Nanostructured Precursors Research Articles

Microwave-assisted solvothermal synthesis of nanostructured Ga-Doped Li7La3Zr2O12 solid electrolyte with enhanced densification and Li-ion conductivity

Garnet-type Li7La3Zr2O12 (LLZO) Li-ion solid electrolytes are promising candidates for safe, next-generation solid-state batteries. In this study, we synthesize Ga-doped LLZO (Ga–LLZO) electrolytes using a microwave-assisted solvothermal method followed by low-temperature heat treatment. The nanostructured precursor (<50 nm) produced by the microwave-assisted solvothermal process has a high surface energy, facilitating the reaction for preparing garnet-type Ga–LLZO powders (<800 nm) within a short time (<5 h) at a low calcination temperature (<700 °C). Additionally, the calcined nanostructured Ga–LLZO powder can be sintered to produce a high-density pellet with minimized grain boundaries under moderate sintering conditions (temperature: 1150 °C, duration: 10 h). The optimal doping concentration was determined to be 0.4 mol% Ga, which resulted significantly increased the ionic conductivity (1.04 × 10−3 S cm−1 at 25 °C) and stabilized the cycling performance over 1700 h at 0.4 mA cm−2. This approach demonstrates the potential to synthesize oxide-type solid electrolyte materials with improved properties for solid-state batteries.

Diblock and Triblock Copolymers as Nanostructured Precursors to Functional Nanoporous Materials: From Design to Application.

Block copolymers have gained tremendous interest from the scientific community in the last two decades. These macromolecular architectures indeed constitute ideal nanostructured precursors for the generation of nanoporous materials meant for various high added value applications. The parallel emergence of controlled polymerization techniques has notably enabled to finely control their molecular features to confer them with unique structural and physicochemical properties, such as low dispersity values (Đ), well-defined volume fractions, and controlled functionality. The nanostructuration and ordering of diblock or triblock copolymers, which can be achieved through various experimental techniques, including channel die processing, solvent vapor or thermal annealing, nonsolvent-induced phase separation or concomitant self-assembly, and nonsolvent-induced phase separation, allows for the preparation of orientated microphase-separated copolymers whose morphology is dictated by three main factors, i.e., Flory-Huggins interaction parameter between constitutive blocks, volume fraction of the blocks, and polymerization degree. This review article provides an overview of the actual state of the art regarding the preparation of functional nanoporous materials from either diblock or triblock copolymers. It will also highlight the major applications of such peculiar materials.

Structural control of heterostructured Co3N-Co nano-corals for boosting electrocatalytic hydrogen evolution based on insulator-confined plasma engineering

A facile phase reconfiguration has been considered as an essential issue in achieving heterostructures for boosting the electrocatalytic H2 production. Compared to chemical approaches, plasma-based technique serves as a favorable strategy to achieve hetero-structured nano-frameworks, but its modulation on nano-structured precursor inevitably leads to multi-step fabrication process and it is difficult to precisely control the partial surface modulation through plasma technique due to complicated interaction environment. To achieve heterostructures with optimized hydrogen evolution reaction (HER) behavior, we design a novel auxiliary insulator-confined plasma system to directly achieve Co3N-Co heterostructure (hCNC) with favorable activity by controlling surface heating process during plasma nitridation. The resultant hCNC nano-framework delivers excellent catalytic performance, evidenced by its overpotential of 97 and 229 mV at current density of 10 and 100 mA cm−2 for HER in alkaline condition, in stark comparison with that of normal plasma fabricated Co3N. Operando plasma diagnostics along with numerical simulation further confirm the effect of surface heating on typical plasma parameters as well as the Co3N-Co nano-structure, indicating the key factor responsible for the high-performance hetero-structured electrocatalyst.

Spontaneous Hetero-attachment of Single-Component Colloidal Precursors for the Synthesis of Asymmetric Au-Ag2X (X = S, Se) Heterodimers.

