Form-finding describes the process of finding a stable equilibrium shape for a structure under a specific set of loading for a set of boundary conditions. Both physical (experimental) and numerical (computational) form-finding methods have been employed by structural engineers and architects for the design of shape-resistant structures: structures whose behavior depends mostly on their global spatial configuration and less on the properties of their individual components. The shape of dielectric elastomer minimum energy structures (DEMES) depends on the equilibrium between the pre-stressed elastomeric membrane and its inextensible frame. Therefore, DEMES can be modeled and analyzed using structural form-finding techniques. We applied dynamic relaxation (DR), a well-established explicit and efficient numerical form-finding and analysis method, to simulate DEMES equilibrium shapes and predict the elastic energy of DEMES. The DR-DEMES model shows generally good agreement with its physical implementation counterpart, as it captures the equilibrium shape and also the elastic energy in function of shape. However, we found that the numerical and the physical models differ in the pre-stress that is required to obtain a specific equilibrium shape. Therefore, in this study we introduce hyper-elasticity in the DR-DEMES model. With this refinement in physical parameters the DR-DEMES model approaches the pre-stress state of the physical DEMES implementation more closely, while it maintains the computational efficiency of the form-finding approach. We conclude that dynamic relaxation, with its low computational cost, is a powerful tool for the design of novel DEMES applications.

We present results of theoretical and experimental studies of whispering-gallery modes in optical microdisk resonators interacting with subwavelength dielectric particles. We predict theoretically and confirm by direct observations that, contrary to the generally accepted models, both peaks of the particle-induced doublet of resonances are red shifted with respect to the position of the initial resonance.

Molecular Dynamics simulation are employed to investigate the structures and mechanical behavior of both symmetric and asymmetric Σ5[0 0 1] tilt grain boundaries (GBs) of copper bicrystal under uniaxial tension and shear deformation. Simulation results indicate that the Σ5 asymmetric GBs can facet into their corresponding symmetric GB structures. The maximum tensile stress of symmetric GBs is higher than the asymmetric ones at both 10 K and 300 K, which suggests the symmetric GBs may have a more stable boundary structures. All the Σ5 GBs investigate in this study can migrate under the shear deformation with different velocity. The migration of Σ5 symmetric GBs is realized by uniform displacement of local atoms and rotation of the atomic group in “E” structural unit, while for the asymmetric GBs, the migration is identified to be a diffusion-related process result from local atoms shuffling.

III-V on Si multijunction solar cells represent an alternative to traditional compound III-V multijunction cells as a promising way to achieve high efficiencies. A theoretical study on the energy yield of GaAs/Si tandem solar cells is performed to assess the performance potential and sensitivity to spectral variations. Recorded time-dependent spectral irradiance data in two locations (Singapore and Denver) were used. We found that a 4-terminal contact scheme with thick top cell confers distinctive advantages over a 2-terminal scheme, giving a yield potential 21% higher than the 2-terminal scheme in Singapore and 17% higher in Denver. The theoretical energy yield benefit of a 4-terminal device emphasizes the need for further technology development in this design space.

The United Kingdom aims to decarbonize its national electricity generation in order to transition to a low carbon economy. Solar, wind, hydro and thermal energy conversion are renewable alternatives to fossil fuels and are currently being explored that may form part of the future generation mix of the country.

How does materials scientist's work addressing energy research challenges for solar and storage (for example) translate into the adoption of new technology? How appropriate are the technology usage visions of the scientists? How can technology users better inform the materials science motivations? This report will focus on how a multidisciplinary team of researchers from the Universities of Sheffield and University of Durham, community members and industry representatives are jointly developing renewable energy projects to try to answer these and other questions. The history of the project will be presented as well as the methodology used to collaboratively engage the community participants.

This work is supported by a grant provided by the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom.

