BULGARIAN ACADEMY OF SCIENCES
CENTRAL LABORATORY
OF MINERALOGY AND CRYSTALLOGRAPHY
ANNUAL REPORT
No 6/2000
| Editor: Dr. Nikola Zidarov; E-mail: nzidarov@interbgc.com |
| © Central Laboratory of Mineralogy and Crystallography, 2001 | ISSN 3033-2206 |
CONTENTS
Project No 2, 16, 23 are financially supported in part by the Bulgarian National Science Fund of the Ministry of Education and Science.
This annual report presents the activities of the Central Laboratory of Mineralogy and Crystallography during the sixth year of its existence.
The topics developed were in accordance with the preliminary specified scientific and applied priorities. The most significant scientific results, published or reported at conferences, can be grouped as follows:
During 2000 our main attempts were aimed at relocation and arrangement of the facilities of CLMK in a another building. Following our reconstruction projects a total renovation of the new building of CLMK in the complex of the Bulgarian Academy of Science was accomplished. The financing of this reconstruction was supplied by the Sofia District Council, BAS, and CLMK. The main building and the reconstruction works were carried out in the period 01.02. - 30.04.2000. This period coincided with the preparation of the equipment for transportation and the transportation itself, which was realized by Bulgarian specialists in the period 01.04. - 30.05.2000. The mounting of the main scientific equipment was over at the end June, but its assembling in a normal work state depended on additional requirements for proper maintenance of the equipment, building of new air conditioning and cooling installations as well as on obtaining some administrative licenses. This prolonged the period of accommodation of CLMK to the end of 2000 and reflected negatively on the research and especially on the experimental and analytical activities. As a result, the research activity and a substantial part of the scientific publications during this year are products of interpretation of already collected experimental and analytical data.
Nikola Zidarov
Sofia, January 2001
RESEARCH TOPICS:
I. MINERAL SYSTEMS:
1. Magmatic and metamorphic minerals and mineral associations in Serbo-Macedonian massif (N. Zidarov, L. Macheva, P. Nenova, E. Tarassova)
Microstructural features and crystal chemistry of metapelites cropping out in Belassitza mountain, S/SE of Petrich town, Bulgaria, are investigated. Their mineral association is presented by Grt+Bi+Ms+Ky+St+Pl+Qtz.
Garnet (Alm75,53-86,16Pyr7,96-17,52Gross 2,54-6,83Spess1,47-2,58) forms porphyroblasts differing in size (up to 2 cm) with oval or elongated along the foliation form and strongly resorbed and corroded rims. The observed slight zonality results from the high-temperature homogenization due to volume diffusion taking place above 650o C. The coarse porphyrhoblasts manifest prograde zonation in which the Pyr component increases from core to rim while Alm and Spess components decrease in the same direction. In their outermost part a reversed zonation is observed (depletion of Pyr and enrichment of Alm or/and Spess component) which results from resorption during the latter cooling and exhumation of rocks. The smaller garnet individuals show a reversed zonation - increase of Alm and Spess components from core to rim, which suggests a complete chemical re-equilibration, reflecting the cooling path and the loss of "memory" for the high temperature metamorphic event.
White mica is found in three microstructural positions differing in its chemical composition: 1) Early-kinematic, forming large-size individuals which are disposed obliquely to the foliation, containing high celadonite component (Si about 3.20 p.f.u.) and Fe+Mg about 0.19-0.25 p.f.u. (on account mainly of Mg); 2) Syn-kinematic, which together with biotite, forms the rock foliation. This type of mica is almost pure muscovite - low Si (3.02-3.08 p.f.u.), Fe and Mg content, and a relatively high content of paragonite component (Na=0.11 p.f.u.); 3). Late-kinematic, formed at the expense of syn-kinematic white mica or as an alteration product of Ky. Its composition is of the ferriphengite type: (Si=3.08-3.14 p.f.u.), medium content of (Fe+Mg) = 0.15-0.17 p.f.u., and relatively low content of paragonite (Na=0.09 p.f.u.). These white mica compositions suggest the following P-T path of the metamorphic process: from HP-MP/HT to LP/LT. The presence of small biotite overgrowths on large early- and syn-kinematic white mica individuals and of parallel intergrowths of Ms and Qtz is in accordance with the idea for the existence of high-silica phengite at earlier stages.
Biotite is close in composition to the phlogopite-annite series. The retrograde boitite formed at the expense of Grt is of a lower Ti- and a higher Al-content,reaching 0.67 p.f.u.
Kyanite forms well preserved prismatic porphyroblasts, plastically bent and usually detected as clusters and bands. It is often spatially associated with other high-Al minerals like Grt and St.
Staurolite forms small prismatic crystals or, together with Grt and Ky, segregates in nests in the rocks. Its formation in a close association with Ky can be related to the retrograde metamorphic reaction Grt + Ky + H2O = St + Qtz, while the replacement of Ky by St, observed in some samples - with another retrograde one, Ky + Bi + H2O =St + Ms +Qtz. The latter reaction governs also the close association of Ky porphyroblasts with biotite.
Chloritoid, the latest formed mineral, associates with Ky, St, and Grt and is manifested by small single crystals or polysynthetic twinnes. These relationships reveal the following Ctd -forming reaction with lowering of pressure and temperature - Alm + St + H2O = Ctd + Qtz. This pathway of chloritoid formation is confirmed also by its high Fe content (fCtd=0,86-0,88 p.f.u.).
The formation of St and Ctd had proceeded in static environment during the decompression stage of the rocks metamorphic evolution.
Plagioclase (An15-16) is fine-lamellar and is observed only in the Al-poor parts of the rock.
Quartz has been found as elongated lenses along the foliation.
The estimated P-T conditions of metamorphism using Gr-Bi thermometer and phengite barometer are: 650o C and 7-8 kbar for the thermal peak of metamorphism and about 550o C and 3-4 kbar for the decompressional stage.
The crystal chemistry of accessory spinels in Riphean metaophiolites from Gega melange body, Ograzden Mt., Bulgaria is investigated.
The spinel in clinopyroxenites is hercynite (picotite) with formulae:
(Na0-0.48Ca0-0.18Mn0-0.02 Zn0-0.21Fe2+4.93-6.11 Mg2.77-3.55)7.7-10.55(V0-0.03 Ti0.03Fe3+0-0.01Cr 0.06-0.43 Al13.97-15.32Si0-0.7)14.03-16.52O 32, where: Mg/(Mg+Fe2+)=0.36-0.45; Cr/(Cr+Al)=0.0039-0.029; Mg*100/(Mg+Al)=31.19-41.26.
The spinel in olivine gabbro-norites is pleonaste, rarely hercynite (picotite) with formulae: (Ca0-0.08Mn0-0.02Zn0-0.28 Fe2+3.51-4.24Mg4.17-5.02)7.68-9.64(Fe3+0-0.03 Cr0-0.4Al14.93-15.67Si0-0.28 )14.93-16.38O32, where: Mg/(Mg+Fe2+)=0.49-0.58; Cr/(Cr+Al)=0-0.026; Mg*100/(Mg+Al)=49.47-57.50.
