3 Structural, morphological and electrical properties of sintered Fe2O3/TiO2 nanopowder mixtures

Starting nanopowders of TiO2 (anatase 99.7%) and a-Fe2O3 (hematite) were mixed in the weight ratio 60:40 and 40:60. Green samples were sintered in the temperature range 750-1250oC in air. Structural, morphological and electrical studies were carried out using XRD, SEM and EDS analysis and Hall measurements with the aim of analyzing the influence of the starting nanopowder structure on the resulting sample composition, density, grain size and electrical resistivity. Compared to pure anatase samples, the presence of hematite lowered the temperature of completion of the anatase to rutile phase transformation to 850oC. Formation of pseudobrookite was also noted at this temperature. Further increase in the sintering temperature lead to increase in sample density and grain size and decrease in the electric resistivity, Hall coefficient and mobility

Reheating of zinc-titanate sintered specimens

The scope of this work was observing dimensional and heat transfer changes in ZnTiO3 samples during heating in nitrogen and air atmosphere. Interactions of bulk specimens with gaseous surrounding induce microstructure changes during heating. Sintered ZnTiO3 nanopowder samples were submitted to subsequent heating. Dilatation curves and thermogravimetric with simultaneous differential thermal analysis TGA/DTA curves were recorded. Reheating was performed in air and nitrogen atmospheres. Reheated samples obtained at different characteristic temperatures in air were analyzed by X-ray diffraction (XRD). Microstructures obtained by scanning electron microscopy (SEM) of reheated sintered samples are presented and compared. Reheating in a different atmosphere induced different microstructures. The goal was indicating possible causes leading to the microstructure changes. © 2015 International Institute for the Science of Sintering (IISS). All rights reserved

Nanostructured Fe2O3/TiO2 thick films prepared by screen printing

Nanostructured single layered (pure TiO2 , pure α-Fe2O3 and mixed Fe2O3 /TiO2 with two different oxide ratios, 2 : 3 and 3 : 2) and double layered (TiO2 layer over a Fe2O3 layer) thick films have been fabricated by screen printing technology on a glass substrate. The pastes used for film preparation were obtained by adding an organic vehicle to the oxide powders together with a small percentage of binding glass frit. Samples were dried up to 100 °C and sintered at 650 °C/60 minutes. Structural, morphological and optical studies have been carried out using XRD, SEM analyses and UV/Vis spectroscopy. The prepared pure and mixed Fe2O3 /TiO2 thick films had a homogenous nanostructure without secondary phases. Indirect band gaps were determined from the measured transmission spectra and the obtained values are in the range of literature data. [Projekat Ministarstva nauke Republike Srbije, br. III45007

Nanostructured Fe2O3/TiO2 thick films

Thick films of nanostructured pure TiO2, -Fe2O3, Fe2O3/TiO2 (ratio 2:3 and 3:2) and a hetero-junction in the form of a TiO2 layer over a Fe2O3 layer have been fabricated by screen printing technology on a glass substrate. The pastes used for film preparation were obtained by adding an organic vehicle to the oxide powders together with a small percentage of binding glass frit. Samples were dried up to 100oC and sintered at 650oC/60 minutes. Structural, morphological and optical studies have been carried out using XRD, SEM, EDS analysis and UV/Vis spectroscopy. Fe2O3/TiO2 thick films had a homogenous nanostructure and no new compounds were formed. Indirect band gaps were determined from the measured transmission spectra

Optimization and Application of NTC Thick Film Segmented Thermistors

NTC thermistor paste for printing thermal sensors on alumina was formed of very fine Ni0.5Cu0.2Zn1.0Mn1.3O4 thermistor powder obtained by a combined mechanical activation/thermal treatment process, organic vehicle and glass frit. Sheet resistivity was measured using an R-test matrix and it was much lower than the value determined for pure nickel manganite thermistors. The thermistor exponential coefficient was calculated from the R[ diagram measured in the temperature range-30 to +120°C in a climatic chamber. Thick film segmented thermistors with reduced dimensions (optimized construction) were printed sequentially layer by layer, dried and fired at 850°C/10 min in air. Electrodes were printed of PdAg conductive and solderable paste. The samples obtained were characterized by electrical and thermal measurements. The obtained NTC segmented thermistors with reduced dimensions were applied in a thermal sensor for water flow in the water mains. It contained a cold thermistor for measuring input water temperature and a self-heating thermistor for measuring the dependence of water current on water flow rate at a set input voltage power. Initial measurements show that the thermal sensor system requires a low input voltage power making it much easier and safer for operation

Structural, morphological and optical study of nanostructured TiO2/Fe2O3 thick film

Thick films of nanostructured TiO2 (60 wt%) and alpha-Fe2O3 (40 wt%) were fabricated by screen printing technology on an alumina substrate. Samples were sintered in the temperature range 750-1350oC in air. Thick film paste was obtained by mixing anatase and hematite nanopowders in the ratio 3:2, an organic vehicle and binding glass frit. Structural, morphological and optical studies were carried out using XRD, SEM and EDS analysis and UV/Vis spectroscopy enabling correlation between optical and structural changes with the aim of applying the fabricated thick films as anodes in hotoelectrochemical cells for hydrogen generation and water splitting

