Thermal transformations in phosphorites

The thermal transformations in phosphorites during flash calcination were investigated by FT-IR spectroscopy, X-ray diffraction and chemical analyses. During flash calcination changes occur, both in the composition of the phosphorite and in the crystallochemistry of the fluor-carbonate-apatite (francolite). The former changes include: decomposition of a great part of the calcite in the rock and oxidation of organic matter. The latter changes include: partial removal of the structural carbonate; partial relocation of the remaining carbonate ions in the apatite structure; a new arrangement of hydroxyl groups and fluorine on the hexagonal axis; partial condensation of the orthophosphate groups and increase of crystallite sizes. Isomorphous substitution of PO ₄ ^–3 in apatite by SO ₄ ^–2 and SiO ₄ ^–4 may take place.Dedicated to Prof. Menachem Steinberg on the occasion of his 65th birthdayThe financial support from Rotem-Amfert-Negev Phosphate Co. is gratefully acknowledged. We thank Dr. B. Pregerson of the Rotem-Amfert-Negev for supplying samples     

Thermo-XRD-analysis of montmorillonite treated with 1,4-diaminoanthraquinone

Charcoals formed during the thermo-XRD-analysis of montmorillonite (MONT) complexes with the dye 1,4-diaminoanthraquinone (DAAQ) were investigated by using curve-fitting calculations. Five saturated dye solutions were prepared (i) in distilled water and (ii–v) in 0.1, 0.5, 1.0, and 2.0 molar HCl. Two series of dye-clay complexes were prepared by using clay suspensions of 0.6 %and of 0.006 % labeled first and second series, respectively. Five dye-clay complexes were prepared of each series by adding 25 mL of dye solution to 25 mL of clay suspension. There is no free dye in complexes of the first series, but those of the second series, which were synthesized with a high ratio between dye and clay, contain non-adsorbed dye even after five washings. Complexes of the first series are loaded with very small amounts of molecular and protonated DAAQ (5–24 mmol DAAQ per 100 g clay), and their spacings are 1.25–1.54 nm suggesting the presence of tactoids with protonated or molecular DAAQ lying parallel to the clay layers. No carbon analyses were performed to the second series complexes. In addition to tactoids with spacing of 1.32 nm, they contain tactoids with spacings of 1.81–1.96 nm, suggesting that intercalated DAAQ are lying perpendicular to the clay layers. Three types of intercalated charcoal are identified in both series during the thermal analysis, one type with a low thermal stability and two types with high thermal stabilities. Charcoals of the second series complexes preserve the geometry of the original complexes up to high temperatures.     

Analysis of thermal phases in calcareous Iron Age pottery using FT-IR and Raman spectroscopy

The work deals with the FT-IR and micro-Raman spectroscopy study of the pseudo-amorphous and crystalline thermal phases in the composition of calcareous Iron Age pottery from the Galilee. The application of second-derivative and curve-fitting techniques improves the identification of the thermal phases in the composition of the pottery and makes it possible to analyze the pseudo-amorphous phases which are formed during the firing of the clayey raw material to pottery. This technique makes it possible to distinguish between meta-smectite and meta-kaolinite and to estimate the firing temperature of the pottery. The Micro-Raman spectroscopy is sensitive to the structural degree of ordering of the thermal phases and enables point analysis of peculiar components in the composition of the pottery. Based on the spectroscopic study, it is concluded that the calcareous pottery contained large amounts of microcrystalline-recarbonated calcite mixed with the meta-clay. The large amount of recarbonated calcite in the pottery material and the relatively low firing temperature indicates that instead of sintering the clay, lime technology was used for the cementation of the calcareous vessels. This process took place after the firing by recarbonation of the decomposed calcite which leads to cementation of the vessels with microcrystalline calcite.     

From Chaos to Ordering: New Studies in the Shannon Entropy of 2D Patterns

Properties of the Voronoi tessellations arising from random 2D distribution points are reported. We applied an iterative procedure to the Voronoi diagrams generated by a set of points randomly placed on the plane. The procedure implied dividing the edges of Voronoi cells into equal or random parts. The dividing points were then used to construct the following Voronoi diagram. Repeating this procedure led to a surprising effect of the positional ordering of Voronoi cells, reminiscent of the formation of lamellae and spherulites in linear semi-crystalline polymers and metallic glasses. Thus, we can conclude that by applying even a simple set of rules to a random set of seeds, we can introduce order into an initially disordered system. At the same time, the Shannon (Voronoi) entropy showed a tendency to attain values that are typical for completely random patterns; thus, the Shannon (Voronoi) entropy does not distinguish the short-range ordering. The Shannon entropy and the continuous measure of symmetry of the patterns demonstrated the distinct asymptotic behavior, while approaching the close saturation values with the increase in the number of iteration steps. The Shannon entropy grew with the number of iterations, whereas the continuous measure of symmetry of the same patterns demonstrated the opposite asymptotic behavior. The Shannon (Voronoi) entropy is not an unambiguous measure of order in the 2D patterns. The more symmetrical patterns may demonstrate the higher values of the Shannon entropy.     

