纳米白炭黑对NBR性能的影响

试验研究表面改性剂品种及其用量、纳米白炭黑粒径及其用量以及纳米白炭黑／炭黑并用比对NBR硫化胶物理性能的影响。结果表明，表面改性剂对纳米白炭黑填充NBR硫化胶物理性能的影响程度大小顺序为硅烷偶联剂KH-550、钛酸酯偶联剂NDZ-201、表面活性剂ABS。用0．6份硅烷偶联剂KH～550对纳米白炭黑进行改性后，当纳米白炭黑粒径为5～15nm（用量为30份）；纳米白炭黑用量为50份（粒径为15～25nm）；纳米白炭黑／炭黑并用比为15／35（纳米白炭黑粒径为15～25nm）时，NBR硫化胶的综合物理性能最佳。     

硅烷偶联剂KH-550对纳米晶纤维素/炭黑/天然橡胶复合材料性能的影响

试验研究硅烷偶联剂KH-550对纳米晶纤维素/炭黑/天然橡胶复合材料性能的影响。结果表明:加入硅烷偶联剂KH-550后,混炼胶的粘性模量和损耗因子减小,硫化胶的硬度和300%定伸应力增大,拉断永久变形减小,耐磨性能提高;当硅烷偶联剂KH-550用量为1~2份时,混炼胶的硫化特性和加工性能,硫化胶的交联密度、耐屈挠性能、压缩疲劳性能和耐磨性能明显改善。     

硅烷偶联剂对OMMT/NR纳米复合材料结构与性能的影响

采用混炼插层法制备有机蒙脱土(OMMT)/NR纳米复合材料,研究硅烷偶联剂对其结构和性能的影响.结果表明,与NR相比,OMMT/NR纳米复合材料的物理性能,热稳定性和动态力学性能均有所提高;采用硅烷偶联剂KH-560改性的OMMT制备的纳米复合材料各项性能均优于采用硅烷偶联剂KH-550改性的OMMT制备的纳米复合材料.     

硅烷偶联剂对蒙脱土/NR纳米复合材料气体阻隔性能的影响

试验研究硅烷偶联剂对蒙脱土（MMT）／NR纳米复合材料性能的影响。结果表明，在MMT／NR复合材料中加入硅烷偶联剂，可提高复合材料的物理性能、耐热空气老化性能、气体阻隔性能和热稳定性。硅烷偶联剂KH-560的改性效果最好，其最佳用量为3份。     

白炭黑在NR/BR/SSBR并用胶中的应用

研究了白炭黑／炭黑填充NR／BR／SSBR并用胶的物理性能，用橡胶加工分析仪(RPA2000)分析并用胶硫化性能和动态粘弹性的变化规律。结果表明，炭黑和白炭黑总量固定．白炭黑的用量增大时，并用胶的物理性能略有下降，固特里奇压缩疲劳性能改善，并用胶的硫化速度减缓，且t90和t10的变化与白炭黑的用量呈线性关系；60℃的tanδ值随白炭黑用量增大而呈下降趋势，即硫化胶的滚动阻力降低。     

废弃椰壳粉/PVC复合材料结构和性能的研究

研究了偶联剂改性椰壳粉的种类及用量、椰壳粉的质量分数对椰壳粉/PVC复合材料性能的影响,并用扫描电镜(SEM)观察了其两相结构和断面形貌.结果表明:硅烷偶联剂KH-550在用量为2%时效果较好,拉伸强度提高了12.6%,冲击强度提高了31%;经过硅烷偶联剂KH-550改性后椰壳粉填充质量分数增大,且降低趋势较小,有效降低复合材料的成本;经过KH-550改性能较大幅度的增大复合材料的耐热变形性能;KH-550改性改善了椰壳粉纤维在PVC基体中分散性和相容性.     

白炭黑对累托石/天然橡胶纳米复合材料结构与性能的影响

采用乳液法制备累托石(REC)/天然橡胶(NR)纳米复合材料,研究白炭黑对REC/NR复合材料结构和性能的影响。结果表明:白炭黑粒子可以插入累托石片层形成网络结构。加入少量白炭黑后,REC/NR复合材料的物理性能变化不大。随着白炭黑用量的增大,复合材料的抗湿滑性能、抗切割性能和耐磨性能提高,压缩生热逐渐增大,当白炭黑用量为15份时,复合材料的耐磨性能最好;当白炭黑用量为20份时,复合材料的抗切割性能和抗湿滑性能较好。     

改性白炭黑/氧化石墨烯协同补强天然橡胶的研究

将硅烷偶联剂KH-550改性以及硅烷偶联剂KH-550和K-MEPTS共同改性的白炭黑与氧化石墨烯(GO)复配补强天然橡胶(NR),研究填料与橡胶基体的界面结合方式对胶料性能的影响。结果表明:由硅烷偶联剂KH-550和K-MEPTS共同改性的白炭黑与GO静电组装制得的改性白炭黑-2/GO填充NR得到的胶料具有低的Panye效应和高的结合胶含量,这表明改性白炭黑-2/GO在橡胶基体中的分散性好且与橡胶基体通过共价连接结合紧密;改性白炭黑-2/GO/NR硫化胶滞后损失小,具有低的压缩疲劳温升和高的拉伸强度。     

受阻酚AO-80/改性白炭黑/NBR复合材料的性能

研究受阻酚AO-80/硅烷偶联剂改性白炭黑/NBR复合材料的性能.结果表明,随着受阻酚AO-80用量的增大,受阻酚AO-80/硅烷偶联剂改性白炭黑/NBR复合材料的玻璃化温度和损耗因子峰值明显升高,阻尼性能明显提高;物理性能下降,但仍可满足使用要求.     

硅烷偶联剂KH-792对白炭黑／环氧化天然橡胶复合材料性能的影响

研究硅烷偶联剂KH-792对白炭黑/环氧化天然橡胶(ENR)复合材料性能的影响。通过硫化特性测试和红外光谱分析发现,ENR与白炭黑和硅烷偶联剂KH-792之间发生了反应。试验结果表明:硅烷偶联剂KH-792改性白炭黑/ENR胶料的结合胶含量高,硫化胶的抗切割性能和耐磨性能优异;当硅烷偶联剂KH-792用量为白炭黑用量的8%时,其改性效果最佳。     

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.     

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.     

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.     

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.     

Dielectric-State Analysis in Solid-Solution Pb(Yb1/2Ta1/2)O3–Pb(Lu1/2Nb1/2)O3

The structure and temperature dependence of complex lead perovskite dielectrics were investigated for the system (1 − x )Pb(Yb_1/2Ta_1/2)O₃– x Pb(Lu_1/2Nb_1/2)O₃. Superlattice reflections for the compositions 0.8 < x < 1.0 were observed by X-ray diffractometry, and the temperature-composition dielectric-state diagram was determined. In the present study, the disordered middle composition, with 0.2 < x < 0.8, showed a diffuse paraelectric–ferroelectric phase transition, whereas the ordered end compositions, with 0 ≤ x < 0.2 and 0.8 < x ≤ 1.0, revealed successive sharp paraelectric–antiferroelectric and weak antiferroelectric–ferroelectric phase transitions. The dielectric state was confirmed by examining the variation of polarization ( P ) with electric field ( E ).