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도재 냉각방법의 차이가 금속-도재간 열팽창 양상과 결합력에 미치는 영향
임애란,임호남,박남수,Lim, Ae-Ran,Lim, Ho-Nam,Park, Nam-Soo 대한치과보철학회 1991 대한치과보철학회지 Vol.29 No.1
Although a number of studies have been performed to assure that residual stress caused by a mismatch of alloy porcelain thermal expansion can contribute to clinical failure of a ceramometal restoratoin, the interactive influence of cooling rate on the magnitude of thermal expansion difference and on bond strength between them have not been extensively analyzed. The objective of this study was to determine the influence of cooling rate and the number of firing cycles on the expansion mismatch and the flexural failure resistance of metal porcelain strip. Tested alloys included one Pd-Ag alloy, one Ni-Cr-Be alloy with two kinds of porcelain, Vita and Ceramco. Metal specimens were cast into rods with a height of 13mm and a diameter of 5mm. Subsequently, the castings were subjected to scheduled firing cycles without porcelain. And the porcelain specimens after being fired were trimmed into a bar with a final dimension of 5 x 5 x 25mm. Thermal expansions of the alloys and porcelains were measured by using a push rod or a differential dialometer respectively. Porcelain glass transition temperatures and expansion values were derived alloy- porcelain pairs were assessed by comparing expansion values of the components at a porcelain glass transition temperature. Calculations were made using combinations of a Ni-Cr alloy or Pd-Ag alloy with each of two porcelain products. Metal- porcelain strip specimens were subjected to four point loading in an Instron testing machine until crack occured at the metal-cramic interface at the time of sharp decrease of load on recorder. On the basis of this study, the following conclusions may be stated : 1. Regardless of the kinds of ceramometal combinations, both of calculated and experimental data revealed that the double fired specimens exhibited a significantly lower flexural strength. 2. By the rise of the amount of mismatch, bond strength were decreased. 3. Thermal expansion value of Pd-Ag alloys were higher than of Ni-Cr alloys. 4. Expansion curves of metal were proportional to the increase of temperature and were not affected by the experimental conditions, however porcelains did not show the same magnitude of metal, and a shift of the glass transition temperature to higher temperatures was observed when cooled rapidly. 5. Alloy- porcelain thermal compatibility appeared more dependent on the porcelain than the alloy.
Study on nuclear magnetic resonance of superionic conductor NH4HSeO4 in rotating frame
임애란 한국자기공명학회 2014 Journal of the Korean Magnetic Resonance Society Vol.18 No.1
In order to obtain information on the structural geometry of NH4HSeO4 near the phase transition temperature, the spectrum and spin- lattice relaxation time in the rotating frame T1ρ for the ammonium and hydrogen-bond protons were investigated through 1H MAS NMR. T1ρ for the hydrogen-bond protons abruptly decreased at high temperature and it is associated with the change in the structural geometry in O–H∙∙∙O bonds. This mobility of the hydrogen-bond protons may be the main reason for the high conductivity.
임애란,정원기 한국자기공명학회 2010 Journal of the Korean Magnetic Resonance Society Vol.14 No.1
The NMR spectrum and spin-lattice relaxation times, T1, of the 1H nuclei in (NH4)2Cd2(SO4)3 single crystals were obtained. The two minima in T1 in the paraelectric phase are attributed to the reorientational motions of the NH4+ groups. The 1H T1 of the (NH4)2Cd2(SO4)3 crystals can be described with Bloembergen-Purcell-Pound (BPP) theory. The experimental value of T1 can be expressed in terms of an isotropic correlation time τH for molecular motions by using the BPP theory, and determine the role of protons in these processes.
도재 냉각방법의 차이가 금속-도재간 열팽창 양상과 결합력에 미치는 영향
임애란,임호남,박남수,Lim, Ae-Ran,Lim, Ho-Nam,Park, Nam-Soo 대한치과보철학회 1990 대한치과보철학회지 Vol.28 No.1
Although a number of studies have been performed to assure that residual stress caused by a mismatch of alloy porcelain thermal expansion can contribute to clinical failure of a ceramometal restoration, the interactive influence of cooling rate on the magnitude of thermal expansion difference and on bond strength between them have not been extensively analyzed. The objective of this study was to determine the influence of cooling rate and the number of firing cycles on the expansion mismatch and the flexural failure resistance of metal porcelain strip. Tested alloys included one Pd-Ag alloy, one Ni-Cr-Be alloy with two kinds of porcelain, Vita and Ceramco. Metal specimens were cast into rods with a height of 13mm and a diameter of 5mm. Subsequently, the castings were subjected to scheduled firing cycles without porcelain. And the porcelain specimens after being fired were trimmed into a bar with a final dimension of $5{\times}5{\times}25mm$. Thermal expansions of the alloys and porcelains were measured by using a push rod or a differential dialometer respecitvely. Porcelain glass transition temperatures and expansion values were derived alloy-porcelain pairs were assessed by comparing expansion values of the components at a porcelain glass transition temperature. Calculations were made using combinations of a Ni-Cr alloy or Pd-Ag alloy with each of two porcelain products. Metal-porcelain strip specimens were subjected to four point loading in an Instron testing machine until crack occured at the metal-cramic interface at the time of sharp decrease of load on recorder. On the basis of this study, the following conclusions may be stated: 1. Regardless of the kinds of ceramometal combinations, both of calculated and experimental data revealed that the double fired specimens exhibited a significantly lower flexural strength. 2. By the rise of the amount of mismatch, bond strength were decreased. 3. Thermal expansion value of Pd-Ag alloys were higher than that of Ni-Cr alloys. 4. Expansion curves of metal were proportional to the increase of temperature and were not affected by the experimental conditions, however porcelains did not show the same magnitude of metal, and a shift of the glass transition temperature to higher temperatures was observed when cooled rapidly 5. Alloy-porcelain thermal compatibility appeared more dependent on the porcelain than the alloy.
Ferroelectric-Paraelectric Phase Transition of CsH2PO4 studied by Static NMR and MAS NMR
임애란,이광세 한국자기공명학회 2015 Journal of the Korean Magnetic Resonance Society Vol.19 No.1
The microscopic dynamics of CsH2PO4, with two distinct hydrogen bond lengths, are studied by static nuclear magnetic resonance (NMR) and magic angle spinning (MAS) NMR. The proton dynamics of the two crystallographically inequivalent hydrogen sites were discussed in terms of the 1H NMR and 1H MAS NMR spectra. Although the hydrogen bonds have two inequivalent sites, H(1) and H(2), distinct proton dynamics for the two sites were not found. Further, the 133Cs spectrum is more or less continuous near TC1 (=153 K). Finally, the phase transition mechanism of TC1 in CsH2PO4 is related to the ordering of protons.