Low-temperature Thermal Treatment Research Articles

Effect of Low-Thermal Treatment on the Particle Size Distribution in Wood Dust after Milling.

The thermal treatment of wood can improve the appearance of the wood product's surface, its dimensional stability, and resistance to fungal attacks. However, the heat treatment changes the technological properties of wood, making it a new engineering material. This work investigates the effect of the low-thermal treatment of birch wood (Betula pendula Roth.), European beech wood (Fagus sylvatica L.), and alder wood (Alnus glutinosa L.) on the fine dust particles creation during woodworking. The samples of thermally treated wood with temperatures commonly used for the change of wood colour (105, 125, and 135 °C) were compared with reference samples made of natural wood. All 12 variants of the tested woods were milled using the 5-axis CNC machining center (20 mm diamond cutter, rotational speed 18,000 rev·min-1, the depth of cut 3 mm, feed rates of 2, 4 and 6 m∙min-1). A sieving analysis method allowed measuring the dust particle size distributions in all dust samples. The experiment's result analysis points out that wood type, thermal treatment, and feed rate meaningfully affect the size distribution of dust particles. Compared to birch wood and beech wood, the milling of alder wood samples created a much higher content of the finest dust particles, with particle sizes smaller than 0.032 mm. Increased temperatures in thermal treatment increase the share of fine dust particles with sizes smaller than 0.125 mm, compared to wood in its natural state. Milling with a lower feed rate (2 m·min-1) creates finer dust than processing with higher feed rates (4 and 6 m·min-1). Generally, the milling of alder in a natural or thermally treated state is a source of fine dust particles, particularly at low feed speed-rate milling, compared to birch and beech wood. In general, these results indicate that the low temperature thermal treatment parameters attribute new technological properties to all thermally modified types of wood tested.

Experimental investigation on electromagnetic induction thermal desorption for remediation of petroleum hydrocarbons contaminated soil

A novel electromagnetic induction low temperature thermal desorption treatment (EMI LTTD) for petroleum hydrocarbons contaminated soil was introduced in this work. The removal rate of total petroleum hydrocarbons (TPH) under various factors, the morphology changes of soils as well as removal mechanism were investigated. Results suggested that increasing the heating temperature significantly increased the removal rate of TPH. At the beginning of 20 min, most of hydrocarbons (93.44–96.91 wt%) was removed with the temperature ranged from 200 °C to 300 °C. Besides, the initial contaminants concentration, particle size and thickness of soil slightly influenced the removal rate of TPH. Desorption kinetic study demonstrated that first-order model was well-described for desorption behavior. Response surface methodology analysis showed the temperature of 216 °C, the residence time of 21 min and the moisture content of 18% was an optimum condition recommended for potentially practical application. Under this condition, the results for the composition of hydrocarbons based on carbon number fractions indicated that the fractions of C10∼C16, C17∼C22 still existed in soil, while C23∼C28 was not detected after EMI LTTD treatment. Proposed mechanism was both hydrocarbons removed by evaporation at any temperature, while parts of heavy hydrocarbons was cracked within the soil close to induction medium, resulting in re-adsorption of light hydrocarbons. A buckwheat germination and growth test indicated that soil treated by EMI LTTD was potential in reutilization for planting.

Reclamation and reuse of graphite from electric vehicle lithium-ion battery anodes via water delamination

A simple approach to the delamination of PVDF bound graphite anode material from electric vehicle batteries is presented. This recovered graphite shows good electrochemical performance after a short low temperature thermal treatment.

