Absolutely Small, Chapter 19: Metals, Insulators, and Semiconductors (An AMA management briefing)

There was a problem providing the content you requested

---

PSS matrices below the percolation threshold. Increases in conductivity within a distinct range in concentration were observed in the dark and under simulated solar illumination. The effect was ascribed to a generalized Poole-Frenkel effect in conjunction with basic properties of heterojunctions and electrostatic dipoles, and verified through data fitting. A difference in behaviour between sphere- and cube-based nanocomposites was also observed. Gold nanostructures encoded by non-fluorescent small molecules in polyA-mediated nanogaps as universal SERS nanotags for recognizing various bioactive molecules.

Chemical Science , 5 , Surface-enhanced Raman scattering SERS has recently been used to design novel nanoprobes called "SERS tags" which hold great promise for the fields of biosensing and nanomedicine. More recent advances have shed new light on the synthesis of uniform nanostructures with interior nanogaps for stable SERS enhancement. However, producing interior nanogap-based SERS nanotags directly and controllably with strong and stable multiplex SERS signals as well as developing a multiplex anal.

To address this challenge, we herein develop a novel approach for the direct synthesis of nanogap-based universal SERS nanotags by mediating poly-adenine polyA and encoding non-fluorescent small mols. The universal nanotags were then functionalized by different types of biol. To the best of our knowledge, this is the first example of using SERS nanotags to develop a simultaneous multianal. Furthermore, the nanotags show great promise for fluorescence-SERS bimodal bioanal. Dipole-induced conductivity enhancement by n-type inclusion in a p-type system: Physical Chemistry Chemical Physics , 16 , Hematite alpha-Fe2O3 nanoparticles of two different shapes but of same size ca.

PSS matrices in various concentration ranges wt to study the consequent changes in conductivity in the dark and under solar illumination conditions. Within a distinct range of concentration, a distinct increase in the conductivity was observed for both spherical and cubical particle population. We ascribed this effect to the generalized Poole-Frenkel theory of conduction in conjunction with the basic depletion width properties of heterojunctions and electrostatic dipole moments, and verified our assumptions through data fitting.

PSS nanocomposites was also observed and ascribed to the electrostatic edge effect on the nanoparticles. The dispersion of alpha-Fe2O3 nanocrystals was confirmed by high-resolution electron microscopy, whereas the electrical properties and modulations thereof were followed by recording current-voltage characteristics. The different chemical configurations of 1 and 2 and differential valence states of cobalt were confirmed by crystal structure determination and comprehensive analytical studies.

Whereas 1 could not be studied by NMR due to the paramagnetic nature of the central atom, 2 was unambiguously characterized by multinuclear 1D and 2D NMR experiments in solution. Both compounds are efficient precursors for catalyst-free growth of Co3O4 nanowires on Si and Al2O3 substrates by a chemical vapor deposition process. Co3O4 nanowires with nanometric diameters nm were obtained irrespective of the chosen cobalt precursor.

Investigations on the humidity sensing behavior of CVD deposits demonstrated their potential as promising sensor materials. ZnO thin films with high cond. Thickness dependent nm changes in crystallog. Increase in film thickness caused a decrease in the bandgap by relaxation of stress in the plane of the film and led to an improvement in crystallinity and cond. The optical studies showed a noticeable change towards the contribution of excitonic and phonon replica to the UV-emission band.

Journal of the American Ceramic Society , 97 , SnO2 spheres upon calcination was confirmed by powder x-ray diffraction data, whereas the hollow interiors of SnO2 particles were verified by scanning and TEM of both intact and broken spheres. Sn-oxide hollow spheres showed an av.

The integration of large surface and nanoscopic voids in the final structures imparted higher sensitivity to the as-printed sensors toward both oxidizing N dioxide and reducing gases methane and EtOH , which validates the enormous potential of printable inorgs. Production and characterization of nanocomposite thin films based on Ni matrix reinforced with SnO2 single-crystalline nanowires for electrical contact applications.

Journal of Alloys and Compounds , , Nanocomposite thin films based on electrodeposited Ni matrix reinforced with SnO2 single-crystalline nanowires grown onto Si substrates by chemical vapor deposition were produced. The composites were characterized by means of scanning and transmission electron microscopy for imaging, selected area diffraction and transmission Kikuchi diffraction , atomic force microscopy for 3D surface profiling and roughness evaluation and 4-point probe electrical resistivity measurements.

The Ni matrices obtained were nanocrystalline in nature 41 nm crystallite mean size even though low direct current electrode-position was used. The topography and roughness of the samples were strongly affected by the presence of the nanowires as so was the electrical resistivity, which could be improved by Ag-coating the nanowires. A comparison with pure Ni produced in the same way is presented for determining the effects of the SnO2 nanowires. Inorganic microporous membranes, presenting pores smaller than 2 nm, have an important potential for large-scale application in gas purification and separation.

First permporometry tests showed that the additional zirconia layer influenced the gas flux through the membrane in dependence of the CVD process parameters and resulted in a reduction of the total pore volume. Sequential physical vapor deposition and chemical vapor deposition for the growth of In2O3—SnO2 radial and longitudinal heterojunctions. Heterostructures of In2O3 and SnO2 were produced by sequential application of the phys.

