共查询到20条相似文献,搜索用时 31 毫秒
1.
Sung Ho Lee Hansoo Lee Jeong-Guk Kim 《Journal of Industrial and Engineering Chemistry》2013,19(5):1606-1610
Pyroprocessing technology is one of the most promising technologies for an advanced fuel cycle with favorable economic potential and intrinsic proliferation-resistance. In pyroprocessing technology, the development of high-temperature transport technologies for molten salt is a crucial prerequisite and a key issue in the industrialization of pyro-reprocessing. However, there have been a few transport studies on high-temperature molten salt. Three different salt transport technologies (gravity, suction pump, and centrifugal pump) were investigated, a suction pump transport method was selected for molten salt transport owing to its flexibility. An apparatus for suction transport experiments was designed and installed for the development of high temperature molten salt transport technology. About 2 kg of LiCl–KCl eutectic salt was prepared by mixing 99.0%, LiCl and KCl and drying in a convection dry oven at 200 °C for 1 h. Predissolution tests of the prepared LiCl–KCl eutectic salt using the melting reactor of the experimental apparatus was carried out to investigate the dissolution behavior of the prepared LiCl–KCl eutectic salt. From the results of the pre-dissolution test, it was found that prepared LiCl–KCl eutectic salt was well dissolved at 500 °C. High temperature molten salt transport experiments by suction are currently being performed using the prepared LiC–KCl eutectic salt. The preliminary experimental results of lab-scale molten salt transport showed a 99.5% transport rate (ratio of transported salt to total salt) under a vacuum range of 100 m torr–10 torr at 500 °C. 相似文献
2.
《Journal of the European Ceramic Society》2007,27(12):3407-3412
ZnAl2O4 powder was synthesised by reacting equimolar ZnO and Al2O3 powders in alkaline chlorides (LiCl, NaCl or KCl). Formation of ZnAl2O4 started at about 700 °C in LiCl and 800 °C in NaCl and KCl. With increasing temperature, the amounts of ZnAl2O4 in the resultant powders increased with a concomitant decrease of ZnO and Al2O3. ZnAl2O4 powder was obtained by water-washing the samples heated for 3 h at 1000 °C (LiCl) or 1050 °C (NaCl and KCl). ZnAl2O4 formed in situ on Al2O3 grains from the surface inwards. The synthesised ZnAl2O4 grains retained the size and morphology of the original Al2O3 powders, indicating that a template formation mechanism dominated formation of ZnAl2O4 by molten salt synthesis. 相似文献
3.
《Ceramics International》2016,42(5):6221-6227
Ultrafine powders of pyrochlore-type La2Zr2O7 were synthesized via a simple molten salt mediated process using zirconium oxide and lanthanum oxide as raw materials, and sodium chloride, potassium chloride and sodium fluoride to form a reaction medium. The effects of reaction temperature, salt/reactant ratio and salt type on the La2Zr2O7 formation were investigated. Among the three attempted salt assemblies (KCl–LiCl, Na2CO3–K2CO3, and NaCl–KCl–NaF), NaCl–KCl–NaF showed the best accelerating effect on the La2Zr2O7 formation. At a given temperature, the La2Zr2O7 content in the final products increased with the increase in the salt amount. Phase pure submicron sized La2Zr2O7 ultrafine powders were obtained after 3 h firing at 1100 °C with the salt/reactant weight ratio of 5:1 or at 1200 °C with salt/reactant weight ratio of 3:1. The synthesis temperature (1100 °C) was much lower than that required by the conventional solid-state mixing method or a wet chemical method. The “dissolution–precipitation” mechanism had dominated the synthesis process. 相似文献
4.
