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Showing papers in "Materials Research Innovations in 2000"


Journal ArticleDOI
TL;DR: In this paper, the perovskite structure is used to illustrate the relationship of structure to composition, and the history of the fundamental science of structure-to-composition is described.
Abstract: Starting with the history of the fundamental science of the relation of structure to composition delineated completely by Goldschmidt, we use the perovskite structure to illustrate the enormous pow...

998 citations


Journal ArticleDOI
TL;DR: Based on the theory of Pilling-Bedworth ratio (PBR) for metals, PBR for oxidation of alloys is suggested as in this paper, where PBR is used for alloys.
Abstract: Based on the theory of Pilling-Bedworth ratio (PBR) for metals, PBR for oxidation of alloys is suggested as

270 citations


Journal ArticleDOI
TL;DR: Optimising this bioactive regenerative capacity of Bioactive glass-ceramics offers great hope for producing biomaterials that can stimulate growth, repair, and regeneration of any human tissue.
Abstract: Many of the present generation biomaterials are still based upon the early concept that implantable materials should be bioinert and therefore designed to evoke minimal tissue response, if none. However, a growing body of clinical data demonstrates that the long survivability of these materials is hampered by high rates of failure, which is primarily attributed to interfacial instability. It has therefore become understood that this approach is not optimal. Modern approaches implicate the use of biomaterials that can actively interact with tissues and induce their intrinsic repair and regenerative potential. This involves control over the cell cycle, the molecular framework that controls cell proliferation and differentiation. Class A bioactive glass-ceramic materials were the first materials shown to endorse these properties and, depending upon the rate of resorption and release of ions, can create chemical gradients with specific biological actions over cells and tissues. Optimising this bioactive regenerative capacity of Bioactive glass-ceramics offers great hope for producing biomaterials that can stimulate growth, repair, and regeneration of any human tissue.

123 citations


Journal ArticleDOI
TL;DR: In this article, the authors used a sol-gel technique to obtain a high specific surface area as measured by capillary adsorption of nitrogen, suggesting their possible use in catalysis.
Abstract: Cupric oxide (CuO) nanoparticles have been prepared in amorphous SiO2 matrix using a novel variant of sol-gel technique. The method is based on the polycondensation of a silica source (sodium silicate) in the presence of an aqueous solution containing complex of Cu(II) with polyvinyl alcohol (CuPVA). After gelation, polymeric complexes containing several thousands Cu atoms each are incorporated into the silica network forming a precursor, which is then annealed in oxygen to get rid of organic components. The formation of CuO nanoparticles was confirmed by electron diffraction studies. The size of nanoparticles can be controlled by varying [Cu2+]/[PVA] ratio in the precursor. Thus prepared CuO/SiO2 nanocomposites are characterized by high specific surface area as measured by capillary adsorption of nitrogen, suggesting their possible use in catalysis.

82 citations


Journal ArticleDOI
TL;DR: In this paper, the crystallographic relations between Ti3SiC2 and TiC were established and described based on the transmission electron microscopy investigation on the Ti3 SiC2/TiC interface in a Si-C2 based material.
Abstract: Ti3SiC2 is a so-called not-so-brittle ceramic that combines the merits of both metals and ceramics. However, many previous works demonstrated that its bonding nature and properties were strongly related to TiC. In this paper the crystallographic relations between Ti3SiC2 and TiC were established and described based on the transmission electron microscopy investigation on the Ti3SiC2/TiC interface in Ti3SiC2 based material. At Ti3SiC2/TiC interface, the following crystallographic relationships were identified: (111)TiC//(001)Ti3SiC2, (002) TiC//(104)Ti3SiC2, and [11¯0]TiC//[110]Ti3SiC2. Based on the above interfacial relations an interfacial structure model was established. The structure of Ti3SiC2 could be considered as two-dimensional closed packed layers of Si periodically intercalated into the (111) twin boundary of TiC0.67 (Ti3C2). The intercalation resulted in the transformation from cubic TiC0.67 to hexagonal Ti3SiC2. In the opposite case, de-intercalation of Si from Ti3SiC2 caused the transformation from hexagonal Ti3SiC2 to cubic TiC0.67. Understanding the crystallographic relations between Ti3SiC2 and TiC is of vital importance in both understanding the properties and optimizing the processing route for preparing pure Ti3SiC2.