A facile and novel method of fabricating large-area-patterned monolayer of polytetrafluoroethylene(PTFE) nanoparticles was achieved using surface charge induced colloidal deposition. Chemical processes of amination and hydroxylation were used to make the silicon substrates positively and negatively charged, respectively, while the PTFE colloidal nanoparticles were anisotropic and negatively charged. After colloidal deposition, an ordered monolayer with microholes was formed on the amination surface, while an island-like monolayer was achieved on the hydroxylation surface. Both of the two kinds of monolayers were as large as 1.5 square centimeters. It is worth pointing out that these large-area-patterned monolayers were fabricated without any templates and the whole process only took several hours. The formation mechanism of the different structures can be generally attributed to the cooperation and competition of three-body, two-body and particle-wall interactions. It is believed that the interesting patterned monolayer formation mechanism, high production efficiency, good adaptability and quality will make this novel method attractive.

This work focuses on the effect of gamma-ray radiation conditions on the stimuli-responsive of polypropylene (PP) films and silicone (SR) rubber substrates grafted with N-vinylcaprolactam (NVCL) and acrylic acid (AAc). PP films and SR rubber were weighed and placed into glass ampoules and exposed to 60Co γ-source in the presence of air at room temperature, at dose rate around 12 kGy h-1 and dose between 5 and 70 kGy. Solutions of NVCL and AAc (1/1, v/v), 50 % monomer concentration (v/v) in toluene were added to the samples, the ampoules were degassed by repeated freeze-thaw cycles (5 times per 20 min) and sealed. The ampoules were heated at 60 or 70 °C at reaction time per 12 h. To extract the residual monomer and homopolymer formed during the grafting, the samples were soaked in ethanol for 24 h and then in distilled water, followed by drying under vacuum to constant weight. The values of grafting percentage achieved at a given irradiation dose were higher for SR than for PP. Samples where characterized by FTIR-ATR, DSC, swelling, LCST, and pH critical point.

The purpose of this paper is to propose the enhancement of device detectors based on p-n junction in 4H-SiC for nuclear instrumentation. Particular emphasis is placed on the interest on using Boron isotope 10 as a Neutron Converter Layer in order to detect thermal neutrons. Here, we present the main results obtained during several irradiation tests performed in the Belgian Reactor 1 (BR1). We show the capability of our detectors by means of first results of the detector response at different reverse voltage biases and at different reactor power.

Phosphorus is incorporated into single crystal diamond during epitaxial growth at higher concentrations on the (111) crystallographic surface than on the (001) crystallographic surface. To form n+-type regions in diamond for semiconductor devices it is beneficial to deposit on the (111) surface. However, diamond deposition is faster and of higher quality on the (001) surface. A preferential etch method is described that forms inverted pyramids on the (001) surface of a substrate diamond crystal, which opens (111) faces for improved phosphorus incorporation. The preferential etching occurs on the surface in regions where a nickel film is deposited. The etching is performed in a microwave generated hydrogen plasma operating at 160 Torr with the substrate temperature in the range of 800-950 °C. The epitaxial growth of diamond with high phosphorus concentrations exceeding 1020 cm-3 is performed using a microwave plasma-assisted chemical vapor deposition process. Successful growth conditions were achieved with a feedgas mixture of 0.25% methane, 500 ppm phosphine and hydrogen at a pressure of 160 Torr and a substrate temperature of 950-1000°C. The room temperature resistivity of the phosphorus-doped diamond is 120-150 Ω-cm and the activation energy is 0.027 eV.