Characteristics and current activation phenomenon of reduced graphite oxide membranes by low temperature thermal treatment for sodium ion battery electrodes

After self-assembly and thermal treatment at low temperature (350∘C), reduced graphite oxide membranes (RGOM) with a specific surface area of 10.6 m2g[Formula: see text] and average interlayer distance of 0.372 nm were obtained. When used as free-standing electrodes for sodium ion battery (SIB), the RGOM could not show good electrochemical performances at high current density ([Formula: see text]52 mAh g[Formula: see text] at 200 mA g[Formula: see text] and [Formula: see text]22 mAh g[Formula: see text] at 500 mA g[Formula: see text]), which may be attributed to dense structure and low specific surface area. Cyclic voltammetry (CV) results showed that the energy storage of RGOM in SIB was ions’ diffusion-dependent. Thus, when the RGOM electrodes went through repeated charge/discharge cycles at 200 mA g[Formula: see text], an obvious improvement of specific capacity was found due to increase of Na[Formula: see text] diffusion speed. After [Formula: see text]300 times charge/discharge cycles, the specific capacity of RGOM was [Formula: see text]120 mAh g[Formula: see text]. Additionally, after the current activation at 200 mA g[Formula: see text], the electrodes also showed better performances at higher current density (from [Formula: see text]85 mAh g[Formula: see text] to [Formula: see text]68 mAh g[Formula: see text] at a current density of 500 mA g[Formula: see text] during 500 times charge/discharge cycles). The current activation phenomenon maybe a promising method for using RGOM as SIB electrodes on a large scale.

NIR photoluminescence in Nd3+-doped gadolinium niobate nanophosphors modified by annealing, water, and PMMA media

The photoluminescence (PL) and structural characteristics of neodymium-doped gadolinium niobate cube-like particles are studied as a function of annealing temperature. The hydrothermally as-prepared nanophosphors contain water which can be eliminated stepwise by low-temperature thermal treatment from 120 °C to 250 °C. This water, when remains in the structure after the annealing at 500 or 800 °C, results in an increased photoluminescence emission intensity up to a factor of 4.6, implying a water-assisted energy transfer mechanism. After the thermal treatment at 500 °C, the Nd3+-doped GdNb2O6 nanophosphors have an orthorhombic aeschynite crystalline structure and near-infrared (NIR) emissions at 881 nm (first biological window) and 1071 nm (second biological window). The annealing at 800 °C results in a mainly monoclinic GdNbO4 structure with NIR PL emissions at 890 and 1065 nm. The studied NIR PL emissions are associated with interelectronic energy levels of the Nd3+ ion, excited with either 358, 586/590, or 808 nm. Given the nanoscale characteristics of these Nd3+-doped particles, they can be readily dispersed in the polymeric media, such as poly (methyl methacrylate) (PMMA), forming a strong interaction between the Nd3+-doped GdNb2O6 nanophosphors and the PMMA matrix. This interaction assists in the energy transfer to the Nd3+ ions, leading to an increase in the NIR PL emission intensity by a factor of 8. In the case of the homogeneous Gd1-xNdxNb2O6/PMMA films, the 881 nm emission peak (4F3/2 → 4I9/2 transition) is the dominant one for the 281/251 nm excitation wavelengths. These results indicate that the neodymium-doped gadolinium niobates cube-like nanophosphors have great potential to be incorporated into a wide variety of applications.

Electrolyte recovery from spent Lithium-Ion batteries using a low temperature thermal treatment process

Electrolyte recovery is seldomly considered in state-of-art lithium-ion battery recycling methods but rather evaporates and decomposes uncontrolled during the pre-treatment steps. However, controlled and safe removal of the electrolyte is inevitable and of high importance to the recycling industry to minimize the environmental impact of the recycling processes by preventing severe threats produced by the inflammable, toxic and hazardous components of the electrolyte. This study investigated the effects of temperature and process time of a low temperature thermal treatment process on electrolyte recovery. The process exhaust gases and recovered products were analyzed by In-Situ Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC–MS) to determine the effectiveness of the significant process parameters. The results show that the electrolyte solvents, which are dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC), were successfully recovered for 80 minutes of processing time at 130 °C. The LiPF6 decomposition products hydrogen fluoride (HF) and phosphoryl fluoride (POF3) were detected in the exhaust gas stream and recovered as acidic solutions. Thermal treatment below 150 °C is a promising approach for the recovery of the electrolyte solvents prior to the metal recycling stage due to its simplicity, feasibility, and environmental benefit.