Finding simple, easily controlled, and flexible synthetic routes for the preparation of ternary and hybrid nanostructured semiconductors is always highly desirable, especially to fulfill the requirements for mass production to enable application to many fields such as optoelectronics, thermoelectricity, and catalysis. Moreover, understanding the underlying reaction mechanisms is equally important, offering a starting point for its extrapolation from one system to another. In this work, we developed a new and more straightforward colloidal synthetic way to form hybrid Au-Ag2X (X = S, Se) nanoparticles under mild conditions through the reaction of Au and Ag2X nanostructured precursors in solution. At the solid-solid interface between metallic domains and the binary chalcogenide domains, a small fraction of a ternary AuAg3X2 phase was observed to have grown as a consequence of a solid-state electrochemical reaction, as confirmed by computational studies. Thus, the formation of stable ternary phases drives the selective hetero-attachment of Au and Ag2X nanoparticles in solution, consolidates the interface between their domains, and stabilizes the whole hybrid Au-Ag2X systems.

Making progress towards promising energetic cellulosic microcrystals developed from alternative lignocellulosic biomasses

ABSTRACT This study reported the valorization of various alternative lignocellulosic feedstocks including giant reed (GR), palm fronds (PF) and esparto grass (EG) for the development of promising nitrated structurally modified cellulosic biopolymers (NNCs). The extracted nanostructured cellulose precursors and their nitrated derivatives were analyzed for their physicochemical properties, chemical structure, crystallinity and thermal stability. Experimental findings confirmed the successful formation of the desired energetic NNCs polymers with increased densities (1.698–1.711 g/cm3) and high nitrogen contents (13.10–13.26%) followed the order NNC-EG>NNC-PF>NNC-GR, which are greater than those of the commonly used nitrocellulose (1.650–1.670 g/cm3 and 12.50–12.70%). Furthermore, isoconversional integral models (TAS, it-KAS and VYA/CE) were exploited based on non-isothermal DSC data to investigate their thermal decomposition kinetics. The predicted kinetic parameters displayed that the synthesized energy-rich NNCs presented close values of Arrhenius parameters within the range of 156 ≤ Eα (kJ/mol) ≤163 and 14.7 ≤ Log(A(s−1) ≤ 15.6, and decomposed following diverse reaction mechanisms. Consequently, the explored lignocellulosic biomasses could be considered as valuable alternative non-woody resources for the production of advanced high-energy dense cellulosic biopolymers for potential application in the next generation of solid propellant formulations and composite explosives.

Material Science for catalysis: Quo vadis?

Material Science for catalysis: Quo vadis?

Narrow-gap, semiconducting, superhard amorphous carbon with high toughness, derived from C60 fullerene

New carbon forms exhibiting extraordinary physico-chemical properties can be generated from nanostructured precursors under extreme pressure. Nevertheless, synthesis of such fascinating materials is often not well understood that results, as is the case of C60 precursor, in irreproducibility of the results and impeding further progress in the materials design. Here the semiconducting amorphous carbon having bandgaps of 0.1-0.3 eV and the advantages of isotropic superhardness and superior toughness over single-crystal diamond and inorganic glasses are produced from transformation of fullerene at high pressure and moderate temperatures. A systematic investigation of the structure and bonding evolution was carried out by using rich arsenal of complimentary characterization methods, which helps to build a model of the transformation that can be used in further high p,T synthesis of novel nanocarbon systems for advanced applications. The produced amorphous carbon materials have the potential of demanding optoelectronic applications that diamond and graphene cannot achieve

Mesoporous TiO2 from Metal-Organic Frameworks for Photoluminescence-Based Optical Sensing of Oxygen

