螺旋碳纤维金属合金催化剂的制备

通过酸化、敏化、活化等工艺对石墨基体进行前处理,采用化学镀法在石墨基体表面沉积Ni-Fe-P合金。考察不同工艺参数对镀层的影响情况,并通过红外光谱(FT-IR)、扫描电子显微镜(SEM)、能谱(EDX)、X射线衍射(XRD)对化学镀各处理步骤及施镀效果进行分析表征,确定出最佳工艺条件。最后采用CVD法,以乙炔为碳源、Ni-Fe-P合金为催化剂、在650℃成功制备出形貌规整的螺旋碳纤维。     

碳纤维表面预处理及化学镀Ni-P工艺对镀层性能的影响

过去,对碳纤维表面预处理、化学镀Ni-P工艺条件影响镀层性能影响的综合报道不多。为此,先对碳纤维表面预处理,再化学镀Ni-P。分析了粗化和活化对碳纤维表面形貌的影响,探讨了镀液温度、pH值、次磷酸钠还原剂和柠檬酸钠配位剂浓度,添加糖精、十二烷基硫酸钠对碳纤维表面化学镀Ni-P沉积速率的影响。采用扫描电镜(SEM)和能谱仪(EDS)观测了Ni-P镀层的表面、截面形貌,测试了不同工艺条件对Ni-P镀层与碳纤维的结合力。结果表明:粗化使碳纤维表面积增大,有助于提高其与镀层的结合力,AgNO3活化后碳纤维表面附着了较多的催化晶核;随着镀液温度、pH值和柠檬酸钠浓度的增加,化学镀Ni-P的沉积速率均呈先增大后减小的趋势;随着次磷酸钠浓度的增加,化学镀Ni-P的沉积速率先增大后相对稳定;加入糖精后的Ni-P镀层平整、光滑,完全覆盖碳纤维表面,与碳纤维结合良好。     

碳纤维表面化学镀的研究进展

近年来,许多导电高分子复合材料已使用碳纤维作为增强体,采用化学镀是改善碳纤维的表面性质的一种很有前途的改性方法。综述了碳纤维表面化学镀的种类,详细地叙述了碳纤维表面预处理技术、化学镀工艺及现阶段国内外研究状况,总结了碳纤维表面化学镀存在的问题及发展趋势。     

碳纤维表面化学镀铜工艺研究

传统的化学镀铜以甲醛作还原剂,污染环境.以环保型还原剂次亚磷酸钠代替甲醛,加入各种不同的稳定剂在碳纤维表面进行化学镀铜,获得了具有一定厚度、均匀、光亮的铜镀层.研究了镀液pH值、温度及还原剂、配位剂、稳定剂用量对化学镀铜溶液稳定性和碳纤维增重率的影响,确定了新的镀铜配方.用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、能谱、冷热循环处理等手段,分析了化学镀铜层的微观形貌、结构及成分.结果表明,通过此新型的环保镀液配方和工艺条件,可获得光亮、致密、均匀及含铜量较高的镀层.     

气相生长纳米碳纤维表面化学镀镍

气相生长纳米碳纤维（ＶＧＣＮＦ）经活化、敏化和催化预处理后、用化学镀（自催化沉积）的方法,在碱性镀液中实施化学镀镍。利用ＳＥＭ观察了镀层的形貌。并利用能主普分析测试了镀层的组成。在气相生长纳米碳纤维聚集体的内层纤维表面沉积了许多细小Ｎｉ颗粒,而外层纤维表面上沉积的是连续、均匀的镍镀层,它们是由许多Ｎｉ颗粒相互堆积连结而形成,除含磷外几乎不含其它杂质,同时,还初步探讨了镍在气相生长纳米碳纤维表面自催化沉积过程。     

铜催化剂纳米粒子的尺寸对碳纤维形貌的影响

通过化学气相沉积法高重复性制备了纳米螺旋碳纤维和直线性碳纤维,并研究了金属铜纳米粒子催化剂的尺寸大小对碳纤维形貌的影响,认为粒径较大的铜纳米粒子容易催化聚合生成直线形碳纤维;反之,粒径较小的铜纳米粒子倾向于合成纳米螺旋碳纤维.利用场发射扫描电镜(FESEM)、透射电镜(TEM)和X射线粉末衍射(XRD)等测试方法对产物进行了表征.     

