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The role of aluminium in the preservation of microbial biosignatures

Geoscience Frontiers 2019年第3期10卷 1125-1138页

作者： Alan Levett Emma J.Gagen Hui Diao Paul Guagliardo Llew Rintoul Anat Paz Paulo M.Vasconcelos Gordon Southam School of Earth and Environmental Sciences University of Queensland centre for microscopy and Microanalysis University of Queensland centre for microscopy Characterisation and Analysis University of Western Australia School of Chemistry Physics & Mechanical EngineeringQueensland University of Technology

Demonstrating the biogenicity of presumptive microfossils in the geological record often requires supporting chemical signatures, including isotopic signatures. Understanding the mechanisms that promote the preservation of microbial biosignatures associated with microfossils is fundamental to unravelling the palaeomicrobiological history of the material. Organomineralization of microorganisms is likely to represent the first stages of microbial fossilisation and has been hypothesised to prevent the autolytic degradation of microbial cell envelope structures. In the present study, two distinct fossilisation textures(permineralised microfossils and iron oxide encrusted cell envelopes)identified throughout iron-rich rock samples were analysed using nanoscale secondary ion mass spectrometry(NanoSIMS). In this system, aluminium is enriched around the permineralised microfossils, while iron is enriched within the intracellularly, within distinct cell envelopes. Remarkably,while cell wall structures are indicated, carbon and nitrogen biosignatures are not preserved with permineralised microfossils. Therefore, the enrichment of aluminium, delineating these microfossils appears to have been critical to their structural preservation in this iron-rich environment. In contrast,NanoSIMS analysis of mineral encrusted cell envelopes reveals that preserved carbon and nitrogen biosignatures are associated with the cell envelope structures of these microfossils. Interestingly, iron is depleted in regions where carbon and nitrogen are preserved. In contrast aluminium appears to be slightly enriched in regions associated with remnant cell envelope structures. The correlation of aluminium with carbon and nitrogen biosignatures suggests the complexation of aluminium with preserved cell envelope structures before or immediately after cell death may have inactivated autolytic activity preventing the rapid breakdown of these organic, macromolecular ***, these results highlig

关键词： Aluminium Microfossils Biosignatures NanoSIMS Organomineralisation

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Helium droplet assisted synthesis of plasmonic Ag@ZnO core@shell nanoparticles

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Nano Research 2020年第11期13卷 2979-2986页

作者： Alexander Schiffmann Thomas Jauk Daniel Knez Harald Fitzek Ferdinand Hofer Florian Lackner Wolfgang E.Ernst Institute of Experimental Physics Graz University of TechnologyA-8010GrazAustria Institute of Electron microscopy and Nanoanalysis&Graz centre for Electron microscopy Graz University of TechnologyA-8010GrazAustria

Plasmonic Ag@ZnO core@shell nanoparticles are formed by synthesis inside helium droplets with subsequent deposition and controlled *** particle size and shape can be controlled from spherical sub-10 nm particles to larger elongated *** advantage of the method is the complete absence of solvents,precursors,and other chemical *** obtained particle morphology and elemental composition have been analyzed by scanning transmission electron microscopy(STEM)and energy dispersive X-ray spectroscopy(EDS).The results reveal that the produced particles form a closed and homogeneous ZnO layer around a 2–3 nm Ag core with a uniform thickness of(1.33±0.15)nm and(1.63±0.31)nm for spherical and wire-like particles,*** results are supported by ultraviolet photoelectron spectroscopy(UPS),which indicates a fully oxidized shell layer for the particles studied by *** plasmonic properties of the produced spherical Ag@ZnO core@shell particles are investigated by two-photon photoelectron(2PPE)*** excitation of the localized surface plasmon resonance in Ag at around 3 eV,plasmonic enhancement leads to the liberation of electrons with high kinetic *** is observed for both Ag and Ag@ZnO particles,showing that even if a Ag cluster is covered by the ZnO layer,a plasmonic enhancement can be observed by photoelectron spectroscopy.

关键词： nanoparticle helium droplet plasmonics photoelectrons

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Electron tomography for sintered ceramic materials by a neural network algebraic reconstruction technique

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Journal of Materials Science & Technology 2022年第5期100卷 75-81页

作者： R.H.Shen Y.T.He W.Q.Ming Y.Zhang X.D.Xu J.H.Chen centre for High Resolution Electron microscopy College of Materials Science and EngineeringHunan UniversityChangsha 410082China

The missing wedge effect in electron tomography introduces various types of artifacts in the tomograms and lowers the reconstruction resolution and *** artifacts produced in tomographic reconstruction of bulk materials can be very severe,particularly for sintered bulk ceramic materials in which there are often nano-pores or pore-like microstructure ***,we report a neural network algebraic reconstruction algorithm with no prior knowledge to perform electron tomography for a sintered SiC material with nano carbon *** results show that the proposed algorithm has a great suppressive effect on the missing wedge artifacts and a high tolerance for *** information in the missing wedge can be partly recovered by this ***,both the shape of the bulk SiC specimen and its irregular inner pore-like features are correctly retrieved in the obtained 3D *** study shows the effectiveness of the neural network algorithm for improving the reconstruction accuracy of electron tomography,in order to reveal sophisticated 3D microstructures generally existing in sintered ceramic materials.

