Synthetic organic chemists have a large toolbox of named reactions to form structural motifs through a retrosynthetic approach when targeting a complex molecule. On the other hand, a comparatively complex inorganic compound may be made through simple mechanochemical reactions of the elements followed by annealing. For complex phases that involve more than two elements, the simple mechanochemical process can be complex with many competing phases, which can negatively impact desired properties. This point has been made recently with a revelation of improved properties of thermoelectric materials upon the removal of impurities. Compounds of the Yb14AlSb11 structure type represent complex Zintl phases with exceptional high-temperature thermoelectric properties but are difficult to prepare in high purity. In this work, a quenching study was used to elucidate the pathway taken by reactions from the elements to form the complex ternary phase, Yb14AlSb11. Through that study, two Yb–Sb binary phases, Yb11Sb10 and Yb4Sb3, were identified as intermediates in the reaction. These two Yb–Sb binaries were investigated for use as reactive precursors to form Yb14MnSb11 in reactions with MnSb. Through this pseudoretrosynthetic approach, reactions from Yb4Sb3 allowed for the synthesis of high-purity Yb14MnSb11 and Yb14MgSb11 through balanced, stoichiometric reactions. The apparent Yb2O3 (∼1%) impurity found in these products was systematically reduced with x in the series Yb14-xMnSb11 (x = 0–0.05), suggesting that the main phase is inherently Yb-deficient and showing the high degree of control obtained through this synthetic approach. The stoichiometric sample of Yb14MgSb11 has a peak zT of 1.3 at 1175 K, and the stoichiometric sample of Yb14MnSb11 has a peak zT of 1.2 at 1275 K. This approach to solid-state synthesis provides reproducible products from balanced stoichiometric reactants to form high-purity complex structure types and can be adapted to other difficult ternary systems.
An entry from the Inorganic Crystal Structure Database, the world’s repository for inorganic crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the joint CCDC and FIZ Karlsruhe Access Structures service and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Over the past six years, an extensive database on the fatigue of offshore joints has been established from Italian research programs. This database contains the results from tests on over 70 reduced-scale plate-to-plate joints and over 45 full-scale tubular joints. A matrix of tests in air and seawater with cathodic protection (CP) and with joints of two baseplate thicknesses (32 and 50 mm) were carried out. In the past few years a consensus has been reached on two topics - the efficiency of cathodic protection and the thickness effect - which previously generated a high degree of cathodic protection and the thickness effect - which previously generated a high degree of controversy. However, this consensus is based on results from testing in 'standard' conditions. In the case of the thickness effect, 'standard' conditions refer to the specimen/environment combinations: plate-to-plate and tubular joints of 32 mm thickness. In this paper the problem of whether the conclusions derived from tests in standard conditions are valid outside these conditions is addressed. Specifically the effect of CP and joint type on the magnitude of the thickness effect is analysed as is the effect of joint thickness on the efficiency of CP. It is concluded that while joint thickness does not appear to have a significant effect on the efficiency of CP, the magnitude of the thickness effect is significantly dependent on both the environment (CP or air) and the type of joint. Thus, in general, while the consensus on CP can be extended to different joint dimensions, the consensus on the thickness effect is not valid outside the standard conditions.
Liquid Crystalline Elastomers (LCEs) are very promising smart materials that can be made sensitive to different external stimuli, such as heat, pH, humidity and light, by changing their chemical composition. In this paper we report the implementation of a nematically aligned LCE actuator able to undergo large light-induced deformations. We prove that this property is still present even when the actuator is submerged in fresh water. Thanks to the presence of azo-dye moieties, capable of going through a reversible trans-cis photo-isomerization, and by applying light with two different wavelengths we managed to control the bending of such actuator in the liquid environment. The reported results represent the first step towards swimming microdevices powered by light.
The paper describes 3D structures made of liquid-crystalline elastomer (LCE) – rings, woodpiles, etc. – fabricated by two-photon absorption direct laser writing with sub-micrometer resolution while maintaining the desired molecular orientation. These results lay the foundations for creating 3D, micrometer-sized, light-controlled LCE structures. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
The Magnéli phase V6O11 was synthesized in gram amounts from a powder mixture of V6O11/V7O13 and vanadium metal, using the spark plasma sintering (SPS) technique. Its structure was determined with synchrotron X-ray powder diffraction data from a phase-pure sample synthesized by conventional solid-state synthesis. A special feature of Magnéli-type oxides is a combination of crystallographic shear and intrinsic disorder that leads to relatively low lattice thermal conductivities. SPS prepared V6O11 has a relatively low thermal conductivity of κ = 2.72 ± 0.06 W (m K)-1 while being a n-type conductor with an electrical conductivity of σ = 0.039 ± 0.005 (μΩ m)-1, a Seebeck coefficient of α = -(35 ± 2) μV K-1, which leads to a power factor of PF = 4.9 ± 0.8 × 10-5W (m K2)-1 at ∼600 K. Advances in the application of Magnéli phases are mostly hindered by synthetic and processing challenges, especially when metastable and nanostructured materials such as V6O11 are involved. This study gives insight into the complications of SPS-assisted synthesis of complex oxide materials, provides new information about the thermal and electrical properties of vanadium oxides at high temperatures, and supports the concept of reducing the thermal conductivity of materials with structural building blocks such as crystallographic shear (CS) planes.
