Home About us Contact
|
Home About us Contact | ||
|
|
||
Excellent Mechanical Properties (excellent + mechanical_property)
Selected AbstractsNano-Scale Design of TiAl Alloys Based on ,-Phase Decomposition,ADVANCED ENGINEERING MATERIALS, Issue 5 2006F. Appel Abstract Phase decomposition and ordering reactions in ,/B2-phase containing TiAl alloys were utilized to establish a novel, previously unreported, type of laminate microstructure. The characteristic constituent of this microstructure are laths with a nanometer-scale substructure that are comprised of several stable and metastable phases. Microstructural control can be achieved by conventional thermomechanical processing and leads to a structurally and chemically very homogeneous material with excellent mechanical properties. The physical metallurgy of this novel type of alloy has been assessed by transmission electron microscope investigations and mechanical testing. [source] Hard Macrocellular Silica Si(HIPE) Foams Templating Micro/Macroporous Carbonaceous Monoliths: Applications as Lithium Ion Battery Negative Electrodes and Electrochemical CapacitorsADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Nicolas Brun Abstract By using Si(HIPEs) as hard, exotemplating matrices, interconnected macro-/microporous carbon monolith-type materials with a surface area of around 600,m2 g,1 are synthesized and shaped. The carbonaceous foams exhibit a conductivity of 20,S cm,1, addressed with excellent mechanical properties (Young's modulus of 0.2,GPa and toughness of 13,J g,1, when the carbon core is optimized). The above-mentioned specificities, combined with the fact that the external shape and size can be easily designed on demand, are of primary importance for applications. The functionality of these carbonaceous monoliths is tested as both an electrochemical capacitor and a lithium ion negative electrode. The electrochemical capacitors' voltage,current profiles exhibit a non-ideal rectangular response, confirming the double-layer behavior of the carbon studied, while the charge-discharge current profile of the electric double-layer capacitor is directly proportional to the scan where the current response during charge and discharge exhibits high reversibility. When acting as a lithium ion negative electrode, after initial irreversibility, a good cyclability is obtained, associated with a stable capacity of 200,mA h g,1 during the first 50 cycles at a reasonable current density (C/10). [source] Energy-Absorbing Hybrid Composites Based on Alternate Carbon-Nanotube and Inorganic LayersADVANCED MATERIALS, Issue 28 2009Qiang Zhang Hybrid materials with aligned carbon nanotubes intercalating naturally layered compounds (see upper figures) are fabricated using general metal-ion intercalation and in situ growth. As indicated by SEM images (lower figures), they exhibit periodic and hierarchical structures. The ability to control their composition resulted in some samples possessing excellent mechanical properties, such as high energy absorption during compression. [source] Preparation and investigation of ethylene,vinyl acetate copolymer/silicone rubber/clay nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009Shoulin Fang Abstract In this article, the combination of silicone rubber (SR) elastomer with synthetic iron montmorillonite (Fe-MMT) to form a kind of new flame-retardant system based on an ethylene,vinyl acetate (EVA) copolymer is first reported. Also, the flame retardancy of the EVA/SR/Fe-MMT hybrid are compared with that of EVA/SR/natural sodium montmorillonite. The structures of the nanocomposites were characterized with X-ray diffraction and transmission electron microscopy. Cone calorimeter tests and thermogravimetric analysis were used to evaluate the flame-retardant properties and thermal stability of the composites, respectively. In addition, tensile tests were carried out with a universal testing machine, and the morphology of the fracture surface was observed with environmental scanning electron microscopy. We found that SR/organophilic montmorillonite (Fe-OMT) was more effective in reducing the primary peak heat release rate of the nanocomposite, and the EVA/SR/Fe-OMT hybrid had a higher thermal stability in the deacetylated polymer than EVA/SR/sodium organophilic montmorillonite. Moreover, the exfoliated EVA/SR/Fe-OMT nanocomposite displayed excellent mechanical properties because of a better dispersion of Fe-OMT in the polymer matrix, and