In situ synthesis and characterization of thin biocompatible hydroxyapatite/passive oxide composite coatings for potential medical use

Definisanje nove metode anodizacije/anaforetske depozicije za nanošenje kalcijum fosfatnih i hibridnih prevlaka na bazi kalcijum fosfatnih keramika na titanijumske spustrate sa unapredjenim svojstvima je bio predmet doktorske disertacije koja je pred Vama. Ova doktorska disertacija daje doprinos rešavanju problema višestepenog pred-tretmana i post-tretmana površine radi dobijanja prevlake na supstratu, adhezije prevlake, antimikrobnih i citotoksičnih svojstava koja se javlјaju kod biomaterijala. Primarno se bavi kreiranjem i optimizacijom novog in situ procesa anodizacije/anaforetske depozicije za dobijanje multifunkcionalnih kompozitnih biomaterijala. In situ metoda rezultira u poboljšanoj adheziji bioaktivne prevlake, povećanoj bioaktivnosti i biokompatibilnosti sa povećanim antimikrobnim svojstvima i odsustvom citotoksičnosti. Izučavani biomaterijali ostvaruju pobolјšana svojstva kao što su: otpornost na koroziju, odsustvo toksičnosti za lјudsko telo i odgovarajuća čvrstoća što omogućava njihovo potencijalno korišćenje u medicini i stomatologiji. Cilј ove doktorske disertacije je bio kreiranje novog in situ procesa anodizacije/anaforetske depozicije i adekvatna modifikacija parametara procesa za nanošenje kompozitnih kalcijum fosfatnih prevlaka na titan i njegove legure, pri čemu se inovativnost ogleda u objedinjavanju procesa sinteze kalcijum fosfatne prevlake i modifikacije površine supstrata delimičnom inkorporacijom keramičke prevlake u kristalnu strukturu supstrata. Karakterizacija ovako dobijenih prevlaka je obavljena različitim fizičko-hemijskim, biohemijskim i biološkim metodama. Ispitivanja su obuhvatila morfološku karakterizaciju i morfološke promene kalcijum fosfatnih prevlaka elektronskim mikroskopijama, pri čemu su korišćene sledeće tehnike karakterizacije: mikroskopija atomskih sila – AFM, skenirajuća elektronska mikroskopija – SEM i visoko-rezoluciona skenirajuća elektronska mikroskopija FE-SEM. Hrapavost podloge se određivala metodama AFM i ručnim meračem linearne hrapavosti (Handheld Roughness Tester). Metodom merenja difrakcije X-zraka (XRD) utvrđeni su kristalografski i fazni sastavi, kao i strukturne promene kompozita. Ova metoda je korišćena i pri dokazivanju bioaktivnosti prevlaka na bazi amorfnog kalcijum fosfata bez i sa hitozan oligosaharid laktatom (ChOL). Atenuiranom totalno refleksujućom infracrvenom spektroskopijom sa Furijeovom trasformacijom (ATR-FTIR) je dokazana uspešnost novog in situ procesa, prvenstveno kada je u pitanju dobijanje hibridnih multifunkcionalnih kompozitnih prevlaka sa ChOL...Completely new method of anodization/anaphoretic deposition for the deposition of calcium phosphate and hybrid coatings based on calcium phosphate ceramics on titanium supstrate with improved properties was the objective of the doctoral dissertation in front of you. The dissertation contributes to solving the problem of multistage pretreatment and posttreatment of the surface in order to obtain a coating on the substrate, adhesion of the coating, antimicrobial and cytotoxic properties that occur in biomaterials. It primarily deals with the application and optimization of the new in situ anodizing/anaphoretic deposition process for obtaining multifunctional composite biomaterials. The in situ method leads to improved bioactive coating adhesion, increased bioactivity and biocompatibility of biomaterials with increased antimicrobial properties and absence of cytotoxicity. Studied biomaterials have improved characteristics such as: corrosion resistance, absence of toxicity for the human body and adequate strength, which enables their possible use in biomedicine. The objective of this doctoral dissertation was to define a completely new in situ anodizing/anaphoretic deposition process and adequate modification of process parameters for the application of composite calcium phosphate coatings on titanium and its alloys, wherein innovation is reflected in combining calcium phosphate coating synthesis and surface modification by partially incorporating a ceramic coating into the crystalline structure of the substrate. The characterization of the coatings obtained in this manner was performed by various physico-chemical, biochemical and biological methods. The experiments of morphological characterization and morphological changes of calcium phosphate coatings included following electronic microscopy characterization techniques: atomic forces microscopy - AFM, scanning electron microscopy - SEM and field emission scanning electron microscopy FE-SEM. The substrate roughness was determined by AFM and Handheld Roughness Tester methods. The X-ray diffraction (XRD) method was used for determination of crystallographic and phase compositions as well as composites structural changes. This method was also used to demonstrate the bioactivity of amorphous calcium phosphate coatings with and without chitosan oligosaccharide lactate (ChOL). Attenuated totally reflective Fourier transform infrared spectroscopy with (ATR-FTIR) was used to prove the successfull execution of the new in situ process, primarily when it comes to obtaining hybrid multifunctional composite coatings with ChOL..