Rehydroxyiation of clay minerals and hydration in ancient pottery from the ‘Land of Geshur’

Rehydroxylation of clay minerals and hydration in Bronze and Iron Age pottery from the Land of Geshur (east of the Sea of Galilee), were investigated by IR thermospectrometry. A weak OH band, which resembles those in smectite or illite, exists in most samples, but it is masked by the water bands at lower temperature. Two types of transformation of clay minerals occur during firing of raw materials, reversible and nonreversible dehydroxylation, taking place at a relatively low and high firing temperatures, respectively.Clay minerals rehydroxylate and reconstruct after relatively higher firing temperatures in noncalcareous raw materials than in calcareous ones. These processes take place after higher temperatures in cooking pots made from the former type of raw material as compared with storage and table-ware vessels made from the latter.The absorbed water in the pottery is mainly connected with the dominant X-ray amorphous matter formed by the firing process.

---

Zusammenfassung Mittels IR-Thermospektrometrie wurde die Rehydroxylierung von Tonerdemineralien und die Hydratierung in Geschirr aus dem Bronze- und Eisenzeitalter, aus dem Land der Geshur (Osten des Galiläischen Meeres) untersucht. Eine schwache OH-Bande, die denen in Smektit oder Illit ähnelt, existiert in den meisten Proben, es wird aber bei niedrigeren Temperaturen durch Wasserbanden verdeckt. Während des Brennens von Rohmaterial finden zweierlei Umwandlungen der Tonerdemineralien statt, bei relativ niedrigen Temperaturen reversible und bei relativ hohen Temperaturen nichtreversible Dehydroxylierung.Tonerdemineralien werden in kalkfreiem Rohmaterial nach relativ höheren Brenntemperaturen rehydroxyliert und wiederaufgebaut als in kalkhaltigen. Diese Prozesse verlaufen nach höheren Temperaturen in Kochtöpfen aus ersterem Rohmaterial im Vergleich zu Vorrats- und Eßgeschirr aus letzterem Material.Das in der Töpferware adsorbierte Wasser ist in erster Linie an dem beim Brennprozeß gebildeten, röntgenmäßig amorphen Material gebunden.

---

---

Dedicated to Prof. Dr. H. J. Seifert on the occasion of his 60^th birthday

---

This research was supported by the Basic Research Foundation administered by the Israel Academy of Sciences and Humanities. This support is gratefully acknowledged.

---

The pottery was excavated by the Land of Geshur Archaeological Project, the Institute of Archaeology, Tel-Aviv University, M. Kochavi, director.

---

The work was carried out while the first author was a visiting scientist at the Geological Survey in Jerusalem. The author expresses his appreciation to Dr. Yaacov Nathan and Mr. Yoetz Deutsch of the Geological Survey, for the hospitality and helpful discussions.

---

The authors express their appreciation to L. Vinitzky from the Institute of Archaeology, Tel-Aviv University for supplying the Intermediate Bronze pottery and useful discussions.     

Formation of carnallite type double salts by grinding mixtures of magnesium and alkali halides with the same anions

The formation of carnallite type double salts by grinding mixtures of hydrated magnesium halide and alkali halides with the same anions was investigated by X-ray diffraction, infrared spectroscopy and thermal analysis. Carnallite (KMgCl₃·6H₂O), cesium-carnallite (CsMgCl₃·6H₂O), bromo-carnallite (KMgBr₃·6H₂O) and cesium-bromo-carnallite (CsMgBr₃·6H₂O) were formed by grinding mixtures of MgCl₂·6H₂O with KCl or CsCl and MgBr₂·6H₂O with KBr or CsBr, respectively. Hydrated solid solutions of magnesium in potassium or cesium halides were obtained from that portion of potassium and cesium halides which did not take part in the formation of the double salt.     

Kinetic analysis of thermal dehydration and hydrolysis of MgCl2·6H2O by DTA and TG

The thermal decomposition of MgCl₂·6H₂O (non-dried and partly dried) and the kinetics of the process were studied by DTA, TG, DTG, IR, X-ray diffraction and chemical analysis of Mg and Cl. The reactions which occurred in the course of the thermal analysis were identified as dehydration (in steps), thermal hydrolysis of MgCl₂·H₂O and dehydrochloridization of magnesium hydroxy chlorides. Melting of the phases MgCl₂·6H₂O, MgCl₂·4H₂O and MgCl₂ was also identified in the thermal curves. Thermal weight loss continued up to 800 °C in flowing air or nitrogen, but only up to 700 °C in static air. MgO was the end-product of thermal treatment in both cases.The kinetic parameters of the reaction, the activation energyE, pre-exponential factorA and apparent order of reactionb, were computed by several methods. The activation energy and the apparent reaction order of dehydration were found to increase with decreasing hydration number of the Mg. The dehydrochloridization process had the highest activation energy.