Please note:

In2O3 nanowires exhibit a single crystal bcc. Nucleation and growth occurred via direct vapor solid VS mechanism competing with catalyst-mediated vapor-liq. SnO2 nanowires were obtained in a single crystal tetragonal cassiterite structure and oriented along the 1 0 1 direction, the growth being promoted by the gold particle at the apex of the In2O3 nanowires.

The size of the catalyst thereby dets. CVD deposition allows precise control of the geometrical features of the heterojunction, also limiting detrimental nucleation of SnO2 on the lateral sides of In2O3 nanowires due to lower longitudinal growth rate.

Semiconductors

These results can help in improving the ability of finely tuning the morphol. Plasma-chemical reduction of iron oxide photoanodes for efficient solar hydrogen production. International Journal of Hydrogen Energy , 39 , The authors demonstrate the effect of hydrogen plasma treatment on hematite films as a simple and effective strategy for modifying the existing substrate to improve significantly the band edge positions and photoelectrochem.

Plasma treated hematite films were consist of mixed phases Fe3O4: The treated samples showed enhance photocurrent densities with max. Hydrogen plasma treatment under nonequil. Use of metallic nanoparticles to improve the thermophysical properties of organic heat transfer fluids used in concentrated solar power. Solar Energy , , One of the approaches to enhance the efficiency, and consequently, reduce costs to produce electricity from concd. Incorporation of metallic nanoparticles into conventional heat transfer fluids could significantly improve the thermal transport properties of the HTFs.

This study reports on the synthesis and investigation of copper nanoparticles synthesized inhouse and dispersed in two synthetic HTFs Therminol 59 TH59 and Therminol 66 TH Suspensions with various copper nanoparticle loadings 0. Characterizations such as the thermal cond. These enhancements in the thermal cond. Dynamic viscosity measurements showed that if good dispersion of nanoparticles is achieved, the composite fluids behave in a Newtonian manner and the dynamic viscosity increases over the base fluid are minor at temps.

Stability of the suspensions with time was also investigated. Based on the measured properties of the suspensions, a figure of merit for heat transfer was calcd. This is one of the first attempts of making WO3 thick film selective at low operating temperature by placing graphene sheets directly on the film surface. The WO3 film was prepared by DC magnetron reactive sputtering of a pure tungsten target and annealing in air. Graphene was synthesized on copper foil using plasma enhanced chemical vapor deposition of methane gas, which was found to produce three monolayers of graphene sheets according to Raman spectroscopic analysis.

The graphene was transferred onto the WO3 film and annealed. The selectivity towards nitrogen dioxide over ammonia and carbon monoxide was achieved with graphene on the tungsten trioxide film at the compromise of sensitivity at both operating temperatures. Ceramic Transactions, Volume ; Singh, D.

Chemosensors , 2 , Targeted uptake of folic acid-functionalized iron oxide nanoparticles by ovarian cancer cells in the presence but not in the absence of serum. Nanotechnology, Biology, and Medicine , 10 , Targeted delivery of nanoparticles to cells or tissues of interest is arguably the "holy grail" of nanomedicine. Using primary human macrophages and ovarian cancer cells, we evaluated the biocompatibility and specific targeting of folic acid FA -conjugated iron oxide nanoparticles with organic poly ethylene glycol , PEG or inorganic SiO2 intermediate surface coatings.

FA-dependent uptake was observed only in the presence of serum proteins. The strategy presented here for receptor-mediated uptake of nanoparticles with pre-defined surface chemistry may enable targeting of nanoparticles for therapeutic and imaging applications. From the clinical editor: In this study the receptor specific uptake of folic acid-functionalized iron oxide nanoparticles was determined in ovarian cancer cells. It was found that the presence of serum proteins is an absolute requirement for the uptake of these nanoparticles.

The described strategy for receptor-mediated uptake of nanoparticles with pre-defined surface chemistry may enable a better targeting of nanoparticles for additional therapeutic and imaging applications. New molecular aluminophosphates of different nuclearity are synthesized by a stepwise process and structurally characterized.

Compound 1 serves as a starting point in construction of larger molecular units by reactions with OP OH OSiMe3 2 as a cage-extending reagent and with diketones, such as Hhfacac 1,1,1,5,5,5-hexafluoropentan-2,4-dione and Hacac pentan-2,4-dione , as capping reagents. Both molecules display Al centers in three different coordination environments. Does carbon coating really improves the electrochemical performance of electrospun SnO2 anodes?

Electrochimica Acta , , Abstract In this paper, we report the influence of carbon coating on the electrochemical performance of hollow structured SnO2 electrospun nanofibers. Li-storage properties are evaluated in half-cell configuration between two different potential windows i. Very high reversibility over 3. In contrary, huge differences in the electrochemical performances are observed for bare and carbon coated SnO2 when the test cell is cycled for conversion reaction.

On page , the calcd. By using the heteroleptic alkoxide complex 2 as metal org. An expedient choice of precursor enabled the replacement of additives like bases or other mineralizer and opens an efficient pathway for controlled nucleation of metal oxide nanoparticles. Small , 9 , In contrast to C60 -fullerenes, GO decreases the intracellular levels of LMP7 immunoproteasome subunits required for processing of protein antigens.

