Amount Of AlN Research Articles

Thermal Properties of Copper Matrix-Ceramic Filler Composite Prepared by Polymer Solution Method

A copper (Cu) metal-ceramic filler composite with high thermal conductivity and a suitable thermal expansion coefficient was designed for application as a high-performance heat dissipation material. The purpose of the designed material was to utilize the high thermal conductivity of Cu while lowering its high coefficient of thermal expansion by using a ceramic filler. In this study, a Cu-sol containing a certain amount of AlN or SiC ceramic filler was prepared using a non-aqueous solvent. A complex was produced by applying a PVB polymer to prepare a homogeneous precursor. The composite sintered without pressure in a reducing atmosphere showed low thermal conductivity due to residual pores, but the hot press sintered composite exhibited improved thermal conductivity. The Cu composite with 30 wt% AlN filler added exhibited a thermal conductivity of 290 W/m·K and a thermal expansion coefficient of 9.2 × 10-6/oC. Due to the pores in the composite, the thermal conductivity showed some difference from the theoretical value calculated from the rule of mixture. However, the thermal expansion coefficient did not show any significant difference.

Effects of Variation in Al Content on the Emission of Eu Doped CaAlSiN3 Red Phosphor Synthesized by Combustion Synthesis Method for White LEDs.

Effects of Al content on the formation and the photoluminescence properties of CaAlSiN3:Eu2+ phosphor (CASIN) were investigated by a combustion synthesis method. XRD (X-ray diffraction), combined with PL (photoluminescence), TEM-EDS (transmission electron microscope equipped with an energy-dispersive X-ray spectroscope), and SAED (selected area electron diffraction) measurements, show that the bar-like CASIN gives a stronger emission than the plate-like and agglomerated fine particles. The emission intensity increases as the Al content increased from Al = 0.2 to Al = 0.8, which resulted from the extent of formation of CASIN increases. Then, the emission intensity decreases as the Al content is increased from Al = 0.8 to Al = 1.5, which resulted from the transformation of morphology of CASIN and a large amount formation of AlN. In addition, the extent of formation of CASIN increases with increasing Al from Al = 0.2 to Al = 1.2 and begins to decrease as Al is further increased to 1.5, and thus the peak emission wavelength increases from 647 nm to 658 nm as the Al molar ratio is increased from 0.2 to 1.2 and begins to decrease when further increasing the Al molar ratio to 1.5, which resulted from the large amount of AlN formed.

In-situ formation of TiN during the hot-pressing of TiC–AlN ceramics

In this investigation, various amounts of AlN (0, 3.5, and 7 vol%) were added to TiC, and the resulted ceramics were studied in terms of microstructures and mechanical properties. The hot-pressing technique was employed as the sintering process at 2000 °C for 2 h under 35 MPa. Though a relative density of ~ 97% was obtained for the AlN free sample, the composite introduced by 7 vol% AlN reached its full density. The precipitation of carbon from the TiC matrix was proved by both X-ray diffractometry and microstructural observations. The deposited graphite contributed to removing the TiO2 surface impurity over sintering. Moreover, TiO2 reacted with AlN additive, generating in-situ TiN. Such a phase mainly dissolved into the AlN phase, leading to the formation of (Al,Ti)N solid solution. The highest Vickers hardness of 2745 HV0.5kg was attained for the monolithic ceramic, thanks to the lack of AlN as a softer phase. Finally, incorporating 7 vol% AlN increased the flexural strength of TiC by almost 33% as a result of porosity removal and fine-grain, standing at 790 MPa.

