Construction of a cement-rebar nanoarchitecture for a solution-processed and flexible film of a Bi_(2)Te_(3)/CNT hybrid toward low thermal conductivity and high thermoelectric performance

Solution processability and flexibility still remain major challenges for many thermoelectric(TE)materials,including bismuth telluride(Bi_(2)Te_(3)),a typical and commercially available TE material.Here,we report a new solutionprocessed method to prepare a flexible film of a Bi_(2)Te_(3)/single-walled carbon nanotube(SWCNT)hybrid,where the dissolved Bi_(2)Te_(3) ion precursors are mixed with dispersed SWCNTs in solution and recrystallized on the SWCNT surfaces to form a“cement-rebar”-like architecture.The hybrid film shows an n-type characteristic,with a stable Seebeck coefficient of^(−1)00.00±1.69μVK^(−1) in air.Furthermore,an extremely low in-plane thermal conductivity of∼0.33Wm^(−1) K^(−1) is achieved at 300 K,and the figure of merit(ZT)reaches 0.47±0.02.In addition,the TE performance is independent of mechanical bending.The unique“cement-rebar”-like architecture is believed to be responsible for the excellent TE performances and the high flexibility.The results provide a new avenue for the fabrication of solution-processable and flexible TE hybrid films and will speed up the applications of flexible electronics and energy conversion.

Synthesis and Thermoelectric Property of 1D Flexible PEDOT: p-TSA/Glass Fiber

Exploiting the thermal insulation properties of glass fiber and excellent conductivity of conducting polymer, a novel one-dimensional (1D) composite thermoelectric material, based on poly(3,4-ethylenedioxythiophene): p-toluenesulfonic acid (PEDOT: p-TSA)/glass fiber, is prepared by coating the PEDOT: p-TSA on the surface of glass fiber with in situ polymerization method. We hope the materials can bring out the performance of the “electron conductor, photon glass”. During the polymerization process, the effects of oxidant concentration and dopant mass fraction on thermoelectric properties of the materials are investigated. The group type of the polymer chain and the morphology of the samples were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), respectively. The maximal Seebeck coefficient (S) and electric conductivity (σ) of the pristine sample are 32 μVK-1 and 169 Sm-1, respectively. After further post-processing with methanol, the thermoelectric properties of materials were improved, and the maximum value of S and σ increased greatly to 48.5 μVK-1 and 3184 Sm-1, respectively. The maximal power factor (PF) of materials also increased from 0.12 μWm-1 K-2 to 6.74 μWm-1 K-2. Moreover, we have proposed a preliminary explanation on the carrier transport mechanism.

Synthesis and characterization of oriented linked LiFePO4 nanoparticles with fast electron and ion transport for high-power lithium-ion batteries

LiFePO4 nanoparticles with different morphologies and sizes were synthesized via a solvothermal method using environmentally benign and low-cost glycerol as the surfactant. The morphology, size, and structure of the particles were found to relate closely to the concentration of glycerol. Oriented linked LiFePO4 nanorods along mostly non-[010] were obtained with the proper concentration of glycerol. The nanorods showed good electronic and ionic conductivities, resulting in superior rate capability and cycling performance. This performance was attributed to the oriented linkages along mostly non-[010], the small particle size along [010], and the occupation of Li at Fe sites. Initial discharge capacities of 162.4 mA.h.g-1 at 0.1 C and 102.1 mA.h.g-1 at 30 C were achieved, with capacity retentions after 500 cycles at 5 and 20 C of 99.5% and 93.2%, respectively. At the rate of 40 C, the solid-solution phase transition dominated during lithiation and delithiation of all samples.

A Wavy-Structured Highly Stretchable Thermoelectric Generator with Stable Energy Output and Self-Rescuing Capability

Thermoelectric generators(TEGs)demonstrate great potential for flexible and wearable electronics due to the direct electrical energy harvested from waste heat.Good wearability requires high mechanical flexibility and preferable stretchability,while current TEGs are primarily developed with rigid or non-stretchable components,which do not conform well to human skin or accommodate human motions,thus hindering further applications.

Annular flexible thermoelectric devices with integrated-module architecture

Organic and composite thermoelectric(TE)materials have witnessed explosive developments in recent years.Design strategy of their flexible devices is vital to achieve high performance and suit various application environments.Here,we propose a design strategy of annular flexible TE devices with integrated-module architecture,where the independent modules made up of alternatively connected p-n couples are connected in series,and then rounded head-to-tail into annular configuration.The achieved devices can not only save plenty of space owing to their highly integrated structure design,but also be directly mounted on cylindrical objects(like pipes)to suit versatile applications.More importantly,the annular TE devices display excellent performances,superior to most previous work and the traditional serial single-layer film structure.For example,the annular device with eight modules consisting of three p-n couples reveals an output power of 12.37μW at a temperature gradient of 18 K,much higher than that of the corresponding single-layer film structure(1.74μW).The integration process is simple and easy to scale up.This architecture design strategy will greatly speed up the TE applications and benefit the research of organic and composite TE materials.

Tailoring microstructure and electrical transportation through tensile stress in Bi_(2)Te_(3) thermoelectric fibers

Bismuth telluride(Bi_(2)Te_(3))has attracted much attention in the field of thermoelectrics since it is one kind of commercial room-temperature thermoelectric material.Herein three kinds of Bi_(2)Te_(3) thermoelectric fibers with internal tensile stress are fabricated utilizing an optical fiber template method.The effects of internal stress on the microstructure and the electrical transportation of Bi_(2)Te_(3) thermoelectric fibers are investigated.The Bi_(2)Te_(3) cores in the fibers are highly crystalline and possess a tensile nanosheet structure with preferential orientation as evidenced by X-ray diffraction and Raman studies.Tensile stress can enhance electrical properties of the fibers.And a paper cup generator covered with 20 pieces of optimized fibers provides a μW-level output power.It is inferred that tensile stress tuning can be an effective tool for the material optimization of thermoelectric performance.

Task scheduling for transport and pick robots in logistics:a comparative study on constructive heuristics

We study the Transport and Pick Robots Task Scheduling(TPS)problem,in which two teams of specialized robots,transport robots and pick robots,collaborate to execute multi-station order fulfillment tasks in logistic environments.The objective is to plan a collective time-extended task schedule with the minimization of makespan.However,for this recently formulated problem,it is still unclear how to obtain satisfying results efficiently.In this research,we design several constructive heuristics to solve this problem based on the introduced sequence models.Theoretically,we give time complexity analysis or feasibility guarantees of these heuristics;empirically,we evaluate the makespan performance criteria and computation time on designed dataset.Computational results demonstrate that coupled append heuristic works better for the most cases within reasonable computation time.Coupled heuristics work better than decoupled heuristics prominently on instances with relative few pick robot numbers and large work zones.The law of diminishing marginal utility is also observed concerning the overall system performance and different transport-pick robot numbers.