ZnTiO3 Ceramic Nanopowder Microstructure Changes During Compaction

ZnTiO3 nanopowder as a constitutive component in compact production was primarily characterised. Scanning electron micrographs of as received powder were recorded. Mercury porosimetry and nitrogen adsorption were also performed on loose powder. Particle size distribution in a water powder suspension was determined with a laser particle size analyser. Compaction was performed on different pressures in a range from 100 to 400 MPa using the uniaxial double sided compaction technique without binder and lubricant. Micrographs of compacted specimens were obtained using scanning electron microscopy and atomic force microscopy. Pore size distribution was also determined by mercury porosimetry and nitrogen adsorption. Results revealed that with increasing pressure during compaction interagglomerate pores diminish in size until they reach some critical diameter related to the intra-agglomerate pore size

Specifična absobcijska energija staklo-poliester kompozitne cijevi pod statičkim tlačnim opterećenjem

The experimental determination of energy of glass-polyester composite tubes static fracture is done. The tubes are of defined structure and known processes of fabrication. The aim was to determine the possibility of their usage as damping elements during impact. Two types of tubular samples with different diameters were tested until fracture under static (low speed) compressive loading. The applied forces and sample lengths were measured until complete destruction of samples. From the diagrams received directly from testing devices, certain energy values explained in the paper were determined.U radu je prikazano eksperimentalno određivanje statičke energije loma staklo-poliester kompozitnih cijevi poznate struktura materijala i postupka izrade. Cilj ispitivanja je bio odrediti mogućnost primjene ugradnje takvih cijevi u elemente za prigušivače udara. Pod djelovanjem spornog statičkog tlačnog opterećenja ispitivana su dva tipa cijevi različitih presjeka. Pri tom su mjerene primenjene sile i duljine uzoraka sve do potpunog loma cijevi. Na osnovu dobivenih dijagrama su izračunate vrijednosti specifičnih energija apsorpcije

The Morphological Characterization of Mechanically Activated ZnO Powder

The authors investigated the morphological characteristics of mechanically activated ZnO powder. ZnO powder was mechanically activated for 2, 5, 10 and 30 minutes in a planetary ball mill. Mechanical activation introduces lattice disorder and defects into ZnO hexagonal wurtzite structure. In order to determine specific surface area and pore volume, we performed N2 porosimetry and SEM in order to investigate the microstructure of non-activated and mechanically activated ZnO powders. Using Kubelka-Munk function, UV-Vis spectra showed the reducing in band gap with activation time. ZnO powder activated for 5 minutes has the narrowest band gap

Structural characterization of mechanically activated MgO-TiO2 system

Mixtures of MgO-TiO2 powders were mechanically activated in a planetary ball mill for time interval from 0 to 120 minutes. On thus obtained powders, structural investigations have been performed. N2 adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results are obtained: specific surface area continuously decreases up to 40 minutes of activation and after that increases, reaching its minimum value of 4.4 m2/g. The influence of mechanical activation on lattice vibrational spectra was examined by Raman spectroscopy at room temperatures. The differential thermal analysis has been performed in order to investigate thermal behavior of the mixtures, indicating at several endothermal peaks in range of RT to 1100oC. SEM gave information about changes in microstructures, showing the clear decrease in particle size

Structural investigation of mechanically activated ZnO powder

Commercially available ZnO powder was mechanically activated in a planetary ball mill. In order to investigate the specific surface area, pore volume and microstructure of non-activated and mechanically activated ZnO powders the authors performed N-2 physisorption, SEM and TEM. Crystallite size and lattice microstrain were analyzed by X-ray diffraction method. XRD patterns indicate that peak intensities are getting lower and expend with activation time. The reduction in crystallite size and increasing of lattice microstrain with prolonged milling time were determined applying the Rietveld's method. The difference between non-activated and the activated powder has been also observed by X-ray photoelectron spectroscopy (XPS). XPS is used for investigating the chemical bonding of ZnO powder by analyzing the energy of photoelectrons. The lattice vibration spectra were obtained using Raman spectroscopy. In Raman spectra some changes along with atypical resonant scattering were noticed, which were caused by mechanical activation

Structural characterization and electrical properties of sintered magnesium-titanate ceramics

