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1.
E. R. SEGNIT 《Journal of the American Ceramic Society》1954,37(6):273-277
Equilibrium relationships in this ternary system were determined by the quenching method. The only ternary compound occurring in the system was found to be Ca2 ZnSi2 O7 , which corresponds to the natural mineral hardystonite. It has a congruent melting point (1425°C.) and a large primary-phase field in the center of the system. Primary-phase fields for cristobalite, tridymite, CaSiO3 , Ca3 Si2 O7 , Ca2 SiO4 , ZnO, and Zn2 SiO4 were also determined in part or in full. The results of this work have some bearing on the minerals and reactions occurring in lead blastfurnace slags and in glazes containing zinc oxide. 相似文献
2.
Arno Kaiser Burkhard Sommer Eduard Woermann 《Journal of the American Ceramic Society》1992,75(6):1463-1471
The system CaO–chromium oxide in air is reinvestigated and the existence of intermediate phases with chromium in oxidation states >3+ (Ca5 Cr3 O12 , Ca3 (CrO4 )2 , and Ca5 (CrO4 )3 ) confirmed. Under reducing conditions these phases are unstable. A metastable, polymorphic form of calcium chromite, δ -CaCr2 O4 , is observed. In the CaO-rich section of the CaO–Al2 O3 –Cr2 O3 system a ternary intermediate phase, chrome-haüyne, Ca4 [(Al,Cr3+ )6 O12 ](Cr6+ O4 ), coexists with calcium chromate and calcium aluminate phases. In air, low melting temperatures are preserved in all assemblages containing calcium chromate phases. Under reducing conditions a new ternary phase, Ca6 Al4 Cr2 O15 , coexists with CaO, CaCr2 O4 , chrome-haüyne, and calcium aluminate phases. The influence of chromium oxide additions on the solidus temperatures of the CaO–Al2 O3 system is insignificant. 相似文献
3.
The effect of crystallization on the stress required for complete constrained sintering of a low-temperature cofirable CaO–B2 O3 –SiO2 glass–ceramics has been investigated under uniaxial constant and cyclic loading. As the formation of crystalline phase of wollastonite (CaSiO3 ) increases, the uniaxial viscosity of the porous glass–ceramics during firing increases. Moreover, the required uniaxial stress to have complete constrained sintering, i.e., zero strain or strain rate at the perpendicular directions, is in the range of 80–180 kPa, which shows no significant dependence on heating rate and firing temperature. The measured data of required stress are close to those calculated using the viscous analogy for the constitutive relationship of a porous sintering compact. 相似文献
4.
The crystallization kinetics of a glass based on one type of mica, NaMg3 AlSi3 O10 F2 , with the addition of a nucleating agent, TiO2 , has been studied using differential thermal analysis (DTA) under both isothermal and nonisothermal conditions. Two distinct crystallization exotherms in the DTA curve are observed and resolved that correspond to the initial formation of magnesium titanate (MgTi2 O5 ) and the later formation of mica. The activation energy for precipitation of each crystalline phase has been evaluated, and the crystallization mechanism has been studied. The results indicate that the growth of mica is a two-dimensional process, controlled by the crystal-glass interface reaction. The average calculated values of activation energies are 256 ± 11 kJ/mol and 275 ± 6 kJ/mol for the precipitation of MgTi2 O5 and mica from the glass matrix, respectively. 相似文献
5.
A complete solid-solution series exists between diopside (CaMgSi2 O6 ) and its nickel analogue, "niopside"(CaNiSi2 O6 ). Activity–composition relations within this solid solution, and the stability of the end member CaNiSi2 O6 , have been determined by equilibrating CaNiSi2 O6 with SiO2 , CaSiO3 , and metallic Ni in atmospheres of known oxygen pressures. Within limits of accuracy of the experiments, the solution is ideal at 1350°C. From the experimental data obtained in the present investigation, the standard free energy (Δ G °) of formation of CaNiSi2 O6 according to the equation CaO + NiO + 2SiO2 = CaNiSi2 O6 is calculated to be Δ G °=−165862 + 42.40 T J. Experiments in the system CaO–NiO–SiO2 have shown that the nickel analogue of the phase pseudo-enstatite (MgSiO3 ) is unstable with respect to SiO2 and nickel olivine (Ni2 SiO4 ), and the nickel analogues of the phases akermanite (Ca2 MgSi2 O7 ) and monticellite (CaMgSiO4 ) are unstable relative to the phase assemblage pseudo-wollastonite (CaSiO3 ) plus NiO. In the system CaO–MgO–NiO–SiO2 , however, substitution of Ni for Mg in these phases was observed. The percentage substitution of Ni for Mg in the phases is given in parentheses: diopside (100%), olivine (100%), enstatite (18%), akermanite (20%), and monticellite (57%). 相似文献
6.
