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1.
Xiaoyuan Sun Zixuan Liu Hao Qian Yunfei Liu Yinong Lyu 《Ceramics International》2021,47(17):24207-24217
A strategy that constructs the morphotropic phase boundary and manipulates the domain structure has been used to design the component of 0.96[Bi0.5(Na0.84K0.16)0.5Ti(1-x)NbxO3]-0.04SrTiO3 (BNKT-4ST-100xNb) to enhance the strain properties for actuator application. Non-equivalent Nb5+ donor doping modulates the phase transition from the mixture of rhombohedral and tetragonal phases to the pseudocubic phase and results in the coexistence of multiple phases. Moreover, the high-resolution TEM confirms the existence of polar nano regions that contribute to the macroscopic relaxor behaviour. The size of the domains is reduced with increasing Nb5+, resulting in an enhanced relaxor behaviour. The ferroelectric-relaxor transition temperature decreases from 85 to below 30 °C, implying a non-ergodic to ergodic relaxor transition. An improved strain of 0.56% and a giant normalized strain of 1120 pm/V were achieved for BNKT-4ST-1.5Nb, which were attributed to the unique domain structure in which nanodomains are embedded in an undistorted cubic matrix. Ferroelectric, antiferroelectric, and relaxor phases coexist. As the electric field is large enough, a reversible phase transition occurs. Furthermore, good temperature stability was obtained due to the stability of the nanodomains, and no degradation in strains was observed even after 104 cycles, which may originate from the reversible phase transition and dynamic domain wall. The results show that this design strategy offers a reference way to improve the strain behaviour and that BNKT-4ST-100xNb ceramics could be a potential material for high-displacement actuator applications. 相似文献
2.
Speciation of copper in high chloride concentrations,in the context of corrosion of copper canisters
Canisters with a cast iron insert for mechanical strength and a 50-mm thick copper shell as corrosion protection are planned to be used for disposal of spent nuclear fuel in Sweden and Finland. Chloride can be considered “beneficial”, as it promotes active dissolution of copper rather than passivation (which might result in pitting), but a high concentration of chloride in solution would increase the driving force for corrosion through the formation of soluble copper chloro complexes. Thermodynamic calculations are performed in this study with the PHREEQC software and three of its accompanying databases, and a comparison with experimental data is performed to select the database to be used when evaluating repository performance. The activity coefficient models are given special attention. For the assessment of chloride-assisted corrosion of a KBS-3 canister, chloride concentrations pessimistically up to 5 mol/kg are used (in Finland and Sweden, the groundwater and bentonite porewater chloride concentrations are not expected to exceed 1 mol/kg). The resulting copper solubilities are then considered in different mass transport cases. 相似文献
3.
Protection and confinement effect of carbon on Co/CoxOy nano-catalyst for efficient NaBH4 hydrolysis
《International Journal of Hydrogen Energy》2022,47(46):20185-20193
The hydrolysis of sodium borohydride (NaBH4) over catalysts is a promising method to produce hydrogen. Although Co-based catalysts exhibit high activity for NaBH4 hydrolysis, they are still far from satisfying practical applications, especially their poor durability in alkaline media. Herein, a carbon shell structure was designed and synthesized to improve the stability of the mixture of Co0 and CoxOy nanofilms (Co/CoxOy@C) during NaBH4 hydrolysis via a facile polymerization-pyrolysis strategy with Co/CoxOy nanofilms as the precursor. As a result, the Co/CoxOy@C catalyst can achieve a remarkable H2 generation rate of 4348.6 mL min?1 gCo?1 with a low activation energy of 43.6 kJ mol?1, which is superior to most previously reported catalysts. Moreover, the catalyst shows high stability with an H2 generation-specific rate of 79% after five cycles. The excellent performance of carbon substrate can well prevent the agglomeration of Co-based nanoparticle and improve the corrosion resistance of the active Co to BO2? and OH?. This work would widen the road for the preparation of nanoconfined catalysts, which has prospective application potentials for H2 production from NaBH4 hydrolysis. 相似文献
4.
