High-resolution Transmission Electron Microscopy Techniques Research Articles

Functionalized Microbial Consortia with Silver-Doped Hydroxyapatite (Ag@HAp) Nanostructures for Removal of RO84 from Industrial Effluent

Considering that freshwater is a necessity for human life, sewage treatment has been a serious concern for an increasing number of scientists and academics in recent years. To clean industrial effluents, innovative catalysts with good adsorption, chemical stability, and physicochemical properties have been constructed. Here, a prospective microbial consortium was extracted from the wastewater and used as a low-cost catalyst that was functionalized with silver and silver-doped hydroxyapatite (Ag@HAp) nanostructures made using a sonochemical approach. The structural, optical, and crystal phases of Ag and Ag-doped hydroxyapatite (Ag@HAp) nanostructures were studied using ultraviolet-visible (UV-Vis), Fourier transfer infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The degradation action of functionalized microbial consortia was examined against reactive orange 84 (RO84) organic discharge. Excellent efficiency for the removal of industrial effluents was found for the Ag NPs and Ag-doped hydroxyapatite (Ag@HAp) loaded with microbial consortia. A maximum of 95% of the decolorization properties of the RO84 dye were obtained in the case of microbial consortia with Ag and Ag@HAp, which was better than the consortia alone (80.32% for 5 ppm and 69.54% for 20 ppm). The consortia/Ag showed 93.34% for 5 ppm and 85.43% for 20 ppm, while was higher for consortia/Ag@HAp (95.34 and 88.43%). The use of these surface-modified nanocatalysts for wastewater treatment and waste effluents discharged from laboratories, the chemical industry, and other sources could be expanded.

Magnetic phase diagram of BHF-NZFO composite at room temperature

Composites of barium hexaferrite (BaFe12O19) and nickel zinc ferrite (Ni0.5Zn0.5Fe2O4) have been prepared by the high-energy planetary ball mill method. The magnetic composites are characterized by employing X-ray Diffraction and High-Resolution Transmission Electron Microscopy (HRTEM) techniques. The percentage of barium hexaferrite (BaFe12O19) and nickel zinc ferrite (Ni0.5Zn0.5Fe2O4) in the composite has been obtained from the Rietveld analysis of XRD patterns. The average crystallite sizes of BHF and NZFO are found to be comparable in the composites. The magnetic properties of (1-x) BHF-(x) NZFO with x = 0 to 1 have been studied by measuring the magnetic hysteresis loop (M-H loop) for all the samples. The M-H loops are analyzed by plotting the loop width (ΔH) versus magnetization (M). The magnetic hysteresis loops for the BHF and NZFO are found to be symmetric in all the quadrants. However, symmetry breaks in M-H loops for composites. The symmetry breaking in magnetic hysteresis loops of the bi-magnetic composite suggests a new approach to analyzing the magnetic interaction between magnetic phases in the magnetic composites.

Tuning reactivity of Bi2MoO6 nanosheets sensors toward NH3 via Ag doping and nanoparticle modification

Noble metal-doping and modification are proved effective in improving the gas-response performance of semiconductor sensors. In this study, we developed a promising Bi2MoO6 (BMO)-based gas sensor capable of sensing ppb-level NH3 at room temperature via introducing silver (Ag). The BMO samples with different Ag doping and modification ratios were successfully formed via one-step solvothermal and glucose reduction techniques, respectively, which could be confirmed by the results of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) techniques. Compared to bare BMO, the gas-sensing properties of both Ag-doped and Ag surface-modified BMO samples were improved to various extents, respectively. In particular, the 5% Ag-modified BMO sensor with the highest response (Gg/Ga = 37.6 to 200 ppb NH3), long-term stability, and low threshold concentration (50 ppb) at 20% RH. Based on the spillover effect and metal–semiconductor junctions of Ag nanoparticles, the enhanced sensing response towards NH3 can be thoroughly illustrated. Combined with the first-principles calculations, the adsorption energy, density of states, and charge transfer of Ag-modified BMO were further performed to demonstrate the high sensing response and ultra-low detection limit.

