Materials Engineering

Lattice materials can be designed through their microstructure while concurrently considering fabrication feasibility. Here, we propose two types of composite lattice materials with enhanced resistance to buckling: (a) hollow lattice materials fabricated by a newly developed bottom-up assembly technique and the previously developed thermal expansion molding technique and (b) hierarchical lattice materials with foam core sandwich trusses fabricated by interlocking assembly process. The mechanical performance of sandwich structures featuring the two types of lattice cores was tested and analyzed theoretically. For hollow lattice core material, samples from two different fabrication processes were compared and both failed by nodal rupture or debonding. In contrast, hierarchical lattice structures failed by shear buckling without interfacial failure in the sandwich struts. Calculations using established analytical models indicated that the shear strength of hollow lattice cores could be...

A new mechanism of fracture toughness enhancement in nanocrystalline metals and ceramics is suggested. The mechanism represents the cooperative grain boundary (GB) sliding and stress-driven GB migration process near the tips of growing cracks. It is shown that this mechanism can increase the critical stress intensity factor for crack growth in nanocrystalline materials by a factor of three or more and thus considerably enhances the fracture toughness of such materials.

EuCARD-2 is a project partly supported by FP7-European Commission aiming at exploring accelerator magnet technology for 20 T dipole operating field. The EuCARD-2 collaboration is liaising with similar programs for high field magnets in the USA and Japan. EuCARD-2 focuses, through the workpackage 10 "Future magnets," on the development of a 10 kA-class superconducting, high current density cable suitable for accelerator magnets, for a 5 T stand-alone dipole of 40 mm bore and about 1 m length. After standalone testing, the magnet will possibly be inserted in a large bore background dipole, to be tested at a peak field up to 18 T. This paper starts by reporting on a few of the highlight simulations that demonstrate the progress made in predicting: dynamic current distribution and influence on field quality, complex quench propagation between tapes, and minimum quench energy in the multitape cable. The multiphysics output importantly helps predicting quench signals and guides the development of the novel early detection systems. Knowing current position within individual tapes of each cable we present stress distribution throughout the coils. We report on the development of the mechanical component and assembly processes selected for Feather-M2 the 5 T EuCARD2 magnet. We describe the CERN variable temperature flowing helium cold gas test system. We describe the parallel integration of the FPGA early quench detection system, using pickup

The nitrogen-doped diamond films have been successfully synthesized by using urea as the nitrogen source. Selected-area deposition of diamond nuclei was formed by using a SiO 2 layer as the masking material. Diamond pads, around 9 mm in diameter, were obtained when the N-doped diamond films were deposited on these patterned diamond nuclei using the chemical vapor deposition process. An emission current density as high as 200 mA/cm2, with a turn-on field of around 8 V/mm, was obtained. However, the diamond emitters broke down easily, which is ascribed to the localized melting of the substrate materials surrounding the diamond pads.

A previously synthesized hyperbranched poly(butylene adipate) (HPBA) polymer was compared with a commercial dendritic polyol (HPOH) as a toughening agent for a commercial one-part epoxy resin. Both modifiers were added in weight percentages of 1, 3, 5, and 10%. The modified epoxies were characterized using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), melt rheological tests, and linear elastic fracture mechanics. Blend morphology and matrix-modifier interactions were evaluated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis, respectively. The toughness-improvement effect was achieved without substantial impairment of thermomechanical properties or degradation of the thermal stability of the epoxy resin. A meaningful decrease in viscosity was achieved with both modifiers, contributing to an easier infusion processability. No evidence of new chemical linking was found although phase separation was observed by SEM, leading to the conclusion that only interfacial linkage occurs between modifiers and epoxy chains. SEM analysis also clearly shows the fracture mode changing from brittle to ductile by addition of modifiers, which was more evident for blends of HPBA.

In this investigation, the effect of coloring voltage and thickness on optical and also electrochromical properties of WO 3 thin films has been studied. The WO 3 thin films were grown on glass and indium tin oxide coated conducting glass substrates by e-beam evaporation at different thicknesses of 200, 400, and 700 nm. Optical properties of the deposited samples were characterized in the ultraviolet-visible range ͑300-1100 nm͒. The optical bandgap energy of the WO 3 was obtained in a range of 3.3-3.5 eV showing its increase by decreasing the film thickness. The refractive index of the WO 3 films was measured around 2 in the visible range. Surface chemical states of the films were studied by X-ray photoelectron spectroscopy, which showed the stoichiometry of our deposited tungsten oxide thin films is acceptable. Atomic force microscopy was used for studying surface morphology of the deposited films. The electrochromic properties of the WO 3 films were characterized using a lithium-based electrolyte. It was shown that there is an optimum coloring voltage for each film thickness, which maximizes the change in optical density during electrochromic process. The coloration efficiency of the samples at the optimum voltage was linearly improved by increasing the film thickness at a constant wavelength ͑500 nm͒.

The local surface chemistry of a low-Ni austenitic stainless steel AISI type 304 used for tensile testing in hydrogen atmosphere is characterized by secondary ion mass spectrometry (SIMS). A chemical map on cylindrical austenitic stainless steel samples can be obtained even after a tensile test. In an effort to obtain the proper chemical element distribution on the samples, the influence of contamination and sample orientation is discussed. An iron oxide on top of a chromium oxide layer is present and Si segregation at grain boundaries is detected. Oxides are judged to reduce the initial hydrogen attack but to be of minor importance for crack propagation during the embrittlement process.

