Shaopeng Li

GaAs-based room-temperature continuous-wave 1.59 {mu}m GaInNAsSb single-quantum-well laser diode grown by molecular-beam epitaxy

Starting from the growth of high-quality 1.3μmGaInNAs∕GaAs quantum well (QW), the QW emission wavelength has been extended up to 1.55μm by a combination of lowering growth rate, using GaNAs barriers and incorporating some amount of Sb. The photoluminescence properties of 1.5μm range GaInNAsSb∕GaNAs QWs are quite comparable to the 1.3μm QWs, revealing positive effect of Sb on improving the optical quality of the QWs. A 1.59μm lasing of a GaInNAsSb∕GaNAs single-QW laser diode is obtained under continuous current injection at room temperature. The threshold current density is 2.6kA∕cm2 with as-cleaved facet mirrors.

Enhanced Negative Thermal Expansion in La1–xPrxFe10.7Co0.8Si1.5 Compounds by Doping the Magnetic Rare-Earth Element Praseodymium

Experiments have been performed to enhance negative thermal expansion (NTE) in the La(Fe,Co,Si)13-based compounds by optimizing the chemical composition, i.e., proper substitution of La by magnetic element Pr. It is found that increasing the absolute value of the average coefficient of thermal expansion (CTE) in the NTE temperature region (200-300 K) attributes to enhancement of the spontaneous magnetization and its growth rate with increasing Pr content. Typically, the average CTE of La(1-x)Pr(x)Fe10.7Co0.8Si1.5 with x = 0.5 reaches as large as -38.5 × 10(-6) K(-1) between 200 and 300 K (ΔT = 100 K), which is 18.5% larger than that of x = 0. The present results highlight the potential applications of La(Fe,Co,Si)13-based compounds with a larger NTE coefficient.

Broad negative thermal expansion operation-temperature window in antiperovskite manganese nitride with small crystallites

Using spark plasma sintering (SPS), Mn3Cu0.6Ge0.4N crystallites have been fabricated with different crystallite sizes, and their magnetic properties and thermal behaviors were systemically investigated. With decreasing crystallite size, the magnetic transition becomes increasingly slow, accompanied by broadening of the negative thermal expansion (NTE) operation-temperature window. The NTE operation-temperature window for the 12-nm crystallite sample reaches at 140 K, which is about 75% larger than that of the 74-nm crystallite sample. The magnetic properties and NTE operation-temperature window can be tuned by varying the crystallite size. This discovery will promote an even wider range of practical applications in precision devices.

The direct adsorption of low concentration gallium from fly ash

ABSTRACT This study is mainly focused on the direct adsorption of low concentration gallium from the feed solution in pre-desilication soda-lime sintering process from coal fly ash. The adsorption kinetics, mechanism, and the influence of impurities, cyclic times, and eluant content are systematically researched. Results showed that the adsorption capacity was 2.89 mg/g resin with gallium concentration of 50 mg/L. The adsorption mechanism could be explained by the interaction between the oxygen atoms and nitrogen atoms of amidoxime group. Gallium was eluted efficiently by NaOH and Na2S mixed solution and the concentration could be reached to 2400 mg/L.

Molecular-Level Investigation of the Adsorption Mechanisms of Toluene and Aniline on Natural and Organically Modified Montmorillonite.

The present work reports the adsorption mechanisms of aniline and toluene in dry and hydrated montmorillonite (MMT-Na and MMT-Na-W) and tetramethylammonium-cation-modified MMT (MMT-TMA) as determined through density functional theory. These theoretical investigations explicitly demonstrate that cation-π interactions between Na(+)/TMA(+) cations and aromatics play the key role in adsorption of organics over MMT-Na and MMT-TMA. Weak hydrogen bonds between the H atoms of organics and basal O atoms of tetrahedral silicate also stabilize the location of organics. The combination of interactions between water and basal O atoms and between organics and water molecules in hydrated MMT complexes strengthens the adsorption of organics on MMT, resulting in higher formation energies in hydrated organically intercalated MMTs than in the corresponding dry complexes. The adsorption of organics also changes frontier orbital distributions and consequently promotes the preferential occurrence of reactions on the organics rather than on the MMT layers. These adsorption mechanisms predicted by theoretical investigation can be used to explicate the adsorption of aromatic organics on aluminosilicates with different external environment.

