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High entropy (HE) materials have received significant attention in recent years, due to their intrinsically high levels of configurational entropy. While there has been significant work exploring HE alloys and oxides, new families of HE materials are still being revealed. In this work we present the synthesis of a novel family of HE materials based on lanthanide oxysulfides. Here, we implement lanthanide dithiocarbamates as a versatile precursor which can be mixed at the molecular scale prior to thermolysis in air at low temperatures in order to produce the high entropy oxysulfide. The target of our synthesis is the HE Ln2SO2 phase, where Ln = Pr, Nd, Gd, Dy, Er or Pr, Nd, Gd, Dy for 5 and 4 lanthanide samples, respectively. We confirmed the structure of samples produced by powder X-ray diffraction, electron microscopy and high-resolution energy dispersive X-ray spectroscopy. Optical measurements show a broad emission feature centered around 450 nm as well as a peak in absorption at around 280 nm.

The transformation of unstable austenite to ferrite or α′ martensite as a result of exposure to Xe+ or Ga+ ions at room temperature was studied in a 304 stainless steel casting alloy. Controlled Xe+ and Ga+ ion beam exposures of the 304 were carried out at a variety of beam/sample geometries. It was found that both Ga+ and Xe+ ion irradiation resulted in the transformation of the austenite to either ferrite or α′ martensite. In this paper, we will refer to the transformation product as a BCC phase. The crystallographic orientation of the transformed area was controlled by the orientation of the austenite grain and was consistent with either the Nishiyama–Wasserman or the Kurdjumov–Sachs orientation relationships. On the basis of the Xe+ and Ga+ ion beam exposures, the transformation is not controlled by the chemical stabilization of the BCC phase by the ion species, but is a result of the disorder caused by the ion-induced recoil motion and subsequent return of the disordered region to a more energetically favorable phase.

In this work, the single event effect of the Silicon-germanium heterojunction bipolar transistor (SiGe HBT) was thoroughly investigated. By considering the worst bias condition, the sensitive area of the proposed device was scanned with a pulsed laser. With the variation of the collector bias and pulsed laser incident energy, the single event transient of the SiGe HBT was studied. Moreover, the single event transient produced by the laser irradiation at 532 nm wavelength was more pronounced than that of the 1064 nm wavelength. Finally, the impact of the equivalent linear energy transfer (LET) of the 1064 nm pulsed laser on the single transient event was qualitatively examined by performing technology computer-aided design (TCAD) simulations, whereas a good consistency between the experimental data and the simulated outcomes was attained.

A 3-MeV proton irradiation experiment was carried out on an AlGaN/GaN high-electron-mobility-transistor (HEMT). The results showed that the device's saturation drain current decreased, the threshold voltage drifted positively, and the maximum transconductance decreased after irradiation. Interestingly, the forward gate leakage current was almost unchanged, and the reverse gate leakage current was reduced by two orders of magnitude. We found that this experimental phenomenon can be well explained by the Poole–Frenkel emission model. Proton irradiation led to deeper defect energy levels and higher defect concentrations of the device. Deeper defect energy levels made it more difficult for electrons to be excited from the trap state into the conduction band. Thus, the reverse gate leakage current decreased. Higher defect concentrations led to degradation of the output and transfer curves of the device. The deep level transient spectroscopy characterization defect further proved the correctness of this model. The reduction in the reverse gate leakage current had a positive impact on AlGaN/GaN HEMT devices in high power or high frequency applications.

Laser surface melting (LSM) was carried out on the SiCp/Al metal matrix composite (MMC) using a KrF excimer laser with a fluence of 7 J/cm2. The re-solidification microstructure was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with energy dispersive X-ray detector, and X-ray diffraction (XRD) analysis. It was found that a 2.5 μm thick melted layer was formed in the near-surface region, in which dissolution of the intermetallics and removal of the SiC particles occurred. The thermal and material response upon laser irradiation was simulated using three models, i.e. analytical model, finite element model (FEM) and smoothed-particle hydrodynamics (SPH) model. The effect of SiC particles on the LSM process, the mechanism of the SiC removal and the re-solidification microstructures in the melted layer were discussed. The simulation results were in good agreement with the experimental results and contributed to the generic understanding of the re-solidification microstructures induced by ns-pulsed lasers.

