bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tantalum Nitride Seed Layers for Bcc Tantalum Coatings Deposited on Steel by Magnetron Sputtering
Authors: Patel Anamika , Gladczuk Leszek , Paur Charanjeet Singh , Sosnowski Marek 
Published: April 2011

ABSTRACTTantalum, a tough refractory metal with excellent corrosion resistance, is an attractive protective coating material for steel subjected to mechanical wear in harsh chemical environments. The coatings deposited by sputtering usually contain a hard and brittle tetragonal phase mixed with the desirable tough and ductile bcc phase of Ta. One of the methods of promoting the growth of the bcc phase at a moderate substrate temperature is deposition of an interfacial or seed layer of tantalum nitride. Ta coatings were deposited by dc magnetron sputtering in argon, and the interfacial nitride layers by reactive sputtering performed in the same chamber with nitrogen gas added to argon. The critical thickness, stoichiometry, and structure of the seed layer required for bcc Ta growth were studied by scanning electron microscopy and X-ray diffraction. The results of adhesion testing of the Ta coatings deposited on the interfacial layers are also reported.
Laser-Assisted Surface Modification of 4340 Steel with Iron-Aluminum Alloys
Authors: Muralidharan G. , Engleman P. G. , Blue C. A. , Sikka V. K. , Singh A. K. , Khangar A. , Dahotre N. B. 
Published: April 2011

ABSTRACTHigh power Nd-YAG laser was used to fuse coatings containing a mixture of FeAl and Al, with 4340 steel. It was observed that good quality coatings could be obtained using this process. Detailed microstructural studies show that Fe aluminides and/or a solid solution of Al in Fe can form within the coating, depending on the processing conditions. Wear measurements show that the best wear properties are obtained in the presence of an aluminide in the coating and that the wear properties significantly degrade when the coating consists primarily of a solid solution of Al in Fe.
Growth of TiN/AlN Superlattice by Pulsed Laser Deposition
Authors: Wang H. , Gupta A. , Tiwari Ashutosh , Zhang X. , Narayan J. 
Published: April 2011

ABSTRACTTiN-AlN binary-components have attracted a lot of interests in coatings of high speed cutting tools, due to their higher oxidation resistance, higher hardness, lower internal stresses and better adhesion. Especially, nanometer-scale multilayer structures of AlN/TiN show superior structural and mechanical properties due to their tremendous interface area and become one of the promising candidates for superhard coatings. Here we present a novel method to grow highly aligned TiN/AlN superlattice by pulsed laser deposition. In this method TiN and AlN targets are arranged in a special configuration that they can be ablated in sequence, giving alternate layer by layer growth of TiN(1nm)/AlN(4nm). X-ray diffraction and transmission electron microscopy (TEM) analysis showed the structure to be cubic for both TiN and AlN in the nanoscale multilayers. Microstructure and uniformity for the superlattice structure were studied by TEM and Scanning transmission electron microscopy with Z-contrast (STEM). Nanoindentation results indicated a higher hardness for this new structure than pure AlN and rule-of-mixtures value. Four point probe electrical resistivity measurements showed overall insulating behavior.
Hardening Mechanisms of Amorphous / Polycrystalline Nanostructured Multilayer Films: Si3N4/CrN and Si3N4/TiN
Authors: Xu Junhua , Yu Lihua , Azuma Yasushi , Hattori Koichiro , Fujimoto Toshiyuki , Kojima Isao 
Published: April 2011

