Electroless Plating Process Research Articles

Sugar‐Based Electroless Copper Deposition on Pectin‐Coated Alumina Microparticles

AbstractA novel approach for fabricating copper‐coated alumina microparticles utilizing a pectin‐based coating subsequently followed by electroless deposition is reported. The biopolymer pectin is modified with phosphate groups covalently binding to the particle surface, while the polymer itself promotes the formation of metal centers on the surface due to the high affinity to metal cations. The sugar‐based (galactose, xylose, and glucose) electroless plating process in combination with an organic‐based treatment ensures a homogeneous metal coating method. As a benefit, precious metal activation of alumina particles and hazardous reducing agents typically employed are not required, creating a low‐cost and sustainable process. Metal plated micro particles show a uniform and homogeneous coating rendering them as ideal additives for application in metal matrix composites. These ceramic metal composites can be used in a wide range of applications where high‐strength metal components are needed.

Development and analysis of a nano-triangular wave-shaped polarizer

As society becomes smarter, advanced optical sensing and imaging technologies utilizing visible and near-infrared regions have become increasingly prevalent. Wire-grid polarizers, which are available for broadband electromagnetic waves, are effective in improving the signal-to-noise ratio of such optical systems and enabling more advanced object detection and analysis. However, to be implemented in everyday products, low-cost manufacturing methods must be developed while maintaining high-performance optical functions. To meet these requirements, we conducted an analysis of the geometry of wire-grid polarizers, and designed and developed a wire-grid polarizer with a nano-triangular wave-shaped structure that can be fabricated using general-purpose manufacturing equipment. Once the mould is prepared, this polarizer can be fabricated via nanoimprinting and metal deposition with a normal angle or electroless plating processes. The polarizer fabricated through electroless Ni plating achieves a transmittance of 40%, which is approximately 1.4 times higher than that achieved in a previous study using electroless Ni plating on a rectangular structure with the same period. In addition, the polarizer fabricated through normal angle Al deposition operates over a wide range of wavelengths from visible light to near-infrared, and achieves a polarization extinction ratio of 24 dB at a wavelength of 550 nm and a high transmittance of 81%. High-performance polarizers can be obtained through normal-angle deposition using general-purpose equipment in contrast to the oblique-angle deposition method employed in the manufacture of conventional rectangular structure-based wire-grid polarizers, thereby contributing to cost reduction and improved manufacturability.

Straightforward Manufacturing of 3D-Printed Metallic Structures toward Customized Electrical Components.

Metalizing three-dimensional (3D)-printed polymers has been spotlighted in the field of manufacturing high-end and customized electrical components. Conventional metalization approaches that rely on the electroless plating (ELP) process typically require the use of noble metal-based catalysts or involve multistep processes, limiting their practical applications. Herein, we propose a straightforward yet effective approach to manufacture 3D-printed polymers with conductive metal layers through a thiol-mediated ELP process without involving an additional catalytic activation process. A photocurable ternary resin based on thiol-ene-acrylate monomers was precisely designed to induce excess thiol moieties on the surface of 3D-printed structures. These exposed thiol moieties served as active sites for metal ion complexion via strong metal-sulfur bonds, allowing the deposition of metal layers on the 3D-printed polymers through the ELP. Diverse metal layers, including Cu, Ag, and NiP, could be deposited onto virtually any 3D-printed structures with high uniformity and adhesion stability. To highlight the potential application of our approach, we fabricated fully functional glucose sensors through the deposition of the Cu layer on 3D-printed electrode models, and these sensors displayed excellent nonenzymatic glucose sensing performance. The proposed approach offers great insights for designing functional metallic structures and opens up new avenues for manufacturing lightweight, customized electrical components.

