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11.
A novel method for the fabrication of highly ordered nanopore arrays with very small diameter of 14 nm was demonstrated by
using low-temperature anodization. Two-step anodization was carried out at 25 V, sulfuric acid concentration of 0.3 M, and
electrolyte temperature of −15 °C. After anodization, a regular pore array with mean diameter of 14 nm and interpore distance
of 65 nm was formed. The pore diameter and regular arrangement were confirmed by scanning electron microscopy (SEM) and fast
Fourier transformation (FFT), respectively. The present results strongly suggest that the diameter of pores in a highly ordered
alumina template can be reduced by lowering the anodization temperature. 相似文献
12.
The present research was focused on the development of a new glass to produce glass–alumina FGMs. The glass formulation, belonging to the CaO–ZrO2–SiO2 system, was doped with cobalt, by adding a small molar percentage (about 0.1 mol%) of CoO, in order to obtain a blue glass, which could be useful to appreciate the final compositional gradient. The glass was accurately characterized, evaluating its thermal behaviour, its mechanical properties, and its attitude to crystallize during a thermal treatment. Subsequently, the glass was used to produce glass–alumina FGMs via percolation and the so obtained specimens were analysed in order to evaluate the effect of the glass infiltration. The possible development of new crystal phases, in particular, was tested via micro X-ray diffraction and the elastic properties gradient associated with the compositional gradient was measured via depth-sensing Vickers microindentation. 相似文献
13.
14.
搪瓷釉料新颖添加剂铝溶胶任岳荣(浙江省明矾石综合利用研究所325028)NewAdditiveAluminaSolforGlazeofEnamel¥RenYuerong(ZhejiangInstituteofComprehensiveUtilizat... 相似文献
15.
L. Ceseracciu F. Chalvet G. de Portu M. Anglada E. Jimnez-Piqu 《International Journal of Refractory Metals and Hard Materials》2005,23(4-6):375-381
Alumina/alumina–zirconia ceramic laminated composites produced by tape casting present a compressive residual stress at the alumina surface due to the thermal expansion mismatch between layers developed during processing. Because of this residual stress, the mechanical properties at the surface, such as wear or surface fracture, have proven to be better than the properties of a monolithic stress-free alumina. In a previous work, it was shown that this laminate composite has better resistance to the development of a ring crack when loaded with a spherical indenter, under both cyclic and static loads below the critical load for cone cracking. In this work, cyclic Hertzian indentations with subcritical loads are performed on the same laminate ceramic and a monolithic alumina, but with a higher number of cycles than the necessary to provoke the first damage (ring crack). Results show that for low and intermediate number of cycles, the laminated composite presents better resistance to damage than the monolithic alumina. However, for high number of cycles, spalling at the surface of the laminate material appears, whereas the monolithic alumina develops secondary cone cracking. This difference is attributed to the fact that laminate ceramics present an enhanced apparent fracture toughness of the material, which implies a higher quasi-plasticity due to shear driven microcracking. For a high number of cycles, these microcracks grow until coalescence at the surface, provoking exfoliation of the material at the contact area, enhanced by the fact that the indented and the indenter material have different elastic properties. 相似文献
16.
Two new types of extraction replicas for precipitate analysis in steels have been developed. These replicas, based on alumina, allow accurate quantification of the carbon to nitrogen ratios in carbo-nitride precipitates using parallel electron energy loss spectroscopy in the TEM. Experiments on microalloyed steels show the importance of the nitrogen content in promoting precipitation even at low temperatures. 相似文献
17.
The role of Ag in simultaneously catalyzing NO reduction and C3H6 oxidation was shown to be strongly dependent on the redox properties of its local environment. Under an atmosphere of 1,000 ppm
NO, 3,000 ppm C3H6, and 1% O2 and a GHSV of 30,000 h−1, a perovskite La0.88Ag0.12FeO3 prepared by reactive grinding is active giving a complete NO conversion and 92% C3H6 conversion at 500 °C. These values are much higher than the NO conversion of 55% and C3H6 conversion of 45% obtained over a 3 wt.% Ag/Al2O3 catalyst under the same conditions. Under an excess of oxygen (10% O2) a good SCR performance with a plateau of N2 yield above 97% over a wide temperature window of 350–500 °C along with C3H6 conversion of 90% at 500 °C was observed over Ag/Al2O3, while minor N2 yields (∼10% at 250–350 °C) and high C3H6 conversions (reaching ∼100% at 450 °C) were obtained over La0.88Ag0.12FeO3. Abundant molecular oxygen is desorbed from Ag substituted perovskite after 10% O2 adsorption as verified by O2- temperature programmed desorption (TPD). This reflects the strongly oxidative properties of La0.88Ag0.12FeO3, which lead to a satisfactory NO reduction at 1% O2 due to the ease of nitrate formation but to a significant C3H6 combustion above that value. The formation of nitrate species over the less oxidizing Ag/Al2O3 was accelerated under an excess of oxygen resulting in an excellent lean NO reduction behavior. The redox properties of silver
catalysts could be adjusted via mixing perovskite with alumina for an optimal elimination of both NO and C3H6 over the whole range of oxygen concentration between 0 to 10%. 相似文献
18.
Low-temperature catalytic growth of carbon nanotubes under microwave plasma assistance 总被引:4,自引:0,他引:4
Various carbon nanotubes (CNTs) including aligned arrays, Y-branching and some other novel morphologies have been catalytically grown on anodic porous alumina template (APAT) and on the alumina-supported catalysts with methane (or benzene) as carbon source under microwave plasma assistance below 520 °C. The growth process could be simply operated since neither heating nor bias-voltage was applied to the catalysts or APAT. The results presented in this paper not only greatly richened the nanostructures of carbon family but also provided with a new technique path for synthesizing CNTs or some other nanostructures with the characteristics of low-temperature which has some special advantages or applications. 相似文献
19.
采用热分析等研究方法,分析了铝炭制品的氧化过程,研究了以阻断铝炭制品与氧气接触来实现防氧化的硼硅酸盐系涂料的高温特性和防氧化机理,以及不同结合剂对涂料与铝炭制品界面行为的影响。 相似文献
20.