bluuebunny/crossref_metadata_2025_split huggingface dataset:
Guiding the design and application of new materials for enhancing sustainability performance: Framework and infrastructure application
Authors: Keoleian Gregory , Kendall Alissa M , Lepech Michael D , Li Victor C 
Published: April 2011

AbstractThis paper presents a framework for guiding the design of new materials to enhance the sustainability of systems that utilize these materials throughout their production, use and retirement. Traditionally, materials engineering has focused on the interplay between material microstructure, physical properties, processing, and performance. Environmental impacts related to the system’s life cycle are not well integrated into the materials engineering process. To address this shortcoming, a new methodology has been developed that incorporates social, economic, and environmental indicators – the three dimensions of sustainability. The proposed framework accomplishes this task and provides a critical tool for use across a broad class of materials and applications. Material properties strongly shape and control sustainability performance throughout each life cycle stage including materials production, manufacturing, use and end-of-life management. Key material parameters that influence life cycle energy, emissions, and costs are highlighted. The proposed framework is demonstrated in the design of engineered cementitious composites, which are materials being developed for civil infrastructure applications including bridges, roads, pipe and buildings. This research is part of an NSF MUSES (Materials Use: Science, Engineering and Society) Biocomplexity project on sustainable concrete infrastructure materials and systems (http://sci.umich.edu).
On-Chip Initiation and Burn Rate Measurements of Thermite Energetic Reactions
Authors: Apperson Steven , Bhattacharya Shantanu , Gao Yuanfang , Senthil Subramanian , Hasan Shameem , Hossain Maruf , Shende Rajesh , Redner Paul , Kapoor Deepak , Nicolich Steven , Gangopadhyay Keshab , Gangopadhyay Shubhra 
Published: April 2011

AbstractBurn rates of various nano-energetic composites were measured by two techniques; on-chip method and conventional optical method. A comparison is presented to confirm the validity of on-chip method. On-chip initiators were prepared using platinum heater films and nanoenergetic composites. Thin film Pt heaters were fabricated with different dimensions and ignition delay was studied using a nano-energetic composite of CuO nano-rods and Al-nano-particles. The ignition delay as a function of electrical power is presented for the same energetic composite. Heater with smaller surface area is found to be more efficient, which may be due to the lower heat losses.
Energy Release Characteristics of Impact-Initiated Energetic Materials
Authors: Ames Richard 
Published: April 2011

AbstractImpact-initiated energetic materials are a class of energetic materials that are formulated to release energy under highly dynamic loads. Under quasi-static or static loads, however, the materials are intended to be inert and carry a material classification of 4.1 flammable solid. In general, these materials are formed by introducing metal powders into a polymer binder but a number of binderless varieties exist (primarily pressed/sintered intermetallics and thermites). Most of the materials are sufficiently insensitive so as not to produce a self-sustaining reaction; as such, they require the mechanical work of a high-strain-rate plastic deformation process to provide the energy required to drive the reaction. Traditional initiation techniques such as exploding bridge wires or flame initiation are not sufficient to maintain a reaction in this class of materials. This paper presents a brief overview of the energy release characteristics of this class of materials, including a discussion of the material formulations, initiation phenomena, and a discussion of the manner in which the material properties affect the energy release characteristics.
Influence of Activating Compounds on Oxidation Mechanisms of Aluminum Powders
Authors: Johnson Curtis , Foley Timothy J. , Higa Kelvin T. 
Published: April 2011

