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Materials, Volume 3, Issue 1 (January 2010), Pages 1-754

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Open AccessArticle Feasibility of Using Multilayer Platelets as Toughening Agents
Materials 2010, 3(1), 1-8; doi:10.3390/ma3010001
Received: 22 October 2009 / Revised: 21 December 2009 / Accepted: 22 December 2009 / Published: 24 December 2009
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Abstract
It is known that the toughness of brittle ceramics can be improved significantly with the addition of hard platelets. In the present study, platelet-shape multilayer ceramic laminates are utilized as a toughening agent for alumina ceramics. They are prepared by laminating the [...] Read more.
It is known that the toughness of brittle ceramics can be improved significantly with the addition of hard platelets. In the present study, platelet-shape multilayer ceramic laminates are utilized as a toughening agent for alumina ceramics. They are prepared by laminating the BaTiO3-based ceramic tapes. Although the elastic modulus of the BaTiO3-based platelets is lower than that of the alumina matrix, and the platelets are also reactive to alumina at elevated temperatures, the weak platelets are found to exhibit the ability to deflect major matrix cracks by forming a large number of microcrack branches within the platelets, thus achieving the desired toughening effect. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Nanoporous Carbide-Derived Carbon Material-Based Linear Actuators
Materials 2010, 3(1), 9-25; doi:10.3390/ma3010009
Received: 30 October 2009 / Revised: 16 December 2009 / Accepted: 22 December 2009 / Published: 24 December 2009
Cited by 18 | PDF Full-text (631 KB) | HTML Full-text | XML Full-text
Abstract
Devices using electroactive polymer-supported carbon material can be exploited as alternatives to conventional electromechanical actuators in applications where electromechanical actuators have some serious deficiencies. One of the numerous examples is precise microactuators. In this paper, we show for first time the dilatometric [...] Read more.
Devices using electroactive polymer-supported carbon material can be exploited as alternatives to conventional electromechanical actuators in applications where electromechanical actuators have some serious deficiencies. One of the numerous examples is precise microactuators. In this paper, we show for first time the dilatometric effect in nanocomposite material actuators containing carbide-derived carbon (CDC) and polytetrafluoroetylene polymer (PTFE). Transducers based on high surface area carbide-derived carbon electrode materials are suitable for short range displacement applications, because of the proportional actuation response to the charge inserted, and high Coulombic efficiency due to the EDL capacitance. The material is capable of developing stresses in the range of tens of N cm-2. The area of an actuator can be dozens of cm2, which means that forces above 100 N are achievable. The actuation mechanism is based on the interactions between the high-surface carbon and the ions of the electrolyte. Electrochemical evaluations of the four different actuators with linear (longitudinal) action response are described. The actuator electrodes were made from two types of nanoporous TiC-derived carbons with surface area (SA) of 1150 m2 g-1 and 1470 m2 g-1, respectively. Two kinds of electrolytes were used in actuators: 1.0 M tetraethylammonium tetrafluoroborate (TEABF4) solution in propylene carbonate and pure ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf). It was found that CDC based actuators exhibit a linear movement of about 1% in the voltage range of 0.8 V to 3.0 V at DC. The actuators with EMITf electrolyte had about 70% larger movement compared to the specimen with TEABF4 electrolyte. Full article
(This article belongs to the Special Issue Molecular Biomimetics and Materials Design)
Open AccessArticle Coordination of {Mo142} Ring to La3+ Provides Elliptical {Mo134La10} Ring with a Variety of Coordination Modes
Materials 2010, 3(1), 64-75; doi:10.3390/ma3010064
Received: 29 November 2009 / Revised: 23 December 2009 / Accepted: 25 December 2009 / Published: 28 December 2009
Cited by 2 | PDF Full-text (616 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A28-electron reduced C2h-Mo-blue 34Ǻ outer ring diameter circular ring, [Mo142O429H10(H2O)49(CH3CO2)5(C2H5CO2)]30- (≡{Mo142(CH3CO2) [...] Read more.
A28-electron reduced C2h-Mo-blue 34Ǻ outer ring diameter circular ring, [Mo142O429H10(H2O)49(CH3CO2)5(C2H5CO2)]30- (≡{Mo142(CH3CO2)5(C2H5CO2)}) comprising eight carboxylate-coordinated (with disorder) {Mo2} linkers and six defect pockets in two inner rings (four and three for each, respectively), reacts with La3+ in aqueous solutions at pH 3.5 to yield a 28-electron reduced elliptical Ci-Mo-blue ring of formula [Mo134O416H20(H2O)46{La(H2O)5}4{La(H2O)7}4{LaCl2(H2O)5}2]10- (≡{Mo134La10}), isolated as the Na10[Mo134O416H20(H2O)46{La(H2O)5}4{La(H2O)7}4{LaCl2(H2O)5}2]·144 H2O Na+ salt. The elliptical structure of {Mo134La10} showing 36 and 31 Å long and short axes for the outer ring diameters is attributed to four (A-D) modes of LaO9/LaO7Cl2 tricapped-trigonal-prismatic coordination (TTP) geometries. Two different LaO2(H2O)7 and one LaO2(H2O)2Cl2 TTP geometries (as A-C modes) for each of two inner rings result from the coordination of all three defect pockets of the inner ring for {Mo142(CH3CO2)5(C2H5CO2)}, and two LaO4(H2O)5 TTP geometries (as D mode) result from the displacement of two (acetate/propionate-coordinated) binuclear {Mo2} linkers with La3+ in each inner ring. The isothermal titration calorimetry (ITC) of the ring modification from circle to ellipsoid, showing the endothermic reaction of [La3+]/[{Mo142(CH3CO2)5(C2H5CO2)}] = 6/1 with DH = 22 kJ×mol-1, DS = 172 J×K-1×mol-1, DG = −28 kJ×mol-1, and K = 9.9 ´ 104 M-1 at 293 K, leads to the conclusion that the coordination of the defect pockets to La3+ precedes the replacement of the {Mo2} linkers with La3+. 139La- NMR spectrometry of the coordination of {Mo142(CH3CO2)5(C2H5CO2)} ring to La3+ is also discussed. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
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Open AccessArticle Improved Mechanical and Tribological Properties of Metal-Matrix Composites Dispersion-Strengthened by Nanoparticles
Materials 2010, 3(1), 97-109; doi:10.3390/ma3010097
Received: 27 October 2009 / Revised: 30 November 2009 / Accepted: 3 December 2009 / Published: 29 December 2009
Cited by 12 | PDF Full-text (1622 KB) | HTML Full-text | XML Full-text
Abstract
Co- and Fe-based alloys produced by powder technology are being widely used as a matrix for diamond-containing composites in cutting, drilling, grinding pplications, etc. The severe service conditions demand that the mechanical and tribological properties of these alloys be improved. Development of [...] Read more.