Electron microscopy characterization of porous ZrB2–SiC–AlN composites prepared by pressureless sintering

This study explores the impact of AlN on the propagation of residual porosity and microstructure of porous ZrB2–SiC-based composites. Several ZrB2–SiC composites were fabricated with various amount of AlN by pressureless sintering method at 1900 °C. The specimens were kept at the maximum temperature for 120 min. Although the AlN-free composite possessed ~13% porosity, the incorporation of AlN to the ZrB2–SiC composites elevated this value for approximately twofold. The prepared porous samples were precisely characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM). XRD analysis revealed the presence of ZrB2, SiC, and C peaks in the pattern of the sample containing 5 wt% AlN. However, no Al compound could be detected therein. The thermodynamic study suggested the formation of a liquid phase comprising the SiO2–B2O3 with Al-based ingredients for the ZrB2–SiC–AlN composites. FESEM fractographs showed that the intergranular fracture was predominant in the specimens. Furthermore, the high resolution TEM images confirmed the progress of the liquid phase sintering, resulted in the formation of clean interfaces.

Effect of Annealing Cycle on Drawability and Microstructure of Cold Rolled Steel Sheet

The effect of the annealing cycle on microstructure, mechanical properties and draw ability of aluminium killed steel sheets at three different heating rates and holding times were investigated. Tensile test, hardness test, optical microscope and transmission electron microscope (TEM) techniques were utilized. The results of samples for different times in laboratory experiments were compared with the production samples. The results for these experiments showed that lower heating rates (12 °C/h) occurred at a lower annealing temperature, increase draw ability. This effect is attributable to the longer time available to initiate nucleation at the lowest heating rate. However, for all three heating rates (12 °C/h, 24 °C/h and 36 °C/h), the aluminium and nitrogen combine to form atmospheres or pre-precipitation clusters at polygonised sub-grains and as rolled boundaries, modifying the development of the recrystallized structure. Different amounts of AlN were precipitated prior to recrystallization for each heating rate resulting in different final recrystallized grain sizes, mechanical properties and drawabilities. The heating rate strongly influences recrystallization and drawability with a lower heating rate reducing both the temperature of the start of recrystallization and the recrystallized grain size. It is inferred that the lower rate promotes nucleation of recrystallization overgrowth of recrystallized. The effect of holding time on mechanical properties was to: (i) decrease tensile strength, yield strength and hardness and (ii) increase drawability, elongation and grain size. Tensile strength and hardness results from laboratory experiments were lower than those for production samples, but the trends were similar.

Electrolytic corrosion of materials of TiCrB2–AlN system in 3% NaCl solution

The corrosion resistance of titanium-chromium-diboride-based ceramic materials and cermets in 3% NaCl solution (to simulate sea water) is studied by the method of potentiodynamic polarization curves. The composition and microstructure of oxidized specimen surfaces are examined. Adding small amounts of AlN (5 to 10 vol %) to TiCrB2 provides an essential improvement of the corrosion resistance. Introduction of an NiAlCr metallic binder into the material composition results in a lower resistance to anodic oxidation.

Improvement of SrAl<sub>2</sub>O<sub>4</sub>:Eu<sup>2+</sup>, Dy<sup>3+ </sup>Phosphor via AlN Incorporation

SrAl2O4:Eu2+,Dy3+ long-lasting phosphors were incorporated AlN successfully by a conventional solid-state reaction in the reductive atmosphere. When a certain amount of AlN was doped, the specimen SrAl2O4-3xN2x: Eu2+, 0.01Dy3+ (x = 0.0-0.2) maintained the phase purity. Under the excitation at 398nm, an intense broadband emission centered at 514 nm, originating from the 4f65d1→4f7 transition of Eu2+, was observed. It is noteworthy that partial nitridation leads to an enhancement in the emission intensity up to 240%. The study of thermal stability shows that the intensity of SrAl2O3.55N0.3:Eu2+,0.01Dy3+ phosphor still remains 72% at 150 °C comparing with the initial, while only 62% for the un-doped phosphor. Taking enhanced photoluminescence (PL) property and good thermal stability into account, SrAl2O4-3xN2x:Eu2+, 0.01Dy3+ is a promising candidate for the phosphors used in alternating current (AC) LEDs.