a possible mechanism is discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Preparation and tribological properties of polyetheretherketone compositesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2010Dangsheng Xiong Abstract Polyetheretherketone (PEEK) is a thermoplastic engineering plastic with excellent mechanical properties. In this article, PEEK and its composites filled with ultrahigh-molecular-weight polyethylene (UHMWPE) were prepared by vacuum hot-pressing method. Tribological properties of these materials were investigated by block-on-ring friction and wear rig. An alloy (CoCrMo) ring and a ceramic (Si3N4) ring were used as friction pairs. The experiments were conducted under deionized water lubrication (DWL), saline lubrication (SL), and calf serum solution lubrication (CSSL). Worn surfaces morphology was observed and analyzed by metallographic microscope. The results indicated that friction coefficients of PEEK/UHMWPE composites were effectively reduced when compared with pure PEEK. When the materials slid against the alloy (CoCrMo) ring, wear rates of PEEK/UHMWPE were also effectively reduced when compared with pure PEEK. Wear mechanisms of PEEK were mainly ploughing and slight scratches under CSSL condition, whereas the quantity of the ploughing and scratches for PEEK/20%UHMWPE were significantly reduced. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [source] Synthesis and properties of amine-containing poly(arylene ether sulfone) as an anion-exchange matrixJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002Won-Keun Son Abstract Poly(arylene ether sulfone) (PSF), showing good thermal stability and excellent mechanical properties, was synthesized as an anion-exchange matrix. It was synthesized by the condensation polymerization between bisphenol A and 4,4,-dichlorodiphenylsulfone. 1°-Amine-containing poly(arylene ether sulfone) (1°-APSF) was synthesized by the reduction reaction of a nitrated PSF. Then, it was transferred to 3°-amine-containing poly(arylene ether sulfone) (3°-APSF) by the alkylation of the amine of 1°-APSF. The properties of PSF, 1°-APSF, and 3°-APSF were investigated by Fourier transform infrared, 1H NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The introduction of the 3°-amine group into PSF increased the glass-transition temperature but decreased thermooxidative stability. The ion-exchange capacities of 1°-APSF and 3°-APSF were shown to be 2.24 and 2.86 mequiv/g, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4281,4287, 2002 [source] Effect of CaF2 and CaO Substituted for MgO on the Phase Evolution and Mechanical Properties of K-Fluorrichterite Glass CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2006Mehdi Mirsaneh Chain silicate glass ceramics based on K-fluorrichterite (KNaCaMg5Si8O22F2, KFR) have potential for use in restorative dentistry and biomedical applications because they may be cast to shape and, when cerammed, have high biaxial flexural strength and fracture toughness. Excess CaO in canasite-based chain silicate compositions is known to enhance their bioactivity. Therefore, two new glass ceramic compositions have been fabricated with 5 mol% CaF2 (Glass A) and 5 mol% CaO (Glass B) substituted for MgO in the KFR formula unit. The phase evolution of Glasses A and B was studied in detail using X-ray diffraction and transmission electron microscopy. In addition, their mechanical properties were assessed. For Glass A, the fracture toughness (FT=2.66±0.02 MPa·m1/2) and biaxial flexural strength (BFS=227.3±24.5 MPa) were optimized for samples heat treated at 900°C for 4 h. In Glass B, however, the best FT (2.08±0.02 MPa·m1/2) and BFS (217.4±4.4 MPa) were obtained at 950°C. In view of their excellent mechanical properties and castability, Glasses A and B are considered potential candidates for fabrication of custom medical devices in restorative dentistry and moderate load-bearing reconstructive bone surgery. [source] Experimental Design Applied to Silicon Carbide SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2003Juliana Marchi Silicon carbide is a promising structural ceramic used as abrasives and applied in metallurgical components, due to its low density, high hardness, and excellent mechanical properties. The composition and content of the additive can control liquid-phase sintering of SiC. Compositions based on the SiO2,Al2O3,RE2O3 system (RE = rare earth) have been largely used to promote silicon carbide densification, but