Biomaterijali na bazi titana Magdalena Jajčinović; Ljerka Slokar Benić
Kemija u industriji; časopis kemičara i tehnologa Jugoslavije,
07/2023, Letnik:
72, Številka:
7-8
Journal Article
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U odnosu na legure na bazi kobalt-kroma i nehrđajuće čelike, titan i legure na bazi titana našle su široku primjenu u biomedicini, gdje se zbog svojih izvrsnih svojstava upotrebljavaju kao ...implantati, ali zbog visoke cijene njihove proizvodnje još uvijek nemaju širu upotrebu. Neka od bitnih svojstava su: izvrsna biokompatibilnost, dobra mehanička svojstva i oseointegracija te otpornost na koroziju. Uz predstavljanje biomedicinskih materijala koji se najčešće upotrebljavaju, ovaj članak prikazuje razvoj biomaterijala na bazi titana i njihovu biomedicinsku primjenu. Biomaterijali se obično upotrebljavaju u biomedicini za popravak, zamjenu ili regeneraciju tjelesnih tkiva. S obzirom na to da je poznat sve veći broj neuspjelih implantacija uzrokovanih patogenom bakterijskom infekcijom, među funkcijama koje bi se mogle dodati biomaterijalima je antibakterijsko djelovanje, koje je od velike važnosti. U novije vrijeme antibakterijske metalne legure pokazale su velik potencijal kao nova vrsta biomedicinskog materijala.
U ovom pregledu prikazan je dio znanstvenih istraživanja pri razvoju legura s prisjetljivošću oblika (engl. Shape Memory Alloy, SMA) na bazi bakra na Metalurškom fakultetu Sveučilišta u Zagrebu u ...razdoblju od 2006. do 2022. godine u suradnji s brojnim visokoškolskim i znanstvenim institucijama u regiji. Istraživane su sljedeće legure SMA: CuAlNi, CuAlMn, itd. Provedeno je fizikalno modeliranje uključujući numeričku simulaciju razvoja mikrostrukture i toplinsku analizu tih legura. Legure SMA rađene su u lučnoj, visokofrekventnoj i indukcijskim pećima pomoću tri različite tehnologije lijevanja: brzo skrućivanje, lijevanje u metalne i/ili grafitne kokile te kontinuirano lijevanje u šipke. Nakon toga odabrane legure su toplo i hladno valjane. Provedena je toplinska obrada (austenitizacija uz naknadno gašenje u vodi i žarenje) i karakterizacija funkcionalnih svojstava legura SMA u različitim stanjima. Za karakterizaciju, osim ispitivanja mehaničkih svojstava, primijenjene su brojne visokosofisticirane metode: optička mikroskopija (OM), pretražna (SEM) i transmisijska elektronska mikroskopija (TEM), energetsko disperzijska-spektroskopija (EDS), pretražna diferencijalna kalorimetrija (DSC), dinamičko-mehanička analiza (DMA), rendgenska difrakcija (XRD), elektrokemijska impedancijska spektroskopija (EIS) itd. Već pri lijevanju kod pojedinih legura SMA, a posebice nakon toplinske obrade austenitizacijom uz naknadno gašenje u vodi, utvrđena je martenzitna mikrostruktura koja je osnovni preduvjet za svojstvo prisjetljivosti oblika. Na temelju provedenih istraživanja po većini parametara (plastičnost, korozijska otpornost itd.) može se zaključiti da su se najbolje pokazale legure CuAlMn.
Kao rezultat provedenih istraživanja na legurama SMA, prema podatcima iz baze CROSBI (na dan 23. prosinca 2022.), istraživački tim objavio je 33 rada u časopisima (od kojih su 23 rada u časopisima indeksiranim u bazi podataka Web of Science), 74 rada u zbornicima međunarodnih konferencija, 18 sažetaka u zbornicima konferencija te pet ostalih radova. Također, obranjena je jedna doktorska disertacija te je izrađeno i obranjeno 12 završnih i 25 diplomskih radova u području tehničkih znanosti iz znanstvenih polja metalurgije i kemijskog inženjerstva.
