Long-term Thermal Stability Research Articles

Enhancing the electrochemical performance of Ni-rich cathode through an in-situ La-doping and La4NiLiO8-coating synergistic strategy

Ni-rich layered oxides offer numerous advantages such as high discharge capacity, cost-effectiveness, and environmental friendliness, making them the mainstream cathodes for high-energy density lithium-ion batteries. However, their widespread commercialization is hindered by critical challenges in cycling performance, stemming from unstable interface and structure, particularly at elevated charge cut-off voltages. Herein, a dual-modification strategy combining La doping and La4NiLiO8 coating was proposed to synergistically enhance the surface/interface and structure stability of the LiNi0.83Co0.11Mn0.06O2 (referred to as NCM83) cathode. Unlike conventional methods, a well-designed La(OH)3 coating pretreatment was employed on the Ni0.83Co0.11Mn0.06(OH)2 precursor. This pretreatment aimed to facilitate the in-situ formation of La doping and La4NiLiO8 during the lithiation of the coated precursor, while ensuring desired uniformity of the La4NiLiO8 coating and La doping. This dual-modification strategy integrated the advantages of both La doping and La4NiLiO8 coating, demonstrating excellent capability to improve the overall performance of NCM83. The La doping, acting as a pillar, not only strengthened the layered structure of the cathode to mitigate volume changes, but also enhanced Li+ diffusion by broadening the c axis spacing. The La4NiLiO8 coating efficiently protected the cathode from H2O/CO2 attack and electrolyte erosion, while also facilitating Li+ transport owing to its favorable Li-conductive properties. Such a dual-modification strategy significantly enhanced the electrochemical performance of NCM83, as demonstrated by the excellent long-term cyclic stability, rate capability, and thermal stability at a high charge cut-off voltage of 4.5 V. This work highlighted the benefits of integrating elemental doping and surface coating, while offering a promising synthetic protocol for straightforward and effective dual-modification of various cathodes.

Impact of Self-Assembled Monolayer Structural Design on Perovskite Phase Regulation, Hole-Selective Contact, and Energy Loss in Inverted Perovskite Solar Cells

Recent studies have shown that self-assembled molecule (SAM)-based hole-selective contacts (HSCs) offer a promising solution to the challenges faced by perovskite solar cells (PVSCs), including minimal material consumption, scalable production, high interface stability, and the use of environmentally friendly solvents. In this study, the efficacy of two designs of SAMs (Cz and PA) as HSCs in inverted PVSCs was investigated by comparing them with the conventional MeO-2PACz (MeO) SAM. Surface analyses showed that the surface of PA is smoother than that of Cz, which helps to reduce interfacial defects. Subsequent perovskite deposition exhibited a reduced formation of the PbI2 phase, incidiating that its phase modulation ability is superior to that of MeO. Further analyses demonstrate the superior charge extraction ability of PA as a result of reduced interfacial defects and non-radiative recombination at the HSC/perovskite interface. By further coupling with phenethylammonium iodide (PEAI) surface passivation, both interfaces of the perovskite film were optimized and the inverted ((FAPbI3)0.85(MAPbBr3)0.15)0.95(CsPbI3)0.05 (bandgap = 1.62eV) PVSC achieves a high power conversion efficiency (PCE) of 23.3% and a very high open-circuit voltage of 1.227V due to the largely reduced energy loss. In addition, the PA PVSC exhibits enhanced long-term thermal stability at 85°C in a nitrogen atmosphere.