This is important for the development of DC-based vaccines. Electrospun core-shell nanofibers for drug encapsulation and sustained release. Fabrication of core-shell nanofibers by coaxial electrospinning system suited for drug delivery applications was investigated based on tetracycline hydrochloride TCH as the core and poly lactide-co-glycolide as the shell materials.

Comparison of drug release from monolithic fibers blend electrospinning and core-shell structures was performed to evaluate the efficacy of the core-shell morphol. The nanofibrous webs are potentially interesting for wound healing purposes since they can be maintained for an adequate length of time to gradually disinfect a local area without the need of bandage renewal.

KGaA , ; pp. Journal of Materials Chemistry A , 1 , Advanced Materials Research , , The demand for novel antibiotic-loaded electrospun nanofibrous structures has increased extremely in the recent years and has engaged the interests of scientists and engineers into a blend configuration of antibiotic drug and biocompatible polymers due to their unique applications in future of better therapeutic effect, reduced toxicity and sustained local antibiotic release over a period of time.

One method to produce these antibiotic-loaded networks is by electrospinning process. However, it is very important to know structural characteristics and morphol. In this paper, fabrication of electrospun nanofibers suited for antibiotic delivery system is investigated based on tetracycline hydrochloride as the antibiotic drug and poly lactic-co-glycolic acid as the biodegradable polymeric matrix. Furthermore, the effect of material and process parameters on morphol. The efficacy of the medicated scaffolds using a static system for bacterial growth on agar plates was also proved. CrystEngComm , 15 , In comparison to single titanium or vanadium oxide shells, the binary Ti-V metal oxide overlayer overcomes the problems related to lattice mismatch and thermochem.

Therefore, the presence of defects such as dislocations and strain fields, which in principle limit the carrier transport properties affecting the elec. Atomic model simulations confirm that structural characteristics related to lattice mismatch and strain accommodation at the heterojunction influence the thermochem.

Organometallics , 32 , The new compounds were characterized by multinuclear NMR spectroscopy, elemental analysis, and mass spectrometry. Tin dioxide nano-wire device for sensing kinetics of acetone and ethanol towards diabetes monitoring. Ceramic Transactions ; Singh, J. High-rate and elevated temperature performance of electrospun V2O5 nanofibers carbon-coated by plasma enhanced chemical vapour deposition. Nano Energy , 2 , Vanadium pentoxide V2O5 nanofibers VNF are synthesized by electrospinning technique and homogeneously coated with carbon by plasma enhanced chem.

Li-insertion behaviors of VNFs are explored as cathode in half-cell configuration by means of both potentiostatic and galvanostatic measurements. Enhanced high rate and elevated temp. Carbon-coating enables improved electronic cond. Columnar Fe2O3 arrays via plasma-enhanced growth: Interplay of fluorine substitution and photoelectrochemical properties. International Journal of Hydrogen Energy , 38 , The fluorine content in the deposits could be adjusted by the sole variation of the deposition temperature controlling, in turn, the optical absorption and energy bandgap.

Photocurrent measurements and Mott-Schottky analyses, carried out in Na2SO4 solution under one sun illumination, evidenced a conductivity switch from n- to p-type upon increasing fluorine amount in the obtained nanomaterials. The sample photocurrent density, donor content and flatband potential support the hypothesis that a progressive substitution of oxygen by fluorine in the iron III oxide lattice can alter electronic structure and extend charge carrier lifetimes, making anion-doped beta-Fe2O3 an efficient water oxidation catalyst.

Published by Elsevier Ltd. A new alkoxide-based sol contg. Electrospinning resulted in well-defined nanofibers and conventional sol-gel synthesis in polydisperse, isotropic nanoparticles. The nanofibrous self-supported electrodes showed superior cycling stability giving an initial discharge capacity of mA h g-1 at 0. ACS Nano , 7 , Successful surface modification and covalent attachment of functional groups and molecules were confirmed by FT-IR spectroscopy and thermal gravimetric analysis. The ability of the surface-grafted biotin terminal groups to specifically interact with streptavidin either horseradish peroxidase HRP -luminol-H2O2 or rhodamine was confirmed by chemiluminescent assay.

A quantitative assessment showed a capture limit of 0. Furthermore, E SPIONs were successfully used to specifically label papain-like cysteine proteases from crude plant extracts. Owing to the simplicity and versatility of the technique, together with the superparamagnetic behavior of FeOx-nanoparticles, the results demonstrate that click chemistry on surface anchored azide group is a viable approach toward bioconjugations that can be extended to other nanoparticles surfaces with different functional groups to target specific therapeutic and diagnostic applications.

Coordination Chemistry Reviews , , One drawback of porphyrin derivs. One of the approaches for improving the absorption properties of porphyrin derivs. Furthermore, parts made of aluminium alloy via DMLS have a particular microstructure that is the result of repeated severe thermal cycles.

In the present work the authors, starting from the description of the parent microstructure of parts made of AlSi10Mg aluminium alloy, study the microstructure evolution occurred within the joint made by Friction Stir Welding, analysing in details the microstructure of the main well recognized zone of the weld bead. The structure of the parent material is characterized by the presence of melting pools with a very fine microstructure. In the joint the recrystallization, the grain refinement and, above all, the redistribution of intermetallic phases occurs, resulting in an homogenization of the microstructure and in an increase of micro hardness.

