In the frame of realization of the research projects at the Division of Materials Science a significant contributions to the fundamental knowledge in chemistry and physics have been made in the year 2003.
Investigation of the influence of the source of silicon on chemical composition of amorphous aluminosilicate gels have shown that the distribution of Na, Si and Al between the solid phase (supernatant) and the amorphous gel as well as the degree of polycondensation of silicates in supernatant depend on the choice of the silicon source. A controlled high-temperature treatment of ammonium form of zeolites A and X resulted in the formation of a mixture of mullite and amorphous silicon dioxide. Heating of the products of the high-temperature treatment of ammonium form of zeolite A in a NaOH solution causes extraction of the amorphous silicon dioxide from the interior of each single particle which results in the formation of mullite micro-vessels. "Memory" effect of amorphous aluminosilicate gels (precursors for zeolite synthesis), which means that the size distribution of zeolite crystals in the product of crystallization depends exclusively on the number and distribution of nuclei in the gel matrix (previously evidenced by the simulation of crystallization processes under different conditions), is proved experimentally by the analysis of the data obtained during crystallization of zeolites under different conditions.
A special attention is given to the study of biomineralization. In this connection, the study of interaction between the solid phase and the synthetic and natural macromolecules is anticipated. In order to remove Cd2+ ions, incorporated in calcium sulphate anhydrite (AH) as an impurity, the liquid membrane (LM) extraction was used. This extraction was realized during the processes of solution-mediated transformation (recrystallization) of cadmium-contaminated unstable AH into the stable calcium sulphate dihydrate (DH). No cadmium was found incorporated in the stable DH phase after the selective extraction. The mechanism of Cd2+ transport through the membrane was proposed. The study of influence of the initial precipitation conditions on the transformation of magnesium ammonium phosphate hexahydrate (struvite) into magnesium phosphate trihydrate (newberyite) has been continued. Besides, the study of the effects that inorganic anions, as well as synthetic and natural polypeptides have on the morphological and chemical properties of calcium carbonate polymorphs have also been continued.
The nanostructured materials with specific magnetic, magneto-optical, electrochromatic, ferroelectric or catalytic properties were investigated. A specific attention was focused to sol-gel synthesis of nanoparticles of metal oxides. Nanomaterials science is a new rapidly expanding area of materials research, which is devoted to understanding changes in fundamental material properties as a function of particle size. Sol-gel method was used in the synthesis of V2O5 and TiO2 nanoparticles. The method of low-frequency Raman scattering was used to determine the nanoparticles size distribution. The naometric TiO2-Fe particles were used in a study of photokilling of squamous cancerogene cells, in vitro. The aim of these experiments was to establish the mechanism of killing of squamous cancerogene cells by photoactivation of nanoparticles of specific metal oxide. The kinetics and mechanism of the formation of ZnO particles in aqueous media were also investigated. Formation of IrO2 and Ir by thermal decomposition of Ir(III)-acetylacetonate and IrO2 from amorphous iridium(IV)-oxide dihydrate has been investigated by XRD, thermal analysis, FT-IR and laser Raman spectroscopy. IrO2 is metal-like electrical conductor, and due to this property, as well as well a high temperature stability, the engineers believe that it will replace gold conductors in advanced computer technology. The chemical reactions between hematite and starch were also investigated. The investigation of the synthesis, properties and polymorphic transformations of ZrO2 and HfO2 was continued.
The characterization of physicochemical effects of ionizing radiations in various model and real systems has been continued. The reactions of free radicals were investigated by both fast technique of laser flash photolysis and a stationary technique by measuring stable products. The rate constant of the reaction between tert-butoxyl radical and ferrous ion, already measured by us, was checked in non-aqueous solvent, which is a model situation for naturally important iron induced reaction of lipid peroxidation. In order to follow oxidation via stable products, the visualization of these products is important. An optoelectronic reader of the personal chemical accident dosimeter, which was developed in our Laboratory, has been presented. The importance of dosimetry in radiation protection was illustrated by measuring the efficacy of the breasts protection in computerized tomography of the head. The characterization of thermoluminescence dosimeters was extended to new thermoluminescent detector based on lithium borate, high sensitivity lithium fluoride and aluminium oxide, as well as to the radiation field of the proton beam contaminated with X-radiation. The application of thermoluminescence dosimetry to environmental radiation monitoring was reviewed. Microbiological decontamination of raw materials and products of the cosmetics industry was investigated.