Jiachen Wang Jian Li Rui Wang Fei-Yue Xu Xin-An Zeng 《International Journal of Food Science & Technology》2022,57(2):791-800
Frozen poultry meat is the most widely consumed animal-based food. However, water loss often leads to quality loss of poultry meat. Therefore, the present study sought to investigate the combined effect of calcium chloride (CaCl2) and pulsed electric fields (PEF) treatment on chicken breast meats and the mechanisms underlying protein degradation. The results showed that the synergistic effect was superior to the single treatment. Compared with the untreated group, the combination of CaCl2 and PEF increased water holding capacity of chicken breast meats by 16.61% and decreased cooking loss by 28.93%. Low-field nuclear magnetic resonance (LF-NMR) results indicated that the synergistic treatment promoted water molecules' binding capacity in myofibrils of poultry meat, which exhibited higher immobilised water. Additionally, the combination of CaCl2 and PEF led to increased degradation of proteins of high-molecular weight and surface hydrophobicity of myofibrillar protein. Furthermore, the extension of the protein molecule and microenvironmental changes promoted interaction between protein and water. In conclusion, the synergistic treatment of CaCl2 and PEF enhanced water retention and improved physicochemical properties of the myofibrillar protein in chicken breast meats. 相似文献
5.
Wafaa Mohamed SHABAN Khalid ELBAZ Mohamed AMIN Ayat gamal ASHOUR 《Frontiers of Structural and Civil Engineering》2022,16(3):329
This study presents a new systematic algorithm to optimize the durability of reinforced recycled aggregate concrete. The proposed algorithm integrates machine learning with a new version of the firefly algorithm called chaotic based firefly algorithm (CFA) to evolve a rational and efficient predictive model. The CFA optimizer is augmented with chaotic maps and Lévy flight to improve the firefly performance in forecasting the chloride penetrability of strengthened recycled aggregate concrete (RAC). A comprehensive and credible database of distinctive chloride migration coefficient results is used to establish the developed algorithm. A dataset composite of nine effective parameters, including concrete components and fundamental characteristics of recycled aggregate (RA), is used as input to predict the migration coefficient of strengthened RAC as output. k-fold cross validation algorithm is utilized to validate the hybrid algorithm. Three numerical benchmark analyses are applied to prove the superiority and applicability of the CFA algorithm in predicting chloride penetrability. Results show that the developed CFA approach significantly outperforms the firefly algorithm on almost tested functions and demonstrates powerful prediction. In addition, the proposed strategy can be an active tool to recognize the contradictions in the experimental results and can be especially beneficial for assessing the chloride resistance of RAC. 相似文献
6.
《Ceramics International》2022,48(12):17185-17195
This study introduces micro-nano bubbles (MNBs) in the process of polishing zirconia ceramics through sodium borohydride hydrolysis to assist in polishing yttria-stabilized zirconia (YSZ). Compared with conventional silica sol, the material removal rate using this MNB-assisted technology is increased by 261.4%, and a lower surface roughness of 1.28 nm can be obtained. Raman, X-ray diffraction, and X-ray photoelectron spectroscopy are used to study the structural changes and phase stability of the YSZ during different polishing periods. The results show that MNBs are the key factor promoting the transformation from the tetragonal phase to the monoclinic phase on the surface of the YSZ during polishing. The H2O molecules (or OH? ions) on the surface of the YSZ are driven by the thermal kinetic energy of the micro-jets formed by the collapse of micro-bubbles, and they permeate to occupy more oxygen vacancies in the crystal lattice. Atomic force microscopy and nano-indentation tests show that the micro-protrusions on the surface of the YSZ preferentially undergo phase transformation, and their hardness decreases. This promotes abrasives to preferentially remove rough spots on the surface and achieve more efficient polishing. We believe this work adds valuable insights regarding low-temperature degradation and ultra-precise machining of YSZ ceramic materials. 相似文献
7.