AbstractThis study involves an investigation of the mechanism underlying activating effects of inorganic additives on the oxidation of aluminum. The oxidation of nano aluminum powders in air was characterized by variable temperature x-ray powder diffraction and thermogravimetric analysis. For a 33-nm aluminum powder the aluminum oxide produced by air oxidation was poorly crystallized until the sample was heated to above 1050°C, where the alpha-alumina phase crystallized. For a mixture of the aluminum with cryolite, crystallization of oxide phases is enhanced, with Na-Al-O phases evident at 550°C and above. Fluorine is lost from the sample between 550 and 850°C, presumably due to reaction with moisture to produce HF. In a similar experiment with aluminum and silver molybdate, the only crystalline product was alpha-alumina, which was observed at 550°C and higher. The general result is that alpha-alumina, the ultimate product in most cases, crystallized at a lower temperature when activating agents were present.
Melting and Oxidation of Nanometer Size Aluminum Powders
Authors: Trunov Mikhaylo A , Umbrakar Swati , Schoenitz Mirko , Mang Joseph T , Dreizin Edward L 
Published: April 2011

AbstractRecently, nanometer-sized aluminum powders became available commercially and their use as potential additives to propellants, explosives, and pyrotechnics has attracted significant interest. It has been suggested that very low melting temperatures are expected for nano-sized aluminum powders and that such low melting temperatures could accelerate oxidation and trigger ignition much earlier than for regular, micron-sized aluminum powders. The objective of this work was to investigate experimentally the melting and oxidation behavior of nano-sized aluminum powders. Powder samples with three different nominal sizes of 44, 80, and 121 nm were provided by Nanotechnologies Inc. The particle size distributions were measured using small angle x-ray scattering. Melting was studied by differential scanning calorimetry where the powders were heated from room temperature to 750 °C in argon environment. Thermogravimetric analysis was used to measure the mass increase indicative of oxidation while the powders were heated in an oxygen-argon gas mixture. The measured melting curves were compared to those computed using the experimental particle size distributions and thermodynamic models describing the melting temperature and enthalpy as functions of the particle size. The melting behavior predicted by different models correlated with the experimental observations only qualitatively. Characteristic step-wise oxidation was observed for all studied nanopowders. The observed oxidation behavior was well interpreted considering the recently established kinetics of oxidation of micron-sized aluminum powders. No correlation was found between the melting and oxidation of aluminum nanopowders.
Patterning PETN and HMX using Dip Pen Nanolithography
Authors: Nafday Omkar , Weeks Brandon , Haaheim Jason , Eby Ray 
Published: April 2011

AbstractRecently there has been a focused effort to develop reliable nanoscopic writing and reading capabilities. Dip-pen nanolithography (DPN) has emerged as a convenient method to deliver nanoscale materials onto a substrate by leveraging scanning probe microscopy capability. A new application for the DPN method is the field of microdetonics which is the microscale decomposition and study of reactions of explosives. Results are presented for patterning pentaerythritol tetranitrate (PETN) and cyclotetramethylene tetranitramine (HMX) on silicon and mica substrates. The ultimate goal is to pattern both energetic materials in nanoscale registry and investigate their reaction and decomposition at the nanoscale due to heating or shock initiation. In addition to patterning of high explosives, a discussion on the effect of surface energy on patterning rates is investigated. This knowledge will be applicable to inks beyond high explosives.
Understanding the Structure of the Mammalian Mineralised Tissues Through Their Development
Authors: Boyde Alan 
Published: April 2011

AbstractMost aspects of the structure and composition of the principal mineralised tissue types [in teeth = enamel, dentine and cementum; in bone organs = woven and lamellar and extrinsic (Sharpey) fibre bone and calcified growth plate cartilage and articular calcified cartilage and calcified fibrocartilage and calcified ligament or tendon] and of the all-important junctions between them can be best understood from a knowledge of developmental mechanisms and the rules and constraints that these generate. We should consider the interface between formative cells and the organic matrices where these are secreted by an appositional mechanism; possible influences of cell movements; mineral crystal orientation and size and maturation; junctions formed by simple apposition of one tissue upon another; junctions involving a prior resorptive (partial destruction and 'etching') step; and interstitial matrix expansion, NB in cartilage.
Crush Absorbing Energy of White Spot Lesion Measured by Indentation Tests
Authors: Fallgatter Alison M. , Ko Ching-Chang , Chou C-H 
Published: April 2011

