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1.
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
2.
The melting behaviors of selected compositions in the Si3 N4 -AlN-Y2 O3 system were determined under 1 MPa of nitrogen. The phase diagrams of the ternary and their binary systems are presented. The lowest melting composition of the ternary system contains 15 mol % Si3 N4 , 25 mol % AIN, and 60 mol % Y2 O3 and has a melting temperature of 1650°C. The binary eutectic compositions and temperatures are 15 mol % Si3 N4 and 85 mol % Y2 O3 at 1720°C, and 20 mol % AIN and 80 mol% Y2 O3 at 1730°C. 相似文献
3.
Sintering kinetics of the system Si3 N4-Y2O3 -Al2 O3 were determined from measurements of the linear shrinkage of pressed disks sintered isothermally at 1500° to 1700°C. Amorphous and crystalline Si3 N4 were studied with additions of 4 to 17 wt% Y2 O3 and 4 wt% A12 O3 . Sintering occurs by a liquid-phase mechanism in which the kinetics exhibit the three stages predicted by Kingery's model. However, the rates during the second stage of the process are higher for all compositions than predicted by the model. X-ray data show the presence of several transient phases which, with sufficient heating, disappear leaving mixtures of β ' -Si3 N4 and glass or β '-Si3 N4 , α '-Si3 N4 , and glass. The compositions and amounts of the residual glassy phases are estimated. 相似文献
4.
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
5.
The subsolidus phase diagram of the quasiternary system Si3 N4 -AlN-Y2 O3 was established. In this system α-Si3 N4 forms a solid solution with 0.1Y2 O3 : 0.9 AIN. The solubility limits are represented by Y0.33 Si10.5 Al1.5 O0.5 N15.5 and Y0.67 Si9 A13 ON15 . At 1700°C an equilibrium exists between β-Si3 N4 and this solid solution. 相似文献
6.
Subsolidus phase relations were established in the system Si3 N4 -SiO2 -Y2 O3 . Four ternary compounds were confirmed, with compositions of Y4 Si2 O7 N2 , Y2 Si3 O3 N4 , YSiO2 N, and Y10 (SiO4 )6 N2 . The eutectic in the triangle Si3 N4 -Y2 Si2 O7 -Y10 (SiO4 )6 N2 melts at 1500°C and that in the triangle Si2 N2 O-SiO2 -Y2 Si2 O7 at 1550°C. The eutectic temperature of the Si3 N4 -Y2 Si2 O7 join was ∼ 1520°C. 相似文献
7.
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
8.
The existence of compounds between Si3 N4 -CeO2 and Si3 N4 -Ce2 O3 was investigated for firing temperatures of 1600° to 1700°C. The two new monoclinic compounds found were Ce2 O3 ·2Si3 N4 with lattice parameters a = 16.288, b = 4.848, and c =7.853 Å and β=91.54° and Ce4 Si2 O7 N2 with lattice parameters a = 10.360, b = 10.865, and c =3.974 Å and β=90.33°. Cerium orthosilicate (Ce 4.67 (SiO4 )3 O) is present during firing as a glassy intermediate phase which promotes sintering and densification and then reacts with silicon nitride to form cerium silicon oxynitrde (CeSiO2 N). 相似文献
9.
The phase relations in the Si3 N4 -rich portion of the Si3 N4 –AlN–Y2 O3 rystem were investigated using hot-pressed bodies. The one-phase fields of β3 and α, the twophase fields of β+α, β+M (M=melilite), and α+M, and the three-phase fields of β+α+M were observed in the Si3 N4 -rich portion. The α- and β-sialons are not two different compounds but an allotropic transformation phase of the Si–Al–O–N system, and an α solid solution expands and stabilizes with increasing Y2 O3 content. Therefore, the formulas of the two sialons should be the same. 相似文献
10.
L. J. BOWEN T. G. CARRUTHERS R. J. BROOK 《Journal of the American Ceramic Society》1978,61(7-8):335-359
The rates of densification and phase transformation undergone by α-Si3 N4 during hot-pressing in the presence of Y2 O3 , Y2 O3 −2SiO2 , and Li2 0−2Si02 as additives were studied. Although these systems behave less simply than MgO-doped Si3 N4 , the data can be interpreted during the early stages of hot-pressing as resulting from a solution-diffusion-reprecipitation mechanism, where the diffusion step is rate controlling and where the reprecipitation step invariably results in the formation of the β-Si3 N4 phase. 相似文献
11.
