Iron Acetylacetonate Research Articles

Investigation of Fe3O4/SBA-15 magnetic nanocomposite synthesized by microwave-assisted solvothermal route as multi-therapeutic agent

In the current study, a facile and in situ synthesis route for the preparation of mesoporous SiO2-Fe3O4 magnetic nanocomposite using iron (III) acetylacetonate via microwave-assisted solvothermal method is proposed. To characterize the samples, XRD, EDS, SEM, TEM, BET, and VSM were applied, and their potential applications as drug carriers, hyperthermia, and MRI contrast agents were investigated. The results confirmed that the magnetic nanocomposite could be used as a drug carrier, and its drug release rate is affected by the magnetic field. Also, the product applications as both hyperthermia and MRI contrast agent for T2 weighted images were approved.

Pyridine‐oxazoline ligated iron complexes: Synthesis, characterization, and catalytic activity for isoprene polymerization

A series of iron(II) dichloride complexes (Fe1–Fe3) bearing 2‐(pyridin‐2‐yl)‐4,5‐dihydrooxazole (L1), 4‐isopropyl‐2‐(pyridin‐2‐yl)‐4,5‐dihydrooxazole (L2), and 4‐(t‐butyl)‐2‐(pyridin‐2‐yl)‐4,5‐dihydrooxazole (L3) and iron(II) acetylacetonate complex (Fe4) bearing L1 were synthesized and characterized by elemental and spectroscopic analyses. Determined by single‐crystal X‐ray crystallography, complex Fe3 adopts an unusual unsymmetrical binuclear core. Upon activation with methylaluminoxane (MAO), the pyridine‐oxazoline (Py‐ox) ligated iron complexes (Fe1–Fe4) showed excellent activity towards isoprene polymerization. Complex Fe1 displayed the highest activity of 8160 kg (mol·h)−1 with 54% of 3,4‐polyisoprene. The ligand environment and counter anion on iron center all displayed significant effects on polymerization activity and selectivity, which reflected the special performance compared with pyridine‐imine. And we propose the possible mechanism through cis‐η4 mode following the σ bond rotation because of the steric effect of t‐butyl substituent of Fe4 to give high trans‐1,4‐polymers. Furthermore, the effects of reaction parameters on the catalytic activity and selectivity were investigated in detail.

Development of Molding Compounds Based on Epoxy Resin/Aromatic Amine/Benzoxazine for High‐Temperature Electronic Packaging Applications

AbstractHeat‐resistant molding of compounds is an indispensable part in encapsulating future electronic power devices. Herein, it is used for polyfunctional epoxy resin (EP) and diamine‐phenol benzoxazine (BOZ) as resin matrix, 4,4'‐diaminodiphenylmethane (DDM) as curing agent, and iron acetylacetonate (Fe(acac)3) as curing accelerator, as well as inorganic fillers and other auxiliaries, to prepare heat‐resistant molding compounds. The curing behavior, processability and thermal performance of the EP/DDM/BOZ (EDB) resin blends containing different contents of DDM, BOZ, and Fe(acac)3 are first systematically investigated. The EDB molding compounds (MCEDB) with suitable BOZ content show good processability, and the molding process can be compatible with that of commercial epoxy molding compounds (EMC). With increasing the BOZ content, the glass transition temperature of cured MCEDB is greatly enhanced to a maximum of 261 °C determined by dynamic mechanical analyzer, owing to the hydrogen‐bond interaction generated after polymerization of BOZ increasing the rigidity of network chains. Moreover, the cured MCEDB also exhibits higher thermal decomposition stability, better high‐temperature (200 °C) mechanical properties, and lower water absorption compared to the cured EMC. After high‐temperature (200 °C) aging for 500 h, the cured MCEDB with suitable BOZ content still maintains outstanding performance. This study provides a promising strategy for preparing heat‐resistant electronic packaging molding compounds.