Co- and Fe-based alloys produced by powder technology are being widely used as a matrix for diamond-containing composites in cutting, drilling, grinding pplications, etc. The severe service conditions demand that the mechanical and tribological properties of these alloys be improved. Development of metal-matrix composites (MMCs) and alloys reinforced with nanoparticles is a promising way to resolve this problem. In this work, we have investigated the effect of nano-sized WC, ZrO2, Al2O3, and Si3N4 additives on the properties of sintered dispersion-strengthened Co- and Fe-based MMCs. The results show an increase in the hardness (up to 10 HRB), bending strength (up to 50%), wear resistance (by a factor of 2–10) and a decrease in the friction coefficient (up to 4-fold) of the dispersion-strengthened materials. The use of designed alloys as a binder of cutting diamond tools gave a 4-fold increment in the service life, without reduction in their cutting speed. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Syntheses and a Solid State Structure of a Dinuclear Molybdenum(V) Complex with Pyridine
Materials 2010, 3(1), 150-157; doi:10.3390/ma3010150
Received: 4 December 2009 / Revised: 29 December 2009 / Accepted: 4 January 2010 / Published: 4 January 2010
Cited by 2 | PDF Full-text (349 KB) | HTML Full-text | XML Full-text
Abstract
A mononuclear complex [MoOCl4(H2O)] readily forms a metal−metal bonded {Mo2O4}2+ core. A high content of pyridine in the reaction mixture prevents further aggregation of dinuclear cores into larger clusters and a neutral, [...] Read more.
A mononuclear complex [MoOCl4(H2O)] readily forms a metal−metal bonded {Mo2O4}2+ core. A high content of pyridine in the reaction mixture prevents further aggregation of dinuclear cores into larger clusters and a neutral, dinuclear complex with the [Mo2O4Cl2(Py)4] composition is isolated as a product. Solid state structures of two compounds containing this complex, [Mo2O4Cl2(Py)4]·2.25Py (1) and [Mo2O4Cl2(Py)4]·1.5PyHCl (2), were investigated by X-ray crystallography. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
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Open AccessArticle Controllable Layered Structures in Polyoxomolybdate-Surfactant Hybrid Crystals
Materials 2010, 3(1), 158-164; doi:10.3390/ma3010158
Received: 19 November 2009 / Revised: 23 December 2009 / Accepted: 4 January 2010 / Published: 6 January 2010
Cited by 10 | PDF Full-text (480 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Inorganic-organic hybrid crystals containing α-octamolybdate (Mo8) or hexamolybdate (Mo6) were isolated by using hexadecyltrimethylammonium (C16) surfactant. The packing mode of the inorganic layers depended on a difference in the polyoxomolybdate molecular structure. The structure for both [...] Read more.
Inorganic-organic hybrid crystals containing α-octamolybdate (Mo8) or hexamolybdate (Mo6) were isolated by using hexadecyltrimethylammonium (C16) surfactant. The packing mode of the inorganic layers depended on a difference in the polyoxomolybdate molecular structure. The structure for both crystals consisted of alternate stacking of C16 organic bilayers and polyoxomolybdate inorganic layers with a periodicity of 24.4–24.6 Å. However, the C16-Mo8 crystals contained Mo8 monolayers, while the C16-Mo6 crystals contained Mo6 bilayers. These lattice structures for the polyoxometalate/organic hybrid will be designed by the molecular structures of polyoxometalate. Full article
(This article belongs to the Special Issue Inorganic-Organic Hybrid Materials)
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Open AccessArticle A New Approach for the Modification of Paper Surface Properties Using Polyoxometalates
Materials 2010, 3(1), 201-215; doi:10.3390/ma3010201
Received: 3 November 2009 / Revised: 28 December 2009 / Accepted: 4 January 2010 / Published: 7 January 2010
Cited by 15 | PDF Full-text (496 KB) | HTML Full-text | XML Full-text
Abstract
A new approach for the chemical modification of the surface of paper based on the application of colloidal mixtures containing cationic starch and polyoxometalates on uncoated base paper is presented. Polyoxometalates with the Keggin-type structure and physical properties similar to those presented [...] Read more.
A new approach for the chemical modification of the surface of paper based on the application of colloidal mixtures containing cationic starch and polyoxometalates on uncoated base paper is presented. Polyoxometalates with the Keggin-type structure and physical properties similar to those presented by coating pigments, namely H3PW12O40·23H2O, H4SiW12O40·24H2O, and K7PW11O39·9H2O, have been used in order to improve the quality of inkjet printing. The analysis of the different samples by FTIR-ATR spectroscopy showed the presence of the polyoxometalates (and the cationic starch) on the top surface of the paper. In addition, the determination of surface energy parameters, namely the polar component (σsp) and the dispersive component (σsd) of the surface energy, by contact angle measurements revealed that, for the new samples, the polar component level was much higher than that of the uncoated base paper. The quality of inkjet printing, evaluated by parameters such as the gamut area and the optical density, was considerably improved by these surface treatments. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
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Open AccessArticle Effect of SO2 Dry Deposition on Porous Dolomitic Limestones
Materials 2010, 3(1), 216-231; doi:10.3390/ma3010216
Received: 1 November 2009 / Revised: 30 December 2009 / Accepted: 4 January 2010 / Published: 7 January 2010
Cited by 10 | PDF Full-text (1130 KB) | HTML Full-text | XML Full-text
Abstract
The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain) used as building material in stone monuments and submitted to artificial ageing by SO2 dry deposition in the presence of humidity. [...] Read more.
The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain) used as building material in stone monuments and submitted to artificial ageing by SO2 dry deposition in the presence of humidity. To investigate the protection efficiency of different polymeric coatings, three commercially available siloxane-based oligomers (Lotexan-N, Silres BS 290 and Tegosivin HL 100) and a newly synthesized hybrid nanocomposite with silsesquioxane units (TMSPMA) were used. A comparative assessment of the data obtained in this study underlines that a better limestone protection was obtained when treated with the hybrid nanocomposite with silsesquioxane units. Full article
(This article belongs to the Special Issue Composite Materials)
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Open AccessArticle Families of Molecular Hexa- and Trideca-Metallic Vanadium(III) Phosphonates
Materials 2010, 3(1), 232-240; doi:10.3390/ma3010232
Received: 30 November 2009 / Revised: 18 December 2009 / Accepted: 22 December 2009 / Published: 8 January 2010
Cited by 5 | PDF Full-text (448 KB) | HTML Full-text | XML Full-text
Abstract The synthesis and structural characterization of two families of low-valent vanadium(III) {V6P4} and vanadium(III/IV) {V13P8} phosphonate complexes are reported. Magnetic characterization is reported for representative examples. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
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Open AccessArticle The Effect of (Ag, Ni, Zn)-Addition on the Thermoelectric Properties of Copper Aluminate
Materials 2010, 3(1), 318-328; doi:10.3390/ma3010318
Received: 21 December 2009 / Revised: 7 January 2010 / Accepted: 8 January 2010 / Published: 11 January 2010
Cited by 23 | PDF Full-text (484 KB) | HTML Full-text | XML Full-text
Abstract
Polycrystalline bulk copper aluminate Cu1-x-yAgxByAlO2 with B = Ni or Zn were prepared by spark plasma sintering and subsequent thermal treatment. The influence of partial substitution of Ag, Ni and Zn for Cu-sites in [...] Read more.
