Differential Thermal Gravity Analysis Research Articles

Preparation of Ce-Doped Gd3(Al, Ga)5O12 Nanopowders via Microwave-Assisted Homogenization Precipitation for Transparent Ceramic Scintillators.

Ce-doped gadolinium gallium aluminum oxide (Ce: GGAG) precursors were first prepared by the microwave-assisted homogeneous precipitation method (MAHP). Thermal gravity-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), specific surface area analysis (BET) and field emission scanning electron microscopy (FE-SEM) were employed to investigate the crystal structure, phase evolution and morphologies of the Ce: GGAG precursors and powders. The influence of Ga ion concentration in the salt solution on the properties of Ce: GGAG powders was investigated. All the precursors were transformed into single-phase GGAG after being calcined at 950 °C in a furnace for 3 h. Monodispersed Ce: GGAG powders were obtained as the Ga ion concentration was lower than 0.06 mol/L. Single-phase and dense Ce: GGAG ceramics were obtained after sintering at 1600 °C in a flowing oxygen atmosphere for 10 h. Specifically, the Ce: GGAG ceramic reached its maximum density of ~6.68 g/cm3, which was close to its theoretical density of 6.70 g/cm3, and exhibited the highest optical transmittance of 65.2% at 800 nm after hot isostatic pressing sintering (HIP) as the Ga ion concentration was 0.02 mol/L. The decay time and light yield of the GGAG ceramic were 35 ns and 35,000 ± 1250 ph/MeV, respectively, suggesting that Ce: GGAG ceramics prepared using MAHP-synthesized nanopowders are promising for scintillation applications.

Synthesis of a bio-based internal plasticizer from cardanol and its evaluations

Cardanol is a substituted phenol obtained from cashew nut shell liquid (CNSL) by the vacuum distillation. It is a feasible alternative to petrochemically derived phenol for many applications. Cardanol has shown potential as a suitable sustainable linker to chemically bind polymers used as internal plasticizers. This research project explores the utilization of cardanol in grafting of cardanol onto neoprene rubber (CR) by click chemistry at room temperature. The products obtained were also assessed by vulcanization characteristics test, the migration test, differential thermal gravity analysis (DTG), rheological analysis and characterization of the fractured surface by scanning electron microscope (SEM). Results of mechanical analysis and migration test indicated the plasticization effect of the cardanol when grafted onto the CR, which can serve as an internal plasticizer to improve the related properties of CR formulations.

A novel approach for recovery of manganese from on-site manganese-bearing wastewater

Acid leaching of rhodochrosite will generate electrolytic manganese residue together with emission of carbon dioxide (CO2). Wastewater containing highly concentrated manganese is being generated when treating electrolytic manganese residue. Although carbonate precipitation has been identified as an effective process for manganese removal, this conventional approach is limited by heavy use of alkaline solution and the obtained MnCO3 precipitates have low purity. In this study, an electrolytic manganese plant in Guangxi, China was selected as the study site. CO2 generated from flue gases was carefully chosen as the potential reagent for the recovery of manganese from wastewater. The effects of operational modes including batch mode, batch mode with external recirculation, continuous mode and continuous mode with external recirculation on the performance of wastewater treatment were systematically investigated in pilot scale, and the obtained precipitates were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and the thermal gravity-differential thermal analysis (TG-DTA). It was found that batch mode with external recirculation is optimal as over 99.99% of Mn2+ can be selectively recovered from Ca2+, Mg2+ and Mn2+-containing wastewater by bubbling with CO2, and the obtained MnCO3 precipitates met the industrial standard in China (grade I). The pH value of the effluent is 6.6 and the concentration of Mn2+ is 1.0 mg L−1, which can be recycled within this system. The present study provides a sustainable technique to solve the problems of treating industrial wastewater containing heavy metals.