Improved Charge Transport across Bovine Serum Albumin-Au Nanoclusters' Hybrid Molecular Junction.

Proteins, a highly complex substance, have been an essential element in living organisms, and various applications are envisioned due to their biocompatible nature. Apart from proteins’ biological functions, contemporary research mainly focuses on their evolving potential associated with nanoscale electronics. Here, we report one chemical doping process in model protein molecules (BSA) to modulate their electrical conductivity by incorporating metal (gold) nanoclusters on the surface or within them. The as-synthesized Au NCs incorporated inside the BSA (Au 1 to Au 6) were optically well characterized with UV–vis, time-resolved photoluminescence (TRPL), X-ray photon spectroscopy, and high-resolution transmission electron microscopy techniques. The PL quantum yield for Au 1 is 6.8%, whereas that for Au 6 is 0.03%. In addition, the electrical measurements showed ∼10-fold enhancement of conductivity in Au 6 (8.78 × 10–3 S/cm), where maximum loading of Au NCs was predicted inside the protein matrix. We observed a dynamic behavior in the electrical conduction of such protein-nanocluster films, which could have real-time applications in preparing biocompatible electronic devices.

Experimental Investigations of Thermophysical Properties and Convective Heat Transfer of Al2O3 and CuO Nanofluids in a Copper Tube: Proposing New Correlations

The performance of the Alumina/water and copper oxide/water nanofluids in a heat exchanger is experimentally investigated for particle weight concentrations ranging from 0.02 wt% to 0.5 wt%. The alumina/water and copper oxide/water nanofluids were prepared using two-step methods in an aqueous solution with 0.01 wt% CTAB (Cetyl Trimethyl Ammonium Bromide) as a surfactant at different concentrations and were characterized using HRTEM (High-Resolution Transmission Electron Microscopy) technique. Laminar forced convective heat transfer analysis using alumina and copper oxide nanoparticles suspended in water in a circular horizontal tube under constant heat flux boundary conditions was performed. The effect of various flow conditions and weight concentrations in the local heat transfer coefficient and pressure drop of both the nanofluids were investigated. Reynolds number varied from 1275 to 2200. Results show that 12.7 & 14.5 % thermal performance enhancement was observed with 0.5 wt% of Al2O3 and CuO nanofluids. Maximum, 50.62 % enhancement was observed in the average heat transfer coefficient by Al2O3 nanofluids, whereas 52.74 % was observed using CuO nanofluids using 0.5 wt% concentrations of the nanofluids and at Reynolds number of 2200. Correlations were proposed for thermal conductivity, viscosity, and Nusselt number for both the nanofluids with the maximum and minimum deviations of ±9 % and ±10 %, respectively.

Anisotropic lithium-ion migration and electro-chemo-mechanical coupling in Sb2Se3 single crystals

Harvesting the promising high energy density of advanced electrode materials in lithium-ion batteries is critically dependent on a mechanistic understanding on how the materials function and degrade along with the battery cycling. Here, we tracked phase transformations during (de)lithiation of Sb2Se3 single crystals using in situ high-resolution transmission electron microscopy (HRTEM) technique, and revealed electro-chemo-mechanical evolution at the reaction interface. The effect of this electro-chemo-mechanical coupling has a complicated interplay on the lithiation kinetics and causes various types of defects at the reaction front, including dislocation dipoles, antiphase boundaries, and cracks. In return, the formed cracks and related defects build a path for fast diffusion of lithium ions and trigger a highly anisotropic lithiation at the twisted reaction front, giving rise to the formation of presumably “dead” Sb2Se3 nanodomains in amorphous LixSb2Se3. The detailed mechanistic understanding may facilitate the rational design of high-capacity electrode materials for battery applications.

