This article presents an overview of the surface chemistry of zirconium, focusing on the relationship of what is known from model studies and how this connects to current and future applications of ...Zr-based materials. The discussion includes the synergistic nature of adsorbate interactions in this system, the role of impurities and alloying elements, and temperature-dependent surface–subsurface transport. Finally, some potential uses of zirconium and its alloys for biomedical and nanolithographic applications are presented.
Titania nanofibers were synthesized by electrospinning and characterized with scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The nanofibers were annealed to ...773
K to achieve the anatase titania crystal structure, and to 1173
K to obtain the rutile phase. In order to create erbia-containing titania nanofibers, erbium (III) oxide particles were added to the pre-cursor solution before electrospinning. After pyrolysis the titania nanofibers supported and encapsulated the erbia particles. Temperature-dependent near-infrared emission spectra demonstrate that the erbia-containing nanofibers emit selectively in the range 6000–7000
cm
−1. Because of their large surface to volume ratios and narrow-band optical emission, these nanofibers can be used as selective emitters for thermophotovoltaic applications.
Fibers are electrospun from aluminum acetate/polymer mixtures and characterized by an array of techniques before and after annealing at 1200
°C. We demonstrate that sodium and boron present in the ...initial starting materials as adducts and stabilizers remain incorporated into the resulting fibers after annealing and pyrolysis of the host polymer. The influence of these minor constituents on the surfaces of the fibers is suggested by infrared and X-ray photoelectron spectroscopic data. The presence of these species may impact potential chemical applications of small diameter ceramic fibers, such as their use as catalytic supports or for chemical decomposition.
According to metaphysical tensism, there is an objective, albeit ever changing, present moment corresponding to our phenomenal experiences (Ludlow in Philosophy of language, Oxford handbook on tense ...and aspect. Oxford University Press, Oxford, 2012; Brogaard and Marlow in Analysis 73(4):635–642, 2013). One of the principle objections to metaphysical tensism has been Einstein's argument from special relativity, which says that given that the speed of light is constant, there is no absolute simultaneity defined in terms of observations of light rays (Einstein in Ann Phys 17:891–921, 1905). In a recent paper, Brogaard and Marlow (Analysis 73(4):635–642, 2013) argue that this objection fails. We argue that Brogaard and Marlow's argument fails to show that special relativity does not pose a threat to metaphysical tensism.
We present a teaching activity whose aim is to enhance students' understanding of color perception by introducing them to intersubjective color variations among normal perceivers. The approach can be ...used in different disciplines, including biology, philosophy, psychology, physics, or statistics, for different purposes and with college students having various levels of sophistication and scientific training.
Zinc oxide nanofibers doped with aluminum oxide were prepared by sol–gel processing and electrospinning techniques using polyvinylpyrrolidone (PVP), zinc acetate and aluminum acetate as precursors. ...The resulting nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–Vis spectroscopy, and current–voltage (
I–
V) properties. The nanofibers had diameters in the range of 60–150
nm. The incorporation of aluminum oxide resulted in a decrease in the crystallite sizes of the zinc oxide nanofibers. Aluminum oxide doped zinc oxide (AOZO) nanofibers exhibited lower bandgap energies compared to undoped zinc oxide nanofibers. However, as the aluminum content (Al/(Al
+
Zn)
×
100%) was increased from 1.70
at.% to 3.20
at.% in the electrospinning solution, the bandgap energy increased resulting in lower conductivity. The electrical conductivity of the AOZO samples was found to depend on the amount of aluminum dopant in the matrix as reflected in the changes in oxidation state elucidated from XPS data. Electrospinning was found to be a productive, simple, and easy method for tuning the bandgap energy and conductivity of zinc oxide semiconducting nanofibers.
