Thermal Route Research Articles

Palmitic acid-coated magnetite nanocubes with high-quality crystallinity and bulk-like magnetic features

We have demonstrated the synthesis of high-quality monocrystalline magnetite nanocubes through the introduction of palmitic acid as surfactant in a thermal decomposition synthesis of an organic Fe precursor. Unlike the standard thermal decomposition synthesis route, we report the avoid of the reducing agent and a modification in the synthesis heating ramp. Structural and magnetic properties were investigated showing well defined cubic shaped nanoparticles with a ∼ 40 nm edge and magnetic features close to bulk magnetite. We associate the bulk-like magnetic performance and properties to the highly crystalline structure of the nanocubes.In addition, we introduce a facile way to make a ligand exchange of nanocubes initial surfactant to citric acid in order to obtain biocompatible hydrophilic nanocubes. The potential application of the obtained sample in magnetic hyperthermia therapy is shown through calorimetric heating measurements on liquid dispersions of the nanocubes. We compute the Specific Absorption Rate to quantify the heating efficiency of the nanocubes.

Char-diesel slurry fuels for microgeneration: Emission characteristics and engine performance

Abstract Diesel engine generators are one of the major methods for off-grid and on-demand electricity generation, particularly in the remote areas of some developing countries. However, access to fossil diesel is often limited by supply or price. In many regions, biomass is an abundant source of energy, but many types are not suitable for producing traditional liquid biofuels such as biodiesel. This paper explores the use of so called ‘slurry fuels’ produced by the blending of micron sized particles of carbonaceous material in diesel and assesses whether these ‘slurry fuels’ can be used in a standard diesel engine generator with minimal modification. Two types of micronized carbon chars were added to diesel, produced by either pyrolysis or hydrothermal carbonization of biomass. The results indicated that at high engine power, the micronized carbon slurry fuels can be run at a similar efficiency as pure diesel. The major issues identified included high engine wear and the blockage of the fuel injector. Hydrothermal carbonization was found to be the best thermal conversion route for producing micronized carbon in terms of emissions when blended with diesel.

Thermal post-curing as an efficient strategy to eliminate process parameter sensitivity in the mechanical properties of two-photon polymerized materials.

Two-photon polymerization direct laser writing (TPP-DLW) is one of the most versatile technologies to additively manufacture complex parts with nanoscale resolution. However, the wide range of mechanical properties that results from the chosen combination of multiple process parameters imposes an obstacle to its widespread use. Here we introduce a thermal post-curing route as an effective and simple method to increase the mechanical properties of acrylate-based TPP-DLW-derived parts by 20-250% and to largely eliminate the characteristic coupling of processing parameters, material properties and part functionality. We identify the underlying mechanism of the property enhancement as a self-initiated thermal curing reaction, which robustly facilitates the high property reproducibility that is essential for any application of TPP-DLW.

The effect of thermal and non-thermal routes on treatment of the Mg–Al layered double hydroxide catalyst dispersed by titania nanoparticles in products distribution arising from poly(ethylene terephthalate) degradation

The development of sustainable catalysts in the chemical recycling of polyethylene terephthalate (PET) can help to improve the circular economy of this material. In this study, the degradation of PET to the bis(2-hydroxyethyl) terephthalate (BHET) monomer and other main products was investigated by Mg–Al layered double hydroxides (LDHs) dispersed by 20 wt% of titania nanoparticles (NPs). The PET conversion and BHET yield of LDHs treated by thermal and non-thermal treatment routes were compared to assess the thermostability and catalytic activity of LDHs. The LDHs loaded by titania NPs showed higher thermal stability than the unloaded LDHs. A synergistic effect between the brucite sheets and titania was found by using a combination of freeze-drying (FD) and dielectric barrier discharge (DBD) plasma routes, associated with the high dispersion of titania with size ranges of 5–10 nm. The PET conversion and the BHET yield of LDH-FD-DBD were higher than the catalysts annealed by calcination. The high stability of the LDH-FD-DBD allowed it to be reused five times without notable catalytic activity reduction. The proposed technique was an effective approach to manipulate the properties of LDH dispersed by titania NPs that enabled the catalyst to display high activity towards PET degradation.