most studies are not systematically presented. The aim of this work is to study the effect of several oxide additives in the SiO2,Al2O3,Y2O3 system on the densification of silicon carbide using experimental design. This technique seems to be effective in optimizing the values of maximum density with minimum weight loss. [source] Synthesis and Properties of Novel Fluorinated Poly(phenylene- co -imide)sMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 3 2007Wenmu Li Abstract A new class of high-performance materials, fluorinated poly(phenylene- co -imide)s, were prepared by Ni(0)-catalytic coupling of 2,5-dichlorobenzophenone with fluorinated dichlorophthalimide. The synthesized copolymers have high molecular weights (,=,5.74,×,104,17.3,×,104 g,·,mol,1), and a combination of desirable properties such as high solubility in common organic solvent, film-forming ability, and excellent mechanical properties. The glass transition temperature (Tgs) of the copolymers was readily tuned to be between 219 and 354,°C via systematic variation of the ratio of the two comonomers. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 66.7,266 MPa, 2.7,13.5%, and 3.13,4.09 GPa, respectively. The oxygen permeability coefficients () and permeability selectivity of oxygen to nitrogen () of these copolymer membranes were in the range of 0.78,3.01 barrer [1 barrer,=,10,10 cm3 (STP) cm/(cm2,·,s,·,cmHg)] and 5.09,6.25, respectively. Consequently, these materials have shown promise as engineering plastics and gas-separation membrane materials. [source] Novel Thermoplastic Composites from Commodity Polymers and Man-Made Cellulose FibersMACROMOLECULAR SYMPOSIA, Issue 1 2006Hans-Peter Fink Abstract Summary: A new class of fibre reinforced commodity thermoplastics suited for injection moulding and direct processing applications has been developed using man-made cellulosic fibres (Rayon tire yarn, Tencel, Viscose, Carbacell) and thermoplastic commodity polymers, such as polypropylene (PP), polyethylene (PE), high impact polystyrene (HIPS), poly(lactic acid) (PLA), and a thermoplastic elastomer (TPE) as the matrix polymer. For compounding, a specially adapted double pultrusion technique has been employed which provides composites with homogeneously distributed fibres. Extensive investigations were performed with Rayon reinforced PP in view of applications in the automotive industry. The Rayon-PP composite is characterized by high strength and an excellent impact behaviour as compared with glass fibre reinforced PP, thus permitting applications in the field of engineering thermoplastics such as polycarbonate/acrylonitrile butadiene styrene blends (PC/ABS). With the PP based composites the influence of material parameters (e.g. fibre type and load, coupling agent) were studied and it has been demonstrated how to tailor the desired composite properties as modulus and heat distortion temperature (HDT) by varying the fibre type or adding inorganic fillers. Man-made cellulose fibers are also suitable for the reinforcement of further thermoplastic commodity polymers with appropriate processing temperatures. In case of PE modulus and strength are tripled compared to the neat resin while Charpy impact strength is increased five-fold. For HIPS mainly strength and stiffness are increased, while for TPE the property profile is changed completely. With Rayon reinforced PLA, a fully biogenic and biodegradable composite with excellent mechanical properties including highly improved impact strength is presented. [source] Electromechanical Behavior of Nanoscale Silver Coatings on PET FibersPLASMA PROCESSES AND POLYMERS, Issue 9 2008Martin Amberg Abstract Plasma-assisted deposition of silver films on PET mono- and multifilament fibers provides conductive fibers for wearable electronics. The nanoscale films were prepared in a continuously running low pressure plasma process using an ICM design for sputtering from a silver target combined with a prior RF cleaning step. The electrical resistance of the as-deposited layers was measured in situ enabling an immediate feedback of the electrical properties, the film quality, applied Ag mass, and film thickness. The deposited quantity of Ag mass on the PET fibers was investigated by ICP-OES and was correlated with the electrical resistance of the film. The metallized fibers showed excellent mechanical properties for wearable electronics as demonstrated by tensile properties measurement. [source] Improvement