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Abstract  

Integral electron Mössbauer spectroscopy (ICEMS) and additionally some electrochemical methods were used to characterize the passivation process of iron (low carbon steel) in sulfate, sulfate+sulfite (a possible model solution of acid rain) solutions and in phospate buffer. The phase compositions and thicknesses of the passive layers formed due to the electrochemical polarizations were analyzed in dependence on the duration of the anodic passivations and on the pH of the used electrolytes. The passive layer, as determined from the Mössbauer spectra, consists mainly of -FeOOH, however in sulfite containing sulfate aqueous solution at pH 3.5 Fe3C and despite ex-situ circumstances FeSO4·H2O was detected after the shortest polarization time. The film thickness, which was found to grow nearly linearly with polarization time in pure sulfate solution and in phospate buffer, reached a maximum of 60–160 nm (depending on pH) in sulfate+sulfite solution after a passivation time of about 4 hours. It has been proved, that HSO3 -ion, which is contained by acid rain, initiate pit formation under acid conditions and so enforces the corrosion of iron. The experimental results furthermore suggest, that not the whole oxidic layer is responsible for the passivity but only a very thin intermediate layer formed between an inner oxide layer of a cubic structure and the rhombic oxide (-FeOOH) cover.

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The thermally stimulated discharge current (TSC) and differential scanning calorimetry (DSC) spectroscopy have been recorded in 25 μm thick samples of pristine polycarbonate (PC) and zinc oxide nano particle-filled polycarbonate. Polycarbonate (PC)/zinc oxide (ZnO) nanocomposites of different mass ratio (e.g., 1, 3, and 5%) were prepared by sol–gel method, followed by film casting. The glass transition temperature of nanocomposite samples increases with increase in concentration of ZnO nano fillers. It is due to the strong interaction between inorganic and organic components. The TSC peaks of nanocomposite and pristine PC indicate the multiple relaxation process. It has been observed that the magnitude of TSC decreases with increase in concentration of nanofillers. The TSC characteristics of 5% filled nanocomposites shows exponential increase of current at higher temperature region. This increase in current is caused by formation of charge-transfer complex between inorganic phase (e.g., ZnO) and organic phase (e.g., PC). Thus, the nano material like zinc oxide transfers the charge carriers from inorganic phase to organic phase rapidly and resultant current increases exponentially. This current is known as leakage current or breakdown current. TSC peak height is observed as a function of the polarizing field. The height of TSC peak increases as the field increases in pristine PC, while TSC peak height is suppressed in nanocomposite samples. This indicates the amount of space charge is smaller in the nanocomposites with a proper addition of ZnO nano fillers than in the pristine PC.

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We report on the design, construction, and testing of a gamma-ray imaging system with spectroscopic capabilities. The imaging system consists of an orthogonal strip detector made from either HgI2 or CdZnTe crystals. The detectors utilize an 8×8 orthogonal strip configuration with 64 effective pixels. Both HgI2 or CdZnTe detectors are 1 cm2 devices with a strip pitch of approximately 1.2 mm (producing pixels of 1.2 mm × 1.2 mm). The readout electronics consist of parallel channels of preamplifier, shaping amplifier, discriminators, and peak sensing ADC. The preamplifiers are configured in hybrid technology, and the rest of the electronics are implemented in NIM and CAMAC with control via a Power Macintosh computer. The software used to readout the instrument is capable of performing intensity measurements as well as spectroscopy on all 64 pixels of the device. We report on the performance of the system imaging gamma-rays in the 20–500 keV energy range and using a pin-hole collimator to form the image.

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Abstract  

Thermal analysis has been used to study the composition of paper and paper-like materials for some decades. The application of these techniques permits to distinguish between the original paper which was used by the artists and possible forgeries. Quite often, however, the identification of the differences demands the simultaneous application of several other techniques. The present investigation includes Asiatic wood-prints from China and Japan, and lithographs of European artists, such as Pablo Picasso, Salvador Dali, and Marc Chagall. Utamaro (1753–1806) is one of the most celebrated artists in the history of the Japanese woodblock print. He became one of the famous painters of ‘Ukiyo-e’ (Ukiyo-e means transitory world). In China Utamaro's pictures were also produced. The differences are found in the kind of paper: The Japanese used Mitsumata paper, while the Chinese printed on Bamboo paper mixed with silk fibers. Hu-j-zong (Nanking, 1619) and a group of famous Chinese painters created the book of the ‘Ten Bamboo Studio’ which contains woodblock prints as visual aids for young artists. A reprint of these woodblock prints appeared in 1717. Later, a bootleg of this book appeared in Japan (1817). The differentiation is possible by thermogravimetric investigation of the used papers. Statistic evaluations in Europe show that more than 1 000 000 bootleg copies of lithographs of Pablo Picasso, Salvador Dali, and Marc Chagall exist. Thermoanalytical measurements allow the distinction between the original artifacts and the bootlegs. Raman spectroscopy gives an additional possibility for the distinction between the applied color pigments.

