Energetic characterization of malt bagasse by calorimetry and thermal analysis

This study evaluates the thermal behavior of bagasse malt fresh and its heat capacity by means of calorimetry for samples with different moisture contents (50, 40, 30, 20, and 15 %). Chemical analysis was used to determine the content of volatiles, fixed carbon, and ash. The thermal degradation of malt bagasse presents two mass loss steps attributed to the release of moisture and to the decomposition of organic material. The calorific value of bagasse malt showed variation with moisture reduction as expected. Also showed variation with density. It was found a high percentage of volatile materials and the low percentage of ash and fixed carbon.     

Energetic characterization of forest biomass by calorimetry and thermal analysis

The rational and sustainable exploitation of natural resources is one the priority objectives of our consumer society as an unavoidable strategy for survival. In previous articles, research group TERBIPROMAT has established the bases for the elaboration of energy maps of forest biomass. With those data, it is possible to classify the species in terms of their energy content and of their possible application as biofuels following European Norm CEN/TS 14961/2005 on solid biofuels. Main forest species used in this study were Populus and Paulownia. These species have a fast growth and produce big amounts of energetic biomass. To complete this study a comparison with autochthonous forest species, Eucalyptus and Pinus, was made. In this study, a thermogravimetric analysis is employed to qualitative study the resistance to thermal degradation of different forest species. These studies complete those made through static bomb calorimetry, elemental analysis, and different mechanical tests trying to get relationships between thermal behaviour and some physical properties.     

Determination of codeine phosphate and codeine in thermal characterization by differential scanning calorimetry

Thermal behaviour of codeine phosphate and codeine crystallized at the several solvents system was studied by DSC, and then, the kinetic parameters and thermochemical data have been obtained. We have found that codeine phosphate and codeine exist in a number of polymorphic formes which may inflicence the bio-availability.     

Rapid,non-destructive determination of butter adulteration by means of photopyroelectric (PPE) calorimetry

The study focuses on the application of the photopyroelectric (PPE) technique combined with gas chromatography to detect adulteration of cow milk-obtained butter. The thermal diffusivity and effusivity have been directly measured using back and front PPE detection, respectively, and the results have been correlated with the composition of adulterated butter samples. The back detection configuration has been used in the case of butter adulterated with palm oil, and a possible correlation of the thermal diffusivity with total amount of monounsaturated fatty acids composition has been proposed. For butter adulterated with soy milk, we used the front PPE configuration in order to measure the samples’ thermal effusivity. A strong dependence of the value of thermal effusivity as a function of soy milk content was found.     

Static and dynamic thermal quantities near the consolute point of the binary liquid mixture aniline-cyclohexane studied with a photopyroelectric technique and adiabatic scanning calorimetry

We studied the thermal conductivity, thermal effusivity, and specific heat capacity at constant pressure of the critical binary liquid mixture aniline-cyclohexane near the consolute point, using a photopyroelectric (PPE) technique and adiabatic scanning calorimetry (ASC). According to recent theoretical predictions based on renormalization group theory calculations, a substantial (but not diverging) enhancement in the thermal conductivity in the homogeneous phase near the critical temperature was expected for this binary system near the consolute point. However, within an experimental precision of 0.05%, we found no deviation from linear behavior in the range of 5 K above Tc down to Tc. The specific heat capacity calculated from the results for the thermal conductivity and effusivity is in good agreement with that measured by ASC. For the ASC results, the theoretical power law expression with the Ising critical exponent was fitted to the specific heat capacity both above and below the transition temperature. Good agreement with theory was found both for the amplitude ratio and the two-scale universality.     

Preparation of cellulose-ZnO hybrid films by a wet chemical method and their characterization

Zinc oxide (ZnO) nanoparticles were immobilized on the surface of regenerated cellulose films by a wet chemical method in which the controlled hydrolysis of a Zn(II)-amine complex leads to the formation of ZnO nanoparticles. Cellulose-ZnO materials were characterized by spectral, thermal and optical methods. Scanning electron microscope and atomic force microscope analyses confirmed the formation of ZnO nanoparticles on the surface of the regenerated cellulose film and X-ray diffraction patterns showed the ZnO had the wurtzite structure. The reported method is very simple, and can immobilize the nanoparticles without the aid of a binder or dendritic side group and without high temperature treatments like calcination. ZnO immobilized on biopolymers like cellulose has many potential applications such as strain sensors, biomedical sensors, flexible display devices and optoelectronics.     