Structural and electrical properties of sintered Fe2O3/TiO2 nanopowder mixtures

Starting nanopowders of TiO2 (anatase 99.7%) and α-Fe2O3 (hematite) were mixed in the weight ratios 60:40 and 40:60. Green samples were sintered in the temperature range 750–1250 °C in air. Structural, morphological and electrical studies were carried out using XRD, SEM and EDS analysis, Hall measurements and electrical conductivity measurements. The aim was analyzing the influence of the starting nanopowder structure on the resulting sample composition, density, grain size and electrical resistivity in view of tailoring properties for developing different applications such as anodes for photoelectrochemical cells, photocatalysts and gas sensors. Compared to pure anatase samples, the presence of hematite lowered the temperature of completion of the anatase to rutile phase transformation to 850 °C. Formation of pseudobrookite was also noted at this temperature. Higher sintering temperatures lead to increased sample density, changes in grain size (grain growth and inhomogenous microstructure) and decreased electric resistivity

Određivanje osmotskih osobina životinjskih eritrocita protočnom citometrijom u cilju njihovog inženjeringa kao nosača lekova

Despite the fact that the methods based on the osmotic properties of the cells are the most widely used for loading of drugs in human and animal erythrocytes, data related to the osmotic properties of erythrocytes derived from animal blood are scarce. This work was performed with an aim to investigate the possibility of use the flow cytometry as a tool for determination the osmotic behaviour of porcine and bovine erythrocytes, and thus facilitates the engineering of erythrocytes from animal blood to be drug carriers. The method of flow cytometry successfully provided the information about bovine and porcine erythrocyte osmotic fragility, and made the initial steps in assessment of erythrocyte shape in a large number of erythrocytes. Although this method is not able to confirm the swelling of porcine erythrocytes, it indicated the differences in porcine erythrocytes that had basic hematological parameters inside and outside the reference values. In order to apply/use the porcine and bovine erythrocytes as drug carriers, the method of flow cytometry, confirming the presence of osmotically different fractions of red blood cells, indicated that various amounts of the encapsulated drug in porcine and bovine erythrocytes can be expected.Uprkos činjenici da su metode koje se baziraju na osmotskim osobinama ćelija najčešće korišćene metode za inkapsulaciju lekova u humane i životinjske eritrocite, podaci o osmotskim osobinama eritrocita životinjskog porekla su vrlo oskudni. Cilj ovog rada bio je ispitivanje mogućnosti korišćenja metode protočne citometrije za određivanje osmotskih osobina svinjskih i goveđih eritrocita, čime bi se olakšao inženjering pomenutih životinjskih eritrocita za otpuštanje lekova. Metodom protočne citometrije uspešno su dobijene informacije o osmotskoj fragilnosti svinjskih i goveđih eritrocita i načinjeni su početni koraci u proceni oblika velikog broja eritrocita. Iako ova metoda nije uspela da potvrdi bubrenje svinjskih eritrocita, ukazala je na razliku u uzorcima svinjskih eritrocita koji su imali osnovne hematološke parametre izvan i unutar referentnih vrednosti. U cilju primene svinjskih i goveđih eritrocita kao nosača lekova, metoda protočne citometrije je, potvrdivši prisustvo osmotski različitih frakcija eritrocita, ukazala na to da se različite količine inkapsuliranog leka u pojedinačnim, kako svinjskim, tako i goveđim eritrocitima mogu očekivati

Far infrared reflectivity spectra of lead-telluride doped with Mn and Yb

PbTe single crystal samples doped with Mn and Yb were grown using the Bridgman method. Far infrared reflectivity spectra were measured at room temperature for samples with different impurity concentrations (total impurity concentration Mn+Yb varied between 0.59 and 2.52 at%, while the impurity Mn/Yb ratio varied between 0 and 3.48). All samples were of the "p" type. Plasma minimum was registered for all samples and varied between 114 and 198 cm-1 depending on the total impurity concentration and ratio. Samples with lower plasma minimum had a higher free hole mobility, with the highest value of 7000 cm2/Vs determined for a sample with the highest Mn/Yb ratio of 3.48 (1.67 at.% Mn and 0.48 at.% Yb)

Preparation and characterization of Cu and Zn modified nickel manganite NTC powders and thick film thermistors

A simple ball milling/thermal treatment procedure was applied to obtain fine thermistor powders. Three different powder compositions were analyzed–Cu0.2Ni0.5Zn1.0Mn1.3O4, Cu0.25Ni0.5Zn1.0Mn1.25O4 and Cu0.4Ni0.5Mn2.1O4. XRD analysis showed that all three powder compositions had a cubic spinel structure. Correlation between the sintering temperature, structure and resulting electrical properties was analyzed on bulk samples. Thick film pastes were composed and segmented thick film thermistors were screen printed on alumina, dried and fired. SEM analysis revealed a typical dendrite structure with small grains and a developed surface area. Thick film sheet resistance was measured on a test matrix and the resistance decreased with increasing Cu content. The temperature dependence of sample resistance was measured in a climatic chamber enabling calculation of the material constant and activation energy. Aging of the obtained segmented thermistors was analyzed and the resistivity drift was 0.23% for the Cu0.2Ni0.5Zn1.0Mn1.3O4 NTC thick film thermistor confirming greater stability of thermistors containing Zn and Cu that in combination with the determined good thermistor characteristics make them good candidates for temperature and heat loss sensor applications