Provodni putevi kod elektroprovodnih kompozita sa biodegradabilnom polimernom matricom

The results of experimental studies of the properties of composite materials based on lignocellulosic (LC) and poly(methylmetacrylate) matrices filled with electrolytic copper powder are presented. Volume fractions of metal fillers in composite materials and tested samples were varied in the range of 0.5-29.8% (v/v). Characterization included examination of the influence of particle size and morphology on the conductivity and percolation threshold of the composites using SEM and AFM. Presence of three dimensional conductive pathways was confirmed

Uticaj pritiska na električnu provodljivost lignoceluloznih kompozita punjenih elektrohemijski dobijenim bakarnim prahom

Ovaj članak se bavi sintezom i karakterizacijom elektroprovodnih kompozitnih materijala pripremljenih hladnim presovanjem mešavina lignoceluloze i elektrohemijski dobijenog bakarnog praha pri različitim pritiscima, kao i ispitivanje uticaja veličine čestica na provodljivost i perkolacioni prag dobijenih kompozita. Udeo elektrohemijski dobijenog bakarnog praha je variran od 2.0 – 29.8 vol%. Analiza najznačajnijih osobina kako pojedinačnih komponenti tako i dobijenih kompozita je uključivala strukturnu analizu i merenja električne provodljivosti. Značajan porast električne provodljivosti može se primetiti kad sadržaj bakarnog praha u kompozitima dostigne perkolacioni prag. Efekat pakovanja i izraženiji međučestični kontakt sa manjim, izrazito poroznim i dendritičnim česticama sa velikim vrednostima specifične površine dovodi do ”pomeranja” perkolacionog praga ka manjim vrednostima udela punioca, koji za čestice <45 μm i najveći pritisak prerade kompozita od 27 MPa iznosi 11.4% (v/v). U ispitivanom opsegu koncentracija elektrohemijski dobijenog bakarnog praha u kompozitima i pritiscima prerade porast električne provodljivosti je iznosio čak četrnaest redova veličine. Primećeno je da se ovaj prelaz javlja pri nižim vrednostima udela punioca nego što je navedeno u literaturi, što može biti posledica upotrebe punioca sa velikim vrednostima specifične površine.This article is concerned with synthesis and characterization of electroconductive composite materials prepared by the compression molding of mixtures of lignocellulose and electrochemically deposited copper powder under different pressures, and investigation of the influence of particle size on conductivity and percolation threshold of obtained composites. Electrodeposited copper powder content was varied from 2.0-29.8 vol%. Analysis of the most significant properties of individual components and prepared composites included structural analysis and measurements of electrical conductivity. The significant increase of the electrical conductivity can be observed as the copper powder content reaches the percolation threshold. The packaging effect and more pronounced interpartical contact with smaller, highly porous, highly dendritic particles with high values of specific area lead to “movement” of percolation threshold towards lower filler content, which for the particles <45 μm and highest processing pressure of 27 MPa was 11.4% (v/v). In the investigated range of electrodeposited copper powder concentrations and applied pressures the increase of the electrical conductivity of composites is as much as fourteen orders of magnitude. It was found that this transition occurs at lower volume fractions than stated in the literature which can be due to the filler with high specific area

Optimizacija zapremine radioaktivnog obeleživača pri merenju zapreminskog protoka u zatvorenim cevovodima