Polycrystalline bulk copper aluminate Cu1-x-yAgxByAlO2 with B = Ni or Zn were prepared by spark plasma sintering and subsequent thermal treatment. The influence of partial substitution of Ag, Ni and Zn for Cu-sites in CuAlO2 on the high temperature thermoelectric properties has been studied. The addition of Ag and Zn was found to enhance the formation of CuAlO2 phase and to increase the electrical conductivity. The addition of Ag or Ag and Ni on the other hand decreases the electrical conductivity. The highest power factor of 1.26 × 10-4 W/mK2 was obtained for the addition of Ag and Zn at 1,060 K, indicating a significant improvement compared with the non-doped CuAlO2 sample. Full article
(This article belongs to the Special Issue Novel Thermoelectric Materials and Applications)
Open AccessArticle Synthesis and Properties of Trehalose-Based Flexible Polymers Prepared from Difurfurylidene Trehalose and Maleimide- Terminated Oligo(dimethylsiloxane) by Diels-Alder Reactions
Materials 2010, 3(1), 369-385; doi:10.3390/ma3010369
Received: 13 November 2009 / Revised: 16 December 2009 / Accepted: 8 January 2010 / Published: 12 January 2010
Cited by 7 | PDF Full-text (858 KB) | HTML Full-text | XML Full-text
Abstract
Difurfurylidene trehalose (DFTreh) was synthesized from trehalose and furfural by an acetalization reaction. Maleimide-terminated dimethylsiloxane oligomers (DMS-BMI) were synthesized from amine-terminated dimethylsiloxane oligomers by condensation with maleic anhydride. Three types of DMS-BMI with different length were prepared. Trehalose-based polymers were synthesized by [...] Read more.
Difurfurylidene trehalose (DFTreh) was synthesized from trehalose and furfural by an acetalization reaction. Maleimide-terminated dimethylsiloxane oligomers (DMS-BMI) were synthesized from amine-terminated dimethylsiloxane oligomers by condensation with maleic anhydride. Three types of DMS-BMI with different length were prepared. Trehalose-based polymers were synthesized by Diels-Alder reaction of DFTreh and DMS-BMI. The reaction proceeded at 40~70 °C to produce a polymer with a maximum weight average molecular weight of ~19,000. The thermal degradation temperature increased with the increase of the length of the oligo(dimethylsiloxane) units. The differential scanning calorimetry (DSC) measurements revealed the glass transition temperature (Tg) of the polymer at -130~-120 °C, and no distinct Tg not observed above room temperature in the DSC measurement. The polymer products are not liquid at room temperature, and solid films can be obtained by casting from solution, implying a phase-separated structure made up of soft and hard segments. The phase-separated structure was confirmed by transmission electron microscope (TEM) study. The DSC curve of the polymer showed a broad endothermic peak at 110~160 °C, suggesting that a retro-Diels-Alder reaction occurred. When a N,N-dimethylformamide solution of the polymer was kept at 100 °C and the resulting solution was analyzed by gel permeation chromatography (GPC), the molecular weight decreased and monomers appeared. Full article
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Open AccessArticle Description of Extrudate Swell for Polymer Nanocomposites
Materials 2010, 3(1), 386-400; doi:10.3390/ma3010386
Received: 7 December 2009 / Revised: 22 December 2009 / Accepted: 25 December 2009 / Published: 12 January 2010
Cited by 4 | PDF Full-text (407 KB) | HTML Full-text | XML Full-text
Abstract
Extrudate swell is often observed to be weakened in nanocomposites compared to the pure polymer matrix. A theory quantifying this would be significant either for optimum processing or for understanding their viscoelasticity. A unified extrudate swell correlation with material properties and capillary [...] Read more.
Extrudate swell is often observed to be weakened in nanocomposites compared to the pure polymer matrix. A theory quantifying this would be significant either for optimum processing or for understanding their viscoelasticity. A unified extrudate swell correlation with material properties and capillary parameters was suggested for polymer melt and their nanocomposites when considering the reservoir entry effect. More importantly, it was the first to find that the composite swell ratio can be the matrix swell ratio multiplied by the concentration shift factor, which is similar to the dynamic moduli expression for composites. The factor is a function of the shear field (stress or shear rate), filler content, filler internal structure and the surface state as well as the matrix properties. Several sets of swell data for nanocomposites were chosen from publications to test the new theories. The proposed quantitative model displayed good fit for the five kinds of nanocomposites, which verified the rationality of the swell theory for nanocomposites. Full article
(This article belongs to the Special Issue Nanocomposites of Polymers and Inorganic Particles)
Open AccessArticle An Incremental Mori-Tanaka Homogenization Scheme for Finite Strain Thermoelastoplasticity of MMCs
Materials 2010, 3(1), 434-451; doi:10.3390/ma3010434
Received: 2 November 2009 / Revised: 22 December 2009 / Accepted: 24 December 2009 / Published: 13 January 2010
Cited by 4 | PDF Full-text (3850 KB) | HTML Full-text | XML Full-text
Abstract
The present paper aims at computational simulations of particle reinforced Metal Matrix Composites as well as parts and specimens made thereof. An incremental Mori-Tanaka approach with isotropization of the matrix tangent operator is adopted. It is extended to account for large strains [...] Read more.
The present paper aims at computational simulations of particle reinforced Metal Matrix Composites as well as parts and specimens made thereof. An incremental Mori-Tanaka approach with isotropization of the matrix tangent operator is adopted. It is extended to account for large strains by means of co-rotational Cauchy stresses and logarithmic strains and is implemented into Finite Element Method software as constitutive material law. Periodic unit cell predictions in the finite strain regime are used to verify the analytical approach with respect to non-proportional loading scenarios and assumptions concerning finite strain localization. The response of parts made of Metal Matrix Composites is predicted by a multiscale approach based on these two micromechanical methods. Results for the mesoscopic stress and strain fields as well as the microfields are presented to demonstrate to capabilities of the developed methods. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Removal of Mn, Fe, Ni and Cu Ions from Wastewater Using Cow Bone Charcoal
Materials 2010, 3(1), 452-466; doi:10.3390/ma3010452
Received: 20 November 2009 / Revised: 4 December 2009 / Accepted: 7 December 2009 / Published: 14 January 2010
Cited by 19 | PDF Full-text (287 KB) | HTML Full-text | XML Full-text
Abstract
Cow bone charcoal (CBC) was synthesized and used for the removal of metals ions (manganese, iron, nickel and copper) from aqueous solutions. Two different adsorption models were used for analyzing the data. Adsorption capacities were determined: copper ions exhibit the greatest adsorption [...] Read more.
