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Matrix Material (matrix + material)
Kinds of Matrix Material Selected AbstractsDifferentiation of the epidermis of scutes in embryos and juveniles of the tortoise Testudo hermanni with emphasis on beta-keratinizationACTA ZOOLOGICA, Issue 3 2005L. Alibardi Abstract The sequence of differentiation of the epidermis of scutes during embryogenesis in the tortoise Testudo hermanni was studied using autoradiography, electron microscopy and immunocytochemistry. The study was mainly conducted on the epidermis of the carapace, plastron and nail. Epidermal differentiation resembles that described for other reptiles, and the embryonic epidermis is composed of numerous cell layers. In the early stages of differentiation of the carapacial ridge, cytoplasmic blebs of epidermal cells are in direct contact with the extracellular matrix and mesenchymal cells. The influence of the dermis on the formation of the beta-layer is discussed. The dermis becomes rich in collagen bundles at later stages of development. The embryonic epidermis is formed by a flat periderm and four to six layers of subperidermal cells, storing 40,70-nm-thick coarse filaments that may represent interkeratin or matrix material. Beta-keratin is associated with the coarse filaments, suggesting that the protein may be polymerized on their surface. The presence of beta-keratin in embryonic epidermis suggests that this keratin might have been produced at the beginning of chelonian evolution. The embryonic epidermis of the scutes is lost around hatching and leaves underneath the definitive corneous beta-layer. Beneath the embryonic epidermis, cells that accumulate typical large bundles of beta-keratin appear at stage 23 and at hatching a compact beta-layer is present. The differentiation of these cells shows the progressive replacement of alpha-keratin bundles with bundles immunolabelled for beta-keratin. The nucleus is degraded and electron-dense nuclear material mixes with beta-keratin. In general, changes in tortoise skin when approaching terrestrial life resemble those of other reptiles. Lepidosaurian reptiles form an embryonic shedding layer and crocodilians have a thin embryonic epidermis that is rapidly lost near hacthing. Chelonians have a thicker embryonic epidermis that accumulates beta-keratin, a protein later used to make a thick corneous layer. [source] In Situ Damage Detection With Acoustic Emission Analysis During Cyclic Loading of Wire Reinforced EN AW-6082,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Kay André Weidenmann In the field of lightweight construction, hybrid structures such as reinforced metal matrix composites are highly qualified materials. The direct composite extrusion process allows for continuous manufacturing of wire reinforced aluminum matrix profiles. The aim is to increase the stiffness and specific strength in a way that the composite material shows better mechanical properties than the single matrix material. To determine and locate damage evolution during cyclic loading of spring steel reinforced EN AW-6082 matrix the acoustic emission analysis is used. Furthermore it allows for getting more information about the damage mechanisms during fatigue of the matrix and the final failure of the reinforcing element. The current work also includes the determination of damage evolution using strain measuring methods. [source] Applying SEM-Based X-ray Microtomography to Observe Self-Healing in Solvent Encapsulated Thermoplastic Materials,ADVANCED ENGINEERING MATERIALS, Issue 3 2010Steven D. Mookhoek In this work X-ray microtomography was used to observe fracture and healing processes in a liquid-based self-healing thermoplastic material. The method was able to produce data of sufficient resolution (<10,,m) to observe ,60,,m microcapsules containing solvent within a polymeric material and in particular their behavior around a crack zone after fracture and healing. The reconstructed data showed the distribution of filled and several empty microcapsules within the matrix material. Additional color segmentation and 3D rendering of the data unambiguously demonstrated a large concentration of ruptured microcapsules near the fracture surfaces, covering ,75,,m span on both sides of the crack. A close investigation of the crack area confirmed the presence of healed and non-healed regions. Further analysis of the segmented data allowed a quantitative determination of the release of the encapsulated solvent. [source] Herbivory in an acid streamFRESHWATER BIOLOGY, Issue 4 2000Mark E. Ledger Summary 1Spatial and temporal variation in the distribution and feeding of non-predatory macroinvertebrates was investigated in a first-order, acid stream in the Ashdown Forest, southern England. 2Stonefly (Nemouridae) and chironomid (Orthocladiinae) larvae were abundant on the upper surfaces of mineral substrata of three sizes (small stones, large stones, bedrock). The density of larvae in each taxonomic group did not vary among substrata of different sizes, although strong seasonal variation existed. 