Severe Agglomeration Research Articles

Poly(glycidyl methacrylate) modified cellulose nanocrystals and their PBAT-based nanocomposites

Melt processing of cellulose nanocrystals (CNCs) reinforced nanocomposites is still a serious challenge due to the hydrophilic nature of CNCs and their severe agglomeration tendency within the polymer melt. In this study, chemical modification of CNC through grafting poly(glycidyl methacrylate) (PGMA) with various degrees was implemented. Wettability of the modified CNCs (mCNCs) were controlled and their structure was characterized through Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), optical microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The nanocomposites of polybutylene adipate terephthalate (PBAT) with 3 wt% CNC and mCNC were prepared using an internal melt mixer. To differentiate the effects of CNC and PGMA molecules on the final properties of nanocomposites, PBAT/PGMA compounds were separately prepared. To confirm the chain characterization and molecular weight of the synthesized PGMAs, 1H NMR and gel permeation chromatography (GPC) analysis were conducted. Melt rheological analysis, dynamic mechanical analysis (DMA), DSC, and atomic force microscopy (AFM) were used to monitor the mCNC dispersion quality and the effect of PGMA modification in PBAT compounds. The results revealed that grafting CNC with longer PGMA considerably improved the CNCs' dispersion quality within PBAT. Such dispersion enhancement of long-chain mCNCs and interfacial interaction of PGMA and PBAT resulted in a noticeable increase in storage modulus and complex viscosity of the final nanocomposites.

Controlled assembly of NiCo-LDH nanosheets into diverse superstructures via concentration-dependent solvothermal method for advanced supercapacitors

The tunable layer structure, composition, and diverse morphologies of layered double hydroxides (LDHs) make them a favorable choice as pseudocapacitive electrode materials for supercapacitors. However, the severe agglomeration and low conductivity of nanosheets are detrimental to obtaining excellent electrochemical performance. In this work, a controllable assembly of nanosheets was achieved by adjusting the concentrations of Ni and Co salt solutions, resulting in a series of 3D-shaped NiCo-LDHs superstructures with diverse morphologies. The prepared structures were found to significantly reduce aggregation and electron transport distance. The results approved that the diameter, thickness and interlayer space of NiCo-LDHs nanosheets and the morphologies of their self-assembled superstructures were subtly controlled, and significantly impacted their electrochemical performance. A stretch trumpet shaped flower-like superstructure in NiCo-LDH-2 was constructed by the large and ultrathin nanosheets with much more accessible active sites and larger interlayer space, which can rapidly promote electron transfer and show the highest specific capacitance of 2265 F g−1 at 1 A g−1 and retention of 86.5% at 20 A g−1. The NiCo-LDHs//AC ASC based on NiCo-LDH-2 and active carbon (AC) reveals a high specific capacitance of 298 F g−1 at 1 A g−1 and an excellent energy density of 105.0 Wh kg−1 at the power density of 820.1 W kg−1. The current work presents a simple way for controlling the nanostructure of NiCo-LDHs in the development of high-performance supercapacitors.

Facile in-suit solid-phase synthesis of carbon-coated Ni2P nanospheres decorated on carbon nanotubes with high performance in both supercapacitors and lithium-ion batteries

Low specific surface area and severe agglomeration are the main defects of the energy storage materials (ESMs) fabricated by the solid-phase synthesis (SPS) method. If these defects could be well addressed, the SPS method would be a promising method for the fabrication of high-performance ESMs with the merits of convenience, eco-friendliness, and cost-effectiveness. In this work, an in-suit solid-phase synthesis method is developed for the synthesis of the Ni2[email protected]/CNT nanocomposite with high performance in both supercapacitor and lithium-ion battery. The carbon-coated Ni2P nanospheres are in-suit synthesized and decorated successfully on the porous high-conductive CNTs framework by the proposed method. An ultra-high specific capacity of 378.5 mAh g−1 at 1 A g−1 and a good rate capacity (189.3 mAh g−1 at 20 A g−1) are presented by the synthesized nanocomposite. Meanwhile, high performance is achieved in both supercapacitor and lithium-ion battery application. Compared to the transition metal phosphide-based nanocomposites reported in literature prepared by the traditional methods, the Ni2[email protected]/CNT nanocomposite prepared by the proposed in-suit SPS method exhibits very competitive performance in both supercapacitor and lithium-ion battery. The proposed in-suit SPS method is proved to be a promising method for the preparation of high-performance ESMs.

