Journal of Thermal Analysis and Calorimetry: An International Forum for Thermal Studies (v.75, #1)
Pyrolysis study of sol—gel derived TiO2 powders: Part III. TiO2-anatase prepared by reacting titanium(IV) isopropoxide with acetic acid
by R. Campostrini; M. Ischia; L. Palmisano (pp. 13-24).
A homogeneous TiO2 gel was obtained by hydrolysing titanium(IV) isopropoxide that was previously modified by reaction with acetic acid. The so stabilized precursor was hydrolysed under strong acidic medium (pH=0 by HCl). Dried TiO2 powders were characterized by FT-IR, XRD, N2 adsorption analyses, coupled thermogravimetric (TG) gas chromatographic (GC) and `mass spectrometric (MS) analyses. A semiquantitative analysis of the main evolved chemical species allowed to depict both the chemical rearrangements occurring in the TiO2 matrix during pyrolysis and the chemical composition of the initial gel.
Keywords: thermogravimetric-mass spectrometric coupled analyses; pyrolysis study; TiO2 gel
Pyrolysis study of sol-gel derived TiO2 powders: Part IV. TiO2-anatase prepared by hydrolysing titanium(IV) isopropoxide without chelating agents
by R. Campostrini; M. Ischia; L. Palmisano (pp. 25-34).
An amorphous TiO2 gel was obtained by hydrolysing titanium(IV) isopropoxide with a stoichiometric amount of water using SnCl2 as catalyst. In these operative conditions, a TiO2 gel matrix containing a lower fraction of organic residual was obtained with respect to samples prepared by previously modifying the titanium alkoxide precursor with chelating ligands. Dried gel powders were characterized by N2 adsorption analyses, FT-IR and XRD measurements. Thermogravimetric (TG) and differential thermal analysis (DTA) coupled with mass spectrometric (MS) and gas chromatographic (GC) measurements were performed in order to identify the organic products released from TiO2 gel pyrolysis. The Tg-MS semiquantitative analysis of the main evolved species allowed to describe both the chemical composition of the initial TiO2 gel and the chemical rearrangements occurring in the matrix during heating up to its crystallisation to anatase form at 420°C.
Keywords: thermogravimetric-mass spectrometric coupled analyses; pyrolysis study; TiO2 gel
Effect of genesis on the properties and hydrogen reducibility of NiO-ZnO mixed oxides
by M. Pospíšil; V. Cuba; D. Poláková (pp. 35-50).
The physico-chemical properties and reactivity tested by hydrogen reduction have been studied for two series of NiO-ZnO mixed oxides of various composition. The solid nickel oxide or zinc oxide in interaction with the solution of nitrate of the second component were used as the precursors in each series. The differences in some physico-chemical parameters of the samples in both series were correlated with their reduction behaviour, followed both in iso- and non-isothermal regime. Moreower, the influence of various factors modifying the reactivity of mixed oxides was also investigated and the results were compared with those obtained from earlier studied analogous systems of quite different origin.
Keywords: hydrogen reduction; physico-chemical properties; NiO-ZnO mixed oxides
Thermal and electrical conductivity properties of some CrIII, MnII and UO 2 II amino alcohol complexes
by M. S. Masoud; S. A. Abou El-Enein; H. A. Motaweh; A. E. Ali (pp. 51-61).
CrIII, MnII and UO2 II amino alcohol complexes were prepared and analyzed. The IR spectra proved that the ligation occurs via oxygen and nitrogen atoms. The nujol mull electronic absorption spectra joined with the room temperature magnetic moment values proved that the complexes are of Oh geometry. The thermal behaviour of the complexes was studied by DTA and TG techniques. The mechanism of the decomposition was suggested. The thermodynamic parameters of the decomposition were evaluated and discussed. The entropy of activation changes, ΔS*, showed that the transition states are more ordered than the reacting complexes. The D.C. electrical conductivity measurements of Cr- and Mn-amino alcohol complexes are of semiconductor behaviour. Empirical equations were deduced for the conduction of the investigated complexes.
Keywords: electrical conductivity; thermal analysis; amino alcohol complexes
Phase equilibria in the Ag4SSe-SnTe system
by V. Vassilev; L. Aljihmani; V. Parvanova (pp. 63-71).
