• 한국재료학회지
• /
• 제18권11호
• /
• pp.604-609
• /
• 2008

The sintering behavior of zircon with silica was investigated. Zircon with 5 vol% of sedimentation $SiO_2$ resulted in the apparent density of $4.45\;g/cm^3$, the diametral tensile strength of $12.125\;kgf/cm^2$, and the micro Vickers hardness of 1283 HV. The dissociation temperature and mechanical characteristics of the $ZrSiO_4$ were changed with different kinds of $SiO_2$. $SiO_2$ addition prevented dissociation of $ZrSiO_4$. Zircon with 5 vol% of sedimentation $SiO_2$ and with 5 vol% of fused $SiO_2$ resulted in increased diametral tensile strength and increased micro Vickers hardness by suppression of $ZrSiO_4$ dissociation and low temperature liquid $SiO_2$ formation. Zircon with fumed $SiO_2$ and quartz $SiO_2$ resulted in decreased diametral tensile strength and decreased micro Vickers hardness because of cristobalite and quartz phase formation and high temperature liquid $SiO_2$ formation. Zircon with 10 vol% of $SiO_2$ resulted in decreased diametral tensile strength and decreased micro Vickers hardness because of weak particle coupling due to excess formation of liquid $SiO_2$.

• 한국재료학회지
• /
• 제21권4호
• /
• pp.220-224
• /
• 2011

Zircon has excellent thermal, chemical, and mechanical properties, but it is hard to make a dense sintered product because of dissociation during the sintering process. This study analyzes how the addition of $SiO_2$ and $Al_2O_3$ affects the mechanical properties of sintered zircon, particularly in regards to reducing the thermal dissociation and improving the mechanical properties of $ZrSiO_4$. Zircon specimens containing different amounts of $SiO_2$ and $Al_2O_3$ were prepared and sintered to observe how the mechanical properties of $ZrSiO_4$ changed according to the differing amount of $SiO_2$ and $Al_2O_3$. The $ZrSiO_4$ that was used for the starting material was ground by ball mill to an average particle size of 3 ${\mu}m$. The $SiO_2$ and $Al_2O_3$ that was used for additives were ground to an average particle size of 3 ${\mu}m$ and 0.5 ${\mu}m$, respectively. Adding $SiO_2$ resulted in transformation in the liquid phase at high temperatures, which had little effect on suppressing the thermal dissociation but enhanced the mechanical properties of $ZrSiO_4$. When $Al_2O_3$ was added, the mechanical properties of $ZrSiO_4$ decreased due to the formation of pores and abnormal grains in the microstructure of the sintered zircon.

• 한국재료학회지
• /
• 제26권4호
• /
• pp.182-186
• /
• 2016

Zircon, having excellent thermal, chemical, and mechanical properties, is utilized in refractory materials, electronic materials, chemical machines, structural materials, etc. However, zircon generally shows thermal dissociation to zirconia($ZrO_2$) and silica($SiO_2$) around the sintering temperature of $1540^{\circ}C$, and when zircon particles are small and impurities are present, thermal dissociation is known to occur at around $1100^{\circ}C$. This reduces the mechanical properties of $ZrSiO_4$. In this research, the effect of adding $SiO_2$ and 3Y-TZP to $ZrSiO_4$ has been studied in order to suppress dissociation and improve the mechanical properties. Addition of $SiO_2$ suppressed the dissociation of $ZrSiO_4$ at lower temperatures. It also enabled optimum packing between the particles, resulting in a dense microstructure and good mechanical properties. When 3Y-TZP was added, recombination with the dissociated $SiO_2$ resulted in good mechanical properties by suppressing the generation of pores and the densification of the microstructure.

• 한국세라믹학회지
• /
• 제23권4호
• /
• pp.23-26
• /
• 1986

The synthetic conditions of $ ZrSiO_4-Cd(S_xS_{1-x})$ stains from CdS, Se, $SiO_2$ , 4ZrO_2$ and Lif were investigated and the colors were examined. Colors of the stains prepared were yellow orange red pink ruby and violet in relation to both the content of CdS-Se in $ZrSiO_4$ and firing temperature. Colors of these series stains were thermally stabilized probably by the structural stability of zirconium silicate. Furthermore by the result of X-ray diffraction analysis it is assumed that color of the zircon cadmium sulphoselenide $ ZrSiO_4-Cd(S_xS_{1-x})$ stain is developed by neither the coloring ions in $ZrSiO_4$ lattice nor the solid solution of $ZrSiO_4$ and $Cd(S_xS_{1-x})$ but by the small crystals of $Cd(S_xS_{1-x})$ being occluded by the zirconium silicate during sintering process.

• 한국재료학회지
• /
• 제26권2호
• /
• pp.95-99
• /
• 2016

In this study, 5 um sized $ZrSiO_4$ was ground to 1.9 um, 0.3 um, and 0.1 um sized powders by wet high energy milling process, and the sintering characteristics were observed. Pure $ZrSiO_4$ itself can-not be sintered to these levels of theoretical density, but it was possible to sinter $ZrSiO_4$ powder of nano-scale size of, -0.1 um to the theoretical density and to lower the sintering temperature for full density. Also, the decomposition of $ZrSiO_4$ with a size in the micron range resulted in the formation of monoclinic $ZrO_2$; however, in the nano sized range, the decomposition resulted in the tetragonal phase of $ZrO_2$. So, it was possible to improve the sintering characteristics of nano-sized $ZrSiO_4$ powders.

