Precursor Composition Research Articles

Emulsion template – based porous silicones with piezocapacitive response

Porous silicones were prepared by thiol-ene photoaddition or hydrolysis - condensation cross-linking in emulsion template in the presence of a pyridyl-modified siloxane oligomer as surfactant, at room temperature. Hexamethyldisiloxane (HMDS) was tested as alternative, more eco-friendly solvent in competition with toluene. Variations in the composition of silicone precursors, thus in cross-linking density and method, allowed tuning of mechanical properties. The piezocapacitive response of the porous silicones was investigated, focusing on the dielectric material as potential sensing element in capacitive pressure sensors. The capacitance variation showed linearity on wide pressure domains, roughly between 2 and 300 kPa, depending on the mechanical properties of the porous monoliths. A direct correlation between sensitivity and Young's modulus was found, which allows tuning of the sensing behavior. The softest material, prepared with a binary mixture of silicone precursors, exhibited a sensitivity of 8.7 × 10−3 kPa−1 on 9–29 kPa pressure range. A porous silicone – MWCNT composite showed spectacular increase in sensitivity, with maximum value of 0.747 kPa−1 and 0–7.5 kPa sensing range when compressed at 30%. Gauge factors of 29.2 in the compressive strain range of 13–30% and as high as 88.8 in the compressive strain range of 25–50% were found.

Effect of precursor composition and heat-treatment on the morphology and physical properties of Ag nanosponges

Nanoporous silver (np-S) was prepared by free corrosion dealloying of a series of Ag–Al thin films containing between 25 and 73 at.% Al. It was found that precursor composition had an important influence on the nanostructures and morphologies of the np-S. In particular the size of the Ag ligaments systematically decreased from 32 to 13 nm as the Al content was increased over the series. In contrast, there was only a weak effect on pore size, which remained in the range 11–15 nm, with the maximum occurring at about 55 at.% Al. There was however a significant increase in the density of the pores as the Al content of the precursor was increased. The electrical resistivity of the np-S increases with the decrease in ligament size, changing from about 3 × 10−8 Ω m for sponges with ligaments of about 32 nm diameter rising to 30 × 10−8 Ω m for the sponge with the 13 nm ligaments. The surface area of the np-S was estimated by the electrochemical capacitance in KNO3 solutions and was estimated to increase by an order of magnitude compared to a smooth Ag surface. There was a systematic change in the optical properties of the sponges, with a trend towards less metallic behaviour as the ligament size decreased and pore density increased. These changes culminated in the sponge prepared from the 73 at.% Al precursor having non-metallic characteristics with regard to visible and near-infrared light. The volume fraction of metal was estimated to be of the order of 40 ± 5%. Prior annealing of the precursor inhibited dealloying.

A diffusion model for liquid metal dealloying. Application to NiCu precursors dealloyed in liquid Ag

Liquid metal dealloying is a promising technique to elaborate porous metallic materials with potential applications for catalysis and energy storage. It consists in the selective dissolution of an element out of a precursor alloy by immersing it in a liquid bath. To model this process, we introduce a one-dimensional diffusion model that relies on the thermodynamic properties of the ternary system, and on a maximum velocity criterion of the reaction front. The model is compared to experimental measurements conducted on NiCu samples dealloyed in liquid Ag. Regarding the kinetics, the model enables to reach experimental time-scales, replicate experimental trends, and reveal the influence of the ligament structure on the dealloying rate. Also, by assuming thermodynamic equilibria between solid and liquid phases in the dealloyed region, the microstructure gradient obtained numerically is in satisfactory agreement with experimental measurements. These numerical results are obtained without adjustable parameters, which opens the possibility to predict dealloyed microstructures as function of the process parameters (precursor and bath composition, dealloying time and temperature, etc.).