The spinel in gabbro-norites is hercynite (picotite) and associates with clinopyroxene, enstatite, plagioclase, ilmenite, and magnetite with formulae: (Na0-0.14Mn0-0.06Zn0-0.05Fe2+4.08-6.11Mg2.39-4.04)6.47-10.4(V0-0.14Ti0-0.55Fe3+0-0.02Cr0.03-0.25Al14.26-15.91Si0-023)14.29-17.10 O32, where: Mg/(Mg+Fe2+)=0.29-0.50; Cr/(Cr+Al)=0.0019-0.0160; Mg*100/(Mg+Al)=28.60-49.50.
The chemical composition of accessory spinels classifies them as a product of ophiolite magmatic cumulates (MORB) because the content of aluminum is much higher than that of chromium.
In additional studies [45] the undeformed finegrained granitoids from the Belassitsa mountain are classified as high potassium calc-alkaline quartzmonzodiorite and quartzdiorite belonging to the magnetite series of the I-type granitoids. The crystallization proceeded at pressures 3.1-4.5 kbar and temperatures 710-750o C.
2. Accessory zircon in orthogneisses of the Ograzdenian block of Serbo-Macedonian massif - morphological, mineralogical and isotope-geochemical study. (R. Titorenkova)
The zircon typology method was used in studying eight orthogneiss samples (metagranites, migmatized gneisses, plagiogneisses, and melanocratic enclaves in metagranites) from the Ograzden mountain, Bulgaria.
The typologic study of zircon populations provides indications on their evolution and for the type of protholites. The crystal peculiarities (colour, zoning, cores, inclusions) suggest that the investigated rocks are of orthomagmatic origin.
It was found that zircon crystals are mainly of two types. One, magmatic, non-recrystallized crystals, with smoothed edges and corners. It is supposed that they underwent a low-to-medium grade metamorphism. Another type are recrystallized, often asymmetrically developed crystals, typicaly observed in migmatitic rocks. The pyramidal termination may be build of many small faces with high indexes, which is attributed to recrystallization under high total pressure and dry environment.
The typologic distribution of zircon populations and their evolutionary trends suggest different processes of mineral formation. The predominant part of the morphological types of zircon from equigranular metagranites is characterized with low values of the chemical index I.A (mainly about 200), which indicates that the melt composition during the whole period of crystallization remains constant. The I.A. values of zircon from porphyritic metagranites are in the range 200-700, which indicates for significant variations in the chemical composition with a tendency of increasing alkaline elements content. The zircon crystals from the plagiogneisses plots in a narrow range of I.A and I.T (temperature index) both being from 200 to 400 at a relatively constant temperature and chemical composition without substantial changes. The variety of zircon crystal morphotypes is most splendid for the melanocratic enclaves in metagranites. The indexes I.A and I.T of the population vary from 200 to 700 and argued that some crystals are high temperature, derived from basic magma protolith, while the low temperature zircon morphotypes revealed more acidic melt.
3. Spectroscopic study of fluorite from Bulgarian ore deposits (B. Zidarova)
The variation of the spectral characteristics is studied as a function of the content and the type of rare earth elements (REE) included in fluorite from the ore deposits Slavyanka, Chiprovci, and Mikhalkovo. All the spectral bands in the photo-, X-ray-, and thermoluminescence, as well as optical-, and infrared-absorption spectra are due to elevated content of REE, U, and Th, which is determined by neutron-activation analysis.
According to photoluminescence spectra fluorite from deposits Slavyanka, Chiprovci, and Mikhalkovo can be related to these with well revealed bands of Eu2+ and Yb2+.
By X-ray luminescence (XRLS) it was found that the flourite studied is characterized by capture and radiation centers caused by internal defects in the fluorite structure (Vk- and F2-centers), impurity ions (centers with local cubic symmetry) - Ce3+, Pr3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, and more complicated centers of non-cubic symmetry for which a local compensation takes place of the excess charge of Na+, O2-, and Fi- ions replacing isomorphically Ca2+ and F- ions in sites or in interstitials of the fluorite lattice (Er3+-Na+, Dy3+-O2-, Er3+-O2-, Sm3+-Fi-). In order to discuss the evolution in the content of centers it is necessary not only to compare the spectra qualitatively rather to calculate the parameters characterizing the variation in the content of the most typical ones and of their combinations. These are exactly the parameters of such centers containing in its composition and structure information on the mineral forming medium. The results obtained show that the parameters in XRLS are determined by the relationships for the selective inclusion of different groups of REE in the fluorite lattice depending on the geochemical features and the thermodynamical parameters of the mineral forming medium. Their variations in fluorite from the investigated deposits are correlated not only with their geochemical and genetic specificity, but also with regional and local changes in the medium' thermal-barometric-geochemical parameters in time. The comparison of XRLS parameters for fluorite in these deposits makes it possible to define similarities and differences between the various types as well as the character of changes (continuity or discreteness) in the physical-chemical conditions of crystallization of fluorite on an individual-mineral body-deposit level.
The existence of thermoluminescence is an indication for the presence of U and Th in fluorite. Higher temperature fluorite is characterized by higher temperature peaks in this kind of spectra. The presence of low temperature maximums on these spectral curves for different types of fluorite is connected with capturing on thermal micro-defects, while higher temperature ones with "activating" levels of capture. Characteristic are both centers without local compensators (TR2+ and Y2+) and such with oxygen type of compensation [(YO2)o (TRO2)o] and donor-acceptor pairs (Dy2+-Ce4+, Sm2+-Ce4+, Y2+-Ce4+) where acceptors are Dy2+, Sm2+, and Y2+, whereas donor is Ce4+.
In the optical spectra of transmission and absorption all absorption lines also depend on the content REE in fluorite. In the ultraviolet spectral region (200-400 nm) the following absorption bands have been observed: at 265 nm (corresponding to Sm2+ and Yb2+), at 300-315 nm (to Ce3+, Sm2+, and Yb2+). In the visible spectral range (400-800 nm) there are lines at 410 and 580 nm (corresponding to internal defects Fi- and 2Fi-) in the fluorite lattice, at 420 and 600-650 nm (to Sm2+), at 500 nm [to (Y,TR)O2], and at 560 nm (to MO2-).
By infrared spectroscopy bands at 1400-1500 cm-1 were observed, originating from the presence of CO32-, at 1630 cm-1 corresponding to deformation vibrations, and at 3400 cm-1 corresponding to stretching vibrations of OH-groups.
4. Genetic model of the barite ore formation in the Kremikovtsi deposit, Bulgaria (Z. Damyanov)
Two mineralogical genetic types of barite were found in the Kremikovtsi deposit:
A. Endogenic barite, which is presented by a variety of differently shaped bodies: individual veins, systems of subparallel and network-like branched veins, veinlets, impregnations, druse-like aggregates, nests, and also greater bodies with lense-, columnar- and stock-like morphology. Representative barite samples of the main types of ore bodies and mineralizations are selected. The main part of endogenic barite forms large- to coarse-grained aggregates with size of the crystals exceeding 1 cm. The large-grained barite is characterized with a highest content of Sr (from 0.6 to 2.1 wt.%). However, the Sr content usually varies between 1-1.5 wt.%. In zonal barite of this type the Sr content increases from core to rim of the grains. The small-grained barite is represented by platy crystals and irregular grains with a thickness of several mm and lateral dimensions up to 2-3 cm. The Sr content in this type of barite is lower than that of the large-grained one and varies from 0.3-0.5 (in the siderite ore) to 1-1.2 wt.% (in the polymetalic mineralization). The Sr content is lowest in the micro-grained barite sized below 1 mm, which forms intensive impregnations in the iron ores of the deposit. Usually it is below 0.1 wt.%. The results obtained show that the Sr content in endogenic barite depends on the size of barite crystals and the greater the size of barite grains the higher is the Sr content and vice versa. This is a peculiarity of hydrothermal barite explained by the degree of solubility of both BaSO4 and SrSO4 components and their thermal dynamic behavior during crystallization from the solution. The structural and textural relationships of endogenic barite with the associated minerals (sulfides and authigenic phyllosilicates) suggest that its formation had proceeded under reduction conditions on the boundary of stability between sulfate and sulfide phases in the hydrothermal solution.