The phase diagram of the system Ag4SSe-SnTe is studied by means of X-ray diffraction, differential thermal and metallographic analyses and measurements of the microhardness and the density of the material. This diagram is divided into two eutectic-type subdiagrams by the composition Ag4SSe·2SnTe. The unit-cell parameters of the intermediate phases 3Ag4SSe·SnTe (phase A) and α-Ag4SSe·2SnTe (phase B) are determined as follows: for phase A: a=0.7851 nm, b=0.7196 nm, c=0.6296 nm, α=101.32°, β=85.90°, γ=111.36°; for phase B: a=0.3662 nm, b=0.3303 nm, c=0.3343 nm,α =90.74°,β =108.94°, γ =91.91°. The phase Ag4SSe·2SnTe melts congruently at 615°C and a polymorphic transition of the phase takes place at T α -β =110°C.
Keywords: phase diagram; differential thermal analysis; Ag4SSe-SnTe; X-ray diffraction
Studies on synthesis, characterization and thermochemistry of Mg2[B2O4(OH)2]·H2O
by L. Zhihong; H. Mancheng; G. Shiyang (pp. 73-78).
A new magnesium borate Mg2[B2O4(OH)2]·H2O has been synthesized by the method of phase transformation of double salt at hydrothermal condition and characterized by XRD, IR, TG and DSC. The enthalpy of solution of Mg2[B2O4(OH)2]·H2O in 0.9764 mol L−1 HCl was determined. With the incorporation of the enthalpies of solution of H3BO3 in HCl (aq), of MgO in (HCl+H3BO3) (aq), and the standard molar enthalpies of formation of MgO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(3185.78±1.91) kJ mol−1 of Mg2[B2O4(OH)2]·H2O was obtained.
Keywords: synthesis; solution calorimetry; standard molar enthalpy of formation; Mg2[B2O4(OH)2]·H2O
Thermal decomposition of lanthanide(III) and Y(III) 3,4,5-trihydroxybenzoates: Preparation, properties
by A. Kula (pp. 79-86).
Complexes of lanthanides(III) (La-Lu) and Y(III) with 3,4,5-trihydroxybenzoic acid (gallic acid) were obtained and their thermal decomposition, IR spectra and solubility in water have been investigated. When heated, the complexes with a general formula Ln(C7H5O5)(C7H4O5)·nH2O (n=2 for La-Ho and Y: n=0 for Er-Lu) lose their crystallization water and decompose to the oxides Ln2O3, CeO2, Pr6O11, and Tb4O7, except of lanthanum and neodymium complexes, which additionally form stable oxocarbonates such as Ln2O2CO3. The complexes are sparingly soluble in water (0.3·10−5−8.3·10−4 mol dm−3).
Keywords: synthesis; IR spectra; complexes; lanthanides; thermal analysis; 3,4,5-trihydroxybenzoates
Thermal properties of fluoride glasses and their gel precursors
by P. Melnikov; R. Rolim; A. Delben; J. R. Delben; A. C. Souza; A. E. Job (pp. 87-93).
Xerogels were prepared from zirconium, barium, aluminum, lanthanum and lithium acetates, corresponding to a Li containing ZBLA composition. The study of their thermal properties (DSC, TG/DTG, FT-IR) showed that they might be used as chemically stable precursors in the preparation of fluoride glasses. Hydrofluoric acid in solution was chosen as a mild fluorinating agent. This newly proposed technique of fluorinating allowed to obtain high quality ZBLALi glass which presents the advantage of higher thermal stability and homogeneity in comparison with the glass obtained using individual commercial fluorides.
Keywords: xerogels; fluoride glasses; glass precursors
Study of the system Pr2O3-SeO2-H2O at 100°C and the properties of the compounds obtained
by G. G. Gospodinov; M. G. Stancheva (pp. 95-100).
The solubility of the system Pr2O3-SeO2-H2O at 100°C was studied. The fields of crystallization of Pr2(SeO3)3·H2O, PrH(SeO3)2, Pr(HSeO3)3 were established. The compounds obtained were identified by means of chemical, X-ray and thermal analysis. The thermal decomposition of Pr2(SeO3)3·H2O, PrH(SeO3)2, and Pr(HSeO3)3 was determined.
Keywords: solubility isotherm; X-ray pattern; reaction mechanisms; praseodymium selenites
Synthesis of ferrites: Thermal analysis of some transition metal tris(maleato)ferrates(III)
by B. S. Randhawa; K. J. Sweety; Manpreet Kaur; J. M. Greneche (pp. 101-111).