3Nemourids and chironomids (H. marcidus) collected from the upper surfaces of substrata exhibited generalist feeding habits, consuming algae (diatoms, coccoid and filamentous green algae), detritus (biofilm matrix material and fine particulate organic matter (FPOM)) and inorganic debris. 4There was spatial variation in the gut contents of nemourids. The proportion of algae in the guts of larvae often increased with the size of the substratum from which they were collected. Strong temporal variation in the composition of the diet also existed. Nemourids ingested a large quantity of attached algae and biofilm matrix from the biofilm in spring and winter, but consumed loose FPOM and associated microflora in summer and autumn. 5We conclude that, in this acid stream, the trophic linkage between algae and grazers is maintained by ,detritivorous' stonefly and chironomid species. The relationship between the feeding habits of these larvae and other life-history attributes, such as mouthpart morphology and mobility, is discussed. [source] Microfluidics: Surface-Treatment-Induced Three-Dimensional Capillary Morphogenesis in a Microfluidic Platform (Adv. Mater.ADVANCED MATERIALS, Issue 47 200947/2009) The cover shows confocal images of 3D sprouting into matrix material in microfluidic channels. Roger Kamm and co-workers report on p. 4863 that robust induction of realistic angiogenesis into the 3D matrix material under simultaneous imaging and a stably controlled concentration gradient of chemoattractants can be achieved. The formation of a 3D vascular network is demonstrated to be a direct consequence of surface treatment of the region of the device-containing matrix material. [source] Surface-Treatment-Induced Three-Dimensional Capillary Morphogenesis in a Microfluidic PlatformADVANCED MATERIALS, Issue 47 2009Seok Chung Robust induction of realistic angiogenesis into a 3D matrix material under simultaneous imaging and a stably controlled concentration gradient of chemoattractants is presented. The formation of a 3D vascular network is demonstrated to be a direct consequence of surface treatment of the region of the device-containing matrix material. [source] Dynamic numerical simulations of void growth and coalescence with stress triaxiality maintained constant,Application to ductile solids with secondary voidsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2008L. Siad Abstract Dynamic explicit finite element analysis is used to investigate void growth and plastic collapse of an axisymmetric unit cell model with a primary spherical void imbedded in a porous matrix material. The Gurson,Tvergaard,Needleman homogenized model is used to describe the plastic behaviour of the matrix material. The simulations are performed under large strain conditions for varying secondary void volume fractions and quasi-static loading controlled by constant stress triaxiality. The proposed accomplishment of constant stress triaxiality associated with dynamic explicit computations provides a method allowing to trace the collapse of the unit cell from the onset of coalescence to practically its final failure. Consistent with experimental and theoretical results available in the literature, the obtained results substantiate the sensitivity of coalescence to the presence of secondary voids. Copyright © 2008 John Wiley & Sons, Ltd. [source] Toughening of basalt fiber-reinforced composites with a cyclic butylene terephthalate matrix by a nonisothermal production methodADVANCES IN POLYMER TECHNOLOGY, Issue 2 2010J. Baets Abstract The interest in thermoplastic composites is growing because of their advantages over thermosets, as well as their recyclability and higher toughness. The melt viscosity of thermoplastic polymers is very high, which makes fiber impregnation difficult. This difficulty can be overcome by the in situ polymerization with cyclic butylene terephthalate (CBT). However, this leads to a brittle polybutyleneterephthalate when isothermal RTM-production is applied. To solve this problem, a nonisothermal production process for composites with CBT as matrix material was developed and the influence on the toughness was investigated. In the nonisothermal production process, different cooling rates were applied to examine their influence on the toughness of the produced composites. The difference in composites properties was related to the difference in the degree of crystal perfection, which was investigated by differential scanning calorimetry. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:70,79, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20176 [source] Addition of nimesulide to small intestinal submucosa biomaterial inhibits postsurgical adhesiogenesis in ratsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2010Mark A. Suckow Abstract Adhesion formation is a common complication in abdominal surgery with incidence as high as 93% and small bowel obstruction a common complication. Because the extracellular matrix material, small intestinal submucosa (SIS), is commonly used in various surgical procedures, methods to inhibit adhesiogenesis are of great interest. This study was undertaken to determine if incorporation of nimesulide (NM), a selective cyclooxygenase (COX)-2 inhibitor, could reduce the extent and tenacity of intraabdominal adhesion formation associated with SIS implantation. Female Sprague,Dawley rats underwent a cecal abrasion surgical procedure to induce adhesiogenesis. Rats were either left untreated or treated by direct application over the injured cecum with polypropylene mesh (PPM); SIS; SIS containing a low dose of NM; or SIS containing a high dose of NM. Rats were euthanized 21 days later, and adhesion extent and tenacity were evaluated using standard scales (0 = minimal adhesiogenesis; 4 = severe adhesiogenesis). Addition of NM to SIS resulted in a significant (p < 0.05) reduction in adhesion extent and in a similar reduction in adhesion tenacity for SIS containing a low dose of NM. Adhesions typically extended from the abraded cecal surface to the body wall and were characterized histologically by fibrous tissue adherent to the cecal wall. In conclusion, addition of the nonsteroidal anti-inflammatory, COX-2 selective drug, NM, to SIS attenuates adhesion extent and tenacity when compared with surgical placement of SIS or PPM alone. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010 [source] Differentiation of snake epidermis, with emphasis on the shedding layerJOURNAL OF MORPHOLOGY, Issue 2 2005Lorenzo Alibardi Abstract Little is known about specific proteins involved in keratinization of the epidermis of snakes. The presence of histidine-rich molecules, sulfur, keratins, loricrin, transglutaminase, and isopeptide-bonds have been studied by ultrastructural autoradiography, X-ray microanalysis, and immunohistochemistry in the epidermis of snakes. Shedding takes place along a shedding complex, which is composed of two layers, the clear and the oberhautchen layers. The remaining epidermis comprises different layers, some of which contain beta-keratins and others alpha-keratins. Weak loricrin, transglutaminase, and sometimes also iso-peptide-bond immunoreactivities are seen in some cells, lacunar cells, of the alpha-layer. Tritiated histidine is mainly incorporated in the shedding complex, especially in dense beta-keratin filaments in cells of the oberhautchen layer and to a small amount in cells of the clear layer. This suggests the presence of histidine-rich, matrix proteins among beta-keratin bundles. The latter contain sulfur and are weakly immunolabeled for beta-keratin at the beginning of differentiation of oberhautchen cells. After merging with beta cells, the dense beta-keratin filaments of oberhautchen cells become immunopositive for beta-keratin. The uptake of histidine decreases in beta cells, where little dense matrix material is present, while pale beta-keratin filaments increase. During maturation, little histidine labeling remains in electron-dense areas of the beta layer and in those of oberhautchen spinulae. Some roundish dense granules of oberhautchen cells rich in sulfur are negative to antibodies for alpha-keratin, beta-keratin, and loricrin. The granules eventually merge with beta-keratin, and probably contribute to the formation of the resistant matrix of oberhautchen cells. In conclusion, beta-keratin, histidine-rich, and sulfur-rich proteins contribute to form snake microornamentations. J. Morphol. © 2005 Wiley-Liss, Inc. [source] Pitting corrosion on 316L pipes in terephthalic acid (TA) dryerMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2009Y. Gong Abstract Grade 316L is a type of austenitic stainless steel with ultra-low carbon content and it exhibits superior corrosion resistance. However, pitting is always observed in 316L steel when it is exposed to media containing halide ions. In the present study, we found that in the presence of acetate acid (HAc) containing chloride or bromide ions, pitting occurred on the surface of the rotary steam pipes with the matrix material of 316L steel in terephthalic acid (TA) dryer. In order to identify the causes of the failure, metallographic structures and chemical compositions of the matrix material were inspected by an optical microscope (OM) and a photoelectric direct reading spectrometer. Beside these, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) as well as ion chromatography (IC) were used to analyze the micromorphologies of the corrosion pits and the chemical compositions of the corrosion deposits within them. Analysis of the results revealed the sources of halide ions and the factors accelerating the corrosion rate. Beside these, detailed mechanisms of pitting were discussed and six out of all the seven theoretical morphologies of pitting features were obtained in practice. [source] In situ reinforcement of poly(butylene terephthalate) and butyl rubber by liquid crystalline polymerPOLYMER COMPOSITES, Issue 5 2009S. Kumar Ternary in situ butyl rubber (IIR)/poly(butylene