Metal−organic frameworks (MOFs) are a class of porous coordination networks extraordinarily varied in physicochemical characteristics such as porosity, morphologies, and compositions. These peculiarities make MOFs widely exploited in a large array of applications, such as catalysis, chemicals and gas sensing, drug delivery, energy storage, and energy conversion. MOFs can also serve as nanostructured precursors of metal oxides with peculiar characteristics and controlled shapes. In this work, starting from MIL125-(Ti), a 1,4-benzenedicarboxylate (BDC)-based MOF with Ti as metallic center, mesoporous TiO2 powders containing both anatase and rutile crystalline phases were produced. A challenging utilization of these porous MOF-derived Ti-based oxides is the optically-based quantitative detection of molecular oxygen (O2) in gaseous and/or aqueous media. In this study, the photoluminescence (PL) intensity changes during O2 exposure of two MOF-derived mixed-phase TiO2 powders were probed by exploiting the opposite response of rutile and anatase in VIS-PL and NIR-PL wavelength intervals. This result highlights promising future possibilities for the realization of MOF-derived doubly-parametric TiO2-based optical sensors.

Boosting high-rate Li storage of bulb-like O-MoS2@C nanoreactors with sulfur vacancies and carbon

Molybdenum sulfide (MoS2) is a promising materials for lithium ion batteries, while the anodes often suffer from low capacity and poor endurability at high current conditions (≥5 A g−1). Here, CTAB was employed as a soft template and carbon source to prepare monodispersed bulb-like O-MoS2@C nanoreactor for high-rate Li storage through an integrated approach. Specifically, bulb-like nanostructured MoS2 precursor were first prepared by microemulsion method. Rich sulfur vacancies were created along with the oxygen doping in anion exchange reaction. And amorphous carbon derived from CTAB is incorporated in the nanoreactor after annealing treatment. The resultant O-MoS2@C delivered average specific capacities of ~1442 mA h g−1 at 0.2 A g−1 and ~394 mA h g−1 at 5 A g−1, and maintained reversible capacities of 1208 mA h g−1 after 200 cycles and ~361 mA h g−1 after 700 cycles, respectively. Density functional theory (DFT) results indicated that the thermodynamic adsorption and kinetic migration of Li can become effortless through introducing carbon and vacancies. This work provides a controllable approach to produce nanoreactor with vacancies and in-situ carbon incorporated for high-rate and durable Li storage performances.

Characterization and oxidation behaviour of nanostructured La2(Zr0.7Ce0.3)2O7/YSZ coatings prepared by calcined precursor precipitate plasma spraying

ABSTRACTIn this study, La2(Zr0.7Ce0.3)2O7 nanostructured coatings were applied by plasma spraying of the nanostructured agglomerates. Initial nanostructured precursor, precursors calcined at 400°C, 600°C and 900°C with La2(Zr0.7Ce0.3)2O7 compound were used to apply top coat layer of the coatings. XRD results and microstructural observations indicated that a uniform distribution of LC phase in LZ matrix was obtained in the coatings applied by the precursors calcined at 400°C, 600°C and 900°C. The coatings were composed of vertical cracks. The isothermal oxidation results showed that TGO layer in the coating applied by the precursor calcined at 600°C (coating 600D60) was composed of Al2O3 protective compound. While, TGO layer in the conventional YSZ coating contained both compounds of protective Al2O3 and Ni(Cr, Al)2O4 detrimental spinel. The coating 600D60 had better isothermal oxidation resistance compared to the conventional YSZ. But, its thermal cycling resistance was approximately equal to the conventional YSZ.

Evaluation of oxidation and thermal insulation capability of nanostructured La2(Zr0·7Ce0.3)2O7/YSZ functionally graded coatings

