Thermochemical Stability Research Articles

High-surface β-Ketoenamine linked covalent organic framework driving broad-spectrum solid phase microextraction on multi-polar aromatic esters

Aromatic esters have been widely used in daily life with non-ignorable dangers, such as plasticizer, flavor, and preservative. Their wide applications and corresponding hazards caused by overuse have promoted the rapid development of sensitively analytical method for effective regulation. However, the variety makes it challenging for broad-spectrum and simultaneous extraction of diverse aromatic esters from the highly complex cosmetic samples. To our delight, a covalent organic framework, named DaTp (1, 3, 5-triformylphloroglucinol-2, 6-diaminoanthracene), possessing high specific surface, excellently thermochemical stability, and abundant electron-rich heteroatoms, has been synthesized and fabricated as a competitive solid phase microextraction coating for extracting the trace analytes with diverse polarity, through the hydrophobic interaction, π-π conjugation and hydrogen bond. Herein, this self-made SPME fiber has been further coupled with gas chromatography-tandem mass spectrometry (GC-MS) to determine the multi-polar aromatic esters in cosmetics packaged with plastic. This developed analytical method showed wide liner ranges, low limits of detection, good repeatability and reproducibility. Finally, the aromatic esters in four cosmetic samples were quantified precisely with satisfactory recoveries (80.7%–118%).

Adsorption and removal of organophosphorus pesticides from Chinese cabbages and green onions by using metal organic frameworks based on the mussel-inspired adhesive interface

Based on the mussel-inspired adhesive interface (Fe3O4-g-C3N4@PDA), a novel bionic metal–organic framework (Fe3O4-g-C3N4-PDA@MIL-101) was successfully prepared. The composite featured a high specific surface area and a multi-microchannel structure, as well as strong thermochemical stability. The structural property of Fe3O4-g-C3N4-PDA@MIL-101(Fe) was characterized, and the results indicated that Fe3O4, PDA, and MIL-101(Fe) were uniformly coated on the g-C3N4 surface. The adsorption and desorption of organophosphorus pesticides with Fe3O4-g-C3N4-PDA@MIL-101(Fe) were evaluated by batch experiments. This composite showed high adsorption efficiency and selective removal of coralox, phosalone, and chlorpyrifos. Under the optimal conditions, three organophosphorus pesticides were adsorbed from Chinese cabbage and green onion samples with Fe3O4-g-C3N4-PDA@MIL-101(Fe). The analytical method exhibited high sensitivity (LOD, 0.19–2.34 μg/L; LOQ, 0.65–7.82 μg/L), excellent practicality, and good stability, suggesting that Fe3O4-g-C3N4-PDA@MIL-101 was an ideal candidate magnetic adsorbent for the removal of organophosphorus pesticides in Chinese cabbage and green onion samples.

Thermal Stability and Thermodynamic Performances of Pure Siloxanes and Their Mixtures in Organic Rankine Cycles

Organic Rankine cycles are often the best solution for the conversion of thermal energy. The many working fluids include silicon oils. One crucial issue that determines the choice of a working fluid is its thermochemical stability, as this sets a limit to the maximum temperature at which the fluid can be used in a power plant. A second subject, much debated today, is the use of mixtures in ORCs. In the first part of this study, an investigation into the thermal stability of siloxanes using two different approaches was carried out. The results confirmed a limit working temperature for the considered siloxanes of about 300 °C, with a degradation that advanced significantly over time at 350 °C. In the second part of the study, an analysis of the thermodynamic performances of some siloxane mixtures was carried out. It was found that the efficiencies of the corresponding thermodynamic cycles were substantially the same as for the pure fluids used today. By changing the composition of the mixture, it was also possible to vary, within reasonable limits, the values of the condensation pressure, adapting the thermodynamic cycle to the different situations that can be encountered in current practice.