Additively manufactured ultrastrong and thermal-resistant Al alloy via engineering the hierarchical intermetallics

An ultrastrong and thermal-resistant aluminum (Al) alloy with dual strengthening sources consisting of hierarchical intermetallics and carbides was developed for laser powder bed fusion (L-PBF). The role of TiC in engineering the microstructure, mechanical properties, and thermal resistance of L-PBF AlFeCr was systematically investigated. The rapid cooling rate and spatiotemporal variation of solidification conditions engender a refined and heterogeneous microstructure in the as-built AlFeCr. This microstructure comprises hierarchical intermetallics, specifically the quasicrystalline icosahedral phase (i-phase) and the θ-Al13(Fe,Cr)2-4 phase at the melt pool boundary, along with fibrous eutectic structures in the melt pool interior. The addition of TiC particles refines the grains through heterogeneous nucleation, which helps heal cracks in AlFeCr. The introduction of TiC improves the long-term thermal stability of AlFeCr by stabilizing the i-phase due to the slower diffusion of Ti relative to Fe and Cr, and by suppressing the coarsening of platelet-like Al13Fe4. The L-PBF TiC/AlFeCr demonstrates an ultrastrong tensile yield strength of 306 MPa at 300 °C and 174 MPa at 400 °C, surpassing those of typically L-PBF Al˗Ce-, Al˗Ni-, and Al˗Cu-based thermal-resistant Al alloys. Additionally, the stabilized hierarchical intermetallics contribute to a higher retention ratio of hardness and strength. The present work can shed light on designing ultrastrong and thermal-resistant Al alloys using dual strengthening sources, including carbides and hierarchical intermetallics.

High-Entropy Boride HfZrTiTaMoB: Promising Materials for Solar Selective Absorption Coatings in Photothermal Applications.

High-entropy borides (HEBs), as a category of high-entropy materials, exhibit remarkable thermal stability, a broad compositional range, and finely tuned electronic structures, leading to an excellent functional performance. Despite these advantages, their application in photothermal materials has rarely been reported. Herein, we employ a HEB target with multiple transition-metal elements to develop solar selective absorption coatings (SSACs) with simple and scalable bilayer structures for photothermal applications. The performance of these coatings is enhanced by designing different antireflective layers. The designed SSACs, both stainless steel (SS)/HEB/Al2O3 and SS/HEB/Si3N4, exhibit high absorptivity and low thermal emittance (α/ε = 90.0%/8.6% and 91.6%/8.6% at 82 °C). Thermal stability tests show that the absorbers could withstand annealing at 500 °C for 5 h, while maintaining a good optical performance. Long-term thermal stability tests indicate that the coatings retained good spectral selectivity after annealing at 400 °C for 100 h. Notably, the coatings demonstrate advanced photothermal conversion efficiencies of 88.3% and 89.9%, respectively, at 400 °C under 100 sun. In practical simulated solar irradiation experiments, the absorber achieves temperatures of about 85 °C under 1 sun, surpassing the performance of commercial nonselective absorbing coatings. Additionally, the absorbers maintained a stable photothermal performance through six on-off cycle experiments. In summary, the designed SSACs based on HEBs exhibit excellent optical properties and efficient photothermal conversion at moderate temperatures. This study highlights the significant benefits and potential advancements in solar energy collection offered by HEB-based SSACs.

Influence of carboxyl functionalized MWCNT loading on the thermal stability and long-term water uptake behavior in tri-layered jute FRCs

Investigations on the influence of carboxyl functionalized MWCNTs on epoxy composites solely reinforced by jute fiber are very scarce. Therefore, an attempt has been made to analyze the long-term moisture absorption behavior and thermal stability at the high-temperature range (30 °C-1200 °C) in jute FRC filled with varying amounts of functionalized MWCNTs (wt. %). Jute fibers derived from needle-punched jute mats were chemically pre-treated and were studied using Fourier Transform Infrared Spectroscopy (FT-IR). The MWCNTs were ultrasonicated to ensure uniform dispersion in the epoxy matrix. Scanning Electron Microscopy (SEM) was performed to observe the fiber, matrix, and filler interactions. As the composites were fabricated using the hand layup technique, air bubbles got entrapped into the specimens for which the void content was also reported. At a substantial saturation state (weight change <5 mg), the composite with 1 % MWCNT absorbed the most water. However, at higher CNT loadings, MWCNT agglomeration stopped water uptake. These results suggest that careful adjustment of MWCNT loading is necessary to balance hydrophilicity and porosity, thereby fine-tuning the water absorption of jute FRC. Thermogravimetric analysis (TGA) has been used in the study to assess the thermal behavior of the composites, indicating that adding MWCNTs at about 1 wt. % CNT loading can increase the thermal stability of jute fiber composites. An elevated concentration of CNTs facilitates agglomeration, impeding moisture absorption, whereas the incorporation of 1 % CNTs improves thermal stability. Consequently, a CNT concentration of 1.5 % is recommended.

