bluuebunny/crossref_metadata_2025 huggingface dataset:
Rock Varnish on a Pre-Columbian Green Jasper From the Tropical Rain Forest (The Ahaw Pectoral)
Authors: Garza-Valdes Leoncio A. , Stross Brian
Published: March 2011

With aging, many rocks surfaces not in direct contact with the soil, develop a black coating. This deposit has been given different names: desert varnish [1,2], rock varnish [3], and biogenic rock varnish [4]. The rock varnish is a dark coating, usually 10 to 30 micrometers thick, with a variation from a few micrometers to over 500 micrometers [5]. It is composed of manganese and iron oxides, silica, and clay minerals. A similar type of coating is accreted in pottery found in ancient tombs [6].
Recent Eco-Archaeometric Studies of Salinization and Desalinization of Karnak Temples, Egypt
Authors: Burns George , Matsui K.M. , Potter R.M. , Billard T.C.
Published: March 2011

Earlier studies demonstrated quantitatively that recent salinization of the Karnak Temples, Egypt, is due to evaporation of saline groundwaters under the temples. Furthermore, it was determined that the high salinity of groundwaters is due to extensive evaporotranspiration over the adjacent irrigated fields. To abate salinization, in 1986, a desalinization station was installed in the central part of Karnak at Lake Amun. Present studies indicate that by 1987, the desalinization effort was already very successful, with the salinity of the Lake being lowered by a factor of more than 37. Some residual salinity was still evident a year after desalinization stations were installed. It appears that this residual salinity is due primarily to leaching of salts which were deposited around the Lake before 1986. Thus, not only the Lake, but also the area adjacent to it appear to be desalinized as a result of construction of the desalinization station.
Hydric Properties of Some Spanish Building Stones: A Petrophysical Interpretation
Authors: Valdeon Luis , Esbert Rosa M. , Grossi Carlota M.
Published: March 2011

The hydric properties of three types of building stone used in certain Spanish monuments of outstanding historical-artistic value have been determined. The stones selected were dolomite, limestone and sandstone used in the cathedrals of Leon (northern Spain), Seville (southern Spain) and Salamanca (central Spain) respectively.

In the work described in this paper, different rock properties related to water were measured (absorption of water and water vapour, evaporation, capillarity and permeability to water vapour). Swelling characteristics of the sandstone were also determined.

The close correlation between the values of the parameters obtained for each property analyzed and the mineralogical-textural features of the rock, notably the porosity and form of the pore system, has been also demonstrated. In these stones, it has been observed that water absorption capacity is linked both to the volume of empty communicating spaces (open porosity) and to the presence and percentage of clay minerals.
Siliconic and Acrylic Resins Dispersed in Water as Protectives for Stone Surface
Authors: Biscontin Guido , Maravelaki P. , Zendri E. , Glisenti A.
Published: March 2011

The aim of the present work is to compare the protective effect of solvent and water dispersed products on marble, Lecce and Istria stones. This choice is justified by the need of products effective also from the ecological and toxicological point of view. To obtain these informations two tests have been chosen: contact angle and water absorption. The contact angle may, in theory, be considered a measure of the water repellency, since complete wetting implies a contact angle of 0° and absolutely no wetting an angle of 180°. This does not apply to the water absorption by capillarity test because the absorption variation may be caused by either the water repellency action of the treatments or by the pore filling. However this test may give practical information about the general effect of the treatments. Moreover, the effect of treatments on permeability was investigated by vapour permeability test. Protective effect was studied after application of the products and at various stages of artificial weathering.
Investigations of the Surface Processes on Exposed Limestones
Authors: Maravelaki Pagona , Bertoncello R. , Biscontin G. , Battaglin G. , Zendri E. , Tondello E.
Published: March 2011

Different decay mechanisms, according to the exposure to rain actions, have been identified on a series of Istria stone samples derived from the Venetian buildings. Enquiries have been carried out on these samples by means of porosity measurements and chemical analysis in depth. In order to identify the decay mechanisms and their.kinetics, simulation tests have been,performed on exposed samples of Istria stone for a period of 19 months. These specimens have been analysed by several techniques in order to verify the chemical dissolution of limestone provoked by the rain action. The initial chemical attack on the exposed samples has been pointed out by XPS and RBS micro-analytical techniques.
Evaluation of Protective Coatings for the ‘In Situ’ Preservation of Historic Timber Buildings in a Harsh Antarctic Environment
Authors: Hughes Janet
Published: March 2011

The Australasian Antarctic Expedition base at Commonwealth Bay (67°S 142°E), also known as ‘Mawson's Huts’ include some of the earliest buildings in Antarctica. The prefabricated timber buildings of Oregon beams and Baltic Pine (Pinus sylvestris) claddings were erected in January 1912 and were occupied for two years: they are thus approximately contemporary with the better known Scott and Shackleton huts near McMurdo Base in the Ross Sea.

The expedition was led by Dr Douglas Mawson, later Professor Sir Douglas Mawson, and its inspiration was scientific rather than a race to the South Pole. The buildings and artefacts remaining on the headland, also called Cape Denison, reflect considerable scientific achievement in geology, upper atmosphere physics, surveying, meteorology and biology and the site constitutes an important monument in the early exploration of this remote and inhospitable continent.

While the huts are of recent date, the rapid rate of deterioration due to the extreme climate means there is some urgency to developing a method of preserving the building. The timbers have been seriously worn, or ‘corraded’ by snow particles carried in the katabatic winds. These winds can exceed 300km per hour, sometimes for days. The isolation of the site, accessible by sea for only three months of the year adds to the logistical difficulties. There has been considerable public debate in Australia about which method of preservation is appropriate.

