bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rapid Prototyping of Patterned Multifunctional Nanostructures
Authors: Fan Hongyou , López Gabriel P. , Jeffrey Brinker C. 
Published: April 2011

ABSTRACTThe ability to engineer ordered arrays of objects on multiple length scales has potential for applications such as microelectronics, sensors, wave guides, and photonic lattices with tunable band gaps. Since the invention of surfactant templated mesoporous sieves in 1992, great progress has been made in controlling different mesophases in the form of powders, particles, fibers, and films. To date, although there have been several reports of patterned mesostructures, materials prepared have been limited to metal oxides with no specific functionality. For many of the envisioned applications of hierarchical materials in micro-systems, sensors, waveguides, photonics, and electronics, it is necessary to define both form and function on several length scales. In addition, the patterning strategies utilized so far require hours or even days for completion. Such slowprocesses are inherently difficult to implement in commercial environments. We present a series of new methods of producing patterns within seconds. Combining sol-gel chemistry, Evaporation-Induced Self-Assembly (EISA), and rapid prototyping techniques like pen lithography, ink-jet printing, and dip-coating on micro-contact printed substrates, we form hierarchically organized silica structures that exhibit order and function on multiple scales: on the molecular scale, functional organic moieties are positioned on pore surfaces, on the mesoscale, mono-sized pores are organized into 1-, 2-, or 3-dimensional networks, providing size-selective accessibility from the gas or liquid phase, and on the macroscale, 2-dimensional arrays and fluidic or photonic systems may be defined. These rapid patterning techniques establish for the first time a link between computer-aided design and rapid processing of self-assembled nanostructures
CFD Modeling of Laser Guided Deposition for Direct Write Fabrication
Authors: Sheu J. C. , Giridharan M. G. , Lowry S. 
Published: April 2011

ABSTRACTA computational model for simulating laser-guided particle deposition process is described. This model solves for the transport of gas and particle phases in a fully coupled manner. The optical forces on the particles are evaluated from Mie theory based on local laser intensity. Simulations were performed for different operating conditions of laser power, ambient pressure, and substrate traverse speed. Simulations revealed potential problems such as particle deflected away from substrate due to ambient air current disturbances, substrate overheating, and optical fiber clogging. Possible solutions for these problems are discussed
Role of Powder Production Route in Direct Write Applications
Authors: Ranade M. B. , Gonen Z. Serpil , Eichhorn Bryan W. 
Published: April 2011

ABSTRACTVarious production techniques are available for many materials for the direct write (DW) applications. Single metals and alloys are prepared from vapor and spray reactors as well as by precipitation techniques. Single and multicomponent oxides such as ferrites are also possible from these techniques in the nanometer to micrometer size ranges. Examples with the use of these techniques for production of metals and ferrites for DW are described with examination of crystallinity and morphology.
Offset Printing of Liquid Microstructures for High Resolution Lithography
Authors: Miller Scott M. , Darhuber Anton A. , Troian Sandra M. , Wagner Sigurd 
Published: April 2011

ABSTRACTWe have investigated the direct printing of polymer solutions from a chemically patterned stamp onto a hydrophilic target substrate as a new high-throughput alternative to optical lithography. The patterns on the stamp, which are typically in the micron size range, define regions of alternating wettability. They are produced by patterning a hydrophobic self-assembled monolayer previously deposited onto a hydrophilic surface, typically a glass slide or silicon wafer with a natural oxide coating. Polar liquids or aqueous polymeric solutions are then deposited only onto the hydrophilic surface patterns by dip-coating the stamp in a liquid reservoir. The deposited film thickness depends critically on the speed of withdrawal and the feature size and shape. For vertically oriented hydrophilic stripes dipped in a reservoir containing a polar liquid, we have developed a theoretical model whose prediction for the maximum deposited film thickness agrees exceptionally well with experimental measurements. After deposition, the wetted stamp is pressed against a target substrate by means of a motion controlled press. In this way we have so far printed 5µm wide polyethylene oxide lines onto a silicon wafer.
Sol–Gel-Derived 0–3 Composite Materials for Direct Write Electronics Applications
Authors: Coleman Steven M. , Parkhill Robert L. , Taylor Robert M. , Knobbe Edward T. 
Published: April 2011

