scholarly journals The Formation of Nanoscale Closed Graphene Surfaces during Fullerite C60 Hot Isostatic Pressing

2021 ◽  
Vol 11 (24) ◽  
pp. 11646
Author(s):  
Danil V. Sivkov ◽  
Olga V. Petrova ◽  
Sergey V. Nekipelov ◽  
Alexander S. Vinogradov ◽  
Roman N. Skandakov ◽  
...  
Keyword(s):  
Stability Region ◽  
Hot Isostatic Pressing ◽  
High Hardness ◽  
Resistant Material ◽  
Covalent Bonds ◽  
Graphene Surface ◽  
X Ray ◽  
Isostatic Pressing ◽  
New Material ◽  
X Ray Absorption

The fullerite C60 modified by hot isostatic pressing (HIP) at 0.1 GPa in argon near and beyond its thermal stability region (920–1270 K temperature interval) was studied by X-ray diffractometry, Raman spectroscopy, ultra soft X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy. It was found that the C60 molecules merge into closed nanocapsules with a graphene surface during the thermal treatment. The conducted studies showed that using HIP treatment of the fullerite C60, it is possible to obtain a chemically resistant material with a high hardness and elasticity, as well as a density lower than that of the graphite. This new material, consisting of closed graphene nanocapsules 2–5 nm in size, formed by sp2 covalent bonds between carbon atoms is promising for various applications, and as a basis for the synthesis of new composite materials.

Structure study of the chalcogens and chalcogenides by X-ray absorption fine structure

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Hiroyuki Ikemoto ◽  
Takafumi Miyanaga
Keyword(s):  
Fine Structure ◽  
Covalent Bond ◽  
Narrow Channel ◽  
Structure Study ◽  
Chain Structure ◽  
Covalent Bonds ◽  
X Ray ◽  
Absorption Fine ◽  
Amorphous States ◽  
X Ray Absorption

AbstractIn this review, we make a survey of the structure studies for the chalcogen elements and several chalcogenides in liquid, amorphous and nanosized state by using X-ray absorption fine structure (XAFS). The chalcogen elements have hierarchic structures; the chain structure constructed with the strong covalent bond as a primary structure, and the weaker interaction between chains as a secondary one. Existence of these two kinds of interactions induces exotic behaviors in the liquid, amorphous and nanosized state of the chalcogen and chalcogenides. XAFS is a powerful structure analysis technique for multi-element systems and the disordered materials, so it is suitable for the study of such as liquid, amorphous and nanosized mixtures. In section 2, the structures for the liquid state are discussed, which show the interesting semiconductor-metal transition depending on their temperatures and components. In section 3, the structure for the amorphous states are discussed. Especially, some of chalcogens and chalcogenides present the photostructural change, which is important industrial application. In section 4, the structures of nanosized state, nanoparticles and isolated chain confined into the narrow channel, are discussed. The studies of the nanoparticle and the isolated chain reveal the alternative role between the intrachain covalent bonds and the interchain interaction.

Microstructure of TiC/Amorphous Hydrocarbon Nanocomposite Coatings

2000 ◽  
Vol 6 (S2) ◽  
pp. 440-441
Author(s):  
D. M. Cao ◽  
J. C. Jiang ◽  
B. Feng ◽  
W. J. Meng
Keyword(s):  
Inductively Coupled Plasma ◽  
High Hardness ◽  
Ceramic Surface ◽  
Edge Structure ◽  
X Ray ◽  
Inductively Coupled ◽  
Transmission Electron ◽  
Wide Range ◽  
Mechanical Components ◽  
X Ray Absorption

Application of an appropriate ceramic surface coating to mechanical components such as bearings and gears can provide longer life and increased performance reliability. Metal-containing hydrocarbon (Me-C:H) coatings possess high hardness, together with low friction and low wear rate. They have also been suggested to adhere better to metallic substrates. This combination of attractive mechanical/tribological properties makes Me-C:H coatings potentially useful for surface modification of a wide range of mechanical components.Using the technique of inductively coupled plasma (ICP) assisted vapor deposition[1], we have synthesized Ti-containing hydrocarbon (Ti-C:H) coatings with a wide range of Ti compositions[2]. Coating mechanical properties such as modulus and hardness have been measured by the technique of nanoindentation and correlated to Ti and hydrogen compositions[2,3].We have performed detailed microstructural examination of Ti-C:H coatings by transmission electron microscopy (TEM), Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, and X-ray Absorption Near Edge Structure (XANES) spectroscopy.

