Fine and stoichiometric barium titanate powders with controlled morphology were synthesized by hydrothermal method. In order to obtain single-phase powders by this route, a new procedure involving the treatment of the resulted suspension with a diluted hydrochloric acid solution before filtration was developed. The influence of some processing factors as pH and synthesis temperature and time on the particle size distribution and morphological characteristics of the resulted powders was pointed out. The transmission electron microscopy analyses indicated the obtaining of pseudo-cubic and tetragonal BaTiO3 particles by dissolution – precipitation mechanism.
The domain of interest approached by research within this study is represented by the synthesis and characterisation of dental porcelain compositions, in the K2O-ZnO-MgO-Al2O3-P2O5-SiO2 system.
The materials were processed by melting at temperatures between 1300 and 15000C, followed by quencing in water. The batch obtained was then milled and shaped, and the resulting samples were sintered at 11000C for two hours.
It was attempted to obtain the porcelain with single thermal treatment step, by sintering the raw materials mixture at temperatures between 1100 and 1500°C, for 2 hours, but the properties of the resulting materials were of lower quality than those of thermally treated samples.
The materials obtained were subjected to apparent porosity measurements, microstructure evaluation by scanning electron microscopy, measurement of compression resistance, granulometry; the biocompatibility through ’’in-vitro’’ tests on cell cultures was also studied.
Resorbability reduction by the incorporation of Mg2+ ions into b-TCP
It is well established that trace elements such as magnesium in calcium phosphate ceramics strongly influence both the biological response of implant materials, and affect the crystallographic, mechanical and chemical properties of manufactured ceramics. In the present work, we describe the synthesis procedures to obtain in the laboratory beta-tricalcium phosphate (β-TCP) and magnesium substituted tricalcium phosphate containing various amounts of Mg2+ and Ca2+ ions (β-TCMP), isostructural with beta-tricalcium phosphate, as well as the characterization methods applied to these materials. β-TCP and β-TCMP were prepared by a solid-state reaction, then calcined at 900ºC for 2 hours, and finally sintered at 1100ºC for 2 hours. Unit cell parameters ao and co, and molar volume Vo decrease linearly for molar ratios Mg2+/ Mg2++Ca2+ varying from 0 to 10 mol.%. The phase composition of the powders, as obtained and after thermal treatments at different temperatures was analyzed semi-quantitatively using X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and infrared spectroscopy (IR). The dissolution behavior of Mg-substituted samples was tested in distilled water, at pH=6.1. The results demonstrated that Mg2+ ions can easily substitute for Ca2+ ions in the TCP lattice. The increase of the Mg2+ content from 0 to 10 mol.% reduces the dissolution rate of Mg-TCP samples.
Managerial working and use of clays from Zalau area in the building ceramic industry
The clays from Dealul Tunari near Zalau were characterized from the point of view of the chemical and mineralogical composition. The mineralogical composition was established by X-ray diffraction by means of a diffractometer DRON 3M. The technological proprieties of the clays and the influence of brick waste addition on these proprieties were determined, thus useful information being obtained on the use of these raw materials in the coarse ceramics industry.
The influence of Cr6+ on the portland cement (with/without slag) hydration and hardening processes
The solidification/stabilization (s/s) of toxic wastes (with heavy metals content) in binding matrices based on Portland cement represents an efficient method for the safe disposal of this type of wastes. The s/s of heavy metals in cementitious matrices should be assessed not only from the point of view of its efficiency but also from the point of view of their influence on the binder’s hydration and hardening processes.
This paper brings information concerning the influence of Cr6+ (present in the system as K2CrO4) on the hydration and hardening processes of Portland cement (OPC) and Portland cement with 30% slag (OPC/BSF).
Immobilization of some wastes containing noxious substances with heavy metals, in binding matrices, determines some influence on hydration-hydrolysis processes, which take place at the hardening of the binder, with consequences on the binding properties.
In a first part of the paper, were presented information concerning the immobilization capacity of some wastes with heavy metals content in binding matrices as Portland cement, slag cement and alkaline activated slag binder, as well as the influence of such wastes on the main properties of binders. In the present paper, are reported some data regarding the influence of these wastes on hydration-hydrolysis processes which take place at the hardening of mentioned binders, for 60 days period of time.
Impactul of co-incinerating waste fuels in clinker kilns on the process and the environment
Widening the range of waste-derived fuels to be employed as alternative fuels in cement manufacture is a major challenge to the cement manufacturers in Romania. Therefore, in a four-stage suspension preheater kiln various ratios and combinations of waste-derived fuels (used tyres, used oil, and ecofuel) were substituted for the traditional fuel (methane gas). The paper presents the effect of using the waste-derived fuels on the process, the emission of toxic compounds (NOx, SO2, and heavy metals), and the quality of the obtained clinker.
Experimental research on glazes fabrication using E-glass fiber waste
The valuable technical and economical potential of the E-glass fibers waste, especially due to the presence of boron oxide and energy content within the glass, represents enough important reasons for their study for a higher and effective capitalization in glaze fabrication.
The favourable influence of using B2O3 in glazes is well – known [1-6, 8-10] but insufficiently exploited. B2O3 is a very strong flux (it reduces the viscosity of melts and surface tension), reducing the surface defects and emphasising more efficiently the colours and it may represent an alternative solution for PbO replacement in glazes (harmful for health).
Present paper deals with some experimentals involving E-glass fibers waste with a content of 70% B2O3 for obtaining glazes for table ware ceramics.