Papers by Keyword: DSC

Abstract: The present work explores the importance of model parameters and input variables when simulating the quenching of thick sectioned nuclear forgings. The modelling approach adopted uses values of specific heat capacity, containing latent heat release, to simulate cooling curves; rather than calculating transformation kinetics based upon a mathematical model. Termed the effective specific heat (Cp_eff), two different methods were used to establish values: differential scanning calorimetry (DSC) and thermos dynamic predictive software. Values were then included in finite element (FE) models to simulate the characteristic cooling at the mid-wall position in a thick section forging and were validated against production thermocouple data. The investigation found that the formation of ferrite, bainite and martensite or lower bainite were all represented by the data established using DSC and critical formation temperatures were comparable with others in the literature. Conversely, values calculated using the thermodynamic software failed to represent ferrite formation and predicted different critical transformation temperatures for bainite. The simulated cooling curve that used the software predicted Cp_eff data was comparable to the thermocouple data either side of the bainite transformation, however during the transformation the effects of latent heat on cooling rate were over predicting leading to disparities. The equivalent DSC cooling curves produced a near exact match.

Abstract: In the present work the copper base alloys with shape memory effects were characterized. The alloys were subjected to three different heat treatments that promoted changes in characteristics of thermoelastic martensitic transformation (transformation temperatures, thermal hysteresis and enthalpies of transformation). The alloys have their microstructures characterized by optical and scanning electron microscopy. Microhardness tests were performed. Differential scanning calorimetry (DSC) was used to evaluate the transformation critical temperatures of alloy and the transformation enthalpies for each heat treated sample. Thermoelastic properties have changed for each heat treatment. In the micrographs of the heat-treated samples was possible to observe the microstructure of the martensitic phase characteristic. They show the presence of martensite platelets (needles) self-accommodation.

Abstract: Despite the benefits associated with the use of natural fibers instead of synthetic ones as composite reinforcement, there are still some limitations to their application. Among the disadvantages associated with natural fibers stands the low thermal resistance. This imposes restrictions to the composite utilization when it is exposed to temperatures above 100 oC. For one point, the hydrophilic nature of lignocellulosic fibers causes absorption of water, but at high temperatures this water is lost, what produce pores and flaws in the composite polymer matrix. Moreover, the fiber cellulose, hemicellulose and lignin are degraded at higher temperatures. The objective of the present work was to conduct a comparative differential scanning calorimetric investigation between polyester and epoxy matrixes composites incorporated with different volume fractions of giant bamboo fibers. A substantial loss of mass was found up to 120 oC. The DSC curves revealed a variation in the enthalpy as a function of the giant bamboo fiber fractions and the corresponding polymeric matrix.

Abstract: State diagram is a map of the different states of a food polymer as a function of water or solids content and temperature. The main advantage of drawing map is in identifying different states of a food polymer which helps in understanding the complex changes when food's water content and temperature are changed. It also assists in identifying food’s stability during storage as well as selecting suitable conditions for processing. This research successfully developed the state diagrams of two Thai rice varieties differing in amylose contents (San-pah-tawng and Phitsanulok 2) by measuring the glass line; glass transition temperature (Tg) vs. solids content, freezing curve; initial freezing point vs. solids content by using the differential scanning calorimetry (DSC) method. Rice with different amylose content exhibited similar freezing curves and glass transition patterns. The state diagrams obtained in this study are in agreement with previously published data. They can be useful in optimizing the drying and freezing processes as well as studying the physicochemical changes during storage of rice.

Abstract: In this paper, the corrosion tests of glass fiber reinforced polymer (GFRP) in high temperature and high pressure acid environment were carried out. The surface morphology and glass transition temperature were observed by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and the mechanical property of GFRP was tested. The results indicated that after being exposed to acid corrosion environment, the structure and organization of GFRP changed, and a variety of defects produced on the surface and interior of GFRP, bending strength and tensile strength of GFRP decreased. The surface analysis also proved that there were some etch pits occurred on the GFRP pipes. Furthermore, their barcol hardness became poor.

