热交换器表面镀层对传热性能的影响

采用化学镀的方法对热交换器表面进行表面改性,使其换热表面沉积一层表面能不同的均匀镀层。传热实验表明,随着磷含量的增大,凝结传热系数增大。进一步可视化实验研究表明,镀层换热表面均表现为珠膜共存状态,增大镀层的磷含量,换热表面促进珠状凝结的效果更加明显。这归于镀层降低了传热表面的表面能值。     

Low-phosporous nickel-coated carbon microcoils: Controlling microstructure through an electroless plating process

Carbon microcoils (CMCs) have been coated with a nickel-phosphorus (Ni-P) film using an electroless plating process, with sodium hypophosphite as a reducing agent in an alkaline bath. CMC composites have potential applications as microwave absorption materials. The morphology, elemental composition and phases in the coating layer of the CMCs and Ni-coated CMCs were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The effects of process parameters such as pH, temperature and coating time of the plating bath on the phosphorus content and deposition rate of the electroless Ni-P coating were studied. The results revealed that a continuous, uniform and low-phosphorous nickel coating was deposited on the surface of the CMCs for 20 min at pH 9.0, plating bath temperature 70 °C. The as-deposited coatings with approximately 4.5 wt.% phosphorus were found to consist of a mix of nano- and microcrystalline phases. The mean particle size of Ni-P nanoparticles on the outer surface of the CMCs was around 11.9 nm. The deposition rate was found to moderately increase with increasing pH, whereas, the phosphorous content of the deposit exhibited a significant decrease. Moreover, the material of the coating underwent a phase transition between an amorphous and a crystalline structure. The thickness of the deposit and the deposition rate may be controlled through careful variation of the coating time and plating bath temperature.     

Preparation of the Ni-P composite coating co-deposited by nano TiC particles and evaluation of it's corrosion property

In current research, low carbon steel plates were coated by Ni-P electroless method. The effect of adding different concentrations (ranging from 0.01 g/l to 0.5 g/l) of TiC nano-sized particles to the plating bath on deposition rate, surface morphology and corrosion behavior of Ni-P-TiC composite coatings were investigated. The surface morphology and the relevant structure were evaluated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Corrosion behavior of the coated steel was evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques. The results showed that addition of TiC nano-particles to Ni-P electroless bath not only changes the surface morphology of Ni-P coating, but also improves corrosion resistance of the steel in comparison with TiC free Ni-P electroless coating. In addition, the deposition rate of coating was also affected by incorporation of TiC particles. It was also found that improvement in corrosion resistance largely depends on the phosphorous and TiC concentrations on the coatings.     

The pH effect on black spots in surface finish: Electroless nickel immersion gold

In order to understand the black spot generation after electroless nickel immersion gold (ENIG) plating, we investigated the pH effect with a combined approach of experiments and computer aided engineering (CAE). As the pH is increased in IG plating solution, the deprotonation of citric acid as chelating agent is enhanced to stabilize the solution by producing Ni-citrate complex ion. For the substitution reaction between nickel and gold, excess citrate ions (deprotonated citric acids) are adsorbed along nodal boundaries of Ni-P layer to decrease the surface reactivity. Since the low reactivity decreases the overall growth rate, the resulting homogeneous Au layer growth avoids the unfavorable galvanic cell corrosion to control black spot. Based on molecular orbital method and kinetic Monte Carlo calculation, our computational approach well explained the capability of citric acid as chelating agent and the Au growth rate along the nodal boundaries of Ni-P layer depending on the surface reactivity.     

Electroless preparation and characterization of magnetic Ni-P plating on polyurethane foam

Magnetic Ni-P plating was coated on surface of polyurethane (PU) foam by electroless plating technique. Morphology, composition, structure, thermal decomposing behavior and magnetic property of PU foam before and after plating were characterized by scanning electron microscopy (SEM), energy diffraction spectrum (EDS), X-ray photoelectron spectroscopy (XPS), infrared spectrometer (IR), X-ray diffraction (XRD), thermogrametric analysis (TG) and vibrating sample magnetometer (VSM), respectively. The results showed that the Ni-P plating was composed by particles whose diameters were in the range of 1-2 μm. Because of the Ni-P plating coated on surface of PU foam, peak intensity of the plated PU foam in IR and XRD were lower than those before plating. TG curves of PU foam before and after plating were composed of two decomposing stages. Because part of Ni in Ni-P plating was oxidized, TG curve of the plated PU foam was uptilt during 650-1000 °C. The plated PU foams are magnetic and can be used in some special application.     

