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Sintering Process (sintering + process)
Selected AbstractsThe Prospects of Carrying and Releasing Drugs Via Biodegradable Magnesium Foam,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Eli Aghion Abstract Powder metallurgy technology was used to produce magnesium foams in order to evaluate their ability to perform as a solid biodegradable platform for drug delivery. The amount and delivery time of the released drug (gentamicin) was controlled by the level of space-holding particles (spacer) that was mixed with the magnesium powder prior to the sintering process. Metallurgical examination of the magnesium foams was carried out using optical and scanning electron microscopy (SEM) and X-ray diffraction analysis. Microtomography CT analysis was used to evaluate the structural characteristics of the magnesium foams and their internal interconnected porosity configuration. The corrosion behavior of the magnesium foams was evaluated by immersion test in a simulated physiological environment (PBS solution). The absorption of gentamicin was obtained by immersing magnesium foams in concentrated gentamicin solutions within a vacuum chamber, followed by water evaporation. The detection of gentamicin in PBS solution was carried out using a Fluorescence Polarimetry analyzer. The results show that the release profile of gentamicin from magnesium foam with 10 and 25% spacer in PBS solution was in accord with common dissolution kinetics of an active ingredient from polymeric drug delivery systems. [source] Screening of the Interactions Between Mg-PSZ and TRIP-Steel and Its Alloys During Sintering,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Christian Weigelt Ceramic,steel compound materials are used in a wide range of applications up to date. Major advantages are the mechanical properties due to the combination of brittle ceramic with tough steel. This study deals with effects of the sintering process on austenitic TRIP-steel/Mg-PSZ composite materials for mechanical load applications. Both, the FeCrNisteel and partially stabilized zirconia offer their special mechanical behavior only in a metastable state. The ability of phase transformation depends mainly on the chemical composition. Mutual interactions of the alloying metals (Cr, Ni, Mn, and Fe) and the ceramic stabilizer (MgO) during sintering may prevent the martensitic phase transformation. This may cause disadvantageous mechanical behavior on mechanical load in use. [source] Barium Non-Stoichiometry Role on the Properties of Ba1+xCe0.65Zr0.20Y0.15O3,, Proton Conductors for IT-SOFCsFUEL CELLS, Issue 5 2008S. Barison Abstract Proton conducting perovskite oxides have been widely investigated because of their potential as electrolytes for intermediate temperature solid oxide fuel cells. Among them, BaCeO3 - based materials exhibit good proton conductivity under a humidified hydrogen-containing atmosphere, but rather poor chemical stability in CO2 atmosphere. The substitution with Zr for Ce improves the chemical stability but reduces proton conductivity due to difficulties in fabricating dense materials. In the present work, single phase nanostructured powders of Ba1+xCe0.65Zr0.20Y0.15O3,, (x,=,0, 0.05, 0.10) solid solutions have been prepared by a modified sol,gel Pechini method with the final aim of evaluating the role of barium on their chemical and electrical properties. A significant influence of barium excess on the preparation and on properties of these materials has been demonstrated. In fact, density measurements evidenced that a 5 or 10,mol% nominal barium excess sensibly favoured the sintering process. Impedance analyses of sintered pellets confirmed the necessity of barium excess in order to avoid the lowering of proton conductivity, which has been evidenced for samples having stoichiometric barium content. Moreover, an unforeseen increase in chemical stability in CO2 -containing atmosphere with the growth of the barium excess was detected by thermogravimetric analyses. [source] Analysis of the parameters of the sintered loop heat pipeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2004K.J. Zan Abstract The purpose of this paper is to establish an experimental formula for sintered dendritic nickel powder. For this reason, wick structures with different porosity ranging from 65 to 80% were fabricated by cold pressing sintering process at fixed porosity and their parameters that included porosity, pore radius, and permeability were also measured. According to both the capillary limitation and the present experimental formula of the sintered dendritic nickel powder, the wick structure parameters that would affect the heat transfer capacity of the loop heat pipe (LHP) were analyzed theoretically and then investigated experimentally. The results showed that there exists an optimal combination of wick structure parameters by which the performance of the LHP would achieve optimization. The maximum heat transfer capacity was up to 500 W and the thermal resistance was 0.12°C/W at the allowable working temperature 80°C. