Abstract
Thermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was ...discovered to exhibit a high ZT of roughly 2.2–2.6 at 913 K, but more practical and deployable polycrystal versions of the same compound suffer from much poorer overall ZT, thereby thwarting prospects for cost-effective lead-free thermoelectrics. The poor polycrystal bulk performance is attributed to traces of tin oxides covering the surface of SnSe powders, which increases thermal conductivity, reduces electrical conductivity and thereby reduces ZT. Here, we report that hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K. Its lattice thermal conductivity is ultralow at roughly 0.07 W m
–1
K
–1
at 783 K, lower than the single crystals. The path to ultrahigh thermoelectric performance in polycrystalline samples is the proper removal of the deleterious thermally conductive oxides from the surface of SnSe grains. These results could open an era of high-performance practical thermoelectrics from this high-performance material.
Scientific databases offer remarkable potential for solving complex questions in materials science, such as global optimization of materials and designing unknown materials for novel properties. ...ThermoElectric materials eXplorer (TEXplorer) is a web-based platform designed to collect and share all types of thermoelectric materials data, including synthesis information, materials characterization, transport measurements, and electronic structures obtained from experiments and computations. TEXplorer also provides valuable tools, such as an easy upload and download system, retrieval, automatic post-processing calculations, visualization of datasets, and toolkits for predicting thermoelectric properties through machine learning models. Using the platform, we collected and managed the thermoelectric dataset of SnSe and Bi2Te3 with various doping/alloying elements in this study in order to investigate the complex relationship between doping/alloying elements and the thermoelectric properties of host materials. The web-based interactive data platform enables efficient management and utilization of experimental and computational datasets, supporting the acceleration of data-driven materials research and autonomous material synthesis.
Objective. This study examined whether glycated hemoglobin (HbA1c) and glycated albumin (GA) are well correlated with the Ankylosing Spondylitis Disease Activity Score (ASDAS)-erythrocyte ...sedimentation rate (ESR), and ASDAS-C-reactive protein (CRP) in AS patients without medical conditions affecting the glycated protein levels. Methods: The data of 76 patients with AS were analyzed. Univariate and multivariate analyses of the variables associated with ASDAS-ESR and ASDAS-CRP were performed using a linear regression test. The patients were divided into active and inactive AS groups based on an ASDAS-CRP of 2.1, and the variables between the two groups were compared. Results. ASDAS-ESR did not correlated with either HbA1c or GA. ASDAS-CRP was positively correlated with HbA1c (r=0.315, p=0.006) and the white blood cell (r=0.288, p=0.012), and inversely correlated with hemoglobin (r=−0.241, p=0.036) and serum albumin (r=−0.262, p=0.022), but not GA. Multivariate analysis revealed HbA1c and white blood cell to be significantly correlated with ASDAS-CRP (β=0.234, p=0.033 and β=0.265, p=0.017). The mean HbA1c, not GA, of the active group was significantly higher than that of the inactive group (p=0.020). In addition, the optimal cut-off value of HbA1c was set to 5.6, and the patients with HbA1c ≥5.6 were found to have a 3.3 times higher risk of active AS than those without. Conclusion. HbA1c was significantly correlated with ASDAS-CRP, and could be a useful marker to reflect ASDAS-CRP in AS patients without medical conditions affecting the glycated protein levels. KCI Citation Count: 0
Doping and alloying are fundamental strategies to improve the thermoelectric performance of bare materials. However, identifying outstanding elements and compositions for the development of ...high-performance thermoelectric materials is challenging. In this study, we present a data-driven approach to improve the thermoelectric performance of SnSe compounds with various doping. Based on the newly generated experimental and computational dataset, we built highly accurate predictive models of thermoelectric properties of doped SnSe compounds. A well-designed feature vector consisting of the chemical properties of a single atom and the electronic structures of a solid plays a key role in achieving accurate predictions for unknown doping elements. Using the machine learning predictive models and calculated map of the solubility limit for each dopant, we rapidly screened high-dimensional material spaces of doped SnSe and evaluated their thermoelectric properties. This data-driven search provided overall strategies to optimize and improve the thermoelectric properties of doped SnSe compounds. In particular, we identified five dopant candidate elements (Ge, Pb, Y, Cd, and As) that provided a high ZT exceeding 2.0 and proposed a design principle for improving the ZT by Sn vacancies depending on the doping elements. Based on the search, we proposed yttrium as a new high-ZT dopant for SnSe with experimental confirmations. Our research is expected to lead to novel high-ZT thermoelectric material candidates and provide cutting-edge research strategies for materials design and extraction of design principles through data-driven research.
