Ultrasound influence on the activation step before electroless coating

This paper is devoted to the electroless plating of non-conductive substrates under ultrasound at 530 kHz. The ultrasonic irradiation is applied to the activation and to the plating steps. Effects are measured by following the final copper thickness obtained in 1 h of plating time, easily correlated to the average plating rate. It appears that ultrasound has a strong influence on the plating rates enhancement, and assumptions can be made that this increase could be linked to the catalyst cleaning. This is confirmed by XPS measurements.     

Studies on the influence of surface pre-treatments on electroless copper coating of boron carbide particles

Boron carbide is one of the hard ceramic particles which find application as structural materials and neutron shielding material due to its high neutron capture cross section. Copper coating on boron carbide particle is essential for the synthesis of metal-ceramic composites with enhanced sinterability and dispersibility. Surface characteristics of the substrate and the coating parameters play a foremost role in the formation of effective electroless coating. The effect of surface pre-treatment conditions and pH on electroless copper coating of boron carbide particles has been studied. Surface pre-treatement of B₄C when compared to acid treated and alkali treated particles were carried out. Uniform copper coating was observed at pH 12 in alkali treated particles when compared to others due to the effective removal of inevitable impurities during the production and processing of commercially available B₄C. A threshold pH 11 was required for initiation of copper coating on boron carbide particles. The growth pattern of the copper coating also varies depending on the surface conditions from acicular to spherical morphology.     

Synthesis and characterization of copper ink and direct printing of copper patterns by inkjet printing for electronic devices

Among the conventional metallic inks used in the printing process, silver exhibits high conductivity and thermal stability. Nevertheless, due to the high cost of silver, it cannot be extensively used for the fabrication of inks. As a competitive alternative, copper can be considered as a substitute for silver; however, copper ink oxidizes under certain atmospheric conditions. To meet these shortcomings, a cost effective, highly conductive, and oxidation-free copper-based ink has been synthesized in this study, wherein, oxidation of the copper particles in the copper-based ink was prevented by using copper complexes. The copper ink thus fabricated was printed on chemically treated Si/SiO₂ substrates followed by the characterization of the printed copper films. The results of this study confirmed that the synthesized copper ink exhibited properties suitable for its use in the inkjet printing process for fabrication of various electronic devices.     

空腔铜靶的化学镀制研究

 介绍了在预处理芯轴(聚甲基丙烯酸甲酯)表面采用化学镀的方法制备铜空腔的技术,研究了镀液中硫酸铜含量、甲醛含量,镀液pH值、温度等对化学镀铜沉积速率和溶液稳定性的影响。根据实验确定了适宜的化学镀铜工艺规范：硫酸铜质量浓度10~20 g/L,TART·K·Na质量浓度10~30 g/L,EDTA·2Na质量浓度10~28 g/L,甲醛体积浓度10~25 mL/L,添加剂质量浓度10 mg/L,pH值12~13,温度35~65 ℃。通过该工艺制备出的镀层厚度达到10～25 μm,均匀性达到95%,表面无砂眼、裂纹等缺陷,刻蚀芯轴后空腔能自持。该方法为ICF研究制备金属或合金材料靶提供了新的途径。     

Comparative study of electroless copper deposition based on the seed layers of Pd, PtPd and AuPd

The article reports on electroless deposition of copper films onto p-silicon (1 0 0) using different seed (co-seed) layers of Pd, PtPd and AuPd. The dependence of the compositions and morphologies of different seed layers on resultant Cu films were comparatively studied in detail by atomic force microscopy (AFM), field emission scanning electron microscope (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The activities of electroless copper deposition on the p-silicon (1 0 0) with different seed (co-seed) layers were evaluated by polarization curve. It is concluded that the bimetallic AuPd seed displayed the highest catalytic activity for electroless copper deposition, and followed by the order of PtPd > Pd.     