scholarly journals Synthesis and characterisation of HIP Ca0.80Ce0.20ZrTi1.60Cr0.40O7 zirconolite and observations of the ceramic–canister interface

MRS Advances ◽  
2021 ◽  
Author(s):  
Lewis R. Blackburn ◽  
Max R. Cole ◽  
Laura J. Gardner ◽  
Daniel J. Bailey ◽  
Merve Kuman ◽  
...  
Keyword(s):  
Oxidation State ◽  
Hot Isostatic Pressing ◽  
Nominal Composition ◽  
Phase Assemblage ◽  
X Ray ◽  
Bulk Ceramic ◽  
Average Oxidation State ◽  
Temperature And Pressure ◽  
X Ray Absorption ◽  
Absorption Features

Abstract A sample of zirconolite with nominal composition Ca0.80Ce0.20ZrTi1.60Cr0.40O7 was processed via Hot Isostatic Pressing (HIP), with a dwell temperature and pressure of 1320 °C/100 MPa maintained for 4 h. The produced wasteform was characterised by powder XRD, SEM–EDS, Ce L3 and Cr K-edge XANES. A significant portion of the Ce inventory did not fully partition within the zirconolite phase, instead remaining as CeO2 within the microstructure. Inspection of the stainless steel–ceramic interface detailed the presence of an interaction region dominated by a Cr-rich oxide layer. No significant Cr or Fe migration was observed, although a greater concentration of perovskite was observed at the periphery, relative to the bulk ceramic matrix. The X-ray absorption features of Cr remained analogous with Cr3+ accommodation within TiO6 octahedra in the zirconolite matrix. The absorption edge of Ce was comprised of contributions from zirconolite-2M and unincorporated CeO2, with an average oxidation state of Ce3.9+. As zirconolite-2M accounted for > 92 wt% of the overall phase assemblage, it is clear that the dominant oxidation state of Ce in this phase was Ce4+. Graphic abstract

scholarly journals Directional charge delocalization dynamics in semiconducting 2H-MoS$$_{2}$$ and metallic 1T-Li$$_{\mathrm{x}}$$MoS$$_{2}$$

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Robert Haverkamp ◽  
Nomi L. A. N. Sorgenfrei ◽  
Erika Giangrisostomi ◽  
Stefan Neppl ◽  
Danilo Kühn ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Structural Phase ◽  
Core Hole ◽  
Covalent Bonds ◽  
Charge Delocalization ◽  
X Ray ◽  
Out Of Plane ◽  
Li Adsorption ◽  
X Ray Absorption ◽  
Accelerated Charge

AbstractThe layered dichalcogenide MoS$$_{2}$$ 2 is relevant for electrochemical Li adsorption/intercalation, in the course of which the material undergoes a concomitant structural phase transition from semiconducting 2H-MoS$$_{2}$$ 2 to metallic 1T-Li$$_{\mathrm{x}}$$ x MoS$$_{2}$$ 2 . With the core hole clock approach at the S L$$_{1}$$ 1 X-ray absorption edge we quantify the ultrafast directional charge transfer of excited S3p electrons in-plane ($$\parallel$$ ‖ ) and out-of-plane ($$\perp$$ ⊥ ) for 2H-MoS$$_{2}$$ 2 as $$\tau _{2H,\parallel } = 0.38 \pm 0.08$$ τ 2 H , ‖ = 0.38 ± 0.08 fs and $$\tau _{2H,\perp } = 0.33 \pm 0.06$$ τ 2 H , ⊥ = 0.33 ± 0.06 fs and for 1T-Li$$_{\mathrm{x}}$$ x MoS$$_{2}$$ 2 as $$\tau _{1T,\parallel } = 0.32 \pm 0.12$$ τ 1 T , ‖ = 0.32 ± 0.12 fs and $$\tau _{1T,\perp } = 0.09 \pm 0.07$$ τ 1 T , ⊥ = 0.09 ± 0.07 fs. The isotropic charge delocalization of S3p electrons in the semiconducting 2H phase within the S-Mo-S sheets is assigned to the specific symmetry of the Mo-S bonding arrangement. Formation of 1T-Li$$_{\mathrm{x}}$$ x MoS$$_{2}$$ 2 by lithiation accelerates the in-plane charge transfer by a factor of $$\sim 1.2$$ ∼ 1.2 due to electron injection to the Mo-S covalent bonds and concomitant structural repositioning of S atoms within the S-Mo-S sheets. For excitation into out-of-plane orbitals, an accelerated charge transfer by a factor of $$\sim 3.7$$ ∼ 3.7 upon lithiation occurs due to S-Li coupling.

