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For the first time, Zr702 coatings were deposited onto an Al6061 alloy using a high-pressure cold spray (HPCS) system. In this work, five different N2 process gas temperatures between 700 and 1100 °C were employed to understand the formation of cold sprayed (CS) Zr coatings and their feasibility for enhanced wear resistance. Results indicated that the N2 processing gas temperature of about 1100 °C enabled a higher degree of particle thermal softening, which created a dense, robust, oxide- and defect-free Zr coating. Across all CS Zr coatings, there was a refinement of crystallinity, which was attributed to the severe localized plastic deformation of the powder particles. The enhanced thermal boost up zone at the inter-particle boundaries and decreased recoverable elastic strain were accountable for the inter-particle bonding of the coatings at higher process gas temperatures. The flattening ratio (ε) increased as a function of temperature, implying that there was a greater degree of plastic deformation at higher N2 gas temperatures. The microhardness readings and wear volume of the coatings were also improved as a function of process gas temperature. In this work, the wear of the Al6061 alloy substrate was mainly plowing-based, whereas the Zr CS substrates demonstrated a gradual change of abrasive to adhesive wear. From our findings, the preparation of CS Zr coatings was a feasible method of enhancing the wear resistance of Al-based alloys.

Rapid screening of tuberculosis by evaluation of associated volatile organic biomarkers in breath is a promising technology that is significantly faster and more convenient than traditional sputum culture tests. Methyl nicotinate (MN) and methyl p-anisate (MPA) have been isolated as potential biomarkers for mycobacterium tuberculosis and have been found in the breath of patients with active pulmonary tuberculosis. A novel approach to detection of these biomarkers in liquid droplets (e.g. from breath condensate) using inexpensive screen-printed electrodes is presented. Previous modelling studies suggest that these biomarkers complex with certain transition metals of particular valence state. This interaction can be exploited by mixing the biomarker sample into an electroactive solution (EAS) containing the functional metal ion and observing the change electrochemically. The study focuses on low biomarker concentrations, determined to be clinically relevant based on preliminary GC-MS studies of the levels found in patient breath. It was found that both the cyclic voltammogram and square wave voltammogram of copper(II) change significantly when as little as 0.1 mM MN is added to the solution, with analysis times of less than 2 min. Copper(II) exhibits three separate peaks during square wave voltammetry. The location and area of each peak are affected differently as the concentration of MN increases, suggesting a reaction with specific oxidation states of the metal. In this way, a "fingerprint" method can be used to identify biomarkers once their known interaction is established.

Nanostructuring is a commonly employed method of obtaining superior mechanical properties in metals and alloys. Compared to conventional polycrystalline counterparts, nanostructuring can provide remarkable improvements in yield strength, toughness, fatigue life, corrosion resistance, and hardness, which is attributed to the nano grain size. In this review paper, the current state-of-the-art of synthesis methods of nanocrystalline (NC) materials such as rapid solidification, chemical precipitation, chemical vapor deposition, and mechanical alloying, including high-energy ball milling (HEBM) and cryomilling was elucidated. More specifically, the effect of various process parameters on mechanical properties and microstructural features were explained for a broad range of engineering materials. This study also explains the mechanism of grain strengthening using the Hall-Petch relation and illustrates the effects of post-processing on the grain size and subsequently their properties. This review also reports the applications, challenges, and future scope for the NC materials.

Additive manufacturing (AM) by laser powder bed fusion (LPBF) has gained significant research attention to fabricate complex 3D Inconel alloy components for jet engines. The strategic advantages of LPBF-based AM to fabricate jet components for aerospace applications are well reported. The jet components are exposed to a high degree of vibration during the jet operation in a variable aqueous environment. The combined vibration and the aqueous environment create a tribological condition that can accelerate the failure mechanism. Therefore, it is critical to understand the tribocorrosion behavior of the Inconel alloy. In the present work, tribocorrosion behavior of the LPBF fabricated standalone coating of Inconel 718 in the 3.5% NaCl aqueous solution is presented. The LPBF fabricated samples are analyzed to determine the impact of porosity, generated as a result of LPBF, on the triobocorrosion behavior of AM Inconel 718. The study includes potentiodynamic tests, cathodic polarization, along with OCP measurements. The corrosive environment is found to increase the wear by 29.24% and 49.5% without the initiation of corrosion in the case of AM and wrought Inconel 718, respectively. A corrosion accelerated wear form of tribocorrosion is observed for Inconel 718. Additionally, the corrosive environment has a significant effect on wear even when the Inconel 718 surface is in equilibrium potential with the corrosive environment and no corrosion potential scan is applied. This study provides an insight into a critical aspect of the AM Inconel components.