Nanocrystalline Al Composites from Powder Milled under Ammonia Gas Flow

The production of high hardness and thermally stable nanocrystalline aluminium composites is described. Al powder was milled at room temperature in an ammonia flow for a period of less than 5 h. NH3dissociation during milling provokes the absorption, at a high rate, of nitrogen into aluminium, hardening it by forming a solid solution. Controlled amounts of AlN and Al5O6N are formed during the subsequent sintering of milled powders for consolidation. The pinning action of these abundant dispersoids highly restrains aluminium grain growth during heating. The mean size of the Al grains remains below 45 nm and even after the milled powder is sintered at 650°C for 1 h.

Electrophoretic Deposition of Aluminum Nitride from Its Suspension in Acetylacetone Using Iodine as an Additive

We have studied electrophoretic deposition of AlN from its suspension in acetylacetone with I2 as an additive. AlN powder with particle size <10 μm is dispersed to produce a positive charge and deposited on the cathode by applying fields greater than 10 V/cm between the electrodes. X‐ray diffraction and FTIR studies indicate that the AlN before and after deposition has the same composition and structure. An increase in the amount of AlN in the suspension, the deposition potential, and the deposition time results in a linear increase in the weight of the AlN deposited. Electrophoretic deposition from 10 g/L AlN suspension shows an initial increase in the weight of AlN deposited with the concentration of I2, and the weight of AlN decreases after reaching a maximum at 0.20 g/L I2.

Order Effect of Vacuum and Ammonia Atmospheres on Aluminium Nitriding by Mechanical Alloying

Aluminium powder was milled under vacuum and/or ammonia atmospheres, in order to evaluate the effect of the order of the atmospheres on the amount of nitrides appearing in the powder after a subsequent heat treatment. All milling experiences were carried out at room temperature for 5 h. The XRD study of sintered powders showed that important amounts of AlN appeared after heating. The use of vacuum and ammonia flow allows controlling the percentage of N rich phases formed. Moreover, the capacity of incorporating nitrogen to the aluminium lattice is very influenced by the vacuum and ammonia flow atmospheres order during the milling process.

Microstructure and Phases of As-Cast and Heat-Treated Al-Si-Mg/AlN Composites Prepared by Stir Casting

Al-Si-Mg/AlN composites were prepared by stir casting technique. The amount of AlN added to Al-Si-Mg alloy was from 2 to 10 wt%. As-cast composites were solutionised at 540 °C for 4 h, quenched in warm water, 60 °C then artificially aged at 180 °C for 4 h. The microstructure of Al-Si-Mg matrix alloy contained dendritic α-Al, needle-like Si and very little inter-metallic compounds. As-cast Al-Si-Mg/AlN composites have rounded α-Al phase and needle-like Si where AlN particles dispersed surrounding α-Al. Needle-like Si transformed to spheroid after artificial aging. The size of α-Al phases of heat-treated composites containing 2 and 5 wt% AlN was bigger than that of as-cast composites whereas the heat-treated Al-Si-Mg/10% AlN composite has thin and elongated dendritic α-Al phases, and larger AlN particles.

Formation of AlN on sapphire surfaces by high-temperature heating in a mixed flow of H2 and N2

Heat treatment of (0001) sapphire substrates in the temperature range 980–1480°C was investigated in an atmospheric-pressure mixed flow of H2 and N2 for various molar fractions of H2 (F°=H2/(H2+N2)). At 1330°C, AlN whiskers formed on the sapphire surfaces only when the heat treatment was performed in the presence of both H2 and N2 (0<F°<1). The amount of AlN that formed was a maximum for F°=0.750, whereas no AlN was formed at F°=0 (N2 flow) or 1.000 (H2 flow). When F°=0.750, AlN whiskers formed in the temperature range 1030–1430°C, whereas no AlN was formed outside this temperature range. These experimental results are explained in terms of thermodynamic analysis.