电镀Ni膜催化生长螺旋纳米碳纤维及其电磁性能研究

采用电镀工艺制备催化剂Ni膜,以化学气相沉积方法合成螺旋纳米碳纤维,通过扫描电镜(SEM)、X射线衍射(XRD)和偏光显微镜对螺旋纳米碳纤维的形态和结构进行表征。研究了电镀时间、电镀电流对螺旋纳米碳纤维生长的影响;并通过波导法对制备出的螺旋状纳米碳纤维测试在12.4～18GHz频段的电磁参数,考察其吸波性能。     

空心玻璃微珠表面化学镀Ni-P合金磁性涂层的研究

采用化学镀工艺在空心玻璃微珠表面包覆了一层磁性的Ni-P合金涂层,对其进行了表面金属化改性.分别用X射线衍射仪(XRD)、傅立叶变换红外光谱仪(FT-IR)、扫描电子显微镜(SEM)以及振动样品磁强计(VSM)对化学镀前后空心玻璃微珠的形貌、组成、结构以及磁性能进行了表征.结果表明:通过化学镀工艺制备的Ni-P合金涂层由原子团簇组成;涂层为非晶结构并具有较好的磁性能;化学镀后空心玻璃微珠的X射线衍射强度和红外透射强度均降低.     

化学镀铜前碳纤维预处理的研究

碳纤维具有疏水性和表面惰性,很难直接镀铜.为此,研究了碳纤维表面的预处理工艺、条件等技术参数.结果表明:高温灼烧除胶、过硫酸铵氧化、氯化银活化较好地改善了碳纤维的疏水性,大大提高了碳纤维表面的粗糙度,使碳纤维表面具有了催化活性.预处理后的碳纤维进行化学镀铜,其镀层光亮、均匀、致密,与基体的结合力较好.     

化学镀可焊性Sn-Pb合金的工艺研究

Sn-Pb合金镀层防腐蚀性好,熔点低,钎焊性好,在工业上应用很广。含Sn10％～40％的Sn-Pb合金镀层多用于电子元器件引线以提高其可焊性。工业生产常采用电镀工艺,对化学镀工艺研究较少。为此,介绍了一种烷基磺酸盐体系化学镀可焊性Sn-Pb合金(Sn：Pb为9：1左右)新工艺,系统研究了络合剂、还原剂、添加剂、时间、温度等因素对化学镀Sn-Pb合金沉积速率及镀层合金成分的影响。该化学镀液稳定性好、沉积速率可达到4．2μm／10min,镀层为银白色无光合金镀层,可焊性优良;当镀液中不添加Pb^2 时,该工艺也可用于化学镀Sn.     

Electroless deposition of Ni-Co-B alloy films and influence of heat treatment on the structure and the magnetic performances of the film

The Ni-Co-B alloy was electrolessly deposited from the bath using potassium borohydride as a reducing agent and ethylenediamine as a stabilizer. The effects of the plating conditions on the plating rate and the composition of the deposit were studied to improve the stability of the plating bath and to control the composition of the Ni-Co-B deposit. The crystallization behavior of the deposit was investigated by X-ray diffraction. The results show that the structure of the as-plated deposit is amorphous, and the deposit was crystallized into cubic Ni₃B and Ni-Co phases at 350 °C. The effect of heat treatment on the magnetic performances of the deposit was studied by vibrating sample magnetometer. The saturation magnetization and the residual magnetization of the coating go up with the increase of heat treatment temperature from 50 °C to 600 °C. The deposit heat-treated at 600 °C is found to be suitable as soft magnetic materials.     

Anisotropic strain on phonons in a-plane GaN layers studied by Raman scattering

The requirement for integration into silicon IC circuitry working at GHz frequencies drives the research into new development of both materials and processes. The formation of electroless Co–Fe–B coatings was investigated on pure copper and 304 stainless steel substrates which were pretreated in a bath containing EDTA (20 g l⁻¹), ethylene diamine (30 g l⁻¹), PdCl₂ (10 g l⁻¹) and NaHPO₂ (4 g l⁻¹). Electroless deposition was performed at 348 K, for 2 h, in a bath that contained sodium tartrate (0.2 M) and sodium citrate (0.05 M) as complexing agents and the bath pH was adjusted between 6.5 and 9.5 using a concentrated solution of sodium hydroxide. The main components of the bath were a source of cobalt (II) ions, a source of iron (II) ions, DMAB as reducing agent and boron source, ammonium sulfate as buffering agent, phosphorous acid as a slow-rate reducing agent, a stabilizer, and an accelerator. Co–Fe–B films having a variety of composition with respect to cobalt, iron, and boron contents were produced by varying the experimental parameters such as pH and the concentration of bath components. The coatings were characterized in terms of composition, structure and corrosion resistance by ICP and EDS, XRD and SEM, and by electrochemical instrumentation, respectively. The magnetic properties of the electroless Co–Fe–B ternary alloy deposits were measured by a DC extraction method. The results indicate that tight control of process parameters enables the tailoring of coercivity and magnetic permeability of the films, and may lead to the microfabrication of innovative and efficient devices having nanofeatures such as nanowires.     

