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Yaqiong Li Yinmin Zhang Yongfeng Zhang Meng Liu Fengchu Zhang Lu Wang 《Journal of Thermal Analysis and Calorimetry》2017,129(3):1333-1339
Thermal behavior of halloysite selected from Erdos, Inner Mongolia Autonomous Region in China, was investigated by thermogravimetry and differential thermal gravity (TG–DTG), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscope (SEM). The XRD results indicated that the mineralogical composition of halloysite sample was determined as 7 Å halloysite with the d (001) value of 0.734 nm, a small amount of 10 Å halloysite with the d (001) value of 0.998 nm, quartz, calcite, anhydrite, siderite, and analcite. The crystal chemical formula of halloysite specimen is (Ca0.007Na0.039K0.048)(Al1.935Fe 0.032 3+ Mn 0.003 2+ Ti 0.002 4+ Mg 0.015 2+ Ca 0.021 2+ )2 [(Si1.935Al 0.065 3+ )2](OH)4·2H2O according to the oxygen atom method. The TG–DTG–DSC data showed that a small amount of water molecule layer in the interlayer and the dehydroxylation was observed at 493.6 °C. The XRD, FT-IR, and SEM data clearly show that the structure changes and dehydroxylation of the halloysite with the temperature increased from 200 to 1200 °C. The dehydration of the halloysite is followed by the loss of intensity and evolution of the OH vibration bands and the change in microstructure. Dehydroxylation is followed by the decrease in the intensity of the bands at 3696 and 3620 cm?1, which is completely disappeared at 700 °C. The thermal behavior of halloysite was influenced by the mineralogy composition and impurities. 相似文献
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Wang Qi Wang Guangwei Zhang Jianliang Wang Haiyang 《Journal of Thermal Analysis and Calorimetry》2019,137(1):193-204
Journal of Thermal Analysis and Calorimetry - In this study, a combustion study of tire pyrolytic carbon black (CBp), gas coal (GC), and their blends was carried out by thermogravimetric analysis... 相似文献
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Gülbanu Koyundereli ??lg? Halil Ceti?li Ramazan Donat 《Journal of Thermal Analysis and Calorimetry》2012,110(1):127-135
In this study the thermal decomposition kinetics of uranyl acetate dehydrate [UO2(CH3COO)2·2H2O] were studied by thermogravimetry method in flowing nitrogen, air, and oxygen atmospheres. Decomposition process involved two stages for completion in all atmosphere conditions. The first stage corresponded to the removal of two?moles of crystal water. The decomposition reaction mechanism of the second stage in nitrogen atmosphere was different from that in air and oxygen atmospheres. Final decomposition products were determined with X-ray powder diffraction method. According to these data, UO2 is the final product in nitrogen atmosphere, whereas U3O8 is the final product in air and oxygen atmospheres. The calculations of activation energies of all reactions were realized by means of model-free and modeling methods. Kissinger?CAkahira?CSunose (KAS) and Flynn?CWall?COzawa (FWO) methods were selected for model-free calculations. For investigation of reaction models, 13 kinetic model equations were tested. The model, which gave the highest linear regression, the lowest standard deviation, and an activation energy value which was close to those obtained from KAS and FWO equations, was selected as the appropriate model. The optimized value of activation energy and Arrhenius factor were calculated using the selected model equation. Using these values, thermodynamic functions (??H*, ??S*, and ??G*) were calculated. 相似文献
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Gülbanu Koyundereli Çılgı Halil Cetişli Ramazan Donat 《Journal of Thermal Analysis and Calorimetry》2014,115(2):2007-2020