Fractal recognition and contact characteristics of ionic electroactive polymer interface based on microstructure analysis

Interface research is one of the basic topics in the study of mass transfer dynamics and actuation deformation processes. The main objective of this paper is to conduct in-depth research on the interface characteristics of ionic electroactive polymers, and this problem has not been studied to a large extent until now. The formation of the interface is closely related to the factors such as substrate pretreatment, the electroless plating process and the adsorption of ions. The interface has an irregular and self-similar microstructure, fractal theory can well analyze its intrinsic fractal characteristics. Based on the three-dimensional rough interface, the fractal characteristics of six two-dimensional cross-sections were identified. The fractal dimension, relative error, correlation coefficient and scale-free interval obtained by these six methods were quantitatively compared. The interfacial morphological characteristics of the ion-activated polymer were analyzed experimentally and the optimal fractal dimension calculation method was determined. A fractal contact model of the ionic electroactive polymer was developed and the calculation of the peel strength of the interface was proposed. The results show that RMSM is a feasible and effective method for the fractal characterization of the profiles of ionically electroactive polymers. The interfacial contact model based on fractal features can effectively characterize the peeling strength of the interface, which can provide a reference for later microscopic fractal studies on the theories of mass transfer process, actuation deformation and ion migration.

Supercritical carbon dioxide-assisted gold metallization of 3D-printed structure and the tensile strength

Gold metallization of 3D printed polymer structures was conducted by a supercritical carbon dioxide (sc-CO2) assisted electroless plating process. Precursor of the Pd catalyst utilized in this study was palladium bis-hexafluoroacetylacetonate for the high solubility in sc-CO2. A Ni–P layer was first formed on the catalyzed polymer structure as a sacrificial layer for the sequential gold deposition. Electrical resistance of the gold metallized 3D printed structure was 0.15 Ω and slightly increased to 0.18 Ω after a tape adhesion test. The fracture strength was 47.6 MPa for the sample with 45 min of the gold deposition time.Graphical abstract

Electroless Deposition of Silver onto Silica Nanoparticles to Produce Lipophilic Core-Shell Nanoparticles

HypothesisThe colloidal stability of noble metal nanoparticles can be tuned for solvents of varying hydrophobicity by modifying the surface chemistry of the particles with different capping agent architectures. Challenges arise when attempting to separately control multiple nanoparticle properties due to the interdependence of this adsorption process on the surface chemistry and metal architecture. A surfactant-mediated, templated synthesis strategy should decouple control over size and stability to produce lipophilic nanoparticles from aqueous reagents. ExperimentsA modified electroless plating process that produces oil-dispersible core–shell silver-silica nanoparticles is presented. Amine-terminated alkanes are utilized as the capping agents to generate lipophilic surface coatings and the particles are temporarily stabilized during the synthesis by adding a Pluronic surfactant that enhances dispersibility in the aqueous reaction medium. The evolution of shell morphology, composition, and colloidal stability was analyzed against capping agent architecture and concentration. The role of particle shape was also tested by interchanging the template geometry. FindingsThe capping agents installed on the silver shell surface displayed both colloidal stability enhancements and a minimum effective capping concentration that is a function of molecular weight without influencing the shell composition. Particle geometry can be controlled by interchanging the silica template size and shape.

An impact on mechanical properties of a Ni-P coated bamboo fibre / nano TiO2 reinforced polyester matrix composite

ABSTRACT Natural fibre-reinforced polymer composites have been most widely used in automotive, aerospace, and structural products in recent years. The synthesis and analysis of mechanical properties of bamboo fibre with polyester matrix nanocomposites produced with titanium oxide nanoparticles are the focus of this research. The electroless plating process was used to prepare bamboo fibre samples that were both uncoated and coated with nickel-phosphorus. These properties were studied both without coating and with coated bamboo fibre content of 4.5, 9, 13.5, and 18 wt. % and nanoparticle weight content of 0.5, 1, 1.5, and 2%. The x-ray diffractometer, field emission scanning electron microscope, and transmission electron microscope were used to investigate the structural and morphological characteristics of polyester matrix composites. Coated bamboo fibre with 13.5 wt.% and 1.5 wt.% titanium oxide. As a result, it can be concluded that the mechanical properties of a polyester matrix-reinforced coated bamboo fibre with nanoparticles have excellent bonding when compared to those of a polyester matrix-reinforced nanocomposite without coated bamboo fibre.