The author, a materials conservator and industrial chemist, visited the site in December 1985 and has been studying the problems of the site as a postgraduate student for the past year.
Influence of Plasma Density and Energy on the Characteristics of Amorphous Silicon Films Prepared by ECR Microwave Plasma CVD
Authors: Tanaka Masahiro , Watanabe Kunihiko , Todoroki Satoru , Suzuki Kazuo
Published: March 2011

The influence of magnetic field on Plasma parameters of ECR plasma were measured by the Langmuir probe technique. And it was shown that the plasma parameters can be controlled by magnetic field. Amorphous silicon films were prepared by ECR plasma CVD method under various magnetic field conditions for the purpose to investigate the effect of plasma density and energy on the property of amorphous silicon films. High plasma density improved the photoconductivity of amorphous silicon but the optical gap and activation of dopant depended on the substrate temperature rather than plasma density.
Synthesis of Al and Al2O3 Coatings by Ion Beam Assisted Deposition
Authors: Kalnas C. E. , Parfitt L. J. , Mashayekhi A. , Jones J. W. , Was G. S. , Hoffman D. W.
Published: March 2011

Films of Al and Al2O3 were formed by physical vapor deposition (PVD) and ion beam assisted deposition (IBAD) onto (100) Si, glass and graphite substrates. Ion to atom arrival rate (R) ratios for IBAD varied from 0.004 to 0.1 and film thicknesses varied from 150 to 1000 nm. The O/Al ratio of oxide films and the oxygen content of Al films decreased with increasing R ratio. Al incorporation into both types of films increased with R ratio up to a value of ∼4 at% at R=0.1. Al films were crystalline with a strong (111) fiber texture becoming more pronounced with increasing R ratio. Film morphology is characterized by large columnar grains at R=0, with a breakup of the columnar structure by R=0.04. Al2O3 films are amorphous under all deposition conditions. Average film stress for PVD Al2O3 films is tensile with a value of 0.68 GPa, becoming compressive at ∼1.3 eV/atom and saturating at a value of ∼-0.65 GPa at R=0.04. Indentation experiments of Al2O3/(100)Si with a 300 g Vickers indenter showed that the changes in crack length are consistent with a model in which the residual film stress is controlling.
Ion-Assisted Deposition of CaF2 Films on (111) Si
Authors: Cook J.G. , Moeller H. , Das S.R. , Zhongming Li
Published: March 2011

CaF2 films have been deposited by evaporation onto H-passivated (111) Si in the presence of an rf discharge. The discharge is seen to promote epitaxy. Emission spectroscopy reveals strong CaF2 bands and a weak Ca line, indicating that deposition is largely molecular but that some breakup of the CaF2 molecules occurs in the discharge. Electrical and optical properties of these films were substantially better than those of sputter-deposited films.
MeV Ion Implantation in Electronic Materials
Authors: Todurello T. A.
Published: March 2011

Using MeV ions for the modification of electronic materials offers a number of advantages: minimizing surface damage; implantation into completed devices – for example, through contacts or photoresist layers; producing controlled radiation damage for flux pinning where the ions pass completely through the sample and thus do not modify its chemical nature; and enhancing the electronic excitation of the target material versus collisional damage, as in adhesion enhancement processes. In all cases, however, one requires a detailed understanding of the new damage mechanisms that occur and how they can be modified in a controlled way by annealing. In this report I shall present examples from a number of our experiments: resistivity and index of refraction modification in semiconductors; adhesion enhancement; mixing of multilayer structures; and modification of the electronic properties of insulators and superconductors.
Adhesion Enhancement Produced by MEV Ions
Authors: Sugden Stephen , Sofield Carl J. , Murrell Martin P.
Published: March 2011

Ionising radiations have been observed to produce significant improvements in thin film adhesion by several experimental groups. We present the results of an exhaustive and conclusive series of experiments on the effect of clean processing and heavy ion irradiation on the adhesion of metal films to substrates of silicon and tantalum. The experiments were performed in a unique research-scale Ultra High Vacuum Cluster tool, to gain control of the all important surface and interface compositions.

Our results show that adhesion is greatest for films deposited on atomically clean surfaces. Such films adhere better than conventionally deposited films subjected to a post deposition irradiation treatment. Clean processed samples show no benefit from subsequent radiation processing. Our results are consistent with the radiation enhanced adhesion phenomenon being due to the radiolysis of interfacial contaminant layers, producing an interface with lower interfacial energy and hence better bonding. Where adhesion enhancement is observed, the process is consistent with a semi-empirical model of the process using an activation energy of some 5 eV per atom.
XPS Study of Chemical Interactions in Ion-Implanted Silica Glasses
Authors: Bertoncello Renzo , Glisenti A. , Granozzi G. , Battaglin G. , Cattaruzza E. , Mazzoldi P.
Published: March 2011