In this study, a compact cold sprayed (CS) Ti coating was deposited on Mg alloy using a +high pressure cold spray (HPCS) system. The wear and corrosion behavior of the CS Ti coating was compared with that of CS Al coating and bare Mg alloy. The Ti coating yielded lower wear rate compared to Al coating and Mg alloy. Electrochemical Impedance spectroscopy (EIS) and cyclic potentiodynamic polarization (CPP) tests revealed that CS Ti coating can substantially reduce corrosion rate of AZ31B in chloride containing solutions compared to CS Al coating. Interestingly, Ti-coated Mg alloy demonstrated negative hysteresis loop, depicting repassivation of pits, in contrast to AZ31B and Al-coated AZ31B with positive hysteresis loops where corrosion potential (Ecorr) &gt, repassivation potential (Erp), indicating irreversible growth of pits. AZ31B and Al-coated AZ31B were most susceptible to pitting corrosion, while Ti-coated Mg alloy indicated noticeable resistance to pitting in 3.5 wt % NaCl solution. In comparison to Al coating, Ti coating considerably separated the AZ31BMg alloy surface from the corrosive electrolyte during long term immersion test for 11 days.

In response to the potential hazards associated with the globalization of the food industry, research has been focused on the development of new sensing techniques to provide the means of contamination detection at any stage in the food supply chain. The demand for on-site detection is growing as pre-emptive sensing of pathogens could eliminate foodborne-related outbreaks and associated healthcare costs. Reduction in food waste is also a driver for point-of-use (POU) sensing, from both an economic and environmental standpoint. The following review discusses the latest advancements in platforms that have the greatest potential for inexpensive, real-time detection, and identification of foodborne pathogens. Specific focus has been placed on the development techniques, which utilize micro- and nanoscale technology. Sample preparation-free techniques are also discussed, as the growing demand to enable POU sensing at any stage in the food supply chain will be a major driver toward the advancements of these nondestructive methods.

Composite electrochemical coatings (CECs) are some of the most widely investigated coatings due to its versatility in tailoring physio-mechanical and tribological properties. The effectiveness of the CECs for tribological applications is dependent on the solid&ndash, liquid interfaces. The active and passive nature of the contact boundaries for a CEC with a solid/liquid interface is defined by the surface energy of these boundaries. Unless the effect of surface energy on the tribological properties of the CEC are understood, it is not possible to get a holistic picture on properties, such as corrosion and tribocorrosion. The present study investigates the surface energy of optimized nickel (Ni) and Ni&ndash, graphene (Ni&ndash, Gr) coatings and their effect on the dynamic friction and wear behavior. It was found that the addition of Gr to the Ni coating in small quantities could decrease the polar component of surface energy significantly than the dispersive component. The presence of Gr in the coating was able to reduce the wear while providing low friction. The Ni&ndash, Gr coating exhibited low surface energy that includes weak adhesive forces, which can prevent embedding of the wear particles during sliding.

Surface modification methods have been applied to metals and alloys to change the surface integrity, obtain superior mechanical properties, and improve service life irrespective of the field of application. In this review paper, current state-of-the-art of peening techniques are demonstrated. More specifically, classical and advanced shot peening (SP), ultrasonic impact peening (UIP), and laser shock peening (LSP) have been discussed. The effect of these techniques on mechanical properties, such as hardness, wear resistance, fatigue life, surface roughness, and corrosion resistance of various metals and alloys, are discussed. This study also reports the comparisons, advantages, challenges, and potential applications of these processes.