A versatile method for positive-type patterning of polyimide (PI) based on a two-layer photosensitive poly(benzoxazole) (PSPBO) and poly(amic acid) (PAA) film has been developed to provide a promising material in the field of microelectronics. This patterning system consisted of a pristine PAA thick bottom-layer and a poly(o-hydroxy amide) (PHA) thin top layer with 9,9-bis[4-(tert-butoxycarbonyl-methyloxy)phenyl]fluorene (TBMPF) as a dissolution inhibitor, and (5-propylsulfonyloxyimino-5H-thiophene-2-ylidene)-(2-methylphenyl)-acetonitrile (PTMA) as a photoacid generator (PAG). The PHA and PAA were prepared from 4,4 0-(hexafluoroisopropylidene)-bis(o-aminophenol) and 4,4 0-oxybis(benzoic acid) derivatives, and 3,3 0 ,4,4 0-biphenyltetracarboxylic dianhydride and 4,4 0-oxydianiline, respectively, in N,N-dimethylacetamide. This two-layer system based on PHA (150-nm thickness) and PAA (1.5-lm thickness) showed high sensitivity of 35 mJ/cm 2 and high contrast of 10.3 when exposed to a 365 nm line (i-line), post-baked at 100°C for 2 min, and developed in a 2.38 wt.% tetramethylammonium hydroxide aqueous solution/5 wt.% isopropanol at 25°C. A clear positive image of a 4-lm line-and-space pattern was printed on a film which was exposed to 100 mJ/cm 2 of i-line by a contact-printing mode and fully converted to the corresponding PBO/PI pattern upon heating at 350°C, confirmed by FT-IR spectroscopy. This two-layer system could be applied to the patterning of various PAAs.

In high-strength steels it is often difficult to distinguish between hydrogen embrittlement and various other brittle failure mechanisms. The objective of this work was to develop a sensitive analytical procedure based on secondary ion mass spectrometry (SIMS) that would allow in-service identification of local hydrogen accumulation, either during quality control or during failure analysis of electroplated items. Dynamic SIMS was found useful in identifying when baking of Cd-plated AISI 4340 steel was not carried out, thus potentially leading to hydrogen embrittlement. In all non-baked samples, an increase in the hydrogen signal was found at the Cd/steel interface. In baked samples, either a peak was not observed at the interface, or it was insignificant based on determination of the ratios between the hydrogen signals in the coating, interface and substrate. This reproducible effect was monitored even after 16 months storage in a desiccator. These observations make the procedure practical in suggesting more accurate, reliable and cost effective recommendations for prevention of failures. The main effect of baking was found to be effusion of hydrogen from the interface and the substrate steel into the atmosphere. A mechanism for delayed failure is suggested.

Weld cladding is a process for producing surfaces with good corrosion resistant properties by means of depositing/laying of stainless steels on low-carbon steel components with an objective of achieving maximum economy and enhanced life. The aim of the work presented here was to investigate the effect of auxiliary preheating of the solid filler wire in mechanized gas metal arc welding (GMAW) process (by using a specially designed torch to preheat the filler wire independently, before its emergence from the torch) on the quality of the as-welded single layer stainless steel overlays. External preheating of the filler wire resulted in greater contribution of arc energy by resistive heating due to which significant drop in the main welding current values and hence low dilution levels were observed. Metallurgical aspects of the as welded overlays such as chemistry, ferrite content, and modes of solidification were studied to evaluate their suitability for service and it was found that claddings obtained through the preheating arrangement, besides higher ferrite content, possessed higher content of chromium, nickel, and molybdenum and lower content of carbon as compared to conventional GMAW claddings, thereby giving overlays with superior mechanical and corrosion resistance properties. The findings of this study not only establish the technical superiority of the new process, but also, owing to its productivity-enhanced features, justify its use for low-cost surfacing applications.

Silica-potash-lime stained-glasses from medieval age in Northern Europe are found in a poor conserv ation state. Their mechanisms of atmospheric corrosion are still not fully understood and need deeper investigation. A multi-scale analysis of K-Ca rich silicate glasses (ancient and model glass), showed modified layers characterised by a multilayer sequence consisting in the repetition of nm-thick laminae with different compositions. Crystalline phases (sulphates, carbonates and phos phates) are observed. The formation of these sequences is due chiefly to interdiffusion, followed by local dissolution pheno mena. Precipitation of secondary phases is enhanced by the presence of fractures, which facilitate fluid circulation.

This paper deals with the problem of the colorimetric fidelity of digitised colour slides of painted works of art. A six-matrix conversion model was derived that permitted the transformation of any RGB device-dependent measurement on digitised colour slides to XYZ CIE 1931 device-independent values. The model was calibrated against a reference colour chart. Eighty-one uniformly-painted colour samples were photographed together with a painting on a 4 × 5 inch colour slide that was digitised using a high resolution scanner. A 3 × 3 transformation matrix, of the corrected R, G and B values and the respective X, Y and Z tristimulus values provided by spectrophotometry, was calculated. The calculated matrix was then applied to a 13th century Byzantine fresco, captured on the same digitised slide, to transform the RGB measurements to XYZ CIE 1931 device-independent values which were then converted into the L*a *b* CIE 1976 colorimetric system. † The VASARI (Visual Arts System for Archiving and Retrieval of Images) project, carried out as part of the European Commission's ESPRIT II programme, aims to provide a high-resolution digital image capture system in order to record images for conservation research and archival purposes. It replaces conventional photography and has assisted in computer-aided learning in the field of art history.

