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Bi2Te3-based materials are dominating thermoelectrics for almost all of the room-temperature applications. To meet the future demands, both their thermoelectric (TE) and mechanical properties need to be further improved, which are the requisite for efficient TE modules applied in areas such as reliable micro-cooling. The conventional zone melting (ZM) and powder metallurgy (PM) methods fall short in preparing Bi2Te3-based alloys, which have both a highly textured structure for high TE properties and a fine-grained microstructure for high mechanical properties. Herein, a mechanical exfoliation combined with spark plasma sintering (ME-SPS) method is developed to prepare Bi0.5Sb1.5Te3 with highly improved mechanical properties (correlated mainly to the dislocation networks), as well as significantly improved thermoelectric properties (correlated mainly to the texture structure). In the method, both the dislocation density and the orientation factor (F) can be tuned by the sintering pressure. At a sintering pressure of 20 MPa, an exceptional F of up to 0.8 is retained, leading to an excellent power factor of 4.8 mW m-1 K-2 that is much higher than that of the PM polycrystalline. Meanwhile, the method can readily induce high-density dislocations (up to ∼1010 cm-2), improving the mechanical properties and reducing the lattice thermal conductivity as compared to the ZM ingot. In the exfoliated and then sintered (20 MPa) sample, the figure-of-merit ZT = 1.2 (at 350 K), which has increased by about ∼20%, and the compressive strength has also increased by ∼20%, compared to those of the ZM ingot, respectively. These results demonstrate that the ME-SPS method is highly effective in preparing high-performance Bi2Te3-based alloys, which are critical for TE modules in commercial applications at near-room temperature.

Textile defect detection and classification is an important part of the textile production process, however, to detect accurately and efficiently is still difficult. In this study, we present an effective formulation for textile defect detection. Unlike traditional textile detecting methods, a conventional neural network (CNN) support vector machine (SVM) is designed to extract the depth features of textile images and to classify defects. The effectiveness of textile feature extraction is improved by optimizing Alexnet to obtain a CNN with better feature extraction and less computation. Textile defect classification is more effective using SVM instead of Softmax. Experimental results demonstrated that the improved Alexnet-SVM gave 99% accuracy in defect classification using the TILDA database. This accuracy was 5% greater than Alexnet and GoogleNet.

Full-Heusler alloy Fe2TiSn was predicted to be a potential thermoelectric material with high mechanical properties and stability. Fe2TiSn was usually prepared by arc-melting followed by annealing for 2 weeks, which takes a long time and consumes a large amount of energy. In this paper, Fe2TiSn was prepared by an ultra-fast method, self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering. The bulk materials with uniform element distribution, well controlled composition and relative densities of over 97.5% were prepared. The undoped Fe2TiSn samples show p-type transport behavior. Co was heavily doped at the Fe site to prepare n-type Fe2−2xCo2xTiSn samples. The thermoelectric properties measurements carried out on the Co-doped samples show a highest ZT = 0.02 at 300 K, which is about tripe the performance of the pristine Fe2TiSn. This study provides a new approach for the rapid and low-cost preparation of full-Heusler thermoelectric materials.

Developing suitable catalysts capable of receiving injected electrons and possessing active sites for hydrogen evolution reaction (HER) is the key to building an efficient dye-sensitized system for hydrogen production. Fe3S4 is generally regarded as an inferior HER catalyst among the metal sulfide family, mainly due to its weak surface adsorption toward H atoms. In this work, we demonstrate a facile metal-organic framework-derived method to synthesize uniform Fe3S4 nanorods and active them for HER by Ni doping. Our experimental results and theoretical calculations reveal that Ni doping can greatly modify the electronic structure of Fe3S4 nanorods, improving their electron conductivity and optimizing their surface adsorption energy toward H atoms. Sensitized by a commercial organic dye (eosin-Y), 1%Ni-doped Fe3S4 nanorods display a high H2 production rate of 3240 μmol gcat-1 h-1 with an apparent quantum yield of 12% under 500 nm wavelength, which is significantly higher than that of pristine Fe3S4 and even higher than that of 1% Pt-deposited Fe3S4. The working mechanism of this dye-sensitized system is explored, and the effect of Ni-doping concentration has been studied. This work presents a facile strategy to synthesize metal-doped sulfide nanocatalysts with greatly enhanced activity toward photocatalytic H2 production.