In chemical processes it is essential that the flow in the process is accurately defined. Fluid velocity measurements are important for fluid flow quality performance in flow systems. This study focuses on determination of the volumetric flow rate and its standard (relative) deviation for calibration of conventional flow meters by using a radiotracer approach. The measurements for flow meter calibration were performed at a pilot-scale flow rig using Technetium-99 m (99mTc) as a radiotracer in the form of pertechnetate ion (99mTcO4-). The measured data were analyzed, and precision of the experimental setup was investigated under two different approaches – IAEA’s RTD software and sum approximation of raw data. For the first time, the variation of standard deviation of calculated flow rate with the injection volume and activity of the radiotracer was determined. Plug flow with axial dispersion was used to simulate the measured RTD curves and investigate the flow dynamics of the flowing water. The results of the study have shown the possibility of in situ calibration of flow meters with a relative error lower than 1 %. They also revealed a slight dependency of the precision of output results on the injection volume as well as similar results for manual and specialized RTD software data processing.U hemijskim procesima od suštinskog značaja je tačno definisan i precizan protok. Merenja brzine fluida su važna za karakterizaciju kvaliteta protoka tečnosti u sistemima. Ova studija se fokusira na određivanje zapreminskog protoka i standardnog (relativnog) odstupanja izmerenih vrednosti u cilju kalibracije konvencionalnih merača protoka korišćenjem metode radioaktivnog obeleživača. Merenja potrebna za kalibraciju merača protoka izvedena su na pilot postrojenju korišćenjem Tehnecijuma-99m (99mTc) kao radiotrejsera u obliku pertehnetatnog jona (99mTcO4-). Izmereni podaci su analizirani, a preciznost eksperimentalne postavke je ispitivana pomoću dva različita pristupa: upotrebom softvera za određivanje raspodele vremena zadržavanja (eng. residence time distribution, RTD) koga je razvila Međunarodna agencija za atomsku energiju i zbirne aproksimacije neobrađenih podataka. Po prvi put je utvrđena varijacija standardne devijacije izračunatog protoka u odnosu na zapreminu i u odnosu na aktivnost ubrizganog radioaktivnog obeleživača. Model protoka sa aksijalnom disperzijom je korišćen za simulaciju izmerenih RTD krivih i istraživanje dinamike protoka vode. Rezultati studije su pokazali mogućnost in situ kalibracije merača protoka sa relativnom greškom manjom od 1%. Takođe su pokazali malu zavisnost preciznosti izlaznih rezultata od količine ubrizganog obeleživača, kao i slične rezultate za manuelnu obradu i specijalizovanu obradu podataka upotrebom RTD softvera

Biodegradable polymers as matrices for electroconductive composites

In this manuscript the results of experimental studies of the properties of composite materials based on lignocellulosic (LC) and poly(methylmethacrylate) matrices filled with electrolytic copper powder are presented. Volume fractions of metal fillers in composite materials and tested samples were varied in the range of 0.5-29.8% (v/v), and the samples were prepared by compression - cold pressing and molding. Characterization included examination of the influence of particle size and morphology on the conductivity and percolation threshold of the composites using a variety of testing techniques: SEM, TGA, AFM. Thermal analysis of the prepared composites showed the improvement of the thermal characteristics of the composites. This was due to the presence of the metallic fillers, which are very good thermal conductors, hence accumulating the heat emitted during TGA measurements primary to matrix, whether it was lignocellulosic or PMMA. Presence of three dimensional conductive pathways was confirmed

Novel Calcium Phosphate Coatings with Selenum on Titanium

This paper deals with the deposition of calcium phosphate and hybrid coatings based on calcium phosphate ceramics on titanium with improved properties by in situ anodization/anaphoretic deposition process. Hybrid coatings consisted of chitosan oligolactate (ChOL) and ChOL with Se as immunomodulatory oligoelement. The paper contributes to solving the problem of multi-stage pre-treatment and post-treatment of titanium and oxidized titanium surface to obtain a coating on the substrate, adhesion of the coating, antimicrobial and cytotoxic properties that occur in biomaterials, as well as reduced immune inflammatory response of the organism. The in situ method results in improved adhesion bioactive coating, increased bioactivity and biocompatibility with increased antimicrobial properties and absence of cytotoxicity. The studied biomaterials have improved properties such as: corrosion resistance, absence of toxicity to the human body and adequate strength, which enables their potential use in medicine and dentistry. The innovation is reflected in combining calcium phosphate coating synthesis and surface modification by partially incorporating a ceramic coating into the crystalline structure of the substrate. The characterization of the coatings obtained in this manner was performed by various physico-chemical, biochemical and biological methods. These characterization techniques included: FE-SEM, XRD, FTIR, cytotoxicity and in vivo testing