Bi2Te3-based materials are a representative thermoelectric system operating near ambient temperature. Their n-type family is very limited and underperforms the p-type counterpart, which is a major ...concern in the thermoelectric community. Here we report that alkali earth metals (AE = Mg, Ca, Sr, Ba) in Group 2 unusually induce n-type thermoelectric properties in Bi2Te3. Mg is the most efficient electron donor among them. The x = 0.01 sample of MgxBi2-xTe3 (x = 0.005, 0.01, 0.015) system exhibits remarkably enhanced power factor and ZT of ~0.8 at 350 K in comparison with pristine Bi2Te3. The improved performance is attributed to simultaneously enhanced electrical conductivity and reduced lattice thermal conductivity. Remarkably, MgxBi2-xTe3 materials show larger Seebeck coefficients than those expected by the theoretical Pisarenko relation.
1% Mg doping increases charge carrier concentration and electrical conductivity. As a result, remarkably high power factor near ambient temperature is obtained in n-type Mg0.01Bi1.99Te3. Coupled with reduced lattice thermal conductivity, a high ZT of ~0.8 at 350 K is achieved for n-type Mg0.01Bi1.99Te3. Display omitted
•Doping divalent alkali earth metals unusually induces n-type conduction in thermoelectric Bi2Te3.•Mg doping (0.5–1.5%) provides extra charge carriers to increase carrier concentration and electrical conductivity.•n-type MgxBi2-xTe3 exhibits larger Seebeck coefficients than those expected by the theoretical Pisarenko relation.•1% Mg doping simultaneously enhances power factor and suppresses thermal conductivity, giving a high ZT of ~0.8 at 350 K.
Extraordinary properties of traditional hyperbolic metamaterials, not found in nature, arise from their man-made subwavelength structures causing unique light–matter interactions. However, their ...preparation requiring nanofabrication processes is highly challenging and merely provides nanoscale two-dimensional structures. Stabilizing their bulk forms via scalable procedures has been a sought-goal for broad applications of this technology. Herein, we report a new strategy of designing and realizing bulk metamaterials with finely tunable hyperbolic responses. We develop a facile two-step process: (1) self-assembly to obtain heterostructured nanohybrids of building blocks and (2) consolidation to convert nanohybrid powders to dense bulk pellets. Our samples have centimeter-scale dimensions typically, readily further scalable. Importantly, the thickness of building blocks and their relative concentration in bulk materials serve as a delicate means of controlling hyperbolic responses. The resulting new bulk heterostructured material system consists of the alternating h-BN and graphite/graphene nanolayers and exhibits significant modulation in both type-I and type-II hyperbolic resonance modes. It is the first example of real bulk hyperbolic metamaterials, consequently displaying the capability of tuning their responses along both in-plane and out-of-plane directions of the materials for the first time. It also distinctly interacts with unpolarized and polarized transverse magnetic and electronic beams to give unique hyperbolic responses. Our achievement can be a new platform to create various bulk metamaterials without complicated nanofabrication techniques. Our facile synthesis method using common laboratory techniques can open doors to broad-range researchers for active interdisciplinary studies for this otherwise hardly accessible technology.
Hyperbolic metamaterials involving artificially crafted subwavelength structures uniquely interact with light to give extraordinary properties not found in nature. However, both predicting ...metamaterial candidates and realizing them are extremely challenging. Preparation processes typically require cutting-edge nanofabrication techniques and are frequently technically or intrinsically impossible. The reported hyperbolic metamaterial systems are merely two-dimensional or assembly of nanostructures. Herein, we report a facile design principle and exemplary fabrication for bulk metamaterials exhibiting tunable hyperbolic dispersions. They are uniquely formed by spontaneous self-assembly reaction between two surface-modified building blocks of few-layer-graphene (FLG) and exfoliated hexagonal boron nitride (h-BN) lamellae. Their mixing ratio, namely, the chemical composition of the bulk materials, is a delicate means of controlling hyperbolic responses. Remarkably, a small amount of rhombohedral BN (r-BN) further finely modulates both type-I and type-II hyperbolic dispersions both along in-plane and out-of-plane directions of the bulk materials. The permittivity of our bulk materials obtained by Kramer-Kronig relation exhibits their capability in negative refraction of incident light, and is delicately altered by the introduction of r-BN and the change in the composition of the FLG and h-BN building blocks both along in-plane and out-of-plane directions of the bulk materials. In other words, r-BN serves a role as a “dopant” in our h-BN/FLG metamaterials, significantly changing properties of bulk systems. Our achievement can be a new platform to readily design and synthesize bulk metamaterials without complicated preparation methods. It also presents that chemical compositions in our bulk metamaterial system are a facile and predictable means of controlling their properties, striking contrast to conventional metamaterials.
