Structure and properties of composite coatings of the SnO2–In2O3–Ag–N system intended for strengthening the copper contacts of powerful electric network switches

Yang X., Gao Z., Wang X., Hu W.

• Pure Zn and Zn-epoxy powder coatings was prepared by zincate electrodeposition. • The addition of epoxy powder improves microstructures and reduce roughness. • The incorporation of epoxy powder enhances the corrosion resistance. • The incorporation of epoxy powder hinders the hydrogen permeation. • The addition of epoxy powder improves the wear resistance. To improve the corrosion and wear resistance of the coating and reduce the effect of hydrogen penetration on the performance of galvanized steel, Zinc-epoxy powder (EP) composite coatings were prepared by alkaline zincate electrodeposition. The results show that the Zn-6 g/L EP coating has the lowest root mean square roughness of 281.99 A. The incorporation of EP enhances the corrosion resistance of the coating. The Zn-6 g/L EP coating has the largest coating resistance and charge transfer resistance. The incorporation of EP can hinder the hydrogen permeation, which may reduce the hydrogen embrittlement of galvanized steel. Tribological experiment shows that the wear resistance of the composite coating is improved. The friction coefficient and wear scar width of the Zn-12 g/L EP coating is the lowest.

Liu Z., Ren L., Jing J., Wang C., Liu F., Yuan R., Jiang M., Wang H.

• The robust mastoid micro/nano-structures can be obtained by a two-step phase separation method. • The organic-inorganic hybrid coating possessed good mechanical durability to resist abrasion damage. • The prepared coating can maintain its superhydrophobicity after high pressure water jetting. • The prepared coating provided excellent corrosion/weather protection against corrosive medium or UV radiation. Artificial superhydrophobic coatings inspired by nature are expected to have extensive applications in several aspects of our daily lives once their poor mechanical and chemical durability is overcome. In this study, we developed a robust superhydrophobic organic-inorganic hybrid coating through the combination of fluorinated ethylene propylene (FEP) and aluminum dihydrogen phosphate (ADP) using a novel two-step phase separation method. An inorganic adhesive of ADP was introduced as a building block to enhance the structural robustness of the superhydrophobic coating. Carboxylated carbon nanotubes (C-CNTs) with good dispersibility in both water and ethanol were employed as emulsifiers to promote the liquid phase separation of FEP and ADP, which was beneficial for the formation of abundant microspheres in aqueous ethanol. After spraying and thermal treatment, the uniform mastoid micro-/nanostructures were formed on the coating surface due to the thermal phase separation of microspheres, which can provide excellent superhydrophobicity with a water contact angle of 162 ± 1.1° and a sliding angle of 5 ± 0.5°. The prepared coating can maintain its outstanding hydrophobicity even after 1000 abrasion cycles with sandpaper and upon jetting with high pressure water flow (200 kPa). Moreover, owing to the chemical inertness of the hybrid micro-/nanostructures, the prepared coating can provide a high level of corrosion protection against strong corrosive mediums as well as weather protection against UV radiation (300 W/m 2 ). Therefore, it is believed that the robust organic-inorganic hybrid superhydrophobic coating prepared by facile phase separation method would present new avenues for expanding the practical applications of superhydrophobic coatings.

Kanwal M., Shahzad N., Tariq M.A., Shahzad M.I.

High conductivity silver pastes are usually incompatible for use with thermally sensitive devices due to their higher sintering temperatures while nanoparticle inks are costly and undergo high particle agglomeration. Effectively transparent contacts (ETCs) have been designed to increase the transmittance, reduce reflectance and overcome shadowing losses in solar cells while enhancing the overall conductivity and charge collection through the grid. In this study, reactive silver ink (RSI) is mixed with a low temperature sintering conductive silver paste (150 °C) for deposition via a microchannel approach. ETCs deposited using the resulting composite were cured at a lower temperature (100 °C) with a conductivity of the order of 10 3 1/Ω-cm and a transparency >90% in the visible region, promising a reduction in optical and electrical losses when compared to bare transparent conductive oxides. The use of low temperature curing conductive material makes ETCs suitable for use in thermally sensitive optoelectronic and photovoltaic devices, hence they were ultimately deposited on perovskite solar cells and the solar cell parameters were measured. • Effectively transparent contacts deposited at low curing temperatures (100 °C) are suitable for thermally sensitive devices. • ETCs offer improved transparency (>90%), high aspect ratio and high conductivity (10^3 1/Ω-cm). • This design mitigates parasitic absorption, reflection and shading losses. • Compositional variations of Reactive Silver Ink were tested to study compatibility with microfluidic approach. • Realization of effectively transparent contacts on perovskites solar cells to explore device performance.

