共查询到20条相似文献,搜索用时 15 毫秒
1.
The effect of Al content on the performance of the Pd–S2O82?/ZrO2–Al2O3 solid superacid catalyst was studied using n-pentane isomerization as a probe reaction. The catalysts were also characterized by ... 相似文献
2.
Al2O3–ZrO2 (AZx), with 25 mol% ZrO2 content, was prepared using the co-precipitation method. Synthesized powders were characterized by thermal reaction using a differential thermal analysis technique (TG–DTA) and were investigated by phase formation using X-ray diffraction. It indicated that the reaction occurred at 850 °C; cubic (c)-ZrO2 phase and Al2O3 were obtained. By increasing temperature to 1100 °C, tetragonal (t)-ZrO2 phase was detected. The Al2O3–25 mol% ZrO2 was sintered for 2 h in the temperature range of between 1300 and 1600 °C. The majority phases of ceramics were m-ZrO2 and α-Al2O3, although a t-ZrO2 phase also appeared as a minor phase and decreased with higher temperature. Moreover, morphology and particle size evolution have been determined via the SEM technique. SEM showed that the particles of powder are agglomerated and basically irregular in shape. An SEM micrograph of ceramics exhibits uniform microstructure without abnormal grain growth. 相似文献
3.
The La –Ni–S2O82−/ZrO2 –Al2O3 (La–Ni–SZA) was prepared and the effect of La and Ni on the structure and isomerization performance of catalyst was investigated. The addition of La could lead to a higher dispersion of metal and more acid sites. The addition of Ni can promote redox performance of catalyst and formation of Lewis acid sites. The highest isopentane yield of 66.5% at a lower reaction temperature of La–Ni–SZA can be attributed to the synergistic interaction between La and Ni. 相似文献
4.
The effects of adding 1–8 wt% Y2O3 on phase formation and fracture toughness of Al2O3–xZrO2–Y2O3(AZY) ceramics were studied. Phase formations of the samples were characterized by the X-ray diffraction (XRD) technique. It was found that the major phase was rhombohedral-Al2O3, while the minor phase consisted of the monoclinic-ZrO2, tetragonal-ZrO2 and monoclinic-Y2O3. It was found that Y2O3 contents did not clearly influence grain shape of AZY ceramics. The results obtained from the microhardness test could be used to evaluate the fracture toughness. It was found that the smaller grains had high fracture toughness. The maximum fracture toughness of 4.827 MPa m1/2 was obtained from 4 wt% Y2O3. Refinement of lattice parameters using Rietveld analysis revealed the quantitative phases of AZY ceramics. This shows that under adding Y2O3 conditions the proportion of tetragonal-ZrO2 phase plays an important role for the mechanical properties of AZY ceramics. 相似文献
5.
Qinghe Yu Chungen Zhou Huiyan Zhang Feng Zhao 《Journal of the European Ceramic Society》2010,30(4):889-897
Nanostructured 13 wt% Al2O3–8 wt% Y2O3–ZrO2 (13AlYSZ) coatings were developed by atmospheric plasma spraying (APS). The phase structure and the morphology of the 13AlYSZ coatings were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). It was found that the as-sprayed coatings mainly consisted of tetragonal zirconia, with the Al element solid solution in ZrO2. Heat treatment at 1100 °C increased the average grain size of the ZrO2 phase from 61 to 120 nm and decreased the porosity from 23.8 to 18%. The addition of the nano-Al2O3 can effectively inhibit the grain growth of the zirconia phase. The mechanism on inhibiting the grain growth of nanostructured 8 wt% Y2O3–ZrO2 thermal barrier coatings has been discussed in detail. 相似文献
6.
7.
Bhogal Sangeeta Sharma Gaurav Kumar Amit Sharma Shweta Naushad Mu. Alam Manawwer Stadler Florian J. 《Topics in Catalysis》2020,63(11-14):1272-1285
Topics in Catalysis - In the present study, Ag2O–Al2O3–ZrO2 based trimetallic oxide nanocatalyst was designed using simple microwave assisted reduction method. It was characterized... 相似文献
8.
