Pure Aluminum Substrate Research Articles

Preparing Ni–Mo coatings for high-temperature Na2S3 molten salt on aluminium

Pure aluminum was susceptible to corrosion as a casing material for sodium-sulfur batteries. In this context, the effects of different electrodeposition parameters on the sulfur anticorrosion of Ni–Mo alloy coatings on pure aluminum substrate were investigated through an orthogonal test. The corrosion process of aluminum with Ni–Mo composite coatings in Na2S3 molten salt at 350 °C was investigated by static immersion test. The results demonstrated that the optimum parameters for achieving high corrosion resistance coating were Na2MoO4·2H2O concentration of 10 g/dm3, current density of 5 A/dm2, pH value of 9 and temperature of 45 °C. The sodium molybdate content played a crucial role in determining the corrosion resistance of the coating. The grain size of the coating decreased and the Mo content increased accordingly as the sodium molybdate content increased. While the presence of Mo element exhibited inhibitory effects on corrosion, an increase in high-energy grain boundaries resulting from grain refinement had an adverse impact. Consequently, in the single-factor experiment with varying Na2MoO4·2H2O contents, when maintaining the sodium molybdate content of 10 g/dm3, the minimum corrosion rate was 0.02632 mm/y after corrosion in Na2S3 molten salt at 350 °C for 72 h. Additionally, it was found that NiS2 as a corrosion product could effectively inhibit further development of corrosion.

Experimental and numerical investigation of Al[sbnd]16Si alloy friction surfacing on AA1050 aluminum substrate: Effect of axial feeding rate

Using the smoothed-particle hydrodynamics (SPH) simulation method and experimental investigation, this study evaluated the effect of consumable rod axial feeding rate on microstructure, mechanical properties, and wear resistance of coatings during the friction surfacing process of an AlSi alloy containing 16.6 wt% silicon on a commercial grade pure aluminum substrate. The interaction of coating and substrate at the interface was investigated using the thermomechanical simulation. According to simulation and experimental results, by increasing the axial feeding rate from 100 to 150 mm/min, the average deposition efficiency has increased from 36 to 43 %. The predicted results achieved from smoothed-particle hydrodynamics simulation show that by increasing the axial feeding rate from 100 to 150 mm/min, the shear stress at the coating/substrate interface increases from 86 ± 4 to 112 ± 6 MPa. By considering the average velocity at the interface, the simulation predicted the roughness with high precision. By increasing the axial feeding rate from 100 to 150 mm/min, interface roughness decreased from 105.2 ± 29.7 to 83.2 ± 26.9 μm. Compared to the pure aluminum substrate, surfacing with an AlSi alloy containing 16.6 wt% silicon results in minimum/maximum hardness and wear resistance increases by 212 / 265 % and 57 / 60 %, respectively.

Enhanced mechanical properties of molybdenum-coated aluminium via laser cladding

ABSTRACT High-quality molybdenum coating has been successfully deposited on the pure aluminium substrate by high-velocity oxygen fuel spraying and subsequent laser remelting and laser cladding process. The microstructure, bonding strength, micro-hardness and wear resistance of the coating were systematically investigated. Results showed that the obtained coating exhibits a good metallurgical bonding interface as well as a dense microstructure with Al8Mo3, AlMo3 and Al5Mo phases, which results in the significant improvement of the mechanical properties of the coating. The bonding strength is increased from 11 ± 1 to 57 ± 4 MPa after laser treatment. Micro-hardness of the coating (480 ± 30 HV) is observed to be increased by about 70% in comparison with the as-sprayed coating (281 ± 8 HV). The wear resistance of the Mo coating was also increased about five to six times by the laser remelting and cladding process.