Mahmood K., Alzaid M., Khalid A., Malik R.A., Qutab H.G., Ahmad S.W., Maqbool A., Alsalh F., Almoisheer N.

The liquid electrolytes for dye-sensitized solar cells (DSSCs) have been identified as one of main obstacles for commercialization. One possible way to resolve this problem is to employ the semi-solid electrolyte. In this respect, we apply two types of electrolytes, namely liquid and low molecular weight organic gelator (LMOG) to fabricate the semi-solid state DSSCs and investigate their effects over the efficiency and long-standing thermal stability of devices. Unlike the conventional TiO2 nanoparticulate films, we have introduce a hybrid oxide layer consisting of nanocomposites of TiO2 nanospheres (NSPs) mingled with ZnO nanofibers (NFs) namely (mixed ZnO NFs + TiO2 NSPs) produced by a novel electrospray technique. This route resulted in an effective contact between the electrolyte and the highly porous layer of dye-coated hybrid film as the gel electrolyte penetrated within the pores. The semi-solid state DSSCs fabricated using hybrid oxide films for the LMGO based electrolyte exhibits power conversion efficiency (PCE) of 9.51%, which is considerably greater compared to cells based on TiO2 nanoparticulate films (5.14%). The semi-solid state DSSCs using the LMOG-based gel electrolyte demonstrate the significantly improved device performance and stability compared to the devices using the liquid electrolyte owing to their enhanced light trapping which serves as a scattering layer. Remarkably, the champion devices based on gel electrolyte produce the maximum PCE of 10.69%, the highest efficiency reported so far for these types of devices.

Kim S., Jo M.C., Kim S., Oh J., Kim S., Sohn S.S., Lee S.

The bending angle at the peak load is regarded as the most important parameter for evaluating bending properties of hot-press-forming (HPF) steels. However, it is not a mechanics-based parameter for the bending criterion, and the data interpretation is difficult because bending criteria in relation with microstructures and associated bending mechanisms have not been verified yet. In this study, effects of coating and baking treatments on bending angles at the peak load of three kinds of 1470 MPa-grade HPF steels were investigated by interrupted three-point bending tests coupled with direct microstructural observation. According to direct observations of sequential cracking processes of V-shaped crack (V-crack), bending procedures were classified into four stages: (1) formation of small V-crack, (2) increase in number and size of V-cracks, (3) initiation of shear-crack propagation from the V-crack tip, and (4) further propagation and opening of the shear crack. The minimum bending angle required for initiating the shear-crack propagation from the V-crack tip was defined as a critical angle, which meant the boundary between the 2nd and 3rd stages. The present bending behavior related with critical bending angle and V-cracking could be interpreted similarly by the fracture-mechanics concept, i.e., the initiation of shear-crack propagation.

Alresheedi F.

This work investigates the effect of film thickness on the optical properties of dysprosium oxide (Dy 2 O 3 ), fabricated onto sapphire (Al 2 O 3 ) substrates using electron beam evaporation. The grazing incidence X-ray diffraction (GI-XRD) analysis showed that all films have a cubic crystalline structure. The average crystallite size was calculated using the Debye–Scherrer equation and was found to increase with the increasing film thickness. Similar behavior was observed in scanning electron microscopy and atomic force microscopy images. The optical properties of the grown layers such as the refractive index (n), extinction coefficient (k), and optical allowed f–f transitions of Dy 3+ were analyzed using spectroscopic ellipsometry (SE). The allowed f–f transitions of Dy 3+ was found to increase from 2.35 eV to 2.50 eV by decreasing the film thickness from 10 nm to 5 nm. UV–Vis spectrophotometry was used to examine the reflectance of Dy 2 O 3 thin films. The results obtained in this study indicated that Dy 2 O 3 with a 5 nm thickness is a better choice to grow an improved anti-reflective layer compared with the 10 nm layer.

Liu Y., Wang Z., Li Y., Yuan H., Li F.

