共查询到20条相似文献,搜索用时 31 毫秒
1.
Solid-state reactions between Li2 O and Al2 O3 were studied in the region between Li2 O.Al2 O 3 and Al2 O 3 . The compound Li2 O Al2 O 3 melts at 1610°± 15°C. and undergoes a rapid reversible inversion between 1200° and 1300°C. Vaporization of Li2 O from compositions in the system proceeds at an appreciable rate at 1400°C, as shown by fluorescence. Lithium spinel, Li2 O -5Al2 O3 , was the only other compound observed. The effect of Li2 O on the sintering of alumina was investigated. 相似文献
2.
Tentative phase relations in the binary system BnOa-A12 O3 are presented as a prerequisite to the understanding of the system Li2 O-B2 O3 -Al2 O3 . Two binary compounds, 2A12 O3 .B2 O3 and 9A12 O3 .-2B2 O3 , melted incongruently at 1030° f 7°C and about 144°C, respectively. Two ternary compounds were isolated, 2Li2 O.A12 O3 .B2 O3 and 2Li2 O. 2AI2 O3 . 3B2 03 . The 2:1:1 compound gave a melting reaction by differential thermal analysis at 870°± 20° C, but the exact nature of the melting behavior was not determined. The 2:2:-3 compound melted at 790°± 20° C to Liz O.-5Al2 O3 and liquid. X-ray diffraction data for the compounds are presented and compatibility triangles are shown. 相似文献
3.
Nine compositions containing 40 to 68% B2 O3 were used to study the high-lithia portion of the system Li2 O-B2 O3 by quenching and differential thermal analysis methods. The compounds 3Li2 O 2B2 O3 and 3Li2 O B2 O3 melted incongruently at 700°± 6°C, and 715°± 15°C., respectively. The compound 2Li2 O B2 O3 is assumed to dissociate slightly below 650°± 15° C., although the data could also be interpreted as in-congruent melting. Below 600°± 6°C. it does dissociate to the 3:2 and 3:1 compounds. In this narrow temperature interval the 2:1 compound had an inversion at 618°± 6°C. Both forms of the 2:1 compound could be quenched to room temperature. X-ray diffraction data for the compounds are tabulated, and the complete phase diagram for the system Li2 O-B2 O3 is presented. 相似文献
4.
Data on compatibility triangles and liquid immiscibility are presented for the portion of the ternary system bounded by SiO2 , Li2 O, SiO2 , Li0 O TiO2 , and TiO2 . X-ray data showed the ternary compound Li2 O. TiO2 . SiO2 to be tetragonal with a = 6.41 a.u. and C = 4.40 a.u. The compound is uniaxial negative with 1.81 < < 1.82 and 1.83 < < 1.84. It melted to two liquids at 1207° 3°C. Seven joins were established by solid-state, fusion, and quenching methods. Using electron microscopy and petrographic microscope and quenching data, liquid immiscibility originating in the binary system SiO2 -TiO2 was shown to extend over a substantial portion of the ternary system. 相似文献
5.
A liquid phase in the Al2 O3 -1 mol% TiO2 -0.5 mol% NaO1/2 composition is confirmed at ±1300°C by an electrical conductivity measurement. The ease of the method led to a study of the Al2 O3 -2 mol% CuO-2 mol% TiO2 system and to the geologically important detection of eutectics (peritectics) in rock materials. 相似文献
6.
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
7.
This paper reports processing of lithium ion-conducting, composite membranes comprised of 14Li2 O·9Al2 O3 ·38 TiO2 ·39P2 O5 glass–ceramic and polyethylene. The processing involved tape casting of 14Li2 O·9Al2 O3 ·38TiO2 ·39P2 O5 glass powder with organic additives into tapes, subjecting the green tape to binder burnout and thermal soaking in the temperature range of 950°–1100°C, and finally infiltrating the porous tape with polyethylene solution. The ionic conductivity and microstructure of 150–350 μm thick membranes were characterized and are discussed in this paper. The crystallites of the glass–ceramic show liquid-like conductivity at ambient temperature, whereas the grain boundary conductivity is lower by a factor of five. The lower grain boundary conductivity is explained on the basis of crystallographic mismatch and the existence of AlPO4 at the grain boundary. The polyethylene infiltration in the porous membrane improved mechanical resilience with a minor adverse effect on conductivity. 相似文献
8.
Yangyang Ji Jingkui Liang Zhan Chen Sishen Xie 《Journal of the American Ceramic Society》1991,74(2):444-446
The phase relations at a temperature below "subsolidus" in the system Al2 O3 –B2 O3 –Nd2 O3 are reported. Specimens were prepared from various compositions of Al2 O3 , B2 O3 , and Nd2 O3 of purity 99.5%, 99.99%, and 99.9%, respectively, and fired at 1100°C. There are six binary compounds and one ternary compound in this system. The ternary compound, NdAl3 (BO3 )4 (NAB), has a phase transition at 950°C ± 15°C. The high-temperature form of NAB has a second harmonic generation (SHG) efficiency of KH2 PO4 (KDP) of the order of magnitude of the form which has been used as a good self-activated laser material, and the low-temperature form of NAB has no SHG efficiency. 相似文献
9.