Advances in Graphene-based Materials for Dye-sensitized Solar Cell Components, Electronic Devices and Prospective Applications: A Critical Review

Abstract: The investigation of a Dye-Sensitized Solar Cell (DSSC) as an alternative approach to the conventional photovoltaic cell (silicon-based) is attracting remarkable attention recently. This stems from the excellent optical properties of graphene, such as impressive transparency, conductance in near-infrared and visible light spectrums, along with its thermochemical stability, as reported in the literature. However, the main limitation of graphene production is the lack of suitable methods for its industrial-scale synthesis. Consequently, the research on industrial applications of graphene development and understanding of how to pragmatize existing theoretical approaches are still ongoing in the related research domain. This is exemplified in single, few, and adhesive layer mechanical cleavage graphene methods, which are not yet practicable, as these methods will restrict the chance for scaling up. These limitations and inadequate reviews on graphene development impelled the authors to compile the advances in graphene synthesis, properties, recent applications, and future directions. The mechanical exfoliation synthesis technique delivers quality graphene films sized from 5 to 10 μm. Graphene-TiO2 hybridization was also found to possess efficiency acclivity as high as 39%. This review provides significant implications for a better understanding of graphene performance indicators and insight for future research in photovoltaic or optical modulation devices.

Advancement in field of Energy storage applications by using Ionic Liquids

Now-a-days the storage and power demands are increasing at a very rapid speed and system has evolved in the form of batteries and other storage devices which lacks some safety measures as well as electrochemical stability factors. As a class of novel media, Ionic liquids pursuing a specific set of properties had made them suitable for a number of energy related applications and modifications in their properties. So to overcome the challenges faced by the storage device, substitution of electrolytes of these devices by Ionic liquid mainly known as green solvents, has proven out to be a promising field by enhancing their properties.This article throws a light on the advancement and development of energy storage applications by the material used i.e., Ionic liquids providing a stable and friendly electrolyte system along with the modified storage system with increased thermochemical and other stability factors.

Enhanced optical nonlinearity and ultrafast carrier dynamics of TiO2/CuO nanocomposites

Transition metal oxides (TMOs) are drawing multitudinous interest due to their strong thermochemical stability. In the present work, we proposed a facile strategy to fabricate TiO 2 /CuO nanocomposites. By using the conventional open- and closed-aperture Z-scan technology, the eminent nonlinear optical (NLO) properties of the as-prepared TiO 2 /CuO nanocomposites were demonstrated. In order to deeply investigate the NLO enhancement mechanism, we established a theoretical model to study the photogenerated carriers transfer dynamics at the interface with rate equations and the fouth-order Runge-Kutta algorithm. The simulation results indicated that under pumping irradiation, the carriers transferring from CuO to TiO 2 promoted the nonlinear optical absorption of CuO nanosheets and increased the modulation depth. Experimentally, the transient absorption spectroscopy and broadband time-resolved pump-probe measurements were presented to study the role of the carrier dynamics in the broadband near-infrared region. To further confirm the enhanced NLO response in TiO 2 /CuO nanocomposites, a highly stable dissipative soliton mode-locked Yb-doped fiber laser with TiO 2 /CuO saturable absorber was constructed at 1 μm for the first time. Our work manifested the key effects of the interface in TiO 2 /CuO nanocomposites to boost the NLO features which can be applied in ultrafast photonics applications.

Assessing pyrolysis behavior of silicon-containing arylacetylene resin via experiments and ReaxFF MD simulations

Silicon-containing arylacetylene resin (PSA), a thermosetting organic-inorganic hybrid resin of high heat-resistance performs well in ablation process, whereas its pyrolysis behavior under high temperature has not been fully interpreted. Herein, the PSA pyrolysis process was in-depth investigated by experiments and ReaxFF molecular dynamics simulation (ReaxFF-MD). TG results show that the temperature of 5% weight loss (Td5) is above 600 ℃, and the residue at 900 ℃ surpass 85%, demonstrating PSA has excellent heat resistance and thermal stability. The on-line FTIR and out-line gas quantify analysis reveals that H2 and CH4 are dominant gaseous products, which are also unveiled by ReaxFF-MD simulation. Molecular reaction tracking indicates PSA pyrolysis is initiated by the cleavage of skeleton in benzene ring, the cleavage of C-C bond and C-Si bond in main chain at elevated temperature. Hydrogen abstraction reactions are primary formation pathways of CH4 and H2, together with conquering high energy barriers. The activation energy of PSA pyrolysis in experiments is 155 kJ/mol, agreeing well with that from ReaxFF MD simulations (144 kJ/mol), which further confirms the thermochemical stability of cured PSA that rich in highly crosslinked aromatic structure. Besides, the influence of silicon side-groups on PSA pyrolysis is screened by MD and results indicate that gases evolution depended largely on side-groups types and decreasing side phenyl groups in PSA is benefit for improving its thermal stability. This work deepens the understanding of PSA pyrolysis mechanism and provides theoretical guidance for improving its heat resistance.