An almost unexplored research field of the ion implantation processes is related to chemical modifications induced in a target by chemically reactive ions. This kind of chemistry is somewhat similar to the “hot atom” chemistry, where chemical transformations are produced by recoil atoms originating from nuclear reactions or radiative decay. XPS technique can provide unique informations on the chemical modifications produced by such processes. XPS results will be reported on silica glasses implanted with titanium, silver and tungsten ions in a dose range from l×1016 to 5×1016 ions cm−2, at energies ranging from 15 keV to few hundreds of keV. Most of samples were also subjected to a second implant with N ions. Radiation damage and chemical effects have been discriminated. Chemical compound formation as well as precipitation of the implanted species have been observed. Interestingly, evidences for reactions between chemical species obtained by the first implant and nitrogen (subsequently implanted) will be reported.
Ultra-Low Damage Chemical Etching of GaAs with a Novel Ion Beam Source
Authors: Beckman Judith , Jackman Richard B.
Published: March 2011

A novel ion beam source has been successfully used in both a CAIBE and RIBE configuration, with chlorine as the chemically active gas, to achieve GaAs etching a rates of around 0.1 µm/hour. The energy of species within the beam from the source is estimated at 10 - 25eV. Under these conditions it can be expected that little or no penetration into the GaAs lattice occurs and that the principle origin of lattice disruption, prior to etching, is chemical; a low damage GaAs etching process results. The source, however, gives rise to a coating, derived from the source liner, which must be washed from all etched samples. The presence of such a coating is likely to be the origin of the slow etch rate achieved. After removal of the coating, smooth, mirror like etched surfaces are apparent. These surfaces perform very well when Schottky diodes are constructed from them showing no deviation from the behaviour of control samples.
Surface Modification of Uranium Alloys by Ion Implantation and Ion Mixing - Effects on Corrosion Behavior
Authors: Ayral A. , Crusset D. , Raboisson G.
Published: March 2011

Ion implantation and ion mixing are applied to improve the corrosion behavior of two uranium alloys: UV0.2 and UTi0.75, in three specific media: hydrogen, humid air and salt fog. This experiments shows particularly that high dose nitrogen implantation might be effective for both corrosive environment, hydrogen and humid air. Ion mixing of aluminum coatings on UTi0.75 alloy induces microcracks in these films and reduce their protective characters in salt fog medium.
Reactive Magnetron Sputtering: In Situ Analyses of Particle Fluxes and Interactions with the Growth Surface
Authors: Abelson J. R. , Doyle J. R. , Mandrell L. , Maley N.
Published: March 2011

Reactive magnetron sputtering (RMS) is a versatile technique for the production of alloy thin film coatings such as hydrides, nitrides, oxides, etc. RMS provides control over (i) film stoichiometry, via the partial pressure of “reactive” gas (H2, N2, etc.) injected, and (ii) film microstructure, via the bombardment of the growing surface by fast neutral or accelerated ionic species. However, few details are known about the fluxes reaching the film surface, and their reactions with it.

This paper reports comprehensive measurements for the RMS growth of hydrogenated amorphous silicon (a-Si:H). The analysis techniques are in situ double modulation mass spectroscopy, plasma probes, isotope replacement experiments, and Monte-Carlo simulations of sputtered particle transport. We determine (i) the composition, energy and angular distributions of the incident flux, (ii) the H coverage of the growing surface, and (iii) the release of H2 from the growing film. For conditions which produce electronic quality a-Si:H, the total H flux arriving at the substrate varies between 0.5–2 times the depositing Si flux; about half of the H flux reflects. The growth surface has excess H varying between 0.5–2 × 1015/cm2, and this surface H coverage is linearly related to the bulk H incorporation. We also find evidence that film density varies with the energy of the arriving sputtered Si atoms.
Amorphization of Thin Multilayer Films by Ion Mixing and Solid State Reaction
Authors: Van Rossum M. , Shreter U. , Johnson W. L. , Nicolet M-A.
Published: March 2011

We have compared the formation of amorphous alloys from Ni-Hf multilayer films by ion mixing and solid state diffusion. We find that ion mixing and solid state reaction produce significant differences in the composition range of the amorphous phase inside the mixed samples. Moreover, the thermochemical parameters which are of primary importance for the solid state reaction also influence the behavior of the Ni-Hf system under ion mixing.
Ion Mixing Kinetics of Thin Layered Films in the Fe-Al System
Authors: Grilhe J. , Riviere J.P. , Delafond J. , Jaouen C.
Published: March 2011

Evaporated bilayers and multilayers of Fe and Al have been studied during ion beam mixing with Xe ions using in-situ electrical resistivity measurements. Experiments have been performed in the composition range 40 – 58 at.% Al and at both temperatures 77 K and 300 K. A semi-empirical model is proposed to explain the observed kinetics. At low doses, a square root dependence of the mixed volume fraction on dose is found at 77 K but not at 300 K. The results are discussed by comparison with the different models proposed for ion beam mixing.
Modulated Structures in Ion Implanted Al-Fe System
Authors: Jata K.V. , Janoff D. , Starke E.A.
Published: March 2011

The results of transmission electron microscopy studies of iron implantation into high purity aluminum foils are described. For both 50 and 100 + 50 keV incident ion energies, modulated structure has been detected in the as-implanted foils. Upon annealing at 793 K the modulated structure decomposes into the Al matrix and Al3Fe precipitates for the 50 keV implantation. A similar annealing treatment for the 100 + 50 keV implantation indicates that the modulated structure is more stable, although some Fe3Al precipitation occurs.
The Dependence of Ion Beam Mixing on Projectile Mass
Authors: Averback R. S. , Thompson L. J. , Rehn L. E.
Published: March 2011

