Cr(N,O) thin films were deposited by radio frequency reactive unbalanced magnetron sputtering on Si(100) or glassy carbon substrates. In this paper, the influence of oxygen content on hardness of Cr(N,O) thin films wa...
Cr(N,O) thin films were deposited by radio frequency reactive unbalanced magnetron sputtering on Si(100) or glassy carbon substrates. In this paper, the influence of oxygen content on hardness of Cr(N,O) thin films was investigated. The compositional analysis was carried out by Rutherford backscattering spectroscopy. It was found that these thin films contained up to 44at.% of oxygen. Phases in the samples were determined by X-ray diffraction. Cr(N,O) thin films show only peaks based on CrN. The microstructure was observed by utilizing a transmission electron microscope. At <1at.% of oxygen, crystallite size was approximately 100nm. Then, in accordance with increasing of oxygen content, crystallite size was decreased. The hardness of thin films was measured by using a nanoindenter. The micro hardness was changed with varying the oxygen content and the microstructure such as crystallite size. Thus, it was thought that the hardening on Cr(N,O) thin films was caused by solution hardening and/or Hall-Petch relationship.
This paper reports that the nanostructured β-FeSi2 bulk materials are prepared by a new synthesis process by combining melt spinning （MS） and subsequent spark plasma sintering （SPS）. It investigates the influence...
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This paper reports that the nanostructured β-FeSi2 bulk materials are prepared by a new synthesis process by combining melt spinning （MS） and subsequent spark plasma sintering （SPS）. It investigates the influence of linear speed of the rolling copper wheel, injection pressure and SPS regime on microstructure and phase composition of the rapidly solidified ribbons after MS and bulk production respectively, and discusses the effects of the microstructure on thermal transport properties. There are two crystalline phases （α-Fe2Si5 and ε-FeSi） in the rapidly solidified ribbons; the crystal grains become smaller when the cooling rate increases （the 20 nm minimum crystal of ε-FeSi is obtained）. Having been sintered for 1 min above 1123K and annealed for 5min at 923K, the single-phase nanostructured β- FeSi2 bulk materials with 200-500 nm grain size and 98% relative density are obtained. The microstructure of β-FeSi2 has great effect on thermal transport properties. With decreasing sintering temperature, the grain size decreases, the thermal conductivity of β-FeSi2 is reduced remarkably. The thermal conductivity of β-FeSi2 decreases notably （reduced 72% at room temperature） in comparison with the β-FeSi2 prepared by traditional casting method.
Ordered microporous carbon molecular sieves with high specific area and well-dispersed Pt nanoparticles have been prepared by chemical vapour deposition method. Electrochemical properties were measured, showing the ni...
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ISBN:
(纸本)9781424435432;9781424435449
Ordered microporous carbon molecular sieves with high specific area and well-dispersed Pt nanoparticles have been prepared by chemical vapour deposition method. Electrochemical properties were measured, showing the nitrogen-doped carbons exhibited excellent performance as an electrochemical supercapacitor.
The ability to fabricate high precision micro- to nanoscale structure in a wide variety of materials is of crucial importance for the advancement of microtechnology, nanotechnology and nanoscience. Also, the ability t...
The ability to fabricate high precision micro- to nanoscale structure in a wide variety of materials is of crucial importance for the advancement of microtechnology, nanotechnology and nanoscience. Also, the ability to create micrometer and sub-micrometer architecture for functional ceramics is a prerequisite of exploring the rich field of ceramic nanotechnology. In this work we fabricated three-dimensional oxide ceramic materials with fine-structure over multiple length scales by combining replication patterning technique, polyvinyl alcohol (PVA), oxide ceramic material (TiO2) nano-sized particles. Our study is based on the idea that PVA can be easily detached from a mold by peeling. We confirmed that micron and sub-micron-sized fine-structured oxide ceramic patterns containing nano-sized pores could be fabricated using this procedure. The results presented demonstrate the compositional and structural diversities that are possible with a facile approach and simple method.