AbstractWhite spot lesions are clinically detectable areas of demineralized enamel that often form during orthodontic treatment. Fluoride has been shown to prevent demineralization from occurring. Mechanical properties of white spot lesions are not well characterized. Bovine enamel slabs, with and without fluoride treatment, were placed under demineralization conditions. Through a series of microindentations at incremental loads, mechanical strength was measured using a novel method, SVAE. Specific Volume Absorbing Energy (SVAE) is equal to work energy divided by the indentation volume. The supra-surface area (outmost 5 μm) of enamel slabs with fluoride demonstrated decreased mechanical strength compared to those without fluoride. Fluoride may not impart protection over long periods of demineralization.
Multi-scale Characterization and Modelling of Human Cortical Bone
Authors: Ho Ba Tho Marie-Christine , Stolz Claude , Vanleene Maximilien , Bensamoun Sabine , Treutenaere Jean-Marc , Rey Christian 
Published: April 2011

AbstractMechanical properties of cortical human bone have been investigated for more than over three decades. The objectives of the present study were 1) to investigate the influence of multiscale structural characteristics of the bone tissue on its mechanical behavior and 2) to perform a micro-macro numerical modelling based on the experimental data. It should be noted that variations of the osteon lamellae elastic properties are higher (40%) at the microstructural level than those found at the macroscopic level (about 15%) for measurements performed in the same anatomical direction. Physico-chemical analyses found that organic components were found to be higher for femurs exhibiting lower mechanical properties. There is a consistency between changes observed at the different levels. These results contribute to a basic understanding of the multiscale mechanical behavior of human cortical bone.
Microaligned collagen matrices by hydrodynamic focusing: controlling the pH-induced self-assembly
Authors: Köester Sarah , Leach Jennie B , Pfohl Thomas , Wong Joyce Y 
Published: April 2011

AbstractThe hierarchical structure of type I collagen fibrils is a key contributor to the mechanical properties of the extracellular matrix (ECM). It is known that the process of in vitro fibrillogenesis strongly depends on the pH of the collagen solution. To date, there are few methods available for precisely controlling and investigating the dependence of collagen fibril assembly on the local pH. The objective of this work was to create highly defined pH gradients to systematically determine the effects of local pH on microscale collagen fibrillogenesis and alignment. We use a microfluidic mixing device to create a diffusion controlled pH gradient, which in turn initiates the self-assembly and concurrent flow-alignment of soluble collagen. Finite element method simulations of the hydrodynamic and diffusive phenomena are used to calculate the local concentrations of the components involved in the reaction. We develop a model to analytically calculate the local pH in the microfluidic device from these concentrations. A comparison with the experimental results from polarized light microscopy are in good agreement with the simulations.
Atomistic modeling of elasticity, plasticity and fracture of protein crystals
Authors: Buehler Markus J. 
Published: April 2011

AbstractThe structure and behavior of proteins plays an overarching role in determining their function in biological systems. In recent years, proteins have also been proposed as basis for new materials to be used in technological applications (Langer and Tirrell, Nature, 2004). It is known that protein crystals show very interesting mechanical behavior, as some of them are extremely fragile, while others can be quite sturdy. However, unlike other crystalline materials like silicon or copper, the mechanical properties of protein crystals have rarely been studied by atomistic computer modeling. As a first step towards more fundamental understanding of the mechanics of those materials, we report atomistic studies of mechanical properties of protein crystals using empirical potentials focusing on elasticity, plasticity and fracture behavior. Here we consider the mechanics of a small protein α-conotoxin PnIB from conus pennaceus. We use large-scale atomistic simulations to determine the low-strain elastic constants for different crystallographic orientations. We also study large-strain elastic properties including plastic deformation. Furthermore, we perform systematic studies of the effect of mutations on the elastic properties of the protein crystal. Our results indicate a strong impact of mutations on elastic properties, showing the potential of mutations to tailor mechanical properties. We conclude with a study of mode I fracture of protein crystals, relating our atomistic modeling results with Griffith's theory of fracture.
Mechanical stability of collagen fibril networks
Authors: Shaw Gordon , McDaniel Dennis , Elliott John , Tona Alessandro , Plant Anne 
Published: April 2011

