Subsequent Thermal Process Research Articles

Management of Marcellus Shale Produced Water in Pennsylvania: A Review of Current Strategies and Perspectives

AbstractThe reuse of produced water generated by natural gas extraction from Marcellus Shale for hydraulic fracturing is the dominant management option in Pennsylvania (PA), USA. The advantages and disadvantages of this management approach are reviewed and discussed together with long‐term concerns and technology development needs. Abandoned mine drainage is a promising alternative make‐up water, but high sulfate concentrations will lead to barite precipitation once it is mixed with the produced water. Bench‐scale studies were conducted to optimize barite separation from this mixture that meets the finished water quality criteria for sulfate. Conventional separation processes are very effective in removing these solids but radium (Ra) co‐precipitation may be a concern for their disposal in municipal landfills. If the produced water volume exceeds the reuse capacity for hydraulic fracturing, lime–soda ash softening can be used to remove divalent cations, including radium, to enable the production of pure salts using subsequent thermal processes.

Structural, Raman scattering and magnetic characteristics of Er+-implanted GaN thin films

Er+ ions were implanted into the n-type, unintentionally-doped (u-type) and p-type GaN epilayers, respectively. Subsequent rapid thermal annealing process was carried out at 800°C in N2 ambience for 5min. It is found that the micro-structure of GaN:Er films have a close relationship with the implantation and annealing process. Four new Raman peaks were introduced by Er+ ions implantation at 300, 362, 670 and 855cm−1, respectively. All the samples exhibit room-temperature ferromagnetism, which can be well explained by the bound magnetic polaron theory. Our experiments also revealed that the magnetic properties of GaN:Er samples are closely related to their conduction type and initial carrier concentration, and the magnetic coupling between the magnetic moments of Er3+ ions and electrons is stronger than that with holes.

A sandwich structure of mesoporous anatase TiO2sheets and reduced graphene oxide and its application as lithium-ion battery electrodes

Mesoporous anatase TiO2 sheets/rGO sandwich-like nanocomposites were facile synthesized by acid-assisted tetrabutyl titanate hydrolysis and subsequent thermal reduction process. Structural, morphological, and compositional properties were characterized by various techniques, such as X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, thermal gravimetric (TG) analysis, and BET surface area analysis. When used as the anode materials of Li-ion batteries, the as-prepared sample delivered reasonable capacity, good cycling stability and rate capability. The optimal sample delivered a high reversible lithium-storage capacity of ∼161.4 mA h g−1 after 50 cycles at a current rate of 0.5 C (1 C = 335 mA g−1), with good cycling stability and rate capability. It is believed that the good electrochemical performance can be attributed to the mesoporous feature, the addition of rGO nanosheets, and the special sandwich-like electrode structure. Therefore, rational design of mesoporous structures and compositing with rGO nanosheets are of importance for improving the lithium-storage performance.

Preparation of flexible ultra-fine Al2O3 fiber mats via the solution blowing method

Alumina fiber and fiber mat are important ceramic materials, which can be used in many fields including high temperature filtration, thermal insulation and catalyst support. This article demonstrates that alumina fiber mats can be obtained by the solution blowing process combined with the sol-gel method and a subsequent thermal treatment process. During the solution blowing process, the as-spun composite fibers were formed after the solvent evaporation and drawing of the gas flow. These fibers successfully converted into γ-Al2O3 and α-Al2O3 under the thermal treatment in air at 900°C and 1100°C. Diameter of as-spun fiber with the range from 2μm to 5μm was influenced obviously by adjusting the spinning parameters, such as gel viscosity and highly pressure gas flow. In addition, the resulting alumina fiber mat performed an excellent flexibility, which was significant to the high temperature filtration and other applications.

Efficient planar perovskite solar cells based on 1.8 eV band gap CH3NH3PbI2Br nanosheets via thermal decomposition.

Hybrid organometallic halide perovskite CH3NH3PbI2Br (or MAPbI2Br) nanosheets with a 1.8 eV band gap were prepared via a thermal decomposition process from a precursor containing PbI2, MABr, and MACl. The planar solar cell based on the compact layer of MAPbI2Br nanosheets exhibited 10% efficiency and a single-wavelength conversion efficiency of up to 86%. The crystal phase, optical absorption, film morphology, and thermogravimetric analysis studies indicate that the thermal decomposition process strongly depends on the composition of precursors. We find that MACl functions as a glue or soft template to control the initial formation of a solid solution with the main MAPbI2Br precursor components (i.e., PbI2 and MABr). The subsequent thermal decomposition process controls the morphology/surface coverage of perovskite films on the planar substrate and strongly affects the device characteristics.