B. Supergenic barite is localized mainly in aposiderite limonites and in partially oxidized siderite ores and is presented by coloform barite aggregates (spherulite crusts), dendrites, "arrow-like" aggregates of parallel and subparallel arranged individuals, amber-yellow colored platy and needle-like crystals. It differs from the endogenic one in the very low content of SrO (from 0.01 to 0.12 wt.%, averaged 0.05 wt.%) which is explained by the greater migration capacity of SrSO4 during dissolution and redeposition of BaSO4 in the process of supergenic alteration of the deposit.
In the Kremikovtsi barite Sr, which is the main harmful component, is in the form mainly of isomorphic impurity and does not form own minerals. This means that it can not be removed from the barite concentrate using the conventional methods and the Ba/Sr ratio in the initial ore will be preserved also in the concentrate. Thus, one can recommend this ratio as well as the crystal morphological characteristics of the mineral to be used as basic criteria in qualifying the bodies for production of high quality barite raw material.
5. Ore mineralization related to the Oman-Fakija pluton, Eastern Srednogorie, Bulgaria (E. Tarassova, P. Petrov)
New data on the ore mineralizations related genetically to the Oman-Fakija pluton are presented. An integrated hydrothermal origin is proposed for both the aposkarn ore mineralizations (Fe-oxide and Fe-Cu-sulphide) in the peripheral pluton parts, and the Fe-Cu-sulphide mineralization in the altered igneous rocks from the central intrusive parts. The bismuth minerals (native bismuth, tetradymite and hammarite) were found as new ore minerals in the region. The sulphide mineralization was found to form in the temperature range 285-210o C. Two facts were observed: (1) a negligible spreading of areas with intensive alteration of igneous rocks, and (2) a presence of exposed skarn ore mineralizations, which indicate a deep erosion of the ore-magmatic system and suggest an insignificant ore potential of the ore mineralizations connected with the pluton [46].
6. Mineralogy and formation conditions of ore associations in ultrabasites and listvenites (Z. Tsintsov)
Relic, hydrothermal, and secondary ore mineralization of vein and metasomatic type are investigated for about fifty hydrothermal ore deposits in Ihtiman Sredna Gora, Bulgaria. These mineralizations are presented by: separate native gold grains sized below 200 mm (for the placers); native gold inclusions in: pyrite (Au content up to 400 ppm, emulsion-like spherical shape with size from 3 to 15 mm); goetite (as irregularly shaped grains with length of 100-120 mm), and in quartz where the grain size is greatest, reaching 350 mm (the native gold composition includes Ag up to 43.73 at.% and Cu (rarely) - up to 3.26 at.% with weak variations in the same grain); kyustelite with irregularly shaped grains sized up to 200-250 mm and surface covered by Fe-hydroxides; pyrite which is often either disolved or transformed into Fe-hydroxides due to progressing processes of oxidation; arsenopyrite with grain size up to 500-600 mm or in the form of dense masses up to 2-3 mm with strongly corroded surfaces; lyolingite; phases in the system Pb-As-S; galena; sphalerite; chalcopyrite; coveline; etc. Specified are six mineral forming stages: I - quartz; II - quartz-arsenopyrite-gold; III - quartz-pyrite with gold; IV - quartz-polymetalic with gold; V - quartz (±pyrite); VI - opal-hydroxide.Characterized are pirhotite, pentlandite, and mauherite included in columnar-fibre magnetite from the ultrabasite massif near Dobromirtsi village, Kurdjali district, Bulgaria. The latter is represented by pieces sized up to 5-6 cm. The magnetite "columns" and "fibres" are impregnated by picrolite-asbestos along which the metamorphoses has taken place. Its compositions is similar to magnetite from other ultrabasic massifs and is typical of hydrothermal ore formations [53].
7. Thermal transfusion model for the distribution of gold in rocks (O. Vitov)
On the basis of the thermal transfusion model for the distribution of gold in rocks it follows that on the interface between a zone of thermal activation and a cold zone in the Earth's crust there should be a stripe of rocks rich in gold. To verify this hypothesis data are dealt with for the content of gold in lithochemical samples from the region of the villages Gorna Dikanya - Dren, Radomir area, Bulgaria, where during and after Cretaceous there had been a thermal contact between the active and relatively hot Srenogorie zone and the relatively passive and cool Rila-Rhodope region. This hypothesis was proved through Fourier analysis and the most perspective region was specified for prospecting of gold ore formation in the area between the above mentioned villages. The model is developed in virtual subspace and then the data were normalized to real coordinate and angular relationships. To eliminate the effect of uncertainties in the course of sampling a methodological improvement is proposed, namely correction of data by a coefficient equal to the ratio between the sum of the content of gold in the samples and that of the content of gold in the model. This correction coefficient works as a compensation coefficient for the loss of gold during the laboratory analysis of the samples. As a result, elimination of the effect of "profile anomalies", i.e. coarse errors in the sampling and analysis of the samples is also achieved.
8. Mineralogical map of the heavy mineral concentrates in Bulgaria (O.Vitov)
The computer program SCH106 is modified and on this basis the program SUBSCH is created, which gives possibility to draw indicative maps of heavy mineral concentrates, prognosis maps, mineral regionning and mineral geochemical maps for an arbitrary part of the country scaled in arbitrary units. The analytical part of the program includes analysis of the completeness of such type of data as well as their statistical analysis.Using the modified program data for near-boundary regions with Turkey, Greece, Macedonia, and Serbia are scaled 1:500 000 and the data are used for estimating the perspectivity of areas in these regions and for searching of possible ore deposits.
II. ENVIRONMENTAL MINERALOGY
9. Mineralogy and geochemistry of coal and coal products (S. Vassilev, Chr. Vassileva)
A systematic study on the geochemistry and mineralogy of Cl and Br in both coal [25] and their combustion products [26] is performed. The results emphasize that despite of similar chemical and geochemical properties of Cl and Br there are some distinct differences in the association, behavior and mode of occurrence of both elements according to their relationships with the chemical and mineral composition, rank, age, ash yield and geographic location of coal [25]. There are also indicative close relationships between the content, redistribution, mode of occurrence and behavior of Cl and Br in fly ash, bottom ash and stack emissions during and after coal combustion [26]. A possibility to produce low-cost catalytic sorbents for selective catalytic reduction (SCR) of NO at low temperatures using transition metals obtained from low-grade waste materials (such as petroleum residua and carbons from cheaper low rank coals) is discussed [61]. The chemical and mineral composition of the Pernik subbituminous coal and their waste products from the Pernik coal preparation plant and the Republica TPS were characterized. The mineralogy and chemical composition of coal from 34 deposits worldwide spread were studied and a model for comparative characterization of their composition is performed. The behavior of mineral matter of 6 types Bulgarian coals during their gradual oxidation and ashing is described.