Miniaturization of efficient thermoelectric (TE) devices has long been hindered by the weak mechanical strength and insufficient heat-to-electricity conversion efficiency of zone-melted (ZM) ingots. Here, we successfully prepared a robust high-performance p-type Bi0.4Sb1.6Te3.72 bulk alloy by combining an ultrafast thermal explosion reaction with the spark plasma sintering (TER-SPS) process. It is observed that the introduced excess Te not only enhances the (00 l )-oriented texture to ensure an outstanding power factor (PF) of 5 mW m−1 K−2 , but also induces extremely high-density line defects of up to 1011– 1012 cm−2. Benefiting from such heavily dense line defects, the enhancement of the electronic thermal conductance from the increased electron mobility is fully compensated by the stronger phonon scattering, leading to an evident net reduction in total thermal conductivity. As a result, a superior ZT value of ~1.4 at 350 K is achieved, which is 40% higher than that of commercial ZM ingots. Moreover, owing to the strengthening of grain refinement and high-density line defects, the mechanical compressive stress reaches up to 94 MPa, which is 154% more than that of commercial single crystals. This research presents an effective strategy for the collaborative optimization of the texture, TE performance, and mechanical strength of Bi2Te3-based materials. As such, the present study contributes significantly to the future commercial development of miniature TE devices.

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In this study, the phase transition from tetragonal BiOBr to monoclinic Bi4O5Br2 was regulated in the presence of branched polyethyleneimine (BPEI) containing massive amino groups via a hydrothermal route. Based on the crystal phase of the products obtained at different concentrations of the BPEI and Br− sources, the relative concentration of BPEI (the concentration ratio of the BPEI and Br− sources, BPEI/Br−) played the decisive role in this phase transition. In particular, a BPEI/Br− value over 0.2 g mmol−1 with excessive BPEI was critical for the phase transition. Further, a reasonable theory referring the synergistic effect of the “drag force” and facet recognition of excessive BPEI underlying this phase transition was confirmed through a series of systematically designed experiments. The protonated amino groups from excessive BPEI could not only act as a “drag force” to extract the bromine ions from the solid-state BiOBr nanosheets but also recognize the (001) facet of BiOBr, thereby distorting the tetragonal structure of the BiOBr nanosheets and forming monoclinic Bi4O5Br2 nanosheets. This work provides a new insight and proof of the regulation of the phase transition of BiOBr to Bi4O5Br2.

An efficient diffusion couple technique is proposed for rapid screening of potential thermoelectric materials and it has been explored in a (GeTe)m (Sb2Te3)n pseudobinary system. In this study, a combinatorial sample library of GeTe-Sb2Te3 diffusion couple with rich compositions and structures was prepared by plasma activation sintering (PAS). The relationship among composition, structure and performance of the materials was revealed by analyzing the chemical composition, crystal structure and thermoelectric properties of the microdomains in the combinatorial sample library, so as to achieve the purpose for rapid identification of Ge-Sb-Te compounds with excellent thermoelectric properties. The scanning results of the Seebeck coefficient of the samples library show that the sample with potential high thermoelectric performance has a chemical composition near Ge33.1Sb13.7Te53.2. The bulk materials with compositions in the vicinity of Ge33.1Sb13.7Te53.2 were prepared by a conventional melting and PAS process. Among these bulk samples, the one with a nominal composition of Ge38Sb10.3Te51.7 achieves a maximum ZT value of 0.55 at 673 K, indicating that the constituent phases Ge0.77Sb0.154Te1 and Ge3.37Sb1.63Te6 observed in this sample could be potential candidates with excellent thermoelectric properties. These two ternary compounds should be investigated for further optimization. The results of this study provide a reference for the application of combinatorial metrology for screening and optimizing new thermoelectric materials.

For the life cycle of a product, the after-sales value-added services of a product can bring huge value-added effects to the product value. The most important after-sales service is the maintenance of the product. It is extremely important to predict the fault type of product accurately and timely. Most of the existing fault type prediction models use a single algorithm, ignoring the limitations of a single algorithm. In this paper, a multi-classification model is established by using the SAMME algorithm and the decision tree constructed by the Classification and Decision Tree algorithm as the base classifier to predict the failure type of the ultrasonic flowmeter. In the ultrasonic flowmeter fault type prediction experiment, the results show that the multi-classification model constructed in this paper is better than the multi-classification model constructed by a single algorithm in accuracy and other indicators. So that it can provide a reference for people who carry out related work in this business domain.

