Zhenghe Hua

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.

Coexistence of low-field positive and negative magnetic entropy change in SmMn2Ge2

Polycrystalline SmMn2Ge2 has been prepared by arc melting method. Large magnetic entropy changes of −3.7 and 3.3J∕kgK are found under a low magnetic field change of 5kOe, near two first-order transition temperatures, T1(112K) and T2(152K), respectively. The coexistence of the large low-field positive and negative magnetic entropy change suggests a potential of SmMn2Ge2 as a magnetic refrigerant in the corresponding temperature range.

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.

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...

Low-Temperature Sol–Gel Autocombustion Synthesis and Magnetic Properties of Magnetite

Using citric acid, ferric nitrate, and ammonia as starting materials, magnetite (Fe3O4) powders were successfully synthesized through a low-temperature sol-gel autocombustion method. The molar ratios Φ of citric acid to ferric nitrate were adjusted from 0.1:1 to 1.5:1. The combustions were activated at a temperature as low as 300 °C. The X-ray diffraction was used in the determination of the phases of the prepared samples. The results illustrate that some of the as-prepared samples have pure Fe3O4 phase. Magnetite can be synthesized within a large range of molar ratio of citric acid to ferric nitrate. Scanning electron microscopy studies show us porous characteristics of the prepared samples. The results of vibrating sample magnetometer studies show us ferrimagnetic properties of the as-prepared magnetite products at room temperature with a maximum saturation magnetization as high as 91 emu/g. The magnetic hysteresis loops reveal soft magnetic properties of these materials. The saturation magnetization value of the sample of Φ = 0.5 is about 99% of the corresponding bulk value, which indicates that Φ = 0.5 is the most suitable molar ratio for the experiment.