Improvement of copper plating adhesion on silane modified PET film by ultrasonic-assisted electroless deposition

Copper thin film on silane modified poly(ethylene terephthalate) (PET) substrate was fabricated by ultrasonic-assisted electroless deposition. The composition and topography of copper plating PET films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Peel adhesion strength, as high as 16.7 N/cm, was achieved for the planting copper layer to the modified PET substrate with ultrasonic-assisted deposition; however, a relative low value as 11.9 N/cm was obtained for the sample without ultrasonic vibration by the same measurement. The electrical conductivity of Cu film was changed from 7.9 × 10⁴ to 2.1 × 10⁵ S/cm by using ultrasonic technique. Ultrasonic operation has the significant merits of fast deposition and formation of good membranes for electroless deposition of Cu on PET film.     

Microwave-assisted activation for electroless nickel plating on PMMA microspheres

A novel microwave-assisted activation method for electroless plating on PMMA microspheres is presented in this study. When the microwave irradiation was applied during the activation step, the amount of the Pd species adsorbed on PMMA surfaces was much higher than that of sample pretreated with a conventional activation process without microwave irradiation. With this activation method, it was also shown that the adsorbed Pd species with a size of 4-6 nm were uniformly distributed on the surfaces of the PMMA microspheres, thus a smooth and uniform nickel-phosphorus coating on the PMMA microspheres was obtained by subsequent electroless plating. The samples after each step were characterized by XPS, TEM, ICP and SEM.     

Fabrication and electrical properties of metal-coated acrylate rubber microspheres by electroless plating

Electroless copper plating on micron-scale acrylate rubber (ACM) microspheres was studied. The core-shell structured Cu-coated ACM microspheres with high conductivity and low density were fabricated by introducing a reaction control method. Via multi-times activating treatment, the acrylate rubber (ACM) microspheres were implanted with more Ag catalytic active centers on the surfaces to promote the formation of coatings. The surface-coating structures and the electrical properties of Cu-coated ACM microspheres were investigated. It was found that the Cu-coated ACM microspheres were a kind of elastic particles. The different coating structures could be produced by controlling the extent of plating reaction. The coated microspheres with different coating structures were conductive, and their volume resistivities decreased remarkably with the increasing of applied pressure and varied with the temperature according to their surface coating structures.     

A novel process for electroless nickel plating on anodized magnesium alloy

In this paper, a novel palladium-free activation electroless nickel (EN) plating process, by which a TiB₂ powders contained intermediate film was used as catalyst, was introduced for anodized magnesium alloy AZ91D. The corrosion behavior of AZ91D without and with coating was compared and the bonding strength of the EN plating to the substrate was also measured. The results showed that the EN plating could easily take place on the intermediate catalytic layer, directly on which a smooth and compact Ni–P alloy layer without obvious flaws, about 20 μm thickness, was successfully deposited. The catalytic function was principally from TiB₂ powder. The adhesive tensile test indicated a good bonding strength of about 11 MPa between the substrate and the catalytic layer. An obvious passivation range and higher E_corr (−0.323 V) for the EN plating during anodic polarization in 3.5 wt.% NaCl solution, implied a typical character of a compact Ni–P alloy layer, with an effective protection for the substrate.     

Experimental study of the voids in the electroless copper deposits and the direct measurement of the void fraction based on the scanning electron microscopy images

Electroless copper deposits were plated on epoxy substrates in various plating solutions at either a high operating temperature (60 °C) or a low one (45 °C). Cross section samples were made using epoxy resin cured in room temperature, and then ground, polished and over-etched. The scanning electron microscopy (SEM) images of the over-etched cross section samples show voids in low temperature deposits and solid structure in high temperature ones. The surface morphology images also indicated such structures in low temperature samples. The SEM image of the cross section of a stand-alone deposit prepared on stainless steel substrate shows similar voids observed on etched cross section samples on epoxy board substrates. An image processing program was written using MATLAB to identify the voids in the over-etched cross sections of the deposits from low temperature solutions and thus the void fraction can be directly measured and compared with the previously published simulation results.     

