We reported on the synthesis of nanosized hydroxyapatite particles by wet chemical precipitation method and the consolidation of the nanoparticles by spark plasma sintering. We studied the effect of the synthesis temperature on the particle size and phase composition of the obtained HAp. During synthesis beyond HAp, another phase supposedly nonstoichiometric HAp was also formed as a by-product that can be detected by thermal analysis combined with XRD. Its amount gradually decreased with the increase in synthesis temperature and practically disappeared at 80°C. Using this nanopowder for sintering, the spark plasma-sintered ceramics retained their nanostructure comprising only HAp phase in contrast to the powders synthesized at lower temperature when transformed products of the nonstoichiometric HAp could also be detected.

A simple synthetic method was developed to prepare 4[Agpy 2 ClO 4 ]Á[Agpy 4 ]ClO 4 in a low-temperature decomposition process of [Agpy 4 ]ClO 4 . A detailed IR, Raman and far-IR study including factor group analysis has been performed, and the assignation of bands is given. The compound decomposes quickly with a multistep ligand loss process with the formation of [Agpy 2 ]ClO 4 and AgClO 4 intermediates and AgCl as an end product around * 85, * 350 and 450°C, respectively. During the first decomposition step, a small fraction of the ligands is lost in a redox reaction: perchlorate oxidizes the pyridine, forming carbon, carbon dioxide, water and NO, while it itself is reduced into AgCl. In the next step, when AgClO 4 forms after complete ligand loss and reacts with the carbon formed in the degradation of pyridine at lower temperatures and produces NO, CO 2 and H 2 O. This reaction becomes possible because the AgCl formed in the redox reactions makes a eutectic melt with AgClO 4 in situ, which is a favorable medium for the carbon oxidation reaction. AgCl is known to reduce the temperature of decomposition of AgClO 4 , in which process forms AgCl as well as O 2 and so is an autocatalytic process. The loss and degradation of pyridine ligand are endothermic; the redox reactions including carbon oxidation and AgClO 4 decomposition into AgCl and O 2 are exothermic. The amount of absorbed/evolved heats corresponding to these processes was determined by DSC both under N 2 and O 2 atmospheres. Keywords Pyridine-silver complexes Á Perchlorates Á Quasi-intramolecular solid-phase redox reaction Á Evolved gas analysis Á DSC Electronic supplementary material The online version of this article (

Hydroxyapatite / graphene (HAP/GNPs) composites were prepared by spark plasma sintering (SPS).Sintering was carried out at various temperatures (700°C and 900°C) and holding times (5 and 10 min). Mechanical and structural properties were studied. The highest relative density ~ 96% was

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Decomposition of poly(vinyl chloride) (PVC) was studied in inductively coupled radiofrequency thermal plasma in neutral, oxidative and reductive conditions. The exhaust gases were analysed by Fourier transform infrared spectroscopy (FT-IR), and their main components were identified as CO, CO 2 , C 2 H 2 , H 2 O and HCl. The weaker bands in the infrared spectra were assigned by density function theory calculations and P-R separation method. The extent of PVC decomposition was calculated from the amount of solid soot, which was also studied by transmission electron microscopy (TEM) for morphology and composition. Organic compounds adsorbed on the surface of the soot were extracted by toluene and analysed by gas chromatography mass spectrometry (GC/MS). The extracts *Marked-up Revised Manuscript Click here to view linked References

Detailed vibrational (IR, Raman, far-IR) and thermal (TGA, TG–MS, DSC) analysis has been performed on di[κ1O,κ2O-carbonatotetraamminecobalt(III)] sulfate trihydrate, ([Co(NH3)4CO3]2SO4·3H2O (1). Its isothermic heating at 100 °C leads to formation of [Co(NH3)4CO3]2SO4 (compound 2). UV and IR studies showed that the distorted octahedral arrangement around cis-O2CoN4 core in compound 1 does not change during dehydration, which explains the reversible water loss and ability of compound 2 to rehydrate into compound 1. Compound 2 decomposes at ~ 240 °C in inert atmosphere giving final decomposition products, which are two modifications of nanosized metallic cobalt (hcp-15 nm, fcc-250 nm) and CoO (55 nm). The redox reaction results in N2 as an ammonia oxidation product. The decomposition intermediate is a cobalt(II) compound, Co2O1,14+δ(SO4)0.86 (δ = the oxygen surplus due to the presence of 2.8% of Co(III) ion). The same reaction in air atmosphere resulted in Co2O1.25+δ(SO4)0.75 (δ = the oxygen surplus due to the presence of 5.3% of Co(III) ion (compound 3a). Compound 3a is oxidized in air at 793 °C into Co3O4. The compound 3a exhibits catalytic activity in photodegradation in Congo red. The photodegradation process follows pseudo-first-order kinetic (kapp = 1.0 and 7.0. at pH = 3.4 and 5.25, respectively).

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Decomposition of chlorobenzene as a model molecule of aromatic chlorinated compounds was studied in radiofrequency (RF) thermal plasma both in neutral and oxidative conditions. Optical emission spectroscopy (OES) was applied for the evaluation of the plasma excitation and molecular rotational-vibrational temperature. Atomic (C, H, O) and molecular (CH, OH, C 2 ) radicals were identified, while the morphology of the formed soot was characterized by electron microscopy. Organic compounds adsorbed on the surface of the soot after plasma processing were comprised of various polycyclic aromatic hydrocarbons (PAH) and chlorinated PAH molecules. Their amount was greatly affected by experimental conditions, especially the oxygen content and plate power. The higher input power reduced the ring number of the PAH molecules. Addition of oxygen significantly reduced the amount of both PAHs chlorinated PAH molecules but enhanced the formation of polychlorinated benzene compounds.