In recent years, an increasing number of studies utilizingin situliquid and/or gaseous cell scanning/transmission electron microscopy (S/TEM) have been reported. Because of the difficulty in the preparation of suitable specimens, these environmental S/TEM studies have been generally limited to studies of nanoscale structured materials such as nanoparticles, nanowires, or sputtered thin films. In this paper, we present two methodologies which have been developed to facilitate the preparation of electron-transparent samples from conventional bulk metals and alloys forin situliquid/gaseous cell S/TEM experiments. These methods take advantage of combining sequential electrochemical jet polishing followed by focused ion beam extraction techniques to create large electron-transparent areas for site-specific observation. As an example, we illustrate the application of this methodology for the preparation ofin situspecimens from a cold-rolled Type 304 austenitic stainless steel sample, which was subsequently examined in both 1 atm of air as well as fully immersed in a H2O environment in the S/TEM followed by hyperspectral imaging. These preparation techniques can be successfully applied as a general procedure for a wide range of metals and alloys, and are suitable for a variety ofin situanalytical S/TEM studies in both aqueous and gaseous environments.

The corrosion and environmentally assisted cracking susceptibility of grade 2205 duplex stainless steel beneath a FeCl3:MgCl2-containing salt deposit has been investigated. Long-term exposure to atmospheric environment at 50°C and 30% relative humidity resulted in different forms of corrosion and the formation of cracks depending on the location under the salt-laden droplet. Selective dissolution with closely-spaced microcracks of the ferrite suggested hydrogen embrittlement toward the center of the droplet, with chloride-induced stress corrosion cracking and selective dissolution of the austenite observed toward the rim of the deposit. Cracks in the ferrite had cleavage-like appearances, typically forming within existing cracks, whereas the austenite had branched cracks, initiating from crevices and pits. These observations are discussed in light of expected electrochemical potential variations beneath the droplet.

Electrochemical measurements and substrate analysis have been employed to study the corrosion of iron in sweet solution (pH = 6.8, T = 80 °C) over a period of 288 h. Correlated with decreasing corrosion rate, diffraction, microscopy, and spectroscopy data reveal the evolution of adhered sweet corrosion scale. Initially, it is comprised of two phases, siderite and chukanovite, with the latter affording little substrate protection. Subsequently, as the scale becomes highly protective, siderite is the sole component. Notably, siderite crystals are concluded to display a somewhat unexpected habit, which may be a trigger for local breakdown of protective sweet scales.

In the present study, potentiodynamic polarization scans followed by potentiostat anodizing tests have been employed to generate the anodic oxide films on commercially pure Ti in 1 M sulfuric acid and 1 M phosphoric acid. The highly stable single-barrier anodic films with a growth ratio of ∼1.5 nm V-1 (sulfuric acid) or ∼1.7 nm V-1 (phosphoric acid) were generated at the anodic voltages from 10 V to 60 V. During the potentiostatic anodizing, the anodic film was formed after the growth of the passive oxide film in the potentiodynamic polarization stage. Oxygen evolution proceeded within both the polarization and the anodizing stages, resulting in the suppression of the current efficiency for the growth of anodic films. The oxygen bubbles were induced by the amorphous-to-crystalline transition within the anodic film, leading to the formation of blister textures. Significant rupture of the anodic film was found that started at 20 V of the anodizing processes in the sulfuric acid; conversely, the significant rupture was started at 50 V in the phosphoric acid. The XRD results indicated that the degree of amorphous-to-crystalline transition in the anodic film formed in the phosphoric acid was less than the film formed in the sulfuric acid. The phosphate titanium oxide layers detected by XPS in the phosphoric acid indicated that more degrees of the amorphous-to-crystalline transition might be inhibited compared with the sulfated titanium oxides found in the sulfuric acid.

