Thermal Gravitational Analysis Research Articles

AC conductivity, dielectric and thermal properties of hybrid composite: bagasse cellulose carbon nanofibers composite

AbstractThis study investigates the impact of incorporating carbon nanofibers (CNFs) into sugar cane cellulose at a high weight ratio (6 wt.%). Composite samples were prepared using a hot hydraulic press technique, and their thermal stability was analyzed through thermal gravitational analysis in a nitrogen environment. The results indicate that the cellulose-CNF composite exhibits a simplified single-stage decomposition compared to the more complex behavior observed in pure cellulose. FTIR analysis reveals the presence of –OH bonds, indicating enhanced hydrophilic properties in the composite. Dielectric spectroscopy, conducted over a frequency range of 100 Hz to 1 MHz, explores the effects of CNFs on the relaxation and conduction mechanisms at different temperatures. Parameters such as dielectric permittivity, AC conductivity, electrical modulus, and complex impedance were studied, incorporating Jonscher’s equation, and the Havriliak–Negami model. The interplay between interfacial charge and cellulose crystallinity emerged as a crucial factor in the observed dielectric behavior. Overall, this research provides insights into the thermal and dielectric properties of cellulose/CNF composites, offering potential applications in diverse fields.

Thermal degradation assessment, impact strength, and hardness of combination epoxy and polystyrene powder composite

The present study investigates the reactions of polystyrene and epoxy/polystyrene powder composites, exploring different weight percentages (8%, 12%, and 16%) of polystyrene during decomposition under highly elevated temperatures within a nitrogen atmosphere. The findings reveal that polystyrene content significantly influences the thermal behavior of pure epoxy, with a higher polystyrene content correlating with the increased thermal stability of the composites. This study observed a three-stage mass loss process by examining the reaction kinetics of thermal decomposition using the Coats-Redfern approach. Initially, weight reduction occurs due to moisture and volatile elimination, followed by a smooth mass loss phase attributed to weaker polymer chain linkages and, ultimately, char formation. Chemical kinetic parameters, such as activation energy and frequency factor, were successfully determined using the Coats-Redfern approach, with a first-order reaction observed across all data points, demonstrating a high R-square mean value of 99.8%. Differential scanning calorimetry (DSC) and thermal gravitational analysis (TGA) analyses revealed an increase in glass temperature from 86.95 to 92.85 °C and an elevation in activation energy from 75.38 to 92.85 kJ/mol with increasing polystyrene content (0–16 wt%). Furthermore, the study investigated the influence of thermodynamic parameters. In terms of mechanical properties, increasing polystyrene content reduced impact strength (from 8.5 to 4.23 Kj/m2). In contrast, hardness increased from 77.5 for pure epoxy to 80.4 at 12 wt% polystyrene content in the composite. These findings underscore the importance of thermal stability results in developing a comprehensive understanding of thermal decomposition processes, informing future research endeavors and industrial applications.

Surface modification of tungsten disulfide nanosheets by pH/temperature sensitive polymers for NIR-triggered drug delivery

Stimuli-responsive polymers are attractive nanocarriers for cancer drug delivery due to their biodegradability and precise control of the release of an anti-cancer drug in response to specific triggers. Herein, the tungsten disulfide nanosheet was modified by pH and thermo-responsive polymer as the novel nanocarrier. The physicochemical characteristics of nanoadsorbent were studied by X-ray diffraction, Fourier transform infrared, field emission-scanning electron microscopy, and thermal gravitational analysis. The maximum adsorption capacity in optimal conditions for flutamide with nanoadsorbent (C0 = 20 mg L−1, pH = 5, contact time = 15 min, stirring speed = 500 rpm, and temperature = 25 °C) was obtained 2.43 mg g−1. The Langmuir equilibrium isotherm and the pseudo-second-order kinetic model fit the adsorption mechanism very well. Around 75.26 % of the drug was released from nanocarrier in simulated human fluid at 6 h and 91.48 % in simulated cancer fluid at 45 °C. The near laser irradiation-triggered effective and controllable release of the loaded drug under near laser irradiation is successfully confirmed. Drug releasing 94.77 % under near laser irradiation within 30 min, which was roughly four folds of that without near laser irradiation. Cytotoxicity/cell viability assays using MTT were carried out for samples in PC-3 prostate cancer cells. Based on the cell viability assay on the PC-3 prostate cancer cell line, the drug loaded pH/thermo-responsive nanocarrier indicated better cytotoxic activity than the free drug. According to these results, it is very promising that pH/thermo-responsive nanocarrier can be used as an effective drug delivery system.