Lithiation Mechanism Change Driven by Thermally Induced Grain Fining and Its Impact on the Performance of LiMn2 O4 in Lithium-Ion Batteries.

The nature of precursors employed in the synthesis of lithium-ion battery cathode materials is a crucial performance-dictating factor. Therefore, it is of great importance to establish a way to manipulate the precursor and seek a comprehensive understanding of its influence on the electrochemical behavior of a targeted electrode material. A thermal route is herein demonstrated for the synthesis of lithium-excess LiMn2 O4 (LMO) by exploiting an intriguing thermal phenomenon, thermally induced grain fining, and sheds light on how it affects the mechanism and kinetics of lithiation, and, furthermore, the electrochemical behavior of LMO. Detailed insights into the lithiation mechanism and kinetics reveal that the use of a finely grained, porous Mn3 O4 , which possesses an open crystal structure, is a key to the success of incorporating excess Li. In addition, this in-depth electrochemical investigation verifies a very recent theoretical prediction of faster Li diffusion kinetics enabled by excess Li.

Spatial Equivalent Circuit Model for Simulation of On-Chip Thermoelectric Harvesters.

Interest in autonomous low-power energy sources has risen with the development and widespread use of devices with very low energy consumption. Interest in thermoelectric harvesters has increased against this background. Thermoelectric harvesters, especially harvesters on-chip, have peculiar properties related to the thermal route, thermal transients, and spatial temperature distribution within the chip. A behavioral model of the harvester is required for engineers to successfully develop voltage converters with maximum power point tracking and energy storage units. There are accurate models based on the finite element method, but these models are usually not compatible with simulators of electrical circuits, and therefore are not convenient for designers. Existing equivalent circuit models fit this requirement, but usually do not consider many parameters. This article proposes an original method that allows simulating spatial thermoelectric processes by analogy with the finite difference method, using electrical circuits simulations software. The study proposes a complete methodology for building the model and examples of simulations of one-, two- and three-dimensional problems, as well as examples of simulation of macro problems in the presence of external thermal and electrical devices, such as heatsink and electrical load.

Catalytic Intermediate Pyrolysis of Cellulose for Hydrocarbons Production in the Presence of Zeolites by Using TGA-FTIR Method

Pyrolysis plays a vital role in biomass conversion as one of the most promising thermal conversion routes. Solid, liquid and gaseous products are obtained from biomass pyrolysis. The liquid is considered as perspective fuel; however, the direct use of bio-oil as fuel may present many difficulties due to its high viscosity, poor heating value and relative instability. This creates a significant economic barrier for production of transportation fuel by pyrolysis process. Catalytic pyrolysis has been widely used as a convenient method for the direct conversion of biomass into higher quality liquid bio-fuels. Intermediate pyrolysis of cellulose (as a model substance for biomass) with or without catalysts was investigated using TGA-FTIR method in order to determine the influence of zeolite on the relative yield of the compounds. The addition of zeolite with medium and weak acidity increased the production of volatile matter from 86.1% to 88.5% and 88.9% under the catalyst of MCM-41 and ZSM-5 (70). Zeolite with high acidity contributes to the formation of coke and simultaneously causing the deactivation of the catalyst, thus decreasing the volatile matter of cellulose from 86.1% to 83.6% and 83.2% by using H-ZSM-5 (23) and H-ZSM-5 (50). All catalysts showed deoxygenation activity. Zeolites had higher activity in the deoxygenation of compounds containing hydroxyl group than compounds containing carbonyl and carboxyl groups. H-ZSM-5 (23) had a substantial effect on the production of monoaromatic hydrocarbons whereas the yield of olefins notably increased in the presence of ZSM-5 (70).

