• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2014.11a
• /
• pp.215-215
• /
• 2014

Composites layer of Al-Cr-Ni-O system was prepared on a steel plate by hydro-thermal process at $700^{\circ}C$ for 12 hours, which phase identification and thermal conductivity were determined. The composites layer consisted of aluminum nitride, alumina, chromium carbide and aluminium, which density was $3.7kg/m^3$. The thermal conductivity of the coating layer determined by thermal data acquisition system was about 98.0 W/m/ which depended on the AlN content. Numerical modelling of the heat transfer behavior of the coating layer was well agreement with the empirical data.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.7 no.2
• /
• pp.250-254
• /
• 2003

A film bulk acoustic resonator (FBAR) device for 2 GHz radio frequency (RF) bandpass filter application is presented. This FBAR device consists of an aluminum nitride (AlN) film sandwiched between top(Al) and bottom(Au) electrodes and an acoustic multilayer reflector of a silicon dioxide/tungsten (SiO2/W). The A/N film deposited using a RF sputtering was observed to have small columnar grains with a strongly preferred orientation towards c axis. In addition to a high quality factor (4300), a large return loss of 37.19 dB was obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.273-273
• /
• 2008

This paper describes the frequency response of two-port surface acoustic wave (SAW) resonator made of 002-polycrystalline aluminum nitride (AlN) thin film on 111-poly 3C-SiC buffer layer. In there, Polycrystalline AlN thin films were deposited on polycrystalline 3C-SiC buffer layer by pulsed reactive magnetron sputtering system, the polycrystalline 3C-SiC was grown on $SiO_2$/Si sample by CVD. The obtained results such as the temperature coefficient of frequency (TCF) of the device is about from 15.9 to 18.5 ppm/$^{\circ}C$, the change in resonance frequency is approximately linear (30-$150^{\circ}C$), which resonance frequency of AlN/3C-SiC structure has high temperature stability. The characteristics of AlN thin films grown on 3C-SiC buffer layer are also evaluated by using the XRD, and AFM images.

• Journal of the Korean institute of surface engineering
• /
• v.54 no.3
• /
• pp.139-143
• /
• 2021

Cr-Al-N coatings were deposited onto WC-Co substrates using a cathodic arc evaporation (CAE) system. CAE technique is recognized to be a very useful process for hard coatings because it has many advantages such as high packing density and good adhesion to metallic substrates. In this study, the influence of deposition temperature as a key process parameter on film growth behavior and mechanical properties of Cr-Al-N coatings were systematically investigated and correlated with microstructural changes. From various analyses, the Cr-Al-N coatings prepared at deposition temperature of 450℃ in the CAE process showed excellent mechanical properties with higher deposition rate. The Cr-Al-N coatings with deposition temperature around 450℃ exhibited the highest hardness of about 35 GPa and elastic modulus of 442 GPa. The resistance to elastic strain to failure (H/E ratio) and the index of plastic deformation (H³/E² ratio) were also good values of 0.079 and 0.221 GPa, respectively, at the deposition temperature of 450℃. Based on the XRD, SEM and TEM analyses, the Cr-Al-N coatings exhibited a dense columnar structure with f.c.c. (Cr,Al)N multi-oriented phases in which crystallites showed irregular shapes (50~100nm in size) with many edge dislocations and lattice mismatches.

• Korean Journal of Materials Research
• /
• v.31 no.12
• /
• pp.697-703
• /
• 2021

Aluminum nitride having a dense hexagonal structure is used as a high-temperature material because of its excellent heat resistance and high mechanical strength; its excellent piezoelectric properties are also attracting attention. The structure and residual stress of AlN thin films formed on glass substrate using TFT sputtering system are examined by XRD. The deposition conditions are nitrogen gas pressures of 1 × 10^-2, 6 × 10^-3, and 3 × 10^-3, substrate temperature of 523 K, and sputtering time of 120 min. The structure of the AlN thin film is columnar, having a c-axis, i.e., a <00·1> orientation, which is the normal direction of the glass substrate. An X-ray stress measurement method for crystalline thin films with orientation properties such as columnar structure is proposed and applied to the residual stress measurement of AlN thin films with orientation <00·1>. Strength of diffraction lines other than 00·2 diffraction is very weak. As a result of stress measurement using AlN powder sample as a comparative standard sample, tensile residual stress is obtained when the nitrogen gas pressure is low, but the gas pressure increases as the residual stress is shifts toward compression. At low gas pressure, the unit cell expands due to the incorporation of excess nitrogen atoms.

