Thermophoretic deposition of palladium aerosol nanoparticles for electroless micropatterning of copper

A method for catalytic activation was introduced by producing palladium aerosol nanoparticles via spark generation and then thermophoretically depositing the particles onto a flexible polyimide substrate through a hole in pattern mask, resulting in a line (24 μm in width) and a square (136 μm × 136 μm) patterns. After annealing, the catalytically activated substrate was placed into a solution for electroless copper deposition. Finally, copper micropatterns of a line (35 μm in width) and a square (165 μm × 165 μm) were formed only on the activated regions of the substrate. Both patterns had the height of 1.6 μm.     

Fabrication of a thin palladium membrane supported in a porous ceramic substrate by chemical vapor deposition

A thin, gas-tight palladium (Pd) membrane was prepared by the counter-diffusion chemical vapor deposition (CVD) process employing palladium chloride (PdCl₂) vapor and H₂ as Pd precursors. A disk-shaped, two-layer porous ceramic membrane consisting of a fine-pore γ-Al₂O₃ top layer and a coarse-pore -Al₂O₃ substrate was used as Pd membrane support. A 0.5–1 μm thick metallic membrane was deposited in the γ-Al₂O₃ top layer very close to its surface, as verified by XRD and SEM with a backscattered electron detector. The most important parameters that affected the CVD process were reaction temperature, reactants concentrations and top layer quality. Deposition of Pd in the γ-Al₂O₃ top layer resulted in a 100- to 1000-fold reduction in He permeance of the porous substrate. The H₂ permeation flux of these membranes was in the range 0.5–1.0 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ at 350–450°C. The H₂ permeation data suggest that surface reaction steps are rate-limiting for H₂ transport through such thin membranes in the temperature range studied.     

Catalytic effect of Pd nanoparticles on electroless copper deposition

This study elucidates the application of Pd nanoparticles as catalysts of electroless copper deposition and their catalytic effect on the deposition kinetics and microstructure in an electroless copper bath. Quartz crystal microgravimetry (QCM) and high-resolution field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDX) demonstrated that the kinetic changes associated with electroless copper deposition (ECD) comprised two stages—the incubation period and the acceleration period. In the incubation period, small copper particles were deposited. In the acceleration period, the ECD rate increased rapidly and continuously conducting films with large grains were formed. Leaner sweep voltammetry (LSV) and mixed potential theory (MPT) were applied to examine the catalytic powers of the prepared Pd nanoparticles and the related electrochemical kinetics in the ECD bath.     

Unsupported palladium alloy foil membranes fabricated by electroless plating

It is desirable to create thin (<25 μm), unsupported, defect-free palladium and palladium alloy foils in a cost-effective manner in order to study intrinsic material properties exclusive of support effects. We have developed a novel technique for producing unsupported palladium films by electroless plating upon mirror-finished stainless steel supports followed by mechanical removal. High quality pure palladium films as thin as 7.2 μm were produced. Single gas steady state permeation experiments were performed using hydrogen and nitrogen to examine permeability and selectivity. The pure palladium membranes showed hydrogen permeabilities comparable to cold-rolled unsupported foils, and high H₂/N₂ selectivity. Palladium-copper membranes were prepared by sequential electroless plating of copper onto palladium foils followed by in situ annealing. The annealing process produces films of desired composition with permeabilities comparable to those in the literature. The annealing process does not appear to produce defects in the film, and the membranes thus produced have performed 15 days without increased leak rates.     

XPS depth profile study of porous zirconia films deposited on stainless steel by spray pyrolysis: the problem of substrate corrosion

Zirconia (ZrO₂) films of tissue‐like structure and narrow pore size distribution have been deposited by spray pyrolysis using aqueous zirconyl chloride octahydrate (ZrOCl₂·8H₂O) precursor solutions. Stainless‐steel sheets, protected or unprotected by a ZnO barrier layer, have been used as the substrate material held at 473 K. The ZnO barrier layers have been deposited on the stainless steel held at 523 K by spray pyrolysis using a zinc acetate precursor. Their property of corrosion protection to stainless steel has been proved by electrochemical polarization measurements in 0.5 M NaCl solution. A complementary study of XPS (depth profiling, mapping) and x‐ray diffraction has shown that the unprotected steel substrates were corroded during ZrO₂ film post‐annealing in air at T ≥ 773 K, whereas steel substrates protected with a compact barrier layer of crystalline ZnO before ZrO₂ film deposition did not show surface corrosion even after annealing up to 997 K. Copyright © 2004 John Wiley & Sons, Ltd.     