Microstructure, mechanical properties, and cavitation erosion performances of cold sprayed CuZn35 coatings

CuZn alloy (as known as brass) is widely used in ship components due to its combination of high hardness and fatigue strength, and therefore good cavitation erosion performance. In this study, CuZn35 powder was for the first-time cold spray deposited on pure aluminum substrates for potential application as cavitation protection of hull pipelines. Parametric studies were carried out and the respective deposition characteristics were analyzed, and cavitation erosion performances of different CuZn35 coatings were characterized in deionized water using ultrasonic vibration experiments. The results showed that with the increase of gas temperature, cold sprayed CuZn35 coatings generally showed better cold sprayability and coating performance on aluminum substrates. The cold sprayed CuZn35 coatings exhibited a dense structure (porosity ~0.43 %), fine grain (~0.549 μm), a relatively high microhardness (~226 HV), and a relatively high bonding strength (54 MPa). The cavitation resistance of cold sprayed CuZn35 coatings showed a lowest volume loss rate of 0.22 mm3/h in deionized water, which was lower than that of as-cast CuZn35 (0.39 mm3/h). After 120 min cavitation, various features such as undulation deformation, pit and crack propagation, and material peeling appeared on cold sprayed CuZn35 coatings. It was noted that cold sprayed CuZn35 coatings, different from the as-cast CuZn35, exhibited the main cavitation mechanism of delamination caused by interlayer crack propagation.

Luminescence of Ti-Sapphire coatings prepared by plasma electrolytic oxidation and their application in temperature sensing

15 µm thick Ti-Sapphire coatings were synthesised at room temperature by the plasma electrolytic oxidation (PEO) method for 20 min from the pure aluminium substrate and with the addition of the TiO2 particles in various concentrations in the supporting electrolyte. The coatings are featured by microscopic pores typical for PEO surfaces. The dominant is the alpha phase of alumina with the small presence of the gamma phase. The estimated average crystalline size is 41 nm. Ti is uniformly distributed in these polycrystalline ceramic coatings and does not affect morphology or phase content. Photoluminescence of PEO-created coatings shows typical absorption, excitation, and emission features of Ti-Sapphire with two broad-overlapping excitation bands in the green and blue spectral region due to the Jahn-Teller splitting of the 2Eg level and the Stokes shifted emission centred at 720 nm. 2Eg energy state splitting is equal to 2195 cm−1 and 10 Dq ≈ 19,300 cm−1. The highest emission intensity was observed in the coating prepared with the 0.1 g/L TiO2 powder concentration, i.e. 0.32 at% of incorporated Ti3+. Emission spectra recorded at temperatures ranging from 100 K to 300 K revealed the Mott-Seitz temperature dependence of emission intensity with the 1180 cm−1 activation energy. The fit to the McCumber-Sturge relation gave, for the first time, the value of Debye temperature of 594 K of Al2O3:Ti. Non-contact, luminescence temperature sensing from the temperature-induced changes in the emission bandwidth gave a high sensitivity of 3.2 cm−1 K−1 and 0.19 K temperature resolution. The PEO created Ti-sapphire coatings are a promising multifunctional barrier level – optical temperature sensor material for applications in harsh environments or on large aluminium surfaces. It shows potential to be used as a planar waveguide Ti-Sapphire laser active medium.

Rapid and tunable growth of a well-ordered hexagonal nanoporous anodic aluminum oxide (AAO) structure by two-step high-temperature anodization

In this study, we have developed a swift and well-ordered growth of a nanoporous anodic aluminum oxide (AAO) structure using two-step high temperature anodization of the pure aluminum substrate. The pre-anodization surface treatment of the aluminum substrate assisted in the formation of well-organized nanoporous structures. The two-step anodization process was performed in 0.3 mol/L of oxalic acid at 20 °C with 40 and 45 V to obtain tunable pore diameters. The high temperature of the electrolyte solution facilitated the rapid growth of the nanoporous AAO structure. The top surface image of AAO shows a well-ordered nanoporous structure with an average pore diameter of 70 nm at 40 V and 100 nm at 45 V. The SEM cross-sectional view also illustrates the well-ordered nano-channel and the elemental mapping elaborates the presence of aluminum and oxygen. The thickness of the nanoporous AAO structure was determined using SEM for three anodization time spans (20, 24, and 28 h), in which an increasing trend was observed. The fabricated AAO has a higher thickness and a well-ordered nanoporous structure, which shows that it can be used as a template for fabricating nanostructured materials.