Investigations of (i) reaction mechanisms of crosslinking, degradation and stabilization with additives and radiation grafting of unsaturated polyester resins and plastomers (ii) the effect of modifiers, kompatibilization conditions and irradiation on structure-properties relationship of polymer blends and (nano)composites with aim of end-use properties optimisation, (iii) kompatibilization effects of block-, graft copolymers and nanocharacteristics of alternirnating copolimers and (iv) polyelectrolites were performed. The development of new investigation methods of polymer materials for solution specific problems of small and medium enterprises.
The investigation of influences of irradiation on mechanical properties of polypropylene/talc composites as a function of modifier used and its content showed that talc reduces the effects of irradiation.
The research programme also included synthesis and characterisation of new intermetallic compounds and metal oxides. The aim of these investigations is to select new materials for potential use for energetic and catalytic purposes. A review of results on crystal structure and hydrogen sorption properties of new alloys of the composition RENi5-xAlx (RE = Gd, Tb, Dy, Ho, Er and Y) was made. In all systems the binary prototype structure of the (CaCu5 type is preserved up to x=2, while beyond this composition a transformation into the YCo3Ga2 structure type occurs. The systems RENi4,5Al0,5-hydrogen (RE=Tb, Y) and RENi4Al-hydrogen (RE=Gd, Tb, Y, Dy, Ho) might be selected as suitable materials for hydrogen storage purposes. The high-temperature oxidation of the Zr-3mass% Cu alloy and Zr2Cu in oxygen is characterized by selective oxidation of zirconium while the excess of copper is accumulated at the alloy-oxide interface forming the Zr8Cu5 phase. The reaction kinetics obeys a parabolic rate law. In the theoretical part of research the electronic structure of intermetallic compounds DyNi4,67Al0,33, DyNi4,5Al0,5, DyNi4Al and DyNi3Al2 of the system DyNi5-xAlx was carried out. The TB-LMTO-ASA method (tight-binding version of the linear muffin-tin orbital method within the atomic sphere approximation) was used.
In the frame of present programme different procedures for the preparation of new inorganic systems are being developed and structural, spectroscopic and magnetic properties of the new compounds have been investigated. This is, in particular, related to the hexanuclear halide clusters of Nb, Ta, Mo and W and also to polynuclear complex compounds of different transition metals like iron, cobalt or nickel, that could possess interesting magnetic properties and serve as potential new magnetic materials.
Reactions of hexanuclear halide clusters of molybdenum and tungsten, M6X12 = [M6(µ3-X)8X2(µ-X)4/2], with methoxide ions have been investigated. It has been found that a selective substitution of the halogen atoms by methoxo groups is possible. Two series of polymeric methoxo clusters have been prepared, the one containing methoxo groups as bridges between neighbouring cluster units, and the other having both, bridging and terminal methoxo groups at the same time. The investigation of the reactions between the hexanuclear tantalum clusters [Ta6X12(ROH)6]X2 (X = Cl, Br; R = CH3, C2H5) and organic halide cations, R4NX, has been continued. Crystal structures, electronic and magnetic properties of the two cluster compounds, [Ta6Cl12(CH3OH)6]Br3 and [Ta6Cl12(CH3OH)6]Br3 •4H2O, containing the paramagnetic [Ta6Cl12]3+ unit, have been correlated. As the first step in the efforts to synthesize high-spin polynuclear molecule-based magnetic compounds the new crystalline solids [M(bpy)3]2[NbO(C2O4)3]Cl•nH2O (M = Fe2+, Co2+, Ni2+; bpy = 2,2'-bipyridine) have been prepared.
