温度对化学镀Ni-Co-P/PTFE复合镀层表面质量与性能的影响

使用扫描电镜、能谱仪、X射线衍射仪和电化学工作站,研究了温度对化学镀Ni-Co-P/PTFE复合镀层的表面质量、成分和耐蚀性的影响,并表征了化学镀Ni-Co-P/PTFE复合镀层的相结构。结果表明:温度升高(65～85℃)使化学镀Ni-Co-P/PTFE复合镀层的表面质量有所改善,PTFE的掺杂量增大,这对提高化学镀Ni-Co-P/PTFE复合镀层的性能是有利的。85℃时制备的化学镀Ni-Co-P/PTFE复合镀层为非晶态结构,其自腐蚀电位为-0.232 V,自腐蚀电流密度为1.32×10~(-6) A/cm~2,极化电阻达到最大值29.1 kΩ·cm~2,腐蚀速率达到最小值0.015 mm/a,此时的化学镀Ni-Co-P/PTFE复合镀层具有优良的耐蚀性。     

非晶纳米复合镀层的摩擦学性能

对纳米陶瓷微粒及自润滑纳米粉改性的非晶纳米复合镀层的摩擦学性能进行了综述.分析了纳米陶瓷微粒ZrO2、SiC、Al2O3及具有自润滑性能的纳米MoS2、PTFE、碳纳米管(CNTs)改性的复合镀层的摩擦学行为,发现具有自润滑性能的复合镀层具有较好的摩擦学性能.     

电刷镀Ni-PTFE复合镀层工艺研究

采用电刷镀技术,在不同工艺参数条件下,制备了Ni-PTFE复合镀层,并研究了各工艺参数对PTFE复合量,以及PTFE复合量对摩擦系数的影响。结果表明,PTFE加入量和镀液温度对复合量的影响较大,而电压和相对运动速度对复合量影响较小;摩擦系数随PTFE复合量的增加先减小,然后保持不变;PTFE加入量为10mL/L、镀液温度为40°C、电压为8V、相对运动速度为12m/min时,可获得PTFE复合量较高且分布均匀、表面形貌好的Ni-PTFE复合镀层。     

齿轮用45钢锰系磷化膜和锰系复合磷化膜的性能比较

在含有聚四氟乙烯(PTFE)颗粒的磷化液中,通过共沉积在齿轮用45钢表面制备了锰系复合磷化膜,比较了锰系磷化膜和锰系复合磷化膜的微观形貌、成分、膜重、结合力、硬度、耐磨性能和耐腐蚀性能。结果表明,锰系复合磷化膜中含有Mn、P、Fe、O、C和F六种元素,与锰系磷化膜相比多了F元素,证实了一定量的PTFE颗粒通过共沉积进入磷化膜中。锰系磷化膜和锰系复合磷化膜的膜重接近,均为16 g/m2左右,且锰系磷化膜和锰系复合磷化膜均与基体结合良好。与锰系磷化膜相比,锰系复合磷化膜的硬度略有提高,硬度值约为253.4 HV,耐磨性能和耐腐蚀性能都明显改善。PTFE颗粒主要填充在磷化膜晶粒间隙处,形成固体润滑膜起到减轻摩擦的作用,同时有效阻止了腐蚀溶液的渗透,故锰系复合磷化膜表现出相对较高的硬度以及更好的耐磨性能和耐腐蚀性能。     

聚四氟乙烯油封在车辆上的应用研究

通过对影响油封密封性的主要因素以及油封在车辆上的使用环境分析,选用了丁腈橡胶、填充聚四氟乙烯（PTFE）、氟橡胶、PTFE复合材料4种密封材料,并对所制成的不同结构的油封进行了对比试验。结果证袜,PTFE复合材料具有良好的耐高低温性、自润滑性、耐磨性和耐压性。PTFE复合油封能提高车辆的密封性,满足车辆的使用要求。     

机械泵旋片基材表面化学镀Ni-P/PTFE复合镀层

在机械泵旋片用45Mn钢板表面制备了化学镀Ni-P/PTFE复合镀层,并研究了PTFE的质量浓度对化学镀Ni-P/PTFE复合镀层的沉积速率、耐磨性、耐蚀性及表面形貌的影响。结果表明:适当增加PTFE的质量浓度,有利于加快沉积速率,提高化学镀Ni-P/PTFE复合镀层的耐磨性和耐蚀性。化学镀Ni-P/PTFE复合镀层表面呈胞状形貌,PTFE均匀分布在表面。当PTFE的质量浓度为8 g/L时,化学镀Ni-P/PTFE复合镀层具有最佳的耐磨性和耐蚀性。     

憎水性Ni-PTFE复合镀层的制备及其摩擦磨损性能的研究

采用复合电镀法制备Ni-PTFE复合镀层,考察了表面活性剂、电流密度、pH值和镀液中PTFE添加量对复合镀层中PTFE含量的影响.并进一步研究了镀层中PTFE含量对复合镀层硬度、摩擦磨损性能和憎水性能的影响.结果表明,最佳工艺条件下制备的复合镀层具有良好的憎水性和优异的摩擦磨损性能.     

PTFE乳液对景观钢结构表面镀层耐蚀性的影响

为了提升景观钢结构的耐腐蚀性能,对Q345钢进行了化学镀镍处理,对比了Ni–P合金镀层和镀液中添加不同体积分数的PTFE乳液后得到的Ni–P–PTFE复合镀层的物相组成、元素成分、显微形貌和电化学腐蚀行为。结果表明,Ni–P合金镀层和Ni–P–PTFE复合镀层都主要为非晶态结构,当PTFE乳液的添加量达到5 mL/L及以上时,Ni–P–PTFE复合镀层中会出现一定量的晶态Fe₃C和P₄S₃。相较于Ni–P合金镀层,Ni–P–PTFE复合镀层的腐蚀电位发生正移,腐蚀电流密度减小,阻抗增大,表明Ni–P–PTFE复合镀层的耐腐蚀性能优于Ni–P合金镀层。PTFE乳液添加量为0.2 mL/L时所得Ni–P–PTFE复合镀层的耐蚀性最好,这主要与此时镀层表面较为平整、致密性较好有关。     

电镀Ni-PTFE复合镀层研究

在对Ni-PTFE复合电镀工艺参数研究的基础上，[1]研究了表面活性剂、PTFE微粒含量、温度及其它因素对复合镀层的影响。用电子探针和电子显微镜对镀层进行了微观结构分析，结果表明镀层质量良好。     

特种设备用Q390E钢防腐蚀处理研究

采用锰系磷化工艺对特种设备用Q390E钢进行防腐蚀处理,将不同浓度的PTFE乳液分别加入磷化液中,在Q390E钢表面制备了锰系磷化膜和三种锰系复合磷化膜.测试了锰系磷化膜和三种锰系复合磷化膜的电化学阻抗谱,并表征了锰系磷化膜和三种锰系复合磷化膜盐雾试验前后的表面形貌.结果表明:与Q390E钢相比,锰系磷化膜和三种锰系复...     

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.     

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 ).     

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.