, the large SC-wafer is found particularly useful for mass production of integrated circuits. By adjusting the halide composition, both the optical absorption and the light emission can be fine-tuned across the entire visible spectrum from 400 nm to 800 nm. It is envisioned that a range of visible lasers and LEDs may be developed using the dual-halide perovskites. With fewer trap states, high mobility, broader absorption, and humidity resistance, it is expected that solar cells with high stable efficiency maybe attainable using the crystalline wafers.