Hardening of Cobalt Ferrite Nanoparticles by Local Crystal Strain Release: Implications for Rare Earth Free Magnets.

In this work, we demonstrate that the reduction of the local internal stress by a low-temperature solvent-mediated thermal treatment is an effective post-treatment tool for magnetic hardening of chemically synthesized nanoparticles. As a case study, we used nonstoichiometric cobalt ferrite particles of an average size of 32(8) nm synthesized by thermal decomposition, which were further subjected to solvent-mediated annealing at variable temperatures between 150 and 320 °C in an inert atmosphere. The postsynthesis treatment produces a 50% increase of the coercive field, without affecting neither the remanence ratio nor the spontaneous magnetization. As a consequence, the energy product and the magnetic energy storage capability, key features for applications as permanent magnets and magnetic hyperthermia, can be increased by ca. 70%. A deep structural, morphological, chemical, and magnetic characterization reveals that the mechanism governing the coercive field improvement is the reduction of the concomitant internal stresses induced by the low-temperature annealing postsynthesis treatment. Furthermore, we show that the medium where the mild annealing process occurs is essential to control the final properties of the nanoparticles because the classical annealing procedure (T > 350 °C) performed on a dried powder does not allow the release of the lattice stress, leading to the reduction of the initial coercive field. The strategy here proposed, therefore, constitutes a method to improve the magnetic properties of nanoparticles, which can be particularly appealing for those materials, as is the case of cobalt ferrite, currently investigated as building blocks for the development of rare-earth free permanent magnets.

(Invited) Metallic Impurity Control in Silicon Processing

In this paper we review the performances of a few techniques for the analysis of metal contamination in silicon. A few case studies are discussed to compare the ability of these techniques in detecting contaminants with different properties as silicon impurities. Common contaminants and elements recently introduced in the fabrication process are considered.TXRF (Total reflection X Ray Fluorescence), recombination lifetime measurement techniques, DLTS (Deep Level Transient Spectroscopy) and micro-photoluminescence analyses are compared. The results reported in this paper show that it is not possible to define a unique recipe that can be applied in all cases. Different approaches are required depending, on one hand, on the contaminant diffusivity and solubility, and, on the other hand, on the process step to be monitored.The techniques for monitoring metal contamination can schematically be divided into two main groups, one consisting of the techniques that measure the chemical concentration at the silicon surface and the other of the techniques that measure the electrical activity of the contaminant in the silicon volume.Mostly in case of metal contamination detection during wafer manufacturing, techniques which intentionally deposit thin films of polysilicon or thermal oxide and then perform chemical etching of them associated to ICP-MS analysis are also used, mostly addressed to detect fast diffusers like Cu and Ni [1], not always associated to clear electrical response. Indeed, these elements retain significant diffusivity even near room temperature, where the solid solubility is negligibly low, so they mostly segregate at the silicon surface or in getter sites, and for this reason they are hardly revealed in the silicon volume. However, these elements can be revealed by the recovery from deep depletion of MOS capacitors, because the segregated metals significantly increase the surface generation velocity.Some medium-fast diffusers like iron diffuse through several hundred microns during an ordinary thermal treatment, and mostly remain in the solid solution in silicon [1]. A comparison was carried out between TXRF and carrier recombination lifetime measurement for their ability to reveal iron contamination after a cleaning process. To prepare the samples for carrier lifetime measurements, the samples had to be thermally treated by RTP (Rapid Thermal Process). This study showed that TXRF and recombination lifetime measurements have essentially the same sensitivity to iron contamination. Vice versa, the detection of slow diffusers is found to be critical, because a very low concentration per unit area (≈107cm-2) may result in a non-negligible volume concentration in the device region (≈1010cm-3). As a consequence, the sensitivity per unit area required for these elements is difficult to reach with surface techniques such as TXRF. Molybdenum and tungsten [1] are examples of this sort. These elements do not diffuse deep enough to be efficiently revealed by recombination lifetime measurements, but they are easily revealed in the silicon volume by DLTS, which is probably the best approach for these elements, though it requires a considerable sample preparation. On the other hand, these elements are very common contaminants in ion implantation or epitaxial processes, and are very harmful for devices sensitive to carrier recombination, such as image sensors. Therefore, a technique able to detect near-surface contamination with no or limited sample preparation would be needed. Band-to-band micro-photoluminescence proved to be a good candidate, though DLTS still has the best sensitivity.Silicon contamination may also happen in the final part of the device process flow when the wafer frontside is protected by several dielectric layers and low-temperature thermal treatments only are allowed. In that case, contamination may come from the wafer backside only, but fast diffusers are still able to reach the wafer frontside and damage the device. In a study of palladium contamination from a contaminated chuck, TXRF proved not to be sensitive enough to palladium contamination. Palladium is best revealed by recombination lifetime measurements, such as the SPV (Surface PhotoVoltage) technique, but a high temperature treatment is required to activate it, so also in this case some sample preparation is required.Finally, we recall that the device itself can be a very sensitive monitor of metal contamination [2], though of course methods that prevent the impact of contamination of the device are generally preferred. The analysis of the dark current in image sensors not only reveals the presence of metal contamination (see the enclosed figure), but also provides some hints about the contaminant element.

