Two-step Heating Method Research Articles

Phase Selectivity of Copper Sulfide: Synthesis and Application

High-purity copper sulfides including CuS, Cu1.75S and Cu2S were synthesized using an easy and controllable two-step heating method in a mixed solution of ethylene glycol and triethylenetetramine. Petal-like CuS, near-spherical Cu2S, and regular hexagonal Cu1.75S were obtained by simply changing the solvent volume ratio (SVR) of the mixed solution, i.e. the phase of the products solely determined by the SVR of the solution. The influence of the solvent on the final products as well as the reaction mechanism of the system were investigated and discussed. The approach is rapid, easily scalable, and environmentally friendly. As a preliminary application demonstration, dye-sensitized solar cells were assembled using the as-synthesized copper sulfides and photoelectric conversion efficiencies up to 3.62% were achieved.

High sulfur-containing organosulfur polymer composite cathode embedded by monoclinic S for lithium sulfur batteries

Lithium sulfur (Li–S) battery is considered as one of the most viable candidates for next-generation rechargeable batteries. However, the development of Li–S battery is severely hindered by the stubborn “shuttle” issue that arises from the dissolution of the intermediate polysulfides. Herein, a new kind of organosulfur polymer composite is designed as cathode material for Li–S batteries. Via a facile two-step heating method, the ring opening S is copolymerized with triallyl isocyanurate. The resulting S-triallyl isocyanurate organosulfur polymer composite (STI) demonstrates a unique two-phase structure: ultrafine monoclinic S particles embedded in the organosulfur polymer matrix, which enables a S content as high as 90 ​wt%. The STI cathode delivers a high initial reversible capacity of 904 ​mA ​h ​g−1 at 0.5 ​C, and an ultraslow capacity decay rate of 0.017% over 350 cycles at 1 ​C. The work offers new insights into the design of S-rich copolymer composite cathode for highly-stable Li–S batteries.

Structure and Properties of Single-Layer MoS₂ for Nano-Photoelectric Devices.

To meet the need for preparing high-performance nano-optoelectronic devices based on single-layer MoS2, the effects of the heating method (one-step or two-step heating) and the temperature of the MoO3 source on the morphology, size, structure, and layers of an MoS2 crystal grown on a sapphire substrate using chemical vapor deposition are studied in this paper. The results show that MoS2 prepared by two-step heating (the heating of the S source starts when the temperature of the MoO3 source rises to 837 K) is superior over that of one-step heating (MoO3 and S are heated at the same time). One-step heating tends to form a mixture of MoO2 and MoS2. Neither too low nor too high of a heating temperature of MoO3 source is conducive to the formation of MoS2. When the temperature of MoO3 source is in the range of 1073 K to 1098 K, the size of MoS2 increases with the rise in temperature. A uniform large-sized triangle with a side length of 100 μm is obtained when the heating temperature of MoO3 is 1098 K. The triangular MoS2 crystals grown by the two-step heating method have a single-layer structure.

Isolation and radiocarbon analysis of elemental carbon in atmospheric aerosols using hydropyrolysis

Radiocarbon (14C) analysis is a powerful tool that can unambiguously distinguish fossil and non-fossil sources of carbonaceous particles. However, one of the big challenges of this method is to isolate elemental carbon (EC) or black carbon (BC) for 14C analysis. Hydropyrolysis (hypy) has proven to be an effective method for separating BC in environmental matrices. The potential of hypy for isolation of EC from atmospheric aerosols is evaluated using typical combustion products from non-fossil (biomass), fossil fuel (coal and petroleum), and ambient aerosol samples collected in Beijing and Guangzhou. Using solid state nuclear magnetic resonance (NMR) along with measurement of carbon content and 14C, hypy conditions of 15 MPa hydrogen pressure and 550 °C temperature was confirmed to effectively separate EC from aerosol samples. Consequently, a comparison study of EC 14C in aerosol samples separated using the two-step heating method (CTO-375), thermal-optical method and hypy was conducted. The results show that hypy is an effective and stable approach for matrix-independent 14C quantification of EC in aerosols.