Synthesis and Voltammetric Determination of Pb(II) Using a ZIF-8-Based Electrode

Zeolite imidazole framework-8 (ZIF-8) was prepared by the hydrothermal process. The obtained ZIF-8 was a characteristic of X-ray-diffraction (XRD), transmission electron microscope (TEM), thermal gravity-differential thermal analysis (TG-DTA), and dynamic light scattering (DLS). The obtained ZIF-8 possessed large specific area and was highly dispersed. Its morphology consisted of nanospherical particles with 30–50 nm in diameter. Chemical stability of ZIF-8 in different conditions was studied. The ZIF-8 was used as an electrode modifier for the determination of trace levels of lead. The parameters including solvents and solution pH were investigated. The repeatability, reproducibility, accuracy, linear range, limit of detection, and limit of quantitation were also addressed. The results showed that ZIF-8 is a potential electrode modifier for differential pulse anodic stripping method to determine Pb(II) in aqueous solution.

Effect of aluminium phases on thaumasite formation in cement slurries containing limestone powder

Under low-temperature conditions with carbonate, sulfate and abundant water, cement-based materials suffer from a severe thaumasite form of sulfate attack. In this study, the effects of aluminium phases on thaumasite formation in tricalcium silicate (C3S) slurries containing limestone powder under gypsum solution conditions was examined using X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, nuclear magnetic resonance, Fourier transform infrared spectroscopy and differential thermal gravity analysis. The results indicate the following: the presence and relative amount of tricalcium aluminate (C3A) are not prerequisites of thaumasite formation; sulfates and carbonates can directly react with the calcium silicate hydrate (C–S–H) gels in cement hydration products, which dissolves the C–S–H gels and produces non-cementitious thaumasite; small amounts of aluminium phases in the reaction are sufficient to accelerate thaumasite formation, and the accelerating effect becomes more noticeable as the aluminium phase content increases. The morphology of erosion products showed that the crystal size become smaller as the C3A dosage increases.

Preparation and Characterization of Pr<sub>2</sub>Ti<sub>2</sub>O<sub>7</sub> by Sol-Gel Process

Using Pr (NO3)3, butyl titanate, ethylene glycol and citric acid as main raw materials, praseodymium titanate (Pr2Ti2O7) was prepared by the sol-gel process. The samples were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), thermal gravity-differential thermal analysis (TG-DTA), diffuse-reflection spectra (DRS) and Fourier transform infrared (FT-IR). The effect of different calcination temperature and illumination time on the photocatalytic properties of Pr2Ti2O7 was investigated. It was found that the single phase Pr2Ti2O7 could be obtained through sol-gel process and calcination at 1000 °C. The Pr2Ti2O7 samples calcination at 1000 °C were uniform , and the resulting product had a particle size of 200 nm and an optical band gap of 3.26 eV. Under ultraviolet light, the degradation of methyl orange arrived to 80.11% after 180 min of photocatalytic reaction. The Pr2Ti2O7 samples showed good photocatalytic activity for decomposition of methyl orange.

Effects of cellulose carbonization on biomass carbon and diatomite composite

The biomass carbon and diatomite composite was prepared by hypoxia pyrolysis method, which adopted diatomite accompanied by cellulose as raw materials. The properties of carbonaceous samples were characterized by Thermal gravity-differential thermal analysis (TG-DTA), X-ray diffraction analysis (XRD), Scanning electron microscope analysis (SEM), Fourier transform infrared spectroscopy analysis (FT-IR), particle size analysis, Zeta potential analysis and MB adsorption capacity analysis. The XRD results showed that the crystallization temperature of opal phase was reduced nearly 350°C by cellulose carbonization in biomass carbon and diatomite composite. The SEM analysis showed that the porous morphology of diatomite was changed by cellulose carbonization at lower temperature. The FT-IR results showed that the absorption peaks of SiOSi around 462cm−1 and 1098cm−1 were significantly weakened as biomass carbon increased. The MB absorption capacity of biomass carbon and diatomite composite was significantly increased by cellulose carbonization, qe was in the range of 39.97–49.82mgg−1, thus the biomass carbon and diatomite composite which was environment friendly and inexpensive had the potential to be an excellent absorbent.