High-Strength Glass-Ceramic Material with Low Temperature Formation

Prospects for development of glass-ceramic materials on the lithium aluminosilicates base in order to increase the reliability of armor protection elements have been analyzed. Compositions of lithium aluminosilicate glasses with low content of lithium oxide have been developed, spodumene glass-ceramic materials were obtained on their base in conditions of low-temperature thermal treatment. Formation of structure of glass-ceramic materials based on model glasses after thermal treatment has been investigated and the influence of phase composition on mechanical properties has been established. It was determined that the developed glass-ceramic materials are feasible for the application against the action of high-energy munitions with significant penetrating ability, especially when used in combination with ceramic elements.

Effect of low-temperature thermal drying on malodorous volatile organic compounds (MVOCs) emission of wastewater sludge: The relationship with microbial communities

Sludge treatment processes are the main source of nuisance odors in wastewater treatment plants. Apart from well-known odorants such as NH3 and H2S, malodorous volatile organic compounds (MVOCs) contribute largely to nuisance odors but are less concerned. In this work, the emission of MVOCs from wastewater sludges at different processing stages was measured, and the effects of dewatering and low-temperature thermal drying on the generation of sludge odor were investigated. The MVOCs were analyzed by olfactory measurements, headspace gas chromatography-coupled ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). Low-temperature thermal drying treatment changed the odor categories and increased the odor intensity (OI) from moderate level (8–9) for raw sludges to strong (>10) for dried sludge. The odor emission capacity of MVOCs, namely the concentration of MVOCs, increased for dried sludge. The major odorants of sludge after different processes included 2-MIB, geosmin, dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), hexanal, and decanal according to their odor activity values (OAVs). The bacterial community structures showed a correlation with the key MVOC odorants. Specifically, there was a significant positive correlation between the concentration of key odorants and the relative abundance of the phyla of Actinobacteria and Chloroflexi. Thus, low-temperature thermal drying had a significant effect on odor formation by acting on the microbial community of sludge.

Amorphous iron oxides anchored on BiOCl nanoplates as robust catalysts for high-performance photo-Fenton oxidation

Semiconductor supported iron oxides are highly promising catalysts to remove organic pollutants in photo-Fenton. Development of robust composite catalysts with both high activity and stability is essential. In this work, amorphous iron oxide layers are uniformly and tightly anchored on two-dimensional (2D) BiOCl nanoplates through post precipitation-deposition and subsequent low-temperature thermal treatment at 150–350 °C. A low iron loading amount (1–2 wt.%) is sufficient to make the resulted composite (BiOCl-Fe) catalysts superior in photo-Fenton oxidation of phenol (10 mg/L) with high mineralization efficiency (up to about 80% in 60 min). The low-temperature thermal treatment can significantly enhance the stability of catalysts with much less iron leached and high photo-Fenton performance maintained. The intimate contact between the amorphous iron oxide layers and the 2D BiOCl nanoplates could guarantee the fluent electron transfer and efficient activation of H2O2 at interfaces. Compared with the pristine BiOCl, the BiOCl-Fe catalysts possess faster separation of the charge carriers. The predominant active species turns from O2•– in photocatalysis to HO• in the photo-Fenton catalysis. This research could provide enhanced understanding on the synthesis of robust catalysts and the structure optimization of BiOCl supported iron oxides for photo-Fenton.

