Shaoguang Yang

Ferromagnetism in Mn-doped CuO

Ferromagnetic properties have been observed in CuO doped with 3.5–15 at. % of Mn. The transition from ferromagnetic to paramagnetic phase at TC=80 K is associated with the metal–insulator transition. Magnetoresistance is weakly negative in the vicinity of the transition, but positive in a wide range of temperatures below TC. The experimental results suggest a possibility of interpretation in terms of the Zener double-exchange mechanism and strong electron–phonon interactions.

Low-density nanoporous iron foams synthesized by sol-gel autocombustion

Nanoporous iron metal foams were synthesized by an improved sol-gel autocombustion method in this report. It has been confirmed to be pure phase iron by X-ray diffraction measurements. The nanoporous characteristics were illustrated through scanning electron microscope and transmission electron microscope images. Very low density and quite large saturation magnetization has been performed in the synthesized samples.

Metal nanotubes prepared by a sol?gel method followed by a hydrogen reduction procedure

A sol?gel method followed by a hydrogen reduction procedure was proposed in this work for the preparation of metal nanotubes. The tube length, diameter, wall thickness and, most importantly, the chemical components can be adjusted conveniently. Several examples of metal nanotubes (Fe, Ni, Pb and CoFe) were prepared by using anodic aluminium oxide (AAO) templates. The fabricated nanotubes are uniform in diameter and wall thickness through the entire tubes. The length of the nanotubes is about 100??m, with an aspect ratio of about 1000.

Multiform structures of SnO2 nanobelts

Multiform SnO2 microstructures were synthesized by a facile thermal evaporation of tin grains. The product was characterized with a variety of techniques to obtain the structural and optical information. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed a large percentage of acute angle zigzag nanobelts with perfectly periodic morphology. High resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns revealed that the zigzag nanobelts were single crystalline and their zone axis was along the [010] crystal direction. The growth mechanism of zigzag nanobelts was proposed based on TEM characterization and thermodynamic analysis. The zigzag nanobelts were deduced to be formed by changing the growth direction from to [101] or vice versa. The photoluminescence (PL) spectroscopy of the nanobelts showed a broad and strong luminescence emission centred at 550?nm.

Controlled synthesis of ZnS nanocombs by self-evaporation using ZnS nanobelts as source and substrates

ZnS nanocombs were fabricated via a two-step growth method. By annealing Au coated ZnS nanobelts with the help of SnO2/C, comb-like nanostructures would be formed. In the absence of SnO2/C, Au coated ZnS nanobelts would be evaporated completely at the same temperature. As revealed by high resolution transmission microscopy, the growth direction of the ZnS nanobelts was [210] while that of the branches was [001], which epitaxially grew on the (00 ± 1) side surfaces of the ZnS nanobelts. Self-evaporation was used to explain the formation of the ZnS nanocombs. Photoluminescence spectrum reveals that the ZnS nanocombs had two emission bands at 570 and 635 nm.

Zinc nanoplates synthesized by a micro-jet under electron-beam irradiation

Zinc nanoplates with interesting shapes have been successfully synthesized by irradiating Zn/ZnS core/shell microballs with electron beams in a transmission electron microscope. The structure characterization reveals that the nanoplates present a wurtzite phase covered with a thin ZnO layer. A systematic study on the microballs has been performed and a formation mechanism for these nanoplates has been proposed. The e-beam radiation technique provides a novel approach for fabrication of novel nanostructured materials.

Synthesis and magnetic properties of single-crystalline Na2-xMn8O16 nanorods.

The synthesis of single-crystalline hollandite-type manganese oxides Na2-xMn8O16 nanorods by a simple molten salt method is reported for the first time. The nanorods were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and a superconducting quantum interference device magnetometer. The magnetic measurements indicated that the nanorods showed spin glass behavior and exchange bias effect at low temperatures. The low-temperature magnetic behaviors can be explained by the uncompensated spins on the surface of the nanorods.

Room temperature ferromagnetism in transition metal-doped black phosphorous

High pressure high temperature synthesis of transition metal (TM = V, Cr, Mn, Fe, Co, Ni, and Cu) doped black phosphorus (BP) was performed. Room temperature ferromagnetism was observed in Cr and Mn doped BP samples. X-ray diffraction and Raman measurements revealed pure phase BP without any impurity. Transport measurements showed us semiconducting character in 5 at. % doped BP samples Cr5%P95% and Mn5%P95%. The magnetoresistance (MR) studies presented positive MR in the relatively high temperature range and negative MR in the low temperature range. Compared to that of pure BP, the maximum MR was enhanced in Cr5%P95%. However, paramagnetism was observed in V, Fe, Co, Ni, and Cu doped BP samples.

Layered tin dioxide microrods

Single-crystalline layered SnO2 microrods were synthesized by a simple tin?water reaction at 900??C. The structural and optical properties of the sample were characterized by x-ray powder diffraction, energy-dispersive x-ray spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, Raman scattering and photoluminescence (PL) spectroscopy. High resolution transmission electron microscopy studies and selected area electron diffraction patterns revealed that the layered SnO2 microrods are single crystalline and their growth direction is along [1 1 0]. The growth mechanism of the microrods was proposed based on SEM, TEM characterization and thermodynamic analysis. It is deduced that the layered microrods grow by the stacking of SnO2 sheets with a (1?1?0) surface in a vapour?liquid?solid process. Three emission peaks at 523, 569 and 626?nm were detected in room-temperature PL measurements.

Large coercivity FePt nanoparticles prepared via a one-step method without post-annealing

L10 FePt nanoparticles were synthesized by a one-step sol-gel autocombustion method, using nontoxic ferric nitrate, hexachloroplatinic acid, and glycine as starting materials. In contrast to common syntheses, high-temperature post-annealing was not required to form the L10 FePt phase. The entire ignition and combustion process lasted no more than one minute. The L10 FePt phase could form in the presence of the high temperature caused by the exothermic combustion reaction. Adjusting the glycine-to-metal ion molar ratio from 0.5 to 6.0 allowed its effects on the phase transformation and magnetic properties of the products to be investigated. X-ray diffraction indicated that pure phase L10 FePt was obtained at a glycine-to-metal ion molar ratio of 1.5. Transmission electron microscopy indicated that the monodisperse L10 FePt nanoparticles had an average particle size of about 20 nm. The reasons why the as-synthesized L10 FePt nanoparticles were not aggregated and sintered could be attributed to the large amo...