In the present work, nanostructured La2(Zr0·7Ce0.3)2O7/YSZ functionally graded coatings were prepared by applying the atmospheric plasma spraying process. The La2(Zr0·7Ce0.3)2O7 compound was synthesized via the calcination process to get a nanostructured precursor precipitate at 600 °C. Two types of nanostructured functionally graded coatings were applied on the Hastelloy X substrates coated with NiCrAlY and 8YSZ. The agglomerates of La2(Zr0·7Ce0.3)2O7 were then used to apply the type I coating. Type II coating was then applied by the plasma spraying of the heat-treated agglomerates of La2(Zr0·7Ce0.3)2O7. The results of the phase and microstructural analysis showed that a nano-composite microstructure comprising the main phases of lanthanum zirconate with the partial solubility of cerium cation (LZ) and the solid solution of cerium lanthanum zirconate (LC) was formed in both types of coatings. Type II coating was relatively denser; so, it could be considered as a dense nanostructured coating. The results of the oxidation tests also showed that only the type II coating had higher oxidation resistance, as compared to that of the conventional YSZ coating. Parabolic oxidation rate constant of this coating was equal to 0.114 μm2/h. On the other hand, the oxidation rate constant for the type I coating and conventional YSZ coating was measured to be 0.141 μm2/h and 0.147 μm2/h, respectively. In addition, the results of the thermal insulation capability test indicated that the thermal barrier capability of the type I coating was 59% higher than that of the conventional YSZ coating. However, under similar conditions, this percentage was 29% for the type II coating.

Nitrogen, phosphorus and sulfur tri-doped hollow carbon nanocapsules derived from core@shell zeolitic imidazolate framework@poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) for advanced supercapacitors

The rational design and facile synthesis of multiple heteroatoms co-doped hollow carbon nanomaterials with high electrochemical performance still remain a challenge. Herein, an effective and facile method is proposed for the fabrication of N, P and S tri-doped hollow carbon nanocapsules (NPS-HCN) via direct carbonization and subsequent acid etching of a rationally designed core@shell nanostructured precursor, which is prepared by coating crosslinked poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) onto the zeolitic imidazolate framework. Due to its distinctive hollow nanostructure feature, large specific surface area (865 m2 g−1), and high heteroatom content (6.01 at% for N, 0.68 at% for P, 1.95 at% for S), the NPS-HCN as supercapacitor electrode material delivers prominent performances with large specific capacitance (351 F g−1 at 1 A g−1), great rate capability (242 F g−1 at 20 A g−1) and long-term cycle stability (97.1% capacitance retention after 10,000 cycles). Remarkably, the constructed symmetric supercapacitor using NPS-HCN delivers a high voltage output of 2.0 V and an excellent energy density of 37.72 Wh kg−1 at a power density of 499.97 W kg−1. These results demonstrate that this study might offer an effective strategy to generate multiple heteroatoms co-doped hollow carbon nanomaterials for achieving advanced energy storage.

Extremely hard and tough high entropy nitride ceramics

Simultaneously hard and tough nitride ceramics open new venues for a variety of advanced applications. To produce such materials, attention is focused on the development of high-entropy ceramics, containing four or more metallic components distributed homogeneously in the metallic sublattice. While the fabrication of bulk high-entropy carbides and borides is well established, high-entropy nitrides have only been produced as thin films. Herein, we report on a newel three-step process to fabricate bulk high-entropy nitrides. The high-entropy nitride phase was obtained by exothermic combustion of mechanically-activated nanostructured metallic precursors in nitrogen and consolidated by spark plasma sintering. The fabricated bulk high-entropy nitride (Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)N demonstrates outstanding hardness (up to 33 GPa) and fracture toughness (up to 5.2 MPa∙m1/2), significantly surpassing expected values from mixture rules, as well as all other reported binary and high-entropy ceramics and can be used for super-hard coatings, structural materials, optics, and others. The obtained results illustrate the scalable method to produce bulk high-entropy nitrides with the new benchmark properties.

Synthesis of magnetite, ceria and magnetite-ceria materials by calcination of nanostructured precursor-minerals

The present short communication reports an original experimental calcination method to synthesize magnetic materials with high thermal stability such as magnetite (Fe3O4) with typical spinel and atypical crystal shape, sub-micrometric rounded crystals of ceria (CeO2) and magnetite-ceria composites with varied shape and size of crystals. Shape and size depending on the nature of mineral precursors (goethite, siderite or ferrihydrite). Herein, it was demonstrated that cooperative redox reactions and simple vacuum can be used to synthesize magnetic composite materials by calcination of nanostructured mineral precursors. In this way, bastnäsite mineral (CeCO3F) is a powerful reducing agent to synthesize magnetite from reductive dehydration of ferric oxyhydroxides.

