玻璃纤维/NR/BR复合材料的制备及性能研究

采用机械共混法制备玻璃纤维/天然橡胶(NR)/顺丁橡胶(BR)复合材料,研究了玻璃纤维部分替代白炭黑对复合材料硫化特性、力学性能、耐磨性及防滑性能的影响,并与白炭黑、纳米凹土部分替代白炭黑填充胶料的性能进行了对比;结果表明,玻璃纤维的添加能缩短胶料的硫化时间,增加胶料的硬度、撕裂强度和湿摩擦系数,当玻璃纤维用量为6份时,胶料的综合性能高于白炭黑、纳米凹土填充胶料的性能,可考虑将玻璃纤维用于浅色鞋底胶料中,提高胶料的防滑性能。     

湿法改性高岭土与不同填料在SBR中的应用

将湿法改性高岭土与未改性高岭土、炭黑、白炭黑以及碳酸钙分别填充到SBR中制备复合材料,并对其性能进行了研究。结果表明,炭黑填充SBR复合材料的综合性能最好,改性高岭土次之,白炭黑填充略好于高岭土填充,碳酸钙填充的性能最差;与未改性高岭土相比,改性高岭土胶料的加工性能得到改善,拉伸强度、定伸应力、撕裂强度均增大,耐磨性及耐老化性能变好。     

硅烷偶联剂表面处理白炭黑对NBR/HSR并用胶的性能影响

以NBR(丁腈橡胶)和HSR(高苯乙烯树脂)并用为主体材料,采用白炭黑为补强剂,研究了硅烷偶联剂表面处理白炭黑对NBR/HSR并用胶工艺性能、力学性能、老化性能、耐磨性、弹性及压变性能的影响;结果表明,KH-845表面处理白炭黑能缩短胶料的焦烧时间,影响操作安全性,胶料的撕裂强度、磨耗体积最大,压缩永久变形最小;KH-570表面处理白炭黑胶料的拉伸强度、300%定伸应力及伸长率最大,磨耗体积最小;硅烷偶联剂对胶料的弹性和老化性能影响不大;整体来看,KH-570表面处理白炭黑胶料的综合性能最好;其硬度、拉伸强度、撕裂强度、磨耗体积、弹性及压缩永久变形分别为HA84、21.31MPa、49.03 N/mm、0.18 cm~3、22%及25%,较好地满足了高性能家用电器配件的性能要求。     

改性凹土在浅色NR/SBR鞋底胶中的应用

研究改性凹土在浅色天然橡胶（NR）/丁苯橡胶（SBR）鞋底胶中的应用。结果表明：加入改性凹土能增加胶料的塑性,延长焦烧时间,提高操作安全性;与白炭黑填充胶相比,随着改性凹土用量的增加,胶料的拉伸强度先升高后降低,撕裂强度明显增加,而耐磨性、弹性和屈挠性能逐渐变差。老化后胶料的拉伸强度、300%定伸应力及伸长率变化率较小,胶料耐老化性能好于白炭黑填充胶。当改性凹土用量为5份时,胶料的综合性能与白炭黑相差不大,可考虑用改性凹土部分替代白炭黑,在满足制品性能要求的同时,降低生产成本。     

凹凸棒土/NBR纳米复合材料的制备和性能研究

采用机械共混法制备凹凸棒土(AT)/丁腈橡胶(NBR)纳米复合材料,研究了AT用量、偶联剂种类对复合材料硫化特性和力学性能的影响,并用透射电镜(TEM)和扫描电镜(SEM)观察了AT及其纳米复合材料的微观结构。结果表明,在机械剪切力的作用下,AT分离并分散在NBR中,形成纳米复合材料。随着AT用量的增加,AT/NBR的t10和t90缩短,硫化速度提高,硬度、拉伸强度、定伸应力和撕裂强度先增大后逐渐减小或不变;当AT用量为40份时,综合性能最好。偶联剂用量相同时,Si69改性效果最好,制得的AT/NBR综合力学性能与白炭黑、炭黑填充NBR性能相近。     