Developing suitable catalysts capable of receiving injected electrons and possessing active sites for hydrogen evolution reaction (HER) is the key to building an efficient dye-sensitized system for hydrogen production. Fe

Guangdong Province is a district with a high incidence of anorectal diseases. In addition, the pathogenic factors of anorectal diseases are complex and diverse. Existing clinical diagnostic techniques are difficult to accurately analyze the pathogenic factors of anorectal diseases. Therefore, in this paper, an association analysis algorithm is proposed for solving the problem of pathogenic factors mining. In order to dig out the valuable information of medical big data, an improved Apriori algorithm is designed. Compared with the classical Apriori algorithm, by deleting the unrelated itemsets which do not contain the specific items, the proposed Apriori algorithm can decrease the run time. Finally, simulation results show the superiority of the proposed algorithm.

While zone-melted (ZM) Bi2Te3 is a standard commercially available thermoelectric (TE) material, it suffers from not being sufficiently mechanically robust due to the presence of the van der Waals bonded Te–Te layers that reduce the product yield and compromise operational reliability. Polycrystalline materials prepared by powder metallurgy techniques exhibit improved mechanical properties but usually lose the desired texture exhibited by ZM ingots, and this affects their TE performance. It is highly desirable to be able to fabricate Bi2Te3-based bulk materials with anisotropies similar to a single crystal, yet being mechanically strong as the polycrystalline specimens. Herein, we combine for the first time the thermal explosion technique with selective laser melting (SLM) to synthesize the highly textured p-type Bi0.4Sb1.6Te3 bulk material. Structural analysis (FESEM and XRD) indicates that the slender columnar grains grew along the building direction (BD) of the structure and the orientation factor reached up to 0.9, close to that representing a single crystal. TEM images revealed a high density of dislocations inside the grains. Since the printed compound has a high degree of texture, the TE and mechanical properties exhibit a highly anisotropic behavior. The maximum ZT of annealed samples parallel to the BD was 1.1, similar to that of the single crystal. However, the compressive strength of the structure reached up to 91 MPa, some 2.5 times the strength of a typical single crystal (37 MPa), and even higher than that of Spark Plasma Sintered (SPS) polycrystalline samples (80 MPa). Meanwhile, the mechanical cutting performance was much superior compared to that of the ZM ingot, and TE legs could be cut to sizes as small as 0.2 mm. A micro-TE module assembled using SLM-printed high performance p-type BiSbTe and SPS-compacted n-type BiTeSe materials showed the maximum cooling temperature difference of 62 °C. The work provides a facile and effective solution for preparation of Bi2Te3-based materials with high texture, robust mechanical properties, and excellent TE performance. As such, it lays a solid foundation for rapid in situ 3D printing of Bi2Te3-based micro-TE devices.

A three dimensional nonlinear transient thermo-mechanically coupled finite element model (FEM) is introduced to analyze the temperature and stress fields during the selective laser melting (SLM) of thermoelectric (TE) SnTe. Considering the powder-to-solid transition and the latent heats of melting and vaporization, we simulate the temperature distribution near the molten pool and the residual stress inside the printed material at room temperature under different laser processing parameters. The calculated results indicate that vaporization gradually weakens as the laser power decreases and the scanning speed increases. Within the optimum forming window, the residual stress rises with the increasing laser power and decreasing scanning speed. The thermal stress mainly concentrates in the middle of the first scanning track, the terminal of each scanning track, and the edges of the forming surface, which is well consistent with the experimental results. This work has laid a significant foundation for rapid manufacturing of bulk SnTe thermoelectric materials using the selective laser melting process and will serve as a guide for laser processing of other thermoelectrics and perhaps even complete thermoelectric modules.

The traditional manufacturing of thermoelectric (TE) modules is a complex process that requires a long processing time and is high cost. In this work, we introduce a novel one-step 3D printing technique for TE module manufacturing, which integrates the Self-propagation High-temperature Synthesis (SHS) with the Selective Laser Melting (SLM) method. As a demonstration of this technique, bulk ZrNiSn samples were successfully fabricated on a Ti substrate. The effect of SLM processing parameters, such as the laser power and the scanning speed, on the quality of the forming ZrNiSn layers was systematically studied and analyzed, and the optimal processing window for the SLM process was determined. Transport property measurements indicate that the SLM-processed ZrNiSn possesses the maximum thermoelectric figure of merit ZT of 0.39 at 873 K. The interface of the ZrNiSn with the Ti substrate shows good adherence and low contact resistivity. The work demonstrates the viability of the SHS-SLM method for rapid fabrication of TE materials, legs and even modules.

