共查询到20条相似文献,搜索用时 31 毫秒
1.
Satya Gopal Rao P. Venkatehwarlu K. Siripuram Rajesh Sripada Suresh 《Glass Physics and Chemistry》2021,47(4):308-320
Glass Physics and Chemistry - The growth of nanocrystalization in TeO2–SeO2–Na2O glasses is achieved by the conventional heat treatment method. The influence of Na2O concentration on... 相似文献
2.
《Journal of the European Ceramic Society》2002,22(13):2357-2363
Silicon carbide green bodies with and without carbon-fibre reinforcement have been infiltrated with MoSi2–Si–X in order to produce high-temperature resistant materials. X is Cr, Ti, Al or B respectively. By adding silicon and one of these components to MoSi2 the melting point is lowered dramatically. The composites therefore could be gained by melt infiltration at max. 1600 °C. During infiltration the additives react within the infiltrated body with carbon or silicon to form high-temperature resistant carbides or silicides. Thermodynamic calculations have been performed to analyse the reactions during infiltration. The infiltration parameters have been studied with respect to the resulting microstructure and properties. By fitting the amount of additives to the quantity of carbon in the SiC-body (or vice versa) no decrease in strength could be observed up to 1500 °C. The fracture toughness can be increased by the use of high-modulus carbon fibres. The most promising X-element for a high-temperature resistant material is titanium. 相似文献
3.
《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
4.
In Na2O–CaO–SiO2–H2O system, systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumina fly ash (HAFA). The results show that crystal composition and phase may be affected by relatively low concentration of NaOH, and sodium ions are rearranged into the structure to form NaCaHSiO4 and Na2Ca3H8Si2O12 with different C/S ratio at high concentration of NaOH. In addition, phases in wollastonite group possess the morphology of nanofiber. Formation of nanofiber is attributed to the difference of surface energies between axial and radial direction, and higher temperatures lead to easier growth along radial direction. The preparation of C–S–H with different phases and morphologies can guide for the application of silicate solution with high alkalinity with different purposes. 相似文献
5.
Chunjie Wang Yue Wang Wenzhi Huang Binglin Zou Zuhair Subhani Khan Yu Zhao Jili Yang Xueqiang Cao 《Ceramics International》2012,38(3):2087-2094
Nanopowders with cubic fluorite-type structure as well as uniform distribution in particle size were synthesized by hydrothermal method in the ternary oxide zirconia–yttria–ceria system with ceria content of 0–25 mol%. X-ray diffraction (XRD), thermogravimetric analysis/differential scanning calorimeter (TG/DSC), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), specific surface area (SBET) and high resolution transmission electron microscopy (HRTEM) were applied to characterize the structure, thermal decomposition, morphological characteristic and crystal growth of the produced powders. Qualitative analyses indicate that the as-synthesized nanoparticles are single-phase crystallites with an average particle size of 4–9 nm. The specific surface area, lattice parameter and microstrain are closely related to Ce4+ concentration. Moreover, activation energy of crystal growth is significantly dependent on the dopant (CeO2) concentration. It firstly increased and then decreased with increasing dopant concentration, and the maximum value was observed at the dopant concentration of 5 mol%. 相似文献
6.
《Journal of the European Ceramic Society》2003,23(13):2193-2202
For the development of a new wear resistant and chemically stable glass-ceramic glaze, the CaO–ZrO2–SiO2 system was studied. Compositions consisting of CaO, ZrO2, and SiO2 were used for frit, which formed a glass-ceramic under a single stage heat treatment in electric furnace. In the sintered glass-ceramic, wollastonite (CaSiO3) and calcium zirconium silicate (Ca2ZrSi4O12) were crystalline phases composed of surface and internal crystals in the microstructure. The internal crystal formed with nuclei having a composition of Ca1.2Si4.3Zr0.2O8. The CaO–ZrO2–SiO2 system showed good properties in wear and chemical resistance because the Ca2ZrSi4O12 crystals positively affected physical and mechanical properties. 相似文献
7.