Hydrogen bonding induced polyphosphazene/MXenes 2D/2D structure loaded with MOFs enabling fire-safe epoxy composite

High thermal runway hazard has been the blocking stone on the way of extended usage of epoxy resin (EP). In such context, the method of preparing fire retardant EP composite with inorganic filler has been adapted, and the shining star of transition metal carbides (MXenes, denoted as MX) has evoked the ardent concern. Nevertheless, the inferior flame retardation efficiency, severe agglomeration, surface scarcity of organic groups have collectively appealed to design MX based flame retardant (FR) with high efficiency. Here, the hydrogen bonding induced strategy and in-situ growth method are utilized to gain FR of P-MX@UIO. Under 2.0 wt% loading, the reductions on peak heat release rate and total heat release reach 48.9% and 45.4%. Meanwhile, the decreases in peak smoke production and total smoke production approach 48.6% and 43.6%. Also, the peak CO production rate is impaired by 48.3%. Such strengths both in suppressing heat and toxicants emissions, are vividly validated via comparison with previous works. Ulteriorly, the inhibited releases of NO and HCN are detected. Peculiarly, the storage modulus is promoted by 75.6% after incorporating P-MX@UIO. This work may inspire the judicious design of MX based FR and fire-safe polymer composites.

3D spatially-confined magnetic anodes towards advanced lithium ion batteries

Magnetic transition-metal oxides show great prospect as alternatives to prevail anodic carbonaceous substances for lithium ion battery in virtue of their splendid theoretical capacity. However, in addition to their intrinsic poor electronic conductivity, the severe agglomeration of the forming magnetic metal nanoparticles during discharging will deteriorate their actual electrochemical performance in a strong magnetic field environment. Here, we demonstrate a 3D spatially-confining magnetic anode to settle all these dilemmas, in which conversion-type magnetic Fe3O4 nanoparticles with a thin carbon encapsulation layer are anchoring onto 3D nickel nanotube arrays skeleton (Ni/Fe3O4@C NTAs). The carbon shell spatially confines the agglomeration of Fe nanoparticles and maintains the exceptional integrity of structure. The Ni/Fe3O4@C NTAs anode exhibits high-capacity lithium storage (∼1286 mAh g−1 at 0.1 C) and superior rate/cycle capability (retaining ∼97 % of initial reversible value at 1 C after long-term 1000 cycles).

Effects of Different Types of Stabilizers on the Properties of Foam Detergent Used for Radioactive Surface Contamination.

Compared with high-pressure water and reagent washing decontamination, foam decontamination has a promising application due to its ability to significantly reduce the volume of radioactive waste liquids and effectively decontaminate the inner surface of the pipes, the interior of the large cavities, and the vertical walls. However, the foam is less stable, leading to a low decontamination rate. Currently, three main types of stabilizers with different stabilizing mechanisms, namely nanoparticles, polymers, and cosurfactants, are used to improve foam stability and thus increase the decontamination rate. Nanosilica (NS), xanthan gum (XG), and n-tetradecanol (TD) were used as typical representatives of nanoparticles, polymers, and cosurfactants, respectively, to improve the stability of the foam detergent with pH < 2 and chelating agents. The differences in the effects of these three types of stabilizers on foam properties were investigated. Although NS, XG, and TD all increase the half-life of the foam from 7.2 min to about 40 min, the concentration of TD is much lower than that of NS and XG in the foaming solution, and TD foaming solution has the highest foaming ratio. Moreover, TD can markedly lower the surface tension, resulting in a significant reduction of the wetting contact angle on the surfaces of glass, ceramic tile, stainless steel, and paint, while NS and XG cannot signally change the surface tension and have no obvious effect on the wetting contact angle. At low shear rates, TD can increase the apparent viscosity of foam by two orders of magnitude, and the wall-hanging time of the foam on the vertical wall is more than 30 min. In contrast, NS and XG cause a limited increase in the apparent viscosity of the foam, and the wall-hanging times are both less than 5 min. In addition, TD foaming solution has excellent storage stability, and the storage time has no obvious effect on the performance of the foam. And after only three days of storage, NS undergoes severe agglomeration and precipitation in the foaming solution, resulting in a complete loss of the stabilizing effect. After 90 days of storage, the half-life of XG foam decreases by 26%. For simulated radioactive uranium contamination on both horizontal and vertical surfaces, TD can significantly improve the decontamination rate, especially for vertical surfaces, where TD can increase the single decontamination rate by more than 50%.