Mesoporous carbon-sulfur composite as cathode for lithium-sulfur battery

A novel carbon-sulfur composite, mesoporous carbon-sulfur, was developed as cathode of lithium/sulfur battery. The mesoporous carbon was prepared with sucrose as carbon precursor and calcium carbonate nanoparticles as pore producer. The sulfur was encapsulated in the mesoporous carbon via a simple chemical deposition strategy and a subsequent low-temperature thermal treatment process. The morphology and structure of the resulting composite were characterized with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller measurement, and thermogravimetric analysis. Its electrochemical performances as cathode of lithium/sulfur battery were evaluated with cyclic voltammetry and charge-discharge test. The prepared carbon showed a specific surface area of 598 m2 g−1 with a bimodal pore distribution centered at 3.6 and 40 nm. The resulting mesoporous carbon-sulfur delivered an initial capacity of 1,380 mAh g−1 at 0.02 C and maintained a capacity of 750 mAh g−1 after 100 cycles at 0.1 C.

The surface-plasmon-resonance and band bending effects on the photoluminescence enhancement of Ag-decorated ZnO nanorods

Doping with noble metal nanoparticles (NPs) is an effective method to tune the photoluminescence (PL) properties of semiconductor materials. The mechanism is widely attributed to the localized surface-plasmon-resonance (SPR) effect of the metal NPs, while the contribution of potential barrier at the interface between metal and semiconductor is less discussed. Taking ZnO nanorods on fused silica substrates as a model system, we present a facile low-temperature fabrication method to derive Ag metal NPs coated ZnO nanorods. Great enhancement of the near-band-edge (NBE) ultraviolet emission of the ZnO nanorods was achieved by the surface decoration with Ag NPs, accompanied with a decrement of deep-level (DL) emission intensity. Since, the Ag NPs are active even at ambient conditions, spontaneous changes in PL properties have been observed with aging time. The influence of oxidation state of Ag on the contacting potential and subsequently on the PL properties of ZnO nanorods were studied by employing a subsequent thermal annealing process. The role of contacting behavior and the varied potential barrier are comprehensively discussed. It was demonstrated that both the SPR effect and band bending effect can enhance the NBE emission and suppress the DL emission. In the Ag-decorated ZnO nanorods, the SPR effect is the main reason for PL enhancement of the metallic silver, while the potential barrier enhancement is the main reason for the oxidized silver.

CuO/Cu2O nanofibers as electrode materials for non-enzymatic glucose sensors with improved sensitivity

CuO nanofibers (NFs) were fabricated via the traditional electrospinning technique and subsequent thermal treatment processes. Using CuO NFs as precursors and glucose as a reducing agent, CuO/Cu2O NFs, with high surface areas and ultralong one dimensional (1D) nanostructures, were obtained by a partial reduction of CuO NFs. Comparing with pure CuO NFs, CuO/Cu2O NFs, as non-enzymatic electrode materials, showed a much higher sensitivity of 830 μA mM−1 cm−2 and a much wider detection range from 0.5 mM to 10 mM for the amperometric detection of glucose. The excellent electrocatalytic performances could be ascribed to the following advantages: (1) the CuO/Cu2O NFs with Cu(II)/Cu(I) multiple oxidation states system could promote the redox reactions between electrode materials and glucose, and the reactive sites became more active due to the synergic effect; (2) the surface of CuO/Cu2O NFs became smoother after partial reduction, resulting in less adsorption of the intermediates during the oxidation of glucose, generating the enlarged detection range. Therefore, the CuO/Cu2O composite NFs electrode materials, with a multiple oxidation states system, would be promising candidates for the development of non-enzymatic glucose sensors.

