• 한국전기전자재료학회논문지
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• 제21권5호
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• pp.463-467
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• 2008

Aluminum nitride (AlN) thin films have been deposited on Au electrodes by using reactive RF magnetron sputtering method in a gas mixture of Ar and $N_2$ at different substrate temperature. It was found that substrate temperature was varied in the range up to $400^{\circ}C$, highly c-axis oriented film can be obtained at $300^{\circ}C$ with full width at half maximum (FWHM) $3.1^{\circ}$. Increase in surface roughness from 3.8 nm to 5.9 nm found to be associated with increase in grain size, with substrate temperature; however, the AlN film fabricated at $400^{\circ}C$ exhibited a granular type of structure with non-uniform grains. The Al 2p and N 1s peak in the X-ray photoelectron spectroscopy (XPS) spectrum confirmed the formation of Al-N bonds. The XPS spectrum also indicated the presence of oxynitrides and oxides, resulting from the presence of residual oxygen in the vacuum chamber. It is concluded that the AlN film deposited at substrate temperature of $300^{\circ}C$ exhibited the most desirable properties for the application of high-frequency surface acoustic devices.

• 한국세라믹학회지
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• 제40권8호
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• pp.720-724
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• 2003

Aluminum nitride (AlN) powders were synthesized by using a mixture of an aluminum nitrate or sulfate salt and carbon (mole ratio of $Al^{3+}$ to carbon=L : 30). The AlN was obtained by calcining the mixture under a flow of nitrogen in the temperature range 1100-1$600^{\circ}C$ and then burning out the residual carbon. The process of conversion of the salt to AlN was monitored by XRD and $^{27}$ Al magic-angle spinning (MAS) NMR spectroscopy. The salt decomposed to ${\gamma}$-alumina and then converted to AlN without phase transition from ${\gamma}$-to-$\alpha$-alumina. $^{27}$ Al MAS NMR spectroscopy shows that the formation of AlN commenced at 110$0^{\circ}C$. AlN powders obtained from the sulfate salt were superior to those from the nitrate salt in terms of homogeneity and crystallinity. A very small amount of AlN whiskers was obtained by calcining a mixture of an aluminum sulfate salt and carbon at 115$0^{\circ}C$ for 40 h, and the growth of the whiskers is well explained by the particle-to-particle self-assembly mechanism.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.298-303
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• 2000

Principles of residual stress measurements by neutron diffraction and the residual stress instrument installed at 30MWt HANARO reactor in KAERI are considered. In-depth residual stress distribution was measured in aluminum VAMAS round robin sample and welded stainless steel plate, which showed high ability of the instrument for the stress measurements in components.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 1998년도 추계학술발표회 초록집
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• pp.75-76
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• 1998

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 1999년도 Pre-symposium of the 10th ISWPC Recent Advances in Paper Science and Technology
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• pp.239-244
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• 1999

aluminum sulfate (alum) as a representative retention aid in papermaking processes was added to pulp suspensions, and the aluminum components adsorbed on the pulp were investigated quantitatively by two types of X-ray elementary analyses with regard to simultaneous changes of their surface charges. X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence analysis (XFA) were applied to determine the aluminum components retained in pulp pads up to ca. 10 nm and 100${\mu}$m depth, respectively. In other words, XPS was utilized to analyze the outermost surface layers of the samples, and XFA was available for measurement of their extensive regions. A particle charge detector (PCD) was used to monitor streaming potentials at various pHs of the pulp mixtures under moderate sharing conditions. At pH 4.5 of pulp suspensions containing alum, surface charges of pulp fibers varied from negative to slight negative (approximately neutral) according to adsorption of aluminum components onto the pulp fibers. Subsequently, when a dilute NaOH solution in limited amounts was added to pulp mixtures, both streaming potentials and surface aluminum content of the pulp fibers increased distinctly although little total aluminum retention increased. Further addition of alkali solutions brought drastic decreases of the surface charges and surface aluminum content, while total aluminum content, on the contrary, increased gradually under neutral conditions. These results indicate that residual aluminum ions remained in pulp suspensions are predominantly adsorbed on surfaces of pulp fibers by adequate alkali additions and they must sufficiently cationize the fiber surfaces with increases of somewhat cationic aluminum complexes formed on the surfaces. On the other hand, aluminum components formed in higher pH ranges have nearly no contribution to improvement of charge properties of the pulp fiber surfaces, even though aluminum retention in pulp pads increases. XPS and XFA analyses combined with streaming potential measurement using a PCD suggest close relationships between aluminum content on the pulp fiber surfaces and their charge properties.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1998년도 학술발표대회 논문집 제17권 2호
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• pp.259-262
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• 1998

In this paper, we have studied measurement technique for inhomogeneous residual stress using acoustic microscopy with quadrature detector. In experiment, aluminum tensile specimen with the flaw has been made and loaded by Instrone. A spherical typed acoustic transducer of center frequency 5MHz has been used for sending a longitudinal acoustic wave into a stressed specimen. It has been shown in experimental results that the phase has largely changed around the flaw that residual stress has been largely distributed and acoustic microscopy has been used in the field of residual stress measurement.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.183-186
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• 2003

Long shafts for power transmission should transmit torsional load with vibrational stability. Hybrid shafts made of unidirectional fiber-reinforced composite and metal have high fundamental bending natural frequency as well as high torque transmission capability. However, thermal residual stresses due to the coefficient difference of thermal expansion of the composite and metal are developed so that the high residual stresses decrease fatigue resistance of the hybrid shafts, especially at low operating temperatures. In this work, axial compressive preload was given to the shaft in order to change the residual stresses. Static and fatigue torsional tests were performed and correlated with stress analyses with respect to the preload and service temperature.

• 한국생산제조학회지
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• 제5권3호
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• pp.31-39
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• 1996

The objective of this study is to investigate the influence of welding residual stresses on the fatigue crack growth behavior of cracks located transverse to the weld bead. For this purpose, G. T. A (Gas Tungsten Arc) welding was performed on hte Al alloy 1100-O plate and the same initial crack is made on HAZ(Heat Affected Zone), weld metal and base meta respectively. Specimens were used CT(Compact Tension) specimens. Initial welding residual stresses were measured by using strai gage sectioning method. All specimens were tested under constant amplitude load with stress ratio R=0.1, It is possible to predict fatigue crack growth behaviors and the fatigue life, using numerical analysis together with distribution of initial residual stress and the values of C and m obtained from $da/dN-{\Delta}K$

• 열처리공학회지
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• 제18권3호
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• pp.157-163
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• 2005

Effects of refinement of primary Si and residual stress on the mechanical properties of Aluminum B.390 alloy have been examined. Calcium was found to have an effect on the size of primary silicon particles. Primary silicon particle was refined as Ca content decreased. Refinement of primary Si particles led to an improvement in mechanical properties of the alloy; increase of elongation was prominent, above all. By the increase of compressive residual stress in the matrix alloy, tensile strength increased but elongation decreased.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.177-182
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• 1996

The objective of this thesis is to investigate the influence of welding residual stresses on the fatigue growth behavior of welding residual stresses on the fatigue growth behavior of cracks located transverse to the weld bead. For this purpose, G.T.A. (Gas Tungsten Arc) welding was performed on the Al. Alloy 1100-0 plate and the same initial crack is made on HAZ(Heat Affected Zone), weld metal and base metal respectively. C.T.(Compact Tension) specimens were used as experimental material. Initial welding residual stresses were measured by using strain gage sectioning method. All specimens were tested under constant amplitude load with stress ratio R=0.1