编译｜李言

Science, 8 JUL 2022, VOL 377, ISSUE 6602

《科学》2022年7月8日，第377卷，6602期

材料科学Material Science

High figure-of-merit and power generation in high-entropy GeTe-based thermoelectrics

高熵 GeTe 热电材料的高性能和发电

 作者：BINBIN JIANG, WU WANGSHIXUAN LIUYAN WANG et al.

 链接：

https://www.science.org/doi/10.1126/science.abq5815

 摘要：

通过调整电子和声子局域化，我们将基于锗碲基的高熵材料在750开尔文下的优值提高到2.7，并在506开尔文的温差下实现了13.3%的高实验转换效率。通过增加熵，增加的晶体对称性使扭曲的菱形结构中的电子分布离域，从而导致能带收敛和改善电性能。

相比之下，熵诱导无序的局域声子抑制了横向声子的传播，这是非谐度增加和晶格热导率大幅下降的原因。我们提供了一种通过熵操纵来调整电子和声子局域化的范例，同时展示了一种提高高熵热电材料性能的途径。

Abstract：

By tuning electron and phonon localization, we enhanced the figure-of-merit value to 2.7 at 750 kelvin in germanium telluride–based high-entropy materials and realized a high experimental conversion efficiency of 13.3% at a temperature difference of 506 kelvin with the fabricated segmented module. By increasing the entropy, the increased crystal symmetry delocalized the distribution of electrons in the distorted rhombohedral structure, resulting in band convergence and improved electrical properties. By contrast, the localized phonons from the entropy-induced disorder dampened the propagation of transverse phonons, which was the origin of the increased anharmonicity and largely depressed lattice thermal conductivity. We provide a paradigm for tuning electron and phonon localization by entropy manipulation, but we have also demonstrated a route for improving the performance of high-entropy thermoelectric materials.

A processable, high-performance dielectric elastomer and multilayering process

一种可加工的高性能介电弹性体和多层工艺

 作者：YE SHI, ASKOUNIS, ROSHAN PLAMTHOTTAMTOM LIBBY et al.

 链接：

https://www.science.org/doi/10.1126/science.abn0099

 摘要：

介电弹性体（DEs）可以作为可变形电容器，在电场作用下产生机械功。DEs通常基于商业丙烯酸和硅酮弹性体。亚克力需要提前拉伸来实现高驱动应变，且缺乏加工上的灵活性。

在这项工作中，我们合成了一种设计弹性体的交联网络（PHDE），并通过调整交联网络中的交联剂和氢键来调整其机电性能。PHDE的最大面应变为190%，在没有预拉伸的情况下，在2Hz时保持大于110%的应变量。

Abstract：

Dielectric elastomers (DEs) can act as deformable capacitors that generate mechanical work in response to an electric field. DEs are often based on commercial acrylic and silicone elastomers. Acrylics require prestretching to achieve high actuation strains and lack processing flexibility. Silicones allow for processability and rapid response but produce much lower strains. In this work, a processable, high-performance dielectric elastomer (PHDE) with a bimodal network structure is synthesized, and its electromechanical properties are tailored by adjusting cross-linkers and hydrogen bonding within the elastomer network. The PHDE exhibits a maximum areal strain of 190% and maintains strains higher than 110% at 2 hertz without prestretching. 

A two-phase model that unifies and extends the classical models of membrane transport

一种可以统一和延伸经典膜传输模型的两相模型

 作者：VARUN H. HEGD, MICHAEL F. DOHERTY AND TODD M. SQUIRES

 链接：

https://www.science.org/doi/10.1126/science.abm7192

 摘要：

两个模型表明了溶剂如何通过膨胀的无孔膜进行传输。基于流体力学的孔流模型适用于多孔膜，而溶液扩散模型则需要分子扩散来处理非多孔膜。

这两种方法都对膨胀聚合物膜提出了有效的论点，但它们在膜内压力和浓度分布的预测上存在分歧。我们使用一个将溶剂和膜基质视为分离相的流固模型，并且证明了这两个经典模型在对同一现象进行互补、并作出相同的预测上，是有效的。

流体-固体模型表明了反渗透测量；与经典测量在定量上一致，并为经验高压限制通量现象提供了可预测的机理基础；并给出了一种处理无孔但机械非均质膜材料的框架。

Abstract：

Two models describe solvent transport through swollen, nonporous membranes. The pore-flow model, based on fluid mechanics, works for porous membranes, whereas the solution-diffusion model invokes molecular diffusion to treat nonporous membranes. Both approaches make valid arguments for swollen polymer membranes, but they disagree in their predictions of intramembrane pressure and concentration profiles. Using a fluid-solid model that treats the solvent and membrane matrix as separate phases, we show both classical models to be valid, to represent complementary approaches to the same phenomenon, and to make identical predictions. The fluid-solid model clarifies recent reverse osmosis measurements; provides a predictive and mechanistic basis for empirical high-pressure limiting flux phenomena, in quantitative agreement with classic measurements; and gives a framework to treat nonporous but mechanically heterogeneous membrane materials.