Temperature Dependent Study of AcFc-FeIII(acac)3 Redox Couple for Non-Aqueous Redox Flow Battery

Energy storage is a vital aspect for the successful implementation of renewable energy resources on a global scale. Non-aqueous redox flow battery (NARFB) is one of the primary response to fulfill the next generation energy demand.1–6 This study describes the temperature dependence electrochemical analysis of acetyl ferrocene (AcFc) and iron(III) acetyl acetonate ([Fe(acac)3]) for NARFBs. An electrochemical cell consisting of AcFc and ([Fe(acac)3]) as catholyte and anolyte species, respectively, was constructed with a cell voltage of 1.41 V and Coulombic efficiencies >99% for up to 50 total cycles at 25o C (RT) and 0o C. Rotating ring disk electrode (RRDE) experiments suggest that diffusion coefficient decreases as the temperature decreases but overall storing capacity far better than aqueous redox flow battery (ARFBs). The electrochemical kinetic rate constant (k0) of AcFc found larger than Fe(acac)3 but remains similar at both temperatures. NMR study shows no structural change in changing temperature and after battery experiments. References (1) Mazumder, M. M. R.; Burton, A.; Richburg, C. S.; Saha, S.; Cronin, B.; Duin, E.; Farnum, B. H. Controlling One-Electron Vs Two-Electron Pathways in the Multi-Electron Redox Cycle of Nickel Diethyldithiocarbamate. ECS Meet. Abstr. 2021, MA2021-01 (1), 52–52. https://doi.org/10.1149/ma2021-01152mtgabs.(2) Islam, R.; Mazumder, M. M. R.; Farnum, B. H. Solvent Dependent Spectroscopic and Electrochemical Studies of Nickel (II) Diethyldithiocarbamate for Energy Storage. ECS Meet. Abstr. 2021, MA2021-01 (1), 54–54. https://doi.org/10.1149/ma2021-01154mtgabs.(3) Saha, S.; Sahil, S. T.; Mazumder, Md. M. R.; Stephens, A. M.; Cronin, B.; Duin, E. C.; Jurss, J. W.; Farnum, B. H. Synthesis, Characterization, and Electrocatalytic Activity of Bis(Pyridylimino)Isoindoline Cu( ii ) and Ni( ii ) Complexes. Dalton Trans. 2021, 10.1039.D0DT03030A. https://doi.org/10.1039/D0DT03030A.(4) Mazumder, M. M. R.; Farnum, B. H. Two One Electron vs One Two-Electron Redox System of Nickel Diethyldithiocarbamate for Redox Flow Battery; ACS, 2021. https://doi.org/10.1021/scimeetings.1c00951.(5) Mazumder, M. M. R.; Farnum, B. H; Burton Andricus. Mechanistic Study of Multi-Electron Redox Cycle of Nickel Dithiocarbamate Complex for Redox Flow Battery Application; ACS, 2021. https://doi.org/10.1021/scimeetings.1c00387.(6) Mazumder, M. M. R. Ni(IV/II) Redox Couple 2e- Reversibility Improvement for Redox Flow Battery. ECS Meet. Abstr. 2021, MA2021-02 (5), 1855–1855. https://doi.org/10.1149/ma2021-0251855mtgabs. Figure 1

Hybridization of Mesoporous Carbon and Iron Oxide for Better Mitigation of Polysulfide Shuttling in Li-S Batteries