Broad Negative Thermal Expansion Operation-Temperature Window Achieved by Adjusting Fe–Fe Magnetic Exchange Coupling in La(Fe,Si)13 Compounds

Cubic La(Fe,Si)13-based compounds have been recently developed as promising negative thermal expansion(NTE) materials, but the narrow NTE operation-temperature window(∼110 K) restricts their actual applications. In this work, we demonstrate that the NTE operation-temperature window of LaFe(13-x)Si(x) can be significantly broadened by adjusting Fe-Fe magnetic exchange coupling as x ranges from 2.8 to 3.1. In particular, the NTE operation-temperature window of LaFe10.1Si2.9 is extended to 220 K. More attractively, the coefficients of thermal expansion of LaFe10.0Si3.0 and LaFe9.9Si3.1 are homogeneous in the NTE operation-temperature range of about 200 K, which is much valuable for the stability of fabricating devices. The further experimental characterizations combined with first-principles studies reveal that the tetragonal phase is gradually introduced into the cubic phase as the Si content increases, hence modifies the Fe-Fe interatomic distance. The reduction of the overall Fe-Fe magnetic exchange interactions contributes to the broadness of NTE operation-temperature window for LaFe(13-x)Si(x).

Giant isotropic magnetostriction in NaZn13-type LaFe13−xAlx compounds

The unusual low-temperature magnetostrictive property is of fundamental interest due to significant applications in rapidly developing cryogenic engineering. Here, we report a giant isotropic magnetostriction (λ = 1500 ppm, ω = 4500 ppm) over a wide temperature range (∼210 K), and the saturated volume magnetostriction can be up to 8400 ppm in cubic NaZn13-type LaFe13−xAlx compounds by optimizing the chemical composition. The large magnetostrictive effect often occurs in ferromagnetic materials. However, we discovered that the magnetic-field-induced volume expansion originates from the change of lattice parameters across the first-order transition from the low-volume antiferromagnetic ground state to the high-volume ferromagnetic state. Moreover, the magnetostrictive materials show an excellent zero thermal expansion (ZTE) property, which guarantees their reliability and stability operating at various temperatures. The present study suggests potential applications of La(Fe, Al)13-based compounds as ZTE and...

Comparison of the structures and electronic properties of sodalites containing alkali metals and alkali-earth metals and their hydrates

Abstract The effects of different alkali and alkali-earth metal ions on the electronic structures and properties of sodalite Mn[AlSiO4]6 (M-SOD) and their hydrates Mn[AlSiO4]6⋅8H2O (M=Li, Na, K, n = 6; M=Ca, n = 3) were studied using density functional theory method. Theoretical calculations predicted that the Al–O–Si bond angle and cation-framework oxide distance in sodalites with alkali metal cations are correlated with cell volumes. The reduced bandwidths in M-SOD (M=Li, Na and K) show that the inter-atomic orbital overlap in sodalites is weaker than those in the hydrate phases. Frontier molecular orbital analysis indicated that oxygen atoms in the frameworks and most metal ions of SOD and their corresponding hydrates exhibit high reactivity. The interactions existing in sodalites and hydrates were qualitative described. The calculated combination energies of metal ions with framework of sodalites are in the order of K+< Na+< Li+< Ca2+. This finding confirms the experimental observation for ion exchange.

Negative thermal expansion in cubic and tetragonal structure coexisted La(Fe,Si)13hydride

In this research, the cubic and tetragonal crystal structure coexisted LaFe10.0Si3.0 compound and its hydride have been prepared by the arc-melting method and the novel electrolytic hydriding. Furthermore, the crystal structure, magneticand negative thermal expansion (NTE) properties of LaFe10.0Si3.0 and its hydride were investigated by the X-ray diffraction (XRD) and physical property measurement system (PPMS). Intriguingly, the NTE operation-temperature window of LaFe10.0Si3.0 has been broadened significantly after introducing interstitial hydrogen atoms. The further magnetic characterizations combined with theoretical analysis reveal that the increase of ferromagnetic to paramagnetic transition temperature due to stronger Fe-Fe magnetic exchange interactions contribute to the broad NTE operation-temperature window in the LaFe10.0Si3.0 hydride.