Thermal Stability Issues Research Articles

Enhancing Magnetic Performance of FeNi50 Soft Magnetic Composites with Double-Layer Insulating Coating for High-Frequency Applications

Soft magnetic composites (SMCs) such as FeNi50 are indispensable in modern electronics due to their high magnetic permeability and low-loss characteristics, meeting the requirements for miniaturization and high-frequency operation. However, the integration of organic materials, initially aimed at reducing the total losses, presents challenges by introducing thermal stability issues at high frequencies. To overcome this obstacle, we propose a double-layer insulating coating method, applying a complete inorganic/organic composite insulation layer to the surface of iron–nickel magnetic powder. The double-layer insulating coating insulation method aims to reduce the total losses, particularly the eddy-current losses prevalent in SMCs. Additionally, the double-layer insulating coating method helps alleviate the thermal stability issues associated with organic materials at high frequencies, ultimately enhancing the magnetic properties of SMCs. We systematically investigated the influence of different resin types on the microstructure of the double-layer insulating coating, accompanied by a comprehensive comparison of the magnetic properties of the resulting samples. The experimental findings demonstrate a significant reduction in the eddy-current losses through the double-layer insulating coating method, with the total losses decreasing by over 95% compared to the initial FeNi50 magnetic powder composite (MPC) materials. Notably, the sodium silicate and silicone resins exhibited superior performances as double-layer insulating coatings, achieving total loss reductions of 1350 W/kg and 1492 W/kg, respectively. In conclusion, the double-layer insulating coating method addresses the challenges related to the total losses and thermal stability in SMCs, offering a promising approach to improve their performance in various electrical and electronic applications.

Stabilized Nickel-Rich oxide cathode by the confining effect of Nb lattice anchoring and epitaxial shielding layer

Ni-rich LiNixCoyMn1−x−yO2 cathodes attract growing attention for high energy density but still face great challenges in terms of cyclic lifespan and thermal stability issues. The structural degradation is primarily caused by the increased oxygen vacancy and lattice oxygen loss, especially at high temperatures. Here, we develop an anchoring-confining strategy to rivet lattice oxygen and inhibit the formation and migration of oxygen vacancy by constructing LiNbO3 & LiF epitaxial layer and Nb5+ lattice doping within LiNi0.92Co0.055Mn0.025O2 (NCM92) cathode. The optimized NCM-FN material exhibits excellent stability with retenion of 93 % after 200 cycles at 1C supassing the pristine one (68.7 %), conspicuous high-temperature capacity retention rate (81.6 % vs. 49.5 %) and superior reversible capacity of 165 mAh/g at 5C. In particular, it even possessed superior thermal safety pushing thermal runaway temperature to 223.65 °C. In-situ X-ray diffraction (XRD) result indicates that Nb5+ lattice substitution coupled with LiNbO3 & LiF epitaxial layer alleviates the irreversibility of H2-H3 phase transition, thus stabilizing the layered structure. Furthermore, the LiNbO3 & LiF epitaxial layer, as both a physical shielding layer and ionic conductive layer, protects interface structural integrity and simultaneously promotes Li+ diffusion. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) results demonstrate that the formation and propagation of oxygen vacancy within NCM-FN material is significantly inhibited. DFT calculation results reveal that Nb5+ introduction can increase the formation energy of oxygen vacancies and inhibit outward migration of active oxygen Oα- (α < 2) to stabilize layer structure by tuning the breaking energy barrier of nearby metal-O bonds. This work not only demonstrates the design of advanced Ni-rich layered cathodes but also underscores the importance of stabilized lattice oxygen for advanced Ni-rich cathodes.

Evaluation and selection of eutectic salts combined with metal foams for applications in high-temperature latent heat thermal energy storage

This study presents a systematic process for selecting eutectic salts for use in latent heat thermal energy storage (LHTES), and provides experimental evidence regarding their performance. One primary goal was to identify the most suitable eutectic salt for use with metallic foams over a temperature range of 450 °C–500 °C. Twenty one eutectic salts were preselected for comparison. The performance and cost-effectiveness of each were evaluated based on the Ragone relation, enabling a fair comparison of each salt's heat storage capacity and power density relative to cost. As a result, MgCl-NaCl, CaCl2-NaCl, and FLiNaK were selected as the most promising candidates. Subsequently, experiments were performed to demonstrate the compatibility of the selected salts with metal foams while the copper and aluminum foams were immersed in the salts at 550 °C for 120 h. Combining C10100 (copper alloy) foam with CaCl2-NaCl was observed to generate the least surface corrosion due to oxidation. The charge/discharge performance and thermal stability of CaCl2-NaCl, both with and without the copper foam, were also tested to confirm the feasibility of this combination. The capsule with the copper foam showed enhanced performance (a 13 % reduced discharge rate) in comparison to the capsule without copper foam. The melting point of the CaCl2-NaCl remained unchanged for 300-h duration of the cyclic melting/solidification experiments, and no thermal stability issues were observed.