《Ceramics International》2020,46(5):6205-6211
This study utilized the single hot thermocouple technique to examine the dissolution behavior of lumped magnesium oxide (MgO) in CaO–Al2O3–SiO2 ternary slags. The aluminum oxide (Al2O3) content in the slag (C/S = 1) varied from 10% to 30%; the MgO sphere with a diameter of 1 mm was placed in molten slags at 1,550 °C. Results showed that the dissolution rate decreased as the Al2O3 content increased up to 20%. Over 20% Al2O3, MgAl2O4 was formed at the interface of MgO and it did not fully melt at 30% Al2O3. The dissolution behavior and the formation of MgAl2O4 were analyzed by a phase diagram provided by Factsage 7.0 software. In the case of less than 20% Al2O3 content, apparent sphere radii were measured; the shrinking core model was then applied to understand the dissolution mechanism. The dissolution rate of both slags was controlled by boundary layer diffusion. The dissolution rate at 20% Al2O3 slag appeared to fit the behavior to the boundary layer diffusion, although it deviated during the middle stage of the dissolution because of MgAl2O4 formation. The 10% Al2O3 slag fitted well to the boundary layer diffusion curve; the obtained diffusion coefficient was 0.94 × 10−9 m2/s. 相似文献
9.
《Ceramics International》2023,49(20):33188-33196
Nowadays, Y2O3–Al2O3–SiO2 (YAS) glass joining is considered to be a promising scheme for nuclear-grade continuous silicon carbide (SiC) fiber reinforced SiC matrix composites (SiC/SiC). CaO has great potential for nuclear applications since it has low reactivity and low decay rate under nuclear irradiation. In this paper, the effect of CaO doping on the structure, thermophysical properties, and crystallization behavior of YAS glass was systematically studied. As the CaO doping content increased, the number of bridge oxygens and the viscosity at high temperatures reduced gradually. After heat treatment at 1400 °C, the main phases in YAS glass were β-Y2Si2O7, mullite, and SiO2 (coexistence of crystalline and glass phases), while that with 3.0% CaO doping turned into a single glassy phase under the same treatment conditions. Moreover, a structural model and the modification mechanism were proposed, which provided a theoretical basis for the subsequent component design and optimization. 相似文献
10.
《Ceramics International》2023,49(15):25261-25268
A new type of glass-ceramic BaO–CaO–Al2O3–SiO2 (BCAS) was developed to join Al2O3 ceramics, adding TiO2 to the glass-ceramics can promote the crystallization behavior of the glass-ceramics. Through the observation of the joints, rutile TiO2 whiskers can grow on the surface of Al2O3 ceramics, and the grown TiO2 whiskers are one-dimensional needle-like whiskers growing in different directions in the joints, providing mechanical support for the joints. The aspect ratio of TiO2 whiskers was changed by controlling the addition of TiO2, and the crystallization behavior and microstructure of the joints were studied. The experimental results show that when the amount of TiO2 added is 10% (wt%), the density of TiO2 whiskers in the joint is the largest, the strengthening effect on the joint is the best, and the shear strength can reach 94.33 MPa. 相似文献
11.
12.
Alzahrani Jamila S. Alrowaili Z. A. Saleh H. H. Al-Baradi Ateyyah M. Alothman Miysoon A. Al-Buriahi M. S. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(11):4300-4312
Journal of Inorganic and Organometallic Polymers and Materials - This research article focuses on the significant role of Tb2O3 content on the optical properties and radiation shielding performance... 相似文献
13.
The structure and properties of Pd/WO3–ZrO2 (W/Zr = 0.2) catalysts with different Pd loadings and precursors were investigated. The results indicate that Pd/WO3–ZrO2 prepared from a PdCl2 precursor was optimum for high activity and selectivity. Moreover, ethylene conversion increased with the Pd loading. The structure and nature of the catalysts were characterized using X-ray diffraction, BET N2 adsorption, H2 temperature-programmed reduction and H2 pulse adsorption techniques. The results reveal that the higher catalytic performance of Pd/WO3–ZrO2 prepared from PdCl2 could be related to the formation of polytungstate species and the existence of well-dispersed Pd particles. 相似文献
14.
The influence of indium on the properties of Pt–Re/Al2O3 catalysts used in naphtha reforming is studied. The addition of indium to the Pt–Re/Al2O3 catalyst produces a big decrease of acidity. It also produces an inhibition of the metal function, i.e., dehydrogenation and hydrogenolysis activity. The reaction of n-C5 isomerization shows that indium addition decreases the total activity of the Pt–Re catalyst but increases the selectivity to the i-C5 isomers. The selectivity to low cost light gases (C1–C3) is particularly decreased. The reaction of n-C7 reforming showed that addition of indium increases the stability of the catalyst and the selectivity to aromatics, and decreases the production of light gases. 相似文献
15.
