换热表面Ni-W-P镀层抗垢特性

通过调整Ni-W-P化学镀镀液中钨酸钠浓度,获得了钨元素含量不同的三元Ni-W-P镀层。进一步的实验研究表明,随着三元Ni-W-P镀层中钨元素含量的增加,其热稳定性得到显著改善,同时,镀层晶粒转变的激活能值呈增大趋势。三元Ni-W-P镀层的抗垢性随着镀层中钨元素含量的增加而降低,而与镀层表面自由能以及表面粗糙度没有必然的联系。     

钨对化学镀Ni-W-P合金镀层结构及性能的影响

通过不同的化学镀工艺配方,获得了4种不同钨含量的化学镀Ni-W-P三元合金镀层.研究了钨含量对镀层结构、硬度及在5%H2SO4溶液中耐蚀性的影响规律.研究发现,化学镀Ni-W-P三元合金镀层的结构受镀层中钨含量的影响较大,非晶态Ni-W-P三元合金镀层所需磷含量较非晶态Ni-P二元镀层所需磷含量要低,并且钨含量越高,所需磷含量越少;镀层硬度随镀层结构从非晶态→混晶态→纳米晶态转变而增加;镀层的耐蚀性随镀层中钨含量增加而变好,且非晶态镀层较混晶态和纳米晶态镀层更易形成钝化区.     

Ni-W-P合金镀层在流动介质中的腐蚀防护效果研究

在管束表面化学镀Ni-W-P合金镀层,并对镀层的表面形貌、成分、结构及耐蚀性进行了测试。结果表明:Ni-W-P合金镀层表面覆盖均匀的胞状物,含有W元素,容易在介质中发生钝化;Ni-W-P合金镀层的耐蚀性良好,其在流动介质中的耐蚀性弱于在静态介质中的耐蚀性。     

电沉积Ni-W-P基纳米微粒复合镀层的组织与结构研究

电沉积Ni-W-P基纳米微粒复合镀层的表面形貌和相结构分析表明:镀液pH的增大,镀层表面粗糙,但镀层较厚,稀土的加入能有效细化晶粒。(Ni-W-P)-SiO2、(Ni-W-P)-CeO2纳米微粒复合镀层在镀态时是非晶态结构,而(Ni-W-P)-CeO2-SiO2纳米微粒复合镀层在镀态时是混晶结构。热处理后的(Ni-W-P)-CeO2-SiO2复合镀层是晶态结构。Ni3P相的衍射峰加强,这说明随着热处理温度的升高,镀层的非晶态形态逐渐减弱,镀层逐渐向晶态转变。     

真空蒸发镀钨金刚石制备工艺及其抗氧化性能研究

采用真空蒸发镀的方法在金刚石表面镀钨,研究了镀覆温度和保温时间对金刚石表面形貌、镀层成分与厚度、镀钨层物相的影响规律,分析了镀钨金刚石的抗氧化性能。结果表明,随着镀覆温度和保温时间的增加,钨元素百分比含量增加,镀层厚度也逐渐增加,镀层由间断变成连续致密的镀膜,并逐渐生成W2C和WC。镀钨后的金刚石抗氧化性提高,在900℃下保温1h的镀钨金刚石起始氧化温度、剧烈氧化温度比未镀钨的金刚石分别提高了18.8%、16.6%。     

Ni-W-P化学镀层对稀土合金钢耐蚀性的影响

为了进一步提高稀土合金钢的耐蚀性,在其表面沉积Ni-W-P化学镀层。对Ni-W-P化学镀层的表面形貌、成分及耐蚀性进行了观察与测试。结果表明:Ni-W-P化学镀层表面的胞状物分布较为均匀,镀层中W的质量分数约为2.0%;Ni-W-P化学镀层比稀土合金钢在硫酸介质中表现出更好的耐蚀性。     

自催化(无电解)镀Ni-W-P合金

本文介绍了通过改变柠檬酸钠(Na_3 C_6 H_5 O_7) 和钨酸钠(Na_2 WO_4) 的浓度,研究自催化(无电解)镀镍-钨-磷(Ni-W-P)合金的槽液成份和操作条件。3～4%(重量比)的钨与镍的共沉积,使镀层中磷含量由8. 9%降到2. 3%(重量比),其结果改善了这种镀层的结晶性。降低磷含量能增加这种镀层的残余应力和导电率。     