The microstructures of dissimilar metal welds between 9Cr-1Mo (Modified) (P91) and austenitic stainless steel (AISI 304) with Ni-based alloy interlayers (Inconel 625, Inconel 600 and Inconel 800H) are reported. These interlayers were deposited by the friction surfacing method one over the other on P91 alloy, which was finally friction welded to AISI 304. In this paper, the results of microstructural evolution in the friction surfaced coated interlayers (Inconel 625, 600, 800H) are reported. For comparative purposes, the microstructures of consumable rods (Inconel 625, 600, 800H) and dissimilar metal base metals (P91 and AISI 304) were also reported. Friction surfaced coatings exhibited dynamic recrystallization. In friction surfaced coatings, the carbide particles were found to be finer and distributed uniformly throughout the matrix, compared to their rod counterparts.

Microfluidic reactors have gained considerable interest for photocatalytic degradation of contaminants in water. These systems have advantages such as large surface-area-to-volume ratio and high control of fluid flow, yet still suffer from drawbacks due to limited mass transport associated with laminar flow. The use of titania nanotubes synthesized on a mesh substrate shows improved photocatalytic performance in comparison to nanotubes synthesized on a foil substrate in a microreactor. At the lowest flow rate (25 μL/min), the area normalized fractional conversion of methylene blue increased from 20% for foil to 46% in the case of nanotubes on mesh. The enhanced photocatalytic performance of the mesh is due to shorter diffusion distance and induction of flow perturbation. Also, the radially outward oriented nanotubes formed over the circumference of the titanium wire leads to the efficient capture of both reflected and refracted light. The device was also applied for inactivation of Escherichia coli O157:H7. At a flow rate of 50 μL/min, the titania nanotubes on a mesh microreactor were able to achieve >99% inactivation of E. coli under AM 1.5 (≈100 mW/cm2) simulated solar light.

In this research, cold sprayed Al coating layer on AZ31B Mg alloy was coated with cold sprayed Ti and Ta/Ti coatings, which noticeably reduced the wear rate of Al coated Mg alloy. Electrochemical corrosion tests and infinite focus 3D measurement results revealed that the high surface activity of commercially pure-Al coating, diffusion-controlled reactions, and formation of corrosion pits could be mitigated using Ti top coating. However, a dense layer of Ta on Ti coating exceptionally improved the corrosion resistance of Ti/Al coated AZ31B Mg alloy in neutral 3.5 wt.% NaCl solution This work gives a new strategy to considerably raise the wear and corrosion resistances of cold spray Al coated Mg alloys by double layered Ta/Ti coatings.

Inconel 625, Inconel 600, Inconel 800H were friction surfaced on steel and Inconel substrates. The interface between steel and Ni-based alloys showed intermixing of two alloys while the interface between two Ni-based alloys showed no such intermixing. The XRD results confirmed that this intermixed zone consisted of mechanical mix two separate metals and no intermetallics were noticed. Friction surfaced Inconel coatings were metallurgically bonded to steel and Inconel substrates with out any physical defects such as voids or cracks. Friction surfaced coatings showed equiaxed fine grained microstructures (4–18 µm) compared with their consumable rod counterparts (12 – 85 µm). Scanning electron microscope electron backscattered diffraction results showed that the coatings consisted of mainly high angle grain boundaries indicative of dynamic recrystallization mechanism. The temperatures recorded using Infra Red camera showed that the temperature attained at the interface between rod and the substrate is about 1100 °C. The grain size of the consumable rod was relatively fine near the coating/substrate interface and relatively coarser away from interface indicating the change in strain and temperature the rod experienced at or away from the interface.

