Physics and Technology Faculty

The corrosion of the surfaces of metallic implants is a very aggressive process, which can
cause inflammation and deposition of metal in the surrounding live tissue. Prevention of
corrosion and improvement of the functional characteristics of different coatings for
application on implant surfaces is essential. Niobium and tantalum anodic oxides of optimal
thickness have enabled the manufacture of a new generation of bioengineering products
displaying minimal corrosion.

Problems connected with the improvement of medical implant fixation in bone tissue are
addressed by the formation of a highly developed surface and by the activation of the implant
surface with an electret coating. The realization of such surface modifications is expedient
for implants manufactured from tantalum or niobium or finished by coatings made from these
metals, as they are chemically more inert than titanium. The techniques have been tested on
animals followed by histological and mechanical analysis.

Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of auto-or allografts is impossible. The objective of the present work was to characterize and study in vivo biodegradation of simple chitosan/hydroxyapatite scaffolds. For this purpose, a series of chitosan/hydroxyapatite composites has been synthesized in aqueous medium from chitosan solution and soluble precursor salts by a one step coprecipitation method. A study of in vivo behavior of the materials was then performed using model linear rats. Cylindrical-shaped rods made of the chitosan/hydroxyapatite composite material were implanted into tibial bones of the rats. After 5, 10, 15, and 24 days of implantation, histological and histo-morpho-metric analyses of decalcified specimens were performed to evaluate the stages of biodegradation processes. Calcified specimens were examined by scanning electron microscopy with X-ray microanalysis to compare elemental composition and morphological characteristics of the implant and the bone during integration. Porous chitosan/hydroxyapatite scaffolds have shown osteoconductive properties and have been replaced in the in vivo experiments by newly formed bone tissue. V C 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 96A: 639-647, 2011.

(Получено 12.02.2016; в отредактированной форме – 02.03.2016; опубликована online 15.03.2016) В работе приведены результаты исследований морфологии, структуры, элементного и фазового со-става кальцинированных фрагментов патологических образований щитовидной железы. Методами рентгеновской дифракции и инфракрасной спектроскопии установлено, что все исследованные пато-логические кальцификаты представляет собой дефектный карбонатзамещенный апатит кальция Ca10(PO4)6(OH)2. Показано, что применение просвечивающей электронной микроскопии в комбинации с микродифракцией электронов позволяет выявить некоторые структурные и морфологические осо-бенности кристаллов апатита щитовидной железы, не обнаруживаемые другими методами. Благода-ря этому, при условии применения тонкого препарирования на стадии анатомических исследований и подготовки пробы, может быть реализован локальный морфологический и структурный анализ мине-ральных составляющих депозита как при одном и том же клиническом случае, так и при их широком разнообразии.

ABSTRACT Composite biomaterials based on chitosan and calcium apatite with different chitosan/apatite ratio were prepared by chemical synthesis of apatite in chitosan solution using one-step co-precipitation method. Initial and annealed samples were characterized by X-ray diffraction, FTIR spectroscopy and scanning electron microscopy coupled to energy-dispersive electron X-ray spectroscopy. The data obtained suggest that the formation of the calcium-phosphate mineral in chitosan solution is substantially modulated by the chemical interaction of the components; apparently, a part of calcium is captured by chitosan and does not participate in the formation of the main mineral phase. The apatite in the composite is calcium-deficient, carbonate-substituted and is composed of dispersed nano-sized crystallites, i.e. has properties that closely resemble those of bone mineral. Varying synthesis, drying and lyophilization conditions, the composite materials can be produced with the desirable chitosan/apatite ratio, both in the dense and porous form. The structural analysis of composite samples after annealing at certain temperatures is examined as an approach to elucidate the mechanism of co-precipitation by one-step method. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Chitosan/hydroxyapatite scaffolds could be used for bone regeneration in case the application of auto-or allografts is impossible. The objective of the present work was to characterize and study in vivo biodegradation of simple chitosan/hydroxyapatite scaffolds. For this purpose, a series of chitosan/hydroxyapatite composites has been synthesized in aqueous medium from chitosan solution and soluble precursor salts by a one step coprecipitation method. A study of in vivo behavior of the materials was then performed using model linear rats. Cylindrical-shaped rods made of the chitosan/hydroxyapatite composite material were implanted into tibial bones of the rats. After 5, 10, 15, and 24 days of implantation, histological and histo-morpho-metric analyses of decalcified specimens were performed to evaluate the stages of biodegradation processes. Calcified specimens were examined by scanning electron microscopy with X-ray microanalysis to compare elemental composition and morphological characteristics of the implant and the bone during integration. Porous chitosan/hydroxyapatite scaffolds have shown osteoconductive properties and have been replaced in the in vivo experiments by newly formed bone tissue. V C 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 96A: 639-647, 2011.

The mechanism of charge transfer in bilayer system Zr-ZrO 2 and its conductivity in the initial state and after degradation were investigated. The anodization parameter was calculated, permitting to set the thickness of the oxide layer at anodic oxidation of zirconium. The degradation mechanism of layer systems Zr-ZrO 2 , determined by increasing the oxide conductivity and accompanied by geometrical growth of oxide layer thickness, is outlined in this article.

The possibility of zinc and cadmium tungstate synthesis by reaction of metal nitrates with ammonium paratungstate by microwave irradiation is studied. Formation of the metal tungstate begins in a liquid phase at the melting point of initial hydrates and is completed at their complete decomposition temperature, at 400-450°C. The microwave activation does not have influence on the mechanism of cadmium and zinc tungstate synthesis, but it considerably accelerates it. It is shown that, during the microwave activation, cadmium tungstate, with scheelite structure (a = 5.170 Å , c = 11.140 Å ), is formed.

