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An AlON carrier with light-transmitting performance and through-hole structure was prepared by carbothermal reduction and nitridation (CRN). The TiO 2 /AlON photocatalyst was prepared by hydrothermal method. Under vertical irradiation of the light source, the degradation rate of MB by TiO 2 (15%)/AlON photocatalyst was 97.3% after 180 min. And 88.8% MB was mineralized by determining the total organic carbon in the solution. An increase in TiO 2 loading can accelerate the efficiency of TiO 2 /AlON degradation of MB within 0–90 min. At the same time, it will also exacerbate the blockage of AlON carrier and increase the amount of free TiO 2. These can all exacerbate light loss, thereby shortening the penetration distance of light in the mixed liquid. Within the range of 90–180 min, the photocatalytic performance of TiO 2 (15%)/AlON powders was better than that of TiO 2 (25%)/AlON (97.3% vs 82.5%). In addition, TiO 2 /AlON photocatalyst was easy to cycle and has stable photocatalytic performance. [ABSTRACT FROM AUTHOR]

Increasing demand for high-performance lightweight materials for structural applications poses a challenge to material research and development; subsequently, the expectation of a single lightweight material to sustain itself in a multi-functional environment is also difficult. The present research attempts to address the above-said issue by developing and examining the structural stability of aluminum oxynitride (ALON)-reinforced Kevlar fabric-impregnated epoxy composite. Three different weight percentages 5, 10, and 15 of ALON particles are employed to fabricate the composite sheet through the hand-layup technique. The novel inclusion of ALON particles in the resin-impregnated composite is expected to improve its structural stability. Tensile, flexural, and dynamic mechanical tests are conducted to assess the improved structural stability conforming to standards. The results comprehend the significant improvement of 1.75 times in tensile, 2.59 times in flexural, and 1.28 times in damping characteristics for the higher composition of ALON particles compared to the ALON-free composite. The collective outcome of the study delineates that the novel composite is the right candidate for structural loading. The fracture study conducted through a scanning electron microscope reveals that the failure propagation is followed by collective delamination. [ABSTRACT FROM AUTHOR]

This paper presents experimental results concerning the one-step preparation of cast divanadium nitride and aluminum oxynitride (AlON) by high-temperature synthesis under 5 MPa of N 2 from green mixtures containing vanadium oxide, aluminum, and aluminum nitride. It was shown that the mixtures with a wide range of component ratios are capable to burn with the temperature exceeding the melting point of the final products, divanadium nitride and aluminum oxynitride, that makes it possible to obtain them in the form of a melt with subsequent separation of vanadium nitride (lower ingot) and aluminum oxynitride (upper ingot). The resulting products had no cohesion and were easily separated from each other. Variation in the content of aluminum nitride in the charge markedly affected the synthesis process, phase composition, and microstructure of the target products. The content of excess aluminum nitride in the starting mixture α = 10% was found to be optimum on a yield/composition of the target products. [ABSTRACT FROM AUTHOR]

The history of occurrence and technological features of obtaining transparent aluminum oxynitride ceramics are examined in detail. It is concluded that high-purity single-fraction powders should be used to obtain optically homogeneous aluminum oxynitride ceramics. The introduction of additives regulating the microstructure and properties of transparent ceramics is recommended. The application area of such ceramics is given. [ABSTRACT FROM AUTHOR]

Un-doped and La2O3–Y2O3 co-doped Aluminum oxynitride (AlON) ceramics were fabricated by reactive spark plasma sintering method (R–SPS) by using Al2O3 and AlN as starting powders with a composition of 70 mol% and 30 mol%, respectively. The effects of co-doping system on densification, microstructure, mechanical properties and optical transmittance of AlON ceramics were investigated. X-ray analysis confirmed the fully transformation of γ-AlON phase for all compositions prepared at 1650 °C in 30 min under 40 MPa under nitrogen. The results indicated that 0.02 wt% La2O3+0.08 wt% Y2O3 added composition had the optimal combination of sintering additives. In an attempt to reduce the graphite contamination, the powder mixture was encapsulated in a Nb-coated graphite foil before subjecting to SPS. Nb-coated graphite foil encapsulated sample was found to reduce carbon contamination leading to high densification (99.6 %) and high transmission (∼81 % at 2500 nm). This study demonstrated that optical transmittance of R-SPSed AlON ceramics is significantly improved without any post-heat treatment by using Nb-coated graphite foil during SPS processing.

The sphericity and fluidity of the powder play a crucial role in the forming and sintering of ceramics. High‐performance AlON spherical powder was prepared for the first time by spray drying of powder fired by solid‐phase reaction, and the preparation of AlON transparent ceramics was realized under pressureless sintering conditions. The effect of AlN dosage on the purity of AlON powder was investigated, and the powder fluidity was improved by spray drying technique. Then the best spray drying process was selected by scanning electron microscopy, AD/TD, green density, MIP and transmittance measurements. The AlON particles obtained under the optimal granulation process have good dispersibility, high green density after pressing, and uniform pore distribution. After dry pressing and sintering at 1900°C for 20 h, the AlON ceramics with linear transmissivity of 84.3% at 2 μm wavelength can be obtained. The excellent pressing and sintering properties of AlON granulated particles make it possible for large‐scale production. [ABSTRACT FROM AUTHOR]