Ion beam mixing in Pt-Si bilayered samples was measured during irradiation with projectiles ranging in mass from 4 amu (He) to 131 amu (Xe) at 10 K, 300 K and 373 K. Using deposited damage energy as a basis for comparing the different irradiations, it was found that the beavier ions were more efficient than the lighter ones for inducing mixing. Moreover, it was observed that the mixing was essentially independent of temperature below 373 K. These results are interpreted on the basis that the mixing is caused by the stimulated motion of defects during the cooling phase of energetic cascades.
The Influence of Implantation Conditions and Target Orientation in High Dose Implantation of Al+ into Si
Authors: Nam-Avar F. , Budnick J. I. , Fasihuddin A. , Hayden H. C. , Pease D. A. , Otter F. A. , Patarini V.
Published: March 2011

We report the preliminary results of a study to determine the dependence of the near surface composition and structure on total dose, dose rate, vacuum condition and substrate orientation for Al implantation into Si (111) and Si (100) with doses up to 2 × 10l8 ions/cm2. Our studies include the results of Rutherford Back Scattering (RBS), Auger Electron Spectroscopy (AES) and x-ray diffraction measurements on samples implanted with a 100 keV energy in a diffusion pumped vacuum (DPV) system (10−6 Torr) with and without a LN2 trap and in an ultra high vacuum (UHV) system (2–4) x 10−8 Torr.

Results of high dose rate (50 μA/cm2 ) implantation into Si (111) in an untrapped DPV system indicate that Al segregates with a preferred (111) orientation. For a dose of 1 × 1018 ions/cm2 the surface is Al-rich to a depth of 2500Å while for lower doses the surface is silicon-rich. A carbon build-yp occurred for samples prepared by low dose rate (5 μA/cm2 ) implantation. However, no Al segregation could be observed for doses of less than 1018 ions/cm2 . A similar behavior has been observed for Si (100) except that Al segregation occurs with a polycrystalline structure. Moreover, the segregated Al is present at depths greater than the projected range.

When implantation was carried out in a DPV system with a LN2 trap, no carbon peaks could be observed by RBS regardless of the dose rate. For these conditions, as well as for the implantation of Al in an UHV system, we find Al segregation with a polycrystalline structure independent of the dose rates and target orientations we used. Al is observed at a depth greater by a factor of two than the expected value from the Rpcalculations. The Al depth penetration increases with the dose of implantation.
Characterization of Ion Implantation Damage in Capless Annealed GaAs
Authors: Kanber H. , Feng M. , Whelan J. M.
Published: March 2011

Arsenic and argon implantation damage is characterized by Rutherford backscattering in GaAs undoped VPE buffer layers grown on Cr-O doped semi-insulating substrates and capless annealed in a H2 −As4 atmosphere provided by AsH3. The damage detected in the RBS channeled spectra varies as a function of the ion mass, the implant depth and the annealing temperature of the stress-free controlled atmosphere technique. This damage is discussed in terms of the stoichiometric disturbances introduced by the implantation process. The as-implanted and annealed damage characteristics of the Ar and As implants are correlated to the electrical activation characteristics of Si and Se implants in GaAs, respectively.
Ion Implantation of Polymers
Authors: Dresselhaus M.S. , Wasserman B. , Wnek G.E.
Published: March 2011

Ion implantation provides a mechanism for radically modifying the electronic and transport properties of a variety of polymers that are normally insulating. By using masks and tailoring the implanted species and ion energies, conducting paths in an insulating medium can be fabricated between specific reference points, an application of obvious relevance to the microelectronics industry. Specific results are reported for modification of the structure, electrical conductivity, thermoelectric-power, optical transmission and electron spin resonance for several polymers under a variety of implantation conditions. The temperature and frequency dependence of the conductivity suggest a onedimensional variable range hopping mechanism for conduction along the polymer chains. Comparison is made between implantation in the 200 keV and 2 MeV energy ranges.
Structure/Majority Carrier Relationships in Ion-Implanted Polymer Films
Authors: Wnek G. E. , Wasserman B. , Loh I.-H.
Published: March 2011

Ion implantation of selected polymer films leads to the formation of semiconductive (σ ~ 10−4 S/cm) derivatives, which are presumably partially carbonacėous products derived from gross structural rearrangements. In support of this contention we find that Br-implanted polyacrylonitrile, PAN, exhibits a narrow ESR signal with a g-value of 2.0033, consistent with the presence of free radicals delocalized within a П-electron system. Thermopower measurements reveal that the sign of the majority carrier is dependent upon the molecular structure of the parent polymer.For example, implantation of PAN with Br+ affords n-type derivatives while under similar conditions poly(p-phenylene sulfide), PPS, and poly(2,6-dimethylphenylene-oxide), PPO, yield p-type semiconductors. It is suggested that the majority carriers arethe ions (carbenium ions or carbanions) which are best stabilized by the parent polymerstructure, remnants of which presumably exist after implantation. Resonance and/or inductive effects are invoked to explain the data. For example, the rather electron-rich backbone of PPQ is expected to stabilize holes more effectively than electrons, and the observed p-type behavior is consistent with this prediction.
Two-Dimensional Ordering of Ion Damaged Graphite
Authors: Elman B.S. , Dresselhaus S. , Braunstein G. , Dressflhaus G. , Venkatesan T. , Wilkens B. , Gibson J.M.
Published: March 2011

