Charge Distribution in Layered Lanthanide-Doped CuCr0.99Ln0.01S2 (Ln = Pr–Tb) Thermoelectric Materials

The charge distribution study of metal atoms in CuCr_0.99Ln_0.01S₂ (Ln = Pr–Tb) solid solutions was carried out using X-ray photoelectron spectroscopy (XPS). The analysis of the binding energy of S2p, Cu2p, Cr2p, Ln3d and Ln4d levels allows one to determine the oxidation state of atoms. Copper atoms were found to be monovalent. Chromium and lanthanide atoms were found to be in the trivalent state. Sulfur atoms were found to be in the divalent state. Cationic substitution was found to occur via an isovalent mechanism of Cr³⁺ to Ln³⁺. The obtained results were used for the interpretation of the Seebeck coefficient increase for CuCr_0.99Ln_0.01S₂ solid solutions in contrast to the initial CuCrS₂ matrix. The largest Seebeck coefficient values of 142 and 148 µV/K were observed at 500 K for CuCr_0.99Sm_0.01S₂ and CuCr_0.99Pr_0.01S₂, respectively. The obtained values are 1.4 times greater in comparison with those for the initial matrix (105 µV/K).     

One Pot Synthesis of Copper Oxide Nanoparticles for Efficient Antibacterial Activity

The unique semiconductor and optical properties of copper oxides have attracted researchers for decades. However, using fruit waste materials such as peels to synthesize the nanoparticles of copper oxide (CuO NPs) has been rarely described in literature reviews. The main purpose of this part of the research was to report on the CuO NPs with the help of apple peel extract under microwave irradiation. Metal salts and extracts were irradiated at 540 W for 5 min in a microwave in a 1:2 ratio. The crystallinity of the NPs was confirmed by the XRD patterns and the crystallite size of the NPs was found to be 41.6 nm. Elemental mapping of NPs showed homogeneous distributions of Cu and O. The NPs were found to contain Cu and O by EDX and XPS analysis. In a test involving two human pathogenic microbes, NPs showed antibacterial activity and the results revealed that the zone of inhibition grew significantly with respect to the concentration of CuO NPs. In a biofilm, more specifically, NPs at 25.0 µg/mL reduced mean thickness and biomass values of S. aureus and E. coli biofilms by >85.0 and 65.0%, respectively, with respect to untreated controls. In addition, environmentally benign materials offer a number of benefits for pharmaceuticals and other biomedical applications as they are eco-friendly and compatible.     

Effect of Applied Pressure on the Electrical Resistance of Carbon Nanotube Fibers

Carbon nanotubes (CNTs) can be spun into fibers as potential lightweight replacements for copper in electrical current transmission since lightweight CNT fibers weigh <1/6th that of an equivalently dimensioned copper wire. Experimentally, it has been shown that the electrical resistance of CNT fibers increases with longitudinal strain; however, although fibers may be under radial strain when they are compressed during crimping at contacts for use in electrical current transport, there has been no study of this relationship. Herein, we apply radial stress at the contact to a CNT fiber on both the nano- and macro-scale and measure the changes in fiber and contact resistance. We observed an increase in resistance with increasing pressure on the nanoscale as well as initially on the macro scale, which we attribute to the decreasing of axial CNT^…CNT contacts. On the macro scale, the resistance then decreases with increased pressure, which we attribute to improved radial contact due to the closing of voids within the fiber bundle. X-ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS) show that applied pressure on the fiber can damage the π–π bonding, which could also contribute to the increased resistance. As such, care must be taken when applying radial strain on CNT fibers in applications, including crimping for electrical contacts, lest they operate in an unfavorable regime with worse electrical performance.     