Revealing the role of hydrogen bond coupling structure for enhanced performance of the solid-state electrolyte

Achieving practical applications of PEO-based composite solid electrolyte (CPE) batteries requires the precise design of filler structures at the molecular level to form stable composite interfacial phases, which in turn improve the conductivity of Li+ and inhibit the nucleation growth of lithium dendrites. Some functional fillers suffer from severe agglomeration due to poor compatibility with the polymer base or grain boundary migration, resulting in limited improvement in cell performance. In this paper, ILs@KAP1 is reported as a filler to enhance the performance of PEO-based batteries. Thereinto, the hypercrosslinked phosphorus ligand polymer-containing KAP1, designed at the molecular level, has an abundant porous structure, hydrogen bonding network, and a rigid skeleton structure of benzene rings. These can be used both to improve the flammability with PEO-based and to reduce the crystallinity of the polymer electrolyte. Ionic liquids (ILs) are encapsulated in the nanochannels of KAP1, and thus a 3D Li+ conducting framework could be formed. In this case, it could not only facilitate the wettability of the contact interface with the electrode, significantly promoting its compatibility and providing a fast Li+ transport path, but also facilitate the formation of LiF, Li3N and Li2O rich SEI components, further fostering the uniform deposition/exfoliation of lithium. The LFP||CPE||Li battery assembled with ILs@KAP1-PEO-CPE has a high initial discharge specific capacity about 156 mAh/g at 1C and a remaining capacity about 121.8 mAh/g after 300 cycles (capacity retention of 78.07%).

CeO2-decorated reduced graphene oxide for lubricative, anticorrosive and photocatalytic purposes

CeO2 decorated reduced graphene oxide (CeO2@rGO) nanocomposites synthesized using a hydrothermal method were studied for their tribological, anti-corrosive and photocatalytic applications. Results showed that CeO2 nanoparticles with an average diameter of ∼12.24 nm were uniformly distributed and covalently bonded onto the surface of rGO. When the nanocomposites were added into PAO5w-40 lubricating oil, the coefficient of friction in the friction test was 31.9% lower than that using the pure lubricating oil. The corresponding wear mechanism was changed from oil-film lubrication to reaction film lubrication, which is mainly attributed to the filling effect of nanostructured CeO2 powers and lubrication effect of rGO. The nanocomposites were also added into chromium-free Dacromet coating and the corrosion current density in the corrosion test was decreased by an order of magnitude. This is mainly due to the formation of various chemical bonds and passivation layer on the modified coating, which improves its density. It is also attributed to the uniformly dispersed rGO, which forms a conductive channel, resulting in the preferred corrosion of the Zn–Al alloy in the coating thus achieving an effective protection effect to the substrate. When the composites were applied as the photocatalyst in an RhB solution under the irradiation of ultraviolet light, the RhB dye was effectively removed with an efficiency up to 90.5%, because the rGO can extend the life time of active electron-hole pairs and prevent CeO2 nanoparticles from severe agglomeration.