Enhancement of catalytic properties and durability in Ni–B–P/Ni foam for hydrazine electrooxidation

Hydrazine is a promising energy carrier of high power density, high theoretical cell voltage, and zero carbon emission to replace fossil fuel-dominated energy sources. Herein, we present a new Ni–B–P/NF catalyst for hydrazine electrooxidation by a facile electroless plating process. The Ni–B–P/NF catalyst exhibits remarkable catalytic activity (290 mA cm−2 at 0.3 V) by combining merits of high intrinsic activity, large specific surface area, satisfactory conductivity, and lattice dislocation. Meanwhile, the Ni–B–P/NF catalyst provides excellent long-term durability (5000 s, 94.4%), which is at the leading level among the reported Ni-based electrocatalysts for hydrazine electrooxidation to date. It is found that the phosphorus-containing coating and its tight binding to the substrate contribute to the long-term durability of Ni–B–P/NF. XPS results and electron models are used to elucidate the electron transition mechanism of the Ni–B–P coating. This work presents a novel catalyst for hydrazine electrooxidation and demonstrates its promising application in energy storage and fuel cell systems.

Hollow porous Ni@SiC nanospheres for enhancing electromagnetic wave absorption

Multi-component and a large number of non-homogeneous interface absorbers have been proven to be the preferred choice of electromagnetic wave (EMW) absorption materials. Herein, hollow porous Ni@SiC nanospheres (HPNS) were successfully constructed by combining a carbothermal reduction preparation strategy and subsequent electroless plating process. The heterogeneous dielectric/magnetic multi-component benefit to excellent EMW absorption properties through forming multiple polarizations, dielectric loss, and magnetic loss effects. Particularly, the HPNS at the optimal ratio with a low filler loading of 20 wt% exhibits the minimum reflection loss (RLmin) value of −62.39 dB at 13.28 GHz and the maximum effective absorption bandwidth (EABmax) is up to 5.36 GHz (12.64–18 GHz), and the corresponding thin matching thicknesses are 1.96 mm and 1.80 mm, respectively. Furthermore, the maximum radar cross section (RCS) reduction of HPNS over PEC reaches 26.02 dB m2 (1.96 mm) under far-field conditions, which means that the prepared HPNS is extraordinarily promising for practical applications. This work guides the preparation of high-performance EMW absorbers as well as radar stealth materials.

Thermal and Mechanical Properties of Cu-Graphite Composites with Spatial Anisotropy

In the present study, we analyzed the thermal and mechanical properties of Cu-graphite composites (CGCs) with spatially anisotropic graphite layers. These composites were fabricated using a combination of electroless plating and spark plasma sintering (SPS) processes. Thermal conductivities and thermal expansion coefficients of the composites were measured using differential thermal analysis (DTA) and a laser flash method. In particular, the thermal expansion coefficients of the composites were investigated by comparative analysis, which was conducted by processing prototypes in a vertical direction with a parallel sector in the direction of the upper and lower axial pressure. The Cu reinforced with the graphite flake showed better thermal properties compared to the graphite fiber, while the graphite fiber led to better mechanical properties. This investigation was conducted to better understand the dependence of thermal properties on the morphologies of the graphite layers (i.e., flake and fiber types) in the Cu matrix. The bending strength and friction coefficient of the composites were also investigated. Taken together, the results from this work offer fruitful, yet practical information to utilize the CGCs as a thermal management material, essential for electric and electronic devices.

Effect of Co-Coated Al2O3 Composite Powders on LPBF-Manufactured CoCrMo Alloy

In this study, we systematically examined the influence mechanisms of introduced cobalt coated alumina (Co-coated Al2O3) particles on the microstructure and properties of cobalt-chromium-molybdenum (CoCrMo) alloy printed by Laser Powder Bed Fusion (LPBF). The Co-coated Al2O3 composite powders with different density of cobalt coating were prepared by varying Al2O3 load from 1 g/150 mL to 2 g/150 mL during the electroless plating process. Then they were mixed with CoCrMo powders in the proportion of 1 wt.% and formed standard samples by LPBF technology. The results showed that the addition of Co-coated Al2O3 particles improved the friction performance of CoCrMo alloys significantly. The wear depth of CCM@2Al2O3 was only 2.18 μm and the wear volume of it was about 10% of pure CoCrMo alloy. The CoCrMo alloy introduced the Co-coated Al2O3 particles with a 1 g/150 mL Al2O3 load formed metal-ceramic bonding interface, which solved the problem of poor wettability between Al2O3 and matrix in LPBF process. Such CoCrMo alloy exhibited excellent tensile properties and the mean microhardness of it reached 379.9 ± 3.5 HV0.5.