Method to reduce the formation of crystallites in ZnO nanorod thin-films grown via ultra-fast microwave heating

This paper discusses the nucleation and growth mechanisms of ZnO nanorod thin-films and larger sized crystallites that form within the solution and on surfaces during an ultra-fast microwave heating growth process. In particular, the work focusses on the elimination of crystallites as this is necessary to improve thin-film uniformity and to prevent electrical short circuits between electrodes in device applications. High microwave power during the early stages of ZnO deposition was found to be a key factor in the formation of unwanted crystallites on substrate surfaces. Once formed, the crystallites, grow at a much faster rate than the nanorods and quickly dominate the thin-film structure. A new two-step microwave heating method was developed that eliminates the onset of crystallite formation, allowing the deposition of large-area nanorod thin-films that are free from crystallites. A dissolution-recrystallization mechanism is proposed to explain why this procedure is successful and we demonstrate the importance of the work in the fabrication of low-cost memristor devices.

Cactus-like iron diphosphide@carbon nanotubes composites as advanced anode materials for lithium-ion batteries

The ball-cactus-like iron diphosphide@carbon nanotubes (FeP2@CNTs) composites are synthesized via a simple chemical vapor deposition (CVD) with two-step heating method. SEM, TEM, XRD and Raman spectrum confirm that FeP2 and CNTs exist as the core and the surrounding spines of the ball-cactus-like composite, respectively, for FeP2@CNTs synthesized under suitable conditions. With optimized FeP2@CNTs composite containing ball-catus-like structure as the anode of LIBs, the assembled batteries exhibit an initial coulombic efficiency of 91.6%. Furthermore, this kind of battery delivers a stable and high discharge specific capacity of 736.2 mAh g−1 at 0.1 C (1 C = 1365 mA g−1) after 100 cycles. Even at a higher rate of 2.5 C, it still delivers a stable discharge specific capacity of 650.2 mAh g−1 within 100 cycles with negligible capacity fading, much higher than the reported results to date. This excellent electrochemical performance of FeP2@CNTs composite is attributed to the cladding of FeP2 with CNTs, which prevent the large volume changes of FeP2 and improve the electrical conductivity of composites.

Quantitative detection of powdered activated carbon in wastewater treatment plant effluent by thermogravimetric analysis (TGA)

For the elimination of potentially harmful micropollutants, powdered activated carbon (PAC) adsorption is applied in many wastewater treatment plants (WWTP). This holds the risk of PAC leakage into the WWTP effluent and desorption of contaminants into natural water bodies. In order to assess a potential PAC leakage, PAC concentrations below several mg/L have to be detected in the WWTP effluent. None of the methods that are used for water analysis today are able to differentiate between activated carbon and solid background matrix. Thus, a selective, quantitative and easily applicable method is still needed for the detection of PAC residues in wastewater.In the present study, a method was developed to quantitatively measure the PAC content in wastewater by using filtration and thermogravimetric analysis (TGA), which is a well-established technique for the distinction between different solid materials. For the sample filtration, quartz filters with a temperature stability up to 950 °C were used. This allowed for sensitive and well reproducible measurements, as the TGA was not affected by the presence of the filter. The sample’s mass fractions were calculated by integrating the mass decrease rate obtained by TGA in specific, clearly identifiable peak areas. A two-step TGA heating method consisting of N2 and O2 atmospheres led to a good differentiation between PAC and biological background matrix, thanks to the reduction of peak overlapping. A linear correlation was found between a sample’s PAC content and the corresponding peak areas under N2 and O2, the sample volume and the solid mass separated by filtration. Based on these findings, various wastewater samples from different WWTPs were then analyzed by TGA with regard to their PAC content. It was found that, compared to alternative techniques such as measurement of turbidity or total suspended solids, the newly developed TGA method allows for a quantitative and selective detection of PAC concentrations down to 0.1 mg/L. The method showed a linearity coefficient of 0.98 and relative standard deviations of 10%, using small water sample volumes between 0.3 and 0.6 L.