Preparation of a palladium alloy composite membrane supported in a porous stainless steel by vacuum electrodeposition

Pinhole-free palladium/nickel (Pd/Ni) alloy membranes deposited on a porous stainless steel (SUS) support have been fabricated. The deposition was made by vacuum electrodeposition technique which could produce the alloy film less than 1 μm thick. This technique allows for the Pd/Ni alloy by employing Pd/Ni complex reagent, and typical Pd/Ni plating had compositions of 78% Pd and 22% Ni. In order to make the surface smooth and enhance the adhesive bond between the top layer and the substrate, a nascent porous SUS disk was treated sequently with submicron nickel powder and CuCN solution. The important parameters that can affect deposition were pore size, defects, and surface roughness of substrate. The membranes were characterized by permeation experiments with hydrogen and nitrogen at temperatures ranging from 623 to 823 K and pressures from 10.3 to 51.7 cmHg. The composite membranes prepared in this technique yielded excellent separation performance for hydrogen: hydrogen permeance of 5.79×10⁻² cm³/cm² cmHg s and hydrogen/nitrogen (H₂/N₂) selectivity was 4700 at 823 K.     

A novel method for the preparation of thin dense Pd membrane on macroporous stainless steel tube filter

Thin Pd membranes were in situ deposited on macroporous stainless steel (MPSS) tubes using an improved electroless plating method consisting of material filling in the substrate pores, Pd plating on the filled substrate, and recovery and activation of the substrate pores. The Pd/MPSS composite membranes resulted from the filling materials of both aluminum hydroxide gel and Pd/aluminum hydroxide gel have been studied in detail and compared with each other. The hydrogen permeation mechanism through both membranes may be controlled by surface reactions, while the hydrogen permeation flux and activation energy for the membrane resulted from Pd/aluminum hydroxide gel are higher than these for the membrane resulted from aluminum hydroxide gel. In the case of the former membrane, which is almost pinhole free, the hydrogen permeation flux is as high as 0.302 mol/(m² s) with a pressure difference of 100 kPa at 773 K. Good membrane stability is also proven by the unchanged membrane surface morphology, the steady hydrogen permeance, and the complete hydrogen selectivity. The deposition mechanism of the membrane has been proposed and interpreted in detail.     

High-performance collection of palladium ions in acidic media using nucleic-acid-base-immobilized porous hollow-fiber membranes

We prepared nucleic-acid-base-immobilized porous membranes of a hollow-fiber form with pore size, porosity, and thickness of 0.2 μm, 70%, and approximately 0.7 mm, respectively. Glycidyl methacrylate was graft-polymerized onto a polyethylene-made porous hollow-fiber membrane, followed by ring-opening of the epoxy group with the amino groups of adenine, guanine, and cytosine. The collection of palladium ions was achievable during the permeation of palladium chloride solution through the adenine-immobilized porous hollow-fiber membrane. The diffusional mass-transfer resistance of palladium ion to immobilized adenine was negligible because palladium ion was transported by permeative flow through the pores. The adenine-immobilized porous membrane with an immobilization density of 0.85 mol/kg of the membrane exhibited the highest molar binding ratio of palladium ion to immobilized adenine of 0.31 in 1 M hydrochloric acid. In addition, a quantitative elution with 4 M hydrochloric acid was experimentally demonstrated.     

Evaluation of electroless gold deposited on porous silica for ligand attachment for metal ion-exchange

A novel ion-exchange system was developed by tethering a small, monofunctional metal ligand, 3-mercaptopropionic acid (MPA), through thiol linkages onto a glass substrate overlaid with gold, using electroless deposition of Au onto 100 mesh controlled pore glass (CPG) particles. Two different CPG glass pore sizes of 22.6 and 104.9 nm were used in an attempt to optimize Au deposition and ligand coverage. It was found that the Au was present on both of the substrates as a nonuniform deposit, possibly existing as small multilayer islands, throughout the CPG particles. The deposit also did not fill the intricate CPG pore network.Au-CPG is a reasonable substrate for the support of small metal binding ligands such as the monofunctional MPA. Typical metal binding capacities were in the range of 7-24 μmol metal/g column, with the smaller pore system binding approximately twice as much metal as the larger pore system due to increased surface area and fractional ligand coverage. The immobilized binding systems were also found to remain chemically and structurally stable in pH environments ranging from pH∼9 to <1 (viz. 1 M HNO₃).     

Thin Pd membrane on α-Al2O3 hollow fiber substrate without any interlayer by electroless plating combined with embedding Pd catalyst in polymer template

Palladium acetate and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) were dissolved in chloroform to form a homogeneous solution. Using this solution, thin polymer template film with embedded Pd catalyst was coated on a porous α-Al₂O₃ hollow fiber substrate. The Pd in the template film was used as the catalyst for electroless plating of Pd membranes. After the template was removed by heat treatment, the thin Pd membranes without any intermediate layers and substrate penetration were synthesized successfully. The as-synthesized Pd composite membranes of thickness less than 5 μm not only have a very high hydrogen permeance/permeability but also have a good hydrogen selectivity. Moreover, the good membrane stability was verified by the long-term operation under the condition of hydrogen permeation and the gas exchange cycles between pure hydrogen and pure helium. The good membrane stability was interpreted by estimating the shear stress of the special membrane configuration with small gap between Pd membrane and porous substrate layer.     

