Formation Of Aluminum Nitride Research Articles

Study of aluminum nitride formation in a plasma with effect of double laser pulses on D16T aluminum alloy in air

In this paper, we propose new opportunities to increase the proportion of various aluminum ions in the near-surface laser plasma in the regimes of ablation of aluminum alloy surfaces by defocused double laser pulses, and AlN nanoclusters under the sequential influence of double pulses on the target (D16T aluminum alloy). Experimental results show that the intensity of the spectral lines of Al ions reaches a maximum when the time intervals between double pulses of the order of 5÷15 us, the pulse energy of 42 mJ (Al II) and 38 mJ (Al III); The percentage of AlN nanoclusters reaches a maximum at energy of pulses of about 40 mJ, defocus of 0 mm and number of pulses of 25÷30. Full Text: PDF References Zheng Biju and Hu Wen, "A novel loss compensation technique analysis and design for 60 GHz CMOS SPDT switch*", Journal of Semicond. 37, 063003 (2016). CrossRef Perez J.A., Vera I.P., Riascos H., Caicedo J.C., "Optical emission spectroscopy of Aluminum Nitride thin films deposited by Pulsed Laser Deposition", Jornal of Physics: Conference Series 511, 1 (2014). CrossRef D.-M. Marin, F. Stokker-Cheregi, M. Dumitru, V. Ion, M. Dinescu, "Aluminium nitride thin films grown by plasma assisted pulsed laser deposition", Romanian Reports in Physics 66, 1118 (2014). DirectLink L. T. Sukhov, Laser spectral analysis (Novosibirsk 1990). Kononenko T. V., Konov V. I., Lubnin E. N., Dausinger F., "Pulsed laser deposition of hard carbon coatings at atmospheric pressure", Quantum electronics 33, 189 (2003). CrossRef Goncharov V. K., Kozadaev K. V., "Formation of the condensed phase of metals exposed to submicrosecond laser pulses", Journal of Engineering physics 83, 80 (2010). CrossRef Fadaiyan A. R., Trinh Ngoc Hoang, Zazhogin A. P., Vestnik BSU 1, 27 (2011). Fadaian A. R., Zazhogin A. P., Vestnik BSU 1, 14 (2009). Kask N. E., Michurin S. V., Fedorov G. M., "Fractal structures in a laser plume", Kvant. electron. 33, 57 (2003). DirectLink Krainov V. P., Smirnov M. B., "???????? ??????? ????????? ??? ????????? ??????????????? ???????????? ????????? ????????" Uspekhi Fizicheskikh Hauk 170, 969 (2000). CrossRef Ilin ?.P., Root L.?., Journal of science of Siberia 1, 91 (2011). Herzberg G., Electronic spectra and structure of polyatomic molecules (Mir Press 1969).

Splat Morphology and Influence of Feeding Rate During Reactive Plasma Spray of Aluminum Powder

Fabrication of aluminum nitride (AlN) coatings using conventional plasma spraying processes directly has been deemed impossible. It is attributed to the thermal decomposition of the AlN feedstock particles during spraying without a stable melting phase. Using the reactivity of the plasma (reactive plasma spraying: RPS) showed a promising consideration for in situ formation of AlN thermally sprayed coatings. Several AlN-based coatings were fabricated through the RPS of aluminum powders in the N2/H2 plasma. The focus of this study is in discussing the morphology of splat deposition during the nitriding of Al particles. Furthermore, the influence of the feeding rate during the RPS and nitriding of Al powders will be investigated. The nitride content, as well as the unreacted molten Al phase, strongly influences splat deposition and morphology during the RPS of Al. The collected splats can be divided into reacted, partially reacted, and unreacted splats. The reacted splats tend to show a disk or egg-shell shape. The partially reacted mainly had outside nitride shells and an unreacted molten Al part in the center. The unreacted splats tended to show a splash shape. The main controlling factor is the time of the droplet impact on the substrate during the reaction sequence. The particle size and spray distance showed significant effects on the splat formation due to their effect on the nitriding conversion and the melting behavior of the particles during RPS nitriding. The powder feeding rate was investigated through increasing the injection rate and by using a low carrier gas flow rate. Increasing the powder feeding rate significantly improved the coating thickness. However, it suppressed the nitriding conversion of the large Al particles. Thus, with increasing the amount of the powder in the plasma, the Al molten particles are easily aggregated and agglomerate together upon colliding on the substrate with an AlN shell on the surface. This prevents the N2 from having access to all of the aggregated particles. Therefore, the fabricated coatings using large Al particles consist of surface AlN layers and the central parts of AlN and Al composite layers. On the other hand, it was possible to fabricate about 500-μm-thick AlN coatings using fine Al particles of 15 μm and increasing the feeding rate. Using the fine particles improved the nitriding reaction due to the improvement of the surface area (the reaction area). Moreover, the nitriding process of the Al particles with increasing the feeding rate was also investigated.