Study on corrosion behavior of Ni–P/Ni–Cu–P superhydrophobic composite coatings preparation on L360 steel by two-step method

The two-step process of electroless plating and electrodeposition was used to successfully prepare a bilayer composite film by electroplating a Ni–Cu–P film with hydrophobic properties on the Ni–P film. The histological features of the two membrane layers were compared. The L360 pipeline steel, Ni–P coating and Ni–Cu–P composite film were evaluated by electrochemical test and erosion corrosion method. Under simulated seawater conditions, the material properties changed before and after different periods of service. The experimental results show that the introduction of Cu can inhibit the growth of cellular structures on the surface of the coating, increase the number of nucleation points, and improve the microstructure of the coating during the deposition of Ni–Cu–P films. The Ni–P/Ni–Cu–P bilayer composite film has a pinecone-like convex structure, which can greatly reduce the surface energy of the film layer and endow the film layer with hydrophobicity. At the same time, it effectively resists the adsorption of water and other external impurities on its surface, and has good anti-fouling performance, thereby slowing down the surface corrosion and improving corrosion resistance. In addition, copper enables the composite coating to have passivation and a uniform and dense coating structure, which is the main reason for the improvement of the corrosion protection performance of the composite coating. The protective effect of the coating can effectively improve the electrochemical resistance and erosion resistance of L360. The Ni–P/Ni–Cu–P bilayer composite film reduces the electrochemical corrosion rate of the substrate from 0.417mmpY to 0.025mmpY, and the scouring weight loss rate of the film decreases to 0.05% of the substrate.

Hybrid additive manufacturing based on vat photopolymerization and laser-activated selective metallization for three-dimensional conformal electronics

Hybrid additive manufacturing technology (HAM) is a great advance of traditional additive manufacturing (AM) processes which enables the direct fabrication of full-functional end-use products rather than individual parts. Three-dimensional (3D) printed electronics is a representative product of HAM that could meet customized functional requirements of the industrial community such as consumer electronics, communication engineering, and automobile and aerospace industries. Herein, we propose a novel HAM technology that combines vat photopolymerization (VPP) 3D printing and the laser-activated electroless plating (ELP) process to fabricate conformal 3D printed electronics. A novel functional liquid photopolymer doped with 3 wt% of antimony tin oxide (ATO) and 1 wt% of titania (TiO2) nanoparticles is developed for this HAM technology. The 3D substrate can be successfully fabricated layer-by-layer with this functional photopolymer by a commercial desktop VPP 3D printer. A near-infrared (NIR) laser system selectively activates the surface of the 3D substrate and induces the SnII seeds for ELP. For 4-hour ELP, the thickness of plated copper layer approaches 11 µm and the electrical conductivity reaches 5.2 × 107 S/m which is close to pure copper (5.8 ×107 S/m). Finally, a selectively copper plated university badge is prepared to demonstrate the fabrication accuracy of the HAM technology, and a 3D conformal light-emitting diode (LED) circuit board is also developed to verify the feasibility of this HAM technology for customizing full-functional electronic products.

Enhanced microwave absorption properties of Ni decorated flaky graphite powders with frequency selective surfaces incorporation

Reasonable design of composition and structure is an effective way to improve microwave absorption performance of absorber. In this study, flaky Ni@Graphite composite powders containing various Ni contents were successfully fabricated through a facile electroless plating process. The phase compositions and microstructure of the composite powders were characterized. XRD and SEM results showed that the Ni particles are successfully reduced from the solution and anchored on the flaky Graphite. The electromagnetic and microwave absorption properties of the Ni@Graphite composite powders were also studied. The results illustrated that although the composite powders with 45 % Ni owned the minimum reflection loss (RLmin) of −18 dB, the maximum effective absorption bandwidth (EABmax) was only 1.1 GHz for the sample with 2.0 mm thickness. So periodic frequency selective surfaces (FSS) were designed to further improve the microwave absorption performance. As the structural parameters of the FSS were C= 14 mm, T1 = 1.78 mm, e= 1.18 mm, R= 1.86 mm and a= 1.6 mm, the optimized RLmin and EABmax of the Ni@Graphite powders were −19.27 dB and 3.2 GHz, respectively. It was worth noting that the strategy of balancing the electromagnetic properties of dual-loss composites by controlling the composition and structure can effectively improve microwave absorption performance. This work contributes to the development of high-performance Ni@Graphite microwave absorption materials.