In this article the influence of ball miling process on structure of MgO-TiO2 system, as well as the electrical properties of samples after sintering, was investigated. The mixtures of MgO-TiO2 powders were mechanically activated in a planetary ball mill for the time period from 0 to 120 min. The influence of mechanical activation and sintering on the lattice vibrational spectra was studied by Raman spectroscopy at room temperature. Structural investigations have been performed on produced powders. Nitrogen adsorption method was used to determine the BET specific surface area and pore size distribution. Unusual results have been obtained: specific surface area continuosly decreased up to 40 min of activation and increased after that, reaching its minimun value of 5.5 m(2)/g. The Raman spectra of activated powders have shown that anatase modes have been decreasing in intensity and broadening as the time of activation extended. Also, the additional modes attributed to TiO2 II, srilankite and rutile phases started to appear as a consequence of activation. The small differences noticed in the Raman spectra of sintered samples have been explained by structural modification of MgTiO3 phase due to the presence of defects. The effects of activation and sintering process on microstructure were investigated by scanning electron microscopy (SEM). The electrical measurements showed difference in dielectric constant (epsilon(r)), loss tangent (tg delta) and specific resistance (rho) as a function of time of mechanical treatment

The effect of mould temperature and cooling conditions on the size of secondary dendrite arm spacing in Al-7Si-3Cu alloy

The secondary dendrite arm spacing (SDAS) is one of the most important microstructure features of as-cast structure in hypoeutectic aluminum alloys. The size of SDAS depends on many factors such as liquid metal treatment, temperature gradient, cooling rate/solidification time and chemical composition of melt. Among them the cooling rate/solidification time have dominant impacts. In industrial production of castings, when the chemical composition of melt has been chosen, the cooling conditions will control the solidification process. In this paper the effect of various pre-heating mould temperatures and cooling conditions (with and without water cooling) on the SDAS in AlSi7Cu3 were studied. For that purpose the permanent metal mould with the cooling system incorporated in one die was designed. The solidification time was affected by the mould temperature. It was found that the influence of mould temperature on SDAS was less pronounced in the presence of water cooling. The experimental results concerning the value of SDAS were compared with calculated value of SDAS obtained as a result of solidification process simulated by WinCast FEM Software

Specific energy absorption capacity of glass-polyester composite tubes under static compressive loading

The experimental determination of energy of glass-polyester composite tubes static fracture is done. The tubes are of defined structure and known processes of fabrication. The aim was to determine the possibility of their usage as damping elements during impact. Two types of tubular samples with different diameters were tested until fracture under static (low speed) compressive loading. The applied forces and sample lengths were measured until complete destruction of samples. From the diagrams received directly from testing devices, certain energy values explained in the paper were determined

Some Applications of the Image Analysis in the Metal Material Science

In different areas of science such as medicine, biology and engineering the image analysis is widely used. Quantitative measuring by the image analysis has also found application in metal materials science, especially in metallographic microstructure analysis. The measuring of the linear and area dimensions of the microconstituents in the metal material structure performed by the image analysis is presented in the paper. The effects of the heat treatment temperature on the brittle phase content in the structure of the heat resistant Ni-Cr-Co-W alloy were analysed. Investigation of the influence of the alloying elements content in the Al alloys for automotive application, on dendrite arm spacing in the cast structure are also presented. Obtained results of the quantitative measured dimensions have shown direct impact of the process parameters on the analysed metals microstructure characteristics. All tests were performed by the light optical microscope with automatic image analyser. Presented experimental results are based on a large number of measurements. A statistical analysis was performed and a high correlation of the results was obtained. For each of the presented investigations and analyzed phenomenon, a statistical mathematical model is suggested with the boundary conditions defined by the investigated intervals of variables

AMPHIPHILIC POLY(HYDROXYETHYLASPARTAMIDE) DERIVATIVE-BASED MICELLES AS DRUG DELIVERY SYSTEMS FOR FERULIC ACID

In this article, in order to obtain tetragonal nanocrystalline BaTiO3, structural investigations of mechanically activated BaTiO3 powder have been performed. A mercury porosimetry analysis and scanning electron microscopy method have been applied for determination of the specific pore volume, porosity and microstructure morphology of the samples. The lattice vibration spectra of nonactivated and activated powders, their phase composition, lattice microstrains and the mean size of coherently diffracting domains were examined by Raman spectroscopy and the X-ray powder diffraction method. The average crystal structure of obtained nanocrystalline powders, estimated from X-ray diffraction data, gave evidence of retained, but slightly sustained tetragonality of powders, even for particles as small as similar to 30 nm. Raman spectroscopy also gave clear evidence for local tetragonal symmetries, in particular through the presence of a band at similar to 307 cm(-1)