Effect of AlN on Microstructure and Mechanical Properties of Mg-Al-Zn Alloy

Effects of AlN addition on the microstructure and mechanical properties of as-cast Mg-Al-Zn magnesium alloy were investigated using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and tensile testing. Five different samples were made with different amounts of AlN(0wt%, 0.12wt%, 0.30wt%, 0.48wt%, 0. 60wt%). The results show that the phases of as-cast alloy are composed of α-Mg,β-Mg17Al12. The addition of AlN suppressed the precipitation of the β-phase. And, with the increase of AlN content, the microstructure of β-phase was changed from the reticulum to fine grains. When AlN content was up to 0.48wt% in the alloy, the β-phase became most uniform distribution. After adding 0.3wt% AlN to Al-Mg-Zn alloy, the average alloy grain size reduced from 102μm to 35μm ,the tensile strength of alloy was the highest. The average tensile strength increased from 139MPa to 169.91MPa, the hardness increased from 77.7HB to 98.4HB, but the elongation changes indistinctively. However, when more amount of AlN was added, the average alloy grain size did not reduce sequentially and increased to 50μm by adding 0.6wt% AlN and the β-phase became a little more. Keywords: Al-Mg-Zn alloy; AlN; β-Mg17Al12; Tensile strength

The effect of AlN and flux addition on luminescence properties of Ce doped TAG phosphor for white light emitting diodes

Abstract A series of Ce 3+ -activated Tb 3 Al 5 O 12 green-yellow phosphors were synthesized using solid state reaction method. The X-ray diffraction peaks of the synthesized phosphor were well matched to the Tb 3 Al 5 O 12 reference peak data. As the addition amount of AlN increase, the relative intensity of diffraction peak increase. But, the addition amount of AlN is over 0.3 mol, the second phase TbAlO 3 diffraction peaks increase. When the addition amount of AlN is 0.3 mol, PL shows the highest emission efficiency. These results were explained by the reducing atmosphere made using AlN. The highest emission intensity was observed when the Ce 3+ concentration is 0.25 mol. The emission intensity of the Tb 2.75 Al 5 O 12 :Ce 0.25 3+ phosphors were increased by adding BaF 2 and KNO 3 as a flux. The yellow emitting Tb 3 Al 5 O 12 :Ce 3+ phosphors obtained could be applied as white LEDs.

The quenching effects of hot band annealing on grain-oriented electrical steel

The grain-oriented electrical steels are widely used in transformers, which demand low iron loss and high induction of core materials. In order to obtain good magnetic properties, a series of rolling, annealing and coating processes are carried out. Hot band annealing, which influences the ductility for cold rolling and the development of AlN inhibitors, is one of the most important processes. This study investigated the phases and different kinds of precipitations in microstructures of annealed hot band by means of the optical and electronic microscopies. On the other hand, a Themo-Calc software and the solubility product equations of AlN are used to calculate the phase diagram of Fe–Si–C alloy and the amount of AlN at high temperature. Microstructures including ferrite, cementite, pearlite and martensite were observed. The size and shape of precipitates, i.e. GP Zone, TiN, AlN, MnS, oxide and carbide, were identified. The relationship between the amount of nano-scale AlN and magnetic properties indicated that the suitable cooling method resulted in lower iron loss and higher magnetic induction. The result could help to realize the following microstructure evolution and mechanism of inhibitors in grain-oriented electrical steel.

Chemical In Situ Synthesis of Aluminum Alloy Composites

Aluminum alloys were reinforced with AlN particles using a novel chemical in situ technique. Thermodynamic analyses were made to identify the conditions for the in situ formation of the AlN in Al alloys. Experiments were conducted in the temperature range of 1173-1473 K by injecting ammonia gas. The composites with AlN quantity varying from 5 to 51 wt % were produced. Effect of process variables such as gas injection time, flow rate of ammonia gas and temperature of the alloy melt on the formation of AlN was studied. Increase in either injection time or flow rate of the ammonia gas increased the nitride content. AlN particles with an average size of 500 nm were produced. The measured Vickers hardness of the composites formed increased with increasing AlN content. The amount of AlN experimentally formed is in good agreement with the thermodynamically predicted data.