Realization of Broadband Near-Infrared Emission with High Thermal Stability in YGa3(BO3)4: Cr3+ Borate Phosphor.

As a key material for phosphor-converted light-emitting diodes (pc-LEDs) applications, broadband near-infrared (NIR) phosphors currently face poor thermal stability issues. In this work, we synthesized a broadband near-infrared phosphor YGa3(BO3)4: Cr3+ (YGBO: Cr3+) with a high thermal stability. The YGBO: Cr3+ sample exhibits a broadband near-infrared emission centered at 770 nm with a full width at half-maximum (fwhm) of 2130 cm-1 under blue light excitation. Benefiting from the borate host crystal's strong structural rigidity, wide optical band gap, and weak electron-phonon coupling strength, YGBO: Cr3+ demonstrates strong luminescence thermal stability, and the corresponding luminescence intensity can maintain 80% at 150 °C compared to room temperature. Furthermore, we fabricated a pc-LED device using a blue light chip and YGBO: Cr3+ phosphor, and confirmed its application potential as a near-infrared light source in the spectral analysis of fruit freshness.

ETL/perovskite interface engineering using cadmium and lead chalcogenide quantum dots

Photovoltaic (PV) technology plays a significant role in renewable energy research, while devices based on hybrid perovskite materials have reached efficiencies which exceed 26 %. Nevertheless, perovskite solar cells (PSCs) are facing chemical, thermal and humidity stability issues, which prevent their commercialization. Thus, the use of quantum dots (QDs) has been proposed as an innovative strategy to tackle with device performance issues. This work investigates the effect of PbS and CdS chalcogenide QDs on the interface modification of CsFAMAPbI3-xBrx PSCs. The successive ionic layer adsorption and reaction (SILAR) method was employed as an innovative engineering approach to adjust effectively the perovskite interface energetics and optimize the solar cell's characteristics. By tuning the deposition conditions of QDs and adding TiCl4 to the electron transport layer (ETL), an efficiency improvement from 15.52 to 18.83 % was recorded. These results highlight the use of a facile and fast method to integrate chalcogenide quantum dots into perovskite-based optoelectronic devices, thus improving the surface crystallinity and overall device performance.

Construction of core@double-shell structured energetic composites with simultaneously enhanced thermal stability and safety performance

The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane (CL-20). Herein, a kind of novel core@double-shell CL-20 based energetic composites were fabricated to address the above issues. The coordination complexes which consist of natural polyphenol tannic acid (TA) and FeIII were chosen to construct the inner shell, while the graphene sheets were used to build the outer shell. The resulting CL-20/TA-FeIII/graphene composites exhibited simultaneously improved thermal stability and safety performance with only 1 wt% double-shell content, which should be ascribed to the intense physical encapsulation effect from inner shell combined with the desensitization effect of carbon nano-materials from outer shell. The phase transition (ε to γ) temperature increased from 173.70 °C of pure CL-20 to 191.87 °C of CL-20/TA-FeIII/graphene composites. Meanwhile, the characteristic drop height (H50) dramatically increased from 14.7 cm of pure CL-20 to 112.8 cm of CL-20/TA-FeIII/graphene composites, indicating much superior safety performance after the construction of the double-shell structure. In general, this work has provided an effective and versatile strategy to conquer the thermal stability and safety issues of CL-20 and contributes to the future application of high energy density energetic materials.

