共查询到20条相似文献,搜索用时 31 毫秒
1.
Serene C. Farmer Larry H. Schoenlein A. H. Heuer 《Journal of the American Ceramic Society》1983,66(7):c107-c109
Decomposition of cubic, MgO-stabilized ZrO2 solid solutions has been studied. Precipitates of the ordered compound, Mg2 Zr5 O12 , form, but only when a two-stage heat treatment involving nucleation at a low temperature followed by growth at a higher temperature is used. Other decomposition products are also present after such a heat treatment . 相似文献
2.
W. C. LUTH 《Journal of the American Ceramic Society》1967,50(4):174-176
Schairer's study (1954) on phase relations in the system KalSi2 O6 –Mg2 SiO4 –SiO2 was extended to include the system KalSiO4 –Mg2 SiO4 –KalSi2 O6 . It is shown that this join is ternary; however, the relatively high vapor pressure of the condensed phases prohibits study by the usual quenching techniques. The apparent intersection of the (KalSiO4 –Mg2 SiO4 –SiO3 ) join with the primary phase volume of spinel is attributed to loss of the alkali-silicate constituents by vapor transport. This results in the effective bulk composition being moved away from this join toward the primary phase volume of spinel in the system K2 O–MgO–Al2 O3 –SiO2 . 相似文献
3.
Ana M. Espino Luis A. Díaz Adolfo Fernández Ramón Torrecillas José S. Moya 《Journal of the American Ceramic Society》2005,88(4):1000-1003
The wettability of binary and ternary glasses belonging to SiO2 –Al2 O3 –ZrO2 diagram has been studied using the sessile drop technique at 1750° and 1800°C. The ternary SiO2 –Al2 O3 –ZrO2 (90–5–5 wt%) glass has proved to be well appropriated as a molybdenum oxidation barrier coating. The addition of 5 wt% of MoO2 slightly improves its wettablity at higher temperatures without affecting its oxidation barrier properties. The Mo comes into the glass network as a mixture of Mo5+ , Mo4+ , and Mo6+ . After oxidation at 1000°C in oxygen atmosphere, the molybdenum remains in the glass network as Mo6+ . 相似文献
4.
Hyun M. Jang Jong H. Moon Cheol W. Jang 《Journal of the American Ceramic Society》1992,75(12):3369-3376
Al2 O3 –ZrO2 –SiC whisker composites were prepared by surface-induced coating of the precursor for the ZrO2 phase on the kinetically stable colloid particles of Al2 O3 and SiC whisker. The fabricated composites were characterized by a uniform spatial distribution of ZrO2 and SiC whisker phases throughout the Al2 O3 matrix. The fracture toughness values of the Al2 O3 –15 vol% ZrO2 –20 vol% SiC whisker composites (∼12 MPa.m1/2 ) are substantially greater than those of comparable Al2 O3 –SiC whisker composites, indicating that both the toughening resulting from the process zone mechanism and that caused by the reinforced SiC whiskers work simultaneously in hot-pressed composites. 相似文献
5.
The Bi2 O3 –Nb2 O5 –NiO phase diagram at 1100°C was determined by means of solid-state synthesis, X-ray diffraction, and scanning electron microscopy. A ternary eutectic with a melting point below 1100°C was found to exist in the field between NiO, Bi2 O3 , and the end-member of the δBi2 O3 –Nb2 O5 solid solution. The existence of the previously reported Bi3 Ni2 NbO9 phase was disproved. A pyrochlore homogeneity range around Bi1.5 Ni0.67 Nb1.33 O6.25 was determined together with all the phase relations in this phase diagram. 相似文献
6.
The cubic ( c -ZrO2 ) and tetragonal zirconia ( t -ZrO2 ) phase stability regions in the system ZrO2 –Y2 O3 –Ta2 O5 were delineated. The c -ZrO2 solid solutions are formed with the fluorite structure. The t -ZrO2 solid solutions having a c/a axial ratio (tetragonality) smaller than 1.0203 display high fracture toughness (5 to 14 MPa · m1/2 ), and their instability/transformability to monoclinic zirconia ( m -ZrO2 ) increases with increasing tetragonality. On the other hand, the t -ZrO2 solid solutions stabilized at room temperature with tetragonality greater than 1.0203 have low toughness values (2 to 5 MPa · m1/2 ), and their transformability is not related to the tetragonality. 相似文献
7.
