Derivative Thermogravimetry Research Articles

Investigation of the Characteristic Properties of Lignin-Modified Bitumen

The main objective of this study was to investigate the characteristic properties of lignin-modified bitumen with different lignin contents. The first step was the characterization of the physicochemical and thermal properties of the kraft lignin powder along with the determination of its microstructure. This was achieved by carrying out an elemental analysis, Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA)/Derivative Thermogravimetry (DTG), Fourier Transformation Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS) and Confocal Microscopy. After the latter tests, three (3) blends with different lignin contents (5%, 10% and 15% by weight of bitumen) were produced. Characteristic properties such as penetration, softening point, elastic recovery, force ductility, dynamic viscosity and storage stability were determined for the reference bitumen and the three lignin blends. The main conclusion was that kraft lignin powder hardens the conventional bitumen. Specifically, the addition of 15% lignin to the bitumen hardened the blend to such a degree that the bitumen changed category from 50/70 to 35/50 with respect to EN 12591.

Assessment of CO2 biofixation and bioenergy potential of microalga Gonium pectorale through its biomass pyrolysis, and elucidation of pyrolysis reaction via kinetics modeling and artificial neural network.

This study investigates CO2 biofixation and pyrolytic kinetics of microalga G. pectorale using model-fitting and model-free methods. Microalga was grown in two different media. The highest rate of CO2 fixation (0.130g/L/day) was observed at a CO2 concentration of 2%. The pyrokinetics of the biomass was performed by a thermogravimetric analyzer (TGA). Thermogravimetric (TG) and derivative thermogravimetric (DTG) curves at 5, 10 and 20°C/min indicated the presence of multiple peaks in the active pyrolysis zones. The activation energy was calculated by different model-free methods such as Friedman, Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Popescu. The obtained activation energy which are 61.7-287kJ/mol using Friedman, 40.6-262kJ/mol using FWO, 35-262kJ/mol using KAS, and 66.4-255kJ/mol using Popescu showed good agreement with the experimental values with higher than 0.96 determination coefficient (R2). Moreover, it was found that the most probable reaction mechanism for G. pectorale pyrolysis was a third-order function. Furthermore, the multilayer perceptron-based artificial neural network (MLP-ANN) regression model of the 4-10-1 architecture demonstrated excellent agreement with the experimental values of the thermal decomposition of the G. pectoral. Therefore, the study suggests that the MLP-ANN regression model could be utilized to predict thermogravimetric parameters.

Structure elucidation, DNA interaction, potential anticancer, molecular docking activities, and γ‐ray irradiation studies on novel mono‐ and binuclear Fe (II), Ni (II), Co (II), and Hg (II) Schiff base complexes

Bis Schiff baseN,N–((1E,2E)‐ethane 1,2diylidene)bis(azanylylidene)di(isonicotinohydrazide) ligand L was reacted with Fe (III), Ni (II), Co (II), and Hg (II) chlorides to yield complexes (1–6). The structure of the synthesized ligand and metal complexes was well established by various spectroscopic techniques (Fourier‐transform infrared [FT‐IR], UV–Vis., and1H NMR), mass spectrometry, elemental analysis (CHN) and physical studies (thermogravimetric analysis [TGA]/first derivative thermogravimetric analysis [DTG], powder X‐ray diffraction, molar conductance, and magnetic moment). Solid powder samples of the binuclear complexes (3and6) were irradiated at two different irradiation doses (150 and 200 kGy) to yield complexes (3Fand3F*) and (6Fand6F*), respectively. For the γ‐irradiated samples, FT‐IR, UV–Vis., and physical studies (TGA/DTG, X‐ray diffraction, molar conductance, and magnetic moment) were performed using the same methods as for the as‐prepared complexes. In addition, calf thymus ct‐DNA binding results monitored by agarose gel electrophoretic method indicated that the as‐prepared binuclear [Hg2LCl4(OH)2] complex (6) and its γ‐irradiated [Hg2LCl4(OH)2] complex (6F) have the ability to cleave ct‐DNA at a concentration of 30 and 70 μg/ml, respectively. Inhibitory activity against hepatocellular carcinoma cells (HepG‐2) and breast carcinoma cells (MCF‐7) of ligand and as‐prepared complexes (3,6, and6F) was evaluated. The results revealed that metal complexes exhibited enhanced activity in comparison to the free ligand, and the as‐prepared complex (6) shows an IC50value of 5.7 ± 0.2 and 8.72 ± 0.6 μg/ml for the two cell lines, respectively. Docking process for the ligand and complexes (3) and (6) with liver cancer protein (ID: 4FM9) and breast cancer protein (ID: 1H7K) has been evaluated.

