No abstract

This paper reviews drivers, resources, and technologies for building the hydrogen economy in China. China is unique in terms of its vast area, huge population and fast economic growth. These factors pose a great challenge to ensure a continuous and sufficient energy supply. In addition, the coal-based energy system of China inevitably results in huge CO 2 emissions. Hydrogen shows the great potential in solving the concerns for improving energy security and reducing greenhouse gas emissions. Hydrogen can be produced from abundant and widely distributed renewable energy resources, which implies an opportunity for China to diversify its energy supplies from a hydrogen economy. Moreover, hydrogen is the cleanest fuel especially when coupled with fuel cell. Chinese government has made ambitious policy and provides strong financial support for research and development of hydrogen and fuel cell technology. All the top-tier universities and institutes in China are conducting related research and Chinese companies express strong interest in the commercialization of hydrogen and fuel cell technology.

No abstract

As important multifunctional oxides, BiFeO 3 -PbTiO 3 (BFPT) based perovskite materials have drawn increasing research interests due to their promising roomtemperature magnetoelectric (ME), [1] piezoelectric/ferroelectric, [2,3] photovoltaic, [4] and tuneable thermal expansion performances. [5] The two end members, BiFeO 3 (BFO) and PbTiO 3 (PT), can form complete solid solution in the (1−x)BFO-xPT system, where a morphotropic phase boundary (MPB) with coexisting rhombohedral and tetragonal phases was found in the composition range around x = 0.3. [6] Due to the high Curie temperatures (T C ) in both end members, the T C for the MPB compositions in BFPT is as high as ≈ 630 °C. [7] Moreover, the MPB is of metastable nature in a relatively wide composition range, [8] where a phase transition can be induced by an applied electric field. [1] Such an MPB-related phase transition could result in a giant and stable piezoelectric response. [9] Indeed, enhanced electromechanical effects were obtained recently in the vicinity of MPB of BFPT and Mn-doped BFPT, [1,10] making the BFPT system particularly interesting for high-temperature piezoelectric/ferroelectric applications.In prototype piezoelectrics such as Pb(Zr x Ti 1−x )O 3 (PZT) and Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (PMN-PT), [11,12] monoclinic phases are found to exist and act as a bridge connecting two phases on both sides of the MPB. In contrast, the MPB compositions of BFPT system show coexistence of two distinct ferroelectric phases inherited from the two respective end members. In addition, it is found in modified BFPT materials [13] that the two different ferroelectric phases also reveal diverse magnetic orderings. In our previous work, the substitution of rare earth Dy for Bi in the BFPT system is proved to induce ferromagnetism in the rhombohedral compositions with magnetic hysteresis loops, while the antiferromagnetic state is retained in the tetragonal compositions [14] at room temperature. These characteristics also make the BFPT system promising materials for the so-called phase-change large ME effects, where large ME Perovskite materials based on BiFeO 3 -PbTiO 3 (BFPT) solid solutions are promising for various applications thanks to the extremely large spontaneous polarization (P s ) and existence of multiferroic morphotropic phase boundary. For applications in piezoelectric and memory devices, complete switching of P s is needed, which is hard to achieve practically. In this work, a simple modified mixed-oxide reaction method is developed allowing to prepare Dy-and Smmodified BFPT ceramics with significantly improved properties. The MPB compositions demonstrate well-saturated ferroelectric hysteresis loops with large switchable remanent polarization of 60 µC cm −2 and enhanced piezoelectric properties with a large-signal piezoelectric coefficient d 33 * = 214 pm V −1 and a direct piezoelectric coefficient d 33 = 128 pC N −1 , which is one and a half times larger than the best d 33 value reported for the BFPT ceramics so far. The Curie temperature reaches...

The magnetic properties and magnetocaloric effects of the ErNi 1-x Cu x Al (x ¼ 0.2, 0.5, 0.8) compounds have been studied. The sample with x ¼ 0.2 is found to be antiferromagnetic below the N eel temperature of T N ¼ 4.6 K, while the sample x ¼ 0.5 is simply ferromagnetic with a Curie temperature of T C ¼ 5.8 K. In contrast, the sample x ¼ 0.8 exhibits a short-range magnetic order, as revealed by AC magnetic measurements, and the transition temperature is 5.5 K. Large magnetic entropy change (DS) without hysteresis losses has been observed around the transition temperature for all the samples. The DS displays a peak between 4 K and 10 K, and the maximal values of DS are-22.6,-25.9, and-24.8 J/kg K for the field changes of 0-5 T, corresponding to the compositions of x ¼ 0.2, x ¼ 0.5, and x ¼ 0.8, respectively. The large DS value as well as no hysteresis loss indicate that ErNi 1-x Cu x Al can be alternative candidates for magnetic refrigerant working at low temperature (<10 K). V

As the reach points of different phases with complex structural features, a morphotropic phase boundary (MPB) in ferroelectric and ferromagnetic solid solutions can significantly enhance the piezoelectric performance and magnetostrictive response, respectively. Recently, the phase-change functional responses related to the multiferroic MPB are proposed to be a promising way to enhance the magnetoelectric coupling in BiFeO3-based single phase multiferroics. In this work, we verify the tunable magnetic ordering and the construction of the multiferroic MPB by engineering the chemical concentrations of the ferroelectric/non-magnetic PbTiO3 end in the (1 – x)Bi0.9Dy0.1FeO3-xPbTiO3 binary solid solution ceramic system. Based on the results obtained in this work and reported in the literature, the structure-ferroic properties phase diagram of the BiFeO3-DyFeO3-PbTiO3 ternary system is established, where a compositional region with coexisting ferroelectric polarization and ferromagnetic moment is found. More importantly, a multiferroic MPB line separating two chemical regions with distinct crystal structures and ferroic orderings is discovered in the phase diagram. The phase changing nature of MPB compositions with temperature and compositions is investigated from room temperature to high temperature paraelectric phase. This work could provide a promising system to explore the highly desired colossal effects on magnetoelectric coupling in single phase multiferroics by phase-change functional responses.

Based on annular crossed cable-truss structure model with diameter of 17.15 m, the type of membrane roof was first studied. Two membrane roof schemes, cable-supported membrane roof and skeleton-supported membrane roof, were proposed. The form-finding analysis of two types of membrane roof structures was carried out. By comparative study, the strengths and weaknesses of two schemes were given, and the feasibility of skeleton-supported membrane roof was demonstrated. Second, skeleton-supported membrane roof was studied by collaborative form-finding and non-collaborative form-finding. The form-finding method being suitable for the structure was given. Finally, load analysis, parametric analysis, and dynamic characteristics of membrane and non-membrane roof structures were carried out. The results show that skeleton-supported membrane roof has the strength to resist to external loads. Poisson’s ratio and self-weight have little influence on membrane roof, and arch height and pretension of membrane surface have great influence on membrane roof. The vibration modes of structure are mainly manifested as up and down vibrations accompanying with local torsion of planar cable-truss frame, which is not bad for overall structure. Meanwhile, film-covering effects of annular crossed cable-truss structure are obvious. The study contents have promoted the application of annular crossed cable-truss structure in practical engineering.

No abstract