AbstractThin films of type 1 collagen fibril networks fabricated on alkanethiol-functionalized surfaces have been previously shown to provide an excellent protein matrix for cultured cells in applications such as drug toxicity studies and studies of cell signaling pathways. Cell phenotypic parameters, including cell morphology and rate of proliferation, can depend on the processing conditions used for fabrication of the protein films. The mechanical characteristics of the collagen fibril network appear to be particularly important, and as such, understanding the mechanical properties of individual fibrils, as well as their interactions with each other and the underlying substrate is critical for assuring a predictable response from cells. In this study, scanning probe microscopy and instrumented indentation are used in conjunction with small force metrology to examine the mechanical properties of these collagen fibrils and fibril networks.
Directed Assembly of Nanoelements Using Electrostatically Addressable Templates
Authors: Xiong Xugang , Makaram Prashanth , Bakhtari Kaveh , Somu Sivasubramanian , Busnaina Ahmed , Small Jason , Mcgruer Nick , Park Jingoo 
Published: April 2011

AbstractDirected assembly of nanoparticles and single wall carbon nanotubes (SWNTs) using electrostatically addressable templates has been demonstrated. Nanoparticles down to 50 nm are assembled on the Au micro and nanowires of the templates in a DC and AC electric fields. The nanoparticles can be assembled in monolayers and thicker layers. Single wall carbon nanotubes (SWNTs) are also assembled without alignment on Au wires using the nanotemplate. As the size of the template wires is reduced to nanoscale dimensions, an AC electric field proves to be more effective for nanoparticle assembly than a DC electric field.
Nano-Structured Beta-Gallia-Rutile Surfaces as Substrates for DNA Self-Assembly
Authors: Empie Nathan , Edwards Doreen 
Published: April 2011

AbstractA nano-structured beta-gallia-rutile (BGR) substrate capable of binding DNA was synthesized. Beta-gallia groups diffuse into [001] single crystal rutile along {210}rplanes, generating hexagonally shaped tunnel sites between the beta-gallia subunits (repeating ∼1 nm). The tunnel sites, approximately 2.5 Å in diameter, are preferred regions for cation incorporation. Divalent cations have been used previously to adsorb DNA to mica surfaces. For the BGR system, the site selectivity of the cations for tunnel sites could lead to controllable / tailor-able DNA adsorption. DNA buffers containing Cu (II), Fe (II), and Ni (II) cations were deposited on BGR substrates. The DNA adsorption was investigated with tapping mode atomic force microscopy (AFM) to determine the suitability of using BGR substrates as a means to self assemble DNA constructs for nano-electronic applications. At the concentrations tested, only solutions containing Ni (II) ions were capable of binding DNA sufficiently for AFM imaging; there was no evidence of site specific attachment.
Nanotubes in spray deposited Nanocrystalline HgTe: I thin films
Authors: Arnepalli Ranga Rao , Viresh Dutta 
Published: April 2011

AbstractHgTe nanotubes have been prepared by spray deposition of solvothermally synthesized iodine doped HgTe nanoparticles on glass substrates at low temperature (200°C). Spray deposition was done without voltage and with an externally applied voltage (700 V) to the nozzle and it is found from TEM studies that the length of the nanotubes increases from ∼4µm in case of without voltage to ∼ 6µm in case of the applied voltage, with an average diameter of ∼ 45nm. The nanotubes are found to have cubic lattice structure having Hg:Te in stoichimetric ratio (52:48).
Nucleation of Semiconductor Quantum Dots on Nanomesas: Role of Stressors and Early Stages of Capping Process
Authors: Meynier Cyril , Priester Catherine 
Published: April 2011