Post implantation annealing of ion-damaged, highly oriented pyrolytic graphite (HOPG) has been studied by Raman spectroscopy, the ion channeling technique and Transmission Electron Microscopy. Complementary information obtained by these methods provides confirmation for the completion of the first step of graphitization of iondamaged graphite at annealing temperatures of ~2300°C. This is manifested by the formation of carbon planes with two dimensional ordering but no correlation in the third (c-axis) dimension.
Maskless Patterning of Cr Films Using Focused Ion Beams
Authors: Gamo K. , Moriizumi K. , Matsui T. , Namba S.
Published: March 2011

Characteristics of maskless patterning of Cr films using focused Sb+ ion implantation have been investigated. Dose and depth dependence of the etching rate of Sb-implanted layers during plasma etching using CCl4 were measured. Sb profiles were also measured by Rutherford backscattering techniques. It was found that a sharp threshold dose exists to form an etch-resistant layer by Sb implantation. It was also found that a latent image of an Sb implanted pattern at a dose ≥3.8×1015/cm2 was developed by the plasma etching, and that Cr patterns with a thickness of a few hundred nanometers were formed by the present maskless patterning technique.
Ion Irradiation Smoothing and Film Bonding for Laser Mirrors
Authors: Pronko P. P. , Mccormick A. W. , Ingram D. C. , Rai A. K. , Woollam J. A. , Appleton B. R. , Poker D. B.
Published: March 2011

Irradiation with high energy heavy ion beams has been investigated as a technique for improving the quality of highly reflecting metallic surfaces to be used as laser mirrors. Properties such as reflectivity, corrosion resistance, film bonding, and threshold to laser surface damage have been examined. Modifications of composition and microstructure of the material associated with the heavy ion irradiation have been measured with RBS, TEM, SEM, Auger, and ESCA. Reflectivity and extinction coefficient measurements were made using ellipsometry techniques. Observations indicate that keV heavy ion irradiations in the fluence range of 1015 to 1016 cm−2 produce significant surface smoothing. Additionally, MeV implants of heavy ions into films of Cu, Ag, Au and Al deposited on molybdenum substrates resulted in improvements to both tarnish resistance and structural bonding integrity.
Radiation Enhanced Diffusion in Ion-Implanted Glasses and Glass/Metal Couples
Authors: Arnold G. W.
Published: March 2011

Ion implantation causes alkali migration to the surface in alkali silicate glasses. Rutherford backscattering spectrometry was used to follow this depletion. Room temperature implantations of 5×1016 250 keV Xe/cm2 in 12M20·88SiO2 (M = Li,Na,K,Rb,Cs) removes approximately equal numbers (within a factor of 2) of alkali from the glass. Low temperature (77K) implants significantly reduce the alkali loss. These results imply a radiationenhanced diffusion mechanism in which the alkali interchanges with the products of the collision cascade, with the kinetics being limited by the radiation damage components. The results for mixed-alkali glasses ((12−x)M2O·xCs20·88Si02) give further evidence for this process. In glass/'metal couples, radiation enhanced diffusion allows the interchange of glass network components with deposited metals. Rutherford backscattering spectrometry was used to follow the interchange of silicate and phosphate glass components with metal ions near the heavy-ion implanted interface between glass substrate and metal (Al,Zr) films.
The Characterization of Nitrogen Implanted WC/Co
Authors: Oblas Daniel W.
Published: March 2011

Although the mechanical properties of nitrogen implanted cemented carbides show significant improvements in performance over unimplanted specimen, the chemical or physical mechanisms giving rise to these improvements are not well understood. Furthermore, the mechanical properties of the implanted samples under thermal stress may not be stable. This study presents analytical results obtained for a series of nitrogen implanted cemented carbides that were subsequently characterized by Auger Electron Spectrometry (AES) and Thermal Desorption Mass Spectrometry (TDMS). Results show that, in the fluence range of 0.5 to 2.5×1017 N2/cm2, peak nitrogen concentration is linear and reaches a maximum concentration of 25 a/o for the highest fluence and 180 keY energy. During vacuum heating, the implanted nitrogen is evolved rapidly between 600–700°C, which corresponds to an activation energy of approximately 7 kcal/mole (.30 ev). A small quantity of nitrogen is still present after heating to 1000°C, at an estimated average concentration of 3 a/o with little diffusional broadening as a result of post-implant heating.
Processing Steels for Tribological Applications by Titanium Implantation
Authors: Singer I.L. , Jeffries R.A.
Published: March 2011

Titanium implantation into steels has been shown to produce superior tribological surfaces. The fluence required to produce a wear resistant surface increases from 2 to 5×1017 Ti/cm2 as the energy increases from 50 to 200 keV/ion. On curved surfaces (e.g., bearings, cutting tools, etc.) higher fluences are necessary due to effects of implantation at angles off normal incidence (i.e. the combined effects of higher sputtering rates, decreased range, and changes in the carburization process associated with duty cycles). Significant improvements in friction and wear have also been observed for surfaces which have been abraded by 600 and 120 grit SiC prior to implantation. Optimal benefits of Ti-implantation are associated with the formation of a modestly thick (>20nm) fully carburized layer.
Ion Mixing in the Ni-Sn System
Authors: Calliari L. , Gratton L.M. , Guzman L. , Principi G. , Tosello C.
Published: March 2011

Nickel substrates were coated with a thin Sn film and implanted with 100 keV Xe+ to fluences between 3 and 7.1015 ions/cm2. Surface chemistry changes were monitored using Auger and Mfssbauer spectroscopies. By comparing between profiles of un-implanted and implanted specimens, it was found that ion implantation through the film caused Ni to move into the Sn film and Sn to penetrate into the Ni substrate. The Mdssbauer analysis disclosed the presence of new surface phases. A substantial increase in the tarnishing resistance of Ni was found by using this treatment.
Synthesis of Ferroelectric Perovskites Through Aqueous Solutions Techniques
Authors: Guzmàn-Martel G. , Aegerter M. A. , Barboux P.
Published: March 2011