Fe-Ni metal particles with smooth Ni, Co, and Cr zoning patterns, wt. Apparently, this condensate metal was not melted during chondrule formation or affected significantly in the solid-state by alteration during parent body processing. Consideration of diffusional redistribution of Ni, Co, Cr and siderophile elements have further constrained the calculated condensation temperatures and cooling rates of the zoned condensates.

These condensate metals have irregular shapes and vary in size from 50 to m as revealed in some detail by optical and SEM techniques. In addition to zoned condensate particles, other types of metal particles have been observed. These include zoned condensates with exsolution-precipitates, unzoned homogeneous metal with no exsolution precipitates, unzoned metal exhibiting exsolution precipitates and high Ni metal grains. Modeling of microstructure evolution in direct metal laser sintering: A phase field approach.

Direct Metal Laser Sintering DMLS is a new technology in the field of additive manufacturing, which builds metal parts in a layer by layer fashion directly from the powder bed. The process occurs within a very short time period with rapid solidification rate. Slight variations in the process parameters may cause enormous change in the final build parts. The physical and mechanical properties of the final build parts are dependent on the solidification rate which directly affects the microstructure of the material.

Thus, the evolving of microstructure plays a vital role in the process parameters optimization. Nowadays, the increase in computational power allows for direct simulations of microstructures during materials processing for specific manufacturing conditions. In this study, modeling of microstructure evolution of Al-SiMg powder in DMLS process was carried out by using a phase field approach. A MATLAB code was developed to solve the set of phase field equations, where simulation parameters include temperature gradient, laser scan speed and laser power.

The effects of temperature gradient on microstructure evolution were studied and found that with increase in temperature gradient, the dendritic tip grows at a faster rate. Microstructure based model for sound absorption predictions of perforated closed-cell metallic foams.

Closed-cell metallic foams are known for their rigidity, lightness, thermal conductivity as well as their low production cost compared to open-cell metallic foams. However, they are also poor sound absorbers. Similarly to a rigid solid, a method to enhance their sound absorption is to perforate them. This method has shown good preliminary results but has not yet been analyzed from a microstructure point of view.

The objective of this work is to better understand how perforations interact with closed-cell foam microstructure and how it modifies the sound absorption of the foam. A simple two-dimensional microstructural model of the perforated closed-cell metallic foam is presented and numerically solved. A rough three-dimensional conversion of the two-dimensional results is proposed. The results obtained with the calculation method show that the perforated closed-cell foam behaves similarly to a perforated solid; however, its sound absorption is modulated by the foam microstructure , and most particularly by the diameters of both perforation and pore.

A comparison with measurements demonstrates that the proposed calculation method yields realistic trends. Some design guides are also proposed. Metallic alloys are a widely used class of structural materials, and the mechanical properties of these alloys are strongly dependent on the microstructure.

Therefore, the scientific design of metallic materials with superior mechanical properties requires the understanding of the microstructural evolution. Computational models and simulations offer a number of advantages over experimental techniques in the prediction of microstructural evolution, because they can allow studies of microstructural evolution in situ, i. In this thesis, we applied a multi-scale modeling approach to study the microstructural evolution in several metallic systems, including polycrystalline materials and metallic glasses MGs.

Specifically, for polycrystalline materials, we developed a coupled finite element model that combines phase field method and crystal plasticity theory to study the plasticity effect on grain boundary GB migration. Our model is not only coupled strongly i. The developed model provides a tool to study the microstructural evolution in plastically deformed metals and alloys. For MGs, we used molecular dynamics MD simulations to investigate the nucleation kinetics in the primary crystallization in Al-Sm system.

We calculated the time-temperature-transformation curves for low Sm concentrations, from which the strong suppressing effect of Sm solute on Al nucleation and its influencing mechanism are revealed. Also, through the comparative analysis of both Al attachment and Al diffusion in MGs, it has been found that the nucleation kinetics is controlled by interfacial attachment of Al, and that. Casting is the first step toward the production of majority of metal products whether the final processing step is casting or other thermomechanical processes such as extrusion or forging.

The high shear melt conditioning provides an easily adopted pathway to producing castings with a more uniform fine-grained microstructure along with a more uniform distribution of the chemical composition leading to fewer defects as a result of reduced shrinkage porosities and the presence of large oxide films through the microstructure.

The effectiveness of high shear melt conditioning in improving the microstructure of processes used in industry illustrates the versatility of the high shear melt conditioning technology. The application of high shear process to direct chill and twin roll casting process is demonstrated with examples from magnesium melts. To determine the effect of porcelain firing cycle on microstructure of 4 metal ceramic alloys, and to analyze the changes of their corrosion resistance in the artificial saliva.

We simulated the process of firing and repolishing when fabricating porcelain-fused-to- metal restoration in clinic,and then observed the microstructures of Ni-Cr, Ni-Cr-Ti, Co-Cr alloys and high gold alloy by field emission scanning electron microscopy and energy dispersive spectroscopy. The electrochemical corrosion behavior of alloys in artificial saliva was analyzed by polarization curves and corrview 2 corrosion analysis software. The data of self-corrosion potential and transpassive potential were obtained and analyzed.