Improved synthesis of aluminium nanoparticles using ultrasound assisted approach and subsequent dispersion studies in di-octyl adipate

The present work reports on an efficient and simple one pot synthetic approach for aluminium nanoflakes and nanoparticles based on the intensification using ultrasound and provides a comparison with the conventional approach to establish the cutting edge process benefits. In situ passivation of aluminium particles with oleic acid was used as the method of synthesis in both the conventional and ultrasound assisted approaches. The aluminium nanoflakes prepared using the ultrasound assisted approach were subsequently dispersed in di-octyl adipate (DOA) and it was demonstrated that a stable dispersion of aluminium nanoflakes into di-octyl adipate (DOA) is achieved. The morphology of the synthesized material was established using the transmission electron microscopy (TEM) analysis and energy dispersive X-ray analysis (EDX) and the obtained results confirmed the metal state and nano size range of the obtained aluminium nanoflakes and particles. The stability of the aluminium nanoflakes obtained using ultrasound assisted approach and nanoparticles using conventional approach were characterized using the zeta potential analysis and the obtained values were in the range of −50 to +50 mV and −100 to +30 mV respectively. The obtained samples from both the approaches were also characterized using X-ray diffraction (XRD) and particle size analysis (PSA) to establish the crystallite size and particle distribution. It was observed that the particle size of the aluminium nanoflakes obtained using ultrasound assisted approach was in the range of 7–11 nm whereas the size of aluminium nanoparticles obtained using conventional approach was much higher in the range of 1000–3000 nm. Overall it was demonstrated that the aluminium nanoflakes obtained using the ultrasound assisted approach showed excellent morphological characteristics and dispersion stability in DOA showing promise for the high energy applications.     

Ultrasound assisted cyanotoxin extraction for nematode inhibition in soil

Root-knot nematodes are one of the plant damaging nematodes in agriculture causing a projected annual yield loss of ∼12 % (∼$160 billion) worldwide. Conventional solutions to control these plant-parasitic nematodes involve chemical nematicides. To reduce the use of harmful chemicals, microalgal extracts can be used as greener alternatives for nematode management. Microalgae produce valuable metabolites, including cyanotoxins which can aid in nematode suppression.In this study, two microalgae species, Trichormus variabilis and Nostoc punctiforme, were treated with ultrasound for intensified recovery of secondary metabolites. Ultrasound results in cell wall disruption of the microalgal species, thus resulting in enhanced release of secondary metabolites. Microalgal biomass was treated with an ultrasound probe at 50 % amplitude, 20 kHz frequency, using water as the extraction medium, for 5–30 min. The extraction efficiency was determined in terms of the total chlorophyll (Chl) content of the extract. Microscopic images of the treated cells were also investigated to gain insight into the effect of the ultrasonication time on the cell morphology. Our results suggest that ultrasonication resulted in the intensified release of secondary metabolites, as established through the total chlorophyll content of the ultrasonicated microalgal samples as well as the microscopic images of the ruptured cells. The best extraction for Trichormus variabilis was achieved with 15 min extraction time where the Total Chl content increased by 29 times (compared to the non-ultrasonicated sample), and for the Nostoc punctiforme, 30 min extraction time gave the highest metabolite recovery of 6.4 times higher than the non-ultrasonicated sample.Ultrasonicated algal extracts were then tested for their nematicidal potential against root-knot nematode, Meloidogyne hapla, in infested field soil samples. Experimental study was conducted using different concentrations of each microalga, Trichormus sp. and Nostoc sp., individually, as well as in combination. The nematode count for the treated soil was compared with that of the control (untreated soil). Ultrasonicated microalgal extracts showed 66% to 100% inhibition on root-knot nematodes in the soil samples tested.     

Development of copper coatings on ceramic powder by electroless technique

Electroless (EL) coating technique is one of the elegant ways of coating by controlling the temperature and pH of the coating bath in which there is no usage of electric current. EL nano-copper coating on ceramic particles of micron size is not reported. In this investigation, ceramic powders of ∼100 μm size have been coated with copper by EL technique in the pH and temperature ranges of 12-13.5 and 60-85 °C, respectively. The optimization of EL copper bath has been evaluated through the combination of process parameters like pH and temperature. The optimized value of pH is found to be 12.5 and temperature as 75 °C. The coated and uncoated powders have been subjected to microstructural studies by scanning electron microscope (SEM) and the phases present have been analyzed by X-ray diffraction. An attempt has been made to understand the bonding mechanism of coating. The adherence with the substrate is attributed to the chemical and mechanical bonding at the interface. A model has been suggested for the mechanical bonding effect at the interface.     