Increased upper critical field for nanocrystalline MoN thin films deposited on AlN buffered substrates at ambient temperature

Molybdenum nitride (MoN) thin films have been deposited using reactive DC magnetron sputtering on aluminum nitride buffered oxidized silicon substrates at ambient temperature. GIXRD of aluminum nitride (AlN) deposited under similar conditions has revealed the formation of wurtzite phase AlN. GIXRD characterization of molybdenum thin films deposited on AlN buffered oxidized silicon substrates has indicated the formation of nanocrystalline MoN thin films. The electrical resistivity measurements indicate MoN thin films have a superconducting transition temperature of ~8 K. The minimum transition width of the MoN thin film is 0.05 K at 0 T. The inferred upper critical field Bc2(0) for these nanocrystalline MoN thin films obtained by fitting the temperature dependence of critical field with Werthamer, Helfand and Hohenberg theory lies in the range of 17–18 T which is the highest reported in literature for MoN thin films.

The effect of dispersing agent on the formation of aluminium nitride nanoparticles/whiskers

The effect of the amount of dispersing agent on the formation of aluminium nitride (AlN) nanoparticles/whiskers is presented. Various levels of the dispersant [rice bran (RB)] concentration, mass ratio of Al/RB ranging from 0.43 (30:70) to 2.33 (70:30), were systematically investigated. After the heat treatment in a nitrogen atmosphere, all samples with different RB contents could be transformed to AlN nanoparticles and nanowhiskers with trace graphite. In this experiment, the dispersant concentration in the starting mixture not only affects the morphologies of the resultant AlN (particles/whiskers) but also makes the morphology of the AlN whiskers evolve. The mechanisms for the formation and the evolution of AlN whiskers are discussed.

Conversion of Alumina to Aluminum Nitride Using Polymeric Carbon Nitride as a Nitridation Reagent

Polymeric carbon nitride, which was synthesized by polymerization of dicyandiamide at 500°C, was used as a nitridation reagent in the conversion of δ‐alumina (δ‐Al2O3) to aluminum nitride (AlN). The products obtained at various reaction temperatures were characterized by powder X‐ray diffraction, 27Al magic‐angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, Raman spectroscopy, and X‐ray photoelectron spectroscopy (XPS). δ‐Al2O3 began to convert to AlN at 900°C, which is the lowest temperature reported for the formation of AlN from Al2O3, and completely converted to AlN at 1400°C. The occurrence of reaction intermediates during nitridation was confirmed by 27Al MAS NMR and XPS. The change in Raman spectra with reaction temperatures indicated that lattice defects in AlN were reduced by calcining at higher reaction temperatures.

Investigation of the Aluminum Nitride Formation During the Aluminum Nanopowder Combustion in Air

The phase formation sequences, intermediate and final products of aluminum nanopowder combustion are studied. The experiments were performed in the Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, at the “Precision Diffractometry II” station (SR beamline No. 6 of the VEPP-3 electron storage ring). The main combustion product was found to be aluminum nitride. In the combustion of aluminum nanopowder aluminum γ-oxide is the first to form, and aluminum nitride arises next. The formation of aluminum nitride probably occurs by successive replacement of oxygen by nitrogen from the aluminum oxide. The use of synchrotron radiation with high photon flux made it possible to determine with moderate time resolution the sequence of stages of formation of crystalline products during combustion of the aluminum nanopowder.

The Resource-Saving Technology of Aluminum Nitride Obtaining During Combustion of Aluminum Nanopowder in Air

The resource-saving technology of aluminum nitride obtaining during the combustion of aluminum nanopowder in air has been analyzed in the article. The investigation of the crystal phases of aluminum nanopowder combustion products obtained under the magnetic field exposure has been made. The experimental results showed the increase of aluminum nitride content up to 86 wt. % in comparison with the aluminum nitride content in combustion products without any exposure. The mechanism of aluminum nitride formation and stabilization in air was due to the oxygen molecules deactivation by light emission during combustion.

