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The present work reports a cuboidal B2-coherently-enhanced body-centered-cubic (BCC) alloy Al 0.7 CoCrFe 2 Ni with prominent tensile properties at both room (ultimate tensile strength  b = 1223 MPa and elongation to fracture = 7.9 %) and high temperatures. This multi-principal-element alloy is developed out of a cluster formula [Al-M 14 ]Al 1 issued from the cluster-plus-glue-atom model of a BCC structure. Here, the [Al-M 14 ] cluster is centered by Al, surrounded by fourteen average atoms M = Co 1/5 Cr 1/5 Fe 2/5 Ni 1/5 , and glued with one Al atom. Its excellent mechanical properties are attributed to a superalloy-like microstructure, characterized by cuboidal B2 nanoprecipitates coherently embedded in the BCC matrix.

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Abstract:The present work primarily investigates the morphological evolution of the body-centered-cubic (BCC)/B2 phases in Al x NiCoFeCr high-entropy alloys (HEAs) with increasing Al content. It is found that the BCC/B2 coherent morphology is closely related to the lattice misfit between these two phases, which is sensitive to Al. There are two types of microscopic BCC/B2 morphologies in this HEA series: one is the weave-like morphology induced by the spinodal decomposition, and the other is the microstructure of a spherical disordered BCC precipitation on the ordered B2 matrix that appears in HEAs with a much higher Al content. The mechanical properties, including the compressive yielding strength and microhardness of the Al x NiCoFeCr HEAs, are also discussed in light of the concept of the valence electron concentration (VEC).

In plasma-hydrogenated p-type Czochralski silicon, rapid thermal donor (TD) formation is achieved, resulting from the catalytic support of hydrogen. The n-type counter doping by TD leads to a p-n junction formation. A simple method for the indirect determination of the diffusivity of hydrogen via applying the spreading resistance probe measurements is presented. Hydrogen diffusion in silicon during both plasma hydrogenation and post-hydrogenation annealing is investigated. The impact of the hydrogenation duration, annealing temperature, and resistivity of the silicon wafers on the hydrogen diffusion is discussed. Diffusivities of hydrogen are determined in the temperature range 270–450°C. The activation energy for the hydrogen diffusion is deduced to be 1.23eV. The diffusion of hydrogen is interpreted within the framework of a trap-limited diffusion mechanism. Oxygen and hydrogen are found to be the main traps.

A novel reflective refractometer based on a thin-core fiber (TCF) sandwiched between a leading single-mode fiber (SMF) and a fiber Bragg grating (FBG) imprinted SMF stub was demonstrated. The reflection from the fiber stub occurs in two well-defined wavelength bands, corresponding to the Bragg core mode and cladding modes. The TCF section functions as a tailorable bridge between the FBG core mode reflection and the surrounding refractive index (SRI). Linear response with enhanced sensitivity of 133.26 dB/refractive index unit for temperature-immune SRI measurement within the biologically desirable sensing range of 1.33-1.41 has been achieved via cost-effective power detection.

The hydrogen-plasma-accelerated formation of shallow thermal donors in silicon has been studied for a wide range of doping concentration and interstitial oxygen content [normalOnormali] by electrical and spectroscopic techniques. The plasma-hydrogenated material has been heat treated for different times in the temperature range of 275–500°C . It is shown that, besides oxygen thermal donors (OTDs), hydrogen-related shallow thermal donors (STDHs) also play a crucial role in the hydrogen-assisted creation of excess carriers. The impact of different factors on the introduction rate of the shallow donors will be discussed, whereby a strong role is played by the doping concentration and type (i.e., the Fermi-level position during the thermal anneal in air). Generally, shallow donor formation is faster in p- compared to n-type Si, which is associated with the different charge state of H. From combined deep-level transient spectroscopy and Fourier transform infrared absorption spectroscopy, it is concluded that the additional free carriers are contributed by both STDH and OTD centers, so that H not only plays a catalytic role but actively takes part in the donor formation, depending on the experimental conditions. Finally, from our data some conclusions can be made regarding the nature of the STDHs, which is still a matter of debate.