10. Synthesis of artificial rocks (SYNROC) (I. Donchev, Fr. Dipchikov, O. Petrov, N. Zidarov)
Experiments for synthesis of small amounts of Synroc ceramic were performed at 1200oC in a TDA/TG apparatus and melts of oxide precursors (TiO2, Al2O3, ZrO2, and BaO) were obtained. Using stoichiometric calculations and directed crystallization at 1350oC and 1400oC for 3 hours ceramic samples were produced. X-ray diffraction phase analysis of the final products reveal the formation of rutile, perovskite, and zirkonolite through solid phase transformation. Synthesis at temperatures 1250 and 1300o C was performed using previously sintered in tablets shiht material. The obtained sample bodies were studied by powder XRD and SEM. It was found that the desired crystalline phases are present - perovskite, zirkonolite, and hollandite and impurities of rutile. In the samples heated to 1250oC there is an intermediate phase, Ba2TiO4 which at 1300o C transforms into hollandite of the type Ba1.23Al2.46Ti5.54O16.
These studies on the design of Synroc makes it possible to incorporate simulative additives of Cs and Sr in the proposed scheme and to prove the stability of the obtained products during dissolution.
11. Oreols of lead spreading in Kamenitsa depression, Kyustendil region, Bulgaria (O. Vitov)
Using a particularly prepared computer program data on the lithochemical oreols of Pb spreading in Kamenitsa depression, Kyustendil region, Bulgaria, are processed. It is found that the aureoles are technogenic (eolic - from the waste reservoirs of MOK "Osogovo" and hydrochemical - from irrigation by waters polluted due to ore processing) and residual oreols from weathered crusts on the western slopes of Lisets mountain. It is found that the prognosing resources of 15 000 t of Pb in the terrace of the Bistritsa river are technogenic pollution. These investigations in this part of the Trans-European corridor No 8 are indicative for the presence of antropogenic and natural pollution, a fact to be considered in building activities along this corridor and in monitoring the environment in its exploitation [28].
12. Spray-dry CuKMo/zeolite-based catalysts for simultaneous removal of soot and nitrogen oxides (Y. Kalvachev)
The activity of copper/potassium/molybdenum catalysts impregnated and spray-dried onto zeolites in order to remove soot and nitrogen oxides is investigated. The spray-drying procedure is suitable for preparation of catalysts for oxidation of soot. In this way the contact surface between the soot and catalyst becomes better which is crucial for the soot oxidation. In the presence of a large amount of catalyst the soot is oxidized at lower temperatures. CuKMo catalysts exhibit a good activity in the simultaneous removal of soot and NOx from the exhaust gasses. It turns out that not only soot reduces the concentration of NO, but also the presence of NO enhances the soot oxidation [6].13. Sorption activity of montmorillonite-vermiculite-clinoptilolite combinations with respect to ion pollutants in model waste waters (B. Vassileva, O. Petrov)
The ion exchange capacity of natural vermiculite from Parapandovtsi deposit, Bulgaria, is studied using ammonium ions. A series of experiments to investigate the sorption activity of vermiculite was carried out. On this basis filter materials from vermiculite and clinoptilolite (from Beli plast deposit, Bulgaria) were designed.The chemical analysis of the water extraction in time was performed by atomic absorption spectroscopy (AAS) and potentiometric analysis using ion-selective electrodes.
These experiments revealed that vermiculite and its combinations with clinoptilolite display a high sorption activity with respect to the cations used (NH4+, K+, Ca2+, Cu2+, Zn2+). Also, it is of interest that vermiculite has a good sorption activity with respect to the anions studied (F-, Cl-, NO3-).
The combined filtering material based on vermiculite and clinoptilolite as well as the pure vermiculite itself can be recommended for cleaning up waste waters from industry.
III. MODELING AND MODIFICATION OF MINERAL SYSTEMS
14. Geometrization of the language of mineralogy (V. Penev, N. Zidarov, B. Zidarova)
Mineralogy, just as the majority of the natural sciences, faces a new, higher evolutionary stage, the geometrization of its language. A complex of such axiomatic formulations of the different systems of logically consentient, noncontradictory and veracious statements of mineralogy that are characterized with large-scale use of entirely mathematical notions and models is to be created during this stage.
Geometrization of the language of mineralogy means solution of the following closely related problems: 1) clarifying the language logical structure in order to formulate correctly the mineralogical notions and relations; 2) constructing of entirely mathematical spatial representations for the latter; 3) formulating a system of basic mineralogical statements playing the role of axiomatics in mineralogy; 4) logical verification of the mineralogical statements which are not axioms, i.e. their deduction from the formulated mineralogical axioms.
The basis for solving of the first problem is the logically correct definition of the triad of cognitive categories structure, composition and construction, to which in mineralogy correspond respectively constitution, composition and crystal structure of minerals. These categories are interconnected through the following system of axiomatic statements:
A. Structure is the unity of particular composition and particular construction of a given complex object in a specified energy state.
B. Composition is the set of relatively independent particular parts of a given complex object in a specified energy state.
C. Construction is the particular mutual disposition in the three-dimensional physical space VE(3) of relatively independent parts of a given complex object in a specified energy state.
In these definitions energy state of a given complex object is the particular value of the internal energy of this object, considered as a thermodynamic system.
The three defined categories (structure, composition and construction) are valid for arbitrary objects, do not include any requirements for ordering in VE(3), and are related to the objects' internal energy. Thus, this triad of categories holds for all types of ideal and real physical, chemical, mineralogical, etc. objects, both ordered and disordered.
Being bound with the internal energy, for these categories it holds that: 1) a change in the energy state is a change in the particular structure, i.e. either in the particular composition or construction, or in both; 2) each particular structure can be interpreted as a particular apparent manifestation of a definite amount of internal energy shared in a definite proportion between particular composition and construction; 3) the different types of construction symmetry in VE(3) can be interpreted as manifestations of corresponding amounts of internal energy.
The solution of the second problem for the mineralogical objects is based on the ideological scheme for entirely mathematical space presentation of arbitrary chemical objects. The composition of every chemical structure (including minerals) is represented mathematically and uniquely through a corresponding set of points in the newly defined Mendeleev's space, VM(3), with respect to the Mendeleev's coordinate system, KM=Ozrj; where the points' z-coordinates represent the number of neutrons, r - the number of protons and j = (n - t)(2p/32); where t is the oxidation number of the presented simple chemical objects and n (n=1,2,...,32) is the number of this column in the corresponding 32-column tabular Periodic system, which contains these chemical objects. The construction of chemical structures is presented mathematically through the corresponding sets of points in the physical space VE(3), with respect to an arbitrary chosen coordinate system KE(3). The Cartesian products VS(6) = VM(3) x VE(3) and KS(6) = KM(3) x KE(3) are a space and a coordinate system of chemical structures. Thus, each chemical structure, including minerals, is presented entirely mathematically and uniquely by specifying the coordinates of the corresponding set of points with respect to KS(6) in VS(6).