This study analyzes the initial experience with minimally invasive mitral valve surgery through a right minithoracotomy in a public teaching hospital in Australia and evaluates early surgical outcomes.A retrospective review of patients who underwent minimally invasive mitral valve surgery between November 2006 and March 2009 was performed.A total of 60 patients included 47 (78%) patients who had mitral valve plasty and 13 (22%) who had mitral valve replacement. The mean age was 61 ± 15 years; 33 (55%) patients were male; and 6 (10%) had had previous cardiac operations. The mean cardiopulmonary bypass and aortic cross-clamp times were 140 ± 46 and 93 ± 35 min, respectively. All patients who underwent mitral valve plasty left the operation room with no more than trivial residual mitral regurgitation. There was no operative mortality. Reoperation for bleeding and stroke occurred in 2 patients each. The mean intensive care unit and hospital stays were 3.1 ± 5.8 and 10.6 ± 8.9 days, respectively. Among the 47 patients with mitral valve plasty, 46 (98%) had mild or less mitral regurgitation on transthoracic echocardiography at discharge. There was one late death. No reoperation for the mitral valve has been observed so far. An echocardiography report was obtained for 34 of the 47 who had had mitral valve plasty at 12.1 ± 7.9 months postoperatively, and 27 (79%) of them had mild or less mitral regurgitation.Minimally invasive mitral valve surgery through a right minithoracotomy was safely performed with no early mortality.

Al-Mg alloy was friction stir processed (FSP) incorporating two different sized SiC particles. Reduction of particle size after FSP was very significant with coarser SiC particles than finer. The density of SiC particles in FSP nugget was found to be uniform from top to bottom with coarser SiC particles, whereas it was more at the bottom than the top with finer. Tool wear after FSP was found to be relatively more with coarser particles than finer.

Formation of iron oxide nanotubes on to pure iron substrate by an electrochemical anodization method was investigated in fluoride containing electrolytes. Anodization of iron foil in fluoride containing borate solution resulted in stacked nano-ring type oxide morphology. Nanoporous oxide layer was observed at low pH and a granular oxide layer was formed at higher pH of phosphate + fluoride solutions. Formation of either nanoporous or nanotubular oxide layer was observed in ethylene glycol (EG) solution containing 0.05–0.1 M fluoride + 1.5–3.0 vol.% water. Transition from nanoporous structure to nanotubular structure was critically controlled by anodization potential, water addition and fluoride concentration of the EG solution. The potential required for this transition decreased with increase in the water content up to 7 vol.% beyond which enhanced dissolution occurred. Annealing of the nanotubes at 500 °C resulted in predominantly α-Fe2O3 crystal structure. The annealed Fe2O3 samples consisting of a single layer of nanotubular structure showed a photo current density of 0.4 mA/cm2 at 0.5 V Ag/AgCl in 1 M KOH solution under simulated solar light illumination.

A synergistic combination of nanostructure synthesis and surface engineering was used to enhance the photoelectrochemical activity of titanium dioxide (TiO2) photoanodes. Titania nanotubular arrays were synthesized by electrochemical anodization of Ti thin foils. An atmospheric-pressure helium plasma followed by exposure to nitrogen was used to modify the surface properties of TiO2 nanotubes. The photocurrent from plasma-treated samples was approximately 25% higher than that from untreated samples. This increase in photoactivity could be ascribed to the following: 1) increased absorption of visible light due to bandgap reduction; 2) efficient charge separation; 3) production of optimal oxygen vacancies; and 4) increased surface area and, hence, enhanced electrode-electrolyte area to provide maximum optical adsorption and efficient charge transfer. The diffused reflectance Ultraviolet-visible (DR-UV-Vis) absorption spectra indicated a marginal increase in absorbance for the plasma-treated samples in the visible region, suggesting a change in surface electronic structure, although bulk electronic properties remain unchanged during plasma treatment.

INCONEL 617 (UNS N06617, also referred as Alloy 617) is an austenitic Ni–22Cr–12Co–9Mo alloy, which is a candidate structural material for next generation high temperature nuclear reactors. High temperature deformation behavior of Alloy 617 has been investigated as a function of strain rate ranging from 10 −3 to 10 −6 s −1 at 600 and 800 °C. Increase in the temperature and decrease in the strain rate decreased the flow stress of the material. Serrated flow was observed at both the test temperatures. The amplitude of serration increased with decrease in the strain rate and increase in the temperature. Microstructural analysis showed that deformation at slow strain rates increased both the grain size and volume fraction of second phase precipitation. Furthermore at slower strain rates, increase in the carbides size and a continuous network of carbides along the grain boundary could be observed. Scanning Kelvin Probe Force Microscopy (SKPFM) was performed on the tested specimen to observe variation in surface potential as a result of microstructural degradation during high temperature deformation at different strain rates. The second phase precipitates of the specimens deformed at higher strain rate (10 −3 s −1 ) showed more positive surface potentials than that of the specimens deformed at slower strain rate.