Research on ZnSe synthesis using microwave (MW) activation was conducted at varying concentrations of alkaline metal halogenides. It was established that ZnSe with a cubic lattice (a = 5.665 ± 0.002 Å ) was formed irrespective of synthesis conditions. The interaction between zinc and selenium under MW radiation occurs at considerably lower temperatures (about 250°C) in comparison with initial components' interaction during thermal heating, which is observed at temperature above 500°C. To avoid sintering of ZnSe particles during interaction between zinc and selenium interaction, the injection of alkaline metal halogenides in a mass ratio 0.5:1 into the initial mixture is proposed. The as-synthesized ZnSe can be used as charge for the growth of optical crystals after preliminary annealing at 800°C for 1 h.

Tetragonal scheelite phase of CdWO 4 powder was synthesized using the microwave (MW) method by decomposition of cadmium nitrate with ammonium paratungstate mixture. The powder is stable in air but reverts to the monoclinic tungstate at temperatures exceeding 200 C. The maximum concentration of scheelite phase (about 70%) is observed during decomposition of initial components mixture in vacuum, which helps reduce synthesis time.

The study of electronic and transport properties of amorphous and nanocomposite superhard carbon films deposited from the mass-separated beam of accelerated C 60 ions with an energy of 5 keV onto a substrate with temperatures (Ts) ranging from 373 K to 773 K is present. The films demonstrate a transition from the amorphous state with sp 2 2D clusters to nanocomposite one with 3D graphite nanocrystals at Ts ∼ 573 K. That is accompanied by the registration of two phases with optical gaps of 3.6 eV and <1 eV. The narrow optical gap (<1 eV) is shown to attribute to the graphite nanocrystals, and a wide one (3.6 eV) to the amorphous diamond-like matrix. Measurement of the electrical conductivity of films at low temperatures showed a gradual transition at Ts increasing from hopping conductivity with variable length of jump in amorphous films to the tunnel one with power-law dependence from temperature for the nanocomposite and further to the percolation conductivity at direct contact of graphite nanocrystals. The role of intergranular insulator at tunneling conductivity of nanocomposite is played by amorphous carbon matrix which has an electronic structure close to amorphous diamond.

In this work, the complex investigation of structural and optical properties of zinc and cadmium selenide semiconductor films deposited by close-spaced vacuum sublimation method using thermal evaporation on non-oriented substrates was carried out. The structural and phase analyses of the layers condensed at different substrate temperatures were performed. The transmission and reflection spectra of the investigated films have been measured and their main optical characteristics have been calculated.

Study of the optical properties of Cd 1 -x Mn x Te films obtained by the close spaced sublimation technique was carried out. Measuring of the optical characteristics of the layers was performed by the spectrophotometric analysis method near the "red boundary" of the semiconductor photoactivity. This research allowed to obtain the spectrum distributions of the transmission T(l), reflection R(l) and absorption a(l) coefficients of the films as well as estimate the band-gap energy of the compound. The values of the band-gap energy were used for determination of manganese concentrations in the films depending on the growth conditions.

 ðîáîò³ ïðîâåäåíî äîñë³äaeåííÿ ìîðôîëî㳿 ïîâåðõí³, ìåõàí³çì³â ðîñòó òà îïòè÷íèõ âëàñòèâîñòåé ïë³âîê CdSe, îäåðaeàíèõ ìåòîäîì òåðì³÷íîãî âèïàðîâóâàííÿ ó êâàç³çàìêíåíîìó îá'ºì³, ÿê³ º ïåðñïåêòèâíèìè äëÿ âèêîðèñòàííÿ ó ÿêîñò³ ïîãëèíàþ÷èõ øàð³â òàíäåìíèõ ñîíÿ÷íèõ åëåìåíò³â òà ôîòîäåòåêòîð³â. Âèì³ðþâàííÿ îïòè÷íèõ õàðàêòåðèñòèê øàð³â çä³éñíþâàëîñÿ ìåòîäàìè ñïåêòðîôîòîìåòðè÷íîãî àíàë³çó ïîáëèçó «÷åðâîíî¿ ìåae³» ôîòîàêòèâíîñò³ íàï³âïðîâ³äíèêà. Ïðîâåäåí³ äîñë³äaeåííÿ äàëè ìîaeëèâ³ñòü îòðèìàòè ñïåêòðàëüí³ ðîçïîä³ëè êîåô³ö³ºíò³â ïðîïóñêàííÿ Ò( ) , â ³ ä á è ò ò ÿ R ( ), ïîãëèíàííÿ ( ) , çàëîìëåííÿ n( ), ðåàëüíî¿ 1 ( ) òà óÿâíî¿ 2 ( ) ÷àñòèí îïòè÷íî¿ ä³åëåêòðè÷íî¿ ñòàëî¿ çðàçê³â òà âèÿâèòè ¿õ çàëåaeí³ñòü â³ä òåìïåðàòóðè îñàäaeåííÿ ïë³âîê.

Для синтеза и очистки исходной соли селенида цинка в работе применялся микроволновой метод. Полученный порошок использовался для нанесения тонких пленок селенида цинка на очищенных ультразвуком стеклянных подложках методом термического испарения в квазизамкнутом объеме при следующих условиях: постоянная температура испарения Te = 800 °С, температура подложки Ts = 100-600 °С. Исследование оптических характеристик конденсатов позволило рассчитать ширину их запрещенной зоны, а также уточнить фазовый состав полученных пленок.