Nanostructured YAG and Er:YAG Powders Synthesized via Glycine–Nitrate Technique for Optically Transparent Ceramics

ABSTRACT Nanostructured precursors of yttria-alumina garnet powders have been synthesized using the glycine–nitrate technique. It was shown that the main characteristics of the powders are determined by the glycine/nitrate (G/N) molar ratio in the initial solution and the temperature of the heat treatment of the precursors. The maximum specific surface area of the powders was obtained for the G/N ratio of 0.4. Subsequently, the powders were subjected to mechanical treatment and sintering. The effects of the treatment conditions and the amount of the sintering additive (Sc2O3) on the properties of the resulting ceramics were studied using erbium-yttrium garnet (Er1,5Y1,5Al5O12) as an example. Ceramics with a transparency of approximately 70% were obtained at 1790°С.

Co3O4 arrays with tailored morphology as robust water oxidation and urea splitting catalyst

A typical hydrothermal preparation approach was successfully exploited and designed for the in situ growth of highly ordered Co3O4 nanostructure precursors on a Ni foam substrates, a series of Co3O4 nanoarray-based electrocatalysts was obtained via a subsequent calcination procedure. The formation of Co3O4 hierarchical structures with different morphologies depended upon the hydrothermal time, which was used to further reveal the growth mechanism of the Co3O4 nanostructures. H2O and CO(NH2)2 were selected as probe molecules to evaluate the electrocatalytic activity over the resulting Co-based electrocatalysts, and the influence of the morphology on the electrocatalytic performance was further investigated via employing different hydrothermal times. It is worth noting that Co3O4/NF-11h nanosheets@nanoneedles heterostructures with a low density of nanosheets presents superior electrocatalytic performance and long-term durability owing to an increased exposure to active sites in the hierarchical nanostructure. The Density Functional Theory (DFT) calculations results show that H2O molecules are preferentially adsorbed at the top of the Co3O4 (111) crystal surface. This work emphasizes the significance of effective structure design for the development of robust and precious metal-free electrocatalysts via the precise control of catalyst morphology.

Tunable Synthesis of Hollow Metal-Nitrogen-Carbon Capsules for Efficient Oxygen Reduction Catalysis in Proton Exchange Membrane Fuel Cells.

Atomically dispersed metal catalysts anchored on nitrogen-doped (N-doped) carbons demand attention due to their superior catalytic activity relative to that of metal nanoparticle catalysts in energy storage and conversion processes. Herein, we introduce a simple and versatile strategy for the synthesis of hollow N-doped carbon capsules that contain one or more atomically dispersed metals (denoted as H-M-Nx-C and H-Mmix-Nx-C, respectively, where M = Fe, Co, or Ni). This method utilizes the pyrolysis of nanostructured core-shell precursors produced by coating a zeolitic imidazolate framework core with a metal-tannic acid (M-TA) coordination polymer shell (containing up to three different metal cations). Pyrolysis of these core-shell precursors affords hollow N-doped carbon capsules containing monometal sites (e.g., Fe-Nx, CoNx, or Ni-Nx) or multimetal sites (Fe/Co-Nx, Fe/Ni-Nx, Co/Ni-Nx, or Fe/Co/Ni-Nx). This inventory allowed exploration of the relationship between catalyst composition and electrochemical activity for the oxygen reduction reaction (ORR) in acidic solution. H-Fe-Nx-C, H-Co-Nx-C, H-FeCo-Nx-C, H-FeNi-Nx-C, and H-FeCoNi-Nx-C were particularly efficient ORR catalysts in acidic solution. Furthermore, the H-Fe-Nx-C catalyst exhibited outstanding initial performance when applied as a cathode material in a proton exchange membrane fuel cell. The synthetic methodology introduced here thus provides a convenient route for developing next-generation catalysts based on earth-abundant components.

