Search

The corrosion behavior and mechanism of 316 stainless steel (316SS) immersed in liquid Pb were investigated in Ar at 650 and 750 °C, respectively. The oxidation corrosion first dominated at 650 °C. The outer layer of the corroded 316SS surface was the loose iron oxide layer, and the inner layer was dense Fe-Cr spinel. However, the selective dissolution of Ni and Cr was dominant at first at 750 °C, and the O diffused to the interface increased with time, then an inner oxide layer is formed with Ni, Cr, and Fe in inner layer of the matrix. The sizes of pores formed by the dissolution gradually increased with the corrosion time increase, and the dissolved area was also partially transformed into the whole. The selective dissolution corrosion of the corroded 316SS was dominant at 750 °C with the time increase. The interaction mechanism between the liquid lead and 316SS was revealed. [ABSTRACT FROM AUTHOR]

The corrosion behaviours of Ni-Mo-Cr alloy and 316 stainless steel samples after immersing in NaCl-KCl-AlCl3 salt at 400.0°C for 168 h were investigated. The surface of Ni-Mo-Cr alloy basically kept its pre-corrosion morphology, with only a few corrosion pits. While NaCl-KCl-AlCl3 salt had stronger corrosivity to 316SS. After corrosion, the grain boundary of the surface of 316SS alloy was clearly visible, and the Fe and Cr atoms on the surface of 316SS were selectively corroded, leaving a Ni- rich layer of about 6.5 µm on the outmost surface of 316SS. At the temperature of 400.0°C, the corrosion resistance of Ni-Mo-Cr alloy to molten NaCl-KCl-AlCl3 salt was better than that of 316SS. [ABSTRACT FROM AUTHOR]

The corrosion resistance of 316 stainless steel (316SS) in molten KCl-MgCl2 salts was studied through static immersion corrosion at high temperatures. Below 600 °C, the corrosion rate of 316SS increased slowly with increasing temperature. When the salt temperature rises to 700 °C, the corrosion rate of 316SS increases dramatically. The corrosion of 316SS is mainly due to the selective dissolution of Cr and Fe at high temperatures. The impurities in molten KCl-MgCl2 salts could accelerate the dissolution of Cr and Fe atoms in the grain boundary of 316SS, and purification treatment can reduce the corrosivity of KCl-MgCl2 salts. Under the experimental conditions, the diffusion rate of Cr/Fe in 316SS changed more with temperature than the reaction rate of salt impurities with Cr/Fe. [ABSTRACT FROM AUTHOR]

Alkali silicate-based ceramics sorbents were regarded as particularly suitable materials for CO 2 capture at high temperatures, however, the CO 2 capture behaviors of Na 4 SiO 4 had been seldom investigated. In this work, the Na 4 SiO 4 ceramics samples were prepared using the one-step synthesized method, and the CO 2 sorption/desorption performances at high temperatures, the thermal stability, and the cycling stability of Na 4 SiO 4 were systematically investigated. It was demonstrated that the maximum CO 2 sorption capacity of SO-3 sample reached 19.4 wt% at 725 °C, and the optimal condition of cycling tests were 750 °C for sorption and 800 °C for desorption based on the sorption/desorption capacity and rate, which exhibited good thermal stability and high cyclic stability. Besides, the kinetic analysis results showed that the diffusion process was the rate-determining step of CO 2 adsorption, which was more dependent on temperature than the chemisorption process. The structure and surface morphology variations were also investigated, it was interesting that there was a special "fish scale" surface structure after the sorption process, revealing that the melting phenomenon happened during the chemisorption reaction process. By comparing with common sorbent Li 4 SiO 4 , the material and CO 2 capture costs of Na 4 SiO 4 were much lower. These results proved that Na 4 SiO 4 was expected to be a suitable high temperature CO 2 capture material as a good supplement to alkali silicate-based ceramics sorbents. [ABSTRACT FROM AUTHOR]

The corrosion behavior and kinetics of the 316 stainless steel (316SS) in the NaCl-KCl-AlCl 3 molten salt and salt vapor were investigated at 400 °C. The corrosion rate of 316 SS in salt vapor is faster than that in molten salt. The corrosion depth of the corroded 316 SS increases with the increase of corrosion time. The corrosion rate of 316 SS did not show a continuous downward trend as usual, but showed a multi-stage trend of stable stage, rapid rise stage and slow growth rate stage due to the formation and evolution of aluminum oxide layer on the alloy surface. • Corrosion kinetics of 316SS in NaCl-KCl-AlCl 3 salt and vapor were investigated. • NaCl-KCl-AlCl 3 salt vapor has stronger corrosion effect on 316SS than molten salt. • Evolution of aluminum oxide on the surface changed the corrosion behavior of 316SS. [ABSTRACT FROM AUTHOR]