Radiation initiated synthesis of (carboxymethyl cellulose/polyacryalmide) hydrogels with polyprotic acid moieties and their utilization in nicotinic acid release

AbstractHydrogels of (carboxymethyl cellulose/polyacrylamide/polyprotic acids) were synthesized via gamma‐irradiation as green initiator. The polyprotic acids were used are oxalic, tartaric, citric and maleic. Effects of irradiation dose and polyprotic acids concentration on gelation (%) and swelling (%) are investigated. The swelling of hydrogels were conducted in the range of pH levels are from 1 to 12 at 37°C. The outcome hydrogels were characterized different techniques of Fourier transform infrared spectroscopy, thermal gravimetric analysis and derivative thermogravimetry, X‐ray diffraction, and scanning electron microscopy. The results confirmed the formation of respective hydrogels. Hydrogels were exploited in release of nicotinic acid as model of drug release. Dry tablets from hydrogels were fabricated as cylindrical discs. Dry hydrogels tablets were subjected to two different pH levels (i) simulated gastric fluid of pH level 1.2 and (ii) simulated intestinal fluid of pH level 7.5. The outcome results showed that there is a difference of nicotinic acid release quantity between the two pH levels. Further, different kinetic models of zero‐order, Korsmeyer–Peppas, Higuchi and Weibull were used to fit the experimental data. Through the results declared that the best fitting model was Weibull.

The effect of formulation and processing parameters on thermal stability of PVC/Poly(epichlorohydrin-co-ethylene oxide)/organoclay nanocomposites prepared by melt mixing

In this work, nanocomposites of polyvinyl chloride poly(epichlorohydrin-co-ethylene oxide)(ECO)/organoclay were prepared via melt processing and various parameters including nanoclay and rubber content (ECO) as well as rotor speed were tuned to find the optimum formulation for the highest thermal stability. The prepared products were characterized by X-ray diffraction as well as thermogravimetric analysis (TGA), derivative thermogravimetric (DTG) and differential thermal analysis XRD results showed that rotor speeds higher than 70 r/min are crucial for obtaining highly intercalated products with good thermal stability. From DTG analyses, it was observed that at lower concentrations of rubber, the rate of mass loss is higher which results in faster dehydrochlorination of the composite. The sample prepared with 2 phr OMMT, 30 phr rubber, and 70 r/min rotor speed showed the highest thermal stability. The selected nanocomposite showed the first weight loss at 294 [Formula: see text]. Results of this research showed that even a slight change in each parameter has a great influence on thermal properties of the nanocomposites. The hydrogen bonding mode between ECO and organoclay were estimated by theoretical calculations using GAUSSIAN software. From the obtained results, the miscibility of OMMT and ECO polymer is related to the hydrogen bonds which are more preferred at chlorine atom of ECO polymer.

Investigation of the microstructural characteristics of heated sandstone by micro-computed tomography technique

Heritage buildings always pose challenges due to experiencing high temperatures and pressure over time. Sandstone is one of the common sedimentary rock types used for these buildings. Therefore, it is very important to understand the microstructural variations of rocks associated with these constructions along with the mechanical variations. In this study, the microstructural and mechanical alteration of selected types of sandstones is investigated after it is heated from room temperature to 800 °C. Micro X-ray computed tomography (µXCT), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG) and derivative thermogravimetry (DTG) techniques were used to identify the physical, chemical, mineralogical and microstructural changes of sandstone after different heat treatments. The mechanical alteration of the heated rock specimens was also studied using the point load index (PLI). The main changes in microstructure were observed when the sandstone’s temperature was greater than 400 °C. The total porosity measured by µXCT of sandstone increased by more than 70% at 800 °C compared to its porosity at room temperature. When the temperature increases, the open porosity increases while the closed porosity decreases. Noticeable changes in rock mineralogy were identified at temperatures exceeding 400 °C, which can be attributed to the phase transition of quartz, decomposition of feldspar and dehydroxylation of kaolinite. The TG and DTG analyses and point load index were in good agreement concerning these changes in rock mineralogy. Microstructural variation is one of the main reasons for the discrepancy in threshold values between different sandstones.