With a higher theoretical capacity, lithium-sulfur (Li-S) batteries have been considered as promising candidates for next-generation batteries. Due to the non-conducting nature of sulfur, however, lithium-sulfur batteries tend to exhibit poor performance at a high current rate (C-rate).Here we demonstrate that Fe3O4, synthesized from precursor iron (III) acetylacetonate (AAI), and mesoporous carbon material, Ketjen Black (KB), can be synergistically combined to enhance the electrochemical performance of lithium-sulfur batteries substantially. Instead of adding commercial magnetite particles into Li-S cathodes, iron oxides are synthesized and imbedded into KB from a precursor, AAI, through thermal treatments in air and Ar. The sulfur, then, is incorporated into iron oxides/KB hybrids by melting at an elevated temperature. With air-controlled electrospray as the processing method, sulfur embedded iron oxides/KB, poly(acrylic acid), and rGO sheets are mixed and directly deposited onto the carbon-coated aluminum collector, to employ as the Li-S battery cathode. X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) studies confirm that Fe3O4 and iron carbide (Fe3C) are synthesized from the precursor, AAI, embedded in mesoporous carbon materials, and reducing the charge transfer resistance of batteries. The rate-capability tests show that systems with KB/Fe3O4 can achieve enhanced performance compared to batteries without iron oxides, especially at high C-rates. With 14 wt % of solid materials as iron oxides and iron carbide, batteries exhibit 750 mAh/g at 2C discharge/charge rates, which is 83% higher compared to systems without iron oxides. However, incorporated via 250 °C for 0.5 hr in air and 850 °C for 2 hr in Ar, the composite of KB/Fe3O4/Fe3C induces irreversible side reactions during the initial charging process, which causes a huge difference in capacity between the first and the second cycle. To achieve an optimal status with improved rate capability and acceptable initial charging time, we modify the thermal treatments and thus increase the proportion of Fe3O4 in the mixture. According to the postmortem analysis, cathodes with iron oxides can interact with soluble polysulfides strongly and alleviate the polysulfide shuttle effect significantly, compared with those without Fe3O4. Such enhanced rate capability by KB/Fe3O4 (synthesized) over KB only or KB/Fe3O4 (commercial) systems suggests that the incorporation of iron oxides can play an important role in improving the electrical conductivity of cathode and mitigating polysulfide shuttle effect. Figure 1

Enhanced EMW absorption properties of SiCN/Fe/Ni ceramics modified with Fe/Ni bimetal

The SiCN/Fe/Ni ceramics codoped with iron acetylacetonate (FA) and nickle acetylacetonate (NA) was synthesized by polymer-derived ceramics (PDCs) method in this study. The microstructure, phase composition and electromagnetic wave (EMW) absorption properties of the samples were analyzed. The polarization loss and conduction loss of materials were analyzed by the direct current (DC) multimeter and the contribution rate of polarization loss was more than 94% in the whole frequency band. The results showed that C, SiC, Fe2Si, Ni3Si, γ- (Fe, Ni) and CNTs were formed after pyrolysis which provided lots of heterogeneous interface and enhanced the interfacial polarization. Meanwhile, Ni could enter the lattice of Fe and formed a unique electronic configuration, which reinforced the conductivity and stability of Fe. In addition, the in-situ generated Fe2Si and Ni3Si provided magnetic loss and conduction loss. The RLmin value of SiCN/Fe/Ni-3 ceramic was −52.06 dB at 1.54 mm and the effective absorption band (EAB, RL ≤ −10 dB) reached 4.21 GHz (13.79–18 GHz, 1.43 mm).

New mixed‐ligand iron(III) complexes containing thiocarbohydrazones: Preparation, characterization, and chemical reactivity analysis through theoretical calculations

Five new mixed ligand Fe(III) complexes, namely, [FeL1(acac)] (L1Fe), [FeL2(acac)] (L2Fe), [FeL3(acac)] (L3Fe), [FeL4(acac)] (L4Fe), and [FeL5(acac)] (L5Fe), were synthesized from the reaction of iron(III) acetylacetonate with [ONS] donor dibasic tridentate symmetrical bisthiocarbohydrazone ligands. Synthesized mixed ligand Fe(III) complexes were characterized with infrared spectra, UV‐Vis spectra, mass spectra, elemental analysis, magnetic susceptibility measurements, and thermogravimetric analysis. The molar conductance measurement in DMF solution confirmed that the complexes are nonelectrolytic. TGA analysis results showed that the thermal stability of the ligands and complexes was high. Antioxidant capacity and free radical scavenging activity of the mixed ligand Fe(III) complexes were investigated using CUPRAC and the DPPH radical scavenging method. Mixed ligand Fe(III) complexes showed higher antioxidant activity than ligands and reference compound. Popular conceptual density functional parameters like hardness, electrophilicity, dipole moment, and chemical potential for new ligands and their Fe(III) complexes were calculated and discussed. Chemical reactivity and stabilities of the studied chemical systems were analyzed with the help of well‐known electronic structure principles like maximum hardness principle (MHP), hard and soft acid–base (HSAB) principle, minimum polarizability principle, and minimum electrophilicity principle. L1Fe, which has the highest chemical hardness value, is the most stable complex according to MHP.