镀液中TiO2对（Ni-W-P）-TiO2复合镀层性能的影响

为了进一步提高Ni-W-P合金镀层的硬度和耐蚀性,用脉冲电沉积法制备了(Ni-W-P)-TiO2复合镀层,并研究了镀液中TiO2加入量对镀层硬度和表面形貌的影响,且通过极化曲线和电化学阻抗谱研究了镀层在3.5%NaCl溶液中的耐蚀性能。结果表明,(Ni-W-P)-TiO2复合镀层的性能优于Ni-W-P镀层,而当镀液中TiO2质量浓度为6g/L时,复合镀层的硬度较高,表面形貌及耐蚀性能较优。自腐蚀电位较正,腐蚀电流密度较小,极化电阻较大,其交流阻抗谱对应的电阻值也较大。     

硫酸镍对Ni-W-P化学镀层性能的影响

在不锈钢表面制备了Ni-W-P化学镀层。研究了硫酸镍的质量浓度对Ni-W-P化学镀层的沉积速率及电化学性能的影响,并用SEM表征了Ni-W-P化学镀层的表面形貌。最终确定硫酸镍的最佳质量浓度范围为25~35g/L。Ni-W-P化学镀层均匀地覆盖不锈钢基体,起到了很好的保护作用。     

电镀不同钨合金抽油杆的耐盐水腐蚀性及力学性能

采用电沉积法,在35CrMo抽油杆表面制备了Ni-W-P和Fe-Ni-W合金镀层,研究了钨合金镀层及其热处理对抽油杆的耐蚀性和室温静态力学性能的影响.采用X射线衍射法表征了钨合金镀层及其热处理后的结构.采用失重法、阳极极化曲线测量和电化学阻抗谱,研究了电镀钨合金抽油杆在质量分数为3.5%的氯化钠水溶液中的耐蚀性.采用扫描电子显微镜分析了电镀钨合金抽油杆拉伸断裂后的断口组织形貌.结果表明:35CrMo抽油杆电镀钨合金后,其耐蚀性明显增强;热处理使镀层的耐蚀性进一步提高;各项力学性能均达到标准要求.电镀钨合金抽油杆可以应用于油田的采油设备中.     

Ni-W-P镀层的防垢性能

在紫铜基体上制备了化学镀Ni-W-P镀层,X射线衍射结果表明,镀层的结构形态为非晶态。污垢附着实验和池沸腾实验结果表明,低表面自由能的化学镀Ni-W-P镀层使污垢沉积速度降低了52%,在硫酸钙溶液中的传热系数则是紫铜表面的1.7倍。用高速摄影仪观察了沸腾表面的气泡行为,由于传热方式的差别形成了两种不同结构的硫酸钙污垢,紫铜表面为针状垢,而镀层表面是粒状垢。     

镍钨磷非晶态合金电刷镀工艺研究

在Ni-P电刷镀工艺的基础上,研究和开发了Ni-W-P电刷镀工艺,镀液中加入钨酸盐。通过试验确定各组分的含量及工艺条件。镀层测试结果表明：Ni-W-P镀层为非晶态镀层,硬度高、耐腐蚀性能好,并具有良好的结合力。可用于工、模具的修复。     

Influence of the adhesion force crystal/heat exchanger surface on fouling mitigation

The accumulation of unwanted crystalline deposits (fouling) reduces the efficiency of heat exchangers considerably. In order to decrease the cost of fouling two strategies have been developed. The first fouling mitigation strategy is based on the modification of energy and geometry related characteristics of the heat transfer surface to realize an increased duration of the induction period. By means of a DSA (drop shape analysis) measurement device the interaction at the interface crystal/heat transfer surface is determined. The deployment of the fracture energy model and the interfacial defect model relates wetting characteristics to the adhesion phenomenon. Hence, a first estimation of the optimal choice of surface material is realized. Furthermore, the influence of surface topography on interfacial interactions has been analyzed. The second fouling mitigation strategy is based on the adjustment of the hydrodynamic flow conditions using a pulsation technique. Here, single strokes of higher velocity are superimposed on the stationary flow. These strokes shift the equilibrium of forces to an improved removal process. Fouling experiments have proved that pulsation is a powerful tool to mitigate the built-up of fouling layers on heat transfer surfaces.     

Environmentally Friendly Solvent‐ and Water‐Based Coatings for Mitigation of Crystallization Fouling

The surface properties of solvent‐based (SB) and water‐based (WB) coatings and their impact on fouling during convective heat transfer of CaSO₄ solutions were investigated. Experiments demonstrated that the SB coatings had generally better non‐adhesive characteristics, especially at higher values of the electron donor component since the deposits could easily be washed away. For the SB coatings, a longer induction period compared to those of untreated surfaces was observed and a significant reduction of the fouling rate could be achieved. Further analysis of surfaces revealed that SB coatings enhanced the acid‐base repulsive force and thus reduced the deposit/solid adhesion energy. For the WB coatings, the Liftshitz‐van der Waals attractive force plays a decisive role in the adhesion process due to the higher apolar component of the surface energy.     