Experimental and theoretical study on the evolution of functional groups in cellulose char during oxidative pyrolysis

Oxidative pyrolysis of biomass is a promising substitute technology for conventional pyrolysis and is also crucial to the related degradation process of biomass materials such as aging, combustion, fire hazard, etc. The intertwining of heterogeneous oxidation and homogeneous oxidation of biomass and its derivative muffles the detailed mechanism of oxidative pyrolysis. To unravel the mechanism of heterogeneous oxidation in the cellulose condensed phase, the real-time evolution of functional groups in cellulose char during oxidative pyrolysis was probed by the in situ diffuse reflectance infrared Fourier transform technology, which is further analyzed by a homemade semi-quantitative analysis program based on the perturbation-correlation moving-window two-dimensional correlation spectroscopy and two-dimensional correlation spectroscopy. The experimental results show the obvious promotion effects of O2 on the direct oxidation of hydroxyls to unconjugated CO and the cleavage of COC in the development stage between the temperatures of the initiation and the maximum rate of weight loss, resulting in the lowered thermostability and devolatilization of cellulose. At elevated temperatures, the hydroxyls and CO were further oxidized by O2 into carboxyls, and released at around 450 °C in the last decline stage, performing the second peak of the derivative thermogravimetry curve for oxidative pyrolysis. Through density functional theory calculation of the hydroxyl oxidation, a low-temperature oxidation mechanism competitive with the transglycosylation and other dehydration reactions was proposed. Its rate is determined by the initiating H abstraction, which highly depends on the spin density (population) for the transition state and pyrolysis temperature.

Hydrochar prepared from municipal sewage sludge as renewable fuels: Evaluation of its devolatilization performance, reaction mechanism, and thermodynamic property

Hydrothermal treatment (HT) of sewage sludge (SS) is a promising method to improve its dewaterability. Effect of HT on devolatilization performance, kinetic parameters, and thermodynamic property during the pyrolysis of SS was investigated by thermogravimetric analysis (TGA), isoconversional method, and master plots method. Derivative thermogravimetry (DTG) curves showed two distinct devolatilization peaks #1 at 283.21 °C and #2 at 327. 43 °C along with a shoulder between 400 and 600 °C. HT temperature influenced peak #2 more significantly as its peak devolatilization rate decreased consecutively from 4.25 % to 1.70 %∙min−1. Meanwhile it moved towards higher temperature and overlapped with the shoulder ultimately. The value of comprehensive pyrolysis index (CPI) decreased greatly from 3.37 × 10−5 to 1.24 × 10−6 %3∙°C−3∙min−2 with HT temperature. Activation energy was determined by Flynn-Wall-Ozawa, Kissinger-Akahira-Sunose, Starink, and Friedman methods. It generally increased against conversion with diverse variation patterns. Its average value reduced obviously after HT. Despite HT, all samples followed identical Avrami-Erofeev model with decreased order of reaction from 7.60 to 6.56. The variation trends of enthalpy, Gibbs free energy, and entropy verified that HT improved the thermal stability of SS, which coincided with CPI. Pyrolysis process of SS evolved from ordered state to disordered state, indicating increased reactivity due to the probable catalytic effect of inorganics in the ash. The work provides guidance for the design, optimization, and upscale of pyrolysis reactors and operation parameters when SS is utilized as renewable fuels.

Role of Gypsum Content on the Long-Term Performance of Lime-Stabilised Soil.

The role of gypsum level on the long-term strength and expansion of soil stabilised with different lime contents is not well understood. This research, therefore, studied the effect of varying gypsum concentrations of 0, 3, 6, and 9 wt% (equivalent to the sulfate contents of 0, 1.4, 2.8, and 4.2%, respectively) on the performance of sulfate soil stabilised with two lime levels (4 and 6 wt%). This was carried out to establish the threshold level of gypsum/lime (G/L) at which the increase in G/L ratio does not affect the performance of lime-stabilised sulfate soil. Both unconfined compressive strength (UCS) and expansion, along with the derivative thermogravimetric (DTG) analysis, were adopted to accomplish the present objective. Accordingly, the result indicated that the strength and expansion were proportional to the lime and sulfate content, of which a G/L ratio of 1.5 was the optimum case scenario for UCS, and at the same time, the worst-case scenario for expansion. This discovery is vital, as it is anticipated to serve as a benchmark for future research related to the design of effective binders for suppressing the sulfate-induced expansion in lime-stabilised gypseous soil.