Adhesive bonding technique is used successfully for joining the carbon fibre reinforced plastics to metals or composite structures. A good design of adhesive joint with either simple or more complex geometry requires its stress and deformation states to be known for different boundary conditions. In case the adhesive joint is subjected to thermal loads, the thermal and mechanical mismatches of the adhesive and adherends cause thermal stresses. The plate-end conditions may also result in the adhesive joint to undergo large displacements and rotations whereas the adhesive and adherends deform elastically (small strain). In this study, the thermal and geometrically non-linear stress analyses of an adhesively bonded composite tee joint with single support plus an angled reinforcement made of unidirectional CFRPs were carried out using the non-linear finite element method. In the stress analysis, the effects of the large displacements were considered using the small displacement -large displacement theory. The stress states in the plates and the adhesive layer of the tee joint configurations bonded to a rigid base and a composite plate were investigated. An initial uniform temperature distribution was attributed to the adhesive joint for a stress free state, and then variable thermal boundary conditions, i.e. air flows with different velocity and temperature were specified along the outer surfaces of the tee joints. The thermal analysis showed that a non-uniform temperature distribution occurred in the tee joints, and high heat fluxes took place along the free surfaces of the adhesive fillets at the adhesive free ends. Later, the geometrical non-linear thermal-stress analysis of the tee joint was carried out for the final temperature distribution and two edge conditions applied to the edges of the vertical and horizontal plates (HP). High stress concentrations occurred around the rounded adherend corners inside the adhesive fillets at the adhesive free ends, and along the adhesive -composite adherend interfaces due to their thermal -mechanical mismatches. The most critical joint regions were adhesive fillets subjected to high thermal gradients, the middle region of HP, the region of the vertical plate corresponding to the free end of the vertical adhesive layer -left support interface. In addition, the support length had a small effect of reducing the peak stresses at the critical adherend and adhesive locations. q

In this study, headspace gas chromatography/mass spectrometry has been used to assess the volatile by-products generated by the ageing of oilimpregnated paper insulation of power transformers. Sealed-glass ampoules were used to age under oxidative conditions 0.5-g specimens of insulating paper in 9 mL of inhibited mineral oil in a temperature range of 60-120 8C and moisture of 0.5, 1 and 2% (w/w). A linear relationship between one of the oil-soluble degradation by-products, i.e. methanol, and the number of ruptured 1,4-b-glycosidic bonds of cellulose, regardless of the type of paper (ordinary Kraft or thermally-upgraded (TU) Kraft paper), was established for the first time in this field. Ageing at 130 8C of model compounds of the Kraft paper constituents (a-cellulose, hemicellulose and lignin) and two cellulosic breakdown byproducts (D-(+)-glucose and 1,6-anhydro-b-D-glucopyranose) confirmed that the a-cellulose degradation was mostly responsible for the presence of this molecule in the system. Furthermore, additional 130 8C-tests with six different papers and pressboard samples under a tight control of initial moisture indicated that at least one molecule of methanol is formed for each rupture of 1,4-b-glucosidic bond of the molecular chains. Stability tests showed that the ageing indicator is stable under the oxygen and temperature conditions of open-breathing transformers. The presence of methanol was detected in 94% of oil samples collected from over than 900 in-service pieces of equipment, confirming the potential for this application. Lastly, the tests have shown that oiloxidation by-products and TU-nitrogenous agents modify the methanol partitioning coefficients in the paper/oil/air system, which makes their study essential over a range of field conditions encountered by power transformers. Results are presented and discussed in comparison with 2-furfuraldehyde, which is the current reference in the domain.

The paper is a concise digest of works presented during the XIth Symposium
on Laser Technology (SLT 2016) [1]. The Symposium is organized
since 1984 every three years [2–8]. SLT 2016 was organized by
the Institute of Optoelectronics, Military University of Technology (IOE
WAT) [9], Warsaw, in cooperation with Warsaw University of Technology
(WUT) [10], Warsaw University [11], and Wrocław University of
Technology [12] in Jastarnia on 27-30 September 2016. Symposium
is a representative portrait of the laser technology research in Poland.
Symposium Proceedings are traditionally published by SPIE [13–21].
The meeting has gathered around 150 participants who presented around
120 research and technical papers. The Symposium, organized
every 3 years, is a reliable image of laser technology and laser applications
development in Poland at university laboratories, governmental
institutes, company R&D laboratories, etc. The SLT also presents the
current technical projects under realization by the national research,
development and industrial teams. The works of the Symposium, traditionally
are divided in two large areas – sources and applications.
The main topics of SLT were: laser sources in near and medium infrared,
picosecond and femtosecond lasers, optical fiber lasers and
amplifiers, semiconductor lasers, high power and high energy lasers
and their applications, new materials and components for laser technology,
applications of laser technology in mea surements, metrology and
science, military applications of laser technology, laser applications in
environment protection and remote detection of trace substances, laser
applications in medicine and biomedical engineering, laser applications
in industry, technologies and material engineering.

The aim of this paper is to demonstrate that atomistic simulations can be used to evaluate the structure of mineral surfaces and to provide reliable data for forsterite surfaces up to a plane index of 2 using the code METADISE. The methods used to calculate the surface structure and energy which have more commonly been used to study ceramics are briefly explained as is a comparison with experimental data, most notable the crystal morphology. The predicted morphologies show that all the methods (Donnay-Harker, Attachment energies and equilibrium) show most of the surfaces that are expressed in observed crystals. The equilibrium morphology calculated from the relaxed surface energies is the only method which expresses the {201} surfaces and the {101} surfaces, which appear only upon relaxation. The more stable surfaces are shown to be those which have the highest surface density and more closely resemble close packed structures with highly coordinated surface ions and silicon as far from the surface as possible. The most stable surfaces the {100} which has alternating layers of MgO and SiO 2 terminating with an MgO layer. The structure is similar to the MgO {100} surfaces and has a similar energy (1.28 Jm Ϫ2 compared to 1.20). The second most stable are the {201} which have a stepped surface topology, but is also compact with a relaxed surface energy of 1.56 Jm Ϫ2. The results indicate that atomistic simulation is well suited to the prediction of surface structure and morphology although care must be taken in choosing potentials which model the structure and elastic properties accurately. Surface methodology The basic approach, used within the METADISE program (Watson et al. 1996), is to consider the crystal as a