纳米纤维粉对NBR/CR并用胶的性能影响研究

以浅色防滑鞋底胶为研究方向,采用NBR(丁腈橡胶)和CR(氯丁橡胶)并用为主体材料,研究了不同类型的纳米纤维粉部分代替白炭黑对NBR/CR并用胶工艺性能、力学性能、耐磨性及老化性能的影响。结果表明,纳米纤维粉的添加能延长焦烧时间,缩短正硫化时间,提高硫化效率;提高胶料的撕裂性能和热老化性能,但会降低胶料的拉伸强度、定伸应力及硬度,影响胶料的耐磨性;综合考虑,采用R-01型纳米纤维粉部分替代白炭黑胶料的综合性能最好;其硬度、拉伸强度、撕裂强度及磨耗体积分别为HA60、10.53 MPa、43.86 N/mm及0.95 cm~3;在降低成本,改善工艺性能的同时,满足胶鞋大底胶料的性能要求。     

碱性白炭黑在NBR/ACM耐油胶管内层胶中的应用研究

研究了碱性白炭黑对NBR/ACM耐油胶管内层胶性能的影响。结果表明,随着碱性白炭黑用量的增加,胶料的拉伸强度逐渐降低,硬度、伸长率、撕裂强度及压缩永久变形逐渐增加;老化后胶料的硬度变大,拉伸强度和伸长率变小;耐介质后胶料的硬度、拉伸强度和伸长率均小于耐介质前,体积变化率呈负数;当N550用量40份,碱性白炭黑用量10份时,胶料的综合性能最好,其拉伸强度、伸长率、撕裂强度以及压缩永久变形分别为15.02 MPa、248%、25.49 kN/m和32%,老化后拉伸强度、伸长率变化率分别为-8%,-12%;高温耐油后,胶料的拉伸强度、伸长率及体积变化率分别为-10%、-21%及-4%;采用碱性白炭黑部分替代N550,可降低炼胶粉尘,保护生产环境。     

改性碳纳米管在不同补强填充体系丁腈橡胶中的应用研究

研究改性碳纳米管（CNTs）在碳酸钙、白炭黑、炭黑N330补强填充体系丁腈橡胶（NBR）中的应用。结果表明：随着改性CNTs用量增大,碳酸钙补强填充体系和白炭黑补强填充体系NBR的MH－ML逐渐增大,t90缩短;炭黑N330补强填充体系NBR的MH－ML增大,t90延长;3种补强填充体系NBR的硬度、100%定伸应力、撕裂强度逐渐增大,碳酸钙补强填充体系NBR的拉伸强度提高,白炭黑补强填充体系和炭黑N330补强填充体系NBR的拉伸强度稍有降低;碳酸钙补强填充体系和白炭黑补强填充体系NBR的表面电阻率（ρs）和体积电阻率（ρv）变化较小,变化规律不明显;炭黑N330补强填充体系NBR的ρs和ρv较小,导电效果较好;3种补强填充体系NBR的导热性能均有所提高,炭黑N330补强填充体系胶料的热扩散率最大。     

高苯乙烯树脂/NBR共混物性能研究

研究高苯乙烯树脂(HSR)/NBR共混比对HSR/NBR共混物性能的影响.结果表明,随着HSR/NBR共混比的增大,共混物邵尔A型硬度、撕裂强度和压缩永久变形增大,拉伸强度先减小后增大,拉断伸长率减小,耐油性能下降;与NBR胶料相比,HSR/NBR共混物的挺性提高.     

叶腊石/白炭黑/NBR复合材料的结构与性能研究

利用机械共混法制备了叶腊石/白炭黑/NBR复合材料,采用RPA2000、SEM、DMA等实验方法研究改性剂的种类、增塑剂DOP用量对复合材料性能的影响。结果表明,偶联剂Si-69不仅可以改善复合填料的分散性,而且可以提高复合填料与NBR之间的相互作用,其改性效果最佳。增塑剂DOP可以改善NBR胶料的加工性能,提高NBR复合材料的耐溶剂性能、回弹性及耐低温性能,对NBR复合材料的补强及耐热空气老化性能不利,但可以降低胶料成本。     

Compact Swelling in Bi1.4Pb0.6Sr2Ca2Cu3.6Oy During the Formation of High-Tc Superconducting Phase

Compact swelling in Pb-doped Bi-Sr-Ca-Cu-O superconductor has been studied by observing the effects of the size of calcined powders, volatilization of materials, and sintering of high- T _c (2223) powders. The bulk density increases at the early stage of sintering, for about 20 h, and then decreases. Densification occurs when the low- T _c (2212) phase and a liquid phase exist, whereas dedensification occurs with the formation of the 2223 phase regardless of the presence of the liquid. Gas evolution from specimens does not appear to be responsible for compact swelling. Compact swelling is explained by anisotropic growth of thin, platelike 2223 grains in random orientation. When 2223 grains grow in a preferred direction, compact swelling is suppressed.     