Pure copper layer formation on stainless-steel and aluminum substrate with a multibeam laser metal deposition system with blue diode laser

Laser metal deposition (LMD), which is one of the additive manufacturing technologies, is suitable for making 3D objects with complex shapes. In this method, a blue diode laser is used to explore the formation of pure copper parts because of the high light absorption of pure copper in blue light. Inspired by this method, in this study, we developed a high-power blue diode laser with a wavelength of 450 nm. This laser had an output power of 100 W and a fiber core diameter of 100 μm. We also developed a multibeam LMD system with the blue diode laser in which metal powder was supplied perpendicularly to the processing point and multiple lasers were irradiated from the surroundings for additively manufactured pure copper. We investigated the differences in copper layer formation that are dependent on the properties of substrates. Upon using the multibeam LMD system, a pure copper layer formed on pure aluminum and stainless-steel substrates. The interaction of pure copper powder and the substrates was observed using a high-speed video camera. After laser irradiation, copper cladding samples were observed with an optical microscope and scanning electron microscope and energy dispersive x-ray spectroscopy to evaluate the cross-sectional area of the pure copper layer and the dilution zone. As a result, a pure copper layer formed on the aluminum surface under the laser irradiation condition under which the aluminum substrate was not subjected to melting by heating with the blue laser. It was suggested that the pure copper powder heated by the laser melted the aluminum and formed a copper layer on the aluminum substrate.

Effect of Eu2+ doping on photoluminescence of Al2O3:Tb3+ functional coatings formed by plasma electrolytic oxidation

Multifunctional coatings of Al2O3 co-doped Tb3+ or Tb3+/Eu2+ were synthesized by the rapid and facile plasma electrolytic oxidation method on pure aluminium substrate. SEM & EDS analysis revealed porous structure independent on the doping concentration, with uniform distribution of co-doped rare-earth elements and incorporated concentrations proportional to the rare-earth particles concentrations added to the basic electrolyte. The gamma phase of Al2O3 increases to the expense of the alpha phase of Al2O3 with rising content of Tb3+. The addition of Eu2+ caused no further phase transformations. The photoluminescence (PL) excitation spectrum of Al2O3:Tb3+ was featured by sharp peaks (due to inter-configurational 4f transitions of Tb3+) and orders of magnitude larger broad-band in the middle ultraviolet region ascribed to the 4f→4f5d transitions. The PL emission spectrum was featured by the typical 4f→4f transitions of Tb3+, with maximum green emission at 541 nm and intensity proportional to the doping concentration. As the Eu2+ emission and Tb3+ excitation overlap, the concentration dependent energy transfer Eu2+→Tb3+ (of dipole-dipole character) occurred, resulting in the 20x increase in total PL and 3.2x increased Tb3+ PL. The PL emission color of Al2O3:Tb3+ was green and concentration independent, while of Al2O3:Eu2+/Tb3+ the color was in the domain of cold white with high correlated color temperature, which slightly decreased with increasing Eu2+ concentration.

Growth of a superhydrophobic coating on an aluminium substrate with strong adhesive properties and showing efficient oil/water separation

This study focused on understanding the growth mechanism of a superhydrophobic (SH) coating with enhanced adhesive properties. A single-step process was used to generate an SH coating, which involved the electrochemical deposition of ZnCl2, α-Al2O3 and lauric acid (C11H23COOH) onto a commercially pure aluminium substrate. The superhydrophobic property of the coating was determined using the static contact angle (170 °). The sliding angle was also measured (1 °) to assess self-cleaning properties. Results of the spectroscopic techniques and field-emission scanning electron microscopy revealed that the coating had a flower-like structure composed of zinc laurate (Zn(C11H20COO)2). Field-emission scanning electron microscopy showed that the growth consisted of three main steps involving metallic nuclei and their oxidation, which led to the formation of new branches growing in different directions all over the surface. Two different tests demonstrated strong adhesive properties of the coating on an aluminium substrate. The coating also separated oil (hexane and petroleum ether) and water efficiently, therefore showing potential for environmental applications.

