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Aluminum Nitride (aluminum + nitride)
Selected AbstractsCharacterization of reactive DC magnetron sputtered TiAlN thin filmsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 10 2008B. Subramanian Abstract Thin films of about 1,m Titanium Aluminum Nitride (TiAlN) were deposited onto mild steel substrates by reactive direct current (DC) magnetron sputtering using a target consisting of equal segments of titanium and aluminum. X-ray diffraction (XRD) analysis showed that the TiAlN phase had preferred orientations along 111 and 200 with the face-centered cubic structure. Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) analyses indicated that the films were uniform and compact. Photoluminescence (PL) spectra reveal that TiAlN thin films are of good optical quality. Laser Raman studies revealed the presence of characteristic peaks of TiAlN at 312.5, 675, and 1187.5 cm,1. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Preparation and Properties of Porous Aluminum Nitride,Silicon Carbide Composite CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004Eirik Hagen Microporous two-phase AlN,SiC composites were prepared using Al4C3 and either Si (N2 atmosphere) or Si3N4 (Ar atmosphere) as precursors. The reaction mechanisms of the two synthesis routes and the effect of processing conditions on reaction rate and the material microstructures were demonstrated. The exothermic reaction between Si and Al4C3 under N2 atmosphere was shown to be a simple processing route for the preparation of porous two-phase AlN,SiC materials. The homogeneous two-phase AlN,SiC composites had a grain size in the range of 1,5 ,m, and the porosity varied in the range of 36%,45%. The bending strength was 50,60 MPa, in accordance with the high porosity. [source] Novel Way to Synthesize Nanocrystalline Aluminum Nitride from Coarse Aluminum PowderJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2003Yu Qiu A new process has been developed for the synthesis of nanocrystalline AlN powder by the nitridation of coarse aluminum powder in flowing NH3 gas, using NH4Cl and KCl as additives. The resulting powders have been characterized using XRD, TEM, and XRF techniques. XRD-pure AlN nanoparticles with a diameter of 10,20 nm can be obtained by nitridation at 1273 K for 5 h. NH3 is proved to eliminate the effect of water impurity. The effects of the additives on the conversion of aluminum are also discussed. [source] Reactive Synthesis and Phase Stability Investigations in the Aluminum Nitride,Silicon Carbide SystemJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2000Ellen M. Carrillo-Heian The effect of AlN on the structure formation of SiC was investigated. SiC was synthesized in the presence of AlN under vacuum at 1500°C, and the result was cubic SiC. The synthesis of AlN,SiC composites through the reaction Si3N4+ 4Al + 3C = 3SiC + 4AlN was also investigated and compared with synthesis via field-activated self-propagating combustion (FASHS). Reactants were heated in a vacuum furnace at temperatures ranging from 1130° to 1650°C. Below 1650°C, the reaction is not complete and at this temperature the product phases are AlN and cubic SiC. At 1650°C, the product contained an outer layer which contained ,-SiC only and an inner region which contained AlN and cubic SiC. 2H-SiC and AlN composites synthesized via field-activated self-propagating combustion were annealed at 1700°C under vacuum. The AlN dissociated and evaporated and the 2H-SiC transformed to the cubic , phase. Reasons for the differences in products of furnace heating and FASHS are discussed. [source] ChemInform Abstract: Ab initio Study of the Electronic Structure and Bonding of Aluminum Nitride.CHEMINFORM, Issue 4 2008Apostolos Kalemos Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Beneficial Effects of AlN as Sintering Aid on Microstructure and Mechanical Properties of Hot-pressed ZrB2,ADVANCED ENGINEERING MATERIALS, Issue 7 2003F. Monteverde Higher density of ZrB2 ceramics than with the pure material is achieved when 4.6,% of aluminum nitride are added before hot-pressing as a sintering aid. AlN supports densification and prevents grain coarsening, mainly by virtue of its ability to remove the boron oxide layer that otherwise covers ZrB2 particles. The new material (see Figure for an SEM image of a polished section) has outstanding mechanical properties, e.g. strength values of 600 and 200 MPa at 25 and 1500,°C. [source] Preparation of Oriented Aluminum Nitride Thin Films on Polyimide Films and Piezoelectric Response with High Thermal Stability and FlexibilityADVANCED FUNCTIONAL MATERIALS, Issue 3 2007M. Akiyama Abstract c -Axis oriented aluminum nitride (AlN) thin films are successfully prepared on amorphous polyimide films by radiofrequency magnetron reactive sputtering at room temperature. Structural analysis shows that the AlN films have a wurtzite structure and consist of c -axis oriented columnar grains about 100,nm wide. The full width at half maximum of the X-ray diffraction rocking curves and piezoelectric coefficient d33 of the AlN films are 8.3° and 0.56,pC,N,1, respectively. The AlN films exhibit a piezoelectric response over a wide temperature range, from ,196 to 300,°C, and can measure pressure within a wide range, from pulse waves of hundreds of pascals to 40,MPa. Moreover, the sensitivity of the AlN films increases with the number of times it was folded, suggesting that we can control the sensitivity of the AlN films