AC conductivity, dielectric and thermal properties of three-phase hybrid composite: PVA/Bi2O3/cotton microfiber composite

The impact of bismuth (III) oxide (Bi2O3) on the characteristics of the cellulose/polyvinyl alcohol (PVA) blend was reported for a high weight ratio of the oxide (15wt%). Composite samples were made with 15wt% oxide and 2:1 weight ratio of PVA to cellulose using a hot hydraulic press technique (5 MPa and 175 °C), which led to samples in the form of a disk. The thermal stability of the composite was illustrated using the thermal gravitational analysis (TGS) at a heating rate of 10 °C min−1 in N2 environment. The results show that the thermal stability of the composite sample was greater than that of the blended sample in the high-temperature region. The blend and composite samples exhibited two weight-loss stages throughout the thermal decomposition process. These two stages correspond to the slow decomposition (200 to 400 °C) and fast decomposition stages (400 to 450 °C for blend and from 430 to 460 °C for composite). Only 5% mass loss for both samples was detected due to heating from 50 °C to 200 °C. Dielectric spectroscopy (from 100 Hz to 1 MHz) was used to investigate the effects of Bi2O3 on the relaxation and conduction mechanisms of the composite samples at different temperatures. Dielectric permittivity, AC conductivity, electrical modulus, and complex impedance were investigated. Jonscher’s equation was applied to the blend and composite samples. The modified Jonscher’s equation fit well at low temperatures. As the temperature increases, the deviation from the normal Jonscher equation decreases. The activation energies of the blend and composite were calculated by determining the bulk resistance (RB) from the Nyquist plots. The activation energy of the blend was increased by adding the filler (Bi2O3).

Selective acetone gas sensing of Cu2(OH)3F/CuO enhanced by hydroxy bonds and fluorine substitution

Acetone gas in human breath could be examined in terms of biomarker applications for diagnosis of diabetes and detection of body fat decomposition. In this work, Cu2(OH)3F is hydrothermally synthesized and then pre-annealed in the interest of low ppm acetone gas-sensing. Cu2(OH)3F/CuO hierarchical structures were built after pre-annealing, and 250°C-annealed samples show the highest response of 23.6 toward 10 ppm acetone gas and 2.1 toward 400 ppb at operating temperature 200 ℃. Upon characterization for Cu2(OH)3F/CuO material properties, 250 ℃-annealed nanobranches show fluent hydroxy bonds, fluorine ion substitutions, and wide bandgap which could enhance the gas-sensing characteristics. The pre-annealing of Cu2(OH)3F between 200 ℃ and 350 ℃ was thoroughly characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), elemental analysis (EA) and thermal gravitational analysis (TGA) to analyze mechanism of the acetone gas-sensing behaviors.

Iron phosphate for photocatalytic removal of Ibuprofen from aqueous media under sun-like irradiation

Ibuprofen (IBP) is one of the most detected pharmaceuticals in wastewater. The conventional methods such as biological treatment, adsorption, etc. are ineffective and usually produce secondary pollution. In this contribution, FePO4 was synthesized using an inorganic sol–gel method assisted by microwave and used to remove IBP from water. X-ray diffraction (XRD), Thermal gravitational Analysis (TGA), Fourier transform infrared spectroscopy (FTIR), physisorption, Diffuse reflectance spectroscopy (DRS), X-ray photoelectron (XPS), and scanning electron microscopy (SEM-EDS) were used to study the phase structure, morphology, and optical properties of the synthesized FePO4. Moreover, for the first time, the photocatalytic property of the as-synthesized FePO4 compound has been evaluated via the degradation of Ibuprophen under artificial sunlight illumination. The findings indicated that FePO4 has a high activity under artificial sunlight irradiation, and the IBP removal was 97 % after 120 min.. Furthermore, the generation cycles indicated the higher stability of the photocatalyst to be effectively recycled up to four times without any considerable reduction in the photocatalytic performance. Finally, the involved mechanism of the photocatalytic performance of FePO4 was proposed based on the active species trapping experiments. Thus, It can be suggested that the FePO4 can serve as a promising photocatalyst in the degradation of IBP under sunlight illumination.