AlON ceramics with high transmittance and strength are essential for transparent armor application. However, high-temperature sintering for long time would result in large grain sizes associated with low strength. In this paper, a low + high temperature two-step sintering method with ultrafine AlON powders was reported for the preparation of high-strength and high-transmittance AlON ceramics. Firstly, the high-purity AlON powders with high specific surface area of 29.77 m2/g was synthesized by solution combustion synthesis-nitridation method and subsequently ball-milling process. Thereafter a sample with 97% density and small grain size (less than 4 μm) can be obtained after sintered at 1750 °C for 3 h, in which the difference of kinetics between grain-boundary diffusion and grain-boundary migration was used to suppress the final stage of grain growth. Further increasing sintering temperature to 1850 °C resulted in the elimination of the residual porosity, and realizing transparent AlON ceramics with high optical transmission (85.4%) and high flexural strength (375.1 MPa) could be achieved. [ABSTRACT FROM AUTHOR]

The interaction of leucosapphire single crystals with high-enthalpy gas fluxes is studied in a system modeling the aerodynamic flow around aircraft surfaces and their heating at flight altitudes of 80–100 km. The recombination rate constant Kw at the surface of leucosapphire with orientation (1120) in an atmosphere of dissociated air and nitrogen is calculated. The microstructure, phase composition, and chemical composition of the surface are investigated. The results cannot readily be explained by existing theories of catalytic recombination and aerodynamic surface heating of aircraft components. [ABSTRACT FROM AUTHOR]

Aluminum oxynitride (AlON) ceramics doped with different sintering aids were synthesized by spark plasma sintering process. The microstructures, mechanical, and optical properties of the ceramics were investigated. The results indicate that the optimal amount of sintering aids is 0.06 wt% La2O3 + 0.16 wt% Y2O3 + 0.30 wt% MgO. The addition of La3+ and Mg2+ decreases the rate of grain boundary migration in ceramics, promotes pore elimination, and inhibits grain growth. The addition of Y3+ facilitates liquid‐phase sintering of AlON ceramics. Moreover, the addition of Mg2+ effectively promotes twin formation in the ceramics, which hinders crack propagation and dislocation motion when the ceramics are loaded. Hence, the AlON ceramic doped with 0.06 wt% La2O3 + 0.16 wt% Y2O3 + 0.30 wt% MgO exhibits a relative density of 99.95%, an average grain size of 9.42 μm, and a twin boundary content of 10.3%, which contributes to its excellent mechanical and optical properties. [ABSTRACT FROM AUTHOR]

Fabrication of transparent AlON ceramics is extra sensitive to both particle size of starting powder and sintering additive due to shuttling transformation between AlON and Al2O3 + AlN during heating. One possible solution is to select robust additive to suppress the shuttling transformation. In this work, three AlON powders with different median particle sizes of 0.6, 0.9, and 1.1 μm were prepared. After studying the effect of CaCO3 on densification process, AlON ceramics with the maximum transmittance of ≥81.1% were successfully fast prepared by pressureless sintering (PS) at 1880°C for only 2.5 h by using three AlON powders doped with different CaCO3 amount. Specifically, AlON ceramics prepared from 1.1 μm with 0.5–0.8 wt.% CaCO3 doping consistently showed the maximum transmittance of ≥85.3%, which indicates that CaCO3 can serve as a robust additive to enable fast fabrication of highly transparent AlON ceramics even by PS. [ABSTRACT FROM AUTHOR]

A skeleton structure AlON (aluminum oxynitride) carrier with light transmission performance was prepared by carbothermal reduction and nitridation (CRN). The AlON carrier can disperse nano active components and enhance its photocatalytic performance. The microstructure of the TiO 2 /AlON composite photocatalyst shows that the dispersion of the agglomerated TiO 2 is achieved by the physical adsorption mechanism, the embedding mechanism and the single particle dispersion mechanism. The morphology of the BiVO 4 /AlON and g-C 3 N 4 /AlON composite photocatalysts further proves the universality of the AlON carrier in the dispersion of nano photocatalyst. The photocatalytic performance of the nano active component was enhanced by combining with AlON carrier. After 240 min of visible light irradiation, the degradation rate of MB increased by 7.4% (BiVO 4 /AlON) and 8.1% (g-C 3 N 4 /AlON), respectively. High light transmittance was the main reason for AlON carrier to improve the photocatalytic performance of loaded active components. In addition, AlON carrier type composite photocatalyst can be reused for many times because it has physicochemical stability and can be recovered easily. [ABSTRACT FROM AUTHOR]

Subcritical crack growth is often observed in oxide ceramics. This effect is ascribed to the interaction between the strained chemical bonds at the crack tip and water molecules present in the working environment of the material. Owing to this reaction, combined with stresses at the crack tip, slow cracking of the material and relevant strength reduction may occur. In non-oxide ceramics (i.e., without significant oxide sintering additives), no subcritical crack growth was observed. The present work demonstrates slow crack propagation in an aluminum oxynitride (AlON) material. AlON samples were prepared via sintering in nitrogen at 1800 °C. This resulted in dense translucent samples. Constant stress rate tests were carried out in both air and water to assess the influence of water on material strength. The strength results were used to further evaluate the effects of subcritical cracking. A clear decrease in strength was observed at low stress rates. Measurement points below 10 MPa/s were used to determine the lowest stress rate for inert strength. The slope of the fitting line indicated the value of subcritical cracking parameter n. [ABSTRACT FROM AUTHOR]