Measurement report: Insights into the chemical composition and origin of molecular clusters and potential precursor molecules present in the free troposphere over the southern Indian Ocean: observations from the Maïdo Observatory (2150 m a.s.l., Réunion)

Abstract. New particle formation (NPF) in the free troposphere (FT) is thought to be a significant source of particles over the oceans. The entrainment of particles initially formed in the marine FT is further suspected to be a major contributor to cloud condensation nuclei (CCN) number concentrations in the marine boundary layer (BL). Yet, little is known about the process and, more broadly, about the composition of the marine FT, which remains poorly explored due to access difficulties. Here we report measurements performed in April 2018 at the Maïdo Observatory with a nitrate-based chemical ionization atmospheric pressure interface time-of-flight mass spectrometer, which have allowed the first molecular-level characterization of the remote marine FT composition. A number of molecules and clusters were identified and classified into nine groups according to their chemical composition; among the identified species, the groups containing methanesulfonic acid (MSA) and C2 amines show signals that are on average significantly higher when the site is under conditions representative of the marine FT (compared to the BL). The correlation analysis revealed apparent connections between the signals of the identified compounds and several variables concurrently measured at the site (under FT conditions) or related to air mass history, suggesting that oxalic acid, malonic acid, and observed C2 amines could be of terrestrial origin, with, in addition, a possible marine source for oxalic acid and amines, while iodic acid, sulfur species, and maleic acid have a dominant marine origin. Identification of FT conditions at the site was based on the analysis of the standard deviation of the wind direction; this parameter, which can easily be derived from continuous measurements at the site, is shown in the first part of the study to be a relevant tracer when compared to predictions from the Meso-NH atmospheric model. Similar to other high-altitude sites, FT conditions are mainly encountered at night at Maïdo; therefore, the link to NPF could not be established, and further research is needed to assess the composition of precursors to nanoparticle formation in the marine FT.

FACILE SYNTHESIS OF ORGANOSILOXANE-MODIFIED HYDROPHOBIC GEOPOLYMER THROUGH PEPTIZATION OF POLYDIMETHYLSILOXANE

We report a scalable, facile synthetic process for hydrophobic geopolymer containing organosilane. Using polydimethylsiloxane (PDMS) as an organic precursor, the surface of sodium and potassium geopolymers of varying precursor composition was functionalized with degraded PDMS oligomers by first partially hydrolyzing PDMS in a hot, concentrated NaOH or KOH solution and subsequently by undergoing geopolymer synthesis with metakaolin. Both types of geopolymer yielded nonporous hydrophobic materials with external surface areas of 0.6475 and 4.342 m2/g for sodium and potassium geopolymer, respectively. The materials showed an oil capacity of 75 and 134 wt%, respectively. X-ray diffraction patterns of the samples indicate that the PDMS functionalized sodium geopolymers contain zeolite A and sodalite, while the potassium geopolymers were amorphous with two overlapping broad humps in contrast to the typical geopolymers.

A Review on the Upgradation of Biomass-derived Hard Carbon Materials

Abstract: Sodium-ion battery is a promising alternative to lithium-ion battery because of its abundant raw material resources, low price, and high specific capacity. Amorphous carbon materials (hard carbon) have micropores and impurities, facilitating the intercalation of sodium ions to form "quasi-metallic sodium," resulting in a high sodium storage capacity and a low sodium storage potential. Consequently, hard carbon is one of the most widely studied negative electrode materials. It can be prepared from biomass by thermochemical conversion and has the advantages of large specific capacity, low cost, good cycling stability, and renewability. This review focuses on the recent advances in biomass-based hard carbon materials. Firstly, the preparation methods of hard carbon, including precursor selection, pretreatment, drying methods, and carbonization processes, are summarized. Secondly, the effects of precursor composition and heteroatom doping structure and properties of hard carbon are examined, and the changes in carbon material pores during the activation process, as well as the selection of optimal drying method, pyrolysis temperature, carbonization temperature, activator dosage, and additive, are discussed. Thirdly, the impact of preparation methods on hard carbon's cost, efficiency, and stability is briefly summarized, and the relevant improvement measures and prospects are proposed. Finally, some insights are provided into preparing highperformance biomass-based anode materials for sodium-ion batteries.

Key Experimental Considerations When Evaluating Functional Ionic Liquids for Combined Capture and Electrochemical Conversion of CO2.