Thermal analysis of some transition metal ferrimaleate precursors, M3[Fe(mal)3]2·xH2O (M=Mn, Co, Ni, Cu) has been studied in static air atmosphere from ambient to 600°C. Various physico-chemical techniques, i.e. TG, DTG, DTA, XRD, IR, Mössbauer spectrometry, have been employed to characterize both the intermediates and final products. After dehydration the anhydrous precursors undergo decomposition to yield an iron(II) intermediate, M[FeII(mal)2] (M=Mn, Co, Ni, Cu) in the temperature range 160-275°C. A subsequent oxidative decomposition of iron(II) species leads to the formation of α-Fe2O3 and MO in the successive stages. Finally a solid-state reaction occurs between the oxides above 400°C resulting in the formation of transition metal ferrites, MFe2O4. The ferrites have been obtained at much lower temperature and in less time than in the conventional ceramic method.
Keywords: ferrites; precursors; solid-state reactions
Thermal transformations of the products of partial hydrolysis of hydrous aluminium nitrate
by B. Pacewska; M. Keshr (pp. 113-123).
Thermal analysis, mass spectrometry, infrared spectrophotometry, X-ray phase analysis, scanning electron microscopy, and sorption methods were used in the study of thermal transformations of the products of partial hydrolysis of hydrous aluminium nitrate in ammonia medium. It has been found that the process of aluminium nitrate hydrolysis under the conditions applied and in the presence of ammonia gives boehmite as the main product, with some admixture of a basic salt.Aluminium oxide obtained from the products of partial hydrolysis of hydrous aluminium nitrate in ammonia medium at 550°C has a crystalline γ-Al2O3 structure. Its specific surface, as determined by low-temperature adsorption of nitrogen, exceeds 200 m2g−1. Features of the products are well developed mesopore structure and considerable ability of benzene adsorption. Calcination of the obtained aluminium oxide for 2 h at 900°C reduces its specific surface to about 110 m2 g−1.
Keywords: TA; hydrous aluminium nitrate; thermal transformations; partial hydrolysis
Study of sulphur in oxidised coals by atmospheric pressure-temperature programmed reduction
by M. Kozlowski; R. Pietrzak; H. Wachowska; J. Yperman (pp. 125-134).
The influence of oxidation of coal, performed with different oxidising agents, on the sulphur species was studied. Conversions of the sulphur species were investigated by the Atmospheric Pressure-Temperature Programmed Reduction method (AP-TPR). The removal of pyrite proved to be advantageous for AP-TPR analysis. It was found that non-thiophene sulphur species undergo easier oxidation by different agent then thiophenic structures.
Keywords: oxidation; coal; sulphur; AP-TPR
Solid-solid interactions in pure and Li2O-doped manganese and magnesium mixed oxides system
by A. M. Ghozza (pp. 135-151).
The solid-solid interactions between manganese and magnesium oxides in absence and in presence of small amounts of Li2O have been investigated. The molar ratios between manganese and magnesium oxides in the form of Mn2O3 and MgO were varied between 0.05:1 to 0.5:1. The mixed solids were calcined in air at 400-1000°C. The techniques employed were DTA, XRD and H2O2 decomposition at 20-40°C.The results obtained revealed that solid-solid interactions took place between the reacting solids at 600-1000°C yielding magnesium manganates (Mg2MnO4, Mg6MnO8, MgMnO4 besides unreacted portions of MgO, Mn2O3 and Mn3O4). Li2O-doping (0.75-6 mol%) of the investigated system followed by calcination at 600 and 800°C decreased progressively the intensity of the diffraction lines of Mn2O3 (Bixbyite) with subsequent increase in the lattice parameter 'a' of MgO to an extent proportional to the amount of Li2O added. This finding might suggest that the doping process enhanced the dissolution of Mn2O3 in MgO forming solid solution. This treatment led also to the formation of Li2MnO3. Furthermore, the doping with 3 and 6 mol% Li2O conducted at 800°C resulted in the conversion of Mn2O3 into Mn3O4, a process that took place at 1000°C in absence of Li2O. The produced Li2MnO3 phase remained stable by heating at up to 1000°C. Furthermore, Li2O doping of the investigated system at 400-1000°C resulted in a progressive measurable increase in the particle size of MgO.The catalytic activity measurements showed that the increase in the molar ratio of Mn2O3 in the samples precalcined at 400-800°C was accompanied by a significant increase in the catalytic activity of the treated solids. The maximum increase in the catalytic activity expressed as reaction rate constant measured at 20°C (k 20°C) attained 3.14, 2.67 and 3.25-fold for the solids precalcined at 400, 600 and 800°C, respectively. Li2O-doping of the samples having the formula 0.1 Mn2O3/MgO conducted at 400-600°C brought a progressive significant increase in its catalytic activity. The maximum increase in the value of k 20°C due to Li2O attained 1.93 and 2.75-fold for the samples preheated at 400 and 600°C, respectively and opposite effect was found for the doped samples preheated at 800°C.