Relevance. The development of geology in the XXI century is impossible without solving the fundamental problems of modern materials science, caused by the tasks of creating new materials for functional purposes. Despite the variety of methods for aluminum and zirconium oxynitride synthesis and consolidating ceramic based on them, currently being developed, scientific and practical interest is the solid phase synthesis during compaction of corresponding mixtures in inert atmosphere. In this case, powders can be pressed into compacts, both before and during sintering. In the latter case various variants of hot pressing and spark plasma sintering can be applied. For refractory ionic-covalent transition metal oxynitrides, the activated sintering is an urgent problem, since it is carried out by a diffusion mechanism. To solve this problem, it is necessary to study the patterns and mechanisms of consolidation of oxynitride ceramic materials and to search for appropriate activating additives and activation methods. The main aim of the research is to develop a method for obtaining high-density durable ceramics based on aluminum and zirconium oxynitride, including the synthesis of combustion of powder mixtures followed by hot pressing in inert atmosphere and to investigate the structure and physico-mechanical properties of the resulting compacts. The methods: sieve analysis of coarse powders using the A20 analyzer, X-ray phase analysis of the samples under study, hydrostatic weighing to determine the apparent density of sintered samples, measurement of the microhardness of sintered samples, scanning electron microscopy, scratch testing. The results. Using a unique method, including the synthesis of Al2O3-AlN powder by burning Al nanopowder and subsequent hot pressing in inert atmosphere, an oxynitride ceramic based on aluminum oxynitride was obtained. The resulting ceramics had the following physical and mechanical properties: modulus of elasticity during indentation EIT=286537 MPa, indentation hardness HIT=13160 MPa, specimen strength σs=2912 MPa. The ultra-high solid oxynitride ceramic ZrO2-ZrN (modulus of elasticity during indentation EIT=323897 MPa, indentation hardness HIT=19244 MPa, specimen strength σs=3381 MPa) was obtained by hot pressing. The obtained materials are proposed for use in the technology of new generation functional ceramics.

An aluminum oxynitride (AlOx:N) resistive memory with a large ON/OFF ratio of 106 at a low read voltage of 0.5 V is proposed. The AlOx:N resistive switching (RS) layer is fabricated using a two-stage thermal oxynitridation process of an evaporated Al film. The Al/AlOx: N/n+-Si device shows write-once–read-many-times (WORM) characteristics and the writing operation is voltage-polarity-independent. The resistance states can be repeatably read $10^{4}\times $ and the data retention time is over 104 s. A high read-disturb immunity is also observed for over 104 s. Data retention and read-disturb characteristics measured at 85 °C predict a ten-year lifetime of the device. The carrier transport and the RS mechanisms are studied and illustrated. [ABSTRACT FROM AUTHOR]

By fast heating the nano‐sized Al2O3 and carbon black mixtures at 50°C/min to 1750°C for 30–120 min, single‐phase AlON powders were successfully obtained by a fast one‐step carbothermal reduction and nitridation (CRN) method. The AlON ceramics pressureless sintered at 1880°C for 150 min by these powders show high transmittances up to 83%–84%, which indicates that the proposed fast one‐step CRN method is an effective and efficient way with strong robustness to synthesize single‐phase AlON powder for highly transparent AlON ceramics. It was found that α‐Al2O3 particles do not have enough time to aggregate and coalesce during heating due to the tremendously shortened heating span, which significantly inhibited particle coarsening until the formation of AlON starts. The fast‐formed AlON further inhibits the coarsening of α‐Al2O3 during dwelling. Consequently, single‐phase AlON powder of small primary particles can be obtained after 30 min dwelling at 1750°C. [ABSTRACT FROM AUTHOR]

The ScxAl1-xN wurtzite structure has been shown theoretically and experimentally to exhibit significantly higher piezoelectric coupling compared to pure AlN. In this work, a plasma-assisted epitaxial growth method has been used to synthesize epitaxial (0002) ScxAl1-xN films on c-sapphire substrates from x = 0.07 to 0.30 by co-evaporating high-purity Sc and Al sources in the presence of a nitrogen plasma generated by an RF plasma source. Epitaxial ScxAl1-xN films with highly oriented (0002) grains and in-plane registry were produced on c-sapphire substrates that were pre-exposed to the nitrogen plasma to form an oxynitride seed layer. Growth of ScxAl1-xN films was carried out at 930°C under both metal-rich and N-rich conditions using precisely controlled Sc, Al, and N-plasma fluxes. Metal-rich depositions yielded non-(0002)-oriented ScxAl1-xN grains and intermetallic ScAl grains. Nitrogen-rich growth with a Sc/Al flux ratio of 1/3 produced the best (0002) epitaxy as determined by x-ray diffraction analysis. Surface acoustic wave resonator (SAWR) devices were fabricated from 500-nm-thick ScxAl1-xN and AlN films to extract their electromechanical coupling coefficients, k2. As the Sc concentration in the films increases, the degree of (0002) epitaxy is reduced, yet the value of k2 increases becasue there is more Sc in the wurzite lattice despite the decreased level of (0002) grain alignment. The use of a 10-nm-thick SixNy capping layer on top of the ScxAl1-xN films aids in preventing etching during SAWR device photolithography and also helps hinder film oxidation up to 800°C. [ABSTRACT FROM AUTHOR]

