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Effects of the hot pressing parameters on the designing of structures and properties of hydroxyapatite/poly-L-lactide biocomposite blocks have been studied. Interdependences of temperature, pressure and time of hot pressing and the density, compressive strength, elasticity modulus, and fracture type of biocomposite blocks were defined. The microstructures of the fracture surfaces were observed by scanning electron microscopy, while the compositions of the constituent phases after hot pressing were determined qualitatively by FT-infrared spectroscopy. A wide spectrum of block properties such as relative density of 86.2–99.6 %, compressive strength of 38–139 MPa and elasticity modulus of 2–10 GPa was obtained by varying the hot pressing parameters.

The main purpose of the present work was to investigate the influence of urea concentration on hydroxyapatite (HAp) synthesis. Calcium nitrate and ammoniumdihydrogenphosphate were used as Ca and P sources. A homogeneous precipitation agent – urea - was applied in the field of ultrasonic irradiation. Different Ca : P : urea molar ratios were applied and the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and infrared spectroscopy (IR). The results reveal the influence of the urea concentration on the phase composition of the system, crystallite size and the particle morphology. Different Ca : P : urea molar ratios led to various system formation: from biphasic OCP and HAp to monophasic HAp. The estimated HAp crystallite size was 24.4 nm. An explanation of the mechanism of the HAp synthesis is given, regarding the formation of the intermediate and final product during ultrasonic irradiation.

The ZnO and ZrO2 powders were prepared by mechanochemical processing and subsequent heat treatment of the starting powder of precursors mixture of ZnCl2 and Ca(OH)2, and ZrOCl2·8H2O and NaOH, respectively. Inert salt matrix, ether CaCl2 or NaCl, which prevents particle agglomeration was formed during mechanochemical solid state reaction. After mechanochemical treatment, samples were calcined at various temperatures. Selective removal of the matrix phase by washing the resulting powder with appropriate solvent yields almost pure ZnO and ZrO2 powders. Characterization of the powders was performed by X-ray diffraction (XRD), differential thermal and thermo gravimetric analysis (DTA−TG) and scanning electron microscopy (SEM).

In order to obtain more accurate properties after compaction of hydroxyapatite (HAp)/poly-L-lactide (PLLA) composite, high-resolution measurement of mechanical properties method is proposed to determine the properties of each phase separately, leading to information that are valuable for the development of new materials as well as for predictive modeling purposes. The PLLA polymer processing conditions used in hot pressing of the composite strongly influence final mechanical properties of the material in the solid state. Since the aim was to measure PLLA material properties, acceptable findings could only be made using unconstrained, cured in situ nanoindentation tests. A finite element analysis of the in situ indentation experiment was performed to determine required size of plain polymer area, needed for indentation test, which would minimize the particle influence on the matrix elastic behavior.

BaTi1-xSnxO3 (BTS) powders, with x ranging from 0 to 1, were synthesized by solid-state reaction technique. The powders were pressed into pellets and sintered at 1370 and 1420 oC. The structural characterization of sintered BTS samples was made at room temperature using X-ray diffraction and Raman spectroscopy measurements. The BTS samples were found to be singlephase solid solutions. Dielectric properties of sintered BTS samples were studied as a function of sintering temperatures and tin contents, too. For samples with x ranging from 0 up to 0.15, it has been found that the Curie temperature decreases while the maximum of the dielectric constant increases with increasing tin content. These samples have relatively high dielectric constants, contrary to x > 0.2 samples with very low dielectric constants. It is noticed that BTS ceramics sintered at 1420 oC exhibit better dielectric properties than those sintered at 1370 oC.

In this paper we report the results on synthesis of a composite biomaterial based on biphasic calcium phosphate (BCP) and poly-(DL-lactide-co-glycolide) (DLPLG). Besides, we have investigated the influence of new synthesis method on the structure and characteristics of the composite. The synthesis of biphasic calcium phosphate from Ca(NO3)2 x 4H2O and (NH4)3 PO4 in alkali environment was performed by means of precipitation technique. Composite material BCP/DLPLG was first prepared from commercial granules using chemical methods. Powdered polymer DLPLG was then homogenized at appropriate ratio with addition of biphasic calcium phosphate into the suspension. All samples were characterized by DSC, IR, X-Ray and SEM techniques.