terephthalate) (PBT) and liquid crystalline polymer (LCP) blends were prepared by compression molding. The LCP used was a versatile Vectra A950, and the matrix material was IIR/PBT 50/50 by weight. Morphological, thermal, and mechanical properties of blends were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), differential scanning calorimetry, and thermogravimetric analysis (TGA). Microscopy study (SEM) showed that formation of fibers is increasing with the increasing amount of LCP A950. Microscopic examination of the fractured surface confirmed the presence of a polymer coating on LCP fibrils. This can be attributed to some interactions including both chemical and physical one. The increased compatibility in polymer blends, consisting of IIR/PBT, by the presence of LCP A950 may be explained by the adsorption phenomena of the polymer chains onto the LCP fibrils. SEM and AFM images provided the evidence of the interaction between IIR/PBT and the LCP. Dynamic mechanical analyses (DMA) and TGA measurements showed that the composites possessed a remarkably higher modulus and heat stability than the unfilled system. Storage modulus for the ternary blend containing 50 wt% of LCP exhibits about 94% increment compared with binary blend of IIR/PBT. From the above results, it is suggested that the LCP A950 can act as reinforcement agent in the blends. Moreover, the fine dispersion of LCP was observed with no extensional forces applied during mixing, indicating the importance of interfacial adhesion for the fibril formation. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Damage evolution in low velocity impacted unreinforced vinyl ester 411-350 and 411-C50 resin systemsPOLYMER COMPOSITES, Issue 6 2000M. Motuku Assistant Professor Damage evolution in plaques made of vinyl ester resin systems was investigated as a function of specimen thickness, impact energy level and matrix material. Dow DERAKANE vinyl ester 411-350 and 411-C50 resin systems, which have low viscosity and are ideally suited for low-cost liquid processing techniques like vacuum assisted resin transfer molding (VARTM), were considered for the low velocity instrumented impact testing. Characterization of damage evolution was undertaken using optical microscopy and analysis of impact load histories recorded during the impact event. Radial cracking, perforations at the point of impact (in the form of a truncated cone), and damage resulting from the support constraints were identified as the dominant failure characteristics in both resin systems. Radial cracking, which originated from the bottom surface, was operative in all failed specimens and was attributed to the catastrophic failure due to extensive flexural tensile strength losses. For specimens that could deflect significantly, radial cracking and support-constraint-induced damage were the operative failure mechanisms. Radial cracking and through-thickness shearing led to failure in stiffer plaques. The DERAKANE 411-350-vinyl ester resin system was found more damage resistant than the 411-C50 system. [source] Mixed matrix membrane materials with glassy polymers.POLYMER ENGINEERING & SCIENCE, Issue 7 2002Part Analysis presented in Part 1 of this paper indicated the importance of optimization of the transport properties of the interfacial region to achieve ideal mixed matrix materials. This insight is used in this paper to guide mixed matrix material formation with more conventional gas separation polymers. Conventional gas separation materials are rigid, and, as seen earlier, lead to the formation of an undesirable interphase under conventional casting techniques. We show in this study that if flexibility can be maintained during membrane formation with a polymer that interacts favorably with the sieve, successful mixed matrix materials result, even with rigid polymeric materials. Flexibility during membrane formation can be achieved by formation of films at temperatures close to the glass transition temperature of the polymer. Moreover, combination of chemical coupling and flexibility during membrane formation produces even more significant improvements in membrane performance. This approach leads to the formation of mixed matrix material with transport properties exceeding the upper bound currently achieved by conventional membrane materials. Another approach to form successful mixed matrix materials involves tailoring the interface by use of integral chemical linkages that are intrinsically part of the chain backbone. Such linkages appear to tighten the interface sufficiently to prevent "nonselective leakage" along the interface. This approach is demonstrated by directly bonding a reactive polymer onto the sieve surface under proper processing conditions. [source] Chemical Vapor Infiltration of RheniumCHEMICAL VAPOR DEPOSITION, Issue 2 2003H.C. King Abstract Rhenium is of interest as a matrix material and fiber coating for high-temperature structural composites. Despite prior success in the CVD of rhenium, there have been no studies on the chemical vapor