AbstractHere is reported, from the theoretical point of view, how a stressor layer included in a nanomesa can modify the growth process of a mismatched material : critical thickness for 2D-3D transition, and optimal location of nucleating dots by means of the induced stress field. This stress field depends on both design parameters and sign of the misfit between the stressor and the mesa material. This is exemplified by the case of InAs deposition on InP mesas which include an InGaAs stressor. A second case in which stress field plays a key role is the capping of dots on top of nanomesas . We investigate the case of Si capping of a system where one Ge dot covers the top of each mesa of a very dense array of Si nanomesas. Upon several basic assumptions, different capping processes are simulated, in order to predict the more stable one. We point out very different behaviors for pure Si capping or SiGe capping. How long it takes for recovering a flat surface strongly depends on the presence of a thin Ge surface layer.
“Smart” Defects in Colloidal Photonic Crystals
Authors: Fleischhaker Friederike , Arsenault André C. , Tétreault Nicolas , Wang Zhuo , Kitaev Vladimir , Peiris Frank , Mihi Agustin , Miguez Hernan , von Freymann Georg , Manners Ian , Zentel Rudolf , Ozin Geoffrey A. 
Published: April 2011

AbstractWe present a bottom-up approach for the construction of "Smart" active defects in colloidal photonic crystals (CPCs). These structures incorporate polyelectrolyte multilayer (PEM) planar defects embedded in silica CPCs through a combination of evaporation induced self-assembly and microcontact transfer printing. We show how the enormous chemical diversity inherent to PEMs can be harnessed to create chemically active defect structures responsive to solvent vapor pressures, light, temperature as well as redox cycling. A sharp transmission state within the photonic stopband, induced by the PEM defect, can be precisely, reproducibly and in some cases reversibly tuned by these external stimuli.These materials could find numerous applications as optically monitored chemical sensors, adjustable notch filters and CPC-based tunable laser sources.
Patterning of Single-Walled Carbon Nanotubes Using Wet Chemical Self-Assembling and Photolithographic Technique
Authors: Jung Myung-Sup , Jung Sung-Ouk , Jung Hee-Tae , Kim Do Yun , Doo Seok Gwang 
Published: April 2011

AbstractSingle-walled carbon nanotubes (SWNTs) have been chemically attached with high density onto a patterned substrate. To form the SWNT pattern, the substrate was treated with acid-labile group protected amine, and an amine prepattern was formed using a photolithographic process with a polymeric photo acid generator. The SWNT monolayer pattern was then formed through the amidation reaction between the carboxylic acid groups of carboxylated SWNTs (ca-SWNTs) and the prepatterned amino groups. A high-density multilayer was fabricated via further repeated reaction between the carboxylic acid groups of the ca-SWNTs and the amino groups of the linker with the aid of a condensation agent. Scanning electron microscopy results show that the patterned SWNT films have uniform coverage with high surface density.
Photochemical Metal Organic Deposition of Patterned Nanostructured Oxide Films
Authors: Zhang Xin , Hill Ross 
Published: April 2011

AbstractIn this paper, we present examples of the use of photochemical metal organic deposition to form nanostructured metal oxide films. In the first example, we use two reactions with very different reaction rates to control the nanostructuring, utilizing tantalum (V) tetraethoxide acetylacetonate (as a thermally reactive source of tantalum oxide) and manganese (II) 2-ethylhexanoate (as a photochemically reactive source of manganese oxide). We prepare homogeneous precursor films of tantalum (V) tetraethoxide acetylacetonate and manganese (II) 2-ethylhexanoate and in the dark allow the tantalum complex to react forming tantalum oxide regions. The film is then exposed and the manganese complex is converted to a matrix surrounding the tantalum regions. The resultant structures are characterized by electron microscopy, energy dispersive X-ray spectroscopy and Auger spectroscopy. In the second example, we use two immiscible precursors, zirconium (IV) 2-ethylhexanoate and yttrium nitrate hexahydrate to form nanostructured precursor films. The nanostructuring of these films is apparent from SEM studies. Exposure of these films results in the formation of nanostructured films consisting of a zirconium oxide matrix with encapsulated yttrium oxide.