ABSTRACTThe amorphous/polycrystalline Si3N4/CrN and Si3N4/TiN nano-structured multilayer films have been fabricated by RF reactive magnetron sputtering. The microstructure and properties of these films were measured by XRD, HRTEM and nano-indenter There is no superhardness effect in the Si3N4/CrN multilayers. The hardness values of Si3N4/CrN multilayers are between those of the constituent CrN and Si3N4 films at a substrate temperature of 20∼C, and are a little higher than those of Si3N4 films at a deposition temperature of 500°C. However, the superhardness effect was found in Si3N4/ TiN multilayers. The hardness of Si3N4/ TiN multilayers is affected not only by modulation periods, but also by layer thickness ratio and deposition temperature. The maximum hardness value is about 40% higher than the value calculated from the rule of mixtures at a deposition temperature of 500°C and a layer thickness ratio (lSi3N4/ lTiN) of 3 / 1. Based on experimental results, the hardening mechanisms in these multilayers have been discussed.
Formation and stability of enhanced superhard nanostructured AlN/VN and AlN/TiN superlattice materials
Authors: Stampfl C. , Freeman A. J. 
Published: April 2011

ABSTRACTUsing density functional theory and the full-potential linearized augmented plane wave (FLAPW) method, we investigate the formation and stability, and atomic structure, of rocksalt AlN/TiN and AlN/VN systems, including properties of the clean surfaces of the constituent materials. Calculations of the adlayer formation energy highlights the effect and interplay of the various energetic contributions on the growth of these strained systems, where the so-called “surface-interface” interaction energy is found to be important for the initial stages of AlN epitaxy. A significant strain energy builds up for increasing number of layers, where it is greater in the AlN/TiN system, which limits the thickness of rocksalt AlN regions that can grow before a structural transition to the lower energy wurtzite phase takes place. From our calculations, together with the known experimental critical thicknesses, we can obtain an accurate estimate of the wurtzite/substrate interface energy. That these values are high explains why the metastable rocksalt phase, which has significantly lower interface energies, is stabilized.
Elastic recovery and reloading of hardness impressions with a conical indenter
Authors: Fischer-Cripps A. C. 
Published: April 2011

ABSTRACTThe present work is concerned with the analysis of elastic unloading data in conventional methods of analysis of nanoindentation test data. Experimental and finite element results are used to show that the reloading of a residual impression with and without the presence of residual stress is an elastic event, and further shows that the estimation of modulus and hardness computed using established techniques is in error due to the assumption the sides of the residual impression are straight. This work calls into question the validity of commonly used methods of test and analysis of instrumented indentation test data that use the elastic unloading data as the basis for the calculation of modulus and hardness of the specimen material.
Planar Extrinsic Biasing Of Thin Film Shape-Memory MEMS Actuators.
Authors: Grummon D. S. , Gotthardt R. , LaGrange T. 
Published: April 2011

ABSTRACTAlthough slow and dissipative, sputtered thin-film shape-memory alloys like equiatomic titanium-nickel can exert a large ohmically-excited force displacement product when deployed in photolithographically micromachined actuators. They give energy densities far exceeding those typically produced by competing microactuator materials [1], and their size can probably be scaled down to the nanometer range (where the benefits of high surface to volume ratio are best exploited for speed and efficiency). But a large, energetic, and resettable actuation stroke is possible only if some agency has imparted a non-trivial initial plastic strain, of between one and five percent, to the martensite phase. Is not always obvious how this strain is to be achieved when discrete mechanical manipulation of the active element is difficult. Furthermore, for cyclic actuation, a resetting-force that periodically re-deforms the martensite during the cooling interval must arise naturally from mechanical elements in the design. Here, several methods responding these requirements are discussed in relation to various kinematic themes.
Assessment of aluminium metallisation by nanoindentation
Authors: Soare S. M. , Bull S. J. , Horsfall A. , Dos Santos J. , O'Neill A. G. , Wright N. G. 
Published: April 2011

ABSTRACTAs the trend for miniaturisation in the microelectronics field continues, metallisation connecting components has smaller and smaller dimensions, especially width and thickness. The mechanical properties of the deposited metal are very different from those of the bulk material and it is important to evaluate them accurately if the reliability of the metallisation is to be optimised. The assessment of the mechanical properties of thin aluminium metallisation is possible by nanoindentation but to extract properties useful for lifetime prediction such as yield stress or creep relaxation behaviour additional modelling is necessary using finite elements analysis (FEA). In this study evaporated aluminium layers from 50nm to 600nm thick on (100) silicon were indented to various depths. Proportional loading was used to minimise the effect of creep. The loading curves were then simulated by FEA and the results compared to identify the yield properties of the coating. Modelling data for thicker samples closely follows experimental data but for thinner coatings there is a considerable gradient in properties through the film thickness.
Deformation Microstructure Under Nanoindentations in Cu Using 3D X-Ray Structural Microscopy
Authors: Yang Wenge , Larson B. C. , Pharr G. M. , Ice G. E. , Swadener J. G. , Budai J. D. , Tischler J. Z. , Liu Wenjun 
Published: April 2011