Effects of Processing Parameters on the Corrosion Performance of Plasma Electrolytic Oxidation Grown Oxide on Commercially Pure Aluminum

The plasma electrolyte oxidation (PEO) process has been considered an environmentally friendly surface engineering method for improving the corrosion resistance of light weight metals. In this work, the corrosion resistance of commercially pure Al and PEO treated Al substrates were studied. The PEO layers were grown on commercially pure aluminum substrates using two different alkaline electrolytes with different addition concentrations of Si3N4 nanoparticles (0, 0.5 and 1.5 gL−1) and different duty cycles (25%, 50%, and 80%) at a fixed frequency. The corrosion properties of PEO coatings were investigated by the potentiodynamic polarization and electrochemical impedance spectroscopy test in 3.5 wt.% NaCl solutions. It showed that the weight gains, layer thickness and surface roughness of the PEO grown oxide layer increased with increasing concentrations of Si3N4 nanoparticles. The layer thickness, surface roughness, pore size, and porosity of the PEO oxide layer decreased with decreasing duty cycle. The layer thickness and weight gain of PEO coating followed a linear relationship. The PEO layer grown using the Na2B4O7∙10H2O contained electrolyte showed an excellent corrosion resistance and low surface roughness than other PEO coatings with Si3N4 nanoparticle additives. It is noticed that the corrosion performance of PEO coatings were not improved by the addition of Si3N4 nanoparticle in the electrolytic solutions, possibly due to its detrimental effect to the formation of a dense microstructure.

Fabrication of an anodized porous alumina relative humidity sensor with improved sensitivity

Sensitivity is an important parameter of any humidity sensor. In recent times, nanostructure materials have been used to fabricate the capacitive-type humidity sensors to improve the sensitivity. However, for the nanostructure sensors, in most cases, the sensitivity improvement is not guaranteed although extra efforts are made in terms of time and cost. Our aim is to improve the sensitivity of an anodized porous alumina capacitive humidity sensor by a simple method. A nanostructure porous film has been formed on each side of a pure aluminum substrate (99% purity) by an electrochemical anodization method. Two parallel plate capacitors are formed by depositing metal plate on each side of the metal oxide film with bulk aluminum as the common electrode. The sensitivity has been increased by connecting the two parallel plate capacitive sensors in parallel. Thus, two capacitive sensors on single substrate are fabricated and connected in parallel to form the third capacitor, which is used as the humidity sensor. The sensitivity, response time, recovery time, and hysteresis of the sensors are determined with variation in the range from 10% to 99% relative humidity (RH). The sensitivity of the sensor obtained by connecting two capacitors in parallel has been increased by almost two times compared to the sensitivity of an individual sensor fabricated on each side.

Sustainable micro-manufacturing of superhydrophobic surface on ultrafine-grained pure aluminum substrate combining micro-embossing and surface modification

A hybrid process combining hot micro-embossing process with subsequent surface modification was proposed to realize an economic, environmental-friendliness and reusable sustainable production of superhydrophobic surfaces on ultrafine-grained (UFG) pure aluminum substrate. Hot micro-embossing was executed using a silicon die at 523 K with the force of 4.5 kN, where an array of micro hexagonal pillar patterns was formed with feature side length ranging from 75 μm to 165 μm. The embossed micro array structures were clearly printed well, with a good geometric transitivity and no obvious disfigurement. After surface modification, the water contact angle of the embossed surface, following by immersed in boiling water with micro/nano hierarchical structures, reached ∼160° which increased by 142% compared with original UFG pure aluminum. Moreover, the mechanism of the obtained superhydrophobic surface with high adhesive force was analyzed, which would be attributed to the Cassie impregnating wetting regime. The research indicates that there is a potential application by using hot micro-embossing process in the mass and sustainable production of superhydrophobic surfaces with excellent adhesive property without pollution.

