Reaction sintering of the 2ZnO-TiO2 system

Sintering kinetics of the mechanically activated ZnO-TiO2 system was studied. Mixtures of ZnO and TiO2 powders were mechanically activated using a high-energy ball mill for different time intervals from 0 to 300 minutes. Formal phenomenological analyses were performed in order to describe the specimen’s behavior during isothermal sintering at 1100oC. Non-isothermal sintering was investigated by dilatometer measurements up to 1100oC with a constant heating rate. The Dorn method was applied in order to give information on the activation energy

Synthesis and characterization of zinc titanate nano-crystal powders obtained by mechanical activation

Development of dielectric materials for microwave frequencies is increasing with rapid progress in mobile and satellite communications systems, where zinc titanates have found application due to their semi-conducting and dielectric properties. Mechanical activation by grinding is a well-known method and common part of the powder preparation route in the field of ceramics. The aim of this work is investigation of the influence of experimental conditions for mechanochemical synthesis of zinc orthotitanate. Starting powder mixtures of ZnO and TiO2, in the molar ratio that is in accordance with the stoichiometry of zinc titanate spinel type Zn2TiO4, were mechanically activated using a high-energy planetary ball mill. The process of mechanical activation was performed during different time intervals from 0 to 300 minutes. Microstructure characterization was determined by X-ray diffraction analysis and scanning electron microscopy. Also, the specific surface area (SSA) of powders samples was measured by a nitrogen gas sorption analyzer using the BET method. The very first traces of zinc titanate are detectable after only 5 minutes of activation. The most interesting occurrence during the mechanical method of activation is that we have an almost pure phase after 90 minutes

Influence of mechanical activation on synthesis of zinc metatitanate

Investigations of a ZnO-TiO2 binary oxide mixture during mechanical treatment were mainly focused on obtaining orthotitanate Zn2TiO4 with a spinel structure. Due to the specific way of energy transfer during mechanical treatment using a high-energy ball mill, the system passes through low temperature ZnTiO3 metatitanate phase formation. Mechanical activation was performed on an equimolar ratio mixture of ZnO and TiO2. The anatase phase was previously submitted to heat treatment for achieving a starting mixture rich in a rutile phase. Milling conditions were preset for observing the formation of a low temperature ZnTiO3 phase with a perovskite structure. The powder microstructure was characterized using scanning electron microscopy. A nitrogen gas sorption analyzer with the BET method was used to determine the specific surface area and porosity, indicating changes of powder sample properties during mechanical activation. Also, X ray powder diffractometry was applied to obtain the phase composition. Powders were then pressed into pellets and their compressibility was observed through density changes. According to microstructures obtained by scanning electron microscopy analysis, the system underwent a primary and secondary agglomeration process. Specific surface area measurements supported that conclusion. Compressibility investigations established the difference between compressibility of the non-activated mixture and activated powders. X-ray diffraction analysis revealed that a perovskite structure forms simultaneously with a spinel phase during the process of mechanical activation

The Influence of Milling Conditions on Mechanochemical Synthesis and Sintering of Zinc Titanate

The aim of this work was an investigation of experimental conditions for mechanochemical synthesis and sintering of spinel zinc titanate (Zn2TiO4). Starting powder mixtures of zinc oxide and titan dioxide in the molar ratio, in accordance with the stoichiometrics of spinel zinc titanate, were mechanically activated by grinding in a planetary ball mill for various periods of time in the interval of 0 to 300 minutes. Changes of physico-chemical characteristics and microstructure parameters in the ZnO—TiO2 system after grinding were followed using specific surface area analysis and X-ray powder diffraction, while thermal behavior was examined by differential thermal analysis and dilatometry. The beginning of zinc titanate formation was noticed after 30 minutes of milling, and prolonged milling led to the formation of spinel zinc titanate as the major phase with an insignificant amount of unreacted zinc oxide and titan dioxide. The main conclusions based on this analysis are that Zn2TiO4 ceramics could be obtained by mechanical activation after a certain time without additional thermal treatment and that sintering temperature as well as the formation temperatures of zinc-titanate are significantly lowered using mechanical treatment

The springtails (Insecta: Collembola) fauna at different microhabitats of Bečići beach, Montenegro

Collembola fauna has been investigated at different microhabitats near the beach in Bečići, Montenegro. Samples were collected from four locations: Hotel 'Tara', 'Sveti Toma' Church (St. Thomas), Hotel 'Naftagas' and 'Zelena Stena' (Green Rock). Each of the location presented different microhabitat: under the palm tree, cypresses tree, larch tree and white pine tree. Samples were taken in May and September 2015 and results presented as qualitative findings. Total number of 30 Collembola species was identified, classified into six families and 17 genera. Representatives of the family Hypogastruridae and Isotomidae were recorded at all of the studied sites, while representatives of the families: Naenuridae, Onychiuridae, Entomobryidae and Sminthuridae were present on some of locations. The biggest number of species and the highest Collembola population density was found at the Green Stone site, 24 species in total, microhabitat- white pine, and the smallest number of species, 6 on site 'St. Thomas' Church, microhabitat- cypresses trees