Cow bone charcoal (CBC) was synthesized and used for the removal of metals ions (manganese, iron, nickel and copper) from aqueous solutions. Two different adsorption models were used for analyzing the data. Adsorption capacities were determined: copper ions exhibit the greatest adsorption on cow bone charcoal because of their size and pH conditions. Adsorption capacity varies as a function of pH. Adsorption isotherms from aqueous solution of heavy metals on CBC were determined. Adsorption isotherms are consistent with Langmuir´s adsorption model. Adsorbent quantity and immersion enthalpy were studied. Full article
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Open AccessArticle Transformation of Tri-Titanium(IV)-Substituted α-Keggin Polyoxometalate (POM) into Tetra-Titanium(IV)-Substituted POMs : Reaction Products of Titanium(IV) Sulfate with the Dimeric Keggin POM Precursor under Acidic Conditions
Materials 2010, 3(1), 503-518; doi:10.3390/ma3010503
Received: 27 November 2009 / Revised: 8 January 2010 / Accepted: 13 January 2010 / Published: 15 January 2010
Cited by 7 | PDF Full-text (518 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Reaction products of titanium(IV) sulfate in HCl-acidic aqueous solution with the dimeric species linked through three intermolecular Ti-O-Ti bonds of the two tri-titanium(IV)-substituted α-Keggin polyoxometalate (POM) subunits are described. Two novel titanium(IV)-containing α-Keggin POMs were obtained under different conditions. One product was [...] Read more.
Reaction products of titanium(IV) sulfate in HCl-acidic aqueous solution with the dimeric species linked through three intermolecular Ti-O-Ti bonds of the two tri-titanium(IV)-substituted α-Keggin polyoxometalate (POM) subunits are described. Two novel titanium(IV)-containing α-Keggin POMs were obtained under different conditions. One product was a dimeric species through two intermolecular Ti-O-Ti bonds of the two tetra-titanium(IV)-substituted α-Keggin POM subunits, i.e., [[{Ti(H2O)3}2(μ-O)](α-PW9Ti2O38)]26- (1). The other product was a monomeric α-Keggin species containing the tetra-titanium(IV) oxide cluster and two coordinated sulfate ions, i.e., [{Ti4(μ-O)3(SO4)2(H2O)8}(α-PW9O34)]3- (2). Molecular structures of 1 and 2 were also discussed based on host (lacunary site)-guest (titanium atom) chemistry. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
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Open AccessArticle Diode Laser Assisted Filament Winding of Thermoplastic Matrix Composites
Materials 2010, 3(1), 563-571; doi:10.3390/ma3010563
Received: 18 November 2009 / Revised: 7 January 2010 / Accepted: 18 January 2010 / Published: 20 January 2010
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Abstract
A new consolidation method for the laser-assisted filament winding of thermoplastic prepregs is discussed: for the first time a diode laser is used, as well as long glass fiber reinforced polypropylene prepregs. A consolidation apparatus was built by means of a CNC [...] Read more.
A new consolidation method for the laser-assisted filament winding of thermoplastic prepregs is discussed: for the first time a diode laser is used, as well as long glass fiber reinforced polypropylene prepregs. A consolidation apparatus was built by means of a CNC motion table, a stepper motor and a simple tensioner. Preliminary tests were performed in a hoop winding configuration: only the winding speed was changed, and all the other process parameters (laser power, distance from the laser focus, consolidation force) were kept constant. Small wound rings with an internal diameter of 25 mm were produced and compression tests were carried out to evaluate the composite agglomeration in dependence of the winding speed. At lower winding speeds, a stronginterpenetration of adjacent layers was observed. Full article
(This article belongs to the Special Issue Composite Materials)
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Open AccessArticle Thermo-Exfoliated Graphite Containing CuO/Cu2(OH)3NO3:(Co2+/Fe3+) Composites: Preparation, Characterization and Catalytic Performance in CO Conversion
Materials 2010, 3(1), 572-584; doi:10.3390/ma3010572
Received: 17 November 2009 / Revised: 23 December 2009 / Accepted: 5 January 2010 / Published: 20 January 2010
Cited by 5 | PDF Full-text (714 KB) | HTML Full-text | XML Full-text
Abstract
Thermo-exfoliated graphite (TEG)/CuO/Cu2(OH)3NO3:(Co2+/Fe3+) composites were prepared using a wet impregnation method and subsequent thermal treatment. The physicochemical characterization of the composites was carried out by powder X-ray diffraction (PXRD), scanning electron microscopy [...] Read more.
Thermo-exfoliated graphite (TEG)/CuO/Cu2(OH)3NO3:(Co2+/Fe3+) composites were prepared using a wet impregnation method and subsequent thermal treatment. The physicochemical characterization of the composites was carried out by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Ar temperature-desorption techniques. The catalytic efficiency toward CO conversion to CO2 was examined under atmospheric pressure. Characterization of species adsorbed over the composites taken after the activity tests were performed by means of temperature programmed desorption massspectrometry (TPD MS). (TEG)/CuO/Cu2(OH)3NO3:(Co2+/Fe3+) composites show superior performance results if lower temperatures and extra treatment with H2SO4 or HNO3 are used at the preparation stages. The catalytic properties enhancements can be related to the Cu2(OH)3NO3 phase providing reaction centers for the CO conversion. It has been found that prevalence of low-temperature states of desorbed CO2 over high-temperature ones in the TPD MS spectra is characteristic of the most active composite catalysts. Full article
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Open AccessArticle Electrical and Electrorheological Properties of Alumina/Natural Rubber (STR XL) Composites
Materials 2010, 3(1), 656-671; doi:10.3390/ma3010656
Received: 18 December 2009 / Revised: 19 January 2010 / Accepted: 21 January 2010 / Published: 22 January 2010
Cited by 3 | PDF Full-text (874 KB) | HTML Full-text | XML Full-text
Abstract
The electrorheological properties (ER) of natural rubber (XL)/alumina (Al2O3) composites were investigated in oscillatory shear mode under DC electrical field strengths between 0 to 2 kV/mm. SEM micrographs indicate a mean particle size of 9.873 ± 0.034 µm [...] Read more.
The electrorheological properties (ER) of natural rubber (XL)/alumina (Al2O3) composites were investigated in oscillatory shear mode under DC electrical field strengths between 0 to 2 kV/mm. SEM micrographs indicate a mean particle size of 9.873 ± 0.034 µm and particles that are moderately dispersed in the matrix. The XRD patterns indicate Al2O3 is of the β-phase polytype which possesses high ionic conductivity. The storage modulus (G′) of the composites, or the rigidity, increases by nearly two orders of magnitude, with variations in particle volume fraction and electrical field strength. The increase in the storage modulus is caused the ionic polarization of the alumina particles and the induced dipole moments set up in the natural rubber matrix. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Preparation of Multi-Walled Carbon Nanotube/Amino-Terminated Ionic Liquid Arrays and Their Electrocatalysis towards Oxygen Reduction
Materials 2010, 3(1), 672-681; doi:10.3390/ma3010672
Received: 10 November 2009 / Revised: 20 January 2010 / Accepted: 22 January 2010 / Published: 25 January 2010
Cited by 6 | PDF Full-text (376 KB) | HTML Full-text | XML Full-text
Abstract
Arrays of aligned multi-walled carbon nanotube-ionic liquid (MIL) were assembled on silicon wafers (Si-MIL). Formation of Si-MIL was confirmed by ATR-FTIR, AFM and Raman techniques. The electrochemical measurements indicated that Si-MIL showed good electrocatalysis towards oxygen reduction compared with MIL drop-cast on [...] Read more.