Jagadeesh Sure A. Ravi Shankar S. Ramya U. Kamachi Mudali 《Ceramics International》2012,38(4):2803-2812
Corrosion studies were performed on uncoated high density graphite and plasma sprayed partially stabilized zirconia (PSZ) coated high density graphite with NiCrAlY bond coat in molten LiCl–KCl eutectic salt at 600 °C for periods of 250 h, 1000 h and 2000 h under inert argon atmosphere. High density graphite showed weight loss while PSZ coated high density graphite showed weight gain. There is no significant attack and degradation of top PSZ coating in molten salt, however microcracks were observed at the bond coat-substrate interface after 2000 h of exposure. PSZ coated high density graphite exhibited excellent corrosion resistance in molten LiCl–KCl salt due to chemical stability and absence of phase transformation as confirmed from scanning electron microscopy, X-ray diffraction and laser Raman studies, however adhesion of the coating has to be improved. 相似文献
5.
A molten salt method was proposed to synthesize SrTiO3 nanocrystals in the eutectic NaCl–KCl at 700 °C for 6 h, by using the homemade TiO2 nanocrystals and commercial Sr(NO3)2 powder as raw materials. Besides, a control experiment with the commercial TiO2 submicron-sized crystallites as a precursor was also conducted. The structure and composition of the obtained products were characterized by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results from XRD and XPS revealed the preparation of pure cubic phase SrTiO3 powders. The TEM observation demonstrated that the nanocrystalline TiO2 precursor played an important role in the current molten salt synthesis of SrTiO3 nanocrystals, which were likely formed by the template formation mechanism. 相似文献
6.
《Journal of the European Ceramic Society》2007,27(10):3201-3205
Rhombohedral LaAlO3 powder was synthesised by reacting equimolar La2O3 and Al2O3 in a molten KF–KCl eutectic salt for 3 h between 630 and 800 °C. The lowest synthesis temperature (630 °C) is about 1000 °C lower than that of conventional mixed oxide synthesis, and close to or lower than those used by most wet chemical methods. The LaAlO3 particle size increased from <3 to 3–7 μm with increasing temperature from 630 to 700 °C, but changed little on further increasing temperature to 800 °C. On the other hand, it decreased with increasing salt/oxide weight ratio from 1:1 to 6:1. The “dissolution–precipitation” mechanism played a dominant role in the molten salt synthesis of LaAlO3. 相似文献
7.
《Ceramics International》2017,43(2):1975-1979
Dy2TiO5 powders were synthesized by molten salt and solid-state methods. The influences of molten medium on phase compositions and microstructures were analyzed. The addition of molten salt lowered significantly the synthesis temperature and resulted in uniform powders. Green bodies compacted from the prepared powders were pressureless sintered at 1600 °C. Sinterability, mechanical properties and neutron absorption performance of the sintered pellets were studied. Results showed that molten salt synthesis resulted in materials with higher fracture toughness and bending strength, excellent hardness and neutron adsorption performance compared to the solid-state process. The neutron absorption rate reached 86.6% for 8 cm thick pellets. 相似文献
8.
Nano-CaZrO3 was successfully synthesized at 800 °C using the molten-salt method, and the effects of salt type and raw materials particle size on the formation of CaZrO3 were investigated. Na2CO3, CaCl2, nano-ZrO2 and micro-ZrO2 were used as starting materials. On heating, Na2CO3 reacted with CaCl2 to form NaCl and in situ CaCO3. Na2CO3–NaCl molten eutectic salt provided a liquid medium for reaction of CaCO3 and ZrO2 to form CaZrO3. The results demonstrated that in both nano- and micro-ZrO2 inclusive samples, CaZrO3 started to form at about 700 °C and that, after the temperature was increased to 1000 °C, the amounts of CaZrO3 in the resultant powders increased with a concomitant decrease in CaCO3 and ZrO2 contents. After washing with hot-distilled water, the samples containing nano- and micro-ZrO2 heated for 3 h at 800 °C and 1000 °C, were single-phase CaZrO3 with 70–90 nm and 400–450 nm particle size, respectively. Also, the synthesis process was completed in lower temperatures using eutectic salts. Furthermore, the synthesized CaZrO3 particles retained the size and morphology of the ZrO2 powders, which indicated that a template formation mechanism dominated the formation of CaZrO3 by molten-salt synthesis. 相似文献
9.