Modulating electronic structure of interfacial Fe sites in Fe2N/CoFe2O4 nano-heterostructure for enhancing corrosion-resistance and oxygen electrocatalysis in zinc-air battery

Interface engineering can regulate electronic structure of transition-metal nitrides to promote their electrocatalytic activities. However, design of iron nitride (Fe2N)-based electrocatalytic interface with desirable properties is still challenging. Here, an in-situ nucleation strategy is developed to construct the highly-dispersed Fe2N/spinal (CoFe2O4) heterojunctions to optimize the electro-conductivity and activity. The heterostructure exhibits robust activities towards ORR (half-wave potential, 0.903 V) and OER (overpotential, 300 mV). Interfacial interactions between Fe2N and CoFe2O4 mitigate the corrosion (leaching) and severe agglomeration of active components in harsh environments to stabilize the electrocatalytic activity, maintaining the integrity of heterostructure and the sustainable exposure of active sites. Theorical calculations confirm the feasibility of incorporating Fe2N into basal plane of spinal lattice (Fe2N (002) and CoFe2O4 (400) is well matched). Modulated electronic state optimizes the adsorption/desorption strength of O-intermediates on the interfacial Fe-sites (the main active sites) of Fe2N/CoFe2O4 for both ORR and OER. Strong coupling of Fe2N and CoFe2O4 bolsters the charge-transfer across the interfaces to substantially accelerate the ORR/OER kinetics. Notably, by vital of a small potential-gap (0.634 V), it displays excellent power-density (225 mW cm−2) and cycling-stability (280 h) in zinc-air battery. This work enriches the understanding of electronic structure modulation of hetero-structured nitride/spinel-based electrocatalysts.

Breaking Boundaries in LED Technology: Exploring the Revolutionary Diode Characteristics of Screen Printed (TiO2)1−x (CuO)x Thick Films

A thick TiO2-CuO composite film is deposited on a Si substrate by a low-cost screen printing method. Both anatase and CuO-doped TiO2 are characterized for diode applications. X-ray Diffraction (XRD) confirms that the composite film exists as an anatase phase of TiO2 and a monoclinic phase of CuO with a maximum diffraction of (101) plane. SEM images depict the less severe agglomeration of particles for the doped TiO2 as compared to the anatase TiO2. The UV–visible spectra reveal a direct band gap shift of 3.35 eV (pure TiO2) to 3.26 eV (doped TiO2). From the PL study, the blue shaded emission is perfectly derived for anatase TiO2 while the color is seen to change to the white zone supporting TiO2-CuO composite formation as depicted by the CIE diagram. The diode parameters such as ideality factor (n) and barrier height (Φb) are calculated with the help of I–V characteristics. This only reported novel effort on screen-printed TiO2-CuO thick film may help in manufacturing possible LEDs for optoelectronic applications.

Unique roles of exfoliated bentonite in S-scheme BiOBr/Bi2MoO6 heterojunction for boosted ciprofloxacin degradation

S-scheme heterojunction retained the strong redox potential of catalysts, yet confronting severe photocorrosion and particle agglomeration, resulting in poor stability. Herein, the dual Bi-based S-scheme heterojunction supported by exfoliated bentonite (BiOBr/Bi2MoO6/BTex) was fabricated via a facile microwave hydrothermal strategy. BTex could promote the dispersion of photocatalysts and reinforce heterojunction stability through intensive surface interaction, thus reducing leakage of metal ions. The optimal BiOBr/10% Bi2MoO6/BTex exhibited excellent visible light photocatalytic performance and 94% ciprofloxacin (CIP) could be degraded within 120 min. Furthermore, the high catalytic efficiency could be maintained within the pH range from 5 to 9, and efficient degradation of tetracycline and dyes could also be achieved. Basing the analysis of band structures and determination of active species, enhanced separation and migration efficiency of photogenerated carriers could be ascribed to the synergistic effect of internal electron field (IEF) from heterojunction and surface charge repulsion from BTex. Additionally, the susceptible sites of CIP were obtained by density functional theory calculations, and three possible degradation pathways, including breakage of the quinolone ring, oxidation of the piperazine ring and defluorination were speculated combined with HPLC-MS results. With prolonging photocatalysis time, the diminished toxicity of intermediates was confirmed. This study supplied new insights to improve performance and control morphology of S-scheme heterojunctions by introducing cost-effective nature bentonite.