infiltration (CVI) of this metal. The current work investigates the CVI of rhenium via the pyrolytic decomposition of ReCl5, prepared both by chlorination of rhenium metal and the sublimation of ReCl5. The feasibility of the CVI of rhenium was demonstrated for both methods. Statistical analyses showed that the amount of rhenium deposited increased for higher chlorine flow rates and lower preform temperatures, 750,°C vs. 900,°C, for the chlorination and sublimation processes, respectively. [source] Stroma remodelling during healing of corneal surface irregularities induced by PTKACTA OPHTHALMOLOGICA, Issue 4 2007Marios Panagiotopoulos Abstract. Purpose:, To study the histopathology of the remodelling process in the stroma after excimer-laser-induced corneal irregular injuries. Methods:, Seven New Zealand white rabbits received in one eye a transepithelial plano photoablation (60 µm) and an additional plano ablation (25 µm). On the denuded stroma, an electron microscopy specimen grid was placed and another 25 µm ablation was applied to produce surface irregularities. Dichlorotriazinyl aminofluorescein (DTAF) was then applied for 45 seconds. Another seven right eyes of seven rabbits were ablated the same way but without using the grid, resulting in a plano ablation. All the rabbits were killed at weekly intervals after treatment. The harvested corneas from both eyes were further processed for haematoxylin-eosin staining and were also stained with monoclonal antibodies directed against Ki-67 antigen and ,-smooth muscle actin (,-SMA). All specimens were examined under light and fluorescence microscope. Results:, The corneal wounds were covered by epithelium during the first week. The 25 µm × 25 µm × 25 µm stromal irregularities were clearly discernible up to 3 weeks after treatment, during which time they melted and disappeared. A homogeneous zone was formed in which stroma cells laid down an initially disorganized stroma. This was sharply visible under a fluorescence microscope as a dark area between the dichlorotriazinyl aminofluorescein (DTAF) fluorescent stroma and autofluorescent epithelium. Very little response was seen in the plano-ablated wound microscopically and in terms of positive stained cells. Conclusion:, As the irregularities are flattened and the homogenous zone becomes repopulated with keratocytes forming extracellular matrix material (ECM), the cornea regains its previous architecture in both groups. The irregular wound surface promotes wound-healing reactivity, a process that allows the cornea to compensate for the irregularities and heal to a functional state. [source] Synthesis and Optical Properties of Europium-Complex-Doped Inorganic/Organic Hybrid Materials Built from Oxo,Hydroxo Organotin Nano Building BlocksCHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2010Wei-Qiang Fan Dr. Abstract Hybrid materials doped with novel europium complexes were synthesized using PMMA- co -Sn12Clusters (copolymers from oxohydroxo-organotin dimethacrylate and methylmethacrylate) as the matrix material. Two types of hybrid materials were obtained: the physically doped product, PMMA- co -Sn12Cluster/Eu(TTA)3phen, and the grafted product, PMMA- co -Sn12Cluster- co -[EuAA(TTA)2phen] (TTA=2-thenoyltrifluoroacetone, phen=phenanthroline and AA=acrylic acid). The hybrid materials exhibited characteristic luminescence of the Eu3+ ions, and also showed relative especial optical properties compared with samples just using PMMA as the matrix material. The PMMA- co -Sn12Cluster matrix exhibited a high physical doping quantity of [Eu(TTA)3phen], which can be attributed to the special structure of this kind of hybrid material. GPC (gel-permeation chromatography), TGA (thermogravimetric analysis), SEM, 1H,NMR, ICP (inductively coupled plasma), 119Sn,NMR, FTIR, and diffuse reflectance techniques were employed to characterize the structures and properties of these hybrid materials. [source] On the origin of rim textures surrounding anhydrous silicate grains in CM carbonaceous chondritesMETEORITICS & PLANETARY SCIENCE, Issue 5 2000Lauren BROWNING Bulk chemical analyses and observations of these rims indicate the presence of phyllosilicates and disseminated opaques. Because phyllosilicates could not have survived the chondrule formation process, chondrule silicate rims must have formed entirely by late-state aqueous reactions. As such, these textures provide a useful benchmark for isolating alteration features from more complex CM matrix materials. Both chondrule silicate and matrix silicate rims exhibit morphological features commonly associated with advancing stages of replacement reactions in terrestrial serpentinites. Contacts between many matrix silicate rims and the adjacent matrix materials suggest that these rims formed entirely by aqueous reactions in a parent-body setting. This contrasts with previous assertions that rim textures can only form by the accretion of nebular dust but does not imply an origin for the rims surrounding other types of CM core components, such as