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(8): 515,526, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20034 [source] Near Zero Shrinkage of an Low-Temperature Co-Fired Ceramic Package by Constrained Sintering Using Screen Printed Alumina PasteINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2010Sang Myoung Lee Conventional free sintering of low-temperature co-firing ceramic (LTCC) technology has several merits such as sintering temperature below 1000°C that enables co-firing with electrode materials of silver or copper metal and multilayer structure formation. But due to the free sintering process, large shrinkage occurs. To fabricate electronic devices and components with near zero shrinkage within x, y directions constrained sintering (CS) technology is required. In this study a constrained sintering paste (CSP) utilizing alumina powder, which has a higher sintering temperature than LTCC powders, was fabricated for CS technology. The effect of CSP formulated using alumina powder on shrinkage was studied according to variation in paste composition. As a result ceramic package structure with a cavity was fabricated with shrinkage control of 0.028%, which is far smaller than the current CS technology shrinkage of approximately 0.1%. [source] Experimental Study of the Aging and Self-Healing of the Glass/Ceramic Sealant Used in SOFCsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2010Wenning N. Liu High operating temperatures of solid oxide fuel cells (SOFCs) require that the sealant must function at a high temperature between 600°C and 900°C and in the oxidizing and reducing environments of fuel and air. This paper describes tests to investigate the temporal evolution of the volume fraction of ceramic phases, the evolution of micro-damage, and the self-healing behavior of the glass,ceramic sealant used in SOFCs. It was found that after the initial sintering process, further crystallization of the glass,ceramic sealant does not stop, but slows down and reduces the residual glass content while boosting the ceramic crystalline content. Under a long-term operating environment, distinct fibrous and needle-like crystals in the amorphous phase disappeared, and smeared/diffused phase boundaries between the glass phase and ceramic phase were observed. Meanwhile, the micro-damage was induced by the cooling down process from the operating temperature to room temperature, which can potentially degrade the mechanical properties of the glass/ceramic sealant. The glass/ceramic sealant exhibited self-healing upon reheating to the SOFC operating temperature, which can restore the mechanical performance of the glass/ceramic sealant. [source] Preparation of Machinable Fluoramphibole Glass,Ceramics from Soda-Lime Glass and FluormicaINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2008Weiyi Zhang A novel route, directly mixing fluormica crystals with recycled soda-lime glass powder and then sintering, is proposed to fabricate machinable fluoramphibole glass,ceramics. The effect of fluormica addition on the sinterability, reactive crystallization behavior, strength, and machinability of the material was investigated. The relative densities of the glass,ceramics decreased with increasing fluormica content. An interaction between fluormica crystals and glass powder occurred during the sintering process. Diopside was formed in the glass,ceramics with 20 wt% fluormica, and fluorrichterite was formed in the glass,ceramics with more than 30 wt% fluormica. Machinability and strength of the glass,ceramics were improved with increasing crystalline phase content. [source] Microfabrication of Three-Dimensional Photonic Crystals of SiO2,Al2O3 Ceramics and Their Terahertz Wave PropertiesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2008Weiwu Chen Dense three-dimensional microphotonic crystals of SiO2,Al2O3 ceramics were fabricated using microstereolithography and successive sintering process. The forming dimensional tolerance for a 50 vol% ceramic paste is 10 ,m and sintering shrinkage is around 12%. Diamond-type photonic crystals with lattice constants of 500 and 125 ,m were formed and sintered successfully. The band gaps of the samples were measured and compared with the theoretically calculated band diagram. [source] Solvent/non-solvent sintering: A novel route to create porous microsphere scaffolds for tissue regenerationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008Justin L. Brown Abstract Solvent/non-solvent sintering creates porous polymeric microsphere scaffolds suitable for tissue engineering purposes with control over the resulting porosity, average pore diameter, and mechanical properties. Five different