Microstructure and tribological property of nanocrystalline Co–W alloy coating produced by dual-pulse electrodeposition

The nanocrystalline Co–W alloy coatings were produced by dual-pulse electrodeposition from aqueous bath with cobalt sulfate and sodium tungstate (Na₂WO₄). Influence of the current density and Na₂WO₄ concentration in bath on the microstructure, morphology and hardness of the Co–W alloy coatings were investigated using an X-ray diffraction, a scanning electronic microscope and a Vickers hardness tester, respectively. In addition, the friction and wear properties of the Co–W alloy coating electrodeposited under different condition were evaluated with a ball-on-disk UMT-3MT tribometer. The correlation between the electrodeposition condition, the microstructure and alloy composition, and the hardness and tribological properties of the deposited Co–W alloy coatings were discussed in detail. The results showed that the microhardness of the deposited Co–W alloy coating was significantly affected by its average grain size, W content and crystal orientation. Smaller grain size, higher W content and strong hcp (1 0 0) orientation favor the improvement of the hardness for Co–W alloy coatings. The deposited Co–W alloy coating could obtain the maximum microhardness over 1000 kgf mm⁻² by careful control of the electrodeposition conditions. The tribological properties of the electrodeposited Co–W alloy coating were greatly affected by its grain size, microhardness, surface morphologies and composition, and could be significantly improved by optimizing the electrodeposition condition.     

Corrosion resistant Zn-Co alloy coatings deposited using saw-tooth current pulse

Micro/nanostructured multilayer coatings of Zn-Co alloy were developed periodically on mild steel from acid chloride bath. Composition modulated multilayer alloy (CMMA) coatings, having gradual change in composition (in each layer) were developed galvanostatically using saw-tooth pulses through single bath technique (SBT). CMMA coatings were developed under different conditions of cyclic cathode current densities (CCCDs) and number of layers, and their corrosion resistances were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) method. Optimal configuration, represented as (Zn-Co)_2·0/4.0/300 was found to exhibit ～ 89 times better corrosion resistance compared to monolithic (Zn-Co)_3·0 alloy deposited for same time, from same bath. The better corrosion resistance of CMMA coatings was attributed to changed interfacial dielectric properties, evidenced by dielectric spectroscopy. Improved corrosion resistance was attributed to formation of n-type semiconductor film at the interface, supported by the Mott-Schottky plot. Further, the formation of multilayer and corrosion mechanism was analysed using scanning electron microscopy (SEM).     

Investigation of solar selective and microstructural properties of molybdenum black immersion coatings on cobalt substrates

Molybdenum black solar selective coatings have been produced on cobalt by immersion in a solution of ammonium paramolybdate and nickel sulphate. The cobalt was electroplated on nickel-plated copper prior to immersion in the paramolybdate solution. The maximum solar absorptance of the resulting molybdenum black coating was about 0.91. The minimum emittance was about 0.1 for coatings on cobalt deposited with an addition agent and about 0.23 for coatings on cobalt deposited without addition agent in the 60 °C plating solution. These differences have been related to the coating morphology determined by scanning electron microscopy. The emittance of coatings on cobalt deposited without addition agent decreases (or remains unchanged) during short-term heat treatment while that of coatings deposited on cobalt plated with addition agent increases somewhat. Reduction of the cobalt plating bath temperature to 45 °C can also lead to good initial coating properties but without the requirement for an addition agent in the cobalt plating bath. XPS studies show that the oxidation state of molybdenum in the coatings is approximately + 5 corresponding to Mo₄O₁₁. This reduces to + 4 after argon ion bombardment. Some cobalt may be present in the coatings in the form of CoO.     