用双锂引发剂制备热塑弹性体S(IB)S

苯乙烯-二烯烃热塑弹性体(SDS)是橡胶代用品和热熔压敏胶的主体材料。其粘接强度低、耐老化性差常需配以增粘剂、防老剂。苯乙烯．异戊二烯嵌段共聚物(SIS)性能比SBS和EvA优越,我国异戊二烯原料不足、价格较高。以正丁基锂为引发剂的热塑弹性体S(IA)S性能与SIS相近。本文以有机双锂为引发剂、苯乙烯、丁二烯和异戊二烯为共聚单体,采用两步加料法合成热塑弹性体S(IB)S,对其结构、性能进行了表征。     

Measurement of thermal conductivity by differential scanning calorimetry

A technique of measurement of thermal conductivity of solid materials by differential scanning calorimetry is presented. It concerns small samples having a diameter less than 8.0 mm, a height less than 2.0 mm and a low thermal conductivity. This method requires many samples with different heights which are heated in such a way that a calibration substance put on their top undergoes a first-order phase transition. The analysis of heat transfer of a such experiment predicts that the slope of the differential power during the transition is proportional to the factor 2 and inversely proportional to the sum of the thermal resistances. A measurement of the thermal conductivity of samples made of polytetrafluoroethylene powder, compressed at the density of 2.10±0.03 g cm⁻³, has been performed; the value obtained is 0.33±0.02 W m⁻¹ K⁻¹. Measurements of thermal conductivity of small metal hydride pellets are also presented. The precision of the measurements are on average 10%.     

Synthesis,characterization of new bisphenol-based benzoxazines and the thermal properties of their polymers

Journal of Thermal Analysis and Calorimetry - New bisphenol-based benzoxazines (BBA-a and BBA-bra) were synthesized from bisphenol containing trityl group, paraformaldehyde, aniline and...     

Preparation of alumina with different precipitants for the gas phase dehydration of glycerol and their characterization by thermal analysis

Journal of Thermal Analysis and Calorimetry - Mesoporous aluminas were prepared using different precipitants at different pH of precipitation and evaluated in the gas phase dehydration of glycerol....     

Morphology characterization of emulsions by differential scanning calorimetry

This article is a review of some results obtained by Differential Scanning Calorimetry (DSC) for characterizing the morphology of emulsions. In a classical DSC experiment, an emulsion sample is submitted to a regular cooling and heating cycle between temperatures that include freezing and melting of the dispersed droplets. By using the thermograms found in the literature for various emulsions, how to get information about the solidification and melting, the presence of solute, the emulsion type, the transfer of matter, the stability and the droplet size is shown.     

Preparation,characterization and electrical conductivity of new heterobimetallic chalcogenates and their 1,10-phenanthroline adducts

New mixed metal chalcogenate coordination polymers, MPb(SCN)₂(SeCN)₂ [M = Co^II, Ni^II or Hg^II], Ag₂-Pb(SCN)₂(SeCN)₂, and the complex heterobimetallic salts, [M(phen)₃][Pb(SCN)₂(SeCN)₂][M = Co^II or Ni^II; phen = 1,10-phenanthroline] that have been prepared and characterized by elemental analyses, i.r. and u.v.–vis. spectra, and by powder XRD patterns. Their solid state electrical conductivities have been investigated, show _rt in the 10^–10–10^–6 S cm^–1 range, and semiconduct at 313–383 K with band gaps in the 0.28–0.91 eV range. [Co(phen)₃][Pb(SCN)₂(SeCN)₂], exhibits a remarkable increase, i.e. 10⁴ order of magnitude, in conductivity at higher temperature, which reflects a disordered metallic system where charge carriers have difficulty in crossing the non-conducting barrier at low temperature.     

Preparation,characterization and application of a novel thermal stable composite nanofiltration membrane

A thermal stable composite membrane was prepared by interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC) on poly(phthalazinone ether amide) (PPEA) ultrafiltration membrane. The effect of reaction parameters on the performance of composite membranes was studied and optimized. The surface morphologies of the composite membrane and the substrate were observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The rejection of optimized composite membrane for dyes Congo red (CGR) and Acid chrome blue K (ACBK), the molecular weight (MW) of which is over 400, was over 99.2%, with a flux at about 180 L m⁻² h⁻¹. While the rejection for NaCl was only 18.2% with a flux over 270 L m⁻² h⁻¹, when tested at 1.0 MPa 60 °C. The composite membrane was applied in the desalination-purification experiment of dye ACBK and NaCl mixed solution. The flux of the membrane increased obviously as the operation pressure and/or temperature increased, while the rejection for dye was constant and kept over 99.3%. The purification experiments were accomplished effectively at 1.0 MPa, 80 °C. Only after five rounds of desalination-concentration experiment, about 160 min, the salt mixed in dye solution was fully removed. The initial flux of the eighth cycle was about 254 L m⁻² h⁻¹, which was only 20 L m⁻² h⁻¹ lower than that of the first round. The rejection of the membrane was constant and kept over 99.3% through out the eight cycles of purification experiment.     