Synthesis and Characterization of Gadolinium-Doped Zirconia as a Potential Electrolyte for Solid Oxide Fuel Cells

Zirconia-based composites with high thermochemical stability and electrochemical activity are the most promising solid electrolytes for manufacturing solid oxide fuel cells (SOFCs). In the present work, nanocrystalline composite powders of gadolinium-doped zirconia (GDZ: Gd2xZr2(1−x)O4−x) with various doping fractions (0.01 ≤ x ≤ 0.16) were synthesized by the Pechini method and applied for the fabrication of several electrolyte pellets to evaluate their physicochemical properties, sinterability, and conductivity. The X-ray diffraction (XRD) patterns and the thermogravimetry/differential thermal analysis (TGA/DTA) of the synthesized powders confirmed the successful formation of nanocrystalline GDZ in the tetragonal phase with complete substitution of gadolinium phase into the zirconia (ZrO2) lattice. The synthesized gadolinium zirconate powders were then shaped into pellet forms using the tape casting method, followed by sintering at 1300 °C (for 2.5 h). The microstructural analysis of the electrolyte pellets showed suitable grain boundary welding at the surface with an acceptable grain growth at the bulk of the T-phase GDZ samples. The impedance measurements indicated that the T-phase GDZ-8 could provide a comparably higher ionic conductivity (with 7.23 × 10−2 S/cm in the air at 800 °C) than the other dopant fractions. The results of this work can help better understand the characteristics and electrochemical performance of the T-phase gadolinium zirconate as a potential electrolyte for the fabrication of SOFCs.

In Situ Exsolution Catalyst: An Innovative Approach to Develop Highly Selective and Sensitive Gas Sensors.

The gas sensing characteristics of oxide semiconductors can be enhanced by loading noble metal or metal oxide catalysts. The uniform distribution of nanoscale catalysts with high thermal stability over the sensing materials is essential for sensors operating at elevated temperatures. An in situ exsolution process, which can be applied to catalysts, batteries, and sensors, provides a facile synthetic route for developing second-phase nanoparticles with uniform distribution, excellent thermochemical stability, and strong adhesion to the mother phase. In this study, we investigated the effect of Co-exsolved nanoparticles on the gas sensing characteristics of La0.43Ca0.37Co0.06Ti0.94O3-d (LCCoT). The amount and size of the Co-exsolved nanoparticles on the surface of the perovskite mother phase were adjusted depending on the reduction temperature of the exsolution process. The LCCoT with Co-exsolved nanoparticles prepared by reduction at 700 °C exhibited a response (resistance ratio) of 116.3 to 5 ppm ethanol at 350 °C, which was 10-fold higher than the response of a sensor without exsolution. The high gas response was attributed to the catalytic effect promoted by the uniformly distributed Co-exsolved nanoparticles and the formation of p-n junctions on the sensing surface during reduction. Additionally, we demonstrated the catalytic effect of Co-exsolved nanoparticles using a proton transfer reaction-quadrupole mass spectrometer. By controlling the amount and distribution of exsolved nanoparticles on semiconductor chemiresistors, a new pathway for designing high-performance gas sensors with enhanced thermal stability can be achieved.

