Wenran Feng

Magnetocaloric effect and magnetic-field-induced shape recovery effect at room temperature in ferromagnetic Heusler alloy Ni?Mn?Sb

The martensitic transition, magnetocaloric effect ( MCE) and shape memory effect ( MSE) of ferromagnetic Heusler alloys Ni50Mn50-x Sb-x (x = 12, 13 and 14) have been investigated. A large positive magnetic entropy change Delta SM was observed in the vicinity of the martensitic transition. The maximum value of Delta SM is 9.1 J kg(-1) K-1 in Ni50Mn37Sb13 at 287K for a magnetic field change of 5 T. This change originates from the first-order transition from a low-temperature weak-magnetic martensitic phase to a high-temperature ferromagnetic parent phase. A magnetic-field-induced shape recovery strain of about 15 ppm at room temperature and at a relatively low magnetic field ( 1.2 T) was observed to accompany the reverse martensitic transformation. The large field-induced MCE and MSE in the NiMnSb system make it a promising material for room-temperature application.

The preliminary discharging characterization of a novel APGD plume and its application in organic contaminant degradation

An atmospheric pressure glow discharge plume (APGD-p) using a dielectric barrier discharge reactor with one conductive liquid electrode was designed in our study. The preliminary characteristics of the plume and application in the degradation of a dye, methyl violet 5BN (MV-5BN), were presented in this paper. The APGD reactor produced a cold plasma plume with temperature not higher than 320 K at power 5 - 50 W. The MV- 5BN solution as a probe for dye wastewater was treated by the downstream gases of the plasma plume. The results indicated that the active argon (Ar) and nitrogen (N-2) gases had little effect on the MV- 5BN degradation, but the air and oxygen (O-2) gas depleted the organic molecules effectively. In particular, the downstream O-2 gas degraded the dye molecules entirely.

Application of a novel atmospheric pressure plasma fluidized bed in the powder surface modification

A novel atmospheric pressure plasma fluidized bed (APPFB) with one liquid electrode was designed, and its preliminary discharge characteristics were studied. The glow discharge in the APPFB was generated by applying a low power with helium (He) gas, and the plasma gas temperature was no higher than 320 K when the applied power was lower than 11 W. The plasma optical emission spectrum (OES) of the gas mixture consisting of He and hexamethyldisiloxane (HMDSO) was recorded by a UV-visible monochromator. The calcium carbonate powders were modified by APPFB using HMDSO in the He plasma. The powder surface energy was decreased greatly by coating an organosilicon polymer onto the powder surface. This surface modification process changed the wettability of the powder from super-hydrophilicity to super-hydrophobicity, and the contact angle of water on the modified powders surface was greater than 160°.

Large low-field inverse magnetocaloric effect in Ni 50−x Mn 38+x Sb 12 alloys

The magnetic properties and magnetocaloric effects of Ni(50-x)Mn(38+x)Sb(12) ferromagnetic shape-memory alloys with x = -1, 0, 1 and 2 that undergo a martensitic transformation were investigated. The magnetic-entropy changes Delta S of nominal Ni(49)Mn(39)Sb(12), or Ni(49.5)Mn(38.6)Sb(11.9), at 279K is 6.15 J kg(-1) K(-1) for a magnetic-field change Delta B = 1 T, with negligible hysteresis loss, as it transforms from a low-temperature martensitic phase to a high-temperature austenitic one. The large inverse Delta S in a small field change and the negligible hysteresis loss, along with the low cost of Sb, indicate that Ni(49)Mn(39)Sb(12) is a promising candidate for room-temperature magnetic refrigeration.

Preparation of nanocones for immobilizing DNA probe by a low-temperature plasma plume

Using allylamine monomer, a matrix of nanocones was fabricated by applying a low-temperature plasma plume without any catalysts and template. This nanocone acted as an adhesion layer immobilizing DNA probe for DNA hybridization assay. A simple conceptual model to describe the growth of the nanocones was also developed. The highest density of amino-labeled DNA probe was about 1.6pM∕cm2 confirmed by the dyed oligonucleotide, and each nanocone contained nearly 3×102 amine groups. This strategy provides a robust procedure to immobilize DNA, which is a very useful substrate for fabricating nanobiosensors.

Characteristics of (Ti,Ta)N thin films prepared by using pulsed high energy density plasma

(Ti,Ta)N films were prepared by pulsed high energy density plasma (PHEDP) from a coaxial gun in N2 gas. The coaxial gun is composed of a tantalum inner electrode and a titanium outer one. Material characteristics of the (Ti,Ta)N film were investigated by x-ray photoelectron spectroscopy and x-ray diffraction. The microstructure of the film was observed by a scanning electron microscope. The elemental composition and the interface of the film/substrate were analysed using Auger electron spectrometry. Our results suggest that the binary metal nitride film, (Ti,Ta)N, can be prepared by PHEDP. It also shows that dense nanocrystalline (Ti,Ta)N film can be achieved.

Large reversible magnetocaloric effect in Dy2In

A large reversible magnetocaloric effect over a wide temperature region has been observed in the compound Dy2In. For a magnetic-field change of 5?T, the maximum magnetic-entropy change ??SM is 9.2?J?kg?1?K?1 at 126?K. The full width at half maximum (?TFWHM) of the ??SM versus T curve has a high value of 80?K and the relative cooling power (RCP) is as high as 736?J?kg?1 with no hysteresis losses. In particular, a large reversible ??SM (4.6?J?kg?1?K?1), large ?TFWHM (50?K) and large RCP (230?J?kg?1) are also achieved for a low field change of 2?T. Therefore, Dy2In may be an interesting material for low-temperature magnetic refrigeration.

Influence of growth conditions on Al-Ga interdiffusion in low-temperature grown AlGaAs/GaAs multiple quantum wells

Low-temperature growth and subsequent rapid thermal anneal were used to intermix Al and Ga atoms in AlGaAs/GaAs multiple quantum wells (QWs). The intermixed samples were characterized by photoluminescence (PL) spectroscopy, and the observed blue shifts in PL energies are interpreted as the result of modification of the QW shape due to the enhanced Al-Ga interdiffusion in the samples. The enhancement of interdiffusion was found to be strongly dependent on the growth and annealing conditions. In addition, the saturation behavior of Al-Ga interdiffusion was also observed.

Low‐temperature AlGaAs/GaAs multiple quantum well structure and its application to photorefractive devices

We report the low‐temperature (LT) growth of a AlGaAs/GaAs multiple quantum well (MQW) structure by molecular beam epitaxy and demonstrate its application to photorefractive devices. The samples are semi‐insulating as grown, and show large electro‐optic effect. Resistivity up to 108 Ω cm has been observed. The electroabsorption approaches 3000 cm−1 and the electrorefraction is higher than 1.5% for dc electric field of 15 kV/cm. The effect of annealing on electrical and optical properties of LT AlGaAs/GaAs MQW has also been investigated.

Pressure dependence of the intersubband transition in strained In0.15Ga0.85As/GaAs multiple quantum wells

The dependence of the intersubband transitions on pressure in strained In0.15Ga0.85As/GaAs multiple quantum wells has been studied in two samples with well widths of 8 and 15 nm, respectively, with photomodulated transmission spectroscopy by using a diamond anvil cell. The pressure coefficients of the energies for the intersubband transitions were found to depend significantly on the well widths and to be smaller than that of the band gap of constituents in bulk form. These results suggested that the critical thickness for strained In0.15Ga0.85As/GaAs layer should be smaller than 15 nm.