Electrodeposition of Simonkolleite as a Low-Temperature Route to Crystalline ZnO Films for Dye-Sensitized Solar Cells

A pulsed electrodeposition procedure has been developed to prepare macroporous films of the semiconducting mineral simonkolleite, Zn5(OH)8Cl2·H2O, on glass/FTO substrates. The morphology is characterized by the presence of smooth, micron-sized hexagonal platelets, and relatively thick films of 6 μm can be prepared in about 15 min. Simonkolleite can be transformed into crystalline, mesoporous ZnO using a relatively low temperature thermal treatment (250 °C). While the macrostructure of hexagonal platelets is maintained, they become mesoporous due to the removal of water and Cl−-containing reaction products. Dye-sensitized solar cells were fabricated with both simonkolleite and ZnO films, using the recently reported fully organic benzothiadiazole-based photosensitizer MG-207, and an electrolyte solution based on either the I−/I3 − or the Co(bpy)3 2+/3+ redox couple. An efficiency of 1.74% has been obtained for ZnO/MG-207/Co(bpy)3 2+/3+ solar cells, illustrating the promise of crystalline, mesoporous ZnO obtained via a low-temperature simonkolleite route for portable and lightweight devices based on flexible substrates.

Influence of heat treatment on tribocorrosion properties of Ni-B composite coatings

Various surface protection technologies, in particular, electrochemical, are used to increase the wear and corrosion resistance of steels and alloys. Composite electrochemical coatings (CEC) technology is more promising than "pure" galvanic coatings. Application of CEC increases the wear, corrosion and fatigue failure resistance of metals. Nickel often is chosen as a CEC matrix because it easily forms uniformly filled defect-free composite structures with many particles of the dispersed phase (DP).
 Physical and mechanical properties of metal coatings determine practical application of such composition. The characteristics of nickel-based CEC are: high hardness and strength, significant corrosion resistance in atmospheric environment, as well as in alkali and mild acidy environments. An effective composition coating with tribological designation can be CEC Ni-B, received in the process of electrolysis from suspension of amorphous boron in nickel electrolyte. A new composite structure of matrix filled type Ni-Ni3B is formed after heat treatment. Composition and structure of coating is determined by regimes of diffusion annealing. Ni-B coatings increase wear resistance of steel in chlorine-based environments. The influence of low-temperature thermal treatment of Ni-B CEC on steel 09Mn2Si on their tribocorrosion behavior is investigated. It is shown that the structural factor has a decisive influence on the efficiency of such friction pairs. The CEC has the least wear and the most positive compromise electrode potential after vacuum annealing at 450°C, when the initial stage of solid-phase interaction of coating components with the formation of Ni-Ni3B occurs.

Plasmonic Strain Sensors Based on Au-TiO2 Thin Films on Flexible Substrates.

This study aimed at introducing thin films exhibiting the localized surface plasmon resonance (LSPR) phenomenon with a reversible optical response to repeated uniaxial strain. The sensing platform was prepared by growing gold (Au) nanoparticles throughout a titanium dioxide dielectric matrix. The thin films were deposited on transparent polymeric substrates, using reactive magnetron sputtering, followed by a low temperature thermal treatment to grow the nanoparticles. The microstructural characterization of the thin films’ surface revealed Au nanoparticle with an average size of 15.9 nm, an aspect ratio of 1.29 and an average nearest neighbor nanoparticle at 16.3 nm distance. The plasmonic response of the flexible nanoplasmonic transducers was characterized with custom-made mechanical testing equipment using simultaneous optical transmittance measurements. The higher sensitivity that was obtained at a maximum strain of 6.7%, reached the values of 420 nm/ε and 110 pp/ε when measured at the wavelength or transmittance coordinates of the transmittance-LSPR band minimum, respectively. The higher transmittance gauge factor of 4.5 was obtained for a strain of 10.1%. Optical modelling, using discrete dipole approximation, seems to correlate the optical response of the strained thin film sensor to a reduction in the refractive index of the matrix surrounding the gold nanoparticles when uniaxial strain is applied.

