Thermal - chemical - mechanical characterization of Anacardium occidentale tree gum.

Anacardium occidentale (cashew) tree gum is being used in several sectors, including the pharmaceutical sector. This gum has been explored more in the medical field by many previous researchers, but there is a big research gap regarding its thermal and mechanical properties. Therefore, this research is intended to reveal the thermal, chemical, and mechanical characteristics of Anacardium occidentale tree gum. The results obtained in this regard are then compared with certain properties of artificial resins. Thermal analysis is carried out using a thermogravimetric analyzer, and differential scanning calorimeter, elemental analysis is carried out using a scanning electron microscope and a micro-X-ray fluorescence analyzer; and mechanical tests are carried out using a nano-indentation tester and a universal testing machine. The pH of 4.76 shows that the gum is acidic in nature, and the peaks obtained from thermal analysis demonstrate that it doesn't have a melting point. The microhardness value, tensile strength, flexural strength, and compressive strength of cashew gum are 218.39 MPa, 1.667 MPa, 3.64 MPa, and 2.667 MPa, respectively. The obtained results show that, Anacardium occidentale tree gum has comparable thermal properties to those of artificial resins and other natural gums.

Thermokinetic Study of Aluminum-Induced Crystallization of a-Si: The Effect of Al Layer Thickness.

The effect of the aluminum layer on the kinetics and mechanism of aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) in (Al/a-Si)n multilayered films was studied using a complex of in situ methods (simultaneous thermal analysis, transmission electron microscopy, electron diffraction, and four-point probe resistance measurement) and ex situ methods (X-ray diffraction and optical microscopy). An increase in the thickness of the aluminum layer from 10 to 80 nm was found to result in a decrease in the value of the apparent activation energy Ea of silicon crystallization from 137 to 117 kJ/mol (as estimated by the Kissinger method) as well as an increase in the crystallization heat from 12.3 to 16.0 kJ/(mol Si). The detailed kinetic analysis showed that the change in the thickness of an individual Al layer could lead to a qualitative change in the mechanism of aluminum-induced silicon crystallization: with the thickness of Al ≤ 20 nm. The process followed two parallel routes described by the n-th order reaction equation with autocatalysis (Cn-X) and the Avrami-Erofeev equation (An): with an increase in the thickness of Al ≥ 40 nm, the process occurred in two consecutive steps. The first one can be described by the n-th order reaction equation with autocatalysis (Cn-X), and the second one can be described by the n-th order reaction equation (Fn). The change in the mechanism of amorphous silicon crystallization was assumed to be due to the influence of the degree of Al defects at the initial state on the kinetics of the crystallization process.

[Quality of moxa from Artemisia argyi and A. stolonifera in different storage years based on simultaneous thermal analysis].

The quality of moxa is an important factor affecting moxibustion therapy, and traditionally, 3-year moxa is considered optimal, although scientific data are lacking. This study focused on 1-year and 3-year moxa from Artemisia stolonifera and A. argyi(leaf-to-moxa ratio of 10∶1) as research objects. Scanning electron microscopy(SEM), Van Soest method, and simultaneous thermal analysis were used to investigate the differences in the combustion heat quality of 1-year and 3-year moxa and their influencing factors. The results showed that the combustion of A. stolonifera moxa exhibited a balanced heat release pattern. The 3-year moxa released a concentrated heat of 9 998.84 mJ·mg~(-1)(accounting for 54% of the total heat release) in the temperature range of 140-302 ℃, with a heat production efficiency of 122 mW·mg~(-1). It further released 7 512.51 mJ·mg~(-1)(accounting for 41% of the total heat release) in the temperature range of 302-519 ℃. The combustion of A. argyi moxa showed a rapid heat release pattern. The 3-year moxa released a heat of 16 695.28 mJ·mg~(-1)(accounting for 70% of the total heat release) in the temperature range of 140-311 ℃, with an instantaneous power output of 218 mW·mg~(-1). It further released 5 996.95 mJ·mg~(-1)(accounting for 25% of the total heat release) in the temperature range of 311-483 ℃. Combustion parameters such as-R_p,-R_v, D_i, C, and D_b indicated that the combustion heat quality of 3-year moxa was superior to that of 1-year moxa. It exhibited greater combustion heat, heat production efficiency, flammability, mild and sustained burning, and higher instantaneous combustion efficiency. This study utilized scientific data to demonstrate that A. stolonifera could be used as excellent moxa, and the quality of 3-year moxa surpassed that of 1-year moxa. The research results provide a scientific basis for the in-depth development of A. stolonifera moxa and the improvement of moxa quality standards.

Experimental selection of the initial dissolution treatment temperature range for the subsequent cold rolling of IN907 superalloy sheet.

The present study aims to determine the optimal temperature range of the dissolution treatment for the cold rolling of the IN907 superalloy. Samples of the IN907 superalloy hot-rolled sheet, after phase characterization by x-ray diffraction (XRD) and simultaneous thermal analysis (STA) experiments, were subjected to dissolution treatment in the temperature range of 940 °C-1000 °C, followed by cooling in air. The samples were then examined for microstructure, microhardness, tensile properties, and plane strain compression (PSC). Unlike the XRD test, the STA curve of the alloy showed two exothermic peaks, the first peak in the 750-950 °C temperature range associated with the intragranular laves phase and the second peak in the 1100-1175 °C temperature range associated with the oxide phase. The results showed that with increased temperature of the initial dissolution treatment from 980 °C to 1000 °C, the complete dissolution of the grain boundary laves phase led to an increase in the average grain size from 45µm to 57µm and a decrease in the yield and tensile strength by 42 MPa. The microhardness test showed that increasing the temperature of the initial dissolution treatment had little effect on the microhardness. Also, the flow stress diagrams and the normalized work hardening rate of the PSC test showed a similar behavior despite the observation of shear bands in the microstructure center of the compressed sample.

Study on the Moisture Absorption and Thermal Properties of Hygroscopic Exothermic Fibers and Related Interactions with Water Molecules.

The aim of this paper is to study the hygroscopic behavior of hygroscopic exothermic fiber-based materials and to obtain a better understanding of the thermal performance of these fibers during the moisture absorption process. The temperature distribution of different kinds of hygroscopic exothermic fibers in the process of moisture absorption, observed by infrared camera, demonstrated two types of heating performance of these fibers, which might be related to its hygroscopic behavior. Based on the sorption isotherms, a Guggenheim-Anderson-de Boer (GAB) multi-layer adsorption model was selected as the optimal moisture absorption fitting model to describe the moisture absorption process of these fibers, which illustrated that water sorption capacity and the water-fiber/water-water interaction had a significant influence on its heating performance. The net isosteric heats of sorption decreased with an increase of moisture content, which further explained the main factor affecting the heat dissipation of fibers under different moisture contents. The state of adsorbed water and water vapor interaction on the fiber surface were studied by simultaneous thermal analysis (TGA-DSC) measurement. The percentage of bound and unbound water formation at low and high humidity had a profound effect on the thermal performance of fibers. It can therefore be concluded that the content of tightly bound water a strong water-fiber interaction was the main factor affecting the heating performance of fibers at low moisture content, and the content of loosely bound water reflected that water sorption capacity was the main factor affecting the heating performance of fibers at high moisture content. This was further proven by the heat of desorption.