Electrodeposition and mechanical and corrosion resistance properties of Ni-W/SiC nanocomposite coatings

Ni-W/SiC nanocomposite coatings with various contents of SiC nano-particulates were prepared by electrodeposition in Ni-W plating bath containing SiC particulates. The influences of the SiC nano-particulates concentration, current density and stirring rate of the plating bath on the composition of the nanocomposite coatings were investigated. The surface morphologies of the Ni-W alloy and Ni-W/SiC nanocomposite coating were observed using a scanning electron microscope (SEM). The morphology of Ni-W/SiC nanocomposite coating is smoother than that of Ni-W alloy coating. The microhardness of composite coatings increases with the increasing content of the SiC nano-particulates in the coatings. The corrosion behavior of Ni-W alloy and Ni-W/SiC nanocomposite coatings was evaluated by the anodic polarization curves in 0.5 mol/L NaCl solution at room temperature. It shows that Ni-W/SiC nanocomposite coating has better corrosion resistance than the Ni-W alloy coating.     

镁合金蓝色微弧氧化膜的制备及其耐蚀性能

过去,将微孤氧化着色用于材料装饰的研究较少。采用微孤氧化技术在ZM5镁合金表面制备了蓝色的微弧氧化层,研究了主盐Na2SiO3、着色剂CoSO4浓度和氧化时间对蓝色膜层的影响。结果表明：在70g／LNa2SiO3,2g／LCoSO4,电压440V,氧化时间20min条件下,能够获得膜层厚度为82μm的致密蓝色微弧氧化膜...     

柠檬酸钠对硫酸盐体系钴-镍合金电沉积的影响

分别在硫酸盐镀液和添加柠檬酸钠的硫酸盐镀液中电沉积钴-镍合金.采用扫描电子显微镜(SEM)、X射线能谱仪(EDS)和X射线衍射仪(XRD)研究了镀层组成、表面形貌和结构.结果表明,柠檬酸钠有利于钴的沉积,易于获得晶粒细小的镀层;而且镀层的结构主要为面心立方(fcc)相,而在硫酸盐镀液中所得镀层结构主要为六方(hcp)相.采用电化学线性扫描技术研究钴-镍合金的沉积过程,发现添加柠檬酸钠使该合金的沉积电位负移.     

Effect of heat treatment on age hardening behaviour of electroless nickel–phosphorus coatings

Abstract

Electroless nickel–phosphorus (EN) coatings have been widely used in various industries such as oil, gas, electronic, chemical, automotive, aerospace, and mining. The EN coating process is based on a redox reaction in which a reducing agent is oxidised and Ni²⁺ ions are reduced on the substrate materials. Once the first layer of Ni is deposited, it acts as a catalyst for the process. Consequently, a linear relation between coating thickness and time usually occurs. If the reducing agent is sodium hypophosphite, the deposit obtained will be a nickel–phosphorus alloy. Also, the actual nickel and phosphorous levels in the EN deposit depend on the composition, temperature, and pH of the plating bath used. In this work, three types of EN coatings have been studied: low, medium, and high phosphorus Ni–P alloys. The techniques used were: differential scanning calorimetry (DSC), SEM, and hardness measurements. Heat treatment resulted in precipitation of nickel phosphides, e.g. Ni₃P, and nickel crystallites. Thus, the phosphorus content of the coating was reduced. The results of isochronal age hardening showed that the peak age hardening temperature for the three EN coatings occurred at ～673 K. However, the time to reach peak hardness during isothermal heat treatment at 593 K varied with phosphorus content. Also, it was found that the temperatures at which peak precipitation reactions occur during DSC scan are influenced by phosphorus content.     

双向脉冲快速电沉积非晶态Ni-P/Al_2O_3复合镀层

采用双向脉冲电沉积法制备出高P非晶态Ni-P/Al_2O_3复合镀层,利用扫描电镜(SEM)和能谱分析(EDS)方法考察镀层的微观形貌和化学组成,采用X射线衍射技术(XRD)表征镀层的相结构,并通过分析金属镀层和复合镀层的电化学测试结果,评价不同种类镀层的耐腐蚀能力。结果表明:与直流电沉积法相比,双向脉冲电沉积法可将镀层中的P含量提高至12.06%(质量分数),有利于非晶态Ni-P合金镀层的形成。采用双向脉冲法制备的Ni-P/Al_2O_3复合镀层比直流电沉积法制备的Ni-P/Al_2O_3复合镀层更平整、结晶更致密。脉冲电沉积法制备的非晶态Ni-P合金镀层具有更好的耐蚀性,而且复合微粒Al_2O_3的加入,对进一步提高非晶态Ni-P合金镀层的耐蚀性有积极作用。