One of the aims of this research programme is to achieve a new knowledge about the changes of structure and physical properties of some technically interesting materials, which can be caused by introducing of metal dopands into the structure of the starting materials. Special attention is paid to determination of the metal oxidation state and position in the structure, and to determination of the oxygen deficiency. The mechanism of antimony incorporation into cassiterite (SnO2) was investigated as to elucidate the change in electrical conductivity caused by Sb doping. Nanocrystalline Sb-doped SnO2 samples (0-14 at% Sb) were prepared using a sol-gel technique followed by hydrothermal treatment. XRD showed that unit-cell parameters of the annealed samples decreased, which suggested that oxidation of the Sb3+ ion took place in the annealing process. 121Sb-Mössbauer spectroscopy confirmed that Sb3+/Sb5+ content ratio in the samples decreased upon annealing. In the scope of structural studies of mullite (3Al2O3•2SiO2) a correlation of the precursors type on microstructure of sol-gel derived mullite was investigated. Mullite samples were prepared using a sol-gel technique followed by thermal treatment of the precursors. Al(NO3)3∙9H2O, γ-Al2O3 or γ-AlOOH were used as the alumina source for precursors and tetraethylsilane (TEOS) as the silica source. It was evidenced that in the mullite formation process from diphasic gels, mullite with approximate 2:1 composition (2Al2O3•SiO2) crystallizes at ~1200 °C which subsequently converts into 3:2(3Al2O3•2SiO2) at higher temperatures. This process is faster for the precursors containing smaller particles. For mullite samples which contained 0-8 mol% Cr2O3 (derived from Al(NO3)3∙9H2O, Cr(NO3)3∙9H2O and TEOS), the crystal structure was solved by the Rietveld method. It was found that Cr3+ ions mainly substitute for Al3+ in the AlO6 octahedra, and in a small amount occupy interstitial sites along the c-axis of the mullite structure. Above the doping level of 7 mol% Cr2O3 the second phase appeared in the system, namely (Al,Cr)2O3. Group for ichtiopathology-biological materials joined to the Division of Materials Chemistry in May 2003. Up to the end of the year the Group was equipped, and established a well-functioning laboratory within the DMC, started scientific and professional activities according to its new program. The Group completed and submitted a STIRP project: Authorized Diagnostic Center for Diseases of Fish, Shellfish and Crustaceans; developed a business plan for the World Bank: Authorized Diagnostic Center for Aquatic Organisms Diseases, which was evaluated as one of the 4 pilot-projects of the Bank within the RBI (TAL Project).
Within existing scientific project “Biochemical and Molecular Reaction of Fish to the Ecosystem Status”, the Group worked on biochemical and molecular research through qualitative and quantitative changes on subcellular and extracellular level of assayed fish.
Very important results were obtained during the realization of two technological projects (HITRA). The scope of first project is application of the Rietveld method in quality control of the aluminate cement clinker. The procedure will enable fast and nondestructive phase and structural analysis of the clinker. The aim of second technological project is to develop a procedure for preparation of precipitated calcium carbonate (PCC), in which, by using kinetic, thermodynamic and hydrodynamic factors and by changing process parameters, the physico-chemical properties of precipitate are controlled. The basic precipitation components will be lime and carbon dioxide. The initial investigations are anticipated to be held at the laboratory scale. In the final phase of the project, the introduction of automation in the process and, if possible, the development of a continuous process is anticipated.
PROCESI I INTERAKCIJE U HETEROGENIM SUSTAVIMA ČVRSTO/TEKUĆE, Ljerka Brečević, voditelj projekta
SINTEZA I MIKROSTRUKTURA METALNIH OKSIDA I OKSIDNIH STAKALA, Svetozar Musić, voditelj projekta
FIZIČKO-KEMIJSKI UČINCI IONIZIRAJUĆIH ZRAČENJA, Dušan Ražem, voditelj projekta
SINTEZA, KARAKTERIZACIJA I MODIFICIRANJE POLIMERA ZRAČENJEM, Franjo Ranogajec, voditelj projekta
