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1.
Mariangela Lombardi Valentina Naglieri Jean-Marc Tulliani Laura Montanaro 《Journal of Porous Materials》2009,16(4):393-400
An improved gel-casting procedure was successfully exploited to produce porous ceramic bodies having controlled porosity features
in terms of mean pore size, total pore volume as well as pore geometry. The gel-casting process in which a natural gelatine
for food industry is used as gelling agent was firstly set-up to prepare dense alumina and zirconia components. Then, commercial
PE spheres, sieved to select proper dimensional ranges, were added to the starting slurries as pore-forming agent. Both alumina
and zirconia porous bodies were then produced, having a porosity ranging between 40 and 50 vol%. The fired components were
characterised by spherical pores surrounded by highly dense ceramic walls and struts, having a homogeneous and fine microstructure.
Their mean pore size was directly dependent on the sieved fraction of the starting PE spheres selected as pore-forming phase. 相似文献
2.
《Ceramics International》2022,48(20):30356-30366
Calcium hexaluminate (CA6) porous ceramics were prepared by gel-casting method, with α-Al2O3 and CaCO3 as raw materials and polymethyl methacrylate (PMMA) microspheres as pore-forming agent. The effects of the amount of pore-forming agent PMMA microspheres on the phase composition, bulk density, apparent porosity, flexural strength, microstructure, thermal shock stability and thermal conductivity of CA6 porous ceramics were systematically studied. The pores of CA6 porous ceramics are mainly formed by the burning loss of PMMA microspheres and the decomposition of organic matter. Adding an appropriate amount of PMMA microspheres as pore-forming agent has a positive effect on the thermal shock stability of CA6 porous ceramics. When the amount of pore-forming agent is 15 wt%, the volume density of CA6 porous ceramics is 1.33 g/cm3, the porosity is 63%, the flexural strength is 13.9 MPa, the thermal shock times can reach 9 times, and the thermal conductivity is 0.293 W/(m·K), which can meet the application in refractory, ceramics or high temperature cement industries. 相似文献
3.
4.
Jeong Gil Seo Min Hye Youn Kyung Min Cho Sunyoung Park Sang Hee Lee Joohyung Lee In Kyu Song 《Korean Journal of Chemical Engineering》2008,25(1):41-45
An Al2O3-ZrO2 xerogel (AZ-SG) was prepared by a sol-gel method for use as a support for a nickel catalyst. The Ni/AZ-SG catalyst was then
prepared by an impregnation method, and was applied to hydrogen production by steam reforming of LNG. A nickel catalyst supported
on commercial alumina (A-C) was also prepared (Ni/A-C) for comparison. The hydroxyl-rich surface of the AZ-SG support increased
the dispersion of nickel species on the support during the calcination step. The formation of a surface nickel aluminate-like
phase in the Ni/AZ-SG catalyst greatly enhanced the reducibility of the Ni/AZ-SG catalyst. The ZrO2 in the AZ-SG support increased the adsorption of steam onto the support and the subsequent spillover of steam from the support
to the active nickel sites in the Ni/AZ-SG catalyst. Both the high surface area and the well-developed mesoporosity of the
Ni/AZ-SG catalyst improved the gasification of adsorbed surface hydrocarbons in the reaction. In the steam reforming of LNG,
the Ni/AZ-SG catalyst showed a better catalytic performance than the Ni/A-C catalyst. Moreover, the Ni/AZ-SG catalyst showed
strong resistance toward catalyst deactivation. 相似文献
5.
V. A. Sokolov T. Ya. Malysheva M. D. Gasparyan 《Refractories and Industrial Ceramics》2008,49(2):146-148
Details are given of the synthesis and testing of flux-cast refractory materials in the alumina-rich region of the Al2O3-MgO-B2O3 system; XRD and petrography indicate that the main structure-forming phases are corundum and magnesian spinel. In subordinate
amounts there are the boroaluminate 9Al2O3·2B2O3 and the previously unknown compound 4Al2O3·MgO·2B2O3, whose composition has been established by microprobe analysis. Corrosion tests showed that three-component systems containing
magnesium and boron oxides at levels of 5–10% do not increase the corrosion resistance of refractories in molten sodium-calcium-silicate
glass and electrovacuum borosilicate glass.
