Galvanic Process Research Articles

Utilization of Industrial Waste Water Treatment Residues in Alkali Activated Cement and Concretes

The paper discloses an effective way of utilization of industrial waste water treatment residues. The wide use of industrial waste water in building materials is difficult due to the presence of heavy metal. However, alkali activated cements showed high ability of immobilization of heavy metals. The compressive strength of AAC systems with water treatment residues (galvanic process waste water) is up to 40 MPa in mortars and 45 MPa in concretes. The leaching behaviour of heavy metals from the cements matrix after soaking up to 28 days was also examined with AAS.

Структура и магнитные свойства нанопроволок из маталлов группы железа, полученных методом матричного синтеза

Abstract —Samples of arrays of nanowires are produced from iron, iron–cobalt and iron–nickel alloys via matrix synthesis based on polymer track membranes with pore diameters ranging from 30 to 300 nm. The influence of stress and pore diameter on the galvanic process and structure of nanowires is studied. The arrays of nanowires are examined by microscopy and X-ray diffraction. The magnetic properties are inspected via magnetometry and Mössbauer spectroscopy. The angular dependences of hysteresis loop shape are obtained and comprehensively discussed. As shown, decreasing the growth stress and/or increasing the pore diameter make the Mössbauer spectra of nanowires similar to those of bulk materials. Furthermore, the higher the growth stress is, the larger is the coercive force of nanowires. For the studied species of nanomaterials, the ability to control the magnetic properties during the synthesis is shown, as well.

Large-scale synthesis of Tellurium nanostructures via galvanic displacement of metals

Tellurium (Te) is an attractive semiconductor material for a wide range of applications in various functional devices including, radiation dosimeters, optical storage materials, thermoelectric or piezoelectric generators. In this work, large scale synthesis of tellurium (Te) nanostructures have been successfully carried out in different concentrations of aqueous solutions containing TeO2 and NaOH, by galvanic displacements of Zn and Al which served as the sacrificial materials. Galvanic displacement process is cost-effective and it requires no template or surfactant for the synthesis of nanostructures. By varying the concentrations of TeO2 and NaOH, etching temperatures and etching times, Te nanostructures of various forms of nanostructures were successfully obtained, ranging from one-dimensional needles and rod-like structures to more complex hierarchical structures. Microscopy examinations on the nanostructures obtained have shown that both the diameters and lengths of the Te nanostructures increased with increasing etching temperature and etching time.

Double Barrel Microelectrode Assembly to Prevent Electrical Field Effects in Potentiometric SECM Imaging of Galvanic Corrosion Processes

There is great interest in elucidating the corrosion mechanism of magnesium, and different experimental methods and techniques are explored with this purpose. Among the scanning probe techniques, scanning electrochemical microscopy (SECM) is delivering some promising results in recent years. In particular, the use of ion selective microelectrodes (ISME) as SECM sensing probes allow monitoring of the temporal and spatial distribution of different ionic species related to the corrosion reactions. However, a serious disturbance in the measured potential can be observed when it comes to galvanic coupling or polarization of the samples. This work explores the factors that affect the magnitude of the electrical field effects associated with the galvanic coupling, and describes an experimental arrangement for potentiometric SECM able to avoid the unwanted contribution of the potential field. The performance of a double barrel electrode assembly comprising an ion selective microelectrode and an internal reference electrode was compared to that of a conventional single barrel ISME in order to establish its applicability for the investigation of corrosion systems presenting electrical field distributions.

Use of sintering to immobilize toxic metals present in galvanic sludge into a stabile glass-ceramic structure

Galvanization process requires the use a large amount of water and produces wastewaters that are usually purified by conventional cost-effective procedure. This kind of treatment generates waste sludge which becomes a hazardous if is not properly stabilized. Hence, the aim of this paper is to investigate the characteristics of galvanic sludge through the inspection of its physicochemical parameters and consider stabilization of waste materials, including waste glass and aluminum slag by their conversion into an eco-designed material referred to as glass ceramics. The obtained products have been studied by X-ray diffraction (XRD). XRD analyses confirmed occurrence of chemical and phase transformations in treated galvanic sludge and binding of toxic metals (Al3+, Cr3+, Cu2+, Cd2+, Ni2+, Pb2+, Zn2+) into crystalline phases and very sTab. structure.