Advanced hybrid composite coatings based on calcium phosphate on titanium for potential biomedical applications

This paper deals with the issue of defining a new method of anodizing/anaphoretic deposition for the application of calcium phosphate and hybrid coatings based on calcium phosphate ceramics on titanium and anodized titanium coatings with improved properties. Hybrid coatings consisted of chitosan oligolactate (ChOL) and ChOL with Se as immunomodulatory oligoelement. The paper contributes to solving the problem of multi-stage pre-treatment and posttreatment of titanium and oxidized titanium surface to obtain a coating on the substrate, adhesion of the coating, antimicrobial and cytotoxic properties that occur in biomaterials, as well as reduced immune inflammatory response of the organism. It primarily deals with the creation and optimization of a new in situ anodizing/anaphoretic deposition process for obtaining multifunctional composite biomaterials. The in situ method results in improved adhesion bioactive coating, increased bioactivity and biocompatibility with increased antimicrobial properties and absence of cytotoxicity. The studied biomaterials have improved properties such as: corrosion resistance, absence of toxicity to the human body and adequate strength, which enables their potential use in medicine and dentistry. The aim of the research was to define new in situ anodizing/anaphoretic deposition process and adequate modification of process parameters for application of composite calcium phosphate coatings on titanium and its alloys, wherein innovation is reflected in combining calcium phosphate coating synthesis and surface modification by partially incorporating a ceramic coating into the crystalline structure of the substrate. The characterization of the coatings obtained in this manner was performed by various physico-chemical, biochemical and biological methods. These characterization techniques included: AFM, SEM, FE-SEM, roughness testing, XRD, FTIR, bioactivity, biocompatibility, cytotoxicity, antimicrobial activity and in vivo testing

Influence of process parameters of simultaneous anodization/anaphoretic electrodeposition synthesis of hydroxyapatite/titanium oxide composite coatings on adhesion

In-situ synthesis of hydroxyapatite/titanium oxide (HAp/TiO2) coating on titanium was performed via anaphoretic deposition of hydroxyapatite (HAp) and simultaneous anodization of Ti to produce highly adherent and strengthened composite coating. The influence of electric potential, time, electrolyte concentration and pH value of the anodization process on titanium surface roughness and anodization of titanium was examined, as well as influence of same process parameters on adhesion strength and compactness of composite HAp/TiO2 coatings was investigated. Prior to novel in situ method of synthesis of hydroxyapatite/titanium oxide composite coatings by simultaneous anodization/anaphoretic electrodeposition described in this manuscript, optimization of anodization process of titanium was performed. Anodization was executed under different electric potentials and different distances of counter electrodes from working electrodes, but all anodization processes had constant quantity of electric charge. Characterization of titanium samples, prepared from grade 6 Ti, and having rectangular contact surfaces of 10×10×0.89 mm included SEM/EDS analyses, X-ray diffraction analyses, AFM surface topography, morphology and roughness analyses and linear measurements of roughness.A chemical precipitation method was used to prepare hydroxyapatite powder by the reaction of calcium oxide (obtained by calcination of CaCO3 for 5 h at 1000 °C in air) and phosphoric acid. A stoichiometric amount of the calcium oxide was stirred in distilled water and phosphoric acid was added drop wise to the suspension in order to obtain hydroxyapatite powder, Ca10(PO4)6(OH)2.Two types of HAp coatings were prepared, in order to compare the adhesion, morphology and consistency of the HAp and composite HAp/TiO2 on Ti, namely cathaphoretic and anaphoretic coatings, respectively [1,2]. The prepared coatings were characterized by field emission scanning electron microscopy, X-ray diffraction and electron dispersive spectroscopy. Adhesion was investigated by ASTM D 3359 – 97 Test method B. Uniform and adherent HAp/TiO2 composite coating on Ti was obtained. Since smaller size of HAp crystals within highly porous coating structures is of improved binding ability to various biomolecules, our coating is expected to be of excellent coverage and compactness. The obtained coating can be good candidate for bone implants due to improved adhesion