of Hardness and Toughness of TiAlN Coating by Nanoscale Multilayered Structurization with Si3N4PLASMA PROCESSES AND POLYMERS, Issue S1 2007Jong-Keuk Park Abstract The Ti(Al)-Si based nitride coating material has been studied due to its excellent mechanical properties such as hardness and oxidation resistance as in the Ti(Al)N/a-Si3N4 nanocomposites with high hardness over 50 GPa. In this study, the effect of microstructure, especially layer thickness of TiAlN and Si3N4 phase, on the mechanical properties of the TiAlN/Si3N4 nanoscale multilayered coating has been investigated. By nanoscale multilayered structurization with a thin Si3N4 layer (,0.3 nm), the hardness and toughness of TiAlN coating were greatly improved. It is known that for the TiAlN/Si3N4 nanoscale multilayered coatings, thickness of the Si3N4 layer is the most important factor and should be carefully controlled to obtain coatings with high hardness and toughness. [source] A new crosslinked protein fiber from gliadin and the effect of crosslinking parameters on its mechanical properties and water stabilityPOLYMER INTERNATIONAL, Issue 10 2008Ying Li Abstract BACKGROUND: Although several cereal proteins have been used to develop fibers and films, it has not been possible to obtain protein materials with good mechanical properties and water stability, even after crosslinking. Previously, high concentrations of glutaraldehyde were used to improve the mechanical properties of protein fibers but the effect of crosslinking conditions on the properties of the crosslinked materials has not been studied in detail. RESULTS: Low concentrations of glutaraldehyde can be used to improve the mechanical properties and water stability of gliadin fibers. Quantitative relationships that can predict the breaking tenacity of the fibers at various crosslinking conditions are developed. Glutaraldehyde crosslinking is more resistant to hydrolysis in neutral pH than under acidic conditions in terms of increasing and retaining the breaking tenacity. The crosslinked fibers show improved resistance to hydrolysis over poly(lactic acid) fibers in aqueous dispersions at pH = 4 and 7 at 50 and 90 °C, respectively. CONCLUSIONS: This study shows that low concentrations of glutaraldehyde can impart excellent mechanical properties to gliadin fibers. The quantitative relationships developed can be used to select the crosslinking conditions such low glutaraldehyde concentration and high temperature or vice versa to obtain the desired improvement in mechanical properties or water stability. Copyright © 2008 Society of Chemical Industry [source] Structure and properties of star-shaped solution-polymerized styrene-butadiene rubber and its co-coagulated rubber filled with silica/carbon black-I: morphological structure and mechanical propertiesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11 2009Xiao Liu Abstract The morphological structure and mechanical properties of the star-shaped solution-polymerized styrene-butadiene rubber (SSBR) and organically modified nanosilica powder/star-shaped SSBR co-coagulated rubber (N-SSBR) both filled with silica/carbon black (CB) were studied. The results showed that, compared with SSBR, silica powder could be mixed into N-SSBR much more rapidly, and N-SSBR/SiO2 nanocomposite had better filler-dispersion and processability. N-SSBR/SiO2/CB vulcanizates displayed higher glass-transition temperature and lower peak value of internal friction loss than SSBR/SiO2/CB vulcanizates. In the N-SSBR/SiO2/CB vulcanizates, filler was dispersed in nano-scale resulting in good mechanical properties. Composites filled with silica/CB doped filler exhibited more excellent mechanical properties than those filled with a single filler because of the better filler-dispersion and stronger interfacial interaction with macromolecular chains. N-SSBR/SiO2/CB vulcanizates exhibited preferable performance in abrasion resistance and higher bound rubber content as the blending ratio of silica to CB was 20:30. Copyright © 2008 John Wiley & Sons, Ltd. [source] Novel Segmented Thermoplastic Polyurethanes Elastomers Based on Tetrahydrofuran Ethylene Oxide Copolyethers as High Energetic Propellant BindersPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 1 2003Fu-Tai Chen Abstract Novel thermoplastic polyurethane (TPU) elastomers based on copolyether (tetrahydrofuran ethylene oxide) as soft segments, isophorone diisocyanate and 1,4-butanediol as hard segments were synthesized