• Journal of the Korean Ceramic Society
• /
• v.46 no.5
• /
• pp.467-471
• /
• 2009

Effects of boron and carbon on the densification and thermal decomposition of an AlN-SiC-$TiB_2$ system were investigated. $SiO_2$ was mostly removed by the addition of carbon, while $Al_2O_3$ formed $Al_4O_4C$ and promoted the densification of the systems above $1850^{\circ}C$. Rather porous specimens were obtained without the additives after hot pressing at $2100^{\circ}C$, while densification was mostly completed at $2000^{\circ}C$ by using the additives. The sintering temperature decreased further to $1950^{\circ}C$ by applying spark plasma sintering. The additives promoted the shrinkage of AlN by forming a liquid phase which was originated from the carbo- and boro-thermal reduction of $Al_2O_3$ and AlN.

• Journal of the Korean Ceramic Society
• /
• v.53 no.6
• /
• pp.635-640
• /
• 2016

Electrical behavior of AlN ceramics sintered with $Y_2O_3$ as a sintering aid has been investigated with respect to additional $TiO_2$ dopant. From the impedance spectroscopy, it was found that the grain and grain boundary conductivities have greatly decreased with addition of $TiO_2$ dopant. The $TiO_2$ dopant also increased the activation energy of the grain conductivity by about 0.37 eV; this increase was attributed to the formation of an associate between Al vacancies and Ti ions at the Al sites. Similarly, the electronic conductivity was reduced by $TiO_2$ addition. However, $TiO_2$ solubility in AlN grains was below the detection limit of typical EDX analysis. Grain boundary was clean, without liquid films, but did show yttrium segregation. The transference number of ions was close to 1, showing that AlN is a predominantly ionic conductor. Based on the observed results, the implications of using AlN applications as insulators have been discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.111-111
• /
• 2009

In this work, we discuss simulation of surface acoustic wave device using Comsol Multiphysics. The structure SAW device based on piezoelectric thin film aluminum-nitride (AlN) on silicon was simulated. Some parameters of SAW device such as surface velocity, displacement of piezoelectric thin film were evaluated by software. Many modes and shapes of wave are also discussed in this paper. For evaluation physical parameters of AlN piezoelectric layer, the SAW resonator was modeled and simulation results were also compared with experiment results. we simulated arid evaluated the surface Rayleigh wave of AlN thin film on silicon substrate. Results simulation and experiment showed the surface velocity of AlN thin film was about 5200 m/s and shape of surface wave was also displayed. This paper has also proposed as method to study SAW characteristic of piezoelectric thin film and found out measurement values accurately of film such as stiffness matrix, piezoelectric matrix. These values are very important in calculation and design SAW device or MEMS device based on AlN piezoelectric layer.

• Journal of the Korean Society for Heat Treatment
• /
• v.12 no.3
• /
• pp.221-230
• /
• 1999

The surface nitrogen permeation of Al alloyed 0.14%C-13%Cr stainless steels was investigated after heat treating at $1050^{\circ}C{\sim}1150^{\circ}C$ in the nitrogen gas atmosphere. The strong affinity between Al and nitrogen permeates the nitrogen through the interior of the steels. Two precipitates of round type and needle type are observed at the surface layer. These precipitates mainly consist of AlN containing plenty of aluminum. The surface layer of 0.53%Al alloyed specimen shows ferrite phase, while the surface layers of 1.65%Al and 2.27%Al alloyed specimens appear ${\gamma}$ plus ${\alpha}$ phases. The depth of nitrogen permeation depends upon the Al content and microstructure of the matrix. The 1.65%Al alloyed specimen representing ${\alpha}+{\gamma}$ matrix phases at the nitrogen permeation temperature shows the maximum case depth in this experiment. Although the surface hardness increases by raising the Al content of the specimen owing to the increase of nitride precipitation density, the nitride precipitation deteriorates the corrosion resistance in the solution of HCl, $H_2SO_4$, and $FeCl_3$.

• Transactions of Materials Processing
• /
• v.25 no.5
• /
• pp.313-318
• /
• 2016

The plasma vapor coatings on two kinds of die steels have been carried out in order to identify the most optimized conditions. When TiN or TiAlN coatings were carried out on the substrates, the coating layer thicknesses were not significantly changed, and the optimized coating thickness was identified as ~ 5 μm. When the optimized coating conditions and stress analysis were applied to the primary piston dies for fabrication of aluminum cylinders, an extended life time of the die was observed. The methodology for extending the life time of dies was discussed in terms of microstructures and stress analysis.