• Journal of Conservation Science
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• v.36 no.4
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• pp.275-283
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• 2020

Iron oxides are the essential coloring oxides in traditional ceramic glazes. However, when Fe is involved in the coloration in the form of ions or colloids in glazes with low Fe content, it is difficult to identify the iron oxide phases. Generally, in many these glazes, Ca-rich minerals are observed by X-ray diffraction (XRD) or microscopic images, owing to their devitrification by the high Ca content. This study attempts to elucidate the correlation between the crystalline structure and coloration in the glazes while mainly focusing on neoformed Ca-rich minerals and Fe content. An experimental firing was carried out to produce tree ash glazes, with pine tree ash and Buyeo feldspar. In the case of oxidation glazes, the scanning electron microscopy (SEM) images and XRD patterns did not exhibit any Ca-rich crystals, and all the visible light reflectance spectra lines exhibited a similar shape. In contrast, the reduction glazes divided into blue glazes and other colored glazes according to the shapes of their reflectance spectra. It was confirmed that the influence of Ca-rich minerals on the glaze color was more pronounced than the blue color of the reduction glazes when the Ca and feldspar contents were sufficiently high and low, respectively, to form wollastonite. As the Ca content increased and the elemental composition of the reduction glazes changed, the neoformation of the Ca-rich minerals, such as wollastonite, anorthite, diopside, and akermanite was sequentially observed.

• Journal of the Korean Ceramic Society
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• v.13 no.3
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• pp.3-12
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• 1976

The corelation between surface tensions and surface appearances of SK O5a opaque glazes for earthen wares were investigated. The surface tension values were theoretically calculated by using Dietzel's factors of constituent oxides of glaze. The surface appearances of glazes, especially the pinhole phenomena were strongly effected by the surface tension values showing the following general tendencies: (1) In the range of 305±3 dynes/cm of surface tensions, glazes showed almost no pjnholes. (2) In the range of surface tensions less than 300 dynes/cm, the large numbers of small pinholes or eggshell textures were observed. (3) In the range of surface tensions higher than 310 dynes/cm, large and deep pinholes were observed. (4) The contact angles of glazes on the wall tile body substrate are in the good proportional agreement with the surface tension values calculated by Dietzel's factors.

• Journal of Ceramic Processing Research
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• v.22 no.5
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• pp.568-575
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• 2021

Glass-ceramic glazes were prepared using a CaO-MgO-Al2O3-SiO2 system and were used to fabricate low-temperature firing,high-hardness glazes in ceramic tiles. Additives (B2O3) and a nucleating agent (TiO2) were added to the glaze, and crystallineglazes were obtained by sintering at 1000 ~ 1100 oC for 30 or 60 min. X-ray diffraction analysis of the glazes suggested thatcordierite (Mg2Al4Si5O18) and anorthite (CaAl2Si2O8) crystal phases were present, and the peak intensity of the cordieritecrystal phase increased with increasing sintering temperature. All samples showed high crystallinities of 70% or more,irrespective of sintering temperature or time. The glaze density increased with increasing sintering temperature and decreasedat 1100 oC. The Vickers hardness test results of the glazes indicated high hardness values of 6.79 and 6.77 GPa after 30 minheat treatment at 1000 oC and 60 min at 1050 oC, respectively. Glass-ceramic glaze with high hardness at low temperature wasfabricated through crystallization of glaze for tiles.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.372-378
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• 2019

Traditional ceramic glazes formulated with copper oxide (CuO) exhibited antibacterial properties on Staphylococcus aureus (Gram Positive) and Escherichia coli (Gram Negative). All the ceramic glazes containing CuO showed antibacterial behavior when fired in reducing atmosphere. However, some of copper glazes presented antibacterial behavior and had no antibacterial properties at all when sintered in an oxidizing atmosphere. To elucidate the antibacterial mechanism, ceramic glazes were studied for phase and microstructure analysis, dissolution behavior and surface zeta potential. Metallic copper was precipitated in the glaze layer when sintered in reducing atmosphere. Less than 0.05 ppm of Cu ion was dissolved from glazes. Ca ion was most dissolved among all the samples. Glaze surface was highly negatively charged when CuO was added over 3 wt.% regardless of the sintering atmosphere. The antibacterial behavior of ceramic glazes seemed to be directly related to the dissolution behavior of cations, but the antibacterial behavior of oxidized specimens was not explained by the dissolution behavior. Surface potential of ceramic glazes appeared to play an auxiliary role in antibacterial properties.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.181-187
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• 1999