ABSTRACTThe use of sol–gel-derived 0–3 composite ceramics for low-temperature direct-write electronics applications was investigated. The 0–3 composite paste materials were prepared using selected metal alkoxides and commercial low- and high-κ' dielectric powders. The composite pastes were deposited onto alumina and polyimide substrates using conventional screening and micro-dispensing techniques. The deposited films were oven-dried at or below 200°C and thermally densified using a CO2 laser. The 0–3 composites exhibited good adhesion and structural density. Electrical characterization of the laser-processed dielectrics revealed κ' values as high as 295 and tan δ as low as 0.02 on polyimide substrates.
Direct Write Metallizations for Ag and Al
Authors: Curtis C. J. , Miedaner A. , Rivkin T. , Alleman J. , Schulz D. L. , Ginley D. S. 
Published: April 2011

ABSTRACTWe have employed inks containing nanometer-sized particles of Ag and Al (nano-Ag and nano-Al, respectively) as precursor inks for the formation of contacts to n- and p-type Si, respectively. The particles as formed by the electroexplosion process were dispersed in toluene, applied to Si and annealed above the respective eutectic temperatures. In the case of nano-Ag, this directly yields an ohmic contact. However, the nano-Al was found to be coated with an oxide layer that impairs the formation of an ohmic contact. A chelating chemical etch involving treatment with hexafluoroacetylacetone was developed to remove this oxide coat. This treated nano-Al produced a good ohmic contact. Smooth, pure Ag films have also been deposited by spray printing organometallic inks prepared from Ag(hfa)(SEt2) and Ag(hfa)(COD). These films are deposited in one step onto heated glass and Si substrates at one atmosphere pressure. The films show resistivities of ∼2 µΩ·cm. These inks appear to be amenable to ink-jet printing of Ag lines and as a low temperature glue for the Ag nanoparticles for thicker metallizations.
Electrostatic Printing, A Versatile Manufacturing Process for the Electronics Industries
Authors: Detig Robert H. 
Published: April 2011

ABSTRACTFunctional materials configured as liquid toners are printed on a variety of substrates for various manufacturing processes. The materials include metal toners, resistor toners, high k dielectric toners, phosphors and glass. The substrates printed upon include glass, bare and coated metal, polymeric films and even paper. A fixed configuration electrostatic printing plate is used in most manufacturing applications though traditional photo receptor plates can be used if electronic addressability is desired.Applications of electrostatic printing for electronic packaging products (printed wiring boards and flex circuits) and of passive electronic components themselves will be shown. Results with a pure silver toner printed on both glass and paper will be reported. Examples of passive electronic components like resistors, capacitors, and even inductors that have been electrostatically printed with liquid toners will be shown. Possible applications of toners to the manufacture of flat panel displays will be discussed.
Microstructures of Laser Deposited 304L Austenitic Stainless Steel
Authors: Brooks John A. , Headley Thomas J. , Robino Charles V. 
Published: April 2011

AbstractLaser deposits fabricated from two different compositions of 304L stainless steel powder were characterized to determine the nature of the solidification and solid state transformations. One of the goals of this work was to determine to what extent novel microstructures consisting of single-phase austenite could be achieved with the thermal conditions of the LENS process. Although ferrite-free deposits were not obtained, structures with very low ferrite content were achieved. It appeared that, with slight changes in alloy composition, this goal could be met via two different solidification and transformation mechanisms.
Gas Phase Solid Freeform Fabrication of Saldvi of SiC Cermets
Authors: Crocker J.E. , Shaw L. , Marcus H.L. 
Published: April 2011