Keywords: H2O2 decomposition; Mg6MnO8MgO; Mn2O3Li2O-doping; Li2MnO3
Synthesis and TG/DTA study on two new metallo(VI)-arsenato(V) heteropolyacids containing vanadium(V)
by A. Fodor; L. Ghizdavu; A. Suteu; A. Caraban (pp. 153-158).
An improved method for the synthesis of two heteropolyacids of the same type: H5[AsMo10V2O40]·13H2O and H5[AsW10V2O40]·16H2O was elaborated. The studied compounds were characterized by elemental analysis, IR spectra and thermal behaviour over 20-800°C temperature range.
Keywords: Keggin triheteropolyacids; IR spectra; thermal behaviour
Thermal and photochemical behaviour of Zn(II) complexes of some cephalosporins
by A. A. M. Aly; A. H. Osman; N. Abo El-Maali; G. A. A. Al-Hazmi (pp. 159-168).
Zn(II) complexes of some cephalosporin antibiotics namely cephalexin, cephapirin, cefamandole, cefuroxime, cefotaxime and ceftazidime were synthesised and characterized. The stoichiometrics and the mode of bonding of the complexes were deduced from their elemental analysis, IR and electronic spectroscopies. Thermal stabilities and the photochemical behaviour of the complexes were studied. The Zn(II) complex of cephalexin exhibited a high light sensitivity. The remaining Zn(II) complexes behaved similarly to their free antibiotics, upon irradiation.
Keywords: thermal stability; photochemical behaviour; Zn(II) complexes; cephalosporins
Investigations on temperature dependent structural evolution of NaPO3 glass
by R. Sridarane; G. Raje; D. Shanmukaraj; B. J. Kalaiselvi; M. Santhi; S. Subramanian; S. Mohan; B. Palanivel; R. Murugan (pp. 169-178).
The understanding of molecular level structural information of phosphate glasses is very much essential. The unique microwave-absorbing ability of NaH2PO4·2H2O was found to be very useful for preparing crystal and glassy sodium super ionic conductors (Nasicon's) as a component of batch mixtures. In this work NaPO3 glass was prepared by both conventional melt quench and microwave heating from NaH2PO4·2H2O as a starting material. The structure of NaPO3 glass and their structural evolution upon heating through glass transition were probed by combination of complementary techniques like differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) and thermo-Raman spectroscopy.
Keywords: NaPO3 glass; structural evolution; thermo-Raman spectroscopy
Investigation of thermal properties of some basalt samples in Egypt
by M. S. Mostafa; N. Afify; A. Gaber; E. F. Abu Zaid (pp. 179-188).
This work aims in studying the temperature dependence of the thermal properties (thermal diffusivity, k, specific heat, C p and thermal conductivity, λ) of some basalt group samples, collected from different regions in the eastern desert of Egypt. The thermal properties of these samples were measured in the temperature range from r.t. to 900 K. The average values of the thermal conductivity of these investigated samples lie in the range from 0.4·10−3 to 2.01·10−3 cal cm−1 s−1 K−1. This means that these samples are considered as thermal insulating materials. The thermogravimetric analysis (TG) confirmed that these investigated samples are dry rocks. X-ray fluorescence (XRF) and X-ray diffraction (XRD) confirmed that these rock samples have a crystalline phase, the peaks of XRD have a small change in their location as a result of heat treatment. This behaviour was attributed to the oxidation and firing of some minerals after the heat treatment.
Keywords: thermal properties; basalt
Thermal analysis study of some transition metal complexes by TG and DSC methods
by M. Sekerci; F. Yakuphanoglu (pp. 189-195).
The thermodynamic and thermal properties of [Cu(L)2·Cl2], [Ni(L)2]·Cl2, [Co(L)2·Cl2]; L=1,2-bis(o-aminophenoxy)ethane (BAFE), complexes have been investigated. The thermal decomposition of the complexes took place in two distinct steps in endothermic reaction up to 700°C. The activation energy E, the entropy change ΔS #, enthalpy ΔH change and Gibbs free energy change ΔG # were calculated from the results of thermogravimetry analysis (TG) and heat capacity from the results of differential scanning calorimetry (DSC). It was found that the thermal stabilities and activation energies of the complexes follow the order Ni(II)>Cu(II)>Co(II) and E Co<E Ni<E Cu, respectively.