In this study, the effect of residual stress on mechanical strength was investigated with 1 kind of whiteware body and 4 kinds of glazes which are produced in succeeding ceramic art place. Using dipping method, the body was coated for different times in order to manipulate the coating thickness and sintered in the different temperatures ($1200^{\circ}C$, $1250^{\circ}C$, $1300^{\circ}C$, $1350^{\circ}C$) for two thus hours. The sintered bodies were characterized by XRD, EPMA, FEM and UTM in order to study the forming of reaction layer between body and glazes, residual stresses and the effects of residual stresses on mechanical strength of pottery. At $1300{\circ}C$, we obtained maximum density and mechanical strength. By the finite element method, the residual stresses in surface of body were minimum in specific thickness of glazes and the mechanical strength of body in that thickness of glazes showed maximum when the firing temperature was settled.

• Journal of the Korean Chemical Society
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• v.7 no.2
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• pp.144-152
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• 1963

A study was made of the effect of composition changes and particle size on appearance of raw bristol glazes fired at cones 5, 8, and 11. Alumina and silica, alkali and lime variations were made to get some of the more promising glazes determining maturing ranges, modulus of rupture, and other factors such as gloss, smoothness, opacity, eggshelling, crazing, pinholing and crawling for each glaze. Modulus of rupture was measured for the glazes fired at only cone 11.

• Journal of the Korean Ceramic Society
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• v.52 no.3
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• pp.197-203
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• 2015

The colorization of $Zn_2SiO_4$ crystal glazes was investigated by adding nucleating seeds with various coloring agents. The addition of color fixing agents such as $Fe_2O_3$, $MnO_2$, and NiO with seeds caused changes in the colors of glazes. The crystallinity and crystal size were dependent on glaze composition and firing schedules. By controlling coloring agents and firing schedules, it was possible to create various colors and sizes of crystals in a zinc-based crystalline glaze.

• Journal of the Korean Ceramic Society
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• v.52 no.3
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• pp.186-191
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• 2015

Tribological properties of whiteware with various transparent glazes, which have different composition and microstructure, were investigated. The wear resistance and friction behavior of the glazed whiteware are a very important aspect if the whiteware is used as tableware and for sanitation purposes. Generally, the wear property is influenced by the microstructure and surface morphology of the material. The whiteware specimens with two kinds of transparent glazes were fabricated by using the commercially available porcelain body. Furthermore, the commercial tableware, such as bone china, and traditional tableware were also examined as reference materials. All of the specimens showed that different pore structures might affect the mechanical and tribological properties. It seems that the wear resistance of whiteware is substantially related to the pore size and distribution of glaze rather than the hardness value of the specimen.

• Journal of Conservation Science
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• v.35 no.2
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• pp.117-129
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• 2019

In this study, black-glazed porcelain excavated from the Shinan shipwreck is analyzed to distinguish its characteristics. Glazes of Hong-Tang kiln are thin and exhibit little vitrification, whereas the Ci-Zhou-type and Cha-Yang kilns are similar in terms of their cross section. However, Raman mapping images reveal difference in the distribution area of magnetite. In this study, firing experiments are conducted to determine how iron oxides change properties in black glazes. The results show that when hematite is fired to a temperature greater than $1250^{\circ}C$, it becomes magnetite. Therefore, it is estimated that a firing temperature of approximately $1200^{\circ}C$ is suitable for the Hong-Tang kiln. In addition, glazes of the Ci-Zhou-type and Cha-Yang kilns are fired at approximately $1300^{\circ}C$. However, when the characteristics of firing in ancient kilns are considered, porcelain can be fired for a sufficiently long period to extend to glaze surfaces.

• Journal of the Korean Ceramic Society
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• v.17 no.4
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• pp.213-216
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• 1980

A glass-ceramics material of composition %SiO_2$: 38.50, $Al_2O_3$: 26.00, $Na_2O$: 18.00, CaO: 6.00, MgO: 4.00, $TiO_2$: 7.50 was strengthened by coating a series of glazes$(SiO_2-B_2O_3-Al_2O_3-CaO-PbO-Na_2O-)$, which has lower thermal expansion coefficient than that of the glass-ceramics. The thermal expansion coefficient of the glazes ranges $80~90{\times}10^{-7}$cm/cm/$^{\circ}C$, whereas that of the glass-ceramics is $115{\times}10^{-7}$cm/cm/$^{\circ}C$. The glass-ceramics was identified to be composed of nepheline, carnegieite low form, and meta sodium silicate crystal by X-ray diffraction phase analysis. The glaze, having lower melting point and appropriate thermal expansion coefficient, was tried to be stable and good at secondary heat treatment.