biodegradable biocompatible polyphosphazenes exhibiting glass transition temperatures from ,8 to 41°C and poly (lactide- co -glycolide), (PLAGA) a degradable polymer used in a number of biomedical settings, were examined to study the versatility of the process and benchmark the process to heat sintering. Parameters such as: solvent/non-solvent sintering solution composition and submersion time effect the sintering process. PLAGA microsphere scaffolds fabricated with solvent/non-solvent sintering exhibited an interconnected porosity and pore size of 31.9% and 179.1 ,m, respectively which was analogous to that of conventional heat sintered PLAGA microsphere scaffolds. Biodegradable polyphosphazene microsphere scaffolds exhibited a maximum interconnected porosity of 37.6% and a maximum compressive modulus of 94.3 MPa. Solvent/non-solvent sintering is an effective strategy for sintering polymeric microspheres, with a broad spectrum of glass transition temperatures, under ambient conditions making it an excellent fabrication route for developing tissue engineering scaffolds and drug delivery vehicles. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Porous Ti-6Al-4V alloy fabricated by spark plasma sintering for biomimetic surface modificationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2004Masayuki Kon Abstract Porous compacts with both biological and biomechanical compatibilities and high strength were developed. Spherical powders of Ti-6Al-4V alloy, which were either as received or surface modified with the use of calcium ions by hydrothermal treatment (HTT), were fabricated by a spark plasma sintering process. The porous compacts of pure Ti were used as reference materials. Porosity was approximately 30%, and compressive strengths were 113 and 125 MPa for the as-received Ti alloy powders and those modified by the HTT process, respectively. The bending strength and elastic modulus of as-received Ti alloy powders were 128,178 MPa and 16,18 GPa, respectively. Each of the compacts was immersed in simulated body fluid (SBF). The amount of adsorption/precipitation of calcium phosphate through the compacts was measured by weight change and was observed by SEM. The compacts were covered with calcium phosphate after 2 weeks of immersion in SBF. The compacts of Ti alloy had plenty of precipitated apatite crystals, and modification by HTT accumulated more precipitation. Because calcium phosphate is a mineral component of bone, apatite, which is precipitated on the surface of the compacts, could adsorb proteins and/or drugs such as antibiotics. It is expected that a large amount of proteins and/or drugs could be impregnated when the porous compacts developed are used. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 88,93, 2004 [source] Effect of BiScO3 and LiNbO3 on the Piezoelectric Properties of (Na0.5K0.5)NbO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Xueyi Sun Lead-free potassium sodium niobate-based piezoelectric ceramics (1,y)(Na0.5,0.5xK0.5,0.5xLix)NbO3,yBiScO3 ( y=0.01, x=0,0.06) have been prepared by an ordinary sintering process. The XRD analysis showed that the structure changes from orthorhombic to tetragonal with the increase of x (at y=0.01, abbreviated as KNNBSL100x). At room temperature, the polymorphic phase transition from the orthorhombic to the tetragonal phase was identified at approximately 0.02,x,0.04. The piezoelectric and ferroelectric properties were significantly enhanced. The temperature dependences of the relative permittivity revealed that the Curie temperature was increased with the addition of LiNbO3. These solid solution ceramics are promising as potential lead-free candidate materials. [source] Preparation of Highly Dense PZN,PZT Thick Films by the Aerosol Deposition Method Using Excess-PbO PowderJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Jong-Jin Choi Lead zinc niobate,lead zirconate titanate thick films with a thickness of 50,100 ,m were deposited on silicon and alumina substrates using the aerosol deposition method. The effects of excess lead oxide (PbO) on stress relaxation during postannealing were studied. Excess PbO content was varied from 0 to 5 mol%. The as-deposited film had a fairly dense microstructure with nanosized grains. The films deposited on silicon were annealed at temperatures of 700°C, and the films deposited on sapphire were annealed at 900°C in an electrical furnace. The annealed film was detached and cracks were generated due to the high residual compressive stress and thermal stress induced by thermal expansion coefficient mismatch. However, the film deposited using powder containing 2% of excess PbO showed no cracking or detachment from the substrate after the postannealing process. The PbO evaporation at elevated temperature during the postannealing process seemed to have reduced the residual compressive stress. The remanent polarization and