Sulfur/carbon composites prepared with ordered porous carbon for Li-S battery cathode

Ordered porous cabon with a 2-D hexagonal structure, high specific surface area and large pore volume was synthesized through a two-step heating method using tri-block copolymer as template and phenolic resin as carbon precursor. The results indicated the electrochemical performance of the sulfur/carbon composites prepared with the ordered porous carbon was significantly affected by the pore structure of the carbon. Both the specific capacity and cycling stability of the sulfur/carbon composites were improved using the bimodal micro/meso-porous carbon frameworks with high surface area. Its initial discharge capacity can be as high as 1200 mAh·g−1 at a current density of 167.5 mA·g−1. The improved capacity retention was obtained during the cell cycling as well.

Tunable monodispersed Fe 3 O 4 nanoparticles prepared by controlled two-step heating method using diesel oil as solvent

Monodispersed magnetite nanoparticles were prepared by two-step heating method, using cost-effective diesel oil as solvent. Monodispersed magnetite nanoparticles with variable sizes from 3 to 20 nm in diameter could be synthesised by selecting distilled fractions of diesel oil with different reflux temperatures. The small nanoparticles are hexagon, whereas the 20 nm nanoparticles are square or triangle. The particle size could be further enlarged by once or twice seed-mediated growth method, using the previous prepared magnetite nanoparticles as the seeds. This is meaningful to the mass production of the monodispersed magnetite nanoparticles, as well as other metal oxide, in a cost-effective way.

Microwave-Assisted One-Step Synthesis of Fenamic Acid Hydrazides from the Corresponding Acids

A facile and efficient method for synthesis of fenamic acid hydrazides from their acids in one-step reaction under microwave irradiation and solvent-free conditions was developed. Compared with the two-step conventional heating method, the process was simple, the reaction time was very short and the yields were almost quantitative.

Influences of extracellular polymeric substances (EPS) on the characteristics of activated sludge under non-steady-state conditions

Laboratory experiments were carried out on activated sludge (AS) to investigate the correlations between the content of extracellular polymeric substances (EPS) and the performance of biosolids–water separation, including sludge flocculation, sedimentation, compression, and dewatering, under non-steady-state conditions. On three stabilized AS reactors changes were made in sludge retention time (SRT), substrate composition, and loading rate, respectively, to bring about unstable operation to the reactors. A two-step heating method was used to extract from the sludge the easily extractable EPS, or loosely bound EPS (LB-EPS), and tightly bound EPS (TB-EPS), respectively. The experimental results demonstrate dynamic changes in sludge characteristic and EPS production under the non-steady-state conditions. During the early phase of transition after a change was imposed, the sludge became generally worse in flocculation, compressibility, and dewaterability. With the acclimatization of the biomass to the new process conditions, biosolids–water separation showed a general trend of improvement. Changes in AS process condition also resulted in considerable variations in EPS production. The change of the LB-EPS content appeared to be more significant than that of the TB-EPS. Throughout the non-steady-state operation, the sludge flocculating behavior, settleability, compressibility, and dewaterability had a positive correlation with the LB-EPS content; however, no correlation could be found between these properties and the TB-EPS content. The results suggest that although EPS is essential to biofloc formation, excessive EPS in the form of LB-EPS would weaken cell attachment and deteriorate the AS floc structure, resulting in poor biosolids–water separation.

Preparation of Apatite-Containing Calcium Phosphate Glass-Ceramics

A new type of glass-ceramic for novel dental fillers, which require excellent chemical durability, was investigated. A 40CaO-5CaF2-25TiO2-30P2O5 (in mol%) glass-ceramic was newly suggested. The glass-ceramic was prepared by a conventional two-step heating method. The resulting glass-ceramic included Nasicontype-CaTi4(PO4)6, titanium phosphates, such as (TiO)2P2O7 and Ti(PO3)3, and TiO2 (anatase) with apatite crystal, which was induced by incorporation of fluorine. In the glass-ceramic, dissolution by acid-treatment was strictly controlled. The excellent chemical durability of the glass-ceramic was suggested to originate from increase in the amount of the crystalline phases and a high content of titanium constituent in the residual glassy phase.