《International Journal of Hydrogen Energy》2022,47(55):23310-23315
Alkaline aqueous solution of sodium borohydride NaBH4 (denoted SB-fuel) is an indirect fuel when it is used to generate H2 by hydrolysis, with the as-generated H2 feeding a fuel cell, and it is a direct fuel when it is an anodic fuel of a direct fuel cell. However, SB-fuel suffers from a major drawback: NaBH4 spontaneously hydrolyzes. Our study falls within this context. We studied the instability, at the NMR scale and over 12 weeks, of a series of SB-fuels (initial NaBH4 concentration from 3.65 to 31.22 wt%, NaOH concentration from 1 to 16 M, and temperature between ?15 and 60 °C) to find the conditions at which SB-fuel can be stored for weeks in relative safety. We found that SB-fuel with a NaOH concentration of ≥8 M is relatively stable under cold conditions (?15 and 4 °C). In these conditions, NaBH4 is not prevented from hydrolyzing, but the reaction is significantly mitigated. Otherwise, our study highlights the gaps in our understanding of the SB-fuel, emphasizes SB-fuel is a new concept of fuel (it should not be seen as any current fuel), and points out the challenges for attaining higher technology readiness levels. 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(11):7242-7251
In the present study, metal-free catalysts for efficient H2 generation from NaBH4 methanolysis was produced for the first time from apricot kernel shells with two-step activation. The first stage of the two-stage activation includes the production of activated carbon with the KOH agent (AKOH), and the second stage includes hydrothermally HNO3 activation with oxygen doping (O doped AKOH + N). The hydrogen production rate (HGR) and the activation energy (Ea) of the reaction with the obtained metal-free catalyst (10 mg) were determined as 14,444 ml min?1 g?1 and 7.86 kJ mol?1, respectively. The structural and physical-chemical properties of these catalysts were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), elemental CHNS analysis, FT-IR (Fourier transform infrared spectroscopy), and nitrogen adsorption analysis. Also, the reusability results of this metal-free catalyst for H2 production are promising. 相似文献
9.
《International Journal of Hydrogen Energy》2021,46(64):32403-32412
Porous carbon nanostructures are promising supports for stabilizing the highly dispersed metal nanoparticles and facilitating the mass transfer during the reaction, which are critical to achieve the high efficiency of hydrogen generation from sodium borohydride dehydrogenation. Herein, the catalytically active porous architectures are simply prepared by using 2-methylimidazole and melamine as reactive sources. The structural and compositional characterizations reveal the coexistence of metallic cobalt and N-doped carbon in porous architectures. Electron microscopy observations indicate that the synthesized products are smartly constructed from the carbon nanosheets with densely dispersed Co nanoparticles. Due to the notable structural features, the prepared Co@NC-600 sample presents the highly efficient activity for catalytic hydrolysis of NaBH4 with a hydrogen generation rate of 2574 mL min−1 gcat−1 and an activation energy of 47.6 kJ mol−1. The catalytically active metallic Co and suitable support-effect of N-doped carbon are responsible for catalytic dehydrogenation. 相似文献
10.
Tao Wang Weihui Jiang Jianmin Liu Guo Feng Lifeng Miao Ting Chen Qian Wu 《Ceramics International》2019,45(4):4514-4519
High quality zirconia whiskers have been successfully prepared by molten salt method, using zirconium oxychloride (ZrOCl2·8H2O) and sodium phosphate tribasic dodecahydrate (Na3PO4·12H2O) as precursor and molten salt, respectively. The effects of types of molten salt and heat treatment temperature on the formation of zirconia whiskers were characterized by XRD, Raman, DTA-TG, FE-SEM, TEM, SAED and HR-TEM. When Na3PO4·12H2O is utilized as molten salt and the heat treatment temperature is 900?°C, the as-prepared zirconia whiskers with length ranging from 4?µm to 8?µm show an average aspect ratio of 25. The obtained ZrO2 whiskers with monoclinic structure are elongated along [010] direction and exhibit a smooth surface with no distinct defects. The XRD and Raman results reveal that the phase transformation from tetragonal zirconia to monoclinic zirconia occurs with the increased crystal size and the water quenching treatment can significantly reduce the content of sodium zirconium phosphate [Na9–4×Zrx(PO4)3] in the final product. The growth mechanism of zirconia whiskers is supposed to be a dissolution-precipitation process. Since the sodium zirconium phosphate [Na9–4×Zrx(PO4)3] effectively promotes the dissolution of zirconia in liquid molten salt, zirconia can grow into zirconia whiskers according to its anisotropy. 相似文献