Densification kinetics and sintering behavior of UO2 and 0.5 wt.%MnO‐doped UO2

AbstractIn this work, the sintering kinetics of pure UO2 and 0.5 wt.%MnO‐doped UO2 was studied by a high‐temperature dilatometer heated up to 1500°C. In addition, the sintering behavior of pure UO2 and 0.5 wt.%MnO‐doped UO2 was studied by pressureless sintering technique. The results showed that MnO doping enhanced the grain boundary diffusion of UO2, which can effectively decrease the densification temperature and promote grain growth. The sintering temperature of UO2 was significantly reduced by about 200°C with the addition of 0.5 wt.%MnO. The microscopic morphology studies showed that there were still fine particles agglomerated, forming sintered spheres in the matrix even if no severe agglomeration and bimodal size distribution were observed in raw UO2 powder. The microstructure evolution of the sintered sphere and UO2 matrix during the densification process was studied by isothermal sintering. Finally, the present analyses indicated that the densification of UO2 matrix can be accelerated by adding MnO or increasing the sintering temperature, thus improving the densification inhomogeneity of UO2 matrix.

Effects of sodium carboxymethyl cellulose and poly (acrylic acid) on the agglomeration behavior of aqueous silicon suspensions

We investigate the effects of carboxymethyl cellulose (CMC) and poly (acrylic acid) (PAA) on the dispersion state of silicon particles and the mechanism thereof. Here, we report severe agglomeration of silicon particles induced by the hydrophobic interaction arising from CMC(degree of substitution; DS 0.7). Although the adsorption amount of CMC (DS 0.7) onto the silicon surface is comparable to that of PAA, its effect on particle dispersion is significantly different. The agglomeration mechanism is systematically explored in terms of polymer-polymer and particle-polymer interactions by varying the DS of CMC and the pH of the suspensions. We demonstrate that the attraction between polymers adsorbed on the silicon surface and the affinity between the particle and polymer determine the degree of silicon agglomeration. The hydrophobic attraction of CMC(DS 0.7) promotes silicon agglomeration significantly, whereas CMC(DS 1.2) deficient in attraction disperses silicon particles well. Silicon particles weakly agglomerate in Si/PAA suspensions due to hydrogen bonding between PAA chains and due to the high affinity between PAA and the silicon surface. The dispersion of Si/CMC(DS 0.7 or 1.2)/PAA suspensions is primarily dominated by PAA through its high affinity with silicon and corresponding favorable adsorption on the silicon surface. This is the first attempt to quantitatively assess and compare the impact of CMC and PAA on the agglomeration behavior of silicon particles and reveal the underlying mechanism. This paper provides a fundamental understanding to control the dispersion homogeneity and stability of silicon-containing electrodes.

Evaluation of mechanical and corrosion properties of AZ91-GNP nanocomposites fabricated using the SMART/MA process

Mg and its alloys are lightweight metallic materials with a low density and high specific strength. The Mg alloy AZ91 is used as a lightweight structural material in automobiles because of its high mechanical strength and corrosion resistance. In Mg-based nanocomposites, wherein graphene nanoplatelets (GNPs) are added as reinforcement materials to the AZ91 matrix, severe agglomeration occurs in the process of mixing the GNPs and Mg alloy powders owing to extensive van der Waals bonds between the GNP layers. This agglomeration of GNPs in the Mg alloy acts as a crack initiation site and lowers the mechanical properties and corrosion resistance of the alloy. In this study, a double-powder mixing process called SMART/MA is developed to inhibit GNP agglomeration. This process produces an AZ91-based composite with a few layers of GNP evenly dispersed throughout the matrix, which improves its mechanical properties and corrosion resistance.

Bi/Bi3Se4 nanoparticles embedded in hollow porous carbon nanorod: High rate capability material for potassium-ion batteries

