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1.
Koichiro Fukuda Iwao Maki Kazuhiro Toyoda Suketoshi Ito 《Journal of the American Ceramic Society》1993,76(7):1821-1824
The α-to-α'H transition of Ca2 SiO4 solid solutions (C2 S(ss)) is a nucleation and growth process. This process was shown on time–temperature–transformation (TTT) diagrams for C2 S(ss) with different concentrations of foreign oxides (Na2 O, Al2 O3 , and Fe2 O3 ). The kinetic cutoff temperature and the activation energy for growth of the α'H phase increase steadily with increasing concentration of impurities. The activation energy for nucleation also increases above 950°C. The α'H phase, which exists in equilibrium with the α phase at 1280°C, is formed at a maximum rate at around 1100°C regardless of the chemical composition. The TTT diagrams enable us to predict, as a function of cooling rate, the phase constitution of C2 S(ss) at ambient temperature. 相似文献
2.
Marie-Noëlle de Noirfontaine Sandrine Tusseau-Nenez Marcel Signes-Frehel Gilles Gasecki Caroline Girod-Labianca 《Journal of the American Ceramic Society》2009,92(10):2337-2344
Alite is the major compound of anhydrous Portland cement: it is composed of tricalcium silicate Ca3 SiO5 (C3 S) modified in composition and crystal structure by ionic substitutions. Alite is also the main hydraulic phase of cement and the most important for subsequent strength development. Using raw meals (rich in Ca3 P2 O8 ) as alternative fuels in cement plants raises the question about the effect of phosphorus on C3 S and its consequences on reactivity with water. This paper deals with a systematic study of C3 S triclinic T1 polymorph doped with P2 O5 in the range 0–0.9 wt%. All the samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and electron-microprobe analysis. The appearance of a phase rich in phosphorus is shown. It displays a structure derivative of the α'H –Ca2 SiO4 polymorph, noted α'H –C2 S(P). As phosphorus content increases, C3 S is more and more decomposed into free lime and α'H –C2 S(P). The α'H phase was detected from 0.1 wt% P2 O5 and located at the interfaces of C3 S grains. Two identification keys are proposed in order to highlight the α'H –C2 S(P) phase: the XRD angular window at 2θCu =32.8°–33.2° and a smooth aspect on SEM micrographs. 相似文献
3.
Koichiro Fukuda Iwao Maki Keisuke Adachi 《Journal of the American Ceramic Society》1992,75(4):884-888
A series of Ba-bearing Ca2 SiO4 solid solutions (C2 S( ss )), (Ba x Ca1− x )2 SiO4 with 0.075 x 0.30, were prepared and examined by X-ray and electron beam diffraction. They are all made up of orthorhombic domains 120° different in orientation around the common c axis of the former α phase. The C2 S solid solution with x = 0.075 shows a superstructure incommensurate along the a axis with λ (modulation wavelength) = 3.5 and commensurate along the c axis with Δ= 3. With x = 0.15, modulation is observed only along the a axis and Δ= 3.4. No evidence of superstructure is found with x = 0.24; the space group and cell dimensions are comparable with those of pure α 'H -C2 S. The C2 S( ss ) with x = 0.30 gives a superlattice with the cell-edge length of 3 b . All the C2 S( ss ), when reheated at 1000°C for 24 h, produced lamellae of the trigonal phase T nearly in parallel with (001) of the host α 'L phase. The crystallographic orientation between the two phases is
This indicates that the above Ba-bearing C2 S( ss ) phases occur as precursors to the thermodynamically more stable two-phase mixtures. 相似文献
This indicates that the above Ba-bearing C
4.
New data obtained on the join Ca2 SiO4 -CaMgSiO4 established a limit of crystalline solubility of Mg in α-Ca2 SiO4 corresponding to the composition Ca1.90 Mg0.10 SiO4 at 1575°C. The α-α'Ca2 SiO4 inversion temperature is lowered from 1447° to 1400°C by Mg substitution in the lattice. α'-Ca2 SiO4 takes Mg into its lattice up to the composition Ca1.94 Mg0.06 SiO4 at 1400°C and to Ca1.96 Mg0.04 SiO4 at 900°C. A new phase (T) reported previously by Gutt, with the approximate composition Ca1.70 Mg0.30 SiO4 , was stable between 979° and 1381°C, and should be stable at liquidus temperatures in multicomponent systems involving CaO–MgO–SiO2 . 相似文献
5.