Film growth mechanism of mist-chemical-vapor-deposited magnetite

Crystal growth techniques using mist precursors, such as mist chemical vapor deposition (mist CVD), are useful for growing epitaxial thin films of various functional oxides under non-vacuum conditions and at relatively low temperatures. Their growth mechanism remains elusive, however, so we developed a home-made reaction chamber for mist CVD and investigated the epitaxial growth mechanism of magnetite Fe3O4 using alcoholic mists of iron acetylacetonate precursors. We show here that grown epitaxial films’ structural and physical properties depend on mist flow rates (or N2 carrier gas flow rates). Increasing the mist flow and promoting mists’ reactions on substrate surfaces produce Fe3O4 epitaxial films having larger magnetizations and lower electrical resistivities and exhibiting the Verwey transition. We also show that films’ properties are modified by changing either water additive concentrations in alcoholic mist solutions or the distance (the joint pipe length) between the mist bottle and the reaction chamber. Our results highlight the significance of the mist-flow-induced reactions for mist CVD epitaxial growth, providing new insight into the mechanism of epitaxial growth by mist CVD.

SIMULTANEOUS SOLAR PHOTO-DEGRADATION OF PVC-FE-DOPED ZNO-NANOCOMPOSITE FLAKES AND METHYLENE BLUE DYE IN WATER

Simultaneous solar photocatalytic decolorization of Methlene Blue (MB) dye and degradation of polymer nanocomposite film in water has been attempted in the present work. The film immobilized iron (Fe)-doped zinc oxide (ZnO) nanoparticles (NPs) in polyvinyl chloride (PVC) matrix. This reduced the cost of separation of nanoparticles from treated water. Doped NPs were prepared sonochemically using zinc acetylacetonate (0.95 mmol) and ferric acetylacetonate (0.05 mmol) precursors in aqueous ethanol medium. XRD, UV-vis spectroscopy, FESEM and EDX were used for characterizing nanoparticles whereas the film was characterized by SEM. During the process, the film also reduced in weight. Degradation of both the dye and the polymer followed pseudo-first order kinetics. About 28% of the initial concentration of dye and about 5.04% of the initial weight of the PVC-film were decreased in the process after a run time of 3 h 45 minutes.

One-Step Route to Fe2O3 and FeSe2 Nanoparticles Loaded on Carbon-Sheet for Lithium Storage.

Iron-based anode materials, such as Fe2O3 and FeSe2 have attracted widespread attention for lithium-ion batteries due to their high capacities. However, the capacity decays seriously because of poor conductivity and severe volume expansion. Designing nanostructures combined with carbon are effective means to improve cycling stability. In this work, ultra-small Fe2O3 nanoparticles loaded on a carbon framework were synthesized through a one-step thermal decomposition of the commercial C15H21FeO6 [Iron (III) acetylacetonate], which could be served as the source of Fe, O, and C. As an anode material, the Fe2O3@C anode delivers a specific capacity of 747.8 mAh g−1 after 200 cycles at 200 mA g−1 and 577.8 mAh g−1 after 365 cycles at 500 mA g−1. When selenium powder was introduced into the reaction system, the FeSe2 nano-rods encapsulated in the carbon shell were obtained, which also displayed a relatively good performance in lithium storage capacity (852 mAh g−1 after 150 cycles under the current density of 100 mA·g−1). This study may provide an alternative way to prepare other carbon-composited metal compounds, such as FeNx@C, FePx@C, and FeSx@C, and found their applications in the field of electrochemistry.