INTERMETALNI SPOJEVI I METALNI HIDRIDI, Želimir Blažina, voditelj projekta
SUPRAVODLJIVI OKSIDI I VIŠENUKLEARNI METALNI KOMPLEKSI, Nevenka Brničević, voditelj projekta
UTJECAJ DOPANADA NA STRUKTURU I SVOJSTVA MATERIJALA ZA TEHNIČKE PRIMJENE, Biserka Gržeta, voditelj projekta
BIOKEMIJSKA I MOLEKULARNA REAKCIJA RIBA NA STANJE EKOSUSTAVA, Rozelinda Čož-Rakovac, voditelj projekta
RAZVOJ ADAPTIVNOG TEHNOLOŠKOG POSTUPKA PRIPRAVE TALOŽNOG KALCIJEVA KARBONATA, Damir Kralj, voditelj projekta
KARAKTERIZACIJA ALUMINATNOG CEMENTNOG KLINKERA POMOĆU RIETVELDOVE METODE, Biserka Gržeta, voditelj projekta
ISTRAŽIVANJE PROCESA KRISTALIZACIJE I PRIMJENE ZEOLITA
RESEARCH OF THE CRYSTALLIZATION PROCESS AND USE OF THE ZEOLITES Voditelj/ica projekta: dr. sc. Boris Subotić
Tel. ++385 1 4680 123 e-mail: firstname.lastname@example.org
Suradnici na projektu: Tatjana Antonić Jelić, doktorica kem. znanosti, znanstvena suradnica
Biserka Biškup, doktorica kem. znanosti, viša asistentica
Sanja Bosnar, doktorica kem. znanosti, viša asistentica
Josip Bronić, doktor kem. znanosti, znanstveni suradnik
Cleo Kosanović, doktorica kem. znanosti, znanstvena suradnica
Ivan Krznarić, doktor kem. znanosti, znanstveni suradnik
Ana Mužic, dipl. inž. kemije, znanstvena novakinja
Boris Subotić, doktor kem. znanosti, znanstveni savjetnik
Tehnički suradnici: Višnjica Dekanić
Program rada i rezultati na projektu:
Istraživanje utjecaja izvora silikata na kemijski sastav amorfnih alumosilikatnih gelova je pokazlo da raspodjela Na, Al i Si između tekuće faze (matičnice) i amorfnog gela kao i stupanj polikondenzacije silikata u matičnici ne ovise o izboru izvora silikata. Opažene razlike u strukturnim i čestičnim svojstvima produkata (zeolita) kristaliziranih uporabom različitih izvora silikata objašnjeni su na temelju kritičnih procesa kristalizacije zeolita (otapanje gela, nukleacija i rast kristala zeolita).
Kontroliranom visokotemperaturnom obradom amonijeve forme zeolita A i X nastaje smjesa mulita i amornog silicij dioksida. Zagrijavanje produkta visokotemperaturne obrade amonijeve forme zeolita A u otopini NaOH dovodi do ekstrakcije amorfnog silicij dioksida iz unutrašnjosti svake pojedinačne čestice i nastajanja mulitnih mikroposudica.
Učinak «pamćenja» amorfnih alumosilikatnih gelova (prekursora sinteze zeolita), naime da raspodjela veličine kristala zeolita u produktu kristalizacije ovisi isključivo o broju i raspodjeli nukleusa u matrici gela (prethodno pokazan simulacijom procesa kristalizacije u različitim uvjetima), eksperimentalno je dokazan analizom podataka dobivenih tijekom kristalizacije zeolita u različitim uvjetima.
Research programme and results:
Investigation of the influence of the source of silicon on chemical composition of amorphous aluminosilicate gels have shown that the distribution of Na, Si and Al between the solid phase (supernatant) and the amorphous gel as well as the degree of polycondensation of silicates in supernatant depend on the choice of the silicon source. Observed differences in the structural and particulate properties of the products (zeolites) crystallized by use of different silicon sources are explained on the basis of critical processes of crystallization of zeolites (dissolution of gel, nucleation and crystal growth of zeolites).
A controlled high-temperature treatment of ammonium form of zeolites A and X results in the formation of a mixture of mullite and amorphous silicon dioxide. Heating of the products of the high-temperature treatment of ammonium form of zeolite A in a NaOH solution causes extraction of the amorphous silicon dioxide from the interior of each single particle which results in the formation of mullite micro-vessels.
«Memory» effect of amorphous aluminosilicate gels (precursors for zeolite synthesis), namely that the size distribution of zeolite crystals in the product of crystallization depends exclusively on the number and distribution of nuclei in the gel matrix (previously evidenced by the simulation of crystallization processes under different conditions), is proved experimentally by the analysis of the data obtained during crystallization of zeolites under different conditions.