With the anticipated widespread usage of metal matrix composites (MMCs) in the near future, the machinability of high performance MMCs needs to be understood. This paper reports research results obtained from the grinding of aluminum-based MMCs reinforced with Al 2 O 3 particles using grinding wheels having SiC in a vitri®ed matrix and diamond in a resin-bonded matrix. The issues discussed are surface roughness, grinding force, type and size of the abrasives, grinding conditions, and the consequential sub-surface integrity. The study used grinding speeds of 1100±2200 m/min, a grinding depth of 15 mm for rough grinding and 1 mm for ®ne grinding, and cross-feeds of 3 and 1 mm for rough and ®ne grinding respectively, while maintaining a constant table feed-rate of 20.8 m/min. The surface integrity of the ground surfaces and sub-surfaces were analyzed using a scanning electron microscope (SEM) and a pro®lometer. The surface ®nish values, R a , were scattered in the range 0.15±0.70 mm for the rough-ground samples, whilst a narrower range of 0.20±0.35 mm was achieved for the ®ne-ground samples. Smearing of aluminum on the ground surfaces was seen for rough grinding, but was negligible for ®ne grinding because all the Al 2 O 3 particles of the ground surfaces were clearly visible when observed with the SEM. Grinding using a 3000-grit diamond wheel at depth of cut of 1 mm produced many ductile streaks on the Al 2 O 3 particles. Both the Al 2 O 3 particles and aluminum matrix were removed by micro machining. There were no cracks and defects found on the ground surfaces. There was almost no sub-surface damage, except for a rare cracked particle being found. Rough grinding with a SiC wheel followed by ®ne grinding with a ®ne-grit diamond wheel is recommended for the grinding of alumina/aluminum composites. # 2002 Published by Elsevier Science B.V.

The kinetics of abiotic oxidation in the dark and the kinetics of biological mineralization in soil and in a compost environment of thermally oxidized LDPE were studied. It was demonstrated that different activation energies are obtained for the thermal oxidation, depending on the composition of the materials. Significantly higher levels of biodegradability have been obtained in a soil environment at 23 C compared with the compost environment at 58 C. After two years of mineralization, 91% conversion to carbon dioxide was obtained in the soil test, compared with 43% in the compost test. The differences between fungal, archaeal and bacterial community structures in soil and compost after 607 days of biodegradability assay were mapped out. It was found that the most dominant bacterial and fungal terminal restriction fragments (TRFs) in the compost containing the test material are significantly different from the TRFs in the other environments.

Novel high hydroxyl number and high functionality polyols were developed using thiol-ene reaction of castor oil with mercaptoethanol or mercaptanized castor oil with allyl alcohol (by photochemical reaction) and 2-hydroxyethyl acrylate (by Michael thiol-ene reaction). The polyols had OH numbers of 220-295 mg KOH/g and functionalities close to 6. Cast polyurethane resins were prepared with methylene diphenyl diisocyanate (MDI), dicyclohexylmethane-4,4'diisocyanate (HMDI) and m-xylylene diisocyanate (XDI). XDI gave rubbery to leathery polyurethanes with all three polyols, while MDI and HMDI gave amorphous glasses with good mechanical properties. Rigid polyurethane foams of good properties were made with MDI and three castor oil-based polyols.

Direct foaming of colloidal suspensions is a simple and versatile approach for the fabrication of macroporous ceramic materials. Wet foams produced by this method can be stabilized by longchain surfactants or by colloidal particles. In this work, we investigate the processing of particle-stabilized wet foams into crack-free macroporous ceramics. The processing steps are discussed with particular emphasis on the consolidation and drying process of wet foams. Macroporous alumina ceramics prepared using different consolidation and drying methods are compared in terms of their final microstructure, porosity, and compressive strength. Consolidation of the wet foam by particle coagulation before drying resulted in porous alumina with a closed-cell structure, a porosity of 86.5%, an average cell size of 35 lm, and a remarkable compressive strength of 16.3 MPa. On the other hand, wet foams consolidated via gelation of the liquid within the foam lamella led to porous structures with interconnected cells in the size range from 100 to 150 lm. The tailored microstructure and high mechanical strength of the macroporous ceramics can be of interest for the manufacture of bio-scaffolds, thermal insulators, impact absorbers, separation membranes, and light weight ceramics.

The structure and thermodynamic properties of atactic and isotactic acrylic and methacrylic polymers containing 16-18 carbon atoms in the n-aliphatic side chains, and of ccpolymers of hexadecyl acrylate with isopropyl acrylate were studied by means of x-ray and differential thermal analysis. The crystallization of branched acrylic and methacrylic polymers and of acrylic copolymers proceeds in the form of a hexagonal crystal, regardless of the configuration of the backbone chain. Methods of ordering branched macromolecules are proposed, and the melting points, heats and entropies of fusion determined. The role of flexibility of the backbone chains in ordering and the crystallization processes was determined. I n the case of poly(n-alkyl acrylates) the backbone chain is involved in the crystalline lattice; this is not the case in methacrylates and copolymers of hexadecyl acrylate with isopropyl acrylate. Some similarity war assumed between the structure of biopolymers and synt.hetic branched polymers.

Nanotechnology has made great strides forward in the creation of new surfaces, new materials and new forms which also find application in the biomedical field. Traditional biomedical applications started benefiting from the use nanotechnology in an array of areas, such as biosensors, tissue engineering, controlled release systems, intelligent systems and nanocomposites used in implant design. In this manuscript a review of developments in these areas will be provided along with some applications from our laboratories.

Plasma-substrate interactions in diamond synthesis via microwave plasma-assisted chemical vapor deposition (CVD) are an important issue in CVD reactor optimization. The hot spot formation observed during single-crystal diamond synthesis in 2.45-GHz cylindrical cavity reactors is examined after long-run deposition.