Abstrac In order to reduce the manufacturing cycle and improve the forming performance of the incremental sheet forming (ISF) process, a hybrid manufacturing process that combines thermal spraying and incremental forming process was firstly proposed. The effects of different thermal spraying parameters on the forming properties and mechanical properties of sheet metal were investigated. Firstly, Fe316L coating was prepared on AA2024-T3 plate by using atmospheric plasma thermal spraying, and then the plate is formed into the target shape with variable angles. In addition, tensile tests were carried out on the plates pretreated by thermal spraying with different parameters. The results showed that the yield strength of the plate decreased up to 70% and the elongation increased by 65% under the appropriate thermal spraying power. In the process of ISF, the axial forming force of sheet metal after thermal spraying decreased obviously and the forming limit increased obviously. In addition, influences of different processing steps (sand blasting and heating) on the forming performance of sheet metal were investigated. It is found that the heating effect in the thermal spraying process has the most obvious effect on the improvement of forming performance, while the sand blasting process has adverse effect. Finally, in order to optimize the thermal spraying area, the influence of thermal spraying at different areas on the forming performance of sheet metal was investigated.

Mahnae S., Hadavi M.S., Azizi H.R.

In this research work, Ag– TiO2 thin films were deposited on microscope glass slides by spray pyrolysis and thermal vacuum evaporation combination techniques. The effect of substrate temperature and silver doping on crystal structure, surface morphology, hydrophilicity, hydrophobicity, and optical properties of the prepared thin layers were investigated by various techniques such as XRD, AFM, SEM, optical and photoluminescence spectroscopy. The results show the root mean square roughness deviation of pure TiO2 films decreased and the water contact angle increased with increasing of substrate temperature as well as silver thickness in the visible range. On the other hand, hydrophilicity nature of Ag–TiO2 layers raised with increase in the time of UV radiation. The optical absorption increased with silver doping due to collective oscillation of free electrons of small noble nanoparticles. The attained results indicate that the optical absorption increases with silver doping, because the radiated photon was trapped by silver nanoparticles in the TiO2 layers and so increases optical absorption. Anatase phase was dominant crystalline phase in all the prepared samples which is the best phase in photo catalyst and self-cleaning applications.

Boakye E.E., Key T.S., Mogilevsky P., Opeka S.J., Corns R., Hay R.S., Cinibulk M.K.

Solutions of YPO 4 were used to precipitate YPO 4 on pre-oxidized Hi-Nicalon-S SiC fibers. Tows of the coated fibers were then infiltrated with a preceramic polymer loaded with SiC particles to form mini-composites. During pyrolysis of the matrix, SiO 2 and YPO 4 on the fibers reacted and formed a Y 2 Si 2 O 7 fiber matrix interphase. Mini-composites were exposed to steam at 1000 °C for 10, 50, and 100 h, tensile tested, and the effect of oxidation in steam on the functionality of the Y 2 Si 2 O 7 fiber coating was investigated. The minicomposites oxidized at 1000 °C for 10 h retained 100 % of their unoxidized strength, and those oxidized for 50 and 100 h retained 92 % and 90 % of unoxidized strength, respectively. Strength retention and fiber pullout in both unoxidized and oxidized minicomposites suggests that the Y 2 Si 2 O 7 interphase was effective in maintaining a weak fiber-matrix interface.

Bhati P., Shrama V., Jha R., Gupta S., Vishnoi M., Mamatha T.G.

In hydropower plants, water is used for the generation of power by the help of turbines due to which the erosion in runner and other components often lead to the losses in power generation and efficiency. Due to these conditions, sometimes turbines is shut down for repair work, replacement of runner, or other components. There are the various reasons for this failure mechanism such as silt erosion, cavitation erosion, and surface fatigue of underwater parts of the turbine and sometimes this leads to the mechanical vibration in the components. These problems can be eliminated by understanding the various causes of erosion and the methods of preventions. High-velocity oxy-fuel technique is most widely used among all of the thermal spray coatings methods. We will have studied the coatings of tungsten carbide, NiCoCrAlY, and chromium carbide by the HVOF spray process in our present work.

Tan X., Wang Y., Huang Z., Sabin S., Xiao T., Jiang L., Chen X.