Fe-Ni-Al mixtures as hot-pressing sintering additive to Titanium diboride （TiB2） were studied. It is found that liquid alloy formed under high temperature hardly has effects on the densification behaviors of TiB2-in...
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Fe-Ni-Al mixtures as hot-pressing sintering additive to Titanium diboride （TiB2） were studied. It is found that liquid alloy formed under high temperature hardly has effects on the densification behaviors of TiB2-independent. Fe-Ni-Al additive just works as filler between TiB2 particles and does not change the TiB2-independent sintering behaviors. Pressing mode has a great effect on the liquid flowing between TiB2 particles. Multiple-steps pressing mode will give more time and space for the liquid flowing and improve the relative density of TiB2-Fe-Ni-Al cermet.
Preparation and thermoelectric properties of nanostructured n-type Mg2Si bulk materials were reported. Nanosized Mg2Si powder was obtained by mechanical milling of the microsized Mg2Si powder prepared by solid-state r...
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Preparation and thermoelectric properties of nanostructured n-type Mg2Si bulk materials were reported. Nanosized Mg2Si powder was obtained by mechanical milling of the microsized Mg2Si powder prepared by solid-state reaction. The bulk materials with 30 nm and 5 μm were prepared by spark plasma sintering of the nanosized and microsized Mg2Si powder, respectively. Both the samples show n-type conduction and the Seebeck coefficient of the sintered samples increase determinately with the grain size decrease from 5 μm to 30 nm. On the other hand, the electrical and thermal conductivity decrease with the decrease of grain size. Accordingly, decreasing their grain size increases their thermoelectric-figure-of-merit. A maximum thermoelectric figure of merit of 0.36 has been obtained for the nanostuctured Mg2Si sample at 823 K, which is 38% higher than that of microsized Mg2Si bulk materials and higher than results of other literatures. It could be expected that the properties of the nanocomposites could be further improved by doping optimization.
Flame retardant epoxy resins were prepared by a simple mixed method using ammonium aluminum carbonate hydroxy hydrate （AACHH） as a halogen-free flame retardant. The prepared samples were characterized by X-ray diffr...
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Flame retardant epoxy resins were prepared by a simple mixed method using ammonium aluminum carbonate hydroxy hydrate （AACHH） as a halogen-free flame retardant. The prepared samples were characterized by X-ray diffraction, thermogravimetric and differential scanning calorimetry, scanning electron microscope and limiting oxygen index（LOI） experiments. Effects of AACHH content on LOI of epoxy resins/AACHH composite and flame retardant mechanism were investigated and discussed. Results show that AACHH exhibites excellent flame-retardant properties in epoxy resin（EP）. When the content of AACHH was 47.4%, the LOI of EP reached 32.2%. Moreover, the initial and terminal decomposition temperature of EP increased by 48 ℃ and 40 ℃, respectively. The flame retarded mechanism of AACHH is due to the synergic flame retardant effects of diluting, cooling, decomposition resisting and obstructing.
Low or zero thermal expansion porous ceramics are required for several applications. In this work near zero thermal expansion porous ceramics were fabricated by using SiC and ZrW2O8 as positive and negative thermal ex...
Low or zero thermal expansion porous ceramics are required for several applications. In this work near zero thermal expansion porous ceramics were fabricated by using SiC and ZrW2O8 as positive and negative thermal expansion materials, respectively, bonded by soda lime glass. The mixture of SiC, ZrW2O8 and soda lime glass was sintered by Pulsed Electric Current Sintering (PECS, or sometimes called Spark Plasma Sintering, SPS) at 700 °C. Sintered samples with ZrW2O8 particle size smaller than 25 μm have high thermal expansion coefficient, because ZrW2O8 has the reaction with soda lime glass to form Na2ZrW3O12 during sintering process. The reaction between soda lime glass and ZrW2O8 is reduced by increasing particle size of ZrW2O8. Sintered sample with ZrW2O8 particle size 45-90 μm shows near zero thermal expansion.
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