After the porcelain firing cycle, the surface composition changed slightly, and the morphological in the 3 predominate base metal alloys also changed. The self-corrosion potential turned to more negative, and the transpassive potential declined. The procedure of porcelain firing cycle can affect the surface microstructure and increase the corrosion of 4 metal -ceramic alloys.

Microstructure Formation in Dissimilar Metal Welds: The difference in physical properties of the base metals and metallurgical features thermodynamics and kinetics of the system influence both macroscopic transport and microstructure development in the weld. Microstructures near the fusion interfaces are markedly different from those inside the weld region. Different morphologies of the latter eutectic constitute the predominant microstructure inside the weld metal region. These results are compared and contrasted with those from laser welding of the same binary couple, and a scheme of solidification is proposed to explain the observations.

This highlights notable departures from welding of similar and other dissimilar metals such as a significant asymmetry in heat transport that governs progress of solidification from each side of the couple, and a lack of unique liquidus isotherm characterizing the liquid-solid front. Microstructure and mechanical properties of hip-consolidated Rene 95 powders.

The microstructure of as-HIP'd specimen was characterized by highly serrated grain boundaries. Mechanical tests and microstructural observations reveal that the serrated grain boundaries improved ductility at both room and elevated temperatures by retarding crack propagation along grain boundaries. This paper presents selected characteristics of the metallic porous materials produced by the sintering of metal powders.

The authors focus on materials produced from the iron powder Fe of ASC It consists of spherical particles of different sizes forming agglomerates. Distaloy SE is also based on the sponge-iron. The porous material is prepared using the patented method of sintering the mixture of iron powder ASC As a result, the materials with open pores of micrometer sizes are obtained. The pores are formed between iron particles bonded by diffusion bridges. The modelling of porous materials containing diffusion bridges that allows for three-dimensional 3D imaging is presented.

Modulating laser intensity profile ellipticity for microstructural control during metal additive manufacturing. Additively manufactured AM metals are often highly textured, containing large columnar grains that initiate epitaxially under steep temperature gradients and rapid solidification conditions. These unique microstructures partially account for the massive property disparity existing between AM and conventionally processed alloys.

Although equiaxed grains are desirable for isotropic mechanical behavior, the columnar-to-equiaxed transition remains difficult to predict for conventional solidification processes, and much more so for AM. In this study, the effects of laser intensity profile ellipticity on melt track macrostructures and microstructures were studied in L stainless steel. As a general trend, columnar grains preferentially formed with increasing laser power and scan speed for all beam profiles.

However, when conduction mode laser heating occurs, scan parameters that result in coarse columnar microstructures using Gaussian profiles produce equiaxed or mixed equiaxed-columnar microstructures using elliptical profiles. Furthermore, by modulating spatial laser intensity profiles on the fly, site-specific microstructures and properties can be directly engineered into additively manufactured parts. Effectiveness of stress release geometries on reducing residual stress in electroforming metal microstructure.

Micro electroforming, as a mature micromachining technology, is widely used to fabricate metal microdevices in micro electro mechanical systems MEMS. However, large residual stress in the local positions of the micro electroforming layer often leads to non-uniform residual stress distributions, dimension accuracy defects and reliability issues during fabrication of the metal microdevice.

To solve this problem, a novel design method of presetting stress release geometries in the topological structure of the metal microstructure is proposed in this paper. First, the effect of stress release geometries circular shape, annular groove shape and rivet shape on the residual stress in the metal microstructure was investigated by finite element modeling FEM analysis.

The simulation results show that presetting stress release geometries can effectively reduce and homogenize the residual stress in the metal microstructures were measured metal microstructure. Then, micro electroforming experiments were carried out corresponding to the simulation models. The residual stresses in the metal microstructures were measured by micro Raman spectroscopy MRS method.

A detailed quantitative microstructural analyses of primarily open cell FeCrAlY and stainless steel metal foams with different relative densities and pores per inch p. Several elements of the microstructure , such as longitudinal and transverse cell sizes, cell areas and perimeters, ligament dimensions, cell shapes and volume fractions of closed and open cells, were measured.

The cross-sections of the foam ligaments showed a large number of shrinkage cavities, and their circularity factors and average sizes were determined. The volume fractions of closed cells increased linearly with increasing relative density.

main navigation

In contrast, the volume fractions of the open cells and ligaments decreased with increasing relative density. The relative densities and p. A phenomenological model is proposed to rationalize the present microstructural observations. The properties of most engineering materials depend on the characteristics of internal microstructures and defects.

In additively manufactured AM metals , these can include polycrystalline grains, impurities, phases, and significant porosity that qualitatively differ from conventional engineering materials. The microscopic details of the interactions between these internal defects, and the propagation of applied loads through the body, act in concert to dictate macro-observable properties like strength and compressibility.

The microstructural details of the material were represented explicitly, such that internal features like second phases and pores are captured and meshed as individual entities in the computational domain. We will discuss the dependence of the high-strain-rate mechanical properties on microstructural characteristics such as the shapes, sizes, and volume fractions of second phases and pores. The microstructure of the weld metal of a duplex stainless steel made with Nd: YAG pulsed laser is investigated at different travel speeds and pulse frequencies.

