scholarly journals Realization of 2D crystalline metal nitrides via selective atomic substitution

2020 ◽  
Vol 6 (2) ◽  
pp. eaax8784 ◽  
Author(s):  
Jun Cao ◽  
Tianshu Li ◽  
Hongze Gao ◽  
Yuxuan Lin ◽  
Xingzhi Wang ◽  
...  
Keyword(s):  
Chemical Conversion ◽  
Metal Nitrides ◽  
Transition Metal Nitrides ◽  
Large Area ◽  
Fundamental Physics ◽  
New Members ◽  
Wide Range ◽  
Atomic Substitution ◽  
Crystalline Metal

Two-dimensional (2D) transition metal nitrides (TMNs) are new members in the 2D materials family with a wide range of applications. Particularly, highly crystalline and large area thin films of TMNs are desirable for applications in electronic and optoelectronic devices; however, the synthesis of these TMNs has not yet been achieved. Here, we report the synthesis of few-nanometer thin Mo5N6 crystals with large area and high quality via in situ chemical conversion of layered MoS2 crystals. The versatility of this general approach is demonstrated by expanding the method to synthesize W5N6 and TiN. Our strategy offers a new direction for preparing 2D TMNs with desirable characteristics, opening a door for studying fundamental physics and facilitating the development of next-generation electronics.

scholarly journals Remediation of the Serbian soils contaminated by radionuclides in the function of the sustainable development

2008 ◽  
Vol 14 (4) ◽  
pp. 265-267 ◽  
Author(s):  
M. Stojanovic ◽  
M. Grubisic ◽  
D. Stevanovic ◽  
J. Milojkovic ◽  
D. Iles
Keyword(s):  
Contaminated Soils ◽  
Water Solution ◽  
Solution Concentration ◽  
Large Area ◽  
The Sustainable Development ◽  
Geological Conditions ◽  
Wide Range ◽  
Uranium Phosphate ◽  
Natural Apatite

Phosphate-induced metal stabilization (PIMS) using apatite stabilizes uranium in situ, by chemically binding it into the new low-solubility (Ksp=10-49) phase. Uranium-phosphate-autunite is stable across a wide range of geological conditions for millions of years. A large area of contaminated soil is suitable for in situ remediation that involves minimizing the mobility of the uranium. Laboratory study was conducted to quantify different forms of apatite sequestration of uranium contaminant. The experiment was done with natural phosphate from Lisina deposit (14.43 % P2O5), with non-treated samples, phosphate concentrate samples with 34.95 % P2O5 and mechanochemically activated of natural apatite. Different concentration of P2O5 in apatite, pH, reaction time, solid/liquid ratio was investigated. The concentrate at pH 5.5 for 7 days sorbed around 93,64 % and nature apatite, with 14,43 % P2O5, for 30 days sorbed 94.54 % of the uranium from the water solution, concentration 100 ?g U/ml. The results show that mineral apatite 'Lisina' is very effective for the treatment of contaminated soils in situ immobilization of U. Mechanochemical activation of natural apatite in vibration mill immobilized 85.37 % of uranium in the 7-day period of acting. This research on natural apatite from the deposit 'Lisina' for immobilization of uranium was the first one of this type in our country.

scholarly journals Synthesis of Manganese Mononitride with Tetragonal Structure under Pressure

Crystals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 511
Author(s):  
Dajian Huang ◽  
Caoping Niu ◽  
Bingmin Yan ◽  
Bo Gao ◽  
Lailei Wu ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Space ◽  
Laser Heating ◽  
Diamond Anvil Cell ◽  
Ambient Pressure ◽  
Tetragonal Structure ◽  
Metal Nitrides ◽  
Transition Metal Nitrides ◽  
Diamond Anvil

The exploration of the vast phase space of transition metal nitrides is critical for discovering novel materials and potential technological applications. Manganese mononitride with a tetragonal structure (space group I4/mmm) was synthesized in a laser-heating diamond anvil cell, which could be quenched to ambient pressure. The bulk modulus of 173 GPa was measured using in situ high-pressure diffraction, and the axial compressibility shows that, under pressure, the a direction is much more compressible than the c direction in tetragonal MnN. DFT results with correction of the on-site repulsion (GGA + U) confirm that tetragonal MnN is energetically stable and antiferromagnetic. This study highlights the need to include on-site repulsion to understand 3d metal nitrides.