Recent Advances in the Design and Fabrication of Strong and Ductile (Tensile) Titanium Metal Matrix Composites

Titanium metal matrix composites (TiMMCs) offer much improved strength, elastic modulus, and wear resistance at both room and elevated temperatures but often at the expense of tensile ductility, which excludes them from most key engineering applications. Recent advances show that this long‐standing strength‐ductility dilemma can be controlled to a large extent by adopting novel design concepts based on powder metallurgy (PM). These include: 1) reinforcing the Ti matrix with a three‐dimensional (3D) network‐like architecture of TiB whiskers or nanowires; 2) the use of nanostructured carbon precursors (nanotubes, fibers, and graphene) to enable in situ formation of TiC reinforcements; and 3) the exploitation of “ductility‐detrimental” interstitial elements (O, N, H) for strengthening. On a laboratory scale, the fabricated TiMMCs all exhibit an excellent combination of tensile strength and elongation, comparable to, or even better than, solution‐treated and aged (STA) wrought Ti–6Al–4V. The mechanisms behind these novel developments are analyzed. New insights into the design and fabrication of stronger and more ductile (tensile) TiMMCs are offered.

Tuning the microstructure of BaTiO3@SiO2 core-shell nanoparticles for high energy storage composite ceramics

Core-shell nanoparticles used as blocks to construct composite ceramics can exhibit high energy storage density, but the effects of original tunable shell thickness on the microstructures and energy storage property of finally sintered bulk ceramics has not been clarified, thus how to achieve the full potential of this technology to improve the energy storage density of ferroelectric-based ceramics remains to be solved. In this study, as precursors to fabricate bulk ceramics, BaTiO3@SiO2 core-shell nanoparticles were successfully synthesized by a wet-chemical method and they were used as models to investigate the effect of the core-shell nanostructured precursors on the energy storage property of the bulk composite ceramics. The original BaTiO3 nanoparticles coated with various homogenous SiO2 shells were acquired by controlling the concentration of tetraethyl orthosilicate (TEOS). The surface microstructure of the bulk composite ceramics observed by scanning electron microscope (SEM) revealed that the SiO2 outer shell of BaTiO3@SiO2 nanoparticles plays an important role in constructing the microstructure of the ceramics. The remodeled microstructure has a great impact on leakage current density and dielectric property, and it makes a leading contribution to the energy storage performance of ceramics. As a result, the optimum SiO2 loading range was confirmed and the maximum energy storage density obtained from BaTiO3@20 wt%SiO2 was ∼4.799 J/cm3 at 370 kV/cm, demonstrating that nanoscale core-shell architecture is an effective strategy to improve the energy storage performance of ferroelectric-based composite ceramics.

Microstructure and phase evolution of Li4TiO4 ceramics pebbles prepared from a nanostructured precursor powder synthesized by hydrothermal method

Li4TiO4 ceramics pebbles have been proposed to be a promising tritium breeder materials for the fusion reactor blanket of the International Thermonuclear Experimental Reactor (ITER). In the present study, the hydrothermal method was first used to synthesize the nanostructured precursor powders for fabricating the Li4TiO4 ceramic pebbles. The precursor powders were composed of LiOH, Li2CO3 and Li2TiO3 with a grain size of 30–80 nm. Moreover, the microstructure and phase evolution of Li4TiO4 ceramics pebbles were investigated. The results indicated that the formation temperature of Li4TiO4 by hydrothermal method was lower than that of other methods. The pure phase Li4TiO4 ceramic pebbles with small grain size (average value 0.50 μm), satisfactory crush load (average value 41 N) and reasonable pore structure was sintered at 750 °C for 4 h in vacuum. This study provides a new method for preparing a high quality Li4TiO4 ceramic pebble, which has potential application as a tritium breeding material.