Arrays of aligned multi-walled carbon nanotube-ionic liquid (MIL) were assembled on silicon wafers (Si-MIL). Formation of Si-MIL was confirmed by ATR-FTIR, AFM and Raman techniques. The electrochemical measurements indicated that Si-MIL showed good electrocatalysis towards oxygen reduction compared with MIL drop-cast on a glassy carbon electrode. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessArticle Pd0@Polyoxometalate Nanostructures as Green Electrocatalysts: Illustrative Example of Hydrogen Production
Materials 2010, 3(1), 741-754; doi:10.3390/ma3010741
Received: 1 December 2009 / Revised: 18 January 2010 / Accepted: 22 January 2010 / Published: 26 January 2010
Cited by 15 | PDF Full-text (632 KB) | HTML Full-text | XML Full-text
Abstract
Green-chemistry type procedures were used to synthesize Pd0 nanostructures encapsulated by a vanadium-substituted Wells-Dawson-type polyoxometalate (Pd0@POM). The cyclic voltammogram run with the Pd0@POM-modified glassy carbon electrode shows well-defined waves, associated with Pd0 nanostructures and the V [...] Read more.
Green-chemistry type procedures were used to synthesize Pd0 nanostructures encapsulated by a vanadium-substituted Wells-Dawson-type polyoxometalate (Pd0@POM). The cyclic voltammogram run with the Pd0@POM-modified glassy carbon electrode shows well-defined waves, associated with Pd0 nanostructures and the VV/VIV redox couple. The Pd0@POM-modified electrode displayed remarkably reproducible cyclic voltammetry patterns. The hydrogen evolution reaction (HER) was selected as an illustrative example to test the electrocatalytic behavior of the electrode. The kinetic parameters of the HER show the high efficiency of the Pd0@POM-modified electrode. This is the first example of electrochemical characterization of a modified electrode based on a vanado-tungstic POM and Pd0 nanostructures. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
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Review

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Open AccessReview Graded/Gradient Porous Biomaterials
Materials 2010, 3(1), 26-47; doi:10.3390/ma3010026
Received: 1 December 2009 / Revised: 21 December 2009 / Accepted: 25 December 2009 / Published: 25 December 2009
Cited by 50 | PDF Full-text (924 KB) | HTML Full-text | XML Full-text
Abstract
Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of [...] Read more.
Biomaterials include bioceramics, biometals, biopolymers and biocomposites and they play important roles in the replacement and regeneration of human tissues. However, dense bioceramics and dense biometals pose the problem of stress shielding due to their high Young’s moduli compared to those of bones. On the other hand, porous biomaterials exhibit the potential of bone ingrowth, which will depend on porous parameters such as pore size, pore interconnectivity, and porosity. Unfortunately, a highly porous biomaterial results in poor mechanical properties. To optimise the mechanical and the biological properties, porous biomaterials with graded/gradient porosity, pores size, and/or composition have been developed. Graded/gradient porous biomaterials have many advantages over graded/gradient dense biomaterials and uniform or homogenous porous biomaterials. The internal pore surfaces of graded/gradient porous biomaterials can be modified with organic, inorganic, or biological coatings and the internal pores themselves can also be filled with biocompatible and biodegradable materials or living cells. However, graded/gradient porous biomaterials are generally more difficult to fabricate than uniform or homogenous porous biomaterials. With the development of cost-effective processing techniques, graded/gradient porous biomaterials can find wide applications in bone defect filling, implant fixation, bone replacement, drug delivery, and tissue engineering. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
Open AccessReview Novel Bioactive Titanate Layers Formed on Ti Metal and Its Alloys by Chemical Treatments
Materials 2010, 3(1), 48-63; doi:10.3390/ma3010048
Received: 30 November 2009 / Revised: 16 December 2009 / Accepted: 22 December 2009 / Published: 25 December 2009
Cited by 15 | PDF Full-text (2643 KB) | HTML Full-text | XML Full-text
Abstract
Sodium titanate formed on Ti metal by NaOH and heat treatments induces apatite formation on its surface in a body environment and bonds to living bone. These treatments have been applied to porous Ti metal in artificial hip joints, and have been [...] Read more.
Sodium titanate formed on Ti metal by NaOH and heat treatments induces apatite formation on its surface in a body environment and bonds to living bone. These treatments have been applied to porous Ti metal in artificial hip joints, and have been used clinically in Japan since 2007. Calcium titanate formed on Ti-15Zr-4Nb-4Ta alloy by NaOH, CaCl2, heat, and water treatments induces apatite formation on its surface in a body environment. Titanium oxide formed on porous Ti metal by NaOH, HCl, and heat treatments exhibits osteoinductivity as well as osteoconductivity. This is now under clinical tests for application to a spinal fusion device. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
Open AccessReview Dental Glass Ionomer Cements as Permanent Filling Materials? – Properties, Limitations and Future Trends
Materials 2010, 3(1), 76-96; doi:10.3390/ma3010076
Received: 1 December 2009 / Revised: 22 December 2009 / Accepted: 25 December 2009 / Published: 28 December 2009
Cited by 27 | PDF Full-text (843 KB) | HTML Full-text | XML Full-text
Abstract
Glass ionomer cements (GICs) are clinically attractive dental materials that have certain unique properties that make them useful as restorative and luting materials. This includes adhesion to moist tooth structures and base metals, anticariogenic properties due to release of fluoride, thermal compatibility [...] Read more.
Glass ionomer cements (GICs) are clinically attractive dental materials that have certain unique properties that make them useful as restorative and luting materials. This includes adhesion to moist tooth structures and base metals, anticariogenic properties due to release of fluoride, thermal compatibility with tooth enamel, biocompatibility and low toxicity. The use of GICs in a mechanically loaded situation, however, has been hampered by their low mechanical performance. Poor mechanical properties, such as low fracture strength, toughness and wear, limit their extensive use in dentistry as a filling material in stress-bearing applications. In the posterior dental region, glass ionomer cements are mostly used as a temporary filling material. The requirement to strengthen those cements has lead to an ever increasing research effort into reinforcement or strengthening concepts. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
Open AccessReview Characterization of Bronze Surface Layer Formed by Microarc Oxidation Process in 12-Tungstophosphoric Acid
Materials 2010, 3(1), 110-126; doi:10.3390/ma3010110
Received: 3 December 2009 / Revised: 22 December 2009 / Accepted: 24 December 2009 / Published: 31 December 2009
Cited by 7 | PDF Full-text (1142 KB) | HTML Full-text | XML Full-text
Abstract
This paper is a brief review of our recent research into novel uses for heteropoly compounds as precursors for thin films that can be used as catalysts and materials with good optical, conductive and other characteristics. In view of this, we have [...] Read more.