Zhensen Liu Junfeng Ma Yong Sun Zuwei Song Jingrui Fang Ye Liu Chang Gao Jingang Zhao 《Ceramics International》2010,36(6):2003-2006
YAlO3 (YAP) powders were successfully synthesized by a unique molten salt method, where YAP precursor was prepared by an electrochemical method at room temperature, followed by calcining it at a temperature of not exceeding 400 °C for 8 h using LiNO3 as the molten salt medium. XRD analysis and TEM observation show that well-crystallized YAP powders can be obtained at 400 °C for a holding time of 8 h with 1:16 ratio of YAP precursor to LiNO3 by weight. Greatly reduced temperature of forming YAP should be attributed to the incorporation of LiNO3 salt in preparing process. 相似文献
10.
This paper reports the development of a new process for the synthesis of spinel nano powder via microwave assisted high energy ball milling of a powder mixture containing Al(OH)3 and Mg(OH)2. X-ray diffraction (XRD), Simultaneous thermal analysis (STA), FTIR spectrometer, BET and scanning electron microscopy (SEM) techniques were utilized to characterize the as-milled and annealed samples. X-ray diffraction results provide evidence for the formation of a completely amorphous phase after milling for 8 h. It is found that highly ordered MgAl2O4 spinel can be obtained by calcination the as-milled powder over 800 °C. Also, SEM observations of synthesized powders showed that the particle size of powders lies in the nano meter range compared with the BET results (about 28–149 nm). The DTA–TG analyses were carried out to investigate the effect of microwave heating on the synthesis temperature compared to the conventional heat treatment by conventional furnace. Synthesis of powders with different heating methods showed that microwave heating reduces the synthesis temperature by about 200 °C. 相似文献
11.
《Ceramics International》2016,42(8):9565-9570
Zirconium diboride (ZrB2) was synthesized by a solution-based technique using zirconyl chloride (ZrOCl2·8H2O, ZOO), boric acid (H3BO3, BA) and gum karaya (GK) as the sources of zirconium, boron and carbon, respectively. The initial formation temperature of ZrB2 was 1200 °C and complete conversion was achieved by 1400 °C. Preceramic precursors and as-synthesized ZrB2 powders were characterized by XRD, TG-DTA, SEM, TEM, EDX and compared with commercial ZrB2 powder made by carbothermic reduction. FT-IR of as-synthesized dried preceramic precursor revealed the formation of Zr–O–C and Zr–O–B whereas SEM showed agglomerated spherical particles with mean diameter of <1 µm. Commercial ZrB2 and as-synthesized fine ZrB2 powder were spark plasma sintered (SPS) at 1900 °C for 10 min. Addition of 10 wt% of synthesized fine powder improved the fired density from 87% to 93% of theoretical. A significant cost benefit arises for the utilization of cheap synthesized fine powder as an additive for the densification of the more expensive commercial powder. 相似文献
12.
Lanthanide hexaaluminate powders of LaMgAl11O19 (LMA), NdMgAl11O19 (NMA) and GdMgAl11O19 (GMA) were synthesized via the solid state reaction or sol–gel and calcination method. The LMA and NMA powders synthesized by the sol–gel and calcination method at 1600 °C for 8 h exhibit a single hexaaluminate phase with magnetoplumbite structure; however, the GMA powder synthesized by the sol–gel and calcination method at 1600 °C for 8 h contains both a hexaaluminate phase and a small amount of second phase GdAlO3 with a perovskite structure. The powders synthesized by the solid state reaction method at 1500 °C for 4 h have a small particle size of 1–3 μm, and a large specific surface area and a good uniformity. The powders synthesized by the sol–gel and calcination method at 1600 °C for 8 h have a particle size of 5–20 μm, and exhibit to a certain extent agglomeration. 相似文献
13.