In situ synthesis of AlN nanoparticles by solid state reaction from plasma assisted ball milling Al and diaminomaleonitrile mixture

In this paper, Aluminum nitride (AlN) nanoparticles from solid state reaction of diaminomaleonitrile (DN) with aluminum (Al) are synthesized by plasma assisted high energy ball milling (p-milling). The structure and morphology of the p-milling products are characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier Transform infra red (FT-IR), Differential scanning calorimetry and Thermal gravimetry (DSC–TG). The XRD results show a correlation between milling time and crystallite size, lattice distortion, specific surface area, and conversion rate of AlN. About 90% AlN has been obtained and specific surface area can reach 52m2g−1 at p-milling 14h. The FT-IR measurements show the solid reaction starts with the deammoniation of DN molecules, followed by the formation of AlN powder as the main solid products after p-milling 8h. The DSC–TG results indicate that DN starts to disintegrate from 180°C to 450°C by the elimination of the N–H and C≡N groups, continue increasing temperature leads to the formation of AlN at 673°C. The activation energy of reaction from p-milling Al and DN mixture is calculated by the Kissinger equation and is about 353.5kJ/mol. Meanwhile, the formation mechanism of AlN in a p-milling process is also investigated.

Synthesis of aluminum nitride in a coke–calcium reduction bed using nitrogen in air

An experimental study on the heating of a mixture of aluminum and lithium hydroxide (LiOH) powders in a reductive bed under air atmosphere is reported. The formation of aluminum nitride (AlN) during this process was the focus of this study. The formation of AlN was achieved using LiOH as an additive and heating the sample in a resistance furnace in a specially designed double crucible within a bed of a mixture of coke and filamentous calcium. The temperature range of the reaction was between 700°C and 1100°C. The optimum temperature of 1100°C and the optimum LiOH amount (5wt%) required to achieve maximum yield were determined by powder X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) micrographs clearly indicated the transformation of grain structures from rods (700°C) to cauliflower shapes (1100°C).

Aluminum Nitride Formation From Aluminum Oxide/Phenol Resin Solid-Gel Mixture By Carbothermal Reduction Nitridation Method

Abstract Hexagonal and cubic crystalline aluminum nitride (AlN) particles were successfully synthesized using phenol resin and alpha aluminum oxide (α-Al2O3) as precursors through new solid-gel mixture and carbothermal reduction nitridaton (CRN) process with molar ratio of C/Al2O3 = 3. The effect of reaction temperature on the decomposition of phenol resin and synthesis of hexagonal and cubic AlN were investigated and the reaction mechanism was also discussed. The results showed that α-Al2O3 powder in homogeneous solid-gel precursor was easily nitrided to yield AlN powder during the carbothermal reduction nitridation process. The reaction temperature needed for a complete conversion for the precursor was about 1700°C, which much lower than that when using α-Al2O3 and carbon black as starting materials. To our knowledge, phenol resin is the first time to be used for synthesizing AlN powder via carbothermal reduction and nitridation method, which would be an efficient, economical, cheap assistant reagent for large scale synthesis of AlN powder.

Effect of dopant concentration on the phase composition and luminescence properties of Eu2+- and Ce3+-doped AlONs

Herein we report the synthesis of aluminum oxynitride (Al5O6N) doped with Eu2+ and Ce3+ and examine the effects of the dopant concentration and the nature of the rare-earth-containing precursor (europium and cerium oxides, Eu(acac)3, and Ce(acac)3) on its properties. At dopant concentrations above the solubility limit of rare-earth aluminates (EuAl12O19 and CeAl11O18) in aluminum oxynitride, we observed the formation of aluminum nitride and aluminum oxide (α-Al2O3) as individual phases. The concentration of the latter phase was higher when the rare-earth oxides were used. The emission intensity in the cathodoluminescence spectra of the samples was shown to have a maximum at Eu2+ and Ce3+ concentrations from 0.1 to 0.5 at %. Concentration quenching of luminescence was observed.

Deposition of AlN on Nimonic 75 by PFD device

In this study, thin films of aluminium nitride (AlN) are deposited on Nimonic 75 substrates using a 4 kJ Mather type plasma focus device (PFD) for 5, 10 and 15 focus shots. For the deposition of AlN films, a solid aluminium fitted anode was used instead of a copper anode. The PFD was operated with nitrogen gas at a pressure of 2 torr. X-ray diffraction results reveal the formation of a nanocrystalline AlN coating on the surface of the substrate. The crystallite size is dependent on the number of focus shots. The density of grains increased with an increase in the number of focus deposition shots, as illustrated by field emission scanning electron microscopy (FESEM). The FESEM images confirm the distribution of spherical grains for 15 focus shots. Energy dispersive X-ray spectroscopy spectra indicate the presence of expected constituent elements such as N and Al.