Preparation and characterization of a new layered double hydroxide, Co-Zr-Si

The layered double hydroxides (LDHs) are nano-ordered layered compounds and well known for their ability to intercalate anionic compounds. Most LDH is prepared conventionally only with divalent and trivalent cations. In this study, Co-Zr-Si LDH, consisting of divalent, tetravalent, and tetravalent cations, was prepared and reacted with monocarboxylic acids at room temperature. The Co-Zr-Si LDH and intercalated compounds have been characterized by energy-dispersive X-ray spectrometry, X-ray powder diffraction, IR spectra, thermal analysis, and scanning electron microscopy (SEM). The insertion of cyanate and carbonate anions into LDH was confirmed by IR spectra. XRD patterns of the prepared Co-Zr-Si LDH showed that the interlayer spacing of the LDH is 0.78 nm. The spacing is similar to that of usual LDH in which chloride, carbonate, or bromide anion is the guest. SEM images showed that Co-Zr-Si LDH can exist as plate-like or fibrous structures.     

Closer relation between thermal analysis and calorimetry

Several DTA experiments followed by calorimetric works are reviewed here to emphasise the importance of complementary role of both techniques. The thermal analysis is advantageous in the sense that it gives quickly the overall view of thermal behaviour of a material under various conditions. Calorimetric work provides accurate heat capacity data which enable to derive thermodynamic functions including the enthalpy and entropy. The latter quantity is especially important in judging whether the material obeys the third law of thermodynamics. However, calorimetric work leads occasionally to an erroneous conclusion if the work is not preceded by thermal analysis performed under various conditions. Sometimes, quality of information obtained by DTA exceeds that obtained by laborious calorimetry.     

Adiabatic calorimetry and thermal analysis on acetaminophen

Molar heat capacities of acetaminophen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 330 K. A solid-solid transition at 149.96 K was found from the C_p,m-T curve. The polynomial functions of C_p,.m(J K^-1 mol^-1) vs. T were established on the heat capacity measurements by means of the least square fitting method. Thermal decomposition processes of acetaminophen have been studied by thermogravimetry. And the thermal decomposition kinetics parameters, such as activation energy E, pre-exponential factor A and reaction order n, were calculated by TG-DTG techniques with the Freeman-Carroll method, Kissinger method and Ozawa method. Accordingly the thermal decomposition kinetics equation of acetaminophen is expressed as: dα/dt=2.67·10⁷e^-89630/RT(1-α)^0.23. The process of fusion has been investigated through DSC. The melting point, molar enthalpy and entropy of fusion are to be (441.89±0.04) K, 26.49±0.44 kJ mol^-1 and 59.80±1.01 J K^-1 mol^-1, respectively.     

Thermal and structural characterization of bitumen by modulated differential scanning calorimetry

Journal of Thermal Analysis and Calorimetry - This paper presents the results of investigation of model bitumens, prepared by mixing of individual fractions of bitumen (saturates, aromatics, waxes,...     

水合醛缩酶热变性的DSC研究

本文采用差示扫描量热法(DSC),研究了水合醛缩酶在含水量h从0.08g/g至2.28g/g范围内的热变性行为。实验结果表明,当h=0.08g/g时,水合醛缩酶样品的温度扫描热谱图呈现了两个吸热峰,其中低温峰很小,高温峰很大。随着h的增大,低温峰变得更小,高温峰则出现了分峰现象。当h=0.22g/g时,低温峰消失,高温峰则分裂成了两个独立的吸热峰。随着h的继续增大,其中前峰的位置不断移向低温,直至h_0.65g/g时,才不再变化。后峰的位置则始终保持不变。当再进行第二次温度扫描时,前峰消失,而后峰却能再现。本文给出了两峰在不同含水量时的转变温度、转变焓和转变焓之和,以及它们与含水量的关系。最后,对上述诸峰的起因作了分析讨论,认为低温峰可能起因于水合醛缩酶结晶的熔化作用,前峰和后峰可能起因于醛缩酶中两种A亚基的热变性。     

Preparation, characterization and thermal dehydration kinetics of titanate nanotubes

Titanate nanotubes were synthesized utilizing the hydrothermal method using titanium dioxide nanoparticles. The experiments were carried out considering the process as a function of reaction temperature, time, NaOH concentration and the acidity of the washing solution. The formation of titanate nanotubes was shown to be affected strongly by variations in any parameter. The optimum conditions for the synthesis of titanate nanotubes were determined to be a reaction temperature of 190 °C, and a reaction time of 12 h, using 10 M NaOH concentration and the washing solution to have a pH of 5.5. In addition, thermogravimetric analysis (TG/DTG) was used to investigate the thermal behaviour and dehydration kinetics of titanate nanotubes. In order to better understand their thermal behaviour, the thermal analysis of bulk hydrogen trititanate was performed. The values of the apparent activation energies of the first and second dehydration stages for titanate nanotubes were 81.44 ± 15.85 and 82.69 ± 7.46 kJ mol^?1, respectively. The values of the apparent activation energies of the first, second and third dehydration stages for bulk hydrogen trititanate were 115.93 ± 5.40, 137.58 ± 6.47 and 138.97 ± 8.47 kJ mol^?1, respectively.