Considering their superior theoretical capacity and low voltage plateau, bismuth (Bi)-based materials are being widely explored for application in potassium-ion batteries (PIBs). Unfortunately, pure Bi and Bi-based compounds suffer from severe electrochemical polarization, agglomeration, and dramatic volume fluctuations. To develop an advanced bismuth-based anode material with high reactivity and durability, in this work, the pyrolysis of Bi-based metal–organic frameworks and in-situ selenization techniques have been successfully used to produce a Bi-based composite with high capacity and unique structure, in which Bi/Bi3Se4 nanoparticles are encapsulated in carbon nanorods (Bi/Bi3Se4@CNR). Applied as the anode material of PIBs, the Bi/Bi3Se4@CNR displays fast potassium storage capability with 307.5 mA h g−1 at 20 A g−1 and durable cycle performance of 2000 cycles at 5 A g−1. Notably, the Bi/Bi3Se4@CNR also showed long cycle stability over 1600 cycles when working in a full cell system with potassium vanadate as the cathode material, which further demonstrates its promising potential in the field of PIBs. Additionally, the dual potassium storage mechanism of the Bi/Bi3Se4@CNR based on conversion and alloying reaction has also been revealed by in-situ X-ray diffraction.

Facile synthesis of high-entropy zirconate nanopowders and their sintering behaviors

The challenge in synthesizing high-entropy ceramic (HEC) nanopowders is to suppress severe grain coarsening and particle agglomeration, which occur at elevated temperatures. This challenge could be addressed by the polyacrylamide gel method. In this work, single-phase high-entropy (La_0.2Nd_0.2Sm_0.2Gd_0.2Yb_0.2)₂Zr₂O₇ and (La_0.2Nd_0.2Y_0.2Eu_0.2Gd_0.2)₂Zr₂O₇ nanopowders without agglomeration were successfully synthesized using the polyacrylamide gel method for the first time. The results showed that phase composition, particle size, and agglomeration degree of the nanopowders were greatly influenced by the molar ratio of acrylamide (AM)/Zr and calcination temperature. These as-synthesized high-entropy zirconate (HEZ) nanopowders could be sintered into fully dense ceramics at 1500 ℃ for 2 h. These HEZ nanopowders showed a phase transformation from a defect-fluorite phase to a pyrochlore phase with the increase of sintering temperature. Additionally, two-step sintering of these nanopowders was conducted, and the HEZ ceramics with fine grains were prepared. The polyacrylamide gel method is simple and easily operated, which is a facile approach of producing the HEC nanopowders with excellent sinterability.

2-Dimensional g-C3N4 nanosheets modified LATP-based “Polymer-in-Ceramic” electrolyte for solid-state lithium batteries

Composite polymer electrolytes (CPEs) are gaining increasing interest due to their combined advantages of polymer and inorganic ceramic. “Polymer-in-Ceramic” (PIC) system containing a large portion of ceramic fillers (higher than 50 wt%), possesses superior safety, electrochemical and mechanical properties, which render it a promising strategy for mass production of inorganic ceramic electrolytes. However, the poor organic-inorganic interface compatibility between polymer and ceramic leads to severe agglomeration of ceramic fillers within the polymer electrolyte, resulting in cracks in the membrane that impedes the transportation of lithium ions. Thus, two-dimensional (2D) g-C3N4 nanosheets are introduced into the PIC-type electrolyte as a bridge between the organic and inorganic components to improve the homogeneity of the electrolyte membrane and build an effective transportation network. In this work, a PIC type g-C3N4/ Li1.3Al0.3Ti1.7(PO4)3(LATP)/Poly(vinylidene fluoride) (PVDF) electrolyte membrane with a thickness of 35.2 µm is prepared via a simple solution-casing method and delivers satisfactory all-around properties (a high conductivity of 5.9 × 10−4 S cm−1 at 25 ℃, a high lithium-ion transference number of 0.63 and superior thermal stability). To further evaluate its practicability, a solid-state lithium battery of LiNi0.8Mn0.1Co0.1O2|CPEs|Li is assembled and provides good cycling and rate performance at room temperature. This work proves the effectiveness of the 2D g-C3N4 nanosheets in resolving the agglomeration issue and optimizing the electrochemical properties of LATP-based polymer-in-ceramic electrolyte, which provides a universal strategy to modify the PIC-type solid-state electrolytes.

Grain Boundary-Rich Copper Nanocatalysts Generated from Metal-Organic Framework Nanoparticles for CO2 -to-C2+ Electroconversion.