Ionic liquids (ILs) are considered functional electrolytes for the electrocatalytic reduction of CO2 (ECO2R) due to their role in the double-layer structure formation and increased CO2 availability at the electrode surface, which reduces the voltage requirement. However, not all ILs are the same, considering the purity and degree of the functionality of the IL. Further, there are critical experimental factors that impact the evaluation of ILs for ECO2R including the reference electrode, working electrode construction, cosolvent selection, cell geometry, and whether the electrochemical cell is a single compartment or a divided cell. Here, we describe improved synthesis methods of imidazolium cyanopyrrolide IL for electrochemical studies in consideration of precursor composition and reaction time. We explored how IL with cosolvents (i.e. acetonitrile, dimethylformamide, dimethyl sulfoxide, propylene carbonate, and n-methyl-2-pyrrolidone) affects conductivity, CO2 mass transport, and ECO2R activation overpotential together with the effects of electrode materials (Sn, Ag, Au, and glassy carbon). Acetonitrile was found to be the best solvent for lowering the onset potential and increasing the catalytic current density for the production of CO owing to the enhanced ion mobility in combination with the silver electrode. Further, the ECO2R activity of molecular catalysts Ni(cyclam)Cl2 and iron tetraphenylsulfonato porphyrin (FeTPPS) on the carbon cloth electrode maintained high Faradaic efficiencies for CO in the presence of the IL. This study presents best practices for examining nontraditional multifunctional electrolytes amenable to integrated CO2 capture and conversion technologies for homogeneous and heterogeneous ECO2R.

Production, characterization and performance of green geopolymer modified with industrial by-products

Industrial by-products; have received a lot of attention as a possible precursor for cement and/or concrete production for a more environmentally and economically sound use of raw materials and energy sources. Geopolymer is a potentially useful porous material for OPC binder applications. The use of industrial wastes to produce a greener geopolymer is one area of fascinating research. In this work, geopolymer pastes were developed using alkali liquid as an activator and metakaolin (MK), alumina powder (AP), silica fume (SF), and cement kin dust (CKD) as industrial by-products. Several geopolymer samples have been developed. Research has been carried out on its processing and related physical and mechanical properties through deep microstructure investigation. The samples were cured in water by immersion with relative humidity (95 ± 5%), and at room temperature (~ 19–23 °C) prior to being tested for its workability and durability. The effect of the different composition of precursors on water absorption, density, porosity, and the compressive strength of the prepared geopolymers have been investigated. The results showed that the compressive strength of geopolymers at 28 days of curing is directly proportional to the ratio of the alkali liquid. Ultimately, the best geopolymer paste mixture (GPD1 and GPD2), was confirmed to contain (15% of CKD + 85% MK and Alumina solution (55 wt%)) and (25% of CKD + 75% MK + Alumina solution (55 wt%)) respectively, with 73% desirability for maximum water absorption (~ 44%) and compressive strength (4.9 MPa).

The first example of hollow polynaphthoylenebenzimidazole fiber preparation

A new unique two-stage method for spinning hollow polynaphthoylenebenzimidazole (PNBI) fibers has been proposed. Polyacrylonitrile (PAN) fiber having a porous morphology was coated with poly(o-aminophenylene)- naphthoylenimide (PANI-O) precursor to form a composite fiber with a core–shell structure and subsequently this composite fiber precursor was heat treated in air. The inner PAN fiber underwent oxidative cyclization, accompanied by its high shrinkage, while the PANI-O shell, due to heterocyclization, turned into a PNBI-O shell, and the inner space of the hollow fiber was only partially filled with cyclized PAN.

Low-temperature synthesis of transparent conducting La-doped BaSnO3via rejuvenation of the dried peroxo-precursor

In this article, we develop a low-temperature route for the synthesis of the high figure-of-merit transparent conductor, La-doped BaSnO3. Towards this, we first study the evolution of the cubic perovskite phase of the undoped BaSnO3 during solution combustion synthesis. A peroxo/superoxo precursor synthesized via H2O2 assisted co-precipitation is employed as the oxidizing agent. Typically, precursor drying is detrimental to the low-temperature conversion of the precursor to crystalline BaSnO3. The synthesis procedure developed herein is agnostic to the altered precursor composition obtained under the particular drying conditions. This is achieved by re-solvation of the precursor with ethyl alcohol prior to the annealing. The added ethanol plays the role of fuel, enabling an exothermic reaction of the components of the mixture, providing the heat of reaction for conversion and crystal growth. Complete conversion of the precursor to phase-pure BaSnO3 with a three-fold increase in the crystallite size at lower temperatures is thus achieved. We then demonstrate the facile incorporation of lanthanum as a dopant through this method. The low-temperature synthesized lanthanum substituted BaSnO3 displays optical absorption in the NIR region corresponding to free carrier generation, and n-type conductivity.