Metal-organophosphate biphasic interfacial coordination reaction synthesizing nanofiltration membranes with the ultrathin selective layer, excellent acid-resistance and antifouling performance

Phytate as a natural strongly charged organophosphate has recently attracted much attention in diverse fields including membrane separations towards water-energy-food nexus. However, the ideal phytate-based nanofiltration membrane with defect-free and ultrathin selective layer for highly-efficient water treatment is still much challengeable due to the typical aggregation of metal ions and uncontrolled reaction between metal ion and organophosphate via conventional coating method. Herein, metal-organophosphate biphasic interfacial coordination reaction is proposed to construct ultrathin (13.4 nm) selective layer of phytate-based nanofiltration membranes with high permeance and excellent stability by controllable coordination assembly. Iron acetylacetonate (Fe(acac)3) as an organic phase monomer with powerful electron-gaining ability is exploited to avoid the aggregation of traditional Fe(III) in aqueous phase, which can also coordinate with phytic acid (PA) to ensure a defect-free ultra-thin selective layer. The architecture of the phytate-based selective layer can be well regulated by optimizing the coordination metal source, the concentration of PA and Fe(acac)3, reaction time, so as to achieve the ultrahigh permeation flux of 190 L m−2 h−1 with excellent dye rejection (99.6%). Most interestingly, our phytate-based nanofiltration membranes with plenty of hydrophilic phosphate groups on the surface and high binding energy of P–O–Fe bond (−315.1 kJ mol−1) exhibited the long-term separation stability, excellent acid-resistance and anti-pollution ability, realizing the stable membrane separation process under harsh conditions.

Flexible and freestanding manganese/iron oxide carbon nanofibers for supercapacitor electrodes

In this study, freestanding carbon nanofibers embedded with bimetallic manganese-iron oxide are fabricated for flexible supercapacitor applications via electrospinning. A polyacrylonitrile solution is used as the carbon source, and poly(methyl methacrylate) functions as a sacrificial template to produce microporous carbon nanofibers. The concentrations of manganese acetate and iron acetylacetonate are varied to determine the fabrication conditions for maximal electrochemical performance. The optimized supercapacitor cell exhibits a capacitance of 467 F g−1 at a current density of 1 A g−1 and a capacitance retention of 94% at the end of N = 10,000 cycles. The higher mechanical durability of the electrode is confirmed by the absence of electrochemical deterioration at the end of performing 500 bending cycles. Overall, the sample comprising carbon nanofibers, in which the optimal amount of manganese-iron oxide is embedded, has the required pseudocapacitive characteristics and is an interesting choice for high-energy-storage supercapacitor electrodes.

Metal-Coordinated Nanofiltration Membranes Constructed on Metal Ions Blended Support toward Enhanced Dye/Salt Separation and Antifouling Performances.

Metal-phenol coordination is a widely used method to prepare nanofiltration membrane. However, the facile, controllable and scaled fabrication remains a great challenge. Herein, a novel strategy was developed to fabricate a loose nanofiltration membrane via integrating blending and interfacial coordination strategy. Specifically, iron acetylacetonate was firstly blended in Polyether sulfone (PES) substrate via non-solvent induced phase separation (NIPS), and then the loose selective layer was formed on the membrane surface with tannic acid (TA) crosslinking reaction with Fe3+. The surface properties, morphologies, permeability and selectivity of the membranes were carefully investigated. The introduction of TA improved the surface hydrophilicity and negative charge. Moreover, the thickness of top layer increased about from ~30 nm to 119 nm with the increase of TA assembly time. Under the optimum preparation condition, the membrane with assembly 3 h (PES/Fe-TA3h) showed pure water flux of 175.8 L·m−2·h−1, dye rejections of 97.7%, 97.1% and 95.0% for Congo red (CR), Methyl blue (MB) and Eriochrome Black T (EBT), along with a salt penetration rate of 93.8%, 95.1%, 97.4% and 98.1% for Na2SO4, MgSO4, NaCl and MgCl2 at 0.2 MPa, respectively. Both static adhesion tests and dynamic fouling experiments implied that the TA modified membranes showed significantly reduced adsorption and high FRR for the dye solutions separation. The PES/Fe-TA3h membrane exhibited high FRR of 90.3%, 87.5% and 81.6% for CR, EBT and MB in the fouling test, stable CR rejection (>97.2%) and NaCl permeation (>94.6%) in 24 h continuous filtration test. The combination of blending and interfacial coordination assembly method could be expected to be a universal way to fabricate the loose nanofiltration membrane for effective fractionation of dyes and salts in the saline textile wastewater.

