• 한국세라믹학회지
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• 제15권1호
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• pp.3-8
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• 1978

Effects on the sintering of zircon by minor additives such as $Al_2O_3$, MgO and CaO were studied at $1450^{\circ}C$~$1550^{\circ}C$ for 30 minutes. Shrinkage, compressive strength, bulk density and apparent porosity of sintered specimens were measured in relation to content of minor additives and temperature. Mineral constitutions of the sintered specimens were idenified with X-ray diffractometer. And microstructures of the sintered specimens were observed by scanning electron microscope. The results obtained were as follow. 1) Effect ofthe minor additives such as Al2O3, MgO and CaO on the sintering of zircon was related to reaction between added oxide and silica by dissociation of zircon. 2) Zircon did not dissociate at $1550^{\circ}C$, but it did slightly on the specimen added by Al2O3 5 wt% at $1550^{\circ}C$. 3) Sintering of zircon was promoted by the addition of MgO, $(Al_2O_3＋CaO)$ and (MgO＋CaO), then, this phenomenon was due to the formation of liquid phase.

• Tribology and Lubricants
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• 제18권3호
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• pp.204-210
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• 2002

Automotive brake pads with four different sizes of zircon particles (average sizes of 1㎛, 6㎛, 75㎛, and 140㎛, respectively) were investigated to evaluate the size effect of abrasive particles on friction performance. Results showed that the brake pads with the larger size of zircon particles tend to show better frictional stability and low pad wear. However, the rotor surface was severely abraded in the case of using larger zircon particles. On the other hand, the small zircon particles in the pads showed the fast increase of the coefficient of friction with friction force oscillation and the tendency was pronounced at low sliding speeds. The brake pads with small particle sizes also exhibited strong fade phenomena at elevated temperatures.

• 한국세라믹학회지
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• 제24권2호
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• pp.186-192
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• 1987

ZrO2 powders having high purity were prepared from domestic zircon sand using the caustic fusion method and the soda ash sintering process. In the caustic fusion method, ZrO2 recovery was reached to 96% when 100/140 mesh zircon was reacted with NaOH at the NaOH/Zircon mole ratio 6 and at 650$^{\circ}C$ for 2 hours. And in the soda ash sintering process, ZrO2 was recovered to 88.5% when -325 mesh zircon was reacted with Na2CO3 at the Na2CO3/Zircon mole ratio 1.1 and 1050$^{\circ}C$ for 2 hours. In both cases, Zr component was extracted to ZrOCl2, subsequently crystallized to ZrOCl2$.$8H2O to increase the purity, and converted to ZrO2 by precipitation. And to increase the sinter ability of powder, Cl- ion was removed and strong agglomeration was avoided by methanol distribution of Zr(OH)4 precipitates.

• 한국재료학회지
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• 제18권11호
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• pp.604-609
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• 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 $SiO_2$.

• 한국세라믹학회지
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• 제14권2호
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• pp.88-94
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• 1977

Zircon sand of two different particle distribution with 2 percent of ground pyrophyllite were adoted to prepare the dense specimens of the stopper nozzle for the tundish. The molding pressure of $600kg/cm^2$ brought about the superior properties to those obtained t the pressure of $300kg/cm^2$, and as the firing temperatures were increased from $1, 350^{\circ}C$ to $1, 600^{\circ}C$, the better characteristics resulted. The addition of 2 percent $MgCr_2O_4$ to zircon pyrophyllite batch was more effective in corrosion-resistance to the blast furnace-slag.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제31회 춘계학술대회
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• pp.180-186
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• 2000

Friction materials with four different sizes of zircon - l${\mu}{\textrm}{m}$, 6${\mu}{\textrm}{m}$, 75${\mu}{\textrm}{m}$, 140${\mu}{\textrm}{m}$- were investigated to evaluate the size effects of abrasive particles used in the automotive brake pads on brake performance. Although the brake pads with the largest size of zircon showed a good frictional stability and low wear, rotors were severely abraded due to the aggressiveness of coarse Bircon. As the siBe of zircon decreased. friction force and the amplitude of friction coefficient increased. Considering the above results, abrasive materials were thought to destroy transfer film and the extent of the destruction depends on the size of zircon. The small size zircon was not effective in developing a transfer layer on the rotor surface while minimizing the damage on the counter surface.

• 한국세라믹학회지
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• 제22권5호
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• pp.71-75
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• 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.