Lamrath Abdul Khalam Sherin Thomas Mailadil T. Sebastian 《International Journal of Applied Ceramic Technology》2007,4(4):359-366
The columbites MgNb2 O6 , MgTa2 O6 , and corundum-type Mg4 Nb2 O9 ceramics were prepared by the conventional solid-state ceramic route. The structure and microstructure of the sintered samples were investigated by X-ray diffraction and scanning electron microscopic techniques. The microwave dielectric properties of the samples were measured by the resonance method in the frequency range 4–6 GHz. The dielectric properties have been tailored by forming a solid solution between MgNb2 O6 and MgTa2 O6 and by the substitution of TiO2 for Nb2 O5 in both MgNb2 O6 and Mg4 Nb2 O9 ceramics. The Mg(Nb0.7 Ta1.3 )O6 has ɛr =29, Q u × f =67 800 GHz, and τf =0.8 ppm/°C and the MgO–(0.4)Nb2 O5 –(1.5)TiO2 composition has ɛr =34.5, Q u × f =81 300 GHz, and τf =−2 ppm/°C. 相似文献
8.
Tsuyoshi Honma Yasuhiko Benino Takumi Fujiwara Takayuki Komatsu Ryuji Sato 《Journal of the American Ceramic Society》2005,88(4):989-992
The glass formation region, crystalline phases, second harmonic (SH) generation, and Nd:yttrium aluminum garnet (YAG) laser-induced crystallization in the Sm2 O3 –Bi2 O3 –B2 O3 system were clarified. The crystalline phases of Bi4 B2 O9 , Bi3 B5 O12 , BiBO3 , Sm x Bi1− x BO3 , and SmB3 O6 were formed through the usual crystallization in an electric furnace. The crystallized glasses consisting of BiBO3 and Sm x Bi1− x BO3 showed SH generations. The formation of the nonlinear optical BiB3 O6 phase was not confirmed. The formation (writing) region of crystal lines consisting of Sm x Bi1− x BO3 by YAG laser irradiation was determined, in which Sm2 O3 contents were∼10 mol%. The present study demonstrates that Sm2 O3 –Bi2 O3 –B2 O3 glasses are promising materials for optical functional applications. 相似文献
9.
The phase domain of Ti3 O5 –Ti2 O3 –Ti(CO) at 1580 K was determined from the formation energies of Ti(C x O y ), as calculated via the Gibbs–Duhem equation. An extensive Ti(CO) domain is attributed to the high affinity between TiC and TiO. The phase domain of Ti3 O5 –Ti2 O3 –Ti(CN) was obtained at 1673 K using the formation energies of Ti(C x N y ). This study shows that the stable region for Ti2 O3 is significantly small in the Ti3 O5 –Ti2 O3 –Ti(CN) phase domain. It demonstrates the absence of TiO and Ti2 O3 in the normal syntheses of TiC and Ti(CN) from TiO2 , respectively. 相似文献
10.
A coating approach for synthesizing 0.9Pb(Mg1/3 Nb2/3 )O3 –0.1PbTiO3 (0.9PMN–0.1PT) and PMN using a single calcination step was demonstrated. The pyrochlore phase was prevented by coating Mg(OH)2 on Nb2 O5 particles. Coating of Mg(OH)2 on Nb2 O5 was done by precipitating Mg(OH)2 in an aqueous Nb2 O5 suspension at pH 10. The coating was confirmed using optical micrographs and zeta-potential measurements. A single calcination treatment of the Mg(OH)2 -coated Nb2 O5 particles mixed with appropriate amounts of PbO and PbTiO3 powders at 900°C for 2 h produced pyrochlore-free perovskite 0.9PMN–0.1PT and PMN powders. The elimination of the pyrochlore phase was attributed to the separation of PbO and Nb2 O5 by the Mg(OH)2 coating. The Mg(OH)2 coating on the Nb2 O5 improved the mixing of Mg(OH)2 and Nb2 O5 and decreased the temperature for complete columbite conversion to ∼850°C. The pyrochlore-free perovskite 0.9PMN–0.1PT powders were sintered to 97% density at 1150°C. The sintered 0.9PMN–0.1PT ceramics exhibited a dielectric constant maximum of ∼24 660 at 45°C at a frequency of 1 kHz. 相似文献
11.