Thermal gelation of salted paste from scallop striated adductor muscle

: Salted muscle paste containing 60–100 mg protein/g paste and 0.5 M NaCl at pH 7.0 was prepared from fresh scallop striated adductor muscle and its heat-induced gelling characteristics were examined in order to produce invertebrate kamaboko-like foods. The heating of the paste to 90°C formed a weak gel. The setting effect on the gelation of the paste was introduced by incubation at 25°C for up to 4 h and was greatly strengthened by the addition of 10 mM Ca2+ due to the activation of an endogenous transglutaminase that preferentially cross-linked myosin heavy chains, but not actin and paramyosin. As a result, the texture of the gel produced by a two-step heating method was almost the same as that of a commercial fish kamaboko. It was also observed that the thermal gelation profile of scallop muscle paste was similar to that of fish myosin, rather than that of actomyosin, by means of a dynamic rheological measurement. Paramyosin also contributed to a characteristic increase in the G′ (storage modulus) value over the thermal gelation process and raised the G′′ (loss modulus) value around 65°C. The G′′ increase resulted in a slightly rigid texture of heated scallop gel. Isolated paramyosin demonstrated a characteristic thermal gelation profile showing a two-step increase in G′ and G′′ values, independent of Ca2+ concentration. The higher NaCl and protein concentrations were required to produce stronger and more elastic gels.

Synthesis of the electron-doped bismuth oxide (Ba0.6Bi0.4)BiO3−x

The electron-doped bismuth oxide (Ba0.6Bi0.4)BiO2.92 has been successfully synthesized by the two-step heating method. Mixed powders of the starting materials have been pelletized and heated in flowing gas of N2 at 800 °C for 12 h. The reacted pellets have been heated at 400 °C first in flowing gas of O2 for 24 h and then under a high oxygen-pressure of 600 atm at 400 °C for 96 h. It has crystallized in a pseudo-cubic symmetry. From the X-ray diffraction and inductively coupled plasma analyses, the substitution of Bi for Ba has been confirmed, but the product has still remained an insulator.

Fabrication of Amerieium-based Nitrides by Carbothermic Reduction Method

Americium-based nitrides such as (Am,Y)N and (Am,Zr)N were synthesized directly from oxide powders of 243AmO25Y2O3 and ZrO2, by a carbothermic reduction technique, where an excess carbon condition was used in order to obtain oxygen-free mixed nitrides. For (Am,Y)N, a two-step heating method (heating at 1573 and 1773 K ) was applied to obtain solid solutions between nitrides of YN and AmN. Nitride solid solutions of (Am,Y)N without oxides were successfully prepared in the composition range of 10-30 mol% AmN. In case of (Am,Zr)N, a two phase solid solution of mixed nitrides was formed for the high Am containing sample.

Effect of pH on the gelation of walleye pollack surimi and carp actomyosin pastes

: The effect of pH on thermal gelation and transglutaminase (TGase; EC2.3.2.13)-induced suwari (setting) of surimi and actomyosin pastes was investigated. A strong and elastic gel was produced from walleye pollack surimi paste at pH 7.0 in the presence of Ca2+ using a two-step heating method. In contrast, walleye pollack actomyosin paste formed a weak gel under the same conditions as a result of the low concentration of endogenous TGase. In the presence of EGTA [ethyleneglycol bis(2-aminoethylether) tetraacetic acid], weak gels were formed at pH values of 7.0 and 6.0. Non-proteolytic modori (gel weakening) occurred extensively in the course of actomyosin gelation, but not in surimi gelation. Maximum TGase-induced myosin heavy chain cross-linking was observed at a slightly higher pH of 7.5 than at the optimal pH of endogenous TGase activity; the difference being derived from different substrates. Gelation of carp actomyosin paste at pH values of 5.5, 6.0, 6.5 and 7.0 was monitored by measuring storage modulus (G′) and loss modulus (G″). A weak gel was formed at all pH values, but a slightly rigid and less elastic gel was obtained at lower pH values. The addition of microbial TGase (MTGase) formed strong elastic gels at pH 7.0 and 6.5. MTGase cross-linked myosin heavy chains even at pH 5.5, but contributed neither to suwari response nor strong gel formation. Overall, results suggest that the optimal pH for the gelation of surimi paste from easy-setting fish species is a compromise between the pH-optima of TGase activity and of preferable actomyosin conformation for myosin cross-linking.