The hydrolysis of niobates in aqueous solutions has been studied as a function of pH and concentration. The process has been applied to the coprecipitation of PbNb2/3Mg1/3O3 leading to a low temperature synthesis of this ferroelectric relaxor ceramic. The effect of hydrolysis conditions such as the concentration of bases and acids used, their rate of addition, temperature and the nature of the precursor salts is described. The homogeneity of the precipitates has been characterized through infrared spectroscopy and X-ray diffraction techniques. The perovskite phase appears after heating at 350°C and is obtained as a pure phase above 750°C after one hour heat-treatment. Relaxor ceramics with high dielectric constant can be obtained by sintering above 1000°C. The process also has been successfully applied to the synthesis of other relaxor ceramic compositions such as PZN (PbNb2/3Zn1/3O3), PFN (PbNb1/2Fe1/2O3) as well as CdNb2O6 and MgNb2O6 compounds.
Stabilization of Metal Alkoxides (M = BA, CU) by Alkamolamines
Authors: Hubert-Pfalzgraf L. G. , Massiani M. C. , Daran J. C. , Vaissermann J.
Published: March 2011

Alcohol interchange reactions between barium and copper(II) methoxides and triethanolamine give Ba(teaH-l)2,2EtOH and [Cu(teaH-2)]4,3tea, respectively. Triethanolamine appears as a tetradentate ligand -chelating in the case of barium, bridging-chelating for copper - and thus ensures high coordination numbers for the metals - eight for Ba and five for Cu - thus decreasing their susceptibility to hydrolysis. The remaining hydroxyl functionality on the coordinated triethanolamine moities favors the formation of solvates with alcohols via H-bonding.
Solid State Structures, Decomposition Pathways, and Vapor Phase Byproducts of Y(acac)3 Type OMVPE Precursors for thin films of Yttrium -Containing Ceramic Materials
Authors: Ree William S. , Luten Henry A. , Carris Michael W. , Doskocil Eric J. , Goedken Virgil L.
Published: March 2011

Several useful ceramic materials target compositions contain yttrium, Y2O3and YBa2Cu3O7-δbeing the two most widely employed. One known CVD precursor for yttrium-containing thin films is Y(tmhd)3H2O (tmhd = 2,2,6,6-tetramethylheptane-3,5-dionato). We have determined the structure and examined the vapor phase decomposition of this species. A related compound, [Y(tmod)3]2(tmod = 2,2,7-trimethyloctane-3,5-dionato), has been prepared, structurally characterized, and studied as an organometallic vapor phase epitaxy (OMVPE) precursor for Y and Y2O3films. Mechanisms of vapor phase decomposition are discussed in terms of solid film deposits and vapor phase by-products. The two precursors are compared to each other with respect to their stability windows, defined as being bound by source volatility on the low side and source stability on the high side.
Heterometallic Aggregates as Intermediates on the Molecular Routes to Multicomponent Oxides
Authors: Hubert-Pfalzgraf Liliane G.
Published: March 2011

Metal alkoxides are often associated with more accessible precursors such as carboxylates, nitrates, B-diketonates, in chemical routes to multicomponent oxides. The molecular constitution of such solutions has been examined for systems based on niobium or zirconium. The heterometallic aggregates MNb2(μOAc)2(μ-0R)4(OR)6 (M = Cd, Mg), PbZr3, (μ4-0)(μ-0Ac)2(μ-0R)5(0R)5 and Gd2Zr6(μ4-O)2(μOAc)6(μOR)10(0R)10 R = iPr have been characterized by X-ray diffraction. Preliminary results on the hydrolysis experiments of these aggregates are given.
Sol-Gel Process from Heterobimetallic Alkoxides to Incorporate Lanthanides in an Alumina Matrix
Authors: Narula Chaitanya K.
Published: March 2011

Gels form on addition of seven or more moles of water diluted withi-PrOH to one mole of M[Al(O-i-Pr)4]3, M = La, Ce dissolved in i-PrOH. Thermal treatment of xerogels derived from La[AI(O-i-Pr)4]3gives amorphous powders below 900°C. LaAIO3crystallizes out at 900°C and residual alumina remains amorphous. CeO2starts to separate out above 600°C from the xerogels prepared from Ce[M(O-i-Pr)4]3. Thermally induced structural changes in xerogels prepared from the mixtures of La[AI(O-i-Pr)4]3and Ce[AI(0-i-Pr)4]3in 1:1 or 1:3 ratio are different from those prepared from individual precursors. These xerogels remain amorphous below 700°C. Crystalline CeO2forms on heating at 900°C but alumina remains amorphous. Sols are formed on hydrolysis of M[AI(0-/-Pr)4]3in excess water and acidifying the reaction mixture with acetic acid. Sols can be converted to gels by slow evaporation of volatiles. This method is useful in preparing coatings.
Complexation of Zr(IV) Precursors in Aqueous Solutions
Authors: Livage J. , Chatry M. , Henry M. , Taulelle F.
Published: March 2011

The sol-gel synthesis of metal oxides can be performed via the hydroxylation and condensation of metal cations in aqueous solutions. The complexation of these ionic species by anions leads to the chemical modification of inorganic precursors at a molecular level. The whole process of hydrolysis and condensation can then be modified allowing a chemical control of the morphology, the structure and even the chemical composition of the resulting powder.