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
6.
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
7.
The liquidus-solidus relations along the join Ca2 SiO4 -Ca(OH), in the system CaO-SiO2 -H2 O have been determined at 1000 atm up to 1110°C. This join is binary and contains the calcium silicate hydrate, calciochondrodite, Ca5-(SiO4 (OH)2 . Calciochondrodite melts incongruently to Ca2 SiO2 + liquid (composition 23 wt% Ca2 Si04 ) at 955°C. The eutectic between calcium hydroxide and calciochondrodite lies at 13% Ca2 Si04 and 822°C. Preliminary experiments, also at 1000 atm, in the ternary system CaO-Ca2 Si04 -Ca(OH), indicate that the eutectic at which the fields of primary Ca(OH)2 , CaO, and Ca2 (Si04 )2 (OH)2 meet is close to the CaO-Ca. (OH), side of the triangle at approximately 805° C. The ternary reaction point Ca2 SiOl + liquid ⇌Ca5 (SiO4 )2 (OH)2 + CaO + liquid is believed to lie in the low-CaO (<5%) high-Ca(OH)2 (>70%) part of the system. 相似文献
8.
Koichiro Fukuda Iwao Maki Susumu Ikeda Suketoshi Ito 《Journal of the American Ceramic Society》1993,76(11):2942-2944
When they are cooled below the stable temperature region of the α phase, crystals of belite (Ca2 SiO4 solid solutions) inverted to the α'H phase without a change in chemical composition and gave six sets of lamellae within the crystals. After this transition remelting reaction occurred within the inverted α'H -phase grains, the liquid phase became nucleated and grew heterogeneously on the lamellae boundaries, resulting in a decrease in impurity concentration in the host α'H phase. When the exsolved liquid wetted the lamellae, complete dissolution of the parent crystals occurred during slow cooling. A variety of microtextures resulted, depending on both quenching temperature and cooling rate. 相似文献
9.
Mary W. Barnes Maria Klimkiewicz Paul W. Brown 《Journal of the American Ceramic Society》1992,75(6):1423-1429
Compositions along the Ca2 SiO4 –Ca3 (PO4 )2 join were hydrated at 90°C. Mixtures containing 15, 38, 50, 80, and 100 mol% Ca3 (PO4 )2 were fired at 1500°C, forming nagelschmidtite + a 1 -CaSiO4 , A -phase and silicocarnotite and a -Ca3 (PO4 )2 , respectively. Hydration of these produces hydroxylapatite regardless of composition. Calcium silicate hydrate gel is produced when Ca2 SiO4 ≠ 0 and portlandite when Ca2 SiO4 is >50%. Relative hydration reactivities are a -Ca3 (PO4 )2 > nagelschmidtite > α 1 -Ca2 SiO4 > A -phase > silicocarnotite. Hydration in the presence of silica or lime influences the amount of portlandite produced. Hydration in NaOH solution produces 14-A tobermorite rather than calcium silicate hydrate gel. 相似文献
10.
IRVIN C. HUSEBY† HANS L. LUKAS GÜNTER PETZOW 《Journal of the American Ceramic Society》1975,58(9-10):377-380
The 1780°C isothermal section of the reciprocal quasiternary system Si3 N4 -SiO2 -BeO-Be3 N2 was investigated by the X-ray analysis of hot-pressed samples. The equilibrium relations shown involve previously known compounds and 8 newly found compounds: Be6 Si3 N8 , Be11 Si5 N14 , Be5 Si2 N6 , Be9 Si3 N10 , Be8 SiO4 N4 , Be6 O3 N2 , Be8 O5 N2 , and Be9 O6 N2 . Large solid solubility occurs in β-Si3 N4 , BeSiN2 , Be9 Si3 N10 , Be4 SiN4 , and β-Be3 N2 . Solid solubility in β-Si3 N4 extends toward Be2 SiO4 and decreases with increasing temperature from 19 mol% at 1770°C to 11.5 mol% Be2 SiO4 at 1880°C. A 4-phase isotherm, liquid +β-Si3 N4 ( ss )Si2 ON2 + BeO, exists at 1770°C. 相似文献
11.