AbstractIn this work, the solid freeform fabrication of cermets was explored. Using a laser-based approach, SiC was deposited by chemical vapor deposition from tetramethylsilane gas into powder layers of Cu, Mo, or Ni. The resulting structures were examined to observe the extent of reaction between the metal powders and the vapor deposited SiC. Silicide formation was observed, most readily with the Ni powder. The thermal expansion of the metals compared to that of the vapor deposited SiC affected the interfacial stresses generated in the cermets during fabrication.
Characterization of Laser Deposited Niobium and Molybdenum Silicides
Authors: Brice C. A. , Schwendner K. I. , Amancherla S. , Fraser H. L. , Zhang X. D. 
Published: April 2011

AbstractRecent advances in laser deposition technology have made the production of advanced composite materials more technically feasible. By utilizing the unique characteristics of the laser deposition process, materials can be made that are difficult to produce by conventional methods. Structural silicide materials hold promise for high temperature applications, unfortunately, their low toughness has prevented their practical use [1-4]. The introduction of a second phase can greatly increase their low temperature mechanical properties. Laser direct deposition can be used to deposit these materials near net shape and produce an in-situ alloy that has the desired structure for improving properties. In-situ alloying was accomplished by using an Optomec LENS™ (Laser Engineered Net Shaping) machine to deposit elemental niobium-silicon and molybdenum-silicon-boron powder blends. The resultant microstructures showed a homogeneous structure with a primary silicide phase surrounded by a continuous eutectic phase. These deposits were characterized using scanning and transmission electron microscopy, x-ray diffraction, and by energy dispersive spectroscopy.
Rapid Electroforming Tooling
Authors: Yang Bo , Leu Ming C. 
Published: April 2011

AbstractA method of rapid electroforming tooling for the production of metal tools including molds, dies, and electrical discharge machining electrodes is developed. Geometry and material of the solid freeform fabricated part, properties of the electroformed metal, and process parameters are significant factors that cause inaccuracy in the manufactured tools. Thermomechanical modeling and numerical simulation are used to simulate thermal stresses induced during the burnout process that removes the rapid prototyping part from the electroform. The analysis demonstrates that appropriate design of the rapid prototyping part geometry and selection of electroform thickness not only reduce thermal stress, thus improving tooling accuracy, but also minimize manufacturing time and cost.
Understanding the Microstructure and Properties of Components Fabricated by Laser Engineered Net Shaping (LENS)
Authors: Griffith M. L. , Ensz M. T. , Puskar J. D. , Robino C. V. , Brooks J. A. , Philliber J. A. , Smugeresky J. E. , Hofmeister W. H. 
Published: April 2011

AbstractLaser Engineered Net Shaping (LENS) is a novel manufacturing process for fabricating metal parts directly from Computer Aided Design (CAD) solid models. The process is similar to rapid prototyping technologies in its approach to fabricate a solid component by layer additive methods. However, the LENS technology is unique in that fully dense metal components with material properties similar to wrought materials can be fabricated. The LENS process has the potential to dramatically reduce the time and cost required realizing functional metal parts. In addition, the process can fabricate complex internal features not possible using existing manufacturing processes. The real promise of the technology is the potential to manipulate the material fabrication and properties through precision deposition of the material, which includes thermal behavior control, layered or graded deposition of multi-materials, and process parameter selection.
Effect of Grain Size Distribution on Tensile Properties of Electrodeposited Nanocrystalline Nickel
Authors: Ebrahimi Fereshteh , Ahmed Zunayed , Morgan Kristin L. 
Published: April 2011

ABSTRACTWe have produced dense and ductile nanocrystalline nickel with various grain size distributions using electrodeposition techniques. The strength of the nickel deposits fell within the scatter band of the general Hall-Petch curve for nickel. However, large variations in yield strength, strain hardening rate and tensile elongation were associated with a relatively small change in the average grain size. The scatter in the elongation data has been attributed to the formation of nodules and the presence of voids. The variations in strength and strain hardening rate have been shown to be associated with the changes in the grain size distribution. A model based on confined dislocation motion and composite behavior has been developed for predicting the stress-strain behavior of the nanocrystalline nickel.
Femtosecond Ultrasonics for the Characterization of Layered Micro- and Nano Structures
Authors: Vollmann Jacqueline , Profunser Dieter , Dual Jürg 
Published: April 2011