Optically transparent, colorless Al-O-N and Al-Si-O-N coatings with discretely varied O and Si contents were fabricated by reactive direct current magnetron sputtering (R-DCMS) from elemental Al and Si targets and O2 and N2 reactive gases. The Si/Al content was adjusted through the electrical power on the Si and Al targets, while the O/N content was controlled through the O2 flow piped to the substrate in addition to the N2 flow at the targets. The structure and morphology of the coatings were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM), while the elemental composition was obtained from Rutherford backscattering spectrometry (RBS) and heavy ion elastic recoil detection analysis (ERDA). The chemical states of the elements in the coatings were analyzed by X-ray photoelectron spectroscopy (XPS). Based on analytical results, a model describing the microstructural evolution of the Al-O-N and also previously studied Al-Si-N [, , , ] coatings with O and Si content, respectively, is established. The universality of the microstructural evolution of these coatings with the concentration of the added element is attributed to the extra valence electron (e–) that must be incorporated into the AlN wurtzite host lattice. In the case of Al-O-N, this additional valence charge arises from the e – acceptor O replacing N in the AlN wurtzite lattice, while the e – donor Si substituting Al fulfills that role in the Al-Si-N system. In view of future applications of ternary Al-O-N and quaternary Al-Si-O-N transparent protective coatings, their mechanical properties such as residual stress (σ), hardness (HD) and Young’s modulus (E) were obtained from the curvature of films deposited onto thin substrates and by nanoindentation, respectively. Moderate compressive stress levels between −0.2 and −0.5 GPa, which suppress crack formation and film-substrate delamination, could be obtained together with HD values around 25 GPa.

Polycrystalline aluminum oxynitride (AlON) powders have been prepared by the carbothermal reduction nitridation of amorphous precursor obtained by solution combustion synthesis (SCS). Firstly, a mixed precursor of amorphous transition alumina and incompletely combusted organic matter has been combustion synthesized of a mixed solution of aluminum nitrate, urea and glucose. Then the pure phase AlON powders with D 50 = 0.846 μm can be prepared by calcining the SCS precursor at 1700 °C for only 10 min. The influences of different urea/aluminum nitrate nonahydrate ratio, calcining temperature and holding time on the properties of products have been discussed in detail. The research can provide a valuable reference for the efficient synthesis of AlON powders. [ABSTRACT FROM AUTHOR]

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Aluminum oxynitride ALON powders obtained by plasma-chemical synthesis are studied using the Rietveld X-ray method and Auger spectroscopy. In addition to the spinel phase, these powders contain aluminum nitride and a long-period polytypoid based on it; the total content of these admixtures is ~50 vol %. The presence of aluminum particles that have not fully reacted with oxygen and ammonia in the quenching chamber is recorded. The results of refinement of the spinel phase structure correspond to the model in which the localization of vacancies is associated with the positions occupied by aluminum atom, while the increase in nitrogen concentration and replacement of oxygen with nitrogen lead to population of the vacancies by aluminum. [ABSTRACT FROM AUTHOR]

Three groups of AlON powders with D 50 = 0.5, 1.1 and 2.7 μm (referred as P0.5, P1.1 and P2.7) were prepared to study the pressureless sintering behavior of AlON. These powders were doped with 0−0.75 wt.% Y 2 O 3 to investigate the combined effect of powder size and doping amount on the phase transformation, microstructure evolution and densification process during heating. The addition of high additive amount to P0.5 and P1.1 powders resulted in massive transformation into α-Al 2 O 3 and AlN, which resulted in agglomeration of α-Al 2 O 3 and isolation of AlN. Although low amount of additive to all three powders can effectively inhibit agglomeration of α-Al 2 O 3 and homogenization of particle size before sintering, its sintering ability is insufficient. 0.05, 0.10 and 0.50 wt.% Y 2 O 3 is the optimal addition to P0.5, P1.1 and P2.7 powders, respectively, to obtain high density, i.e. the larger of AlON powder size, the more Y 2 O 3 is needed. [ABSTRACT FROM AUTHOR]

In view of the application of γ‐AlON as transparent structural materials, it is significant to have a deep understanding of mechanical properties of γ‐AlON as well as their response to external pressure. First‐principles calculation combined with bond valence models was used to reconstruct Fd3m structure, and explore the composition and applied pressure dependence of mechanical properties of Al24−8/3xO24+8xN8−8x. The reconstructed Fd3m structure of Al24−8/3xO24+8xN8−8x was proved to be reasonable. The investigation demonstrated that the hardness and bulk modulus of bonds can be enhanced by increasing the ratio of bond valence to bond length and the bonds in octahedra contribute more to hardness and bulk modulus of Al24−8/3xO24+8xN8−8x. The applicability of the inferences was assessed by MgAl2O4 and c‐Si3N4. It can be inferred that the inferences cannot be applied to other spinel‐type compounds but also provide guidance to designing new spinel‐type compounds with desirable hardness and bulk modulus. [ABSTRACT FROM AUTHOR]

The kinetics of the direct interaction of oxide and aluminum nitride at temperatures of 1700 and 1780°C at a low pressure of p ≤ 1 Pa was studied. It was shown that the reaction without weight loss gives a two-phase nonequilibrium product ALON + AlN with the composition of ALON enriched with aluminum oxide. The reaction occurring under reducing conditions is accompanied by weight loss and gives an equilibrium two-phase product ALON + AlN, in which oxynitride spinel is enriched with aluminum nitride. The main methodological requirements for the direct synthesis of ALON with high optical and mechanical characteristics were determined. [ABSTRACT FROM AUTHOR]