Young Jun Kwak Byung-Soo Lee Hye Ryoung Park Myoung Youp Song 《Journal of Industrial and Engineering Chemistry》2013,19(6):1963-1967
A sample with a composition of 84 wt% MgH2–10 wt% Ni–2 wt% NaAlH4–2 wt% Ti–2 wt% CNT (named MgH2–10Ni–2NaAlH4–2Ti–2CNT) was prepared by milling in a planetary ball mill under H2. Activation of the sample was not required. At the first cycle, the sample absorbed 3.75 wt% H for 10 min, and 4.17 wt% H for 60 min at 593 K under 12 bar H2. Reactive mechanical grinding of Mg with Ni, NaAlH4, Ti, and CNT is thought to create defects on the surface and in the interior of Mg, as well as to reduce Mg particle size. 相似文献
8.
Markov M. A. Ordan’yan S. S. Vikhman S. V. Perevislov S. N. Krasikov A. V. Bykova A. D. Staritsyn M. V. 《Refractories and Industrial Ceramics》2019,60(4):385-388
Refractories and Industrial Ceramics - Technological conditions for preparing ceramics based on MoSi2 hardened by SiC and ZrB2 that have enhanced physicomechanical properties (relative density... 相似文献
9.
《Journal of the European Ceramic Society》2003,23(5):685-690
The difference of Gibbs free energy between tetragonal and monoclinic phases in ZrO2–CeO2–Y2O3 as a function of composition and temperature is thermodynamically calculated from the three related binary systems. In 8 mol% CeO2–0.5 mol% Y2O3–ZrO2, the equilibrium temperature between tetragonal and monoclinic phases, T0, is obtained as 832.5 K and the Ms temperature of this alloy with a mean grain size of 0.90 μm is calculated as 249.9 K using the approach derived by Hsu et al. [J. Mater. Sci., 18(1983)3206; 20(1985)23; Acta Metall., 37(1989)3091; Acta Metall. Mater., 39(1991)1045; Mater. Trans. JIM, 37(1996)1284], which is in good agreement with the experimental one of 253 K. 相似文献
10.
Sergey Sirotkin Robert Meszaros Lothar Wondraczek 《International Journal of Applied Glass Science》2012,3(1):44-52
We report on chemical stability and corrosion behavior of highly depolymerized sulfophosphate glasses from the system ZnO–Na2O–SO3–P2O5 in aqueous solution, providing data on weight loss, ion release rates, and modifications of surface topology as a function of time, temperature and pH value. Observations seem consistent with the previously developed structural model of chemical heterogeneity, where cations Na+ and Zn2+ cluster selectively in the vicinity of sulfate and phosphate anions, respectively. 相似文献
11.
We successfully fabricated uniform SnO2–SiO2–Pt composite nanofibres (NFs) by using a co-electrospinning technique, in which we set up two coaxial capillaries. Morphology control of NFs was investigated, along with their structural properties and chemical compositions. Furthermore, to systematically investigate the morphological changes in SnO2–SiO2–Pt composite NFs, the relative weight ratios of the Sn precursor to the Si precursor including the 4 wt% Pt precursor were controlled at 3:1, 1:1, and 1:3. To demonstrate the formation mechanism of the composite NFs, the precursor positions of the shell section and the core section in co-electrospinning were reversed. The resultant composite NFs were investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). These results showed that in the case of the optimum weight ratio (1:1) of the Sn precursor in the shell section to the Si precursor including the 4 wt% Pt precursor in the core section, SnO2 and Pt nanoparticles were uniformly grown on SiO2 NFs, implying the successful formation of uniform SnO2–SiO2–Pt composite NFs. 相似文献
12.
《Journal of the European Ceramic Society》1999,19(1):139-142
Dielectric ceramics in the BaO–Nd2O3–TiO2–Ta2O5 system were prepared and characterized. The ceramics with tungsten–bronze structure based on the compositions Ba2NdTi2Ta3O15 and Ba5NdTi3Ta7O30 had a high dielectric constant (>100) with a lower frequency-dependency when complete densification was achieved; a low dielectric loss was obtained in the former. 相似文献
13.
