Sinc collocation approach through thermal analysis of porous fin with magnetic field

Journal of Thermal Analysis and Calorimetry - The extended surfaces, known as fins, are of great importance in various industrial applications in electric/electronic devices, heat exchangers, power...     

An investigation of the thermal decomposition of gold acetate

The thermal decomposition characteristics of gold acetate to produce gold nanoparticles were investigated. A rapid and violent fragmentation of the gold acetate particles was observed at approximately 103±20°C when a rapid heating rate of 25°C min⁻¹ was used, leading to formation of nanosized spherical and partially coalesced gold particles. Particle size analysis was used to investigate possible relationships between the gold acetate crystallite size and the gold nanoparticles produced by thermal decomposition. The results indicate rapid (<0.14 ms) coalescence of the gold particles occurs for fragments in close proximity.     

An investigation of porous membranes saturated with hydrophobic solvents as ion-selective electrodes

The ion-selective characteristics of Orion nitrate, chloride, calcium electrode membranes and Millipore filters saturated with organic solvents (o-dichlorobenzene, 1,2-dichloroethane, 2,2-dichlorodiethyl ether and 1,1,2,2-tetrachloroethane) have been studied. The saturated membranes were not inert, but showed ion-selective qualities. Almost Nernstian behaviour was obtained for several anions. The additition of an ion exchanger scarcely affected the potentiometric behaviour for most ions, except when a selective interaction occurred.     

An investigation of the accelerated thermal degradation of different epoxy resin composites using X-ray microcomputed tomography and optical coherence tomography

Epoxy resin composites reinforced with hollow glass microspheres, microlight microspheres, 3D parabeam glass, and E-Glass individually were subjected to accelerated thermal degradation conditions. X-ray microcomputed tomography (XμCT) was used to evaluate density changes, reinforcement filler damage, homogeneity, cracks and microcracks in the bulk of the different epoxy resin composites. XμCT 3D images, 2D reconstructed images and voids calculations revealed microspheres damage, filler distributions and showed cracks in all composites with different shapes and volume in response to the thermal degradation conditions. In addition, expansion of air bubbles/voids was observed and recorded in the microsphere and microlight epoxy composite samples. In a complementary way, optical coherence tomography (OCT) was used as a novel optical characterisation technique to study structural changes of the surface and near-surface regions of the composites, uncovering signs of surface shrinkage caused by the thermal treatment. Thus, combining XμCT and OCT proved useful in examining epoxy resin composites' structure, filler-resin interface and surface characteristics.     

The investigation of thermal runaway propagation of lithium-ion batteries under different vertical distances

Journal of Thermal Analysis and Calorimetry - The time of safety valve cracks and thermal runaway propagation are influenced seriously by vertical distance and the stage of charge (SOC). In this...     

Differential thermal analysis of porous silicon

Porous silicon materials, macro- and mesoporous silicon, obtained by electrochemical anodic etching of n- and p-Si were studied by differential thermal analysis at a steady temperature rise and under isothermal conditions in nitrogen atmosphere and in air. The method was used to estimate the presence and amount of phases of surface volatile compounds. The possibility was studied to perform a comparative estimate of the specific surface area of different types of porous silicon from data on the surface oxidation kinetics determined by the dynamic differential thermal analysis in air.     

An investigation on characterization and thermal analysis of the Aughinish red mud

Summary Red mud is insoluble, fine-grained waste residue which is generated as a by product during the production of alumina from the Bayer process. In this article, the thermal behavior of Aughinish red mud was investigated using thermal gravimetric analysis (TG) and differential thermal analysis (DTA). For identification of oxide and mineral phases in the red mud sample, XRD method, scanning electron microscopy (SEM), EDAX were used. Iron (30.4%), aluminium (23.6%) and titanium (17.85%) oxides are major oxides in the sample. Two endothermic peaks were shown on DTA curve. The total mass loss in the red mud was found to be 10.1%, which was associated with moisture and water molecules in gibbsite and boehmite phases.     

Micropatterning of living cells on a heterogeneously wetted surface

We report a simple approach to fabricate heterogeneously wetted surfaces which can be used to pattern living cells or biomolecules. An array of pedestals composed of SU-8 was fabricated on a glass surface which was then derivatized with a hydrophobic silane. Upon addition of aqueous solutions to the array, air was trapped within the hydrophobic cavities between the pedestals. The trapped air formed a "virtual wall" blocking access to these cavities. Cells cultured on the array were forced to grow only on the tops of the pedestals, i.e., the surfaces wetted by aqueous media. The virtual walls were stable during manipulation of the array and over long time periods (months).     