Effect of temperature and silicon resistivity on the elaboration of silicon nanowires by electroless etching

The morphology of silicon nanowire (SiNW) layers formed by Ag-assisted electroless etching in HF/H₂O₂ solution was studied. Prior to the etching, the Ag nanoparticles were deposited on p-type Si(1 0 0) wafers by electroless metal deposition (EMD) in HF/AgNO₃ solution at room temperature. The effect of etching temperature and silicon resistivity on the formation process of nanowires was studied. The secondary ion mass spectra (SIMS) technique is used to study the penetration of silver in the etched layers. The morphology of etched layers was investigated by scanning electron microscope (SEM).     

Effect of catalytic graphitization on the electric heating performance of electroless nickel-coated carbon fibers

Graphite possesses several desirable properties, which facilitate its applications in several materials. However, the applications of graphitic materials depend on the extent of graphitization. Generally, the heat treatment of carbon is carried out at temperatures above 3000 °C. However, in this study, the catalytic graphitization of carbon fiber (CF) with an electroless Ni–P coating was studied at low temperature. The surface morphology and structural, thermal, and electrical properties of CF with and without electroless Ni–P coating were characterized through scanning electron microscopy, X-ray diffraction, Raman spectroscopy, infrared thermal imaging, and four-probe volume resistivity testing. The results showed that the catalytic graphitization of CF considerably improved at relatively low temperatures when a Ni–P coating was present. Moreover, when the average P content was 15.88 wt%, the degree of catalytic graphitization of Ni–P-coated CF markedly increased with heat treatment at 600 °C.     

Ultrasound assisted three phase partitioning of a fibrinolytic enzyme

The present investigation is aimed at ultrasound assisted three phase partitioning (UATPP) of a fibrinolytic enzyme from Bacillus sphaericus MTCC 3672. Three phase partitioning integrates the concentration and partial purification step of downstream processing of a biomolecule. Three phase system is formed with simultaneous addition of ammonium sulfate to crude broth and followed by t-butanol. UATPP of a fibrinolytic enzyme was studied by varying different process parameters such as ammonium sulfate saturation concentration, pH, broth to t-butanol ratio, temperature, ultrasound frequency, ultrasonication power, and duty cycle. The optimized parameters yielding maximum purity of 16.15-fold of fibrinolytic enzyme with 65% recovery comprised of 80% ammonium sulfate saturation, pH 9, temperature 30 °C, broth to t-butanol ratio 0.5 (v/v), at 25 kHz frequency and 150 W ultrasonication power with 40% duty cycle for 5 min irradiation time. SDS PAGE analysis of partitioned enzyme shows partial purification with a molecular weight in the range of 55–70 kDa. Enhanced mass transfer of UATPP resulted in higher fold purity of fibrinolytic enzyme with reduced time of operation from 1 h to 5 min as compared to conventional TPP. Outcome of our findings highlighted the use of UATPP as an efficient biosepartion technique.     

Electroless plating of copper on surface-modified glass substrate

This work focuses on developing a novel convenient method for electroless copper deposition on glass material. This method is relied on the formation of amino (NH₂)-terminated film on the surface of glass substrate, by coating polyethylenimine (PEI) on glass matrix and using epichlorohydrin (ECH) as cross-linking agent. The introduced amino groups can effectively adsorb the palladium, the catalysts which could initiate the subsequent Cu electroless plating, onto the glass substrate surface. Finally, a copper film is formed on the palladium-activated glass substrate through copper electroless plating and the surface-coppered glass material is therefore acquired. X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscopy (SEM) images combined with energy diffraction X-ray (EDX) analysis demonstrate the successful copper deposition on the surface of glass substrate.     