Synthesis and characterization of polyethylene glycol- polymethyl methacrylate infused multiwalled carbon nanotube nanocomposite as an efficient thermal energy storage

Organic phase change materials (O-PCMs) are recommended thermal energy storage materials due to low super-cooling, non-corrosive in nature and no phase segregation. Nevertheless, the issue of low thermal conductivity and thermal stability in O-PCMs hinders their extensive use in thermal energy storage (TES). To address this problem, multiwalled carbon nanotube (MWCNT) is employed as nano conductive filler to improve thermal properties. In addition, polymethyl methacrylate (PMMA) as supporting material is used to reduce the steric hindrance effect of the PEG-1000 and enhance the chemical stability. In this research work, an ultrasonication technique is adopted to develop PEG-PMMA/MWCNT composite with different weight fractions of MWCNT to evaluate the optimum thermal conductivity. Moreover, morphological behaviour, chemical stability, optical absorptivity, thermal property & thermal reliability of developed PEG-PMMA/MWCNT composite are experimentally characterized and scientifically discussed. The highest thermal conductivity is found to be 92.30% at 0.7 wt% of MWCNT. Further, 500 thermal cycles were performed which confirmed the thermal reliability of developed nanocomposites.

Three pesticide-pesticide eutectic systems of boscalid: Mechanochemical preparation, characterization and mechanism analysis

Preparation of eutectic mixture is considered to be an efficient means to improve physical and chemical properties in many fields. In this work, three pesticide-pesticide eutectic systems of boscalid with diniconazole, uniconazole and 3,6-dichloropicolinic acid were prepared by mechanochemical method. The formation of eutectic mixtures was identified by differential scanning calorimetry and powder X-ray diffraction characterizations. From the constructed solid–liquid phase diagrams, it is discovered that these eutectic systems could form a eutectic when the molar fraction of boscalid is 0.500. In addition, all eutectic temperatures are more than 29 K lower than the higher melting points of the constituents in the systems, which eliminates the issue of the poor thermal stability of constituents and enables the treatment of them using melting-based operations. Ideal model and COSMO-RS theory also calculate these solid–liquid phase diagrams relatively accurately, and the calculated activity coefficient values prove that these systems do not deviate significantly from the ideal state. The distinct non-ideality at the eutectic composition of the three systems also suggests that the interactions of the three coformers and the boscalid differ. The formation of eutectic mixtures was further confirmed by other solid state characterizations including mid-infrared spectroscopy, Raman spectroscopy and etc. The accelerated stability test indicates the good stability of the three eutectic mixtures. Furthermore, the water solubility study suggests the boscalid in the eutectic systems has a higher solubility than raw boscalid. By using COSMO-RS modelling, the most typical homo/hetero-molecular complexes of these pesticides were obtained and analyzed. Based on the trend of affinity characterized by the Gibbs free energy of the generation of molecular complexes, it could be inferred that eutectic point could be viewed as the state for which affinity of hetero-molecular complexes is greatest. The affinity of hetero-molecular complexes also presents the interaction between boscalid and 3,6-dichloropicolinic acid is greater than the other two pesticides at the eutectic point. Furthermore, the calculated solvation free energies document the intermolecular interaction plays an important role in stabilizing the three eutectic systems. These eutectic systems solve the problem that the three coformers are unsuitable for melting-based procedures and improve the solubility, making them potential options for future pesticide formulation development.

In-situ embedding of carbon dots in boron nitride for enhancing phosphor stability and fluorescent film heat dissipation

The aggregation-induced quenching effect and poor thermal stability issues of carbon dots (CDs) limit their further development in the solid-state lighting and display field. In this work, a red carbon dot/boron nitride nanosheet (rCDs/BNNS) composite was synthesized using boron nitride as a carrier by in-situ embedding of rCDs. Thanks to the uniform dispersion of rCDs and the restraint of BNNS, the prepared rCDs/BNNS composite has excellent fluorescence stability and thermal stability. rCDs/BNNS composites as fluorescent markers can be used to detect potential fingerprints on various surfaces. Furthermore, rCDs/BNNS were dispersed into polyvinyl alcohol (PVA) polymers to prepare rCDs/BNNS/PVA flexible luminescent films. In addition to the excellent stability inherited from rCDs/BNNS, the thin film also exhibits high heat dissipation by reason of the establishment of a heat transfer channel in the PVA by rCDs/BNNS. Moreover, thin films can still maintain original fluorescence after undergoing hundreds or thousands of bends, while possessing sufficient tensile strength. This study provides a facile pathway for the preparation of highly stable CDs luminescent materials, and has a promising application in the forensic identification and flexible luminescent devices' thermal management fields.