59 citations


Journal ArticleDOI
TL;DR: In this article, the Rayleigh surface wave speed (cR) was shown to be the limiting speed of propagation for mode-I cracks in constitutively homogeneous, isotropic, linear elastic m...
Abstract: Classical dynamic fracture theories predict the Rayleigh surface wave speed (cR) to be the limiting speed of propagation for mode-I cracks in constitutively homogeneous, isotropic, linear elastic m...

58 citations


Journal ArticleDOI
TL;DR: In this paper, the stress-time correspondence principle discovered experimentally by O'Shaughnessy already in 1948 [1] is considered and the Doolittle formula for the viscosity as a function of free volume is used.
Abstract: Stress-time correspondence principle discovered experimentally by O'Shaughnessy already in 1948 [1] is considered. Using the Doolittle formula for the viscosity as a function of free volume [2], an...

52 citations


Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the general flexibility of ion implantation and irradiation techniques for producing unique near-surface nanocomposite microstructures in irradiated host materials.
Abstract: Ion implantation is a versatile and powerful technique for producing nanocrystal precipitates embedded in the near-surface region of materials. Radiation effects that occur during the implantation process can lead to complex microstructures and particle size distributions, and in the present work, we focus on the application of these effects to produce novel microstructural properties for insulating or semiconducting nanocrystals formed in optical host materials. Nanocrystal precipitates can be produced in two ways: by irradiation of pure (i.e., non-implanted) crystalline or amorphous materials, or by ion implantation followed by either thermal annealing or subsequent additional irradiation. Different methods for the formation of novel structural relationships between embedded nanocrystals and their hosts have been developed, and the results presented here demonstrate the general flexibility of ion implantation and irradiation techniques for producing unique near-surface nanocomposite microstructures in irradiated host materials.

37 citations


Journal ArticleDOI
TL;DR: In this article, a high-strength ceramic Al31Gd9O60 continuous fiber with a fiber diameter of about 20 µm and an amorphous structure could be made successfully by using the melt extraction method.
Abstract: A high-strength ceramic Al31Gd9O60 continuous fiber with a fiber diameter of about 20 µm and an amorphous structure could be made successfully by using the melt extraction method. This fiber can be freely shaped by viscous flow deformation in the supercooled liquid state (about 1193 K). The fiber strength is about 2 GPa and this strength is maintained up to around 973 K. A high-strength ceramic continuous fiber with a uniform GdAlO3 nanocrystalline in an amorphous matrix can also be obtained with a suitable crystallization from the amorphous state by heat treatment. The heat resistance, Young’s modulus, and other properties are therefore improved. The amorphous ceramic fiber is promising as a ceramic that can be easily shaped at a relatively low temperatures (around 1193 K) in agreement with temperature range of superplastic processing of Ti alloys.

27 citations


Journal ArticleDOI
TL;DR: In this paper, the peroxy derivatives of phenol-formaldehyde resins (PhFRs) have been elaborated, and the results were also used to create three-dimensional networks involving an unsaturated polyester resin.
Abstract: Methods of obtaining peroxy derivatives of phenol-formaldehyde resins (PhFRs) have been elaborated. Three different procedures have been pursued: i) chemical modification of PhFRs with hydroperoxides; ii) modification of PhFRs with 1.2-epoxy-3-tert-butylperoxypropane; and iii) polycondensation of peroxy phenols with formaldehyde. Structures of the resins were determined by chemical and spectroscopic methods. The results were also used to create three-dimensional networks involving an unsaturated polyester resin. IR-spectroscopy of the networks shows that, in addition to the peroxy groups and unsaturated bonds, others functional groups participate in the network formation.

21 citations


Journal ArticleDOI
TL;DR: In this paper, the fabrication and characterization of fine scale piezoelectric composites with 1-3 connectivity using fibers derived from a metal alkoxide sol-gel process was described.
Abstract: This paper reports on the fabrication and characterization of fine scale piezoelectric composites with 1–3 connectivity using fibers derived from a metal alkoxide sol-gel process. Using this technique, pure thickness mode resonance for this type of composite has been increased from 15 MHz up to 70 MHz by maintaining pillar aspect ratio requirements. Piezoceramic fibers of Nb or La modified lead zirconate titanate (PZT) were produced with final diameters ranging from 15 to 50 µm.