relative dielectric constant of the 50 ,m thick films annealed at 900°C were 43.1 ,C/cm2 and 1400, respectively, which were comparable with the values of a bulk specimen prepared by a powder sintering process. [source] Microstructures and Piezoelectric Properties in the Li2O-Excess 0.95(Na0.5K0.5)NbO3,0.05LiTaO3 CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2007Min-Soo Kim As a candidate for lead-free piezoelectric materials, Li2O-excess 0.95(Na0.5K0.5)NbO3,0.05LiTaO3 (NKN,5LT) ceramics were developed by a conventional sintering process. The sintering temperature was lowered by adding Li2O as a sintering aid. Abnormal grain growth in NKN,5LT ceramics was observed with varying Li2O content. This grain-growth behavior was explained in terms of interface reaction-controlled nucleation and growth. In the 1 mol% Li2O excess NKN,5LT samples sintered at 1000°C for 4 h in air, the electromechanical coupling factor and the piezoelectric constant of NKN,5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively. [source] Sintering Behavior of Gehlenite.JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2007Macro-/Mesoporous Gehlenite, Mechanical, Microstructure, Part I: Self-Forming, Physical Properties, Pore-Forming Mechanism A novel kind of pore self-forming macro-/mesoporous gehlenite (2CaO·Al2O3·SiO2) ceramic (abbreviated C2AS) having a highest porosity of 80% corresponding to a volume expansion of 134% during sintering has been developed. The pore self-forming ability, microstructure, mechanical, and thermal physical properties of the porous ceramic are related to the sintering temperature. The gehlenite ceramic shows a very good pore self-forming ability over a very wide range of temperature from 900° to 1450°C. No vesicant is required and no hydrothermal treatment is needed, as is generally the case for other kinds of porous ceramics or glasses. The pore self-forming ability of the C2AS porous ceramic can be attributed to the escape of the adsorbed water vapor during the sintering process, due to automatic hydration of the fine, amorphous, flakey-shaped starting C2AS powder particles synthesized by the organic steric entrapment (PVA) method, as well as to their fine, porous microstructure. The pores of the ceramics can be either open or closed, and the average pore size ranges from 0.6 to 1.1 ,m, corresponding to a porosity of 75%,80%, respectively. The porous ceramic can preserve nanometer-sized (26,50 nm) crystallites up to 1000°C. Sintered or thermally treated under different conditions, the porous ceramics exhibit relatively high flexural strengths ranging from 9.1 to 15.4 MPa, with a standard deviation of 0.3 and 4.2 MPa, respectively. Thermal properties of the porous ceramic up to 1000°C, including thermal expansion coefficient, thermal diffusivity, specific heat, and thermal conductivity, were investigated, and the stability of the porous ceramic in boiling water was also studied. [source] Two-Stage Sintering of Alumina with Submicrometer Grain SizeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2007Katarína Bodi This work verifies the applicability of two-stage sintering as a means of suppressing the final stage grain growth of submicrometer alumina. The first heating step should be short at a relatively high-temperature (1400°,1450°C) in order to close porosity without significant grain growth. The second step at temperatures around 1150°C facilitates further densification with limited grain growth. Fine-grained alumina with a relative density of 98.8% and a grain size of 0.9 ,m was prepared by two-stage sintering. A standard sintering process resulted in ceramics with identical relative density and a grain size of 1.6 ,m. [source] Effect of Green Density on the Thermomechanical Properties of a Ceramic During SinteringJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006Sam E. Schoenberg The thermomechanical properties of a commercial barium titanate were experimentally or theoretically determined for samples with green densities ranging from 45% to 55%. For stresses less than 300 kPa, sample deformation was determined to be linear viscous for all three stages of sintering. The shrinkage rates at a given temperature can differ by up to ,25% as the green density changes from 45% to 55%, and the maximum shrinkage rate increased with decreasing green density. The increase in shrinkage rate with lower green density samples persisted through the final sintering stage. The viscosity was determined by cyclic loading dilatometry to range from 5 to 6 GPa·s in the initial stage of sintering, to 2 GPa·s in the intermediate stage, and to increase to 10,20 GPa·s for all specimens in the final stage of sintering. Differences in the final-stage viscosity were attributed to grain size differences. Relaxation times for the sintering body were estimated to be less than 1 s, indicating that viscous behavior is dominant