Performance Optimization of ZnO Nanorods ETL Based Hybrid Perovskite Solar Cells With Different Seed Layers

This article discusses the direct effect of the seed layers on the growth of the ZnO nanorods (ZNRs) and related photovoltaic parameters of the hybrid perovskite solar cell (PSC). Four different types of ZnO seed layer samples are prepared to analyze the growth of ZNRs over the respective seed layers. Various device parameters for the respective PSCs made of different seed layers are investigated. The ZnO quantum dot-based seed layer shows the well-aligned, vertical, and uniform distribution of ZNRs and improves SC parameters over the other three samples. The ZnO seed layer deposited via drop cast methods results in less density, random, and nonuniform distribution of the ZNRs. The surface morphology, optical absorption, transmission, and crystalline structure were analyzed with high resolution scanning electron microscopy (HRSEM), TEM, UV-visible absorption, and X-ray diffraction (XRD) techniques. 10.69&#x0025; of power conversion efficiency with improved open-circuit voltage (<inline-formula> <tex-math notation="LaTeX">${V}_{OC}$ </tex-math></inline-formula>) of 1.01 V is achieved for device structure, fluorine doped tin oxide (FTO)/ZnO QDs seed layer/ZNRs/perovskite/poly[bis(4-phenyl)(2,5,6-trimethylphenyl)amine (PTAA)/gold (Au).

Evidence of Au(II) and Au(0) States in Bovine Serum Albumin-Au Nanoclusters Revealed by CW-EPR/LEPR and Peculiarities in HR-TEM/STEM Imaging.

Bovine serum albumin-embedded Au nanoclusters (BSA-AuNCs) are thoroughly probed by continuous wave electron paramagnetic resonance (CW-EPR), light-induced EPR (LEPR), and sequences of microscopic investigations performed via high-resolution transmission electron microscopy (HR-TEM), scanning transmission electron microscopy (STEM), and energy dispersive X-ray analysis (EDS). To the best of our knowledge, this is the first report analyzing the BSA-AuNCs by CW-EPR/LEPR technique. Besides the presence of Au(0) and Au(I) oxidation states in BSA-AuNCs, the authors observe a significant amount of Au(II), which may result from a disproportionation event occurring within NCs: 2Au(I) → Au(II) + Au(0). Based on the LEPR experiments, and by comparing the behavior of BSA versus BSA-AuNCs under UV light irradiation (at 325 nm) during light off-on-off cycles, any energy and/or charge transfer event occurring between BSA and AuNCs during photoexcitation can be excluded. According to CW-EPR results, the Au nano assemblies within BSA-AuNCs are estimated to contain 6–8 Au units per fluorescent cluster. Direct observation of BSA-AuNCs by STEM and HR-TEM techniques confirms the presence of such diameters of gold nanoclusters in BSA-AuNCs. Moreover, in situ formation and migration of Au nanostructures are observed and evidenced after application of either a focused electron beam from HR-TEM, or an X-ray from EDS experiments.

Fast detection of isocarbophos using bis-propargylcalix[4]arene-stabilized silver nanoparticles.

Bis-propargylcalix[4]arene-stabilized silver nanoparticles (BPCA-Ag NPs), as a chemosensor for detecting an isocarbophos (ICP) pesticide in an aqueous medium, are reported in this work. The nanoparticles were characterized by UV-visible spectroscopy, dynamic light scattering, zeta potential and high-resolution transmission electron microscopy techniques. It was observed that the BPCA-Ag NPs had a high selectivity for isocarbophos with a detection limit of 1.0 × 10-6M. According to the result of this research, the BPCA-Ag NPs were found to be useful for the colorimetric detection of isocarbophos in an aqueous medium. It provides a new method for in situ detection of isocarbophos using host-guest interaction.