Journal ArticleDOI
A. Ya. Goldman1, C. J. Copsey1
TL;DR: The level of toughness increase achieved by the addition of CaCO3 is close to the toughness produced using rubber at 23°C, and even better at lower temperatures as discussed by the authors, and demonstrated in Dynatup and Izod impact tests at low temperatures down to -40°C.
Abstract: filled materials increased significantly at ambient temperature for both material samples and molded plastic parts A similar improvement was demonstrated in Dynatup and Izod impact tests at low temperatures down to –40°C The level of toughness increase achieved by the addition of CaCO3 is close to the toughness produced using rubber at 23°C, and even better at lower temperatures

Journal ArticleDOI
TL;DR: In this article, it is shown that the R-curve equation correctly predicts K∞, which is comparable to the conventional measured Mode I plain-strain fracture toughness, KIc, of the same material.
Abstract: is the crack resistance at ”infinite” crack length. It is convincingly shown that this so-called R-curve equation correctly predicts K∞, which is comparable to the conventionally measured Mode I plain-strain fracture toughness, KIc, of the same material. The fundamental constants in the fracture-mechanics-based equations are discussed, emphasizing the aspects pertinent to the small specimens used in the MDBT. Results are presented on 8 materials: ZnS, glass-ceramic, Si3N4, Ti5Si3, SiC, Ni3Ge, NiAl and Ti-46.5A1-2.1Cr-3.0Nb-0.2W. All are brittle except for the latter two, which undergo slight plastic deformation before fracturing. The resulting values of K∞ are in excellent agreement with published values derived from conventional measurements, providing considerable confidence in the method.

Journal ArticleDOI
TL;DR: BICUVOX ionic conductors with enhanced electrical conductivity were produced through a new route of synthesis, using powders obtained from melting as discussed by the authors, and they were investigated with the general formula Bi4V(2x)MexO(11-x) with x varying from 0.07 to 0.20
Abstract: BICUVOX ionic conductors with enhanced electrical conductivity were produced through a new route of synthesis, using powders obtained from melting. Compositions with the general formula Bi4V(2-x)MexO(11-x) with x varying from 0.07 to 0.20 were investigated using this new process, and high electrical conductivity was observed in the temperature range of 100 to 400°C with high density materials at 750°C.

Journal ArticleDOI
TL;DR: Based on the theoretical predicted anisotropic electronic structure and properties, two-dimensional Ti2SnC plates were synthesized through a solid-liquid reaction process utilizing elemental Ti, Sn and C as starting materials as discussed by the authors.
Abstract: Titanium tin carbide (Ti2SnC) is a novel layered ternary compound. The ab initio calculations on the electronic structure and bonding properties indicated that Ti2SnC exhibit anisotropy of chemical bonding and properties. The electrical conductivity parallel to the basal plane is metallic and is much higher than that in c-axis. Thus Ti2SnC material in two-dimensional quasi-infinite form with the sheet surface parallel to the basal plane will show superior properties and have diverse device applications. Based on the theoretical predicted anisotropic electronic structure and properties, two-dimensional Ti2SnC plates were synthesized through a solid–liquid reaction process utilizing elemental Ti, Sn and C as starting materials. X-ray diffraction and scanning electron microscopy demonstrated that the morphology of the as-prepared plates were two-dimensional sheets. And the sheet surface was parallel to the (001) plane of Ti2SnC.

Journal ArticleDOI
TL;DR: The first cyclotriphosphate of mixed ammonium-bivalent cations with a new general formula MIINH4P3O9·nH2O was reported in this paper.
Abstract: Ammonium and barium cyclotriphosphate mo-nohydrate, BaNH4P3O9·1H2O, was prepared for the first time by using Boulle’s process [1] by Durif et al. [2] who reported a complete description of the atomic arrangement. BaNH4P3O9·1H2O is monoclinic P21/n with the following unit-cell dimensions: a=11.70(1)A, b=12.12(1)A, c=7.559(5)A, β=101.05(5) and Z=4. There-fore, some discrepancies appear in the literature and stimulated further investigation of this compound to conclude concerning hydration level and structure. The thermal behavior of BaNH4P3O9·nH2O [3] showed that this cyclotriphosphate is a dihydrate and up to now no other hydrate has been described for this salt. So, the present study reports the chemical preparation, thermal behavior and crystal structure of BaNH4P3O9·2H2O, the first cyclotriphosphate of mixed ammonium-bivalent cations MII with a new general formula MIINH4P3O9·nH2O. Dehydration and decomposition of such cyclotriphosphates lead generally to long-chain polyphosphates, [MII(PO3)2]∞ which can be used as corrosion inhibitors [4]. The title compound has been studied through the following techniques: X-ray diffraction, IR spectrometry and thermal analyses TGA-DTA coupled.