化学Chemistry

Maximizing noble metal utilization in solid catalysts by control of nanoparticle location

通过控制纳米颗粒的位置，最大化贵金属在固体催化剂中的利用率

 作者：KANG CHENG, C. J. SMULDERS, LARS I. VAN DER WAL et al.

 链接：

https://www.science.org/doi/10.1126/science.abn8289

 摘要：

最大化贵金属的利用率对于催化等应用至关重要。我们发现，通过在纳米尺度上合理安排功能位点，可以将工业双功能催化剂正构烷烃加氢转化所需的最小铂载量降低10倍或更多。

有意在氧化铝粘结剂或沸石晶体外而不是在沸石晶体内表面沉积铂纳米颗粒的痕迹，可以增强同分异构体选择性，同时不影响活性。

铂和沸石酸位点之间的分离通过限制金属团簇对微孔的堵塞和加强对金属位点的进入，可以保持金属和酸的功能。还原的铂纳米颗粒比强结合的铂单原子活性更高。

Abstract：

Maximizing the utilization of noble metals is crucial for applications such as catalysis. We found that the minimum loading of platinum for optimal performance in the hydroconversion of n-alkanes for industrially relevant bifunctional catalysts could be reduced by a factor of 10 or more through the rational arranging of functional sites at the nanoscale. Intentionally depositing traces of platinum nanoparticles on the alumina binder or the outer surface of zeolite crystals, instead of inside the zeolite crystals, enhanced isomer selectivity without compromising activity. Separation between platinum and zeolite acid sites preserved the metal and acid functions by limiting micropore blockage by metal clusters and enhancing access to metal sites. Reduced platinum nanoparticles were more active than platinum single atoms strongly bonded to the alumina binder.

古生物学Paleontology

Ultrastructure reveals ancestral vertebrate pharyngeal skeleton in yunnanozoans

超微结构揭示云南虫中的脊椎动物咽骨

 作者：QINGYI TIAN, FANGCHEN ZHAO, HAN ZENG et al.

 链接：

https://www.science.org/doi/10.1126/science.abm2708

 摘要：

咽弓可能有助于进化的颚和脊椎动物的大脑，是一个关键的进化创新。长期以来，人们一直假设，脊椎动物的祖先（如非脊椎动物文昌鱼），咽弓（鳃）是由一个没有关节的软骨杆进化而来的，但这种祖先解剖学是否存在仍是未知的。

有争议的寒武纪动物，云南虫，其咽骨可能包含了限制这些弓的早期进化的最古老的化石证据，但它与脊椎动物的相关性仍然不明。通过使用新技术（例如，x射线显微断层扫描、扫描和透射电子显微镜以及能量色散光谱元素绘图）检查额外标本，我们发现云南虫的鳃弓由细胞软骨组成，细胞外基质由微原纤维主导，这是被认为是脊椎动物特有的特征。我们的系统发育分析进一步证明云南虫是脊椎动物。

Abstract：

Pharyngeal arches are a key innovation that likely contributed to the evolution of the jaws and braincase of vertebrates. It has long been hypothesized that the pharyngeal (branchial) arch evolved from an unjointed cartilaginous rod in vertebrate ancestors such as that in the nonvertebrate chordate amphioxus, but whether such ancestral anatomy existed remains unknown. The pharyngeal skeleton of controversial Cambrian animals called yunnanozoans may contain the oldest fossil evidence constraining the early evolution of the arches, yet its correlation with that of vertebrates is still disputed. By examining additional specimens in previously unexplored techniques (for example, x-ray microtomography, scanning and transmission electron microscopy, and energy dispersive spectrometry element mapping), we found evidence that yunnanozoan branchial arches consist of cellular cartilage with an extracellular matrix dominated by microfibrils, a feature hitherto considered specific to vertebrates. Our phylogenetic analysis provides further support that yunnanozoans are stem vertebrates.

编辑 | 方圆

排版 | 郭刚

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