Phase transformation analysis of the phosphate containing and carbon doped titania nanotubes, prepared by a simple anodization method, reveals complete transformation from amorphous to anatase phase in air between 360 and 400 °C. Activation energies for formation of anatase phase are evaluated and compared for the two types of titania nanotubes. A detailed analysis of the phase transformation characteristics and stability of the anatase phase is reported.

The TiO 2 nanotubes have demonstrated potential in the photoelectrocatalytic degradation of methyl orange dye (MO). TiO 2 nanotubes were prepared using anodization of titanium foils in phosphoric acid (PA) and ethylene glycol (EG) by mechanical stirring and ultrasonic method. The TiO 2 nanotubes prepared in EG under ultrasound followed by annealing in nitrogen atmosphere showed higher activity towards dye degradation as compared to the stirring method. Dye degradation shows improved activity under an external bias compared to degradation performed in the absence of an external bias. An increase in the external bias from +0.0 to +0.1 V versus calomel electrode (SCE) is sufficient to improve the degradation rates of MO from 22% to 57% within the first 10 min. At +0.1 V, a complete degradation of 40 μM MO is observed within 30 min. The addition of oxidants such as oxygen and hydrogen peroxide demonstrate improvement in the MO degradation.

AlSb is a group III–V compound semiconductor material that is conventionally grown by high temperature processes such as Czochralski and Bridgman methods. Development of a method to synthesize AlSb at room temperature will be more economical to help modulate the electronic properties. In this investigation, a pulsed potential electrodeposition method using a room temperature molten salt system (aluminum trichloride, AlCl 3 /1-methyl-3-ethylimidazolium chloride, EMIC) with an addition of SbCl 3 is discussed. The potential pulse parameters were established by carrying out cyclic voltammetry at different concentrations of SbCl 3 and with varying molar ratios of AlCl 3 /EMIC. Stoichiometric AlSb deposits were obtained from an acidic AlCl 3 /EMIC (1.5:1 molar ratio) melt containing 4 × 10 −3 mol/l of SbCl 3 onto an ordered TiO 2 nanotubular template. The AlSb compound was predominantly amorphous in as-deposited condition and annealing at 350 °C for 2 h in argon transformed into crystalline phase. The AlSb deposit showed a high resistivity in the order of 10 9 Ω-cm and a defect concentration of 10 16 cm −3 which was attributed to presence of carbon. The deposits obtained from a basic melt (0.67:1 molar ratio of AlCl 3 /EMIC) were enriched with antimony.

Electron−hole (e-h) recombination loss is a major practical problem in using TiO2 as a photocatalyst. This paper describes the use of organic additives to reduce e-h recombination losses which significantly improved the photocurrent density of the integrated TiO2 nanotube/Ti photoanode. Studies on photoelectrochemical hydrogen generation using nanotubular arrays of TiO2 photoanodes were carried out in 1 M KOH with the addition of three different organic additives, namely, methanol (one hydroxyl group), ethylene glycol (two hydroxyl groups), and glycerol (three hydroxyl groups) using a simulated solar light. Ethylene glycol was found to be the best among the investigated organic additives to reduce electron hole recombination. The addition of ethylene glycol produced a photocurrent density of 3.3 mA/cm2 at 0.2 VAg/AgCl compared to 0.87 mA/cm2, using a 87 mW/cm2 light intensity in 1 M KOH solution. On the other hand, methanol and glycerol showed a photocurrent density of 2.43 and 2.55 mA/cm2 under the same ...

The flocculation of −38 mm hematite aqueous suspensions by the yeast Candida parapsilosis, and by products derived from the ultrasonic rupture of this microorganism was studied. Results obtained are compared to the flocculation of comparable suspensions by cooked corn starch and a polyacrylamide (average molecular weight 106.

