Effect of Water Content in Ethylene Glycol Solvent on the Size of ZnO Nanoparticles Prepared Using Microwave Solvothermal Synthesis

Zinc oxide nanoparticles (ZnO NPs) were obtained by the microwave solvothermal synthesis (MSS) method. The precursor of the MSS reaction was a solution of hydrated zinc acetate in ethylene glycol with water addition. It was proved that by controlling the water concentration in the precursor it was possible to control the size of ZnO NPs in a programmed manner. The less the water content in the precursor, the smaller the size of ZnO NPs obtained. The obtained NPs with the average particle size ranging from 25 nm to 50 nm were characterised by homogeneous morphology and a narrow distribution of particle sizes. The following parameters of the obtained ZnO NPs were determined: pycnometric density, specific surface area, phase purity, chemical composition, lattice parameters, average particle size, and particle size distribution. The average size of ZnO NPs was determined using Scherrer’s formula, Nanopowder XRD Processor Demo web application, by converting the results of the specific surface area, and TEM tests using the dark field technique. ZnO morphology and structure were determined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The test performed by the X-ray powder diffraction (XRD) confirmed that crystalline ZnO, pure in terms of phase, had been obtained

Al₁₃Fe₄-Al Composites with Nanocrystalline Matrix Manufactured by Hot-Pressing of Milled Powders

The paper describes composites with the matrix containing a nanocrystalline intermetallic Al13Fe4 phase and microcrystalline aluminium. Mechanically alloyed Al80Fe20 powder, containing a metastable nanocrystalline Al5Fe2 phase, was mixed with 20, 30, and 40 vol.% of Al powder and consolidated at 750 °C under the pressure of 7.7 GPa. During the consolidation, the metastable Al5Fe2 phase transformed into a nanocrystalline Al13Fe4 phase. In the bulk samples, Al13Fe4 areas were wrapped around by networking Al regions. The hardness of the Al13Fe4-Al composites was in the range of 4.52–5.50 GPa. The compressive strength of the Al13Fe4-30%Al and Al13Fe4-40%Al composites was 805 and 812 MPa, respectively, and it was considerably higher than that of the Al13Fe4-20%Al composite (538 MPa), which failed in the elastic region. The Al13Fe4-30%Al and Al13Fe4-40%Al composites, in contrast, showed some plasticity: namely, 1.5% and 9.1%, respectively. The density of the produced composites is in the range of 3.27–3.48 g/cm3 and decreases with the increase in the Al content

Spectroscopic Studies of Nanopowder and Nanoceramics La2Hf2O7:PrLa_2 Hf_2 O_7:Pr Scintillator

Sintered nanoceramics of Pr-doped lanthanum hafnate, $La_{2}Hf_{2}O_{7}:Pr$, were prepared by means of a high-pressure sintering technique using nanopowders made by Pechini method. Structure, morphology, and spectroscopic properties of the ceramics compared to the starting powder are presented and discussed. Emission and excitation spectra recorded at room temperature as well as at 7 K using synchrotron radiation are presented together with results of luminescence kinetics measurements. In ceramics, at 7 K, the $Pr^{3+}$ luminescence from $^{3}P_{0}$ (blue-green, green, and red region) and $^{1}D_{2}$ (red) levels is accompanied by a broad-band emission located in the 380–530 nm range of wavelengths, whereas powders gives only the $Pr^{3+}$-related luminescence. Depending on the excitation wavelength, the broad-band emission maximum moves between 430 and 470 nm indicating superposition of at least two components. In sintered nanoceramics, the lifetimes of $Pr^{3+}$ emissions from $^{3}P_{0}$ and $^{1}D_{2}$ levels were by 10%–20% shorter compared to the powder. The existence of different luminescence centers was proved by the selective emission decays examination. The fast 5$\mathit{d}$ $\rightarrow$ 4$\mathit{f}$ luminescence of $Pr^{3+}$ was not observed from either of the two types of $La_{2}Hf_{2}O_{7}:Pr$ materials

Influence of Temperature and Pressure on the Possibility of Obtaining Al2O3/Ni-P Nanocomposite through Hot Pressing Process

score: 0collation: 147-15

Microstructural evolution during mechanical alloying and hot pressing of a powder blend of aluminium and 316 stainless steel

The paper examines the phase evolution in blends consisting of different proportions of stainless steel (SS316) and Al (0, 25, 65 and 85 wt. %) powders during high-energy ball milling by x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy. An attempt has also been made to study the mechanical property of the bulk samples obtained by hot pressing the ball milled powder blend at suitable a temperature and pressure. The results of microstructural changes and mechanical property and the ability of consolidation of the amorphous/nanocrystalline powders by high-pressure techniques to develop engineering components has been discussed and highlighted

Effect of Sintering Temperature on Structure and Properties of Al2O3/Ni-P Composites with Interpenetrating Phasess

score: 0collation: 161-16