Synthesis and Characterization of Monodispersed Spherical Calcium Oxide and Calcium Carbonate Nanoparticles via Simple Pyrolysis.

In this study, calcium carbonate nanoparticles (CCNPs) and calcium oxide nanoparticles (CONPs) are synthesized by the carbonization/calcination of calcium oleate. CONPs are an essential inorganic material, and they are used as catalysts and as effective chemisorbents for toxic gases. CCNPs are widely used in plastics, printing ink, and medicines. Here, calcium oleate is used as a starting material for the preparation of CCNPs and CONPs. This calcium oleate is prepared from calcium hydroxide and oleic acid in ethanol under mild reflux conditions. The effect of the calcination temperature of calcium oleate is examined during the synthesis of CCNPs and CONPs. By simple carbonization/calcination, calcite-type CCNPs and CONPs are prepared at <550 °C and >600 °C, respectively. The synthesized nanomaterials are analyzed by various physicochemical characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA) with derivative thermogravimetry (DTG), and scanning electron microscopy (SEM) with energy dispersive X-ray analysis. An X-ray diffractometer and the Scherrer formula are used to analyze the crystalline phase and crystallite size of prepared nanoparticles. TGA techniques confirm the thermal stability of the calcium oleate, CCNPs, and CONPs. The SEM analysis illustrates the dispersive behavior and cubic/spherical morphologies of CCNPs/CONPs. Furthermore, the obtained results are compared to the CCNP and CONP samples prepared using calcium hydroxide. As a result, the carbonization/calcination of calcium oleate produces monodispersed CONPs, which are then compared to the CONPs from calcium hydroxide. Additionally, from calcium oleate, CONPs can be prepared on a large scale in a cheap, convenient way, using simple equipment which can be applied in various applications.

Experimental Insights into Mesoporous Polyaniline-Based Nanocomposites for Anionic and Cationic Dye Removal.

This work presents the preparation of inorganic-organic hybrid nanocomposites, namely three-dimensional polyaniline (Pani)/activated silica gel (ASG) (3D Pani@ASG), their characterization, and in removing application as a potential adsorbent for cationic brilliant green (BG), crystal violet (CV), and anionic Congo red (CR), and methyl orange (MO) dyes. Pani@ASG nanocomposites have been prepared by the in situ polymerization method and characterized using various techniques such as Fourier transform infrared (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) with selected area electron diffraction, thermogravimetric analysis with derivative thermogravimetry, zeta potential analyses, and Brunauer-Emmett-Teller (BET). The scanning electron microscopy (SEM) study confirms the average particle size of the Pani@ASG nanocomposite is in the range of 5 nm. FESEM, TEM, FTIR, and XRD analysis proved the successful decoration of ASG over Pani. The BET result of Pani@ASG shows a mesoporous nature with a pore diameter of less than 3 nm and a surface area of 423.90 m2 g-1. Both SEM and TEM analyses show the proportional distribution of ASG over Pani's surface. The adsorption trend of BG and MO on the studied materials at pH 7 was found as follows: Pani@ASG > Pani > ASG. The highest sorption capacities of MO and BG on Pani@ASG were 161.29 and 136.98 mg/g (T = 298.15 K, and Pani@ASG dose: 0.04 g for MO and 0.06 g for BG), which were greater compared with bare Pani and bare ASG, respectively. The interaction mechanism behind the adsorption of BG and MO dyes onto the Pani@ASG nanocomposite includes electrostatic interaction, π-π interaction, and hydrogen bonding. The mechanistic pathway and the interactions between the targeted dyes and Pani@ASG were further studied using adsorption isotherm, adsorption kinetics, and thermodynamics.