chondrules. [source] Thermal expansion co-efficient of nanotube,metal compositesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009Sheikh M. Uddin Abstract Thermal expansion exhibits considerable challenges developing residual stresses at the interfaces of different materials treated at high temperature. Electrical devices containing materials with different thermal expansion behaviour very often suffer this problem. Thermal expansion co-efficient (TEC) of different metals can be tuned by using carbon nanotube (CNT). Metal matrix composites (MMCs) using CNT are fabricated by hot-press sintering method and TEC of the composites are investigated throughout a wide range of temperature (,155 to 275,°C). Reduction of TEC of the composite materials was observed up to 20% compared to that of pure metals. The effect of CNTs in the matrix materials and the mechanism behind the improvement are explained from the microscopic investigation of the composites. [source] Experiments on single levitated particles: a novel approach for investigations of electronic properties of structured II-VI-semiconductor nanoparticles in selected environmentsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2007C. Graf Abstract A novel approach for investigations of the electronic structure of II-VI semiconductor nanoparticles in selected environments is presented. CdSe/ZnS core shell nanoparticles are dispersed in a liquid non-volatile siloxane graft/block copolymer and injected in an electrodynamic trap, where a single liquid microdroplet is stably stored under ultra high vacuum conditions. In this way, it is possible to investigate quantum dots by soft X-ray spectroscopies in a liquid environment, which is not influenced by any outer surface. NEXAFS spectra of stored nanoparticles were recorded at the Zn 2p-, S 2p-, and Cd 3d-edge by measuring X-ray excited optical luminescence or the element-selective charging current of single, trapped microdroplets. The spectra are compared to those of similar CdSe/ZnS nanoparticles, which are dispersed in a controlled way in solid silica colloids as well as to those of matrix materials. An analysis of the data reveals that the electronic structure of the ZnS shell is significantly influenced by the outer functionalization and the dispersive media whereas the electronic structure of the core is shown to be independent from the surroundings. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Impression creep of PMR-15 resin at elevated temperaturesPOLYMER ENGINEERING & SCIENCE, Issue 1 2010Rong Chen The polyimides formed from the polymerization of monomeric-reactants (PMR) approach have been increasingly used as matrix materials in fiber-reinforced composites on aerospace and space structures for high temperature applications. The performance of PMR-based structures depends on the mechanical durability of PMR resins at elevated temperatures, including creep and stress relaxation. In this work, the creep behavior of PMR-15 resin was studied using the impression technique in the temperature range of 563,613 K and the punching stress range of 76,381 MPa. It was found that there existed a steady state creep for the creep tests performed at temperatures of 563 K and higher, from which a constant impression velocity was calculated. The steady state impression velocity increased with temperature and punching stress with the stress exponent in the range of 1.5,2.2. The average of the apparent activation energy of the PMR-15 was calculated as 122.7 ± 6.1 kJ/mol. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Mixed matrix membrane materials with glassy polymers.POLYMER ENGINEERING & SCIENCE, Issue 7 2002Part Mixed matrix materials comprising molecular sieve entities embedded in a polymer matrix can economically increase membrane permselectivity, thereby addressing a key challenge hindering the widespread use of membrane-based gas separations. Prior work has clarified the importance of proper selection of the dispersed sieve phase and the continuous matrix phase based on their intrinsic transport properties. Proper material selection for the two components, while necessary, is not sufficient since the interfacial contact zone appears to be equally important to achieve optimum transport properties. Specifically, it was found that chemical coupling of the sieve to the polymer can lead to better macroscopic adhesion but to even poorer transport properties than in the absence of the adhesion promoter. This counterintuitive behavior may be attributed to a nanometric region of disturbed packing at the polymer sieve interphase. The poor properties are believed to result from "leakage" of gas molecules along this nanometric interface. The Maxwell model was modified to take into account these complexities and to provide a first order quantification of the nanometric interphase. The analysis indicates that optimization of the transport properties of the interfacial region is key to the formation of ideal mixed matrix materials. This approach is used in the second