Transformation of an Aqueous Micellar Phase to a Bilayer of Gemini Surfactants on Gold Nanoparticles: A Steady-State and Time-Resolved Fluorescence and Fluorescence Anisotropy Study by Tuning the Precise Locations of Probes

The present work reports the transformation of aqueous micelles of gemini surfactants (12-4-12,2Br– or 12-8-12,2Br–) to a bilayer of surfactants on the surface of gold nanoparticles (AuNPs) capped with citrate during their in situ synthesis. The synthesized AuNPs are characterized using surface plasmon resonance (SPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), scanning transmission electron microscopy (STEM), and high-resolution transmission electron microscopy (HR-TEM) techniques. The transformation of micelles to a surfactant bilayer with time is understood with the help of fluorescence measurements such as steady-state and time-resolved fluorescence and fluorescence anisotropy, probed by tuning the precise locations of two fluorophores, Coumarin-480 (C-480) and rhodamine 6G (Rh6G), present in the micelles. As the formation of AuNPs initiates, the dyes get relocated from micelles to a site near the NP surface, which results in fluorescence quenching and a decrease in lifetime due to the nanomaterial surface energy transfer (NSET) from the donor dye to the acceptor AuNPs. The results indicated that Rh6G lies close to the head groups of the surfactant in micelles. Fast segmental/tumbling motions of Rh6G in micelles/bilayers are primarily responsible for the decay of anisotropy to zero. Lateral diffusion is responsible for slow rotational relaxation. With the growth of rod/needle-shaped NPs, the average lifetime and rotational relaxation time increase with an increase in fluorescence intensity due to the transfer of dye molecules from the NP surface to the interior of the bilayer. A significant change in the weightage of the slow component of C-480 compared to that of Rh6G with the formation of the bilayer supports that the former dye is located deep inside the bilayer with an equal contribution to depolarization from both the rotational motions at equilibrium. The excitation wavelength-dependent rotational relaxation time of Rh6G in the bilayer supports the prolate ellipsoidal shape of AuNPs surrounded by the bilayer. This study can help understand the mechanism of drug loading in forming metal NP-based hybrid drug delivery systems in an aqueous micellar solution of gemini surfactants.

Preparation of Dual Z-scheme Bi2MoO6/ZnSnO3/ZnO Heterostructure Photocatalyst for Efficient Visible Light Degradation of Organic Pollutants

In this study, a double Z-type Bi2MoO6/ZnSnO3/ZnO heterostructure photocatalyst was prepared by hydrothermal method to realize effective charge separation and improve photocatalytic activity. The synthesized samples were carefully examined by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy, photoluminescence (PL), and other analytical techniques. Meanwhile, the photocatalytic performance was further evaluated by multi-mode photocatalytic degradation with crystal violet (CV). The results show that the composite material has a relatively homogeneous cubic structure in size and shape. In the cubic structure, a heterogeneous structure exists between Bi2MoO6, ZnSnO3 and ZnO. Simultaneously, the dramatic changes in physical morphology, such as the specific surface area and particle size of the composites, led to a series of unique properties, such as a significant climb in light absorption properties and superior photocatalytic activity. In addition, compared to ZnO, Bi2MoO6 and ZnSnO3/ZnO, the Bi2MoO6/ZnSnO3/ZnO composite material shows lower PL intensity, smaller arc radius, and stronger photocurrent response. Meanwhile, Bi2MoO6/ZnSnO3/ZnO shows higher photocatalytic efficiency for CV and tetracycline hydrochloride (TC), and maintains good stability after 3 cycles of photodegradation experiments. Based on experimental results, the existence of heterojunctions between ZnO, ZnSnO3 and Bi2MoO6 and the possible photocatalytic mechanism for the degradation of CV by dual Z-scheme composites are proposed. In conclusion, this study provides a feasible strategy for the photocatalytic degradation of organic pollutants by introducing ZnSnO3 and Bi2MoO6 to successfully construct composite catalysts with dual Z-scheme heterostructures.