Heat-induced Transparent Gel from Hen Egg Lysozyme by a Two-step Heating Method.

The effects of ionic strength and dithiothreitol concentration, a reducing agent, on the heat-induced gelation of a lysozyme solution were examined at pH 7. Two different heating methods were used, one involving single heating, and the other, a two-step heating process in which a sample solution was heated twice under different medium conditions. With 7.5 mM dithiothreitol, a 5% lysozyme solution gave a transparent sol, a transparent gel, a translucent gel and a turbid gel after a single heating with 0, 40, 50, and 60mM NaCI, respectively. When the transparent sol obtained without NaCI was reheated with 50mM NaCI, it produced a firm and transparent gel. This gel was at least 6 times harder than the transparent lysozyme gel obtained by the one-step heating method. High-resolution scanning electron microscopy showed that the transparent gel produced by the two-step heating method had a fine network of linear polymers composed of heat-denatured lysozyme molecules.

Heat-induced Transparent Gel Formation of Bovine Serum Albumin.

The formation of transparent gels by 6% bovine serum albumin (BSA), pH 7.5, was examined by one- and two-step heating methods. Heating of the BSA solutions at various NaCl concentrations produced transparent gels at 25-50mM NaCl and transparent sols at 0-20 mM NaCl (one-step heating method). The transparent sol obtained by heating without NaCl was reheated after mixing with various amounts of NaCl (two-step heating method I). The result was almost identical to that obtained by the one-step heating method. However, when the first heating was done with 10 mM NaCl, transparent gels were obtained over a wide range of NaCl concentrations with a second heating (two-step heating method II). Analyses of sols obtained at various NaCl concentrations by gel permeation chromatography and transmission electron microscopy showed the presence of linear polymers in the heated BSA sol (10 mM NaCl) and gel networks formed by the linear polymers (20 mM NaCl). The mechanism of transparent gel formation in BSA may be similar to that in ovalbumin.

Preparation of xrd single-phase thallium 2-1-2-2 and 2-2-2-3 compounds by a two-step heating method

XRD single-phase 2-1-2-2 and 2-2-2-3 compounds have been prepared by a two-step heating process starting with the 2:1:2:2 and 2:2:2:3 stoichiometries, respectively. T1 2O 3, BaCuO 2, CaO and CuO have been used as reactants. In the first step, the powder mixture was heated for 2 h at the relatively low temperature of 775°C, at which the loss of Tl is negligible, but the T1 2O 3 reacts with other oxides to form less volatile compounds. In the second step, the partially reacted powders were heated at 865°C for appropriate time intervals (20 min for the 2:1:2:2 and 30 min for the 2:2:2:3 stoichiometry) and the single-phase compounds were formed without major loss of Tl. Further annealing at 775° C for 12 h did not affect the XRD single-phase 2-1-2-2 compound, whereas the XRD single-phase 2-2-2-3 compound partially decomposed to the 2-1-2-2 compound.

Heat-induced and transparent gel prepared from hen egg ovalbumin in the presence of salt by a two-step heating method.

Heat-induced transparent gels from ovalbumin solution can be prepared, but only at low ionic strength, which limits their practical uses. We describe here their preparation at different salt concentrations. Ovalbumin solution (5% w/v) was heated at 80°C, pH 7.0, for 1 hr without salt to give a transparent solution. This solution was cooled and reheated with 0.2 m NaCl, which converted it to a transparent gel. At higher NaCl concentrations, the gel was harder and slightly turbid. We examined the change in the ovalbumin molecule when heated without salt. Gel filtration showed that with heating, the amount of ovalbumin monomers decreased and another peak appeared. After 30 min of heating, there was only one peak. This was a soluble aggregate. SDS- HPLC showed that this soluble aggregate was composed of monomers and oligomers connected by a disulfide bridge or bridges. A conformational change was detected with the difference spectrum. The number of sulfhydryl residues decreased slightly.