Robust and superhydrophobic coating highly resistant to wear and efficient in water/oil separation

Here, we report a straightforward and rapid process using fatty acids to produce a stable superhydrophobic hybrid composite coating on aluminium substrate which is highly resistant to wear under environmental conditions. Furthermore, this novel superhydrophobic metal surface is highly efficient at separating of water/oil systems. The single-step process we adopt involves electrochemical deposition of ZnCl2, α-Al2O3 and lauric acid (C11H23COOH) onto commercial pure aluminium substrate. The resultant static contact angle (170°) and sliding angle (1°) are those of a superhydrophobic coating with self-cleaning properties; while chemical analysis shows that this is the result of generation of zinc laurate (Zn(C11H20COO)2) as a major compound that increases the superhydrophobic character of the coating, generating a flower-like structure 70 nm thick. Different wear tests show the coating is resistant to severe conditions, confirming its real potential against weathering, including sand and water erosion. Finally, a water/oil separation test determined 99% separation efficiency in hexane and ether petroleum systems, in a laboratory-made storage tank.

Superhydrophobic Coating Bioinspired on Rice Leaf: A First Attempt to Enhance Erosion Resistance Properties at Environmental Conditions with Ceramic Particles

This study develops a new, facile and rapid process bioinspired on rice leaf with the aim of producing a hybrid composite coating in a first attempt to obtain a superhydrophobic coating with enhanced erosion resistance properties. Rice leaves (Oryza sativa L.) are made of hierarchical structures consisting of micropapillae and waxy nanobumps which confer to the surface a contact angle of 164° as Lotus leaf does. In particular, rice leaves accumulate amorphous silica inside and on the surface with various morphologies. This kind of silica is produced by absorbing silicates from the soil under specific conditions of temperature and pressure. The presence of biosilica in rice leaves is useful for preventing diseases or improves mechanical properties of the leaves. Single-step and two-step processes are the two strategies applied for generating a superhydrophobic coating by electrochemical deposition of ZnCl2, α-Al2O3 and lauric acid (C11H23COOH) onto commercial pure aluminum substrate. The static contact angle measured on the coating gives values of 170° and 1° for the sliding angle conducing to a coating with superhydrophobic and self-cleaning properties. Various characterization techniques are used to determine chemical and morphological structure such as FESEM, XPS or FTIR. On one hand, in morphological analysis, flower-like structure is obtained with petals thickness of 70nm corresponding to the nanostructured contribution to the system. On the other hand, chemical analysis concludes the generation of zinc laurate (Zn (C11H23COO)2) as a major compound contributing to the reduction of surface tension and increasing the superhydrophobic character of the coating as well.

Investigation of nanomechanical and adhesion behavior for AlN coating and AlN/Fe2-3N composite coatings created by Active Screen Plasma Nitriding on Al 1050

This study investigated the effect of nitriding time and temperature on the mechanical properties of the composite AlN/Fe2-3N coating deposited on the pure aluminium substrate using the novel Active Screen Plasma Nitriding (ASPN) method. ASPN treatment was performed for 2, 5, 10, 15 h at temperatures of 450,500, and 550 °C and Conventional Plasma Nitriding (CPN) treatment was carried out for 5 h at 500 °C. All treatments were performed at the 10 KHz frequency with 80% duty cycle on the Al1050 substrate under 20%H2+80%N2 atmosphere. Phase and microstructure studies were performed using, respectively, the grazing incidence x-ray diffraction (GIXRD) system and the field emission - scanning electron microscopy (FE-SEM) system equipped with energy-dispersive spectroscopy (EDS) analyzer. The mechanical strength of the coating was evaluated by the roughness, nano-hardness, nano-scratch, and adhesion strength tests performed on coated and uncoated specimens. According to the results, the uncoated Al1050 specimen, the CPN-treated specimen, and the ASPN-treated specimen had a mean nano-hardness of 0.7 ± 0.1 GPa, 10.9 ± 0.6 GPa, and 9.6 ± 0.5 GPa, respectively. It was also found that the single-phase AlN coating has a better adhesion strength and scratch strength (LC3 = 12 N) than the composite AlN/Fe2-3N coating (LC3 = 10 N). Examination of scratch mechanisms in hard AlN and AlN + Fe2-3N coatings deposited on a soft aluminium substrate showed that the failures in these coatings are due to tensile-type Hertzian cracks. However, as the load increases, the substrate undergoes increasing deformation and failures shift to chipping and interfacial spallation.