Thermal decomposition of U(C2O4)2·6H2O was studied using TG method in nitrogen, air, and oxygen atmospheres. The decomposition proceeded in five stages. The first three stages were dehydration reactions and corresponded to removal of four, one, and one mole water, respectively. Anhydrous salt decomposed to oxide products in two stages. The decomposition products in nitrogen atmosphere were different from those in air and oxygen atmospheres. In nitrogen atmosphere UO1.5(CO3)0.5 was the first product and U2O5 was the second product, while these in air and oxygen atmospheres were UO(CO3) and UO3, respectively. The second decomposition products were not stable and converted to stable oxides (nitrogen: UO2, air–oxygen: U3O8). The kinetics of each reaction was investigated with using Kissinger–Akahira–Sunose and Flynn–Wall–Ozawa methods. These methods were combined with modeling equations for thermodynamic functions, the effective models were investigated and thermodynamic values were calculated. 相似文献
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Halil Ceti?li Gülbanu Koyundereli ??lg? Ramazan Donat 《Journal of Thermal Analysis and Calorimetry》2012,108(3):1213-1222
The thermal decomposition kinetics of UO2C2O4·3H2O were studied by TG method in a flowing nitrogen, air, and oxygen atmospheres. It is found that UO2C2O4·3H2O decomposes to uranium oxides in four stages in all atmosphere. The first two stages are the same in the whole atmosphere that correspond to dehydration reactions. The last two stages correspond to decomposition reactions. Final decomposition products are determined with X-Ray powder diffraction method. Decomposition mechanisms are different in nitrogen atmosphere from air and oxygen atmosphere. The activation energies of all reactions were calculated by model-free (KAS and FWO) methods. For investigation of reaction models, 13 kinetic model equations were tested and correct models, giving the highest linear regression, lowest standard deviation, and agreement of activation energy value to those obtained from KAS and FWO equations were found. The optimized value of activation energy and Arrhenius factor were calculated with the best model equation. Using these values, thermodynamic functions (??H *, ??S *, and ??G *) were calculated. 相似文献
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W. L. Tan M. Abu Bakar N. H. H. Abu Bakar 《Journal of Thermal Analysis and Calorimetry》2014,117(3):1111-1122
The thermal and kinetic studies of epoxidized natural rubber (ENR) and its polymer electrolytes, LiX/ENR PEs, (where X = ClO 4 ? , CF3SO 3 ? , COOCF 3 ? , I?, and BF 4 ? ) were carried out using thermogravimetric analysis at different heating rates. The thermal behaviors for LiX/ENR PEs are closely related to the morphology and interactions between the LiX and ENR chains. The LiCF3SO3, LiCOOCF3, and LiI form pseudo-crosslinking within the ENR; their thermal behavior resembled purified ENR. The LiClO4 tends to form aggregates within the ENR. This phenomenon has promoted a much earlier decomposition of epoxide in the ENR. The occurrence of ring-opening and complexation or cross-linking reactions in and between the ENR chains in the LiBF4/ENR has produced a thermally stable macrostructure. The activation energy for the thermal degradation (E d) of purified ENR was 239.8 and 239.9 kJ mol?1 using Kissinger and FWO methods, respectively. According to the Coats–Redfern method, the degradation mechanism of purified ENR follows the F1 type model, while the Criado method revealed that the degradation starts with F1 followed by D3 type models. The E d for LiX/ENR (X = COOCF 3 ? , CF3SO 3 ? , I?, and BF 4 ? ) PE’s obtained via the Kissinger method are 258.5, 257.0, 251.0, and 198.9 kJ mol?1, respectively, and the corresponding E d values obtained by FWO are 236.0, 223.6, 349.7, and 206.6 kJ mol?1, respectively. The degradation of ENR in these PEs followed the D3 type model. However, for LiClO4/ENR, the presence of two distinct degradations of ENR gave two E d values. These are 174.5 and 234.7 kJ mol?1 using Kissinger and 117.8 and 293.6 kJ mol?1 using FWO method. The degradation mechanism of ENR in the LiClO4/ENR PE was similar to purified ENR that is F1 followed by D3 type models. 相似文献
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Introduction TheabilitytoextractandanalyzeDNAfrom ancientremainshasarelativelyshorthistory.Early ancientDNA(aDNA)studiesconcentratedonitsnature ofphysicsandchemistryincludingdegradation,frag mentationandoxidationduringlongpreservation.The fieldwasrevoluti… 相似文献