Facile synthesis and characterization of ZnFe2O4/ZnO nanocomposite: An insight into structure and formation

Structural properties of nanocomposites strongly depend on preparation method as well as heat treatment and greatly affect their physical properties. This paper presents a comprehensive study on structure of ZnFe2O4/ZnO nanocomposite prepared by using a low-temperature thermal treatment process. Crystal structure, microstructure, local structure, composition, valence state, morphology, magnetic properties, and photocatalytic activities of the nanocomposite have been systematically investigated by using Fourier transform infrared spectra, synchrotron X-ray diffraction, X-ray absorption spectroscopy, field emission scanning electron microscope, vibrating sample magnetometer and UV–vis spectrophotometer. The obtained results have shown that the nanocomposite is composed of sphere-like ZnFe2O4 nanoparticles with high inversion parameter combined with rod-like nanostructures of ZnO. The nanocomposite exhibits superparamagnetic behavior at room temperature and good photocatalytic activity toward methylene blue degradation. The effects of ZnO precipitation process on structure of the ZnFe2O4 nanoparticles as well as the role of the nanoparticles in formation and growth of ZnO have been clarified based on the detailed structural information identified from synchrotron X-ray diffraction data using the Rietveld refinement method and extended X-ray absorption fine structure analysis.

Luminescence-enhanced conjugated polymer dots through thermal treatment for cell imaging.

Conjugated polymer dots (Pdots) are often used as excellent fluorescent probes in the biomedical field. In the process of preparing Pdots, the rapid change of the solvent polarity will result in a messy and defective stacking of the polymer chains in the particle, and these stacking defects of the polymer chains may weaken its luminescence properties. Here, we try to optimize the stacking of the conjugated polymer chains by the thermal annealing treatment. After the low temperature thermal treatment, the fluorescence intensity of Pdots can be enhanced by about 11%-29%, and Pdots maintain their original stability and biosafety. We used transmission electron microscopy (TEM) and single particle fluorescence imaging to reveal the possible mechanism of the chain stacking optimization process, that is, the thermal annealing process of Pdots is the competition between internal chain rearrangement in the particle and particle aggregation. The luminescence-enhanced Pdots exhibit good cellular imaging performance. These results prove that it is feasible to extend the thermal annealing treatment from planar polymer devices to polymer nanoparticles. It provides the possibility to realize stable and complex biological imaging applications using Pdots with a simple molecular structure, and a mature improvement scheme for the mass preparation of Pdots.

Hydrolysis kinetics for solubilizing waste activated sludge at low temperature thermal treatment derived from multivariate non-linear model

Low temperature thermal pre-treatment is a low-cost method to break down the structure of extracellular polymeric substances in waste activated sludge (WAS) while improving the sludge biodegradability. However, previous models on low temperature thermal pre-treatment did not adequately elucidate the behaviour of sludge hydrolysis process for the duration ranging from 5 to 9 h. Therefore, this work had developed an inclusive functional model to describe the kinetics of sludge hydrolysis for a wide range of treatment conditions (30 °C–90 °C within 0 and 16 h). As compared with treatment duration, the treatment temperature played a greater impact in solubilizing WAS. Accordingly, the 90 °C treatment had consistently produced WAS with the highest degree of solubility. Nonetheless, the mediocre discrepancies between 90 °C and 75 °C may challenge the practicality of increasing the treatment temperatures beyond 75 °C. The effects of treatment duration on soluble chemical oxygen demand, soluble carbohydrate and soluble protein were only significant during the first 4 h, except for humic substances release that continued to increase with treatment duration. Finally, a good fit with R2 > 0.95 was achieved using an inclusive multivariate non-linear model, substantiating the functionality to predict the kinetics of sludge hydrolysis at arbitrary treatment conditions.