15. Investigation of the system Na2O-K2O-TiO2-SiO2-H2O (V. Kostov-Kytin, S. Ferdov, O. Petrov)
Alternating TiO6 and SiO4 units build the rigid zeolite-type frameworks of the members of a new family of microporous materials known as titanosilicates. In recent years, interest has been turned to them with respect to host-guest chemistry, ion-exchange properties and shape selective catalysis. Most detailed data concerning the syntheses, characterization and properties were reported for the small pore ETS-4 (3.7 ?) Na9Si12Ti5O38 (OH).12H2O and STS (4 ?) K2TiSi3O9.H2 O, and the large pore ETS-10 (8 ?) (Na1.5K0.5)TiSi5O 13. Yet, little is known for the influence of the physicochemical parameters of preparation on the structure, composition and morphology of the final products. A comprehensive study was undertaken aiming at creating diagrams of crystallization fields for ETS-4 and STS. Investigations on the influence of Ti, Na and K contents and ratios in the initial batches on the size and morphology of the run-products were also carried out. These might be useful in future preparation of oriented layers and membranes. The system studied and the syntheses conditions are described in [35]. Most detailed results were obtained in the system: aNa2O-bK2O-cTiO2-10SiO2-dH2O where 1 ? a ? 9, 0 ? b ? 8, a+b=9, 0.9 ? c ? 2.9, 675 ? d ? 1100. Low contents of TiO2 and Na2O in the initial gels contribute to formation of STS. Within the field of its crystallization, with the increase of the TiO2 content the morphology of the run products varies from leaf-shaped aggregates (40 mm) through rhombohedral single crystals (25 mm) to spherical aggregates of 15 mm size. High concentration of TiO2 or Na2O in the starting mixture leads to formation of ETS-4. The aggregates are butterfly-shaped at lower TiO2 and Na2O contents and with their increase they become coin-shaped. ETS-4 particles of 35 mm size were obtained at the following conditions: 4.5Na2O-4.5K2O-2.4TiO2 -10SiO2-675H2O. The particle size of both synthesized titanosilicate phases increases from 25 to 40 mm with the increase of water content in the system. In addition, at 2.5Na2O-2.5K2O-0.5TiO2 -10SiO2-675H2O composition of the initial gel unknown crystalline phase with the following XRD characteristics was synthesized: d(I): 7.222(30); 6.945(10); 4.412(50); 3.608(100); 3.450(40); 3.282(35); 3.139(15); 2.977(20); 2.815(10); 2.520(15); 2.468(10); 2.427(5); 2.356(10).
16. Chemical and structural transformation of tungsten minerals under low-temperature (exogenic) conditions - experiment, analysis, and modeling (M. Tarassov, B. Mihailova)
In the zone of oxidation of Grantcharitza ore deposit (West Rhodopes, Bulgaria) amorphous gels of composition WO3.xFe2O3.nH 2O were found, which are chemical analogues of already described minerals in the deposit - ferritungstite and X-ray amorphous iron containing tungsten ochre. The powder X-ray diffraction patterns of the gels contain a weak amorphous halo centered at about 3.3-3.6 ?, while the obtained electron diffraction patterns are typical of amorphous materials. The Raman spectra of the material in the range 600-1050 cm-1 contain two broad bands. The first one, maximizing at about 785 cm-1, is symmetric, whereas the second one is composed of several peaks, the most pronounced and narrow one maximizing at about 952 cm-1.
This peak corresponds to vibrations of the double bond W=O characteristic of WO3.nH2O (n=1, 2). In spite of the high structural disorder in the gels Raman spectroscopy data show that the short range ordering in the structure of the material differs from that in other tungsten minerals. The position of the first peak in the spectrum of gels (about 785 cm-1) gives evidence that: (1) the tungsten oxygen octahedra building the clusters in the gels are three-dimensionally arranged rather than quasi-two-dimensionally which is the case in tungstite and hydrotungstite and as has been established in synthetic WO3.nH2O gels upon subsequent condensation of tungsten ions in aqueous solutions; (2) the average distances W-O in the gels are smaller than those in ferritungstite (about 1.92 ?) which can be explained by tungsten-oxygen octahedra being bonded not only in apexes but also along edges. This conclusion is in a good accordance with literature data pointing out that the primary gel product of tungsten in aqueous solutions is formed on account of meta-tungstate ions.
17. Electrochemically induced transport processes in basaltic and rhyolitic melts (N. Zidarov, J. Mouhovski, N. Zotov)
Parameters of ion-transport processes in anhydrous basaltic melts are investigated experimentally in a rectangular electrochemical cell by a constant electric field intensity ranging from 0.174 to 1.74 V/cm and by keeping a constant melt temperature in the range 1302 - 1321o C. Under these conditions a quasi-stationary ionic current in the range 0.24 and 5 mA was measured through the cell. The investigated sample together with a reference one, the later not beeing imposed to electric field, are quenched after the melt treatment by a quick withdrawal from the furnace of a ceramic platform whereon the cells with both samples are placed closed to each other.
Microprobe analyses of the sample imposed to the highest intensity of 1.74 V/cm and of the adjacent reference are performed (CAMECA, 15 kV, 15 nA defocused beam current).
Frozen elemental profiles are obtained at three longitudinal sections of the samples positioned being at approximately one and the same distance from one another and from the top and the bottom of the samples. The mean data profiles for each melt component show a completely homogeneous elemental distribution into the reference sample, whereas into the sample imposed to a constant electric field a significant alteration of the concentration of the majority of components is observed within a region with length of about 1000 mm from the cathode surface. In this region the concentration decreases for some components (Fe, Na and K), determining the ionic-current and acting as network-modifiers. Surprisingly, however, the concentration of Ca and Mg, which also are ionic-carriers, increases.
On the other hand, the chain-related ions (Si, Al and Ti), acting as network-formers, display a uniform longitudinal distribution, except for a slightly pronounced minimum nearby the cathode.
Vertically to the bottom, a smoothing of the concentration gradients in the nearby cathode region and gradually alterations of their concentration along the sample's length are observed for all the components. In the region near the bottom, a significant enrichment with Mg and Fe is established and the microscope photos indicate the presence of a crystalline phase, most likely pyroxene. Into a layer next to the bottom cell a significant increase of the Al concentration was observed. It can be explained by a forced diffusion from the ceramic cell to the melt layer next to the cell wall due to a partial ionization of Al into the heated ceramic medium, so that the formed high mobility ions may easily penetrate into this layer.
The obtained results indicate that the overall rate of the electrochemical reduction of Fe, Na and K proceeding on the cathode have been determined by the final velocity of the diffusing cations of these components to the electrode surface, whereas for Ca and Mg - by the velocity of back-diffusing products of the reduction from the cathode. At the same time, the forced reduction processes at high current density induce a crystallization into the melt close to the bottom of the cell, thus causing therein a significant increase in the concentration for Fe and Mg and especially of Al.
It was established that when the intensity of the constant electrical field imposed to the electrochemical cell is enlarged by an order of magnitude compared with that at low intensity field (about 0.17 V/cm), the components' distributions into the frozen melt undergo significant changes. With increasing the current density significant diffusion limitations arise on the transport of Fe-cations to the cathode surface as well as such on the transport of the products of the electrochemical reduction of Ca and Mg cations. Nearby the bottom of the electrochemical cell, the concentration alterations penetrate gradually along the whole length of the melt. These results indicate that when a sharply current enlargement characterizes the electrolyze in molten basalt, the transport processes in the melt are significantly complicated as a result of the simultaneously acting electrochemical, chemical and crystal-chemical reactions [52].