CESARE BRlSl 《Journal of the American Ceramic Society》1957,40(5):174-178
Cuspidine is a well-defined ternary compound with a stability field in the subsystem CaF2 –CaSiO3 –Ca2 SiO4 . Cuspidine is easily formed by solid-state reactions in the subsystem mentioned and is stable above its apparently congruent fusion point if heated in welded platinum containers. Above 1450° decomposition and the formation of a mixture of CaF2 and Ca2 SiO4 is observed. Cuspidine also is easily formed by secondary reactions in solid mixtures of the subsystem CaF2 –CaSiO3 and in ternary mixtures of these with free SiO2 if heated in open crucibles. The existence of double compounds of CaF2 and CaSiO3 is not confirmed. 相似文献
7.
Nakshatra B. Singh Awadhesh K. Singh Shashi Prabha Singh 《Journal of the American Ceramic Society》1990,73(10):3063-3068
Hydration occurring in the system Ca3 Al2 O6 –CaSO4 · 2H2 O–Ca(OH)2 –H2 O has been studied at different temperatures and it was found that the reactions are diffusion controlled. The kinetic data obeyed Jander's equation and the rate of reaction increased with increasing temperature. X-ray diffraction studies and calorimetric measurements show that when gypsum is consumed, ettringite is converted into monosulfate. The rate of this conversion also increased with the increasing temperature and decreased in the presence of citric acid. Spectroscopic studies showed that there was some interaction between citric acid and the cement and that the product of hydration is of colloidal nature. Zeta potential measurements show that retardation of Ca3 Al2 O6 hydration in the presence of gypsum and Ca(OH)2 is not due to SO2− 4 adsorption. Electrical conductivity and thermoelectric potential measurements of solid Ca3 Al2 O6 show that Ca3 Al2 O6 is an n -type semiconductor and contains defects. The retardation of Ca3 Al2 O6 may be due to poisoning of reaction sites by gypsum and Ca(OH)2. 相似文献
8.
Simple expressions of activities, as functions of composition, were developed from structural models for some borosilicate melts. Their applicability was tested with data from the liquidus curves of phase diagrams. If the heat of fusion is known, a value of the activity-composition function can be calculated for each temperature of the liquidus curve. These values are compared with activities computed from the structural model. Calorimetric heats of fusion were available for the calcium borates studied. Experimental data from published phase diagrams for the systems Ca3 (BO3 )2 –Ca2 SiO4 , Ca2 B2 O6 –Ca2 SiO4 , Ca3 (BO3 )2 –CaSiO3 , Ca(BO2 )–CaSiO3 , Ca2 B2 O5 –CaSiO3 , CaSiO3 –BaSiO3 , and CaSiO3 –K2 SiO3 were used. Simple ionic models seemed to be applicable in most cases, except for melts of highly polymerized mixed ions (metaborate-metasilicate), for which the so-called "group" model appeared to be useful. A value for the heat of fusion of CaSiO3 was calculated from this work (13,200 cal. per mole). 相似文献
9.
The kinetics of crystallization of Li2 Si2 O5 from glasses in the Li2 O-SiO2 system were studied using quantitative X-ray diffraction. Analysis of the data using the Johnson-Mehl-Avrami equation showed that crystallization occurred through the nucleation and growth of rods. The spherulitic nature of the crystals was substantiated by petrographic examinations of the partially crystalline glass. Analysis of the temperature dependence of the crystallization rate using a modification of the Johnson-Mehl-Avrami equation showed that the activation energy for nucleation was a function of composition and thermal treatment. 相似文献
10.
Results are presented of a study in air of mixtures in the system CaO-Cr2 O3 -SiO2 . The phase equilibrium diagram shows relations at liquidus temperatures for all but the high-lime part of the system. In this omitted part chromium in the mixtures oxidizes in air to higher valence forms. The compound Ca3 Cr2 Si3 O12 (uvarovite) occurs at subsolidus temperatures, decomposing at 1370°C. to α-CaSiO3 and Cr2 O3 . The inhibiting action of chromium oxide on the inversion of high-temperature forms of Ca2 SiO4 to the low-temperature γ-Ca2 SiO4 is discussed in the light of new data. Evidence is presented for the existence of a pentavalent chromium compound, Ca3 (CrO4 )2 , having solid-solution relations with Ca3 SiO4 . 相似文献
11.