Composite biomaterials, like calciumphosphate/bioresorbable polymer, offer excellent potential for reconstruction and reparation of bone tissue defects induced by different sources. In this paper synthesis of calciumphosphate/poly-DL-lactide-co-glycolide (BCP/DLPLG) composite biomaterial formed as filler and blocks was studied. BCP/DLPLG composite biomaterial was produced in the form of spherical granules of BCP covered by a DLPLG layer, average diameter of 150-250 µm. By cold and hot pressing of granules at up to 10000 kg/cm2, blocks with fine distribution of phases and porosity up to 3% were obtained. Characterization was performed by wide-angle X-ray structural analysis (WAXS), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), infrared spectroscopy (IR), and mechanical properties by defining the compressive strength. In vitro citotoxicity research was carried out on cellular cultures of fibroblasts of human (MRC5) and mouse (L929). In vivo research was performed in two steps. Reparatory ability of BCP/DLPLG in mice was examined in the first step, and then bone tissue reconstruction possibilities on 10 patients in the next step. In vitro tests showed very good fibroblast adhesion and non-citotoxicity of the composite. A material is considered non-cytotoxic if the cell survival is above 50 %, and in our case it was 90%. In vivo research on mice indicated high level of reparatory ability of this composite with formation of new bone and vascular tissue six weeks after reparation. Application of this composite for healing infrabone defects of patients showed a high level of osseous regeneration.

This study descripts processing of biphasic calcium-phosphate (BCP) and poly-L-lactide (PLLA) biocomposite implant material. The composite was obtained by mixing completely dissolved PLLA with granules of high crystalline BCP and was compacted by hot pressing using cylindrical dies at 450 K temperature and 98.1 MPa pressure, for 30 and 60 minutes. Wide-angle Xray structural (WAXS) analyses of BCP, PLLA and BCP/PLLA composite blocks were made followed by calorimetric (DSC) tests in the 320-520 K temperature range. Compression tests revealed that Young’s modulus and compressive strength of the composite increased with extended hot pressing time and were found to be within the bounds of the cortical bone values.

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In this work a radiospectroscopic investigation of the B-C, B-C-Ti and B-C-Cr systems was made in the range of 0 to 30 at % carbon at 4.2, 77 and 300 K. It is shown that in the B-C system, with a change of carbon content from 0 to 30% there are two concentration ranges in which a change occurs in the character of EPR signal: the first from 0 to 13% carbon and the second where the carbon content is 18 to 30%. The g factor, the width, the form and the intensity of EPR lines indicate that in the first range the EPR signal is due to the B12C complexes, which represent the lattice of a-boron with one carbon atom. In the second range the experimental data indicate that probably the introduction of four carbon atoms occurs, so that the formation of B12C4 centres is in question. The change in intensity of the signal on introduction and increase of titanium and chromium contents indicates different mechanisms of interaction of the basic components in this system. Keeping in mind that with increasing content of addition the microhardness of samples increases, while the intensity of the EPR signal decreases, it is probable that larger amounts of the B13C2-phase, which is characterized by a higher microhardness, are then formed.

A thermal and kinetic investigation of the behaviour of amorphous and crystal powder alloy Ni78P22 was performed in a hydrogen atomsphere. It was shown that the amorphous alloy absorbs hydrogen within the temperature range 393 to 520 K. After that it is transformed into the crystal (stable) state in two steps at 615 and 670 K, respectively, thus forming stable Ni and Ni3P phases. The crystal form of the same sample also adsorbs hydrogen, but at lower temperatures ranging from 310 to 520 K, The activation energies of the crystallization process, as well as the frequency factors, the rate constants and the enthalpy of crystallization were determined. Both kinetic and thermal parameters of the hydrogen adsorption process taking place in at least two steps, as in the crystallization process, were also determined.

