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排序方式: 共有1410条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2022,48(6):8155-8168
In the present study, the effect of oxy-acetylene flame angle on the erosion resistance of SiC/ZrB2–SiC/ZrB2 multilayer coatings with the gradient structure was investigated. To this aim, first, the SiC inner layer was applied by the reactive melt infiltration (RMI) technique; then ZrB2 and ZrB2–SiC layers with 10, 20 and 30%wt. SiC were applied on graphite by the plasma spraying technique. To prevent the oxidation of ZrB2 and SiC particles, the plasma spraying process was performed by a solid protective shield. To evaluate the performance of the coatings in erosive environments, the samples were exposed to oxy-acetylene flame at the angles of 30°, 60° and 90° for 360 s; the destruction mechanism of SiC/ZrB2–SiC/ZrB2 multilayer coatings appeared to be controlled mechanically and chemically. The results of the erosion test showed that at the low flame angles of about 30°, due to the shear forces of oxy-acetylene flame, mechanical erosion overcame the chemical one. With increasing the flame angle, due to raising the surface temperature, chemical erosion overcame the mechanical one; so, most chemical destruction occurred at the flame angle of 90°. Also, the results of the erosion test showed that the total chemical and mechanical destruction at the angle of 60° was greater than that in other angles. Also, among the coatings tested, SiC/ZrB2- 20% wt. SiC/ZrB2 coatings had the best erosion resistance; so, the weight changes under the oxy-acetylene flame at the angles of 30° and 60°, respectively, were about ?0.038%. and ?0.355%; meanwhile, at the angle of 90°, it was about +4.3%.  相似文献   
2.
Nickel-graphite self-lubricating composites are a promising candidate to be used in turbine constructions that are usually exposed to high temperature oxidation and wear.However,the high-temperature stability of graphite as well as the effect that the oxide scale will play on the following wear process are still yet in debate.In this work,oxidation behavior of a NiCrAl-graphite composite and the subsequent friction and wear performances were studied.Results indicate that graphite is stable in the composites after oxidation at T≤400 ℃ for 300 h,which contributes synergistically with the thin oxide film to self-lubrication.The friction coefficient is below 0.20 and the wear rate is ~1.43×10~(-5) mm~3 N~(-1) m~(-1).The composite has the highest friction coefficient and wear rate when it was suffered from the high temperature oxidation at 500 ℃.Once it was oxidized at 600 ℃,a glaze layer would develop during the subsequent sliding.It plays a positive role in improving tribological properties though in the absence of lubricant phase of graphite,with to be exactly the friction coefficient and wear rate reduced by 13% and 21%,respectively,in comparison with the case of oxidation at 500℃.  相似文献   
3.
随着工业的发展,化石燃料消耗巨大,环境问题也日益突出,寻找一种绿色新型能源已成为一个被广泛讨论的问题。氢气是一种清洁、可再生燃料,利用光催化剂分解水制氢气是一种制取氢气的有效途径。石墨碳氮化物(g-C3N4)作为光催化剂不仅成本低、反应稳定,而且其尺寸、厚度、结构、形貌等可控,在众多光催化剂中脱颖而出。但g-C3N4目前在光催化领域主要存在两个局限:g-C3N4不能有效地吸收光来产生足够多的光生电子-空穴对;g-C3N4不能有效的运输及分离光生电子-空穴对,以至于电子与空穴的复合率较高。文章综述了g-C3N4在光催化制氢领域的进展成果,分析了g-C3N4存在的问题并总结了其改进方法,最后对g-C3N4进行了展望,以期为设计高效、稳定的光催化制氢材料提供参考。  相似文献   
4.
The impact of graphite nanoplatelets (GNPs) on the physical and mechanical properties of cementitious nanocomposites was investigated. A market-available premixed mortar was modified with 0.01% by weight of cement of commercial GNPs characterized by two distinctively different aspect ratios.The rheological behavior of the GNP-modified fresh admixtures was thoroughly evaluated. Hardened cementitious nanocomposites were investigated in terms of density, microstructure (Scanning Electron Microscopy, SEM and micro–Computed Tomography, μ-CT), mechanical properties (three-point bending and compression tests), and physical properties (electrochemical impedance spectroscopy, EIS and thermal conductivity measurements). At 28 days, all GNP-modified mortars showed about 12% increased density. Mortars reinforced with high aspect ratio GNPs exhibited the highest compressive and flexural strength: about 14% and 4% improvements compared to control sample, respectively. Conversely, low aspect ratio GNPs led to cementitious nanocomposites characterized by 36% decreased electrical resistivity combined with 60% increased thermal conductivity with respect to the control sample.  相似文献   
5.