Quantification of complex protective surface oxide layer formed during plasma jet exposure of multicomponent ultra-high temperature carbides

Multi-component ultra-high temperature ceramics (MC-UHTCs) has garnered attention due to their improved thermo-mechanical and oxidation properties. MC-UHTC was progressively formed by adding a UHTC component at each step, producing binary, ternary and quaternary UHTC systems, processed by spark plasma sintering (SPS).We investigate the role of multi-elements and thermochemical stability of the surface oxide layer formed during plasma arc jet exposure (T > 2500 °C) of MC-UHTCs using core-level X-ray photoelectron spectroscopy (XPS) correlated with the structural investigation. The results indicate that adding a UHTC component improves oxidation resistance due to the assemblage of refractory phases forming complex mixed oxides via preferential oxidation. XPS spectra of Ta4f, Nb3d, Ti1p, and Hf4f showed that the nature of the chemical bonds switched from metal carbides to metal oxides (and metal oxy-carbides) in the binary system with retained metal carbides in ternary and quaternary UHTCs. The absence of a metal carbide peak in the high-resolution C1s scan of the binary system also supports this finding. The principal complex mixed oxide phases emanated in the exiguous oxidation of MC-UHTCs are quantified using Rietveld analysis. Overall, this study suggests that MC-UHTC is a promising material for possible application in thermal protection systems (TPS).

Predicting the Probability of Observation of Arbitrary Graphene Oxide Nanoflakes Using Artificial Neural Networks

AbstractAlthough it has been well established that the stability and properties of graphene oxide nanostructure are strongly influenced by the concentration, type, and distribution of oxygen groups on the surface, there has yet to be a definitive way of predicting the thermochemical stability in advance of detailed and time‐consuming experimentation or simulation. In this study, a data set of over 60 000 unique graphene oxide nanoflakes and supervised machine learning methods are used to predict the probability of observation (stability) with perfect accuracy, based on a limited set of structural features that can be controlled in advance. A decision tree is used to show how the features determine the stability, and a neural network provides an equation to predict the thermodynamic stability of virtually any configuration in minutes. This enables researchers to use machine learning as research planning tool or to assist in analyzing results from microanalysis.

High-entropy ceramics: Propelling applications through disorder

Disorder enhances desired properties, as well as creating new avenues for synthesizing materials. For instance, hardness and yield stress are improved by solid-solution strengthening, a result of distortions and atomic-size mismatches. Thermochemical stability is increased by the preference of chemically disordered mixtures for high-symmetry superlattices. Vibrational thermal conductivity is decreased by force-constant disorder without sacrificing mechanical strength and stiffness. Thus, high-entropy ceramics propel a wide range of applications: from wear-resistant coatings and thermal and environmental barriers to catalysts, batteries, thermoelectrics, and nuclear energy management. Here, we discuss recent progress of the field, with a particular emphasis on disorder-enhanced properties and applications.

ZrO2 Matrix Toughened Ceramic Material‐Strength and Toughness

ZrO2 ceramic exhibits the characteristics of high hardness, good thermochemical stability, desirable biocompatibility, and unique stress‐activated tetragonal to monoclinic transformation toughening, thus having broad development prospects. However, as a typical ceramic material, it has the common shortcoming of brittleness and seriously limits the possible applications. In recent years, worldwide efforts have been made to improve the toughness of ZrO2 ceramic materials, which has great significance in promoting its industrial application. Herein, the influences of phase composition, stabilizer, grain size, and sintering method on fracture toughness of ZrO2 ceramic are introduced. The mechanism of phase transformation toughening, single‐phase and multiphase material dopant toughening, and lamellar ceramic toughening are also summarized. Moreover, the prevailing applications of toughened ZrO2‐based materials in structural ceramics, coatings, and biomaterials are discussed. The present review may offer insights in designing and fabricating ZrO2 materials with high strength and toughness to provide better performances in diverse applications fields.

Desalination Characteristics of Cellulose Acetate FO Membrane Incorporated with ZIF-8 Nanoparticles.

