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This paper presents the results of thermal and microstructural analysis of Cu-Al-Ni shape memory alloy before and after heat treatment. After casting, a bar of Cu-12.8 Al-4.1 Ni (wt.%) alloy, obtained by the vertical continuous casting technique, was subjected to a certain heat treatment procedure. Solution annealing was performed at 850 °C for 60 min, followed by water quenching. Tempering was then performed at four different temperatures (150 °C, 200 °C, 250 °C and 300 °C). The microstructural results were obtained by optical and scanning electron microscopy. Thermodynamic calculation of ternary Cu-Al-Ni system under equilibrium was performed using Thermo-Calc 5 software. Phase transformation temperatures were determined by differential scanning calorimetry (DSC). The DSC results show the highest values of transformation temperatures in as-cast state. After solution annealing and tempering, the transformation temperatures show lower values with exceptional stability of Ms temperature (martensite start temperature). This work is licensed under a Creative Commons Attribution 4.0 International License., U radu su prikazani rezultati toplinske i mikrostrukturne analize Cu-Al-Ni slitine s prisjetljivosti oblika prije i nakon toplinske obrade. Nakon lijevanja, šipka slitine Cu-12.8 Al-4.1 Ni (mas. %) dobivena tehnikom vertikalnog kontinuiranog lijevanja, podvrgnuta je određenom postupku toplinske obrade. Provedeno je homogenizacijsko žarenje pri 850 °C, zadržavanje na toj temperaturi 60 min i hlađenje u vodi. Nakon toga je provedeno popuštanje na četiri različite temperature (150 °C, 200 °C, 250 °C i 300 °C). Mikrostrukturna analiza provedena je optičkim i pretražnim elektronskim mikroskopom. Termodinamički proračun ravnotežnog ternarnog Cu-Al-Ni sustava proveden je pomoću Thermo-Calc 5 softvera. Temperature fazne transformacije određene su diferencijalnom pretražnom kalorimetrijom (DSC). Rezultati DSC-a pokazuju najveće vrijednosti temperatura fazne transformacije u lijevanom stanju. Nakon homogenizacijskog žarenja i popuštanja temperature fazne transformacije pokazuju niže vrijednosti s iznimnom stabilnošću Ms temperature (temperatura početka nastajanja martenzita). Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.

Magistrsko delo obravnava analizo uklona cevi, ki je izdelana iz materiala z oblikovnim spominom. Narejen je bil sistematičen pregled literature, ki obravnava termo-mehanske modele in lastnosti teh materialov. Razvit je bil numerični model, ki omogoča določitev kritične uklonske sile. Model temelji na metodi končnih elementov in inkrementalnem obremenjevanju oziroma iterativnem izračunu. Izveden je bil eksperiment, s katerim smo pridobili materialne podatke, na podlagi katerih smo določili teoretično kritično uklonsko silo. The master thesis deals with the buckling analysis of a pipe, which is made from a shape memory material. A systematic overview of the literature that deals with thermo-mechanical models and properties of these materials has been made. A numerical model was developed that enables the determination of a critical buckling force. The model is based on the finite element method and the incremental loading and iterative calculation. Experiments to obtain values of material parameters served as a basis on which we determined the theoretically critical buckling force.