High-purity, fine-grained oxide ceramic powders that are commonly used for ZnO-based varistors were synthesized by means of the reaction spray process. Processing steps included formation of the solutions of zinc nitrate and/or certain metal additives and spraying of the solution into a heated reaction column using a two-phase nozzle. After water evaporation from the droplets, the precursor salts were decomposed at elevated temperatures (up to 1473 K) in order to obtain homogeneous oxide powders with complex compositions corresponding to the final multicomponent varistor system. The decomposition behaviour of the precursors, as well as the characteristics of the resulting powders: crystallinity, phase composition, particle shape, morphology and particle-size distribution, were examined. It was shown that the characteristics of the reaction spray-derived powders can be controlled by adjusting the system and the solutions parameters.

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The influence of the defect structure of ZnO grains on the electrical properties of ZnO varistors, on sintering parameters and temperature of subsequent heat treatment, was studied. By analysis of the Mn2+ spectrum obtained by the electron paramagnetic resonance technique, the dependence of electrical properties of ZnO varistors on the defect structure of ZnO grains and impurity ions, was shown.

Differnetial thermal analysis (DTA) and thermal gravimetric analysis (TGA), at a heating rate of 10 °C/min, revealed a complete reduction of NiCl2by hydrogen in a temperature interval of 375 °C to 450 °C. However, addition of 0.1 mass pct of Pd, Cu, or Ni to the sample caused the reduction to occur at considerably lower temperatures, in the rather narrow range of 315 °C to 370 °C. The activation energy of NiCl2reduction by hydrogen (between 300 °C and 550 °C) without additives is 54 kJ/mol, and with Pd and Cu or Ni added, under isothermal conditions (from 260 °C to 380 °C), is 33 and 50 kJ/mol, respectively. These values confirm a positive effect of additives on the reduction kinetics. The positive effect of Pd is a consequence of the dissociation and spillover of hydrogen, whereas in the case of Cu and Ni(HCOO)2, it is manifested in a decrease in bonds energy in the nickel lattice because of good Cu solubility, and in the formation of artificial nickel nuclei that intensify the reduction, respectively. Scanning electron microscopy (SEM) analysis of nickel powders obtained under isothermal conditions shows relatively rounded spherical particles (0.321 to 0.780 µm in size) of powder samples with additives, and particles of irregular shape (2.085 µm mean size) of the sample without additives. This illustrates the positive effect of Pd, Cu, or Ni added in the reduction process, in decreasing the size of nickel particles and in the production of a more uniform particle shape.

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Shock compaction of AlMgSi0.5 was realized by using a LEXAN projectile with a velocity of 1655 ms-1. The dynamic pressure in the zone of impact was 8 GPa in the sample in the target at room temperature. The sample consisted of spheres of two particle size fractions (100–200 µm and 200–315 µm) separated in layers through which the same shock wave was passing. The appearance of non-porous interparticle contacts in the impact zone, with the content of melted areas up to 10% was detected in the case of the larger particle fraction only. Smaller particles had no tendency to form the strong interparticle contacts, not even in the first layers in the direction of the shock wave. TEM analysis showed the presence of an intensively deformed structure in the zone of the planar shock wave, as well as the structures with very poor signs of recovery and recrystallization in particle contact areas. The hardening effect of the shock wave was obvious, so that microhardness in the zone of the planar wave in larger particles had reached the value of 120 Hv, much higher than the microhardness of the initial powder (70 Hv).

The sintering kinetics of non-stoichiometric uranium dioxide powders have been studied in the temperature range 700 to 950° C. The results of the relative linear shrinkage during the stepwise heating of samples, were analysed as a function of sintering temperature and time. It has been shown that it is impossible to explain the exceptionally large shrinkage of UO2+xcompacts in the temperature range 0.3 to 0.4 Tm by means of a single sintering mechanism.