《Journal of the European Ceramic Society》2007,27(13-15):3591-3595
Lead-free KNbO3 (KN) powder was fabricated by sol–gel process from metal alkoxides. KN precursor solutions were prepared by different preparation conditions such as the order of reflux process for alkoxides and the kinds of solvent. KN powders were sintered at 900 °C with a heating rate of 10 °C/min. Single phase KN powder was obtained using precursor solution prepared by reflux at 120 °C. We considered that the crystallinity of KN powder was affected by the dimer in Nb-pentaethoxide of the starting chemicals. On the other hand, grain shape of the KN powder also depended on the existence of secondary phase K4Nb6O17, and the grain size of the fine powder fabricated from precursor solution prepared by reflux at 80 °C using 2-methoxethanol and ethanol solvents was estimated to be about 500 nm and 1 μm, respectively. 相似文献
14.
《Ceramics International》2016,42(3):4285-4289
Decreasing the electrolyte thickness is an effective approach to improve solid oxide fuel cells (SOFCs) performance for intermediate-temperature applications. Sm0.2Ce0.8O2−δ (SDC) powders with low apparent density of 32±0.3 mg cm−3 are synthesized by microwave combustion method, and SDC electrolyte films as thin as ~10 μm are fabricated by co-pressing the powders onto a porous NiO–SDC anode substrate. Dense SDC electrolyte thin films with grain size of 300–800 nm are achieved at a low co-firing temperature of 1200 °C. Single cells based on SDC thin films show peak power densities of 0.86 W cm−2 at 650 °C using 3 vol% humidified H2 as fuel and ambient air as oxidant. Both the thin thickness of electrolyte films and ultra-fine grained anode structure make contributions to the improved cell performance. 相似文献
15.
R. Fazli M. Fazli Y. Safaei-Naeini F. Golestani-fard A. Mirhabibi 《Ceramics International》2012,38(7):5363-5368
Nano-particles of CaZrO3 were successfully synthesized at 800 °C using the molten-salt method, and the effects of processing parameters, such as temperature, holding time and amount of salt on the crystallization of CaZrO3 were investigated. Na2CO3, CaCl2 and nano-ZrO2 were used as starting materials. On heating, Na2CO3 reacted with CaCl2 to form NaCl and in situ CaCO3. Na2CO3–NaCl molten eutectic salt provided a liquid medium for reaction of CaCO3 and ZrO2 to form CaZrO3. The results demonstrated that CaZrO3 started to form at about 700 °C and that, after the temperature was increased to 1000 °C, the amounts of CaZrO3 in the resultant powders increased with a concomitant decrease in CaCO3 and ZrO2 contents. After washing with hot-distilled water, the samples heated for 3 h at 800 °C were single-phase CaZrO3 with 70–90 nm particle size. Furthermore, the synthesized CaZrO3 particles retained the size and morphology of the ZrO2 powders, which indicated that a template formation mechanism dominated the formation of CaZrO3 by molten-salt synthesis. 相似文献
16.
《Ceramics International》2017,43(14):11132-11141
Dy3+ doped calcium bismuth borate glasses were synthesized in the composition range of xLiCl-(30 − x)CaO-20Bi2O3-50B2O3 + 1 mol% Dy2O3 (x = 0, 2, 5, 7, 10 and 15 mol%, LC0, LC2, LC5, LC7, LC10 and LC15 respectively) using conventional melt-quench technique. Broad XRD profiles confirmed non-crystalline nature of synthesized compositions. The compositional dependencies of structural changes (using FTIR spectra), thermal behavior (using DSC thermographs) and optical band gap (using UV–Vis–NIR spectra) were discussed. Photoluminescence (PL) excitation spectra recorded at 577 nm yielded six different excitation peaks belonging to Dy3+ ions. The PL emission spectra recorded at 451 nm were analyzed to extract different light emission parameters viz. Y/B ratio, color coordinates, correlated color temperature (CCT) following CIE 1931 chromaticity diagram. The emission colors were found to lie in white light region and lies very close to standard white light emission. The CCT of sample LC10 (5335 K) is closest to CCT of standard white light (5615 K) which depicted the optimized concentration of LiCl for application of these glasses in WLED application. 相似文献
17.