Alloy 617 (nickel based austenitic alloy) is a candidate structural material for next generation high temperature nuclear reactor. The secondary phases present in the Alloy 617 has been identified as TiN and M 23 C 6 by optical microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). Surface potentials of these phases have been evaluated by Scanning Kelvin Probe Force Microscope (SKPFM). SKPFM investigation showed higher surface potential of the secondary phases than that of the austenite matrix. The surface potential of the TiN was nobler than that of M 23 C 6 indicating that these precipitates could act as cathodic sites during oxidation reaction. Difference in the local chemistry of these phases results in variation of the chemical potentials, which in turn could lead to enhanced oxidation at localized areas in the vicinity of the secondary phase precipitates that act as cathodic sites.

This work studies the removal of arsenic (V), arsenate, and arsenic (III), arsenite, from aqueous solution using calcined Quintinite-3T. The two adsorbents Quintinite-3T was prepared, calcined at different temperatures, and characterized by XRD, BET, and SEM. The surface area of the calcined Quintinite-3T was 193.4 m2/g. The particles size ranged from 12 to 56 nm for the uncalcined Quintinite-3T and from 24 to 42 nm for the calcined Quintinite-3T. Kinetic analysis, adsorption isotherm, and factors affecting the adsorption were investigated. Calcined Quintinite-3T retained As(v) and did not release it back to water even after an entire month.

Photoelectrochemical hydrogen (H2) production from water is a key method of addressing energy needs using an environmentally friendly approach. In the last two decades we have witnessed the evolution of many different expensive catalysts, photoelectrodes and related technologies, especially those involving precious metals and use of acidic or basic electrolytes for hydrogen production. Cu2ZnSnS4 (CZTS) is a relatively new candidate in the category of efficient photocathodes, due to its high absorption coefficient and near optimal energy band gap. In this paper, we demonstrate photoelectrochemical viability of CZTS in combination with other photoanodes such as TiO2, BiVO4, and WO3 for H2 production with the use of an electrolyte of near neutral pH, a single redox mediator, and insignificant potential biasing. A systematic study was performed to understand CZTS performance with each photoanode, band energetics of CZTS with other photoanodes, impedance behavior of each photoelectrode, and utility of a CZTS photocell in place of a CZTS photocathode. Our assessment indicates that a protected CZTS photocell performs well when used in a Z-scheme containing TiO2 nanotubular array-CZTS or nanocrystalline WO3-CZTS. Preliminary experiments indicated that apart from band energetics, porosity and effective surface area of the photoanodes play a crucial role in determining the photoelectrochemical performance of the system.

This work reports the synthesis of multiwalled carbon nanotubes (MWCNTs) on nanoporous titanium dioxide (TiO2) templates. TiO2 nanotubular templates for MWCNTs are produced by anodization of titanium followed by pulsed electrodeposition (PED) of cobalt inside the TiO2 nanotubes. Cobalt acts as a catalyst for the growth of MWCNTs using chemical vapor deposition (CVD) technique. The cobalt catalyst initiates the growth of well graphitized MWCNTs inside the titania pores as well as beyond the titania pores. These materials have been characterized by SEM, EDS, GXRD, XPS, TEM, and ED techniques. The MWCNTs were about 10 mu in length and 80-120 nm in diameter.

The dissolution of copper from chalcopyrite was investigated in the presence of hydrogen peroxide and ethylene glycol. Hydrogen peroxide was used as oxidant in the leaching process. Addition of a small amount of ethylene glycol significantly improved the copper dissolution. The copper leaching mechanism was established by examining the influence of various parameters on the reaction rate in the presence of ethylene glycol. The effect of temperature on the reaction kinetics suggests that the leaching reaction follows the surface reaction-controlled model. The linear relationship between the log of reaction rate constant and log of particle radius supports the proposed reaction model. The reaction order was calculated with respect to hydrogen peroxide which indicates that hydrogen peroxide has greater influence on the leaching kinetics. Stirring speed and sulfuric acid concentration are not important variables. Most of the sulfide ions were transformed to elemental sulfur during the reaction. The elemental sulfur was present on the surface of chalcopyrite residue as discrete crystalline particles instead of a coating of continuous film which causes the passivation of chalcopyrite surface. Ethylene glycol was found to stabilize the hydrogen peroxide at elevated temperature which could be another reason for enhanced recovery.