PROCESI I INTERAKCIJE U HETEROGENIM SUSTAVIMA ČVRSTO/TEKUĆE
PROCESSES AND INTERACTIONS IN HETEROGENEOUS SOLID/LIQUID SYSTEMS Voditelj/ica projekta: dr. sc. Ljerka Brečević
Osnovni je cilj predloženih istraživanja, doći do novih spoznaja o uvjetima nastajanja termodinamički nestabilnih i stabilnih čvrstih faza iz prezasićenih elektrolitnih otopina te o njihovim fizikalno-kemijskim svojstvima. Isto je tako cilj saznati, što je moguće više o mehanizmima interakcija tih čvrstih faza sa stranim ionima i molekulama te o kinetikama i mehanizmima procesa koji u tome sudjeluju. Također je svrha, istraživanjem dobro definiranih modelnih sustava, doći do novih i proširiti već postojeće temeljne spoznaje o mehanizmima procesa taloženja, što se posebno odnosi na teško i umjereno topljive ionske soli, interesantne u brojnim područjima ljudskog interesa (na pr. tehnologiji, ekologiji, geologiji, medicini,...) s posebnim naglaskom na proučavanje biomineralizacije. S tim su u svezi predviđena istraživanja interakcije čvrste faze sa sintetičkim i prirodnim makromolekulama.
Slijedom toga, u protekloj su godini dana obavljana slijedeća istraživanja:
Kako bi odstranili Cd2+ ione ugrađene kao nečistoće u bezvodni kalcijev sulfat (AH), primjenjena je tehnika ekstrakcije tekućim membranama (TM). Ekstrakcija je provedena tijekom procesa transformacije (rekristalizacije) nestabilnog AH, kontaminiranog kadmijem, u stabilni kalcijev sulfat dihidrat (DH). Pri tome je iskorištena već ranije utvrđena činjenica, da se taj proces zbiva putom otopine, t.j. otapanjem termodinamički nestabilne i taloženjem stabilne čvrste faze. Primjenjeni su ekstraktanti (tridodecilamin – Alamin 304 i trioctilamin – Alamin 336), koji selektivno prenose Cd2+ u odnosu na Ca2+, pri čemu je kao otapalo upotrijebljen kerozin. TM je priređena u obliku t.zv. "bulk" tekuće membrane (BTM), budući da se ta konfiguracija pokazala najprikladnijom u obradi suspenzije kalcijeva sulfata. Nakon tako provedene selektivne ekstrakcije, nije nađeno ugrađenog kadmija u stabilnom DH. Osim toga, predložen je mehanizam transporta Cd2+ kroz tekuću membranu.
Nastavljena su istraživanja utjecaja početnih uvjeta taloženja na transformaciju magnezijeva amonijeva fosfata heksahidrata (struvit) u magnezijev fosfat trihidrat (njuberit). Također su nastavljena proučavanja učinka anorganskih aniona te sintetičkih i prirodnih polipeptida na morfološka i kemijska svojstva polimorfa kalcijeva karbonata.
Research programme and results:
The basis of the investigations proposed is to gain new knowledge about the factors influencing the formation and physical-chemical properties of thermodynamically metastable and stable solid phases from the supersaturated electrolyte solutions. Likewise, the goal is to learn as much as possible about the mechanisms of interaction between these solid phases and the foreign ions and molecules, and about the kinetics and mechanisms of the processes involved. The purpose of this project is to acquire new and to extend the existing basic knowledge about the mechanisms of precipitation processes of sparingly and moderately soluble salts interesting in different fields of human scopes (e.g. technology, ecology, geology, medicine, etc.), by studying well defined model systems. A special attention is given to the study of biomineralization. In this connection, the study of interaction between the solid phase and the synthetic and natural macromolecules is anticipated.
In the frame of realization of this project, the following subjects were studied during the past period of a year:
In order to remove Cd2+ ions, incorporated in calcium sulphate anhydrite (AH) as an impurity, the liquid membrane (LM) extraction was used. This extraction was realized during the processes of solution-mediated transformation (recrystallization) of cadmium-contaminated unstable AH into the stable calcium sulphate dihydrate (DH). The extractants that transport Cd2+ selectively over Ca2+ ions (tridodecylamine – Alamine 304 and trioctylamine – Alamine 336), diluted in the appropriate organic solvent (kerosene), were applied. Liquid membrane was designed in a form of the so-called bulk liquid membrane (BLM), which was found to be the most suitable configuration for the treatment of calcium sulphate suspension. No cadmium was found incorporated in the stable DH phase after the selective extraction. The mechanism of Cd2+ transport through the membrane was proposed.
The study of influence of the initial precipitation conditions on the transformation of magnesium ammonium phosphate hexahydrate (struvite) into magnesium phosphate trihydrate (newberyite) has been continued. Besides, the study of the effects that inorganic anions, as well as synthetic and natural polypeptides have on the morphological and chemical properties of calcium carbonate polymorphs have also been continued.