Optimization of electromagnetic wave absorption properties of CoNi/MoSe2 composites with 3D flower-like by controlling the Co/Ni molar ratio

Developing composite materials with a rational composition structure has been a critical strategy to obtain superior electromagnetic (EM) wave absorption materials. CoNi/MoSe2 composites were synthesized by a two-step method in this work. Firstly, the flower-like MoSe2 was synthesized by hydrothermal method, and then the CoNi alloy was loaded on the MoSe2 surface by an electroless plating method. It is worth noting that in this paper, PdCl2 was not used for activation during the electroless plating process, and the flower-like structure of MoSe2 was not destroyed. In order to investigate the effect of different Co/Ni molar ratios on the absorption performance of the CoNi/MoSe2 composites, three samples with Co to Ni molar ratios of 1:3, 1:1, 3:1 and two other samples with only one metal (Ni or Co) were prepared. The analysis results show that the minimum reflection loss(RL) value of Ni/MoSe2 is −18.01 dB and the maximum effective absorption bandwidth(EAB) of Co/MoSe2 is 2.16 GHz. In comparison, the CoNi/MoSe2 composite exhibits the best EM wave absorption performance when the Co/Ni ratio is 1:3, and the minimum RL can reach −48.6 dB at a matching thickness of only 1.8 mm. And when the matching thickness is 1.4 mm, the broadest EAB is 3.76 GHz. Therefore, this work provides a new research idea for the design of broadband and efficient EM wave absorbers.

A CMOS Multi-Electrode Array for Four-Electrode Bioimpedance Measurements.

This work demonstrates how a multi-electrode array (MEA) dedicated to four-electrode bioimpedance measurements can be implemented on a complementary metal-oxide-semiconductor (CMOS) chip. As a proof of concept, an 8 × 8 pixel array along with dedicated amplifiers was designed and fabricated in the TSMC 180 nm process. Each pixel in the array contains a circular current carrying (CC) electrode that can act as a current source or sink. In order to measure a differential voltage between the pixels, each CC electrode is surrounded by a ring shaped pick up (PU) electrode. The differential voltages can be measured by an on-board instrumentation amplifier, while the currents can be measured with an on-bard transimpedance amplifier. Openings in the passivation layer exposed the aluminum top metal layer, and a metal stack of zinc, nickel and gold was deposited in an electroless plating process. The chips were then wire bonded to a ceramic package and prepared for wet experiments by encapsulating the bonding wires and pads in the photoresist SU-8. Measurements in liquids with different conductivities were performed to demonstrate the functionality of the chip.

Wire-grid polarizer sheet with low reflectance in the visible and near-infrared regions fabricated by a nanoimprinting and electroless plating process.

In near-infrared systems for optical sensing and imaging technologies, an improved signal-to-noise ratio and more advanced object detection and analysis using polarizers are required. Such polarizers are limited, and broadband wire-grid polarizers are potential candidates. However, their high reflectivity and high cost limit their application. Herein, we fabricated a low-reflectivity wire-grid polarizer sheet that can be used in visible and near-infrared regions by a simple process using only nanoimprinting and nickel electroless plating; further, metal removal steps such as chemical mechanical polishing were not required. The results obtained by optimizing the structural shape of the mold and precisely controlling the thickness of the electroless plating confirmed that the polarizer could be used for visible and near-infrared light. Because the sheets can be manufactured using general-purpose equipment upon mold preparation, they can be employed in wide-ranging applications with small capital investment.