Assessment of Mechanical,Chemical, and Biological Properties of Ti-Nb-Zr Alloy for Medical Applications

The purpose of this work is to obtain comprehensive reference data of the Ti-13Nb-13Zr alloy base material: its microstructure, mechanical, and physicochemical properties. In order to obtain extensive information on the tested materials, a number of examination methods were used, including SEM, XRD, and XPS to determine the phases occurring in the material, while mechanical properties were verified with static tensile, compression, and bending tests. Moreover, the alloy’s corrosion resistance in Ringer’s solution and the cytotoxicity were investigated using the MTT test. Studies have shown that this alloy has the structure α’, α, and β phases, indicating that parts of the β phase transformed to α’, which was confirmed by mechanical properties and the shape of fractures. Due to the good mechanical properties (E = 84.1 GPa), high corrosion resistance, as well as the lack of cytotoxicity on MC3T3 and NHDF cells, this alloy meets the requirements for medical implant materials. Ti-13Nb-13Zr alloy can be successfully used in implants, including bone tissue engineering products and dental applications.     

Hybrid Organic‐Inorganic Nanostructured Acrylic Films Based on Methacylate Modified Zirconium Oxocluster

Organic‐inorganic nanostructured acrylic films, based on methacrylate‐modified zirconium oxocluster, were prepared by UV‐induced polymerization, which yielded transparent and crack‐free layers. TEM analysis evidenced that all the inorganic particles are well dispersed with no significant macroscopic agglomerations. FT‐IR kinetic investigations showed that the presence of the zirconium oxocluster does not affect the photopolymerization rate or acrylic double bond conversion. An increase on T_g values of the cured films is evident at 15 wt.‐% load of the inorganic filler. A thermal stability increase was also achieved in the presence of the zirconium oxocluster. Surface studies performed by XPS analyses showed the presence of homogeneously distributed zirconium oxoclusters, which induces important improvements of the surface hardness evidenced on the basis of the pencil test.

     

The Initial Oxidation of HfNiSn Half-Heusler Alloy by Oxygen and Water Vapor

The MNiSn (M = Ti, Zr, Hf) n-type semiconductor half-Heusler alloys are leading candidates for the use as highly efficient waste heat recovery devices at elevated temperatures. For practical applications, it is crucial to consider also the environmental stability of the alloys at working conditions, and therefore it is required to characterize and understand their oxidation behavior. This work is focused on studying the surface composition and the initial oxidation of HfNiSn alloy by oxygen and water vapor at room temperature and at 1000 K by utilizing X-ray photoelectron spectroscopy. During heating in vacuum, Sn segregated to the surface, creating a sub-nanometer overlayer. Exposing the surface to both oxygen and water vapor resulted mainly in Hf oxidation to HfO₂ and only minor oxidation of Sn, in accordance with the oxide formation enthalpy of the components. The alloy was more susceptible to oxidation by water vapor compared to oxygen. Long exposure of HfNiSn and ZrNiSn samples to moderate water vapor pressure and temperature, during system bakeout, resulted also in a formation of a thin SnO₂ overlayer. Some comparison to the oxidation of TiNiSn and ZrNiSn, previously reported, is given.     

Surface Modification of Nanoporous Anodic Alumina during Self-Catalytic Atomic Layer Deposition of Silicon Dioxide from (3-Aminopropyl)Triethoxysilane

Changes associated to atomic layer deposition (ALD) of SiO₂ from 3-aminopropyl triethoxysilane (APTES) and O₃, on a nanoporous alumina structure, obtained by two-step electrochemical anodization in oxalic acid electrolyte (Ox sample) are analysed. A reduction of 16% in pore size for the Ox sample, used as support, was determined by SEM analysis after its coverage by a SiO₂ layer (Ox+SiO₂ sample), independently of APTES or O₃ modification (Ox+SiO₂/APTES and Ox+SiO₂/APTES/O₃ samples). Chemical surface modification was determined by X-ray photoelectron spectroscopy (XPS) technique during the different stages of the ALD process, and differences induced at the surface level on the Ox nanoporous alumina substrate seem to affect interfacial effects of both samples when they are in contact with an electrolyte solution according to electrochemical impedance spectroscopy (EIS) measurements, or their refraction index as determined by spectroscopic ellipsometry (SE) technique. However, no substantial differences in properties related to the nanoporous structure of anodic alumina (photoluminescent (PL) character or geometrical parameters) were observed between Ox+SiO₂/APTES and Ox+SiO₂/APTES/O₃ samples.     