Microstructural Evaluation of Double-Dip Galvanized Coatings on Carbon Steel

AbstractThe objective of this research is to evaluate the microstructure of a coating layer composed of Zn / Zn-5 % Al. It was performed by the double-dip method of a steel AISI 1020. The temperature of the immersion bath was 550°C and the coatings were performed using different immersion times. Microstructural characterization was done using optical microscopy, SEM, EDX and XRD. All coatings showed three defined zones. The first zone, corresponding to the steel/coating interface, it presents typical properties of a traditional galvanization process at high temperatures. In zone II, a very heterogeneous microstructure was observed; zone III showed a Zn-Fe matrix with compounds particles of Fe2Al5Znx. The XRD characterization detected the presence of Zn and Fe2Al5Zn0,4. It was concluded than microstructural properties of the coatings were similar for the three immersion times. It is important to remark that the presence of Fe and Al throughout the coating, due to the diffusion of iron from the base metal and aluminum, presents in the second immersion bath.

Hollow PdCu2@Pt core@shell nanoparticles with ordered intermetallic cores as efficient and durable oxygen reduction reaction electrocatalysts

Carbon-supported hollow PdCu2@Pt core@shell nanoparticles with ordered intermetallic cores were prepared as an efficient and durable oxygen reduction reaction (ORR) electrocatalyst for polymer electrolyte membrane fuel cells (PEMFCs). PdCu2 cores prepared using a chemical reduction method were thermally treated to produce ordered intermetallic structures. A Pt shell was then deposited via a galvanic displacement process. The effect of the galvanic displacement conditions on the properties and structure of the obtained core–shell nanoparticles was investigated by varying the solution pH and anion concentration. Acidic conditions and low Cl− concentrations were found to provide a uniform Pt layer with a hollow core, while maintaining the ordered intermetallic core structure. These hollow PdCu2@Pt core@shell nanoparticles showed high activity and stability for ORR electrocatalysis in PEMFCs.

Influence of MAO Treatment on the Galvanic Corrosion Between Aluminum Alloy and 316L Steel

To slow down the galvanic corrosion of aluminum alloy and 316L stainless steel in subsea water, a micro-arc oxidation (MAO) coating was prepared on the surface of the Al alloy, and no treatment was performed on the surface of the 316L. The surface morphology of MAO-coated Al alloy was evaluated using a scanning electron microscope (SEM) before and after corrosion. A micro-hardness tester was used to measure the micro-hardness. Corrosion behaviors were evaluated by open-circuit potential (OCP), potentiodynamic polarization (PDP) and electrode impedance spectroscopy (EIS) tests in a 3.5 g/L NaCl solution. The results of PDP testing show that the corrosion potential of the MAO-coated galvanic pair was more positive than that of the uncoated galvanic pair and that the corrosion current density was smaller than that of the uncoated galvanic pair. EIS results show that the impedance of the galvanic pair increased after MAO coating. SEM images show that the corrosion damage of the uncoated Al alloy was more severe than that of the MAO-coated one, and the post-corrosion images of the surface of the 316L connected with MAO-coated Al alloy were more compact than those of the 316L connected with uncoated Al alloy. A physical model was developed to discuss the influence of MAO treatment on the galvanic corrosion process and corrosion mechanism.

Ultra-fine Line Multi-Redistribution Layers with 10 μm Pitch Micro-Vias for Wafer Level and Panel Level Packaging realized by an innovative Excimer Laser Dual Damascene Process

Abstract Multi-chip integrated Fan-Out packages and high I/O CSPs demands for higher routing density on wafer level. Due to that, the classical mask aligner lithography and photosensitive thin-film polymers used for BEOL reach its limits and new technologies and materials are necessary to generate lines and space down to two μm. These multi-metal layers set also higher demands on the mechanical properties of the materials. This paper presents a new excimer laser dual damascene process for ultra-fine routing for BEOL. Various materials like low cure temperature polyimide, BCB and 15-μm thick dry-film ABF material are structured by using an excimer laser stepper with a reticle mask to realize feature size below four μm with a high throughput. Micro-vias with a diameter below five μm are realized with high aspect ratio, which overcome the photolithographic limitations of the common used photosensitive thin-film polymers. The laser structuring allows to use innovative dielectric materials for WLP with optimized mechanical and electrical parameters for example inorganic filled polymers like dry-film ABF materials, which do not have to be photosensitive. The ablations depth per laser pulse and the cross-section of the ablated structures in dependence of the ablation parameters was investigated. The depth of embedded lines was set by number of pulses aside of integrated micro-vias. The lines and micro-vias were metallized with copper by galvanic process and the following CMP step removes the copper outside the ablated structures. The CMP removes only the copper and the metal of the seed-layer, which has the functions of an adhesion and barrier layer, stays intact. The under-etching of the conventional wet etch seed layer removal is a major problem for the fine line structures realized by the Laser Dual Damascene process. Due to that, the removal of the seed layer (usually titan) was investigated and it could be shown, that this layer can be removed by the excimer laser system. The stepper like system allows a sub-micron alignment accuracy with no need of a capture pad of the embedded lines. Test structures have been designed and fabricated with lines and spaces below 10 μm to demonstrate the dense multi-layer routing capability where the excellent reliability can be proven by air to air thermal cycling (from −55°C up to 125°C), current leakage and electro migration test.

