Browsing by Author "Chen, Jian"

Now showing 1 - 6 of 6
  • Thumbnail Image
    ItemOpen Access
    Bismuth ferrite materials for solar cells: Current status and prospects
    (Elsevier, 2018-10-09) Chen, Guang; Chen, Jian; Pei, Weijie; Lu, Yinmei; Zhang, Qingfeng; Zhang, Qi; He, Yunbin
    Different from classical semiconductor photovoltaic devices, for ferroelectric photovoltaic devices, the open-circuit voltage (Voc) can be four and even more orders of magnitude larger than the band gap of the ferroelectric, and the built-in electric field arising from the remnant polarization of the ferroelectric is throughout the bulk region, which is good for obtaining giant power conversion efficiency. Among ferroelectric materials, BiFeO3 with remnant polarization of as high as ∼100 μC/cm2 has the narrowest direct band gap (∼2.7 eV). These indicate that high power conversion efficiency may be obtained in BiFeO3-based photovoltaic devices. Also, some significant research results about photovoltaic effects of BiFeO3 materials have been recently acquired. In order to better promote the development of BiFeO3-based photovoltaic devices, in this paper, we present a comprehensive review on the latest research progress in photovoltaic effects of BiFeO3 materials with different kinds of topography, including bulk, thin film, and nanomaterials.
  • Thumbnail Image
    ItemOpen Access
    Experimental and kinetic study of thermal decomposition behaviour of phytoremediation derived Pteris vittata
    (Springer, 2016-12-20) Duan, Lunbo; Chen, Jian; Jiang, Ying; Li, Xiaole; Longhurst, Philip J.; Lei, Mei
    Combustion and gasification for biomass to energy conversion is often suggested for the management of residual Pteris vittata from phytoremediation. In this study, the thermal behaviour of P. vittata was studied on a thermogravimetric analyser, and the kinetic triplet of biomass sample was further determined for different stages of the thermochemical processes using the Ozawa and KAS methods, subsequently modified by an iterative procedure. Results show that thermal decomposition under combustion condition was complete at a lower temperature of ~500 °C compared to ~700 °C for gasification, indicating the both easily complete conversion of P. vittata by combustion and gasification. Kinetic study shows that although activation energy for each stage under combustion condition is mostly larger than that under gasification, the reaction rate of thermal decomposition of P. vittata under combustion condition is still great larger than that under gasification condition. These findings strongly suggest that thermochemical processes offer suitable methods for the volume reduction and energy production of P. vittata.
  • Thumbnail Image
    ItemOpen Access
    Exploration on the origin of enhanced piezoelectric properties in transition-metal ion doped KNN based lead-free ceramics
    (Elsevier, 2018-06-12) Xu, Fang; Chen, Jian; Lu, Yinmei; Zhang, Qingfeng; Zhang, Qi; Zhou, Taosheng; He, Yunbin
    In this work, we studied effects of Ni2O3 and Co2O3 doping on crystal structures, microstructures, orthorhombic and tetragonal phase transition temperature (To-t), and electrical properties of [Li0.06(Na0.57K0.43)0.94][Ta0.05(Sb0.06Nb0.94)0.95]O3 (LNKTSN) lead-free ceramics. The experimental results showed that the Ni2O3 addition with appropriate amount could shift the To-t downwards to the room temperature, and thus obviously increasing the room-temperature piezoelectric coefficient (d33), dielectric coefficient (εr) and electromechanical coupling coefficient (kp) of the LNKTSN ceramics. These were consistent with previous experimental results obtained in Fe2O3 doped LNKTSN ceramics. On the contrary, Co3+ doping shifted continuously the To-t upward and deteriorated obviously piezoelectric properties of LNKTSN ceramics. Fe, Co and Ni had similar ion radii and were expected to result in the same (donor or acceptor) doping effects on electrical properties of LNKTSN ceramics. The different doping effects between Co3+ (deterioration) and Ni3+ or Fe3+ (improvement) on the electrical properties of LNKTSN ceramics suggested that the coexistence of orthorhombic and tetragonal phases at room temperature due to downward shift of To-t, rather than ion doping (donor or acceptor doping) effects was the main cause for enhanced room-temperature piezoelectric properties. This conclusion can be extended to all KNN-based materials in general, thus offering principle guide for future development of new lead-free materials with good piezoelectric properties.
  • Thumbnail Image
    ItemOpen Access
    A facile one-pot synthesis of CaO/CuO hollow microspheres featuring highly porous shells for enhanced CO2 capture in combined Ca-Cu looping process via a template-free synthesis approach
    (Royal Society of Chemistry, 2019-07-25) Chen, Jian; Duan, Lunbo; Shi, Tian; Bian, Ruoyu; Lu, Yuxiao; Donat, Felix; Anthony, Edward J.