Anodization of Ti using fluoride containing polyhydric alcohols such as ethylene glycol or glycerol as electrolyte results in ordered arrays of TiO2 nanotubes with a smooth surface and a very high aspect ratio. However, the reproducibility of the result is affected by many experimental parameters, notably the water content. In this investigation, anodizations of Ti foil in anhydrous ethylene glycol +0.2 wt% NH4F solution (EG solution) with 0–1.0 wt% water additions were carried out at 20 V for 45 min in a dry-argon filled controlled-atmosphere glove box. It was observed that a minimum amount of 0.18 wt% of water addition was required to form a well ordered TiO2 nanotubular arrays. When the anhydrous EG solution was reused for third time, ordered arrays of nanotubes started to form. When the water addition to the EG solution was more than 0.5 wt%, formation of ridges was observed on the nanotubes. XPS results showed presence of un-anodized Ti element in the anhydrous condition and presence of organic and (NH4)2TiF6 type compounds in all the anodized samples in addition to the regular TiO2 phase. The results underline the influence of water content and local pH condition to form the ordered nanotubular arrays. Keywords: Nanotubular TiO2, Anodization, Ethylene glycol, Oxide film

Titanium and its alloys are being used in many orthopedic and bioimplant applications. In order to render these materials bioactive and to enhance osteointegration, the surfaces are coated with hydroxyapatite (HAp). Adhesion of bone cell to the implant surface, bond strength and durability of the implants are highly dependent upon the characteristics of the Ti substrate and the methods utilized in the hydroxyapatite coating process. In this paper we have reported an innovative method of preparation of a nanotubular titania surface and subsequent electrodeposition of hydroxyapatite nanocrystalline coating. Growth of the hydroxyapatite onto the nanotubular titania surface was accomplished by a pulsed electrodeposition process. Prior to the electrodeposition, the nanotubular titania surface was subjected to an alkaline treatment, which provided a template for nucleation of the hydroxyapatite inside the nanotubes. This process resulted in a vertical growth of the hydroxyapatite crystals and increased the bond strength of the coating. Bond strength was further improved by annealing the hydroxyapatite coated nanoporous titania in an argon atmosphere.

Vertically oriented nanotubular TiO2 arrays were formed by a simple anodization process. Hydrogen storage studies were carried out on the TiO2 nanotubular arrays having different diameters by charging and discharging hydrogen with potentiostatic/galvanostatic control. The hydrogen storage capacities of the nanotubes were only marginally affected by the tube diameter. Concentration of oxygen vacancies as defects influenced the hydrogen storage of the nanotubes. Annealing of the TiO2 nanotubes in argon atmosphere increased the defect density and decreased the hydrogen discharge during initial charge–discharge cycles. Hydrogen storage studies through electrochemical route did not show significant storage capacity of TiO2 nanotubes. Diffusion of hydrogen as protons and interference of the double layer capacitance of nanotubes could be attributed to the lower hydrogen storage capacity.

Alloy 22, a nickel base Ni-22Cr-13Mo-3W alloy has an excellent corrosion resistance in oxidizing and reducing environments. Most of the corrosion studies on Alloy 22 have been conducted using conventional chemical or electrochemical methods. In the present investigation, the specimen was directly heated instead of heating the electrolyte, thereby simulating the nuclear waste package container temperature profile. Corrosion behavior of Alloy 22 and evaporation conditions of water diffusing on the container were evaluated using the newly devised heated electrode corrosion test (HECT) method in simulated acidified water (SAW) and simulated concentrated water (SCW) environments. In this method, the concentration of the environment varied with test duration. The corrosion rate of Alloy 22 was not affected by the continuous increase in ionic strength of the SAW (pH 3) environment. Passivation kinetics was faster with increase in concentration of the electrolytes. The major difference between the conventional test and HECT was the aging characteristics of the passive film of Alloy 22. The heated electrode corrosion test can be used for evaluating materials for construction of heat transfer equipments such as evaporators.