This article models bubble removal in centrifugal casting of the thermosetting silicone polydimethylsiloxane (PDMS). Given spin speeds, mold geometry, and resin properties for centrifugal casting, it is possible to predict the amount of spin time required to produce bubble-free parts. For the particular conditions and materials considered in this work, required spin times range from seconds to minutes. The model itself balances two complementary physical behaviors: bubble dissolution and buoyancy. Diffusion dominates the removal of small bubbles below a critical size, while buoyancy dominates the removal of bubbles above a critical size. To simulate the removal of bubbles from a spinning solution, two first-order nonlinear differential equations are solved numerically. To verify simulated results, designed sets of experiments related the number of remaining bubbles in cured parts to spin times and speeds. Dow Corning Sylgard 184, Sylgard 186, and 3-6121 were the silicones tested in this work. POLYM. ENG. SCI.,

A first principles-based model has been developed to simulate the capacity fade of Li-ion batteries. Incorporation of a continuous occurrence of the solvent reduction reaction during constant current and constant voltage ͑CC-CV͒ charging explains the capacity fade of the battery. The effect of parameters such as end of charge voltage and depth of discharge, the film resistance, the exchange current density, and the over voltage of the parasitic reaction on the capacity fade and battery performance were studied qualitatively. The parameters that were updated for every cycle as a result of the side reaction were state-of-charge of the electrode materials and the film resistance, both estimated at the end of CC-CV charging. The effect of rate of solvent reduction reaction and the conductivity of the film formed were also studied.

We present an electrode arrangement for the inline measurement of the conductivity of droplets in segmented flow by impedance spectroscopy. We use a thin-walled glass capillary with electrodes contacting the outer surface, so that the contactless measurement of conductivity of the liquid within the capillary is possible. The surface of the glass capillary is silanized resulting in a single hydrophobic surface across which droplets can freely move. We model the impedance of such insulated electrodes and use the model to optimize the electrode system. Measurement of solutions with various salt concentrations allows the performance of the electrode structure to be characterized. Subsequently, the measurement of the impedance response of the aqueous segments in two-phase flow was demonstrated. Measurements were firstly performed with an impedance analyzer and subsequently with a multi-sine measurement setup that is better suited to high-speed measurement of droplets. Previous electrical measurements of segmented flow sensed the difference in dielectric constant between the aqueous phase and the carrier fluid through measurement of capacitance. This work describes an electrical measurement of the conductivity of droplets in segmented flow, that is, the sensor senses a variable property of the droplet itself.

A large number of products, both natural and synthetic, have been and are used for the consolidation of flaking or fragile paint layers occurring on paintings, polychrome sculpture, furniture and other cultural objects. Most products in use, which include natural as well as synthetic materials, remain untested. Most synthetic materials used for consolidation of paint layers consist of a solution or dispersion of a single polymeric component, and may not have the proper physical and mechanical properties, as well they have not been formulated using knowledge and expertise from the field of adhesion science. The only material that has been specifically formulated as an adhesive for the conservation field is BEVA® 371, which contains several components. It was designed as a hot-melt adhesive for the lining of canvas paintings in the early 1970s, but has since then become a popular adhesive for paint layers in need of consolidation. Its stability, an important parameter for this application, was however never fully investigated. This paper investigates the photo-chemical stability of BEVA® 371 as a whole, and each of its components independently using Fourier transform infrared spectroscopy, size exclusion chromatography and solubility tests.

A new colloidal route leading to the production of B99% dense 3-mol% yttria-stabilized zirconia nanostructured ceramics, while retaining a final average grain size of B75 nm, has been developed. The process was based on the production of stable, homogeneous nanosuspensions with solids contents of up to 28 vol% (70 wt%), but viscosities o0.05 Pa . s at any shear rate in the range of study were obtained. The suspensions were formed by the concentration and optimization of precursor, dilute (5.0 vol%) commercial nanosuspensions, the approach requiring a change of pH, from the 2.4 of the as-received suspension to 11.5, and the use of an appropriate anionic dispersant. Exposure of the nanosuspensions to ultrasound also helped to reduce the viscosity further, although it only worked when the dispersant was optimized. The nanosuspension was slip cast to form homogenous green bodies with densities of B55% of the theoretical without agglomeration in the nanostructure; these were subsequently densified using a two-step sintering technique.

Nanocomposite films based on poly(lactic acid)-poly(hydroxybutyrate) (PLA-PHB) blends and synthesized cellulose nanocrystals (CNC) or surfactant modified cellulose nanocrystals (CNCs), as bio-based reinforcement, were prepared by melt extrusion followed by film forming. The obtained nanocomposites are intended for short-term food packaging. Thus, the mechanical, optical, barrier and wettability properties were studied. Functionalized CNCs contribute to enhance the interfacial adhesion between PLA and PHB, leading to improved mechanical stiffness and increased film stretchability. The synergic effects of the PHB and CNCs on the PLA barrier properties were confirmed by increases in oxygen barrier properties and reductions in surface wettability of the nanocomposites. In addition, the measurements of the viscosity molecular weight for ternary systems showed practically no degradation of PLA and smaller degradation of PHB during processing due to nanocrystal presence. The disintegration process in composting conditions of PLA was delayed by the addition of PHB, while CNC speeded it up. PLA-PHB-CNCs formulations showed enhanced mechanical performance, improved water resistance, reduced oxygen and UV-light transmission, as well as appropriate disintegration in compost suggesting possible applications as packaging materials.

It is the objective of this article to investigate the influence of surface preparation on the cold roll bonding (CRB) process. In this context, the effects of surface preparation parameters consisting of surface preparation method, surface roughness, scratch-brushing parameters, and the delay time between surface preparation and rolling are investigated on the bond strength of aluminum strips. The bond strength of two adjacent aluminum strips produced by the CRB process is evaluated by the peeling test. Furthermore, the interface region is investigated by metallographic observations. Our findings indicate that higher surface roughness values and shorter delay times improve the bond strength. It is also found that degreasing followed by scratch-brushing yield the best bonding properties.

