Influence of deposition parameters on surface morphology and application of CuInS2 thin films in solar cell and photocatalysis

Copper indium disulfide (CuInS₂) thin films as an absorption layer for solar cell and photocatalytic degradation of organic pollutants, were successfully electrodeposited on the FTO coated glass substrate using the simple and inexpensive electrodeposition method and a sulfurization process. The effects of the Cu/In molar ratio, annealing temperature and kind of Cu²⁺ precursor (Cu(salen) and Cu(acac)₂ as novel Cu²⁺ precursors) on the structural and morphological properties of samples were examined. The XRD diffraction patterns and energy dispersive spectroscopy measurements exhibit that high-quality film with superior crystalline structure was formed in the presence of Cu(salen) as Cu²⁺ precursor. Also, we found that a suitable heat treatment temperature could suppress the CuS phases and form well-crystallized CIS. As we know, this is the first reported efficiency for any CuInS₂ superstrate solar cell to date that fabricated using Cu(salen) as Cu²⁺ precursor. In addition, the photocatalytic degradation of organic dye in the presence of as-synthesized CuInS₂ thin films was studied. The as-prepared semiconductor photocatalysts have a good reusability; it can be successfully reused for 5 times recycling photoactivity tests.     

Electrochemical insertion of lithium into a doped diamond film grown on carbon felt substrates

This paper summarizes the preliminary results obtained from lithium electrochemical intercalation into boron-doped diamond films grown on carbon felt (BDD/CF electrode). BDD films have been grown by Hot Filaments Chemical Vapor Deposition (HFCVD) and have been characterized by Scanning Electron Microscopy (SEM) and Raman Scattering spectroscopy. BDD/CF composite electrodes, which contain a diamond layer, lead to higher conductivity and smaller grain sizes. In turn, they are richer in boundary or sp² sites, and present a reversible specific capacity that is much larger than that of the substrate alone, indicating that the diamond layer effectively participates in lithium storage. Diamond layers displaying boron doping levels of 10¹⁹ and 10²¹ part cm^− 3 provide a specific capacity of 160 and 370 mA h g^− 1, respectively, which is associated with lithium storage.     

Mechanical,forming and biological properties of Ti-Fe-Zr-Y alloys prepared by 3D printing

Biomedical Ti-Fe-Zr-Y alloys were prepared by 3D printing on pure titanium substrate. The influences of Zr on mechanical, forming, and biological properties of the alloys were investigated in detail. The results showed that with increasing the Zr addition, the surface roughness, friction coefficient and worn volume decrease at first and then increase, the lowest values obtained at 5.86 at.% Zr addition. The ultimate compression stress and specific strength gradually decrease. The studied alloys have no cytotoxicity. They can promote the early adhesion and proliferation of cells. The eutectic alloy with 5.86 at.% Zr addition has the best ability of apatite deposition, it exhibits a better comprehensive performance among the studied alloys, which is superior to the Ti_70.5Fe_29.5 and Ti-6Al-4 V alloys.     

Corrosion kinetics and patina evolution of galvanized steel in a simulated coastal-industrial atmosphere

The corrosion kinetics and patina (corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn₅(OH)₆(CO₃)₂ and Zn₄(OH)₆SO₄ are identified as the main stable composition and exhibit an increasing relative amount; while Zn₁₂(OH)₁₅Cl₃(SO₄)₃ cannot stably exist and diminish in the patina layer as the corrosion develops.     

Low-valence ion addition induced more compact passive films on nickel-copper nano-coatings

Ni-Cu nano-coatings were prepared by pulsed electroplating technique in the baths containing various amount of boric acid. Their microstructure, morphologies and corrosion resistance were characterized in detail. The addition of boric acid strongly influences on the microstructure of the Ni-Cu coatings. The coating with a grain size of 130 nm, obtained from the bath containing 35 g L⁻¹ boric acid, shows the highest corrosion resistance. This is attributed to the low-valence Cu ion (Cu⁺) additions in nickel oxide, which could significantly decrease the oxygen ion vacancy density in the passive film to form a more compact passive film. The higher Cu⁺ additions and the lower diffusivity of point defects (D₀) are responsible for the formation of more compact passive film on the coating obtained from the bath with 35 g L⁻¹ boric acid.     

