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[en] The effect the initial structure of a two-component reaction powder mixture has on the dynamics of its isothermal homogenization is investigated. Relations for determining the duration of homogenization are obtained. A technique for calculating kinetic parameters is proposed.
[en] The structure stabilities and electronic properties of Mg-X (X = Ni, Pd, Ti, Nb) interfaces are studied by first-principles calculations, including the atomic mixture effect. In particular, the Mg-X interface structures are systemically investigated by minimizing the lattice mismatch, including the lattice constants, cell area, and included angle of the lattice (cell shape). It is found that the optimal interface matches are 4:7, 3:4, 7:8, 9:4 in surface cell atom numbers (limited up to 10 in consideration of computational cost) for Mg-Ni, Mg-Pd, Mg-Ti, Mg-Nb, and the corresponding interface energies are −0.01, −0.9, 0.4, 0.9 J m−2, respectively. We find that atomic mixing at the interface affects the strain, and even stablize the interfaces in the large-mismatch cases. Furthermore, exemplified with the Mg-Pd interface, we find the atoms at the interface can be exchanged under practical condition with assitance of vacancies at the interface. (paper)
BackgroundBiocidal products are mixtures of one or more active substances (a.s.) and a broad range of formulation additives. There is regulatory guidance currently under development that will specify how the combined effects of the a.s. and any relevant formulation additives shall be considered in the environmental risk assessment of biocidal products. The default option is a component-based approach (CBA) by which the toxicity of the product is predicted from the toxicity of ‘relevant’ components using concentration addition. Hence, unequivocal and practicable criteria are required for identifying the ‘relevant’ components to ensure protectiveness of the CBA, while avoiding unnecessary workload resulting from including by default components that do not significantly contribute to the product toxicity. The present study evaluated a set of different criteria for identifying ‘relevant’ components using confidential information on the composition of 21 wood preservative products. Theoretical approaches were complemented by experimentally testing the aquatic toxicity of seven selected products.
ResultsFor three of the seven tested products, the toxicity was underestimated for the most sensitive endpoint (green algae) by more than factor 2 if only the a.s. were considered in the CBA. This illustrated the necessity of including at least some additives along with the a.s. Considering additives that were deemed ‘relevant’ by the tentatively established criteria reduced the underestimation of toxicity for two of the three products. A lack of data for one specific additive was identified as the most likely reason for the remaining toxicity underestimation of the third product. In three other products, toxicity was overestimated by more than factor 2, while prediction and observation fitted well for the seventh product. Considering all additives in the prediction increased only the degree of overestimation.
ConclusionsSupported by theoretical calculations and experimental verifications, the present study developed criteria for the identification of CBA-relevant components in a biocidal product. These criteria are based on existing criteria stated in the regulation for classification, labelling and packaging of substances. The CBA was found sufficiently protective and reliable for the tested products when applying the here recommended criteria. The lack of available aquatic toxicity data for some of the identified relevant components was the main reason for underestimation of product toxicity.
[en] Numerical simulations are used to study the settling of heavy particles in a background suspension of equal size, neutrally buoyant particles while the suspension as a whole is subject to a uniform shear flow. The heavy particles are settling in the direction of shear and the system is nominally homogeneous. The total volume fraction of the particles is in the range 20%–40% and the fraction of heavy particles varies between 0.05 and 0.3. While the shear flow is a dominant factor compared to the settling motion, the suspension remains in a mixed homogeneous state but as the Stokes settling velocity increases there is a transition with the heavy particles separating to form a band of rapidly settling particles. Segregation of a bidisperse suspension of particles sedimenting under gravity is a known phenomenon but here the shear flow stabilizes the system. The dependence of the mean particle velocities on the suspension parameters is evaluated both for a mixed state and with segregation. Additional results are given for the velocity fluctuations and the particle stresses of each phase. (paper)
[en] We present the design of a new system of mechanized supply of slag-forming mixtures to the mold of a continuous caster during the production of slabs with a very large cross section and the results of studying the energy-force parameters of its prototype. These results support the correctness of our technical solutions and can be used to determine the parameters for a commercial version of the system.
[en] Highlights: • Triboelectric nanogenerator was prepared using force-assembled colloidal arrays. • The electrical performance was determined by the structures and colloidal size. • They displayed high electric output, stability, and humidity resistance. We introduce a novel, robust, cost-effective, and scalable approach for the preparation of a large-area force-assembled triboelectric nanogenerator (FTENG), which allows a stable and high electric output under a wide range of humidity conditions through its dual-sized morphology (i.e., microstructures and nanostructures). In this study, hexagonally packed colloidal arrays prepared by a force assembly approach rather than by conventional self-assembly were used as a mold for a triboelectric poly(dimethylsiloxane) (PDMS) replica with desired pattern shapes (intaglio and embossed structures) and sizes. The morphological size of the PDMS films was determined by the diameter of the force-assembled colloids. The electrical output performance of FTENGs composed of electrodes and a PDMS film increased substantially as the size of the micropores (for intaglio-structured PDMS) or embossed features (for embossed-structured PDMS) decreased. Furthermore, the triboelectric PDMS film with micro-/nanosized features (i.e., dual-embossed PDMS) displayed a remarkable electrical output of 207 V (open-circuit voltage under a compressive force of 90 N in relative humidity (RH) of 20%) and high hydrophobicity compared to that of PDMS films with flat, intaglio or embossed structures. This device maintained a high electric output even in a high-humidity environment (i.e., open-circuit output voltage ~175 V in RH 80%). Our approach using force-assembly and hierarchical surface morphology will provide a novel and effective framework for developing strong power sources in various self-powered electronics.
[en] A mathematical model of solid-phase chemical synthesis in a binary powder mixture is constructed and studied with allowance for the shrinking of the mixture and the change in the reaction surface as a result of particle caking. Relations are obtained to estimate the number of similar and dissimilar interparticle contacts. Depending on the parameters of the mixture (the stoichiometric ratio between components, the particle size ratio, and the porosity), different modes are revealed that affect the rate of chemical transformation. The optimum conditions for an intense chemical interaction are determined.
[en] Full text: Small molecule gel (SMG) is a class of supramolecular material that is formed by low molecular weight gelators in solvents. SMGs have important application in many fields such as foods, cosmetics and pharmaceutics. The properties of these materials depend on their multi-level (hierarchical) structure and affect their applications. Significant efforts in the past years have been devoted to developing novel gelators in order to achieve gels with desirable structure and properties. However,the molecular assembly property of a gelator is heavily dependent on solvent properties. Therefore, molecular design is not an efficient approach. Recently, it has been proven that the structure formation in SMGs is a nucleation and growth process. On the basis of this mechanism, the hierarchical structure and hence the properties of the gels can be conveniently manipulated by controlling the thermodynamics and kinetics of nucleation. In this presentation, different approaches, in particular, molecular additive-assisted approach, that have developed to control the hierarchical structures of SMGs will be covered. (author)