The formation of anodic oxide films on the Ti6Al4V alloy in the NaTESi electrolyte has been studied in the present paper. An anodic film with a shallow pore-like texture was formed after anodizing to 10 V. Porous anodic films with increased porosity were generated after anodizing from 20 to 40 V, and the pores were developed mainly within the α phase. Significant amounts of sodium species were incorporated in the films, and the amount increased with increasing anodizing voltage. The current efficiency for the anodic film growth increased from 10 to 30 V, but decreased from 30 to 40 V due to the occurrence of more oxygen evolution. The film thicknesses determined by RBS were 15 nm, 65 nm, 115 nm and 250 nm at 10, 20, 30 and 40 V respectively. The film thickness generated at 10 V showed good agreement with the thickness of 11 nm revealed by transmission electron microscopy. The Raman spectra indicated that the degree of crystallinity of the anodic film increased at higher voltages. The dielectric permittivity of the film was estimated as ∼118 according to the results from transmission electron microscopy and electrochemical impedance spectroscopy. Single-lap shear bonding tests were employed to compare the strength of adhesively joined titanium alloy anodized to different voltages. The results revealed appreciable increase in bond strength with increasing anodic film thickness.

In the present study, two composites, reinforced with 25 vol% SiC particles with average sizes of 3 μm (micrometer-sized, composite A) and 0.7 μm (submicrometer-sized, composite B), respectively, were evaluated to investigate the effect of reinforcements on the corrosion behavior of SiCp/Al Alloy 2124 (UNS A92124) metal matrix composites. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements performed in a 0.6 M NaCl solution revealed that composite B, whose corrosion resistance was close to that of AA2124, exhibited higher corrosion resistance than composite A. It was found that the composition and distribution of the intermetallic particles in the aluminum matrix were altered by the addition of SiC particles. Preferential precipitation of Al2Cu (θ-phase) and Mg segregation in the SiC/Al interfacial regions were observed and are believed to be responsible for the inferior corrosion performance of composite A. The improved corrosion resistance of composite B was attributed t...

Ag–TiO2 nanoparticles were synthesised in ice water using a picosecond laser with a 1064-nm wavelength, at a 200-kHz repetition rate, a laser pulse energy of 42–43.79 µJ, and laser fluences of 0.342–0.357 J/cm2, by ablation of solid Ag and Ti targets. The absorption spectra and size distribution of the colloidal nanoparticles were obtained by UV–Vis spectroscopy and transmission electron microscopy, respectively. The morphology and chemical composition of the nanoparticles were characterised using high-angle annular dark-field-scanning transmission electron microscope and energy-dispersive X-ray spectroscopy. The results show that the sizes of the Ag–TiO2 nanoparticles range from less than 10–130 nm, with some large particles above 130 nm, of which the predominant size is 20 nm. A significant reduction in the energy gap of TiO2 nanoparticles was obtained to 1.75 eV after the modification with Ag nanoparticles during co-ablation. The role of Ag nanoparticles in the reduction in the energy band gap of the TiO2 nanoparticles can only be seen during laser ablation in an ice environment but not in deionised water at room temperature. Furthermore, the TiO2 nanoparticles were produced in ice and deionised water under the same laser and experimental conditions; the results show that the nanoparticles in both media have the same energy gap (about 2.4 eV). The antibacterial activity of the Ag–TiO2 nanoparticles generated was then tested against E. coli bacteria under standard laboratory light conditions. The results show that the nanoparticles can effectively kill E. coli bacteria much more effectively than laser-generated TiO2 nanoparticles.

Excimer laser surface melting (LSM) was performed to improve the corrosion resistance of the SiCp/AA2124 metal matrix composite (MMC). Corrosion evaluation of the MMCs showed evident improvement of the corrosion resistance after LSM, which was mainly attributed to the formation of a highly homogeneous surface layer with the dissolution of intermetallic particles and the redistribution of the alloying elements, as well as Si and C resulted from the decomposition of SiC particles. The elimination of micro-pores and micro-crevices introduced by the SiC particles after LSM also contributed to the improved corrosion resistance of the MMC.

In this work, a bulk Ti/Ag alloy was used, for the first time, to produce Ag–TiO2 compound nanoparticles using picosecond laser ablation in deionised water. Spherical Ag–TiO2 compound nanoparticles with an average size of 31 nm were produced. They were characterised using UV-VIS spectrometry, transmission electron microscopy (TEM), High-Angle Annular Dark-Field-Scanning Transmission Electron Microscopy (HAADF-STEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Diffraction (XRD) methods to identify the nanoparticle size distribution, morphology, chemical composition, phase and surface properties. It was found that Ag-doped TiO2 nanoparticles were produced. The optical absorption spectra of the Ag–TiO2 compound nanoparticles shifted to longer wavelengths. The antibacterial activity of the Ag–TiO2 compound nanoparticles against Gram-negative Escherichia coli (E. coli) bacteria was examined and compared with those using laser generated Ag and TiO2 nanoparticles and distilled deionised water (as the control). It was found that the antibacterial activity of the Ag–TiO2 compound nanoparticles was better than laser generated TiO2 nanoparticles and chemically produced Ag nanoparticles, and was almost as good as laser generated Ag nanoparticles while Ag–TiO2 was used at a much lower Ag concentrations. The reason behind this is discussed.