In the system TiO2 —Al2 O3 , TiO2 (anatase, tetragonal) solid solutions crystallize at low temperatures (with up to ∼ 22 mol% Al2 O3 ) from amorphous materials prepared by the simultaneous hydrolysis of titanium and aluminum alkoxides. The lattice parameter a is relatively constant regardless of composition, whereas parameter c decreases linearly with increasing Al2 O3 . At higher temperatures, anatase solid solutions transform into TiO2 (rutile) with the formation of α-Al2 O3 . Powder characterization is studied. Pure anatase crystallizes at 220° to 360°C, and the anatase-to-rutile phase transformation occurs at 770° to 850°C. 相似文献
10.
Phase equilibrium relations in the system Li2 O-GeO2 were determined using standard quenching techniques. In contrast to published literature five congruently melting compounds were found to exist. They are Li2 O·7GeO2 , 3Li2 O O·8GeO2 , Li2 O O·GeO2 , 3Li2 O O·2GeO2 , and 2Li2 O.-GeO2 . The melting points, respectively, are 1033°± 5°C, 953°± 5°C, 1245°± 15°C, 1125°± 15°C, and 1280°± 15°C. Simple binary eutectic relations exist among the compounds. The eutectic temperature between 1:7 and GeO2 is 1025°± 1h0°C at about 96.8 wt% GeO2 ; the eutectic temperature between the 1:7 and 3:8 compounds is 935°± 10°C at about 90.9 wt% GeO2 ; the eutectic temperature between the 3:8 and 1:1 compounds is 930°± 10 °C at about 89.8 wt% GeO2 . Liquidus data for compositions richer in lithia than the 1:1 compound are only approximate because of the difficulty of quenching them; the phase relations between the 1:1 and 3:2 and between the 3:2 and 2:l compounds, however, are found to be of the simple binary eutectic type. The glass–forming region was also determined. Melts allowed to cool in air crystallized. When, however, the melts were quenched, glasses containing as much as 8 wt% GeO2 could be prepared in 5–g quantities. Both the refractive index–composition and density–composition curves for the glasses showed maxi–mums at about 6 to 8 wt% Li2 O. 相似文献
11.
The Li2 O-TiO2 pseudobinary phase diagram was determined from 50 to 100 mol% TiO2 by DTA, microscopy, and X-ray analysis; Li2 Ti3 O7 effectively melts congruently at 1300° and decomposes eutectoidally at 940°C. A solid solution based on Li2 TlO3 from 50 to ∼65 mol% TiO3 was observed to exist at >930°C. A new metastable phase was discovered with a composition of ∼75 mol% TiO2 and with a hexagonal unit cell (8.78 by 69.86 × 10−1 nm). Discrepancies in the literature regarding some of these phase equilibria are reconciled. 相似文献
12.
The UO2 –Al2 O3 phase equilibrium system was found to contain no new compounds or solid solutions. Uranium dioxide melted at 2878°± 22°C. and Al2 O3 melted at 2034°± 16°C. The eutectic temperature was approximately 1930°C. There is an indication that two immiscible liquids formed above the eutectic temperature between 53 and 74 mole % Al2 O3 . 相似文献
13.
The system TiO2 -P2 O5 was investigated in the compositional range TiO2 .P2 O5 to 100% TiO2 . Two compounds exist, TiO2 .P2 O5 and 5TiO2 .-2P2 O5 . TiO2 .P2 O5 begins to lose P2 O5 at 1400°C. and both fusion and vaporization proceed rapidly at 1500°C. 5TiO2 .2P2 O6 melts congruently at 1260°± 3°C. to a glass which can be retained in substantial quantities at room temperature. Physical properties of certain compositions are described. 相似文献
14.
G. Bhattacharya S. Zhang D. D. Jayaseelan W. E. Lee 《Journal of the American Ceramic Society》2007,90(1):97-106
Lithium borate (Li2 B4 O7 ) and sodium borate (Na2 B4 O7 ) mineralize spinel formation from stoichiometric MgO and Al2 O3 between 1000° and 1100°C. Mineralization with both compounds is shown to be mediated by B-containing liquids which form glass on cooling. However, the liquid compositions depend on the type of mineralizer and temperature, suggesting that templated grain growth or dissolution–precipitation mechanisms are operating, one dominating over the other under certain conditions. Na2 B4 O7 -mineralized compositions show predominantly templated grain growth at 1000°C, which changes to dissolution–precipitation at 1100°C, whereas Li2 B4 O7 -mineralized compositions show dissolution–precipitation from 1000°C. Li2 B4 O7 is a stronger mineralizer as spinel formation is complete with 3 wt% Li2 B4 O7 at 1000°C and with ≥1.5 wt% addition at 1100°C, whereas Na2 B4 O7 -mineralized compositions are found to retain some unreacted corundum even at 1100°C. 相似文献
15.