This paper aims to reveal the mechanisms of ductile mode machining for AlON ceramics. The removal characteristics during machining were studied through ultra-precision grinding experiments. The machined surface consists of fractured and smooth areas, which were generated by brittle and ductile removal, respectively, of the individual AlON grains. The material removal mode has a determining effect on the surface/subsurface quality. The proportion of the fractured areas on the ground surface decreased gradually with a decrease in the depth of cut. The crystal indices of the grains most prone to brittle removal on the workpiece surface were determined using micro-area X-ray diffraction (μXRD) analysis performed using a beam with 50 μm diameter. The results showed that the ductile removal of the {111} planes is critical for the ductile mode machining of AlON. Nanoindentation tests based on electron back-scattered diffraction (EBSD) indicated that AlON shows strong anisotropy in its mechanical properties and machinability. The (111) plane has the highest hardness and lowest fracture toughness, at 22.91 GPa and 1.8 MPa m1/2, respectively. The material removal mechanism during the grinding of AlON was discussed in detail. The minimum and maximum d c(hkl) values must be known for classifying whether the removal mode of the workpiece is brittle or ductile. A damage-free surface could be obtained during ductile mode grinding by controlling h max to be less than d c(111). The subsurface deformation mechanism during ductile mode grinding was analysed. An amorphous layer was observed close to the ground surface. Further, dense dislocations with no particular orientation were present beneath this amorphous layer. As the crystal structure became clearer with an increase in the depth, the plastic deformation shifted to stacking faults parallel to the {111} planes. [ABSTRACT FROM AUTHOR]

For the first time, aluminum oxynitride (ALON) powders were synthesized using the precursors processed through aqueous sol–gel procedures. Appropriate quantities of aluminum nitride (AlN) powder and aqueous boehmite sol were mixed to obtain molecular stoichiometry of AlON. However, during the course of process, AlN powders reacted with the aqueous boehmite sol and disintegrated into its hydrated compounds. Such reactions altered the molecular stoichiometry between boehmite and AlN which was initially formulated for the eventual formation of AlON. Extensive investigations were carried out to analyse the behavior of AlN during the sol–gel processing. Hydrolysis of AlN in the aqueous sol–gel medium was circumvented by subjecting AlN to a surface modification process. The homogeneously dispersed boehmite sol and AlN mixture was further gelled, dried, and heat treated at temperatures between 1600 and 1850 °C for the formation of AlON powder. AlON phase formation was confirmed through XRD investigations, and its physical and microstructural properties were also evaluated through FESEM and TEM analyses. AlON powder with an average particle size of 490 nm was successfully synthesized in this study. This process is suitable for producing AlON powder in bulk quantities, and it can be used readily for further processes such as shaping and sintering to produce various optical products based on AlON. Highlights: For the first time, Aluminum Oxynitride (AlON) powders were synthesized using aqueous sol–gel processing. AlN powders and aqueous boehmite sol were used as precursors. Surface modification treatement was carried out for AlN powder prior to its addition with the boehmite sol to retain its phase intact during the processing. Single-phase AlON powders with average particle size of 490 nm was successfully synthesized. [ABSTRACT FROM AUTHOR]

We report an experimental study concerned with the synthesis and luminescence properties of Al5O6N aluminum oxynitride doped with Tb3+ in the concentration range 0.025–0.5 at %. All of the samples, prepared by firing appropriate mixtures in a nitrogen atmosphere at 1600°C, consisted predominantly of phase-pure γ-ALON (Al5O6N), with small amounts of impurity phases: Al7O3N5 aluminum oxynitride and Tb3Al5O12 terbium aluminate. Their pulsed cathodoluminescence and photoluminescence spectra contain emission bands typical of Tb3+ ions. The concentration threshold for luminescence quenching corresponds to a Tb3+ concentration at a level of 0.4 at %. A Tb3+ cross relaxation effect found in Al5O6N:Tb3+ is discussed and photoluminescence spectra are shown to be inhomogeneous at low Tb3+ concentrations in Al5O6N. [ABSTRACT FROM AUTHOR]

Optically transparent, colorless Al-O-N and Al-Si-O-N coatings with discretely varied O and Si contents were fabricated by reactive direct current magnetron sputtering (R-DCMS) from elemental Al and Si targets and O2 and N2 reactive gases. The Si/Al content was adjusted through the electrical power on the Si and Al targets, while the O/N content was controlled through the O2 flow piped to the substrate in addition to the N2 flow at the targets. The structure and morphology of the coatings were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM), while the elemental composition was obtained from Rutherford backscattering spectrometry (RBS) and heavy ion elastic recoil detection analysis (ERDA). The chemical states of the elements in the coatings were analyzed by X-ray photoelectron spectroscopy (XPS). Based on analytical results, a model describing the microstructural evolution of the Al-O-N and also previously studied Al-Si-N [1, 2, 3, 4] coatings with O and Si content, respectively, is established. The universality of the microstructural evolution of these coatings with the concentration of the added element is attributed to the extra valence electron (e–) that must be incorporated into the AlN wurtzite host lattice. In the case of Al-O-N, this additional valence charge arises from the e – acceptor O replacing N in the AlN wurtzite lattice, while the e – donor Si substituting Al fulfills that role in the Al-Si-N system. In view of future applications of ternary Al-O-N and quaternary Al-Si-O-N transparent protective coatings, their mechanical properties such as residual stress (σ), hardness (HD) and Young's modulus (E) were obtained from the curvature of films deposited onto thin substrates and by nanoindentation, respectively. Moderate compressive stress levels between −0.2 and −0.5 GPa, which suppress crack formation and film-substrate delamination, could be obtained together with HD values around 25 GPa. [ABSTRACT FROM AUTHOR]

