A mixed-cation mixed-anion borohydride NaY(BH4)2Cl2

A new sodium-yttrium borohydride-chloride, NaY(BH₄)₂Cl₂, is obtained by a combination of mechanochemical synthesis and annealing of NaBH₄–YCl₃ mixtures and is characterized by in-situ synchrotron radiation X-ray powder diffraction, density functional theory, thermal analysis and vibrational spectroscopy. Several simultaneous and coupled reactions occur during the synthesis, also yielding Na₃YCl₆ and Na(BH₄)_1−xCl_x besides the title compound. The polymeric pseudo-orthorhombic crystal structure of NaY(BH₄)₂Cl₂ (space group P2/c) is built of edge- and corner-sharing octahedral coordination polyhedra of yttrium (4Cl + 2BH₄) and sodium (2Cl + 4BH₄). The structure is isomorphous to the high temperature polymorph of NaYCl₄. The BH₄ units in NaY(BH₄)₂Cl₂ are located only on the larger of the two independent anion sites in NaYCl₄. Density functional theory optimization of the experimental structure suggests that the BH₄ units act as η³-ligands (face-sharing) towards yttrium and η¹-ligands (corner-sharing) towards sodium. Raman spectroscopy confirms this BH₄ configuration. NaY(BH₄)₂Cl₂ decomposes at ∼300 °C under formation of Na₃YCl₆, while the latter compound at higher temperatures reacts with Na(BH₄)_1−xCl_x to form NaCl and possibly amorphous products. The reactions are associated with mass losses of 2.62 and 3.78 wt% for the NaBH₄–YCl₃ (3:1) and (4:1) samples, respectively.     

Multifunctional Visible‐Light Powered Micromotors Based on Semiconducting Sulfur‐ and Nitrogen‐Containing Donor–Acceptor Polymer

Photosensitive micromotors that can be remotely controlled by visible light irradiation demonstrate great potential in biomedical and environmental applications. To date, a vast number of light‐driven micromotors are mainly composed from costly heavy and precious metal‐containing multicomponent systems, that limit the modularity of chemical and physical properties of these materials. Herein, a highly efficient photocatalytic micromotors based exclusively on a purely organic polymer framework—semiconducting sulfur‐ and nitrogen‐containing donor–acceptor polymer, is presented. Thanks to precisely tuned molecular architecture, this material has the ability to absorb visible light due to a conveniently situated energy gap. In addition, the donor‐acceptor dyads within the polymer backbone ensure efficient photoexcited charge separation. Hence, these polymer‐based micromotors can move in aqueous solutions under visible light illumination via a self‐diffusiophoresis mechanism. Moreover, these micromachines can degrade toxic organic pollutants and respond to an increase in acidity of aqueous environments by instantaneous colour change. The combination of autonomous motility and intrinsic fluorescence enables these organic micromotors to be used as colorimetric and optical sensors for monitoring of the environmental aqueous acidity. The current findings open new pathways toward the design of organic polymer‐based micromotors with tuneable band gap architecture for fabrication of self‐propelled microsensors for environmental control and remediation applications.     

Synthesis of an orthorhombic high pressure boron phase

The densest boron phase (2.52 g cm^-3) was produced as a result of the synthesis under pressures above 9 GPa and temperatures up to ∼1800 °C. The x-ray powder diffraction pattern and the Raman spectra of the new material do not correspond to those of any known boron phases. A new high-pressure high-temperature boron phase was defined to have an orthorhombic symmetry (Pnnm (No. 58)) and 28 atoms per unit cell.     

Effect of Chromium on the Structure and Properties of Boride Diffusion Coatings

We have studied the effect of the chromium concentration in an impregnating borochromating powder mixture on the change in the lattice parameters of the rhombic FeB phase of boride coatings on carbon steels, their microhardness, and the BK _α energy spectra. An increase in the microhardness of the boride phases for chromium concentration 3.5-6 mass% in powder boron-impregnating mixtures is accompanied by a decrease in the FeB lattice parameters. Interpretation of the BK _α spectra has allowed us to establish that this fact is due to an increase in the covalent component of the Fesd ― Bp bond.     