Fermilab is developing and investigating different high-field magnet designs for present and future accelerators. The magnet R&D program was focused on the 10-12 T accelerator magnets based on Nb 3 Sn superconductor and explored both basic magnet technologies for brittle superconductors-wind-and-react and react-and-wind. Magnet design studies in support of LHC upgrades and VLHC are being performed. A series of 1-m long single-bore models of cos-theta Nb 3 Sn dipoles based on wind-andreact technique was fabricated and tested. Three 1-m long flat racetracks and the common coil dipole model, based on a singlelayer coil and wide reacted Nb 3 Sn cable, have also been fabricated and tested. Extensive theoretical studies of magnetic instabilities in Nb3Sn strands, cable and magnet were performed which led to successful 10 T dipole model. This paper presents the details of the Fermilab's high field accelerator magnet program, reports its status and major results, and formulates the program next steps.

To prepare miscible polyethylene glycol diacrylate/polyvinylidene fluoride ͑PEGDA/PVdF͒ blend gel polymer electrolytes, low molecular weight (M ϭ 742) liquid PEGDA oligomer was mixed with PVdF-HFP dissolved in ethylene carbonate/dimethyl carbonate/LiPF 6 liquid electrolytes, and then cured under ultraviolet irradiation. Room temperature conductivity of PEGDA/PVdF blend films was found to be comparable to that of PVdF-HFP gel polymer electrolytes, and they were electrochemically stable up to 4.6 V vs. Li/Li ϩ. Scanning electron micrographs revealed that PEGDA/PVdF blend electrolytes have pore size intermediate between dense PEGDA and highly porous PVdF-HFP. It was confirmed by weight change measurement that liquid electrolyte was likely to evaporate through large pores in PVdF-HFP at 80°C, while PEGDA/PVdF blend showed better liquid electrolyte retention ability. This result was in good agreement with more stable interfacial properties of PEGDA/PVdF blend at 80°C in ac impedance analysis. Consequently, both PVdF-HFP and PEGDA/PVdF gel polymer electrolytes delivered similar discharge capacity at room temperature, but PEGDA/PVdF blend gel polymer electrolyte showed much better cycle performance than pure PVdF-HFP at 80°C.

Standard fused filament fabrication (FFF)-based 3-D printers fabricate parts from thermopolymers, such as polylactic acid (PLA). A new range of metal based PLA composites are available providing a novel range of potential engineering materials for such 3-D printers. Currently, limited material data, specifically thermal property characterization is available on these composites. As a result, the application of these materials into functional engineered systems is not possible. This study aims to fill the knowledge gap by quantifying the thermal properties of copperFill, bronzeFill, magnetic iron PLA, and stainless steel PLA composites and provide insight into the technical considerations of FFF composite 3-D printing. Specifically, in this study the correlation of the composite microstructure and printing parameters are explored and the results of thermal conductivity analysis as a function of printed matrix properties are provided. Considering the relative deviation from the filament raw bulk analysis, the results show the printing operation significantly impacts the resultant component density. Experimentally collected thermal conductivity values, however, do not correlate to the theoretical models in the literature and more rigorous quantitative exercises are required to determine true percent porosity to accurately model the effect of air pore volume fraction on thermal conductivity. Despite this limitation, the thermal conductivity values provided can be used to engineer thermal conductivity into 3-D printed parts with these PLA-based composites. Finally, several high-value applications of such 3-D printed materials that look metallic, but have low thermal conductivity are reviewed.

Timber from eucalyptus and pines trees used in contact with the ground requires preservative treatment to prolong their useful life under natural condition. To obtain resistant timber fence posts to xylophagous attack, this research aimed to evaluate the preservative treatment with CCB applied in Eucalyptus dunnii Maiden and Pinus taeda L woods by sap substitution method. We found that Eucalyptus and pine treated posts had equilibrium moisture content of 17.33% ± 0.51 and 17.02% ± 0.27, respectively. The equilibrium moisture content was 10% higher for eucalyptus and 5 % higher for pine than that for untreated fence post. The mean basic density was 438 kg/m³ ± 21 and 395 kg/m³ ± 23 respectively, and the porosity of both woods was about 59%. Eucalyptus and pine wood presented high porosity and low density, which may promote a good impregnation of CCB preservative. The mean active ingredients of treated fence posts were 6.18 kg i.a/m 3 ± 0.41 for eucalyptus and 5.88 kg i.a/m 3 ± 0.73 for pine. Finally, the treated fence posts had a low cost. The average cost of treatment for eucalyptus and pine was US$ 1.55 per meter ± 0.14 and US$ 1.63 per meter ± 0.07, respectively. This price can be even lower if the owners had the wood in their properties. In conclusion, the treatment reached the minimum requirement of 5 kg of active ingredient per cubic meter of treated timber with a low cost, being the fence post apt to be used directly in contact with the ground.

The corrosion resistance of anodized Al 6061 produced by two different anodizing and sealing processes was evaluated using electrochemical impedance spectroscopy (EIS). The scanning electron microscope (SEM) was employed to determine the surface structure and the thickness of the anodized layers. The EIS data revealed that there was very little change of the properties of the anodized layers for samples that were hard anodized in a mixed acid solution and sealed in hot water over a 365 day exposure period in a 3.5 wt% NaCl solution. The specific admittance A s and the breakpoint frequency f b remained constant with exposure time confirming that the hard anodizing process used in this study was very effective in providing excellent corrosion resistance of anodized Al 6061 over extended exposure periods. Some minor degradation of the protective properties of the anodized layers was observed for samples that were hard anodized in H 2 SO 4 and exposed to the NaCl solution for 14 days.

Effect of Porosity on the Capacity Fade of a Lithium-Ion Battery. [Journal of The Electrochemical Society 151, A1104 (2004)]. Godfrey Sikha, Branko N. Popov, Ralph E. White. Abstract. ... In this model these values are measured from a commercial Sony US 18650 cell. ...