This paper describes combusting loose powder beds of mixtures of aluminum metal powders and aluminum oxide powders with various grain sizes under various nitrogen pressure. The synthesis conditions required at least 20/80 weight ratio of aluminum metal powder to alumina powder in the mix to reach approximately 80 wt% of γ-AlON in the products. Finely ground fused white alumina with a mean grain size of 5 μm was sufficient to achieve results similar to very fine alumina with 0.3 μm grains. A lower nitrogen pressure of 1 MPa provided good results, allowing a less robust apparatus to be used. The salt-assisted combustion synthesis upon addition of 10 wt% of ammonium nitrite resulted in a slight increase in product yield and allowed lower aluminum metal powder content in mixes to be ignited. Increasing the charge mass five times resulted in a very similar γ-AlON yield, providing a promising technology for scaling up. Synthesis in loose powder beds could be utilized for effective production of relatively cheap and uniform AlON powder, which could be easily prepared for forming and sintering without intensive grounding and milling, which usually introduce serious contamination.

Aluminum oxynitride (AlON) can be effectively finished by ultra-precision grinding. In this work, the ultra-precision grinding experiment was conducted on AlON to investigate surface characteristics and material removal mechanism. The ground surface has an unusual non-uniform morphology resulted from the different material removal modes. Grazing incidence X-ray diffraction (GIXRD), nanoindentation and Electron Back-Scattered Diffraction (EBSD) were carried out to study the micro-properties of AlON. The results revealed that the micro mechanical properties vary with the grain orientation on the surface. The morphologies of ground surface are consistent in the twinned grains and change with the grain orientation. By comparing the relationship of machining size and grain size, the material removal modes of individual grains should be taken into consideration during ultra-precision grinding. Based on this, a simple theoretical model was proposed to explain the material removal mechanism of AlON under ultra-precision grinding. [ABSTRACT FROM AUTHOR]

Convected particle domain interpolation, which is known to boost the accuracy of the material-point method, is applied in a form called convected-particle tetrahedron interpolation (CPTI). CPTI exploits the efficiency of tetrahedral tessellations to represent complex structural geometries, while still solving field equations on a rectilinear background grid. Advantages include anti-locking and an ability to handle extremely large deformations without suffering typical Eulerian advection errors. CPTI is demonstrated to resolve long-standing errors caused by spuriously ragged (stair-stepped) surfaces, and it is also shown to accommodate mathematically rigorous evaluation of surface integrals in models for contact and friction. Benefits of this work are illustrated in mesoscale simulations of an aluminum oxynitride ceramic. [ABSTRACT FROM AUTHOR]

Abstract Aluminum oxynitride (AlO x N y) films with different nitrogen concentration are prepared by thermal atomic layer deposition (ALD) for flexible nano-textured silicon (NT-Si) surface passivation. The AlO x N y films are shown to exhibit a homogeneous nitrogen-doping profile and the presence of an adequate amount of hydrogen, which is investigated by Time-of-Fight Elastic Recoil Detection Analysis (ToF-ERDA). The effective minority carrier lifetimes are measured after the NT-Si surface passivation; the minimum surface recombination velocity (SRV) of 5 cm-s−1 is achieved with the AlO x N y film in comparison to the Al 2 O 3 and AlN films (SRV of 7–9 cm-s−1). The better SRV with AlO x N y film is due to the collective effect of field-effect passivation by the presence of fixed negative charges, and chemical passivation by the presence of hydrogen within the film. The capacitance-voltage, and conductance measurements also are carried out using metal-oxide-semiconductor structure to determine the fixed negative charge density (N i,ox), and defect density of states (D it) in the AlO x N y films. The better surface passivation is attributed to unusually large N i,ox of ~6.07 × 1012 cm−2, and minimal D it of ~1.01 × 1011 cm−2-eV−1 owing to the saturation of Si dangling bonds by the hydrogen within the AlO x N y film matrix after the annealing step. Highlights • Superior surface passivation of flexible nano-textured silicon demonstrated by ALD grown Aluminum oxynitride (AlO x N y) films. • Presence of hydrogen and homogeneous nitrogen-doping profile in AlO x N y film investigated by the ToF-ERDA. • Minimum surface recombination velocity of ~5 cm‐s−1 achieved from silicon surface with AlO x N y passivation films. • Hydrogen and nitrogen ions' negative charge in the film provided chemical and field-effect passivation, respectively, on the silicon surface. [ABSTRACT FROM AUTHOR]

Abstract High synthesis temperatures and long soaking times are generally required to fabricate AlON powders, which can cause coarsening and aggregation of the powder. Solid-state reaction methods form AlON powders by a direct reaction of Al 2 O 3 and AlN, enabling rapid synthesis of AlON powder at low temperatures. In this work, single phase AlON powders were fabricated by a solid-state reaction method using Al 2 O 3 and AlN powders as raw materials. To lower the synthesis temperature and shorten the soaking time, the raw materials particle sizes and the homogeneity of the Al 2 O 3 /AlN mixture were investigated. The effects of AlN content, synthesis temperature, and soaking time on the synthesis of AlON powders were examined. When the AlN content was 27 mol%, single phase AlON powders were synthesized by calcining Al 2 O 3 /AlN mixture at 1680 °C for 20 min. After ball-milling at 250 rpm for 24 h, the synthesized AlON powder was ground into a single phase fine AlON powder with an average particle diameter of 320 nm, a narrow size distribution, and good dispersibility. Transparent AlON ceramics with dimensions of Φ100 mm × 1 mm were fabricated by pressureless sintering the produced fine AlON powder. [ABSTRACT FROM AUTHOR]