Influence of process parameters of simultaneous anodization/anaphoretic electrodeposition synthesis of hydroxyapatite/titanium oxide composite coatings on adhesion

In-situ synthesis of hydroxyapatite/titanium oxide (HAp/TiO2) coating on titanium was performed via anaphoretic deposition of hydroxyapatite (HAp) and simultaneous anodization of Ti to produce highly adherent and strengthened composite coating. The influence of electric potential, time, electrolyte concentration and pH value of the anodization process on titanium surface roughness and anodization of titanium was examined, as well as influence of same process parameters on adhesion strength and compactness of composite HAp/TiO2 coatings was investigated. Prior to novel in situ method of synthesis of hydroxyapatite/titanium oxide composite coatings by simultaneous anodization/anaphoretic electrodeposition described in this manuscript, optimization of anodization process of titanium was performed. Anodization was executed under different electric potentials and different distances of counter electrodes from working electrodes, but all anodization processes had constant quantity of electric charge. Characterization of titanium samples, prepared from grade 6 Ti, and having rectangular contact surfaces of 10×10×0.89 mm included SEM/EDS analyses, X-ray diffraction analyses, AFM surface topography, morphology and roughness analyses and linear measurements of roughness.A chemical precipitation method was used to prepare hydroxyapatite powder by the reaction of calcium oxide (obtained by calcination of CaCO3 for 5 h at 1000 °C in air) and phosphoric acid. A stoichiometric amount of the calcium oxide was stirred in distilled water and phosphoric acid was added drop wise to the suspension in order to obtain hydroxyapatite powder, Ca10(PO4)6(OH)2.Two types of HAp coatings were prepared, in order to compare the adhesion, morphology and consistency of the HAp and composite HAp/TiO2 on Ti, namely cathaphoretic and anaphoretic coatings, respectively [1,2]. The prepared coatings were characterized by field emission scanning electron microscopy, X-ray diffraction and electron dispersive spectroscopy. Adhesion was investigated by ASTM D 3359 – 97 Test method B. Uniform and adherent HAp/TiO2 composite coating on Ti was obtained. Since smaller size of HAp crystals within highly porous coating structures is of improved binding ability to various biomolecules, our coating is expected to be of excellent coverage and compactness. The obtained coating can be good candidate for bone implants due to improved adhesion

Study of the effects of active bromine species presence in electrolytic desulfurization of subbituminous coal

The removal of organic and inorganic sulfur from the Bogovina Basin subbituminous coal by electrochemical redox reactions was performed. The effect of presence of active bromine species on the desulfurization process was monitored. The desulfurization was performed in inorganic acidic solutions that contained different bromide concentrations and in pure acid solution. To determine the optimal conditions for the desulfurization process, polarization curves were recorded in three different electrolytes: 0.1 M H2SO4, 0.1 M H2SO4 + 0.01 M KBr, and 0.1 M H2SO4 + 0.1 M KBr using graphite and dimensionally stable anode (DSA) electrodes as the anode, while in all cases stainless steel S31603 electrode was used as cathode. By analyzing the results obtained from the polarization curves, 0.1 M H2SO4 and 0.1 M H2SO4 + 0.1 M KBr were chosen as the most suitable electrolytes. Also, it was found that the DSA anode showed better results in terms of energy efficiency of the process compared to the graphite anode and therefore it was selected for the coal desulfurization process. It is considered that finely suspended coal particles in an electrolyte can behave according to bipolar electrochemistry. Coal was treated for 4 hours in two selected electrolytes. The suspension was sampled at different times up to 240 min from the beginning of the process. Sulfur content in coal was determined by elemental analysis. The results showed that the sulfur content decreases faster in the case of the electrolyte containing KBr, i.e. that the desulfurization effect is significantly better than in the case of the system containing only H2SO4. It can be concluded that active bromine species accelerate the desulfurization process and thus improve energy efficiency