Exploring the preparation of Ni/TiCSiC catalysts for hydrogen production from ammonia

This work explores an innovative and effective approach to address the climatic challenges by designing efficient, novel, and stable nickel catalysts based on a commercial TiCSiC composite as a support material. Through a simple wet impregnation synthesis, these catalysts were successfully synthetized, enabling completely COx-free hydrogen production from ammonia decomposition. To comprehensively understand the nature of the prepared catalyst, a complete characterization was performed. Results revealed that a pretreatment in air at 700 °C optimized catalyst performance, attributed to the TiO2 species emerged in the crystalline structure of the composite and its optimal crystallite size. Moreover, the nickel content affected the metal crystallite size and reducibility and, consequently, the ammonia conversion at moderate temperatures. Thus, the selected catalyst required only 5 wt% of Ni after a calcination in air at 700 °C, converting a notable 91.5 % of ammonia at 500 °C with a hydrogen production rate of 61.3 mmol H2·gNi−1·min−1. The optimized catalyst also demonstrated a long-term thermal stability after more than 45 h in ammonia reactions. These promising findings not only improve catalytic efficiency in current green hydrogen technology, but also contribute significantly to transition towards a sustainable future by using hydrogen vectors and non-critical metals as active phase of catalysts.

Novel cinnamon essential oil-bacterial cellulose microcapsules for enhanced preservation of prefabricated meat

Bacterial cellulose, a naturally porous nanomaterial, shows significant potential in encapsulation and sustained-release applications. However, effective methods to construct bacterial cellulose microcapsules (BCM) are lacking, resulting in low embedding rates and poor slow-release effects. This study presents a novel and efficient BCM preparation strategy using mercerization to embed cinnamon essential oil (CEO). The CEO-BCM system was evaluated for its efficacy in preserving prefabricated meat. Results demonstrated that BCM, embedded with CEO through mercerization, achieved an embedding rate of 94.9 % and an average particle size of 63.7 μm. Mercerization transformed BC crystalline into cellulose type II, densifying the BCM structure, while intermolecular hydrogen bonding between BCM and CEO enhanced the stability of CEO-BCM. Release kinetics analysis indicated that CEO release was primarily diffusion-driven (Peppas-Sahlin model) with sustained release performance up to 20 days. Additionally, CEO-BCM exhibited excellent long-term antibacterial (≥81.2 % within 20 days), antioxidant, and thermal stability, effectively extending the shelf life of prefabricated meat products from 5 to 10 days. The developed BCM construction strategy not only addresses the challenges of direct BCM preparation and the limitations in core embedding and controlled release, but also enhances the stability of the CEO. This advancement further expands the application areas of bacterial cellulose (BC), and the prepared CEO-BCM system holds significant potential for food preservation applications.

Dopant-Free Hole Transport Material Based on Non-Covalent Interaction for Efficient Perovskite Solar Cells.