The distribution and selective decontamination of carbon-14 from nuclear graphite

• A detailed 14 C release profile from irradiated graphite is constructed. • A reducing gradient of 14 C from gas-facing surfaces is observed and discussed. • The 14 C-enriched surface layer persists deeper than any carbonaceous deposit. • The 14 C release profile is repeatable for a given graphite source and location. This work investigates 14 C release behaviour from UK Magnox reactor sourced irradiated graphite under relatively low temperature oxidation conditions: a 1% oxygen in argon atmosphere at temperatures ranging from 600°C to 700°C, and durations from 4 to 120 hours. A method is used for construction of a detailed 14 C release profile with mass loss. The 14 C release profile is predictable between samples, and an empirical release profile is derived to predict releases to higher mass losses than in this work. An accelerated 14 C release rate at small mass losses is observed, indicative of a 14 C-enriched surface region with a depleting concentration gradient into the material, and the source terms and complexities associated with predicting where the 14 C arose from are discussed. Selective decontamination of a fraction of the 14 C is possible, with the limitation of a reducing efficiency with mass loss and time. This work demonstrates a method for determining the distribution of 14 C between near-surface regions and the bulk material in differing sources of irradiated graphite, and provides data in support of making an informed assessment for the adoption of low temperature thermal treatment and isotopic reduction of irradiated graphite wastes.

Freezing-low temperature treatment facilitates short-chain fatty acids production from waste activated sludge with short-term fermentation

This study proposed a novel and high-efficiency strategy, i.e., freezing followed by low-temperature thermal treatment, to significantly promote short-chain fatty acids (SCFAs) production from waste activated sludge compared to traditional freezing/thawing treatment. The maximal production of SCFAs was 212 mg COD/g VSS with a shortened retention time of five days, and the potentially recovered carbon source, including SCFAs, soluble polysaccharides and proteins, reached 321 mg COD/g VSS, increased by 92.1 and 28.3% compared to sole freezing and thermal treatment. Both the solubilization and hydrolysis steps of WAS were accelerated, and the acid-producing microorganisms, such as Macellibacteroides, Romboutsia and Paraclostridium, were greatly enriched, with a total abundance of 13.9%, which was only 0.54% in control. Interestingly, the methane production was inhibited at a shortened retention time, resulting in SCFAs accumulation, whereas it was increased by 32.0% at a longer sludge retention time, providing a potential solution for energy recovery from WAS.

A controllable preparation of two-dimensional cobalt oxalate-based nanostructured sheets for electrochemical energy storage

Well-defined two-dimensional (2D) cobalt oxalate (CoC2O4·2H2O) nanosheets exhibit more excellent property than common bulk cobalt oxalate due to high specific surface areas and high-efficient transport of ion and electron. However, the delicate control of the 2D morphology of CoC2O4·2H2O during their synthesis remains challenging. Herein, 2D CoC2O4·2H2O nanosheets (M1), grown by straightforward chemical precipitation, can be tuned from three-dimensional (3D) structure during their synthesis with no templates or capping agents. This control is obtained by rationally changing the ratio of reactants with ethylene glycol as solvent. Moreover, Co3O4/CoC2O4 composites (M1-250) have been fabricated through low-temperature thermal treatment of the M1 precursor in air, which possess porous surfaces with the 2D morphology maintained. Benefiting from the porous surfaces, more redox-active sites and better electrical conductivity of Co3O4, the constructed M1-250//AC aqueous device manifest improved kinetics of the electrochemistry process with energy density of 27.9 Wh/kg at 550.7 W/kg and good cycling stability with sustaining 73.0 mAh/g after 5000 cycles.