This study deals with evaluation of mechanical properties (tensile, flexural and impact strength), that verified reinforcing potential of nanofibres in polymeric composites and their applicability in dependence on the filler content of nanofibres of natural and synthetic origin. Considering the hydrophilic nature of natural nanofibres and hydrophobic polypropylene matrix was applied chemical modification that ensures effective interlock of nanofibres with the matrix, namely maleic anhydride grafted polypropylene and ionic modifier. Polymeric nanocomposites were prepared by twin screw extrusion that made possible mixing of all three components together. After cooling in water bath the composites were cut on pellets and dried for further injection moulding. The specimens were made of two- or three-phase component systems that included PP matrix, coupling agent in the volume of 4 wt.% and reinforcing nanofillers in the volume of 2, 4 and 6 wt.%. The presence of nanoparticles and coupling agents had not unambiguous impact on analysed mechanical properties. Coupling agent presence was dominant for impact strength, however, flexural and tensile properties were influenced mainly by the nanofiller type and origin. The dispersed phase and compatibilizer improved flexural modulus but tensile modulus of pure PP were not achieved by three-phase composite, not even with the highest analysed nanoparticle load. Cellulose fibres proved as more proper than the synthetic ones not only for their biodegradability and renewability but for their better toughness as well.

Transport properties have been measured transverse to the plane of sheared and un-sheared thin-film nanocomposites of isotactic Polypropylene (iPP) and multiwall carbon nanotubes (MWCNTs) at various MWCNT concentrations. The sheared samples were processed in the melt at 200 0C at 1 Hz in a Linkan microscope shearing hot stage. The thermal and electrical conductivity measurements were performed on the same cell arrangement with the transport perpendicular to the thin-film plane using a DC method. The thermal and electrical conductivity perpendicular to the surface of the films are higher for the un-sheared as compared to the sheared samples. Interestingly, the percolation threshold appears smeared in both conductivity measurements likely due to pressing and shear treatment of the films, or the spacing between the data points. Important for electronics packaging and materials for which those anisotropic properties are highly desired this work presents important advances in understanding the structure-transport property relations.

High-brightness green phosphorescent hybrid inorganic-organic light-emitting diodes (HyLEDs) and inverted HyLEDs (IHyLEDs) have been demonstrated. The devices comprised a transparent and conductive WO3 layer deposited by thermal evaporation, which improved both hole injection and transport, and led to more balanced charge injection and significant performance enhancement. At 20 mA/cm2, the HyLEDs had a low operation voltage of 6.1 V, 0.8 V lower than that of OLEDs with an organic hole transport layer. With an optimized layer structure, the HyLEDs reached 104 cd/m2 brightness at 7.3 V. At this brightness level, the current efficiency was 55.2 cd/A, 57% higher than that of the OLEDs. In the IHyLEDs, facile hole injection and transport through WO3 was balanced by electron injection from the indium-tin-oxide (ITO) cathode overcoated with nanometer-thick Ca, leading to a low turn-on voltage of ∼6 V. Brightness of 8133 cd/m2 was reached at 20 mA/cm2 and the corresponding current efficiency was 40 cd/A. The hybrid devices also exhibited markedly improved stability under constant-current stressing due to the robust WO3 hole transport layer.

A novel and fundamental method was reported to judge states of lithium ion batteries (LIBs) using the capacitance and the voltage of the cells that were estimated from the real-time currents and voltage characteristics of the cells. We measured the differential capacitance, that is, dQ/dV or delta Q/ delta V that is equal to the currents (I) divided by differential voltages (dV/dt) calculated from the current and the voltage characteristics of the cell during the charging/ discharging, where Q is the charge that flows through the cell, V is the voltage of the cell and t is time. It is thought that the capacitance decrease with the degradation of the cell because the effective area of the electrodes is decreasing due to formation of undesirable compounds. The differential capacitance in some specific voltage range for the LIBs was approximately directly proportional to the state of the degradation of the cell. Therefore, it is concluded that the novel method is very useful to judge the state of the LIBs.

Absorption, scattering and fluorescent properties of several different types of nanodiamond samples are measured to characterize them for various applications. Two different methods, spectrophotometry and photothermal spectroscopy were used to measure absorption properties of nanodiamonds suspended in aqueous solutions. Photothermal spectroscopy provides the advantage of measuring absorption of photoactive nanodiamonds with high-sensitivity. Spectral fluorescence properties of nanodiamond samples were studied using a commercial spectrofluorometer and a home-built inverted microscope integrated with a light-sensitive imaging spectrograph. Characteristic fluorescence spectrum of nitrogen-vacancy defects in single diamond nanocrystals was obtained using the light-sensitive instrument.