Keywords: transition metal complexes; thermal analysis; thermodynamic parameters
Use of DTA-TG in the evaluation of autoclaved cement-based systems: Part I. Cement-brick waste blends
by D. S. Klimesch; M. Gutovic; A. Ray (pp. 197-204).
Fired-clay products such as bricks, tiles and pavers, are made in large volumes for use in a variety of construction applications throughout the world. A significant proportion of them ends up being a waste product either during their production process or the demolition of buildings. High pressure steam curing or autoclaving has proven extremely versatile for the manufacture of cement-based building products incorporating waste materials such as fly-ash and blast furnace slag. The nature of hydration products in an autoclaved cement based system incorporating different amounts of finely ground brick waste was investigated by means of thermal analysis and XRD, and is the subject of this paper.
Keywords: autoclaving; C-S-H; brick waste; hydrogarnet; 1.1 nm tobermorite
Curing adhesives of urea-formaldehyde type with collagen hydrolysates of chrome-tanned leather waste
by F. Langmaier; J. Šivarová; M. Mládek; K. Kolomazník (pp. 205-219).
Condensation of dimethylol-urea (DMU) mixed with urea (U) and collagen hydrolysate (H), obtained through enzymatic hydrolysis of chrome-tanned leather waste, without added acid curing agents in the solid phase was studied through DSC and TG techniques in a temperature interval up to 220°C. Among both techniques TG proved be more useful.While the DMU+U mix produced methylene-oxide (-CH2-O-CH2-) and methylene (-CH2-) bridges at a ratio of approx. 1:1, urea substituted for collagen hydrolysate increased the proportion of more stable methylene bridges to methylene-oxide bridges to a ratio of approx. 2:1. Methylene-oxide bridges are considered to be the main potential sources of formaldehyde emissions from cured urea-formaldehyde type adhesives, and thus the use of collagen hydrolysate in preparation of urea-formaldehyde adhesive types is a suitable way how to make such adhesives more environmental friendly.
Keywords: curing; hydrolysates of chromed leather waste; amino-resins; formaldehyde emission
Thermal degradation of wood treated with guanidine compounds in air: Flammability study
by Ming Gao; Caiyun Sun; Kai Zhu (pp. 221-232).
Wood has been treated with guanidine phosphate, guanidine nitrate, guanidine carbonate and guanidine chloride to impart flame retardancy. The samples were subjected to differential thermal analysis (DTA) and thermogravimetry (TG) from ambient temperature to 800°C in air to study their thermal behaviors. From the resulting data, kinetic parameters for different stages of thermal degradation were obtained following the method of Broido. For the decomposition of wood and flame retardant wood, the activation energy was found to decrease from 116 to 54 kJ mol−1; the char yield was found to increase from 5.6 to 34.9%, LOI from 18 to 41.5, which indicated that the flame retardancy of treated wood was improved. Effects of the different compounds on the degradation and flammability of wood have also been proposed.
Keywords: DTA; pyrolysis; wood; flame retardant; degradation; TG
Crystallization and melting of isotactic polypropylene in response to temperature modulation
by A. Genovese; R. A. Shanks (pp. 233-248).
Isotactic polypropylene (iPP) was crystallized using temperature modulation in a differential scanning calorimeter (DSC) to thicken the crystals formed on cooling from the melt. A cool-heat modulation method was adopted for the preparation of the samples under a series of conditions. The effect of modulation parameters, such as temperature amplitude and period was monitored with the heating rate that followed. Thickening of the lamellae as a result of the crystallization treatment enabled by the cool-heat method lead to an increase in the peak melting temperature and the final traces of melting. For instance, iPP melting peak shifted by up to 3.5°C with temperature amplitude of 1.0°C while the crystallinity was increased from 0.45 (linearly cooled) to 0.53. Multiple melting endotherms were also observed in some cases, but this was sensitive to the temperature changes experienced on cooling. Even with a slower underlying cooling rate and small temperature amplitudes, some recrystallization and reorganization occurred during the subsequent heating scan. The crystallinity was increased significantly and this was attributed to the crystal perfection that occurred at the crystal growth surface. In addition, temperature modulated differential scanning calorimetry (TMDSC) has been used to study the melting of iPP for various crystallization treatments. The reversing and non-reversing contribution under the experimental time scale was modified by the relative crystal stability formed during crystallization. Much of the melting of iPP was found to be irreversible.
Keywords: crystallization; melting; DSC; isotactic polypropylene; TMDSC
Flammability of butadiene-acrylonitrile rubbers
by P. Rybinski; G. Janowska; M. Helwig; W. Dabrowski; K. Majewski (pp. 249-256).