The role of anions during the formation of condensed phases from inorganic precursors in aqueous solutions has to be taken into account. The complexing ability of these anions is described in the frame of the Partial Charge Model as a function of pH and the mean electronegativity of anionie and cationic chemical species. Experimental evidence for the complexation of zirconyl species in aqueous solutions will be given using multinuclear NMR of anions.
Silicon-29 NMR Study on the Initial Stage of the Co-Hydrolysis of Tetraethoxysilane and Methyltriethoxysilane
Authors: Sugahara Yoshiyuki , Tanaka Yoichi , Sato Shuji , Kuroda Kazuyuki , Kato Chuzo
Published: March 2011

The hydrolysis and initial condensation processes of the mixtures of TEOS and MTES have been studied by GC-MS and 29Si-NMR in the systems with TEOS:MTES:ethyl alcohol:water:HCl=1:1:14:28:6×1O-4 and 0.5:1.5:14:28:6×10-4. Thedimer CH3(HO)2SiOSi(OH)3 possessing both TEOS- and MTES-derived units was identified, indicating that the condensation between a hydrolyzed TEOS-derived monomer and a hydrolyzed MTES-derived monomer was one of dominant dimerization.
Structural Characterization of Gels Prepared from Co-Hydrolysis of Tetraethoxysilane and Dimethyldiethoxysilane.
Authors: Babonneau Florence , Bois Laurence , Livage Jacques
Published: March 2011

This work is part of a more general study on the structural characterization of organically modified silica gels that are usually prepared from tetrafunctional, trifunctional and difunctional alkoxides. The systems that were investigated in this paper are gels prepared from co-hydrolysis of dimethyldiethoxysilane (DEDMS) and tetraethoxysilane (TEOS). The condensation process was followed by 29Si and 17O liquid NMR and shows clearly evidence for co-condensation reactions. Gels with various DEDMS/TEOS ratios were studied by 29Si and 1H MAS-NMR. The results are clearly correlated to the change in physical properties of the materials, from flexible polymeric gels at high DEDMS content to crosslinked brittle networks at low DEDMS content.
Further Studies on Aluminum Oxoalkoxide Clusters
Authors: Sinclair R. A. , Brostrom M. L. , Gleason W. B. , Newmark R. A.
Published: March 2011

Evidence for a tetranuclear aluminum oxoalkoxide cluster Al4(μ4-0) (μ2OBμi)5(OBui)6 is presented, drawing on data from X-ray, NMR, MS and other spectroscopie and experimental investigations. In principle, these compounds are derived from the well-authenticated aluminum alkoxide tetramers by hydrolytic loss of only one alkoxy group. They contain a single central oxo ligand and only 5-coordinate aluminum atoms. They are the simplest discrete oxoalkoxide structures so far reported for aluminum and may be helpful in understanding the hydrolysis and condensation steps leading to hydrated aluminum oxide sols and gels.
Stress and Phase Transformation Phenomena in Oxide Films: Real-Time Spectroscopic Measurements
Authors: Exarhos Gregory J. , Hess Nancy J.
Published: March 2011

In situ optical methods are reviewed for characterization of phase transformation processes and evaluation of residual stress in solution-deposited metastable oxide films. Such low density films most often are deposited as disordered phases making them prone to crystallization and attendant densification when subjected to increased temperature and/or applied pressure. Inherent stress imparted during film deposition and its evolution during the transformation are evaluated from phonon frequency shifts seen in Raman spectra (TiO2) or from changes in the laser-induced fluorescence emission spectra for films containing rare earth (Sm+3:Y3Al5O12) or transition metal (Cr+3 :Al2O3) dopants. The data in combination with measured increases in line intensities intrinsic to the evolving phase are used to follow crystallization processes in thin films. In general, film deposition parameters are found to influence the crystallite ingrowth kinetics and the magnitude of stress and stress relaxation in the film during the transformation. The utility of these methods to probe crystallization phenomena in oxide films will be addressed.
Low Temperature Formation of Ferroelectric thin Films
Authors: Kong Kwok Chi , Desu Seshu B.
Published: March 2011

Two novel processes have been developed to lower the transformation temperature of ferroelectric lead zirconate titanate (PZT) thin films with high Zr/Ti ratio. One process makes use of high pressure and the other process uses seeding to encourage the transformation.

A previous study has shown that nucleation is the rate-limiting step for the perovskite formation. Therefore, any process that enhances the kinetics of the nucleation will likely decrease the transformation temperature. In this process, a very thin seeding layer, which has a low effective activation energy for perovskite formation, is used to provide nucleation sites needed for the low temperature perovskite formation. In this study, the pyrochlore to perovskite phase transformation temperature of PbZrxTi1−xO33 films of high Zr/Ti ratio (e.g. x = 53/47) can be lowered by as much as 100°C.
Preparation and Characterization of Sol-Gel Thin Films of KTIOPO4.
Authors: Harmer Mark A. , Roelofs Mark G.
Published: March 2011

