Papers by Keyword: Thermal Analysis

Abstract: To preserve the environment and its resources for future generations, research must focus on alternate methods of producing materials that begin with an environmentally friendly and sustainable source. In view of this, nanosize reinforcing fillers were obtained from date palm agricultural waste without use of any toxic chemicals. Date nanofillers (DNF) with typical filler sizes ranging from 30-110 nm in width and 1-10 mm in length were obtained using rotary mechanical ball milling methods. This filler was then dry blended with the polypropylene (PP) to make a biocomposites thin film to study processability characteristics of this fillers. The loading of this filler was kept in the range of 1-5wt. % and film were melted cast through a slit height of 0.6mm. The resulting PP/DNF biocomposites films were subsequently analyzed by various analytical techniques to established structure property relationship. The change in thermal properties with loading of this filler was investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA study showed that the thermal stability of film samples improved up to 20 °C when compared to the neat PP, representing an 8% enhancement. While the DSC measurement indicated that the crystallinity of the highest filler loading sample reduced from 52.89% to 41.79% in comparison to the PP sample. The surface morphology of some samples shows the compact and smooth feature, indicating the incorporation of fiber fillers could improve the structure of polymer. Therefore, study gave some insight into the processing behavior of such composites, which may be useful in some packaging applications.

Abstract: Understanding heat transfer phenomena is crucial in high-power amplifiers to keep components within safe operating temperatures. This article investigates the GaN Power Amplifier (PA) thermal analysis for the optimum design of the heatsink. GaN PAs are roughly separated into junction, package, and heat sink layers to calculate the junction’s transient thermal response. It has been proven that allowing individual components to operate at temperatures over their maximum rated junction temperatures significantly reduces the system's operational reliability as a whole. This analysis investigates two different heat sinks for the optimum case temperature (T_case) for these different PAs. These PAs are operating S-band (2-3.4 GHz) and C-Ku-band (5-18 GHz) with drain efficiency of 60-65% and 9-22%, respectively. The design analysis of the heat sink for optimal performance is explored in this work.

Abstract: Microchannels based on Micro Electromechanical Systems (MEMS) have garnered a great lot of interest over the past 40 years from the fields of microfluidics and biomedicine. In order to address the problem of heat dissipation in incredibly small integrated circuits with up to 790 W/cm² of huge heat dissipation capabilities, Tuckerman et al. [1] first proposed the microchannel heat rejection idea in 1981. These channels are typically at the microscale, with characteristic dimensions on the order of micrometers 10^-6 m or smaller as shown in Figure 1 [2]. These channels often exist at the microscale and have characteristic diameters of micrometres 10^-6 m or less. Microchannels display distinct fluidic behaviour as a result of their small size. Because the flow is normally laminar and the Reynolds number is low, the flow pattern is predictable. Capillary forces and other surface forces become comparatively more important. As a result, fluid behaviour in microchannels is greatly influenced by surface wetting characteristics and channel surface roughness.

Abstract: The effects of nanocellulose extracted from pineapple leaf fiber on the physico-chemical and thermal properties of epoxy nanocomposite are reported. Nanocellulose was added to the epoxy in different amounts of loadings (0.5, 1.0, 1.5, and 2.0 wt.%) to prepare nanocomposites. The physico-chemical and thermal properties of the nanocellulose reinforced epoxy nanocomposites were investigated. Surface characterization of the nanocomposite was done using scanning electron microscopy (SEM). Functional groups of the nanocomposites were evaluated using fourier transform infrared (FTIR) spectroscopy. Thermal properties of the nanocomposites were investigated using thermogravimetric analyzer (TGA) and differential thermal analyzer (DTA). Experimental results revealed that the 0.5, 1.0, and 1.5 wt.% nanocellulose loadings were homogeneously distributed and well-dispersed in the composite matrix as indicated in the SEM images. However, aggregation was observed in the matrix with 2.0 wt.% nanocellulose loading. Moreover, FTIR spectra revealed that the absorbance of the vibrational mode corresponding to the interaction of nanocellulose and epoxy matrices significantly increases as the nanocellulose loading ratio increased. Furthermore, thermal analysis (TGA/DTA) showed that the incorporation of nanocellulose improved significantly the thermal properties of epoxy nanocomposites.

Abstract: The thermal analysis will be realised in a Computer Aided Parametric Design program for three tools with different pin geometries to determine the transfer and distribution of the thermal energy produced during the process and to observe the influence of the pin geometry has on the distribution. Due to the fact that the joining process can be done at a lower temperature than the melting point of the material certain steps must be followed prior and correct selection of the machine’s parameters. Information on the parameters for specific materials and the preparation of the base material are readily available but considering the method of producing the thermal energy necessary for the process the quality of the weld is highly influenced by preheat time (of the material and tool), room temperature, cooling of the tool or work piece if the machine is equipped with such a configuration. We will observe in this study the effect of tool pin geometry over dwell time for reaching a uniform temperature of the tool in the shortest amount of time. The parameters used for the acquiring the data needed for the thermal analysis regarding tool material are tungsten carbide and the material of the plates will be aluminium 1200. The paper’s subject will be the realisation of a thermal analysis of the FSW (Friction Stir Welding) tools.