The paper discusses the test results of butadiene-acrylonitrile rubber, Perbunan NT 1845 and Perbunan NT 3945, flammability and properties that characterise these elastomers under fire conditions. The flammability was tested by means of oxygen index and thermovision methods. The thorough testing of flammability performed by means of a cone calorimeter made it possible to assess the behaviour of these polymers under fire conditions. The following properties of the tested copolymers were taken into account in this assessment: ignitability, heat release during combustion, smoke-forming capability and toxicity of the gaseous products of thermal decomposition and combustion. It has been found that the increase in the acrylonitrile unit content in the copolymer decreases its flammability and the relative toxic fire hazard, but clearly increases the smoke-forming capability and so the specific extinction area.The interpretation of test results of the elastomers under investigation takes into consideration their thermal stability assessed on the basis of differential thermal analysis, thermogravimetry and other complementary methods.
Keywords: elastomer; thermal stability; flammability; flame temperature; thermal analysis
Characterization of drawn and undrawn poly-L-lactide films by differential scanning calorimetry
by J. F. Turner; A. Riga; A. O'Connor; J. Zhang; J. Collis (pp. 257-268).
Poly-L-lactic acid (PLLA) is an optically active, biocompatible and biodegradable polymer that has been widely investigated as an artificial cell scaffold material. In its most crystalline form, PLLA is highly anisotropic and is one of the most piezoelectric polymers known. Conversely, amorphous PLLA exhibits little, if any, piezoelectric behavior. Compression molded PLLA films can be endowed with varying amounts of crystalline character and piezoelectricity by uniaxially stretching the polymer in a hot air bath. Understanding the precise crystalline architecture of PLLA that results from tensile drawing is important for constructing cell scaffolds that have highly tailored biodegradation and cell guiding properties. In our work here, we investigate the changes in the thermal properties of PLLA at draw ratios between 1.0 and 5.5 using differential scanning calorimetry (DSC). The crystallinity of the compression molded undrawn starting material is characterized using X-ray diffraction. Our DSC results show an increase in percent crystallinity with increasing draw up to a draw ratio of 4.0. At greater draw ratios, there is a decrease in the crystalline character exhibited by PLLA.
Keywords: DSC; biomaterials; poly-L-lactic acid
Characterization of snake skin by thermoanalytical techniques
by K. Bhasi; A. T. Riga; K. S. Alexander (pp. 269-276).
Snake skin is a viable and readily available material as a model for human skin. Pharmaceutical applications use shed snake skin to study the effects of sunscreens on exposure to UV radiation (e.g. benzophenone on Boa integument). In order to understand the effects of radiation or drug transport through this model skin, one must determine its basic physical properties. This preliminary study evaluated two types of snake skin, namely Cuban Boa a 'dark' skin (Epicrates angulifer) and Green tree python a 'light' skin (Morelia viridis). Previous studies by other investigators have used pig, rabbit and snake skin as a human skin substitute. The structure of both snake skins was comparable based on IR spectroscopy and were functionally amino acids and moisture. Photomicrography by light and scanning electron microscopy revealed strong anatomic similarities. Morphologically there were two structures visible, namely a cellular and hinge-fibrous area. The thermal techniques indicated a phase transition at 35-75°C, which is associated with lipid melting. There was an 8 and 12% mass loss for the light skin and dark skin, respectively, which is interpreted, in part, as moisture loss at <100°C. The physical and analytical properties establish a base line that will be used in the future to differentiate various sunscreen types, such as benzophenone and octyl salicylate. Study was also done to determine the effect of an application of a commercially available sunscreen using SEM.
Keywords: Epicrates anguliferUVA; UVC; DSC; snake skin; UVB; TMAMorelia viridisSEM; thermal analysis
Thermal decomposition of humboldtine: A high resolution thermogravimetric and hot stage Raman spectroscopic study
by R. L. Frost; M. L. Weier (pp. 277-291).
Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates. These oxalates form as a film like deposit on rocks and other host matrices. Humboldtine as the natural iron(II) oxalate mineral is a classic example. Thermogravimetry coupled to evolved gas mass spectrometry shows dehydration takes place in two steps at 130 and 141°C. Loss of the oxalate as carbon dioxide occurs at 312 and 332°C. Dehydration is readily followed by Raman microscopy in combination with a thermal stage and is observed by the loss of intensity of the OH stretching vibration at 3318 cm-1. The application of infrared emission spectroscopy supports the results of the TG-MS. Three Raman bands are observed at 1470, 1465 and 1432 cm-1 attributed the CO symmetric stretching mode. The observation of the three bands supports the concept of multiple iron(II) oxalate phases. The significance of this work rests with the ability of Raman spectroscopy to identify iron(II) oxalate which often occurs as a film on a host rock.