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Abstract  

Thermal decomposition of poly(lactic acid) (PLA) has been studied using thermogravimetry coupled to Fourier transform infrared spectroscopy (TGA-FTIR). FTIR analysis of the evolved decomposition products shows the release of lactide molecule, acetaldehyde, carbon monoxide and carbon dioxide. Acetaldehyde and carbon dioxide exist until the end of the experiments, whereas carbon monoxide gradually decreases above the peak temperature in that the higher temperature benefits from chain homolysis and the production of carbon dioxide. A kinetic study of thermal degradation of PLA in nitrogen has been studied by means of thermogravimetry. It is found that the thermal degradation kinetics of PLA can be interpreted in terms of multi-step degradation mechanisms. The activation energies obtained by Ozawa–Flynn–Wall method and Friedman’s method are in good agreement with that obtained by Kissinger’s method. The activation energies of PLA calculated by the three methods are 177.5 kJ mol−1, 183.6 kJ mol−1 and 181.1 kJ mol−1, respectively.

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Commercial light-cured dental composites were used in this study. Two laboratorial composites, Resilab (Wilcos/Brazil), Epricord (Kuraray/Japan) were compared under cured and uncured conditions. Thermal analysis, infrared spectroscopy and scanning electron microscopy were used to evaluate the dental composites. The mass change and heat flow signals (TG–DSC) were recorded simultaneously by using STA 409 PC Luxx (NETZSCH), in the 25–800 °C temperature range at a heating rate of 10 °C/min under nitrogen atmosphere (70 mL/min). Employing thermo-microbalance TG 209 C F1 Iris (NETZSCH) coupled to the BRUKER Optics FTIR TENSOR, the samples were analyzed by combined thermogravimetric and spectroscopic methods (TG–FTIR). The initial sample mass was about ~12 mg, the data collection have been done in the 35–800 °C temperature range at a heating rate of 20 K/min in nitrogen atmosphere (flow rate: 40 mL/min). Finally, superficial topographic was analyzed by scanning electron microscopy (SEM). Dental composite evaluation suggests a high thermal stability and inorganic content in RES D sample. Degrees of conversion (DC) values were almost the same and there was no direct relationship between DC and amount of particles and size. Similar compositions were found in all samples.

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Abstract  

The activity concentration of radionuclides, such as 238U, 226Ra and 40K of limestone rocks in northern Iraq was measured using gamma spectroscopy. The radionuclide activities were obtained and discussed. CR-39 nuclear track detector was used to measure the radon exhalation rates as well as the effective radium contents of these samples and are found to correspond with uranium concentration values measured by NaI(Tl) detector in the corresponding limestone rocks samples. The absorbed gamma dose rates in air due to the presence of 238U, 226Ra, 40K and cosmic ray contribution varied between 105.3 and 223.11 nGy/h. The annual effective dose of each sample has been calculated. The correlation between activities of 226Ra, 222Rn exhalation rates and 238U is explained. Results show a symmetrical distribution of activity concentrations of primordial of radionuclides in selected samples. The values of all studied radionuclides are considered to be a typical level of natural background and compared with results of similar investigations carried out else where.

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99mTc compounds play a very important role in modern medicine. These compounds are among the most widely used radiopharmaceuticals. Unfortunately, due to the necessity of working with small quantities of materials, the chemistry of these materials is not completely understood. Currently, the structure of the 99mTc-DTPA (a common renal imaging agent) is unknown. In this paper, we show that X-ray absorption spectroscopy (XAS) can be used to determine the structure of Tc ycompounds b comparing XAS results to those from X-ray diffraction (XRD). Specifically, XAS data and fits for TcCl6 2-, TcOCl4-, and TcNCl4- were found to be in excellent agreement with the known structures from XRD. Finally, we show the XAS spectrum from a 77 ng sample of 99Tc-DTPA. To our knowledge this is the first XAS spectrum taken from this material. The near-edge region (XANES) was visible after a single scan on this material. This clearly indicates that we will be able to determine the local atomic structure of this material.

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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 750-850C 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.

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Abstract

Cyclohexane oxidation is an economically important process. To maintain high selectivities of 70 to 90%, the reaction is performed at low conversion up to 6%. To improve this process, investigations on the reaction mechanism are of high interest, which requires measurement techniques able to detect chemical species precisely even at very low concentrations. For this purpose, an in-situ measurement technique based on laser Raman spectroscopy with superior detection sensitivity and an optically transparent microchannel to monitor the process of cyclohexane oxidation has been developed.

The challenge is now to adapt this system to required conditions. In this article, we show that the influence of pressure is negligible. However, increasing temperatures influence the intensity of the Raman spectra significantly. As the temperature influence on the intensity of the Raman light is specific for each species, a temperature dependent calibration must be done to determine the concentrations of the chemical species precisely. In order to reach low detection limits also at high temperatures, the charge-coupled device (CCD) integration time had to be increased. For temperatures below 486 K, the limits of detection are less than 0.05 m/m %.

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