18. Hydration heats of clinoptilolite for evaluation of heat exchangers (N. Petrova, T. Mizota, K. Fujiwara)
Due to their open porous structure zeolites are capable of absorbing large quantities of water molecules at room temperature. Thermodynamic data of hydration processes of zeoiltes are essential to evaluate zeolites as heat exchangers for heat pump systems. [42, 67].
Hydration enthalpies (DHh) of purified clinoptilolite from Beli Plast tuff deposit, Bulgaria, and various cation-exchanged types such as Na-, K-, Ca- and Mg-clinoptilolite were determined in the adiabatic water-vapor absorption calorimeter in order to: clarify the influence of hydration energy of exchanged cations on enthalpy values; identify suitable clinoptilolite forms to use them as heat exchangers. The samples were dehydrated in evacuation and heated at 80, 100, 120, 140, 180 and 300o C, for 1 h. The hydration amount was determined as weight-difference for the sample before and after the hydration in the calorimeter. Dependence of values of DHh on fractional water content (q) is presented on the figure, where q is a ratio between the hydration amount of water and the fully saturated water content for each sample. According to hydration characteristics of exchanged cations the hydration enthalpy for different forms becomes less exothermic in the sequence Mg, Ca, Na, K at low q, but converge to similar values at high q.
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Hydration heats values (q), normalized to the zeolite mass, were introduced for evaluating heat exchange ability of the zeolite. The q-value for Na-clinoptilolite attains - 469 Jg-1, when it is dehydrated at 300o C, and shows -524 Jg-1 for the complete dehydration. Na-clinoptilolite exchanges were most effective of all the cation-exchanged types in a wide temperature interval (180-300o C), while Mg-clinoptilolite is preferable at higher temperature, namely 300-350o C. This supports the structural variation in zeolites during dehydration.
19. Entropy of zeolitic water (T. Mizota, N. Petrova, N. Nakayama)
Zeolitic water is a key material for the zeolite-water heat pump system. Most entropy values of zeolitic water have been given so far to be intermediate between those of liquid water (69.9 JK-1mol-1 at 298K) and ice (41.5 JK-1mol-1 at 273K). Direct measurements of hydration enthalpies claim that the value is very small or almost zero, based on the assumption of the independent component of water in the zeolite and the values of equilibrium vapor pressure on the zeolite should be specified for evaluating the true entropy of zeolitic water, because the adiabatic hydration calorimeter used was insufficient for estimating the pressure. Precise measurements of P-T-C were therefore desirable. The vapor pressure measurements for zeolites are not so easy because of the condensation nature of free water at around room temperatures. The Clausius-Clapeyron method gave true relations among the hydration enthalpy, the equilibrium pressure and the temperature. The calorimetric measurements proved however that the entropy value for Mg-exchanged A-type zeolite is so small, even at the ambient temperature, as to be compared with the residual entropy of ice, 3.37 JK-1mol-1 [37, 56, 59, 60].
20. Mechanical triboactivation of dolomite (Y. Pelovski, I. Dombalov,V. Petkova)
Mechanochemical activation is a widely used method for increasing the reaction activity of solids and, respectively, to accelerate solid phase reactions and to reduce the temperature regions of the subsequent thermal decomposition. New data about thermal stability and phase transitions of mechanochemically activated dolomite under different conditions, namely using various numbers and kind of milling balls and the duration of activation, are presented. Temperature regions of decomposition of MgCO3 and CaCO3 are specified. Experiments are performed on the way to determine the thermal stability and the rate of thermal decomposition of activated dolomite [39, 63].
IV. SYNTESIS, COMPOSITION, STRUCTURE AND PROPERTIES OF MINERALS AND NEW MATERIALS
21. Synthesis of microporous zirconium-silicates build of differently coordinated polyhedra (V. Valtchev)
The incorporation of octahedrally coordinated cations such as Ti, Sn, and Zr in "open" zeolite-type structures results in two negative charges in the skeleton and substantially modifies the properties of this kind of materials. In this study results on the synthesis of zirconium-silicate materials with zeolitic properties are presented. All the syntheses were performed without stirring at temperature 200o C and under authigenic pressure. The duration of the experiments varied between 2 and 35 days and using the following reactants: Na-silicate; zirconium chloride; potassium fluoride; sodium base; potassium base; HCl; and tetramethylammonium bromide. After the synthesis the solid product was washed by deionized water and dried at room temperature.
The powder X-ray diffraction (XRD) analysis of the synthesized products showed that several different phases were obtained, among which the most interesting are the synthetic analogues of the minerals elpidite, geidonaite, and umbite. The synthesized Zr-silicates exhibited a good thermal stability and the thermal treatment at 400o C did not change their XRD patterns. Thermal gravimetric analysis of the products revealed that they contain between 7 and 11 wt.% H2O released in the temperature range 35-350o C. BET(N2) analysis of the samples' specific surface indicates very low values of this parameter. This result shows that the micropores in these materials are smaller than the kinetic diameter of the nitrogen molecule. On the other hand, the data on the structure and adsorption of water (isotherm of the I type) allows to classify them to the group of the microporous materials.
These results reveal that the synthesis of microporous Zr-silicate phases is possible under low temperature hydrothermal conditions. The possibilities for modifying the starting system are very wide and further experiments may point at the synthesis of new microporous Zr-silicates. The synthesized phases are interesting as ion-exchangers and can be used for separation of small molecules of gass mixtures.
22. Temperature and concentration regions for crystallization of CsLi6O10 in the ternary system Li2O-B2O3-Cs2 O (D. Shumov, A. Nenov, O. Petrov)
An investigation of the possible choice of solvents in the ternary system Li2O-B2O3-Cs2O for growing CsLiB6O10 (CLBO) crystals was carried out. CsLiB6O10 is a congruently melting compound, but serious difficulties arise in growing these crystals by the Czochralski and Kiropulos methods, because of the necessity to keep a zero temperature gradient at the growth interface. In order to avoid these difficulties CLBO crystals have to be grown from solutions. Due to that the concentration and temperature regions of the existence of CsLiB6O10 - phase in the Li2O-B2O3-Cs2 O system was examined. Ten different solvents S1, S2,…,S10 were investigated and the results are presented in the Table, where Tb and Te denote, respectively, the temperatures in the beginning and the end of CLBO crystallization, and Cb and Ce are the corresponding CLBO concentration in the solution [17].
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The only solvent suggested till now is S7. As seen from the Table, there are some other solvents (S1, S4 ,S8 ,S9 and S10 ) which offer suitable temperature and concentration regions for growing CLBO crystals. According to preliminary assessment only S1 has a remarkable high viscosity, while all the rest solutions are of approximately the same viscosity.
The obtained new experimental data make it possible to compare the solvents investigated and to choose the suitable ones for growing CsLiB6O10crystals. It was found that NBS Crystal Data File for CsLiB6O10 phase does not exist and precise powder X-ray diffraction data of CLBO crystals were obtained. Accurate viscosity measurements of the solutions are necessary in order to choose the most appropriate solvent.