Due to severe contemporary energy issues, generating C2+ products from electrochemical carbon dioxide reduction reactions (eCO2 RRs) gains much interest. It is known that the catalyst morphology and active surface structures are critical for product distributions and current densities. Herein, a synthetic protocol of nanoparticle morphology on copper metal-organic frameworks (n-Cu MOFs) is developed by adjusting growth kinetics with termination ligands. Nanoscale copper oxide aggregates composed of small particulates are yielded via calcining the Cu-MOF nanoparticles at a specific temperature. The resulting nanosized MOF-derived catalyst (n-MDC) exhibits Faradaic efficiencies toward ethylene and C2+ products of 63% and 81% at -1.01V versus reversible hydrogen electrode (RHE) in neutral electrolytes. The catalyst also shows prolonged stability for up to 10h. A partial current density toward C2+ products is significantly boosted to -255mA cm-2 in an alkaline flow cell system. Comprehensive analyses reveal that the nanoparticle morphology of pristine Cu MOFs induces homogeneous decomposition of organic frameworks at a lower calcination temperature. It leads to evolving grain boundaries in a high density and preventing severe agglomeration of copper domains, the primary factors for improving eCO2 RR activity toward C2+ production.

Microwave drying method investigation for the process and kinetics of drying characteristics of high-grade rutile TiO2

Titanium dioxide has been extensively applied in aviation, cosmetics, the chemical industry, and coatings. Currently, the primary way to prepare high-grade rutile TiO2 is the chlorination method, which mainly uses ilmenite or titanium slag as raw material through the chlorination process and then reacts it in an oxidation furnace to prepare titanium powders. However, the TiO2 material produced by the liquid-phase method contains a large amount of water, which makes the equipment vulnerable to corrosion in the subsequent process. Meanwhile, the sharp temperature change will lead to the accumulation of water vapor, which may lead to explosion and severe agglomeration, resulting in high research costs and reduced product performance. Therefore, drying equipment with high drying efficiency, high product quality, and low carbon is urgently needed. This paper used microwave drying equipment to assist in drying rutile TiO2 powders. Results indicated that the microwave power, moisture content, and initial mass positively related to the drying rate. The drying process was simulated and analyzed using four common thin-layer kinetic models. A good agreement was that the Modified Page model was in good agreement with the actual drying process of TiO2. The effective diffusion coefficient was calculated. After calculation, the activation energy of microwave-drying TiO2 was 8.22 g/W. This article offers a kinetic theoretical basis and abundant data guidelines for actual products to reinforce the drying of high-grade TiO2 powders.

Interaction behavior of sand-diluted and mixed Fe-based oxygen carriers with potassium salts

Oxygen carriers, in the form of metal oxide particles, are bed materials that transport oxygen in solid form in fluidized bed applications, such as in chemical-looping applications. In biofuel applications, it is well known that alkali from the fuel ash can react with the bed material and cause, among other operation issues, agglomeration. When using oxygen carriers in a fluidized bed, it is likely that the bed material is either a mixture of different metal oxide materials or partly diluted with sand. This is to improve or combine the chemical properties of the materials used or simply for economic reasons.This work investigates how three potassium salts K2CO3, K2SO4 and KH2PO4 interact with the oxygen carriers: Steel converter slag (LD slag), ilmenite, mixtures of the two and each carrier diluted with silica sand. The salts were used as model compounds that can occur in biofuel ash. The set-up used was a fixed bed where a small sample of bed material is mixed with a potassium salt equivalent to 4 wt-% of potassium. The mixture was then exposed to reducing (H2 in steam) conditions at 900 °C during several hours in a tubular furnace. This provides a worst-case scenario for solid–solid interaction in a fluidized bed. If a solid–solid reaction does not take place in this setup, it will most likely never occur in a fluidized bed.When LD slag and ilmenite were combined, the potassium from the salts would prefer to accumulate in the ilmenite rather than the LD slag. Ca from LD slag interacted with KH2PO4 resulting in a less severe agglomeration than when ilmenite was used separately with the same salt. When the oxygen carriers were diluted with silica sand, potassium salt interaction resulted in agglomeration for both the oxygen carriers with all potassium salts. K2CO3 and K2SO4 formed potassium silicates, while KH2PO4 formed a phosphorus-containing melt. When LD slag was present, phosphorus was located in a K-Ca-P phase that was not present if ilmenite was present.