Understanding and controlling the interaction of water with solid surfaces is relevant from both technological and fundamental viewpoints. Since Zircaloy-4 serves as a structural magerial exposed to ...hot water in nuclear reactors, understanding the oxidation by water is of applied interest, The interaction of H2O with Zircaloy-4 (Zry-4) is investigated using Auger electron spectroscopy (AES) and temperature programmed desorption (TPD) methods. Following adsorption of H2O at 150 K the Zr(MNV) and Zr(MNN) Auger features shift by -6.5 and 4.5 eV, respectively, indicating surface oxidation. Heating H2O/Zry-4 results in molecular desorption of water at both low and high temperatures. The low-temperature desorption is attributed to ice multilayers, whereas, three overlapping high-temperature features are presumably due to recombinative desorption. This high-temperature desorption begins before the surface oxide is dissolved, continues upon its removal, and is atypical for water/metal systems. Unexpectedly, no significant desorption of hydrogen is observed near 400 K, as is typically observed following O2 adsorption on Zr-based materials. However, we do observe that H2O adsorption on Zry-4 surfaces roughened by argon ion sputtering results in H2 desorption.
We investigate the adsorption of CO2 onto Zircaloy-4 (Zry-4) surfaces at 150, 300 and 600K using Auger electron spectroscopy (AES). Following CO2 adsorption at 150K the graphitic form of carbon is ...detected, whereas upon chemisorption at 300 and 600K we detect the carbidic phase. As the adsorption temperature is increased, the carbon Auger signal increases, whereas the oxygen signal decreases. Adsorption at all three temperatures results in a shift of the Zr Auger features, indicating surface oxidation. The effect of adsorbed CO2 on the Zr(MVV) and Zr(MNV) transitions depends on adsorption temperature and is less pronounced at higher temperatures. On the other hand, changes in the Zr(MNN) feature are similar for all three adsorption temperatures. The changes in the Zr Auger peak shapes and positions are attributed to oxygen from dissociated CO2, with the differences observed at various temperatures indicative of the diffusion of oxygen into the subsurface region.
SiO
2 nanofibers have been produced by the electrospinning method by two different approaches: direct spinning of silica precursor-containing nanofibers and spinning of polymer nanofibers followed by ...sol–gel silica coating. After pyrolysis of the resulting materials, both methods yield silica nanofibers. We extend this work by coating the silica nanofibers with AlN films using a reactive magnetron sputtering technique. Substrate temperature, input gas composition and radio frequency (rf) power are the critical operating parameters for the formation of different crystal structures of the AlN shells. The AlN/SiO
2 core-shell heterostructures demonstrate that electrospinning has the potential to produce low-mass, high-surface-area flexible nanofibers for potential space-based applications.
The most common clinical cause of long-term failure in total joint replacement surgery is inflammatory aseptic osteolysis; a condition in which bone surrounding the prosthetic implant, and to which ...the implant is attached, is resorbed, rendering the artificial device loose and painful. Historically, the severity of this bone resorptive process has been thought to be predominately attributed to the size and shape of wear-debris particles, particularly the metallic particulates that interact biologically/immunologically with cells in the joint. Because the cytotoxic reactions are the result of interactions between the cells and the surfaces of the particulates, it is not clear in the realm of orthopedics to what extent different surface stoichiometric ratios contribute to instigating bioreactive or cytotoxic cellular responses that can lead to aseptic osteolysis. Using energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS), this study presents data and analyses concerning the respective bulk and surface stoichiometric ratios of two commercially pure metal micro-particulates (tantalum and titanium), two prosthetic F75 cobalt–chromium–molybdenum alloy micro-particulates, and prosthetic F136 titanium–aluminum–vanadium alloy micro-particulates, each containing elements common to total joint replacement surgery. Cell culture viability data from four volunteer donors are also presented, which suggest that micro-particulates containing large percentages of surface titanium and aluminum can cause moderate cellular toxicity, and micro-particulates containing large percentages of surface cobalt can result in extremely severe cellular toxicity. This work further suggests that surface analysis techniques, such as XPS, are essential to determine surface elemental characterization of metallic materials prior to interpreting cellular response results.
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