__________
Translated from Novye Ogneupory, No. 3, pp. 161–163, March, 2008. 相似文献
6.
An investigation on viscosity was conducted 2 weeks after the Al2O3-water nanofluids having dispersants were prepared at the volume concentration of 1-5%. The shear stress was observed with
a non-Newtonian behavior. On further ultrasonic agitation treatment, the nanofluids resumed as a Newtonian fluids. The relative
viscosity increases as the volume concentrations increases. At 5% volume concentration, an increment was about 60% in the
re-ultrasonication nanofluids in comparison with the base fluid. The microstructure analysis indicates that a higher nanoparticle
aggregation had been observed in the nanofluids before re-ultrasonication. 相似文献
7.
8.
S. A. Nemov A. V. Marchenko P. P. Seregin E. A. Tomil’tsev 《Glass Physics and Chemistry》2007,33(6):658-660
Triply and doubly charged states of europium are revealed by 151Eu Mössbauer spectroscopy in the structure of glasses of the composition (mol %) 19.5Al2O3, 31.5SiO2, 26.5MnO, and 22.5Eu2O3. The isomer shifts in the Mössbauer spectra of Eu3+ and Eu2+ ions in the structure of glasses differ from the isomer shifts in the spectra of the Eu2O3 and EuO compounds. This difference is explained by the fact that the electron density at 151Eu nuclei is affected by the manganese and aluminum atoms, which are not bound directly to the europium atoms. The broadening of the spectra of the Eu2+ ions in glasses is caused by the nonuniform isomer shift. 相似文献
9.
Woo-Hee Kim Hyungjun Kim Han-Bo-Ram Lee 《Journal of Coatings Technology and Research》2017,14(1):177-183
Thin film optics, based on light interference characteristics, are attracting increasing interest because of their ability to enable a functional color coating for various applications in optical, electronic, and solar industries. Here, we report on the dependence of coloring characteristics on single-layer TiO2 thicknesses and alternating TiO2/Al2O3 multilayer structures prepared by atomic layer deposition (ALD) at a low growth temperature. The ALD TiO2 and Al2O3 thin films were studied at a low growth temperature of 80°C. Then, the coloring features in the single-layer TiO2 and alternating TiO2/Al2O3 multilayers using both the ALD processes were experimentally examined on a TiN/cut stainless steel sheet. The Essential Macleod software was used to estimate and compare the color coating results. The simulation results revealed that five different colors of the single TiO2 layers were shown experimentally, depending on the film thickness. For the purpose of highly uniform pink color coating, the film structures of TiO2/Al2O3 multilayers were designed in advance. It was experimentally demonstrated that the evaluated colors corresponded well with the simulated color spectrum results, exhibiting a uniform pink color with wide incident angles ranging from 0° to 75°. This article advances practical applications requiring highly uniform color coatings of surfaces in a variety of optical coating areas with complex topographical structures. 相似文献
10.
Synthetic spinels of the system MgO-Cr2O3-Al2O3-Fe2O3 are considered and the desirability of organizing their production for the refractory industry is demonstrated.
Translated from Novye Ogneupory, No. 6, pp. 32–35, June 2008. 相似文献
11.
The maximization of the total surface area of Pt-SnO2/Al2O3 catalyst was studied by using the Taguchi method of experimental design. The catalysts were prepared by sol-gel method. The
effects of HNO3, H2O and aluminum nitrate concentrations and the stirring rate on the total surface area were studied at three levels of each.