    The preparation of bifunctional CaO/CuO composites with high performance is essential for the development of the combined Ca–Cu looping process, in which the exothermic reduction of CuO with methane is used in situ to provide the heat required to calcine CaCO3. However, the rapid decline in CO2 uptake of CaO/CuO composites remains an important problem to be solved, despite their excellent redox characteristic. Herein we report a facile one-pot template-free synthesis approach to yield CaO/CuO hollow microspheres, aimed at enhancing the CO2 capture performance of CaO/CuO composites. CaO/CuO hollow microspheres feature highly porous shells and a homogeneous elemental distribution, and demonstrate significantly enhanced CO2 capture performance. After ten repeated cycles in a fixed-bed reactor, the CO2 uptake capacity of the best-performing CaO/CuO hollow microspheres exceeded that of the reference materials, i.e., CaO/CuO composites synthesized via wet mixing or a co-precipitation method, by 222% and 114%, respectively. Moreover, from cycle number eight onwards, the CO2 uptake was very stable over the tested 20 cycles, suggesting good cyclic stability of CaO/CuO hollow microspheres. Oxidation was always fast with O2 uptake capacities greater than 0.13 gO2 gmaterial−1. On the basis of N2 adsorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations, the significantly enhanced CO2 capture performance of the CaO/CuO hollow microspheres resulted from the unique hollow microsphere structure with highly porous shells, which were retained throughout the cyclic operations.
  • Thumbnail Image
    ItemOpen Access
    Hybrid design based on wire and arc additive manufacturing in the aircraft industry
    (Cranfield University, 2012-12) Chen, Jian; Mehnen, Jorn; Lockett, Helen L.
    Wire and Arc Additive Manufacturing (WAAM) is a developing rapid prototyping and manufacturing technology which allows the production of large custom-made metal parts with high deposition rates, a major concern of the aircraft industry. Despite this, there is little research on the design method and application of WAAM technology in the aircraft industry. The overall research aim is to develop a step-by-step design method to create and assess hybrid design solutions based on WAAM technology. The main objectives are to: (i) analyse existing design methods and software tools; (ii) collect and analyse technical data about aircraft structure design and WAAM process; (iii) develop a hybrid design method based on WAAM technology; (iv) validate the developed design method through industrial case studies. These four objectives were achieved through the adoption of a four-phase research methodology. A hybrid design method was developed based on mature design models such as the VDI 2221model, BS 7000 design model and Pahl and Beitz’s design model and required prior knowledge of WAAM technology and aircraft structure design. This design method includes a hybrid design model and a WAAM feature based design guideline which enables the designers to create hybrid design solutions step by step and assess the proposed solutions by using the evaluation matrix chart. Hybrid design in this research encompasses design for hybrid manufacturing processes, which means that an object is to be designed partly made from prefabricated or off-the-shelf parts and partly added by WAAM process. Furthermore, Finite Element Analysis is introduced in the design method to check the performance of the preliminary design and the final design. Three case studies were carried out to verify the developed hybrid design method. The integral panel, a typical structure in aircraft, demonstrates the significant cost advantage of WAAM technology. The pylon frame and forward fitting are the structural parts provided by the Chinese aircraft industry. It shows that the cost of the final design is significantly lower than that of the preliminary design. In addition, topology optimisation is applied to achieve lower weight. The hybrid design method is validated through academic experts and industrial experts. This research project has contributed to an effective design method based on WAAM technology in the aircraft industry.
  • Thumbnail Image
    ItemOpen Access
    Self-activated, Nanostructured Composite for Improved CaL-CLC technology
    (Elsevier, 2018-06-28) Chen, Jian; Duan, Lunbo; Donat, Felix; Müller, Christoph R.; Anthony, Edward J.; Fan, Maohong
    The development of bifunctional CaO/CuO matrix composites with both high and stable reactivity is a research priority and key for the development of calcium looping integrated with chemical looping combustion (CaL-CLC), a new CO2 capture technology that eliminates the requirement for pure O2 for the regeneration of CaO-based sorbents. In this work, a simple but effective approach was first used, i.e., solution combustion synthesis (SCS), to produce various nanostructured CaO/CuO matrix composites with homogenous elemental distributions. All CaO/CuO matrix composites possessed increased CO2 uptake in the form of self-activation and excellent cyclically stable O2 carrying capacity over as many as 40 reaction cycles. For instance, the final carbonation conversion of CaO-CuO-1-800-30 was 51.3%, approximately 52.7% higher than that of the original material (33.6%). Here, the self-activation phenomenon have been observed for the first time in contrast to the rapid decay in CO2 uptake capacity previously reported, due mainly to the increase of both specific surface area and pore volume. In-situ X-ray diffraction (in-situ XRD) analysis revealed that no side reactions occurred between CaO/CaCO3 and CuO/Cu during the overall process. All of these results make CaO/CuO matrix composites an attractive candidate for CaL-CLC.