Abstract: This paper explores the possibilities of utilization of waste diatomite in foam glass production. Chemical and mineralogical composition, granulometry and high temperature behaviour of waste diatomite were characterized. Different possibilities of waste diatomite utilization in foam glass production were explored mainly via means of thermal analysis and hot stage microscopy. The effects of diatomite addition to waste glass were evaluated. Possibility of using NaOH as a foaming agent for foam glass production from waste diatomite and the effects of NaOH amount and reaction time on waste diatomite were investigated. Partial conversion of diatomite and clay to hydrates due to the reaction with NaOH lead to the decrease of the melting temperature and foaming of the melt was observed via hot stage microscopy. 30 wt. % NaOH addition allowed foaming of waste diatomite in the temperature ranges typical for foam glass production. Increased reaction time led to the intensification of the foaming process.

Abstract: The objective of the present research is to investigate the degradation phenomenon of Polyvinyl Chloride (PVC) cable jacket exposed under accelerated thermally aged at 100°C for 4 days then irradiated under n’s flux of 1.5x 10¹¹ n’s / cm².sec for 1 hr in PARR-2 reactor at PINSTECH. Thermal, mechanical and chemical etc. properties of degraded cable jacket were studied with respect to fresh sample. It was examined that plasticizer content in PVC matrix started to deplete under the effect of temperature which made the matrix more rigid. In addition, the interaction of radiation with polymeric chains weakens the hydrocarbon bonding. The hydrogen and chlorine ions ejected from PVC molecular chains recombine to form hydrogen chloride (HCl) which induces porosity by creating localized pitting. This phenomenon is known as dehydrochlorination which created scissioning in PVC materials. Hence, due to the synergistic effects of temperature and radiation aging, cracks were observed on the outer surface of cable jacket in 2 years equivalent time. This study concludes that cables having PVC insulation are not suitable for long term exposure (i.e. decades) in thermo-irradiation environment.

Abstract: Despite its promising advantages, the application of directed energy deposition (DED) to produce large metal parts is hindered by challenges inherent to the process. Undesired residual stresses, distortions and heterogeneous material properties mainly originate from a part’s thermal history. Fast part-scale thermal models therefore facilitate improved applicability of DED by enabling the prediction and mitigation of these unwanted effects. In this work, the efficiency of a discontinuous Galerkin-based thermal model with heat input by hot element addition, is evaluated and improved to allow such fast simulations. It is found that the model permits the use of a coarse discretization around the heat source, which significantly reduces simulation time while maintaining accurate solutions. It is also shown that the model naturally facilitates the use of local time stepping, which can considerably improve the efficiency of thermal additive manufacturing simulations.

Abstract: Clay from the Khmelnytskyi region was enriched in montmorillonite by separation of a fraction with a particle size  0.5 ∙ 10^-6 m. The X-ray diffraction and thermal analyses suggest that the enriched clay composition is close to mono-mineral, that is, represented by ferric-type montmorillonite in the form of Ca and Mg. The mineral interlayer spacings are partially filled with natural organic matter. An exchange capacity of montmorillonite is 0.78 mmol/g as shown by the photocolorimetry studies of the adsorption of the cationic methylene blue (MB) dye. It is recommended that studied clay be used as an effective natural adsorbent for wastewater treatment and for the arrangement of geochemical barriers to prevent harmful substances from entering the environment.

Abstract: One of the ways to enhance thermal stability and reduce the flammability of polymers is the introduction of fillers with flame retardant properties. The paper studies the effect of natural zeolites of the Sakhaptinsk and Shivyrtuysk deposits on the thermal stability and flame retardancy of epoxy composites. The thermal stability of epoxy composites was characterized by thermogravimetric analysis in oxidizing (air) and inert (argon) atmospheres. The parameters of thermo-oxidative degradation and thermal degradation of the samples with a filler concentration of 0, 1, 5, and 10 wt% were studied. Flame retardancy of epoxy composites filled with zeolite was evaluated using the limiting oxygen index. The limiting oxygen index increases with increasing concentration of natural zeolites in the epoxy matrix. The study revealed some differences in the first and second stages of heating the epoxy composites depending on zeolite type and did not reveal significant difference in the thermal behavior of the epoxy composites in the third stage of the heating. Thermal stability and flame retardant properties are more dependent on the zeolite content in the epoxy matrix than zeolite type.