Hiroyasu Kido Sridhar Komarneni Rustum Roy 《Journal of the American Ceramic Society》1991,74(2):422-424
The La2 Zr2 O7 phase was prepared from metal acetylacetonates by a sol—gel route without any intermediate phase formation. X-ray peaks appeared at a temperature as low as 500°C at the positions expected for La2 Zr2 O7 , although they were broad. The crystal structure of La2 Zr2 O7 was found to be of the fluorite type below 900°C and of thepyrochlore type above 1000°C. The substitution of a small amount of Eu for La was carried out to investigate the crystal structure from the viewpoint of fluorescence, and these results confirmed the formation of fluorite type La2 Zr2 O7 below 900°C. 相似文献
12.
Activity–composition relations of FeCr2 O4 –FeAl2 O4 and MnCr2 O4 –MnAl2 O4 solid solutions were derived from activity–composition relations of Cr2 O3 –Al2 O3 solid solutions and directions of conjugation lines between coexisting spinel and sesquioxide phases in the systems FeO–Cr2 O3 –Al2 O3 and MnO–Cr2 O3 –Al2 O3 . Moderate positive deviations from ideality were observed. 相似文献
13.
Masahide Okamoto Hironori Kodama Kazuo Shinozaki 《Journal of the American Ceramic Society》2008,91(4):1110-1114
The sintering of a composite of MgO–B2 O3 –Al2 O3 glass and Al2 O3 filler is terminated due to the crystallization of Al4 B2 O9 in the glass. The densification of a composite of MgO–B2 O3 –Al2 O3 glass and Al2 O3 filler using pressureless sintering was accomplished by lowering the sintering temperature of the composite. The sintering temperature was lowered by the addition of small amounts of alkali metal oxides to the MgO–B2 O3 –Al2 O3 glass system. The resultant composite has a four-point bending strength of 280 MPa, a coefficient of thermal expansion (RT—200°C) of 4.4 × 10−6 K−1 , a dielectric constant of 6.0 at 1 MHz, porosity of approximately 1%, and moisture resistance. 相似文献
14.
Phase relations within the "V2 O3 –FeO" and V2 O3 –TiO2 oxide systems were determined using the quench technique. Experimental conditions were as follows: partial oxygen pressures of 3.02 × 10−10 , 2.99 × 10−9 , and 2.31 × 10−8 atm at 1400°, 1500°, and 1600°C, respectively. Analysis techniques that were used to determine the phase relations within the reacted samples included X-ray diffractometry, electron probe microanalysis (energy-dispersive spectroscopy and wavelength-dispersive spectroscopy), and optical microscopy. The solid-solution phases M2 O3 , M3 O5 , and higher Magneli phases (M n O2 n −1 , where M = V, Ti) were identified in the V2 O3 –TiO2 system. In the "V2 O3 –FeO" system, the solid-solution phases M2 O3 and M3 O4 (where M = V, Ti), as well as liquid, were identified. 相似文献
15.
C. C. Khaw C. K. Lee Z. Zainal G. C. Miles A. R. West 《Journal of the American Ceramic Society》2007,90(9):2900-2904
The subsolidus phase diagram of the system Bi2 O3 –ZnO–Ta2 O5 in the region of the cubic pyrochlore phase has been determined at 1050°C. This phase forms a solid solution area that includes the ideal composition P, Bi3 Zn2 Ta3 O14 ; possible solid solution mechanisms are proposed, supported by density measurements of Zn-deficient solid solutions. The general formula of the solid solutions is Bi3+ y Zn2− x Ta3− y O14− x − y , based on the creation of Zn2+ , O2− vacancies in Zn-deficient compositions and a variable Bi/Ta ratio. 相似文献
16.
