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81.
Brazing of Ti3Al alloys with the filler metal NiCrSiB was carried out at 1273–1373 K for 60–1800 s. The relationship of brazing parameters and shear strength of the joints was discussed, and the optimum brazing parameters were obtained. When products are brazed, the optimum brazing parameters are as follows: brazing temperature is 1323–1373 K, brazing time is 250–300 s. The maximum shear strength of the joint is 240–250 MPa. Three kinds of reaction products were observed to have formed during the brazing of Ti3Al alloys with the filler metal NiCrSiB, namely, TiAl3 (TiB2) intermetallic compounds formed close to the Ti3Al alloy. TiAl3+AlNi2Ti (TiB2) intermetallic compounds layer formed between TiAl3 (TiB2) intermetallic compounds and the filler metal and a Ni[s,s] solid solution formed in the middle of the joint. The interfacial structure of brazed Ti3Al alloy joints with the filler metal NiCrSiB is Ti3Al/TiAl3 (TiB2)/TiAl3+AlNi2Ti (TiB2)/Ni[s,s] solid solution/TiAl3+AlNi2Ti (TiB2)/TiAl3 (TiB2)/Ti3Al, and this structure will not change with brazing time once it forms. The formation of over many intermetallic compounds TiAl3+AlNi2Ti (TiB2) results in embrittlement of the joint and poor joint properties. The thickness of TiAl3+AlNi2Ti (TiB2) intermetallic compounds increases with brazing time according to a parabolic law. The activation energy Q and the growth velocity K0 of the reaction layer TiAl3+AlNi2Ti (TiB2) in the brazed joints of Ti3Al alloys with the filler metal NiCrSiB are 349 kJ/mol and 24.02 mm2/s, respectively, and the growth formula was y2=24.04exp(−41977.39/T)t. Careful control of the growth of the reaction layer TiAl3+AlNi2Ti (TiB2) can influence the final joint strength. 相似文献
82.
为探究矿粉表面能与其组成化学成分间的内在关系,通过灰色关联法与主成分分析法,以矿粉的化学成分质量分数为媒介,对采用毛细管上升法测得的5种矿粉、5种化学成分表面能之间的关系模型进行量化分析.结果表明:矿粉的表面能实测值与通过其化学成分表面能计算的计算值之间存在良好的关联度;提出了变化的矿粉表面能、化学成分质量分数与不变的化学成分表面能之间定量关系模型,通过该模型可对不同岩石加工的矿粉,在测得其化学成分质量分数后,直接计算得到矿粉的表面能,可为矿粉表面能在道路工程中应用的深入研究提供理论指导. 相似文献
83.
对于给定的树脂、颜填料体系,采用丹尼尔流动点理论对分散剂进行定性选择和用量试验,并将设计配方推广至生产应用。 相似文献
84.
This Special Issue “Biodegradable Materials” features research and review papers concerning recent advances on the development, synthesis, testing and characterisation of biomaterials. These biomaterials, derived from natural and renewable sources, offer a potential alternative to existing non-biodegradable materials with application to the food and biomedical industries amongst many others. In this Special Issue, the work is expanded to include the combined use of fillers that can enhance the properties of biomaterials prepared as films. The future application of these biomaterials could have an impact not only at the economic level, but also for the improvement of the environment. 相似文献
85.
A new kind of anhydrous, transparent, and flexible potassium dihydrogen phosphate (KH2PO4 or KDP)/polyvinyl alcohol (PVA) composite in the form of film (0.10 mm) has been prepared by solution casting technique. KDP is well dispersed in the polymer matrix as observed from the microstructural studies. Frequency and temperature dependent dielectric properties of the composites have been studied with varying KDP concentrations. The PVA/KDP composite films exhibited extraordinarily high relative permittivity ε′ ∼ 430 (80 times higher compared with pure PVA and even higher than KDP) near the percolation threshold (ϕC = 2.5 wt % KDP) with low dielectric losses (∼ 0.15) at 1 kHz and room temperature. Such flexible, low loss and high dielectric permittivity material has enormous importance for application in devices. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
86.
Linseed cake (LC), a byproduct of linseed oil extraction, is used as a functional filler for production of biodegradable composites. To determine the influence of residual linseed crude oil contained in lignocellulosic filler on the properties of the poly(lactic acid) (PLA)-based composites with 5–30% filler content, two types of LC were analyzed: a defatted and an unmodified one. Complex analysis of the composites' properties change was conducted in relation to their structure modification caused by the addition of a waste filler. It was found that the addition of LC resulted in simultaneous plasticization and improved crystallization of PLA. Lignocellulosic particles and crude linseed oil contained in the LC powder provided a modifying effect, influencing the level of crystallinity and mechanical and thermomechanical properties. Using LC may thus overcome one of the main drawbacks of PLA, which is brittleness and low crystallinity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47152. 相似文献
87.
88.
This work is part of a program on composites used in thermoelectric devices. Tribological properties of dynamic vulcanizate blends of polypropylene and ethylene‐propylene‐diene rubber filled with 5 wt% of microscale powder have been studied. The microscale thermal‐shock‐resistant ceramic filler contains α‐Al2O3, mullite (3Al2O3 · 2SiO2 or 2Al2O3SiO2), β‐spodumene glass‐ceramic and aluminium titanate. We found that our ceramic particles are abrasive; they cause strong abrasion of softer steel ball surfaces during dry sliding friction. To overcome the difficulty of particle dispersion and adhesion, the filler was modified through grafting using three types of organic molecules. Dry sliding friction was measured using four types of counter‐surfaces: tungsten carbide, Si3N2, 302 steel and 440 steel. Thermoplastic vulcanizate filled with neat ceramic powder shows the lowest friction compared to composites containing the same but surface‐treated powder. We introduce a ‘bump’ model to explain the tribological responses of our composites. ‘Naked’ or untreated ceramic particles protrude from the polymer surface and cause a decrease of the contact area compared to neat polymer. The ball partner surface has only a small contact area with the bumps. As contact surface area decreases, so does friction and the amount of heat generated during sliding friction testing. Chemical coupling of the ceramic to the matrix smoothens the bumps and increases the contact surface, giving a parallel increase in friction. Copyright © 2012 Society of Chemical Industry 相似文献
89.
90.
Curing enhancement and network effects in multi‐walled carbon nanotube‐filled vulcanized natural rubber: evidence for solvent sensing 下载免费PDF全文
Deepalekshmi Ponnamma Konnanilkunnathil Thomas Varughese Mariam Al Ali Al‐Maadeed Sabu Thomas 《Polymer International》2017,66(6):931-938
Electrically and thermally conductive polymer composites offer great possibilities in various electronic fields because of their low weight and ease of processing. This paper addresses the curing behaviour and network properties of conducting multi‐walled carbon nanotube (MWCNT)‐reinforced natural rubber (NR) nanocomposites, emphasizing the sensing and diffusion performances. NR/MWCNT composites were prepared following a special master batch technique which allows the appropriate distribution of nanotubes within the elastomer. The sensing responses of the composites towards solvents were observed as variations in electrical resistance. Thermal resistance and glass transition behaviour were examined and correlated with the swelling measurements as evidence for solvent sensing. An optimum level of 3 phr of MWCNTs is understood to lead to the best properties for the NR/MWCNT composites. Finally, the structural morphology and interfacial interactions were found to have correlations with cure reactions, glass transition temperatures and sensing responses of all compositions. © 2017 Society of Chemical Industry 相似文献