Ion Beam Texturing Research Articles

Reducing the Specular Properties of Metalized Teflon Coverings on Canadian Mobile Servicing Station on the International Space Station

A surface modification process was developed for the metalized Teflon coverings used for thermal protection of electronic equipment on the International Space Station [1]. The developed modification process of Teflon surfaces reduced substantially the specularity of Ag-Inconel coated Teflon thermal control films by changing the morphological appearance of their surfaces by ion-beam texturing in a controlled manner from a metallic-like and shiny to complete milky, white appearance without significantly affecting the thermal optical properties.
 A number of space hardware units covered with the textured Silver-Teflon were exposed to the open space environment between June 2002 and June 2006 and delivered back to Earth at the end of 2006. Remarkable performance was demonstrated by the treated Ag/Teflon, with the solar absorptance and total emittance values and the α/ε ratio remaining very close to the original values as measured before the flights [2].
 In an attempt to protect further the textured surfaces of Teflon from possible erosion by atomic oxygen and VUV in LEO environment, an additional novel surface modification process was developed that created an SixOyCzFn type of structure on the treated surface. The textured Teflon samples before and after surface treatments were tested in a space simulator facility under a combined atomic oxygen/vacuum ultraviolet exposure. A number of advanced characterization techniques were used to evaluate the properties of the modified films [3].

Ion-beam Texturing at Nucleation – Manipulation of Crystallographic Orientation in Cubic Materials at the Nanometer Scale

AbstractThe use of an ion beam assist during the concurrent deposition of cubic materials can result in the growth of crystallographically oriented thin films. A model system, magnesium oxide (MgO), has been successfully used as a biaxially textured template film and develops texture in a different manner from that of other well-studied materials, like yttria-stablized zirconia. Here, we present data on the initial nucleation of biaxial texture in this model system using a novel in-situ quartz crystal microbalance (QCM) substrate combined with in-situ reflected high-energy electron diffraction (RHEED). Temporal correlation of mass uptake with the RHEED images of the growing surface can be used to elucidate the mechanism of texture development in these films. Experimental data shows that the initially polycrystalline MgO film develops biaxial crystallographic texture at a thickness of ˜2 nm, regardless of the ion-to-molecule ratio. RHEED images show the onset of texture occurs quickly and is somewhat analogous to a solid phase re-crystallization process with crystallite sizes of ˜3 to 4 nm. Imaging with transmission electron microscopy has corroborated these observations. Changes in the ion-to-molecule ratio can influence the crystallite size and affect the nucleation density of these films. Growth of these films on various substrates changes the sticking coefficient of the MgO and influences the nucleation density and film growth mode as well. This opens the possibility of using MgO and other materials to develop biaxially textured crystallites with a narrow, specified size distribution for nanoscale applications.

Surface texturing using pulsed air arc treatment

Texturing of contact surfaces has a remarkable influence on their tribological properties. Various texturing techniques such as machining, ion beam texturing, etching techniques and laser texturing are employed for preparation of micrometer-sized valleys. Modern modification of surface layers for friction applications combines surface texturing and filling of textured layers by solid lubricant MoS 2/WS 2 or other compositions. In this work pulsed air arc treatment (PAAT) was used to texture the surface layers. The textured surfaces were obtained and then filled by solid lubricant. Some burnishing methods were used to deposit solid lubricant films on steel surfaces. The tribological properties of solid the lubricant films on textured surfaces were compared with the behavior of solid lubricant films burnished on ground surfaces. The wear rate and wearability of solid lubricant films were assessed. It was shown that application of PAAT and filling of micro-reservoirs by solid lubricant particles provide longevity under dry friction conditions.

Ion-beam texturing of uniaxially textured Ni films

The formation of biaxial texture in uniaxially textured Ni thin films via Ar-ion irradiation is reported. The ion-beam irradiation was not simultaneous with deposition. Instead, the ion beam irradiates the uniaxially textured film surface with no impinging deposition flux, which differs from conventional ion-beam-assisted deposition. The uniaxial texture is established via a nonion beam process, with the in-plane texture imposed on the uniaxial film via ion beam bombardment. Within this sequential ion beam texturing method, grain alignment is driven by selective etching and grain overgrowth.