All Solution‐Processed Chalcogenide Solar Cells – from Single Functional Layers Towards a 13.8% Efficient CIGS Device

Solution processing of inorganic thin films has become an important thrust in material research community because it offers low‐cost and high‐throughput deposition of various functional coatings and devices. Especially inorganic thin film solar cells – macroelectronic devices that rely on consecutive deposition of layers on large‐area rigid and flexible substrates – could benefit from solution approaches in order to realize their low‐cost nature. This article critically reviews existing deposition approaches of functional layers for chalcogenide solar cells with an extension to other thin film technologies. Only true solutions of readily available metal salts in appropriate solvents are considered without the need of pre‐fabricated nanoparticles. By combining three promising approaches, an air‐stable Cu(In,Ga)Se₂ thin film solar cell with efficiency of 13.8% is demonstrated where all constituent layers (except the metal back contact) are processed from solutions. Notably, water is employed as the solvent in all steps, highlighting the potential for safe manufacturing with high utilization rates.     

A systematic procedure for the design of piezoelectric inchworm precision positioners

Design equations are developed and integrated into a computerized design tool in order to facilitate the creation of inchworm piezoelectric based positioners. Fundamental to the development of the design tool is the piezoelectric actuator and motor frame stiffness interaction and its influence on positioner performance. A generalized motor frame configuration for each of the motor subsystems is presented and used to generate key initial positioner frame geometry. An inchworm precision positioner is implemented based on the generalized motor frame and the computerized design tool and it is shown experimentally and through finite-element analysis that the design approach is effective for precision positioner design. The prototype of the inchworm positioner developed is shown to have a stiffness in the direction of motion of 88 N//spl mu/m, a maximum thrust of 150 N and a traversing speed of up to 20 mm/s.     

Simulation of heat extraction from crystalline rocks: The influence of coupled processes on differential reservoir cooling

Processes operating during the extraction of heat from fractured rocks influence dynamically their fluid flow and heat transport characteristics. The incorporation of pressure- and temperature-dependent rock parameters, coupled with geomechanical deformation, is particularly important for predictive modelling of geothermal reservoirs hosted in crystalline rock masses. Changes in flow and transport parameters of fractures caused by variations in local effective stress are computed using an experimentally validated geomechanical model [McDermott, C.I., Kolditz, O., 2006. Geomechanical model for fracture deformation under hydraulic, mechanical and thermal loads. Hydrogeol. J. 14, 487–498]. Local effective stress changes are linked to alterations in reservoir fluid pressures, and to in situ stress conditions, including the build-up of thermal stresses resulting from the cooling of the rock mass. These processes are simulated using a finite-element model in order to study the behaviour of the Spa Urach (southwestern Germany) potential geothermal reservoir. The model couples mechanical deformation and alteration of fracture parameters with pressure-, temperature- and salinity-dependent fluid parameter functions. The effects of potential reservoir damage on reservoir productivity are investigated to help identify optimal heat recovery schemes for the long-term economical exploitation of geothermal systems. Simulation results indicate that preferential fluid flow paths and shortcuts may develop, depending on the mechanical and thermal stress releases that occur during intense exploitation of these systems.     

The material balance of organic matter of Domanic shale formation after thermal treatment

In this paper, we discuss the amount of generated gaseous and liquid hydrocarbons as a product of artificial maturation of organic matters of Domanic black shale. The material balance of organic matter for initial rock sample and after thermal treatment at 300 and 500?°С were estimated. The amount of generated liquid hydrocarbon was minimum at 500?°С. As a result of kerogen destruction, no asphaltenes were observed during generation of liquid hydrocarbons. Based on the results of elemental analysis, Van Krevelen diagram was plotted.