• Journal of the Korean institute of surface engineering
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• v.39 no.5
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• pp.235-239
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• 2006

The aluminum nitride(AlN) layer on Al7075 substrate has been formed through nitrogen ion implantation process. The implantation process was performed under the conditions : 100 keV energy, total ion dose up to $2{\times}10^{18}\;ions/cm^2$. XRD analysis showed that aluminum nitride layers were formed by nitrogen implantation. The formation of Aluminum nitride enhanced surface hardness up to 265HK(0.02 N) from 150HK(0.02 N) for the unimplanted specimen. Micro-Knoop hardness test showed that wear resistance was improved about 2 times for nitrogen implanted specimens above $5\;{\times}\;10^{17}\;ions/cm^2$. The friction coefficient was measured by Ball-on-disc type wear tester and was decreased to 1/3 with increasing total nitrogen ion dose up to $1\;{\times}\;10^{18}ions/cm^2$. The enhancement of mechanical properties was observed to be closely associated with AlN formation. AES analysis showed that the maximum concentration of nitrogen increased as ion dose increased until $5\;{\times}\;10^{17}\;ions/cm^2$.

• Journal of the Korean institute of surface engineering
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• v.57 no.1
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• pp.49-56
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• 2024

Superhydrophobic surfaces have been expected to be able to provide considerable performance improvements and introduce innovative functions across diverse industries. However, representative methods for fabricating superhydrophobic surfaces include etching the substrate or attaching nanosized particles, but they have been limited by problems such as applicability to only a few materials or low adhesion between particles and substrates, resulting in a short lifetime of superhydrophobic properties. In this work, we report a novel coating technique that can achieve superhydrophobicity by electrophoretic deposition of aluminum nitride (AlN) nanopowders and their self-bonding to form a surface structure without the use of binder resins through a hydrolysis reaction. Furthermore, by using a water-soluble adhesive as a temporary shield for the electrophoretic deposited AlN powders, hierarchical aluminum hydroxide structures can be strongly adhered to a variety of electrically conductive substrates. This binder-free technique for creating hierarchical structures that exhibit strong adhesion to a variety of substrates significantly expands the practical applicability of superhydrophobic surfaces.

• Journal of the Korean Ceramic Society
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• v.39 no.3
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• pp.299-307
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• 2002

In this proposed study, a new emerging shape forming technique Direct Coagulation Casting(DCC) which enables to fabricate complex-shaped ceramic parts has been investigated using colloid surface chemistry. Various process variables affected by dispersant, coagulation agent and sintering additives, have been evaluated in order to achieve highly concentrated stabilized silicon nitride suspensions. A high solid loading of 51 vol% in the dispersed silicon nitride suspension was prepared with 1.0wt% Tetraethylammonium Hydroxide (TEAH), which obtained a stable silicon nitride suspension with sintering additives $(Al_2O_3\;and\;Y_2O_3)$ in alkaline regions. The addition of hydroxyaluminium diacetate into the suspension, which decomposed at elevated temperatures, led to coagulate of a silicon nitride suspension. In a basic medium, aluminum ions precipitated to aluminum hydroxide $(Al(OH)_3)$, leading to decreased $OH^-$ concentration and, thus, coagulated suspension.

• Elastomers and Composites
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• v.55 no.1
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• pp.59-66
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• 2020

Herein, we investigated the thermal conductivity and thermal stability of natural rubber composite systems containing hybrid fillers of boron nitride (BN) and aluminum nitride (AlN). In the hybrid system, the bimodal distribution of polygonal AlN and planar BN particles provided excellent filler-packing efficiency and desired energy path for phonon transfer, resulting in high thermal conductivity of 1.29 W/mK, which could not be achieved by single filler composites. Further, polyethylene glycol (PEG) was compounded with a commonly used naphthenic oil, which substantially increased thermal conductivity to 3.51 W/mK with an excellent thermal stability due to facilitated energy transfer across the filler-filler interface. The resulting PEG-incorporated hybrid composite showed a high thermal degradation temperature (T₂) of 290℃, a low coefficient of thermal expansion of 26.4 ppm/℃, and a low thermal distortion parameter of 7.53 m/K, which is well over the naphthenic oil compound. Finally, using the Fourier's law of conduction, we suggested a modeling methodology to evaluate the cooling performance in thermal management system.