Enhanced Dielectric Loss and Magnetic Loss Properties of Copper Oxide-Nanowire-Covered Carbon Fiber Composites by Porous Nickel Film

The porous nickel film with agglomerate nanoparticles and 1.5~2.0 μm in thickness was used to enhance microwave absorption and ferromagnetic properties of nanowire-like copper oxide-covered carbon fiber composites. Firstly, the porous nickel film/carbon fiber composites were prepared by plating route, when the current intensity was 120 mA for 30 min (sample S1) and 40 min (sample S2), respectively. Then, the copper oxide/porous nickel/carbon fiber (CNCF1 and CNCF2) composites were synthetized by electroless deposition copper and thermal oxidation route (the sample S1 and sample S2), respectively. The microwave absorption properties of composites were investigated over frequency range, 1-18 GHz. The results showed that the strongest reflectivity loss (RL) values of CuO/carbon fiber (CCF) and CNCF1-2 composites were -25.93 dB at 3.59 GHz with a matching thickness layer of 2.4 mm, -27.87 dB at 6.67 GHz with a matching thickness layer of 2.5 mm, and -54.82 dB at 9.23 GHz with a matching thickness layer of 2.192 mm. When the RL values of CCF and CNCF1-2 composites were lower than -10 dB, the absorption frequency range from 8.12 to 9.64 GHz (1.52 GHz in absorption bandwidths, 1.5 mm in thickness), 6.45 to 8.81 GHz (2.36 GHz in absorption bandwidths, 2.4 mm in thickness) and 10.51 to 14.35 GHz (3.84 GHz in absorption bandwidths, 1.8 mm in thickness), respectively. Therefore, the CNCF2 composites showed more excellent microwave absorption properties, and are potential microwave absorption candidates for making a thin thickness, strong absorption and wide-frequency.

Formations and emissions of CO/NO2/NOx in the laminar premixed biogas-hydrogen flame undergoing the flame-wall interaction: Effects of the variable CO2 proportion

Experimental and numerical studies were conducted to investigate the effects of CO2 proportion on the formation processes and overall emissions of CO and NOx of the laminar premixed biogas-hydrogen flames undergoing the flame-wall interaction (FWI). The overall EICO, EINOx, EINO2 and NO2/NOx ratio were obtained. The near-wall combustion processes of the wall-impinging flame at different separated distance (H) were simulated numerically using a computational model, and four major routes (thermal route, prompt route, NNH intermediate route and N2O intermediate route) of the NO production were calculated separately. The results show that the EICO decreases at small H but increases at large H with the increased CO2 proportion, which is dominated by the cooling plate and dilution/chemical effects of CO2, respectively. This indicates that the overall EICO of biogas fuel can be reduced effectively with the enhanced CO2 proportion when the FWI effects are intensive. The overall EINOx is decreased obviously with the increased CO2 proportion owing to the declined temperature and reduced active radicals. With the increased CO2, the contributions of thermal route and N2O route are decreased considerably while the importance of prompt route and NNH route are increased evidently. The strong FWI effects can increase the importance of prompt route while decrease the contribution of thermal route effectively. The EINO2 of biogas-H2 flame is decreased with the increased CO2 proportion. The dilution effects of CO2 can improve the NO2 conversion efficiently but this NO2 conversion process can be suppressed effectively by the intensive FWI effects.

Catalytic hydrolysis of sodium borohydride solution for hydrogen production using thermal plasma synthesized nickel nanoparticles

In the present study nickel nanoparticles were synthesized by thermal plasma route. In this method we obtained highly crystalline almost spherical nanoparticles with maximum number of particles having size around 30–50 nm. These nanoparticles were thoroughly characterized and employed as a catalyst for hydrogen production using hydrolysis of sodium borohydride (NaBH4). The effect of initial concentration of NaBH4, pH and temperature of solution on the rate of hydrogen production was investigated. Nickel nanoparticles exhibits first order reaction with respect to NaBH4 concentration at elevated temperatures. After hydrolysis, the nickel nanoparticles showed presences of B–O and B–OH species on the nickel surface. The catalyst was found to be stable during 5 sequential cycles of test.

