E.T. Bender

Electrical, structural, and chemical properties of semiconducting metal oxide nanofiber yarns

The electrical, structural, and chemical properties of twisted yarns of metal-oxide nanofibers, fabricated using a modified electrospinning technique, are investigated in this report. In particular, synthesized zinc oxide and nickel oxide yarns having diameters in the range of 4–40μm and lengths up to 10cm were characterized, whose constituent nanofibers had average diameters of 60–100nm. These yarns have one macroscopic dimension for handling while retaining some of the properties of nanofibers.

A comparison of the effects of prosthetic and commercially pure metals on retrieved human fibroblasts: The role of surface elemental composition

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.

Synthesis and characterization of erbia doped metal oxide nanofibers for applications in thermophotovoltaics

Titania (TiO2) nanofibers doped with erbia (Er2O3) have been synthesized by electrospinning mixtures of polymers, titanium-containing materials, and erbia particles. These electrospun nanofibers are subsequently annealed at temperatures of 800, 900, 1000, and 1050°C to remove the organics and leave behind the metal oxides. The crystal structure and optical properties of the metal oxides depend on the annealing temperature, and we characterize these nanofibers using x-ray diffraction and Fourier transform infrared spectroscopy (FTIR). An Er2Ti2O7 phase is formed in an amount which depends on the annealing temperature, and relationships between the nature of FTIR spectra and the relative amounts of different phases are demonstrated. Finally, the relevance of this work to thermophotovoltaics and other applications is discussed.

Differences in the surface composition of seemingly similar F75 cobalt-chromium micron-sized particulates can affect synovial fibroblast viability

We present data and analyses concerning the cytotoxicity and bioreactivity associated with the surface composition of fine metal particulates that are similar to those commonly released in the body by prostheses used in total joint replacement surgery. Here we study the bulk and surface compositions of three separately procured cobalt-chromium-molybdenum (CoCrMo) micron-sized particulate powders, each identified by their corresponding vendor as being ASTM F75 grade material. We use energy dispersive spectroscopy (EDS) to verify the bulk metallic composition and X-ray photoelectron spectroscopy (XPS) to examine the surface metallic composition of each CoCrMo powder. Cultured synovial fibroblasts were then exposed to the particulate powders to see how the metallic surfaces might affect cellular viability. Results indicate that while the bulk metallic composition of each CoCrMo powder was similar, the surface metallic compositions were found to be dramatically different and yielded equally dramatic differences in terms of cytotoxicity and bioreactivity of synovial fibroblast in culture.

Nanofiber Based Er(III) Metal Pyrochlore Oxides: Synthesis and Characterization

Erbium(III) doped TiO 2 nanofibers (Er 2 Ti 2 O 7 ) have been synthesized by electrospinning mixtures of polymers, metal-containing materials, and erbium acetate. These electrospun nanofibers were subsequently annealed at temperatures of 550, 750, 950, and 1150 oC to remove the organics and leave behind the metal oxides. The crystal structure and optical properties of the nanofiber pyrochlores were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier transformation IR (FTIR) spectroscopy. Different crystal structures were formed by controlling the annealing conditions. XRD data are compared with near-IR spectra to better understand the effects of annealing temperature on the Er (III) thermally-excited selective optical emission process.