Musa Paradaisica and &amp;lt;i&amp;gt;Vitis vinifera&amp;lt;/i&amp;gt; Functionalised Ag-NPs: Electrochemical and Optical Detection of &amp;lt;i&amp;gt;Escherichia coli&amp;lt;/i&amp;gt; in Seawater

Herein, we demonstrate a simple and inexpensive one-pot green synthesis of silver nanoparticles (Ag-NPs) functionalised with a combination of banana peel (Musa paradisiaca) and grape (Vitis vinifera) fruit extracts. The reaction mixture of aqueous silver nitrate, banana peel and grapefruit extracts revealed a dark brown colour after a reaction time of 18 minutes, which indicates the presence and the successful synthesis of silver nanoparticles. The optical and structural properties of the green synthesised nanoparticles were analysed using UV-Visible spectroscopy (UV-Vis) which confirmed an absorption band at 440 nm. The polydispersity nature and the AgNPs sizes of 30 nm were revealed using small angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HR-TEM) techniques. Fourier transform infrared spectroscopy (FT-IR) studies revealed the structure of these nanoparticles which included carbonyl groups, primary amine groups, OH groups and other stabilizing functional groups characteristic of the properties of combined extracts. A simple, quick, less time-consuming surface plasmon resonance (SPR) and electrochemical method in the form of optical and electrochemical sensors have been developed for the detection of Escherichia coli 0157:H7. The obtained limit of detection (LOD) values for SPR and GBPE-Ag-NPs/GCE-based sensor systems were found to be 1 × 102 CFU/mL and 3.5 × 101 CFU/mL, respectively. The obtained values fall within the range for E. coli 0157:H7 in seawater.

Investigation of Deoxidation Process of MoO3 Using Environmental TEM.

In situ environmental transmission electron microscope (ETEM) could provide intuitive and solid proof for the local structure and chemical evolution of materials under practical working conditions. In particular, coupled with atmosphere and thermal field, the behavior of nano catalysts could be directly observed during the catalytic reaction. Through the change of lattice structure, it can directly correlate the relationship between the structure, size and properties of materials in the nanoscale, and further directly and accurately, which is of great guiding value for the study of catalysis mechanism and the optimization of catalysts. As an outstanding catalytic material in the application of methane reforming, molybdenum oxide (MoO3)-based materials and its deoxidation process were studied by in situ ETEM method. The corresponding microstructures and components evolution were analyzed by diffraction, high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectrum (EELS) techniques. MoO3 had a good directional deoxidation process accompanied with the process of nanoparticles crushing and regrowth in hydrogen (H2) and thermal field. However, in the absence of H2, the samples would exhibit different structural evolution.

Enhanced magnetic performance in exchange-coupled CoFe2O4–LaFeO3 nanocomposites

Nanocomposite oxide system of (x)CoFe2O4–(100-x)LaFeO3 with different weight percent of core-shell structured CoFe2O4 (x = 0, 20, 40, 50, 80, 100) and LaFeO3 were fabricated, via a two-step sol-gel wet-chemical synthesis technique. The phase formation of the composites was confirmed by x-ray diffraction and the structural parameters of both the phases were attained from the Rietveld refinement results of XRD patterns. The elemental composition and microstructure of the resulting nanocomposites were examined by using energy-dispersive x-ray spectroscopy and high-resolution transmission electron microscopy technique, respectively. The detailed magnetometry studies at 300 K and 5 K reveal that the inter-and intra-phase magnetic interactions affect the saturation magnetization (M S), remanence magnetization (M R) and coercivity (H C) values of this bi-magnetic system. The remarkable feature of ‘pinched magnetic hysteresis loop’ was evidenced in the [(50) CoFe2O4 - (50)LaFeO3] composite, leading to a lesser magnetic loss factor and better magnetic performance of this sample. The report depicts an improved interfacial exchange coupling at 5 K, for the nanocomposites of core-shell morphology and offers an understanding or explanation of improved magnetic performance for the (50)CoFe2O4 - (50)LaFeO3 nanocomposite and opens up an important way to design new multiferroic applications in low magnetic fields.