Agricultural Pea Waste as a Low-Cost Pollutant Biosorbent for Methylene Blue Removal: Adsorption Kinetics, Isotherm And Thermodynamic Studies

Biosorbents are an alternative pollutant adsorbent, usually sourced from waste biomass and requiring little to no treatment. This makes them cheaper than conventional adsorbents. In this paper, green pea (Pisum sativum) haulm was used as a biosorbent for the adsorption of methylene blue dye. The potential application of pea haulm as a biosorbent has not been investigated before. Characterisation using scanning electron microscopy, infrared spectroscopy and thermal gravitational analysis showed the surface to be coarse, detected functional groups important for adsorption and identified the composition of key biomass components. The effects of particle size, contact time, agitation, dosage, solution pH, temperature and initial dye concentration on the removal of MB by pea haulm were investigated. Using the data from these studies, the best fitting kinetic and isotherm models were found and the thermodynamic properties were identified. The maximum theoretical adsorption capacity was 167 mg/g, which was relatively high compared to other recent biosorbent studies. The pseudo-second-order adsorption kinetic and Freundlich adsorption isotherm models were the best fitting models. The biosorption process was exothermic and spontaneous at low temperatures. It was concluded that pea haulm was an effective adsorbent of methylene blue and could perhaps find application in wastewater treatment.

A Low-Density Polyethylene (LDPE)/Macca Carbon Advanced Composite Film with Functional Properties for Packaging Materials.

Macca carbon (MC) powder, a biomass derived from macadamia nut cultivation that emits far-infrared (FIR) radiation, was incorporated into low-density polyethylene (LDPE) by melt-compounding and subsequent melt-extrusion operations. Optical microscopy, scanning electron microscopy, differential scanning calorimetry, thermal gravitational analysis, mechanical properties, FIR emission power, barrier properties, transmission properties, antimicrobial activity assays, and storage tests were used to evaluate the manufactured LDPE/MC composite viability sheets for antimicrobial packaging applications. The physical properties and antibacterial activity of composite films were significantly correlated with the amount of MC powder used. The higher the MC powder content in the LDPE/MC composite film, the better the FIR emission ability. Only the MC powder at 0.5% by weight displayed adequate fundamental film characteristics, antibacterial activity, and storage performance, allowing lettuce and strawberries to remain fresh for more than 7 and 5 days, respectively, outside the refrigerator. This study demonstrates that FIR composites made from MC powder are a distinct and potential packaging material for future application in the food industry.

Highly Dispersed NixGay Catalyst and La2O3 Promoter Supported by LDO Nanosheets for Dry Reforming of Methane: Synergetic Catalysis by Ni, Ga, and La2O3.

A highly active and stable Ni-based catalyst is the focal point for research on dry reforming of methane (DRM). Here, NixGay/La2O3-LDO catalysts composed of highly dispersed NixGay and La2O3 nanoparticles supported by the MgO/Al2O3 layered double oxide (LDO) nanosheets were synthesized by chemical methods. According to transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), CO2-TPD, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and thermal gravitational analysis (TGA), a synergistic reaction mechanism was proposed to explain the superior performance of the Ni0.8Ga0.2/La2O3-LDO catalyst. The NixGay alloy catalyst provides an effective way to balance the speed of CH4 cracking and CO2 disassociation, and the La2O3 promoter enriched the CO2 and ensured the generation of active O in time. They worked together to inhibit carbon accumulation and significantly improve the catalyst's activity and stability.

