Elastic properties of Mo1 ? xSix alloy films with 0 ≤ x ≤ 1 have been investigated by the Brillouin light scattering technique thanks to the analysis of the surface acoustic waves in the film on substrate: the so-called Rayleigh surface wave and the Sezawa waves. A transition from crystalline to amorphous state is observed for a Si content, x = 0.19. This transition is accompanied by different modifications of the elastic constants, namely, C11, C33, C13 and C44 that are necessary with C12 to define the effective hexagonal symmetry for the textured <110> polycrystalline alloys. A pronounced softening of the shear elastic C44 constant is observed, from 110 to 60 GPa when x varies from 0 to the critical threshold composition x = 0.19. The longitudinal C33 constant estimated in this work from the BLS measurements shows also a softening from 425 to 315 GPa. An intrinsic consequence of the high supersaturation of MoSi alloys is the development of an important lattice instability. In the amorphous state, the evolution of the elastic properties, that can be defined by the two independent constants C11 and C44 = (C11 ? C12)/2, exhibits two distinct behaviors depending on the electronic properties and the interatomic bonding of the amorphous alloys. 相似文献
Epitaxial growth of ZrN/W multilayers with bilayer periods Λ ranging from 2.5 to 50 nm has been achieved at 300 °C on MgO (001) substrates by means of dual ion beam sputtering, which is a novelty compared to polycrystalline growth reported so far in this system. X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) experiments reveal the following epitaxial relationship [110] (001) W // [100] (001) ZrN // [100] (001) MgO. Nanoindentation tests indicate a hardness increase proportional to Λ− 0.54, with maximum of 25.8 GPa at Λ = 2.5 nm. However, there is no hardness enhancement relative to rule-of-mixtures value, which could be ascribed to delamination at the W on ZrN interfaces, as observed by TEM and related to large compressive stress, as determined by XRD. Another explanation could be related to the small difference in shear modulus between the two materials. 相似文献
Here we describe the important role played by the pH on the morphology and structure of the reduced graphite oxide (rGO) samples obtained by hydrothermal treatment of the previously prepared GO. The nature of the resulting samples has been studied on the basis of a complete battery of experimental techniques. 相似文献
Capsicum spp. fruit is one of the most produced vegetables around the world, and it is consumed both as fresh vegetable and as a spice like a food additive for their characteristic red color and, in many cases, its pungency. In addition to its economic importance, the bioactivity of some important compounds such as capsaicinoids and carotenoids has promoted its research. The use of Capsicum oleoresins has been increased due to its advantages comparing with the traditional dry spice. These include obtaining higher quality products with the desired content of bioactive and flavored substances. The wide diversity of extraction methods including water extraction, organic solvent extraction, microwave-assisted extraction, and ultrasound assisted extraction as well as supercritical fluid extraction among others are discussed in the present review. Moreover, pretreatments such as chemical treatments, osmotic dehydration, sun and oven drying, and freeze-drying commonly used before the extraction are also presented. Due to its importance, Capsicum oleoresins produced with “green” solvents and the improvement of fractional extraction techniques that allow to obtain separately the various bioactive fractions will continue under research for further development. 相似文献
Shrimp is one of the most popular seafood items worldwide, and has been reported as a source of chemopreventive compounds. In this study, shrimp lipids were separated by solvent partition and further fractionated by semi-preparative RP-HPLC and finally by open column chromatography in order to obtain isolated antiproliferative compounds. Antiproliferative activity was assessed by inhibition of M12.C3.F6 murine cell growth using the MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide) assay. The methanolic fraction showed the highest antiproliferative activity; this fraction was separated into 15 different sub-fractions (M1–M15). Fractions M8, M9, M10, M12, and M13 were antiproliferative at 100 µg/mL and they were further tested at lower concentrations. Fractions M12 and M13 exerted the highest growth inhibition with an IC50 of 19.5 ± 8.6 and 34.9 ± 7.3 µg/mL, respectively. Fraction M12 was further fractionated in three sub-fractions M12a, M12b, and M12c. Fraction M12a was identified as di-ethyl-hexyl-phthalate, fraction M12b as a triglyceride substituted by at least two fatty acids (predominantly oleic acid accompanied with eicosapentaenoic acid) and fraction M12c as another triglyceride substituted with eicosapentaenoic acid and saturated fatty acids. Bioactive triglyceride contained in M12c exerted the highest antiproliferative activity with an IC50 of 11.33 ± 5.6 µg/mL. Biological activity in shrimp had been previously attributed to astaxanthin; this study demonstrated that polyunsaturated fatty acids are the main compounds responsible for antiproliferative activity. 相似文献
In this work, two medium Mn steels (5.8 and 5.7 wt pct Mn) were subjected to a quenching and partitioning (Q&P) treatment employing a partitioning temperature which corresponded to the start of austenite reverse transformation (ART). The influence of a 1.6 wt pct Ni addition in one of the steels and cycle parameters on austenite stability and mechanical properties was also studied. High contents of retained austenite were obtained in the lower quenching temperature (QT) condition, which at the same time resulted in a finer microstructure. The addition of Ni was effective in stabilizing higher contents of austenite. The partitioning of Mn and Ni from martensite into austenite was observed by TEM–EDS. The partitioning behaviour of Mn depended on the QT condition. The lower QT condition facilitated Mn enrichment of austenite laths during partitioning and stabilization of a higher content of austenite. The medium Mn steel containing Ni showed outstanding values of the product of tensile strength (TS) and total elongation (TEL) in the lower QT condition and a higher mechanical stability of the austenite.
Based on 22MnB5 hot stamping steel, three model alloys containing 0.5, 0.8, and 1.5 wt pct Si were produced, heat treated by quenching and partitioning (Q&P), and characterized. Aided by DICTRA calculations, the thermal Q&P cycles were designed to fit into industrial hot stamping by keeping partitioning times ≤ 30 seconds. As expected, Si increased the amount of retained austenite (RA) stabilized after final cooling. However, for the intermediate Si alloy the heat treatment exerted a particularly pronounced influence with an RA content three times as high for the one-step process compared to the two-step process. It appeared that 0.8 wt pct Si sufficed to suppress direct cementite formation from within martensite laths but did not sufficiently stabilize carbon-soaked RA at higher temperatures. Tensile and bending tests showed strongly diverging effects of austenite on ductility. Total elongation improved consistently with increasing RA content independently from its carbon content. In contrast, the bending angle was not impacted by high-carbon RA but deteriorated almost linearly with the amount of low-carbon RA. 相似文献
In this work, a dynamical model of the heartbeat is studied using nonlinear dynamics and considering the time delays inherent in the system. Two fixed points are associated to sustained oscillations which might be interpreted as the diastole and systole These parameters are associated with blood flow in human body called arterial pressure and are very important in the cardio-vascular diagnostic. 相似文献