How Ag Nanospheres Are Transformed into AgAu Nanocages.

Bimetallic hollow, porous noble metal nanoparticles are of broad interest for biomedical, optical and catalytic applications. The most straightforward method for preparing such structures involves the reaction between HAuCl4 and well-formed Ag particles, typically spheres, cubes, or triangular prisms, yet the mechanism underlying their formation is poorly understood at the atomic scale. By combining in situ nanoscopic and atomic-scale characterization techniques (XAFS, SAXS, XRF, and electron microscopy) to follow the process, we elucidate a plausible reaction pathway for the conversion of citrate-capped Ag nanospheres to AgAu nanocages; importantly, the hollowing event cannot be explained by the nanoscale Kirkendall effect, nor by Galvanic exchange alone, two processes that have been previously proposed. We propose a modification of the bulk Galvanic exchange process that takes into account considerations that can only occur with nanoscale particles. This nanoscale Galvanic exchange process explains the novel morphological and chemical changes associated with the typically observed hollowing process.

Encapsulation in ceramic material of the metals Cr, Ni, and Cu contained in galvanic sludge via the solidification/stabilization method

The stabilization/solidification (S/S) process at the semi-industrial level in the recovery of sludge from industrial wastewater treatment plants used in galvanic processes with a high content of the metals Cu, Cr, and Ni was evaluated. As the encapsulating agent, red clay, traditionally used in the manufacture of ceramic tiles, was used. The capacity of the retention of the metals Cu, Cr, and Ni in the ceramic material was determined for different contents of sludge: 1%, 5%, and 10% by weight of sludge compared with the ceramic material without sludge. The sintering process was carried out at two temperatures, 1120°C and 1190°C, in a semi-industrial roller kiln with a firing cycle of 30min. The effectiveness of the ceramic for the retention of the metals Cu, Cr, and Ni was determined on the basis of the leaching test in order to characterize the toxicity (TCLP) according to norm EPA 1311. For the characterization of the ceramic materials, technical, mechanical, and micro-structural properties were evaluated. The results show that at 1190°C, around 99% of the metals is retained, and at 1120°C between 95% and 99% is retained.

Failure Analysis to Clarify Unambiguous Hydrogen Fracturing in Steels

Hydrogen can get into metallic components and damage them in very different ways. Liquid-phase metallurgical processes such as casting and welding can lead to the formation of “fish-eyes” and “flakes”. Apart from metallurgical sources, semi-finished and finished components can also absorb hydrogen from galvanic processes or as a result of corrosion. In these cases hydrogen diffuses into regions of higher stress and strain causing cracking, often unexpectedly and after significant periods of time, which is referred to as “delayed fracture” and “cathodic stress corrosion cracking”. In failure analysis the clarification of hydrogen-induced component damages is based on fractographic examinations in combination with H-analysis. However, a systematic approach of consecutive steps is required in order to clarify hydrogen-induced fractures unambiguously. In failure analysis a delayed fracture is a strong evidence for a damage caused by hydrogen. If a sample taken from the as-received component breaks delayed during a clamping test, this can only be caused by hydrogen which has been present in the component. If too much of the hydrogen has escaped in the space of time from failure to investigation, a clamping test with simultaneous hydrogen uptake can be performed. The fractographic comparison of a sample broken in a clamping test and the primary fracture of the component, as well as the final fracture is necessary. As these three fractures arise from the identical material, the comparison should lead to an unambiguous result. Finally there is the possibility to selectively detect the diffusible (damaging) hydrogen using the HCA method.

