Magnetic-field-induced nonlinear transport in HfTe5

The interplay of electron correlations and topological phases gives rise to various exotic phenomena including fractionalization, excitonic instability, and axionic excitation. Recently-discovered transition-metal pentatellurides can reach the ultra-quantum limit in low magnetic fields and serve as good candidates for achieving such a combination. Here, we report evidences of density wave and metal-insulator transition in HfTe5 induced by intense magnetic fields. Using the nonlinear transport technique, we detect a distinct nonlinear conduction behavior in the longitudinal resistivity within the a-c plane, corresponding to the formation of a density wave induced by magnetic fields. In high fields, the onset of the nonlinear conduction in the Hall resistivity indicates an impurity-pinned magnetic freeze-out as the possible origin of the insulating behavior. These frozen electrons can be gradually re-activated into mobile states above a threshold electric field. These experimental evidences call for further investigations into the underlying mechanism for the bulk quantum Hall effect and field-induced phase transtions in pentatellurides.Comment: 13 pages, 4 figure

Sustainable supply chain management: Confirmation of a higher-order model

Drawing from the research of green supply chain management and corporate social responsibility, this research proposes a hierarchical structure of sustainable supply chain management and develops a multi-item measurement scale to reflect the specific management practices of sustainable supply chain management. In this research, sustainable supply chain management is operationalised as a third-order factor reflected by three second-order factors, namely external green supply chain management, internal green supply chain management and corporate social responsibility. Utilising a rigorous, multi-step scale development method and data from 293 Chinese manufacturers, this research validates a 31-item measurement scale and approves the proposed third-order structure. The results confirm the multidimensionality of sustainable supply chain management, which suggests that it is necessary for the future researches to consider both environmental and social aspects. The valid measurement scales provide managers with a “to do list” to make the specific business decisions to achieve sustainable development in the supply chain

Mechanical properties of zirconia octet truss structures fabricated by DLP 3D printing

Zirconia ceramic octet-truss structures with various strut size and unit cell numbers were successfully fabricated through a DLP-based 3D printing method. The mechanical properties and energy absorption capacity under compressive load were investigated systematically. The sides of all cubes are 10 mm, the strut size was changed from 0.25 mm to 2 mm, cells number was in the range of 1(1 × 1 × 1)–125(5 × 5 × 5). It has been seen that the relative density, compressive strength and energy absorption increases with the increase of strut size when cell numbers remain the same. It can be concluded that the strength and energy absorption were affected by the relative density, strut size and the stacking mode of the unit cells. So far, with this study, a high compressive strength of 75.3 MPa and a reasonably good energy absorption of 6.76 × 10 ^5 J m ^−3 can be achieved at a relative density of 48.57%

Largely enhanced dielectric properties of carbon nanotubes/polyvinylidene fluoride binary nanocomposites by loading a few boron nitride nanosheets

International audienceThe ternary nanocomposites of boron nitride nanosheets (BNNSs)/carbon nanotubes (CNTs)/polyvinylidene fluoride (PVDF) are fabricated via a combination of solution casting and extrusion-injection processes. The effects of BNNSs on the electrical conductivity, dielectric behavior, and microstructure changes of CNTs/PVDF binary nanocomposites are systematically investigated. A low percolation value (fc) for the CNTs/PVDF binary system is obtained due to the integration of solution and melting blending procedures. Two kinds of CNTs/PVDF binary systems with various CNTs contents (fCNTs) as the matrix are discussed. The results reveal that compared with CNTs/PVDF binary systems at the same fCNTs, the ternary BNNSs/CNTs/PVDF nanocomposites exhibit largely enhanced dielectric properties due to the improvement of the CNTs dispersion state and the conductive network. The dielectric constant of CNTs/PVDF binary nanocomposite with 6 vol. % CNTs (fCNTs  fc), it displays a 43.32% improvement from 1325 to 1899 after the addition of 3 vol. % BNNSs. The presence of BNNSs facilitates the formation of the denser conductive network. Meanwhile, the ternary BNNSs/CNTs/PVDF systems exhibit a low dielectric loss. The adjustable dielectric properties could be obtained by employing the ternary systems due to the microstructure changes of nanocomposites

Constructing a continuous amorphous carbon interlayer to enhance dielectric performance of carbon nanotubes/polyvinylidene fluoride nanocomposites

International audienceCarbon nanotubes (CNTs) based percolative polymer nanocomposites own a high dielectric constant at a small amount of CNTs. However, CNTs are easy to connect with each other directly in the vicinity of percolation threshold (fc), which unavoidably leads to an abrupt increase in dielectric loss. Herein, we propose a facile way to fabricate core-shell structured CNTs@amorphous carbon (CNTs@AC) hybrids by chemical vapor deposition (CVD). The CNT@AC hybrids were subsequently integrated into polyvinylidene fluoride (PVDF) matrix to fabricate CNTs@AC/PVDF dielectric nanocomposites by the combination of solution casting and extrusion-injection procedures. The uniform AC shell provides an insulative interlayer for the adjacent CNTs, which not only hinders the direct contact of CNTs but also improves the dispersibility of CNTs in PVDF matrix. Compared with pristine CNTs (P-CNTs)/PVDF nanocomposites, the fc increases from 7.16 vol % to 11.81 vol % and the dielectric loss decreases from 83.66 to 1.35 for the CNTs@AC-60/PVDF nanocomposites, which indicates that the percolation behavior is delayed. The results indicate that the influence of AC interlayer on the dielectric performance of the nanocomposites after percolation is much more evident than that before percolation. All these results demonstrate that this strategy is effective to enhance the dielectric performance of polymer nanocomposites and the design concept could be extended to other carbon hybrids materials