《应用陶瓷进展》2013,112(4):203-209
AbstractGlass samples in Li2O–SiO2–CaO–P2O5–CaF2 system with different contents of P2O5, CaO and CaF2 in relative ratios responded to fluoroapatite (FA) composition (referred to P2O5 addition) have been prepared and heat treated at 550 and 750°C to obtain glass ceramics. Bioactivity of all samples has been proved in vitro by the presence of new layer of apatite-like phases formed after soaking in simulated body fluid (SBF). The development and the apatitic character of created layers have been demonstrated by Fourier transform infrared analysis. Scanning electron microscopy and electron probe microanalysis have demonstrated that the density and the thickness of new layer depend on P2O5 content, crystallisation temperature and immersion time. The bioactivity has been enhanced by P2O5 addition as well in the case of the base glasses as in the case of glass ceramics. The additional heat treatment appeared to inhibit the bioactive behaviour, though the longer SBF acting leads to the additional formation of apatite-like layer. The mechanical properties, expressed as Vicker hardness, have been found higher and increasing with P2O5 in glass ceramics treated at 750°C comparatively with base glass samples and the highest value of 7˙37 GPa has been achieved by 14 wt-%P2O5 addition. The same content of P2O5 in glass ceramics heat treated at 550°C resulted in a decrease in hardness to a minimum value from all samples. The increase and decrease in hardness responded to development and suppression of crystallisation respectively. The inhibition of crystallisation has been affected by the presence of 'amorphous' FA according to X-ray diffraction and differential thermal analysis results. 相似文献
14.
《Ceramics International》2016,42(7):7943-7949
This paper reports the investigation of the performance of Li2O–B2O3–SiO2 (LBS) glass as a sintering aid to lower the sintering temperature of BaO–0.15ZnO–4TiO2 (BZT) ceramics, as well as the detailed study on the sintering behavior, phase evolution, microstructure and microwave dielectric properties of the resulting BZT ceramics. The addition of LBS glass significantly lowers the sintering temperature of the BZT ceramics from 1150 °C to 875–925 °C. Small amount of LBS glass promotes the densification of BZT ceramic and improves the dielectric properties. However, excessive LBS addition leads to the precipitation of glass phase and growth of abnormal grain, deteriorating the dielectric properties of the BZT ceramic. The BZT ceramic with 5 wt% LBS addition sintered at 900 °C shows excellent microwave dielectric properties: εr=27.88, Q×f=14,795 GHz. 相似文献
15.
《Ceramics International》2020,46(1):156-164
Spark plasma sintering (SPS) route was employed for preparation of quadruplet ZrB2–SiC–ZrC–Cf ultrahigh temperature ceramic matrix composites (UHTCMC). Zirconium diboride and silicon carbide powders with a constant ZrB2:SiC volume ratio of 4:1 were selected as the baseline. Mixtures of ZrB2–SiC were co-reinforced with zirconium carbide (ZrC: 0–10 vol%) and carbon fiber (Cf: 0–5 vol%), taking into account a constant ratio of 2:1 for ZrC:Cf components. The sintered composite samples, processed at 1800 °C for 5 min and 30 MPa punch press under vacuumed atmosphere, were characterized by densitometry, field emission scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry as well as mechanical tests such as hardness and flexural strength measurements. The results verified that the composite co-reinforced with 5 vol% ZrC and 2.5 vol% Cf had the optimal characteristics, i.e., it reached a relative density of 99.6%, a hardness of 18 GPa and a flexural strength of 565 MPa. 相似文献
16.
《Journal of the European Ceramic Society》2000,20(14-15):2499-2508
A large region of glass formation was found in the system SrO–MgO–ZrO2–SiO2 and some properties have already been reported. Detailed studies have shown that glasses with only 40 wt% silica unusually durable in 1 M NaOH and also in model cement extract solutions. Glasses with higher silica contents are more easily attacked; zirconia and magnesia are the constituents giving the best durability. These results suggest that these glasses could be of interest for reinforcement of cement and concrete. 相似文献
17.