Branko Matovic Georg Rixecker Fritz Aldinger 《Journal of the American Ceramic Society》2004,87(4):546-549
This paper deals with the densification and phase transformation during pressureless sintering of Si3 N4 with LiYO2 as the sintering additive. The dilatometric shrinkage data show that the first Li2 O- rich liquid forms as low as 1250°C, resulting in a significant reduction of sintering temperature. On sintering at 1500°C the bulk density increases to more than 90% of the theoretical density with only minor phase transformation from α-Si3 N4 to β-Si3 N4 taking place. At 1600°C the secondary phase has been completely converted into a glassy phase and total conversion of α-Si3 N4 to β-Si3 N4 takes place. The grain growth is anisotropic, leading to a microstructure which has potential for enhanced fracture toughness. Li2 O evaporates during sintering. Thus, the liquid phase is transient and the final material might have promising mechanical properties as well as promising high-temperature properties despite the low sintering temperature. The results show that the Li2 O−Y2 O3 system can provide very effective low-temperature sintering additives for silicon nitride. 相似文献
12.
The compressive creep behavior and oxidation resistance of an Si3 N4 /Y2 Si2 O7 material (0.85Si3 N4 +0.10SiO2 +0.05Y2 O3 ) were determined at 1400°C. Creep re sistance was superior to that of other Si3 N4 materials and was significantly in creased by a preoxidation treatment (1600°C /120 h). An apparent parabolic rate constant of 4.2 × 10−11 kg2 ·m-4 ·s−1 indicates excellent oxidation resistance. 相似文献
13.
Chunli Guo Zheng Xing Xiaojian Ma Liqiang Xu Yitai Qian 《Journal of the American Ceramic Society》2008,91(5):1725-1728
Silicon nitride nanowires or nanorods have been synthesized from SiCl4 , NaN3 , and metallic Mg at temperatures ranging from 200° to 300°C. X-ray powder diffraction patterns indicated that the as-obtained products were mainly β-Si3 N4 . Scanning electron microscope and high-resolution transmission electronic microscopy showed that the samples mostly consisted of Si3 N4 nanowires or nanorods. As metallic iron powder was used, α-Si3 N4 was mainly formed at 250°C. 相似文献
14.
Tzer-Shin Sheu 《Journal of the American Ceramic Society》1994,77(9):2345-2353
The in situ β-Si3 N4 /α'-SiAlON composite was studied along the Si3 N4 –Y2 O3 : 9 AlN composition line. This two phase composite was fully densified at 1780°C by hot pressing Densification curves and phase developments of the β-Si3 N4 /α'-SiAlON composite were found to vary with composition. Because of the cooperative formation of α'-Si AlON and β-Si3 N4 during its phase development, this composite had equiaxed α'-SiAlON (∼0.2 μm) and elongated β-Si3 N4 fine grains. The optimum mechanical properties of this two-phase composite were in the sample with 30–40%α', which had a flexural strength of 1100 MPa at 25°C 800 MPa at 1400°C in air, and a fracture toughness 6 Mpa·m1/2 . α'-SiAlON grains were equiaxed under a sintering condition at 1780°C or lower temperatures. Morphologies of the α°-SiAlON grains were affected by the sintering conditions. 相似文献
15.
pela Kunej Sreo D. kapin Danilo Suvorov 《Journal of the American Ceramic Society》2009,92(10):2373-2377
In this study we used solid-state synthesis to determine the phase relations in the pyrochlore-rich part of the Bi2 O3 −TiO2 −Nd2 O3 system at 1100°C. The samples were analyzed using X-ray powder diffraction and scanning electron microscopy with energy- and wavelength-dispersive spectroscopy. A single-phase pyrochlore ceramic was obtained with the addition of 4.5 mol% of Nd2 O3 . We determined the solubility limits for the three solid solutions: (i) the pyrochlore solid solution Bi(1.6–1.08 x ) Nd x Ti2 O(6.4+0.3 x ) , where 0.25< x <0.96; (ii) the solid solution Bi4− x Nd x Ti3 O12 , where 0< x <2.6; and (iii) the Nd2− x Bi x Ti2 O7 solid solution, where 0< x <0.35. The determined phase relations in the pyrochlore-rich part are presented in a partial phase diagram of the Bi2 O3 −TiO2 −Nd2 O3 system in air at 1100°C. 相似文献
16.