In terms of the solidification pattern, the weld microstructure is shown to be composed of two distinct zones. The presence of two competing heat transfer channels to the relatively cooler base metal and the relatively hotter previous weld spot is proposed to develop two zones. At high overlapping factors, an array of continuous axial grains at the weld centerline is formed.

At low overlapping factors, in the zone of higher cooling rate, a higher percentage of ferrite is transformed to austenite. This is shown to be because with extreme cooling rates involved in pulsed laser welding with low overlapping, the ferrite-to-austenite transformation can be limited only to the grain boundaries. Modeling macro-and microstructures of gas- metal -arc welded HSLA steel. Fluid flow and heat transfer during gas- metal -arc welding GMAW of HSLA steel were studied using a transient, three-dimensional, turbulent heat transfer and fluid flow model.

The temperature and velocity fields, cooling rates, and shape and size of the fusion and heat-affected zones HAZs were calculated. A continuous-cooling-transformation CCT diagram was computed to aid in the understanding of the observed weld metal microstructure. The computed results demonstrate that the dissipation of heat and momentum in the weld pool is significantly aided by turbulence,m thus suggesting that previous modeling results based on laminar flow need to be re-examined.

Furthermore, finger penetration, a unique geometric characteristic of gas- metal -arc weld pools, could be satisfactorily predicted from the model. The ability to predict these geometric variables and the agreement between the calculated and the measured cooling rates indicate the appropriateness of using a turbulence model for accurate calculations. The microstructure of the weld metal consisted mainly of acicular ferrite with small amounts of bainite.

At high heat inputs, small amounts of allotriomorphic and Widmanstaetten ferrite were also observed. The observed microstructures are consistent with those expected from the computed CCT diagram and the cooling rates. The results presented here demonstrate significant promise for understanding both macro-and microstructures of steel welds from the combination of the fundamental principles from both transport phenomena and phase transformation theory. The computed results demonstrate that the dissipation of heat and momentum in the weld pool is significantly aided by turbulence, thus suggesting that previous modeling results based on laminar flow need to be re-examined.

A comparison of the calculated fusion and HAZ geometries with their corresponding measured values showed good agreement. This article describes in detail the effect of the modes of metal transfer on the microstructure and mechanical properties of gas metal arc-welded modified ferritic stainless steel SSP M sheets as received of 4 mm thickness.

The welded joints were prepared under three modes of metal transfer, i. The welded joints were evaluated by means of microstructural , hardness, notched tensile strength, Charpy impact toughness, and high cycle fatigue. It was observed that the microstructure as well as the tensile, Charpy impact, and high cycle fatigue of weld metal is significantly affected by the mode of metal transfer and filler wire used. However, the heat-affected zone HAZ is affected only by the modes of metal transfer.

The results have been correlated with the microstructures of weld and HAZ developed under different modes of metal transfer. Studies on microstructure , mechanical and corrosion properties of high nitrogen stainless steel shielded metal arc welds. The present work is aimed at studying the microstructure , mechanical and corrosion properties of high nitrogen stainless steel shielded metal arc SMA welds made with Cromang-N electrode.

Basis for selecting this electrode is to increase the solubility of nitrogen in weld metal due to high chromium and manganese content. Microstructures of the welds were characterized using optical microscopy OM , field emission scanning electron microscopy FESEM and electron back scattered diffraction EBSD mainly to determine the morphology, phase analysis, grain size and orientation image mapping. Hardness, tensile and ductility bend tests were carried out to determine mechanical properties.

Potentio-dynamic polarization testing was carried out to study the pitting corrosion resistance using a GillAC basic electrochemical system. Constant load type testing was carried out to study stress corrosion cracking SCC behaviour of welds. The investigation results shown that the selected Cr—Mn—N type electrode resulted in favourable microstructure and completely solidified as single phase coarse austenite. Mechanical properties of SMA welds are found to be inferior when compared to that of base metal and is due to coarse and dendritic structure.

Finally, we will draw the conclusions from the present work as shown in Section 4. The prospect of extending existing metal -ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties.

This kind of reactive systems challenges conventional methods for successfully processing corresponding metal -ceramic composites. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed. With increasing dendrite content, the topology changes such that neither the harder glass nor the softer dendrites dominate the microstructure.

Plate-impact experiments were performed using the mm single-stage gas gun over impact stresses up to 18 GPa. VISAR interferometry was used to obtain rear free-surface velocity profiles revealing the velocity pullback spall failure signals. The spall strengths were higher than for Ti-6Al-4V alloy, and remained high up to impact stress. The influence of microstructure on the spall strength is indicated by the constants of the power law fit with the decompression strain rate.

Differences in fracture behavior reveal void nucleation as a dominant mechanism affecting the spall strength. The results allow projection of spall strength predictions for design of in-situ formed metallic glass composites. Microstructure images of metallic materials play a significant role in industrial applications. To address image degradation problem of metallic materials, a novel image restoration technique based on K-means singular value decomposition KSVD and smoothing penalty sparse representation SPSR algorithm is proposed in this work, the microstructure images of aluminum alloy AA material are used as examples.

To begin with, to reflect the detail structure characteristics of the damaged image, the KSVD dictionary is introduced to substitute the traditional sparse transform basis TSTB for sparse representation. The results of simulation and two practical cases demonstrate that the proposed method has superior performance compared with some state-of-the-art methods in terms of restoration performance factors and visual quality.