《Ceramics International》2016,42(9):10908-10912
Pure chemosynthetic Al2O3–2SiO2 powders fabricated by a sol–gel method exhibit high phosphoric acid-activated properties and high compressive strengths. The phosphoric acid-activated properties could be characterized by compressive strength. The phase structure evolution of synthetic powders and the resulting geopolymers were investigated by DTA-TG, XRD, FTIR and MAS NMR analysis. These results show that the phosphoric acid-activation region of the synthetic powders was in the range of 200–800 °C, which was much lower than the temperature at which kaolinite was converted into metakaolinite. 31P MAS NMR analysis revealed that [PO4] tetrahedra were part of the geopolymer structure. 相似文献
18.
A. I. Priven 《Glass Physics and Chemistry》2001,27(4):360-370
A method for calculating the viscosity from composition and temperature for melts in the R
m
O
n
–B2O3–SiO2systems is proposed. The change in the concentrations of structural groups depending on the melt composition is taken into account in calculations. The results of calculations are compared with the experimental data available in the literature on the viscosity of 1200 melts with the use of the SciGlass information system. The root-mean-square deviation between the experimental and calculated characteristic temperatures varies from 30 K (for the glass transition temperature and the Littleton point) to 50 K (for a viscosity of 104P). 相似文献
19.
《Powder Technology》2001,114(1-3):106-111
The surface characteristics of ternary ceramic powders in the system TiO2–SiO2–Al2O3 prepared by a sol–gel technique were studied through nitrogen gas adsorption at liquid nitrogen temperature and application of the Brunauer–Emmett–Teller (BET) equation. The total surface area, total pore volume and pore radius of the powders were calculated through the construction of plots relating the amount of nitrogen gas adsorbed V1 and the thickness of the adsorbed layer t (V1−t plots). These results permitted the detection of the different types of pores present in the samples. In a first approximation, the V1−t plots seem to demonstrate the correctness of the results obtained for the total specific area of the investigated samples. The influence of thermal treatment (drying, calcination) on the surface characteristics of the investigated powders was assessed. 相似文献
20.
《Ceramics International》2020,46(7):9207-9217
Modification of glass network and crystallization process of a CaO–Al2O3–MgO–SiO2 (CAMS) based glass ceramic to form diopside through addition of iron oxide were investigated using differential thermal analysis (DTA), Raman spectrum, X-ray diffraction, SEM and EBSD techniques. The experimental results showed that addition of Fe2O3 led to remarkable reductions in both the glass transition temperature (Tg) and crystallization temperature (Tp) of the CAMS glass ceramic. At addition level below 5 wt%, the Tg and Tp temperatures were 651°C and 903°C, respectively, and the crystallization only occurred on the surface of the glass ceramic samples. Increasing the addition level to 10 wt% and 15 wt%, not only led to reduction in the Tg and Tp temperatures to 643-641°C and 892-876°C, respectively, but also promoted the formation of crystalline diopside throughout the CAMS samples. Based on the results of Raman spectrums, it was confirmed that Fe2O3 addition reduced the strength of glass connection as a result of chemical reactions between the isolated Si–O tetrahedron and Fe3+ ion, forming Fe3+O4–SiO4, which can be regarded as Q2 unit. And this is the first experimental evidence that proving the approach of Fe3+ mending glass network. Microstructural examination also identified the formation of large numbers of spherical Fe-enriched regions within the CAMS glass matrix as a result of the amorphous phase separation due to the Fe2O3 addition. The interfaces between the Fe-enriched regions and the glass matrix acted as preferred nucleation sites for the diopside, facilitating the crystallization. Crystallographic analysis using EBSD technique determined the <001> as the most favorite growth direction for the diopside crystals in the CAMS based glass ceramic. 相似文献