Abstract Al 2 O 3 /Aluminum oxynitride (AlON) and AlON/ Aluminum nitride (AlN) composites were prepared via two-step carbothermal reduction nitridation (CRN) method. A solvothermal method was selected to synthesize alumina (Al 2 O 3)/Polyacrylonitrile (PAN) nanocomposite as a first-precursor of products. Then, this Al 2 O 3 /PAN sample was held under pyrolysis conditions (800 °C for 2 h in an argon atmosphere) for fabricating Al 2 O 3 /Carbon nanocomposite. Eventually, using two-step CRN method (first at 1450–1550 °C for 2 h in argon (Ar) flow and so 1700–1800 °C for 1 h in N 2 flow) Al 2 O 3 /AlON and AlON/AlN composites were achieved. Results show that a change in the residual carbon content in second-precursor (alumina/carbon nanocomposite) is a key factor in controlling the composition of the final product. [ABSTRACT FROM AUTHOR]

Abstract Aluminum oxynitride (Al-O-N) is a material suitable for hard, transparent thin films. Its physical properties and structure can be adjusted through the O-to-N ratio. Reactive Direct Current Magnetron Sputtering (R-DCMS) is a practical, widespread technique for the deposition of coatings. However, it proves to be challenging in the case of Al-O-N. The reason for this is the high reactivity of O 2. Poisoning of Al targets by O 2 causes formation of insulating oxide islands and consequently leads to target destruction and a failure of the deposition process. Here, we show that with two separate gas inlets for the two reactive gases, a good process stability can be achieved over the entire range of O-to-N ratios. Highlights • A technique is shown that allows for the stable, reproducible deposition of Al-O-N. • No costly hardware is needed. • The high reactivity of O 2 is successfully kept under control. • Thin films of Al-O-N with an adjustable O-to-N ratio can be grown. [ABSTRACT FROM AUTHOR]

In this paper, we analyzed the methods of synthesis and sintering of aluminum oxynitride powders. Samples of a ceramic material based on aluminum oxynitride were produced. The effectiveness of two sintering methods in induction and resistance furnaces was evaluated in the temperature range of 1750–1950°C and for the exposure time from 2 to 10 h. Structures of the obtained samples were studied by scanning electron microscopy, while the phase composition was studied using X-ray phase analysis. The effect of the heating parameters, sintering atmosphere, and quality of the initial powders on the formation of the aluminum oxynitride phase was considered. A sample sintered in a vacuum furnace without a nitrogen atmosphere did not have the aluminum oxynitride phase because of the release of nitrogen from the sample volume and had a strong shrinkage. Induction sintering in a nitrogen atmosphere made it possible to achieve ~85% concentration of the target phase, aluminum oxynitride, with density of 85% of theoretical (3.69 g/cm3). These results were obtained in the mode of exposure for 10 h at 1750°C. [ABSTRACT FROM AUTHOR]

High heating rates ranging from 50 to 250°C/min are selected to rapidly sinter transparent aluminum oxynitride (AlON) ceramics by spark plasma sintering (SPS) at 1600°C under 60 MPa using a bimodal AlON powder synthesized by the carbothermal reduction and nitridation method. With 1 minute holding time before cooling, all the specimens show high density and high transparence. The maximum transmittance is up to 74.5%‐80.6%, where the maximum transmittance is positively correlated with the heating rate. Further analysis reveals that faster heating rates enable the decrease in the amount of the AlON phase decomposed into the α‐Al2O3 and AlN phases during heating. These α‐Al2O3 and AlN phases have to be converted back to AlON at the final stage of sintering, which indicates that a decrease in the amount of the α‐Al2O3 and AlN phases via the boosted heating leads to the higher transmittance of the AlON ceramics. The high heating rates and short holding duration of the SPS utilized in this study result in the fine grain size of the obtained ceramics (1‐6 μm) compared to that of the AlON ceramics fabricated by the conventional sintering method. This effect of high heating rates is confirmed by the coupled densification‐grain growth modeling. In turn, the obtained AlON specimens exhibit a Vickers hardness of 15.87‐16.62 GPa. [ABSTRACT FROM AUTHOR]

This study investigated the effects of a thin aluminum oxynitride (AlOxNy) gate insulator on the electrical characteristics of AlGaN/GaN-on-SiC metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs). The fabricated AlGaN/GaN-on-SiC MIS-HEMTs exhibited a significant reduction in gate leakage and off-state drain currents in comparison with the conventional Schottky-gate HEMTs, thus enhancing the breakdown voltage. The effects of gate recess were also investigated while using recessed MIS-HEMT configuration. The Johnson’s figures of merit (= fT × BVgd) for the fabricated MIS-HEMTs were found to be in the range of 5.57 to 10.76 THz·V, which is the state-of-the-art values for GaN-based HEMTs without a field plate. Various characterization methods were used to investigate the quality of the MIS and the recessed MIS interface.