关键词： Neural network Missing wedge Electron tomography Sintered ceramics

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Crystallization behavior of Ni_(54)Mn_(25.1)Ga_(20.9) ferromagnetic shape memory thin film

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Rare Metals 2007年第S1期26卷 139-142页

作者： MARTIN Saunders centre for microscopy and Microanalysis University of Western AustraliaNedlandsW.A.6009Australia

NiMnGaferromagnetic shape memory thin film was deposited onto Al foil using *** sputtering *** crystallization behavior of the film was investigated by XRD and *** activation energy of crystallization of the film was calculated by Kissinger’s *** results show that the crystallization temperature of NiMnGafree-standing thin film in martensite state is 372 ℃,and the activation energy of crystallization is about 191.9 kJ·mol-1.

关键词： Ni-Mn-Ga ferromagnetic shape memory alloys thin films crystallization

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Three-dimensional size and orientation of the precipitates in AZ91 magnesium alloys measured by TEM techniques

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Chinese Physics B 2009年第10期18卷 4370-4379页

作者：郑鸥马家艳王建波周嘉萍金磊赵东山王仁卉 Department of Physics and Key Laboratory of Acoustic and Photonic Materials and Devices of Ministry of Education Wuhan University centre for Electron microscopy Wuhan University

Knowledge of the microscopic structure, including three-dimensional （3-D） size and orientation of the precipitates, is essential to fully understand the mechanical properties of the magnesium alloys and designing the alloys with better performance. Analytical TEM with high spatial resolution offers the simultaneous measurements of 3-D size, structure, orientation, composition of the precipitates from one typical sample along an established crystallographic axis. Besides popular Burgers orientation relationship （OR）, other ORs such as Pitsch-Schrader OR, Crawley OR, Potter OR and a new OR with the form of [0001]α 1.0° from [311]γ and （1120）α 2.0° from （033）γ between the magnesium matrix and the precipitate γ-MglTAl 12 are identified by TEM imaging and diffraction techniques. As a case study, the thicknesses of the individual precipitates with Burgers OR are further measured to be 100 200 nm through both electron energy-loss spectroscopy and x-ray energy dispersive spectroscopy combining differential x-ray absorption and extrapolation, which are in agreement with the overall 3-D size statistic distribution results obtained through analysing various samples along various directions. Furthermore, the fabricated wedge-shape structure provides a platform on which to study the dependence of the interfacial strain on the variation of the thickness.

关键词： transmission electron microscopy microstructure Mg electron energy loss spectroscopy

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Compositional design and microstructure analysis of Zr-based bulk metallic glasses

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中国有色金属学会会刊：英文版 2007年第6期17卷 1433-1440页

作者：严明邹进沈军孙剑飞 School of Materials Science and Engineering Harbin Institute of Technology School of Engineering and centre for microscopy and Microanalysis University of Queensland QLD 4072 Australia

The systematical studies of Zr-based BMGs were summarized in terms of their compositional design and their structural characterization. In particular, several key issues of BMG materials were focused, including initial alloy design and subsequent composition optimization, solidification microstructure characterization and crystallization process specification. The results show that a compositional designing approach is successfully developed and, through extensive microstructure characterization using transmission electron microscopy, several new crystalline phases are discovered in these newly developed Zr-based BMG alloys. Crystallization behavior of Zr-based BMG is also determined based on the microstructure analysis.

关键词：金属玻璃微观结构凝固结晶

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Observation of Pt-{100}-p(2×2)-O reconstruction by an environmental TEM

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Progress in Natural Science:Materials International 2016年第3期26卷 308-311页

作者： Hengbo Li Wentao Yuan Ying Jiang Zhengfei Zhang Ze Zhang Yong Wang centre of Electron microscopy and State Key Laboratory of Silicon Materials School of Materials Science and Engineering Zhejiang University

The surface structure of noble metal nanoparticles usually plays a crucial role during the catalytic process in the fields of energy and environment. It has been studied extensively by surface analytic methods, such as scanning tunneling microscopy. However, it is still challenging to secure a direct observation of the structural evolution of surfaces of nanocatalysts in reaction(gas and heating) conditions at the atomic scale. Here we report an in-situ observation of atomic reconstruction on Pt {100} surfaces exposed to oxygen in an environmental transmission electron microscope(TEM). Our high-resolution TEM images revealed that Pt-{100}-p(2×2)-O reconstruction occurs during the reaction between oxygen atoms and{100} facets. A reconstruction model was proposed, and TEM images simulated according to this model with different defocus values match the experimental results well.