Hole transport materials (HTMs) have a critical impact on the performance of perovskite solar cells (PSCs). Especially, the dopant-free HTMs could avoid the usage of hygroscopic dopants and reduce costs, which are important for device stability. Most of the current organic dopant-free HTMs are polycyclic aromatic hydrocarbons-based planar conjugated structures. Yet, the synthesis of conjugated fused heterocycles is often complicated. In this work, intramolecular non-covalent interaction is introduced to construct two organic HTMs (DCT and DTC), which can be facilely obtained through simple reactions. Compared to DTC with hexyl chain on the central benzene ring, DCT with hexyloxy chains shows better planarity in the core structure, as a result of the intramolecular non-covalent interactions between oxygen on hexyloxy and sulfur atom on the adjacent thiophene, as reflected from its single crystal structure. Moreover, DCT in a pristine state shows a decent hole mobility comparable to the doped Spiro-OMeTAD. Ultimately, conventional devices using dopant-free DCT as HTM show a high efficiency of 22.50%, with excellent long-term stability, and light and thermal stability. The results show that the noncovalent interaction is a useful and simple design strategy for dopant-free HTMs, that can effectively improve the efficiency and stability of PSCs.

Insights into the thermal stabilization mechanism of zeolitic imidazolate framework-8 for poly(vinyl chloride)

The thermal stability of zeolitic imidazolate framework-8 (ZIF-8) for poly(vinyl chloride) (PVC) has received attention, but its thermal stabilization mechanism needs further clarification. Herein, the stearic acid-modified ZIF-8 with high specific surface area and large pore volume was effectively synthesized by using zinc stearate as the zinc source for the first time. Modification of stearic acid results in larger adsorption capacity of ZIF-8 for HCl and better thermal stability effect for PVC, especially long-term thermal stability. Moreover, the thermal stability mechanism of ZIF-8 for PVC was demonstrated by experiments and theoretical calculations. In addition to absorbing HCl to eliminate autocatalytic degradation of PVC, ZIF-8 disintegrates and may form 2-methylimidazole-Zn-Cl salt complex instead of free ZnCl2, avoiding the negative zinc burning effect. Furthermore, the Diels-Alder reaction between imidazole ring and degraded PVC prevents the extension of the conjugated double bonds of PVC and delays the deepening of the color of PVC.

Thermal performance and flash point analyses of concentrator photovoltaic (CPV) system using multiple types of PCMs and various panel inclination angles under the effect of a constant heat flux

This numerical study conducts a comparative analysis of various phase change materials (PCMs) including Lauric Acid, Paraffin, RT 24, RT 31, RT 35, RT 38, RT 42, RT 47, RT 50, and Lithium Nitrate Trihydrate (LiNO3.3H2O) to assess their suitability for optimizing the thermal management of a solar concentrator photovoltaic (CPV) system. The analysis focuses on the temperature regulation capabilities, melting dynamics of the used PCMs, along the electrical efficiency of the CPV system across a range of inclination angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) under a constant heat flux of 1000 W/m². The research aims to identify the most effective solutions for enhancing the efficiency and reliability of solar concentrator systems. Key considerations such as PCM’s flash points, liquid fraction and convective behavior are addressed for each PCM type. Numerical results obtained using ANSYS Fluent indicate that Lithium Nitrate Trihydrate (LiNO3.3H2O) outperformed most paraffin-based PCMs, such as RT 24 and RT 35, with around 24 % higher electrical efficiency. Although Lauric Acid was approximately 19.5 % less efficient than Lithium Nitrate Trihydrate, it offered superior long-term thermal stability due to its slower melting rate and phase change temperature of 43–44°C, taking 45.33 % longer to melt compared to Paraffin RT 24. RT 50, with its higher melting temperature of 50°C, provided a balance between melting period and efficiency, making it an ideal PCM for applications requiring both moderate efficiency and sustained thermal regulation.