Simple and fast fabrication of single crystal VO2 microtube arrays

Single crystal VO2 is a strongly correlated electron material that has shown great potential for a wide range of high-performance modern device applications, such as microbolometers, lithium ion batteries, microactuators and strain sensors. However, the present fabrication methods for single crystal VO2 almost always require complicated procedures, strict conditions and long reaction times of up to one week. Here, we report a simple, fast, low-cost and green method for fabricating single crystal VO2 using a thermal oxidation route based on resistive heating of a vanadium foil in air. Our method not only reduces the complete fabrication time from hours to tens of seconds but also naturally forms single crystal VO2 microtube arrays that are nearly vertically aligned on the surface of a V2O5 substrate. Microstructure characteristics and the reversible phase transition between the monoclinic VO2 and rutile VO2 phases demonstrate that the obtained single crystal VO2 is the same as that achieved by other fabrication methods.

Development of Generic Criteria for Evaluating the Disposability of Thermally Treated Wastes

The potential to generate wasteforms with enhanced properties that support safe storage and disposal is one of the key factors driving thermal treatment of radioactive waste. Depending on the specific treatment method and waste substrate, thermal treatment can greatly reduce chemical reactivity, yielding a primary product that is more durable than wasteforms produced via non-thermal routes and with reduced potential for gas generation and other detrimental behaviour in a storage / disposal environment. On the other hand, thermal treatment can concentrate radioactivity into a smaller volume, potentially affecting waste handling and / or classification. It also generates secondary wastes whose management requires consideration as part of a holistic evaluation of thermal treatment. Moreover, some thermal treatment routes do not generate a primary product that is directly disposable without further conditioning. Generic disposability criteria have been derived that can be used to evaluate the primary products from any form of thermal treatment. These generic disposability criteria highlight the factors that are relevant for waste product disposability and the ways in which thermal treatment can impact on these factors (both positively and negatively). They are equally applicable to any packaging or disposal concept, regardless of the engineered barriers that are present, and in any disposal environment, regardless of its characteristics and the nature of the host rock / geology. They could aid waste management organisations in developing their own disposability criteria, tailored to a particular context, for application in national waste management programmes.

Characterization of the combustion of the mixtures biogas-syngas at high strain rates

Applying gasification on the residue generated by the biogas process would increase flexibility and efficiency of waste treatment plants while leading to a simultaneous production of biogas and syngas. Existing electricity conversion systems at biogas and gasification plants are usually designed to operate with a single bio-fuel (biogas/syngas). It is, hence, necessary to identify the combustion characteristics of these blended fuels in order to implement them efficiently in the existing systems.The aim of this work is to characterize the structure and emission of mixtures of biogas and syngas in counter-flow flame configuration at laminar regime. Particular attention is paid to the chemical effects of CO2 contained in the biogas and radiative heat losses of the flame. Several compositions of biogas and syngas have been considered in the fuel mixture.The results show that the flame properties are very sensitive to fuel composition. An increase in the volume of methane in the biogas or hydrogen in the syngas improves the Low Heat Value (LHV) of the fuel. Moreover, the addition of a volume of syngas exceeding half of that of biogas allows a reduction of harmful emissions while maintaining a constant level of operating temperature. At the flame front, the NO species is found to be governed by thermal route whereas it is generally produced by prompt path before and after the flame front. In addition, the chemical effect of CO2 reduces the maxima of temperature and emission. This effect remains constant in the syngas mixtures while it is very sensitive to biogas composition where it decreases with the amount of CH4 in biogas.

Discussion and Study of Technical Route of Smart Power Plant of Thermal Power

Digital smart power plant is an important development direction of thermal power technology. Smart thermal power plant technical route and development direction is presented considering characteristics of production and management of thermal power enterprises. The smart thermal power plant’s system framework is discussed. The key technical field of smart thermal power plant is studied. An open-ended smart thermal power plant technical system including 5 technical platforms of smart data, smart safety, smart producing, smart operation, smart integrated management, is summarized. Meanwhile, the development status of key technologies of diverse systems and functions is discussed, the future development direction of key technologies is presented constructively, and three principled suggestions on the construction of smart power plant are presented finally.

