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91.
稀土树脂相分光光度法研究 总被引:4,自引:1,他引:3
在HCl—KCl(pH0.5)介质中,稀土—三溴偶氮胂二元络合物能较好地被阴离子交换树脂吸附。RE_2O_8在0~8μg/25ml范围内符合比尔定律,以双波长等吸收点法(测量波长λ_1=650nm,参比波长λ_2=740nm)扣除树脂背景影响,应用于稀土矿中稀土总量测定,结果令人满意。 相似文献
92.
Fracture toughness and fatigue crack propagation (FCP) of plain and modified anhydride-cured epoxy resin (EP) were studied at ambient temperature. Liquid carboxyl-terminated acrylonitrile-butadiene (CTBN) and silicon (SI) rubber dispersions were used as tougheners for the EP. The morphology of the modified EP was characterized by dynamic mechanical analysis (DMA) and by scanning electron microscopy (SEM). The fracture toughness, Kc, of the compositions decreased with increasing deformation rate. Kc of the EP was slightly improved by CTBN addition and practically unaffected by incorporation of the SI dispersion when tests were performed at low cross-head speed, v. Both modifiers improved Kc at high v, and also the resistance to FCP, by shifting the curves to higher stress intensity factor ranges, ΔK, by comparison with the plain EP. It was established that both fracture and fatigue performance rely on the compliance, JR, at the rubbery plateau, and thus on the apparent molecular mass between crosslinks, Mc. The failure mechanisms were less dependent upon the loading mode (fracture, fatigue), but differed basically for the various modifiers. Rubber-induced cavitation and shear yielding of the EP were dominant for CTBN, whereas crack bifurcation and branching controlled the cracking in SI-modified EP. The simultaneous use of both modifiers resulted in a synergistic effect for both the fracture toughness at high deformation rate and the FCP behavior. 相似文献
93.
D Ganguli 《Bulletin of Materials Science》1993,16(6):523-531
The various parameters related to sol-gel processing are discussed with special reference to those which usually attract less
attention but depending on the final product in mind, can play important roles. The versatility of the sol-gel technique in
materials preparation is demonstrated by discussing the various products developed at the author’s laboratory by using this
processing method. 相似文献
94.
树脂热解炭制备碳化硅晶须 总被引:6,自引:1,他引:5
用自制的配合醛树脂热解和炭源,用SIO2超细汾作原,根据碳热还原原理,利用常规加热和微波加热两种方式,分别制备了直径在纳米级的SiC晶须,X射线衍射、透射电检测结果表明:制备工艺和条件对SiC晶须的性质有较大的影响。 相似文献
95.
96.
己二酸二乙酯合成新工艺的研究 总被引:2,自引:0,他引:2
本文以离子交换树脂作为液固相酯化反应的催化剂 ,甲苯作为带水剂 ,合成己二酸二乙酯。应用本法 ,酯化反应产率高达 78%。同时对影响产率的诸因素进行了考察 ,其最佳反应条件为 :酸醇摩尔比 1∶4 ,催化剂用量为酸质量的 2 5 % ,反应时间为 10小时 ,反应温度 86~ 87℃ ,催化剂重复使用 4次 ,未出现活性明显下降 ,此工艺操作简单 ,反应条件温和 ,产率高 ,具有显著的工业应用价值。 相似文献
97.
丙烯酸酯与甲基丙烯酸酯的共聚及性能研究 总被引:22,自引:0,他引:22
采用悬浮聚合法,以丙烯酸-2-乙基-己酯与甲基丙烯酸十二酯为单体,合成了共聚型高吸油性树脂。研究了共聚单体的配比、交联剂用量、引发剂用量诸因素对高吸油性树脂的性能影响。制得的树脂可以吸其自身质量的11.8倍的煤油、14.7倍的苯、6.5倍的泵油。 相似文献
98.
Oxygen Tracer Diffusion in Vitreous Silica 总被引:2,自引:0,他引:2
Joseph D. Kalen Rethia S. Boyce James D. Cawley 《Journal of the American Ceramic Society》1991,74(1):203-209
Oxygen diffusion in vitreous silica glass is studied using the gas exchange technique. The tracer concentration profiles are consistent with a model based on two mechanisms, one network and the other interstitial. These processes are coupled through limited network–interstitial exchange. Nuclear reaction analysis and secondary ion mass spectrometry techniques are performed and compared. These results are compared to experiments on transport in thin silica films grown on single-crystal silicon. 相似文献
99.
Dielectric relaxation measurements are reported over a frequency range from 10−1 to 109 Hz as a function of exposure time for an epoxy resin-carbon fibre composite, ageing at 60 °C in water. Investigation of the nature of the dipole relaxation of the water molecules, indicates the nature of their interaction with the polymer matrix. Analysis of the dielectric relaxation spectra allow identification of processes that can be attributed to ‘free’ and ‘bonded’ water, water in micro-cracking, located in carbon fibre disbonds and plasticizing the polymer matrix. Identification of the various types of location in which water exists was aided by use of the Ng factor from the Kirkwood-Frölich equation, which describes the constraints on free dipole ration nature imposed by the environment in which it is located. These data indicate the power of the dielectric technique for quantitative analysis of water ingress into epoxy composites. 相似文献
100.
Y. Cohen K. Landskron N. Ttreault S. Fournier‐Bidoz B. Hatton G.A. Ozin 《Advanced functional materials》2005,15(4):593-602
The synthesis and characterization of a novel silicon–silica nanocomposite material are reported. A self‐assembly method allows the encapsulation of silicon nanoclusters within the channels of a periodic mesoporous silica thin film. The result is the formation of a silicon–silica nanocomposite film with bright, room‐temperature photoluminescence in the visible range, and a nanosecond luminescence lifetime. The properties of the nanocomposite material have been studied by several analytical techniques, which collectively show the existence within the channels of non‐diamondoid‐structure‐type silicon nanoclusters with various hydrogenated silicon sites. It is estimated that the silicon nanoclusters in the silica mesoporous films occupy up to 39 % of the accessible pore volume. The nanocomposite film shows improved resistance to air oxidation compared to crystalline silicon. The high loading and chemical stability to oxidation under ambient conditions are important advantages in terms of the development of silicon‐based light‐emitting diodes from this class of materials. 相似文献