Long-term thermal aging effects in ferritic-martensitic steel HT9

The ferritic-martensitic steel HT9 is a candidate material for fuel cladding and core components in advanced nuclear reactors, such as sodium-cooled fast reactors, thanks to their high temperature mechanical properties and low susceptibility to irradiation induced swelling phenomena. However, thermal stability and elevated temperature microstructural evolution in these alloys may impact their long-term behavior and reliability. In this work, the effects of thermal aging on the microstructural and mechanical properties of HT9 have been investigated through complementary electron microscopy, synchrotron X-ray diffraction, microhardness, and thermodynamic modeling. Plates of HT9 were aged up to 50 kh at relevant sodium-cooled fast reactor operational temperatures (360 °C - 700 °C). Trends in microstructure as a function of aging time and temperature were apparent from qualitative and quantitative analysis. These observations were further supported by thermodynamic modeling of the bulk and precipitate phases. Specific phases observed include BCC Fe, FCC M23C6, HCP and FCC MX phase and Laves M2X phase. Through the application of our multi-scale and multi-modal approach, clear information on the aging mechanism of HT9 was obtained, allowing for a more informed prediction, and understanding of the long-term behavior, performance and thermal stability of ferritic-martensitic alloys exposed to elevated temperatures.

Development and Evaluation of Insulation Materials for Deepwater Cementing.

Marine oil and gas resources are abundant in deepwater regions, where the shallow seabed harbors natural gas hydrate layers due to the cold temperature and high-pressure environment. Hydrates are prone to thermal decomposition, which can compromise the integrity of cement sealing and even lead to accidents like blowouts. While current low-hydrated heat cement systems mitigate hydrate decomposition from cement hydration heat during the waiting period for cementing, they do not address heat transfer from deep strata to shallow hydrate layers through fluid circulation in the tubing during deep oil and gas development. Rather than utilizing costly pipe insulation technology, adjusting the thermal conductivity of well cement emerges as a cost-effective approach to prevent heat loss in the wellbore to the hydrate layer and thus inhibit hydrate decomposition. The critical aspect lies in utilizing insulation functional materials. This study delves into the functional and structural design of insulation materials suitable for cement slurry systems in well cementing, outlining the preparation methods and processes for two insulation materials (SDBW and SDBW-II) tailored for deepwater well cementing. SDBW and SDBW-II are both nuclear shell structural materials. The core is made of high-strength hollow microspheres, produced by using a reverse suspension polymerization method to form spheres followed by high-temperature sintering. The shell consists of a wear-resistant BPA epoxy resin layer, with the surface of SDBW-II also containing highly reflective glass microspheres. Incorporating 20% of material SDBW into the cement reduces the thermal conductivity of the cement stone from 0.8 to 0.31 W·(m·K)-1 while achieving a compressive strength of 6 MPa after 24 h at 20 °C. Material SDBW-II offers both thermal resistance and reflection functions, increasing reflectivity (R) from 0.3 to 0.5. By adding 20% of this material to the cement, under the same conditions, although the compressive strength decreases to 4.2 MPa, the thermal conductivity can be reduced to 0.27 W·(m·K)-1. Furthermore, there is no significant change within 180 days, demonstrating long-term thermal insulation stability. These developed insulation materials can effectively improve the thermal insulation performance of the cement sheath, thereby maintaining the stability of the upper natural gas hydrate layer in the oil and gas production process of deepwater wells, providing an innovative solution for the long-term operation of deepwater oil and gas wells.

Revealing the Impact of Aging on Perovskite Solar Cells Employing Nickel Phthalocyanine-Based Hole Transporting Material.

The enhancement of the photovoltaic performance upon the aging process at particular environment is often observed in perovskite solar cells (PSCs), particularly for the devices with 2,2',7,7'-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9'-spirobifluorene (spiro-OMeTAD)as hole transporting material (HTM). In this work, for the first time the effect of aging the typical n-i-p PSCs employing nickel phthalocyanine (coded as Bis-PF-Ni) solely as dopant-free HTM is investigated and as an additive in spiro-OMeTAD solution. This study reveals that the prolong aging of these devices at dry air condition (RH= 2%, 25°C) is beneficial for the improvement of their performances. Various bulk and surface characterization techniques are utilized to understand the factors behind the spontaneous efficiency enhancement of the devices after storage. As a result, the changes in properties of the Bis-PF-Ni layer are observed and at perovskite/Bis-PF-Ni interface, which ultimately improves the charge transport and reduces non-radiative recombination. In addition, the devices with Bis-PF-Ni HTM reveal enhanced long-term ambient and thermal stability compared to the PSCs based on doped spiro-OMeTAD.