Phase relations in the system Na2 O· Al2 O3 -CaO· Al2 O3 -Al2 O3 at 1200°C in air were determined using the quenching method and high-temperature X-ray diffraction. The compound 2Na2 O · 3CaO · 5Al2 O3 , known from the literature, was reformulated as Na2 O · CaO · 2Al2 O3 . A new compound with the probable composition Na2 O · 3CaO · 8Al2 O3 was found. Cell parameters of both compounds were determined. The compound Na2 O · CaO-2Al2 O3 is tetragonal with a = 1.04348(24) and c = 0.72539(31) nm; it forms solid solutions with Na2 O · Al2 O3 up to 38 mol% Na2 O at 1200°C. The compound Na2 O · 3CaO · 8Al2 O3 is hexagonal with) a = 0.98436(4) and c = 0.69415(4) nm. The compound CaO · 6Al2 O3 is not initially formed from oxide components at 1200°C but behaves as an equilibrium phase when it is formed separately at higher temperatures. The very slow transformation kinetics between β and β "-Al2 O3 make it very difficult to determine equilibrium phase relations in the high-Al2 O3 part of the diagram. Conclusions as to lifetime processes in high-pressure sodium discharge lamps can be drawn from the phase diagram. 相似文献
16.
Byong-Taek Lee Rajat Kanti Paul Hyun-Jin Hong Kap-Ho Lee 《Journal of the American Ceramic Society》2009,92(4):911-915
Using a multipass extrusion process, continuous porous Al2 O3 body (∼41% porosity) was produced and used as a substrate to fabricate continuous porous TiO2 /Al2 O3 composite membrane. The diameter of the continuous pores of the porous Al2 O3 body was about 150 μm. The TiO2 nanopowders dip coated on the continuous pore-surface Al2 O3 body existed as rutile and anatase phases after calcination at 520°C in air. However, after aging of the fabricated continuous porous TiO2 /Al2 O3 composite membrane in 20% NaOH at 60°C for 24 h, a large number of TiO2 fibers frequently observed on the pore surface. The diameter of the TiO2 fibers was about 150 nm having a high specific surface area. However, after 48-h aging period, the diameter of the TiO2 fibers increased, which was about 3 μm. Most of the TiO2 fibers had polycrystalline structure having nanosized rutile and anatase crystals of about 20 nm. 相似文献
17.
Phase equilibria were determined by standard quench methods in binary systems NIO-B2 O3 , the binary join Li2 O.B2 O3 -NiO, and three other sections through the Li2 O.B2 O3 -B2 O3 -NiO system. The only new compound observed was 2NiO.B2 O3 , which is stable from 1303° to 1480°C. 相似文献
18.
J. P. COUTURES 《Journal of the American Ceramic Society》1985,68(3):105-107
A tentative phase diagram for the system Al2 03 -Nd2 O3 is presented. Three compounds were obtained: a β -A12 O3 -type compound, the perovskite NdAlO3 , and Nd4 Al2 O9 . The perovskite melts congruently (mp 2090°C), and the two other compounds exhibit incongruent melting behavior: β -Nd/Al2 O3 , mp 1900°C; Nd4 Al2 O9 , mp 1905°C. Two eutectics exist with the following compositions and melting points: 80 mol% Al2 O3 , 1750°C; 23 mol% Al2 O3 ,1800°C. Nd4 Al2 O9 decomposes in the solid state at 1780°C. 相似文献
19.
Phase equilibria have been determined in the system CaO-Al2 O3 -H2 O in the temperature range 100° to 1000°C. under water pressures of up to 3000 atmospheres. Only three hydrated phases are formed stably in the system: Ca(OH)2 , 3CaO·Al2 O3 ·6H2 O, and 4CaO·3Al2 O3 -3H2 O. Pressure-temperature curves delineating the equilibrium decomposition of each of these phases have been determined, and some ther-mochemical data have been deduced therefrom. It has been established that both the compounds CaO·Al2 O3 and 3CaO·Al2 O3 have a minimum temperature of stability which is above 1000°C. The relevance of the new data to some aspects of cement chemistry is discussed. 相似文献
20.
Heromichi Okamura Eric A. Barringer H. Kent Bowen 《Journal of the American Ceramic Society》1986,69(2):22-C-
An unagglomerated, monosized Al2 O3 TiO2 composite powder was prepared by the stepwise hydrolysis of titanium alkoxide in an Al2 O3 dispersion. Particle size was controlled by selecting the particle size of the starting Al2 O3 powder; TiO2 content was determined by the amount of alkoxide hydrolyzed. A composite-powder compact containing 50 mol% TiO2 , when fired at 1350°C for 30 min, showed nearly theoretical density with aluminum titanate phase formation. 相似文献