Forward osmosis membranes have a wide range of applications in the field of water treatment. However, the application of seawater desalination is restricted, so the research of forward osmosis membranes for seawater desalination poses new challenges. In this study, zeolitic imidazolate framework-8 (ZIF-8) was synthesized by a mechanical stirring method, and its crystal structure, surface morphology, functional group characteristics, thermochemical stability, pore size distribution and specific surface area were analyzed. The cellulose acetate (CA)/ZIF-8 mixed matrix forward osmosis membrane was prepared by using the synthesized ZIF-8 as a modified additive. The effects of the additive ZIF-8 content, coagulation bath temperature, mixing temperature and heat treatment temperature on the properties of the CA/ZIF-8 forward osmosis membrane were systematically studied, and the causes were analyzed to determine the best membrane preparation parameters. The structure of the CA membrane and CA/ZIF-8 mixed matrix forward osmosis membranes prepared under the optimal conditions were characterized by Fourier Transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), contact angle and Atomic force microscope (AFM). Finally, the properties of the HTI membrane (Membrane manufactured by Hydration Technology Innovations Inc.), CA forward osmosis membrane and CA/ZIF-8 mixed matrix forward osmosis membrane were compared under laboratory conditions. For the CA membrane, the water flux and reverse salt flux reached 48.85 L·m−2·h−1 and 3.4 g·m−2·h−1, respectively. The reverse salt flux and water flux of the CA/ZIF-8 membrane are 2.84 g·m−2·h−1 and 50.14 L·m−2·h−1, respectively. ZIF-8 has a promising application in seawater desalination.

Cross‐linked boron nitride‐piperazine amide thin film nanocomposite membranes for rejection and concentration of per‐ and poly‐fluoroalkyl substances (PFAS)

Per- and poly-fluoroalkyl substances (PFAS)-contaminated wastewaters present major public health risks given the PFAS thermo-chemical stability and its demonstrated adverse impacts on aquatic life, extended to the entire food chain. To date, remediation of PFAS-contaminated wastewaters have been mainly undertaken with poorly cost-effective strategies, involving multi-step processes. Advanced separation systems enabling the selective capture and concentration of PFAS must be developed. In this work, the potential of nanofiltration (NF) membranes to reject short chain length PFAS, potassium nonafluoro-1-butanesulfonate (C4F9SO3K), is demonstrated with both bare polymeric and amine functionalized-boron nitride BN(NH2) nanosheet-decorated membranes. The BN(NH2)-decorated membranes exhibited almost 1.04 times higher permeation upon C4F9SO3K filtration compared to the bare poly(piperazine amide) (PPA) membranes (53 versus 26 L m−2 h−1), while maintaining very high C4F9SO3K rejection levels above 93%. A commercial membrane exhibited similar permeation to BN(NH2)-decorated membrane, but only retained ∼65% of the C4F9SO3K. The improved filtration performance of the BN(NH2)-decorated membrane was rationalized based on advanced characterization results to its enhanced wettability and negative charge density, resulting in weak interactions between the C4F9SO3K and BN(NH2) nanosheets. This communication demonstrates the role and potential of fine surface modifications of NF membranes to support improved separation performance towards PFAS removal.

Carboxylate‐Functionalized Zeolitic Imidazolate Framework Enables Catalytic N‐Formylation Using Ambient CO2

AbstractCatalytic upgrading of CO2 into value‐added chemicals to build the excess carbon cycle is of great significance. In this work, carboxylate‐functionalized zeolitic imidazolate framework (F‐ZIF‐90) with good crystallinity and porosity is constructed from ZIF‐90 and employed as a robust heterogeneous catalyst to boost the reductive N‐functionalization of various amines with CO2 to furnish N‐formyl compounds (up to 99% yield) in the presence of PhSiH3 under an ambient environment. The imidazole carboxylate species (COO‐) can not only activate hydrosilane and CO2 to form the key intermediate formoxysliane but also activate amines to participate in the N‐formylation reaction to obtain the target product. Moreover, it can enhance the catalyst capture and exchange ability toward ambient CO2. The powerful adsorption capacity of the F‐ZIF‐90 catalyst toward CO2 is conducive to elevating CO2 concentration around the active species. Theoretical calculations show that the carboxylate‐mediated conversion path undergoes the transition state of hydrosilane activation with a relatively lower energy barrier (ΔG = 26.9 kcal mol–1). F‐ZIF‐90 exhibits good thermochemical stability with no obvious activity attenuation after repeated use 5 times. This strategy opens a new avenue based on ZIFs to develop heterogeneous catalysts for reductive upgrading of CO2.