Bio-based eutectic composite phase change materials with enhanced thermal conductivity and excellent shape stabilization for battery thermal management

Organic phase change materials (PCMs) are commonly used for battery thermal management. Organic petroleum-based PCMs such as paraffin have an adverse effect on environment. Fatty acids as environmentally friendly bio-based PCMs, have enormous potential in sustainable development strategies. Nevertheless, the application of fatty acids in battery thermal management (BTMS) is restricted by the leakage of liquid PCM, poor thermal performance and the improper phase change temperature. We proposed a novel bio-based eutectic composite phase change materials (CPCM) with enhanced thermal conductivity and excellent shape-stabilization, composed of ethylene-vinyl acetate (EVA), Aluminum nitride (AlN), and the eutectic PCM of Lauric acid (LA) and Stearic acid (SA). Significantly, the screened eutectic PCM of LA-SA possesses a suitable phase change temperature(37.03 °C) corresponding to the battery operating temperature, and long-term thermal cycling stability of up to 100 cycles. And the cross-linked structure of EVA effectively encapsulated the eutectic PCM, whose mass only lost below 4% after being heated at 80 °C for 24 h. Simultaneously, the introduction of AlN can greatly improve their heat transfer ability and mechanical properties. LA-SA/EVA/AlN composites with 5 wt% AlN has adequate latent heat of 107.94 J.g−1 and high thermal conductivity of 0.726 W.(m·K)−1 as well as with low flexural strength of 1.72 MPa. Additionally, the proposed CPCM with 5 wt% AlN achieved the maximum temperature of battery below 45 °C during 4C discharging test. It suggested that the CPCM incorporated with AlN is capable effective cooling battery and dissipate energy inside PCM rapidly.

Multifunctional molecular bridge enabled interface passivation and strain release for stable and efficient all-inorganic perovskite solar cells

The precise management of the buried interface in n-i-p perovskite solar cells (PSCs) to achieve efficient charge extraction and transport is crucial for improving the photovoltaic performance. Here, a 4-chloro-2,5-dimethoxyaniline (CDA) modifier with multifunctional groups is utilized as a molecular bridge at the TiO2/CsPbBr3 buried interface to enhance the qualities of TiO2 and CsPbBr3 films and the arrangement of interface energy level. The chlorine atom in CDA can heal the oxygen vacancies defects on the TiO2 film surface, thereby improving its electron mobility and conductivity. The –O– and -NH2 groups in CDA play a passivation effect on the ions defects of CsPbBr3 film, and especially the two –O– groups can anchor the lattice Pb atoms of CsPbBr3 perovskite, which effectively reduce the trap states of CsPbBr3 film and release the residual lattice strain. The modification of CDA also improves the wettability and energy level of TiO2 film to optimize CsPbBr3 crystal growth and charge transport, respectively. Consequently, the CsPbBr3 PSCs with CDA molecular bridge free of encapsulation achieve a highly increased power conversion efficiency of 10.85%, in contrast with 8.16% value of the control device. After 720 h of storage at 85 °C and in air environment with 85% relative humidity, the efficiency of the CDA-modified device retains 93.1% of the initial value, demonstrating excellent long-term humidity and thermal stability.

Role of TiC on the microstructure, tensile property and thermal stability of laser powder bed fusion fabricated AlSi10Mg alloy