Mark I. Pownceby Keri K. Constanti-Carey Michael J. Fisher-White 《Journal of the American Ceramic Society》2003,86(6):975-980
Subsolidus phase equilibria in the system Fe2 O3 –Al2 O3 –TiO2 were investigated between 1000° and 1300°C. Quenched samples were examined using powder X-ray diffraction and electron probe microanalytical methods. The main features of the phase relations were: (a) the presence of an M3 O5 solid solution series between end members Fe2 TiO5 and Al2 TiO5 , (b) a miscibility gap along the Fe2 O3 –Al2 O3 binary, (c) an α-M2 O3 ( ss ) ternary solid-solution region based on mutual solubility between Fe2 O3 , Al2 O3 , and TiO2 , and (d) an extensive three-phase region characterized by the assemblage M3 O5 +α-M2 O3 ( ss ) + Cor( ss ). A comparison of results with previously established phase relations for the Fe2 O3 –Al2 O3 –TiO2 system shows considerable discrepancy. 相似文献
17.
Mi-Ri Joung Jin-Seong Kim Myung-Eun Song Sahn Nahm Jong-Hoo Paik Byung-Hyun Choi 《Journal of the American Ceramic Society》2009,92(7):1621-1624
The formation process and microwave dielectric properties of the Mg2 V2 O7 ceramics were investigated. The MgV2 O6 phase that was formed at around 450°C interacted with remnant MgO above 590°C to form a homogeneous monoclinic Mg2 V2 O7 phase. Finally, this monoclinic Mg2 V2 O7 phase was changed to a triclinic Mg2 V2 O7 phase for the specimen fired at 800°C. Sintering at 950°C for more than 5 h produced high-density triclinic Mg2 V2 O7 ceramics. In particular, the Mg2 V2 O7 ceramics sintered at 950°C for 10 h exhibited the good microwave dielectric properties of ɛr =10.5, Q × f =58 275 GHz, and τf =−26.9 ppm/°C. 相似文献
18.
The phase diagrams in the Al2 O3 –Cr2 O3 and V2 O3 –Cr2 O3 systems have been assessed by thermodynamic modeling with existing data from the literature. While the regular and subregular solution models were used in the Al2 O3 –Cr2 O3 system to represent the Gibbs free energies of the liquid and solid phases, respectively, the regular solution model was applied to both phases in the V2 O3 –Cr2 O3 system. By using the liquidus, solidus, and/or miscibility gap data, the interaction parameters of the liquid and solid phases were optimized through a multiple linear regression method. The phase diagrams calculated from these models are in good agreement with experimental data. Also, the solid miscibility gap and chemical spinodal in the V2 O3 –Cr2 O3 system were estimated. 相似文献
19.
Yaping Zhang Yunxia Yang Yuwen Ou Wei Hua Jiahua Zheng Guorong Chen 《Journal of the American Ceramic Society》2009,92(8):1881-1883
Glasses with compositions 50Bi2 O3 – x Sb2 O3 –10B2 O3 –(40– x ) SiO2 ( x =0, 1, 3, 5, 8, 10) have been prepared by conventional melt quench technique. Substitution of Sb2 O3 for SiO2 exerted an obvious effect on properties of glasses, especially, increased glass transition temperature ( T g ) and crystalline temperature ( T c ) greatly. Results of infrared transmission spectra attributed the effect to the formation of new bridging bonds of Sb–O–B and Sb–O–Si in glass network. 相似文献
20.
Naoto Hirosaki Yoshinobu Yamamoto Toshiyuki Nishimura Mamoru Mitomo Junichi Takahashi Hisanori Yamane Masahiko Shimada 《Journal of the American Ceramic Society》2002,85(11):2861-2863
Phase relationships in the Si3 N4 –SiO2 –Lu2 O3 system were investigated at 1850°C in 1 MPa N2 . Only J-phase, Lu4 Si2 O7 N2 (monoclinic, space group P 21 / c , a = 0.74235(8) nm, b = 1.02649(10) nm, c = 1.06595(12) nm, and β= 109.793(6)°) exists as a lutetium silicon oxynitride phase in the Si3 N4 –SiO2 –Lu2 O3 system. The Si3 N4 /Lu2 O3 ratio is 1, corresponding to the M-phase composition, resulted in a mixture of Lu–J-phase, β-Si3 N4 , and a new phase of Lu3 Si5 ON9 , having orthorhombic symmetry, space group Pbcm (No. 57), with a = 0.49361(5) nm, b = 1.60622(16) nm, and c = 1.05143(11) nm. The new phase is best represented in the new Si3 N4 –LuN–Lu2 O3 system. The phase diagram suggests that Lu4 Si2 O7 N2 is an excellent grain-boundary phase of silicon nitride ceramics for high-temperature applications. 相似文献