23. Vibration and electron states in defect many-component materials (L. Konstantinov, B. Mihailova, E. Dinolova et al.)
The Raman spectra of wave-guides of H:LiNbO3 are analyzed in the framework of a simple cluster model, the transversal Raman-active modes of LiNbO3 being modeled in terms of a cluster of two Li, two Nb and six O atoms with imposed periodic boundary conditions. Using this approach, the calculated vibration modes of a cluster in which one or two Li atoms are replaced by protons are considered and compared with polarized spectra of samples with high concentration of protons. The results obtained show that the additional peaks at about 65 cm-1 and in the spectral range 500-700 cm-1, observed for samples of HxLi1-x NbO3, are directly related to the formation of Nb-O-H groups in the niobium-oxygen network. It is also proved that the additional Raman peaks in the spectral range 100-300 cm-1 upon proton exchange are due to breaking of the bulk structure symmetry and to formation of new crystalline phases [13].
Using reflectance-absorption infra-red spectroscopy (RAIRS), scanning electron microscopy and X-ray diffraction thin films of silicalite-1 on gold surfaces seeded by colloidal nano-sized crystals are investigated in order follow the formation of defects and to determine the optimal conditions for the growth of films with a low concentration of defects. It is shown that the use of colloidal crystals sized about 60 nm leads to the formation of low-defect layers of a thickness of 100-300 nm, predominantly oriented perpendicularly to the substrate surface. The hydrothermal treatment of such layers as well as the use of seeds of a larger size, promotes the formation of defects. The processes of nucleation and crystallization of layers of TPA-silicalite-1 are studied as a function of the silicon precursor. The results obtained makes it possible to specify the process of synthesis of thin zeolite layers [11, 21, 23, 24].
By calculating the electron structure of representative clusters the optical absorption spectra are analyzed for zeolite-type titanium silicate K2TiSi3O9.H2 O. The calculation is performed on the basis of a discrete variation DV-Xa method and a good agreement between the calculated and measured experimentally optical spectrum is demonstrated in the range 150-1000 cm-1, where the optical absorption originates due to electron transitions between the valence and conduction bands. It is shown that the intense absorption in this spectral band results from electron transitions between oxygen and titanium states and that the experimentally observed splitting of the band of optical absorption results from the contribution of K+ ions to the inter-atomic interactions in the system of SiO4 tetrahedrons and TiO6 octahedrons [2].
24. TEM study of natural aerinite (D. Nihtianova, I. Queralt, V. Yamakov)
Aerinite is an nonclassified hydrated aluminosilicate, often found as fibres or powders. However, there are uncertainties in obtaining its exact space group symmetry, which depends on the chemical composition, structural changes with temperature, and the difficulty to get suitable single crystals to carry out structural studies.
The aerinite cell parameters are not definitively established till now. Recently, the values a=14.690 ?, b=16.872 ?, c=5.170 ?, b=94.75° are the best fitted to the obtained powder X-ray diffraction patterns for Ca4[(Mg,Fe2+,Mn)(Al,Fe3+ )]10 Si12O36(OH)12 CO2.12H2O (aerinite). Previous data have showed an equal possibility to index the XRD results for Ca2(Mg0.7Fe3+Al 1.1)[Si6Al2O22 ].16H2O in both orthorhombic (a=14.733 ?, b=16.936 ?, c=5.303 ?;) and monoclinic (a=15.235 ?, b=16.944 ?, c=5.276 ?, b=104.52°) unit cells (mmm or 2/m) .
In order to get a new approach to the aerinite structure we performed a resolutive X-ray diffraction (XRD) powder analysis and selected area electron diffraction (SAED) on aerinite of high degree of purity. The SAED observations were carried out by EM 420-T, Philips, at accelerating voltage 80 keV in a conventional mode.
The obtained XRD data allow us to recognize more than seventy peaks assigned to aerinite. In this sense, the presence of 8.46 ? and 7.32 ? d-spacings, not previously identified, are very suitable for more exact structural characterization of aerinite.
Simulated theoretical SAED patterns and registered microdiffraction data are compared within 2% accuracy and the best fit is achieved for A2, Am and A2/m monoclinic space groups. The present SAED results show unambiguously that: (1) The unknown space group of aerinite may be either A2, or Am, or A2/m; (2) Two types of aerinite (aerinite-I: a=15.235 ?, b=16.944 ?, c=5.276 ?, b=104.52° and aerinite-II: a =14.94 ?, b=16.87 ?, c=5.26 ?, b=101.5°) are observed which display small variations of cell parameters and angles b; (3) This problem can be explained by the complicated microstructure of natural aerinite: coherent intergrowths between these two types of aerinite are determined by the possible changes of their composition.
25. Electron microscopic study of colored SnO2 (cassiterite) single crystals (D. Nihtianova, A. Toshev, L. Petrov)
Undoped SnO2 (cassiterite) single crystals grown by chemical transport of the powdered SnO2 with CCl4 or Cl2 are investigated by a Philips 515 SEM equipped with EDAX 9100 X-ray energy dispersive analyzer and EM 420-T/EDAX, Philips.
The color of the obtained crystals changes under growth conditions.During chemical transport of SnO2 with Cl2 at a temperature gradient of 110° C agglomerated violet crystals were obtained. At lower temperature gradients up to 60° C both colorless and pale-yellow whiskers were produced. The chemical transport of SnO2 flowed by CCl4 at a temperature gradient of 60° C leads to formation of three types of SnO2 crystals: colorless, pale-orange and black. The violet crystals contain Al impurities, while the black ones both Cl and Fe impurities. The pale-yellow, colorless and pale-orange crystals were also analyzed, their impurity contents being under the sensitivity threshold of EPMA.
The present investigations indicate that the colorless and colored SnO2 crystals are of differing microstructures. Numerous pale-orange, pale-yellow, violet and black crystal fragments contain planar faults grouped rather than isolated. The SAED patterns of crystal particles with fault planes parallel to the electron beam allow these planes to be indexed as {101} and 
. Extra spots appearing on the electron diffraction patterns conform with defects which can be considered as twin planes. At such orientation of the crystal particles the twin axis is perpendicular to the electron beam and the twin diffraction picture is obtained by a simple rotation. The rotation up to 180° around the twin axis conforms with the mirror reflection of the matrix diffraction pattern. When the faults are closely spaced then a streaking is observed on the SAED patterns along [101] and 
directions. Such planar faults are not observed in the colorless crystals.
Our investigations point out that the origin of the coloration of these crystals may be related to the presence of twin faults. Besides the qualitative character of the EPMA data, they show that the accommodation of impurities in the twin crystal regions can not be ignored.
26. Thermal analysis of polymer-silicate nanocomposites (R. Kotsilkova, V. Petkova, Y. Pelovski)
The thermal behavior of epoxy-smectite nanocomposites (hybrids) is examined by non-isothermal thermogravimetry (TG, DTG and DTA) in air atmosphere. It has been shown that the thermal stability of hybrids is much grater than that of epoxy resin and strongly depends on both the smectite loading and the type of the gallery cations of organically modified smectites. The kinetics of degradation of nanocomposites is significantly influenced by the presence of smectites and proceeds in three stages. The stage I is attributed to the effect of qaternized ammonium ion exchanged smectite, while the stages II and III are associated with the decomposition of the bulk epoxy resin. Due to interfacial interactions and the silicate-polymer multi-layered nanoscale organization, the nanocomposites act as an excellent heat insulator and mass transport barrier, shifting the thermal decomposition peaks towards much higher temperatures [36, 57].