Lanthanum strontium cobaltite as interconnect in oxide thermoelectric generators

Issues related to use of metallic interconnects in oxide thermoelectric generators (TEGs) need to be addressed to secure performance and durability. Metal interconnects suffer from high cost of noble metals or chemical instability and contact resistance of non-noble metals, arising from oxidation, evaporation, and delamination in the oxidising conditions of ambient air at high operating temperatures. This work introduces the use of a stable and highly conducting ceramic oxide, in our case p-type lanthanum strontium cobaltite (La0.6Sr0.4CoO3, LSC) as interconnect. We verified the thermochemical stability of LSC in contact with p-type Ni0.98Li0.02O (Li–NiO) and n-type Zn0.98Al0.02O (Al–ZnO) and examined the electrical characteristics. An area specific contact resistance (ASRc) of ∼1800 Ω cm2 for a direct p-n junction was reduced to ∼400 mΩ cm2 for a p-LSC-n junction at a temperature of 300 °C, validating the concept. The use of a screen-printed LSC/Al–ZnO composite as a thin interconnect layer was found to decrease the contact resistance of the junction further to ∼260 mΩ cm2 at 300 °C, attributed to increased effective area of the LSC/Al–ZnO p-n junction.

Exsolution of nanoparticles on A-site-deficient lanthanum ferrite perovskites: its effect on co-electrolysis of CO2 and H2O

La0.7Sr0.2Ni0.2Fe0.8O3 (LSNF), having thermochemical stability, superior ionic and electronic conductivity, and structural flexibility, was investigated as a cathode in SOECs.

Nanoemulsion: An emerging technology for oilfield applications between limitations and potentials

Nanoemulsions (NEs) are kinetically stable dispersions with droplet sizes on the order of 100 nm. Properties of NEs, such as the kinetic stability and rheology, have attracted substantial consideration in the oil and gas industry. This comprehensive review stretches from the theoretical mechanisms and fundamentals all the way to oilfield applications. Current low-energy and high-energy laboratory and industrial scale emulsification routes are included with detailed insight on synthesis challenges and opportunities. An included compendium of NE characterization techniques encompasses their applicability, advantages, and disadvantages. The oilfield applications segment covers recent uses of NEs in drilling, reservoir, and production operations. The review touches economical aspects for NEs oilfield scale implementations, and proposes solutions to mitigate foreseen challenges. This review emphasizes the scientific aspects of NE preparation and provides insight from the engineering and economic point of view of the oil and gas industry. • The paper summarizes different Nanoemulsions state-of-the-art synthesis methods. • A comprehensive list of current characterization techniques with the cons and pros. • Nanoemulsions thermochemical stability under reservoir conditions. • Nanoemulsions suitability for versatile subsurface applications. • Provide insight on the complexity of making Nanoemulsions out in the field.

A broom-like tube-in-tube bundle O-doped graphitic carbon nitride nanoreactor that promotes photocatalytic hydrogen evolution

Metal-free graphite carbon nitride (g-C3N4) is an ideal catalyst in the field of photocatalytic hydrogen evolution due to its visible light response, thermochemical stability and low cost. However, limited by the high photogenerated electron-hole recombination rate and poor light trapping ability of bulk g-C3N4 prepared by thermal condensation, it remains a great challenge in boosting the photocatalytic hydrogen (H2) evolution performance. Herein, a broom-like O-doped g-C3N4 nanoreactor (O-CN-NTs) oriented by tube-in-tube was developed for the first time through the “calcination-hydrothermal-calcination” method. The tube-in-tube nanoreactor not only can facilitate the scattering of incident light inside the cavity to enhance the utilization of light, but also can reduce the transport distance of carriers from the bulk to the surface to facilitate electron-hole separation. The morphology design of the tube-in-tube nanoreactor plays a very important role in improving the performance of photocatalytic H2 production. Furthermore, the density functional theory (DFT) calculation results manifest that the charge redistribution around the doped oxygen atoms accelerates the separation of electron-hole. The doping of oxygen atoms in g-C3N4 nanoreactor further enhanced the photocatalytic H2 production performance. Attributed to above advantages, the visible-light-driven (≥420 nm) photocatalytic H2 production rate of O-CN-NTs can achieve 13.61 mmol g-1h−1, which is approximately 71.63 times that of bulk g-C3N4 (CN550).