Despite their great self-cleaning, anti-dust, and anti-icing properties superhydrophobic coatings show great promise in various practical applications in solar cells, car windows, powerlines, etc., superhydrophobic coatings encounter a large resistance in large-scale practical applications due to their unsatisfactory long-term mechanical, chemical, thermal, and weathering durability. This study demonstrates a cost-effective, large-scale applicable, mechanical, chemical, thermal, and long-term weathering durable fluorine-free superhydrophobic coating. This coating can be prepared with a simple spin-coating or doctor-blade painting or spray-brush method, using SiO2 nanoparticles coated with methyl MQ silicone resin (Me-MQ), and y-methacryloxypropyltrimethoxysilane (KH-570). This coating displays remarkable super-hydrophobic performance with a large water contact angle of 168.8°, and a small sliding angle less than 1.0°, which survives tape peeling, sand impact, sandpaper abrasion, etching in acidic and alkaline environments, baking at high temperature up to 550 °C, and long-term exposure to outdoor natural environment (under 16 months’ natural sunlight irradiation, UV irradiation, rain falls, high PM2.5, dust accumulation, etc.). The materials used are non-fluorine, non-toxic, environmentally friendly, and can be effectively applied to large glass surfaces using cost-effective doctor-blade painting and spray-brush methods towards large-scale applications. Therefore, this work can inspire and advance researches on superhydrophobic coatings towards practical applications.

Shmorgun V.G., Bogdanov A.I., Kulevich V.P., Iskhakova L.D., Taube A.O.

• A uniform coating without defects is formed on the NiCr alloys by hot-dip aluminizing. • The initial coating consists of an Al matrix with C r A l 7 , N i 2 A l 9 , F e N i A l 9 , N i A l 3 , N i 2 A l 3 intermetallic inclusions. • The addition of Fe into the Ni-Cr-Al system leads to a change in the diffusion interaction processes. • Heating of the coatings leads to a diffusion redistribution of the elements and the formation of precipitates with a high Cr content. • A protective oxide film of α − A l 2 O 3 is formed on the coating surface during heating. In this paper, the results of a study of the structure and phase composition of diffusion coatings formed on the surface of Ni80Cr20 and Ni60Cr15 alloys after hot-dip aluminizing and subsequent high-temperature heating are presented. It is shown that as a result of aluminizing on the surface of NiCr alloys a uniform coating without defects is formed.The coating consists of an Al matrix with C r A l 7 , N i 2 A l 9 , F e N i A l 9 , N i A l 3 , N i 2 A l 3 intermetallic inclusions. It is found that heating of the coatings at 1100 °C leads to a diffusion redistribution of the elements over their thickness and the formation of a layered quasi-two-phase structure of Cr (in case Ni80Cr20 alloy) or Cr and Fe (in case Ni60Cr15 alloy) solid solutions in N i A l with different Al (Al-rich) and Ni (Ni-rich) saturations. At the interfacial boundary of N i A l phases with different composition precipitates are presented as a randomly distributed individual inclusions of solid solutions based on Cr and C r 3 S i . At the ”coating - substrate” interface they are presented as a continuous secondary reaction zone, consisting of a large number of precipitates C r ( N i ) and C r ( N i , A l ) (Ni80Cr20 alloy) and a smaller amount of C r ( F e , N i ) and C r ( F e , A l , N i ) (Ni60Cr15 alloy). The formation of these heterogeneity elements is due to the limited solubility of Cr in N i A l . A protective oxide α − A l 2 O 3 is formed on the coating surface as a result of heating. An increase in the exposure time leads to the formation of the N i A l 2 O 4 spinel type oxide along with A l 2 O 3 on the surface of the coating on the Ni80Cr20 alloy.

Ziervogel F., Boxberger L., Bucht A., Drossel W.

Additive manufacturing is establishing new forms of manufacturing processes to produce functional parts. It is thus seen as a hope for a shift towards decentralised production and the associated positive effects on the environment. The most widespread process, Fused Filament Fabrication, already impresses with a large variety of materials and the possibility of including non-polymeric additives as fibre materials. To support this development, this paper describes a form of wire implementation as an add-on for existing FFF systems, that can be realised without major changes to hardware or software. The aim is to integrate electrical functions directly into the component - in one manufacturing process. The process is based on a hybrid material made of PLA with a copper core, which was developed in advance. Within this work, two retrofittable units for FFF printers are described, which cut a continuous wire with a diameter of 0.2 mm embedded in a polymer in a fully automatic manner. Furthermore, two thermal contacting processes are presented, which make it possible to contact the embedded wire via the heated extruder nozzle and metallic inserts. Thereby, a best contact resistance of 0.009 ± 0.0023 Ω (50% confidence interval) could be achieved for a screw contact. For a plug-in or solder contacts, a contact resistance of 0.059 ± 0.028Ω (50% confidence interval) was realised. In terms of process technology, the wire deposition within the plastic structure could be reliably realised at printing speeds of 10 mm/s on straight sections and 1 mm/s in curves with a radius of 5 mm. The developed process was successfully validated using a functional demonstrator. The functional sample can be selectively heated to the glass transition temperature and reversibly formed. In summary, the developed methods are suitable for cost-effectively expanding existing FFF systems to integrate electrical functions during the 3D printing process.

