A chemometric approach to the historical and geographical characterisation of different terracotta finds

The development of modern analytical instrumental techniques has allowed to solve a lot of problems concerning all kinds of disciplines, but often we can obtain for the analysed samples very numerous data, obtained by means of analytical techniques. So the effort of the analysts is more and more paid on the elaboration of a so high number of data. We can find a typical example in the classification and study of archaeological finds. In the archaeometry, that is the application of scientific methods and analysis techniques to archaeological issues, one of the most important step is the statistical elaboration of multivariate data obtained by physical and chemical analysis of ancients artefacts. This study was carried out on 20 different pottery samples coming from different periods. The 20 analysed terracotta finds come from 4 different archaeological sites, three Italian and one Libyan. For the analysis we used ICP–AES, thermogravimetric (TG) and thermomechanical (TMA) techniques; the main technique used to elaborate the data was the Principal Component Analysis (PCA). We already knew, approximately, the “burning age” of the finds and we had to check if some eigenvector of Principal Components Analysis could fit with that age. Few milligrams of finds were used for ICP–AES, TGA and TMA analysis obtaining, after a reduction, a matrix of 11 variables. The results show a good correlation between age and PC1.     

The specific surface area and catalytic properties of the calcination products of δ-FeOOD

The effect of calcination temperature on the structure, specific area and catalytic activity of samples obtained from -FeOOH and -FeOOD was studied. It was found that, as a result of dehydratation, the samples differ mainly in specific surface area and in their catalytic properties.

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Spezifische Oberfläche und katalytische Eigenschaften der Calcinierungsprodukte von -FeOOD

Zusammenfassung Der Effekt der Calcinierungstemperatur auf die Eigenschaften von Proben aus -FeOOH und -FeOOD wurde untersucht. Die dehydratisierten Produkte unterschieden sich—bei sehr ähnlichen Strukturen—hauptsächlich bezüglich spezifischer Oberfläche und katalytischer Aktivität.

     

Die Kristallstrukturen der Dicaesium-Dodekahalogeno-closo-Dodekaborate Cs2[B12X12] (X = Cl,Br, I) und ihrer Hydrate

The Crystal Structures of the Dicesium Dodecahalogeno-closo-Dodecaborates Cs₂[B₁₂X₁₂] (X = Cl, Br, I) and their Hydrates The perhalogenated derivatives Cs₂[B₁₂X₁₂] (X = Cl - I) have been synthesized by reaction of Cs₂[B₁₂H₁₂] with the respective elemental halogens (Cl₂, Br₂ and I₂). Upon recrystallization from aqueous solution colourless, face-rich single crystals of the dihydrates (Cs₂[B₁₂X₁₂] · 2 H₂O) are obtained first which can be dehydrated topotactically via the monohydrates (Cs₂[B₁₂X₁₂] · H₂O) leaving to the solvent-free compounds (Cs₂[B₁₂X₁₂]) behind without loss of their crystallinity. The ionic cesium salts were characterized by single crystal X-ray diffraction. All three halogenoborates are isostructural and they crystallize at room temperature in the trigonal space group (Cs₂[B₁₂Cl₁₂]: a = 959.67(3) pm, c = 4564.2(2) pm; Cs₂[B₁₂Br₁₂]: a = 997.92(3) pm, c = 4766.4(3) pm; Cs₂[B₁₂I₁₂]: a = 1047.05(4) pm, c = 5018.3(3) pm; Z = 6). The crystal structures consist of a cubic closest packed host lattice formed by two crystallographically inequivalent quasi-icosahedral [B₁₂X₁₂]^2- anions (Cs₂[B₁₂Cl₁₂]: d(B-B) = 178 - 179 pm, d(B-Cl) = 179 - 180 pm; Cs₂[B₁₂Br₁₂]: d(B-B) = 176 - 180 pm, d(B-Br) = 195 - 197 pm; Cs₂[B₁₂I₁₂]: d(B-B) = 177 - 182 pm, d(B-I) = 214 - 217 pm). By ordered occupation of half of the tetrahedral and formally all octahedral interstices in every intermediate layer with Cs⁺ cations, a structure emerges where (Cs1)⁺ is trigonally non-planar coordinated by three (CN = 9) and (Cs2)⁺ tetrahedrally coordinated by four (CN = 12) [B₁₂X₁₂]^2- anions. Thereby triangular faces of halogen atoms of the icosahedral clusters are coordinatively effective in both cases. In their mono- and dihydrates the incomplete coordination sphere of (Cs1)⁺ is completed by one and two water molecules, respectively. The thermal decomposition of the dicesium dodecahalogeno-closo-dodecaborate hydrates and their dehydration products was investigated using DTA/TG methods in a temperature range between room temperature and 1200 °C. Additionally the compounds were also characterized by ¹¹B-NMR spectroscopy in aqueous solution.     