Effect of phase distribution and defect passivation on amplified spontaneous emission of quasi-2D Dion–Jacobson perovskite

Quasi-2D Dion–Jacobson (DJ) halide perovskites with large exciton binding energy, self-assembled quantum wells, and high quantum yield attract growing attention in light-emitting diodes and solar devices. DJ-layered perovskites have the eliminated van der Waals gap and show improved photophysical features. However, there are a variety of defects and complex phase distributions produced during the solution procedure and the fast crystal development. In this paper, we reveal the effect of phase distribution and defect passivation on amplified spontaneous emission of quasi-2D perovskite (PDMA)(MA)2Pb3Br10 thin films through solvent engineering and additive methods, by establishing the correlation between the precursor compositions and the photophysical performance of the layered DJ perovskites. The energy transfer rate and the photoluminescence quantum yield increase due to the spatially homogeneous domain distribution and the reduced defect density after the addition of KBr in the DMSO:DMF. More importantly, we realize green amplified spontaneous emission and single-mode vertical-cavity surface-emitting lasing with low thresholds of 8.8 and 10.5 μJ cm−2, respectively. This work provides a guideline to achieve low-threshold multicolor lasers based on DJ perovskites.

Inorganic Fullerene-Like WS2 Reinforced Polyamide Powders for Improved Mechanical Properties in Laser Sintered Nanocomposite Parts

Polyamide (PA) is a widely utilized engineering polymer, and its thermal and mechanical properties can be further improved by adding nanofillers. However, adding inorganic fullerene-like tungsten disulfide (IF-WS2) nanoparticles (NPs) to PA to produce composite precursor powders for additive manufacturing is challenging. Here, we report a novel and cost-effective method for fabricating PA-12 based nanocomposite (NC) powders with fixed/partially encapsulated IF-WS2 nanoparticulate fillers utilizing an advanced mixing technique because simple wet mixing (WM) can only attach fillers weakly to the powder surfaces when compared to the proposed method. The resulting nanocomposite powders maintained nearly the original particle size distribution of PA-12. They also exhibited improved rheological properties, melting, and crystallization behaviors compared with those prepared by the WM method. The laser-sintered PA-12 nanocomposite specimens revealed enhanced powder thermal stability and higher tensile strengths than pristine PA-12, validating the advantages of the novel technique for the fabrication of polyamide nanocomposite powders and their suitability for utilization in laser sintering additive manufacturing. These results demonstrate that high-performance engineered PA-12 nanocomposite components can be directly laser sintered, and this technique can potentially be extended to fabricate other engineered polymeric nanocomposite powders.

Recent Advances in Preceramic Polysilazane Precursors in Additive Manufacturing

Si3N4/SiCN ceramics have been extensively explored for applications in the aerospace, mechanical engineering, and biomedical fields. Recently, there has been significant focus on the additive manufacturing (AM) of polymer-derived ceramic (PDC) technology for fabricating Si3N4/SiCN ceramics. The chemical structure and composition of the preceramic polymer precursors have a crucial influence on the performance of ceramic products. In this paper, recent advances in the use of polysilazane and polycarbosilazane precursors in AM are reviewed and an outlook for future development is presented. The findings of this study could spark inspiration and reflection regarding AM applications and synthetic technology. It is believed that the development of PDCs in ceramic fabrication will become more versatile and application-oriented and provide more freedom in the design of high-performance ceramics.