Mechanical properties of high-strength strain-hardening cementitious composites (HS-SHCC) with hybrid supplementary cementitious materials under various curing conditions

This study aimed to achieve improved tensile performance of strain-hardening cementitious composites (SHCCs) utilizing various types of supplementary cementitious materials (SCMs) along with polyethylene (PE) fibers. Ground granulated blast-furnace slag (GGBS), silica fume (SF) and cement kiln dust (CKD) were used as SCMs, with at least two types of SCMs incorporated into SHCC to improve the mechanical performance through hybrid effect of SCMs. Additionally, reaction sensitivity and hydration products were evaluated using specimens manufactured under various curing temperatures (20 °C, 40 °C, and 90 °C) in consideration of different chemical compositions of the SCMs. It was confirmed that the 40 °C curing condition has the most positive effect on the compressive and tensile strengths of SHCC and strain capacity. The absence of SF led to a decrease in the strain capacity, significantly affecting the low strain energy density of the corresponding specimens. The specimen cured at a temperature of 40 °C after incorporating all three SCMs exhibited remarkably long-lasting strain-hardening behavior and achieved the highest strain capacity and strain energy density among all the specimens. Crack investigation after a tensile test was conducted to confirm traces of strain-hardening behavior, which improved a reliability of the mechanical tests. Moreover, derivative thermogravimetry analysis was performed to identify the residual amounts of hydrates affecting the performance of the cement composites. The high Ca(OH)2 residue was the basis for explaining insufficient hydration reactions, and the key factors for the low strength of some specimens was found in a low produced amount of CaCO3.

Influence of Emerging Semiconductive Nanoparticles on AC Dielectric Strength of Synthetic Ester Midel-7131 Insulating Oil.

Exploring impressively effective dielectric nanofluids for transformers to improve dielectric strength and thermal stability is indispensable. It is crucial to determine the modification mechanism of dispersed nanomaterials in insulating oil for operative applications in power transformers. This paper aspires to authenticate the experimental evidence of the enhancing AC dielectric strength of synthetic ester Midel-7131 using two newly introduced semiconductive nanoparticles, CdS and Co3O4, and uncover the potential reasons for enhanced AC dielectric strength. The AC breakdown voltage (BDV) of synthetic ester and nanofluids was investigated and statistically evaluated. The mean AC breakdown voltage of SE/CdS and SE/Co3O4 was increased by 31.9% and 31.3%, respectively. The augmentation in AC breakdown strength is possibly due to the facilitated charge-scavenging ability owing to the large specific surface area and wide bandgap. Simultaneous thermogravimetric analysis, differential scanning calorimetry, and derivative thermogravimetry analyses (TGA–DSC–DTG) confirmed that the initial decomposition temperature was high and heat dissipation was low, indicating that the nanofluids were thermally stable in both air and nitrogen. Hence, emerging semiconductive CdS and Co3O4-based nanofluids of synthetic ester possess remarkable dielectric strength and thermal stability enhancement for their application in power transformers.

Management of university solid waste in China through gasification technology: An analysis of waste composition and energy potential.

This study explored the composition and energy potential of university solid waste (USW) in China. Five combustible components, namely hard plastics (HP), paper (PP), soft plastics (SP), biomass (BM), and rubber (RB), were screened with the compositions 51%, 29%, 9%, 4%, and 3%, respectively. Each USW sample was gasified using a thermogravimetric analyzer (TGA) coupled with mass spectrometry (MS) at the heating rates of 5, 10, and 15 ℃/min and a final process temperature of 900 ℃. Thermal weight loss (TG) curves exposed the degradation in the order HP > SP > RB > BM > PP. Derivative thermogravimetric (DTG) peaks revealed that HP, PP, BM, and SP were degraded in three temperature-oriented phases in the range 172-731 ℃. The RB took an additional phase in the range 584-660 ℃. Major released gases, H2, CH4, CO, and CO2, were detected using MS via mass-to-charge (m/z) ratios. Higher H2 and total gas yield produced in the case of the HP dominated other materials at the lower heating rate of 5 ℃/min. Validation of data was assessed by equating experimental and calculated curves; therefore, the regression coefficient (R2) ranged between 0.884 and 0.997. The kinetics of the process were estimated by applying the Flynn-Wall-Ozawa (FWO) model at the conversion rates (α) of 0.2, 0.5, and 0.8, which presented reasonable results. Overall, the lower heating rates supported higher thermal conversion and a high quantity of gaseous products for all the components.