Synthetic routes to nanoscale BxCyNz architectures

B_xC_yN_z nanoscale materials, hybrids of h-BN and graphite, have been recently synthesised using various techniques. Here, we present the latest advances in the synthesis and characterisation of B-C-N nanotubes and nanofibres. In particular, we focus on layered BC₂N, BN, BC and CN_x systems, reviewing their production methods as well as their structural and electronic properties. These materials may find important applications in the fabrication of nanotransistors, robust nanocomposites, conducting polymers, storage components and field emission sources.     

Microwave Dielectric Properties of CaTiO3-CaAl1/2Nb1/2O3 Ceramics Doped with Li3NbO4

The microwave dielectric properties of CaTi_{1− x} (Al_1/2Nb_1/2) _x O₃ solid solutions (0.3 ≤ x ≤ 0.7) have been investigated. The sintered samples had perovskite structures similar to CaTiO₃. The substitution of Ti⁴⁺ by Al³⁺/Nb⁵⁺ improved the quality factor Q of the sintered specimens. A small addition of Li₃NbO₄ (about 1 wt%) was found to be very effective for lowering sintering temperature of ceramics from 1450–1500° to 1300°C. The composition with x = 0.5 sintered at 1300°C for 5 h revealed excellent dielectric properties, namely, a dielectric constant (ɛ_r) of 48, a Q × f value of 32 100 GHz, and a temperature coefficient of the resonant frequency (τ_f) of −2 ppm/K. Li₃NbO₄ as a sintering additive had no harmful influence on τ_f of ceramics.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Structure Evolution from Pb(Mg1/3Nb2/3)O3 to La(Mg2/3Nb1/3)O3

The crystal structure of lanthanum-modified lead magnesium niobates having composition (Pb_{1− x} La _x ) (Mg_{(1+ x )/3}-Nb_{(2− x )/3})O₃ with X = 0 to 1 was investigated by X-ray powder diffraction. It was found that the fundamental reflections from perovskite structure remain in the whole range of composition. The superlattice reflections from the A(B'_1/2-B"_1/2)O₃ ordered structure are also well preserved for La content greater than 50 at.%; however, a series of extra peaks of mixing indices appears, with intensities gradually enhanced with the increase of La content. For the complete substitution of Pb by La, a splitting of some reflections can be observed in the diffraction pattern. The results indicate that the crystal structure evolves continuously with the La content, from disordered cubic perovskite of space group Pm 3 m for X = 0, to ordered cubic perovskite of space group Fm 3 m for X = 0.5, distorted cubic perovskite of space group Pa 3 for 0.5 < X < 0.9, and finally to a rhombohedral perovskite, possibly belonging to the space group R 3 , for X ≥ 0.9. In the evolution of structure, a linear reduction of the lattice constant of the perovskite cell from 4.048 to 3.964 Å was observed.     

Characteristic Spherulitic Microstructure in Partial-Melt-Processed YBa2Cu3Ox/HfO2

The microstructure of partial-melt-processed YBa₂Cu₃O _x /HfO₂ has been studied by transmission electron microscopy. A characteristic spherulitic microstructure is formed in the system. A model for the growth mechanism has been proposed. The critical heterogeneous nucleation of the YBa₂Cu₃O _x phase appears to occur from the melt in an epitaxially controlled manner on CuO particles. Subsequent growth of YBa₂Cu₃O _x platelets from the nucleus region is repeatedly interrupted by the nucleation of hafnium-rich phases in the liquid at the solid/liquid interface in a manner that again appears to be epitaxially controlled and that promotes the splay of the c orientation of the YBaCuO grain.