The incorporation of ceramic particles is frequently employed to enhance the printability of high-strength aluminum (Al) alloys in laser powder bed fusion (L-PBF). However, their influence on the long-term thermal stability and elevated temperature mechanical properties of the Al alloy is seldom studied. This study aims to address this gap by investigating the role of micron-sized TiC particles in the microstructure, long-term thermal stability, and elevated temperature tensile properties of an L-PBF-fabricated AlSi10Mg alloy. The results indicate that highly dense TiC/AlSi10Mg samples can be fabricated, featuring fine equiaxed grains rather than the coarse columnar grains typically formed in the AlSi10Mg alloy. This columnar-to-equiaxed transition is attributed to the residual TiC and the in-situ formation of Al3Ti particles, which act as nucleating agents. Moreover, the incorporation of TiC significantly enhances the long-term thermal stability of the AlSi10Mg alloy by improving the stability of the eutectic network and retarding the coarsening of Si particles by inhibiting Si diffusion. Compared to the AlSi10Mg counterpart, the TiC/AlSi10Mg composite exhibits a higher hardness retention ratio (56 % versus 45 %) after thermal exposure at 400 °C for 192 h. The residual TiC and in-situ formed Al3Ti have high thermal stability and can impede dislocation motion, thereby contributing to enhanced long-term thermal stability. This study offers insights into the design of L-PBF ceramic-reinforced Al alloys with improved thermal stability for high-temperature applications.

Polymeric ionic liquids containing copper(I) and copper(II) ions as gas chromatographic stationary phases for olefin separations

Copper(I) ions (Cu+) are used in olefin separations due to their olefin complexing ability and low cost, but their instability in the presence of water and gases limits their widespread use. Ionic liquids (ILs) have emerged as stabilizers of Cu+ ions and prevent their degradation, providing high olefin separation efficiency. There is limited understanding into the role that polymeric ionic liquids (PILs), which possess similar structural characteristics to ILs, have on Cu+ ion-olefin interactions. Moreover, copper ions with diverse oxidation states, including Cu+ and Cu2+ ions, have been rarely employed for olefin separations. In this study, gas chromatography (GC) is used to investigate the interaction strength of olefins to stationary phases composed of the 1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([C6MIM+][NTf2−]) IL and the poly(1-hexyl-3-vinylimidazolium [NTf2−]) (poly([C6VIM+][NTf2−])) PIL containing monovalent and divalent copper salts (i.e., [Cu+][NTf2−] and [Cu2+]2[NTf2−]). The chromatographic retention of alkenes, alkynes, dienes, and aromatic compounds was examined. Incorporation of the [Cu2+]2[NTf2−] salt into a stationary phase comprised of poly(dimethylsiloxane) resulted in strong retention of olefins, while its addition to the [C6MIM+][NTf2−] IL and poly([C6VIM+][NTf2−]) PIL allowed for the interaction strength to be modulated. Olefins exhibited greater affinities toward IL and PIL stationary phases containing the [Cu2+]2[NTf2−] salt compared to those with the [Cu+][NTf2−] salt. Elimination of water from both copper salts was observed to be an important factor in promoting olefin interactions, as evidenced by increased olefin retention upon exposure of the stationary phases to high temperatures. To evaluate the long-term thermal stability of the stationary phase, chromatographic retention of probes was measured on the [Cu2+]2[NTf2−]/[C6MIM+][NTf2−] IL stationary phase after its exposure to helium at a temperature of 110 °C.

Pyrolysis mechanism of silicone rubber thermal protection system materials in service environment

The excellent oxidation and ablation resistance of silicone rubber thermal protection system (TPS) materials have made them extensively utilized in large-area thermal protection applications, such as ramjet engines and spacecraft reentry capsules, where air is present in the service environment. The ablation resistance is significantly influenced by the pyrolysis reactions, which serves as the foundation for subsequent ceramic transformation and the development of anti-erosion structures. The majority of previous research has been conducted in inert gas environments. To investigate the pyrolysis mechanism of silicone rubber TPS materials in realistic service environments, thermal analysis tests were performed using a range of analytical instruments including a thermal analyzer, mass spectrometer, infrared spectrometer, and X-ray photoelectron spectrometer from room temperature up to 1300 K in air atmosphere and compared with the results in argon atmosphere. The results demonstrate that silicone rubber TPS materials undergo both pyrolysis and oxidation reactions in air atmosphere. The primary pyrolysis of the matrix is attributed to cyclization reactions and side-chain cross-linking reactions. In comparison to argon atmosphere, the oxidation reaction produces a greater amount of organic gases, thereby diminishing the extent of cross-linking reaction and the thermal stability of the pyrolysis residue. The prolonged exposure to elevated temperatures allows for an extended duration of oxidation reactions, consequently diminishing the long-term thermal stability of TPS materials. The increase in mass of TPS materials at temperatures exceeding 1100 K can be attributed, in part, to the formation of new organic groups through oxidation reactions. The observed morphology of the residue, along with the weight gain from oxidation and SiO2 formation, promotes ceramic transformation of the materials at elevated temperatures.