---

Zusammenfassung Die thermische Zersetzung von MgCl₂·6H₂O (nicht und teilweise getrocknet) und die Kinetik dieses Prozesses wurden mittels DTA, TG, DTG, IR, Röntgendiffraktometrie und chemischer Analyse von Mg und Cl untersucht. Die im Verlaufe der thermischen Analyse vor sich gehenden Reaktionen sind Dehydratisierung (in Schritten), thermische Hydrolyse von MgCl₂·H₂O und Chlorwasserstoffaustritt aus Magnesiumhydroxychloriden. Das Schmelzen der Phasen MgCl₂·6H₂O, MgCl₂·4H₂O und MgCl₂ ist in den thermischen Kurven ebenfalls zu erkennen. Im Luft- und Stickstoffstrom erfolgt ein Gewichtsverlust bis 800 °C, in statischer Luftatmosphäre dagegen nur bis 700 °C. MgO war in beiden Fällen Endprodukt der thermischen Behandlung. Die kinetischen Parameter der Reaktion (AktivierungsenergieE, präexponentieller FaktorA, scheinbare Reaktionsordnungb) wurden nach verschiedenen Methoden berechnet. Aktivierungsenergie und scheinbare Reaktionsordnung der Dehydratisierung nehmen mit abnehmendem Hydratationsgrad des Mg zu. Die Chlorwasserstoffabspaltung erfordert die höchste Aktivierungsenergie.

---

, , , , ( ) . : ( ), . , . 800 °C, - 700 °C. B . , . , . .

---

---

The authors express their appreciation to Dr. Jacob Nathan and Mr. Yoetz Deutch from th Geological Survey, Jerusalem, for the use of the thermal analysis instrument and for useful discussion, and to Mrs. Sarah Erlich from the same institute, for the chemical analysis. The financial support by Everyman's University, Tel-Aviv, and by the Hebrew University of Jerusalem is acknowledged.     

Analyzing the calcination of sulfur-rich calcareous oil shales using FT-IR spectroscopy and applying curve-fitting technique

The thermal processes during progressive calcination of sulfur-rich calcareous oil shales were analyzed using FT-IR spectroscopy and applying curve-fitting technique. The spectroscopic analysis is advantageous in the analysis of amorphous and short-range ordered thermal phases lacking of XRD peaks. The raw calcareous oil shales are composed of organic matter, kaolinite, smectite, calcite, and apatite (francolite). The principal thermal phases are metakaolinite, meta-smectite, free lime, anhydrite, gehlenite, and ellestadite. The thermal reactions observed with increase temperatures includes decomposition of organic matter followed by release of sulfur gas; dehydroxylation of kaolinite; and smectite at 500–600 °C; and thermal transformation to metakaolinite and meta-smectite; decarbonation of microcrystalline calcite to free lime at 600 °C; reaction of the sulfur gas with the free lime; formation of anhydrite at 600 °C; reaction of apatite and formation of ellestadite at 800 °C; reaction of the metakaolinite; the meta-smectite with the free lime; formation of gehlenite at 900 °C. Owingto the sulfatization process, a great part of the sulfur content of the raw oil shales is retained in the calcined ashes and the release of sulfur gas to the atmosphere decreases. Thus, the combustion of calcareous oil shales for energy source has less pollution effect than that of the clayey oil shales. FT-IR spectroscopy and spectral analysis seems to be useful methods for phase analysis of oil shales in combustion industry.     

Thermo-FTIR spectroscopy analysis as a method of characterizing ancient ceramic technology

The Iron Age ceramic technology used in the manufacturing of cooking pots was studied by thermo-FTIR spectroscopy analysis. The pottery was excavated at Tel Hadar on the eastern shore of the Sea of Galilee. The results demonstrate that the cooking pots were manufactured using noncalcareous or slightly calcareous raw material proceeds from soil. The firing was at about 750-850°C and the cementation to ceramic was obtained by low temperature sintering of the clay. The use of soil raw material composed of smectitic (montmorillonitic) clay enabled the low temperature sintering. The clay from soil is relatively poorly crystallized and rich in natural iron oxide, both of which induce earlier sintering. Most of the cooking pots were tempered with broken pieces of large calcite crystals that were added to the clayey raw material from an additional source. Alternative tempering with limestone particles composed of polycrystalline calcite is inappropriate as it brings about earlier and intense decarbonation during the firing, which causes defects in the pots.