多孔玻璃载体自转晶B-Al-MFI型沸石膜的原位合成

在乙胺和水的混合蒸汽相中,首次通过载体自转晶,在多孔玻璃表面原位合成了B-Al-MFI型沸石膜。X射线衍射和扫描电镜观察证明,膜中沸石晶体的取向是随机的。晶体尺寸约为15～25μm,单层晶体厚的膜约为10～20μm。在焙作去有机模板剂后的沸石膜上,O~2和N~2的透过性分别为0.095×10^-^8和0.15×10^-^8mol/(m^2·s·Pa)。计算的O~2/N~2的理想选择值(0.63)明显低于诺森扩散的理想选择性值(0.94)和透过原载体的理想选择性值(0.91)。     

An oxygen reduction sensor based on a novel type of porous carbon composite membrane electrode

The development of a simple, efficient and sensitive sensor for dissolved oxygen is proposed using a novel type of porous carbon composite membrane/glassy carbon electrode based on the low-cost common filter paper by a simple method. The resulting device exhibited excellent electrocatalytic activities toward the oxygen reduction reaction. Scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurements demonstrated that the porous morphology and uniformly dispersed Fe₃C nanoparticles of the PCCM play an important role in the oxygen reduction reaction. A linear response range from 2μmol/L up to 110 μmol/L and a detection limit of 1.4 μmol/L was obtained with this sensor. The repeatability of the proposed sensor, evaluated in terms of relative standard deviation, was 3.0%. The successful fabrication of PCCM/GC electrode may promote the development of new porous carbon oxygen reduction reaction material for the oxygen reduction sensor.     

Preparation of a pinhole-free Pd–Ag membrane on a porous metal support for pure hydrogen separation

A pinhole-free palladium membrane with a thickness of 3 μm has been prepared on the surface of a porous sintered stainless steel tube coated with a thin silver layer as a diffusion barrier. Filling of aluminum hydroxide gel in the surface pores of the tube is effective in preventing defect formation during electroless plating of the palladium layer, while the volume of the hydroxide beneath the membrane decreases greatly upon thermal treatment up to 500 °C. The hydrogen flux at 400–500 °C is reasonably proportional to the pressure difference between the two sides of the membrane. Addition of a 2 μm Pd_0.8Ag_0.2 alloy layer on the membrane by electroplating does not greatly decrease the hydrogen permeability.     

Performance of a photocatalytic hybrid system coupled with a stainless steel membrane for removal of humic acid

The objective of this study was to evaluate the performance of a photocatalysis/H₂O₂/metal membrane hybrid system in the degradation of humic acid. A metal membrane of nominal pore size 0.5 μm was used in the experiment for separation of TiO₂ particles. Hydrogen peroxide was tested as an oxidant. The efficiency of removal of COD_Cr and color increased rapidly for initial hydrogen peroxide concentrations up to 50 mg L⁻¹. The efficiency of removal of COD_Cr and color by 50 mg L⁻¹ initial hydrogen peroxide concentration was approximately 95 and 98%, respectively. However, addition of hydrogen peroxide over 50 mg L⁻¹ inhibited the efficiency of the system. Addition of hydrogen peroxide to a UV/TiO₂ system enhanced efficiency of removal of COD_Cr and color compared with no addition of hydrogen peroxide. This may be ascribed to capture electrons ejected from TiO₂ and to the production of OH radicals. Application of the metal membrane in the UV/TiO₂/H₂O₂ system enhanced the efficiency of removal of COD_Cr and color because of adsorption by the metal membrane surface and the production of OH radicals. By application of a metal membrane with a nominal pore size of 0.5 μm, TiO₂ particles were effectively separated from the treated water by metal membrane rejection. The photocatalytic metal membrane had much less resistance than the humic acid, TiO₂, and humic acid/TiO₂ because of the degradation of humic acid by the photocatalytic reaction.     

Facile synthesis of palladium nanoparticles supported on urea-based porous organic polymers and its catalytic properties in Suzuki-Miyaura coupling

By using urea linked porous organic polymers as template, a new nano palladium catalyst with low Pd loading can be easily prepared (1.0 wt% Pd only). Although such less amount of Pd was contained in this new catalyst, it is still an effective catalyst for the Suzuki-Miyaura coupling of aryl iodines and aryl boric acids, affording biphenyl products in excellent yields with outstandingly enhanced turnover numbers (up to 10,536) under green solvent (water).     