The reciprocal salt pair Sr2 SiO4 -Sr2 GeO4 -Ba2 GeO4 -Ba2 SiO4 was investigated using X-ray powder diffraction and DTA. Unlimited solubility in the low-K2 SO4 structure type (α') occurs throughout the system above 85°C. The nonlinear changes of some lattice constants of the solid solutions are discussed. A stable monoclinic low-temperature (β) form of Sr2 SiO4 was found which converts reversibly to the high-temperature α'-modification at 85°C. The enthalpy of the β-α' transition is 51 cal/mol. In the reciprocal salt pair the β-form solid solutions occur in a very narrow region below 85°C. 相似文献
12.
Koichiro Fukuda Iwao Maki Suketoshi Ito 《Journal of the American Ceramic Society》1996,79(11):2969-2970
A series of Sr-bearing Ca2 SiO4 solid solutions (C2 S( ss )), (Sr x Ca1−x )2 SiO4 with 0 ≤ x ≤ 0.12, was prepared. They were examined by high-temperature powder X-ray diffractome-try to determine the start and finish temperatures of the α'L -to-β and β-to-α'L martensitic transformations. The thermal hysteresis was positive with x < 0.045, nearly equal to zero at x = 0.045, and negative with x > 0.045. The zero and negative hysteresis were consistent with the thermoelasticity of the transformations. With increasing x from 0.02 to 0.08, the hysteresis decreased steadily from positive to negative, suggesting a continuous increment in the stored elastic energy. 相似文献
13.
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
14.
Thommy Ekström Harald Herbertsson Matthew James Ian Fleck 《Journal of the American Ceramic Society》1994,77(12):3087-3092
β-sialon and Nd2 O3 -doped α-sialon materials of varying composition were prepared by sintering at 1775° and 1825°C and by glass-encapsulated hot isostatic pressing at 1700°C. Composites were also prepared by adding 2–20 wt% ZrO2 (3 mol% Nd2 O3 ) or 2–20 wt% ZrN to the β-sialon and α-sialon matrix, respectively. Neodymium was found to be a fairly poor α-sialon stabilizer even within the α-phase solid solution area, and addition of ZrN further inhibited the formation of the α-sialon phase. A decrease in Vickers hardness and an increase in toughness with increasing content of ZrO2 (Nd2 O3 ) or ZrN were seen in both the HIPed β-sialon/ZrO2 (Nd2 O3 ) composites and the HIPed Nd2 O3 -stabiIized α-sialons with ZrN additions. 相似文献
15.
The system Ba2 SiO4 -Ca2 SiO4 was studied by heating mixtures of Ba2 SiO4 and Ca2 SiO4 at 1723 K. Six distinct phases resulted; they were examined by both X-ray diffraction and differential thermal analysis. The phases β -(Ba0.05 Ca1.95 )SiO4 and α-(Ba0.15 Ca1.85 )SiO4 are isostructural with corresponding high-temperature modifications of Ca2 SiO4 . The X phase (Ba0.48 Ca1.52 SiO4 ) is orthorhombic, is a pure phase rather than a solid solution, and is defined for the first time in the present work. The T phase (Ba1.31 Ca0.69 SiO4 ) is hexagonal and interpreted in terms of a unit cell with a doubled c parameter, in contrast with literature data. 相似文献
16.
Sung-Woo Choi Seong-Hyeon Hong Young Jin Kim 《Journal of the American Ceramic Society》2009,92(9):2025-2028
The green emitting Ca2 SiO4 :Eu2+ (C2 S:Eu) phosphors were synthesized by the polymeric precursor process (Pechini-type), and the effects of calcination temperature and europium (Eu) doping concentration on the luminescent properties were investigated. The crystalline β-C2 S was obtained in the calcination temperature of 1100°–1400°C, and Eu was reduced into Eu2+ by annealing in 5% H2 /N2 atmosphere. The obtained C2 S:Eu2+ phosphors exhibited a strong emission at 504 nm under the excitation of λexc =350 nm. The highest photoluminescence (PL) intensity was observed in the C2 S:Eu2+ phosphors either calcined at 1300°C or doped with 3 mol% Eu. The obtained PL properties were discussed in terms of crystal structure, particle size and shape, surface roughness, and effect of concentration quenching. 相似文献
17.