This paper is a brief review of our recent research into novel uses for heteropoly compounds as precursors for thin films that can be used as catalysts and materials with good optical, conductive and other characteristics. In view of this, we have chosen thin film obtained with 12-tungsphosphoric acid on aluminum substrates. In all cases, a relatively new, microarc oxidation technique has been used to prepare oxide coatings on substrate surfaces. Advanced physicochemical methods, AFM and SEM-EDS, XRD, Raman and Micro-Raman, and luminescence spectroscopy, as the most powerful techniques, have been used for the characterization of new materials. Possible applications have been discussed as well. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Open AccessReview Recent Developments in Carbon Nanotube Membranes for Water Purification and Gas Separation
Materials 2010, 3(1), 127-149; doi:10.3390/ma3010127
Received: 17 November 2009 / Revised: 23 December 2009 / Accepted: 24 December 2009 / Published: 4 January 2010
Cited by 78 | PDF Full-text (2881 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Carbon nanotubes (CNTs) are nanoscale cylinders of graphene with exceptional properties such as high mechanical strength, high aspect ratio and large specific surface area. To exploit these properties for membranes, macroscopic structures need to be designed with controlled porosity and pore size. [...] Read more.
Carbon nanotubes (CNTs) are nanoscale cylinders of graphene with exceptional properties such as high mechanical strength, high aspect ratio and large specific surface area. To exploit these properties for membranes, macroscopic structures need to be designed with controlled porosity and pore size. This manuscript reviews recent progress on two such structures: (i) CNT Bucky-papers, a non-woven, paper like structure of randomly entangled CNTs, and (ii) isoporous CNT membranes, where the hollow CNT interior acts as a membrane pore. The construction of these two types of membranes will be discussed, characterization and permeance results compared, and some promising applications presented. Full article
(This article belongs to the Special Issue Porous Materials)
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Open AccessReview Functionalization of Artificial Freestanding Composite Nanomembranes
Materials 2010, 3(1), 165-200; doi:10.3390/ma3010165
Received: 30 October 2009 / Revised: 4 January 2010 / Accepted: 6 January 2010 / Published: 7 January 2010
Cited by 13 | PDF Full-text (3848 KB) | HTML Full-text | XML Full-text
Abstract
Artificial nanomembranes may be defined as synthetic freestanding structures with a thickness below 100 nm and a very large aspect ratio, of at least a few orders of magnitude. Being quasi-2D, they exhibit a host of unusual properties useful for various applications [...] Read more.
Artificial nanomembranes may be defined as synthetic freestanding structures with a thickness below 100 nm and a very large aspect ratio, of at least a few orders of magnitude. Being quasi-2D, they exhibit a host of unusual properties useful for various applications in energy harvesting, sensing, optics, plasmonics, biomedicine, etc. We review the main approaches to nanomembrane functionalization through nanocompositing, which ensures performance far superior to that of simple nanomembranes. These approaches include lamination (stacking of nanometer-thin strata of different materials), introduction of nanoparticle fillers into the nanomembrane scaffold, nanomembrane surface sculpting and modification through patterning (including formation of nanohole arrays and introduction of ion channels similar in function to those in biological nanomembranes). We also present some of our original results related to functionalization of metal matrix composite nanomembranes. Full article
(This article belongs to the Special Issue Composite Materials)
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Open AccessReview Scaffold Characteristics for Functional Hollow Organ Regeneration
Materials 2010, 3(1), 241-263; doi:10.3390/ma3010241
Received: 10 December 2009 / Revised: 5 January 2010 / Accepted: 7 January 2010 / Published: 8 January 2010
Cited by 6 | PDF Full-text (355 KB) | HTML Full-text | XML Full-text
Abstract
Many medical conditions require surgical reconstruction of hollow organs. Tissue engineering of organs and tissues is a promising new technique without harvest site morbidity. An ideal biomaterial should be biocompatible, support tissue formation and provide adequate structural support. It should degrade gradually [...] Read more.
Many medical conditions require surgical reconstruction of hollow organs. Tissue engineering of organs and tissues is a promising new technique without harvest site morbidity. An ideal biomaterial should be biocompatible, support tissue formation and provide adequate structural support. It should degrade gradually and provide an environment allowing for cell-cell interaction, adhesion, proliferation, migration, and differentiation. Although tissue formation is feasible, functionality has never been demonstrated. Mainly the lack of proper innervation and vascularisation are hindering contractility and normal function. In this chapter we critically review the current state of engineering hollow organs with a special focus on innervation and vascularisation. Full article
(This article belongs to the Special Issue Advances in Biomaterials)
Open AccessReview Interface Reactions and Synthetic Reaction of Composite Systems
Materials 2010, 3(1), 264-295; doi:10.3390/ma3010264
Received: 11 November 2009 / Revised: 29 December 2009 / Accepted: 4 January 2010 / Published: 8 January 2010
Cited by 2 | PDF Full-text (2752 KB) | HTML Full-text | XML Full-text
Abstract
Interface reactions in composite systems often determine their overall properties, since product phases usually formed at interfaces during composite fabrication processing make up a large portion of the composites. Since most composite materials represent a ternary or higher order materials system, many [...] Read more.
Interface reactions in composite systems often determine their overall properties, since product phases usually formed at interfaces during composite fabrication processing make up a large portion of the composites. Since most composite materials represent a ternary or higher order materials system, many studies have focused on analyses of diffusion phenomena and kinetics in multicomponent systems. However, the understanding of the kinetic behavior increases the complexity, since the kinetics of each component during interdiffusion reactions need to be defined for interpreting composite behaviors. From this standpoint, it is important to clarify the interface reactions for producing compatible interfaces with desired product phases. A thermodynamic evaluation such as a chemical potential of involving components can provide an understanding of the diffusion reactions, which govern diffusion pathways and product phase formation. A strategic approach for designing compatible interfaces is discussed in terms of chemical potential diagrams and interface morphology, with some material examples. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview On Micro-Macro Transition in Non-Linear Mechanics
Materials 2010, 3(1), 296-317; doi:10.3390/ma3010296
Received: 31 October 2009 / Revised: 10 December 2009 / Accepted: 14 December 2009 / Published: 8 January 2010
Cited by 2 | PDF Full-text (197 KB) | HTML Full-text | XML Full-text
Abstract
This paper is devoted to the description of the general relationships between microscopic and macroscopic mechanical quantities in non-linear mechanics. From a thermodynamical viewpoint, it is only necessary to know the two macroscopic potentials (macroscopic free energy and macroscopic potential of dissipation) [...] Read more.
This paper is devoted to the description of the general relationships between microscopic and macroscopic mechanical quantities in non-linear mechanics. From a thermodynamical viewpoint, it is only necessary to know the two macroscopic potentials (macroscopic free energy and macroscopic potential of dissipation) to describe the state of the body and its quasistatic evolution. These global potentials are the averages of the local ones. We point out some particular cases of non-linearities, especially the case of damaged materials. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview Friction Stir Processing of Particle Reinforced Composite Materials
Materials 2010, 3(1), 329-350; doi:10.3390/ma3010329
Received: 29 October 2009 / Revised: 14 December 2009 / Accepted: 8 January 2010 / Published: 11 January 2010
Cited by 20 | PDF Full-text (8971 KB) | HTML Full-text | XML Full-text
Abstract
The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers [...] Read more.