Thermal vibrational and gravitational analysis of a hybrid aqueous suspension comprising Ag–MgO hybrid nano-additives

The incorporation of simultaneous passive and active techniques for enhancing heat transfer has been a promising area of research in the last decades. As such, in the present study, thermal convection heat transfer of a hybrid nanofluid in a square cavity subjected to simultaneous effects of gravitational and vibrational forces has been addressed. Initially, the cavity, saturated with Ag-MgO hybrid nanofluid, is stagnant and in thermal equilibrium. Then, the sidewalls of the cavity are heated isothermally, and the cavity starts vibrating in a vertical direction. The upper and lower walls are kept adiabatic. Galerkin finite element method with a very small- and adaptive-time step has been used to precisely capture the impact of vibrational force on the flow and thermal fields in high frequencies. Impacts of vibration frequency, gravitational and vibration Rayleigh numbers, and the volume fraction of hybrid nano-additives are studied. It has been revealed that the external vibration amplifies the rate of heat transfer for all the studied frequencies. Moreover, although the presence of the nanoparticles seems to have a very limited effect on the effectiveness of heating, the effect of the nanoparticle concentration on the heat transfer intensity varies with time.

Effect of Metal Precursor Solution on Morphology of Porous LaCoO<sub>3</sub>

Porous materials are attractive in various applications such as energy storage and production, industrial processing, environmental treatment, and catalysis. Porous LaCoO3 was prepared using three different metal precursor solutions: i) 40%v/v methanol-ethylene glycol (40%Me/EG), ii) Lysine (Lys), and iii) Lysine/citric acid (Lys/Cit) with poly(methyl methacrylate) colloidal crystal as porous templates (PMMA-CCT). PMMA-CCT filled with metal precursor solution were carbonized under N2 followed by oxidized under 50% O2 in N2 atmosphere. X-ray diffraction patterns of the obtained porous LaCoO3 are rhombohedral LaCoO3 phase without impurity. The scanning electron microscopy (SEM) was carried out to examine the morphology of porous LaCoO3. The SEM image of the LCO-Lys/Cit exhibits better connected particles and a well-defined pore structure compared to those prepared by Lys or 40%Me/EG metal precursor solutions. The evolution of pore formation of LCO-Lys/Cit was investigated by SEM, Fourier transform infrared spectroscopy (FT-IR), and thermal gravitational analysis (TGA). The materials show high catalytic properties for the electrochemical water oxidation reaction. The high capacitances of all porous LaCoO3 are attributed to the controlled three-dimensional porous morphology of the catalysts. This synthesis approach can achieve porous materials with promising properties for catalysis applications.

Aerosol‐Assisted Chemical‐Vapour Deposition of Zinc Oxide from Single‐Source β‐Iminoesterate Precursors

AbstractSingle‐source zinc β‐iminoesterate precursors have been used for the first time in the aerosol‐assisted chemical‐vapour deposition (AACVD) of ZnO thin films. Depositions at 450 °C on silica‐coated glass substrates produced strongly adherent films with excellent coverage of the substrate. The zinc β‐iminoesterates [Zn(L1)2] (1) and [Zn(L2)2] (2) were synthesised by the reaction between ZnEt2 and 2 equiv. of a synthesised β‐iminoester ligand CH3C[NHCH(CH3)2]CHC(O)OCH2CH3 (L1) and CH3C(NHCH3)CHC(O)OCH2CH3 (L2). The synthesised complexes were isolated and characterised by 1H and 13C NMR spectroscopy, mass spectrometry and thermal gravitational analysis (TGA). The structures of the compounds were determined by single‐crystal X‐ray diffraction. The ZnO films deposited from 1 and 2 were analyzed by glancing‐angle X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS) and their optical properties determined by UV/Vis/NIR transmission spectroscopy. These results reveal that the organic ligand attached to the N moiety of the zinc complex has a significant effect on the level of carbon incorporated into the deposited thin film. Upon annealing, highly transparent hexagonal wurtzite ZnO thin films were produced.

Preparation and Structure of Double Complex Compounds [La(HMPA)4(NO3)2][Cr(NH3)2(NCS)4

This paper presents the results of chemical analysis, IR- spectroscopic analysis, thermal gravitational analysis, X-ray phase analysis, and X-ray structural analysis, conducted to determine the composition, structure and properties of the double complex salts - tetra(isotiocyanato)diaminechromates(III) of complex lanthanon(III) of ceric group with hexamethylphosphorotriamide (HMPA) and nitrate-groups as ligands.