• 한국세라믹학회지
• /
• 제36권10호
• /
• pp.1080-1086
• /
• 1999

Mullite/zirconia composite was synthesized by adding zirconia and Zircon to mixture of Hapcheon kaolin(grade pink A) and aluminium nitrate salt in order to enhance strength of the mullite specimens. Kaolin and aluminium nitrate salt was mixed milled and calcined at 100$0^{\circ}C$ and then 5wt% mullite seed was added to increase mullite content. The influence of the additives(ZrO2 and ZrSiO4) and sintering temperature on the strength of the sintered specimens was investigated. The flexural strength of the specimens containing 10wt% zirconia was enhanced from 150MPa without the additive up to 300MPa after heat treatment at 156$0^{\circ}C$ In the case of addition of 15wt% zircon the strength of the specimens systhesized at 1$600^{\circ}C$ was 225 MPa.

• 한국재료학회지
• /
• 제18권7호
• /
• pp.352-356
• /
• 2008

Effect The effect of sintering additives ($SiO_2$, $Al_2O_3$, Clay) on the mechanical characteristics of sintered zircon was investigated. 1 vol% of additives in zircon powder was was sintered at $120{\sim}1500^{\circ}C$, the mechanical characteristics were measured, and microstructure analysis were was conducted. $Al_2O_3$ and clay additions increase the formation of monoclinic and tetragonal-$ZrO_2$ formation. An addition of SiO2 addition suppressed the formation of tetragonal-$ZrO_2$ formation., The A specimen sintered at $1400^{\circ}C$ showed the a density of $4.05\;g/cm^3$ and the a microhardness of 1120 HV, respectively.

• 한국세라믹학회지
• /
• 제32권7호
• /
• pp.853-857
• /
• 1995

ZrSiO4 powders were prepared from partially hydrolyzed solution of Si(OC2H5)4 and ZrOCl2.8H2O solution by the sol-gel method and formation rate of ZrSiO4 on the reaction parameter was investigated. In order to prepare homogeneous ZrSiO4 precursor gels, the H2O/Si(OC2H5)4 molar ratio of about 2, the pH of the ZrOCl2.8H2O solution fo about 4 and stirring time of the mixed solutions of about 2 hrs were appropriate. Formation of temperature of ZrSiO4 reduced about 15$0^{\circ}C$ by milling and formation of ZrSiO4 at 1300~135$0^{\circ}C$ showed an accelerative increase through the hedvall effect by silica.

• 분석과학
• /
• 제6권3호
• /
• pp.275-282
• /
• 1993

지르콘사 광물에서 지르코니아를 회수하기 위하여 지르콘사를 분해 반응시킨 소성산물 중의 $SiO_2$와 $ZrO_2$를 DC arc source를 이용한 직독식 분광기로 동시 분석하였다. 순수한 금속산화물을 혼합하여 합성표준시료를 만들고 완충제(흑연)와 융제($Li_2B_4O_7$)의 혼합비를 조절하면서 최적의 들뜸조건을 선정하였다. 완충제와 흑연의 비를 0.22:1로 하고 시료와의 혼합비를 40배로 하였을 때 가장 좋은 들뜸조건을 얻을 수 있었다. 분석 결과의 표준편차는 $SiO_2$는 1.3%, $ZrO_2$는 4.9%였다.

• 한국세라믹학회지
• /
• 제22권5호
• /
• pp.71-75
• /
• 1985

This study deals with sintering and corrosive behavior of sintered zircons mixed with 5wt% of clay $Cr_2O_3$ $CrO_3-MgO$ aqueous solution and $CrO_3-Mg(OH)_2$ aqueous solution. Measurements were conducted by firing specimens at 135$0^{\circ}C$ 145$0^{\circ}C$ and 155$0^{\circ}C$ 1$650^{\circ}C$ for 3hrs in oxidized and reduced atmospheric conditions. Following results were obtained. 1. Sintered zircon with 5 wt% clay showed that highest compressive strength and the lowest apparent porosity and the other showed less positive result than above specimen in order of zircon with $CrO_3-MgO$ aqueous solution $CrO_3-Mg(OH)_2$ aqueous solution and $Cr_2O_3$. 2. The more firing temperature increased the more its strength improved and porosity decreased and specimen which was fired over 155$0^{\circ}C$ and in reduced atmospheric condition showed better results. 3. Zircon with additives which was fired over 155$0^{\circ}C$ showed the evidence of thermal dissociation but it was not rebonded completely during cooling. 4. Zircon with $CrO_3-MgO$ aqueous solution and $CrO_3-Mg(OH)_2$ aqueous solutiion showed more corrosive resistance than zircon itself and zircon-clay system.