ABSTRACTThe precise measurement of thicknesses, mechanical properties, and film-substrate bonding qualities of sub-micron metallic films, multi-layers, and microstructures in a nondestructive way is of growing importance for the semiconductor industry as well as for MEMS manufacturers.Short laser pulses having durations of less than 100 fs are an ideal – not to say the only –way in order to provide sub-surface visualization in nanometer scale perpendicular to the film surface.In this investigation, an enhanced pump-probe set up is presented. A dual frequency modulation technique is implemented in order to eliminate optical and electrical cross talk between the excitational pump pulse and the measuring probe pulse.Up to the 5th acoustic echo in an aluminum film having a thickness of 50 nm on a sapphire substrate has been measured. From the time of flight and from the amplitude decay between the echoes the material properties of the film and of the substrate have been derived.Further directions of the on going research project are presented.
Positron Lifetime Measurements in Nanostructured Ni-Al Samples
Authors: Petegem S. Van , Segers D. , Dauwe C. , Torre F. Dalla , Swygenhoven H. Van , Yandouzi M. , Schryvers D. , Tendeloo G. Van , Kuriplach J. , Hou M. , Zhurkin E.E. 
Published: April 2011

ABSTRACTPositron lifetime spectroscopy is an effective tool to study various types of defects in materials including nanostructured ones. The size of free volumes associated with defects can be estimated using the lifetime components found in the measured spectra. Positron lifetime experiments are performed on nanocrystalline Ni-Al samples synthesized by the inert-gas condensation technique. The samples are further characterized by means of X-ray diffraction, electron diffraction and microscopy techniques as well as density measurements. In the lifetime spectra we observe three lifetime components corresponding to different annihilation sites in the samples. These lifetimes are compared with the results of simulations of positron lifetimes in modeled Ni-Al samples obtained using molecular dynamics and Monte Carlo calculations. Finally, we present positron lifetime results for nanocrystalline Ni3Al samples which were produced or annealed at different temperatures.
Superelastic Deformation of Adaptive Nano-Composites
Authors: Roytburd Alexander L. , Slutsker Julia 
Published: April 2011

ABSTRACTAn adaptive composite containing a shape memory alloy as an active component is the subject of the paper. The elastically heterogeneous nano-composite containing ultra-thin layers of a passive material and thin layers of an active material is investigated in this paper. The superelastic modulus of the composite depends on the fraction of the active layer and can be negative if relative thickness of the active layer exceeds some critical value depending on the ratio between the elastic moduli of the layers and the characteristics of transformation. The negative superelastic modulus corresponds to the thermodynamic instability of superelastic deformation and results in stress-strain hysteresis. The relation between the elastic properties of the composite's components and relative thickness of the layers, which enable to stabilize the superelastic deformation, is obtained.
Size-dependent melting of matrix-embedded Pb-nanocrystals
Authors: Ehrhardt H. , Weissmüller J. , Wilde G. 
Published: April 2011

ABSTRACTWe report calorimetric data for the size-dependence of the melting temperature as well as the enthalpy and entropy of melting for nanoscale Pb particles in an Al matrix, prepared by high energy ball-milling. The results are discussed with respect to various models for the melting of small confined systems. We can rule out models based on a temperature-independent Gibbs excess free energy of the particle-matrix interface, and a model based on an increased meansquare displacement of the interfacial layer. The best agreement to the data is provided by modeling the interface as an inert layer of finite thickness, which does not participate in the phase transition.
Stacking Faults Created by Mechanical Milling in Nanostructured WC-Co Composite Powder
Authors: Zhimin Yang , Changhui Mao , Jun Du , Daniel Michel , Yannick Champion , Serge Hagège , Martin Hÿtch 
Published: April 2011