The photochemical and thermal behaviour of bisphenol-A polycarbonate (PC) and trimethylcyclohexane-polycarbonate (TMC-PC) have been compared. The ageing of films, irradiated at short (l=254 nm) and long (l > 300 nm) wavelengths in the absence and in the presence of oxygen or thermo-oxidised at 170 C, has been analysed by different spectroscopic and chromatographic methods. A dual photochemistry is shown to account for the photodegradation of TMC-PC, as previously reported for PC. Under excitation at the shortest wavelengths, the mechanism involves photo-Fries rearrangements of the aromatic carbonate units and a photo-induced oxidation of the aliphatic moieties. Under excitation at 254 nm, the second photo-Fries rearrangement is lowered in TMC-PC at the expense of the formation of yellowing structures. Moreover, under short and long wavelengths exposures, the rate of photo-oxidation of TMC-PC was observed to be higher than that of PC. Such effects have been attributed to a reduced mobility of the macromolecules and to a steric effect due to the trimethylcyclohexylidene structure that contains tertiary carbon atoms. Experimental results confirmed that, regarding oxidation which initially involves hydrogen abstraction, tertiary and secondary sites of TMC-PC are more oxidisable than the primary aliphatic ones contained in PC. #

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing filament. The device design takes advantage of both the open source hardware methodology and the paradigm developed by the open source self-replicating rapid prototyper (RepRap) 3-D printer community. Specifically, this paper describes the design, fabrication and operation of a RepRapable Recyclebot, which refers to the Recyclebot's ability to provide the filament needed to largely replicate the parts for the Recyclebot on any type of RepRap 3-D printer. The device costs less than $700 in mate rials and can be fabricated in about 24 h. Filament is produced at 0.4 kg/h using 0.24 kWh/kg with a diameter ±4.6%. Thus, filament can be manufactured from commercial pellets for <22% of commercial filament costs. In addition, it can fabricate recycled waste plastic into filament for 2.5 cents/kg, which is <1000X commercial filament costs. The system can fabricate filament from polymers with extrusion temperatures <250 °C and is thus capable of manufacturing custom filament over a wide range of thermopolymers and composites for material science studies of new materials and recyclability studies, as well as research on novel applications of fused filament based 3-D printing.

Reconocer, identificar y conocer las propiedades de los materiales es muy importante en el campo de la ingeniería, ya que son ellos los que aportan las características de resistencia y estabilidad de lo que se va a diseñar. Si no se tuviese en cuenta las características de los materiales en los diseños y simplemente se construyera, existiría una amplia posibilidad de que fallaran las estructuras y/u objetos.

A series of highly cross-linked polysiloxane was synthesised via hydrosilylation and condensation reaction. Structural identification using Fourier Transform Infrared (FTIR) and 1 H-NMR confirmed their chemical structures. Their thermal and, mechanical properties, and crystallinity, were analysed and related to the level of cross-link density. These systems displayed elevated thermal and hardness properties at an increased cross-link density. Furthermore, the level of crystallinity was reduced as displayed by XRD analysis. Along with this observation, the calculated fractional free volume (FFV) showed a decreasing trend leading to the 'densification' effect. It was envisaged that the linear polysiloxane chain segments aligned parallel to each other in a triclinic crystal system to generate a crystalline domain. The spacing between these stacking chains was found to be about 7.2 Å as measured from simulated XRD pattern.

Solder paste is used for reflow soldering of Surface Mount Devices (SMDs). In this paper we discuss how the various stages of the stencil printing cycle affect the rheological properties of the solder paste. First the heat generated in the paste roll is examined to see what effect it has on solder paste rheology, then we analyse in detail the process of paste withdrawal from a metal mask stencil and discuss those properties of solder paste that lead to a good print in terms of the size and shape of the solder paste particles, and their packing. In order to do this, we review some of the experiments and phenomena that have been shown to occur in dense suspensions, and see what aspects of that work are applicable to solder paste printing.

The effect of polyaniline (PANI) nanofibers content on the electrochemical properties of composites based on SnO 2 nanoflakes was studied. PANI nanofibers and SnO 2 nanoflakes were synthesized and characterized (SEM, BET, FTIR, XPS, and XRD) and mixed in solution at different proportions. The resulting composites were characterized electrochemically (CV, EIS, and GCD) to determine their specific capacitance, electric resistance, and cyclic stability to be used as electrochemical capacitor electrodes (ECs). It was found that the SnO 2 -PANI-(80/20) composite at 5 mVs −1 exhibited higher specific capacitance (C AS  = 1.1 Fg −1 ) than SnO 2 (C AS  = 0.99 Fg −1 ); meanwhile, SnO 2 -PANI-(95/5) at 100 mVs −1 exhibited higher capacitance (C AS  = 0.66 Fg −1 ) than PANI (C AS  = 0.42 Fg −1 ). The GCD results indicate that SnO 2 , PANI, and their composites presented coulombic efficiencies higher than 90% after 5000 cycles. Also, the highest initial capacitance (C = 0.4 Fg −1 , at 2 mAcm −2 ) was found for SnO 2 -PANI-(80/20), and the highest final capacitance (C = 0.28 Fg −1 , 5000 cycles at 2 mAcm −2 ) was for SnO 2 -PANI-(95/5). Finally, PEIS behavior was studied, and the equivalent circuits were proposed, resulting that the contact resistance to charge transfer (R CT ) of composites (R CT  = 1.61–2.28 Ω) were lower than precursors (SnO 2 , R CT  = 3.66 Ω; PANI, R CT  = 4.47 Ω). In addition, it was observed that the capacitance of composites increased, and resistance to charge transfer decreased with the PANI content. Electrode material presents a synergetic effect promoted by the appropriate mixing in solution along with the nanoscale morphologies of the components showing improved specific capacitance, and low both contact and charge transfer resistances, with high coulombic efficiencies (&gt; 90% after 5 k cycles).