27. Investigation of the thermal properties of Fe2O(SO4)2 (V. Petkova, Y. Pelovski)
The data on the thermal decomposition of FeSO4.H2O upon various regimes of heating and gaseous environment prove the formation of intermediate products of types Fe2O(SO4)2 and FeOHSO4, their stability and amount being determined mainly by temperature and oxygen-reduction potential. Results on the synthesis and characterization of Fe2O(SO4)2 are presented. The synthesis was carried out using a laboratory thermal equipment operating under conditions in the temperature range 713 - 813 K in a gaseous environment either poor in oxygen or containing 100% oxygen. The experimental conditions under which Fe2O(SO4)2 is stable are established. The effect of three basic parameters on the synthesis of Fe2O(SO4)2 is clarified: the oxygen partial pressure, the ratio PH2O/PO2 and the temperature and the mode of heating. Moessbauer spectroscopy and X-ray diffraction data for Fe2O(SO4)2 are also presented.
The existence of differences between the structures of Fe2O(SO4)2 and Fe2(SO4)3 is proved on the basis of a detailed thermal study of Fe2O(SO4)2 upon dynamic heating (differential thermal analysis) and upon isothermal heating (thermal-analytic balance) in various gaseous environments and kinetics of the decomposition of both compounds [40, 41, 64, 65].
28. Synthesis, structure, and phase characterization of etylphosphonate salts as active component for plant protection compounds (K. Kosev)
The synthesis of dialkyl-1,2-epoxyalkyl and dialkyl-1-hydroxy-2-chloroalkyl phosphonates from a-haloketones and dialkylphosphonates is studied in phase transfer catalysis conditions (Fig. 1).
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It is found that the interaction between dimethylphosphonate and chloroacetone by use of tetramethylammonium chloride catalyst the reaction results in the formation of dimethyl 2-chlor-1-hydroxy-1-methylphosphonate. When tetrabutylammonium bromide catalyst is used the reaction yields dimethyl 1-methyl-1,2-epoxyethyl phosphonate.
The interaction of calcium dibromide with dimethyl 1-methyl-1,2-epoxyethyl phosphonate leads to the formation of calcium salt of the respective alkylphosphonic acid - calcium methyl 1-methyl-1, 2-epoxyethyl phosphonate. The interaction of tetrabutylammonium bromide with dimethyl 1-methyl-1,2-epoxyethyl phosphonate results in the formation of tetrabutylammonium methyl 1-methyl-1,2-epoxyethyl phosphonate (Fig. 2).
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The structure of the obtained compounds is proved by infrared-, 1H-, 13C-NMR-spectroscopy. The studied compounds are structural analogues precursors of "Fosfomicin".
INTERINSTITUTES PRORAMS:
PUBLICATIONS AND REPORTS AT CONFERENCES AND LOCAL MEETINGS:
1. Borissov M., J.Burov, L. Konstantinov. 2000. Possibility for terestrial observation of gravitational waves by acousto-electron amplification. - J. of Bulg. Acad. of Sci., v.2, 31-35. (in Bulgarian)
2. Dinolova, E., V.Ganev, L. Konstantinov, 2000. UV-VIS spectra of zeolitic K2TiSi3O9.H2 O-experiment and molecular orbital calculation. - In: Proc.13th Conf.on Glassand Ceramics, Eds.: B. Samuneva, S.Bachvarov, I.Gutsov and Y.Dimitriev, Science Invest Publ.House, Sofia Vol. 2, 72-74.
3. Dimov, V, A. Ilieva, N. Khaltakova, L. Filizova. 2000. Structural model of Al-13-pillared montmorillonite. - Clay and Clay Minerals, 48, 1, 1-9.
4. Donchev, I. 2000. Enviromental mineralogy - development and priorities. - Geology and Mineral Resources, 8, 32-33. (in Bulgarian).
5. Engstroem V., B. Mihailova, J. Hedlund, A. Holmgren, S. Sterte. 2000. The effect of seed size on the growth of silicalite-1 films on gold surfaces. - Microporous and Mesoporous Materials, 38 , 51-603.
6. Kalvachev, Yu., F. Verpoort. 2000. CuKMo catalysts for simultaneous removal of diesel soot and nitrogen oxides. -In: Heterogeneous Catalysis (eds. L.Petrov, Ch. Bonev, G. Kadinov), Proc. 9th Intern. symp. Inst. of catalysis, Bulg. Acad. of Sciences, 713-718.
7. Konstantinov, L., V. Valtchev, S. Mintova, B. Mihailova. 2000. Investigation of nano-sized particles and thin films of zeolite-type materials - Proc. of the Annual meeting'2000 on Nanotechnology. - Sofia, 2000, Bulg.Acad. of Sci Publ. house (ed. J.Dragieva, A.Burov), 42-45. (in Bulgarian)
8. Kostov-Kytin, V. 2000. Investigation in the PbS-Sb2S3-PbCl2 system. - Compt. rend. Acad. bulg. Sci., 53, 2, 69-72.
9. Kostov-Kytin, V. 2000. Structural proposal for a synthetic Pb-Sb Cl sulphosaly phase. - Compt. rend. Acad. bulg. Sci., 53, 5, 67-70.
10. Lilkov, V., N. Djabarov, G. Bechev, O.Petrov. 2000. Properties and hydration products of lightweight and expansive cements. Part 2: Hydration products. - Cem. Concr. Res., v.29/10, 1641-1646.
11. Li, Q., B. Mihailova, D. Creaser, J. Sterte. 2000. The nucleation period for crystallization of nanosized TPA-silicalite-1 with varying silica source. - Microporous and Mesoporous Materials, 40 , 53-62.
12. Maleev, M. Chr, V. Kostov-Kytin. 2000. On the growth of the hexagonal prism of a-quartz. - Compt. rend. Acad. bulg. Sci., 53, 8, 61-64.
13. Mihailova, B., I. Savatinova, I. Savova, L. Konstantinov.2000. Modeling of raman spectra of H:LiNBO3. - Solid State Communications, 116, 11-15.
14. Penev, V., L.Konstantinov, M.Marinov. 2000. The problem of geometrization of the language of chemistry. - Academic Open Internet Journal, V.2, Part2: Chemistry (http://www.crosswinds.net/~aoij/2000/v2/part2/p2/index.html).
15. Penev, V., L.Konstantinov, M.Marinov. 2000. Logical structure of the fundamentals of chemistry, conceptual schemes of its geometrization and spatial mathematical models of the sets of different species of simple chemical objects. - Academic Open Internet Journal, V.2, Part2: Chemistry (http://www.crosswinds.net/~aoij/2000/v2/part2/p3/index.html).
16. Petrova, R. ,T. Todorov, S. Bakardjieva, B. Mihailova, O. Angelova. 2000. Crystal structures of Cd(ReO4)2.4U, Cd(ReO4)2.6U and Ca(ReO4)5.5U. Synthesis and characterization of urea adducts from the system M(ReO4)2-U-H2O, M= Ca, Sr, Ba, Pb; U= urea. - Z. Kristallography, 215, 309-316.
17. Shumov, D. 2000. LiB3O5 single crystals: growth and main growth defects. - Physics and Chemistry of Glasses, v. 41, 397-398.
18 . Shumov, D. 2000. Solvents in the BaO-B2O3 system suitable for the growth of NdAl3(BO3) 4 crystals. - Physics and Chemistry of Glasses, v.41, 399-402.
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