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Gebremeskel Desalegn Ketema Chaubey A. K. 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(6):2735-2741
Journal of Radioanalytical and Nuclear Chemistry - In this study, natural radioactivity levels of 226Ra, 232Th, and 40K, as well as the related harmful radiological features, were determined for... 相似文献
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Zhilong Gong Corinna Watt Bin He Zhixiong Ning X. Chris Le 《Analytica chimica acta》2006,555(1):181-187
Arsenic in drinking water affects millions of people around the world. While soluble arsenic is commonly measured, the amount of particulate arsenic in drinking water has often been overlooked. We report here determination of the acid-leachable particulate arsenic and soluble arsenicals in well water from an arsenic-poisoning endemic area in Inner Mongolia, China. Water samples (583) were collected from 120 wells in Ba Men, Inner Mongolia, where well water was the primary drinking water source. Two methods were demonstrated for the determination of soluble arsenic species (primarily inorganic arsenate and arsenite) and total particulate arsenic. The first method used solid phase extraction cartridges and membrane filters to separate arsenic species on-site, followed by analysis of the individual arsenic species eluted from the cartridges and filters. The other method uses liquid chromatography separation with hydride generation atomic fluorescence detection to determine soluble arsenic species. Analysis of acidified water samples using inductively coupled plasma mass spectrometry provided the total arsenic concentration. Arsenic concentrations in water samples from the 120 wells ranged from <1 to ∼1000 μg L−1. On average, particulate arsenic accounted for 39 ± 38% (median 36%) of the total arsenic. In some wells, particulate arsenic was six times higher than the soluble arsenic concentration. Particulate arsenic can be effectively removed using membrane filtration. The information on particulate and soluble arsenic in water is useful for optimizing treatment options and for understanding the geochemical behavior of arsenic in groundwater. 相似文献
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D. C. Breban N. Paunescu J. Moreno-Bermudez R. Margineanu 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(3):503-508
Radioactive concentrations of several artificial and natural radionuclides were determined in water and sediment samples collected
from various locations in the NW Black Sea in December 1999. For water samples, 90Sr and 137Cs activity concentrations were of approximately 11 mBq/l and 26.3-41.2 mBq/l, respectively. The concentration of tritium
ranged from 7 to 24 T.U. In sediment samples, maximum concentrations of 137Cs, 239+240Pu and 241Am were found of 128±6 Bq·kg-1, 1.8±0.1 Bq·kg-1 and 0.05±0.04 Bq·kg-1, respectively. For U and Th radionuclides, the concentrations ranged from 20-80 Bq·kg-1 and 30-50 Bq·kg-1, respectively. The results were consistent with those reported in earlier research for the Black Sea.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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A. C. Prieto J. M. Lobón J. M. Alía F. Rull F. Martin 《Journal of Thermal Analysis and Calorimetry》1991,37(5):969-981
A set of seven natural trioctahedral chlorites have been studied. Thermogravimetric techniques and infrared spectroscopy were used to determine the thermal dehydroxylation of the samples. Relationships between the compositions of the chlorites and their thermograms were established. A kinetic analysis was also undertaken.
The authors thank the Museum of Natural History in Paris and the Museum of Natural Science in Bern for providing the samples studied. 相似文献
Zusammenfassung Es wurde eine Reihe von sieben natürlichen trioktaedrischen Chloriten untersucht. Mittels TG-Techniken und IR-Spektroskopie wurde die thermische Dehydroxylierung der Proben untersucht. Es konnten ZusammenhÄnge zwischen der Zusammensetzung der Chlorite und ihrer Thermogramme festgestellt werden. Weiterhin wurde eine kinetische Analyse vorgenommen.