Meanwhile, the grain size parameters and grain boundaries of microstructure image are discussed before and after they are restored by proposed method. Designed microstructure based on color filter and metallic nanoslit for multiband spectral compatible control. Controlling the spectral characteristics by regulating the geometry of microstructure has become an effective method to meet the requirements of various applications.

To mediate the spectral characteristics, metallic subwavelength slits with different structures and color filters consisting of diverse materials were discussed, and then a designed microstructure composed of color filter and metallic slits, which were surrounded by grooves, was put forward for a compatible effect of controlling the spectral characteristics. Afterward, the spectral characteristics of the proposed structure were simulated by finite-difference time-domain method in the wavelength range of to 10, nm.

Additionally, the effects of geometric parameters on the spectral characteristics were studied. In conclusion, the compatible spectrum control in three bands i. A thermally activated dislocation-based constitutive flow model of nanostructured FCC metals involving microstructural evolution. This theoretical framework offers the opportunity to tune the microstructures in the polycrystalline materials to synthesise high performance engineering materials with high strength and great ductility.

The key emphasis has been on understanding processing-microstructure-property relationships. Initial studies have shown that sound joints can be made between dissimilar materials such as MA alloy cladding tubes and HT-9 end plugs, and MA and HT-9 coupons. Similar joint strength observations have also been made by performing simple bend tests. Metallized compliant 3D microstructures for dry contact thermal conductance enhancement.

Microstructured three-dimensional 3D materials can be engineered to enable new capabilities for various engineering applications; however, microfabrication of large 3D structures is typically expensive due to the conventional top-down fabrication scheme. Herein we demonstrated the use of projection micro-stereolithography and electrodeposition as cost-effective and high-throughput methods to fabricate compliant 3D microstructures as a thermal interface material TIM. This novel TIM structure consists of an array of metallized micro-springs designed to enhance the dry contact thermal conductance between nonflat surfaces under low interface pressures 10ss kPa.

Direct generation of superhydrophobic microstructures in metals by UV laser sources in the nanosecond regime. The current availability of new advanced fiber and DPSS lasers with characteristic pulse lengths ranging from ns to fs has provided a unique frame in which the development of laser-generated microstructures has been made possible for very diverse kinds of materials and applications. At the same time, the development of the appropriate laser-processing workstations granting the appropriate precision and repeatability of the respective laser interaction processes in line with the characteristic dimension features required in the microstructured samples has definitively consolidated laser surface microstructuring as a reference domain, nowadays, unavoidable for the design and manufacturing of current use microsystem: MEMSs, fluidic devices, advanced sensors, biomedical devices and instruments, etc.

Completing the broad spectrum of applications developed mostly involving the generation of geometrical features on a subtrate with specific functional purposes, a relatively new, emerging class of laser- microstructuring techniques is finding an important niche of application in the generation of physically structured surfaces particularly of metallic materials with specific contact, friction, and wear functionalities, for whose generation the concourse of different types of laser sources is being found as an appropriate tool.

In this paper, the application of laser sources with emission in the UV and at ns time regime to the surface structuration of metal surfaces specifically Al for the modification of their wettability properties is described as an attractive application basis for the generation of self-cleaning properties of extended functional surfaces.

The samples produced at the optimum conditions with respect to. Mechanisms, Microstructure and Properties. The technology of high-density electropulsing has been applied to increase the performance of metallic materials since the s and has shown significant advantages over traditional heat treatment in many aspects. However, the microstructure changes in electropulsing treatment EPT metals and alloys have not been fully explored, and the effects vary significantly on different material. When high-density electrical pulses are applied to metals and alloys, the input of electric energy and thermal energy generally leads to structural rearrangements, such as dynamic recrystallization, dislocation movements and grain refinement.

The enhanced mechanical properties of the metals and alloys after high-density electropulsing treatment are reflected by the significant improvement of elongation. As a result, this technology holds great promise in improving the deformation limit and repairing cracks and defects in the plastic processing of metals.

This review summarizes the effect of high-density electropulsing treatment on microstructural properties and, thus, the enhancement in mechanical strength, hardness and corrosion performance of metallic materials.

Subscription Options

It is noteworthy that the change of some properties can be related to the structure state before EPT quenched, annealed, deformed or others. The mechanisms for the microstructural evolution, grain refinement and formation of oriented microstructures of different metals and alloys are presented. Future research trends of high-density electrical pulse technology for specific metals and alloys are highlighted.

The formation of metallic lithium microstructures in the form of dendrites or mosses at the surface of anode electrodes e. In this work, we present here a direct, relative quantitative analysis of lithium deposition on graphite anodes in pouch cells under normal operating conditions, paired with a model cathode material, the layered nickel-rich oxide LiNi 0.

With the absence of apparent kinetic e. This insidious effect is found to initiate at a very early stage of cell operation metal dissolution and drastically improved cyclability. In conclusion, our results may also be applicable to studying the unstable electrodeposition of lithium on other substrates, including Li metal. Chemical and microstructural analyses for heavy metals removal from water media by ceramic membrane filtration.