Fabrication of AlN-TiC/Al composites by gas injection processing

The fabrication of AIN-TiC/Al composites by carbon- and nitrogen-containing gas injection into Al-Mg-Ti melts was studied. It was shown that AlN and TiC particles could be formed by the in situ reaction of mixture gas (N 2 + C 2H 2 + NH 3) with Al-Mg-Ti melts. The condition for the formation of AlN was that the treatment temperature must be higher than 1373 K, and the amounts of AlN and TiC increased with the increase of the treatment temperature and the gas injection time. It was considered that AlN was formed by the direct reaction of Al with nitrogen-containing gas at the interface of the gas bubble and the melt. However, the mechanism of TiC formation is a combination mechanism of solution-precipitation and solid-liquid reaction.

Electrical Properties of AlN-SiC Ceramics

AlN-SiC ceramics with 0 to 75 mol% of AlN were fabricated through pressureless sintering of very fine AlN and SiC. Powder compacts with different amounts of AlN were fired at 2000°C for 1 h in Argon gas flow using an induction-heating furnace. The microstructure and phases present in the products were evaluated using SEM and XRD. The AlN-SiC ceramics had a porous structure with 30% porosity, and the grain size was increased with the addition of AlN. XRD analysis showed that 2H was a main phase in all samples, though 3C and 6H phases were found in 25 mol%AlN-75 mol%SiC ceramic. The electrical properties of the AlN-SiC ceramics were evaluated at various temperatures ranging from room temperature to 300°C. The electrical conductivity of the AlN-SiC ceramics depended on the amount of AlN and on the temperature. The 75 mol%AlN-SiC ceramic had higher electrical resistance, though the other samples were electrical conductors. The highest electrical conductivity was obtained with the 25 mol% AlN composition, which was 7 S/m at room temperature and 30 S/m at 300°C. The Seebeck coefficient for the AlN-SiC ceramics increased with rising temperatures. The AlN-SiC ceramics with 50 mol%AlN had the highest Seebeck coefficient of 220 2V/K at 300°C.

Nanostructured Ni–AlN composite coatings

Electrodeposited Ni composite coatings embedded with AlN particles were deposited on mild steel substrates. AlN whiskers of 40–150 nm size were successfully prepared by nitriding method. Coatings were produced from Ni Watt's bath and the optimum conditions of plating process were determined. The wear resistance and friction coefficients of Ni–AlN composite coatings containing various amounts of AlN have been studied. The corrosion rates of composite coatings were measured in 1 M HCl solution. Surface morphology of the coatings was analyzed by using a scanning electron microscope (SEM). Thermal stability of the pure Ni and composite coatings were studied at 900–1100 °C. The thermal expansion coefficients of the coatings were investigated in the temperature range of 100–650 °C. The results referred that increasing the incorporation rate of AlN particles leads to an increase in both of the hardness and friction coefficients of the films. The composite coatings containing 41 wt.% of AlN exhibited high resistance against wear and corrosion. The addition of low expansion AlN particles restricted the expansion of matrix through interfaces.

Mechanical and Wear Properties of Silicon Nitride Added with AlN

Silicon nitride with various amount of AlN as a sintering aid was sintered by a hot press method. Densified silicon nitrides were obtained, and it was found that the mechanical and wear properties were dependent on the contents of AlN. The effect of a/b phase on the mechanical and wear properties of silicon nitride was investigated. The properties were changed depending on the amount of a/b phase. In the brittle materials, tribological behaviors were dependent on the microstructure as well as hardness and fracture toughness. We focus on the relationship between the microstructure and mechanical/wear properties of silicon nitride including AlN additives.