ABSTRACTWe have used a recently developed x-ray structural microscopy technique to make nondestructive, submicron-resolution measurements of the deformation microstructure below a 100mN maximum load Berkovich nanoindent in single crystal Cu. Direct observations of plastic deformation under the indent were obtained using a ∼0.5 μm polychromatic microbeam and diffracted beam depth profiling to make micron-resolution spatially-resolved x-ray Laue diffraction measurements. The local lattice rotations underneath the nanoindent were found to be heterogeneous in nature as revealed by geometrically necessary dislocation (GND) densities determined for positions along lines beneath a flat indent face and under the sharp Berkovich indent blade edges. Measurements of the local rotation-axes and misorientation-angles along these lines are discussed in terms of crystallographic slip systems.
Effect of Crystal Orientation on Microwear of Si Single Crystal and The Wear Structure
Authors: Takagi M. , Arima N. , Iwata H. , Imura T. , Sasaki K. , Saka H. 
Published: April 2011

ABSTRACTMicrotribology of Silicon single crystals is one of the important factors for the practical use of MEMS. In this study, the effect of crystal orientation on microwear of Silicon single crystal and the wear structure were mainly investigated. Microfriction experiments using atomic force / friction force microscope (AFM / FFM) were carried out to investigate the effect of crystal orientation on the microwear depth of Silicon single crystals. In these experiments, the scanning-scratching directions of a tip of AFM / FFM were <100> and <110> on Si(100) surface and <112> on Si(111) surface. As a result, it was found that the depth of the wear marks generated on Silicon surfaces increased in the following order: <112>, <100>, <100>. Cross-sectional TEM observations of the microwear marks were carried out. As a result, it was found that the small dislocation loops were generated in the surface region at the first stage of the microwear, and the size and the number of dislocations increased with the progress of the microwear.
Investigation of Surface Grooves from Migrating Grain Boundaries
Authors: Munoz Nicole E. , Gilliss Shelley R. , Ravishankar N. , Barry Carter C. 
Published: April 2011

ABSTRACTVisible-light microscopy (VLM) and atomic-force microscopy (AFM) were used to study the progression of grain-boundary grooving and migration in high-purity alumina (Lucalox™). Groove profiles from the same grain boundaries were revisited using AFM following successive heat-treatments. The grooves measured from migrating grain boundaries were found to have asymmetric partial-angles compared to those measured from boundaries that did not migrate during the experiment. For a moving boundary, the grain with the larger partial-angle was consistently found to grow into the grain with the smaller partial-angle. Migrating boundaries were observed to leave behind remnant thermal grooves. The observations indicate that the boundary may be bowing out during the migration process.
Electron Beam Induced Carbon Depositionand Etching
Authors: Sun Y.-M. , Eklund J. , Wang Q. , Gay D. , White J. M. 
Published: April 2011