ICF玻璃靶丸化学镀磁性Ni-Co-Fe-P四元合金涂层

采用化学镀技术在ICF玻璃靶丸表面均匀包覆一层磁性Ni-Co-Fe-P四元合金涂层,通过扫描电子显微镜、原子力显微镜、能量衍射谱仪和振动样品磁强计对ICF玻璃靶丸表面化学镀Ni-Co-Fe-P四元合金涂层的形貌、组成和磁性能进行了表征。结果表明:化学镀Ni-Co-Fe-P四元合金涂层的ICF玻璃靶丸,表面由平均直径为50 nm的细小颗粒组成,表面粗糙度小,磁性能高,可望用于磁悬浮实验研究。     

Electroless Ni-P/Ni-B duplex coatings for improving the hardness and the corrosion resistance of AZ91D magnesium alloy

The Ni-P/Ni-B duplex coatings were deposited on AZ91D magnesium alloy by electroless plating process and their structure, morphology, microhardness and corrosion resistance were evaluated. The duplex coatings were prepared using dual baths (acidic hypophosphite- and alkaline borohydride-reduced electroless nickel baths) with Ni-P as the inner layer. The coatings were amorphous in as-plated condition and crystallized and produced nickel borides upon heat-treatment. SEM observations showed that the duplex interface on the magnesium alloy was uniform and the compatibility between the layers was good. The Ni-P/Ni-B coatings microhardness and corrosion resistance of having Ni-B coating as the outer layer was higher than Ni-P coatings. The Ni-P/Ni-B duplex coatings on AZ91D magnesium alloy with high hardness and good corrosion resistance properties would expand their scope of applications.     

Corrosion resistance and lubricated sliding wear behaviour of novel Ni-P graded alloys as an alternative to hard Cr deposits

Alternative process to hexavalent chromium, substitute materials and new designs are urgently needed owing to the requirement of “clean” manufacture. This comparative study was conducted to systematically investigate the corrosion resistance and lubricated sliding wear behavior of graded Ni-P alloy deposits produced from a single plating bath by electrodeposition and hard Cr deposits, using potentiodynamic polarization and reciprocating ball-on-disc tribometer. Results showed that Ni-P deposits heat-treated at 400 °C with maximum hardness exhibited more than two orders of magnitude higher corrosion resistance than hard Cr deposits in 10 wt.% HCl solution. The Stribeck curves for the heat-treated Ni-P gradient deposits and hard Cr under lubrication conditions were obtained with accurate control of normal load and sliding speed during the wear process, three main different regimes corresponding to different lubrication mechanism were identified. Heat-treated Ni-P gradient deposits showed relatively poor wear resistance than hard Cr deposits under the lubrication conditions, which may be attributed to superior oil-retaining surface structure and the unique “nodular” effect of hard Cr in wear process.     

ZrO2-reinforced Ni-P plate: An effective catalytic surface for hydrogen evolution

Nickel and its alloys have recently been emerged as potential catalytic electrode materials for hydrogen evolution reaction in alkaline media. The present work contemplates reinforcement of electroless Ni-P plate with ZrO₂. The plate showed very high stability and excellent electrocatalytic activity. In situ incorporation of ZrO₂ resulted in increase in the rate of deposition of Ni on steel substrate. There was high activation during the initial stage of the plating also. The electrocatalytic activity of the ZrO₂-reinforced Ni electroless plate was found to be highly reproducible and long lasting when used for hydrogen evolution reaction.     

Electroless nickel plating on APTHS modified wood veneer for EMI shielding

A new activation process was developed for electroless plating to prepare wood-based EMI shielding material. Pd(II) was adsorbed on a wood surface modified with γ-aminopropyltrihydroxysilane (APTHS) formed by the hydrolysis of γ-aminopropyltriethoxysilane (APTES). After reduction of Pd(II), electroless plating was successfully initiated and an Ni-P coating was deposited on the wood veneer. The activation process and resulting coating were characterized by XPS, SEM-EDS and XRD. The metal deposition, surface resistivity and electromagnetic shielding effectiveness were measured. XPS analysis proved that Pd(II) was bonded to the amino group of APTHS and was reduced to Pd(0). The Ni-P coating was uniform, compact and continuous, and consisted of 3.39 wt.% phosphorus and 96.61 wt.% nickel. XRD analysis indicated that the coating was crystalline, which is thought to be related to the low phosphorus content. The plated birch veneers exhibited electromagnetic shielding effectiveness greater than 60 dB in the frequency range 10 MHz-1.5 GHz.     