Microstructure and Properties of Cladding Layers Prepared by Argon-Shielded Arc Cladding of CuZn40-WC Powders on Pure Aluminum Substrate

Aluminum and aluminum alloys have the advantage of a high strength-to-weight ratio, but their low hardness and poor wear resistance often cause wear damage. In the present study, the cladding layer was prepared using argon-shielded arc cladding of CuZn40-WC powders which were pre-coated on a pure aluminum substrate. The effects of WC proportion on the morphology, microstructure, and properties of cladding layers were investigated in detail. The results indicated that the optimal WC proportion in CuZn40-WC powders was 60 wt.%. With the increase of WC proportion, although the morphology of the cladding layer became slightly worse, the surface quality of the cladding layer was acceptable for industrial application until the WC proportion was 80 wt.%. Meanwhile, the top width and maximum depth of the cladding layer decreased. The maximum microhardness and optimal wear resistance of the cladding layer were 4.5 and 2.5 times that of the aluminum substrate, respectively. The increased microhardness and wear resistance were mainly attributed to the formation of Al4W in the cladding layer. The wear scar of the high wear resistance specimen was smoother and some bulk Al4W compounds were clearly observed on the wear surface.

Antimony Tri-Sulfide (Sb2S3) Nanowires Synthesis and Characterization

During the past decade, one-dimensional (1D) nanostructures such as wires, rods, belts, and tubes have been explored extensively in nanotechnology due to their excellent properties, which may lead to unique applications in various nanoscale device. It is known that nanowires with high aspect ratios can provide a low-scattering transport path of the carriers and the electron and hole energy states become discrete due to the spatial confinement, which are highly beneficial for achieving high-performance electrical or optical properties. Antimony tri-sulfide (Sb2S3) is a low-toxic and earth-abundant semiconductor and important binary chalcogenide, that with an energy band gap varying between 1.78 and 2.2 eV has attracted particular attention and . Owing to its good photovoltaic properties, high thermoelectric power, suitable valence band position, and broad spectrum the response. Sb2S3 used in technological applications such as photo-catalysis, photovoltaics, and thermoelectric devices[1-2] . It has a direct band gap with large absorption coefficient (>104 cm−1) in the visible region. Especially, it has wide application in optical property because of wide band gap and the other point is the thermoelectric property of Sb2S3. The Sb2S3 of NWs show excellent light-to-heat performance. In this work, Sb2S3 nanowires (NWs) were fabricated by a vacuum hydraulic pressure injection process using anodic aluminum oxide (AAO) as templates. The AAO quality depends on the purity of Al substrate. The higher Al purity, such as 99.999% (5N), the better quality of AAO with uniform pore diameter can be obtained. The AAO templates with, 70 nm, and 100 nm diameters are manufactured by anodizing a pure aluminum (Al) substrate (99.999%) in acid solutions of oxalic acid (COOH)2. It will help us to easily get a large quantity and uniform Sb2S3 NWs. The nanomaterials arrayed photoelectric devices have great potential to obtain high sensitivity, fast response, and low energy consumption. The highly ordered array nanostructure can be achieved with high-aspect-ratio template. Porous anodic aluminium oxide played a significant role for the fabrication of Sb2S3, which controlled the diameter of NWs. Compare to the other synthesis, vacuum hydraulic pressure injection process is easy way to fabricate heterogeneous structure. First, antimony tri-sulfide powder was prepared by Sb/S=2/3 in a vacuum quartz tube and make the powder homogeneous mixing. Then, it was melted at 650 oC for 20 min and homogenized at 520 oC for 1 day. Then, the Sb2S3 of ingot was slowly cooling to room temperature. After Sb2S3 ingot was obtained, mechanical polishing was conducted to remove surface oxide. Second, the ingot of Sb2S3 was placed between the two plates of AAO template. Next, the