L9 orthogonal array leading nine experiments was used in the experimental design. The parameter levels that give maximum total
surface area were determined and experimentally verified. In the range of conditions studied it was found that, medium levels
of HNO3 and H2O concentration and lower levels of aluminum nitrate concentration and stirring rate maximize the total surface area. 相似文献
12.
The phase composition and structure of fusion-cast refractories composed of 57.0 – 84.2% Cr2O3, 4.3 – 36.1% MgO, 2.0 – 9.7% Al2O3, and 2.4 – 6.9% SiO2 have been studied by petrographic and x-ray spectral microprobe analysis methods. Refractories high in MgO with modulus M = (Cr2O3 +Al2O3)/MgO = 1.64 – 3.1 are shown to consist of spinel phase Mg(Cr, Al)2O4 and silicate glass. Refractory materials (80.8 – 84.2% Cr2O3, 4.3 – 4.7% MgO, 2.0 – 9.7% Al2O3, and 2.7 – 6.9% SiO2 with M = 18.7 – 20.2) are three-phase systems composed of spinel, escolaite, and glass phase. These materials, owing to their high corrosion resistance, have promising potentiality for practical applications.__________Translated from Novye Ogneupory, No. 12, pp. 69 – 74, December, 2004. 相似文献
13.
Analysis of the formation of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> + Fe nanocomposites
O. Yu. Goncharov O. V. Karban’ O. M. Nemtsova I. A. Il’in 《Glass Physics and Chemistry》2009,35(2):210-218
The formation of Al2O3 + Fe nanocomposites (in the range 0–20 wt % Fe) in the course of three sequential processes, such as dispersion, compaction, and sintering at a temperature of 1573 K, is investigated. It is revealed that the sintering is accompanied by the formation of the spinel phase at interfaces. It is demonstrated that the composition of the sintered samples corresponds to an equilibrium composition at a temperature of approximately 1073 K and that the spinel phase serves as a barrier layer preventing oxidation of iron 相似文献
14.
The hydrogel of the mixed oxide Al2O3-30% Y0.1Zr0.9O2 was prepared by precipitation of ammonia from a water-alcohol mixture (1 : 5). The Al2O3-30% Y0.1Zr0.9O2 compound thus synthesized was characterized using differential scanning calorimetry, transmission electron microscopy, and
the BET adsorption method. The obtained sample consisted of spherical particles with an average size of 16–20 nm and a specific
surface area of 167 m2/g. The Al2O3-30% Y0.1Zr0.9O2 powder was pressed at 300 MPa and then calcinated at 1600°C for 2 h in air. The topographic and structural features of the
prepared ceramics were determined using atomic force microscopy and X-ray electron probe microanalysis. The porosity, the
Vickers microhardness, and the tensile strength were determined by mercury porometry. 相似文献
15.
Kang Shanjiao Dou Tao Li Qiang Duan Aijun Zheng Yanying Pan Huifang 《Journal of Porous Materials》2008,15(2):159-162
This paper presents the direct synthesis of super-low SiO2/Al2O3 ratio zeolite beta molecular sieve through a novel route, by which some of aluminium species are added during crystaling
process. The IR results show that with the increase of aluminium content in the framework, the frequency of the band in the
range of framework vibration (1060–1090 cm−1) shifts to the lower wave-number; the BET surface-area decreases and the basicity of zeolite becomes stronger. In a second
step, new adsorbents were obtained by solid-state ion exchanging zeolite beta with Cu(I), Ag(I) cations. The deep-desulfurization
(sulfur levels of <1 ppmw) tests were performed using fixed-bed adsorption technique, the sulfur content of the treated and
untreated gasoline was analyzed by microcoulometry. The experimental results show that the desulfurization performance of
sorbents decreases in order: Cu(I)beta > Ag(I)beta > Na-beta. The best sorbent, Cu(I)beta, has breakthrough adsorption capacities
of 0.236 mmolS/g of sorbent for model gasoline. 相似文献
16.