Visible-Light Mediated Oxidative Fragmentation of Ethers and Acetals by Means of Fe(III) Catalysis.

A new method employing iron(III) acetylacetonate along with visible light is described to effect oxidative ring opening of cyclic ethers and acetals with unparalleled efficiency. The method allows for a photocatalytic radical chemistry approach to functionalize relatively inert cyclic ethers into useful synthetic intermediates. The methodology sheds further light on the use of underexplored iron complexes in visible-light photochemical contexts and illustrates that simple Fe(III) complexes can initiate redox processes from 4LMCT excited states.

Carbon Dots/Iron Oxide Nanoparticles with Tuneable Composition and Properties.

We present a simple strategy to generate a family of carbon dots/iron oxide nanoparticles (C/Fe-NPs) that relies on the thermal decomposition of iron (III) acetylacetonate in the presence of a highly fluorescent carbon-rich precursor (derived via thermal treatment of ethanolamine and citric acid at 180 °C), while polyethylene glycol serves as the passivation agent. By varying the molar ratio of the reactants, a series of C/Fe-NPs have been synthesized with tuneable elemental composition in terms of C, H, O, N and Fe. The quantum yield is enhanced from 6 to 9% as the carbon content increases from 27 to 36 wt%, while the room temperature saturation magnetization is improved from 4.1 to 17.7 emu/g as the iron content is enriched from 17 to 31 wt%. In addition, the C/Fe-NPs show excellent antimicrobial properties, minimal cytotoxicity and demonstrate promising bioimaging capabilities, thus showing great potential for the development of advanced diagnostic tools.

Engineering chemical pathways for phase-tuned nanocrystalline iron oxides in microwave-assisted solvothermal synthesis.

In microwave-assisted solvothermal synthesis (MASS) of nanocrystalline iron oxides, we have analysed chemical pathways to explore the role played by the temperature and heating rate in deciding the phases and crystallographic orientations. We have achieved control over synthesis parameters by using tailored mixtures of solvents. These kinetically controlled pathways are engineered by suitably mixing high microwave dielectric loss solvents - ethanol and water, with 1-decanol. We propose two new pathways, and combinations of different pathways, to explain the observed phases in reactions between metal acetylacetonates and these solvents, using Fe(acac)3 as a representative. The proposed pathways also explain the changes in the local geometry from octahedral to square pyramidal, enroute to tetrahedral in oxides. Mixing solvents to alter tan δ is shown to provide an energy-efficient way to control the specific geometry of grown phases. The results demonstrate new ways of analysing and tuning the synthesis of complex oxides in pure and mixed solvents, under microwave irradiation.

Synthesis of surface-modified iron oxide nanocrystals using supercritical carbon dioxide as the reaction field.

In the synthesis of surface-modified nanocrystals (NCs), a simple and green chemistry approach to reduce liquid waste, particularly a solventless process, has been desired. In this study, we applied the supercritical CO2 technology, which is an excellent solventless process, to the synthesis of surface-modified iron oxide NCs. The synthesis was performed at 30.0 ± 0.8 MPa of CO2, 18 h and 100 °C, where iron(iii) acetylacetonate, pure water and decanoic acid were used as starting materials. As a result, the supercritical CO2 medium gave the NCs of α-Fe2O3 and γ-Fe2O3 with unimodal size distribution, where the mean size was 7.8 ± 2.0 nm. In addition, they were self-assembled on the TEM substrate and the mean nearest-neighbor spacing was close to the chain length of decanoic acid. Furthermore, FT-IR and TG analyses indicate that decanoic acid chemically attaches to the surface of iron oxide NCs that are dispersed in cyclohexane. These results suggest that the supercritical CO2 medium could be the new appealing reaction field to fabricate densely modified NCs without liquid waste.