Removal of Heavy Metals and Pharmaceuticals From Contaminated Water Using Waste Sludge – Kinetics and Mechanisms

The aim of this study was to investigate the adsorption of heavy metals (CrTOT, Ni2+, Cu2+, and Zn2+) in wastewater originated from galvanization process and pharmaceuticals (ciprofloxacin and dexamethasone) in aqueous solutions on waste sludge. To get the insight in the adsorption process, the adsorption kinetics and mechanisms are described. The physico‐chemical properties of the waste sludge were determined by scanning electron microscopy coupled with energy dispersive spectroscopy, X‐ray diffraction technique, energy dispersion X‐ray spectrometry, surface area and gas adsorption porosimetry, and laser diffraction. The adsorption on waste sludge was performed as batch tests and the concentration of heavy metals and pharmaceuticals was monitored by atomic absorption spectrometry and UV/Vis spectrophotometry, respectively. The rates of pharmaceuticals adsorption dependent on different initial concentration were explained. The kinetics of heavy metal ions and pharmaceuticals adsorption on the sludge was analyzed using four different models. The pseudo second‐order model assuming chemical adsorption as the rate limiting process showed the best agreement. Furthermore, the results revealed that the adsorption involves complex processes, including film diffusion and intraparticle diffusion. The investigated industrial waste sludge is a promising non‐hazardous and a low cost sorbent with relatively high surface area which can be used for removal of heavy metal ions (CrTOT, Ni2+, Cu2+, and Zn2+), and pharmaceuticals (ciprofloxacin and dexamethasone) from wastewater.

Confining the Nucleation of Pt to In Situ Form (Pt-Enriched Cage)@CeO2 Core@Shell Nanostructure as Excellent Catalysts for Hydrogenation Reactions.

Ultrathin (Pt-enriched cage)@CeO2 core@shell nanostructures are successfully fabricated via a facile hard-template method. It is found that the usage of Pd@Ag@CeO2 bi-metallic core@shell nanostructure as the hard template plays an important role in avoiding the independent nucleation of Pt metal during the galvanic replacement process between K2 PtCl4 and Ag components. This unique core@shell samples show extraordinary activity and selectivity for the cinnamaldehyde hydrogenation reaction. It can achieve over 95% conversion with 87% selectivity of hydrocinnamaldehyde in 5 h under 1 atm H2 pressure. It is considered that such high catalytic performance could be attributed to the densely CeO2 -coated core@shell hybrid form as well as the ultrathin nature of the Pt-enriched cage.

Effects of Pt content on the crystallinity and optical properties of Ag/Pt nanoboxes: from solid to single and polycrystalline mesoporous nanostructures

Synthetic methods to obtain hollow-like systems based on galvanic reaction are of wide importance due to the simplicity and efficiency of the method, yet due to fast and spontaneous reduction, the reaction for platinum-based structures is usually not well controlled. Systematic studies over the evolution of the galvanization process are still important in order to determine key feature on the structural transformation. On this paper, electron microscopy techniques were used to correlate the crystallinity of Ag/Pt nanoboxes of 78 nm in size with low and high-index facets surfaces from Ag nanocubes template. It was observed that 1.6 μmol addition of platinum precursor is enough to produce Ag/Pt nanoboxes. However, the crystallinity of the walls was tune from single crystal to polycrystalline by increasing the amount of platinum. More importantly, electron tomography reconstructions allow us to identify the concavities sides on the polycrystalline double-layer porous sample. Platinum content and nanostructure has been also associated to the optical properties were an extinction of the absorption band is observed after the solid template has been fully transformed to a nanobox. The final Ag/Pt porous/hollow nanoboxes with concave sides were tested on a model reaction for the reduction of 4-ntp to 4-amp.

Tunable rose petal effect of cobalt coated zinc surfaces via a facile electroless galvanic deposition process

The rose petal effect (large apparent contact angles accompanied by high affinity to water) has greatly inspired researchers recently. In this paper, the rose-petal surfaces with tunable high water adhesion have been prepared successfully via a facile electroless galvanic deposition process as well as the subsequent modification with stearic acid on zinc substrates. We have regulated the concentration of CoSO4 solution in the process of electroless galvanic deposition to control the surface topography. After being modified with stearic acid, the as-prepared cobalt coated films showed similar apparent contact angles larger than 150° but contrast high water adhesion. To the best of our knowledge, the fabrication of rose petal surfaces with tunable water adhesion is still scarce. The largest water droplet volumes suspended on the tunable rose petal surfaces were 8, 24 and 28 μL, respectively. In addition, based on the different water adhesion on the rose petal surfaces, the selective transportation of microdroplets with different volumes has been demonstrated. We believe that these tunable adhesive rose petal surfaces would have great potential in the droplet-based microreactors.