Nanometre scale island-type texture with controllableheight and area ratio formed by ion-beam etching onhard-disk head sliders

It has been common practice to apply a surface texture to the disk surface in a harddisk drive in order to minimize the stiction force caused by the contact of theextremely smooth surfaces of the head slider and disk. The surface of head slidersis usually made as smooth as possible without any purposely formed texture. In thiswork, a texture on the hard-disk slider surface was formed by ion-beametching as a result of the different etching rates among the different phasescomposingthe material of the hard-disk slider. By this method, an island-type texture canbeformed on the air-bearing surface of the hard-disk slider. The relation between thetexturing condition, the slider material and the shape of the obtained texture isdiscussed. The texture area ratio was 6-36%, and the diameter of the island was inthe range of 0.3-4 µm. The texture area ratio and island diameter could bechanged by changing the composition of head slider material. The height ofisland could be linearly controlled from 3-20 nm with an accuracy of ±1 nm bychanging the dose of the ion beam. It is concluded that ion-beam texturing is apromising method for producing texture on the slider surface, with the advantage ofsimple processing.

Ion Beam Texturing of Heat-Transfer Surfaces

Nucleate boiling heat transfer is examined as a means of energy conservation. Nucleate boiling curves were obtained for ion beam textured copper surfaces, untreated cooper surfaces, copper surfaces which had been polished and surfaces which had been coated with a plasma deposited polymer. Results show that texturing aids heat transfer while polishing has the opposite effect. The polymer coatings did not change nucleate boiling behavior. Aging effects were observed for untreated and for polished surfaces, while no such effects were noticed for textured surfaces. These data suggest that aging may be dependent on surface microgeometry, which is important in nucleate boiling heat transfer.

Ion beam texturing of surfaces

Portales Valley, Sombrerete, and Northwest Africa (NWA) 176 are three unrelated meteorites, which consist of silicate mixed with substantial amounts of metal and which likely formed at elevated temperatures as a consequence of early impacts on their parent bodies. Measured 39Ar–40Ar ages of these meteorites are 4477 ± 11 Ma and 4458 ± 16 Ma (two samples of Portales Valley), 4541 ± 12 Ma, and 4524 ± 13 Ma, respectively (Ma = million years; all one-sigma errors). The Ar–Ar data for Portales Valley show no evidence of later open system behavior suggested by some other chronometers. Measured 129I–129Xe ages of these three meteorites are 4559.9 ± 0.5 Ma, 4561.9 ± 1.0 Ma, and ∼4544 Ma, respectively (relative to Shallowater = 4562.3 ± 0.4 Ma). From stepwise temperature release data, we determined the diffusion characteristics for Ar and Xe in our samples and calculated approximate closure temperatures for the K–Ar and I–Xe chronometers. Adopting results and interpretations about these meteorites from some previous workers, we evaluated all these data against various thermal cooling models. We conclude that Portales Valley formed 4560 Ma ago, cooled quickly to below the I–Xe closure temperature, then cooled deep within the parent body at a rate of ∼4 °C/Ma through K–Ar closure. We conclude that Sombrerete formed 4562 Ma ago and cooled relatively quickly. NWA 176 likely formed and cooled quickly ∼4544 Ma ago, or later than formation times of most meteorite parent bodies. For all three meteorites, the Ar–Ar ages are in better agreement with I–Xe ages and preferred thermal models if we increase these Ar–Ar ages by ∼20 Ma. Such age corrections would be consistent with probable errors in 40K decay parameters in current use, as suggested by others. The role of impact heating and possible disruption and partial reassembly of meteorite parent bodies to form some meteorites likely was an important process in the early solar system.

Adhesive bonding of ion-beam-textured metals and fluoropolymers

An electron bombardment argon ion source was used to ion etch various metals and fluoropolymers. The metal and fluoropolymers were exposed to 0.5–1.0-keV Ar ions at ion current densities of 0.2–1.5 mA/cm2 for various exposure times. The resulting surface texture is in the form of needles or spires whose vertical dimensions may range from tenths to hundreds of micrometers, depending on the selection of beam energy, ion current density, and etch time. The bonding of textured surfaces is accomplished by ion beam texturing mating pieces of either metals or fluoropolymers and applying a bonding agent which wets in and around the microscopic conelike structures. After bonding, both tensile and shear strength measurements were made on the samples. Also tested, for comparison’s sake, were untextured and chemically etched fluoropolymers. The results of these measurements are presented in this paper.

Ion beam texturing of surfaces

Textured surfaces, typically with conical structures, have been produced previously by simultaneously etching a surface and seeding that surface with another material. A theory based on surface diffusion predicts a variation in cone spacing with surface temperature, as well as a critical temperature below which cones will not form. Substantial agreement with theory has been found for several combinations of seed and surface materials, including one with a high sputter yield seed on a low sputter yield surface (gold on aluminum). Coning with this last combination was predicted by the theory for a sufficiently mobile seed material. The existence of a minimum temperature for the formation of cones should also be important to those interested in ion-beam machining smooth surfaces. Elements contained in the environmental contaminants or in the sputtered alloys or compounds may serve as seed material.