Stabilizing α-FAPbI3 at FAPbI3/SnO2-X Interface By Reducing Oxygen Vacancies in SnO2-X

CH3NH3PbI3 (CH3NH3 + is denoted MA hereinafter) was selected as the photoactive material in the early stage of perovskite solar cell (PSC) research. However, MAPbI3 shows poor thermal stability due to high volatility of the MA organic cation. Replacing the MA organic cation with a CH(NH2)2 + (CH(NH2)2 + is denoted FA hereinafter) organic cation was suggested to resolve the thermal stability issue. Additionally, FAPbI3 holds higher potential for high-efficiency solar cells with a broader photoresponse range in the solar spectrum than MAPbI3. However, fabricating FAPbI3 thin films is more challenging than MAPbI3. FA exhibits a larger ionic size (2.56 Å) than MA (2.17 Å), making incorporation of FA into PbI6 octahedra difficult. Incorporating FA induces tilting of PbI6 octahedra, which causes reversible deformation of perovskite-phase FAPbI3 (α-phase) into unfavorable phases (δ-phase and PbI2) at room temperature. Several reports on stabilizing the α-phase of FAPbI3, such as through heterogeneous cation or anion mixing, have been presented. For example, mixing smaller ions such as MA, Cs, and Br reduces the unit cell volume of FAPbI3, enhancing hydrogen bonding between FA and the PbI6 octahedron. This hydrogen bonding prevents reversible deformation of and stabilizes the α-phase of FAPbI3 in ambient atmosphere. In conventional PSCs, the perovskite layer usually forms an interface with an electron or hole transport layer (ETL or HTL). The compatibility of materials forming the interface is significant for separating charges from the perovskite with minimal loss. Nevertheless, although stabilizing FAPbI3 in a bulk manner is widely studied, stabilizing FAPbI3 at the interface is relatively overlooked. Stabilizing FAPbI3 at the interface is more important since the interface contains a high portion of structural defects compared to the bulk, almost 100-fold. Unfavorable phases, such as δ-phase FAPbI3 and PbI2, formed at the interface will hinder the charge extraction process from FAPbI3 to the transport layer, similar to defects. Especially, in the n-i-p structure, the perovskite is epitaxially deposited over the ETL, and tuning the interface after deposition is nearly impossible, which stresses the importance of the surface structure of the ETL. In the case of FAPbI3/SnO2-x, Sn and O are the key atoms for stabilizing the PbI6 octahedron and organic cation, respectively, which affects the growth of the perovskite at the interface. Oxygen vacancies in the surface of SnO2-x can cause distortion of the perovskite structure at the interface, inducing unfavorable phases, such as the δ-phase, PbI2, or other unknown phases. Furthermore, oxygen vacancies are more prevalent issue in SnO2-x than TiO2-x due to the stronger multivalency of Sn, which further emphasizes control of oxygen vacancies in SnO2-x. Since the open-circuit voltage (Voc) and fill factor (FF) show greater potential for improvement than the short-circuit current density (Jsc), stabilizing α-FAPbI3 at the interface may be a necessary step for researchers to further increase the power conversion efficiency (PCE) and stability of PSCs. In this work, we systematically studied the formation of δ-phase FAPbI3 and PbI2 induced by oxygen vacancies of the SnO2-x surface at the FAPbI3/SnO2-x interface. Using X-ray diffraction (XRD) and transmission electron microscopy (TEM), we observed PbI2 segregation and δ-phase FAPbI3 formation adjacent to SnO2-x. The generation of iodine interstitials at the interface was revealed as the driving force of the unfavorable phase transition. The absence of oxygen atoms interacting with tin atoms lowered the energy barrier for iodine interstitial generation almost by half, and the iodine interstitials accelerated the unfavorable phase transition of FAPbI3. For the first time, organic cation loss at the FAPbI3/SnO2-x interface was also observed as a severe drawback to forming an ideal heterojunction. Oxygen vacancies in the SnO2-x surface, which act as hydrogen bonding sites for FA cations, induced withdrawal of FA cations, which was revealed by X-ray photoelectron spectroscopy (XPS) measurements. Inspired by this phenomenon, we fabricated a SnO2-x layer with reduced oxygen vacancies by using oxidized black phosphorus quantum dots (O-BPs). The multiple P=O bonds of O-BPs effectively assisted the formation of a SnO2-x layer with minimal oxygen vacancies. After P=O passivation, most of the detrimental effects were mitigated, showing highly stable α-FAPbI3 crystal structures. Consequently, we achieved a maximum PCE of 23.43% with enhanced thermal and operational stability.