• Journal of the Korean Ceramic Society
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• v.22 no.6
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• pp.80-86
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• 1985

Aluminum nitride (AlN) was synthesized from aluminum (Al) powders as a starting material in the tempe-rature range of 450~1, 15$0^{\circ}C$ in the presence of 90% $N_2$-10%$H_2$ gases. The thermogravimentric analysis showed that the nitridation of Al powders started at about 43$0^{\circ}C$ and escalated greatly from 53$0^{\circ}C$. The scanning electron microcopic observation revealed that AlN crystals were different in shape with varying temperature of nitridation. The crystals of AlN which were formed in the lower temperature than the melting point of Al were spherical while those of AlN in the higher temperature were fibrous. The yield of AlN was determined quantitatively by both XRD method and weight gain between before and after the nitridation of Al compacts. It was considered that the former was available for the specimen which was made in the high nitriding temperature. But the latter was unavilable for the same one probably because of the volatile loss of Al in the higher temperature.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1362-1368
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• 1994

The hydrolysis of aluminum nitride was increased gradually with increasing reaction time from 1 hrs to 24 hrs and/or with decreasing the addition of the reaction water from 100 mι 100mι. Amorphous aluminum hydrate, formed in the beginning of the reaction, was transformed to bayerite and to pseudoboehmite at below and above 8$0^{\circ}C$, respectively. Aluminum oxynitride was synthesized by heating the partially hydrolyzed aluminum nitride at 1$700^{\circ}C$ for 4 hrs or at 175$0^{\circ}C$ for 30 min. AlON specimen with 1 wt% of Y2O3 that was molded and then sintered pressurelessly at 190$0^{\circ}C$, exhibits 98% of the theoretical density and a translucency of 68% in the visible ray zone.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1294-1295
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• 2006

Various reactions and the in-situ formation of new phases can occur during the mechanical alloying process. In the present study, Al powders were strengthened by AlN, using the in-situ processing technique during mechanical alloying. Differential thermal analysis and X-ray diffraction studies were carried out in order to examine the formation behavior of AlN. It was found that the precursors of AlN were formed in the Al powders and transformed to AlN at temperatures above $600^{\circ}C$. The hot extrusion process was utilized to consolidate the composite powders. The microstructure of the extrusions was examined by SEM and TEM. In order to investigate the mechanical properties of the extrusions, compression tests and hardness measurements were carried out. It was found that the mechanical properties and the thermal stability of the Al/AlN composites were significantly greater than those of conventional Al matrix composites.

• Korean Journal of Materials Research
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• v.16 no.12
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• pp.771-776
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• 2006

In this study, we report a method to synthesize the aluminum nitride (AlN) powders from aluminum oxyhydroxide (AlOOH). AlOOH powders were prepared from the aluminum hydroxide ($Al(OH)_3$) by heattreatment at the reaction temperature of $350^{\circ}C$. Simple heat treatment of AlOOH in the flow of $NH_3$ gas leads to the formation of hexagonal AlN powders through intermediate conversion of ${\delta}-,\;{\gamma}-$ and ${\alpha}-Al_2O_3$. The FTIR transmission spectra show a broad peak related to Al-N bonds centered around 690 $cm^{-1}$ confirming the presence of AlN. The major peaks in Raman spectra were observed in 250 $cm^{-1}$ and 659 $cm^{-1}$. From the results, synthesized powders from the AlOOH powders were confirmed AlN powders.

• Transactions of Materials Processing
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• v.29 no.1
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• pp.44-48
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• 2020

Aluminum nitride (AlN), as a substrate material in electronic packaging, has attracted considerable attention over the last few decades because of its excellent properties, which include high thermal conductivity, a coefficient of thermal expansion that matches well with that of silicon, and a moderately low dielectric constant. AlN films with c-axis orientation and thermal conductivity characteristics were deposited by using Pulsed Laser Deposition (PLD). The epitaxial AlN films were grown on sapphire (c-Al₂O₃) single crystals by PLD with AlN target and Y₂O₃ doped AlN target. A comparison of different targets associated with AlN films deposited by PLD was presented with particular emphasis on thermal conductivity properties. The quality of AlN films was found to strongly depend on the growth temperature that was exerted during deposition. AlN thin films deposited using Y₂O₃-AlN targets doped with sintering additives showed relatively higher thermal conductivity than while using pure AlN targets. AlN thin films deposited at 600℃ were confirmed to have highly c-axis orientation and thermal conductivity of 39.413 W/mK.

• Journal of the Korean Ceramic Society
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• v.51 no.3
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• pp.201-207
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• 2014

High-purity aluminum nitride nanopowders were synthesized using an RF induction thermal plasma instrument. Ammonia and nitrogen gases were used as sheath gas to control the reactor atmosphere. Synthesized AlN nanopowders were characterized by XRD, SEM, TEM, EDS, BET, FTIR, and N-O analyses. It was possible to synthesize high-purity AlN nanoparticles through control of the ammonia gas flow rate. However, additional process parameters such as plasma power and reactor pressure had to be controlled for the production of high-purity AlN nanopowders using nitrogen gas.