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71.
碳纳米管增强镍基复合镀层的形貌及摩擦磨损行为研究 总被引:26,自引:4,他引:26
利用碳纳米管作为增强相制备了镍基复合镀层 ,并对其表面形貌和摩擦磨损性能进行了探讨 .结果表明 :碳纳米管均匀地嵌镶于基体中 ,且端头露出 ,覆盖于基体表面 ;镍基复合镀层具有优良的耐磨性和自润滑性 ,可以显著改善金属表面的耐磨和减摩性能 ;复合镀层优良的耐磨和减摩性能归因于碳纳米管的超强超韧特性和自润滑性能 ,碳纳米管以网络和缠绕形态分布于复合镀层基体中 ,使复合镀层在摩擦磨损过程中不易脱落拨出 相似文献
72.
73.
采用经典分子动力学方法研究了压力驱动作用下水在石墨烯碳纳米管复合结构中的渗透特性.研究结果表明,水分子渗透通过石墨烯碳纳米管复合结构的渗透率明显高于石墨烯碳纳米管组合结构.水在石墨烯碳纳米管复合结构中的渗透率随着压强的升高而增大,随着电场强度的增大而减小.考虑了温度和复合结构中双碳管轴心距对水渗透性的影响规律.系统温度越高,水的渗透率越高;随着双碳管轴心距的增加,水的渗透率逐渐降低.通过计算分析水流沿渗透方向的能障分布,解释了各参数变化对水在石墨烯碳管复合结构中渗透特性的影响机理.研究结果将为基于石墨烯碳管复合结构的新型纳米水泵设计提供一定的理论依据. 相似文献
74.
Connecting one armchair carbon nanotube(CNT) to several zigzag graphene nanoribbons(ZGNRs) we find that the topologically-protected edge states of ZGNRs and the massless Dirac particle inherited from CNT still hold from the analysis of the band structure and the edge state. Furthermore, the lowest conductance step at the valley bottom increases proportionally with increasing the number of ZGNR wings. A novel conductance step of a peak occurs in the valley, which is two steps higher than the lowest step at the valley bottom. In addition, with increasing the number of ZGNR wings the width of the novel conductance step becomes narrow. 相似文献
75.
76.
Multi-walled carbon nanotubes (CNTs) have been treated using 20 kHz ultrasound in combination with dilute nitric and sulfuric acids at much lower concentrations than previously reported. The measurements revealed an optimum set of sonication conditions (in this case 30 min at 12 W cm−2) exists to overcome aggregation of the nanotubes and to allow efficient dispersion in ethanol or in chitosan. Transmission electron microscopy and Raman spectroscopy suggested the removal of amorphous material and reduction of the CNT diameter as well as modifications to their defect structures. The surface oxidation was determined by FTIR spectroscopy. At longer times or higher ultrasound intensities, degradation such as nanotube shortening and additional defect generation in the graphitic network occurred and the benefits of using ultrasound decreased. The modified CNTs were used as fillers for chitosan films and gave a tenfold increase in tensile strength and integrity of the films. The methodology was combined with sonochemical generation of gold or iron oxide nanoparticles to produce a range of functional membranes for catalytic reductive hydrogenation or dye degradation under conditions that are more environmentally benign than those previously used. Our results further add to the usefulness of sonochemistry as a valuable tool in preparative materials chemistry but also illustrate the crucial importance of careful control over the experimental conditions if optimum results are to be obtained. 相似文献
77.
Although discovered more than 100 years ago, X-ray source technology has evolved rather slowly. The recent invention of the carbon nanotube (CNT) X-ray source technology holds great promise to revolutionize the field of biomedical X-ray imaging. CNT X-ray sources have been successfully adapted to several biomedical imaging applications including dynamic micro-CT of small animals and stationary breast tomosynthesis of breast cancers. Yet their more important biomedical imaging applications still lie ahead in the future, with the development of stationary multi-source CT as a noteworthy example. 相似文献
78.
The global greenhouse effect makes it urgent to deal with the increasing greenhouse gases.In this paper the performance of MgO-decorated carbon nanotubes for CO 2 adsorption is investigated through first principles calculations.The results show that the MgO-decorated carbon nanotubes can adsorb CO 2 well and are relatively insensitive to O 2 and N 2 at the same time.The binding energy arrives at 1.18 eV for the single-MgO-decorated carbon nanotube adsorbing one CO 2 molecule,while the corresponding values for O 2 and N 2 are 0.55 eV and 0.06 eV,respectively.In addition,multi-molecule adsorption is also proved to be very satisfactory.These results indicate that MgO-decorated carbon nanotubes have great potential applications in industrial and environmental processes. 相似文献
79.
Factors affecting the dimerization of persistent nitrogen‐centered 1‐phenyl urazole radicals to tetrazanes 下载免费PDF全文
1‐Phenyl urazole radicals are persistent air‐stable nitrogen‐centered radicals that engage in an equilibrium with the corresponding N―N tetrazane dimers in solution. While the equilibrium typically weakly favors the dimer form, for some 1‐phenyl urazole radicals bearing substituents at the ortho position of the benzene ring, the equilibrium instead strongly favors the dimer form. With the recent surge of interest in the properties and potential applications of heterocyclic radicals, the factors that affect this equilibrium are important to determine. We examined the effect of the extent of ortho substitution (none, 1, or 2 substituents) on the equilibrium by experimentally using variable temperature 1H nuclear magnetic resonance and UV‐visible spectroscopy in addition to supporting computational investigations at the (U)B3LYP/6‐311G(d,p) level of theory. We confirmed that the equilibrium generally favored the dimer in all cases. However, the equilibrium was more favorable towards dimer formation for urazole radicals substituted with 1 and 2 ortho substituents on the aromatic ring. The activation enthalpies for dissociation of singly substituted dimers were greater than that for dimers without ortho substituents, but lower than that for doubly substituted dimers. The greater preference for dimer formation for the ortho‐substituted urazole radicals is attributed to a greater enthalpic advantage for N―N bond formation. This advantage may be traced to a higher concentration of spin density on the urazole unit of the radicals and a lesser deformation energy required for N―N bond formation. 相似文献
80.
Nanosized ZnOs were synthesized on the surface of α brass coated a film of nickel catalyst at 500-700 °C under atmosphere of O2 and CH4 gases. The nanosized ZnOs have shapes including pillar, leaf, sheet and rod, which were determined by the synthesis temperature and the flow rates of O2 and CH4 gases. The nanosized ZnOs were characterized by electron microscopy including transmission electron microscope for crystal structure, morphology and high resolution images, both field emission scanning electron microscope and scanning electron microscope for morphology, and energy dispersive X-ray spectroscope equipped in electron microscope for chemical composition. A mechanism was proposed for the growth of nanosized ZnO obtained in this work. 相似文献