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Motor Frame Design
Published in Wei Tong, Mechanical Design and Manufacturing of Electric Motors, 2022
The electroless plating technology has been developed for many decades. Electroless plating is the process of plating a coating with the aid of a chemical reducing agent (e.g., formaldehyde) in solution without the passage of external power. Compared with electroplating, electroless plating has some superior characteristics: (a) Without using electric current in the plating process, it is easier to obtain uniform coatings on parts. This feature is especially suitable for parts with irregular, complex-shaped geometries. (b) It is applicable to non-conductive substrates such as glass and plastic. (c) Electroless plating can deposit particles from different materials to obtain composite coatings readily for adapting to different application requirements. For instance, nickel–phosphorus coatings are used to enhance corrosion resistance. Alternatively, thin cobalt–phosphorus coatings offer superior sliding wear, enhanced lubricity and corrosion resistance, and improved fatigue properties. Because they exhibit some magnetic properties, they are also of interest to the magnetic recording community.
Introduction to Membrane Reactors and Membrane Contactors
Published in Chandan Das, Sujoy Bose, Advanced Ceramic Membranes and Applications, 2017
The electroless plating looks to be an attractive method as it requires very simple processing equipment and is able to coat a complexly shaped component with a layer of uniform thickness. Like CVD, it is a very prolonged process, but controlling thickness of a film is not easy by electroless plating. However, a significant advantage of this plating is that it is well matched to applications on available commercial membranes [92]. The catalytic dehydrogenation of isopropanol using a Cu/SiO2 catalyst is performed in a Pd–Cu alloy membrane reactor. The membrane is prepared by electroless plating of alumina supports, followed by heat treatment after electroplating [93]. Two types of Ni–P alloy/ceramic membranes are prepared by the conventional electroless Ni-plating technique and the recrystallization technique for dehydrogenation of ethanol to acetaldehyde. Ethanol conversion is considerably higher in the former than in the membrane reactor using the recrystallized membrane [94].
LIGA and Micromolding
Published in Mohamed Gad-el-Hak, MEMS, 2005
Besides stabilizers, the metal salt, and a reducing agent, electroless solutions may contain other additives such as complexing agents, buffers, and accelerators. Complexing agents exert a buffering action and prevent the pH from decreasing too fast. They also prevent the precipitation of metal salts and reduce the concentration of free metal ions. Buffers keep the deposition reaction in the desired pH range. Accelerators, also termed exaltants, increase the rate of deposition to an acceptable level without causing bath instability. These exaltants are anions, such as CN−, thought to function by making the anodic oxidation process easier. In electroless copper, for example, compounds derived from imidazole, pyrimidine, and pyridine can increase the deposition rate to 40 μm hr−1. The electroless deposition must occur initially and exclusively on the surface of an active substrate and subsequently continue to deposit on the initial deposit through the catalytic action of the deposit itself. Since the deposit catalyzes the reduction reaction, the term auto-catalytic is often used to describe the plating process. Electroless plating is an inexpensive technique enabling plating of conductors and nonconductors alike (plastics such as ABS, polypropylene, Teflon, polycarbonate, etc., are plated in huge quantities). A catalyzing procedure is necessary for electroless deposition on nonactive surfaces such as plastics and ceramics. The most common method for sensitizing those surfaces is by dipping into SnCl2/HCl or immersion in PdCl2/HCl [Mallory and Hadju, 1990]. This chemical treatment produces sites that provide a chemical path for the initiation of the plating process.
Ultrasonic-assisted Ni–Mo–P doping hydrothermal synthesis of clustered spherical MoS2 composite coating: wear and corrosion resistance
Published in Surface Engineering, 2020
Jibo Jiang, Yaoxin Sun, Yukai Chen, Qiongyu Zhou, Haibo Rong, Xiaomin Hu, Haotian Chen, Liying Zhu, Sheng Han
The original materials are more and more difficult to meet the needs of some special environments in the industry. Especially when the material is under high temperature, high pressure, rotted candle medium, etc., the surface is prone to defects such as oxidation, abrasion, corrosion, etc., and these defects often lead to failure of the entire part. Mild steel has low strength and hardness, good ductility and toughness. However, it has poor wear resistance and corrosion resistance. Therefore, in order to prolong its service life, save resources, and improve production efficiency, it is necessary to improve the surface properties of materials [1,2]. Electroless plating technology has been widely used in the industry due to its simple equipment, convenient operation, flexible process, uniform coating thickness, and high surface quality [3,4]. It is a common and important process in the surface treatment industry. Electroless plating is a process in which metal ions in a solution are deposited on a catalytic surface by a reducing agent, which is essentially a redox reaction, that is, a chemical deposition process in which electron transfer is performed but no external power source is present. However, with the development of science, in order to improve the comprehensive performance of binary alloy coatings and meet the needs of materials working under more complicated and more demanding conditions, people have continuously improved the electroless plating process and developed multi-alloy coatings and composite coatings.
Alternative tribological coatings to electrodeposited hard chromium: a critical review
Published in Transactions of the IMF, 2020
Electroplating and electroless deposition processes are commonly used to deposit a surface layer from an aqueous solution. In electroplating, the desired reaction of metal deposition from the reduction of soluble metal ions, takes place directly at the cathode surface. The anode uses an inert material or the same metal being plated in order to continuously replenish the ions in the electrolyte bath. In contrast, electroless plating involves a spontaneous, autocatalytic reduction of metallic ions in an aqueous solution by a reducing agent in the bath to deposit the metal at open-circuit without the use of external electrical power. The advantages of electroless plating include the uniformity of thickness on a substrate and the ability to deposit onto complex geometrical surfaces and internal tubular components.95 The downside is that it is usually more expensive and slower to create a thick coating and less cost-effective due to difficulties in controlling solution stability. Compared to electroless plating, electrodeposition has the advantages of lower cost, a faster deposition rate and more stable, tolerant baths; over 95% of metal industrially deposited is by electroplating.96
The effect of heat treatment on Ni–B–Ce electroless coatings
Published in Surface Engineering, 2019
Wei Qian, Huanming Wei, Haotian Chen, Liying Zhu, Yaoxin Sun, Sheng Han, Hualin Lin, Jibo Jiang
Heat treatment also is a significant aspect which could affect the appearance, structure and properties of coatings and lots of scholars have focused the effect of heat treatment on electroless Ni–B coatings. Serin et al. [14] studied the effect of annealing temperature on the mechanical properties of electroless Ni–B–Mo coatings. They observed the high hardness and low friction coefficient after heat treatment. Moreover, the use of ultrasound as a special form of energy-assisted deposition has recently attracted attention in material technology because of its capacity to improve the deposition rate. Several works have reported the improvement of mechanical and electrochemical properties of ultrasonic-assisted electroless deposited coatings as well. Niksefat and Ghorbani [15] reported the corrosion resistance of ultrasonic-assisted electroless Ni–B–TiO2 coating. The addition of ultrasonic waves accelerates the deposition rate and increases the mechanical and electrochemical performance of the coating. Electroless plating technology, which shows great important application value, has become an environmentally friendly surface treatment process in many fields due to low cost and small environmental pollution. Previous studies usually studied the effect of heat treatment or ultrasound on Ni–P or Ni–B coatings and rarely combined these two factors with electroless deposition [16–20]. And few people have focused on the effect of heat treatment on ultrasonic-assisted electroless Ni–B–Ce coatings.