Synthesis and characterization of kinked GaAs nanowires by Sb surfactant

In this study, GaAs/GaSb and GaAs/GaSb/GaAs heterostructure nanowires (NWs) were grown on Si (111) substrates by self-catalyzed vapor-liquid-solid (VLS) mechanism using the ultrahigh vacuum (UHV) molecular beam epitaxy (MBE) system. The GaAs/GaSb/GaAs heterojunction NWs may kink away from [111] to another crystallographic direction, as observed by electron microscopy. The smallest NWs prefer growth along the ⟨220⟩ axis, while the larger GaAs NWs chose either ⟨111⟩ or ⟨002⟩ axis, and the kink angles of 55°, 71°, 109°, 125°, and 145°, respectively. Moreover, significant lateral growth was observed at the GaSb segment in the GaAs/GaSb heterojunction NWs, and lateral growth was clearly evidenced by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray (EDX) techniques. This behavior was attributed to the surfactant effect of Sb, leading to a significant change in the contact angle that ultimately caused the expansion of the Ga droplets. This study is also widely applicable to other III-V nanomaterials and provides conditions for the diversification of optoelectronic devices, such as photodetector or field-effect transistor.

In-situ atomic-scale observation the escape of irradiation-induced dislocation loops in magnesium

The formation of dislocations or dislocation loops in irradiated materials significantly alters the physical and mechanical properties of the materials. In this research, by applying in situ high-resolution transmission electron microscopy techniques, the dynamics of dislocation and self-interstitial atom (SIA) loops in magnesium (Mg) under electron beam (e-beam) irradiation at the atomic scale were observed directly. The structural characteristics of dislocation and dislocation loops were investigated with transmission electron microscopy. The in situ atomic-scale observation demonstrated that the edged dislocation gradually grew along the [1¯100] direction, while the SIA loop shrank along the same direction and eventually disappeared. The proposed processes resulted from the climbing of the dislocation and dislocation loops, which was related to the e-beam-induced anisotropic diffusion of the Mg atoms in the vicinity of the dislocations or dislocation loops. Significantly, only one side of the SIA loop near the thinner area was observed to shrink during the whole escape process, namely, a pinning phenomenon. The relevant mechanisms are discussed. The results present the detailed escape process of SIA dislocation loops at unprecedented resolution, and these results provide a significant insight into the advancement of irradiation resistance of materials.

Self-Assembly of a Bilayer 2D Supramolecular Organic Framework in Water.

Accurate control of the layer number of orderly stacked 2D polymers has been an unsettled challenge in self-assembly. Herein we describe the fabrication of a bilayer 2D supramolecular organic framework from a monolayer 2D supramolecular organic framework in water by utilizing the cooperative coordination of a rod-like bipyridine ligands to zinc porphyrin subunits of the monolayer network. The monolayer supramolecular framework is prepared from the co-assembly of an octacationic zinc porphyrin monomer and cucurbit[8]uril (CB[8]) in water through CB[8]-encapsulation-promoted dimerization of 4-phenylpyridiunium subunits that the zinc porphyrin monomer bear. The bilayer 2D supramolecular organic framework exhibits structural regularity in both solution and the solid state, which is characterized by synchrotron small-angle X-ray scattering and high-resolution transmission electron microscopic techniques. Atomic force microscopic imaging confirms that the bilayer character of the 2D supramolecular organic framework can be realized selectively on the micrometer scale.

Highly Catalytic Selectivity for Hydrogen Peroxide Generation from Oxygen Reduction on Nd-Doped Bi4Ti3O12Nanosheets