Cilj: Ispitati kako uporaba probiotskih preparata utječe na korozijsku stabilnost ortodontskih žičanih lukova nikal-titanijeve legure (NiTi). Materijal i metode: Testirani su NiTi lukovi dimenzija ...0,508 × 0,508 mm i duljine 2,5 cm, te (sastav Ni = 50,4 %; Ti = 49,6 %) neobložene, nitrirane i rodirane površine. Površinska mikrogeometrija istraživana je skenirajućim elektronskim mikroskopom pri povećanju od 1000 puta, a površinska hrapavost mjerena je profilometrom te izražena u sljedećim vrijednostima: prosječna hrapavost, maksimalna visina i maksimalna dubina hrapavosti. Vrsta i dinamika korozije ispitani su elektrokemijskom metodom cikličke polarizacije. Rezultati: Legura rodirane površine u slini ima značajno veću opću koroziju od nitirirane i neobložene, uz veliku snagu efekta (p = 0,027; η2 = 0,700). Probiotski preparat povećava opću i lokaliziranu koroziju rodirane žice i malo manjuje opću, te povećava lokaliziranu koroziju neobložene žice, a u slučaju nitrirane žice vrlo je mala mogućnost od pojave korozije. Razlike u površinskoj hrapavosti između nikal-titanijevih žica prije korozije nisu značajne. Izloženost umjetnoj slini smanjuje prosječnu hrapavost rodiranih žica (p = 0,015; η2 = 0,501). Medij ne utječe znatno na površinsku mikrogeometriju nitriranih i neobloženih žica. Zaključak:
Probiotski preparat utječe na opću i lokaliziranu koroziju, ovisno o vrsti nikal-titanijeve obloge. Povećava opću koroziju rodirane žice te uzrokuje pojavu lokalizirane korozije neobložene i rodirane žice. Probiotski preparat nema značajan utjecaj na površinsku hrapavost, osim utjecaja same sline.
In this work, the main aim was to determine the effect of Mg addition on the crystallization kinetics and microstructure of Zn-10Al-1Cu alloy. The effectiveness of magnesium addition was detected on ...the basis of microstructure morphology investigations and changes occurring in the cooling curves of the investigated alloys. To describe the phenomena that occurred in the material during solidification under various conditions caused by a change in the chemical composition as a result of the appliance of modifiers, it was decided to use methods of thermal derivative analysis, allowing to effectively and accurately describe the crystallization kinetics of the tested materials. The scientific goal of the presented work was examination of the impact of magnesium addition and effect of the crystallization kinetics on the examined alloys. Determining the relationship between the changes in the derivative curve and the related microstructure, the influence of modifiers addition was analysed. The addition of Mg caused a shift of the solidification temperature values of phases and eutectics and monotectoid transformation (???) to lower temperature values, as well as the change of the morphology of the occurring eutectic ??+?.
In the present study, the corrosion mechanism of commercial FeCrAl alloy (Kanthal AF) during annealing in nitrogen gas (4.6) at 900?C and 1200?C is outlined. Isothermal and thermo-cyclic tests with ...varying total exposure times, heating rates, and annealing temperatures were performed. Oxidation test in air and nitrogen gas were carried out by thermogravimetric analysis. The microstructure is characterized by scanning electron microscopy (SEM-EDX), Auger electron spectroscopy (AES), and focused ion beam (FIB-EDX) analysis. The results show that the progression of corrosion takes place through the formation of localized subsurface nitridation regions, composed of AlN phase particles, which reduces the aluminum activity and causes embrittlement and spallation. The processes of Al-nitride formation and Al-oxide scale growth depend on annealing temperature and heating rate. It was found that nitridation of the FeCrAl alloy is a faster process than oxidation during annealing in a nitrogen gas with low oxygen partial pressure and represents the main cause of alloy degradation.
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Differential Scanning Calorimetry (DSC) was applied to determine the critical temperatures of phase transformations in the Gd40Ti30Zr30 alloy (wt%). The comparative measurements were carried out ...using three types of measuring devices at a temperature RT- 1650?C in the same flowing gas (Ar, 99.9992%) but applying different testing procedures, which allowed obtaining dissimilar oxygen contents in the surrounding atmosphere. The high temperature interaction and reactivity taking place between molten alloy samples and ZrO2 container during DSC tests were evaluated by structural analysis of the resulting interfaces using alloy samples solidified inside the ZrO2 containers. The conducted research has demonstrated methodological difficulties accompanying measurements of the thermophysical properties of Gd-rich alloys by the container-assisted DSC method, particularly when the tests are performed in flowing argon atmosphere with significantly reduced oxygen content. Under non-oxidizing conditions, the degradation of ZrO2 container can take place during DSC testing because the selected Gd40Ti30Zr30 alloy reacts with the ZrO2 to form a continuous interfacial reaction product layer. Under slightly oxidizing conditions, the gadolinium oxide formed in situ on the alloy surface, plays the role of a barrier for direct contact between molten alloy and container and thus may suppress or even prevent the degradation of the container and its subsequent strong bonding with the holder.