化学镀Ni-W-P镀液及工艺优化研究

采用正交试验,以镀层的耐硝酸变色时间为评价标准,得到化学镀Ni—W—P溶液最佳配方为：20g／L硫酸镍、20g／L钨酸钠、20g／L次磷酸钠、40g／L络合剂、20g／L缓冲剂、pH值为60对该优化镀层的沉积速度、耐蚀性、孔隙率及结合力进行了测定,并与Ni—P二元合金镀层进行了比较。结果表明,该优化镀层的性能优于Ni—P二元合金。采用扫描电镜及X-射线衍射仪分别对该优化镀层的微观形貌、组成及结构进行的分析表明,该镀层结构致密,磷含量高达13.9％,且为非晶态结构。     

Calcium phosphate fouling on TiN-coated stainless steel surfaces: Role of ions and particles

Modifying the surface properties of the stainless steel used in heat exchangers to decrease its tendency for the building-up of milk deposits seems to be a promising strategy to reduce fouling during heat treatment in the dairy industry. In this work, several modified stainless steel surfaces, obtained by reactive magnetic sputtering, were used as fouling supports for a milk-simulating mineral solution under constant conditions of temperature, pH and calcium concentration. The aim of the work was to quantify deposition and removal parameters, based on the influence of surface energy properties on the type of deposit. The fouling process was characterized by the surface reaction coefficient of the ions present in solution, as well as the adhesion coefficients of the particles formed in the bulk. An insight on the mechanisms of deposition and removal processes was achieved, as well as by the dependence between those two processes and the electron-donor component (γ^-) of the surface energy of the stainless steel-based materials. The surfaces with lower γ^- were found to have lower amounts of deposit, and this deposit could be more easily cleaned than for the other surfaces (including the non-modified stainless steel).     

Electrochemical studies on electroless ternary and quaternary Ni-P based alloys

The autocatalytic (electroless) deposition of Ni-P based alloys is a well-known commercial process that has found numerous applications because of their excellent anticorrosive, wear, magnetic, solderable properties, etc. It is a barrier coating, protecting the substrate by sealing it off from the corrosive environments, rather than by sacrificial action. The corrosion resistance varies with the phosphorus content of the deposit: relatively high for a high-phosphorus electroless nickel deposit but low for a low-phosphorus electroless nickel deposit. In the present investigation ternary Ni-W-P alloy films were prepared using alkaline citrate-based bath. Quaternary Ni-W-Cu-P films were deposited by the addition of 3 mM copper ions in ternary Ni-W-P bath. X-ray diffraction (XRD) studies indicated that all the deposits were nanocrystalline, i.e. 1.2, 2.1 and 6.0 nm, respectively, for binary, ternary and quaternary alloys. Corrosion resistance of the films was evaluated in 3.5% sodium chloride solution in non-deaerated and deaerated conditions by potentiodynamic polarization and electrochemical impedance (EIS) methods. Lower corrosion current density values were obtained for the coatings tested in deaerated condition. EIS studies showed that higher charge transfer resistance values were obtained for binary Ni-P coatings compared to ternary or quaternary coatings. For all the coatings a gradual increase in the anodic current density had been observed beyond 740 mV. In deaerated condition all the reported coatings exhibited a narrow passive region and all the values of E_p, E_tp and i_pass were very close showing no major changes in the electrochemical behavior. In the non-deaerated conditions no passivation behavior had been observed for all these coatings.     

Experimental Study on Microbial Fouling Inhibition Performance of Ni-P-NanoTiO2 Composite Surfaces

Microbial fouling of heat exchangers causes serious issues including increased fuel consumption, flow resistance, and maintenance cost expenditure. Composite Ni-P-nanoTiO₂ coatings were prepared for inhibiting and mitigating the heat exchanger microbial fouling deposition. The surface energy components and wall adhesion work of microbial fouling medium had a significant effect on the microbial fouling deposition process. Compared with carbon steel coupons, the microbial fouling deposition on Ni-P-nanoTiO₂ coatings was reduced by about 90 % and the wall adhesion work and microbial fouling deposition rate of these coatings were less. The Ni-P-nanoTiO₂ coatings might not only be advantageous for controlling the initial microbial adhesion, but also effective for reducing the fouling deposition rate.