Shengmin Guo

Morphology and electromagnetic interference shielding effects of SiC coated carbon short fibers

The electromagnetic shielding effectiveness of C–SiC/epoxy composites was investigated and compared with that of carbon fiber/epoxy composites. C–SiCs, short fibers with carbon cores and silicon carbide shells, were fabricated by a carbothermal reduction process using chopped carbon fibers (CFs) and rice husk ash. After presenting the morphology and structure of the C–SiC fibers, the electromagnetic interference shielding effect of SiC coated carbon short fibers is discussed. The Kα-band (26.5–40.0 GHz) shielding studies revealed that the maximum total shielding effectiveness (SET) of the composite with 25 vol% of C–SiCs is 17.07 dB, dominated by absorption, while the composite with 25 vol% of the same sized carbon fibers has a SET of 8.44 dB only.

High magnetic field sensor using LaSb2

The magnetotransport properties of single crystals of the highly anisotropic layered metal LaSb2 are reported in magnetic fields up to 45 T with fields oriented both parallel and perpendicular to the layers. Below 10 K the perpendicular magnetoresistance of LaSb2 becomes temperature independent and is characterized by a 100-fold linear increase in resistance between 0 and 45 T with no evidence of quantum oscillations down to 50 mK. The Hall resistivity is hole-like and gives a high field carrier density of n∼3×1020u2009cm−3. The feasibility of using LaSb2 for magnetic field sensors is discussed.

Structural and mechanical stability of dilute yttrium doped chromium

Rare earth element doping of chromium is much desired for various applications, but is technically difficult because of dopant segregation. Using a room temperature mechanical alloying method, dilute yttrium doping into nanosized chromium was achieved. Synchrotron-based high-pressure X-ray diffraction indicated that the Cr-Y alloy (Cr0.97Y0.03) was stable at up to 39 GPa, and the bulk modulus was 203u2009±u20092.6u2009GPa. The experimental results were consistent with first-principles density functional theory simulation. The diffraction line broadening profiles indicated the deformation anisotropy of the nanoalloy. This study suggests that Cr0.97Y0.03 alloy is promising for ultrahigh stress applications such as airplane engines and land-based turbines.

A thermodynamic study of corrosion behaviors for CoCrFeNi-based high-entropy alloys

To better understand the corrosion behaviors of CoCrFeNi-based high-entropy alloys (HEAs), the CALculation of PHAse Diagrams (CALPHAD) method was used to simulate the Pourbaix diagrams for CoCrFeNi, CoCrFeNiCu and CoCrFeNiAl HEAs. Although the CALPHAD simulations were performed under equilibrium conditions, assisted by published experimental results on CoCrFeNi, CoCrFeNiCu and CoCrFeNiAl0.5 HEAs, the CALPHAD simulations provide insights into the corrosion behaviors, such as the oxidation layer pitting and forming potential, of the CoCrFeNi-based HEAs.

Unexpected pressure induced ductileness tuning in sulfur doped polycrystalline nickel metal

The sulfur induced embrittlement of polycrystalline nickel (Ni) metal has been a long-standing mystery. It is suggested that sulfur impurity makes ductile Ni metal brittle in many industry applications due to various mechanisms, such as impurity segregation and disorder-induced melting etc. Here we report an observation that the most ductile measurement occurs at a critical sulfur doping concentration, 14 at.% at pressure from 14 GPa up to 29 GPa through texture evolution analysis. The synchrotron-based high pressure texturing measurements using radial diamond anvil cell (rDAC) X-ray diffraction (XRD) techniques reveal that the activities of slip systems in the polycrystalline nickel metal are affected by sulfur impurities and external pressures, giving rise to the changes in the plastic deformation of the nickel metal. Dislocation dynamics (DD) simulation on dislocation density and velocity further confirms the pressure induced ductilization changes in S doped Ni metal. This observation and simulation su...

Supporting data for senary refractory high-entropy alloy Cr x MoNbTaVW

This data article is related to the research paper entitled “senary refractory high-entropy alloy CrxMoNbTaVW [1]”. In this data article, the pseudo-binary Cr-MoNbTaVW phase diagram is presented to show the impact of Cr content to the senary Cr-MoNbTaVW alloy system; the sub-lattice site fractions are presented to show the disordered property of the Cr-MoNbTaVW BCC structures; the equilibrium and Scheil solidification results with the actual sample elemental compositions are presented to show the thermodynamic information of the melted/solidified CrxMoNbTaVW samples; and the raw EDS scan data of the arc-melted CrxMoNbTaVW samples are also provided.

Computational Design and Experimental Validation of New Thermal Barrier Systems

This project (10/01/2010-9/30/2014), “Computational Design and Experimental Validation of New Thermal Barrier Systems”, originates from Louisiana State University (LSU) Mechanical Engineering Department and Southern University (SU) Department of Computer Science. This project will directly support the technical goals specified in DE-FOA-0000248, Topic Area 3: Turbine Materials, by addressing key technologies needed to enable the development of advanced turbines and turbine-based systems that will operate safely and efficiently using coal-derived synthesis gases. In this project, the focus is to develop and implement novel molecular dynamics method to improve the efficiency of simulation on novel TBC materials; perform high performance computing (HPC) on complex TBC structures to screen the most promising TBC compositions; perform material characterizations and oxidation/corrosion tests; and demonstrate our new thermal barrier coating (TBC) systems experimentally under integrated gasification combined cycle (IGCC) environments.