Microwave-Assisted Syntheses of Vegetable Oil-Based Monomer: A Cleaner, Faster, and More Energy Efficient Route

Modification of vegetable oil into monomers and polymers is essential nowadays, considering petroleum depletion. The reaction of vegetable oils with maleic anhydride is widely known, and the final product can be obtained by a thermal conventional route, which requires 3 h for total reaction. The aim of this work was to provide a more efficient, faster, and cleaner alternative synthetic route assisted by microwave irradiation. A comprehensive experimental design indicated that it is possible to obtain higher anhydride incorporation onto vegetable oil structure with only 15 min of microwave irradiation, a reaction time 12 × less than the thermal conventional route, as well as 6 × less energy consumption. Furthermore, the higher performance was supported by the Mid-Infrared Spectroscopy (MIR), Nuclear Magnetic Resonance (1H-NMR), and UV–Vis analyses. The viscosity and colorimetric analyses were used to determine the aspect of modifications of final product. Thermogravimetry (TG) is fundamental to afford thermal stability and steps of mass loss, and Differential Scanning Calorimetry (DSC) provides information about melting point, which proves the incorporation of the anhydride.

Effects of unburned gases velocity on the CO/NO2/NOx formations and overall emissions of laminar premixed biogas-hydrogen impinging flame

Experimental measurements and numerical simulations were both conducted to study effects of unburned gases velocity on the formations and overall emissions of CO and NOx of the laminar premixed biogas-hydrogen impinging flame. Emission indexes (EI) of CO and NOx and NO2/NOx ratio were obtained based on the measured data, while four major routes to produce the NO were isolated and calculated in the simulation. The results show that EICO is decreased with Re at small H, while it is increased with Re at large H. The thermal NO is improved with Re as the flame front is affected strongly by the cold plate, while it is suppressed at larger H due to the reduced residence time and relatively insufficient oxidizer. The N2O route is decreased with Re, while the increased NO amounts of prompt route and NNH route are dominated by the higher flame temperature and more available active radicals. The contributions of thermal route and N2O route are decreased with Re while that of prompt route and NNH route are increased. With the increased Re, EINO2 and NO2/NOx ratio are decreased at small H but increased at large H.

RuO2 nanoparticles decorate belt-like anatase TiO2 for highly efficient chlorine evolution

Chlorine gas, mainly produced by the chlor-alkali industry, plays a crucial role in chemical synthesis, water treatment and electronics industry. Herein, facile hydrothermal growth followed by electrodeposition is applied to fabricate a RuO2@TiO2 electrode with nanostructured morphology toward the chlorine evolution reaction (CER), which contributes to reducing energy consumption and environmental pollution in comparison with the traditional thermal decomposition route to form a “mud-crack” structure. The appropriate amount of RuO2 nanoparticles (NPs) decorated on TiO2 nanobelt arrays (NBs) is determined by controlling the electrodeposition time to realize aligned morphological features instead of typically calculating various molar ratios of Ti and Ru to determine the best catalytic activity. Benefitting from the nanostructure of broadly outstretched TiO2 NBs and the perfect decoration of highly catalytically active RuO2 NPs roughening the nanomaterial surface, the RuO2 NPs@TiO2 NBs electrode exhibits enhanced catalytic activity with splendid stability and high selectivity toward the CER. It requires an extremely low potential of 1.34 V (overpotential 80 mV) to achieve a catalytic current density of 50 mA/cm2 and the current efficiency of the material electrode for chlorine evolution is up to 90%, making it among the best CER anodes reported so far.

High-Performance Ambient-Condition-Processed Polymer Solar Cells and Organic Thin-Film Transistors.