A reliable method by utilizing thermo-responsive palladium nanocomposite for fabricating Nickel coating on nylon 6 fabrics

Flexible conductive textiles are one of the best choices for smart textiles due to their comfortable wearing and good compliance with the human body. The great adhesion and durability of metal coatings onto substrate surfaces are important indicators for the high-performance requirements of smart textiles. The main bottleneck for the development of flexible conductive textiles is the poor adhesion between the metal coating and the substrate, so efforts have been made to improve it on a variety of fabrics. Herein, we reported a facile and economical method to fabricate flexible conductive fabrics using commercial nylon 6 fabrics as substrates. In brief, Styrene-co-N-Isopropylacrylamide/Pd (St-co-NIPAAm/Pd) nanocomposites acted as activators and adhesive interlayers for electroless plating to improve the adhesion of the nickel layer onto the nylon 6 surface. A highly conductive nylon 6 fabric was prepared by a coating of St-co-NIPAAm/Pd nanocomposite and followed by Ni-P electroless plating. The optimal electroless plating process parameters for fabricating adhesion-enhanced and highly reliable nickel coating were also investigated in the study. Its reliable conductivity and high durability mean it is promising for smart textiles, even via a series of repeated bending and washing tests. In addition, we explain the mechanism by which St-co-NIPAAm/Pd nanocomposites change at a temperature below or beyond the lower critical solution temperature (LCST). To sum up, the developed conductive nylon 6 fabric can lay the groundwork for the subsequent development of smart textiles.

D-Band Waveguide Diplexer Fabricated Using Micro Laser Sintering

We report a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$ </tex-math></inline-formula> -band waveguide diplexer, with two passbands of 130–134 and 151.5–155.5 GHz, fabricated using micro laser sintering (MLS) additive manufacturing with stainless steel. This is the first demonstration of metal 3-D printing technology for multiport filtering devices at a sub-terahertz (THz) frequency. For comparison, the same diplexer design has also been implemented using computer numerical controlled (CNC) milling. The diplexer, designed using coupling matrix theory, employs an all-resonator and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -plane split-block structure. The two channels are folded for compactness. A staircase coupled structure is used in one channel to increase the isolation performance. The printed waveguide flanges are modified to adapt to the limited printing volume from the MLS. Effects of fabrication tolerance on the diplexer are investigated. An effective and unconventional electroless plating process is developed. The measured average insertion losses of the gold-coated diplexer are 1.31 and 1.37 dB, respectively. The respective frequency shifts from design values are 0.92% and 1.1%, and bandwidth variations are 4% and 15%. From a comprehensive treatment of the end-to-end manufacturing process, the work demonstrates MLS to be a promising fabrication technique for complex waveguide devices at a sub-THz frequency range.

Conducting and stretchable emulsion styrene butadiene rubber composites using SiO2@Ag core-shell particles and polydopamine coated carbon nanotubes

In the present scenario of development in technology, the applications of stretchable conductive elastomers in modern electronic equipments have aroused great interest. Non-covalent bonding modification of carbon nanotubes (CNTs) using dopamine has improved the dispersion of CNT@PDA and interfacial interaction with the rubber matrix. The SiO2@Ag core-shell particles were prepared by coated with silver nanoparticles (AgNPs) on the surface of SiO2 using dopamine oxidation self-polymerization and electroless plating process. ESBR composites were prepared by latex co-coagulation method, where CNT@PDA and SiO2@Ag were used to develop an 1D-3D synergistic conductive network in ESBR composites. One-dimensional (1D) CNT@PDA were incorporated in three-dimensional (3D) spherical SiO2@Ag core-shell particles, which effectively prevented the agglomeration of SiO2@Ag and CNT@PDA. Again, 1D CNT@PDA could also be used as bridges to interact with 3D SiO2@Ag to develop the charge transfer more effectively in ESBR composites. The optimum electrical conductivity of the ESBR/CNT@PDA/SiO2@Ag composites was 0.2 S/cm, which was found to be higher than that of single filler. Moreover, the high electrical conductivity can be controlled at low tensile strain. The mechanical property of ESBR/CNT@PDA/SiO2@Ag composite was also improved by 105.4% as compared by ESBR/CNTs. This work provides a new idea for the fabrication of stretchable conductive elastomer composites with high performance.