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Zhang, L. M.

Publications and source records attributed to Zhang, L. M..

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Microstructures, Martensitic Transformation, and Mechanical Behavior of Rapidly Solidified Ti-Ni-Hf and Ti-Ni-Si Shape Memory Alloys

In this work, the microstructure and mechanical properties of rapidly solidified Ti{sub 50−x/2}Ni{sub 50−x/2}Hf{sub x} (x = 0, 2, 4, 6, 8, 10, and 12 at.%) and Ti{sub 50−y/2}Ni{sub 50−y/2}Si{sub y} (y = 1, 2, 3, 5, 7, and 10 at.%) shape memory alloys (SMAs) were investigated. The sequence of the phase formation and transformations in dependence on the chemical composition is established. Rapidly solidified Ti-Ni-Hf or Ti-Ni-Si SMAs are found to show relatively high yield strength and large ductility for specific Hf or Si concentrations, which is due to the gradual disappearance of the phase transformation from austenite to twinned martensite and the predominance of the phase transformation from twinned martensite to detwinned martensite during deformation as well as to the refinement of dendrites and the precipitation of brittle intermetallic compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of sintering temperature on structural, magnetic and electrical transport properties of La0.67Ca0.33MnO3 ceramics prepared by Plasma Activated Sintering

Highlights: • La{sub 0.67}Ca{sub 0.33}MnO{sub 3} were prepared by using Plasma Activated Sintering technology. • Detailed studies of sintering temperature effect on structural, magnetic and electrical transport behaviors were investigated. • The observed behaviors have been explained by oxygen vacancy effect in combination with grain size effect. - Abstract: La{sub 0.67}Ca{sub 0.33}MnO{sub 3} (LCMO) ceramics were prepared by Plasma Activated Sintering (PAS). The effect of sintering temperature on structural, magnetic and electrical transport properties of the LCMO ceramics were investigated. XRD and SEM characterizations of the LCMO ceramics indicated that all samples exhibited single orthorhombic phase. Also, through PAS dense LCMO ceramics were obtained. Certain interesting phenomena were observed from the PAS sintering temperature effect on the magnetic and transport behaviors of LCMO ceramics, which were significantly different from traditional sintering methods The magnetization decreased and the resistivity increased as the sintering temperature increased, whereas the T{sub C} and T{sub IM} shifted towards the lower temperature side. The conduction mechanism of all samples was electron-magnon scattering process in the ferromagnetic low-temperature region, while the paramagnetic high-temperature region mechanism was explained with the variable range hopping (VRH) model. All these behaviors were explained through the oxygen vacancy effect in combination with the grain size effect.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Generalized spectral method for near-field optical microscopy

Electromagnetic interaction between a sub-wavelength particle (the “probe”) and a material surface (the “sample”) is studied theoretically. The interaction is shown to be governed by a series of resonances corresponding to surface polariton modes localized near the probe. The resonance parameters depend on the dielectric function and geometry of the probe as well as on the surface reflectivity of the material. Calculation of such resonances is carried out for several types of axisymmetric probes: spherical, spheroidal, and pear-shaped. For spheroids, an efficient numerical method is developed, capable of handling cases of large or strongly momentum-dependent surface reflectivity. Application of the method to highly resonant materials, such as aluminum oxide (by itself or covered with graphene), reveals a rich structure of multi-peak spectra and nonmonotonic approach curves, i.e., the probe-sample distance dependence. These features also strongly depend on the probe shape and optical constants of the model. For less resonant materials such as silicon oxide, the dependence is weak, so that the spheroidal model is reliable. The calculations are done within the quasistatic approximation with radiative damping included perturbatively.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Amplitude analyses of the decays χ c1 →ηπ⁺π⁻ and χ c1 →η'π⁺π⁻

Using a data sample of 2.59×10⁷ ψ(2S) decays obtained with the CLEO-c detector, we perform amplitude analyses of the complementary decay chains ψ(2S)→γχ c1 ; χ c1 →ηπ⁺π⁻ and ψ(2S)→γχ c1 ; χ c1 →η'π⁺π⁻. We find evidence for an exotic P-wave η'π amplitude, which, if interpreted as a resonance, would have parameters consistent with the π₁(1600) state reported in other production mechanisms. We also make the first observation of the decay a₀(980)→η'π and measure the ratio of branching fractions B(a₀(980)→η'π)/B(a₀(980)→ηπ)=0.064±0.014±0.014. The ππ spectrum produced with a recoiling η is compared to that with η' recoil.

Adams, G. S.↗
DOE OSTI2011

Studies of D⁺→{η',η,Φ}e⁺ν e

We report the first observation of the decay D⁺→η'e⁺ν e in two analyses, which combined provide a branching fraction of B(D⁺→η'e⁺ν e )=(2.16±0.53±0.07)×10⁻⁴. We also provide an improved measurement of B(D⁺→ηe⁺ν e )=(11.4±0.9±0.4)×10⁻⁴, provide the first form factor measurement, and set the improved upper limit B(D⁺→Φe⁺ν e )<0.9×10⁻⁴ (90%C.L.).

Yelton, J.↗