This article examines the substrate/coating interface of a coating deposited onto mild steel and stainless steel substrates using an ambient temperature blast coating technique known as CoBlast. The process uses a coincident stream of an abrasive blast medium and coating medium particles to modify the substrate surface. The hypothesis for the high bond strength is that the abrasive medium roughens the surface while simultaneously disrupting the passivating oxide layer of the substrate, thereby exposing the reactive metal that then reacts with the coating medium. The aim of this study is to provide greater insight into the coating/substrate bonding mechanism by analysing the interface between a hydroxyapatite coating on both mild and stainless steel substrates. The coating adhesion was measured via a tensile test, and bond strengths of approximately 45 MPa were measured. The substrate/coating interface was examined using transmission electron microscopy and selected area diffraction. The analysis of the substrate/ coating interface revealed the presence of ultrafine grains in both the coating and substrate at interface associated with deformation at the interface caused by particle impaction during deposition. The chemical reactivity resulting from the creation of these ultrafine grains is proposed to explain the high adhesive strength of CoBlast coatings. Programme for Research in Third Level Institutions (PRTLI), Ireland

Kesterite, Cu2ZnSnS4 (CZTS), is a promising absorber layer for use in photovoltaic cells. We report the use of copper, zinc and tin xanthates in melt reactions to produce Cu2ZnSnS4 (CZTS) thin films. The phase of the as-produced CZTS is dependent on decomposition temperature. X-ray diffraction patterns and Raman spectra show that films annealed between 375 and 475 °C are tetragonal, while at temperatures

High angle annular dark field scanning transmission electron microscope imaging and electron energy loss spectroscopy was used to elucidate the elemental distribution (Gd, Zn, Mn) within the long-period stacking ordered (LPSO) structure in a Mg-15Gd-0.8Zn-0.8Mn (wt%) alloy. While Gd and Zn enrichment was observed within the LPSO structure, no significant enrichment in Mn was observed. After averaging over a large region, a very weak Mn signal was resolved but no significant variations in Mn signal were observed over this region, suggesting that Mn is indeed present. These results provide useful information to support the future development of high performance Mg alloys.

High angle annular dark field scanning transmission electron microscope (HAADF-STEM) imaging and quantitative energy-dispersive X-ray spectroscopy (EDX) analysis was used to elucidate the Cu segregation on the interface between Al2O3 substrate and Al-1.4Cu alloy. A significant Cu segregation (about 2 at%) was observed, which can be mainly attributed to the enhanced diffusion caused by the high strain between Al2O3 substrate and Al-1.4Cu alloy. This investigation highlights the importance of Cu segregation and subsequent eutectic reaction on the heterogeneous nucleation of Al on Al2O3 substrate.

The present study examines the formation of anodic oxide films on commercially pure titanium in NaTESi electrolyte at a constant current density of 20 mA cm − 2 . The barrier-type titanium oxide films of ~ 30, 37 and 67 nm thick are formed when anodized to 5, 10 and 20 V. However, a porous film of approximately 80.0 nm thick is developed after anodizing to 40 V. Significant sodium species were found throughout the oxides and the concentration increases with the increase of anodic voltage. The growth efficiency is reduced by increasing the anodic voltage, due to formation of crystalline phase in the oxide, which induces oxygen generation. The degree of crystallinity of the anodic oxide film formed on titanium is increased associated with the increase of the anodic voltage. The dielectric permittivity of the anodic oxide film is estimated as 2.35 based on the oxide thickness measured when anodized to 10 V.