• 암석학회지
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• 제23권2호
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• pp.139-144
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• 2014

저어콘 음극선발광영상의 입체적 연구를 위해, 단계적 연마를 사용한 연쇄단층촬영과 영상 후처리작업으로 저어콘 내부 누대구조의 3차원 복원을 최초로 시도하였다. 연구에 사용된 시료는 경상분지 북동부 영덕화강암체에서 분리한 고생대말 시기의 저어콘으로 평면 음극선발광영상에서는 전형적인 진동누대구조가 관찰된다. 시료의 연쇄단층촬영을 위해 에폭시마운트 제작 후 $3{\mu}m$과 $1{\mu}m$ 연마액을 이용한 연마와 후방산란전자영상과 음극선발광영상 촬영을 시료가 소진될 때까지 반복하였다. 단계별 두께의 차이는 약 $3{\mu}m$이며, 약 80여개의 저어콘 중 7개를 선정하여 같은 면적 영상파일로 저장한 후 영상편집 소프트웨어인 Image J와 Volume Viewer를 이용하여 3차원 내부구조를 복원하여, 저어콘의 진동누대 및 덧성장구조를 입체적으로 재현하는데 성공하였다. 3차원적 내부구조 영상은 2차원적으로 관찰하는 단면영상의 내부구조와 달리 특정방향에 따른 단면관찰이 가능하고 다양한 변화양상을 재현할 수 있다. 이 방법은 고분해능 이차이온질량분석기 연대결과가 복잡하게 나오는 저어콘이나 미세구조 파악이 필요한 다른 지질시료의 입체적인 성장 및 재결정작용의 내부 구조연구에 응용될 수 있다.

• Geosciences Journal
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• 제22권6호
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• pp.921-938
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• 2018

The Motzfeldt intrusions in the Gardar Province, southern Greenland, split into syenitic plutonic and hypabyssal rocks, in which the latter include ring dykes and sheet intrusions. Sheet intrusions, considered as the source for rare earth elements (REE) and high field strength elements (HFSE), comprise sheets of peralkaline microsyenite (SPM), syenitic pegmatite (SP), and peralkaline microsyenite (PM). SP exhibits extremely high concentrations of REE and HFSE, which are positively correlated with increasing alkalinity from early towards late intrusion, caused by magmatic processes. In contrast, some of the SPM and PM are also significantly enriched in REE and HFSE, caused by post-magmatic fluids. The REE- and HFSE-rich phases in SP consist mainly of zircon and allanite with smaller amounts of pyrochlore in pseudomorph from the inferred eudialyte, whereas some of the PM and SPM consist of pyrochlore, REE-carbonate, and zircon in the matrix. The zircon grains in the Motzfeldt Sø Formation (MSF) syenite occur in interstitial spaces, exhibiting an association with magnetite and a bipyramidal form in texture. They are characterized by a highly fractured and embayed rim. Zircons from PM and SP are clearly enriched in Fe, Al, Ca, Na, Y, P, Hf, Y, P, Nb, Ta, and REE, and are depleted in Zr and Si in comparison with magmatic zircon. They also show a clear trend of higher LREE/HREE and $Eu/Eu^{\star}$ ratios, and lower $Ce/Ce^{\star}$ ratios, which define them as typical hydrothermal zircons. In contrast, zircons from the MSF syenite show a relatively lower LREE/HREE ratio and Eu and Ce anomalies of a similar magnitude compared with those from SP and PM. The occurrence and mineral composition of the zircon suggest that post-magmatic fluids have played an important role in the remobilization of REE and HFSE as well as the primary concentration of REE and HFSE, caused by magmatic processes.

• Journal of Ceramic Processing Research
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• 제19권6호
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• pp.504-508
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• 2018

Diopside is a ceramic material with excellent physical and chemical properties. However, when it is applied as an LED packaging material, heat dissipation of the LED element is not sufficient due to its relatively lower thermal conductivity, which may cause degradation of the LED function. In this study, glass-ceramics based on a $ZrO_2-CaO-MgO-SiO_2$ system, in which diopside is the main crystal phase, were prepared by heat-treating the glass, which was composed of zircon ($ZrO_2-SiO_2$) powders and diopside ($CaO-MgO-2SiO_2$) powders. The possibility of using the glass-ceramics as a packaging material for LEDs was then investigated by analyzing the density, shrinkage, thermal conductivity, and phases generated according to the amount of zircon powder added. The density and shrinkage of specimens decreased slightly and then increased again with the amount of $ZrO_2-SiO_2$ added within a range of 0~0.38 mol. Even though the crystal phase of zircon does not appear in the $ZrO_2-CaO-MgO-SiO_2$ system, the glass containing 0.38 mol zircon powder showed the highest thermal conductivity, 1.85 W/mK, among the specimens fabricated in this study: this value was about 23% higher than that of pure diopside. It was found that the thermal conductivity of the glass-ceramics based on a $ZrO_2-CaO-MgO-SiO_2$ system was closely related to the density, but not to the phase type. Zirconia ($ZrO_2$), a component oxide of zircon, plays an important role in increasing the density of the specimen. Furthermore the thermal conductivity of glass-ceramics based on a $ZrO_2-CaO-MgO-SiO_2$ system showed a nearly linear relationship with thermal diffusivity.