Papers by Keyword: Thermal Activation Energy

Abstract: Microtopography of fiber of Discorea nipponica Makino before and after mechanical activated by AGO-2 planetary mill was observed by SEM, and they changed the thick floccules to fine particles (D50 particle sizes were 10.18μm). Discorea fiber powder after mechanical activation had a narrow size distribution. According to XRD, the granularity and structures of discorea fiber with and without mechanical activation significantly differed, and the crystalline of discorea fiber was significantly converted into amorphous state after mechanical activation. On the basis of TG–DSC analysis, the activity of discorea fiber was enhanced, and certain internal energy were stored, and complete decomposition in advance. According to FT-IR, none of the functional groups of the mechanically activated discorea fiber disappeared, and no new functional groups appeared, which indicate that mechanical activation does not induce a chemical transformation of discorea fiber. According to the activation energy analysis, the thermal activation energy of dioscorea fiber after mechanical activation was18.49 kJ•mol, and the mechanical transfer activation energy was 56.06 kJ•mol, indicating that about 1/3 of the mechanical transfer activation energy was stored in the activated dioscorea fiber fine powder in the form of surface energy and internal energy.

Abstract: A new Al-Mg-Si-Cu aluminum alloy was hot compressed at temperatures between 320°Cand 530°Cand strain rates between 0.001 s¹ and 10 s¹ using a Gleeble-1500 thermo-simulation machine. The effects of deformation heating on flow stress were analyzed and corrected, and a comparison was made of hyperbolic-sine constitutive equations with and without correction. The results show that the deformation heating apparently increases the flow stress at strain rates of 1 s¹, 10 s¹. The thermal activation energy values were 325.12 KJ/mol and 304.47 KJ/mol before and after correction, respectively.

Abstract: We investigated sensing properties on NOx (g) of single tellurium (Te) nanoribbon-based nanodevices. The synthesized Te nanoribbons were aligned at well-defined locations using a lithographically patterned nanowire electrodeposition (LPNE) technique. The shape and length were feasibly modified by the designed lithographical pattern, and the width was tailored by the applied electrochemical parameters. Temperature-dependent electrical resistance was analyzed with as-synthesized and annealed Te nanoribbons in the temperature ranging from 15 K to 300 K, where the calculated thermal activation energies of as-synthesized and annealed Te nanoribbons were 35.7 meV and 19.2 meV, respectively. Room-temperature sensor performance of as-synthesized and annealed single Te nanoribbons on detecting NOx (g) was investigated as a function of the tailored concentration of NOx (g). Compared to a sensitivity of 16±2.9% on detecting NOx (g) of 10 ppm in the as-synthesized single Te nanoribbon sensor aligned between Au/Cr electrodes, the sensitivity of 21±3.2% on detecting NOx (g) of 10 ppm at room temperature was demonstrated by single Te nanoribbon-based sensor annealed at 200oC for 1 hour in 5 % H2/N2 (g). The effects of annealing on sensing properties have demonstrated the improved sensitivity in the annealed Te nanoribbons..

Abstract: We investigated non-equilibrium carrier dynamics in ~20μm thick 3C-SiC layers, grown by sublimation epitaxy directly on 6H-SiC substrate or buffered by a 3C seed layer. Differential transmission and light-induced transient grating techniques were applied to determine the ambipolar diffusion coefficient, carrier lifetime, and thermal activation energy of defects. The temperature dependences of ambipolar mobility and lifetime in 80-700 K range revealed the carrier scattering processes as well the impact of defects on the recombination rate, thus indicating slightly improved photoelectrical parameters of the homoepitaxially grown 3C layer. The determined thermal activation energies of 35 and 57 meV were attributed to the nitrogen impurity.

Abstract: We report effects of the size and the energy state distribution on the electrical and optical properties in self-assembled InAs quantum dots. The results of characteristics measured using atomic force microscopy, photoluminescence and dark current are analyzed by way of a simulation assuming a Gaussian distribution in size and related energies. The samples investigated in this study are InAs/GaAs quantum dot infrared photodetector structures with an AlGaAs blocking layer grown by molecular beam epitaxy at different growth modes.