Thermal hazards assessment of three azo nitrile compounds

Commercially available azo radical compounds provide efficient initiation of many chemical reactions. However, such energetic azo group initiators have thermal stability issues at ambient or even sub-ambient temperatures. Azo decomposition initiated by heat and/or light can generate significant amounts of nitrogen gas with rapid pressure increases, presenting a safety challenge for shipping, storage and usage. In this study, three azo nitrile compounds were examined using various thermal calorimetry techniques with only 5 mg to 1 g scale samples. We obtained calorimetric data on exothermic activity and gas generation. The testing results were subsequently analyzed by using differential iso-conversional methods to obtain key decomposition kinetics parameters, including activation energy and pre-exponential factor. The model was then validated and utilized for prediction of several key safety parameters for scale-up applications, including Self-Accelerating Decomposition Temperature (SADT), Time to Maximum Rate (TMR), temperature profiles at iso- or non-isothermal conditions for shelf-life evaluation, adiabatic temperature rise, and rate of pressure increase. For compounds such as 2,2’-azobis-(2,4-dimethylvaleronitrile) and 1,1’-azobis(cyclohexane-1-carbonitrile) which went through phase transitions associated with thermal decomposition, the thermal decomposition behavior of liquid and solid state was found to differ in characteristic. This methodology for thermal decomposition kinetics assessment enables safe storage, handling, and scale-up process preparation.

Low-temperature sintering of Li0.33La0.55TiO3 electrolyte for all-solid-state Li batteries

Ceramic solid-state Li batteries have promising electrochemical properties. However, their device integration is hampered by the required high sintering temperature step to obtain good ionic conductivity. The sintering temperature often leads to thermal decomposition of the cathode active material. Advanced sintering techniques, such as field-assisted sintering technology/spark plasma sintering (FAST/SPS), utilizing applied mechanical pressure to achieve a lower sintering temperature and shorter dwell time, are helpful in overcoming thermal stability challenges. While thermal stability issues are overcome by a lower sintering temperature, new challenges in the form of surface impurities arise. Low-temperature sintering does not thermally decompose surface impurities which causes low grain boundary conductivity and thus low total ionic conductivity. In this work, a cleaning method and a low-temperature sintering process is exemplarily developed for Li0.33La0.55TiO3 (LLTO) and the impact of applied mechanical pressure during FAST/SPS on the total ionic conductivity and the phase stability of LLTO is revealed.

Device‐Level Optimization ofn‐Type Mg3(Sb, Bi)2‐Based Thermoelectric Modules toward Applications: A Perspective

AbstractIn recent decades, improvements in thermoelectric material performance have made it more practical to generate electricity from waste heat and to use solid‐state devices for refrigeration. However, despite the development of successful strategies to enhance the figure‐of‐meritzT, optimizing devices for large‐scale applications remains challenging. HighzTvalues do not guarantee excellent device performance, and maintaining highzTover a wide temperature range is difficult. Thus, device‐level structural optimization is crucial for maximizing overall energy conversion efficiency. Proper interfacial and structure design strategies, including contact layer selection, multi‐stage optimization, and size matching for then‐ andp‐type thermoelectric legs, are necessary for advancing device performance. Additionally, thermal stability issues, device assembly techniques, mechanical properties, and manufacturing costs are crucial considerations for large‐scale applications. To achieve actual applications, the thermoelectric community must look beyond simply aiming for highzTvalues. This article focuses on modules based onn‐type Mg3(Sb, Bi)2, one of the most promising commercially available thermoelectric materials, and discusses the influence of various parameters on the modules and on the corresponding device‐level optimization strategies.

Dimerized Small-Molecular Acceptor Enables the Organic Bulk-Heterojunction Layer with High Thermal Stability.