The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have investigated this technology for treating other alloys and materials including stainless steels, magnesium, titanium, and copper. It is shown that FSP technology is very effective in microstructure modification of reinforced metal matrix composite materials. FSP has also been used in the processing and structure modification of polymeric composite materials. Compared with other manufacturing processes, friction stir processing has the advantage of reducing distortion and defects in materials. The layout of this paper is as follows. The friction stir processing technology will be presented first. Then, the application of this technology in manufacturing and structure modification of particle reinforced composite materials will be introduced. Future application of friction stir processing in energy field, for example, for vanadium alloy and composites will be discussed. Finally, the challenges for improving friction stir processing technology will be mentioned. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview Ceramics for Dental Applications: A Review
Materials 2010, 3(1), 351-368; doi:10.3390/ma3010351
Received: 1 December 2009 / Revised: 5 January 2010 / Accepted: 7 January 2010 / Published: 11 January 2010
Cited by 66 | PDF Full-text (3290 KB) | HTML Full-text | XML Full-text
Abstract
Over the past forty years, the technological evolution of ceramics for dental applications has been remarkable, as new materials and processing techniques are steadily being introduced. The improvement in both strength and toughness has made it possible to expand the range of [...] Read more.
Over the past forty years, the technological evolution of ceramics for dental applications has been remarkable, as new materials and processing techniques are steadily being introduced. The improvement in both strength and toughness has made it possible to expand the range of indications to long-span fixed partial prostheses, implant abutments and implants. The present review provides a state of the art of ceramics for dental applications. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
Open AccessReview Synthetic Fabrication of Nanoscale MoS2-Based Transition Metal Sulfides
Materials 2010, 3(1), 401-433; doi:10.3390/ma3010401
Received: 9 December 2009 / Accepted: 12 January 2010 / Published: 12 January 2010
Cited by 16 | PDF Full-text (873 KB) | HTML Full-text | XML Full-text
Abstract
Transition metal sulfides are scientifically and technologically important materials. This review summarizes recent progress on the synthetic fabrication of transition metal sulfides nanocrystals with controlled shape, size, and surface functionality. Special attention is paid to the case of MoS2 nanoparticles, where [...] Read more.
Transition metal sulfides are scientifically and technologically important materials. This review summarizes recent progress on the synthetic fabrication of transition metal sulfides nanocrystals with controlled shape, size, and surface functionality. Special attention is paid to the case of MoS2 nanoparticles, where organic (surfactant, polymer), inorganic (support, promoter, doping) compounds and intercalation chemistry are applied. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview A New Approach to the Computer Modeling of Amorphous Nanoporous Structures of Semiconducting and Metallic Materials: A Review
Materials 2010, 3(1), 467-502; doi:10.3390/ma3010467
Received: 8 November 2009 / Revised: 20 December 2009 / Accepted: 11 January 2010 / Published: 15 January 2010
Cited by 7 | PDF Full-text (3696 KB) | HTML Full-text | XML Full-text
Abstract
We review our approach to the generation of nanoporous materials, both semiconducting and metallic, which leads to the existence of nanopores within the bulk structure. This method, which we have named as the expanding lattice method, is a novel transferable approach which [...] Read more.
We review our approach to the generation of nanoporous materials, both semiconducting and metallic, which leads to the existence of nanopores within the bulk structure. This method, which we have named as the expanding lattice method, is a novel transferable approach which consists first of constructing crystalline supercells with a large number of atoms and a density close to the real value and then lowering the density by increasing the volume. The resulting supercells are subjected to either ab initio or parameterized—Tersoff-based—molecular dynamics processes at various temperatures, all below the corresponding bulk melting points, followed by geometry relaxations. The resulting samples are essentially amorphous and display pores along some of the “crystallographic” directions without the need of incorporating ad hoc semiconducting atomic structural elements such as graphene-like sheets and/or chain-like patterns (reconstructive simulations) or of reproducing the experimental processes (mimetic simulations). We report radial (pair) distribution functions, nanoporous structures of C and Si, and some computational predictions for their vibrational density of states. We present numerical estimates and discuss possible applications of semiconducting materials for hydrogen storage in potential fuel tanks. Nanopore structures for metallic elements like Al and Au also obtained through the expanding lattice method are reported. Full article
(This article belongs to the Special Issue Porous Materials)
Open AccessReview Brushite-Forming Mg-, Zn- and Sr-Substituted Bone Cements for Clinical Applications
Materials 2010, 3(1), 519-535; doi:10.3390/ma3010519
Received: 26 November 2009 / Revised: 12 January 2010 / Accepted: 15 January 2010 / Published: 18 January 2010
Cited by 12 | PDF Full-text (560 KB) | HTML Full-text | XML Full-text
Abstract
Calcium phosphate cements have been in clinical use for the last 10 years. Their most salient features include good biocompatibility, excellent bioactivity, self-setting characteristics, low setting temperature, adequate stiffness, and easy shaping to accomodate any complicated geometry. They are commonly used in [...] Read more.
Calcium phosphate cements have been in clinical use for the last 10 years. Their most salient features include good biocompatibility, excellent bioactivity, self-setting characteristics, low setting temperature, adequate stiffness, and easy shaping to accomodate any complicated geometry. They are commonly used in filling bone defects and trauma surgeries as mouldable paste-like bone substitute materials. Substitution of trace elements, such as Mg, Sr and Zn ions, into the structure of calcium phosphates is the subject of widespread investigation nowadays, because of their impending role in the biological process. Subtle differences in composition and structure of these materials may have a profound effect on their in vivo behaviour. Therefore, the main goal of this paper is to provide a simple, but comprehensive overview of the present achievements relating to brushite-forming cements doped with Mg, Zn and Sr, and to identify new developments and trends. In particular, the influence of ionic substitution on the chemical, physical and biological properties of these materials is discussed. Full article
(This article belongs to the Special Issue Ceramics for Healthcare)
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Open AccessReview Porous Dielectrics in Microelectronic Wiring Applications
Materials 2010, 3(1), 536-562; doi:10.3390/ma3010536
Received: 7 December 2009 / Revised: 1 January 2010 / Accepted: 14 January 2010 / Published: 18 January 2010
Cited by 17 | PDF Full-text (349 KB) | HTML Full-text | XML Full-text
Abstract
Porous insulators are utilized in the wiring structure of microelectronic devices as a means of reducing, through low dielectric permittivity, power consumption and signal delay in integrated circuits. They are typically based on low density modifications of amorphous SiO2 known as [...] Read more.
Porous insulators are utilized in the wiring structure of microelectronic devices as a means of reducing, through low dielectric permittivity, power consumption and signal delay in integrated circuits. They are typically based on low density modifications of amorphous SiO2 known as SiCOH or carbon-doped oxides, in which free volume is created through the removal of labile organic phases. Porous dielectrics pose a number of technological challenges related to chemical and mechanical stability, particularly in regard to semiconductor processing methods. This review discusses porous dielectric film preparation techniques, key issues encountered, and mitigation strategies. Full article
(This article belongs to the Special Issue Porous Materials)
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Open AccessReview Geometrical Description in Binary Composites and Spectral Density Representation
Materials 2010, 3(1), 585-613; doi:10.3390/ma3010585
Received: 20 November 2009 / Revised: 18 January 2010 / Accepted: 19 January 2010 / Published: 21 January 2010
Cited by 14 | PDF Full-text (640 KB) | HTML Full-text | XML Full-text
Abstract
In this review, the dielectric permittivity of dielectric mixtures is discussed in view of the spectral density representation method. A distinct representation is derived for predicting the dielectric properties, permittivities ε, of mixtures. The presentation of the dielectric properties is based [...] Read more.