Barrier-type, nanocrystalline anodic films have been formed on a ZE41 magnesium alloy under a constant current density of 5 mA cm-2 in a glycerol/fluoride electrolyte, containing 5 vol.% of added water, at 293 K. The films contain magnesium, fluorine and oxygen as the major species, and lower amounts of alloying element species. The films grow at an efficiency of ∼0.8 to 0.9, with a formation ratio in the range of ∼1.2 to 1.4 nm V -1 at the matrix regions and with a ratio of ∼1.8 nm V -1 at Mg-Zn-RE second phase. At the former regions, rare earth species are enriched at the film surface and zinc is enriched in the alloy. A carbon- and oxygen-rich band within the film suggests that the films grow at the metal/film and film/electrolyte interfaces. © 2014 The Authors. Published by Elsevier Ltd.

Interpreting the remaining oil saturation in polymer flooding reservoir is very important for the oil exploration and development. Based on the original physical model of Archie formula, a kind of remaining oil saturation interpretation method for the polymer flooding reservoir is proposed, on the analysis of the variation rules of Archie parameters caused by the polymer influences in the reservoir microscopic pore structure, conductivity and wettability in this article. Theoretical analysis and actual applications show that Archie formula is still applied to calculate the remaining oil saturation for polymer flooding reservoir. This formula form is simple, easy to calculate the parameters, the interpretation accuracy can satisfy the practical development needs, and can be widely used for polymer flooding reservoir.

The reaction between (NH4)2TiF6 and H3BO3 in the presence of varying quantities of PEG-6000 was used to form NH4TiOF3 mesocrystals (MCs). The amount of PEG-6000, employed as a template, is crucial to the formation of defect free, non-agglomerated NH4TiOF3 MCs; high concentrations lead to MC agglomeration, lower ones result in centralized defects. This polymer-mediated formation process may be understood using an analogy with known polymerization reactions. The oxofluorotitanate MCs readily undergo a thermal topotactic transformation to give anatase MCs with photocatalytic activity. The TiO2 MCs are porous, with highly orientated lamellar crystallites that form part of the larger mesocrystal structure.

Materials ultramicrotomy has been progressed at Manchester for many years, enabling generation of suitably thin specimens for transmission electron microscopy. In addition, the remaining block specimen from which thin, electron transparent specimens have been generated also provides the basis for specimen preparation for high resolution backscattered electron imaging in the scanning electron microscope. This knowledge allows generation of serial sections of appropriate specimens that are oxide- and contamination-free for high resolution observation in the backscattered imaging mode. With recent instrumental developments, i.e. the GATAN 3View System, enabling ultramicrotomy to be performed in-SEM, relatively rapid sectioning and imaging can now be performed with ready reconstruction of electron tomographs. Further, correlative microscopy can be undertaken by utilising the GATAN XuM system in the same scanning electron microscope, enabling non-destructive X-ray tomography in addition to destructive electron tomography. The in-SEM, serial sectioning of selected aluminium alloys is considered here, as well as correlation of the X-ray and electron tomography approaches on the penetration of localised corrosion into an AA2024 T351 aluminium aerospace alloy. Copyright ?? 2013 John Wiley & Sons, Ltd. Copyright ?? 2013 John Wiley & Sons, Ltd.

Based on the sequence stratigraphy principle, reservoir forming elements has been detailed analysis in Cretaceous system of Hailaer basin, by using core, logging and 3-D seismic data. The study shows that the thick mudstone layer in the transgressive systems tract of the super-sequence is good regional source rock .and regional caprock, meanwhile the sandbody developed in transgressive systems tract and highstand systems of the super-sequence become the regional reservoir of depression. The main hydrocarbon migration pathway is uncomformable surface, fault, frame-sandstone, or that the hydrocarbon born in source rock went into the sandstone of sublacustrine fan directly, and then, lithologic reservoirs was formed.

Semiconductive composites have been examined using advanced scanning electron microscopy (SEM). For the first time, voltage contrast and energy contrast between the conductive filler and the polymer matrix have been revealed using a secondary electron detector placed inside the lens system and an energy selective backscattering detector respectively. Critical parameters, including loading level, distribution, dimension and shape of conductive fillers, correlating to the electrical conductivities of the composites, have been investigated and quantitatively determined. These parameters are essential for performance predictions, product quality control and new product development. The volume fractions of the conductive fillers in the two investigated composites were determined as 20.9% and 14.2% respectively. Higher frequency of distribution distance between the conductive filler aggregates within the ranges of 20–100 nm was revealed for the composite with volume fraction of 20.9%. The aggregates of conductive fillers showed mainly branched shapes. The information obtained provides further insight into the conductivity mechanism of conductive filler loaded polymer composite.