Effects of Sintering Atmosphere on the Mechanical Properties of Al-Fe Particle-Reinforced Al-Based Composites

Al-based composites reinforced by Al-Fe intermetallic compounds have been fabricated by powder metallurgy technique. The reinforcements were formed in the aluminum matrix by in situ solid-state reaction between pure Al and pure Fe powders. The effects of sintering atmosphere on the microstructures and mechanical properties of the composites were systematically studied by scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction analysis, and compressive tests. It has been shown that Al-Fe intermetallic particles (including a large number of the Fe-Al5Fe2 core-shell structured particles) were the dominant reinforcements in the composites sintered under Ar atmosphere, while pure Fe particles were the dominant reinforcements in the composites sintered under N2 atmosphere. N2 atmosphere is more effective than Ar atmosphere in increasing the sintered density of the composites due to the formation of aluminum nitride, which can effectively fill the pores. Thus, the compressive mechanical properties of the composites sintered under N2 atmosphere are higher than those of the composites sintered under Ar atmosphere.

Formation of aluminum nitride from metal–organic precursors synthesized by reacting aluminum tri-chloride with bis(trimethylsilyl)carbodiimide

Metal–organic precursor for aluminum nitride (AlN) ceramics was synthesized by reacting aluminum tri-chloride (AlCl3) with bis(trimethylsilyl)carbodiimide (BTSC). Fourier transform infra-red (FT-IR) spectrum of the synthesized precursor exhibited characteristic absorption bands assigned to the carbodiimide (N=C=N) group at 2150–2250, and 851 cm−1, while the solid state 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectrum of the precursor exhibited single signal at 103 ppm which was thought to correspond to Al(N=C=N)4 unit. To examine the potential as a precursor for AlN ceramics, the intrinsic thermal conversion behavior up to 1800°C of the synthesized precursor was investigated under argon atmosphere. X-ray diffraction analysis revealed that the crystallization of AlN was found to start above 800°C, and fully crystallized AlN ceramics was synthesized by the additional heat treatment at 1800°C. In addition to the FT-IR and NMR spectroscopic analyses for studying the synthetic parameters such as reaction temperature and use of catalyst for the formation of polymeric precursors derived from AlCl3 and BTSC, the effects of heat treatment condition on the polymer/ceramics conversion yield, impurity and crystallinity of the AlN ceramics have been studied by using a thermogravimetric analyzer coupled with a quadrupole mass spectrometer (TG-MS). The results were discussed from a viewpoint to develop a novel synthesis method for AlN ceramics through the polymer precursor route.

Effect of Addition of 4 % Al on the High Temperature Oxidation and Nitridation of a 20Cr–25Ni Austenitic Stainless Steel

In high temperature applications, the alumina forming austenites (AFA) have recently gained more focus. These utilise the advantageous effect of Al on oxidation resistance, and also have good mechanical properties. Two experimental alloys [20Cr–25Ni–1Mn–0.5Si–Fe (wt.%)] were prepared. To one of the alloys 3.77 wt.% Al was added. The alloys were studied in air and air/water at 700 °C and 1,000 °C, in a sulphidising/chlorinating environment at 700 °C and in a nitriding atmosphere at 1,000 °C. The time of exposure was 100 h, except for one 1,000 h exposure in air/water. At 700 °C in air and air/water, the AFA displayed lower mass gain than the reference material. After exposure in the sulphidising-chlorinating environment, the material displayed a surface alumina layer with some spallation. In air or air/water at 1,000 °C, internal aluminium nitride and alumina formation occurred, appreciably reducing the sound metal thickness. The nitridation was enhanced in the nitriding environment.

Deposition of rock salt AlN coatings by magnetron sputtering

Cubic aluminium nitride (AlN) coatings were successfully deposited on stainless steel 304L substrates by balanced magnetron sputtering. Grazing incidence X-ray diffraction measurement confirmed the formation of rock salt cubic AlN having a preferred orientation along (111) plane. Scanning electron microscopy revealed nodular microstructure of the coating. Thermal diffusivity of AlN coated sample was found to be significantly higher than that of the uncoated sample. Microscratch adhesion test showed no adhesive failure below 20 N loads.