Dual role of conditioner CaO in product distributions and sulfur transformation during sewage sludge pyrolysis

Product distributions and sulfur transformation during sewage sludge pyrolysis are essential to subsequent thermal disposal process, both of which are strongly affected by calcium-based compounds. Considering that lime (CaO) is widely applied in sludge conditioning pre-treatment, this study investigated the dual role of conditioner CaO in sludge pyrolysis behavior and sulfur evolution at the temperature range of 873–1273K. Specific compositions in three phases, such as solid residual, tar and gas, were also determined to further clarify the mechanisms involved. According to the results, conditioner CaO increased the fraction of ash and more stable organics in sludge particles, which contributed to higher yield of char comprising lots of carbon and hydrogen. The ring-opening of aromatic hydrocarbons followed by addition reaction of H2O in solid phase facilitated H2 and CO generation, leaving a large number of COH and CO in char. Meanwhile, conditioner CaO catalyzed tar cracking, further increasing the productions of H2 and CO. More interestingly, residual calcium was still capable of fixing sulfur in solid product. Raw sludge matrix prevented sulfur releasing mainly through cyclization reactions, and the relative ratio of char-S only accounted for less than 50%. Correspondingly, most of SO2, CS2, C2H6S2, H2S, COS, and CH4S were emitted. In contrast, char-S yields reached up to 92.8% mainly through forming thermal stable sulfide and sulfate promoted by conditioner CaO, which drove down the final production of sulfurous gases. These indicate that reusing conditioner CaO is a promising strategy for increasing combustible gases and char yields efficiently and reducing the formation of polluting S-containing gases dramatically.

Effect of lithium chloride on crystallization process of neodymium disilicate

Tetragonal neodymium disilicate (i.e., Nd2Si2O7) powder was synthesized in the absence and presence of 5wt% lithium chloride (i.e., LiCl) as a mineralizer by sol–gel method and subsequent thermal treatment process. The effect of LiCl on the crystallization process of the synthesized xerogel was investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The crystallization kinetic was analyzed at different heating rates (i.e., 2, 5, 10 and 20K/min) by a non-isothermal differential thermal analysis method. The activation energies of the tetragonal Nd2Si2O7 crystallization calculated by the Kissinger and the Ligero methods are 673kJ/mol for the xerogel without LiCl and 586kJ/mol for the xerogel with 5wt% LiCl. In addition, the crystallization mechanism was also discussed, indicating that the crystallization mechanism of the tetragonal Nd2Si2O7 changes from bulk and homogeneous to two-dimension crystallization in the presence of 5wt% LiCl.

Erratum to: Preparation of gold nanoparticle-loaded silica gels and their localized surface plasmon resonance sensing properties

Localized surface plasmon resonance (LSPR) of gold nanoparticles (AuNPs) has been used for biosensing and chemical sensing applications because the LSPR peak wavelength depends on the dispersion state and local refractive index of the surrounding medium. In this study, AuNP-loaded silica gels were prepared as sensing chips with high transparency and solution holding capability. The silica gels were prepared at various sintering temperatures from 500 to 900 °C, and the AuNPs precipitated in the gels by using a subsequent thermal reduction process. At sintering temperatures of 700, 800, and 900 °C, transparent and crack-free AuNP-loaded silica gels were obtained. Transmission electron microscopy observation revealed the AuNP size to be approximately 20 nm, and they were highly dispersed in all the silica gel samples. However, the sintering temperature of the silica gels strongly affected the LSPR property of the AuNPs and the porous property of the silica gel. The samples sintered at higher temperature exhibited a lower LSPR sensing ability against the refractive index of immersing solvents. The low sensing ability was considered as a result of a decrease in the contact area between the AuNPs and immersing solvent caused by an increase in the silica gel density with sintering temperature.

Aging behavior and mechanism of bio‐based engineering polyester elastomer nanocomposites

ABSTRACTBio‐based elastomers used in industry have attracted much attention. We prepared bio‐based engineering polyester elastomer (BEE) nanocomposites by mixing bio‐based engineering polyester elastomers with carbon (CB). The CB/BEE nanocomposites were exposed to an artificial weathering environment for different time periods. Both its aging behavior changes and aging mechanism were investigated in this article. The tensile strength retention rates were each above 90% after aging at 100°C and 125°C for 72 h. CB/BEE nanocomposites exhibited good anti‐aging properties. Furthermore, the chemical changes were detected by Fourier transform infrared spectroscopy and differential scanning calorimetry. The crosslink density changes during aging of BEE were determined as well. A plausible aging mechanism of BEE was proposed. It can be concluded that the thermal oxidation process gives priority to further crosslinking in the initial period of aging. As the aging time increases, chain scission becomes the dominant element in the subsequent thermal oxidation process. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40862.