Keywords: hot stage Raman spectroscopy; infrared emission spectroscopy; oxalate; thermogravimetric analysis; high resolution; humboldtine
Microcalorimetric study on the transcription start site mutagenesis
by Y. Yang; Y. Liu; J. Zhu; P. Shen (pp. 293-300).
The microcalorimetric method and DNA site-directed mutagenesis technique were used together to study the effect of transcription start site mutagenesis on RM07 promoter activity and gene transcription efficiency in Escherichia coli. The results revealed that once the putative transcription start site G was mutated to T, the promoter activity of RM07 promoter fragment was decreased and the transcription strength of cat reporter gene was weakened. Our work suggests that the nucleotide component of transcription start site is very critical for the promoter strength and the gene transcription efficiency. Our research also provides a new and useful technique for determining the transcription start site using both chemical and biological method.
Keywords: transcription efficiency; site-directed mutagenesisE. colimicrocalorimetry
Lead(II) and cadmium(II) compounds with 2,4-dichlorophenoxyacetic acid (2,4D) and 2-(2,4-dichlorophenoxy)-propionic acid (2,4DP): Synthesis and properties
by B. Ptaszynski; Z. Zwolinska (pp. 301-315).
The paper presents the conditions under which compounds of the commercial herbicides, 2,4-dichlorophenoxyacetic acid (2,4D; C8H6O3Cl2) and 2-(2,4-dichlorophenoxy)-propionic acid (2,4DP; C9H8O3Cl2), with lead(II) and cadmium(II) are formed and the results of the examination of their properties.On the basis of the elemental analysis and Pb and Cd determination, the following molecular formulae for the obtained compounds were proposed: Pb(C8H5O3Cl2)2.H2O, Cd(C8H5O3Cl2)2.2H2O, Pb(C9H7O3Cl2)2·H2O and Cd(C9H7O3Cl2)2·H2O. Water solubility of the synthesized complexes at room temperature was examined. X-ray powder analysis was carried out. The discussion of IR spectra and conductivity data is presented. Thermal decomposition of these compounds in air was studied by TG/MS methods.
Keywords: complexes; 2,4-dichlorophenoxyacetic acid; 2-(2,4-dichlorophenoxy)-propionic acid; IR spectra; mass spectrometry; solubility; thermal decomposition; X-ray powder diffraction
Characterization of some essential oils and their key components: Thermoanalytical techniques
by A. Hazra; K. Alexander; D. Dollimore; A. Riga (pp. 317-330).
The present study was aimed at determining the kinetics of evaporation and establishing vapor pressure curves for both single and multi-component systems by thermogravimetry (TG) and differential scanning calorimetry (DSC). Essential oils (e.g. lavender oil, orange oil, clove oil and eucalyptus oil, etc.) are typically multi-component systems consisting of various volatile pure components (e.g. linalyl acetate, limonene, cinnamaldehyde, etc.) which resemble single component systems. In this study linalyl acetate was taken as the calibration compound for TG. The vapor pressure curves for the pure substances were plotted using TG and vapor pressure plots for clove oil and eucalyptus oil were constructed using DSC. The thermodynamic and kinetic parameters of the pure compounds were compared to that of the multi-component systems to quantitatively and qualitatively measure the influence of different compounds on each other. The k-value from the vapor pressure data for linalyl acetate was calculated as 112006 Pa kg0.5mol0.5s-1 m-2 K-0.5. The vapor pressure values were used to determine the Antoine constants using the SPSS 10.0 software.
Keywords: essential oils; vapor pressure curves; DSC; antoine equation; Langmuir equation; TG; multicomponent system
Low temperature heat capacity of the coordination compound: Nickel(II) nitrate with 4-amine-1,2,4-triazole at temperatures from 11 to 317 K
by V. G. Bessergenev; Yu. A. Kovalevskaya; L. G. Lavrenova; I. E. Paukov (pp. 331-336).