Structural and optical characterisation of undoped and chromium doped tin oxide prepared by sol–gel method

Transparent semiconductor thin films, Cr doped SnO2 (Sn1−xCrxO2: x=0.0, 0.02, 0.04, 0.06, 0.10, 0.20) were deposited onto glass substrates by a sol–gel method. The thermal gravitational analysis showed that mass lost happened at 120°C due to evaporation of water and ethanol. X-ray diffraction analysis showed that the Cr doped SnO2 were polycrystalline with SnO2 phases. The crystalline sizes were in the range of 3.7–4.9nm. The optical property measured using UV-Vis spectrophotometer showed that the transparency of all samples was more than 90% and the calculated band gaps were in the range of 3.84–3.96eV which was due to the Cr dopant that increased the samples energy band gap.

두께를 증가시킨 셀룰로오스 Electro-Active Paper 의 제조와 특성평가

This paper reports fabrication and characterization of cellulose Electro-Active Paper (EAPap) with increased thickness. Usual thickness of cellulose EAPap was 15 μm. This thickness needs to be increased to enhance the mechanical force output of EAPap. To fabricate thick cellulose EAPap, the fabrication process parameters including casting and drying processes should be investigated. In this paper, the casting thickness is increased from 800 μm to 1500 μm, and heating times on a hot plate before and after curing process are introduced at 40 and 60℃ for 30 and 60 minutes, respectively. Thickness measurement, Thermal Gravitational Analysis (TGA), UV-transmittance, Young’s modulus, and piezoelectric charge constant are measured. Heated EAPaps with increased thickness have similar TGA result, higher transmittance, higher Young’s modulus and lower piezoelectric charge constant.

Fabrication of polyethersulfone-mesoporous silica nanocomposite ultrafiltration membranes with antifouling properties

Fouling is regarded as the bottleneck in membrane filtration process. One of the practical strategies to decrease fouling is the use of advanced anti-biofouling membrane material. In this study, mesoporous silica (MS) particles was synthesized as inorganic fillers, and fabricated with polyethersulfone (PES) to achieve nanocomposite membranes with antifouling properties by phase inversion method. The effect of the MS particles on the microstructure and properties of the resulting hybrid membranes were investigated by scanning electron microscopy (SEM), thermal gravitational analysis (TGA), and ultrafiltration (UF) experiments. The results indicated that the nanocomposite membrane with 2% MS exhibited excellent hydrophilicity, water permeability and good antifouling performance. In addition, the TGA results showed that the introduction of the MS particles improved the thermal stability of the nanocomposite membranes. The protein adsorption on the membrane surface decreased significantly from 45.8μg/cm2 to 21.4μg/cm2 when the MS content increased from 0% to 2%. Most importantly, the protein UF experiments revealed that the incorporation of MS particles reduced membrane fouling, especially irreversible fouling, which reduced dramatically. No benefit was gained from higher MS content (4%), which resulted in significant particle agglomeration.

Effect of silver loaded sodium zirconium phosphate (nanoAgZ) nanoparticles incorporation on PES membrane performance

Polyethersulfone (PES) based ultrafiltration membranes were fabricated via phase inversion by adding silver-loaded sodium zirconium phosphate nanoparticles (nanoAgZ) in PES casting solutions. The effect of nanoAgZ concentration on the membrane performance, i.e., morphology, hydrophilicity, thermal stability, permeation and antifouling properties was investigated. The results of thermal gravitational analysis (TGA) showed that the thermal stability of the hybrid membrane had been improved by the addition of nanoAgZ particles. Contact angle results indicated that the hydrophilicity of the modified membranes was enhanced. The contact angle of the membrane decreased from 71.5° to 52.6° with the increase of the nanoparticle content in the casting solution. Permeation experiment results showed that the modified PES membranes demonstrate better separation performance over the pure PES membrane. The pure water flux of PES membrane increased from 82.1 L/m 2 h to 100.6 L/m 2 h with the addition of the nanoparticles. Most importantly, the incorporation of the nanoAgZ particles enhanced the BSA fouling resistance and also the anti-biofouling performance of the membrane.