Improved separation of palladium species in biological matrices by using a combination of gel permeation chromatography and isotachophoresis

The binding of palladium to high-molecular-mass compounds in palladium-treated lettuce is investigated as an example for a biological matrix. The total palladium concentration in lettuce leaves is 10.3 ng/g wet weight. After homogenization, high-molecular-mass compounds (> 10 kDa) are isolated by ultrafiltration. For separation of these palladium species a combination of preparative gel permeation chromatography (GPC) and preparative isotachophoresis (ITP) is used. Palladium is determined in separated fractions by using a highly sensitive total reflection X-ray fluorescence (TXRF) method after preconcentration. After GPC separation, four main fractions of palladium species are collected, each containing palladium in ng quantities (3-10 ng). Two of these fractions are further separated by ITP, yielding at least three main peaks per GPC fraction, each containing palladium in the range of 0.3-3 ng. These palladium containing peaks are characterized by high-performance size exclusion chromatography (HPSEC) and capillary isotachophoresis (cITP) in parallel. HPSEC enables the estimation of the molecular mass of six main palladium peaks, covering a molecular mass range of 69-200 kDa. It is also shown that the estimation of molecular mass after separation is more reliable than the respective estimation directly in the first GPC run. However, cITP reveals that each of the separated peaks is still a mixture of at least five different compounds.     

A biofilm resistance surface yielded by grafting of antimicrobial peptides on stainless steel surface

Anti‐biofilm formation on the surface is a severe issue in medical implants, hull surface, and food industry. Antimicrobial peptide, magainin II, was covalently bound to stainless steel surfaces through multi‐step modification. The untreated and modified samples were analyzed by SEM‐EDS, XPS, and contact angle, respectively, which indicated the peptide was immobilized on the surfaces. The antimicrobial tests of modified samples were conducted using Staphylococcus aureus and Escherichia coli, and the results revealed that peptide modified surface decreased the biofilm and bacteria quantity of stainless steel surface.     

Development of a membrane reactor for decomposing hydrogen sulfide into hydrogen using a high-performance amorphous silica membrane

We have successfully developed a membrane reactor for decomposing hydrogen sulfide into hydrogen using an amorphous silica membrane for the first time. The membrane was prepared by the CVD method with tetramethoxysilane and oxygen, and showed excellent hydrogen permeance at 873 K of the order of 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ and high hydrogen/nitrogen permselectivity of 10⁴. The membrane reactor constructed with our membrane and a commercially available catalyst decomposed hydrogen sulfide into hydrogen with higher conversion than the equilibrium conversion. This conversion enhancement was because of the selective extraction of hydrogen from the reaction side to the permeate side by the silica membrane.     

Photoelectron spectroscopic studies of the formation of hydroxyapatite films on 316L stainless steel pretreated with etidronic acid

The valence band and core‐level X‐ray photoelectron spectroscopy was used to probe hydroxyapatite films formed on the surface of stainless steel. These films formed on steel may find application in medical implants. The key to the successful adhesion of the hydroxyapatite films is shown to be the initial formation of a thin, oxide‐free etidronate film on the metal. It was not found possible to prepare the hydroxyapatite films directly on the metal surfaces. Since hydroxyapatite is a key component of bone and teeth, it is likely that the coated metals will have desirable biocompatible properties. The hydroxyapatite film was exposed to air, water, and 1M sodium chloride solution as representative components of the environment of the film in the human body, and these exposures led to no detectable decomposition of the film. The thin hydroxyapatite and etidronate film on the metal show differential charging effects that caused a doubling of the peaks in some core level spectra. The valence band spectra proved especially valuable in the identification of the surface chemistry of the films, and these spectra were interpreted by comparing the experimental spectra with spectra calculated using band structure calculations which showed good agreement with experiment. The calculated spectrum of etidronic acid was found to be significantly different to that of etidronate. Copyright © 2012 John Wiley & Sons, Ltd.     

Oxide and nitride protective layers on stainless steel studied by AES,WDS and XPS

Protective surface layers on AISI 321 stainless steel were prepared by thermal treatments at two different temperatures in air and two controlled atmospheres. Different oxide and/or nitride layers were formed. Surface morphology of the layers was investigated by scanning electron microscopy (SEM). Auger electron spectroscopy (AES) depth profiling of the samples was performed. Since depth profiling suggested layer thicknesses of the order of hundreds of nanometres, an attempt was made to obtain some fast, averaged information about the layer compositions using wavelength dispersive spectroscopy (WDS) at two different beam energies to obtain probing depths best suited to the layer thickness. X‐ray photoelectron spectroscopy (XPS) profiling of one layer was also performed to obtain information about the chemical states of the elements inside the layer. The analysed samples showed considerable differences with respect to their surface morphology, oxide/nitride layer thicknesses, compositions and layer–metal interface thickness. Copyright © 2007 John Wiley & Sons, Ltd.