Nguyen Van Minh

Synthesis of five metal based nanocomposite via ultrasonic high temperature spray pyrolysis with excellent antioxidant and antibacterial activity

A unique five metal (Zn, Cu, Ni, Fe, and Mg) based nanocomposite material was prepared via ultrasonication high temperature spray pyrolysis maintained at 1200 °C. The influence of different concentrations (0.001 M, 0.01 M, and 1 M) on size and crystalline phase were analyzed. The nanocomposite exhibited excellent antioxidant and antibacterial activity.

Improved Electrochemical Performance of Nanostructured Fe2O3 Anode Synthesized by Chemical Precipitation Method for Lithium-ion Batteries

Fe2O3xa0nanoparticles (Fe2O3-NPs) with spherical morphology were synthesized by a facile chemical precipitation method followed by post-annealing treatment. The as-synthesized NPs have a uniform particle size with a diameter of about 20–200xa0nm with an average particle size of 80xa0nm. The NPs showed an improved electrochemical performance in terms long cycle life as well as rate capability. The observed reversible capacities after 200 cycles are 776, 445 and 343xa0mAxa0hxa0g−1 at the current densities of 150, 500 and 1000xa0mAxa0hxa0g−1, respectively. These excellent electrochemical properties can be attributed to the nanometer dimension of anode materials which offers smooth charge-transport pathway, short diffusion paths of lithium ions and adequate spaces for volume expansion during Li+ insertion.

Nitrobacter sp. extract mediated biosynthesis of Ag2O NPs with excellent antioxidant and antibacterial potential for biomedical application

In this study, extracellular extract of plant growth promoting bacterium, Nitrobacter sp. is used for the bioconversion of AgNO3 (silver nitrate) into Ag2O (silver oxide nanoparticles). It is an easy, ecofriendly and single step method for Ag2O NPs synthesis. The bio-synthesized nanoparticles were characterized using different techniques. UV-Vis results showed the maximum absorbance around 450 nm. XRD result shows the particles to have faced centered cubic (fcc) crystalline nature. FTIR analysis reveals the functional groups that are involved in bioconversion such as C-N, N-H and C=O. Energy-dispersive X-ray spectroscopy (EDAX) spectrum confirms that the prepared nanoparticle is Ag2O NPs. Particle size distribution result reveals that the average particle size is around 40 nm. The synthesized Ag2O NPs found to be almost spherical in shape. Biosynthesized Ag2O NPs possess good antibacterial activity against selected Gram positive and Gram negative bacterial strains namely Salmonella typhimurium, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae when compared to standard antibiotic. In addition, Ag2O NPs exhibits excellent free radical scavenging activity with respect to dosage. Thus, this study is a new approach to use soil bacterial extract for the production of Ag2O NPs for biomedical application.

Enhancement of densification and sintering behavior of tungsten material via nano modification and magnetic mixing processed under spark plasma sintering

In the present study, the influence of nano additives (Ni, Fe) and different mixing (turbular and magnetic) on the densification, microstructure and micro-hardness of the tungsten material under spark plasma sintering is analyzed. After turbulent mixing the nanoparticles are distributed widely in the W interparticle gaps but after magnetic mixing the nanoparticles are distributed not only on the gaps of the W particles but also on the broken surfaces. Ni incorporated tungsten materials achieved the maximum density of 98.3% at 1400 °C (turbular mixing) and 97.9% at 1300 °C (magnetic mixing). Fe incorporated tungsten material showed density of 97.7% at 1600 °C and 97.2% at 1400 °C after turbular and magnetic mixing. The influence of nanoparticles in the densification process was explained by Laplace force, boundary slip and Agte-Vacek effect. The microstructural analysis showed that nano-modification reduced the degree of porosity, and provides a compact material at low temperatures. X-ray fluorescence analysis reveals that magnetic mixing shows more uniform distribution of nanoparticles than turbular mixing. The nanoparticles incorporation increased the micro hardness of tungsten material. Hence, it is clear that magnetic mixing and nano modification greatly improved the densification and sintering behavior of the tungsten material.

Effect of Mixing Modes and Nano Additives on the Densification and Sintering Behavior of Tungsten Material Under Spark Plasma Sintering

The influence of 0.5xa0wt% nano tungsten and different mixing (turbular and magnetic mixing) on the densification, microstructure, microhardness and dilatometric properties, of tungsten materials was investigated under spark plasma sintering. The dilatometric analysis confirms that sintering process was started at 1100xa0°C for magnetic mixed samples but there were no sign of sintering for samples after turbular mixing. Nano tungsten and magnetic mixing increased the density of tungsten up to 98.5% at 1400xa0°C with the increased micro hardness value of 592xa0HV. The major impact after magnetic mixing is morphology changes in tungsten, development of active sites on the surface, breakdown of agglomerates and even distribution of nanoparticles throughout the bulk tungsten powder. This facilitates the mass transfer between nano tungsten and bulk tungsten which results in the increase in the Laplace force which plays an important role in mass transfer diffusion process during sintering. As a result, it leads to an enhancement of densification process of tungsten powder mixture during sintering and, hence a decrease in the sintering temperatures. Thus, this is a novel approach to use magnetic mixing and nano tungsten to improve densification and sintering behavior of tungsten under spark plasma sintering.