Crystals of Ca2 SiO4 doped with K, P, Al, and Fe were grown and examined by means of both X-ray and electronbeam diffraction. They are made up of domains 120° different in orientation around the c axis of the previous α phase. Each of the domains gives an orthorhombic superstructure whose cell is incommensurate with the underlying orthorhombic subcell with a=0.540, b=0.936, and c=0.681 nm. This orthorhombic phase, characterized by the cell edge length of 3.8a, is termed 3.8aC2 S(ss). Both the domain and the incommensurate structure strongly suggest that this is the precursor to a phase thermodynamically more advantageous at lower temperatures. 相似文献
18.
The phase relations in the systems MgO-Y2 O3 -ZrO2 and CaO-MgO-ZrO2 were established at 1220° and 1420°C. The system MgO-Y2 O3 -ZrO2 possesses a much-larger cubic ZrO2 solid solution phase field than the system CaO-MgO-ZrO2 at both temperatures. The ordered δ phase (Zr3 Y4 O12 ) was found to be stable in the system ZrO2 -Y2 O3 at 1220°C. Two ordered phases φ1 (CaZr4 O9 ) and φ2 (Ca6 Zr19 O44 ) were stable at 1220°C in the system ZrO2 -CaO. At 1420°C no ordered phase appears in either system, in agreement with the previously determined temperature limits of the stability for the δ, φ1 , and φ2 phases. The existence of the compound Mg3 Yz O6 could not be confirmed. 相似文献
19.
F. P. GLASSER 《Journal of the American Ceramic Society》1962,45(5):242-249
Phase equilibrium data resulting from quenching experiments are presented for the ternary system CaO-MnO-SiO2 . An atmosphere of controlled oxygen pressure having Po2 , ≅ 10−6 atm at 1555°C was used to maintain the manganese in the divalent state. The ternary liquidus surface is largely one of low-lying liquidus temperatures. Three ternary liquidus minima dominate this surface. These have the following compositions (in weight percent CaO, MnO, and SiO2 ): (a) 5.0, 48.4, and 46.6%, (b) 17.5, 45.0, and 37.5%, and (c) 15.0, 53.0, and 32.0%. Temperatures measured at these points are (a) 1265° C, (b) 1195°C, and (c) 1204°C. Isofracts of the quenched glasses are presented. Crystallization paths of ternary mixtures are represented by a series of fractionation curves and selected isothermal planes. Partition of manganese between coexisting pairs of crystalline phases (e.g., meta-silicate, olivine, and (Ca,Mn)O solid solutions) favors concentration of manganese in the more basic phase. Subsolidus equilibria involving these phases and also Ca3 Si2 O7 and Ca3 SiO5 are discussed. Ca3 Si2 O7 and Ca3 SiO6 do not admit any appreciable amounts of Mn++ into their lattices. 相似文献
20.
Jin-Seong Kim Ngoc-Huan Nguyen Myung-Eun Song Jong-Bong Lim Dong-Soo Paik Sahn Nahm Jong-Hoo Paik Byung-Hyun Choi Soon-Jae Yu 《International Journal of Applied Ceramic Technology》2009,6(5):581-586
Bi2 O3 was added to a nominal composition of Zn1.8 SiO3.8 (ZS) ceramics to decrease their sintering temperature. When the Bi2 O3 content was <8.0 mol%, a porous microstructure with Bi4 (SiO4 )3 and SiO2 second phases was developed in the specimen sintered at 885°C. However, when the Bi2 O3 content exceeded 8.0 mol%, a liquid phase, which formed during sintering at temperatures below 900°C, assisted the densification of the ZS ceramics. Good microwave dielectric properties of Q × f =12,600 GHz, ɛr =7.6, and τf =−22 ppm/°C were obtained from the specimen with 8.0 mol% Bi2 O3 sintered at 885°C for 2 h. 相似文献