本文基于一维纳米材料的气—液—固(Vapor-Liquid-Solid,VLS)生长机理,采用简单的物理气相沉积法,以硒化铟(In_(2)Se_(3))粉末为前驱体,在镀金(Au)的泡沫钛基底上实现生长出高密度的一维In_(2)Se_(3)纳米棒.通过扫描电子显微镜(Scanning...本文基于一维纳米材料的气—液—固(Vapor-Liquid-Solid,VLS)生长机理,采用简单的物理气相沉积法,以硒化铟(In_(2)Se_(3))粉末为前驱体,在镀金(Au)的泡沫钛基底上实现生长出高密度的一维In_(2)Se_(3)纳米棒.通过扫描电子显微镜(Scanning Electron Microscope,SEM)的结果表明,相比于普通的单晶硅基底,在泡沫钛基底上生长的一维In_(2)Se_(3)纳米棒具有更高的密度,且泡沫钛基底能够重复使用,在提高制备效率的同时极大降低了制备成本.展开更多
目前生产 Si Cw(碳化硅晶须 )的方法主要有气相反应法和固体材料法两大类 .气相反应法应用最为普遍的是气相沉积法 ( CVD法 ) ;固体材料法生产 Si Cw主要有 VLS机理和 VS机理 .生产出的 Si Cw主要用作高强度、高硬度结构材料的增强、增...目前生产 Si Cw(碳化硅晶须 )的方法主要有气相反应法和固体材料法两大类 .气相反应法应用最为普遍的是气相沉积法 ( CVD法 ) ;固体材料法生产 Si Cw主要有 VLS机理和 VS机理 .生产出的 Si Cw主要用作高强度、高硬度结构材料的增强、增韧 .使用 Si Cw增强、增韧的材料 ,可广泛用于航空航天。展开更多
This paper reports that/3-Ga2O3 nanorods have been synthesized by ammoniating Ga2O3 films on a V middle layer deposited on Si（111） substrates. The synthesized nanorods were confirmed as monoclinic Ga2O3 by x-ray dif...This paper reports that/3-Ga2O3 nanorods have been synthesized by ammoniating Ga2O3 films on a V middle layer deposited on Si（111） substrates. The synthesized nanorods were confirmed as monoclinic Ga2O3 by x-ray diffraction,Fourier transform infrared spectra. Scanning electron microscopy and transmission electron microscopy reveal that the grown β-Ga2O3 nanorods have a smooth and clean surface with diameters ranging from 100 nm to 200 nm and lengths typically up to 2μm. High resolution TEM and selected-area electron diffraction shows that the nanorods are pure monoclinic Ga2O3 single crystal. The photoluminescence spectrum indicates that the Ga2O3 nanorods have a good emission property. The growth mechanism is discussed briefly.展开更多
Magchrome bricks,as the inner lining of RH snorkels,have played a vital role in the operation of RH degassers for a long term.In chrome-free campaigns,resin-bonded,Al-containing magnesia bricks have been an alternativ...Magchrome bricks,as the inner lining of RH snorkels,have played a vital role in the operation of RH degassers for a long term.In chrome-free campaigns,resin-bonded,Al-containing magnesia bricks have been an alternative of magchrome bricks with a comparable performance in the last decade.It is important to have found whisker formation in the matrix of Alcontaining magnesia bricks above 1100°C and in the correlation to their high performance of RH snorkels.In this paper,the bonding mechanisms of both refractories are investigated to differentiate from other refractories.In magchrome bricks,the bonding modes of fused magchrome grains are characterized by the reactions between magnesia and chrome ore at different burning temperatures.At 1500°C,liquid forms around chromite grains.It is sucked into surrounding magnesia and a gap forms around chromite grains at 1600°C.Plenty of Fe2O3,Cr2O3 and Al2O3 have diffused from chrome ore into magnesia at 1670°C.A complete dissolution of the chrome ore takes place at 1750°C,with chromite precipitating entirely.In unburnt,Al-containing magnesia bricks,a dense network of whiskers is formed during heating,which is a prevailing bonding feature,instead of traditional particle growing and merging.It is believed that the whiskers are formed by vapoursolid mechanism since there is no liquid droplet observed at the tip of whiskers.In most stringent working conditions of RH snorkels,the bonding mechanisms are emphasized for their application,instead of chromia component.展开更多
This paper reports that the large-scale single crystalline boron carbide nanobelts have been fabricated through a simple carbothermal reduction method with B/B2O3/C/Fe powder as precursors at 1100℃. Transmission elec...This paper reports that the large-scale single crystalline boron carbide nanobelts have been fabricated through a simple carbothermal reduction method with B/B2O3/C/Fe powder as precursors at 1100℃. Transmission electron microscopy and selected area electron diffraction characterizations show that the boron carbide nanobelt has a B4C rhomb-centred hexagonal structure with good crystallization. Electron energy loss spectroscopy analysis indicates that the nanobelt contains only B and C, and the atomic ratio of B to C is close to 4：1. High resolution transmission electron microscopy results show that the preferential growth direction of the nanobelt is [101]. A possible growth mechanism is also discussed.展开更多
Large scale, high density boron carbide nanowires have been synthesized by using an improved carbothermal reduction method with B/B203/C powder precursors under an argon flow at 1100℃. The boron carbide nanowires are...Large scale, high density boron carbide nanowires have been synthesized by using an improved carbothermal reduction method with B/B203/C powder precursors under an argon flow at 1100℃. The boron carbide nanowires are 5-10 μm in length and 80-100 nm in diameter. Transmission electron microscopy （TEM） and selected area electron diffraction （SAED） characterizations show that the boron carbide nanowire has a B4C rhombohedral structure with good crystallization. The Raman spectrum of the as-grown boron carbide nanowires is consistent with that of a B4C structure consisting of B11C icosahedra and C-B-C chains. The room temperature photoluminescence spectrum of the boron carbide nanowires exhibits a visible range of emission centred at 638 nm.展开更多
文摘本文基于一维纳米材料的气—液—固(Vapor-Liquid-Solid,VLS)生长机理,采用简单的物理气相沉积法,以硒化铟(In_(2)Se_(3))粉末为前驱体,在镀金(Au)的泡沫钛基底上实现生长出高密度的一维In_(2)Se_(3)纳米棒.通过扫描电子显微镜(Scanning Electron Microscope,SEM)的结果表明,相比于普通的单晶硅基底,在泡沫钛基底上生长的一维In_(2)Se_(3)纳米棒具有更高的密度,且泡沫钛基底能够重复使用,在提高制备效率的同时极大降低了制备成本.