Ching-Tai Cheng Michael Lanagan Beth Jones Jiang-Tsair Lin Ming-Jen Pan 《Journal of the American Ceramic Society》2005,88(11):3037-3042
The nucleation and crystallization kinetics of PbO–BaO–SrO–Nb2 O5 –B2 O3 –SiO2 -based glass–ceramics have been investigated. Strontium barium niobate (Sr0.33 Ba0.67 Nb2 O6 ) with a tetragonal tungsten–bronze structure formed as the major crystalline phase, which nucleates and grows on the surface region of samples. The results of the present study showed an apparent activation energy of 193 kJ/mol for nucleation, which was controlled by the viscous flow of the glass. Quantitative X-ray analysis and differential thermal analysis showed that the rate-limiting mechanism of crystallization appeared to be a three-dimensional interfacial growth, which has an apparent activation energy of 386–430 kJ/mol, a value that is close to the dissociation of Si–O bonds in the glass system. 相似文献
12.
Arnaud Quintas Odile Majérus Daniel Caurant Jean-Luc Dussossoy Philippe Vermaut 《Journal of the American Ceramic Society》2007,90(3):712-719
The effect of varying R =[CaO]/([CaO]+[Na2 O]) ratio on the crystallization of a rare earth-rich aluminoborosilicate glass (16 wt% RE2 O3 , RE=Nd or La) is investigated. The crystallization of a silicate apatite with Ca2+ x RE8− x (SiO4 )6 O2−0.5 x composition ( x ≈0.4–0.7), is responsible for a drop of the rare earth solubility in the melt. When successive nucleation and growth stages are performed, crystallization processes change across the glass series as a consequence of glass-in-glass phase separation. An exotic phase of composition close to Ca10 Nd7 Si20.75 O62 grows at the expense of silicate apatite. 相似文献
13.
Jau-Ho Jean Yu-Ching Fang Steve X. Dai David L. Wilcox Sr. 《Journal of the American Ceramic Society》2001,84(6):1354-1360
The devitrification kinetics and mechanism of a low-dielectric, low-temperature, cofirable K2 O–CaO–SrO–BaO–B2 O3 –SiO2 glass-ceramic have been investigated. Crystalline phases including cristobalite (SiO2 ) and pseudowollastonite ((Ca,Ba,Sr) SiO3 ) are formed during firing. Activation energy analysis shows that the nucleation of the crystalline phases is controlled by phase separation of the glass. The crystallization kinetics of both cristobalite and pseudowollastonite obey Avrami-like behavior, and the results show an apparent activation energy close to that of the diffusion of alkaline and alkali ions in the glass, suggesting that diffusion is rate limiting. The above conclusion is further supported by analysis of measured growth rates. 相似文献
14.
Yusuke Kaminaga Hisanori Yamane Takahiro Yamada 《Journal of the American Ceramic Society》2007,90(6):1917-1920
Compounds in a CaO–Y2 O3 –SnO2 system were prepared by a solid-state reaction at 1673 K. The phase relation in this system was investigated by powder X-ray diffraction. Besides the previously reported ternary compounds, CaSnO3 , Ca2 SnO4 , Y2 Sn2 O7 , and a quaternary compound Ca0.4 Y1.2 Sn0.4 O3 , solid-solution series of Ca2− x Y2 x Sn1− x O4 with 0≤ x ≤0.5, and Ca1− y Y2 y Sn1− y O3 with 0≤ y ≤0.2 and 0.95≤ y ≤1.0 were found. The cell parameters of these solid-solution series were refined. The changes of rhombohedral cell parameters in the samples prepared in the range 0.565< y <0.714 of Ca1− y Y2 y Sn1− y O3 suggested the existence of solid solutions of Ca0.4 Y1.2 Sn0.4 O3 , although their single phases could not be prepared, except at y =0.6. 相似文献
15.
Yuheng Liu Yuanhua Lin Zhan Shi Ce-Wen Nan Zhijian Shen 《Journal of the American Ceramic Society》2005,88(5):1337-1340
The precursor powders of Ca3 Co4 O9 were synthesized by a sol–gel method. The results of X-ray diffraction and thermogravimetric and differential thermal analyses patterns indicate that pure Ca3 Co4 O9 powders could be obtained by calcining the precursor at 800°C for 2 h. High dense Ca3 Co4 O9 ceramic samples (∼99% of theoretical density) were prepared by the spark plasma sintering (SPS) method. Compared with the conventional sintering (CS), the SPS samples exhibit much higher electrical conductivity and power factor which are respectively about 118 S/cm and 3.51 × 10−4 W·(m·K2 )−1 . The SPS method is greatly effective for improving the thermoelectric properties of Ca3 Co4 O9 oxide ceramics. 相似文献
16.