磁性ICF玻璃靶丸的化学镀工艺

 采用化学镀工艺在ICF玻璃靶丸表面包覆了一层磁性的Ni-P合金镀层,制备出磁性ICF玻璃靶丸。研究了化学镀主盐质量浓度、还原剂质量浓度、络合剂质量浓度、施镀温度及镀液pH值对沉积速率与镀液稳定性的影响,获得了化学镀制备磁性ICF玻璃靶丸的最佳工艺为：主盐硫酸镍30 g/L,还原剂次亚磷酸钠30 g/L,络合剂柠檬酸钠50 g/L,pH值10,温度(40±2) ℃。     

Growth behavior of electroless Ni-Co-P deposits on Fe

The electroless Ni-Co-P films were deposited on Fe film in plating baths using sodium hypophosphite as reducing agent and nickel and cobalt sulphates as ion source at pH value of 9 and plating temperature from 60 to 85 °C. The effect of the mol ratio of CoSO₄/CoSO₄ + NiSO₄ in plating bath on the growth behavior of electroless Ni-Co-P films was studied. The electroless Ni-Co-P films were characterized by transmission electron microscopy for the microstructure and thickness, and energy dispersive spectrometer for the composition. The results showed that the electroless Ni-Co-P films can be deposited on Fe films without the step of sensitization and activization; the surface of electroless Ni-Co-P film on Fe is quite even; the more the Co²⁺ ion in plating bath, the larger the activation energy and the smaller the plating rate of electroless Ni-Co-P films; and the mol ratio of Co/Co + Ni in film is larger than that in plating bath (with the exception of the film deposited in the bath with 0.9 mol ratio of CoSO₄/CoSO₄ + NiSO₄)     

A novel method to fabricate water-soluble hydrophobic agent and super-hydrophobic film on pretreated metals

This paper demonstrated a convenient method to prepare water-soluble hydrophobic agent and create super-hydrophobic film on the basic material of phosphating film and electroless Ni-P composite coating on carbon steels. Water contact angles and rolling angles of super-hydrophobic films were 155-168° and 2-3° on phosphating films, respectively, 145-155° and 15-20° on electroless Ni-P composite coatings, respectively. This water-soluble hydrophobic agent was white latex and had lots of micro-particles suspending in it. The thickness of the single-layer super-hydrophobic film with good corrosion resistance and stability was about 2-3 μm. The microstructure of super-hydrophobic film was discussed using XRD, EDS, optical and electronic microscope as analytical methods. This kind of super-hydrophobic film had a great many micro-particles dispersing in the surface, which contained F and Si and greatly increased the roughness of the surface.     

Effect of nickel on the initial growth behavior of electroless Ni-Co-P alloy on silicon substrate

In this work the small amounts of NiSO₄ was added to a basic electroless plating bath of CoSO₄ with Na₂H₂PO₂ as reducing agent for the deposition of Co-Ni-P film on a silicon substrate. The initial growth behavior, containing plating rate, chemical composition, crystal structure, surface morphology and micro-structure, of the electroless plating film was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). The results showed that the growth morphology variation of the Co-Ni-P films deposited in the basic CoSO₄ + small amounts of NiSO₄ bath is the same as that of Co-P film deposited in the basic CoSO₄ bath, the plating rate of the Co-Ni-P film is much more rapid than that of the Co-P film, the Ni/Co wt.% in the Co-Ni-P film is greatly larger than that in the plating bath, and the structure of as-deposited film is crystalline at first stage and later stage.     

Comparison of the coating properties and corrosion rates in electroless Ni-P/PTFE composites prepared by different types of surfactants

The effects of the addition of three types of surfactants (cationic, anionic, non-ionic) at different concentrations in the plating bath on the deposition rate, PTFE content and surface morphology of electroless Ni-P/PTFE composite coatings were investigated. It was demonstrated that the cationic and non-ionic surfactants created a uniform distribution of PTFE particles in the coatings. The effects of the surfactant type and concentration on the corrosion properties of Ni-P/PTFE coatings were also studied. The corrosion resistance was increased by the incorporation of PTFE particles into the Ni-P matrix. The level of improvement depended largely on the type and concentration of the applied surfactants.     