Journal ArticleDOI
TL;DR: In this paper, a diffusion-reaction model is proposed as the mechanism for the diffusion of hydrogen in amorphous and crystalline silicon, where molecular hydrogen dissolves and diffuses interstitially in the open silicon structure.
Abstract: A diffusion-reaction model is proposed as the mechanism for the diffusion of hydrogen in amorphous and crystalline silicon. In this model molecular hydrogen dissolves and diffuses interstitially in the open silicon structure. Dissolved molecular hydrogen reacts with silicon to form SiH groups. Equations derived for this model give profiles that fit well with experimental hydrogen profiles in amorphous silicon. Other experimental features, such as steps in hydrogen and deuterium concentrations at interfaces, exponential profiles at short times, and a decrease of the effective diffusion coefficient with increasing time, arise naturally in the diffusion-reaction model.

Journal ArticleDOI
TL;DR: In this article, waste rice husk was used for fiber reinforcement to strength the hydrothermal hot pressed calcium silicate compacts, which is expected to be useful in the development of an environmentally friendly processing route for making artificial wood.
Abstract: Hydrothermal hot-pressing (HHP) technique was used to solidify calcium silicate hydrate powders at a relatively low temperature as 200°C and low pressure (20 MPa) with short reaction time (30 min). Diatomaceous earth, α-quartz, fly ash and silicic acid were used as the Si sources. Waste rice husk was used for fiber reinforcement to strength the hydrothermal hot pressed calcium silicate compacts. The tensile strength of the solidified bodies with and without rice husk was tested. The solidified bodies with reinforced by 5% rice husk exhibit high tensile strength (∼9 MPa), which is almost three times lager than their non-additives compacts. There is no effect of additives for the density of solidified bodies, which remains almost constant at ∼2gcm–3 similar to their non-additive compacts. The developed low temperature solidification method is expected to be useful in the development of an environmentally friendly processing route for making artificial wood.

Journal ArticleDOI
TL;DR: In this article, the dispersion and fine crystalline structure of oxide and pyrrhotite particles were studied as the function of mechanical load, sulfiding temperature and mode of preparation.
Abstract: Genesis of pyrrhotite catalysts from different iron ore concentrates and pure iron oxides was investigated using the method of mechanochemical treatment in a planetary mill. The dispersion and fine crystalline structure of oxide and pyrrhotite particles were studied as the function of mechanical load, sulfiding temperature and mode of preparation. Methods for the preparation of high performance iron ore-based catalysts for brown coal hydrogenation have been developed.

Journal ArticleDOI
TL;DR: In this article, an aluminium matrix-zirconia nanoparticles-reinforced composites were prepared by the infiltration technique, and the metallic matrix for these composites stabilizes the tetragonal phase of ZIRconia at low temperature (450 °C) whereas at 610 °C a mixture of Tetragonal and monoclinic was obtained.
Abstract: Aluminium matrix-zirconia nanoparticles-reinforced composites were prepared by the infiltration technique. The metallic matrix for these composites stabilizes the tetragonal phase of zirconia at low temperature (450 °C) whereas at 610 °C a mixture of tetragonal and monoclinic was obtained. The wear resistance of zirconia-modified aluminium was significantly improved due to the presence of the ceramic nanoparticles embedded into the matrix.