throughout the sintering process. [source] Fractographic Montage for a Si3N4,SiC NanocompositeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2006Monika Ka, iarová A silicon nitride,silicon carbide nanocomposite has been prepared by an in situ method that utilizes C+SiO2 carbo-thermal reduction during the sintering process. The materials consist of a silicon nitride matrix, with an average grain size of 140 nm, and inter- and intragranular SiC particles with sizes of approximately 250 and 45 nm, respectively. The four-point bending strength and its distribution were investigated. The fracture origins were identified and characterized using fractographic methods, and a fractographic montage of the Weibull plot and fracture origins was constructed. The fracture origins were subsurface and volume located processing defects with sizes from 5 to 460 ,m, mainly in the form of clusters of pores, together with clusters of large SiC grains. [source] Sintering Behavior and Properties of Iron-Rich Glass-CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2004Alexander Karamanov Iron-rich glass-ceramics were obtained by the sintering of two glass powders, labeled G1 and G2, at heating rates of 5° and 20°C/min followed by an isothermal step in the 850°,1050°C temperature interval. The sintering process was evaluated by the linear shrinkage; the closed porosity was estimated by density measurements; the structure and the morphology of the glass ceramics were observed by scanning electron microscopy. The bending strength, the Young modulus, and Vickers hardness of the glass-ceramics materials were evaluated. The results showed that the sintering process and morphology of the glass-ceramics depends on the amount of magnetite and pyroxene formed. With a low percentage of crystal phase formed (25%,30% typical of G1) the structure is characterized by closed porosity; at higher crystallization (45%,50% typical of G2) open porosity is mainly formed. The properties of the glass-ceramics were not influenced by the heating rate but improved with an increase in the degree of crystallization. [source] Particle size effect on the film-forming process of PS/PBA composite latexesPOLYMER COMPOSITES, Issue 9 2010aziye U In this work, the effect of hard particle size and blend ratio on the film formation behavior of hard polystyrene (PS) and soft poly(n -butyl acrylate) (PBA) latex blends was studied by means of steady-state fluorescence and UV,visible techniques in conjunction with atomic force microscopy. Three different sets of latexes were synthesized: PBA latex (diameter 97 nm), pyrene (P)-labeled large PS (LgPS; diameter 900 nm), and small PS (SmPS; diameter 320 nm). Two different series of latex blends (LgPS/PBA and SmPS/PBA) were prepared with varying blend composition at room temperature separately. Films were then annealed at elevated temperatures above glass transition (Tg) temperature of PS. Fluorescence intensity (IP) from P and photon transmission intensity (Itr) were measured after each annealing step to monitor the stages of film formation. The results showed that a significant change occurred in IP and Itr at a certain critical weight fraction (Rc) of PBA. Below Rc, two distinct film formation stages, which are named as void closure and interdiffusion, were seen. However, at PBA concentrations nearer to or above Rc, no film formation can be achieved. Comparing to the LgPS/PBA, the sintering process of SmPS/PBA particles occurred at much lower temperatures. Film formation stages for R < Rc were modeled, and related activation energies were calculated. Void closure (,H) and interdiffusion (,E) activation energies for SmPS/PBA were also found smaller in comparing with LgPS/PBA series. However, ,H and ,E values were not changed much with the blend composition for both series. POLYM. COMPOS., 31:1637,1652, 2010. © 2009 Society of Plastics Engineers [source] The rotational molding of a thermotropic liquid crystalline polymerPOLYMER ENGINEERING & SCIENCE, Issue 3 2005Eric Scribben Thermotropic liquid crystalline polymers (TLCPs) exhibit a number of mechanical and physical properties such as excellent chemical resistance, low permeability, low coefficient of thermal expansion, high tensile strength and modulus, and good impact resistance, which make them desirable as a rotationally molded storage vessel. However, there are no reports in the technical literature of the successful rotational molding of TLCPs. In this article, conditions are identified that lead to the successful rotational molding of a TLCP, Vectra B 950. First, a technique was developed to produce particles suitable for rotational molding because TLCPs cannot be ground into a free-flowing powder. Second, because the viscosity at low shear rates can be detrimental to the sintering process, coalescence experiments with isolated particles were carried out to determine the thermal