《Journal of the European Ceramic Society》2000,20(12):2133-2141
Three different spinel compositions with MgO:Al2O3 molar ratios 2:1, 1:1 and 1:2 were studied using TiO2 as an additive up to 2 wt.%. Solid state reaction sintering technique was employed for all the compositions in the temperature range of 1550–1650°C. Attrition milling was done for the reduction of particle size. Sintered products were characterised in terms of densification and shrinkage studies, phase analysis, strength evaluation both at ambient temperature and at elevated temperature, strength retention after different number of thermal cycles at 1000°C, quantitative elemental analysis and microstructural studies. 相似文献
16.
《应用陶瓷进展》2013,112(6):352-357
AbstractMgO–Al2O3–SiO2 (MAS) cordierite based glass ceramics were prepared by volume crystallisation. X-ray diffraction, Scanning electron microscopy and Energy diffraction scanning were used to investigate crystallisation behaviour and the influence of P2O5 on microstructure MAS based glass ceramics. The results showed that P5+ could promote the phase separation of MAS glass and that the glass was divided into two areas, such as Mg4Al2Ti9O25 and the containing P5+ area at <900°C. Mg4Al2Ti9O25 and Mg3(PO4)2 in the area were both advantageous to the precipitation of μ cordierite, which further transformed to α cordierite due to P5+ in the residual glassy phase. However, P5+ inhibited the presence of cordierite when the heat treatment temperature was >900°C. 相似文献
17.
The glass structure, wetting behavior and crystallization of BaO–Al2O3–B2O3–SiO2 system glass containing 2–10 mol% Al2O3 were investigated. The introduction of Al2O3 caused the conversion of [BO3] units and [BO4] units to each other and it played as glass network former when the content was up to 10 mol%, accompanied by [BO4] → [BO3]. The stability of the glass improved first and then decreased as Al2O3 increased from 2 to 10 mol%, the glass with 5 mol% Al2O3 being the most stable one. The wetting behavior of the glasses indicates that excess Al2O3 leads to high sealing temperature. The glass containing 5 mol% Al2O3 characterized by a lower sealing temperature is suitable for SOFC sealing. Al2O3 improves the crystallization temperature of the glass. The crystal phases in the reheated glasses are mainly composed of Ba2Si3O8, BaSiO3, BaB2O4 and BaAl2Si2O8. Al2O3 helps the crystallization of BaSiO3 and BaAl2Si2O8. 相似文献
18.
《Ceramics International》2015,41(8):9337-9343
This article focused on effect of the content of barium oxide on microstructure of the glass–ceramic materials based on the system SiO2–Al2O3–Na2O–K2O–CaO. The following characterisation techniques have been used: X-ray diffraction (XRD), scanning electron microscopy with micro-analyser (SEM–EDS), mid-infrared analysis (MIR), far-infrared analysis (FIR) and Raman Spectroscopy. Significant differences were observed in microstructure of silica–alumina network of glassy phase and phase composition related to changes in the amount of the barium oxide additive. Discussed results are part of a larger project implemented under the PBS Applied Research Programme, in order to determine the compositions of glass–ceramic materials with potential application as a chemically resistant hard coatings or/and resistant to thermal shock or as construction materials. 相似文献
19.
The phase diagram of the Na2O–Al2O3–ZrO2 system was experimentally studied at 1500°C–1650°C by a classical equilibration/quenching method and differential thermal analysis followed by X-ray diffraction phase analysis and electron probe micro-analysis. A sealed Pt crucible was utilized to prevent the volatile loss of Na2O during high-temperature phase equilibrium experiments and the hydration upon quenching. The phase diagram of the Na2O–Al2O3–ZrO2 system was revealed for the first time. Based on the present experimental data and available binary modeling results in literature, the thermodynamic modeling of the ternary system was performed using the Calculation of Phase Diagram method and the phase diagram of the entire the Na2O–Al2O3–ZrO2 system was constructed and the optimized thermodynamic properties for all solids and liquid phase within the ternary system were obtained. 相似文献
20.
《Ceramics International》2019,45(15):18215-18221
Al2O3–Cr2O3 refractories are completely substitutional solid solutions and exhibit better corrosion and abrasion resistance. To enable the comprehensive utilization of it, the microstructure and properties of Al2O3–Cr2O3 samples with different corundum sources were investigated in this study. The starting sources of corundum sources included sintered tabular corundum, fused white corundum, or brown corundum with minor impurities of β-Al2O3 and TiO2. The results of mechanical test showed that the introduction of white corundum deteriorates the physical structure, while brown corundum acts in an opposite manner. The optimum bonding strength of the Al2O3–Cr2O3 brick was reached by combining white and brown corundum, whereby rapid neck growth occurred via surface diffusion during solid-phase sintering. 相似文献