Thin films of aluminum nitride and oxynitride were deposited by atomic layer deposition (ALD) in the temperature range from 170 to 290°C (optimal deposition temperature 200-230°C). Tris(dimethylamido) aluminum and ammonia were used as precursors for the atomic layer deposition of aluminum nitride (AlN). The average AlN film thickness per ALD cycle (deposition rate) at 200°C was ~0.8 Å. Films were deposited on a silicon <100> substracte with a native oxide layer. The N/Al atomic concentration ratio in the obtained films was ~1.3. Aluminum oxynitride films obtained by periodical dose of water vapor in the course of atomic layer deposition of AlN at 200°C. The composition of the deposited oxynitride films was Al0.5O0.43N0.07. [ABSTRACT FROM AUTHOR]

Abstract: γ‐aluminum oxynitride (γ‐AlON) with spinel structure has attracted much attention for structural and functional application. γ‐AlON powders were successfully prepared by direct nitridation method of Al/Al(OH)3 starting mixture in ammonia and then calcined at high temperature. XRD, SEM, TEM, EDX, and photoluminescence were conducted to investigate the detail procedure and the optical properties of AlON: xEu phosphors. Nitrogen was introduced by the nitridation of metallic aluminum, appropriate Al amount and nitridation condition was necessary to obtain phase pure γ‐AlON. The as‐prepared AlON powders exhibited multifaceted grain morphology with fine particle size (1‐5 μm). Eu2O3 activator was reduced and transformed to EuAl12O19 by reaction with alumina, which remained in the product when x > 0.25%. Under 331 nm excitation, AlON: xEu phosphors exhibited emission bands of 475 and 410 nm. 475 nm band reached a plateau at x = 0.25% due to the solubility of Eu2+ ion in AlON, whereas 410 nm band showed a linear increase in intensity with Eu2+ doping amount, which was believed to be the contribution of EuAl12O19. The present approach combination of direct nitridation in ammonia and postcalcination process showed potential application for AlON ceramic and AlON phosphors. [ABSTRACT FROM AUTHOR]

Experimental studies on the synthesis of aluminum oxynitride nanopowders in a reactor with a confined plasma jet by the interaction of disperse aluminum with ammonia and oxygen in a flow of nitrogen plasma generated in an electric arc plasma torch are performed. Preliminary calculations of the equilibrium compositions and thermodynamic characteristics of the multicomponent Al-O-N system are carried out. An optimal design of the reaction prechamber of the reactor is performed. Powders having a cubic structure and consisting of aluminum oxynitride phases with an average particle size in the range from 20 to 200 nm are obtained. It is established that the specific surface area of the obtained powders increases from 20 to 71 m2/g, and the nitrogen content in the nanopowders increases from 3.6 to 14.7 wt % with an increase in the flow rate of quenching gas from 1.8 to 6.0 m3/h. At the same time, the oxygen content decreases from 35.5 to 25.5 wt %. At a minimal flow rate of the quenching gas, the metallic aluminum and its oxide phases are present in the obtained powders. With an increase in the amount of quenching gas, the conditions for the mixing of aluminum vapors with oxygen and atomic nitrogen from decomposing ammonia are improved, which leads to the formation of aluminum oxynitride and aluminum nitride. The variation of the synthesis parameters allows us to obtain aluminum oxynitride nanopowders having a specific surface area ranging from 28 to 50 m2/g containing from 1 to 11 wt % of nitrogen and from 25 to 40 wt % of oxygen. [ABSTRACT FROM AUTHOR]

Laser gas assisted texturing of alumina surface is carried out, and formation of nitride and oxynitride compounds in the surface vicinity is examined. The laser parameters are selected to create the surface topology consisting of micro/nano pillars with minimum defect sites including micro-cracks, voids and large size cavities. Morphological and hydrophobic characteristics of the textured surface are examined using the analytical tools. The characteristics of the environmental dust and its influence on the laser textured surface are studied while mimicking the local humid air ambient. Adhesion of the dry mud on the laser textured surface is assessed through the measurement of the tangential force, which is required to remove the dry mud from the surface. It is found that laser texturing gives rise to micro/nano pillars topology and the formation of AlN and AlON compounds in the surface vicinity. This, in turn, lowers the free energy of the textured surface and enhances the hydrophobicity of the surface. The liquid solution resulted from the dissolution of alkaline and alkaline earth metals of the dust particles in water condensate forms locally scattered liquid islands at the interface of mud and textured surface. The dried liquid solution at the interface increases the dry mud adhesion on the textured surface. Some dry mud residues remain on the textured surface after the dry mud is removed by a pressurized desalinated water jet. [ABSTRACT FROM AUTHOR]

Aluminum oxynitride (AlON), which can be regarded a nitrogen-stabilized cubic γ-Al2O3, has attracted attention in terms of its good mechanical, chemical, and optical stability. Because of its optical inertness, however, photoluminescence ( PL) emission from nominally pure AlON has not been carefully investigated and evaluated. In this work, we prepared visibly luminescent AlON by nitridation of γ-Al2O3 under N2 atmosphere without adding aluminum nitride (AlN) using a high-frequency induction heating unit. The resulting AlON exhibits a broad PL emission in the blue/green spectral region under excitation with light of ~260 nm. In the luminescent AlON sample, the excitation and emission events will occur at different sites; the electron transfer from the excitation site to the emission site is preceded by the radiative recombination process. It has also been found that the PL peak wavelength shows an anomalous blue shift by ~50 nm with increasing temperature from 78 to 500 K. The observed temperature dependent PL characteristics are governed by thermalization among multiple emitting levels. Aluminum vacancies and oxygen vacancies, both of which are introduced into the crystalline lattice during nitridation without the presence of AlN, are very likely candidates for the excitation and emission centers, respectively. Hence, the present direct nitridation method provides a simple and effective way to add an additional optical functionality to otherwise optically inactive AlON. [ABSTRACT FROM AUTHOR]