Magnetic polyacrylamide-based gel with tunable structure and properties and its significance in conformance control of oil reservoirs

The polyacrylamide-based gel used for oilfield conformance control exhibits poor temperature and salt resistance. This paper proposes the use of inorganic-organic core-shell materials as chemical crosslinkers for the polyacrylamide-polyethyleneimine (PAM-PEI) gel system to regulate and design its gel structure, enabling it to withstand harsh reservoir conditions. To achieve this, Fe3O4@PEI nanoparticles were prepared using a facile one-pot method and employed as chemical crosslinkers for the PAM-PEI gel. Herein, the Fe3O4 "core" provides strong stability derived from the inorganic material, and the PEI "shell" reacts with the PAM molecular chain in a transamidation reaction, so that the Fe3O4@PEI nanoparticles are riveted inside the gel by chemical crosslinking, which greatly enhances the gel structure. The Fe3O4@PEI nanoparticles exhibit a nearly spherical shape with an average diameter of approximately 75.6 nm and demonstrate excellent dispersion in water, possessing a zeta potential of 40.8 mV. In comparison to the control PAM-PEI gel, the PAM-PEI-Fe3O4@PEI gel exhibited significantly enhanced gel strength, rheological properties, long-term thermal stability, and anti-salt properties. It demonstrated a tan(δ) value of 0.12, indicative of its behavior as a nearly robust gel. Even after 360 days of placement at 90 °C in a 20 g/L NaCl solution, the gel maintained its Sydansk code at code I. Moreover, NaCl was observed to act as a retarder for this gel, while its Sydansk strength remained unaffected. In addition, the PAM-PEI-Fe3O4@PEI gel is magnetically responsive, so it can be utilized with a magnet generator to enhance its plugging performance and control its directional movement. By monitoring the magnetization rate of the gel in the reservoir, high permeability layers can be accurately identified, thus providing important practical applications in reservoir management.

Effect of Phosphate-Bridged Monomer on Thermal Oxidative Behavior of Phthalonitrile Thermosets.

Phthalonitrile thermosets are known for their excellent mechanical, physico-chemical, and fire-retardant properties, making them attractive for aerospace and mechanical engineering applications. When producing and applying phthalonitrile-based structural parts, it is essential to consider aspects such as processability and the long-term stability of the material's properties at high temperatures. In our previous studies, we demonstrated that resins containing phosphate-bridged bisphthalonitrile monomers are easily processable due to their low melting temperature and wide processing window. In this study, we investigated the impact of bis(3-(3,4-dicyanophenoxy)phenyl)phenyl phosphate (PPhPN) monomer content on physico-chemical and mechanical properties, thermal stability, and thermal oxidative stability. This research highlights the importance of conducting long-term thermal oxidative aging studies in addition to thermogravimetric analysis to properly assess the stability of thermosets. The findings indicate that adding less than 15% of PPhPN results in the formation of a crystalline phase, which impairs the resin's processability. Conversely, a high PPhPN content reduces the material's thermal oxidative stability. Therefore, based on mechanical and physico-chemical tests after thermal oxidative aging, it can be concluded that a 10-15% concentration of the phosphate-containing monomer enables easy processability of the phthalonitrile resin and provides excellent long-term thermal oxidative stability at temperatures up to 300 °C, while maintaining a flexural strength exceeding 120 MPa and an elasticity modulus of 4.3 GPa.