In this review, the dielectric permittivity of dielectric mixtures is discussed in view of the spectral density representation method. A distinct representation is derived for predicting the dielectric properties, permittivities ε, of mixtures. The presentation of the dielectric properties is based on a scaled permittivity approach, ξ = (εeεm)(εi εm)−1, where the subscripts e, m and i denote the dielectric permittivities of the effective, matrix and inclusion media, respectively [Tuncer, E. J. Phys.: Condens. Matter 2005, 17, L125]. This novel representation transforms the spectral density formalism to a form similar to the distribution of relaxation times method of dielectric relaxation. Consequently, I propose that any dielectric relaxation formula, i.e., the Havriliak-Negami empirical dielectric relaxation expression, can be adopted as a scaled permittivity. The presented scaled permittivity representation has potential to be improved and implemented into the existing data analyzing routines for dielectric relaxation; however, the information to extract would be the topological/morphological description in mixtures. To arrive at the description, one needs to know the dielectric properties of the constituents and the composite prior to the spectral analysis. To illustrate the strength of the representation and confirm the proposed hypothesis, the Landau-Lifshitz/Looyenga (LLL) [Looyenga, H. Physica 1965, 31, 401] expression is selected. The structural information of a mixture obeying LLL is extracted for different volume fractions of phases. Both an in-house computational tool based on the Monte Carlo method to solve inverse integral transforms and the proposed empirical scaled permittivity expression are employed to estimate the spectral density function of the LLL expression. The estimated spectral functions for mixtures with different inclusion concentration compositions show similarities; they are composed of a couple of bell-shaped distributions, with coinciding peak locations but different heights. It is speculated that the coincidence in the peak locations is an absolute illustration of the self-similar fractal nature of the mixture topology (structure) created with the LLL expression. Consequently, the spectra are not altered significantly with increased filler concentration level—they exhibit a self-similar spectral density function for different concentration levels. Last but not least, the estimated percolation strengths also confirm the fractal nature of the systems characterized by the LLL mixture expression. It is concluded that the LLL expression is suitable for complex composite systems that have hierarchical order in their structure. These observations confirm the finding in the literature. Full article
(This article belongs to the Special Issue Composite Materials)
Open AccessReview Semiconductor Nanocrystals Hybridized with Functional Ligands: New Composite Materials with Tunable Properties
Materials 2010, 3(1), 614-637; doi:10.3390/ma3010614
Received: 31 December 2009 / Accepted: 21 January 2010 / Published: 22 January 2010
Cited by 15 | PDF Full-text (516 KB) | HTML Full-text | XML Full-text
Abstract
Semiconductor nanocrystals hybridized with functional ligands represent an important new class of composite nanomaterials. The development of these new nanoscale building blocks has intensified over the past few years and offer significant advantages in a wide array of applications. Functional ligands allow [...] Read more.
Semiconductor nanocrystals hybridized with functional ligands represent an important new class of composite nanomaterials. The development of these new nanoscale building blocks has intensified over the past few years and offer significant advantages in a wide array of applications. Functional ligands allow for incorporation of nanocrystals into areas where their unique photophysics can be exploited. Energy and charge transfer between the ligands and the nanocrystal also result in enhanced physical properties that can be tuned by the choice of ligand architecture. Here, progress in the development and applications involving this new class of composite materials will be discussed. Full article
(This article belongs to the Special Issue Composite Materials)
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Open AccessReview Current Strategies in Cardiovascular Biomaterial Functionalization
Materials 2010, 3(1), 638-655; doi:10.3390/ma3010638
Received: 11 November 2009 / Revised: 15 January 2010 / Accepted: 20 January 2010 / Published: 22 January 2010
Cited by 15 | PDF Full-text (97 KB) | HTML Full-text | XML Full-text
Abstract
Prevention of the coagulation cascade and platelet activation is the foremost demand for biomaterials in contact with blood. In this review we describe the underlying mechanisms of these processes and offer the current state of antithrombotic strategies. We give an overview of [...] Read more.
Prevention of the coagulation cascade and platelet activation is the foremost demand for biomaterials in contact with blood. In this review we describe the underlying mechanisms of these processes and offer the current state of antithrombotic strategies. We give an overview of methods to prevent protein and platelet adhesion, as well as techniques to immobilize biochemically active molecules on biomaterial surfaces. Finally, recent strategies in biofunctionalization by endothelial cell seeding as well as their possible clinical applications are discussed. Full article
(This article belongs to the Special Issue Biocompatibility of Materials)
Open AccessReview Inorganic Hybrid Materials with Encapsulated Polyoxometalates
Materials 2010, 3(1), 682-703; doi:10.3390/ma3010682
Received: 16 December 2009 / Revised: 19 January 2010 / Accepted: 22 January 2010 / Published: 25 January 2010
Cited by 21 | PDF Full-text (614 KB) | HTML Full-text | XML Full-text
Abstract
This review describes the synthesis and characterization of inorganic materials containing polyoxometalates encapsulated in oxide matrices. Examples illustrating key aspects in terms of synthesis and applications are presented according to the nature of the final hybrid material: those based on non-structured silicas, [...] Read more.
This review describes the synthesis and characterization of inorganic materials containing polyoxometalates encapsulated in oxide matrices. Examples illustrating key aspects in terms of synthesis and applications are presented according to the nature of the final hybrid material: those based on non-structured silicas, on mesostructured silicas, on macrostructured silicas and on other oxides. In each part, key points of the synthetic protocols are highlighted and structural features and properties of the resultant hybrid nanocomposites are discussed. Full article
(This article belongs to the Special Issue Polyoxometalate Compounds)
Open AccessReview Influence of Chemical Conditions on the Nanoporous Structure of Silicate Aerogels
Materials 2010, 3(1), 704-740; doi:10.3390/ma3010704
Received: 3 November 2009 / Revised: 24 December 2009 / Accepted: 20 January 2010 / Published: 26 January 2010
Cited by 35 | PDF Full-text (932 KB) | HTML Full-text | XML Full-text
Abstract
Silica or various silicate aerogels can be characterized by highly porous, open cell, low density structures. The synthesis parameters influence the three-dimensional porous structures by modifying the kinetics and mechanism of hydrolysis and condensation processes. Numerous investigations have shown that the structure [...] Read more.
Silica or various silicate aerogels can be characterized by highly porous, open cell, low density structures. The synthesis parameters influence the three-dimensional porous structures by modifying the kinetics and mechanism of hydrolysis and condensation processes. Numerous investigations have shown that the structure of porous materials can be tailored by variations in synthesis conditions (e.g., the type of precursors, catalyst, and surfactants; the ratio of water/precursor; the concentrations; the medium pH; and the solvent). The objectives of this review are to summarize and elucidate the effects of chemical conditions on the nanoporous structure of sol-gel derived silicate aerogels. Full article
(This article belongs to the Special Issue Porous Materials)

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