ABSTRACTNanostructured WC-Co powders obtained by mechanical milling were investigated by combination of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) techniques. HRTEM image analysis shows that in the as-milled nanostructured powder, many WC grains contain stacking faults lying on the plane{10.0}. Analysis of phase images showed that these defects were nearly periodically ordered along the [10.0] direction. Based on these observations, a structural model is proposed for the WC grains with ordered stacking faults, which is in fact equivalent to a superstructure of WC with space group Amm2. When this model is introduced together with the normal WC structure (space group P6m2) into the Rietveld refinement, a much better agreement between the calculated and experimental XRD profiles is obtained. This study allowed obtaining the lattice parameters, grain size, microstrain and other structural information on the as-milled powders.
Structure and Electrical Properties of an Assembly of Au Nanoclusters
Authors: Muralidharan G. , Maya L. , Thundat T. 
Published: April 2011

AbstractConduction through an assembly of nanosized clusters coupled by tunneling barriers is of significant interest both for understanding the fundamental physics involved and for potential applications. In this study, we describe a technique for preparing relatively large (dimensions of a few 100 µm to a few mm in size) monolayer films consisting of 3 nm diameter Au clusters coated with mercaptododecanoic acid, using low molecular weight-polymers as coupling agents. Electrical measurements of the assembly show non-linear characteristics. Below a certain threshold voltage, the current does not vary with an increase in voltage. Above this threshold voltage, current increases with voltage and can be described by a power-law relationship with an exponent close to unity. These characteristics of the I-V curve are discussed with specific reference to theoretical studies on conduction through an array of capacitance-coupled metallic islands and previous experimental results in similar systems.
Convenient Molecular Approach of Size and Shape Controlled ZnSe and ZnTe Nanocrystals
Authors: Jun Young-wook , Park Jong-Il , Cheon Jinwoo 
Published: April 2011

AbstractOur study describes a convenient one-step synthesis of ZnSe and ZnTe nanocrystals (NC) whose sizes and shapes are precisely tuned by varing the growth temperature or stabilizing surfactants. We utilized molecular precursors, bis(phenylselenolate or phenyltellurolato)zinc -N,N,N',N'-tetramethylethylenediamine (TMEDA), which effectively produce 0-dimensional sphere or 1-dimensional nanorods of ZnSe or ZnTe, respectively. Nanocrystals are highly monodispersed and luminescent; the emission wavelength varies over a wide range depending on the particle size. This study constitutes a nice demonstration of direct size and shape controlled synthesis of semiconductor nanocrystals and this method can be extended to the synthesis of nanocrystals of other materials.
Nanoparticle Assembly via Hydrogen-Bonding: IRS, TEM and AFM Characterizations
Authors: Han Li , Maye Mathew M. , Zhong Chuan-Jian 
Published: April 2011

AbstractThis paper reports results of the characterizations of nanoparticle assembly formed via spontaneous core-shell and shell-shell reactivities at thiolate-capped gold nanoparticles. Gold nanoparticles of two different core sizes and thiols with carboxylic acid terminals are exploited as a model system. The reactivities involve covalent Au-thiolate bonding and non-covalent hydrogen-bonding with anisotropic linking character. We employed infrared reflection spectroscopy (IRS), atomic force microscopy (AFM) and transmission electron microscopy (TEM) for the characterizations. While IRS provides structural assessment, TEM and AFM imaging measurements probe the morphological properties.
4-Point Resistance Measurements of Individual Bi Nanowires
Authors: Cronin Stephen B. , Lin Yu-Ming , Gai Pratibha L. , Rabin Oded , Black Marcie R. , Dresselhaus Gene , Dresselhaus Mildred S. 
Published: April 2011

AbstractWe have synthesized single crystal bismuth nanowires by pressure injecting molten Bi into anodic alumina templates. By varying the template fabrication conditions, nanowires with diameters ranging from 10 to 200nm and lengths of ~50[.proportional]m can be produced. We present a scheme for measuring the resistance of a single Bi nanowire using a 4-point measurement technique. The nanowires are found to have a 7nm thick oxide layer which causes very high contact resistance when electrodes are patterned on top of the nanowires. The oxide is found to be resilient to acid etching, but can be successfully reduced in high temperature hydrogen and ammonia environments. The reformation time of the oxide in air is found to be less than 1 minute. Focused ion beam milling is attempted as an alternate solution to oxide removal.