ABSTRACTElectron induced carbon deposition and etching was investigated by Auger electron spectroscopy in a custom designed vacuum system. The Auger electron spectrometer was used to provide a high flux electron beam to induce reactions and to monitor surface composition. During the e-beam induced deposition or etching, the gas phase pressure was 10-4 to 10-5 Torr. Several carbon precursors: benzene, cyclohexane and propane were used for deposition. The deposition rate depended on the precursor sticking coefficient and bonding structure. Among the three precursors tested, the deposition rate of carbon was cyclohexane > benzene > propane. The e-beam induced etching of carbon films was carried out in 1 × 10-4 torr oxygen ambient and the carbon film was prepared by reactive physical vapor deposition. The etching process can be divided into three stages: bulk film, interface, and substrate. For the bulk carbon film, the decrease of film thickness varies linearly with the e-beam flux, while at the interface, the film thickness shows an exponential decay with the electron flux. For the C in the Si substrate, a very slow etching rate was observed. The etching rate for bulk carbon film was ∼ 0.1 nm/min under the experimental conditions, which is equivalent tp 2.4 × 10-27 cm3/electron. At the interfacial region, the cross section of carbon removal by electrons was ∼ 4.6 × 10-21 cm2. Based on the change of the carbon line shape at the interface, we concluded that the etching rate is related to the chemical nature of the carbon species.
Multiple Layers of Copper Thin Films of Alternating Textures
Authors: Huang Hanchen , Wei H. L. , Liang H. Y. , Woo C. H. , Zhang X. X. 
Published: April 2011

ABSTRACTIn this paper, we present a preliminary study of texture development during copper thin film deposition. Using direct current (DC) magnetron sputtering technique, we deposit copper films on a SiO2/Si(111) substrate. A thin layer of copper of <111> texture first develops, and another thin layer of <110> ensues. As deposition continues, a third layer of copper of <111> texture forms on the top, leading to a copper thin film of alternating <111> and <110> textures. The multiple layers of copper thin films of alternating textures form during continuous deposition without changing deposition conditions. The film morphology is characterized with scanning electron microscopy (SEM) and atomic force microscopy (AFM), and the texture with X-ray diffraction (XRD). Based on anisotropic elastic analyses and molecular dynamics simulations, we propose a model of texture evolution during the formation of multilayers, attributing the texture evolution to the competition of surface and strain energies.
Preparation of V-based Alloy Membranes using Chemical Transport Process
Authors: Ozaki Tetsuya , Zhang Yi , Komaki Masao , Nishimura Chikashi 
Published: April 2011

ABSTRACTNovel preparation process of V-Ni alloys for hydrogen purification membrane using chemical transport was investigated. Vanadium, NH4Cl, and PtCl2 as evaporating source were put in one side of a fused-silica tube, and Ni substrate was put in the other side. The fused-silica tube was sealed in vacuo, and set in a furnace with temperature gradients. Evaporating source temperature was 1173–1273 K. Substrate temperature was 3–100 K higher than the evaporating source temperature. This process consists of formation of HCl from NH4Cl and PtCl2, chemical transport of vanadium under temperature gradient via chlorides in the presence of HCl, and diffusion of the transported V into the Ni substrate. EDX line profile of cross section of the substrates after the process demonstrated that V diffused into the Ni substrates. Distribution of V concentration in the substrates was dependent on the substrate temperature and the temperature difference between the substrate and the evaporating source. Heating condition was optimized to obtain homogeneous V-Ni alloy. When the substrate temperature and evaporating-source temperature were 1228 K and 1223 K, respectively, V diffused homogeneously into the Ni substrate with thickness of 20 μm, and V concentration attained in the substrate was higher than 70at%.
Packed-Bed Reactor Performance Enhancement by Membrane Distributed Feed: The Case of Methanol Oxidative Dehydrogenation
Authors: Diakov Victor , Varma Arvind 
Published: April 2011

ABSTRACTFor methanol oxidative dehydrogenation to formaldehyde, the performance of the packed-bed membrane reactor (PBMR) is compared with that of the conventional fixed-bed reactor (FBR) over a wide range of operating conditions. The reaction was studied in three reactor configurations: the conventional FBR and the packed-bed membrane reactor, with either methanol (PBMR-M) or oxygen (PBMR-O) as the permeating component. The kinetics of methanol and formaldehyde partial oxidation reactions were determined and incorporated in a PBMR model. Both experimental data and model considerations demonstrate that the PBMR enhances reactant conversion and selectivity.Small oscillations in CO production were observed experimentally. Their amplitude was taken as a basis for comparison of packed-bed operation instability. The likely source of oscillatory behavior is the non-uniformity in reaction conditions along the reactor. It was found that membrane distributed feed, by providing a more uniform reactor operation, is an effective remedy from these instabilities.It is found, both by simulations and experimental observations, that relative reactor performance depends strongly on the operating conditions. Using formaldehyde yield as the basis for optimization, optimal reactor performances are determined to be in the order: PBMR-O > FBR > PBMR-M. Further PBMR productivity enhancement is possible by optimizing the membrane feed distribution pattern.
How can Microwave Heating Contribute to the Development of Zeolite Membranes
Authors: Julbe Anne , Motuzas Julius , Charmette Christophe , Guizard Christian 
Published: April 2011