In this paper we describe a novel route for the formation of thin films of potassium titanyl phosphate (KTiOPO4 KTP) via a sol-gel route. The ability to form films of high optical quality depends upon the precursor chemistry developed. Formation of stoichiometric films is especially challenging in three component systems and a number of precursors have been investigated. The basic chemistry, processing and resulting microstructure will be described. Transparent, dense and continuous films have been prepared with grain sizes typically of 0.3μm or less depending upon the processing conditions. Some textured growth patterns are observed although the films are essentially polycrystalline. Using the prism coupling technique the films have been found to exhibit waveguiding.
Molecular Recognition on Acoustic Wave Devices: Modified Zeolite-Silica Thin Films With Tailored Adsorption Properties
Authors: Yan Yongan , Bein Thomas , Brown Kelly D. , Forrister Ray , Jeffrey Brinker C.
Published: March 2011

Microporous thin films composed either of zeolite crystals embedded in sol-gel derived glass or of a molecular coupling layer, zeolite crystals and a porous silica overlayer, were formed on the gold electrodes of Quartz Crystal Microbalances (QCM). The microporosity of the thin films was characterized by in situ nitrogen and vapor sorption isotherms. Both preparation methods result in thin films with substantial microporosity. Selective adsorption based on molecular size exclusion from the microporous films could be achieved.
Structure of Thin Sol-Gel Coatings Near The Surface of Substrates
Authors: Hirashima Hiroshi , Kusaka Takao
Published: March 2011

ABSTRUCT

The sol-gel method is one of the most appropriate technologies for the preparation of functional thin oxide coatings. However, few studies on the structure near the interface between sol-gel coatings and substrates have been reported. In this study, the structures of thin TiO2 gel coatings were investigated by XPS in order to elucidate the interaction between the coatings and the glass substrates. TiO2 gel coatings were prepared from Ti-alkoxide by hydrolysis and dip-coating on silica glass plates. Thickness and refractive index measurements were made by ellipsometry. Changes in Ols spectra for the coatings were observed at locations near the interface. Dynamic microhardness measurements for the coatings and the coated glasses were made. These results suggest the formation of a Ti-O-Si bond at the interface.
Electrophoretic Deposition of Sol-Gel-Derived Ceramic Coatings
Authors: Zhang Yining , Jeffrey Brinker C. , Crooks Richard M.
Published: March 2011

The physical, optical, and chemical characteristics of electrophoretically- and dip-coated sol-gel ceramic films are compared. The results indicate that electrophoresis may allow a higher level of control over the chemistry and structure of ceramic coatings than dip-coating techniques. For example, controlled-thickness sol-gel coatings can be prepared by adjusting the deposition time or voltage. Additionally, electrophoretic coatings prepared in a four-component alumino-borosilicate sol display interesting optical characteristics. For example, the ellipsometrically-measured refractive indices of electrophoretic coatings are higher than the refractive indices of dip-coated films cast from identical sols, and they are also higher than any of the individual sol components. This result suggests that there are physical and/or chemical differences between films prepared by dip-coating and electrophoresis.
Protective Zirconia Thin Films on Metal Substrates.
Authors: Tomasi Andrea , Scardi Paolo , Marchetti Fabio
Published: March 2011

Stabilized Zirconia thin films were deposited by R. F. Magnetron Sputtering onto iron substrates. Deposition parameters such as gas pressure and R. F. voltage were optimized to obtain homogeneous and well adherent protective coatings. The morphology and structure of films before and after thermal treatments were investigated by Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Thermogravimetrical Analysis (TGA).

Auger Electron Spectroscopy (AES) depth profiling techniques were used to obtain the chemical distribution of the elements in order to study the influence of two important parameters on the adhesion of the ceramic: the presence of a thin layer of native metal oxide and the residual surface roughness after polishing.

The effectiveness of coatings to protect the metal substrate against high temperature oxidation in air was evaluated by thermogravimetrical analysis at 773K. The protective action of the ceramic film was well demonstrated.
Plasma Sprayed Alumina-Titania Coatings
Authors: Steeper T. J. , Rotolico A. J. , Nerz J. E. , Riggs W. L. , Varacalle D. J. , Wilson G. C.
Published: March 2011

This paper presents an experimental study of the air plasma spraying (APS) of alumina-titania powder using argon-hydrogen working gases. This powder system is being used in the fabrication of heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic testing. Experiments were conducted using a Taguchi fractional-factorial design parametric study. Operating parameters were varied around the typical spray parameters in a systematic design of experiments in order to display the range of plasma processing conditions and their effect on the resultant coatings. The coatings were characterized by hardness and electrical tests, surface profilometry, image analysis, optical metallography, and x-ray diffraction. Coating qualities are discussed with respect to dielectric strength, hardness, porosity, surface roughness, deposition efficiency, and microstructure. Attempts are made to correlate the features of the coatings with the changes in operating parameters.
A Microporous Silica Membrane
Authors: Maier Wilhelm F. , Schramm Herbert O.
Published: March 2011

The separation properties of a microporous silica membrane, prepared be e-beam evaporation of quarz onto a mesoporous support membrane is reported.
Thermal Stability of Supported Titania Membranes
Authors: Kumar Krishnankutty-Nair P. , Zaspalis V. T. , De Mul F. F. M. , Keizer Klaas , Burggraaf Anthonie J.
Published: March 2011

The beneficial effects of the support constraint on the improved thermal stability of supported titania membranes were studied by following the anatase to rutile phase transformation in supported and unsupported titania membranes. This was studied using Raman spectroscopy and XRD. Supported membranes showed a higher transformation temperature, about 150°C higher, (slower rate of transformation) compared to the unsupported ones. Unsupported membranes showed a slight thickness dependence on the phase transformation temperature, but less significant compared to the difference in phase transformation behaviour between supported and unsupported membranes of similar thicknesses.