A single step non-aqueous electrodeposition of cadmium zinc telluride (CZT) nanowires on nanoporous TiO 2 substrate was investigated under pulsed-potential conditions. Propylene carbonate was used as the non-aqueous medium. Cyclic voltammogram studies were carried out to understand the growth mechanism of CZT. EDAX and XRD measurements indicated formation of a compound semiconductor with a stoichiometry of Cd 1− x Zn x Te, where x varied between 0.04 and 0.2. Variation of the pulsed-cathodic potentials could modulate the composition of the CZT. More negative cathodic potentials resulted in increased Zn content. The nanowires showed an electronic band gap of about 1.6 eV. Mott-Schottky analyses indicated p-type semiconductor properties of both as-deposited and annealed CZT materials. Increase in Zn content increased the charge carrier density. Annealing of the deposits resulted in lower charge carrier densities, in the order of 10 15 cm −3 .

Thermal analysis of an alternative boiling water reactor (BWR) waste package design for permanent disposal in the Yucca Mountain Repository is reported in this paper. The new design implements an increase in the holding capacity of the BWR waste packages from 44 to 52 assemblies and a modified arrangement sequence of waste packages in the emplacement drift. The design is favorable from the perspective of a generally drier emplacement drift due to an increase in heat load in the waste packages and the resulting higher temperatures. The analysis addresses heat transfer issues inside the waste package and those pertinent to satisfying the safe thermal limits for the waste package components. Key parameters in the analysis are the spent nuclear fuel assembly effective conductivities, the number of aluminum shunts, and the gap backfill with pressurized helium insidethewastepackages.Thefeasibilityoftheproposed design is demonstrated by the internal waste package thermal model and the thermal-hydrologic environment in the emplacement drift. The conformity of the alternative thermal design to safe temperatures, in spite of the additional heat load, led to another innovative design with radial arrangement of assemblies in the waste packages that would further support the sustenance of drier emplacement drifts. These radial configurations are also discussed in this paper.

Room temperature anodization of titanium foil specimens was carried out in 0.5 M phosphoric acid solution with addition of various halide ions. Addition of 0.138 M HF or NaF resulted in self-ordered nano-tubular oxide structure. Addition of bromide and chloride ions initiated only pitting and nano-pores were not observed during anodization. Acidified fluoride solution is found to be necessary to obtain ordered nano-structure as neutral fluoride solution did not form nano-pores. Instability of the oxide layer during anodization and formation of the self-ordered structure can be explained by the perturbation theory. Separation of individual nano-tubes of titanium oxide layer from the inter-connected nano-pores could be attributed to the possible repulsion forces of the cation vacancies.

Nanotubular anodic oxide layer was grown on titanium surface by room temperature anodization in 0.5 M H3PO4 + 0.138 M fluoride solution. The inner surface of the nanotubular oxide walls contained adsorbed anions from the solution that were predominantly phosphate. Hydroxy apatite was electrodeposited on the anodized surface of Ti. Adsorbed phosphate ions facilitated nucleation of nanophase calcium phosphate material inside the nanotubular structure that resulted in vertical growth of apatite crystals. Bond strength of the calcium phosphate coating was found to be good, and cohesive mode of failure of the coating was observed after tensile testing.

Anodic aluminium oxide (AAO) templates for multi-walled carbon nanotube (MWCNT) growth were produced by anodization of aluminium followed by pulse-reverse electrodeposition of cobalt inside the AAO pores. Cobalt functioned as the catalyst for H2/C2H2 chemical vapour deposition (CVD) growth of fairly well graphitized MWCNTs initiating inside the majority of the AAO pores and quickly growing beyond the pore confines. A technique is introduced for the production of AAO templates that fill evenly during pulsed electrodeposition. The electrodeposition produced an active metallic catalyst in the pore bottoms, with minimal over-filling. This process also eliminates the reduction step necessary when alternating current (AC) electrodeposition is used for filling AAO pores.