Computational thermodynamic study on CVD of silicon oxynitride films from Si–O–N–H and Si–O–N–H–Cl systems

High-throughput thermodynamic analysis of chemical vapor deposition of silicon oxynitride films from the Si–O–N–H and Si–O–N–H–Cl systems are performed based on the CALPHAD (CALculation of PHAse Diagram) approach. The considered deposition conditions are 800 °C, 200 Pa, NH3/SiH4 ratios of 0.05–50 and NH3/N2O ratios of 0.05–10. The influence of precursor composition on the phase and composition of the coatings as well as the optimal window for obtaining high-purity Si2N2O are discussed. The formation of SiO2 favors low NH3/N2O ratios and its fraction decreases with increasing NH3/N2O ratio. The content of Si2N2O increases monotonously with increasing NH3/N2O ratio until reaching 100 at.%. Free Si is suppressed to almost 0 at.% when the NH3/SiH4 ratio is greater than 1. The introduction of Cl in the precursor can not only reduce the formation of free Si but also expand the deposition window for preparing pure Si2N2O. Our calculated results agree well with available experimental data.

Laser-Induced Thermal Decomposition of Uranium Coordination Compounds with Non-oxidic Ligands to Produce Nitride and Carbide Materials.

The production of ceramics from uranium coordination compounds can be achieved through thermal processing if an excess amount of the desired atoms (i.e., C or N), or reactive gaseous products (e.g., methane or nitrogen oxide) is made available to the reactive uranium metal core via decomposition/fragmentation of the surrounding ligand groups. Here, computational thermodynamic approaches were utilized to identify the temperatures necessary to produce uranium metal from some starting compounds─UI4(TMEDA)2, UCl4(TMEDA)2, UCl3(pyridine)x, and UI3(pyridine)4. Experimentally, precursors were irradiated by a laser under various gaseous environments (argon, nitrogen, and methane) creating extreme reaction conditions (i.e., fast heating, high temperature profile >2000 °C, and rapid cooling). Despite the fast dynamics associated with laser irradiation, the central uranium atom reacted with the thermal decomposition products of the ligands yielding uranium ceramics. Residual gas analysis identified vaporized products from the laser irradiation, and the final ceramic products were characterized by powder X-ray diffraction. The composition of the uranium precursor as well as the gaseous environment had a direct impact on the production of the final phases.

The effect of the pyrolysis temperature and biomass type on the biocarbons characteristics.

The conversion of biomass and natural wastes into carbon-based materials for various applications such as catalysts and energy-related materials is a fascinating and sustainable approach emerged during recent years. Precursor nature and characteristics are complex, hence, their effect on the properties of resulting materials is still unclear. In this work, we have investigated the effect of different precursors and pyrolysis temperature on the properties of produced carbon materials and their potential application as negative electrode materials in Li-ion batteries. Three biomasses, lignocellulosic brewery spent grain from a local brewery, catechol-rich lignin and tannins, were selected for investigations. We show that such end-product carbon characteristic as functional and elemental composition, porosity, specific surface area, defectiveness level, and morphology strictly depend on the precursor composition, chemical structure, and pyrolysis temperature. The electrochemical characteristics of produced carbon materials correlate with the characteristics of the produced materials. A higher pyrolysis temperature is shown to be favourable for production of carbon material for the Li-ion battery application in terms of both specific capacity and long-term cycling stability.

Construction of Robust Organic–Inorganic Interface Layer for Dendrite‐Free and Durable Zinc Metal Anode

AbstractConstructing artificial interface layer is an effective approach to facilitate the utilization rate of zinc metal, but the practical application is still hindered by the inferior mechanical strength, low ionic conductivity, and poor stability. Herein, robust organic–inorganic layer (Nafion/BM@Zn) is coated on zinc metal through ultrasonic spraying method with boehmite and Nafion as the composite precursor. As demonstrated, the high cation selectivity and high hydrophilicity of Nafion, as well as the zincophilic property and layered structure of boehmite, synergistically contribute to the low nucleation barrier, uniform deposition, and fast transport kinetics of Zn2+ ions. As a result, the Nafion/BM@Zn anode exhibits superior reversibility with a high Coulombic efficiency of 99.9% for 9000 cycles in asymmetrical cells and durable cycling stability for 4200 h in symmetrical cells at 5 mA cm−2−1 mAh cm−2. Even in the seawater‐based electrolyte, the Nafion/BM@Zn anode still displays reversible deposition behavior for 820 h and high Coulombic efficiency of 99.91% for 2800 cycles at 5 mA cm−2−1 mAh cm−2. Furthermore, the corresponding Nafion/BM@Zn//NH4V4O10 cell presents high capacity of 258.4 mAh g−1 after 1500 cycles at 5 A g−1. This work provides a new design strategy for high‐efficiency interfacial layer of zinc metal anode.