Syntheses,crystal structures and thermoanalyses of alkaline earth metal complexes derived from dinitropyridone

Six new alkaline-earth metal compounds derived from dinitropyridone ligands (3,5-dinitropyrid-2-one, 2HDNP; 3,5-dinitropyrid-4-one, 4HDNP and 3,5-dinitropyrid-4-one-N-hydroxide, 4HDNPO) were synthesized and characterized by elemental analysis, FT-IR and partly by powder XRD, TG-DSC and X-ray single-crystal diffraction analysis. The structural determination revealed that one molecule of both magnesium salts (Mg(2DNP)₂ ·?8H₂O, (1), and Mg(4DNP)₂ ·?6H₂O (4)) comprise one cation [Mg(H₂O)₆]²⁺ and two anions displaying centro-symmetry with the Mg atom located at the center. Two anions (and crystalline water molecules) are joined by hydrogen bonds. The barium salt Ba(4DNP)₂ ·?4H₂O (5), is a centro-symmetric dimer with each Ba(II) being coordinated by one monodentate ligand anion, two bidentate ligand anions (different coordination pattern) and five water molecules. Another barium salt, Ba(4DNPO)₂ ·?6H₂O (6), is a coordination polymer, the ten-coordinate (BaO₁₀) barium environment comprising four water molecules, a pair of 4DNPOs via the pyridine-N-oxide oxygen, and one 4DNPOs from an adjacent metal atom offering chelating nitro group oxygen, bridging adjacent bariums. Abundant intermolecular hydrogen bonds link the molecules of each complex into multi-dimensional chains. The X-ray powder diffraction analysis confirmed the phase homogeneity of the polycrystalline samples. The TG-DSC results revealed that Mg(2DNP)₂ ·?8H₂O and Ba(4DNP)₂ ·?6H₂O each has three main weight-loss stages. The first step is the loss of all water molecules and the last step is the loss of the nitro groups and/or decomposition of the pyridine rings with the release of heat.     

基于1H-苯并咪唑-2-羧酸的三个镧系超分子化合物的结构、热分解动力学和荧光性质

在水热条件下合成了三个镧系超分子化合物[Ln(HBIC)₃]_n [Ln=Sm (1), Ho (2), Yb (3); H₂BIC=1H-苯并咪唑-2-羧酸], 其中化合物1、2呈单晶态, 化合物3则为粉末样品; 借助单晶X射线衍射(XRD)、粉末衍射、元素分析、红外(IR)光谱、热分析等手段对化合物进行了表征. 结构分析表明, 1-3为同构化合物, 都呈现二维的平面结构, 其中每一个镧系金属中心与来自五个HBIC^-配体的三个氮原子和五个氧原子以两种新的配位模式配位形成一个轻微扭曲的双帽三棱柱几何构型, 相邻的二维(2D)平面进一步通过强的氢键作用形成了一个三维(3D)的超分子结构. 热重分析结果表明, 化合物1-3在360 ℃前均保持稳定, 呈现出良好的热稳定性. 基于Kissinger和Ozawa-Doyle两种方法, 通过差示扫描量热(DSC)技术研究得到了化合物1热分解的动力学参数(指前因子A_K=1.286×10⁸ s^-1; 活化能E_K=199.3 kJ·mol^-1, E_O=205.2 kJ·mol^-1). 另外, 也研究了室温下化合物1和3的固态发光性能, 结果表明, 化合物1和3分别在可见光区和近红外光区呈现出相应镧系金属离子的特征发射.     

Decomposition of tetra-alkylammonium thiomolybdates characterised by thermoanalysis and mass spectrometry

The decomposition pattern of tetraalkyl-tetrathiomolybdates with general formula (R₄N)₂MoS₄ (with R increasing from methyl to heptyl) was determined by means of differential thermal analysis (DTA), thermogravimetric analysis (TGA) and mass spectroscopy (MS) techniques. The complexity of thermal decomposition reactions increases with the size of the R₄N group. Prior to decomposition at least one phase transition seems to occur in all complexes. The onset of thermal reactions was also a function of the tetra-alkylammonium precursor. All compounds decompose without forming sulfur rich MoS_2+x intermediates. For R = methyl to pentyl precursors the MoS₂ produced was nearly stoichiometric, however for R = hexyl and heptyl the S content was significantly reduced with a Mo:S ratio of about 1.5. The carbon and hydrogen residual contents in the product increased with the number of C atoms in R₄N; for N contamination no clear trend was obvious. SEM images show that the formation of macro-pores was also a function of the alkyl group in R₄N. The MoS₂ materials obtained show a sponge-like morphology. Results of DSC experiments in combination with in situ X-ray diffraction also revealed the complex thermal behavior of (R₄N)₂MoS₄ materials; reversible and irreversible phase transitions and glass-like transformations were identified in the low temperature range (35-140 °C), before the onset of decomposition.     