Reactive Plasma Spraying of Fine Al2O3/AlN Feedstock Powder

Reactive plasma spraying (RPS) is a promising technology for in situ formation of aluminum nitride (AlN) coatings. Recently, AlN-based coatings were fabricated by RPS of alumina (Al2O3) powder in N2/H2 thermal plasma. This study investigated the feasibility of RPS of a fine Al2O3/AlN mixture and the influence of the plasma gases (N2, H2) on the nitriding conversion, and coating microstructure and properties. Thick AlN/Al2O3 coatings with high nitride content were successfully fabricated. The coatings consist of h-AlN, c-AlN, Al5O6N, γ-Al2O3, and a small amount of α-Al2O3. Use of fine particles enhanced the nitriding conversion and the melting tendency by increasing the surface area. Furthermore, the AlN additive improved the AlN content in the coatings. Increasing the N2 gas flow rate improved the nitride content and complete crystal growth to the h-AlN phase, and enhanced the coating thickness. On the other hand, though the H2 gas is required for plasma nitriding of the Al2O3 particles, increasing its flow rate decreased the nitride content and the coating thickness. Remarkable influence of the plasma gases on the coating composition, microstructure, and properties was observed during RPS of the fine particles.

Preparation of aluminum nitride fibers from alumina gel fibers by nitridation in ammonia

Aluminum nitride (AlN) fibers were prepared from alumina gel fibers and by heat-treatment in ammonia. The influence of silica on the formation of AlN was investigated. It was shown that phase transformation of alumina (γ-Al2O3 to α-Al2O3) and nitridation reaction took place above 1,100 °C for pure alumina fiber. The addition of a small amount of silica (3 wt%) suppressed the formation of α-Al2O3 and preserved the highly reactive metastable alumina, and nitridation rate was enhanced. Fine grain (~20 nm) AlN fibers were obtained for pyrolysis at 1,150–1,250 °C for 3 h in ammonia, and AlN was identified as the sole crystalline phase.

Investigation of the formation of Al, Fe, N intermetallic phases during Al pack cementation followed by plasma nitriding on plain carbon steel

Plain carbon steels are not suitable for nitriding as they form an extremely brittle case that spalls off readily, and the hardness increment of the diffusion zone is small. In this research, the effect of plasma nitriding time and temperature variation on the microstructure of the pack cemented aluminized plain carbon steel is investigated. All samples were aluminized at 900°C for 2h; the aluminized samples were subsequently plasma nitrided at 500°C, 550°C and 600°C for 2.5, 5, 7.5 and 10h. The phases formed on the sample surface were detected by X-ray diffraction (XRD). The cross section and samples surface were investigated by optical and scanning electron microscopy (SEM). Microhardness test was conducted to determine hardness change from the surface to the sample core. Results showed that by aluminizing the steel, Fe3Al phases as well as Fe–Al solid solution were formed on the surface and some aluminum rich precipitates were formed in solid solution grain boundaries. Plasma nitriding of the aluminized layer caused the formation of aluminum and iron nitride (AlN, Fe4N) on the sample surface. Consequently, surface hardness was improved up to about eight times. By increasing the nitriding temperature and time, aluminum-rich precipitates dissociated. Moreover, due to the diffusion of nitrogen through aluminized region during ion nitriding, iron and aluminum nitrides were formed in aluminized grain boundaries. Increasing nitriding time and temperature lead to the growth of these nitrides in the grain boundaries of the substrate. This phenomenon results in the increment of sample hardness depth. Plasma nitriding of aluminized sample in low pressure chamber with nitrogen and hydrogen gas mixture reduced surface aluminum oxides which were formed in aluminizing stage.

Nucleation Criteria for the Formation of Aluminum Nitride in Aluminum Matrix by Nitridation

Synthesis of in situ metal matrix composites using liquid metallurgy technique involves processing the melt to generate ceramic particles and entrap them into the matrix during solidification. The process parameters such as temperature, holding time and buoyancy effect generated in the molten bath are crucial factors governing the size and distribution of ceramic particles into the matrix. Temperature being most important parameter and its role is easy to comprehend for in situ formation of ceramic particles using established nucleation criteria. In the present research paper, thermodynamic study is carried to understand the role of temperature on formation of aluminum nitride by nitridation of aluminum melt using ammonium chloride and calcium oxide. Mechanism of aluminum nitride formation by heterogeneous nucleation and its growth has also been discussed based on the nucleation theory. An attempt is also made to correlate nucleation theory for the formation of AlN in Al matrix at different temperatures. The mechanical behavior under compressive loading is carried out on synthesized composites to understand its capability to withstand static loading. Composite strength is analyzed and attempt is made to correlate nucleation dynamics of AlN particles.