ABSTRACTIn this work the growth of both a zeolite (MFI) and a zeolite-like material (SOD) were investigated in/on αAl2O3 tubular support, using hydrothermal conditions and microwave (MW) heating. The method reveals efficient for the rapid synthesis of MFI/αAl2O3 membranes although gentle conditions were required in order to limit the thermal degradation of the template. Promising results were also obtained for directly growing SOD in/on the support. In both MFI and SOD MW synthesis the chemical dissolution of the αAl2O3 support influences the final membrane characteristics. In the case of SOD synthesis, this phenomena which increases with both temperature and support size, alters the membrane homogeneity (composition and structure). In order to get round it, MWs were used to prepare SOD small crystals which were deposited on/in the αAl2O3 support and submitted to a secondary growth. Homogeneous membranes were then obtained whose ideal selectivities αH2/N2 and αHe/N2 reaches respectively 4.5 at 20°C and 6.2 at 115°C (these selectivities are lower than 2 for a ZSM-5 membrane in similar conditions).
Hydrophilic Surface Modification of Microporous Polymer Membranes Using A Variety of Low-Temperature Plasma Treatments
Authors: Wavhal Dattatray S. , Kull Kristen R. , Steen Michelle L. , Fisher Ellen R. 
Published: April 2011

ABSTRACTA variety of plasma treatments have been employed to achieve permanent hydrophilic surfaces throughout the membrane structure. Specifically, we have modified microporous polyethersulfone (PES) membranes using H2O, CO2, and N2 plasma treatments to implant polar functional groups; alternatively, Ar-plasma treatment followed by grafting of hydrophilic monomers (acrylic acid and acrylamide) in the vapor phase has also been successful at modifying PES membranes. PES membranes treated with H2O and CO2 plasmas as well as the grafted membranes are found to be permanently hydrophilic (for a minimum of six months), and the entire membrane cross-section is modified. Chemical changes to the modified PES membranes were determined with FTIR and XPS measurements. Furthermore, water bubble point measurements and electron microscopy results reveal that pore sizes of the modified membranes are only slightly affected, depending on the treatment. Incorporation of polar functionalities results in an increase in the glass transition temperature (Tg) and a moderate change in tensile strength of the modified membranes. Most importantly, the surfaces of the modified membrane are less susceptible to absorption by bovine serum albumin (BSA) proteins.
Stochastic Reconstruction and Permeation of Ceramic Membranes Prepared by the Sol-Gel Method
Authors: Kikkinides E. S. , Zaspalis V. T. , Burganos V. N. 
Published: April 2011

ABSTRACTIn the present work we study the relation between structural and permeation properties of ceramic membranes made by the sol-gel process. For this purpose, we have developed γ-Al2O3 mesoporous membranes via the sol-gel route, on top of multi-layer asymmetric α-Al2O3 macroporous supports, to induce mechanical stability. Subsequently, we employ stochastic techniques to generate three-dimensional reconstructions of the membrane and the support that share the basic structural properties of the original materials determined directly from SEM and TEM studies. The permeability of each material is estimated by solving numerically the momentum equation in the void space of the reconstructed images. The very good agreement between predicted and experimentally measured permeability values, without the need to resort to any fitting parameter, renders the proposed reconstruction methodology quite promising for reliable characterization and representation of the pore structure of this type of membranes.