Corrosion behaviors of 304 stainless steel (304SS) in NaCl–MgCl 2 eutectic salts with purification treatment at high temperature were firstly studied by static immersion under Ar. The weight loss of 304SS were 1.61 mg/cm2 at 500°C and 1.80 mg/cm2 at 600°C, respectively. The annual corrosion rate of 304SS was less than 100 μm, indicating that 304SS possessed excellent corrosion resistance at high temperature. The intergranular corrosion of 304SS at high temperature was accompanied by dissolution of active chromium and iron. Its corrosion of 304SS gradually intensified with temperature increase, especially after 600°C, which provided strong data support for materials selection at high temperature in the future. Owing to the compatibility of 304SS with NaCl–MgCl 2 salt, 304SS is suitable for use in the container at high temperature. [Display omitted] • Corrosion behavior of 304SS alloy in NaCl–MgCl 2 was firstly studied. • Annual corrosion rate of 304SS in purified NaCl–MgCl 2 was less than 100 μm • 304SS has good corrosion resistance in purified NaCl–MgCl 2 not exceeding 600°C. • Intergranular corrosion is obvious and selective dissolution of Cr was decisive. • Low-cost 304SS can be used the candidate medium in the next generation CSP. [ABSTRACT FROM AUTHOR]

Corrosion tests of 316 stainless steel (316SS) in NaCl–KCl–NaF reciprocal salts were conducted at different temperatures. Results showed that the reciprocal salts had perfect compatibility with 316SS even without special treatment, and a stable Cr–O enriched layer was first observed. The stabilization mechanism of chromium oxides in molten salts was explored, where the low oxoacidity was conducive to from the stable chromium oxides. These findings can provide a new direction for the design and corrosion control of molten salts. • Corrosion behavior of 316SS in NaCl-KCl-NaF salts was studied at high temperature. • NaCl-KCl-NaF salts had perfect compatibility with 316SS without special treatment. • Corrosion zone of three-layer structure and stable protective layer were observed. • Stabilization mechanism of Cr oxides protective layer in molten salts was explored. [ABSTRACT FROM AUTHOR]

• Microstructural evolution of XPTFE were firstly studied using in-situ USAXS. • The size and spacing of scatterers are more unequal in XPTFE. • Lamellae crystals in XPTFE are elongated and thinned along the tension direction. • Broken crystals and voids in irradiated XPTFE are oriented with stretching. Cross-linked polytetrafluoroethylene (XPTFE) with excellent wear and radiation resistant is expected to be applied in strong radiation fields. In this study, synchrotron ultra-small angle X-ray scattering (USAXS) techniques combined with in-situ uniaxial stretching were firstly used to study the mechanical property degradation mechanism of XPTFE in terms of micro-structural evolution in real time. As the increase of cross-linking degree, the size and spacing of the scatterers for XPTFE were more unequal. When XPTFE was uniaxially stretched at room temperature, its molecular chains were tilted, and lamellae crystals were elongated and thinned along the stretching direction. When XPTFE was irradiated by γ-rays under air, with increasing absorbed doses, the long period decreased first and then increased, while the gyration radius was reversed. After high-dose irradiation, the mechanical properties of XPTFE were lost, making their stretching processes were dominated by the orientation of some small broken crystals along the stretching direction and accompanied by the formation of voids. But for XPTFE under constant stress uniaxial stretching at variable temperature, its chain segments and molecular chains cannot be oriented even at elevated temperatures, maintaining a degree of thermal stability. [ABSTRACT FROM AUTHOR]