Jian Rong Tao Zhang Fengxian Qiu Mingliang Chen 《Korean Journal of Chemical Engineering》2017,34(1):41-53
Hierarchical porous NiO/Al2O3 composites were successfully prepared by two-steps. First, the core-shell structured Al2O3 microspheres were prepared via a template-free hydrothermal route using KAl(SO4)2·12H2O and Al2(SO4)3·18H2O as aluminum source. Then, the NiO/Al2O3 composites with micro- and nano-hierarchical structures were prepared by a hydrothermal method combining the subsequent calcination process. The obtained characterization result presented that the morphology of hierarchical Al2O3 microsphere tuned to irregular platelets by simply varying Ni/Al ratios. The BET analysis showed that the special surface area from 52.12m2 g?1 to 214.8m2 g?1 after two hydrothermal complex process. Effects of Ni/Al ratio, adsorbent dosage, Congo red (CR) concentration, coexisting ions, adsorption time and temperature were investigated. The obtained results indicated that NiO/Al2O3 composite had the high adsorption efficiency (99.6%) and great adsorption capacity (186.9mg g?1) under the optimum conditions. The adsorption isotherm and kinetics data were found to be well fitted and in good agreement with the Langmuir isotherm model and pseudo-second order model, respectively. The hierarchical porous NiO/Al2O3 composites presented remarkably higher adsorption efficiency during five recycling, which showed their potential as the highly efficient adsorbent for removal of CR in wastewater. 相似文献
17.
Cong Luo Ying Zheng Ning Ding Chuguang Zheng 《Korean Journal of Chemical Engineering》2011,28(4):1042-1046
To improve the stability of CaO adsorption capacity for CO2 capture during multiple carbonation/calcination cycles, modified CaO-based sorbents were synthesized by sol-gel-combustion-synthesis
(SGCS) method and wet physical mixing method, respectively, to overcome the problem of loss-in-capacity of CaO-based sorbents.
The cyclic CaO adsorption capacity of the sorbents as well as the effect of the addition of La2O3 or Ca12Al14O33 was investigated in a fixed-bed reactor. The transient phase change and microstructure were characterized by X-ray diffraction
(XRD) and field emission scanning electron microscopy (FSEM), respectively. The experimental results indicate that La2O3 played an active role in the carbonation/calcination reactions. When the sorbents were made by wet physical mixing method,
CaO/Ca12Al14O33 was much better than CaO/La2O3 in cyclic CO2 capture performance. When the sorbents were made by SGCS method, the synthetic CaO/La2O3 sorbent provided the best performance of a carbonation conversion of up to 93% and an adsorption capacity of up to 0.58 g-CO2/g-sorbent after 11 cycles. 相似文献
18.
Kamila Michalska Paweł Kowalik Wiesław Próchniak Tadeusz Borowiecki 《Catalysis Letters》2018,148(3):972-978
19.
The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity
and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on
the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity
increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the
thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values
when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of
particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical
application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser
for thermal conductivity and Krieger and Dougherty for viscosity. 相似文献
20.
Bismuth sodium zirconate titanate ceramics with the formula Bi0.5Na0.5Zr1-xTixO3 [BNZT], where x = 0.3, 0.4, 0.5, and 0.6, were prepared by a conventional solid-state sintering method. Phase identification was investigated
using an X-ray diffraction technique. All compositions exhibited complete solubility of Ti4+ at the Zr4+ site. Both a decrease of unit cell size and phase transition from an orthorhombic Zr-rich composition to a rhombohedral crystal
structure in a Ti-rich composition were observed as a result of Ti4+ substitution. These changes caused dielectric properties of BNZT ceramics to enhance. Microstructural observation carried
out employing SEM showed that average grain size decreased when addition of Ti increased. Grain size difference of BNZT above
0.4 mole fraction of Ti4+ displayed a significant increase of dielectric constant at room temperature. 相似文献