and environmental conditions at which sintering should occur. These conditions were then applied to static sintering experiments to determine whether coalescence and densification of the bulk powder would occur. Finally, the powders were successfully rotationally molded into tubular structures in a single axis, lab-scale device. The density of the molded structure was essentially equivalent to the material density and the tensile strength and modulus were approximately 18 MPa and 2 GPa, respectively. POLYM. ENG. SCI., 45:410,423, 2005. © 2005 Society of Plastics Engineers [source] New interdigital design for large area dye solar modules using a lead-free glass frit sealingPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 8 2006R. Sastrawan Abstract A new interdigital design for large area dye solar modules is developed for an area of 30×30,cm2. This design requires fewer holes in the glass substrate for electrolyte filling, than the conventional strip design. A complete manufacturing process of this module,ranging from screen printed layers to semi-automated colouring and electrolyte filling,in a laboratory-scale baseline is illustrated. As primary sealing method, a durable glass frit sealing is used. It is shown, that the lead (Pb) content present in many glass frit powders contaminates the catalytic platinum electrode during the sintering process, resulting in a lowering of the fill factor. A screen printable lead-free glass frit paste is developed, which solves this problem. Long term stability tests are presented on 2·5,cm2 dye solar cells, which have been completely sealed with glass frit. In consecutively performed accelerated ageing tests under 85°C in the dark (about 1400,h) and continuous illumination with visible light (1 sun, about 1700,h), a 2·5,cm2 dye solar cell with an electrolyte based on propylmethylimidazolium iodide showed an overall degradation of less than 5% in conversion efficiency. In a subsequently performed thermal cycling test (,40°C to +85°C, 50 cycles) a 2·5,cm2 dye solar cell with the same electrolyte composition also showed only a slight degradation of less than 5% in conversion efficiency. Copyright © 2006 John Wiley & Sons, Ltd. [source] Photoluminescent Properties of SrTiO3:Pr, Al Nanophosphors Synthesized by Microemulsion,Microwave HeatingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2007Qi Pang A novel approach for the preparation of SrTiO3:Pr, Al nanophosphors by microemulsion,microwave heating is reported in this paper. In comparison with the conventional solid-state sintering processes, this novel method provides a limited small space in a micelle for the formation of nanosized precursors and requires a very short heating time, thus reducing the energy consumption. As a result, small-sized particles with a narrow size distribution and high purity were produced. Transmission electron microscopy characterizations indicated that the synthesized particles were almost spherical with an averaging diameter of ,24 nm and agglomerates slightly. The X-ray diffraction analysis revealed the perovskite cubic structure of SrTiO3:Pr3+ nanoparticles. The luminescent of SrTiO3:Pr, Al phosphors were investigated by photoluminescence. Under 350 nm excitation, SrTiO3:Pr, Al showed a strong red emission, peaking at around 615 nm. The photoluminescence excitation intensity was enhanced by the addition of Al3+ ions. [source] Spark Plasma Sintering of AluminaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2002Zhijian Shen A systematic study of various spark plasma sintering (SPS) parameters, namely temperature, holding time, heating rate, pressure, and pulse sequence, was conducted to investigate their effect on the densification, grain-growth kinetics, hardness, and fracture toughness of a commercially available submicrometer-sized Al2O3 powder. The obtained experimental data clearly show that the SPS process enhances both densification and grain growth. Thus, Al2O3 could be fully densified at a much lower temperature (1150°C), within a much shorter time (minutes), than in more conventional sintering processes. It is suggested that the densification is enhanced in the initial part of the sintering cycle by a local spark-discharge process in the vicinity of contacting particles, and that both grain-boundary diffusion and grain-boundary migration are enhanced by the electrical field originating from the pulsed direct current used for heating the sample. Both the diffusion and the migration that promote the grain growth were found to be strongly dependent on temperature, implying that it is possible to retain the original fine-grained structure in fully densified bodies by avoiding a too high sintering temperature. Hardness values in the range 21,22 GPa and fracture toughness values of 3.5 ± 0.5 MPa·m1/2 were found for the compacts containing submicrometer-sized Al2O3 grains. [source] | |||||||||||||