scholarly journals On the Origin of Reversible and Irreversible Reactions in LiNixCo(1-x)/2Mn(1-x)/2O2

2021 ◽  
Author(s):  
Karin Kleiner ◽  
Claire A. Murray ◽  
Cristina Grosu ◽  
Bixian Ying ◽  
Martin Winter ◽  
...  
Keyword(s):  
Transition Metal Oxides ◽  
Redox Reactions ◽  
Bond Formation ◽  
Reversible Capacity ◽  
Redox Processes ◽  
Li Ion Batteries ◽  
Covalent Bonds ◽  
X Ray ◽  
Li Ion ◽  
X Ray Absorption

Abstract Bond formation and breakage is crucial upon energy storage in lithium transition metal oxides (LiMeO2, Me = Ni, Co, Mn), i.e., the conventional cathode materials in Li ion batteries. Near-edge x-ray absorption finestructure spectroscopy (NEXAFS) of the Me L and O K edge performed upon the first discharge of LiNixCo(1-x)/2Mn(1-x)/2O2 (x = 0.33: NCM111, x = 0.6: NCM622, x = 0.8: NCM811) in combination with charge transfer multiplet calculations provide unambiguous experimental evidence that redox reactions in NCMs proceed via a reversible oxidation of Ni associated with the formation of covalent bonds to O neighbors, and not, as widely assumed, via pure cationic or more recently discussed, pure anionic redox processes. Correlating these electronic changes with crystallographic data using operando synchrotron X-ray powder diffraction shows that the amount of ionic Ni limits the reversible capacity - at states of charge where all ionic Ni is oxidized (above 155 mAh/g), the lattice parameters collapse, and irreversible reactions are observed. Yet the covalence of the Ni-O bonds also triggers the electronic structure and thus the operation potential of the cathodes.

Selective Laser Melting of Stainless Steel with Subsequent Processing

2020 ◽  
Vol 989 ◽  
pp. 845-849
Author(s):  
A.S. Raznoschikov ◽  
D.A. Kochuyev ◽  
Anna A. Voznesenskaya
Keyword(s):  
Stainless Steel ◽  
Phase Composition ◽  
Selective Laser Melting ◽  
Hot Isostatic Pressing ◽  
Phase Changes ◽  
Laser Melting ◽  
Metallographic Study ◽  
X Ray ◽  
Isostatic Pressing ◽  
Subsequent Processing

In this work we describe the results of selective laser melting of stainless steel. The obtained samples were processed by hot isostatic pressing. Metallographic study of samples obtained after selective laser melting and hot isostatic pressing procedure was conducted. Comparison of the structure of obtained samples and a significant decrease in porosity after hot isostatic pressing was registered. The results of the phase composition by X-ray diffractometry are presented. Identified significant structural and phase changes at the study of a surface of the obtained microsections of samples, and a change in the hardness of the samples were recorded.

