During sintering of the 2MgO-2Al2O3-5SiO2 system, cordierite, an attractive ceramic material because of its properties, is obtained. Effects of mechanochemical activation of stoichiometric mixtures, performed to investigate possibilities of lowering cordierite formation temperature during sintering, were monitored by thermogravimetric and differential thermal analyses. Specific surface areas of the mechanically activated powder mixtures were determined by the BET method. Kinetics of the specific surface area increase was analyzed using the Boltzmann model. It was confirmed that with activation time increase, temperatures of phase transformations were shifted to lower values and, according to FTIR analysis no significant changes occurred during material aging. According to the obtained results, it may be concluded that since mechanochemical activation has an influence on the treated powder mixture, lowering of the cordierite formation temperature during the sintering process is expected.

The aim of this research is complex analysis of non-transparent non-crystal silica obtaining and process optimization by determining of process control algorithm. Experiments were realized using electro resistance furnace. Raw material was floated quartz sand. ThV camera was used for observing the melting. On the basis of these measurements, temperature profiles in the system were obtained. Working models of the process were also defined. Models were the basis for determination of controloptimization algorithm. The “black box” method making connection between temperature and time was applied. Namely, on the basis of the virtual process defined by different models, sets of parameters used for the process control are determined.

Mechanochemical activation in high-energy devices (micronizers) as a way of giving mechanical energy to solid-state materials has become very popular. During the mechanochemical activation various structural changes of material and at the same time changes of its properties (chemical, electrical, thermal, mechanical etc.), as well as reactivity increase are taking place. Whereas numerous chemical reactions are happening during the glass production, investigating of the influence of previous mechanochemical treatment on those reactions and on the glass production at once is very attractive. Because of the great interest for low-melting glasses, PbO-B2O3-SiO2 system, with following chemical composition: 40 mol% (69,4 wt%) of PbO, 34 % (18,4 wt%) of B2O3 and 26 mol % (12,2 wt%) of SiO2 was chosen for investigation in this research. In the experimental work, minium (Pb3O4), boric acid (H3BO3) and quartz sand (SiO2) were used as raw materials for preparation of glass mixtures. Five glass mixtures were prepared. Mechanochemical activation was a realized in high-energy vibro mill with rings. Following times of mechanical activation were used: 7 min., 14 min., 28 min., and 49 min. The referent, non-activated glass mixture and four mechanochemically activated glass mixtures were subjected to differential thermal analysis (DTA). Applied method for the quantification of mechanochemical activation results showed that the effects of mechanochemical activation on the properties of glass mixtures for obtaining low-melting glasses were considerable. Mechanochemical activation had a significant influence on temperature changes in the investigated system, during heating. Differential thermal analysis showed the existence of qualitative changes in thermal properties of prepared glass mixtures depending on the time period.

This paper is occupied by track and control of single component raw materials melting process. Experiments were performed in an electric-resistance furnace with a horizontally placed movable graphite electrode (heater). Used raw material was floated quartz sand, while obtained material was electrofused SiO2, also called quartz glass. Height of the electrode elevation and total melting time were varied. The process is considered as non-stationary process due to existence of captured gas bubbles in the viscous melt and many accompanying effects, as well. Tracking of processing parameters was enabled by thermovision as the source of information. In that regard, infrared camera was used. On the basis of these measurements, temperature profiles in the system during the melting process were obtained. Working models of the process were defined by correlation of the temperature changes with time at distances of 1, 3 and 5 cm from the heater. The “black box” method that correlates temperature and time in a model was applied. Powered functions are obtained as models of proposed system. These models were the base for processing control. Namely, based on virtual process defined by different models, sets of parameters for the process control are determined.

This paper looks at the possibilities in the valorization of combustion ash from power plants for the production of sintered aggregates in rotary sintering kilns and its use in the preparation of lightweight concrete. Although the sintering strand is usually used for obtaining sintered aggregates, this paper proves that lightweight aggregates (Lytag) of satisfactory quality can be produced in rotary sintering kilns. The sintered aggregate obtained together with cement and water is used in the preparation of both concrete mixtures and lightweight concrete. The quality of the sintered aggregate was checked by testing the quality of the concrete obtained. The following work was undertaken with the aim of investigating the valorization of combustion ash: characterization of the combustion ash, sintering of the combustion ash into a lightweight aggregate, characterization of the lightweight aggregate and, for that purpose, the characterization of lightweight concrete made using the aggregate. The aggregate is characterized by low bulk density, a porous structure and excellent thermal-insulating properties, so aggregate produced by rotary sintering kilns can be used as lightweight aggregate and also for the production of structural insulating and lightweight concretes.

Die Erfindung betrifft ein dentales Implantatsystemteil mit einer Beschichtung, wobei das dentale Implantatsystemteil mit einer Schicht beschichtet ist, die ein oder mehrere Antiphlogistika und/oder ein oder mehrere Steroide und/oder ein oder mehrere Prostagladine und/oder ein oder mehrere Bisphosphonate und/oder ein oder mehrere Statine enthalt.

Thermal power plants in Serbia use lignite for electrical power production The secondary product of coal combustion is fly ash in the amount of 17%. Fly ash causes the pollution of air, water and soil, and also cause many human, especially lung diseases. Secondary sulphur is a product of crude oil refining. The aim of this study was to investigate the use of sulphur as a bonding material in ultra fine particle agglomeration (smaller than 63 μm) in fly ash. The agglomeration should make the ash particles larger and heavy enough to fall without flying fractions. The experiments showed that during the homogenization of the ashes and sulphur from 150 to 170 °C in a reactor with intensive mixing, an amount of 15% sulphur was sufficient to bond particles and cause agglomeration without visible flying fractions.

In this paper we present the results of investigations into the possibility of substituting sulfate bearing materials for natural gypsum as setting retarder in Portland cement (PC). The effects on setting and mechanical properties of phosphogypsum (GFS) and nitrogypsum (GNL) added in ratios 2, 4, 6, 8 and 10 mass-% to PC of different specific surfaces (Sp 1 = 3680 cm 2 g -1 and Sp 2 = 4110cm 2 g -1 ) were studied and compared with a PC containing natural gypsum. The results obtained for setting and compressive strength show that GFS and GNL may be used instead of natural gypsum. Similar results were obtained for two different grades of clinker fineness, so there is no need to grind clinker to the specific surface <3800 cm 2 /g. The cement of lower specific surface (Sp 1 ) made with GFS and GNL set faster compared with cement made with natural gypsum. The final setting time for cement with GFS and GNLforthe higher specific surface (Sp 2 ) was longerthan that obtained with cement made with natural gypsum.

that ALCC samples eroded predominantly at the surface, while the mullite samples exhibited more significant degradation by depth.