Preparation, Crystal Structure and Properties of a New Crystal Form of Diammonium 5,5′‐bistetrazole‐1,1′‐diolate

AbstractA new crystal form of diammonium 5,5′‐bistetrazole‐1,1′‐diolate (1) was prepared by two novel methods and fully characterized by using IR, NMR spectroscopy, elementary analysis, single crystal X‐ray crystallography and thermal gravity/differential thermal analysis (TG/DTA). Crystalline 1 was found as monoclinic and space group of P21/c (14). The TG/DTA analysis showed that the decomposition temperature of 1 was 287.8°C with a mass loss of 91.2% in the range of 220–300°C at a heating rate of 5°C/min. The sensitivities test towards impact, friction of 1 indicated that 1 has much lower sensitivities than those of RDX/HMX and is comparable to those of TNT, which suggested that 1 could be used as a good candidate of new insensitive energetic compound.

Hydration mechanism of low quality fly ash in cement-based materials

The hydration mechanism of low quality fly ash in cement-based materials was investigated. The hydration heat of the composite cementitious materials was determined by isothermal calorimetry, and the hydration products, quantity, pore structure and morphology were measured by X-ray diffraction (XRD), thermalgravity-differential thermal analysis (TG-DTA), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM), respectively. The results indicate that grinding could not only improve the physical properties of the low quality fly ash on particle effect, but also improve hydration properties of the cementitious system from various aspects compared with raw low quality fly ash (RLFA). At the early stage of hydration, the low quanlity fly ash acts as almost inert material; but then at the later stage, high chemical activity, especially for ground low quality fly ash (GLFA), could be observed. It can accelerate the formation of hydration products containing more chemical bonded water, resulting in higher degree of cement hydration, thus denser microstructure and more reasonable pore size distribution, but the hydration heat in total is reduced. It can also delay the induction period, but the accelerating period is shortened and there is little influence on the second exothermic peak.

Researches on Purification and Sodium-Modification of Ca-Bentonite by Tri-Roller Grinder

To fully evaluate the usability of a raw Ca-bentonite source and to deeply understand the property of bentonite mineral are critical for applications of these special layered materials. Due to sodium bentonites have several advantages over calcium bentonites, especially in expansibility, cation exchange capacity, cohesive force, dispersibility, and thermostability, sodium-modification of Ca-bentonite is regarded as a top priority of effective utilization of abundant Ca-bentonite source in China. In present work, the purified Na-montmorillonite was synthesized by purification and sodium-modification of a raw Ca-bentonite source (Liaoning, China) by tri-roller grinder. Important influencing factor rolling times in purification and sodium modification process was investigated. Mineral compositions, microscopic morphology, and thermal stability were characterized by using different techniques. The crystalline phases and compositions were identified by X-ray powder diffraction (XRD). The morphology and structure were evaluated by scanning electron microscopy (SEM). The thermal properties were investigated using differential thermal gravity analysis (DTG) and differential thermal analysis (DTA) analysis.

The Effects of Cation Concentration in the Salt Solution on the Cerium Doped Gadolinium Gallium Aluminum Oxide Nanopowders Prepared by a Co-precipitation Method

Cerium doped gadolinium gallium aluminum oxide (GAGG:Ce) nanopowders were prepared by a co-precipitation method with different cation concentrations of the mother salt solution, followed by calcination at different temperatures. The influence of cation concentrations (0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 mol/L) in the mother salt solution on GAGG:Ce nanopowders was investigated by thermal gravity-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). The GAGG phase was formed after calcining at 950 degree C for 2 h for all samples. The primary particle sizes of powder calcined at the same temperature decrease with the increase of cation concentration, which is suggested by the analysis of SEM and specific surface area measurement. However, the nonuniformity of particle size was observed for samples prepared using the salt solutions with cation concentrations > 0.3 mol/L, especially for the 0.6 mol/L sample. The photoluminescence spectrum intensity indicates that the 0.2 mol/L and 0.3 mol/L samples have higher degree of crystal perfection than others. Considering all the factors above, samples synthesized by using salt solution with 0.3 mol/L cation concentration were chosen for ceramic scintillators preparation in our future work.