Incorporation of a non-fullerene acceptor (NFA) into an organic bulk-heterojunction currently has realized the extendable spectral response and high photocurrent generation in organic photodiodes. However, to allow these organic materials to be industrially commercialized, the thermal stability which enables the materials to survive under the process integration and operation needs to be considered. Generally, NFA small molecules showed high crystallinity, which aggregated through heating and led to the poor thermal stability. To tackle the thermal stability issue of highly efficient NFAs, two IDIC-based NFA dimers─IDIC-T Dimer and IDIC-TT Dimer─were designed, synthesized, and characterized; the thermal stability of the BHJ layer incorporating these dimer molecules was evaluated and compared with that of the BHJ layer using the monomer, IDIC-4Cl, as acceptors. Eventually, a power conversion efficiency of 9.44% was achieved for organic photovoltaic devices based on the NFA dimer. The dimers also showed remarkable thermal stability than the IDIC-4Cl monomer, which provided a promising direction for the polymer/small-molecule system in organic photodiodes for industrial practicability.

Nanographene Coupled with Interfacial Pyrene Derivatives for Thermally Stable Perovskite Solar Cells

Although high-efficiency perovskite solar cells (PSCs) have been achieved using a hole-extracting material, spiro-MeOTAD, thermal stability has been unattainable due to the low glass transition temperature of spiro-MeOTAD and additives therein. Here, we report on the use of nanographene-based hole-transporting materials coupled with a pyrene derivative as an interface modifier for thermally stable and high efficiency PSCs. Asymmetric methyl and methoxy groups are introduced in the diphenylamino group that is attached to the hexa-peri-hexabenzocoronene (HBC) nanographene core, coded HBC-DPAMeOMe. 1-Pyrenemethylammonium iodide is coupled to enhance the chemical interaction between perovskite and HBC-DPAMeOMe, which leads to a power conversion efficiency over 23%. A thermal stability test at 85 °C for 1000 h reveals that 83.6% of the initial efficiency (23.04% → 19.25%) is maintained for the device with HBC-DPAMeOMe, while a significant degradation from 20.69% to 5.08% is observed for the device with spiro-MeOTAD. Nanographene-based hole conductors shed light on the thermal stability issue in PSCs.

Enhancement of thermal stability and device performances through XTe2/TaxSb2Te3-based phase-change heterostructure

Phase-change heterostructure (PCH) devices with alternately stacked layers of phase-change materials (PCMs) and XTe2-based confinement materials (CMs) have been introduced to suppress the long transport distance of atoms during device operation. Although the PCH has yielded improvements in terms of the resistance drift, cycling endurance, and noise of phase-change memory devices, the issue of low thermal stability remains a challenge. Furthermore, only TiTe2 has been reported as an XTe2-based CM layer; therefore, the applicability of other materials must be demonstrated in PCH devices. This study entails an investigation of an XTe2/TaxSb2Te3-based superlattice-like PCH device, wherein a Ta-doped PCM and newly applied CM layers are alternately stacked to enhance the thermal stability and electrical properties of the device. The surface roughness of the optimized device was observed to be < 0.2 nm in both the amorphous and crystalline states. The XTe2/TaxSb2Te3-based PCH device operated at a low voltage (VSET ≈ 0.9 V and VRESET ≈ 2.0 V) with enhanced durability due to the low drift coefficient (ⱱSET ≈ 0.001 and ⱱRESET ≈ 0.002), long cycle endurance (<1.6 × 109 cycles), and high switching speed (∼1.1 V/50 ns). The results indicate that the proposed material configurations can be implemented to improve the overall performance of phase-change memory devices.

Approaching the Fill Factor Limit in Dopant-Free Hole Transporting Layer-Based All-Inorganic Perovskite Solar Cells.

As an important part of perovskite solar cells (PSCs), hole transporting layer (HTL) has a critical impact on the performance and stability of the devices. In an attempt to alleviate the moisture and thermal stability issues from the commonly used HTL Spiro-OMeTAD with dopant, it is urgent to develop novel HTLs with high stability. In this study, a new class of polymers D18 and D18-Cl are applied as undoped HTL for CsPbI2Br-based PSCs. In addition to the excellent hole transporting properties, we unveil that D18 and D18-Cl with larger thermal expansion coefficient than that of CsPbI2Br could impose a compressive stress onto the CsPbI2Br film upon thermal treatment, which could release the residual tensile stress in the film. As a result, the efficiency of CsPbI2Br-based PSCs with D18-Cl as HTL reaches 16.73%, and the fill factor (FF) exceeds 85%, which is one of the highest FF records for the conventional-structured device to date. The devices also show impressive thermal stability with over 80% of the initial PCE retained after 85 °C heating for 1500 h.