Traditional methods of quantifying cell movement in response to a chemotactic factors provide either a binary count of cell migration in response to a known concentration of the factor of interest in solution, as in Boyden chamber assays, or a method of tracking cells to determine velocities across a solubilized protein gradient where exact concentrations vary over time and are difficult to define, as in the Ibidi chemotaxis gradient assay. Using a silane self-assembling monolayer (SAM)-based procedure pioneered by V Hlady and associates, we have developed an assay capable of covalently binding a wide variety of proteins to an optically transparent surface in a 2D pattern via amine linkages. The pattern was then verified by contact angle and Raman and X-ray photoelectron spectroscopy. This new assay provides greater control of protein concentration and gradient intensity than when using only solubilized proteins.

TiO2-supported bimetallic Au-Rh and Au-Pd nanocrystals were synthesized using both impregnation and colloidal approaches employing HAuCl4 and RhCl3 as precursors. The as-obtained bimetallic catalysts were then supported onto TiO2 rutile nanorods in order to provide catalytic systems with well-defined metal-support interactions for HRTEM characterization. The results revealed the superiority of the colloidal approach over the impregnation technique to obtain bimetallic nanoparticles (4 nm in size) with tunable composition. However, for Au-Rh/TiO2, optimization of the procedure of the sol immobilization onto the TiO2 support was required to avoid possible Rh re-dissolution. Preparation of Au-Pd/TiO2 followed the same procedure but with more acidic conditions necessary to perform immobilization on the support. UV-vis spectroscopy and XRD results suggest formation of a Rh-rich shell over an Au core center for Au-Rh NPs, while Au-Pd NPs present a pure alloy structure. Au-Rh/TiO2 was used for performing the high-pressure hydroconversion of tetralin in the presence or not of H2S. The results indicate a strong thioresistance induced by the addition of Au to Rh.

3D scaffolds with different pore sizes, using single-walled carbon nanotubes (SWCNTs) and nanoparticles of different size were constructed. Biotinylated glucose oxidase (GOX-B) and anti-cholera toxin (anti-CT) were immobilized onto the one and two level nanoscaffolds, functionalized with pyrene-β-cyclodextrin for the construction of glucose based enzyme sensors and immunosensors, respectively. For enzyme sensors, highest current density and sensitivity (41.72 μA cm-2, 3 mA M-1 cm-2) were obtained with two level scaffolds made with 100 nm nanoparticles. In contrast to this, for immunosensors, highest current density and sensitivity (11.71 μA cm-2, 116.2 μA M-1 cm-2) were obtained with two level scaffolds made with 500 nm nanoparticles, indicating that the pore sizes can be adjusted using different size of nanoparticles for the respective applications.

The contamination of water by a large variety of molecules is a major environmental issue that will require the use of efficient and versatile materials to purify hydrological systems from source to point-of-use. The present study describes the aqueous-phase adsorption of heavy metal ions and multiple organic compounds at environmentally relevant concentrations onto graphene-single-walled carbon nanotube free-standing hybrid papers. Optical absorption spectroscopy results clearly showed that the hybrid nanocomposites exhibit superior adsorption properties compared to activated carbon, the most widely used adsorbent to date.

We investigated electronic structure of one-dimensional biradical molecular chain which is constructed by exploiting the covalency between organic molecules of a diphenyl derivative of s-indacenodiphenalene (Ph2-IDPL). To control the crystallinity, we used gas deposition method. Ultraviolet photoelectron spectroscopy (UPS) revealed developed band structure with wide dispersion of the one-dimensional biradical molecular chain.