Two-dimensional (2D) BiOBr nanosheets (NSs) have attracted considerable interest as photocatalysts. The surface active sites of BiOBr NSs are crucial in determining the photocatalytic performance of these materials under visible light. The modification of the surface state of BiOBr NSs with multiple charged groups has been scarcely studied as a way to increase the number of surface active sites and the corresponding photocatalytic activity. Herein, vanadate-rich 2D BiOBr/Bi NSs were in-situ fabricated without adding strong reductants and subsequently used for visible-light-driven photocatalysis. Even under reductant-free condition, we were able to simultaneously deposit Bi0 and vanadate groups on the surface of pristine BiOBr NSs. The corresponding formation mechanism was also explored in a subsequent step. Compared to pristine BiOBr NSs and BiOBr/Bi NSs, the vanadate-rich BiOBr/Bi NSs prepared herein exhibited superior adsorption and enhanced photodegradation of Rhodamine B (RhB) under visible light illumination.

Interactions among various film growth parameters, such as the substrate temperature (Tsub), film thickness (d), and composition, play a crucial role in controlling the type and density of the intrinsic point defects. In turn, the point defects modulate and control electronic transport properties of Bi2Te3 films. We have grown n-type Bi2Te3 films with different d by molecular beam epitaxy at different Tsub. The formation of point defects was analyzed by a combined use of angle-resolved photoelectron spectroscopy (ARPES) and electronic transport measurements. Two important findings were made: (i) the negatively charged vacancies, V Te · ·, initially the dominant intrinsic defects, transform gradually during the growth process into positively charged anti-site defects, B i Te ′, driven by thermal annealing from a continuously heated substrate; and (ii) from the film's surface into the inner strata of the film, the density of V Te · · decreases while the density of B i Te ′ increases, leading to a gradient of vacancies and anti-site defects along the film growth direction. As a result, the electron density in Bi2Te3 films decreases monotonically with increasing d. Moreover, elevating Tsub leads to a more significant in situ annealing effect and an eventual onset of intrinsic excitations that deteriorates electronic transport properties. The thinnest Bi2Te3 film (16 nm) grown at Tsub = 245 °C has the highest electron concentration of 2.03 × 1020 cm−3 and also the maximum room temperature power factor of 1.6 mW m−1 K−2 of all grown epitaxial films. The new insights regarding the defect formation and transformation pave the way for further optimization of electronic transport properties of n-type Bi2Te3-based films.

Organic–inorganic metal halide perovskite solar cells (PSCs) have been emerging as one of the most promising next generation photovoltaic technologies with a breakthrough power conversion efficiency (PCE) over 22%. However, aiming for commercialization, it still encounters challenges for the large-scale module fabrication, especially for flexible devices which have attracted intensive attention recently. Low-temperature processed high-performance electron-transporting layers (ETLs) are still difficult. Herein, we present a facile low-temperature synthesis of crystalline SnO2 nanocrystals (NCs) as efficient ETLs for flexible PSCs including modules. Through thermal and UV-ozone treatments of the SnO2 ETLs, the electron transporting resistance of the ETLs and the charge recombination at the interface of ETL/perovskite were decreased. Thus, the hysteresis-free highly efficient rigid and flexible PSCs were obtained with PCEs of 19.20 and 16.47%, respectively. Finally, a 5 × 5 cm2 flexible PSC module with a PCE...

Living things have the ability to adapt themselves to various environmental conditions and keep the whole system functioning even if a part of it is out of order. Recently, biological systems of living things which can be modeled as autonomous distributed systems have become the focus of attention. In this paper the modeling of the rhythmic movement generating mechanism of dragonfly wings using nonlinear oscillators is described. A wing is approximately modeled as a 1-DOF or 2-DOF beam and the equations of motion are derived. The central pattern generators(CPG)which generate the rhythmic movement of wings are modeled as a set of Van der Pol nonlinear oscillators. By solving the equations of motion of the wing and the equations of oscillators simultaneously, the rhythmic movement of a dragonfly wing model is obtained. The synchronization of multiple wings is obtained by the interconnection of oscillators. It is found that various autonomous vibrations of dragonfly wings can be reproduced using this model.