聚偏二氯乙烯热解过程的原位红外光谱

聚偏二氯乙烯是一种热不稳定性的高分子材料，可作为制备含碳材料的前驱体。以红外光谱在线检测功能实现了聚偏二氯乙烯热分解过程的原位分析，通过谱图分析了聚偏二氯乙烯分解过程的机理和温度效应。     

Synthesis and Crystal Structure of Manganese‐tris(1,2‐ethanediamine)tetratelluride [Mn(en)3]Te4 Exhibiting Intermolecular Interactions between the Tetratelluride Anions

Air‐sensitive black crystals of the new compound [Mn(en)₃]Te₄ were synthesized by reacting MnCl₂ · 4 H₂O, K₂Te₃ and elemental Te in 1,2‐ethanediamine (en) under solvothermal conditions at 433 K. The compound crystallizes in the monoclinic space group P2₁/n with lattice parameters a = 839.51(7) pm, b = 1551.3(1) pm, c = 1432.6(1) pm, and β = 90.28(2)°. Isolated [Mn(en)₃]²⁺ cations and Te₄^2– anions are arranged in an alternating fashion parallel to the crystallographic b‐axis. One terminal Te atom of the Te₄^2– anions exhibits a short intermolecular contact to a neighboured anion thus forming Te₈^4– anions. A slightly longer interionic Te…Te separation is observed between two of the inner Te atoms of neighboured Te₈^4– anions. Taking these longer separations into account infinite Te‐chains are formed running parallel to [001]. The intermolecular Te…Te interactions affect the Te–Te bond lengths within the Te₄^2– anion leading to a lengthening of the average Te–Te distance. Short N–H…Te distances indicate hydrogen bonding between the cations and anions. DTA‐TG measurements show that at 441 K the material decomposes in one step. The resulting crystalline material consists of MnTe₂ and Te.     

Transition metal-chalcogen systems,VI: The zirconium-tellurium phase diagram

In the binary Zr–Te system isopiestic, thermoanalytical, and X-ray studies were carried out. The results were combined with data from literature to construct a partial phase diagram. Tetragonal Zr₅Te₄ exists at 44.4 at %Te. Hexagonal ZrTe (WC structure) with a composition between 49 and 50 at %Te is found from 723 to 1,273 K. NiAs-type Zr _1–x Te has a range of homogeneity above 1,273 K from 52.0 to 66.6 at %Te, and at 973 and 723 K from 57.0 to 66.6 at %Te. Within this range the NiAs-type structure transforms into the Cd(OH)₂-type structure. At 60 at %Te Zr _1–x Te has a melting point of about 1,970 K. At 75 at %Te monoclinic ZrTe₃ is found which decomposes peritectically at 903 K. At 778 K orthorhombic ZrTe₅ transforms into liquid and ZrTe₃, and at 712 K ZrTe₅ forms a eutectic with Te.

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Übergangsmetall-Chalcogen-Systeme, 6. Mitt.: Das Zirkonium-Tellur-Phasendiagramm

Zusammenfassung Im binären Zr–Te-System wurden isopiestische, thermoanalytische und röntgenographische Untersuchungen durchgeführt. Die Resultate wurden mit Literaturdaten kombiniert und ein partielles Phasendiagramm aufgestellt. Tetragonales Zr₅Te₄ existiert bei 44.4 At %Te. Hexagonales ZrTe (WC-Struktur) mit einer Zusammensetzung zwischen 49 und 50 At %Te ist zwischen 723 und 1273 K beständig. Zr _1–x Te mit NiAs-Struktur hat oberhalb 1273 K einen Homogenitätsbereich von 52.0 bis 66.6 At %Te, bei 973 und 723 K einen solchen von 57.0 bis 66.6 At %Te. Innerhalb dieses Bereiches geht die NiAs-Struktur in die Cd(OH)₂-Struktur über. Zr _1–x Te mit einer Zusammensetzung von 60 At %Te hat einen Schmelzpunkt von etwa 1,970 K. Bei 75 At %K. wurde monoklines ZrTe₃ gefunden, welches bei 903 K peritektisch zerfällt. Bei 778 K reagiert orthorhombisches ZrTe₅ zu ZrTe₃ und Schmelze, bei 712 K bildet ZrTe₅ mit Te ein Eutektikum.

     

Solvothermal synthesis and crystal structure of Sb(III) and Sb(V) thioantimonates: [Mn(en)3]2Sb2S5 and [Ni(en)3(Hen)]SbS4

Thioantimonate compounds of [Mn(en)₃]₂Sb₂S₅ (1) and [Ni(en)₃(Hen)]SbS₄ (2) (en=ethylenediamine) were prepared by reaction of transition metal chloride with Sb and S₈ powders under solvothermal conditions. Compound 1 consists of discrete [Sb₂S₅]⁴⁻ anion, which is formed by corner-sharing SbS₃ trigonal pyramids. Compound 2 is composed of discrete tetrahedral [SbS₄]³⁻ anion. The compounds 1 and 2 are charge compensated by [M(en)₃]²⁺ cations, whereas in the crystal of 2 there is another counter ion of [Hen]⁺. The results of the synthesis suggest that the temperature, the concentration and the existing states of the starting materials and so on are important for the structure and composition of the final products. In addition, the oxidation-state of antimony might be related to the molar ratio of the reactants. Excess amount of elemental S is beneficial to the higher oxidation-state of thioantimonate (V). Compound 1 decomposes from 150°C to 350°C, while compound 2 decomposes from 200°C to 350°C remaining Sb₂S₃ and NiSbS as residues.