Influence of Convective and Vacuum-Type Drying on Quality, Microstructural, Antioxidant and Thermal Properties of Pretreated Boletus edulis Mushrooms.

Freshly harvested Boletus edulis mushrooms are subjected to rapid loss of quality due to the high moisture content and enzymatic activity. Drying time, quality characteristics, microstructural and thermal properties were studied in mushrooms ground to puree subjected to hot air drying (HAD), freeze drying (FD) and centrifugal vacuum drying (CVD). The influence of hot water blanching and UV-C pretreatments was additionally investigated. The rehydration ability of mushroom powders was improved by FD, especially without pretreatment or combined to UV-C exposure. The HAD and CVD, with no pretreatment or combined to UV-C, ensured good preservation of phenolics and antioxidant activity of dried mushrooms. The total difference in color of mushroom pigments extracted in acetone was lower in samples dried by CVD and higher in ones by FD. Blanching before HAD produced whiter product probably due to the reduced polyphenoloxidase activity. Scanning Electron Microscopy (SEM) analysis showed fewer physical changes in FD-samples. Heat-induced structural changes were noticed by Differential Scanning Calorimetry (DSC), Thermogravimetry (TG) and Derivative Thermogravimetry (DTG) analysis, in particular of biopolymers, confirmed by ATR-FTIR analysis. Based on our complex approach, the UV pretreatment of mushrooms could be a better alternative to water blanching. Centrifugal vacuum emerged as a new efficient drying method in terms of bioactive compounds, color and thermal stability, while FD led to better rehydration ability and microstructure.

Behaviour of strain hardening geopolymer composites at elevated temperatures

Strain hardening geopolymer composite (SHGC) is a sustainable fibre-reinforced material that exhibits superior strain-hardening and multiple cracking behaviour under tension. The geopolymer binder synthesised through alkali-activation of aluminosilicate precursors sourced from industrial by-products is chemically stable at elevated temperatures. This paper presents a systematic experimental study on behaviour of fly ash-slag based SHGC reinforced with polyvinyl alcohol (PVA) fibres exposed to elevated temperatures up to 800 °C through weight loss, uniaxial compressive, ultrasonic pulse velocity (UPV) and uniaxial tensile tests as well as thermal analysis using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and derivative thermogravimetry (DTG), X-ray diffraction (XRD), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP). Results indicate that the compressive strength of SHGC is increased until exposure to 250 °C, followed by a decline up to 600 °C and a regain at 800 °C. The strength gain mechanisms include further geopolymerisation that refines the microstructure, fibre bridging action and sintering that densifies the binder gels, while the strength reduction can be attributed to the damage induced by internal moisture removals and evaporation of fibres, decomposition of calcium compounds, and empty channels introduced by vanished fibres. Besides, the SHGC specimens exposed up to 250 °C exhibit high ductility performance with saturated microcracks when subjected to uniaxial tension, whilst those at 105 °C demonstrate the best strain-hardening degree because of the desired fibre-matrix interaction and enhanced matrix strength. Moreover, no spalling can be observed in SHGC due to its relatively porous structure.

Thermal behaviour and inertia effect in calcium aluminate cement pastes with microsilica

The main contribution of this research is the study of the effect of thermal inertia in the activation energy in calcium aluminate cement pastes. For this, several formulations of calcium aluminate cement pastes (CACPs) with 51 wt% and 71 wt% of alumina (Al2O3) were made at 0.4 water-to-cement ratio, and with additions of 0.0 wt% and 20 wt% of silica content. The characterisation was done using X-ray fluorescence and X-ray diffraction, and the behaviour of the phases with temperature was studied using thermal gravimetric analysis, including the corresponding derivative thermogravimetry (DTG). The influence of the thermal inertia on the activation energies and its dependence on the heating rate is established. The effect of thermal inertia on peaks of DTG curves and activation energies is analysed. The activation energies for dehydroxylation of the gibbsite were calculated based on the Kissenger–Akahira–Sunose method. The activation energy values obtained, in kJ/mol, for CACP71 – 0, 20 wt% and CACP51 – 0, 20 wt% silica content were 19.9, 6.37 and 19.8, 17.2, respectively. The influence of silica on phase formation, activation energies and the effect of thermal inertia is also analysed.