The Effects of Substrate Orientation on Galvanic Growth of ZnO Structures

Electrochemical route has been a favorite technique for the fabrication of ZnO as it is relatively cheap and capable of producing abundance amount of materials. In this paper, we investigate the morphologies of hydrothermally synthesized ZnO structures assisted by galvanic process on conducting Au-coated silicon substrate. To induce the galvanic process, the substrate was in contact with aluminum so that the difference in the reduction potentials between the two materials provided the driving force for the formation of the ZnO structures. The galvanic process was found to promote compact and anisotropy growth of ZnO nanorods along the (001) plane. It was also found that substrate orientations in the electrolyte solution had an important bearing on the morphologies of ZnO. Well aligned periodic hexagonal arrays of ZnO nanorods of homogeneous diameters were obtained on gold-coated Si substrate with face-down orientation in the electrolyte solution.

Improved metal adhesion with galvanic nickel plating to silicon solar cells

Nickel galvanic displacement (NiGD) plating to silicon surfaces allows for the deposition of self-limiting sub-micron nickel layers. This paper reports the use of NiGD plating as an adhesion-promoting seed layer for light-induced plated nickel and copper (LIP-NiCu) contacts on chemically-etched silicon surfaces. The improved adhesion, which is attributed to surface roughening caused by the oxidation and subsequent etching of silicon in the fluoride-containing electrolyte, is quantified by stylus-based scratch measurements and shown to increase with the duration of sintering at 350°C. The width-normalised cut-off force for NiGD layers, sintered for 10min, was approximated by a normal distribution with a mean of 114±32N/mm. Unsintered NiGD and sintered LIP-only control samples, plated onto similar chemically-etched silicon surfaces, were insufficiently adherent to be measured. The poor adhesion of the unsintered NiGD contacts was attributed to the formation of voids and an oxide-rich interface layer during the galvanic displacement process. Although sintering at 350°C appeared to reduce the thickness of the interfacial oxide and eliminate the voids, the oxide was not totally removed and contributed to the measured contact resistance of sintered NiGD-treated contacts of ~ 15mΩ cm2 being more than an order of magnitude higher than laser-ablated LIP-NiCu contacts on a similar n-type emitter surface. Adhesion priming layers formed using NiGD were used to metallise selective-emitter cells patterned using aerosol jet etching and having planarised contact regions. Although the LIP-NiCu contact grid was strongly adherent, the average area-normalised series resistance (Rs) was 0.96±0.18Ωcm2, the majority of which is attributed to high contact resistance arising from a residual interfacial oxide.

From Galvanic to Anti-Galvanic Synthesis of Bimetallic Nanoparticles and Applications in Catalysis, Sensing, and Materials Science.

The properties of two alloyed metals have been known since the Bronze Age to outperform those of a single metal. How alloying and mixing metals applies to the nanoworld is now attracting considerable attention. The galvanic process, which is more than two centuries old and involves the reduction of a noble-metal cation by a less noble metal, has not only been used in technological processes, but also in the design of nanomaterials for the synthesis of bimetallic transition-metal nanoparticles. The background and nanoscience applications of the galvanic reactions (GRs) are reviewed here, in particular with emphasis on recent progress in bimetallic catalysis. Very recently, new reactions have been discovered with nanomaterials that contradict the galvanic principle, and these reactions, called anti-galvanic reactions (AGRs), are now attracting much interest for their mechanistic, synthetic, catalytic, and sensor aspects. The second part of the review deals with these AGRs and compares GRs and AGRs, including the intriguing AGRs mechanism and the first applications.

Pentatwinned Cu Nanowires with Ultrathin Diameters below 20 nm and Their Use as Templates for the Synthesis of Au‐Based Nanotubes

AbstractWe report a one‐pot method for the facile synthesis of Cu nanowires in high purity, together with ultrathin diameters well below 20 nm. Selected area electron diffraction and high‐resolution transmission electron microscopy studies confirm that the Cu nanowires are grown along the <110> direction to give pentatwinned, one‐dimensional nanostructures, enclosed by five {100} facets on the side surface. A systematic study further indicates that it is critical to conduct the synthesis under an argon atmosphere in order to improve the purity and uniformity of the nanowires while keeping their diameters thinner than 20 nm. We also demonstrate the use of these nanowires as sacrificial templates for the synthesis of Au‐based nanotubes through a galvanic replacement process.