Journal ArticleDOI
TL;DR: In this paper, the temperature coefficient of the resistance of a semiconducting diamond, combined with classic NTC, and platinum thermistors, was calculated and combined with a boron-doped diamond.
Abstract: Based on material parameters of diamond and typical experimental data of inverse temperature dependence of electrical conductivity, the temperature coefficient of the resistance of a semiconducting diamond, has been calculated and combined with classic NTC, and platinum thermistors. The results indicate that a boron-doped diamond is postulated to be used as a thin-film NTC high-temperature thermistor. The use of diamond for thermistors extend the operating speed and temperatures because of inherent material advantages.

Journal ArticleDOI
TL;DR: By measuring the imaginary part of the magnetic susceptibility of a GdBa2Cu3O7-x film, Wang et al. as discussed by the authors found the effect of N2, O2 and Ar molecules low temperature adsorption on the superconducting properties of the film.
Abstract: By measuring the imaginary part of the magnetic susceptibility of a GdBa2Cu3O7-x film, we found the effect of N2, O2 and Ar molecules low temperature adsorption on the superconducting properties of the film The low temperature adsorption of the gases affects the critical transport current and the transition temperature In all cases, the transition region broadens, as the degree of coverage of the film with the gas molecules increases By processing the experimental data, we found the critical current either growing linearly (for argon and nitrogen) or decreasing exponentially (for oxygen) with increasing surface coverage by the adsorbed gas molecules

Journal ArticleDOI
TL;DR: In this paper, the authors explore the current views of the interface community and to develop an understanding of the present state of play, research specialisation which studies knowledge development, has been applied to research variation in the community's ways of experiencing the "interface" as a phenomenon in composite materials.
Abstract: In order to explore the current views of the interface community and to develop an understanding of the present state of play, research specialisation which studies knowledge development, has been applied to research variation in the community’s ways of experiencing the ’interface’ as a phenomenon in composite materials. Ten leaders of the field were interviewed and the transcripts of those interviews collated and analysed. Four dimensions of variation in the ways researchers view the interface were uncovered. It is found that there is not even general agreement as to whether the interface is an object which can be measured, or an illusive concept. The resulting ’outcome space’ or ’collective consciousness’ may lead to a broader understanding of the issues involved.

Journal ArticleDOI
TL;DR: In this article, the hydrogen content of pure iron specimens was found to depend more on hydrogen than those of low angle, and thus specimens with low angle grain boundaries were less susceptible to hydrogen damage.
Abstract: The trapping of hydrogen by various interfaces in iron and steels has been studied. The hydrogen content of pure iron specimens was found to depend more on hydrogen than those of low angle, and thus specimens with low angle grain boundaries were less susceptible to hydrogen damage. Inclusions and thermo-mechanical treatments were also significant in determining the hydrogen pick-up in iron. A critical volume fraction of inclusions was detected, below which no hydrogen- induced cracking occurred. Ferrite/pearlite and pearlite/pearlite colony interfaces in steel were found to trap hydrogen, whereas the ferrite/comentite interface within the pearlitic colonies had little effect on the hydrogen occlusivity.

Journal ArticleDOI
TL;DR: In this article, a method to synthesize diamond crystal by using a well developed chemical vapor deposition process, but on a liquid substrate, while substrates of prevailing practice are solid.
Abstract: This paper is to report a novel method to synthesize diamond crystal by using a well developed chemical vapor deposition process, but on a liquid substrate, while substrates of prevailing practice are solid. The substrate materials are metals which become liquid at diamond deposition temperature, such as elements Sn and Ga, and eutectic alloys of Cu-Ge, Sn-Ge. One result is that, while reported diamond crystal size was about 10 to 40 micrometers on the solid substrate, on the liquid substrate, the crystal size has reached so far about 300 micrometers.

Journal ArticleDOI
TL;DR: In this article, the structure and surface properties of nanocomposites based upon framework zirconium phosphates with supported WO 3, MoO 3 and Pt nanoparticles were studied by using combination of structural and spectral methods.
Abstract: Nanocomposites based upon framework zirconium phosphates with supported WO 3 , MoO 3 and Pt nanoparticles were synthesized via the incipient wetness impregnation of high-surface-area mesoporous phosphate samples with water solutions of corresponding salts followed by drying and calcination. The structure and surface properties of nanocomposites were studied by using combination of structural and spectral methods. Due to a strong interaction between supports and supported species, the structure of the latter differs considerably from that of the bulk phases. Surface acid centers typical for zirconium phosphates disappear suggesting their participation in bonding nanoparticles of promoters. Instead, new types of strong acid sites associated with tungsten oxide clusters emerge. The effect of these promoters on performance of zirconium phosphates in the reaction of pentane and hexane isomerization is considered.