Synthesis and Characterization of Cu(II), Ni(II), Co(II), Mn(II), and Cd(II) Transition Metal Complexes of Tridentate Schiff Base Derived from O-Vanillin and N-Aminopyrimidine-2-Thione

Monobasic tridentate Schiff base ligand having ONS donor sequence was prepared by condensing N-aminopyrimidine-2-thione with o-vanillin. The complexes were formed by reacting ligand and the metal acetates of Cu(II), Ni(II), Co(II), Mn(II), and Cd(II) in methanol to get a series of mononuclear and dinuclear complexes. The characterization of ligand and metal complexes were carried out by elemental analyses, conductivity measurements, magnetic susceptibility data, FTIR, UV-vis, NMR, and API-ES mass spectral data. The structure of the complexes was confirmed on the basis of elemental analyses, magnetic susceptibility, API-ES mass spectral data and thermal gravitational analysis (TGA).GRAPHICAL ABSTRACT

Analytical characterization of gold nanoparticle primary particles, aggregates, agglomerates, and agglomerated aggregates

Gold nanoparticles have been studied for many biomedical applications. However, alterations in the gold nanoparticles’ environment frequently lead to the formation of aggregates and agglomerates, which have not been well characterized. These new structures could significantly change the biological impact of the nanoparticles, so the appropriate characterization of these structures prior to biological administration is vital for the correct interpretation of toxicology results. By varying the solvent or heating under pressure, four reproducible gold nanoparticles structures were created: 10 nm primary particles, aggregates of the primary particles that contain non-reversible bonds between the individual nanoparticles, agglomerates of primary particles that contain reversible interactions between the individual nanoparticles, and agglomerated aggregates that have reversible bonds linking individual aggregates. Ultraviolet–visible (UV–Vis) spectroscopy, thermal gravitational analysis, and neutron activation analysis were each found to accurately measure the concentration of the primary particles. The primary particles measured 10 nm by dynamic light scattering (DLS) and had a spherical morphology by transmission electron microscopy (TEM) while the aggregates measured 110 nm by DLS and had a distorted morphology by TEM. The agglomerate and aggregated agglomerate samples both measured >1,000 nm by DLS, but the individual particles had significantly different morphologies by TEM. Multiple other analytical techniques, including ultracentrifugation, gel electrophoresis, and X-ray diffraction, also showed unique traits for each structure. The structural differences did not change in the presence of cell culture media or rat serum. In addition, the primary particles, aggregates, and agglomerates each had a unique UV–Vis spectrum, allowing for an inexpensive, rapid method to differentiate between the structures.

Effect of TiO 2 nanowire addition on PVDF ultrafiltration membrane performance

A new PVDF-TiO 2 nanowire hybrid ultrafiltration membrane was prepared via phase inversion by dispersing TiO 2 nanowires in PVDF casting solutions. The characteristics of the hybrid membranes, i.e., crystal structure, thermal stability, morphology, hydrophilicity, permeation performance, and mechanical properties, were investigated. Results of X-ray diffraction (XRD), thermal gravitational analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) analysis showed that the interaction existed between TiO 2 nanowires and PVDF and the thermal stability of the hybrid membrane had been improved by the addition of TiO 2 nanowires. Concurrently, dynamic contact angles indicated that the hydrophilicity of the hybrid membranes was enhanced by the addition of TiO 2 nanowires. The effects of the TiO 2 nanowires in the PVDF on the permeation properties, membrane strength, and antifouling performance were examined. The experimental results indicated that PVDF-TiO 2 nanowire hybrid membranes exhibited significant differences in surface properties and intrinsic properties due to TiO 2 nanowires addition. Most importantly, PVDF-TiO 2 nanowire hybrid membrane can avoid some of the drawbacks of PVDF-TiO 2 nanoparticle hybrid membrane, such as, aggregate and leak out of TiO 2 nanoparticles, also declining elongation ratio.