The authors thank the Museum of Natural History in Paris and the Museum of Natural Science in Bern for providing the samples studied. 相似文献
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I. Outola S. Nour H. Kurosaki K. Inn J. La Rosa L. Lucas P. Volkovitsky K. Koepenick 《Journal of Radioanalytical and Nuclear Chemistry》2008,277(1):155-159
The comparator instrumental neutron activation analysis (INAA) method was used for certification of arsenic in Korea Research
Institute of Standards and Science (KRISS) reference materials 108-04-001 (Oyster Tissue). The certified value was determined
by analyzing one sample of approximately 0.15 g from ten bottles selected by random sampling. Potentially significant sources
of uncertainty were taken into consideration using the guideline given by ISO. A complete evaluation of all sources of uncertainty
yielded an expanded uncertainty for the mean value of this reference material of 4.7% at approximately 95% level of confidence. 相似文献
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Gamma-ray spectroscopic and PIXE analysis of selected samples from the phosphorite deposits of Northwestern Saudi Arabia 总被引:1,自引:0,他引:1
A. Aksoy M. Ahmed W. S. A. Matter Z. R. El-Naggar 《Journal of Radioanalytical and Nuclear Chemistry》2002,253(3):517-521
Phosphorite deposits from northwestern Saudi Arabia were analyzed by natural radioactivity measurements to detect the presence of radioactive elements. PIXE was used to obtain an average elemental composition of these deposits. From the analysis of radiations from 238U, 232Th and 40K isotopes, the samples were found to contain U, Th and K in concentrations up to 130 ppm, 30 ppm and 2.5 wt%, respectively. PIXE showed the presence of a number of trace elements such as Ca, V, Cr, Fe, Ni, Cu, Zn, As, Sr, Y and U in concentrations ranging from a few ppm to several hundred ppm. The occurrence of these radioactive and non-radioactive elements are discussed for their geological significance in the phosphorite deposits. 相似文献
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Dimitris S. Achilias Maria M. Karabela Irini D. Sideridou 《Journal of Thermal Analysis and Calorimetry》2010,99(3):917-923
Thermal degradation kinetics of copolymers based on bis-phenol A ethoxylated dimethacrylate (Bis-EMA) with triethylene glycol
dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA) with TEGDMA in wt/wt ratios 30/70, 50/50, or 70/30 were investigated
using thermogravimetric analysis as a means to provide specific information regarding the internal structures of these resins.
Thermogravimetric scans were taken at four different heating rates to perform an isoconversional analysis to determine the
change of the effective activation energy as a function of conversion. A two-step degradation mechanism was found to occur
in almost all copolymer compositions attributed to the existence of inhomogeneities in the macromolecular structure and the
formation of weak links inside the polymeric network. 相似文献
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内蒙和吉林马勃的产地对比分析 总被引:1,自引:1,他引:0
采用扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)和裂解-气质联用(Py-GCMS)从微观形貌、元素组成、主要类别及小分子的化学组成等方面对产自内蒙和吉林的马勃中药材直接进行原位分析,并对产自两地的马勃进行区分。 SEM结果表明,内蒙马勃属于灰包科栓皮马勃属栓皮马勃;吉林马勃属于灰包科静灰球属长根静灰球菌。 FTIR光谱显示,内蒙马勃在酰胺Ⅰ带吸收峰1636 cm-1,而吉林马勃的在1654 cm-1。 吉林马勃二阶导数红外光谱在1625 cm-1有较强的吸收峰说明吉林马勃含芳香环骨架的化合物含量高于内蒙马勃,与Py-GCMS的结论中吉林马勃苯酚、对甲苯酚含量明显高于内蒙马勃相符。 另外,Py-GCMS结果可以分析出两地马勃的裂解成分及含量的差异。 相似文献
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The development of nuclear power releases large amounts of radionuclides into the natural environment. Herein, the sorption of radionuclide 63Ni on bentonite from Gaomiaozi county (Inner Mongolia, China) at different experimental conditions such as pH, contact time, ionic strength, foreign cations and anions, and temperatures were investigated by using batch technique. The results indicated that the sorption of 63Ni on the bentonite was quickly at first contact time and then increased slowly with increasing contact time. The sorption of 63Ni was strongly dependent on