Low-temperature heat capacity of the coordination compound of nickel(II) nitrate with 4-amine-1,2,4-triazole was measured in the temperature range from 11 to 317 K using a computerized vacuum adiabatic calorimeter. The thermodynamic functions have been derived from the smoothed experimental data over the whole temperature interval covered and at standard conditions. At 298.15 K, the heat capacity is 574.7±1.2 J K-1 mol-1, the entropy is 599.2±1.2 J K-1 mol-1, the enthalpy is 91070±200 J mol-1, and the reduced Gibbs energy is 293.7±1.2 J K-1 mol-1. The results on Cp(T) were compared with those for Cu(NH2trz)3(NO3)2·0.5H2O. It was revealed that the slope of the curve dCp/dT (T) changes essentially for both compounds at 110-120 K. It implies that additional degrees of freedom appear in the heat capacity at these temperatures.
Keywords: heat capacity; thermodynamic functions; nickel complex compounds; triazole derivatives
Thermal dissociation processes for clathrates [CuPy4(No3)2]·2G (G=tetrahydrofurane, chloroform)
by E. A. Ukraintseva; V. A. Logvinenko; D. V. Soldatov; T. A. Chingina (pp. 337-345).
The thermal dissociation processes of clathrates [CuPy4(NO3)2]·2G (G=tetrahydrofuran, chloroform) were studied. Thermodynamic parameters (ΔH AV 0,ΔS 298 0 and ΔG 298 0) of the processes, producing solid host complex [CuPy4(NO3)2] and gaseous guest (G), were determined from the strain measurements. These data are compared with previous data for clathrates of the host complex with benzene and pyridine. Quasi-equilibrium thermogravimetry was used to investigate the step-by-step character of the dissociation processes. Kinetic studies were carried out for clathrate [CuPy4(NO3)2]·2THF.
Keywords: kinetic parameters; thermal dissociation; chloroform; vapour pressure; clathrate; Q-thermogravimetry; tetrahydrofuran; thermodynamic parameters; Cu(II)
Densities and relative permittivities for mixtures of 2-methoxyethanol with DEA and TEA, at various temperatures
by C. M. Kinart; W. J. Kinart; D. Checinska-Majak; A. Bald (pp. 347-354).
Densities (ε) and relative permittivities (ε) of numerous binary mixtures of 2-methoxyethanol (ME) (1)+diethylamine (DEA) (2) at four temperatures and 2-methoxyethanol (1)+triethylamine (TEA) (2) at five temperatures, between (291.15 and 313.15) K, are reported. These results are used to calculate excess molar volumes, and deviations in the relative permittivities. The results are fitted to the Redlich-Kister polynomial equation to estimate the binary coefficients and standard errors. Furthermore, the experimental results are used to disclose the nature of binary interactions in the bulk of studied the binary mixtures.
Keywords: physicochemical properties; diethylamine; 2-methoxyethanol; intermolecular interactions; triethylamine
The Kissinger law and isokinetic effect: Part II. Experimental analysis
by A. Mianowski; R. Bigda (pp. 355-372).
On the basis of copper sulphate pentahydrate thermal dissociation, for analyzed reactions I to IV, 6 thermokinetic equations was discussed. Arrhenius law parameters were determined and the isokinetic effect (IE) and Kissinger law appearing was analyzed. It was found that only dependence resulting from isokinetic effect, in the form k m=q/T m, relates to the suitable thermokinetic Eq. (2) and Kissinger law in modified form (14). The confirmation was made that the possibility of determining the averaged activation energy from thermokinetic equations using suitable correction coefficients exists.
Keywords: isokinetic effect; Kissinger law; thermokinetic equations; CaC2O4·H2O; thermal decomposition; arrhenius law; CuSO4·5H2O
Nanocrystallization of hydrogen-charged Mg76Ni19Y5 amorphous alloy
by V. Rangelova; T. Spassov; N. Neykov (pp. 373-378).
The crystallization of a hydrogen-charged melt-spun Mg76Ni19Y5 amorphous alloy was studied in order to understand the influence of hydrogen absorbed on the crystallization kinetics and mechanism. Hydrogenation does not affect the thermal stability, but decreases significantly the enthalpy of crystallization. The glass transition, which is well manifested in the hydrogen-free alloy, is not observed after hydrogen charging. The main crystalline phases in the H-free and H-charged alloys are the same after complete transformation, but with finer microstructure for the hydrogenated samples.Analysis of the crystallization kinetics reveals that during annealing of hydrogen charged Mg76Ni19Y5 growth of nanocrystals surrounded by amorphous phase takes place just in the beginning of the transformation, followed by grain growth in fully crystallized material, which is the main process.
Keywords: nanocrystallization; amorphous materials; Mg-alloys; kinetics
by L. Niinistö (pp. 379-379).