part of this paper to form successful mixed matrix membrane materials. [source] Mixed matrix membrane materials with glassy polymers.POLYMER ENGINEERING & SCIENCE, Issue 7 2002Part Analysis presented in Part 1 of this paper indicated the importance of optimization of the transport properties of the interfacial region to achieve ideal mixed matrix materials. This insight is used in this paper to guide mixed matrix material formation with more conventional gas separation polymers. Conventional gas separation materials are rigid, and, as seen earlier, lead to the formation of an undesirable interphase under conventional casting techniques. We show in this study that if flexibility can be maintained during membrane formation with a polymer that interacts favorably with the sieve, successful mixed matrix materials result, even with rigid polymeric materials. Flexibility during membrane formation can be achieved by formation of films at temperatures close to the glass transition temperature of the polymer. Moreover, combination of chemical coupling and flexibility during membrane formation produces even more significant improvements in membrane performance. This approach leads to the formation of mixed matrix material with transport properties exceeding the upper bound currently achieved by conventional membrane materials. Another approach to form successful mixed matrix materials involves tailoring the interface by use of integral chemical linkages that are intrinsically part of the chain backbone. Such linkages appear to tighten the interface sufficiently to prevent "nonselective leakage" along the interface. This approach is demonstrated by directly bonding a reactive polymer onto the sieve surface under proper processing conditions. [source] Characterization of an insoluble polyimide oligomer by matrix-assisted laser desorption/ionization time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 20 2002Anthony P. Gies In the past two years, papers have appeared in the literature which demonstrate that matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra can be obtained from matrix-analyte preparations which have been produced by grinding the two materials together until a powder of small particle size is obtained. In the present study that methodology was modified and applied to an insoluble polyimide oligomer, poly(4,4,-oxydiphenylenepyromellitimide) (POPM). Two matrix materials were employed in this analysis, 1,8 dihydroxyanthrone (dithranol) and 3-aminoquinoline, with and without an additional cationizing agent. The spectra obtained by this method are shown to be sensitive to the matrix employed in the analysis as well as the quantity of cationizing agent combined with the matrix. Copyright © 2002 John Wiley & Sons, Ltd. [source] Low-Temperature Plasticity of Naturally Deformed Calcite RocksACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2002LIU Junlai Abstract Optical, cathodoluminescence and transmission electron microscope (TEM) analyses were conducted on four groups of calcite fault rocks, a cataclastic limestone, cataclastic coarse-grained marbles from two fault zones, and a fractured mylonite. These fault rocks show similar microstructural characteristics and give clues to similar processes of rock deformation. They are characterized by the structural contrast between macroscopic cataclastic (brittle) and microscopic mylonitic (ductile) microstructures. Intragranular deformation microstructures (i.e. deformation twins, kink bands and microfractures) are well preserved in the deformed grains in clasts or in primary rocks. The matrix materials are of extremely fine grains with diffusive features. Dislocation microstructures for co-existing brittle deformation and crystalline plasticity were revealed using TEM. Tangled dislocations are often preserved at the cores of highly deformed clasts, while dislocation walls form in the transitions to the fine-grained matrix materials and free dislocations, dislocation loops and dislocation dipoles are observed both in the deformed clasts and in the fine-grained matrix materials. Dynamic recrystallization grains from subgrain rotation recrystallization and subsequent grain boundary migration constitute the major parts of the matrix materials. Statistical measurements of densities of free dislocations, grain sizes of subgrains and dynamically recrystallized grains suggest an unsteady state of the rock deformation. Microstructural and cathodoluminescence analyses prove that fluid activity is one of the major parts of faulting processes. Low-temperature plasticity, and thereby induced co-existence of macroscopic brittle and microscopic ductile microstructures are attributed to hydrolytic weakening due to the involvement of fluid phases in deformation and subsequent variation of rock rheology. During hydrolytic weakening, fluid phases, e.g. water, enhance the rate of dislocation slip and climb, and increase the rate of recovery of strain-hardened rocks, which accommodates fracturing. [source] | ||||||||||||||||||||||