ionic strength at low pH values and independent of ionic strength at high pH values. The sorption of 63Ni on bentonite was mainly dominated by outer-sphere surface complexation or ion exchange at low pH values, whereas inner-sphere surface complexation was the main sorption mechanism at high pH values. The Langmuir, Freundlich, and D–R models were applied to simulate the sorption isotherms of 63Ni at three different temperatures, and the thermodynamic parameters (i.e., ΔH°, ΔS° and ΔG°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of 63Ni on bentonite was an endothermic and spontaneous process. Experimental results indicate that the bentonite is a suitable material for the preconcentration and solidification of 63Ni from large volume of solutions in radionickel pollution cleanup. 相似文献
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F. Rodante G. Marrosu G. Catalani 《Journal of Thermal Analysis and Calorimetry》1992,38(12):2669-2682
The thermal analysis of some pesticides using simultaneous TG-DSC measurements and kinetic calculations by the dynamic TG technique have been carried out.With this technique it was attempted to group compounds with similar structures according to the shape and number of peaks of their thermoanalytical curves and to characterize their features by means of thermodynamic and kinetic quantities.Small variations in the structure of the components of a class make larger variations in the thermodynamic and kinetic values being in close agreement with the observed differences in their biological behaviour.
Zusammenfassung Mittels simultanen TG-DSC-Messungen und kinetischen Berechnungen bei der DTG-Technik wurde eine thermische Analyse einiger Pestizide durchgeführt.Mit dieser Methode wurde versucht, Verbindungen mit ähnlichen Strukturen anhand der Form und Anzahl von Peaks ihrer thermoanalytischen Kurven zu gruppieren und ihre Eigenschaften mittels thermodynamischen und kinetischen Mengen zu charakterisieren.Geringe Änderungen in der Struktur der Komponenten einer Klasse verursachen größere Veränderungen der thermodynamischen und kinetischen Größen, was in enger Übereinstimmung mit den beobachteten Unterschieden ihrer biologischen Aktivität steht.相似文献
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J. T. Elliston S. E. Glover R. H. Filby 《Journal of Radioanalytical and Nuclear Chemistry》2005,263(2):301-306
Summary In the analysis of biological samples with sub ng/g uranium concentrations, pre-concentration has been shown to improve the detection limit for the determination of uranium. Recovery corrected kinetic phosphorescence analysis (KPA) combines pre-concentration and separation of uranium by anion-exchange from human tissues dissolved in 6M HCl, with the radiochemical yield determined by alpha-spectrometry, using 232U as a tracer. Total uranium is determined by KPA after correction for chemical recovery. Twenty-one randomly selected dissolved tissue samples from the United States Transuranium and Uranium Registries (USTUR) Case 0242 were chosen for comparative analyses. The set of samples included dissolved bone and soft tissues. Uranium concentrations for seven of the samples had not been previously reported. Direct KPA could not be used to determine uranium concentrations of five unreported tissues. Three of these tissues had uranium concentrations at or below the KPA LQ value of 0.028 ng/ml and two tissues had known matrix interferences. All seven of the unreported tissues were successfully analyzed by recovery corrected KPA; concentrations ranged from 9 to 1380 ng per tissue, including those that could not be analyzed by direct KPA due to matrix problems. Recovery corrected KPA gives results similar to direct KPA where matrix interferences and low detection limits are not encountered. A comparison of the direct method of KPA versus recovery corrected KPA shows marked improvement for the determination of uranium in samples that heretofore either uranium was not detected or the sample had to be drastically diluted to minimize matrix effects in order to measure uranium. 相似文献