Carbon cloth modified by direct growth of nitrogen-doped carbon nanofibers and its utilization as electrode for zero gap flow batteries

The synthetic procedure and characterization of carbon nanofibers (CNFs) grown on carbon cloth (CC) are explored in this study, with a focus on their potential application as electrodes in vanadium redox flow batteries (VRFBs). CC offers an attractive platform for surface modification owing to its conductive properties and three-dimensional architecture, while the N-doped CNFs formed by nitrogen (N) rich composition of melamine precursor enhance wettability of electrolyte and redox reactivity of vanadium ions. Electrochemical assessments reveal that NCC electrodes significantly increase voltage efficiency (VE) and capacity retention in VRFBs compared to bare CC (BCC) electrodes. Notably, NCC demonstrates a VE of 65.9%, surpassing the 55.9% of BCC electrodes. Additionally, NCC maintains superior capacity retention under varying current densities, a crucial factor for VRFBs. Long-term stability tests over 1000 cycles highlight the NCC electrode's durability, with only a minimal decrease in VE. Post-experiment analysis confirms the structural integrity of the CNFs on the CC electrodes, validating their resilience in VRFB operations. In summary, the study introduces a novel approach for fabricating N-doped CNFs on CC, resulting in electrodes that significantly boost VRFB performance in terms of efficiency, capacity retention, and stability, marking a notable advancement in flow battery technology.

Advances in flame synthesis of nano-scale architectures for chemical, biomolecular, plasmonic, and light sensing.

Flame spray pyrolysis (FSP), a key technique under the broader category of flame aerosol synthesis, is being increasingly explored for the design of advanced miniaturized sensor architectures with applications including chemical, biomolecular, plasmonic, and light sensing. This review provides an overview of the advantages of FSP for the fabrication of nanostructured materials for sensing, delving into synthesis strategies and material structures that meet the increasing demands for miniaturized sensor devices. We focus on the fundamentals of FSP, discussing reactor configurations and how process parameters such as precursor compositions, flow rates, and temperature influence nanoparticle characteristics and their sensing performance. A detailed analysis of nanostructures, compositions, and morphologies made by FSP and their applications in chemical, chemiresistive, plasmonic, biosensing, and light sensing is presented. This review identifies the challenges and opportunities of FSP, exploring current limitations and potential improvements for industrial translation. We conclude by highlighting future research directions aiming to establish guidelines for the flame-based design of nano-scale sensing architectures.

ПРЕКУРСОРЫ ОКСИДНЫХ СИСТЕМ AL2O3-ZRO2-DY2O3 И AL2O3-ZRO2-ND2O3, ПОЛУЧЕННЫЕ ЭЛЕКТРОХИМИЧЕСКИМ МЕТОДОМ

The study is devoted to the preparation of precursors of complex oxide systems by electrochemical method based on the processes of anodic dissolution of aluminium in the electrolyte containing Cl-, NO3-, Al3+, Zr4+, Y3+, Dy (III), Nd (III) ions. The synthesis of precursors of complex oxide systems was carried out in a coaxial diaphragmless electrochemical reactor with substantially different area electrodes. The process of precursor formation proceeds in the volume of the electrochemical reactor due to the interaction of electrogenerated Al3+, OH- ions and electrolyte components. It is caused by hydrolysis of anode dissolution products, formation of polyheteronuclear metal-hydroxo-aqua complexes, their polycondensation, formation of primary particles of solid phase and enlargement of the latter. A comparative analysis of the particle size distribution of samples differing in the content of Dy2O3 and Nd2O3 demonstrates the bimodal character of the distribution, expressed more clearly in the case of the system containing Nd. The average particle size of the synthesised precursors is approximately in the same range, except for the system containing Nd and obtained from an electrolyte with a higher content of this element. The results of particle size measurements are confirmed by electron microscopy data. These data correlate with the time dependence of ξ-potential of synthesised precursors of alumina-zirconium oxide systems containing REE. The proposed approach allows to obtain precursors of complex oxide systems based on aluminium, zirconium, REE oxides. Using X-ray fluorescence and particle size analysis methods, the particle size and chemical compositions of precursors of oxide systems were investigated.