文摘目前生产 Si Cw(碳化硅晶须 )的方法主要有气相反应法和固体材料法两大类 .气相反应法应用最为普遍的是气相沉积法 ( CVD法 ) ;固体材料法生产 Si Cw主要有 VLS机理和 VS机理 .生产出的 Si Cw主要用作高强度、高硬度结构材料的增强、增韧 .使用 Si Cw增强、增韧的材料 ,可广泛用于航空航天。
基金Project supported by the State Key Program of the National Natural Science Foundation of China (Grant No 90201025)
文摘This paper reports that/3-Ga2O3 nanorods have been synthesized by ammoniating Ga2O3 films on a V middle layer deposited on Si（111） substrates. The synthesized nanorods were confirmed as monoclinic Ga2O3 by x-ray diffraction,Fourier transform infrared spectra. Scanning electron microscopy and transmission electron microscopy reveal that the grown β-Ga2O3 nanorods have a smooth and clean surface with diameters ranging from 100 nm to 200 nm and lengths typically up to 2μm. High resolution TEM and selected-area electron diffraction shows that the nanorods are pure monoclinic Ga2O3 single crystal. The photoluminescence spectrum indicates that the Ga2O3 nanorods have a good emission property. The growth mechanism is discussed briefly.
文摘Magchrome bricks,as the inner lining of RH snorkels,have played a vital role in the operation of RH degassers for a long term.In chrome-free campaigns,resin-bonded,Al-containing magnesia bricks have been an alternative of magchrome bricks with a comparable performance in the last decade.It is important to have found whisker formation in the matrix of Alcontaining magnesia bricks above 1100°C and in the correlation to their high performance of RH snorkels.In this paper,the bonding mechanisms of both refractories are investigated to differentiate from other refractories.In magchrome bricks,the bonding modes of fused magchrome grains are characterized by the reactions between magnesia and chrome ore at different burning temperatures.At 1500°C,liquid forms around chromite grains.It is sucked into surrounding magnesia and a gap forms around chromite grains at 1600°C.Plenty of Fe2O3,Cr2O3 and Al2O3 have diffused from chrome ore into magnesia at 1670°C.A complete dissolution of the chrome ore takes place at 1750°C,with chromite precipitating entirely.In unburnt,Al-containing magnesia bricks,a dense network of whiskers is formed during heating,which is a prevailing bonding feature,instead of traditional particle growing and merging.It is believed that the whiskers are formed by vapoursolid mechanism since there is no liquid droplet observed at the tip of whiskers.In most stringent working conditions of RH snorkels,the bonding mechanisms are emphasized for their application,instead of chromia component.
基金Project supported by the National 863 (Grant No 2007AA03Z305)973 (Grant No 2007CB935503) programthe National Science Foundation of China (Grant Nos 60571045, 60620120443, Guo-JI He-Zuo)
文摘This paper reports that the large-scale single crystalline boron carbide nanobelts have been fabricated through a simple carbothermal reduction method with B/B2O3/C/Fe powder as precursors at 1100℃. Transmission electron microscopy and selected area electron diffraction characterizations show that the boron carbide nanobelt has a B4C rhomb-centred hexagonal structure with good crystallization. Electron energy loss spectroscopy analysis indicates that the nanobelt contains only B and C, and the atomic ratio of B to C is close to 4：1. High resolution transmission electron microscopy results show that the preferential growth direction of the nanobelt is [101]. A possible growth mechanism is also discussed.
基金Project supported by the National High Technology Development Program of China (Grant No 2007AA03Z305)the state Key Development Program for Basic Research of China (Grant No 2007CB935503)the National Science Foundation of China (Grants Nos 60571045, 60620120443 and Guo-JI He-Zuo)
文摘Large scale, high density boron carbide nanowires have been synthesized by using an improved carbothermal reduction method with B/B203/C powder precursors under an argon flow at 1100℃. The boron carbide nanowires are 5-10 μm in length and 80-100 nm in diameter. Transmission electron microscopy （TEM） and selected area electron diffraction （SAED） characterizations show that the boron carbide nanowire has a B4C rhombohedral structure with good crystallization. The Raman spectrum of the as-grown boron carbide nanowires is consistent with that of a B4C structure consisting of B11C icosahedra and C-B-C chains. The room temperature photoluminescence spectrum of the boron carbide nanowires exhibits a visible range of emission centred at 638 nm.