Influence of cerium content on the corrosion behavior of Al-Co-Ce amorphous alloys in 0.6 M NaCl solution

The effect of cerium content on the corrosion behavior of Al-Co-Ce amorphous alloys in 0.6 M NaCl solution was investigated by cyclic polarization, Mott-Schottky and X-ray photoelectron spectroscopy techniques. Results indicated that the open circuit potential of Al-Co-Ce amorphous alloys displayed a decreased tendency with the increase in Ce content, and the amorphous alloy with 4 at.% Ce presented both the lowest passive current density and donor density indicating the best corrosion resistance, while adding excess Ce led to the reduced corrosion resistance of Al-Co-Ce alloys. Furthermore, it was found that a low Ce content is beneficial to the formation of a more protective passive film on Al-Co-Ce amorphous alloys, and the corrosion inhibition reactions of Al-Co-Ce alloys in 0.6 M NaCl solution were changed with the increase in Ce content and the detailed reasons were discussed.     

Analytical and numerical comparisons of biogeography-based optimization and genetic algorithms

We show that biogeography-based optimization (BBO) is a generalization of a genetic algorithm with global uniform recombination (GA/GUR). Based on the common features of BBO and GA/GUR, we use a previously-derived BBO Markov model to obtain a GA/GUR Markov model. One BBO characteristic which makes it distinctive from GA/GUR is its migration mechanism, which affects selection pressure (i.e., the probability of retaining certain features in the population from one generation to the next). We compare the BBO and GA/GUR algorithms using results from analytical Markov models and continuous optimization benchmark problems. We show that the unique selection pressure provided by BBO generally results in better optimization results for a set of standard benchmark problems. We also present comparisons between BBO and GA/GUR for combinatorial optimization problems, include the traveling salesman, the graph coloring, and the bin packing problems.     

Thaumasite formation in limestone filler cements exposed to sodium sulphate solution at 20 °C

This paper presents a microstructural analysis of mortars made with OPC (C₃A=6%) and two SRPCs (C₃A < 2% and C₃S=40% and 74%) containing 20% of limestone filler. Specimens analysed were immersed in Na₂SO₄ solution (5% w/w or 0.352 M) with pH control during two years at 20 ± 2 °C. The evolution of attack was determined using XRD semi-quantitative analysis on the material obtained by wearing in layers by millimetre to millimetre of the specimens. Complementary SEM and EDS studies were carried out to confirm the presence of thaumasite. Results show that OPC and high-C₃S SRPC containing 20% limestone filler were found to be more susceptible to sulphate attack than the corresponding plain cement. The attack was characterised by the inward front leading first to the formation of ettringite, later formation of gypsum and finally thaumasite formation, when the decalcification of the mortar lead to the breakdown of C–S–H, providing the required silica. The reaction sequence in Portland limestone cements is essentially the same as in plain Portland cements. The main change is that thaumasite is formed at later stages with decomposition of the ettringite formed during the firsts stage of attack. In SRPC with low C₃S, the attack was limited to the first millimetres and the thaumasite was not detected.     

Chemically dealloyed MgCuGd metallic glass with enhanced catalytic activity in degradation of phenol

Nanoporous Cu with tunable pore size (20–50 nm) are synthesized through chemical dealloying of the Mg₆₅Cu₂₅Gd₁₀ metallic glass in sulfuric acid solution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) demonstrated the formation of mixing structures consisting of amorphous matrix and fcc-Cu ligaments with nanoporous structure in the dealloyed samples. The nanoporous alloy obtained shows superior catalytic activity in degrading phenol-containing wastewater, e.g., the degradation rate increases by 2–4 times as compared to the un-dealloyed Mg-based metallic glass. It was also found that surface wettability plays an important role in degradation, which results in a better catalytic performance in the sample with coarser nanoporous structure although it has relatively less specific surface area as compared to the samples with finer pores. Finally, the mechanism for degradation of phenol is discussed.     

High resolution transmission electron microscopy study on polyacrylonitrile/carbon nanotube based carbon fibers and the effect of structure development on the thermal and electrical conductivities

Polyacrylonitrile (PAN) and PAN/carbon nanotube (CNT) based carbon fibers at various CNT content have been processed and their structural development was investigated using high resolution transmission electron microscope (HR-TEM). In CNT containing carbon fibers, the CNTs act as templating agents for the graphitic carbon structure development in their vicinity at the carbonization temperature of 1450 °C, which is far below the graphitization temperature of PAN based carbon fiber (>2200 °C). The addition of 1 wt% CNT in the gel spun precursor fiber results in carbon fibers with a 68% higher thermal conductivity when compared to the control gel spun PAN based carbon fiber, and a 103% and 146% increase over commercially available IM7 and T300 carbon fibers, respectively. The electrical conductivity of the gel spun PAN/CNT based carbon fibers also showed improvement over the investigated commercially available carbon fibers. Increases in thermal and electrical conductivities are attributed to the formation of the highly ordered graphitic structure observed in the HR-TEM images. Direct observation of the graphitic structure, along with improved transport properties in the PAN/CNT based carbon fiber suggest new applications for these materials.