This paper presents the measurement of the Ab initio molecular dynamics of a Zn-Al-Fe alloy system. The structural and electronic properties of the Zn-Al-Fe alloy at different temperatures are ...simulated, and the partial density of states, radial distribution function, coordination number, mean square displacement, and diffusion coefficient are obtained. It provides a theoretical analysis of the vacuum separation of Zn-Al-Fe alloys. The simulation results show that when the temperature was 1073 K, the disorder degree of the system was the largest, the diffusion coefficient was 1.29?10?8m2s?1), and the coordination number was 9.48. It means that the Zn-Al-Fe alloy can be separated into its constituent metals easily by vacuum distillation, and that the optimum temperature to achieve this is 1073 K.
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A systematic study of the stacking fault energy (?SF) for the dilute Al-based alloys (Al23X, Al47X and Al71X, where X = Al, Ag, Be, Ca, Cd, Co, Cu, Cr, Fe, Ga, Ge, Hf, In, K, La, Li, Mn, Mg, Ni, Na, ...Pb, Sc, Sn, Sr, Si, Ti, V, Zn, and Zr) has been performed by means of first-principles calculations. Alias shear deformation is adopted in the present investigations. The presently calculated ?SF for Al is in favorable accordance with experimental and other theoretical data. For the targeted elements, the calculations indicate that Na, Si, K, Ca, Sc, Ga, Ge, Sr, Zr, In, Sn, La, Hf, and Pb, in any concentration we considered, decrease the ?SF of Al, while Ag, Be, Cd, Co, Cu, Cr, Fe, Li, Mn, Mg, Ni, Ti, V, and Zn increase the ?SF of Al, when the concentration of alloying elements is 1.39 at. % in the system. With increasing concentration of alloying elements, Li, Mg, V, Ti, and Cd change from increasing the ?SF of Al to decreasing it, based on present investigations. Among the alloying elements, which decrease the ?SF of Al, La decreases the ?SF most significantly. It is also found that the ?SF of Al-X generally decreases with the increase of equilibrium volume. The results obtained in the present work provide an insight into the design of Al based alloys.
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Experimental studies of the Cu-Sb-Sn and Ni-Sb-Sn systems have been carried out by the wetting tests, followed by the analysis of the microstructural evolution occurring at the interface between the ...liquid alloy and solid substrate. The wetting experiments on the Sb30Sn70 / (Cu, Ni) and Sb38.4Sn61.6 / (Cu, Ni) systems have been performed by using a sessile drop apparatus. The wetting behaviour of the two alloys in contact with Cu-substrate differs from that observed in the case of Ni-substrate. The Sb-Sn alloy / substrate interface was characterised by SEM-EDS analyses. For each system, the solidliquid interactions and the phases formed at the interface were studied with the help of the corresponding phase diagrams.
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To efficiently extract nickel from low grade limonitic laterite ore, a separation method of iron-nickel alloy nugget by selfreduction of coal composite limonitic laterite ore briquette was ...investigated. In this investigation, in order to decrease the separation temperature of iron-nickel alloy nugget, the selective reduction by control of C/O ratio was introduced and reductant added in the briquette was inadequate for the reduction of nickel and iron. Nickel was preferentially reduced in the reduction process, while iron was partially reduced due to the lack of reductant. After reduction, a certain amount of FeO existed in the reduced product. This residual FeO had a great role in the formation of low melting point slag, which could promote the formation and the separation of iron-nickel alloy nugget at relatively low temperature. In this investigation, the reduction experiments were all conducted at 1300?C. To evaluate the formation and the separation of iron-nickel alloy nugget in the reduction process, we observed the patterns of reduced products under different C/O ratio, CaO addition ratio and holding time conditions. And then the effect of C/O ratio and CaO addition ratio on nickel content of nugget and nickel recovery ratio were investigated. The results showed that 0.7 of C/O ratio, 8% of CaO addition ratio and 40min of holding time were suitable for the separation of iron-nickel alloy nugget from limonitic laterite ore. Nickel and iron content of the nugget and the nickel recovery ratio were 4.75%, 89.51% and 85%, respectively. Nuggets were easily separated from slag by crushing and screening. This separation method could be applied to any limonitic laterite ore by adjusting C/O ratio and CaO addition ratio.
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