Implementation of the One Health approach to fight arbovirus infections in the Mediterranean and Black Sea Region: Assessing integrated surveillance in Serbia, Tunisia and Georgia

Background In the Mediterranean and Black Sea Region, arbovirus infections are emerging infectious diseases. Their surveillance can benefit from one health inter-sectoral collaboration; however, no standardized methodology exists to study One Health surveillance. Methods We designed a situation analysis study to document how integration of laboratory/clinical human, animal and entomological surveillance of arboviruses was being implemented in the Region. We applied a framework designed to assess three levels of integration: policy/institutional, data collection/data analysis and dissemination. We tested the use of Business Process Modelling Notation (BPMN) to graphically present evidence of inter-sectoral integration. Results Serbia, Tunisia and Georgia participated in the study. West Nile Virus surveillance was analysed in Serbia and Tunisia, Crimea-Congo Haemorrhagic Fever surveillance in Georgia. Our framework enabled a standardized analysis of One Health surveillance integration, and BPMN was easily understandable and conducive to detailed discussions among different actors/institutions. In all countries, we observed integration across sectors and levels except in data collection and data analysis. Data collection was interoperable only in Georgia without integrated analysis. In all countries, surveillance was mainly oriented towards outbreak response, triggered by an index human case. Discussion The three surveillance systems we observed prove that integrated surveillance can be operationalized with a diverse spectrum of options. However, in all countries, the integrated use of data for early warning and inter-sectoral priority setting is pioneeristic. We also noted that early warning before human case occurrence is recurrently not operationally prioritized

Enhancing Synthesis and Sintering of Zinc Titanate Using Mechanical Activation

Mechanical activation and sintering are used for obtaining zinc titanate, Zn2TiO4. Starting powder mixtures of ZnO and TiO2, in the molar ratio that is in accordance with the stoichiometry ofzinc titanate Zn2TiO4, were echanically activated using a planetary mill during different time intervals from 0 to180 minutes. Scanning electron microscopy was employed to probe the powdersmicrostructure. Progress of the solid-state reaction from the starting powders and evolution of the phases were followed using X-ray powder diffraction. Sintering kinetics was investigated duringisothermal heating at 1100oC from 0 to 120 minutes. The main conclusion based on the analysis made is that Zn2TiO4 ceramics could be obtained by mechanical activation after a certain time without additional thermal treatment. Also, shorter activation times together with calcination at 900oC show that the required sintering temperature and sintering time could be lower than those reported in literature.Materials Science Forum 453-45

Dilatometer Investigations of Reactive Sintering of Zinc Titanate Ceramics

Starting powder mixtures of ZnO and TiO2, at the molar ratio that is in accordance with the stoichiometry of zinc titanate Zn2TiO4, were mechanically activated using a planetary ball mill in different time intervals from 0 to 90 minutes. X-ray diffraction analysis, scanning electron microscopy and non-isothermal dilatometric measurements were performed in order to investigate zinc titanate formation. Processes occurring during mechanical activation led to the formation of a specific structure of obtained powders that promoted and accelerated solid-state reactions and densification during sintering. The main conclusion based on analysis is that mechanical activation enables better compaction of activated powders, i.e. possibility of achieving higher densities of green bodies without binders, but first of all that Zn2TiO4 ceramics can be obtained by mechanical activation after a certain time with appropriate thermal treatment, i.e. heating rate and sintering time, at temperatures lower than those when non-activated mixtures were used

Morphological characteristics of the Hermann's tortoise (Testudo hermanni Gmelin, 1789) in the south-eastern part of Kosovo and Metohija

In this paper we present the results of the analysis of morphological characteristics of the Hermann's tortoise from three localities in south­eastern part of Kosovo and Metohija. 75 adult Hermann's tortoises (33 males and 42 females) have been analyzed. Morphometric analysis has been done on 7 traits. We considered the plastron black pigmentation patterns and frequencies for each pigmentation states were calculated. Females were larger than males for all morphometric traits. Based on the most important dimensions of carapace and plastron length and width, the Hermann's tortoises from the south-eastern part of Kosovo and Metohija are the most similar to the individuals of the population from the southern part of the Balkan Peninsula (the southern part of Serbia and the northern part of Greece). In relation to the populations from central and eastern Serbia, individuals from our studied area have higher values

MORPHOLOGICAL CHARACTERISTICS OF THE HERMANN'S TORTOISE (TESTUDO HERMANNI GMELIN, 1789) IN THE SOUTH-EASTERN PART OF KOSOVO AND METOHIJA

ABSTRACT In this paper we present the results of the analysis of morphological characteristics of the Hermann's tortoise from three localities in southeastern part of Kosovo and Metohija. 75 adult Hermann's tortoises (33 males and 42 females) have been analyzed. Morphometric analisys has been done on 7 traits. We considered the plastron black pigmentation patterns and frequencies for each pigmentation states were calculated. Females were larger than males for all morphometric traits. Based on the most important dimensions of carapace and plastron length and width, the Hermann's tortoises from the south-eastern part of Kosovo and Metohija are the most similar to the individuals of the population from the southern part of the Balkan Peninsula (the southern part of Serbia and the northern part of Greece). In relation to the populations from central and eastern Serbia, individuals from our studed area have higher values