《Ceramics International》2016,42(6):7210-7215
VC–Co nanocomposite powders were obtained by mechanochemical combustion synthesis from a mixture of V2O5, Co3O4, C and Mg powders. The synthesized powders were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). VC–Co nanocomposite was directly produced after 10 min milling through a mechanically induced self-sustaining reaction without further heat treatment. TEM analysis showed that a nanostructured powder with a mean particle size of 100 nm was procured in the sample milled for 10 min. 相似文献
18.
《Ceramics International》2016,42(7):7974-7979
In this paper forsterite (Mg2SiO4) nanopowder with particle size in the range of 33 and 112 nm was synthesized by a combination of sol–gel and ball milling methods. Magnesium nitrate and silica were used as the sources of magnesium and silicon in the forsterite nanopowder. Thermogravimetry (TG) analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and dynamic light scattering (DLS) techniques were utilized to characterize the synthesized powders. Single-phase nanocrystalline forsterite powder with mean crystallite size of about 16 nm was obtained from sol–gel method with subsequent ball milling for 5 h and heat treatment at 750 °C for 1 h. A combination of sol–gel and mechanical activation led to the formation of more homogeneous powder and subsequently lower sintering temperature to produce forsterite powder. In vitro biological studies were performed by immersing the forsterite samples in simulated body fluid (SBF). The results showed that nanostructure forsterite is bioactive and possessed apatite formation ability. 相似文献
19.
S. Vandarkuzhali Nibedita Gogoi Suddhasattwa Ghosh B. Prabhakara Reddy K. Nagarajan 《Electrochimica acta》2012
The electrochemical behaviour of lanthanum was studied at inert tungsten electrode and reactive aluminium electrode in LiCl–KCl eutectic melt in the temperature range 698–798 K using transient electrochemical techniques. Reduction of La(III) to La(0) at the tungsten electrode takes place in a single step. The reduction shows quasi-reversible behaviour for polarization rates, 25 ≤ ν ≤ 150 mV s?1 and is predominantly controlled by charge transfer of La(III) ions for scan rates higher than 75 mV s?1. The heterogenous rate constant of the process was estimated from impedance spectroscopy and from the semi-integrals of the cyclic voltammograms. The redox potential of the La(III)/La couple at the Al electrode was observed to be more positive than that at the inert electrode. This potential shift is due to the lowering of the activity of La in the metal phase caused by the formation of the intermetallic compound Al11La3. Thermodynamic properties such as Gibbs energy of formation of Al11La3, excess Gibbs energy and the activity coefficient of La in Al were calculated from the open circuit potential measurement. 相似文献
20.
《Journal of the European Ceramic Society》2005,25(4):473-480
Ni/Sm-doped ceria (SDC) cermet was prepared from two types of NiO/SDC mixed powders: Type A—Mechanical mixing of NiO and SDC powders of micrometer-sized porous secondary particles containing loosely packed nanometer-sized primary particles. The starting powders were synthesized by calcining the oxalate precursor formed by adding the mixed nitrate solution of Ce and Sm or Ni nitrate solution into oxalic acid solution. Type B—Infiltration of Ni(NO3)2 solution into the SDC porous secondary particles subsequently freeze-dried. Type B powder gave denser NiO/SDC secondary particles with higher specific surface area than Type A powder. The above two types powders were sintered in air at 1100–1300 °C and annealed in the H2/Ar or H2/H2O atmosphere at 400–700 °C. Increased NiO content reduced the sinterability of Type A powder but the bulk density of Type B powder compact showed a maximum at 34 vol.% NiO (25 vol.% Ni). Type B cermet was superior to Type A cermet in achieving fine-grained microstructure and a homogeneous distribution of Ni and SDC grains. The electrical resistance of the produced cermet decreased drastically at 15 vol.% Ni for Type B and at 20 vol.% Ni for Type A. 相似文献