The geological structures of Zaobei area are broken seriously, because of the whole region was divided many blocks by many faults, which could bring huge difficulty to stratigraphic correlation. The high resolution sequence stratigraphy on Zao IV group in Zaobei oilfield was studied by using core data, logging and 3D seismic data. Features of sequence boundary in all available data were identified, and the characteristics of different levels of cycles were analyzed. Zao IV group in target zone was divided into one long-term base-level cycles, seven mid-term base-level cycles and twenty one short-term base-level cycles Based on the integrated research of core data description in single well logging data Correlation in wells and large scale horizontal Correlation Constrained by 3D scismic data, the high resolution sequence frame of Zao IV group is established, it provides important basis for future reservoir prediction and description.

Over the last two decades, hollow nanoparticles have received considerable attention from researchers due to their specific properties that do not appear in other forms of nanoparticles. It has been recognised that TiO2 hollow nanoparticles have superior photocatalytic properties than solid TiO2 nanoparticles. Previous methods of producing hollow TiO2 nanoparticles typically involve multiple-steps. In this paper, we report the production of hollow and porous TiO2 nanoparticles in a single step via high-repetition rate picosecond laser ablation in deionised water. The absorption spectra of the colloidal nanoparticles were obtained by UV-VIS spectroscopy. The size distribution and morphology were characterised by transmission electron microscopy (TEM). The morphology and chemical composition of the nanoparticles were characterised using a High-Angle Annular Dark-Field - Scanning Transmission Electron Microscope (HAADF-STEM) and Energy Dispersive X-ray Spectroscopy (EDS). In addition, the crystalline structures were investigated using X-ray diffraction (XRD). The results show that a higher ratio of crystalline hollow and porous TiO2 nanoparticles (20 - 160 nm in size with majority of hollow nanoparticles at 20 nm and an average size of 37 nm) of mixed anatase, rutile and brookite phases, was produced at lower laser energy; the yield was increased from 8% to 25% by reducing the laser power from 9.12 W to 3.35 W respectively. High laser powers result in reduced energy gap in the nanoparticles produced. The work shows that laser power can be used to control the yield of hollow nanoparticles.

Silver–titania (Ag–TiO2) nanoparticles with smaller Ag nanoparticles attached to larger TiO2 nanoparticles were generated by hybrid ultrasonic vibration and picosecond laser ablation of Ag and Ti bulk targets in deionised water, for the first time. The laser has a wavelength of 1064 nm and a pulse duration of 10 ps. It was observed that without the ultrasonic vibration, Ag and TiO2 nanoparticles did not combine, thus the role of ultrasonic vibration is essential. In addition, colloidal TiO2 and Ag nanoparticles were generated separately for comparison under the same laser beam characteristics and process conditions. The absorption spectra of colloidal Ag–TiO2 cluster nanoparticles were examined by UV–Vis spectroscopy, and size distribution was characterised using transmission electron microscopy. The morphology and composition of Ag–TiO2 nanoparticles were examined using scanning transmission electron microscopy in high-angle annular dark field, and energy-dispersive X-ray spectroscopy. The crystalline structures were investigated by X-ray diffraction. The size of larger TiO2 particles was in the range 30–150 nm, and the smaller-sized Ag nanoparticles attached to the TiO2 was mainly in the range of 10–15 nm. The yield is more than 50 % with the remaining nanoparticles in the form of uncombined Ag and TiO2. The nanoparticles generated had strong antibacterial effects as tested against E. coli. A discussion is given on the role of ultrasonic vibration in the formation of Ag–TiO2 hybrid nanoparticles by picosecond laser ablation.

This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the C=C bond completely through the chain scission process whereas C=C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the C=C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (C-O and C=O bond) and nitrogen-rich (C-N) functional groups.