关键词： Pt nanoparticles Surface reconstruction In Situ TEM Environmental transmission electron microscopy(ETEM)

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Application of Electron Energy Loss Spectroscopy and Energy Filtering Transmission Electron microscopy for Microchemical Studies in 2.25Cr-1Mo Steel

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Journal of Materials Science & Technology 2005年第3期21卷 361-366页

作者： P.Parameswaran Ilse Papst F.Hofer W.Grogger V.S.Raghunathan Materials Characterisation Group Research Institute for Electron MicroscopyResearch Institute for Electron MicroscopyResearch Institute for Electron MicroscopyMaterials Characterisation Group Indira Gandhi Centre for Atomic ResearchKalpakkam 603 102IndiaTech.Univ.A-8010GrazAustriaTech.Univ.A-8010GrazAustriaTech.Univ.A-8010GrazAustriaIndira Gandhi Centre for Atomic ResearchKalpakkam 603 102India

Electron enregy loss spectroscopy (EELS) and energy filtering transmission electron microscopy (EFTEM) investigation on 2.25Cr-lMo steel was carried out to understand the nature of evolution of secondary carbides. The filtered images obtained from two different ageing treatments indicate that the steel evolves to a more stable carbide namely M23C6 in comparison to M2C. Microchemical information was generated from EELS spectra. Suitable choice for estimating the microchemical state was discussed. To evaluate the behaviour of ageing an elemental ratio of Fe to Cr is employed.

关键词： Ferritic steels 2.25Cr-lMo steel EFTEM EELS Ageing

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Low-temperature conversion of ammonia to nitrogen in water with ozone over composite metal oxide catalyst

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Journal of Environmental Sciences 2018年第4期30卷 265-273页

作者： Yunnen Chen Ye Wu Chen Liu Lin Guo Jinxia Nie Yu Chen Tingsheng Qiu Jiangxi Key Laboratory of Mining & Metallurgy Environmental Pollution Control Jiangxi University of Science &Technology Monash centre for Electron microscopy (MCEM) Monash University

As one of the most important water pollutants, ammonia nitrogen emissions have increased year by year, which has attracted people＇s attention. Catalytic ozonation technology, which involves production of ·OH radical with strong oxidation ability, is widely used in the treatment of organic-containing wastewater. In this work, MgO-Co3O4 composite metal oxide catalysts prepared with different fabrication conditions have been systematically evaluated and compared in the catalytic ozonation of ammonia（50 mg/L） in water. In terms of high catalytic activity in ammonia decomposition and high selectivity for gaseous nitrogen, the catalyst with MgO-Co3O4 molar ratio 8：2, calcined at 500°C for 3 hr, was the best one among the catalysts we tested, with an ammonia nitrogen removal rate of 85.2% and gaseous nitrogen selectivity of44.8%. In addition, the reaction mechanism of ozonation oxidative decomposition of ammonia nitrogen in water with the metal oxide catalysts was discussed. Moreover, the effect of coexisting anions on the degradation of ammonia was studied, finding that SO2-4 and HCO-3 could inhibit the catalytic activity while CO2-3 and Br-could promote it. The presence of coexisting cations had very little effect on the catalytic ozonation of ammonia nitrogen. After five successive reuses, the catalyst remained stable in the catalytic ozonation of ammonia.

关键词： Ammonia Metal oxide catalyst Catalytic ozonation Gaseous nitrogen Wastewater treatment

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Effect of Thermo-Mechanical Processing on Precipitate Formation in Next Generation HSLA Steel

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Journal of Iron and Steel Research International 2011年第S1期18卷 478-481页

作者： Mukherjee S Timokhina I B Ringer S P Hodgson P D centre for Material and Fibre Innovation Deakin UniversityGeelongVic 3217Australia Australian Key centre for microscopy and Microanalysis University of SydneyNSWAustralia

Development of advanced high strength steels (AHSS) using a conventional rolling setup is one of the biggest challenges to steel *** has been found that fine precipitation in a soft matrix,formed after hot rolling,can markedly improve the mechanical *** this work,three dimensional atom probe tomography (3D-APT) has been used to study the formation of precipitates in thermomechanically simulated steel.3D-APT data reveals co-existence of numerous nano clusters with ***,quantitative analysis of the nano clusters and precipitates shows clusters are as small as 1nm in *** are found to be disc shaped with the composition of equilibrium precipitates (TiMo)***,3D-APT is seen as an ideal technique to complement TEM to understand the nanoscale features in thermomechanically processed steel for further improvements in the mechanical properties of AHSS.

关键词： TMCP 3D-APT precipitate cluster

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