White-rot fungal pretreatment of wheat straw with Phanerochaete chrysosporium for biohydrogen production: simultaneous saccharification and fermentation

This paper demonstrates biohydrogen production was enhanced by white-rot fungal pretreatment of wheat straw (WS) through simultaneous saccharification and fermentation (SSF). Wheat straw was pretreated by Phanerochaete chrysosporium at 30 °C under solid state fermentation for 12 days, and lignin was removed about 28.5 ± 1.3 %. Microscopic structure observation combined thermal gravity and differential thermal gravity analysis further showed that the lignocellulose structure obviously disrupted after fungal pretreatment. Subsequently, the pretreated WS and crude cellulases prepared from Trichoderma atroviride were applied in SSF for hydrogen production using Clostridium perfringens. The maximum hydrogen yield was obtained to be 78.5 ± 3.4 ml g(-1)-pretreated WS, which was about 1.8-fold than the unpretreated group. Furthermore, the modified Gompertz model was applied study the progress of cumulative H(2) production. This work developed a novel bio-approach to improve fermentative H(2) yield from lignocellulosic biomass.

Preparation of ultra-fine fibrous Fe–Ni alloy powder by coordinated co-precipitation–direct reduction process

The precursor prepared by coordinated co-precipitation was direct reduced by hydrogen to ultra-fine fibrous Fe–Ni alloy powder. The effects of concentrations of reactants, pH value, reaction temperature and additive on the preparation of precursor were systematically investigated. The structures, thermal decomposition processes and morphologies of the precursors were characterized by X-ray diffraction (XRD), thermal gravity-differential thermal analysis (TG-DTA) and scanning electron microscoy (SEM). The results show that using 2% polyvinylpyrrolidone (PVP) (in mass fraction) as additive, a well-dispersed precursor with a uniform morphology can be obtained in a solution with Fe2+ and Ni2+ total concentration (1:1) of 0.8 mol/L, pH value of 6.2 at 60 °C, and a pure and well dispersed fibrous iron-nickel powder can be prepared by direct reduction of this precursor in a mixed atmosphere of nitrogen and hydrogen at the temperature of 420 °C.

Preparation and Characterization of Ni(OH)2and NiO Mesoporous Nanosheets

Mesoporous nanosheets of single-crystallineβ-nickel hydroxide (β-Ni(OH)2) were successfully synthesized via a facile hydrothermal method using Ni(NO3)2 · 6H2O as precursor in a mixed solution of sodium hydroxide (NaOH) and sodium dodecylbenzenesulfonate (SDBS). Single-crystalline nickel oxide (NiO) mesoporous nanosheets can be obtained through a thermal decomposition method usingβ-Ni(OH)2mesoporous nanosheets as precursor. The influences of SDBS and hydrothermal treatment were carefully investigated; the results showed that they played important roles in the formation ofβ-Ni(OH)2mesoporous nanosheets. The as-obtainedβ-Ni(OH)2and NiO were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermal gravity-differential thermal analysis (TG-DTA), and specific surface area, and pore size test.

Biomimetic synthesis of CdS nanocrystals in the pepsin solution

CdS nanocrystals with an average size of 6.3 nm and narrow size-distribution were synthesized in the pepsin aqueous solution at room temperature. The obtained CdS nanocrystals were characterized by XRD, TEM, UV-vis, photoluminescence (PL) and thermal gravity-differential thermal analysis (TG-DTA). The results indicate that the pepsin not only induce the nucleation, but inhibit the further growth of CdS nanocrystals. The effect of Cd 2+ on pepsin and the change of the pepsin secondary structure were studied. The possible mechanism of CdS nanocrystals formation was also discussed.