Characteristics and electrochemical performance of Ni-coated ZnO prepared by an electroless plating process

ZnO was coated homogeneously with amorphous Ni film by an electroless plating process. After electroless Ni plating, transmission electron microscope (TEM) images and energy dispersive spectrometry spectra (EDS) of ZnO clearly indicated that Ni was coated on the surface of ZnO, the coatings and ZnO contacted enough. X-ray diffraction and high-resolution TEM showed that the Ni film on ZnO was amorphous. Electrochemical performance of Ni-coated ZnO was investigated by the galvanostatic charge/discharge cycling test. Compared to that of uncoated ZnO, the charging–discharging performance of Ni-coated ZnO was obviously improved, e.g. the average discharge capacity of the Ni-coated ZnO increased 71.5% at the stage of stable cycling test.     

ICF玻璃靶丸化学镀磁性Ni-P涂层的研究

 采用化学镀方法对ICF空心玻璃微球靶丸进行处理,使其表面均匀包覆一层磁性Ni-P合金镀层,从而使得ICF玻璃靶丸具有一定的磁性,可望用于进行磁悬浮ICF定位打靶实验研究。用X射线衍射仪、扫描电子显微镜和振动样品磁强计对涂层的组成、结构、形貌及磁性能进行了表征。结果表明：对 ICF玻璃靶丸进行化学镀处理,其球形度、同心度和壁厚均匀性都与化学镀前未发生明显改变,其饱和磁化强度和矫顽力分别为3.883×10^-3 A/g和1.046×^-3 T。     

Incorporation of nano zinc oxide for improvement of electroless nickel plating

The advantages of electroless nickel plating (EN) include excellent corrosion resistance, wear resistance, solderability, low porosity and uniform thickness even on complex parts and ability to plate on nonconductors. In the present study nano ZnO particles were synthesized by using an electrochemical technique and incorporated the particles into Ni-P plates. An alkaline bath was selected and used for nano zinc oxide incorporation. The electrochemical and metallurgical properties of the Ni-nano ZnO-P plates were evaluated and compared with that of the un-reinforced Ni-P plates. The incorporation of the nano ZnO particles resulted in improvement of metallurgical and corrosion resistance characteristics of the plates.     

磁性ICF靶丸的化学镀工艺制备与表征

 采用化学镀工艺在ICF聚苯乙烯靶丸表面包覆了一层磁性的Ni-P合金镀层,并分别用扫描电子显微镜、能谱仪、X射线衍射仪以及振动样品磁强计对其形貌、组成、结构和磁性能进行了表征。结果表明：通过化学镀工艺制备的Ni-P合金镀层厚度约为4 μm,且为非晶结构,并具有一定的磁性;该磁性ICF靶丸可望用来进行磁悬浮实验研究。最后,对聚苯乙烯靶丸表面磁性涂层的制备机理进行了讨论。     

Nanocrystalline soft ferromagnetic Ni-Co-P thin film on Al alloy by low temperature electroless deposition

Soft ferromagnetic ternary Ni-Co-P films were deposited onto Al 6061 alloy from low temperature Ni-Co-P electroless plating bath. The effect of deposition parameters, such as time and pH, on the plating rate of the deposit were examined. The results showed that the plating rate is a function of pH bath and the highest coating thickness can be obtained at pH value from 8 to10. The surface morphology, phase structure and the magnetic properties of the prepared films have been investigated using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and vibrating magnetometer device (VMD), respectively. The deposit obtained at optimum conditions showed compact and smooth with nodular grains structure and exhibited high magnetic moments and low coercivety. Potentiodynamic polarization corrosion tests were used to study the general corrosion behavior of Al alloys, Ni-P and Ni-Co-P coatings in 3.5% NaCl solution. It was found that Ni-Co-P coated alloy demonstrated higher corrosion resistance than Ni-P coating containing same percent of P due to the Co addition. The Ni-Co-P coating with a combination of high corrosion resistance, high hardness and excellent magnetic properties would be expected to enlarge the applications of the aluminum alloys.