• Pyrolysis mechanism and products of bischofite was firstly obtained. • Pyrolysis temperature and heating rate will greatly affect the pyrolysis product. • High purity MgO was obtained after secondary calcination. • Mixture of MgO and Mg(OH)Cl coexisted at 550 and 600 °C. The thermal behavior of bischofite waste and MgCl 2 •6H 2 O was investigated by thermogravimetric analysis–derivative thermogravimetry (TGA-DTG) and X-ray diffraction (XRD). TGA-DTG results showed that the pyrolysis behavior and weight loss of bischofite were different from those of MgCl 2 •6H 2 O due to large number of impurities. The effects of temperature, atmosphere, and heating rate on the pyrolysis mechanism and products of bischofite were studied in detail by using XRD. The pyrolysis temperature remarkably affected the pyrolysis products. The mixture of MgO and Mg(OH)Cl coexisted at high temperatures of 550 and 600 °C. However, the presence of MgCl 2 was confirmed by calcination at 650 and 700 °C for 0.5 h except MgO. Through calcination at 700 °C for up to 2.0 h, the pyrolysis products of bischofite and MgCl 2 •6H 2 O were predominantly MgO, and the atmosphere had no effect on the content of MgO. Low heating rate was favorable for pyrolyzing bischofite into MgO, and the content of MgO reached 94.1% at the heating rate of 5.0 °C/min. After further purification by washing, the content of MgO in the final product increased to 99.0%. This study provided an effective route for the comprehensive utilization of bischofite resources in salt lakes. [ABSTRACT FROM AUTHOR]

• Free radicals of PAN nano-fibers were stable in vacuum but decayed fast in air. • The polyimine radicals show higher stability at room and elevated temperatures. • Radiation oxidation occurred throughout PAN nano-fibers due to smaller diameter. • Radiation oxidation facilitated dehydrogenation to drive the stabilization process. Radiation technique was found to accelerate the stabilization process of PAN nano-fibers in the production of carbon nano-fibers. The evolution and decay of the free radicals of electrospun PAN nano-fibers induced by gamma-rays irradiation were investigated using electron spin resonance. Mainly alkyl and polyimine radicals were formed and the total free radical concentration reached saturation of 1.3×1019spins/g at the dose of 200 kGy in vacuum. The free radicals were very stable with a half-life period longer than 40 days in vacuum but rapidly decayed in air. PAN nano-fibers were subject to radiation oxidation due to their small diameter when irradiated in air. The polyimine radicals were found to be more stable than alkyl radicals at room and elevated temperatures. Mainly polyene radicals were formed resulting from dehydrogenation during the stabilization process and the irradiated sample always contained higher radical concentration. The radiation oxidation facilitated the dehydrogenation to drive the thermal stabilization process. [ABSTRACT FROM AUTHOR]

The NaCl–KCl–NaF eutectic salt was designed and developed by Pandat software and experiment. Thermal transport and storage performances were determined by experimental measurements. The melting point of the NaCl–KCl–NaF eutectic salt is 604.1 °C and the fusion enthalpy is up to 398.4 J/g. The thermal conductivity average value was 1.037 ± 0.074 W/m−1·°C−1. The weight loss of NaCl–KCl–NaF eutectic salt is still less than 6.0% even up to 900 °C and the eutectic salt have very excellent thermal stability. The NaCl–KCl–NaF eutectic salt with high latent and suitable temperature have good economy performance even with expensive individual salt of NaF. The NaCl–KCl–NaF eutectic salt with suitable phase change temperature, low cost, high latent heat, excellent stability and good economy performance can be a candidate phase change material for next generation concentrated solar power with supercritical CO 2 cycles. • NaCl–KCl–NaF eutectic salts were designed and developed by Pandat and experiment. • T m of the eutectic salts is 604.1 °C and the fusion enthalpy is up to 398.4 J/g. • The eutectic salts have very excellent thermal stability. • The eutectic salts with high latent & suitable temperature have good economy performance. [ABSTRACT FROM AUTHOR]

• Corrosion behaviors of 316SS were studied in purified NaCl-MgCl 2 eutectic salt. • Good corrosion resistance of 316SS was found in purified NaCl-MgCl 2 at 600°C. • 316SS corrosion rate in purified NaCl-MgCl 2 was very low even at 700 °C. • Corrosion mechanisms of 316SS in purified NaCl-MgCl 2 were obtained. The effects of temperature on the corrosion of 316 stainless steel (316SS) in purified NaCl-MgCl 2 eutectic salt under Ar were investigated through immersion test. The corrosion of samples accelerated and intergranular corrosion became obvious with increased temperature. The corrosion of 316SS was attributed to the selective dissolution of Cr, and corrosion had strong temperature dependence. The corrosion mechanism under the NaCl-MgCl 2 eutectic salt was the combined effect of a dissolution mechanism with matrix metal element, which was attributed to the accelerating effect of surface chromium-dissolution and intergranular-diffusion rates with increased molten salt temperature. [ABSTRACT FROM AUTHOR]