entire chamber was vacuumed and heated to 600 oC again, holding the temperature for 5 min, load 50 kgf / cm2 for 1 min to press. Then, the melting Sb2S3 is pressed into the AAO template to form Sb2S3 nanowire array. Finally, the entire chamber was cooled down under air atmosphere and etch the AAO of Sb2S3. It will obtain the nanowires. Moreover, we will observe the different condition of NWs by controlling the time of etching. The time of etching decides the cleanness of NWs. As the time is longer the mass of bundles will decrease. Also, the difference of acid solutions is one of the important condition of etching the NWs, such as phosphoric acid (H3PO4), chromic acid (H2CrO4). In this work, we use chromic acid to etching the AAO to obtain the NWs. The temperature of the acid solution also affect the rate of etching speed. The temperature of etching is kept at around 60 oC. Combination of above conditions, the diameter of NWs is around 70 nm, the length of NWs is about 6 µm. Furthermore, The morphologies and crystal structures of Sb2S3 NWs were characterized by using optical microscopy (OM), field-emission scanning electron microscope (FE-SEM), X-Ray diffraction (XRD), UV-Vis spectrophotometry, Raman spectroscopy and transmission electron microscopy (TEM). The composition was analyzed with energy dispersive x-ray spectroscopy (EDS) attached the SEM. In the future, we can fabricate the heterogeneous structure of Sb system and Sb2S3 NWs to increase the diversity of the research on electrical and optical applications. Ref. [1] Kai Zhang, Tao Luo, Haoran Chen, Zheng Lou and Guozhen Shen, Au-nanoparticles-decorated Sb2S3 nanowirebased flexible ultraviolet/visible photodetectors.. J. Mater. Chem. C, 2017, 5, 3330-3335. [2] Godël, K. C.; Choi, Y. C.; Roose, B.; Sadhanala, A.; Snaith, H. J.; Seok, S. I.; Steiner, U.; Pathak, S , K.Efficient Room Temperature Aqueous Sb2S3 Synthesis for Inorganic-Organic Sensitized Solar Cells with 5.1% Efficiencies. Chem. Commun, 2015, 51, 8640– 8643.

Plastic-deformation-driven SiC nanoparticle implantation in an Al surface by laser shock wave: Mechanical properties, microstructure characteristics, and synergistic strengthening mechanisms

Laser shock-wave-driven nanoparticle implantation (LSWNI) in alloys is a novel surface strengthening technique based on plastic deformation induced by laser shock processing and the excellent properties of hard-phase nanoparticles. In the present work, 50–100 nm silicon carbide (SiC) nanoparticles were successfully implanted into commercially pure aluminum (Al) substrates under the effect of a laser shock wave. After the implantation, stable nanoparticle-reinforced layers were fabricated, and their microstructural response and grain refinement were characterized by X-ray diffraction (XRD), focused ion beam (FIB), and transmission electron microscopy (TEM). In addition, the mechanical properties, including residual stress, nanohardness, elastic modulus, and wear resistance, were investigated. Experimental results showed that Al samples subjected to LSWNI exhibited superior mechanical properties because of the good combination between the gradient microstructure induced by plastic deformation and the gradient distribution of the implanted SiC nanoparticles along the depth direction. Therefore, the overall strengthening effect generated by the LSWNI process can be described as two different modes: (i) the gradient microstructure induced by plastic deformation contributed mainly to the enhancement of residual stress and nanohardness, and (ii) the gradient distribution of the implanted SiC nanoparticles was dedicated primarily to the improvement of the wear resistance. As indicated by the strengthening effect during the LSWNI process, three competing strengthening mechanisms, namely, SiC nanoparticle strengthening, refined grain strengthening, and dislocation strengthening, existed in the gradient-reinforced layers. The detailed contribution of each mechanism to the overall properties of the reinforced layer was determined using the modified Clyne computational model and was described herein. Finally, the wear mechanism of the reinforced layer fabricated by the LSWNI process is revealed.