Abstract: Mixed and preliminarily consolidated powders of aluminium and nickel (90 mass % Al and 10 mass % Ni) were hot extruded. As results the rod, 8 mm in diameter, was obtained. As-extruded material was subjected to the microstructural investigations using scanning electron microscopy (SEM/EDS) and X-ray analysis (XRD). The differential scanning calorimetry (DSC) and thermo-mechanical analysis (TMA) were also performed. The mechanical properties of as extruded material were determined by the tensile test and Vickers hardness measurements. In order to evaluate the thermal stability of PM alloy, samples were annealed at the temperature of 475 and 550 °C. After annealing Vickers hardness measurements and tensile tests were carried out. The plastic consolidation of powders during extrusion was found to be very effective, because no pores or voids were observed in the examined material. The detailed microstructural investigations and XRD analyses did not reveal the presence of the intermetallic phases in the as-extruded material. During annealing, the Al₃Ni intermetallic compound was formed as the result of chemical reaction between the alloy components. The hardness of the alloy after annealing at the temperature of 475°C was found to be comparable to the hardness in as-extruded state. Annealing of the material at the temperature of 550°C results in hardness decreasing by about 50%, as the consequence of porosity formation and Al₃Ni cracking.

Abstract: In the paper, the influence of homogenization parameters on the microstructure and properties of the 5019 alloy DC-cast billets was analysed. At the first stage, the microstructure of the alloy in as-cast state was investigated using SEM/EDS technique. Additionally, a DSC test and hardness measurements were performed. In the as-cast material, the presence of the dendritic microstructure with a pronounced microsegregation of magnesium in the dendrites cross-section was found. Subsequently, the specimens were subjected to laboratory homogenization experiments, with different soaking conditions and water quenching. The microstructural effects of the investigated variants of homogenization were evaluated using the same techniques as in the case of the as-cast alloy. It was found that after homogenization, with soaking at the temperature of 530 °C for 6 hours, the microsegregation is eliminated and the concentration of magnesium in the grains centres is over two times greater than in the dendrites cores before annealing. The solidus temperature rises by about 12 °C in comparison to the as-cast state. Neither extending the soaking time nor rising the temperature contributes to a further increase of the solidus temperature, or the magnesium concentration in the grains interiors. However, the tendency of dispersoids to grow and the change of Fe-bearing constituents chemical composition were observed after the high temperature, or prolonged annealing variants.

Abstract: Explicit impact on the technical and economic indicators of the smelting ferrosilicon process, has an exchange quartzite, which implements the criteria of the chemical composition in the mixture charging. The article shows the laboratory testing methods to determine the optimal usefulness of quartzite as a charge material for smelting of ferrosilicon. Describes a comparative tests of phase transformations and heat tests ego three quartzites using high-temperature calorimeter Multi HTC company Setaram.

Abstract: The benefit of dammar resin as an alternative renewable energy sources can be optimized by knowing the thermal characteristics. The purpose of this study is to perform thermal analysis of dammar resin. The differential scanning calorimetry (DSC) methods have been used to do this analysis. The results obtained indicate that the dammar resin has a melting temperature of 70.88 °C and 303.02 °C evaporation temperature, dammar resin also has a melting enthalpy of 7.6041 J/g and the enthalpy of vaporization 55.0395 J/g.

Abstract: Cu-Al-Be Ternary alloys are prepared by ingot metallurgy route, which exhibits parent phase or Austenite phase at high temperature and Martensite phase at low temperature and also exhibits shape memory effect upon quenching to lower temperature. The Cu-Al-Be SMA was in the range of 10-12wt% of Al and 0.4-0.5 wt% of Be is chosen for present study and different amount of quaternary element is added to the ternary alloy. The variation in shape memory effect, transformation temperature and microstructure is studied by using bend test, differential scanning calorimeter and Optical microscope.