X-ray diffraction in the pulsed laser heated diamond anvil cell

We have developed in situ x-ray synchrotron diffraction measurements of samples heated by a pulsed laser in the diamond anvil cell at pressure up to 60 GPa. We used an electronically modulated 2-10 kHz repetition rate, 1064-1075 nm fiber laser with 1-100 μs pulse width synchronized with a gated x-ray detector (Pilatus) and time-resolved radiometric temperature measurements. This enables the time domain measurements as a function of temperature in a microsecond time scale (averaged over many events, typically more than 10,000). X-ray diffraction data, temperature measurements, and finite element calculations with realistic geometric and thermochemical parameters show that in the present experimental configuration, samples 4 μm thick can be continuously temperature monitored (up to 3000 K in our experiments) with the same level of axial and radial temperature uniformities as with continuous heating. We find that this novel technique offers a new and convenient way of fine tuning the maximum sample temperature by changing the pulse width of the laser. This delicate control, which may also prevent chemical reactivity and diffusion, enables accurate measurement of melting curves, phase changes, and thermal equations of state.     

Recrystallization Behavior of CVD ZnSe during Fe Diffusion Doping

This paper examines the effect of diffusion doping with divalent Fe ions in different atmospheres on the microstructure of polycrystalline CVD ZnSe. The activation energy for the recrystallization process in Fe²⁺:ZnSe is determined in the temperature range 900–1150°C, and the mechanisms underlying the effect of the dopant on grain growth in Fe²⁺:ZnSe are discussed.     

Characterization of mouthguard materials: A comparison of a commercial material to a novel thiolene family

The goal of this study is to compare the thermal and mechanical properties of a commercial mouthguard material with a novel class of thermoset polymers based on thiolene “click” chemistry. Ternary thiolene systems modified with urethane or acrylate [urethane‐modified thiolene network (UMTEN) and acrylate‐modified thiolene network (AMTEN), respectively] were synthesized and their properties compared with commercially available Polyshok™. Durometer hardness (ASTM D2240‐05), water absorption [ASTM D570‐98 (2005)], tear strength (ASTM D624‐00), and impact attenuation [ASTM D6110‐06f (modified)] were measured for physical property comparison. Differential scanning calorimetry and dynamic mechanical analysis were used as a means to compare thermal properties. One‐way analysis of variance and independent t tests were used to test for differences between Polyshok™, AMTEN and UMTEN samples. It was found that the novel thiolene networks exhibit higher impact attenuation at intraoral temperature compared with Polyshok™, although Polyshok™ demonstrates lower water absorption and hardness, as well as higher tear strength. With further modification, this family of thiolene materials may provide a platform for developing next‐generation mouthguard materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40402.     

High‐efficiency black silicon interdigitated back contacted solar cells on p‐type and n‐type c‐Si substrates

This work demonstrates the high potential of Al₂O₃ passivated black silicon in high‐efficiency interdigitated back contacted (IBC) solar cells by reducing surface reflectance without jeopardizing surface passivation. Very low reflectance values, below 0.7% in the 300–1000 nm wavelength range, together with striking surface recombination velocities values of 17 and 5 cm/s on p‐type and n‐type crystalline silicon substrates, respectively, are reached. The simultaneous fulfillment of requirements, low reflectance and low surface recombination, paves the way for the fabrication of high‐efficiency IBC Si solar cells using black silicon at their front surface. Outstanding photovoltaic efficiencies over 22% have been achieved both in p‐type and n‐type 9‐cm² cells. 3D simulations suggest that efficiencies of up to 24% can be obtained in the future with minor modifications in the baseline fabrication process. Copyright © 2015 John Wiley & Sons, Ltd.     

Components of the radio-frequency system for traveling-wave deflecting structures

Components of a radio-frequency system for deflecting structures of the S-frequency range, which are included in the electron-beam diagnostic complexes for a free-electron laser (XFEL, Germany), were designed. Waveguide-coaxial and waveguide-strip directional couplers, a waveguide absorbing load, a waveguide window, and an E-bend were developed. A connecting element between two deflecting structures in the form of a U-shaped rectangular-waveguide section was also calculated.