Polycrystalline thin films of rhenium disulfide (ReS2) and the alloys Mo1−xRexS2 (0 ≤ x ≤ 0.06) have been deposited by aerosol-assisted chemical vapour deposition (AA-CVD) using [Re(μ-SiPr)3(SiPr)6] (1) and [Mo(S2CNEt2)4] (2) in different molar ratios at 475 °C. The deposited films were characterised by p-XRD, SEM, and ICP-OE, Raman, and EDX spectroscopies. The p-XRD patterns of the films deposited from (1) correspond to ReS2 (x = 1) and those deposited from (2) matched to MoS2 (x = 0). Re-doping of up to 6% was achieved in MoS2 thin films by using different concentrations of precursor (1), the morphology of the doped films changed from lamellar for pure MoS2 to clusters at 6 mol% alloying with rhenium. The films are promising candidates as models for the incorporation of technetium into transition metal dichalcogenides as a means of immobilisation in nuclear waste processing. Exfoliation of these films is also a potential route towards modification of the optoelectronic properties of 2D molybdenite.

The anodizing behaviour of constituent particles (Al–Fe–Mn–Cu) and dispersoids (Al–Cu–Mn–Li and β′(Al3Zr)) in AA2099-T8 has been investigated. Low-copper-containing Al–Fe–Mn–Cu particles anodized more slowly than the alloy matrix, forming a highly porous anodic oxide film. Medium- and high-copper-containing Al–Fe–Mn–Cu particles were rapidly dissolved, resulting in defects in the anodic film. The anodizing of Al–Cu–Mn–Li dispersoids is slightly slower than the alloy matrix, forming a less regular anodic oxide film. β′(Al3Zr) dispersoids anodized at a similar rate to the alloy matrix. Further, the potential impact of the discontinuities in the resultant anodic films on the performance of the filmed alloy is discussed.

In the present study, Sn-0.7Cu and Sn-3.5Ag lead-free solders used in the electronics packaging industry were reinforced with different volume percentages of nano-size alumina and tin oxide particulates, respectively, to synthesize two new sets of nanocomposites. These composites were developed using microwave-assisted powder metallurgy route followed by extrusion. The effects of addition of particulates on the physical, microstructural, and mechanical properties of the nanocomposites were investigated. Mechanical properties (microhardness, 0.2% YS, and UTS) for both composite systems increase with the presence of particulates. The best tensile strength was realized for composite solders reinforced with 1.5 vol.% alumina and 0.7 vol.% tin oxide particulates, which far exceeds the strength of eutectic Sn-Pb solder. The morphology of pores was observed to be one of the most dominating factors affecting the strength of materials.

Nano-size aluminum powder (Alp) reinforced magnesium composites were successfully synthesized using a powder metallurgy technique. Microstructural characterization of the materials revealed fairly uniform distribution of reinforcement. Mechanical properties characterization revealed that the presence of aluminum nanoparticles ⩽1 vol.% leads to an increase in hardness, 0.2% yield strength and ultimate tensile strength of magnesium. The average ductility of the composites was higher when compared with pure magnesium ⩽0.75 vol.% and decreased thereafter. An attempt was made in the present study to correlate the presence of nano-size aluminum reinforcement particles and their increasing number with the microstructural, physical and mechanical properties of magnesium.

Anodizing of sputtering-deposited magnesium and Mg-0.75at.%Cu and Mg-1.23at.%W alloys has been carried out in a fluoride/ glycerol electrolyte. The aims of the study were to investigate the enrichment of alloying elements in the alloy immediately beneath the anodic film and the migration of alloying element species in the film. The specimens were examined by electron microscopy and ion beam analysis. An enrichment of copper is revealed in the Mg-Cu alloy that increases with the anodizing time up to ∼6×1015 Cu atoms cm-2. Copper species are then incorporated into the anodic film and migrate outwards. In contrast, no enrichment of tungsten occurs in the Mg-W alloy, and tungsten species are immobile in the film.