Nanostructuring of the surface of silicate glass by femtosecond laser pulses in the UV range

The electron dynamics and surface ablation of silicate glass excited by single UV femtosecond pulses have been studied by photoluminescence and contact ultrasound diagnostics. At low energy densities of the laser radiation, the photoluminescence signal reveals the linear character of the photogeneration of the electron–hole plasma, accompanied by its radiative recombination, carrier autolocalization, and point-defect generation. At high energy densities, rapid Auger recombination of the dense electron–hole plasma saturates the luminescence output, allowing only ultrasound diagnostics of the photoexcitation and subsequent thermal processes, including spallation and fragmentation ablation. The results of the experimental studies of the electron dynamics are confirmed by the results of its numerical modelling in terms of the quantum kinetic model, based on a solution of the Boltzmann equation. Surface nanolattices are generated on the surface of the glass in the multipulse laser-excitation regime.

Constructing Fe3O4@N-rich Carbon Core-Shell Microspheres as Anode for Lithium Ion Batteries with Enhanced Electrochemical Performance

Highly regulated peanut-like Fe3O4@N-rich carbon (Fe3O4@CN) core-shell microspheres were prepared using a solvothermal method, combined with a facile surfactant (sodium dodecyl sulfate) directed chemical polymerization and subsequent thermal treatment process. As anode electrode materials for Li-ion batteries, the as-prepared Fe3O4@CN composites exhibit higher specific capacity and better cyclic stability than bare Fe3O4. The reversible specific capacity of Fe3O4@CN composite is 670 mAh g−1 in the voltage range of 0.01-3.0V after 30 cycles with no noticeable fading compared with bare Fe3O4(100 mAh g−1). The enhanced electrochemical performance of the composites can be attributed to peanut-like Fe3O4@CN core-shell structure in which monodisperse Fe3O4 particles are entirely coated in the controllable and uniform carbon shell, and the surface contact among carbon shells further improves electronic conductivity due to slight agglomeration of composites after thermal treatment. Moreover, the residual nitrogen in the carbon crystal lattice resulted from the carbonization of polypyrrole enhances the electronic conductivity and brings active defects for the diffusion of lithium ion.

Influence of Magnetic Nanoparticle Size on the Particle Dispersion and Phase Separation in an ABA Triblock Copolymer

Oleic acid modified iron oxide nanoparticles (IONs) with different sizes were synthesized and mixed with styrene-butadiene-styrene block copolymer (SBS) with a lamellar structure. The octadecene segments on the oleic acid molecules have chemical affinity with the polybutadiene (PB) blocks, which makes IONs tend to be selectively confined in the microphase-separated PB domains. However, the dispersion state strongly depends on the ratio of the particle diameter (d) to the lamellar thickness (l) of the PB domains, which further changes the phase separation of SBS. When d/l ∼0.5, most of IONs are concentrated in the middle of the PB layers at low particle loading. Upon increasing the particle loading, part of IONs contact each other to form long strings due to their strong magnetic interactions. Away from the strings, IONs are either selectively dispersed in the middle and at the interfaces of the PB domains, or randomly distributed at some regions in which the phase separation of SBS is suppressed. The phase separation of SBS transforms from the lamellar structure to a cylinder structure when the IONs loading is higher than 16.7 wt %. As d is comparable to l, IONs aggregate to form clusters of 100 to 300 nm in size, but within the clusters IONs are still selectively dispersed in the PB domains instead of forming macroscopic phase separation. It is interpreted in terms of the relatively small conformational entropy of the middle blocks of SBS; thus, incorporation of nanoparticles does not lead to much loss of conformational entropy. Although incorporation of IONs with d/l ∼1 significantly increases the interfacial curvature and roughness, it has less influence on the phase separation structure of SBS due to the inhomogeneous dispersion. When d is larger than l, IONs are macroscopically separated from the SBS matrix to form clusters of hundreds of nanometers to several micrometers. More interestingly, the phase separation of SBS transforms from the lamellar structure to a two-phase co-continuous structure, probably due to the rearrangement of SBS molecules to cover the clusters with PB segments and the strong magnetic interaction exerting additional force on the SBS matrix during the evaporation of the solvent and the subsequent thermal annealing process.

Evaluation of crystalline silicon solar cells by current-modulating four-point-probe method

A current-modulating four-point-probe method (CMR) is proposed as a method to determine the conversion efficiency of crystalline Si solar cells. This technique was implemented based on the comprehensive consideration of multiple problems or factors that are present in crystalline Si wafers and the subsequent thermal processes during solar cell fabrication, rather than employ conventional lifetime mapping or diffusion length mapping. A single parameter measurement of Ith–Is from the CMR method reflects the effective resistivity or minority carriers of an entire wafer, to quickly characterize the quality or conversion efficiency of all kinds of crystalline Si.