Journal ArticleDOI
TL;DR: In this article, the thermoluminescent (TL) emission was studied as a function of the zirconia for temperatures from 100 to 300 °C, and it was shown that there exists a self-inhibited process possible due, on the one hand to the segregation effects of both components, and on the other to the stabilization of either tetragonal or monoclinic ZIRconia phases.
Abstract: Zirconia–silica materials prepared by the sol-gel method at different compositions were gamma irradiated with a dosage of 40 Krads for different irradiation periods. The thermoluminescent (TL) emission was studied as a function of the zirconia for temperatures from 100 to 300 °C. Pure zirconia produces a strong TL signal, followed by 50% zirconia sample, while pure silica and the 5% zirconia sample show a weak TL signal. This means that there exists a self-inhibited process possible due, on the one hand to the segregation effects of both components, and on the other to the stabilization of either tetragonal or monoclinic zirconia phases. This effect opens the possibility to control the TL signal in a wide range of dosages allowing to use this system as a wide range dosimeter.

Journal ArticleDOI
TL;DR: In this paper, a method to characterize segregation effects in silica-zirconia materials prepared by the sol-gel method through the alkoxide route is reported, using the Radial Distribution Function obtained from the X-ray diffractograms.
Abstract: A novel method to characterize segregation effects in silica-zirconia materials prepared by the sol-gel method through the alkoxide route is reported. These segregation effects were studied by using the Radial Distribution Function obtained from the X-ray diffractograms. The information obtained by this technique allows one to predict the spatial distribution of one of the oxides into the other as a function of the annealing temperature and the relative concentration of both constituents. Silica and Zirconia were chosen for preparing the alloys since Si and Zr have the same oxidation state and, in spite of both ions being of different atomic radius, they do not produce distortion in the oxygen sub-lattice (due to an oxygen deficiency) which could influence the spatial distribution of both cations into the lattice.

Journal ArticleDOI
TL;DR: In this paper, the concept of tense grity is incorporated into a passive hydrophone device, where six PZT 5H™ bars acting as compressional elements in the tensegrity structure have been coupled with tensional bands of either polyaramid or carbon fiber.
Abstract: The concept of tensegrity as conceived by Buckminster Fuller has been incorporated into a passive hydrophone device. Tensegrity is described as the physical phenomenon that produces a stable geometric structure using solid compressional elements arranged in tandem with flexible tensional cables. In the devices built by the authors, six PZT 5H™ bars acting as compressional elements in the tensegrity structure have been coupled with tensional bands of either polyaramid or carbon fiber. This stable system is then wrapped with an outer layer of either polyaramid or carbon fiber and rubber film to form a sealed device, which is referred to as a piezotensegritive device in this paper. The six bars are arranged in parallel electrical connectivity for all devices described. The resonant frequency for these devices ranged from 19.5 to 20.3 kHz depending on the material used for wrapping the piezoelectric bars. These devices were also tested in a hydrostatic environment to determine the relevant piezoelectric coefficients. For devices wrapped with carbon fiber, dh peaked at ∼6000 pC/N and gh at ∼275 mVm/N. For devices wrapped with polyaramid, dh peaked at ∼2000pC/N and gh at ∼100mVm/N. Sensitivities from –182–195 db ref. 1V/µPa were calculated for these devices.

Journal ArticleDOI
TL;DR: In this article, temperature variations of a polypropylene melt in the barrels of an injection molding and a twin screw extruder under an isothermal state were investigated, and the major parameters influencing the melt temperature profiles were shear heating and heating conduction effects, residence time, flow length and the flow patterns of the flowing PP melt.
Abstract: This article investigated temperature variations of a polypropylene melt in the barrels of an injection moulding and a twin screw extruder under an isothermal state. The melt temperature profiles in the barrel of an injection moulding machine were observed to be different from those a twin screw extruder, this being associated with differences in the flows occurring in the barrels of each processing equipment. The major parameters influencing the melt temperature profiles were shear heating and heating conduction effects, residence time, flow length and the flow patterns of the flowing PP melt in the barrel.