Core-shell nanoparticles have unusual physical, chemical and biological properties. Until now, for the Ag and TiO2 combination, only Ag core and TiO2 shell nanoparticles have been practically demonstrated. In this investigation, novel TiO2@Ag core-shell (TiO2 core and Ag shell) nanoparticles were produced via ultrasonic vibration of Ag-TiO2 compound nanoparticles. A bulk Ti/Ag alloy plate was used to generate colloidal Ag-TiO2 compound nanoparticles via picosecond laser ablation in deionised water. The colloidal nanoparticles were then sonicated in an ultrasonic bath to generate TiO2@Ag core-shell nanoparticles. They were characterised using a UV-VIS spectrometer, transmission electron microscopy (TEM), high-angle annular dark-field-Scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The Ag-TiO2 compound and the TiO2@Ag core-shell nanoparticles were examined for their antibacterial activity against Escherichia coli (E. coli) JM109 strain bacteria and compared with those of Ag and TiO2 nanoparticles. The antibacterial activity of the core-shell nanoparticles was slightly better than that of the compound nanoparticles at the same concentration under standard laboratory light conditions and both were better than the TiO2 nanoparticles but not as good as the Ag nanoparticles.

Mn-doped ZnO diluted magnetic semiconductor nanoparticles are prepared by an ultrasonic assisted solgel process. Transmission electron microscopy shows pseudo-hexagonal nanoparticles with an average size of about 24 nm. From the analysis of X-ray diffraction, the Mn-doped ZnO nanoparticles are identified to be a wurtzite structure without any impurity phases. The magnetic properties are measured by using superconducting quantum interference device. For the ZnO with 2% Mn doping concentration, a good hysteresis loop indicates fine ferromagnetism with a Curie temperature higher than 350 K.

In the present study, elemental magnesium was reinforced with nano-size alumina particulates. Synthesis of materials was accomplished using the powder metallurgy route. Energy dissipation in the form of damping capacity was determined using free–free type suspended beam arrangement coupled with circle-fit approach. This technique is based on classical vibration theory, by which the geometry and material properties of the metallic specimen are related to measured resonant frequency and structural damping. Using the fact that the ratio of the vibration response to the applied force fits to a circle in the Argand plane for each resonant frequency of the test specimen, the damping factor and natural frequency is predicted accurately for the test specimen. The results revealed that an increase in the alumina content up to 0.4% volume percentage lead to an increase in the damping capacity up to 34%. Attempt is made to correlate the increase in damping with the various microstructural changes arising due to the presence of the nano-size alumina particulates in the composite sample.

In present study, elemental magnesium was reinforced with nano-size alumina particles (50-nm). The composite samples were synthesized using the technique of powder metallurgy and the effect of extrusion temperature and sintering on the end properties was particularly investigated. The results of microstructural characterization studies confirmed the presence and reasonably uniform distribution of alumina particles. Results obtained from extruded unsintered samples revealed that the hardness and dimensional stability of magnesium increases with an increasing presence of alumina particles while the 0.2%YS, UTS and ductility deteriorated. Results further revealed that including sintering step and extruding at higher temperature lead to an increase in dimensional stability, hardness, 0.2%YS, UTS and ductility for an alumina content as low as one percent by weight.

A combined single-source precursor approach has been developed for the deposition of thin films of Cr-doped molybdenum disulfide (MoS2) by aerosol-assisted chemical vapor deposition (AACVD). Tris(diethyldithiocarbamato)chromium(III) can also be used for the deposition of chromium sulfide (CrS). Films have been analyzed by a range of techniques including scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Raman spectroscopy, and powder X-ray diffraction (pXRD) to elucidate film morphology, composition, and crystallinity. The presence of Cr in the MoS2 films produces a number of striking morphological, crystallographic, and nanomechanical changes to the deposited films. The chromium dopant appears to be uniform throughout the MoS2 from the scanning transmission electron microscopy (STEM) EDX spectrum imaging of nanosheets produced by liquid-phase exfoliation of the thin films in N-methyl-2-pyrollidone.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

The effect of post-anodizing rinsing on the morphology and composition of anodic films formed on titanium at 20 V in 0.2 M ammonium fluoride solution in glycerol, containing 0 and 5 vol.% water is investigated. The films generated in the electrolyte with added water or those rinsed with water exhibited nanotubular morphologies. In contrast, anodizing in the electrolyte with no added water followed by rinsing with ethanol resulted in a porous film appearance due to the presence of a fluoride-rich matrix surrounding the nanotubes. The films rinsed with water revealed less fluorine, oxygen and titanium compared with those rinsed with ethanol that was attributed to dissolution of the fluoride-rich matrix by water. Addition of water to the electrolyte enables the formation of nanotubular films directly due to dissolution of the matrix during anodizing.