Green and Sustainable Software has emerged as a new and highly active area in the software community. After several years of research and work, we believe that it is now necessary to obtain a general snapshot of how the research in this area is evolving. To do so, we have applied the 5Ws (why, when, who, where, and what), a formula for getting the complete story on a subject. We have therefore carried out a study, using 542 publications related to Green and Sustainable Software research; these were recovered using SCOPUS. The results obtained allow us to conclude that it is important to identify key elements of the research to allow researchers be fully aware of the state of the research on Green and Sustainable Software (why); the study uses papers published between 2000 and the beginning of November 2018 (when); the most prolific authors are mainly from Europe, although the USA is the most active country, Green and Sustainable Software being a very interactive area with a good number of multinational publications (who); the top five keywords related to sustainable aspects are Green Software, Green IT, Software Sustainability, Energy Consumption, and Energy Efficiency (what); finally, as regards the places authors prefer to publish in, there is almost a complete balance between conferences and journals, with a trend towards an increase in the number of publications (where).

Materials with the olivine LixMPO4 structure form an important new class of materials for rechargeable Li batteries. There is significant interest in their electronic properties because of the importance of electronic conductivity in batteries for high rate applications. The density of states of LixMPO4 (x = 0, 1 and M = Fe, Mn) has been determined with the ab initio GGA+U method, appropriate for these correlated electron systems. Computed results are compared with the optical gap of LiFePO4, as measured using UV-Vis-NIR diffuse reflectance spectroscopy. The results obtained from experiment (3.8-4.0 eV) and GGA+U computations (3.7 eV) are in very good agreement. However, standard GGA, without the same level of treatment of electron correlation, is shown to make large errors in predicting the electronic structure. It is argued that olivines are likely to be polaronic conductors with extrinsically determined carrier levels and that their electronic conductivity is therefore not simply related to the band gap.

We tested the detection properties of four MOX sensors toward different ozone mixtures to identify sets of sensing layers and interfering compounds concentrations most suitable for a reliable detection of ozone. The measurement campaign lasted 1 year divided in four sessions. We collected a substantial amount of measurements (more than 500) with diverse interfering gases: ammonia, ethanol, ethylene, carbon monoxide and humidity. Due to the dimension of the data set it could not be analyzed using the conventional methods generally applied for characterizing gas sensors: evaluating the sensor performance by visual inspection of the sensors responses is unfeasible. For this reason we systematically applied the exploratory data analysis methodology. We used some simple but effective statistical techniques to insight the data. This approach allows us to draw sound conclusions about the causes of variation in the data, e.g. time (sensors' long-term stability) or interfering effects of different chemical compounds. All the analysis techniques employed in this work are implemented in a software package developed at our laboratory.

This paper aims to predict the hand values (HVs) and total hand values (THVs) of functional fabrics by applying the fuzzy logic model (FLM) and artificial neural network (ANN) model. Functional fabrics were evaluated by trained panels employing subjective evaluation scenarios. Firstly, the FLM was applied to predict the HV from finishing parameters; then, the FLM and ANN model were applied to predict the THV from the HV. The estimation of the FLM on the HV was efficient, as demonstrated by the root mean square error (RMSE) and relative mean percentage error (RMPE); low values were recorded, except those bipolar descriptors whose values are within the lowermost extreme values on the fuzzy model. However, the prediction performance of the FLM and ANN model on THV was effective, where RMSE values of ∼0.21 and ∼0.13 were obtained, respectively; both values were within the variations of the experiment. The RMPE values for both models were less than 10%, indicating that both models are ro...

The application of polymer nanocomposites packaging materials in industrial, food and agricultural products is a superior alternative to traditional packaging materials such as glass, paper, and metals due to their functionalization, flexibility, and minimal cost. However, usage of these materials has been hindered due to their inferior mechanical and barrier behaviors, which are susceptible to improvement through inclusion of functionalized reinforcing macro-or nanofillers. Furthermore, most reinforced materials exhibit inferior matrix-filler interfacial interactions, which are enhanced with reducing filler dimensions. Hence, this review elucidates functionalization of composites interfacial interaction and its relationship to enhancement of the properties of packaging materials, especially antimicrobial tendencies, enzyme immobilization behavior, biosensing affinity, and so on. Thus, a fundamental understanding of interfacial structure and its relationship to the overall improvement of properties are presented. Therefore, nanomaterials, such as cellulose, nanoclay, halloysite nanotubes, carbon allotropes (graphene and carbon nanotubes), silica, and so on, are discussed relative to their surface treatment approaches and effects on composites films properties for effective packaging. Recently, emerging innovations in nanostructured polymeric composite materials and electrical-sensors, their current applications and future outlook as food, agricultural and industrial packaging materials are also herewith elucidated.

Depth sensing indentation is a powerful experimental technique for determining mechanical properties of materials. In this work a computational routine was developed based on Oliver-Pharr method for measuring a more precise values of elastic modulus using a Fischerscope H100-depth sensing indentation apparatus, with a Vickers indenter. This computational routine aims also to measure Vickers hardness, as the equipment does not have software for this purpose. From indentation data it was possible to determine initial unloading stiffness, contact depth, projected contact area, reduced modulus, elastic modulus and Vickers hardness of materials. The validity of the routine was verified analyzing two coatings and nine bulk specimens with different elastic-plastic behaviors. It was verified that the elastic moduli determined through the software of the equipment resulted in great discrepancies when low loads were applied. A good estimate of the elastic moduli of the tested materials is given by the developed routine. For several testing loads, the diagonals determined by means of analytical procedure were compared with the same diagonals measured by image analysis. A good estimate of the Vickers hardness of the above-mentioned materials is given by the developed routine using different testing loads.

A 44-pass fiber optic surface plasmon resonance (SPR) sensor coupled with a field-assist capability for measurement of refractive index change due to positive and negative ions is shown. The field-assist feature forces ions to the SPR surface, causing the SPR signal response to change which reflects a decrease or increase in refractive index depending on whether positive or negative ions are being attracted to the surface. This technique offers the potential for the sensitive detection of cations and anions in a solution.