Polycrystalline silicon films obtained by crystallization of amorphous silicon on aluminium based substrates for photovoltaic applications

The fabrication of crystalline silicon thin films on foreign substrates is an attractive and alternative approach to the ingot casting aiming to the reduction of the total costs of photovoltaic cells and modules. The purpose of this work is to describe the CRYSTALSI process which aims at forming polycrystalline silicon films thanks to the thermal crystallization of amorphous silicon layer deposited on aluminium based substrates. The latest are used as a catalyzer for silicon crystallization but also as a back metal contact and reflector for photovoltaic solar cells. Two types of aluminium substrates were applied in these studies: a pure aluminium substrate (99.7% purity) and a silicon rich aluminium substrate containing about 12% of silicon. Silicon thicknesses between 1 and 10μm were deposited and then annealed at temperatures of 490°C, 520°C and 550°C and for duration times from 5min to 12h. The crystallized silicon films were then characterized by Raman spectroscopy, by scanning electron microscopy and by electron backscatter diffraction. The analyses show that the resulting annealed film is composed of two distinct layers: a thin polycrystalline silicon film located just above the substrate and a thicker layer made of a mixture of silicon and aluminium. Contrary to the case of the pure aluminium substrate, the silicon rich aluminium substrate allow to obtain thick and continuous polycrystalline silicon layers due to a controlled diffusion of the silicon within the substrate. As a result, the crystallization at 550°C of 5μm thick amorphous silicon on silicon rich aluminium substrate led to the formation of a thick polycrystalline silicon layer composed of grains of few micrometers in size. A low activation energy of about 2eV is extracted suggesting that the silicon rich aluminium substrate is a catalyzer for the crystallization of amorphous silicon. As for the AIC process, it can be noticed that the limiting step of the CRYSTALSI process is the diffusion of the silicon in the aluminium. A chemical etching using a HNO3, HF, H2O (72.5ml/1.5ml/28ml) solution is found to be appropriate to remove the residual top layer, in order to have access to the polycrystalline silicon layer. This work demonstrates that the CRYSTALSI process can lead to the formation of polysilicon films that can serve as a seed layer for the growth of a thicker absorbing silicon film for photovoltaic applications.

Plasma current analysis using discrete wavelet transform during plasma electrolytic oxidation on aluminum

Plasma electrolytic oxidation (PEO) was performed on commercially pure aluminum substrate at a constant applied potential of 520V in a solution composed of 0.05 M KOH, 0.04 M Na4P2O7 and 0.04 M NaAlO2 compounds. Orthogonal discrete wavelet transform (ODWT) was employed to analyze plasma currents at different time stages of the PEO process. The results of wavelet transform were presented in the form of energy distribution (ED) and standard deviation of partial signal (SDPS) plots. The variations of PEO coating morphology with processing time were also studied by scanning electron microscope (SEM). The comparison of the ED plots at different processing time stages indicated that the current transient shapes remained unchanged during the whole PEO process. Similarly, a detailed comparison of the SDPS plots indicated that the intensity and lifetime of plasma discharges increased and their frequentness decreased with processing time. The SEM micrographs of the surface and cross section of the coating supported the findings of wavelet transform in case of both pore size and population. It was also shown that the lifetime of B-type plasma discharges which were responsible for the dielectric breakdown phenomena and coating thickness enhancement, increased from ~80μs to ~160μs with time. In addition, increasing the intensity and lifetime of B-type plasma discharges led to regeneration of the interfacial voids and discontinuities, particularly in the last stages of the process.