U ovoj doktorskoj disertaciji ispitane su mogućnosti dobijanja monetita (CaHPO4) i nanosferičnog karbonatno stroncijskog hidroksiapatita [Sr10(PO4)6(OH)(2-2x)(CO3)x ] bržim, jednostavnijim i ekonomski isplativijim postupcima sinteze od dosada korišćenih. Sinteza monetita (CaHPO4) urađena je korišćenjem tehnike mlevenja brušita (CaHPO4∙2H2O) u vibracionom mlinu pri čemu dolazi do njegove fazne transformacije. Ispitivan je uticaj dužine mlevenja na fazni sastav i mikrostrukturne parametre tretiranog materijala. Prikazan je i mehanizam fazne transformacije brušit - monetit pri kratkom vremenu mlevenja (ukupno 12,5 min.). Uočeno je da se monetit formira nakon 5,0 minuta mlevenja u vibracionom mlinu faznim prelazom brušit-monetit. Primenom metode rendgenske difrakcije na polikristalnim materijalima izučavan je fazni sastav i mikrostrukturni parametri sintetisanih i mlevenih kalcijum fosfatnih (CaP) materijala. Ramanska spektroskopija, kao komplementarna metoda rendgenskoj difrakcionoj analizi, upotrebljena je za ispitivanje početnog brušitnog materijala. Infracrvena spektroskopija sa Furijeovom transformacijom iskorišćena je za ispitivanje i praćenje toka promena faznog sastava tokom mlevenja. Adsorpciono-desorpciona metoda (BET) korišćena je za određivanje poroznosti materijala mlevenog 5,0 min, dok su morfološke karakteristike materijala i semikvantitativni sastav ispitane korišćenjem metodom skenirajuće elektronske mikroskopije sa energijsko disperzivnom analizom (SEM-EDS). Mezoporozni monetitski material dobijen je nakon 5,0 minuta mlevenja u vibracionom mlinu. Ovako dobijen material korišćen je za adsorpciju fosfatnog pesticida-malationa iz vodenog rastvora. Rezultati adsorpcije pokazali su da se malation može uspešno odstraniti iz vodenog rastvora korišćenjem monetita kao adsorbenta... In this doctoral dissertation the main goal was to examine the possibilities for obtaining monetite (CaHPO4) and nanospheric strontium carbonate hydroxyapatite [Sr10(PO4)6(OH)(2-2x)(CO3)x ] materials by using faster, easier and cost-effective methods for synthesis. Monetite (CaHPO4) material was obtained by milling previously synthesized brushite (CaHPO4∙2H2O), in a vibratory mill resulting in its phase transformation occures. The effect of the different time periods of milling treatment on the phase composition and microstructural parameters of the treated material was also examined. The mechanism of phase transformation brushite-monetite during short time milling (12.5 minutes in total) was also shown. It was found that after 5.0 minutes of milling monetite phase starts to form, after brushite-monetite phase transition. The X-Ray powder diffraction (XRPD) method was used to investigate microstructural and phase properties of synthesized and milled calcium phosphate (CaP) samples. Raman spectroscopy, as a complementary method to XRPD analysis was used to confirm the purity of synthesized initial brushite material. Fourier transformation infra red spectroscopy (FTIR) was used for investigation and monitoring of the phase composition changes during milling treatment. The adsorption-desorption method (BET) was used to determine the porosity of the material milled for 5,0 min., whereas the morphological characteristics and semiquantitative analysis of obtained materials was observed using the method of scanning electron microscopy with energy dispersive analysis (SEM-EDS). Monetite material with mesoporous properties was obtained after 5,0 minutes of milling in a vibratory mill. This material was further applied as adsorbent for adsorption of phosphate-pesticides i.e. malathion from aqueous solution...

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V doktorski disertaciji je obravnavan problem vpliva večosnega napetostnega stanja na začetek in potek superelastičnega področja pri spominski zlitini Ni-Ti. Za raziskovalno delo je bila uporabljena komercialno dostopna ortodontska žica Ni-Ti z vsebnostjo 50,6 at.%Ni. V prvem delu raziskav smo izvedli karakterizacijo izbranega materiala. Določili smo transformacijske temperature Ms, Mf, As, Af, module elastičnosti, napetosti in deformacije na začetku in koncu superlastičnega področja ter analizirali mikrostrukturo v izhodnem nedeformiranem stanju. Z in-situ merjenjem električnega upora med obremenjevanjem pri enoosnem nategu na napravi za simulacijo enoosnega napetostnega stanja smo potrdili uporabnost te metode za določitev prehoda v superelastično stanje oziroma za spremljanje napetostno inducirane martenzitne fazne transformacije. Na osnovi teh rezultatov smo v drugem delu raziskav razvili napravo za simulacijo večosnega napetostnega stanja z možnostjo in situ merjenja električne upornosti in mikrotrdote. Z upogibom, torzijo ter kombinacijo torzije in upogiba smo simulirali obremenitve, ki so prisotne pri ortodontskem zdravljenju. S sočasnim merjenjem električnega upora smo za ta večosna napetostna stanja določili prehod v superelastično področje. Z analizo mikrostruktur pred in po obremenitvah smo identificirali spremembe in postavili modele razvoja mikrostrukture za različna napetostna stanja. This doctoral thesis deals with the problem of the influence of the multi-axial stress state at the beginning and end of the superelastic plateau in the Shape Memory Alloy Ni-Ti. For our research work commercially available orthodontic wire Ni-Ti was used with a content of 50,6 at.% Ni. In the first part of the research we determined the characterization of the selected material. We determined the transformation temperatures Ms, Mf, As, Af, modulus of elasticity, stress and strain at the beginning and end of the superelastic plateau, and analysed the microstructure of the output un-deformed state. With in-situ measurement of the electrical resistance during uni-axial loading on the device we simulated a uniaxial stress state, which confirmed the usefulness of this method for determination of the transition into superelastic condition or accompanying the stress-induced martensitic phase transformations. Based on these results, in the second part of the research we developed a device to simulate the multi-axial stress state with the possibility of in-situ measurement of electrical resistance and microhardness. We simulated the bending, torsion and combined torsion and bending loads which are present in orthodontic treatment. The simultaneous measurement of electrical resistance for this multi-axial stress state was defined during the transition into the superelastic area. By analysing the microstructures before and after load changes were identified and an evolution model of microstructure was erected for different stress states.