Sea-Hoon Lee Gerhard Kaiser Georg Rixecker Fritz Aldinger Jae-Young Park Keun-Ho Auh Sung-Churl Choi 《Journal of the American Ceramic Society》2008,91(2):679-682
The surface of Si3 N4 ceramics was hydrothermally treated with HCl or H2 SO4 using an autoclave. The thickness of the oxide layers formed on the Si3 N4 samples decreased to one-fourth after oxidation at 1400°C by the treatment. The oxide layer of the treated samples was dense, and flaw formation in and beneath the layer did not occur at 1400°C. The avoidance of low melting Y-silicates by leaching Y2 O3 is the reason for the improved oxidation resistance of the hydrothermally treated Si3 N4 , despite an increase in surface porosity through a 70 μm layer. 相似文献
17.
Siddharta Bandyopadhyay Michael J. Hoffmann † Günter Petzow 《Journal of the American Ceramic Society》1996,79(6):1537-1545
Different SiAION composites based on α'-SiAION are investigated, with respect to the phase relationships, densification behavior, and mechanical properties. The compositions are located on a phase-diagram line parallel to the Si3 N4 -Y2 O3 9AIN compound in the Si3 N4 -SiO2 -AlN-Al2 O3 -Y2 O3 -YN system. Analysis of the reaction sequences shows that the formation of the composites is associated with the transient appearance of Y4 A12 O9 (YAM), yttrium-aluminum-garnet (YAG), melilite, and a nitrogen-rich liquid phase. The small shift of compositions on the Si3 N4 -Y2 O3 -9AIN compound phase-diagram line toward the Al2 O3 -rich side offers the advantage of a higher sinterability and the removal of the melilite phase from a wide range of compositions containing α'-SiAlON and polytypes. The α'/β'-SiAlON composites show better mechanical properties in comparison to pure α'-SiAlON and composites of α'-SiAION and polytypes. A post-heat-treatment causes the crystallization of YAG as a grain-boundary phase and leads to excellent strength retention up to temperatures of 1350°C. 相似文献
18.
Full-density Si3 N4 -SiO2 -Ce2 O3 compositions were prepared by sintering with 2.5 MPa nitrogen pressure at temperatures of 1900° and 2090°C. Room-temperature flexural strengths near 700 MPa for sintered material compared favorably with the strength of hot-pressed material. At 1370°C, where flexural strengths as high as 363 MPa were obtained, it was observed that the coarsest structure was the strongest and the finest structure was the weakest. One of the compositions tested, Si3 N4 -8.7 wt% SiO2 -8.3 wt%-Ce2 O3 , was found to have excellent 200-h oxidation resistance at 700°, 1000°, and 1370°C, without incidence of 700° to 1000°C phase instability and cracking. 相似文献
19.
Solid-liquid equilibria in the system Si,Al,Y/N,0 were determined for the compatibility triangle bounded by the β-SiAlON solid-solution line and the compound Y3 Al5 O12 . X-ray diffraction was used to determine the crystalline phases present in the equilibrated, rapidly cooled specimens. The liquid phase was quantified with volume fraction measurements performed on scanning electron micrographs. The solid-liquid tie lines at 1650° and 1750°C were established from lattice parameters of the β-SiAlON phase and from the amount of liquid phase in equilibrium with the crystalline solid. The liquid phase was crystallized to verify the location of the starting composition. 相似文献
20.
Jae-Yuk Kim Takayoshi Iseki Toyohiko Yano 《Journal of the American Ceramic Society》1996,79(10):2744-2746
The effect of aluminum and yttrium nitrate additives on the densification of monolithic Si3 N4 and a Si3 N4 /SiC composite by pressureless sintering was compared with that of oxide additives. The surfaces of Si3 N4 particles milled with aluminum and yttrium nitrates, which were added as methanol solutions, were coated with a different layer containing Al and Y from that of Si3 N4 particles milled with oxide additives. Monolithic Si3 N4 could be sintered to 94% of theoretical density (TD) at 1500°C with nitrate additives. The sintering temperature was about 100°C lower than the case with oxide additives. After pressureless sintering at 1750°C for 2 h in N2 , the bulk density of a Si3 N4 /20 wt% SiC composite reached 95% TD with nitrate additives. 相似文献