Preparation of three-dimensional (3D) networks has received significant attention as an effective approach for applications involving transport phenomena, such as thermal management materials, and several nanomaterials have been examined as potential building blocks of 3D networks for the improvement of heat conduction in polymer nanocomposites. For that purpose, nanocarbons such as graphene and graphite nanoplatelets have been spotlighted as suitable filler materials because of their excellent thermal conductivities (ca. 102–103 W·(m·K)?1 along their lateral axes) and morphological merits. However, the implications of morphological features such as the lateral length and thickness of graphene or graphene-like materials have not yet been identified. In this study, a controlled dissociation of bulk graphite to graphite nanosheets (GNSs) using a low-cost, ecofriendly bead mill process was extensively examined and, when configured in a 3D framework architecture formation, the size-controlled GNSs demonstrated that the thermal conductivities of a 3D interconnected framework of GNSs and the corresponding polymer nanocomposite were intimately correlated with the size of the GNSs, thus demonstrating the successful preparation of an efficient thermal management material without highly sophisticated efforts. The capability of controlling the lateral size and thickness of the GNSs as well as the use of a 3D interconnected framework architecture should greatly assist the commercialization of high-quality graphene-based thermal management materials in a scalable production process.  相似文献   
6.
In order to improve the gas permeability and thermal shock resistance of the ceramic membranes applied in high temperature gas-solid separation techniques, fused silica and graphite particles were used as the primary raw material and pore-former agent, and the spray coating based-on PVA sealing was applied to prepare the separation membrane. These approaches remarkably decreases filtration resistance by increasing support permeability and reducing the intrusion of ceramic membrane forming particles into the support as well as the thickness of the membrane. The fabricated membrane had an average pore diameter of 9.85?μm and a gas permeability value of 8.2?×?104?m3/(m2 h bar), its dust removal efficiency reached 98.6%.  相似文献   
7.
《Ceramics International》2021,47(23):33405-33412
In this study, SnO2@MnO2@graphite (SMG) anode material is prepared via a facile ball-milling approach combined with hydrothermal treatment. SnO2 and MnO2 nanoparticles are evenly dispersed on numerous sheet-like graphite. MnO2 can not only play a catalytic role for facilitating the conversion reaction of Sn/Li2O to SnO2, but also as a barrier to impede the coarsening of Sn in the composite. Meanwhile, graphite nanosheets could serve as an ideal volume expansion buffer and good electron conductor. Consequently, the SMG anode delivers superior reversible capacity of 1048.5 mAhg−1, ideal rate capability of 522.2 mAhg−1 at 5.0 A g-1 and stable long-life cyclic performance of 814.8 mAhg−1 at 1.0 A g-1 after 1000 cycles. This result indicates that the incorporation of MnO2, graphite nanosheet and SnO2 have a great potential in enhancing the performance of SnO2-based anode for battery applications.  相似文献   
8.
黑龙江某石墨矿属于晶质石墨矿石,原矿固定碳含量9.3%。通过对该地区鳞片石墨矿进行选矿试验研究,得出适宜的浮选条件为:粗选磨矿细度为-75μm含量60%的条件下,煤油用量为52g/t,2#油用量为56g/t。进行一段粗选两段扫选、粗精矿五段再磨六段精选,中矿循序返回的闭路试验流程,最终获得产率9.19%,固定碳品位94.08%,回收率94.82%的石墨精矿产品,为该地区石墨资源的开发利用提供了技术依据。  相似文献   
9.
Hydrolytic dehydrogenation of ammonia borane (AB) driven by efficient catalysts has attracted considerable attention and is regarded as a promising strategy for hydrogen generation. Herein, RuP2 quantum dots supported on graphitic carbon nitride (g-C3N4) were successfully prepared by in-situ phosphorization, yielding a highly efficient photocatalyst toward AB hydrolysis. The catalysts were characterized by field-emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction, x-ray photoelectron microscopy, inductively coupled plasma atomic emission spectroscopy, UV–visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. A conventional water-displacement method was employed to record the hydrogen volume as a function of reaction time. Owing to visible-light irradiation, the initial turnover frequency of the AB hydrolysis was significantly enhanced by 110% (i.e., 134 min?1) at room temperature. Furthermore, the apparent activation energy decreased from 67.7 ± 0.9 to 47.6 ± 1.0 kJ mol?1. The photocatalytic hydrolysis mechanism and catalyst reusability were also investigated.  相似文献   
10.
通过熔融共混方法制备导电高分子复合材料丙烯腈-苯乙烯-丙烯酸酯共聚物(ASA)/天然石墨(NGR)/炭黑(CB),采用电磁屏蔽测量仪、四探针电阻率测量仪和动态热机械分析仪对复合材料的电性能和力学性能进行详细研究。结果表明,ASA/NGR复合材料的体积电阻率随着炭黑含量增加而增加;同时在30 MHz~1500 MHz范围内,复合材料的电磁屏蔽性能从28 dB提高到38 dB,符合商业要求。炭黑的加入大大改善了材料力学性能,弯曲强度从31 MPa增加到41 MPa;动态储能模量从4.6 GPa增加到14.5 GPa。  相似文献   
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