The work includes manufacturing ceramic membranes with dimensions of 15 by 15 cm and 2 cm thickness. The membranes were made from low cost materials of local clay mixed with different sawdust percentages of 0. Aqueous solutions of heavy metals were prepared in the laboratory and filtered through the ceramic membranes. The influence of the main parameters such as pH, initial driving pressure head, and concentration of heavy metals on their removal efficiency by ceramic membranes was investigated. Water samples were collected before and after the filtration process and their heavy metal concentrations were determined by chemical analysis.

Moreover, a microstructural analysis using scanning electronic microscope SEM was performed on ceramic membranes before and after the filtration process. SEM images approved these results by showing adsorbed metal ions on sides of the internal pores of the ceramic membranes.

Microstructural and hardness investigations on a dissimilar metal weld between low alloy steel and Alloy 82 weld metal. The results indicated that there were two kinds of FBs, martensite FB and sharp FB, with obvious different microstructures , alternately distributed in the same FB. The hardness maximum of the martensite FB was much higher than that of the sharp FB, which was attributed to the martensite layer at the martensite FB. The layer-by-layer building of monolithic, 3D metal components from selectively melted powder layers using laser or electron beams is a novel form of 3D printing or additive manufacturing.

Microstructures created in these 3D products can involve novel, directional solidification structures which can include crystallographically oriented grains containing columnar arrays of precipitates characteristic of a microstructural architecture. These microstructural architectures are advantageously rendered in 3D image constructions involving light optical microscopy and scanning and transmission electron microscopy observations.

This paper compares 3D microstructural architectures in Co-base and Ni-base superalloys, columnar martensitic grain structures in PH alloy, and columnar copper oxides and dislocation arrays in copper. Microstructure of a base metal thick film system. A base metal thick film conductor system using glass frits with base metal oxide additions was investigated as metallization for hybrid microcircuits. Application of previous work on wetting and chemical bonding was made to this system. The observation of changes in the properties of the thick film was made by photomicrographs of screened samples and sheet resistivity measurements.

In addition to the chemical and wetting properties, the effect of glass frit particle size on conductivity was also analyzed. Electron Backscattering Diffraction and optical microscopy were used to relate the presence, size, and shape of porosity to local microstructure. Results from analysis of these damage sites show that the presence of a GB-affected zone, where strain concentration occurs next to a GB, correlates strongly with damage localization at these sites, most likely due to the inability of maintaining strain compatibility across these interfaces, with additional effects due to the inclination of the GB with respect to the shock.

Results indicate that strain compatibility plays an important role on intergranular spall damage in metallic materials. As copper interconnects have scaled to ever smaller dimensions on semiconductor devices, the microstructure has become increasingly detrimental for performance and reliability.

Small grains persist in interconnects despite annealing at high temperatures, leading to higher line resistance and more frequent electromigration-induced failures. Conventionally, it was believed that impurities from the electrodeposition pinned grain growth, but limitations in analytical techniques meant the effect was inferred rather than observed. Recent advances in analytical techniques, however, have enabled this work to quantify impurity content, location, and diffusion in relation to microstructural changes in electroplated copper.

Surface segregation of impurities during the initial burst of grain growth was investigated. After no surface segregation was observed, a microfluidic plating cell was constructed to plate multilayer films with regions of intentionally high and low impurity concentrations to determine if grain growth could be pinned by the presence of impurities; it was not. An alternate mechanism for grain boundary pinning based on the texture of the seed layer is proposed, supported by time-resolved transmission electron microscopy and transmission electron backscatter diffraction data.

The suggested model posits that the seed in narrow features has no preferred orientation, which results in rapid nucleation of subsurface grains in trench regions prior to recrystallization from the overburden down. These rapidly growing grains are able to block off several trenches from the larger overburden grains, inhibiting grain growth in narrow features. With this knowledge in hand, metallic capping layers were employed to address the problematic microstructure in 70nm lines. The capping layers chromium, nickel, zinc, and tin were plated on the copper overburden prior to annealing to manipulate the stress gradient and microstructural development during annealing.

Microstructure and thermal characterization of dense bone and metals for biomedical use.

Long Haul Ebook Ocean Passages And Landfalls Chm By Rod Heikell | Sites For Download Of Free Books.

We present a microstructural study and thermal diffusivity measurements at room temperature in two different sections of bull dense bone, bull bone and commercial hydroxyapatite, the last two in powder form. A comparison was realised between these measured values and those obtained from metallic samples frequently used in implants, as high purity titanium and L stainless steel.

Our results show that the porosity and its orientation in the bone are two important factors for the heat flux through the bone. On the other hand, we obtained that the hydroxyapatite, in compact powder form, presents a thermal diffusivity value close to those obtained for the samples of bone which gives a good thermal agreement between these materials. Thallium Antidotes in Depth A Prussian Blue Chapter Please enter User Name. Use this site remotely Bookmark your favorite content Track your self-assessment progress and more! View All Subscription Options.

Best of the Blogs. Pop-up div Successfully Displayed This div only appears when the trigger link is hovered over.

• Kater Konstantin: Sammelband (German Edition)
• Regards croisés sur le cannabis: Un état des lieux de sa consommation dans la société (Psy) (French Edition)
• Approaching Business Models from an Economic Perspective (SpringerBriefs in Business)
• Tiento XIV (partido de dos tiples)
• My Cute Shiba (A Learn to Read Picture Book for Kids) An easy reader series