An investigation of the thermal and thermo‐oxidative degradation of polybenzoxazines with a reactive functional group

The thermal behavior of a series of polybenzoxazines based on 3‐aminophenylacetylene has been investigated. The effect of reactive amine on the thermal cleavage of the Mannich base is examined under both inert and oxidative environments. It has been shown that the thermal stability of polybenzoxazines is substantially improved by the reactive amine. Various biphenols are found to have insignificant effect on the thermal stability of this series of polybenzoxazines. These nitrogen containing phenolic resins are nonflammable polymers. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 647–659, 1999     

Composite thermal conductivity in a large heterogeneous porous methane hydrate sample

By employing inverse modeling to analyze the laboratory data, we determined the composite thermal conductivity (k(theta), W/m/K) of a porous methane hydrate sample ranged between 0.25 and 0.58 W/m/K as a function of density. The calculated composite thermal diffusivities of porous hydrate sample ranged between 2.59 x 10(-7) m(2)/s and 3.71 x 10(-7) m(2)/s. The laboratory study involved a large heterogeneous sample (composed of hydrate, water, and methane gas). The measurements were conducted isobarically at 4.98 MPa over a temperature range of 277.3-279.1 K. Pressure and temperature were monitored at multiple locations in the sample. X-ray computed tomography (CT) was used to visualize and quantify the density changes that occurred during hydrate formation from granular ice. CT images showed that methane hydrate formed from granular ice was heterogeneous and provided an estimate of the sample density variation in the radial direction. This facilitated quantifying the density effect on composite thermal conductivity. This study showed that the sample heterogeneity should be considered in thermal conductivity measurements of hydrate systems. Mixing models (i.e., arithmetic, harmonic, geometric mean, and square root models) were compared to the estimated composite thermal conductivity determined by inverse modeling. The results of the arithmetic mean model showed the best agreement with the estimated composite thermal conductivity.     

Synthesis,crystallographic, and thermal properties of a new porous silica

A new porous tectosilicate has been synthesized in the presence of boric acid and 1, 2, 2, 6, 6-pentamethylpiperidine as guest molecules. It crystallizes in the monoclinic system with a_o=9.91 (1) Å, b_o=20.62 (3) Å, c_o=9.80 (2) Å, and -99.7 (2)⁰. After heat treatment at 820°C for 1 hour the guest molecules are set free whereas the silica host framework is retained. From crystal morphology and thermal behaviour it is concluded that the new material possesses channel-like voids.     

Morphological and thermal behavior of porous biopolymeric nanoparticles

The aim of the present work is to design, develop and characterize biodegradable polymeric nanoparticles having well defined size and porous morphology. Poly(dl-lactide-co-glycolide) (PLGA) and poly(l-lactide) (PLLA) nanoparticles (NPs) were prepared by double emulsion method with subsequent solvent evaporation. NPs were characterized by electron microscopes, dynamic light scattering, XRD and thermal properties by differential scanning calorimetry and thermogravimetry. Finally, the in vitro degradation analysis was also performed. Biodegradable NPs display a spherical surface structure with a homogeneous size distribution, and an average diameter of 180 nm for PLLA and 218 nm for the PLGA. The NP nanoporous structure was analyzed by an innovative thermal method: thermoporosimetry, providing information about nanopore dimensions. In vitro degradation studies demonstrate the gradual surface aggregation and degradation of NPs and the effects on polymer properties. Biopolymeric porous nano-systems may offer promise properties for revolutionary improvements in tissue engineering, diagnosis and targeted drug delivery systems.     

An unsteady state method for the measurement of polymer thermal diffusivity: I. Development of a cell

In this work the development of a cell able to determine the thermal diffusivity of polymers in their fused or solid state, using an unsteady state technique, is presented. In this case a step down perturbation method was used because of its easy experimental setup. For each experimental run a temperature step down perturbation of 10 °C was applied, and the temperature evolution with time and position were registered and saved. Thermal diffusivities were then determined by regression using those data and a simple analytical model. The polymers used to test the cell were high density polyethylene and polypropylene (PP). For the first polymer, the thermal diffusivity was found to be 2.05×10⁻⁷ m²/s, which compare satisfactorily with a value of 1.97×10⁻⁷ m²/s calculated from reported values of density, heat capacity and heat conductivity. For the PP the value was found to be 7.08×10⁻⁷ m²/s with a positive deviation of 5.05% when compared with a computed value of 6.74×10⁻⁷ m²/s. Taking into account experimental errors, and the natural variations between different stocks of materials, the observed differences are acceptable.     

An investigation about the solid state thermal degradation of acetylsalicylic acid: polymer formation

An investigation about the thermal degradation of acetylsalicylic acid (ASA) is performed. It is verified that the thermal degradation of ASA produces not only salicylic acid (SA) and acetic acid (AA) as products but also an ASA polymer, which is transparent and solid. And also verified that the temperature in which the polymer is obtained influences its physical consistence (solid or semi-solid). Furthermore, the ASA polymer is very stable from a thermic point of view, as verified by TG and DSC analysis. X-ray diffraction patterns obtained for the ASA polymer show that it exhibits a low crystallinity.     

A thermal investigation of the stability of crystalline cross-linked carboxypeptidase a

Crystals of carboxypeptidase A were cross-linked with glutaraldehyde, and samples of the enzyme and apoenzyme were examined by thermogravimetric, dif- ferential thermal and thermomechanical analyses. Further samples were heat-treated under vacuum for various lengths of time, and examined by thermal analysis. Enzymatic activities were measured using the substrate carbobenzoxy-glycyl-L-phenyl- alanine. It proved possible to put forward explanations for all the phenomena observed, and in particular to identify the peak obtained due to loss of water from the zinc ion situated at the active site of the enzyme. The great stability of the cross- linked crystals, which had previously been commented on, was confirmed and the importance of water as a stabilising factor was indicated.