A review study on methanol steam reforming catalysts: Evaluation of the catalytic performance, characterizations, and operational parameters

Conventional fossil-based energy sources have numerous environmental demerits; sustainable and renewable sources are attracting the undivided attention of researchers owing to their valuable physical and chemical features. Several industrial-scale technologies are employing hydrogen as a green energy source as the most preferential source. Not only is hydrogen a potent energy carrier but also it is not detrimental to the environment. Among many other hydrogen production processes, steam reforming of methanol (SRM) is deemed a practical method due to its low energy consumption. Cu, Ni, noble metals, etc., are the salient catalysts in SRM. Many researchers have conducted thorough studies incorporating improvement of the catalysts’ activity, mechanism predictions, and the impacts of operational parameters and reformers. This review concentrates on the SRM catalysts, supports, promoters, and the effect of the operational parameters on the process efficiency and H2 production yield. In this regard, the methanol conversion, H2 and CO selectivity, and operating parameters are notably contingent on the surface characterization and chemistry of the catalysts. Herein, Cu-, Ni-, and noble metal-based catalysts on various metal oxide supports, such as Al2O3 and ZnO, are assessed meticulously in the SRM process from the standpoint of mechanism and catalyst characterization. Most of the peer-reviewed studies had encountered agglomeration, metal particle sintering at high temperatures, coke formation, and deactivation of catalysts as the prevalent barriers. Hence, the novel methods of conquering the above-mentioned obstacles are evaluated in this review. Employment of diverse synthetic methods, bimetallic catalysts, distinct catalyst promoters, and unconventional supports, such as metal–organic frameworks, carbon nanotubes, and zeolites, are the salient routes to overcome the metal dispersion and thermal stability issues. In addition, the influence of operational parameters (temperature of the process, steam/carbon ratio, and feed flow rate) has been weighed painstakingly, along with introducing the research gap and future perspectives in the territory of SRM catalysts.

Unlocking AlN Piezoelectric Performance with Earth‐Abundant Dopants

AbstractThe increasing demand for high‐performance piezoelectric materials and toxicity and thermal stability issues of the widely used lead zirconate titanates (PZT) have spurred a search for better alternatives in electronic devices. In comparison to PZT, group III nitrides such as aluminum nitride (AlN), are only weakly piezoelectric, but doping AlN with scandium (Sc) improves the piezoelectric response by nearly 500%. Relative to PZT, doped‐AlN piezoelectric materials are advantageous because they are far more compatible with complementary metal–oxide–semiconductor (CMOS) materials, and they maintain both piezoelectric and thermodynamic stability up to very high temperatures. Unfortunately, rare‐earth metals are notoriously expensive, and fabricating stable films with rare‐earth dopants is also challenging, limiting their use in industrial applications. In this work, ab initio calculations are combined with targeted fabrication and experimentation to identify alternative earth‐abundant dopants for AlN from the periodic table d‐block. Amongst the 23 elements screened, it is found that group IVB metals, titanium, zirconium, and hafnium induce large piezoelectric enhancements comparable to Sc. This improvement is traced to shifts in the atomic sublattice structure and changes in the local charge states. In demonstrating a highly accessible and affordable path for technological adaptation of AlN‐based piezoelectrics, this work provides the foundation for sustainable, next‐generation electronics.

Poly(ether ether ketone)-Induced Surface Modification of Polyethylene Separators for Li-Ion Batteries

With the global effort to reduce fossil fuels and to use eco-friendly energy, interest in Li-ion batteries (LIBs) is rapidly increasing. In the LIB system, the separator is an important component for determining the rate performance and safety of cells. Although polyolefin separators are commercially used in LIBs, they still suffer from inferior electrolyte wettability and low thermal stability issues. Here, we introduce a chemical surface modification for polyethylene (PE) separators using a poly(ether ether ketone) (PEEK) coating. The separators were pretreated in a tannic acid solution to enforce the adhesion of the coated layers. Then, PEEK was coated onto the PE surface by a doctor blading method. The separators were examined by infrared spectroscopy, and the surface properties were characterized by electrolyte uptake and contact angle measurements. The treated surface was hydrophilic, and the ionic conductivity of the cell with the modified separator was significantly improved. As a result, the corresponding rate performance was significantly improved. The surface modification strategy proposed here can be applied to polyolefin-based separators as well.