U prvom dijelu ovog pregleda prikazali smo sličnosti i razlike između fiziološke i patološke biomineralizacije, tj. nastajanja kostiju i zubi, osteoartikulame i zubne patologije, te urolitijaze. Pojednostavljeno možemo ove procese smatrati taloženjem ionskih kristala iz otopina visoke ionske jakosti na i/ili unutar organske matrice. Prisutnost ili manjak promotora ili inhibitora kristalizacije u svim su slučajevima od izuzetne važnosti. Međutim, dok je fiziološka mineralizacija strogo biološki kontrolirana, urolitijaza je uglavnom kontrolirana fizičko-kemijskim faktorima kao sto su prezasićenost urina, pomanjkanje inhibitora kristalizacije i agregacije, itd. U drugom dijelu preglednog rada opisana su fizičko-kemijska istraživanja, izvedena zbog boljeg razumijevanja procesa biomineralizacije. Konstruirani su taložni dijagrami za sustave kalcij i magnezij fosfata, kalcij oksalata, mokraćne kiseline, te natrij i kalcij urata za slučaj taloženja iz otopina visoke ionske jakosti u biološki relevantnim uvjetima. Prikazan je generalni taložni dijagram kalcij fosfata sa granicom taloženja i granicom između područja, gdje kristali nastaju direktnim rastom i onim gdje nastaju putem transformacije prekusorske faze. Istraživanja kinetike taloženja prikazana su dijagramima, koje možemo interpretirati u smislu sukcesivnih ili paralelnih taložnih procesa, kao što su nukleacija, kristalni rast i agregacija. Kinetičkom studijom fazne transformacije amorfnog kalcij fosfata (ACP) u oktakalcij fosfat i/odn. apatit pokazali smo, da makromolekule, kao što su poli-L-glutamat i poli-L-lisin mogu imati dvostruko djelovanje, tj kada su prisutne u niskoj koncentraciji djeluju kao promotori, a u visokim koncentracijama kao inhibitori sekundarnog taloženja kristalne faze na površini amorfnih čestica. U trećem dijelu pregleda opisana su primijenjena interdisciplinarna istraživanja. Razrađene su tri kemijske metode za testiranje inhibitorskog potencijala nerazrijeđenog urina. Metode su jednostavne i pogodne su za primjenu u kliničkim laboratorijima za razlikovanje urina pacijanata s urolitijazom od urina zdravih osoba. U posljednje vrijeme pripremljene su nove vrste organsko - anorganskih kompozita. kao presvlake za bioinertne metalne implante. Postupak pripreme uključuje „in situ” rast kristala kalcij fosfata unutar organsko - anorganske matrice (anorganska komponenta je ACP), koja je ranije adsorbirana na metalnu površinu. Tako pripremljene presvlake čvrsto prianjaju uz površinu supstrata i imaju izvrsna biološka svojstva, što smo provjerili „in vitro” i „in vivo” biološkim testovima., In the first part of this review similarities and differences between physiological and pathological biomineralization (bone and tooth formation, osteoarticular and tooth pathologies, urolithiasis) are discussed. Both processes may be seen as the deposition of ionic crystals from high ionic strength solutions upon / within a preformed organic matrix and the presence or deficiency of crystallization promoters or inhibitors plays a decisive role. However, while physiological mineralization is strictly biologically controlled, urolithiasis is more likely driven by physicochemical factors, such as urinary supersaturation and lack of inhibitors of crystallization and aggregation. In the second part of the review physicochemical research, performed to facilitate understanding ot biomineralization processes is described. It comprises precipitation diagrams for calcium and magnesium phosphates, calcium oxalates, uric acid, sodium and calcium urates, precipitating from high ionic strength solutions at biologically relevant conditions. Here we present a general precipitation diagram of the calcium phosphate system, in which the precipitation boundary and the boundary between the regions of direct crystallization and crystallization via precursor phases are defined by the mean ion activity products and the pH. Kinetic diagrams of spontaneously precipitating systems are represented, which may be interpreted in terms of subsequent or parallel precipitation processes, such as nucleation, crystal growth and aggregation. The dual role of macromolecules, poly-L-glutamate and poly-L-lysine, as crystallization promoters and/or inhibitors is demonstrated by a kinetic study of the phase transformation of amorphous calcium phosphate, ACP, into octacalcium phosphate and/or apatite. It is shown that the polyelectrolytes at low concentrations induce and at higher concentrations inhibit secondary precipitation of the crystalline phase. In the third part of the review applied interdisciplinary research is described. Three chemical methods for testing the inhibitory potential of whole urine were developed. The methods are simple and can be used in a clinical laboratory for discrimination between urines of calcium stone formers and healthy persons. Furthermore a new class of biomimetic organic inorganic composites, as coatings for bioinert metal implants was recently developed. The coating procedure involves “in situ’ growth of calcium phosphate crystals within an organic - inorganic matrix, the inorganic part being ACP. The coatings are tightly anchored to the substrate and exhibit excellent biological properties as verified by in vitro testing and animal experiments.

Kinetika kristalizacije i fazna transformacija amorfnog Al78W22 tankog filma promatrana je kontinuiranim in situ mjerenjemm električnog otpora pod izotermnim i neizotermnim (izokronim) uvjetima....