Ultrasound assisted synthesis of amide functionalized metal-organic framework for nitroaromatic sensing

Nano plates of zinc(II) based metal-organic framework (MOF) were prepared via ultrasonic method without any surfactants at room temperature and atmospheric pressure. Control of particle size and morphology was enhanced in this synthesis method. Nano plates of an interpenetrated amide-functionalized metal-organic framework, [Zn₂(oba)₂(bpfb)]·(DMF)₅, TMU-23, (H₂oba = 4,4′-oxybis(benzoic acid); bpfb = N,N′-bis-(4-pyridylformamide)-1,4-benzenediamine, DMF = N,N-dimethyl formamide), was synthesized under ultrasound irradiation in different concentrations of initial precursor. The nano structure and morphology of the synthesized MOF were characterized by Field Emission Scanning Electron Microscopy (FE-SEM), powder X-ray diffraction, thermo gravimetric analysis (TGA), elemental analysis and FTIR spectroscopy. Moreover, Fluorescence emissions of nanoplates have been studied. Amide-functionalized MOF shows high selectivity for sensing of nitroaromatic compounds such as nitrophenol, nitroaniline, and nitrobenzene in acetonitrile solution. Fluorescence intensity decreased with increasing contents of nitroaromatics in acetonitrile solution due to fluorescence quenching effect.     

Ultrasound assisted modulation of yeast growth and inactivation kinetics

The yeast Saccharomyces cerevisiae is well known for its application in the food industry for the purpose of developing fermented food. The ultrasound (US) technology offer a wide range of applications for the food industry, including the enhancement of fermentation rates and inactivation of microbial cells. However, a better understanding and standardization of this technology is still required to ensure the scaling-up process. This study investigated the effect of the US technology on the growth of S. cerevisiae using frequencies of 20, 25, 45 and 130 kHz, treatment periods from 2 to 30 min. Furthermore, yeast kinetics subjected to US treatments were evaluated using modelling tools and scanning electron microscopy (SEM) analysis to explore the impact of sonication on yeast cells. Yeast growth was monitored after different US treatments plotting optical density (OD) at 660 nm for 24 h at 30 ⁰C. Growth curves were fitted using models of modified Gompertz and Scale-Free which showed good parameters of the fit. In particular, US frequencies of 45 and 130 kHz did not have a disruptive effect in lag phase and growth rate of the yeast populations, unlike the frequency of 20 kHz. Moreover, inactivation curves of yeast cells obtained after exposure to 20 and 25 kHz also observed the best fit using the Weibull model. US frequency of 20 kHz achieved significant reductions of 1.3 log cfu/mL in yeast concentration and also induced important cell damage on the external structures of S. cerevisiae. In conclusion, the present study demonstrated the significant effect of applying different US frequencies on the yeast growth for potential application in the food industry.     

Ultrasound assisted chrome tanning: Towards a clean leather production technology

Nowadays, there is a growing demand for a cleaner, but still effective alternative for production processes like in the leather industry. Ultrasound (US) assisted processing of leather might be promising in this sense. In the present paper, the use of US in the conventional chrome tanning process has been studied at different pH, temperature, tanning time, chrome dose and US exposure time by exposing the skin before tanning and during tanning operation. Both prior exposure of the skin to US and US during tanning improves the chrome uptake and reduces the shrinkage significantly. Prior exposure of the skin to US increase the chrome uptake by 13.8% or reduces the chrome dose from 8% to 5% (% based on skin weight) and shorten the process time by half while US during tanning increases the chrome uptake by 28.5% or reduces the chrome dose from 8% to 4% (half) and the tanning time to one third compared to the control without US. Concomitantly, the resulting leather quality (measured as skin shrinkage) improved from 5.2% to 3.2% shrinkage in the skin exposed to US prior tanning and to 1.3% in the skin exposed to US during the tanning experiment. This study confirms that US chrome tanning is an effective and eco-friendly tanning process which can produce a better quality leather product in a shorter process time with a lower chromium dose.