Cristina Siligardi Luca Lusvarghi Monia Montorsi Cecilia Vernia 《Journal of the American Ceramic Society》2008,91(3):990-995
In this work several complementary techniques have been employed to carefully characterize the sintering and crystallization behavior of CaO–Al2 O3 –ZrO2 –SiO2 glass powder compacts after different heat treatments. The research started from a new base glass 33.69 CaO–1.00 Al2 O3 –7.68 ZrO2 –55.43SiO2 (mol%) to which 5 and 10 mol% Al2 O3 were added. The glasses with higher amounts of alumina sintered at higher temperatures (953°C [lower amount] vs. 987°C [higher amount]). A combination of the linear shrinkage and viscosity data allowed to easily find the viscosity values corresponding to the beginning and the end of the sintering process. Anorthite and wollastonite crystals formed in the sintered samples, especially at lower temperatures. At higher temperatures, a new crystalline phase containing ZrO2 (2CaO·4SiO2 ·ZrO2 ) appeared in all studied specimens. 相似文献
17.
Yuan Chang Guo Hua Kun Liu Shi Xue Dou 《Journal of the American Ceramic Society》2000,83(7):1675-1680
(Bi,Pb)2 Sr2 Ca2 Cu3 O10 (Bi2223) precursor powders with large and small amounts of Ca2 PbO4 phase were prepared and used to make superconductor/silver composite tapes. The melting behavior of the powders and tapes was examined by differential thermal analysis (DTA). The influence of Ca2 PbO4 on the formation and microstructure of Bi2223, and electrical properties of the tapes, was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and critical current measurements. It was found that the melting onset temperature ( T m,onset ) of precursor powders and composite tapes was strongly dependent on the amount of Ca2 PbO4 . Tapes with a small amount of Ca2 PbO4 had a higher T m,onset and a higher optimum sintering temperature compared with tapes with a large amount of Ca2 PbO4 . Also because of the higher sintering temperature, the total sintering time required for the former tapes was drastically shortened compared with the latter ones (250 vs 110 h). Furthermore, the microstructure and the current-carrying capacity of the tapes were significantly improved by reducing the Ca2 PbO4 content of the precursor powders. These results are of practical significance for the commercialization of Bi-based high-temperature superconductors. 相似文献
18.
Sintering, crystallization, microstructure, and thermal expansion of Li2 O·Al2 O3 ·4SiO2 glass-ceramics doped with B2 O3 , P2 O5 , or (B2 O3 + P2 O5 ) have been investigated. On heating the glass powder compacts, the glassy phase first crystallized into high-quartz s.s., which transformed into β-spodumene after the crystallization process was essentially complete. The effects of dopants on the crystallization of glass to high-quartz s.s. and the subsequent transformation of high-quartz s.s. to β-spodumene were discussed. The major densification occurred only in the early stage of sintering time due to the rapid crystallization. All dopants were found to promote the densification of the glass powders. The effect of doping on the densification can fairly well be explained by the crystallization tendency. All samples heated to 950°C exhibited a negative coefficient of thermal expansion ranging from about −4.7 × 10-6 to −0.1 × 10-6 K-1 . Codoping of B2 O3 and P2 O5 resulted in the highest densification and an extremely low coefficient of thermal expansion. 相似文献
19.
Koichiro Fukuda Ken-ichi Matsunaga Takahiro Bessho Hideto Yoshida 《Journal of the American Ceramic Society》2005,88(4):954-962
The phase stability in part of the P2 O5 -bearing pseudoquaternary system CaO–SiO2 –Al2 O3 –Fe2 O3 has been studied by electron probe microanalysis, optical microscopy, and powder X-ray diffractometry. At 1973–1653 K, the α-Ca2 SiO4 solid solution [α-C2 S(ss)] and melt coexisted in equilibrium, both chemical variations of which were determined as a function of temperature. The three phases of melt, calcium aluminoferrite solid solution (ferrite), and C2 S(ss) coexisted at 1673–1598 K. On the basis of the chemical compositions of these phases, a melt-differentiation mechanism has been, for the first time, suggested to account for the crystallization behavior of Ca3 Al2 O6 solid solution [C3 A(ss)]. When the α-C2 S(ss) and melt were cooled from high temperatures, the melt would be induced to differentiate by the crystallization of ferrite. Because the local equilibrium would be continually attained between the rims of the precipitating ferrite and coexisting melt during further cooling, the melt would progressively become enriched in Al2 O3 with respect to Fe2 O3 . The resulting ferrite crystals would show the zonal structure, with the Al/(Al+Fe) value steadily increasing up to 0.7 from the cores toward the rims. The C3 A(ss) would eventually crystallize out of the differentiated melt between the zoned ferrite crystals in contact with their rims. 相似文献
20.
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