by changing the geometric form. These results were achieved by a combination of preparing the oriented AlN thin films on polyimide films, and sandwiching the AlN and polymer films between top and bottom electrodes, such as Pt/AlN/polyimide/Pt. They are thin (less than 10,,m), self powered, adaptable to complex contours, and available in a variety of configurations. Although AlN is a piezoelectric ceramic, the AlN films are flexible and excellent in mechanical shock resistance. [source] Enhancement of Piezoelectric Response in Scandium Aluminum Nitride Alloy Thin Films Prepared by Dual Reactive CosputteringADVANCED MATERIALS, Issue 5 2009Morito Akiyama A high-temperature piezoelectric material exhibits a good balance between high maximum use temperature and large piezoelectricity. This is achieved by the combination of the discovery of a phase transition in scandium aluminum nitride (ScxAl1,,,xN) alloy thin films, and the use of dual cosputtering, which leads to nonequilibrium alloy thin films. [source] Preparation and Thermal Ablation Behavior of HfB2,SiC-Based Ultra-High-Temperature Ceramics Under Severe Heat ConditionsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2009Xinghong Zhang HfB2,SiC-based ultra-high-temperature ceramics with aluminum nitride (AlN) as a sintering aid were hot pressed at 1850°C. The sinterability and mechanical properties were investigated and compared with the composite without a sintering aid. It was shown that the addition of AlN greatly improved the powder sinterability and enabled the production of a nearly full-dense composite. The mechanical properties, especially the flexural strength, were enhanced remarkably through the improvement in the sinterability and microstructure. The oxidation resistance of a composite doped with 10 vol% AlN was evaluated by a plasma arc heater and the ablation mechanism was discussed. [source] Thermodynamic Studies on the AlN Sintering Powders Treated With Phosphate SpeciesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Susana Maria Olhero The processing of aluminum nitride (AlN) ceramics in aqueous media requires the use of a surface layer to protect the surface of the particles against hydrolysis. This surface layer might influence the densification, affecting the reactions between AlN and sintering additives. The present paper describes a thermodynamic and experimental approach to evaluate the effects of a phosphate-based protecting surface layer on the densification of AlN in the presence of YF3,CaF2 as sintering aids, and to predict the densification behavior during sintering using thermodynamic assessments. Based on thermodynamic calculations and the measured weight loss of the samples during heating to sintering temperature, the chemical reactions occurring during firing were proposed. The proposed reactions were related to the experimental results as well as the final properties of the AlN samples, namely, thermal conductivity, microstructure, secondary phases, and density. [source] Sintering of AlN Using CaO-Al2O3 as a Sintering Additive: Chemistry and Microstructural DevelopmentJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2002Eirik Hagen The densification of aluminum nitride using Ca12Al14O33 as a sintering aid has been studied with emphasis on the effect of using coarse or fine powder, the amount of sintering aid, the sintering temperature, and embedding. Both crystalline and amorphous grain boundary phases were observed. Significant weight losses were observed for coarse-grained samples, and if suitable embedding was not used. Porous and coarse-grained ceramics with high contiguity and minor amounts of secondary phases were obtained by enhanced evaporation while dense ceramics were obtained limiting the evaporation. High weight losses in the graphite environment resulted in formation of a dense AlN surface layer. [source] Microstructural Characterization of High-Thermal-Conductivity Aluminum Nitride CeramicJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2002Hiromi Nakano An aluminum nitride (AlN) ceramic with a thermal conductivity value of 272 W·(m·K),1, which is as high as the experimentally measured thermal conductivity of an AlN single crystal, was successfully fabricated by firing at 1900°C with a sintering aid of 1 mol% Y2O3 under a reducing N2 atmosphere for 100 h. Oxygen concentrations were determined to be 0.02 and 0.03 mass% in the grains and in the grain-boundary phases, respectively. Neither stacking fault in the grains nor crystalline phase in the grain-boundary regions was found by transmission electron microscopy. An amorphous phase possessing yttrium and oxygen elements was detected between the grains as thin films with a thickness of <1 nm. Because the amount of grain-boundary phase was small, the high-thermal conductivity of the ceramic was attributable to the low oxygen concentration in the AlN grains. [source] Elastic constants of aluminum nitridePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2007M. Kazan Abstract We report on the application of Brillouin spectroscopy as an approach to non-destructive optical characterization of the elastic constants of semiconductors with the wurtzite symmetry. Three different configurations were used to achieve a complete determination of the elastic stiffness constants of bulk AlN substrates grown by the Physical Vapor Transport (PVT) method. The scattering diagrams of these three configurations are presented showing the geometrical arrangements necessary to observe all the elastic stiffness constants for the partially nontransparent wurtzite type of the crystal structure. Because aluminum nitride (AlN) is a suitable material for the fabrication of light emitting devices, the characterization of its elastic constants was carried out very precisely to provide a reliable data which can be used for the determination of residual stress arising during the growth of AlN thin films or wide band gap semiconductor thin films on substrates of AlN. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Surface Modification of Aluminum Using a Combined Technique of Barrel Nitriding and Plasma NitridingPLASMA PROCESSES AND POLYMERS, Issue S1 2009Masahiro Okumiya Abstract In this study, a new nitriding process is proposed to produce the aluminum nitride on the aluminum surface. A process of combined barrel and plasma nitriding techniques was used. By using the barrel nitriding process, an aluminum nitride layer with high thickness can be formed within a matter of hours, and the surface hardness can be improved by using the plasma nitriding. It is suggested that a combined technique of the barrel nitriding and the plasma nitriding is one of the most promising surface treatments for the aluminum. [source] New composites with high thermal conductivity and low dielectric constant for microelectronic packagingPOLYMER COMPOSITES, Issue 2 2010Wei Ling Three composites based on cyanate (CE) resin, aluminum nitride (AlN), surface-treated aluminum nitride [AlN(KH560)], and silicon dioxide (SiO2) for microelectronic packaging, coded as AlN/CE, AlN(KH560)-SiO2(KH560)/CE, and AlN-SiO2/CE composite, respectively, were developed for the first time. The thermal conductivity and dielectric constant of all composites were investigated in detail. Results show that properties of fillers in composites have great influence on the thermal conductivity and dielectric constant of composites. Surface treatment of fillers is beneficial to increase the thermal conductivity or reduce dielectric constant of the composites. Comparing with binary composite, when the filler content is high, ternary composites possess lower thermal conductivity and dielectric constant. The reasons leading to these outcomes are discussed intensively. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] Thermomechanical studies of aluminum nitride filled shape memory polymer compositesPOLYMER COMPOSITES, Issue 3 2007Muhammad Yasar Razzaq High thermal conductivity polyurethane shape memory polymer (SMP) composites filled with aluminum nitride (AlN) were fabricated, and their thermal and thermomechanical properties were studied. The purpose of this microstructure is to improve the thermal properties of the SMPs at low filler content. Morphology of AlN filler in polyurethane SMP matrix and the resulting thermal conductivity was also investigated. Thermal studies have shown that AlN is an effective filler for reinforcement of the polyurethane SMP and that it does not deteriorate the stable physical crosslink structure of the polyurethane, which is necessary to store the elastic energy in the service process of the shape memory material. The thermal conductivities of these SMP composites in relation to filler concentration and temperature were investigated, and it was found that the thermal conductivity can increase up to 50 times in comparison with that of the pure SMP. Furthermore, differential scanning calorimetry tests have shown a significant decrease in the glass transition temperature of the switching segment. Dynamic mechanical studies have shown that the storage modulus of the composites increase with higher AlN content in both glassy and rubbery state. Damping peak decreases and also the curve of damping becomes broader with increasing filler content. Strain fixity rate which expresses the ability of the specimens to fix their strain has been improved slightly in the presence of AlN filler but the final recovery rate of the shape memory measurement has decreased evidently. POLYM. COMPOS., 28:287,293, 2007. © 2007 Society of Plastics Engineers [source] Thermal conductivity and mechanical properties of aluminum nitride filled linear low-density polyethylene compositesPOLYMER ENGINEERING & SCIENCE, Issue 5 2009Junwei Gu To acquire polymer composites with high thermal conductivity and mechanical properties, the aluminum nitride (AlN) microparticles modified with titanate coupling reagent of isopropyltrioleictitanate (NDZ-105) were employed to blend linear low-density polyethylene (LLDPE) via powder mixing method. Thermal conductive coefficient of the AlN/LLDPE composites was measured using hot disk thermal analyzer, and the thermal stability characteristics of AlN/LLDPE composites were mainly investigated via thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC). The results indicated that the use of AlN particles modified by NDZ-105 significantly enhanced thermal conductivity and mechanical properties of AlN/LLDPE composites. The thermal conductivity coefficient , was 1.0842 W/mk with 30% volume fraction of AlN, about three times higher than that of native LLDPE. The tensile strength of composites was maximum (17.42 MPa) with 20% mass fraction of AlN. DSC analyses results indicated that AlN had an influence on the melting temperature and the crystallinity of LLDPE. Additionally, TGA analyses showed that the thermal stability of LLDPE was significantly increased with addition of AlN. POLYM. ENG. 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