The electrochemical two-electron oxygen reduction reaction (2e–1ORR) is a promising route for renewable H2O2 generation as an alternative method to the anthraquinone process. The development of efficient and highly selective catalytic materials is a highly meaningful and challenging subject due to the strong competition from the traditional four-electron oxygen reduction reaction (4e–1ORR). Here, we synthesized bismuth titanate (Bi4Ti3O12) nanosheets as a type of new electrocatalyst for H2O2 generation from 2e–1ORR. The structure of the Bi4Ti3O12 nanosheets is characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray techniques. The electrochemical measurements show that the obtained bismuth titanate (Bi4Ti3O12), especially the neodymium (Nd)-substituted Bi4Ti3O12, has high catalytic activity and selectivity for O2 to H2O2. For the ORR catalyzed by Bi4Ti3O12 nanosheets, 83–89% H2O2 selectivity can be achieved in a wide range of potentials, while Nd-substituted Bi4Ti3O12 nanosheets afford a higher selectivity of 93–95%. Moreover, in a two-chamber H-cell, H2O2 production of 208 mol kgcat–1 can be achieved at 0.36 V under the catalysis of Nd-substituted Bi4Ti3O12 for 1 h with a Faraday efficiency of 97.6%. The high O2-to-H2O2 catalytic performance could be ascribed to the large surface area and the abundant exposed active sites of the nanosheets.

HRTEM observation of morphological and structural evolution of aromatic fringes during the transition from coal to graphite

The maximum reflectance of vitrinite or graphite microcrystals in Yongan Coalfield, Fujian Province, China, ranges from 5.33% to 10.21%, comprising meta-anthracite, semi-graphite, and graphite. The morphological characteristics of aromatic fringes during different evolution stages were quantitatively analyzed using high-resolution transmission electron microscopy and image processing techniques. The results show that a nonlinear evolution of aromatic fringe morphology in the process of coal graphitization is manifested in four aspects, involving the rapid connection and growth, enhancement of ordering alignment, increase of stacking and development of straightening. In meta-anthracite samples, 3 × 3 aromatic rings representing short aromatic fringes are dominated, a majority of aromatic fringes were curved, disjoint or separate, and show a turbostratic layers, with poorly aligned. The spacing between adjacent aromatic fringes exceeded the range of graphitized carbon, and structural defects, such as nanopores were generally visible. In semi-graphite samples, in addition to 3 × 3 aromatic rings, the proportion of >8 × 8 aromatic rings represented longer aromatic fringes increasing significantly, along with ordering alignment and straightening. Stacking with two more layers increased and the spacing between adjacent aromatic fringes decreased to the range of graphitized carbon, and the structural defects decreased considerably. In graphite sample, the proportion of >8 × 8 aromatic rings increase significantly, the length, stacking, and ordering alignment of aromatic fringes increased abruptly, the spacing between adjacent aromatic fringes remained within the range of natural graphite, and a rapid graphite-like structure with flat aromatic fringes formed. A stage evolution of aromatic fringe morphology, whereas remaining almost constant of mainly organic elements, which imply the evolution of aromatic fringes in meta-anthracite originated from ring condensation dominated by late coalification, graphitization starts at semi-graphite stage and enhanced during graphite stage. The making up, originating from linkup and pileup, considered as a special mechanism for the graphitization of aromatic fringes.

Morphological and nanostructure characteristics of soot particles emitted from a jet-stirred reactor burning aviation fuel

Aircraft engine soot emissions have been a growing concern because of their adverse impacts on global climate and human health. In this study, soot emissions from a Jet-Stirred Reactor (JSR) which could be considered as a basic aero-engine combustor were investigated under different combustion conditions including varying combustion pressures, fuel flow rates, and inlet air temperatures. The emitted soot particles were collected onto quartz fiber filters and then examined using high-resolution transmission electron microscopic (HRTEM) and Raman techniques. The HRTEM images and Raman spectra of the filter-laden soot samples were analyzed to determine the morphology and the nanostructure characteristics of the soot particles. It turned out that compared to the reference point, both high combustion pressure and high flow rate led to an increase in primary particle size. The HRTEM and Raman studies showed that there was no amorphous carbon present in the soot particles generated under high combustion pressure. Inlet air temperature exhibited a significant influence on the size and the morphology of soot particles; a large quantity of amorphous carbon with a lower degree of graphitization was generated under the low inlet temperature condition presumably due to poor fuel spray breakup and atomization in the JSR. In addition, we found that nanostructure parameters, such as soot fringe length and fringe tortuosity could be strongly dependent upon the residence time and the inlet air temperature.