Thermochemical and Fluid Dynamic Model of a Bench-Scale Torrefaction Reactor

In biomass-to-energy systems, torrefaction represent an interesting pre-treatment, as it increases the feedstock energy content and its suitability for the subsequent thermal conversion process. The aim of this work is to develop and validate a numerical model for the torrefaction of common reed (Phragmites australis). In order to predict the rate of the biomass decomposition (i.e., yield of the reaction products) and characterise the thermofluidynamics of the reactor, a heat, mass and momentum transfer model based on a finite volumes method (f.v.m.) representation has been developed and supplemented with a torrefaction kinetic model, consisting of a two-step scheme previously proposed. The kinetic model has been calibrated utilizing the results of thermogravimetric analysis applied to common reeds. Experimental tests have been also performed on reeds in a bench-scale batch apparatus, varying the main process parameters. The validation of the proposed kinetic scheme has been carried out following two different approaches. Through the first (simplified) approach, the finite elements model has been used to estimate the temperature distribution inside the reactor during the experimental tests. An average (experimental) torrefaction temperature has been then calculated and used as input of the kinetic model. In the second approach, the proposed kinetic scheme has been implemented directly in the f.v.m. model, solving numerically the mass and energy conservation equation. The results obtained by means of the two modelling approaches have been then compared with the experimental data. The proposed thermochemical and fluid dynamic model seems to be a suitable tool for the simulation of a torrefaction reactor and useful for the characterisation and optimization of such kind of systems.

Novel Sb-doped ruthenium oxide electrode with ordered nanotube structure and its electrocatalytic activity toward chlorine evolution

An electrochemical method for the fabrication of nanostructured ruthenium oxide composite electrode from TiO2 nanotube arrays (TNTs) is presented. Briefly, activated TNTs support with improved electrical property was obtained by heat treatment, and ruthenium was subsequently deposited along the inner and outer surface of TiO2 nanotubes by electrochemical method. The as-prepared electrode showed a highly ordered nanotube structure with high specific surface area. Furthermore, the addition of Sb3+ into electrolyte could benefit the electrodeposition of ruthenium and the subsequent thermal oxidation process, which were proved by the more loaded RuO2 nanoparticles and the smaller particle size. Sb-doped RuO2/TNTs electrode prepared from the electrolyte containing a low concentration of Sb3+ showed a high electrocatalytic activity toward chlorine evolution, and the anodic current reached 170mAcm−2 at 1.2V. Excess Sb3+ in electrolyte, however, would lead to a remarkable decrease in electrode property as antimony is not an active ingredient for chlorine evolution reaction. A model Rs(Q1(R1(R2Q2))) was proposed to analyze the electrochemical impedance characteristic of the nanostructured electrodes. The charge transfer resistance on the Sb-doped RuO2/TNTs electrode was much smaller than that on a RuO2/TNTs electrode.

An easy method for the room-temperature growth of spongelike nanostructured Zn films as initial step for the fabrication of nanostructured ZnO

Spongelike nanostructured zinc films were grown by room temperature sputtering processes and pure wurzitic zinc oxide nanostructured films were obtained by a subsequent thermal annealing process. This method allowed growing films with a thickness of a few micrometers with a relatively short deposition time. A study on the influence of the process parameters on the morphology of the films was carried out. The radio frequency power applied to the cathode appeared to be the main factor in order to achieve nanostructures with different morphological features. The physical and chemical characteristics of the nanostructured ZnO obtained with the method herein described make it suitable to be used as photoanode in Dye-sensitized Solar Cells.

Synthesis and characterization of Fe/C core–shell nanoparticles

Carbon-encapsulated Fe nanoparticles have been successfully synthesized by a two-step procedure method of hydrothermal and subsequent thermal reduction process. The introduction of hydrogen atmosphere helps to obtain pure α-Fe phase and the lower annealing temperature (at 550°C). The morphological characterization indicates that the nanoparticle presents a quasi-spherical shaped, core–shell structure with diameter ranged from 10 to 20nm and a carbon shell of about 4nm. The results of X-ray diffraction and Raman spectrum demonstrate that carbon in the as-synthesized product is in amorphous phase. Magnetic measurements reveal the ferromagnetic behavior of the product.