Long-Term Corrosion Testing of Zy-4 in a LiOH Solution under High Pressure and Temperature Conditions

The fuel cladding is one of the most important structural components for maintaining the integrity of a fuel channel and for safely exploitation of a nuclear power plant. The corrosion behavior of a fuel cladding material, Zy-4, under high pressure and temperatures conditions, was analyzed in a static isothermal autoclave under simulated primary water conditions—a LiOH solution at 310 °C and 10 MPa for up to 3024 h. After this, the oxides grown on the Zy-4 sample surface were characterized using electrochemical measurements, gravimetric analysis, metallographic analysis, SEM and XPS. The maximum oxide thicknesses evaluated by gravimetric and SEM measurements were in good agreement; both values were around 1.2 µm. The optical light microscopy (OLM) investigations identified the presence of small hydrides uniformly distributed horizontally across the alloy. EIS impedance spectra showed an increase in the oxide impedance for the samples oxidized for a long time. EIS plots has the best fit with an equivalent circuit which illustrated an oxide model that has two oxide layers: an inner oxide layer and outer layer. The EIS results showed that the inner layer was a barrier layer, and the outer layer was a porous layer. Potentiodynamic polarization results demonstrated superior corrosion resistance of the samples tested for longer periods of time. By XPS measurements we identified all five oxidation states of zirconium: Zr⁰ located at 178.5 eV; Zr⁴⁺ at 182.8 eV; and the three suboxides, Zr⁺, Zr²⁺ and Zr³⁺ at 179.7, 180.8 and 181.8 eV, respectively. The determination of Vickers microhardness completed the investigation.     

Influence of oxygen,albumin and pH on copper dissolution in a simulated uterine fluid

Objectives?The aim of this paper is to study the influence of albumin content, from 5 to 45?g/L, on copper dissolution and compounds composition in a simulated uterine solution.

Methods?Experiments were performed in atmospheric pressure conditions and with an additional oxygen pressure of 0.2 atmospheres, at 6.3 and 8.0 pH values, and at a temperature of 37?±?0.1° C for 1, 3, 7, and 30 days experimentation time.

Results?The copper dissolution rate has been determined using absorbance measurements, finding the highest value for pH?8.0, 35?g/L albumin, and with an additional oxygen pressure of 0.2 atmospheres: 674?μg/day for 1 day, and 301?μg/day for 30 days. X-ray photoelectron spectroscopy (XPS) results show copper(II) as the main copper oxidation state at pH?8.0; and copper(I) and metallic copper at pH?6.3.

Conclusions?The presence of albumin up to 35?g/L, accelerates copper dissolution. For high albumin content a stabilisation on the copper dissolution takes place. Corrosion product layer morphology is poorly protective, showing paths through which copper ions can release.     

The surface analysis of implant materials. The surface composition of a titanium dental implant material.

The surfaces of titanium (Ti) plates, as models for Ti implants, have been characterized by X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (TOF SIMS). Plates were prepared with rough and smooth surface topographies ‐ the rough being similar to that of an implant. The XPS data has been used to construct a model of the plates' surface chemical structure, from the gas‐solid interface through to pure Ti metal. At the surface of as‐received plates, which underwent the same preparative procedure as an implant, considerable surface contamination was detected. In particular, high levels of carbon (C) contaminants were detected; the nature of this C was elucidated by fitting the C 1s core line and from the secondary ion mass spectra. The oxygen (0) 1s core line could not be fitted using a minimum of 2 gaussian peaks, demonstrating the multiplicity of 0 environments. The detection of other elements in the XPS analysis further demonstrated that, in nominally pure Ti plates, the surface chemical composition deviates considerably from that of the bulk. The data obtained from the plates were confirmed by examination of a Ti abutment. The handling of Ti plates with stainless steel tweezers was investigated. No obvious change in surface chemistry was detected. All the above results bring into serious questions the validity of rigorous protocols demanded, in some techniques, in the 1 handling and use of Ti implants.