for the purpose of using as propellant binders. In order to increase the miscibility of thermoplastic polyurethane elastomers with nitrate ester, polyethylene glycol (PEG) is incorporated in the co-polyether (tetrahydrofuran ethylene oxide) as soft segment. When the molecular weight and content of polyethylene glycol are controlled to 4000 and 6% of soft segments, respectively, the properties of thermoplastic polyurethane elastomers are most perfect. If plasticizing ratio of nitrate ester to thermoplastic polyurethane elastomers exceeds 4 no crystallinities are determined at room temperature. The propellant samples were prepared by a conventional absorption-rolling extrusion process and the mechanical and combustion properties evaluated afterwards. The maximum impulse reaches up to 265,270 s which is a little bit higher than that of a HTPB propellant. The measured results reveal a promising TPE propellant candidate which shows good processing temperature (<393,K) and excellent mechanical properties. An attracting feature which can be pointed out is that the burning rate pressure exponent reaches as low as 0.36 without the addition of burning rate catalysts. This enables an easy control of propellant combustion. [source] Pulsatile Ventricular Assist Device with Pericardial Inner LiningARTIFICIAL ORGANS, Issue 11 2001Adolfo A. Leirner Abstract: Preserved pericardium in contact with blood is not thrombogenic, therefore avoiding the use of anticoagulants, and has excellent mechanical properties. Our objective is to take advantage of these characteristics and build a pulsatile ventricular assist device (VAD) with pericardium used as the inner lining of the blood chamber. A mold is used for the tanning of the pericardium, rendering it with an exact shape. A flexible polymeric structure is designed to serve as a base for the pericardium, guiding it and limiting its rate of strain. It consists of two halves, which when outfitted with the interior pericardium lining and connected to each other, form the blood chamber. This assembly is housed in rigid polyvinyl chloride (PVC) shells making up the air chamber for the pneumatic activation. Valves are likewise made of pericardium. Sealing of the chambers was tested statically up to 300 mm Hg with no air or fluid leakage. The device was tested for 60 continuous days in a mock loop, demonstrating hydrodynamic performance adequate for ventricular assist. Micrographs (confocal laser and scanning electron microscopy) were obtained of several pericardium areas, especially on the flexing regions that are a transition between the wet and dry regions. No sign of damage to the pericardium was observed either with the naked eye or at the microscopic level. From the hydraulic performance and materials viewpoints, a completely pericardium-lined pulsatile VAD displaying a polymeric structure that avoids unpredictable bending and limits strain is feasible. The results warrant further studies regarding biocompatibility and strength advantages. [source] Solid-State NMR Characterization of the Multiphase Structure of Polypropylene In-reactor AlloyMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 10 2010Haijin Zhu Abstract A variety of solid-state NMR techniques were used to characterize the chain dynamics, miscibility and the micro-phase structure of a polypropylene (PP) in-reactor alloy system. The alloy was physically separated into three fractions, and the molecular dynamics and relaxation behavior of the pure fractions was then compared with the components in the alloy to achieve comprehensive understanding of the phase structure of the PP in-reactor alloy. The miscibility among different components of the alloy was studied by the rotational frame spin-lattice relaxation time. Proton spin-diffusion methods were used to quantify the domain thicknesses of different regions in the alloy. The results show that the alloy is composed of three phases, namely, a homo-polyethylene (HPE) matrix, a homo-polypropylene (HPP) dispersed phase, and a linear low-density polyethylene (LLDPE) interphase. The thickness of the LLDPE interphase is estimated to be 7.7,nm at room temperature, and changes dramatically with temperature. Finally, based on all the solid-state NMR results, a model for the micro-phase-structure of the PP in-reactor alloy is proposed, and a correlation between the micro-phase structure and the excellent mechanical property is established. [source] | ||||||||||||||||||||||