Morphology-controlled hydrothermal synthesis and photocatalytic Cr(VI) reduction properties of α-Fe2O3

Hematite (α-Fe2O3) with different morphologies were synthesized via hydrothermal treatment of ferric acetylacetonate in deionized water, simply by changing the hydrothermal temperature and time. Their photocatalytic performance was assessed based on the photocatalytic reduction of aqueous Cr(VI) under visible-light. It was found that the α-Fe2O3 nanorods synthesized at 175 °C for 2 h (Fe2O3-175 °C/2 h) had better photocatalytic activity than the other products. Moreover, Fe2O3-175 °C/2 h also demonstrated good photocatalytic reusability and stability. The reasons underlying the photocatalytic activity difference of different morphologies of α-Fe2O3 were proposed, by comparing their specific surface area, photoabsorption capability, and photogenerated charge transfer and separation efficiency. Various factors influencing the photocatalytic reduction of Cr(VI) by Fe2O3-175 °C/2 h were also investigated. Finally, Fe2O3-175 °C/2 h was tested for photocatalytic treatment of the diluted black chromium electroplating solution under visible-light, and a good treatment result was obtained. Hence, α-Fe2O3 nanorods have great potential for photocatalytic treatment of Cr(VI) wastewater.

Micro‐/nanostructure evolution of C/SiFeO(N,C) polymer‐derived ceramic papers pyrolyzed in a reactive ammonia atmosphere

AbstractSiFeO(N,C)‐based ceramic papers were prepared via a one‐pot synthesis approach by dip‐coating a cellulose‐based paper template with a polymeric perhydropolysilazane precursor modified with iron(III)acetylacetonate. The preceramic composites were subsequently pyrolyzed in ammonia atmosphere at 500, 700, and 1000°C, respectively, and the characteristics of the three resulting ceramic papers were comparatively investigated.Scanning electron microscopy revealed that in each sample, the morphology of the template is successfully transferred on the ceramic system, with the cellulose‐derived fibers being converted to elemental carbon encased by a SiFeO(N,C) coating. Electron transparent cross‐sectional samples for transmission electron microscopy (TEM) were prepared from the ceramic papers, employing a standard ultramicrotomy slice cutting procedure, allowing for a detailed characterization of their in situ generated micro‐/nanostructure as well as occurring crystalline phases.TEM imaging and diffraction revealed that depending on pyrolysis temperature a different microstructure with a distinct phase assemblage is generated in the polymer‐derived ceramic papers. Crystallization from the polymer precursor starts with the precipitation of wüstite (Fe(1‐x)O) nanoparticles at 700°C inside the ceramic coating and secondary ε‐FexN at the fiber‐coating interface. Upon pyrolysis at 1000°C however, the sample primarily accommodates metallic α‐iron nanocrystals that impart ferromagnetic characteristics to the ceramic paper.The results show that the template‐assisted polymer‐derived ceramic route is a feasible approach in the production of complex ceramic compounds with fibrous paper‐like morphology. By adjusting the pyrolysis temperature, microstructure and phase composition of the ceramic paper can be conveniently tailored to the needs of its respective application.

Synergy of Iron Doping and Cyano Groups for Enhanced Photocatalytic Hydrogen Production over C3 N4.

Improving the insufficient carrier separation dynamics is still of significance in carbon nitride (C3 N4 ) research. Extensive research has been devoted to improving the carrier separation efficiency through a single strategy, while ignoring the synergistic enhancement effect produced by coupling two or more conventional strategies. Herein, we reported the fabrication of cyano group-containing Fe-doped C3 N4 porous materials via direct co-calcination of iron acetylacetonate and melamine for synergistically improving the photocatalytic performance. Iron acetylacetonate can promote the generation of cyano groups and form Fe-doping in C3 N4 , thereby increasing the visible-light absorption and reactive sites. Further, the internal donor-acceptor system formed by cyano groups and Fe-doped sites promoted charge carrier separation and inhibited the radiation recombination of e- -h+ pairs. The optimized photocatalytic activity of Fe-CN-2 sample was 4.5 times of bulk C3 N4 (BCN).