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Three types of composites consisting of Ca10(PO4)6(OH)2 and Ca3(PO4)2 with composition: 75% (wt) Ca10(PO4)6(OH)2: 25%(wt) Ca3(PO4)2; 50%(wt) Ca10(PO4)6(OH)2: 50%(wt)Ca3(PO4)2 and 25 %(wt) Ca10(PO4)6(OH)2: 75%(wt) Ca3(PO4)2 were the subject of our investigation. Sintered compacts were in thermal equilibrium, which was proved by the absence of hysteresis effect of the dependence ΔL/L=f(T) during heating /cooling in the temperature interval 20-1000-200C. Sintered compacts with the previously mentioned composition possess 26-50% higher values of the E-modulus, G-modulus and K-modulus indicating the presence of a synergism effect. Several proposed model equations for predicting the thermal expansion coefficient in dependence of the thermal and elastic properties of the constitutive phases and their volume fractions, given by: Turner, Kerner, Tummala and Friedberg, Thomas and Taya, were used for making correlations between mechanical and thermal-expansion characteristics of the Ca10(PO4)6(OH)2 - Ca3(PO4)2 composites. Application of the previously mentioned model equations to all kinds of composites leads to the conclusion that the experimentally obtained results for the thermal expansion coefficient are in an excellent agreement with the theoretical calculated values on account of the volume fraction of each constitutive phase and with all applied model equations, with a coefficient of correlation from 98.16-99.86 %

The toxicity and non‐biodegradation of heavy metals, as well as their tendency to accumulate in the soils, water resources and the living organisms, makes them the significant environmental pollutants. Therefore, the reduction and elimination of heavy metal ions from aqueous systems is very important from the ecological, nutritional and environmental reasons. The aim of this study is to investigate whether the natural peanut husks, an agricultural waste, and their chemically modified form are capable to remove Ni(II) ions from aqueous solutions using batch method and to compare their efficiency. The effects of the mass of the natural peanut husks and the initial pH of the solution were studied to find the optimal conditions for maximal removal of Ni(II) ions. MATLAB/Curve Fitting Toolbox was implemented to determine the adequate adsorption isotherm as well as to optimise the equilibrium state of the investigated systems.

Hydroxyapatite is a particularly attractive material for human tissue implantation. The intrinsic poor mechanical properties of hydroxyapatite material can lead to instability and unsatisfactory duration of the implant in the presence of body fluids and local loading. Addition of TiO2 in the hydroxyapatite matrix can enhance the mechanical properties of the obtained composite. The composite with 15 % TiO2 content shows a thermal stability of the system and improved mechanical properties

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