Pan Z., Bui L., Yadav V., Fan F., Chang H., Hanjaya-Putra D.

Encapsulation of single cells in a thin hydrogel provides a more precise control of stem cell niches and better molecular transport. Despite the recent advances in microfluidic technologies to allow encapsulation of single cells, existing methods rely on special crosslinking agents that are pre-coated on the cell surface and subject to the variation of the cell membrane, which limits their widespread adoption. This work reports a high-throughput single-cell encapsulation method based on the "tip streaming" mode of alternating current (AC) electrospray, with encapsulation efficiencies over 80% after tuned centrifugation. Dripping with multiple cells is curtailed due to gating by the sharp conic meniscus of the tip streaming mode that only allows one cell to be ejected at a time. Moreover, the method can be universally applied to both natural and synthetic hydrogels, as well as various cell types, including human multipotent mesenchymal stromal cells (hMSCs). Encapsulated hMSCs maintain good cell viability over an extended culture period and exhibit robust differentiation potential into osteoblasts and adipocytes. Collectively, electrically induced tip streaming enables high-throughput encapsulation of single cells with high efficiency and universality, which is applicable for various applications in cell therapy, pharmacokinetic studies, and regenerative medicine.

Enishetty R., Narayan R., K.V.S.N. R.

• Synthesis of Ferrocene containing Polyol (Fc-PL) assisted by catalyst free Click Chemistry. • Development of various polyurethane coating samples from Fc-PL. • Characterization of various properties of coating samples by TGA, DMTA, Taffel polarization technique, contact angle measurements and disk diffusion test. The present work delineates the development of ferrocene (Fc) fortified, multifunctional, hybrid polyurethane coating films. Initially ferrocene containing polyol (Fc-PL) was successfully synthesized with the assistance of catalyst free azide-alkyne click chemistry and each step of the synthesis was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance ( 1 H NMR), carbon-13 nuclear magnetic resonance ( 13 C NMR), Ultraviolet-visible spectroscopy (UV/Vis) spectroscopy and Electrospray ionization mass (ESI-mass) spectrometry. Polyurethane coatings of varying concentrations of Fc-PL, polypropylene glycol (PPG), trimethylol propane (TMP) were prepared in such a way that to maintain Fc concentrations in 0, 5, 10, 15 weight percentages with respect to polyol mixture and mixed with polymeric diphenylmethane diisocyanate (PMDI) at a OH: NCO ratio of 1:1.05 and cured under atmospheric moisture to obtain corresponding polyurethane coatings and labeled as Fc-0, Fc-5, Fc-10, Fc-15. Successful incorporation of Fc into PU coatings was confirmed by energy-dispersive X-ray spectroscopy (EDS) analysis. Effect of ferrocene on thermal stability and thermo-mechanical properties was assessed by thermo-gravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) respectively and TGA suggests that onset decomposition temperature, 30 % weight loss temperature, 50 % weight loss temperature and weight % remaining at 500°C increased as Fc wt% increases from 0 to 15 wt%, which implies that thermal stability enhanced with increasing the ferrocene concentration. DMTA demonstrated that mechanical properties i.e., storage modulus enhanced and glass transition temperature (T g ) declined with increasing the ferrocene concentration, on account of redistribution of intermolecular hydrogen bonds and metal-polymer complex formation. Ferrocene effect on corrosion resistant property, water contact angle and anti-fungal susceptibility was studied by electrochemical polarization analysis, contact angle measurements and disk diffusion test respectively. Electrochemical polarization analysis revealed that corrosion resistant property improved as the ferrocene content increases from Fc-0 to Fc-15. Ferrocene additionally imparted hydrophobicity to synthesized PU coatings. Fc-5 PU coating sample showed better hydrophobicity than other samples i.e, Fc-0, Fc-10 and Fc-15. These PU coatings are anti-fungal in nature due to the presence of hydrogen bonded triazole ring formed by click chemistry.

Romanov D.A., Pochetukha V.V., Moskovskii S.V., Sosnin K.V., Ivanov Y.F., Gromov V.E.