Even a tiny amount of the r-BN additive finely tunes hyperbolic dispersions and permittivity of the bulk hyperbolic metamaterials consisting of few-layer-graphene and h-BN nanosheets, serving as a delicate modulator for negative refraction of our bulk hyperbolic metamaterial. Display omitted
•A new facile design principle for bulk hyperbolic metamaterials is presented.•The composition of the building blocks is key to controlling hyperbolic dispersion.•Bulk hyperbolic metamaterials can exhibit negative refraction for all directions.•Hyperbolic dispersion of our materials is finely tuned by a doping level additive.
Objective. This study examined whether glycated hemoglobin (HbA1c) and glycated albumin (GA) are well correlated with the Ankylosing Spondylitis Disease Activity Score (ASDAS)-erythrocyte ...sedimentation rate (ESR), and ASDAS-C-reactive protein (CRP) in AS patients without medical conditions affecting the glycated protein levels. Methods: The data of 76 patients with AS were analyzed. Univariate and multivariate analyses of the variables associated with ASDAS-ESR and ASDAS-CRP were performed using a linear regression test. The patients were divided into active and inactive AS groups based on an ASDAS-CRP of 2.1, and the variables between the two groups were compared. Results. ASDAS-ESR did not correlated with either HbA1c or GA. ASDAS-CRP was positively correlated with HbA1c (r=0.315, p=0.006) and the white blood cell (r=0.288, p=0.012), and inversely correlated with hemoglobin (r=-0.241, p=0.036) and serum albumin (r=-0.262, p=0.022), but not GA. Multivariate analysis revealed HbA1c and white blood cell to be significantly correlated with ASDAS-CRP (β=0.234, p=0.033 and β=0.265, p=0.017). The mean HbA1c, not GA, of the active group was significantly higher than that of the inactive group (p=0.020). In addition, the optimal cut-off value of HbA1c was set to 5.6, and the patients with HbA1c ≥5.6 were found to have a 3.3 times higher risk of active AS than those without. Conclusion. HbA1c was significantly correlated with ASDAS-CRP, and could be a useful marker to reflect ASDAS-CRP in AS patients without medical conditions affecting the glycated protein levels. (J Rheum Dis 2018;25:131-139)
Objective. We investigated the association of platelet distribution width (PDW) and mean platelet volume (MPV) with disease activity indices of ankylosing spondylitis (AS) in patients whose ...laboratory results or medical conditions would not affect PDW and MPV levels. Methods. We analysed demographic and laboratory data of 88 patients with AS. On the same day as the laboratory tests were done, we assessed AS disease activity using the Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index, Bath Ankylosing Spondylitis Patients Global Score and Ankylosing Spondylitis Disease Activity Score (ASDAS), including erythrocyte sedimentation rate (ESR) (ASDAS-ESR) and C-reactive protein (CRP) (ASDAS-CRP). The association was analyzed by linear regression. Results. The median age of 88 patients was 38.0 years and the median length of observation was 5.5 years. The median platelet count was 266,500.0/μL, the median PDW was 10.7 fL and the median MPV 9.6 fL. The median ESR was 19.0 mm/hr and CRP was 2.5 mg/L. Among acute reactants, only CRP was negatively correlated with MPV, but not PDW (r=−0.218, p＜0.041). However, both PDW and MPV were not significantly correlated with any disease activity index of AS. On multivariate linear regression analysis, only the length of observation was significantly correlated with MPV (β=0.224, p＜0.044). Conclusion. PDW and MPV were not potent surrogate markers to reflect AS activity, with potential confounding strictly controlled, to affect MPV and PDW levels. KCI Citation Count: 0
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