RESEARCH ON SHAPING TECHNOLOGY OF NANOCOMPOSITE WC-6Co POWDER AND PROPERTIES OF SINTERED COMPACTS

2006 ◽  
Vol 05 (02n03) ◽  
pp. 233-238 ◽  
Author(s):  
XIAOLIANG SHI ◽  
GANGQIN SHAO ◽  
XINGLONG DUAN ◽  
RUNZHANG YUAN
Keyword(s):  
Rupture Strength ◽  
Hot Isostatic Pressing ◽  
High Hardness ◽  
Cold Isostatic Pressing ◽  
Sintered Specimen ◽  
Volume Distribution ◽  
Vacuum Sintering ◽  
Transverse Rupture Strength ◽  
Isostatic Pressing ◽  
Die Pressing

The influences of powder extrusion molding (PEM), die pressing and cold isostatic pressing (CIP) on the green compacts and the sintered compacts of nanocrystalline WC-6 Co composite powder produced by spray pyrogenation-continuous reduction and carburization technology were researched. The results showed that the pore volume distribution, density and scanning electron microscopy (SEM) morphologies of fractured surface of powder extrusion molding or die pressing followed by the cold isostatic pressing consolidation green compacts were better than that of powder extrusion molding or die pressing. The green compacts were sintered by using vacuum sintering plus hot isostatic pressing (HIP), the sintered specimens were characterized by testing density, Rockwell A hardness, saturated magnetization, coercivity force, transverse rupture strength (TRS) and atomic force microscope (AFM) images, the results showed that sintered specimen of the green body that prepared by powder extrusion molding or die pressing followed by cold isostatic pressing had excellent properties of high strength and high hardness, transverse rupture strength of sintered specimen was more than 3100 MPa, Rockwell A hardness of sintered body was more than 93. Ultrafine WC-6 Co cemented carbide rods with excellent mechanical properties and fine microstructure were obtained.

Rapid synthesis of bulk Ti2AlC by self-propagating high temperature combustion synthesis with a pseudo–hot isostatic pressing process

2009 ◽  
Vol 24 (8) ◽  
pp. 2528-2535 ◽  
Author(s):  
Yuelei Bai ◽  
Xiaodong He ◽  
Yibin Li ◽  
Chuncheng Zhu ◽  
Sam Zhang
Keyword(s):  
High Temperature ◽  
Combustion Synthesis ◽  
Hot Isostatic Pressing ◽  
X Ray Diffraction ◽  
Phase Purity ◽  
X Ray ◽  
Isostatic Pressing ◽  
Pressing Process ◽  
Temperature Combustion ◽  
High Temperature Combustion

In this study, the dense polycrystalline Ti2AlC was synthesized by self-propagating high-temperature combustion synthesis with the pseudo–hot isostatic pressing process (SHS/PHIP). The resultant phase purity is highly dependent on the mol ratio of raw powders. The Ti2AlC was densified by applying pressure after the SHS reaction. The resultant sample mainly contains typical plate-like nonstoichiometric Ti2AlCx (x = 0.69) with grain size of ∼6 µm. The sample shows the Vickers hardness of 5.5 GPa, highest flexural strength of 431 MPa, compressive strength of 1033 MPa, and fracture toughness of 6.5 MPa·m1/2. No indentation cracks in Ti2AlCx were observed, indicative of a damage material nature. The reaction mechanism for the formation of SHS/PHIP-derived Ti2AlC is also discussed based on differential thermal analysis and x-ray diffraction results.

Formation of Superconducting La2−xSrxCaCu2O6−δ Ceramic with Application of O2-HIP Technique

1991 ◽  
Vol 251 ◽  
Author(s):  
Kiyoshi Oshima ◽  
Yuichi Watanabe ◽  
Masasuke Takata ◽  
Kozo Ishizaki
Keyword(s):  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Strong Correlation ◽  
Hot Isostatic Pressing ◽  
Lattice Parameters ◽  
Superconducting Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Isostatic Pressing ◽  
Diffraction Patterns

ABSTRACTSuperconducting La2−xSrxCaCu2O6−δ ceramics (x=0−0.6) were prepared with application of the oxygen-hot-isostatic pressing (O2-HIP) technique. The Tc of various samples was found to depend on both the Sr content and the applied oxygen partial pressure in the HIP treatment. The maximum Tc onset of 50K was observed for samples of the composition x=0.3 and 0.4 HIPped at 1050°C under 60atm oxygen partial pressure, and x=0.1 and 0.2 HIPped at 1050°C under 400atm oxygen partial pressure, respectively. From the analysis of x-ray diffraction patterns for superconducting substances, it was found that there existed a strong correlation between superconducting properties and the lattice parameters.

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