Antimicrobial activity of moringa peregrina seed oil: chemical composition and effect of extraction procedure

Background and objective: The importance of new sources of oils has recently emerged, one such source being Moringa. There is an urgent need to choose the most appropriate extraction method regarding its impact on the properties and stability of the extracted oil.The objective of this research work is to study the impact of two extraction methods on the chemical and thermal properties as well as the antimicrobial activity of Moringa peregrina seed oil.Methods: Moringa peregrina seeds were collected from their original growing locations in Sudan. Cold pressing (CP) and maceration inn-hexane (MH) was used to extract the oil, and their yields were found to be 9.12% and 21.87%, respectively. Chemical properties of the oil were studied and in each case triplicate analyses were completed. The mean and the standard deviation were then determined (mean±SD).Results: Besides the peroxide value, the chemical properties of the oil extracted by the two methods remained relatively unchanged. Additionally, the results revealed a higher activity of the cold pressed oil against all tested organisms (Bacillus subtilis, Staphylococcus aureus Escherichia coli, Pseudomonas aeruginosa, Candida albicans) compared to the one obtained by maceration method. Furthermore, the thermogravimetric analysis and derivative thermogravimetric analysis (TGA and DTGA) demonstrated significant variations in the onset of degradation between the oil samples extracted by the two methods: 200◦C (cold pressing) against 274◦C (maceration). The maximum mass loss for the oil extracted by the two methods does not differ significantly, and the final degradation temperature was similar. Conclusion: The differential scanning calorimeter (DSC) thermograms for the oil extracted by the two methods showed somewhat similar characteristics regarding the heating curves, while the cooling curves differed considerably. Keywords: Antimicrobial activity; Cold press; Maceration; Moringa peregrina; Thermal properties.

Effect of borax-boric acid and ammonium polyphosphate on flame retardancy of natural fiber polyethylene composites

Wood fiber filled high density polyethylene composites (WPCs) were prepared using twin screw extruder and maleated polyethylene as a coupling agent. Bamboo fibers were initially treated with alkali (NaOH), boric acid - borax (Ba-Bx) and borax (Bx). The treated and untreated fibers were used in combination with ammonium polyphosphate (APP) to investigate their synergistic effects on thermal stability, flame retardancy and mechanical properties. Alkali pretreatment (5 % NaOH) of fibers showed significant improvement in performance of APP by increasing thermal stability in WPCs. The derivative thermogravimetric (DTG) results indicate significance of Ba-Bx in promoting char induction at lower temperatures (340 ºC) and thereby, improved the thermal stability in WPCs. Flammability decreased with addition of flame retardant additives. As compared to pure WPCs, composites containing APP 10 % / Ba-Bx 5 % exhibited maximum reduction in average heat release rate (HRR) by 69 %, peak heat release rate (PHRR) by 59 %, total heat released rate (THR) by 48 % and also increased time to ignition (TTI) by 62 %. However, no significant difference was found among the combinations i.e., APP with or without compounds towards reducing the flammability of WPCs. The strength properties also reduced significantly when boron compounds were added along with APP. In general, APP alone (15 %) is enough for imparting thermal stability and flame retardancy in WPCs.

Non-isothermal solid-state synthesis kinetics of the tetragonal barium titanate

The solid-state synthesis kinetics of the barium titanate is investigated through thermogravimetry analysis (TGA), and derivative thermogravimetry (DTG). The XRD results confirmed the formation of pure tetragonal BaTiO3 after thermal analysis. The thermodynamic parameters (ΔH,ΔS,ΔG) are calculated for all possible reactions involved during the formation of BaTiO3. The thermodynamic analysis predicted the formation of intermediate compounds (BaO, Ba2TiO4). The thermal kinetic analysis is also performed by using the deconvolution kinetic method. The thermal profile is convoluted in three peaks and the kinetic triplets are calculated. The activation energy is calculated by using the iso-conversional KAS kinetic model based on the Straink approximation. The order of the average activation energy is Peak III (225.81 ​kJ/mol) ​> ​Peak II (223.88 ​kJ/mol) ​> ​Peak I (197.67 ​kJ/mol). The reaction mechanism and pre-exponential are identified by the integral master plot method. The F1, R2 and A4 reaction mechanisms dominated the reaction occurring in peak I, peak II and peak III, respectively.