Large-scale commercial synthesis of bulk-heterojunction (BHJ) solar cell materials is very challenging and both time and energy consuming. Synthesis of π-conjugated polymers (CPs) with uniform batch-to-batch molecular weight and low dispersity is a key requirement for better reproducibility of high-efficiency polymer solar cells. Herein, a conjugated polymer (CP) PTB7-Th, well known for its high performance, has been synthesized with high molecular weight and low dispersity in a closed microwave reactor. The microwave reaction procedure is known to be more controlled and consumes less energy. The precursors were strategically reacted for different reaction time durations to obtain the optimum molecular weight. All different CPs were well characterized using 1H NMR, gel permeation chromatography (GPC), UV–vis, photoluminescence (PL), electron spin resonance (ESR), and Raman spectroscopy, whereas the film morphology was extensively studied via atomic force microscopy (AFM) and grazing incidence X-ray diffraction (GIXRD) techniques. The effect of molecular weight on a conventional BHJ solar cell with PC71BM acceptor was investigated to derive systematic structure–property relationships. The CP obtained after 35 min of reaction time and integrated into BHJ devices under ambient conditions provided the best performance with a power conversion efficiency (PCE) of 8.09%, which was quite similar to the results of CPs synthesized via a thermal route. An enhanced PCE of 8.47% was obtained for the optimized polymer (35 min microwave reaction product) when device fabrication was carried out inside a glovebox. The organic thin-film transistor (OTFT) device with the microwave-synthesized CP displayed better hole mobility (0.137 cm2 V–1 s–1) as compared to that with the thermally synthesized CP. This study also proved that the device stability and reproducibility of the microwave-synthesized CP were much better and more consistent than those of the thermally developed CP.

Effect of hydrogen addition on NOx formation mechanism and pathways in MILD combustion of H2-rich low calorific value fuels

Hydrogen is a major component of low heating value (LHV) fuels like syngas, coke oven gas, and blast furnace gas. These fuels can potentially replace methane in the industrial process under MILD combustion conditions. NOx formation mechanism in MILD combustion regime is different from conventional air combustion due to uniform temperature distribution and low oxygen concentration. Hence, it is important to investigate the effect of hydrogen addition inmethane (CH4) on different NOx formation mechanism and pathways under MILD combustion conditions. A well-stirred reactor (WSR) model with atmospheric pressure and long residence time was employed to simulate the ideal MILD combustion conditions with Chemkin Pro software and GRI Mech 2.11. H2 and CH4 blends ranging from 0% H2 (100% CH4) to 60% H2 (B60 = 40%CH4/60%H2) were selected as fuels to emulate MILD combustion of LHV fuels. The oxygen mass fraction was kept from 3% to 9%, and the fuel blends were altered. The results showed that hydrogen addition enhanced NNH route while decreasing prompt route and N2O intermediate route whereas thermal NOx route was insignificant for lower O2 mass fraction of 3% and 6%. It was observed that H2 addition reduced NO-reburning which led to more NOx emission. Moreover, the sensitivity analysis was conducted to analyze the pathway of NOx formation and to quantitively separate the relative contribution of the individual route on the total NOx formation, which was beneficial to control the NOx emission of LHV fuels during MILD combustion.

Recrystallization of Single-Crystalline VO2 Microtube Arrays on V2O5 Substrate

Single-crystalline VO2 microtube arrays on V2O5 substrate were fabricated through a thermal oxidation route based on resistive heating V foil in air. Four sheets of as-fabricated single-crystalline VO2 microtube arrays on V2O5 substrate were then, respectively, heated to approximately 855 °C and 1660 °C to melt V2O5 or VO2. Thereafter, the melted V2O5 or VO2 was cooled rapidly or slowly to recrystallize the liquid V2O5 or VO2. The morphologies and phases of the recrystallization products were characterized by scanning electron microscopy and X-ray diffraction. This study proposes that the peak temperature of heating and the cooling rate are responsible for the recrystallization products of single-crystalline VO2 microtube arrays on V2O5 substrate.