Metal-Ceramic Composites Prepared through In Situ Decomposition of Transition Metal Nitrides

2007 ◽  
Vol 352 ◽  
pp. 125-128
Author(s):  
Xi Hai Jin ◽  
Lian Gao ◽  
Jing Sun
Keyword(s):  
Transition Metal ◽  
Ceramic Composites ◽  
Metal Particles ◽  
Metal Nitrides ◽  
Transition Metal Nitrides ◽  
Microstructure And Properties ◽  
Uniform Microstructure ◽  
Metal Ceramic ◽  
In Situ Decomposition

Co/ZnO and Ni/Al2O3 composites were prepared by in-situ decomposition of CoNx and NiNx during sintering, using CoNx/ZnO and NiNx/Al2O3 mixtures synthesized through an in-situ nitridation method as the starting powders. It was found that these composites showed a very uniform microstructure with metal particles homogeneously distributed among matrix grains. The microstructure and properties were tentatively studied.

scholarly journals In situ epitaxial engineering of graphene and h-BN lateral heterostructure with a tunable morphology comprising h-BN domains

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Dechao Geng ◽  
Jichen Dong ◽  
Lay Kee Ang ◽  
Feng Ding ◽  
Hui Ying Yang
Keyword(s):  
Density Functional ◽  
Hexagonal Boron Nitride ◽  
2D Materials ◽  
Chemical Vapor ◽  
Large Area ◽  
Atomic Lattice ◽  
Cvd Method ◽  
Wide Range ◽  
Tunable Morphology

Abstract Graphene and hexagonal boron nitride (h-BN), as typical two-dimensional (2D) materials, have long attracted substantial attention due to their unique properties and promise in a wide range of applications. Although they have a rather large difference in their intrinsic bandgaps, they share a very similar atomic lattice; thus, there is great potential in constructing heterostructures by lateral stitching. Herein, we present the in situ growth of graphene and h-BN lateral heterostructures with tunable morphologies that range from a regular hexagon to highly symmetrical star-like structure on the surface of liquid Cu. The chemical vapor deposition (CVD) method is used, where the growth of the h-BN is demonstrated to be highly templated by the graphene. Furthermore, large-area production of lateral G-h-BN heterostructures at the centimeter scale with uniform orientation is realized by precisely tuning the CVD conditions. We found that the growth of h-BN is determined by the initial graphene and symmetrical features are produced that demonstrate heteroepitaxy. Simulations based on the phase field and density functional theories are carried out to elucidate the growth processes of G-h-BN flakes with various morphologies, and they have a striking consistency with experimental observations. The growth of a lateral G-h-BN heterostructure and an understanding of the growth mechanism can accelerate the construction of various heterostructures based on 2D materials.

scholarly journals Stress-controlled decomposition routes in cubic AlCrN films assessed by in-situ high-temperature high-energy grazing incidence transmission X-ray diffraction

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
M. Meindlhumer ◽  
S. Klima ◽  
N. Jäger ◽  
A. Stark ◽  
H. Hruby ◽  
...  
Keyword(s):  
High Temperature ◽  
Transition Metal ◽  
Stress Level ◽  
Grazing Incidence ◽  
High Energy ◽  
Metal Nitrides ◽  
Transition Metal Nitrides ◽  
X Ray Diffraction ◽  
X Ray

AbstractThe dependence of decomposition routes on intrinsic microstructure and stress in nanocrystalline transition metal nitrides is not yet fully understood. In this contribution, three Al0.7Cr0.3N thin films with residual stress magnitudes of −3510, −4660 and −5930 MPa in the as-deposited state were in-situ characterized in the range of 25–1100 °C using in-situ synchrotron high-temperature high-energy grazing-incidence-transmission X-ray diffraction and temperature evolutions of phases, coefficients of thermal expansion, structural defects, texture as well as residual, thermal and intrinsic stresses were evaluated. The multi-parameter experimental data indicate a complex intrinsic stress and phase changes governed by a microstructure recovery and phase transformations taking place above the deposition temperature. Though the decomposition temperatures of metastable cubic Al0.7Cr0.3N phase in the range of 698–914 °C are inversely proportional to the magnitudes of deposition temperatures, the decomposition process itself starts at the same stress level of ~−4300 MPa in all three films. This phenomenon indicates that the particular compressive stress level functions as an energy threshold at which the diffusion driven formation of hexagonal Al(Cr)N phase is initiated, provided sufficient temperature is applied. In summary, the unique synchrotron experimental setup indicated that residual stresses play a decisive role in the decomposition routes of nanocrystalline transition metal nitrides.

Noncontact Surface-Hardness Measurement Using Laser-Based Ultrasound

MRS Bulletin ◽  
1996 ◽  
Vol 21 (10) ◽  
pp. 53-57 ◽  
Author(s):  
A. Safaeinili ◽  
A.D.W. McKie ◽  
R.C. Addison
Keyword(s):  
Composite Structures ◽  
Elevated Temperatures ◽  
Surface Hardness ◽  
Case Depth ◽  
Ultrasonic Waves ◽  
Inspection System ◽  
Large Area ◽  
Science Center ◽  
Wide Range

A noncontact inspection system that uses lasers to both generate and detect ultrasonic waves has been developed at the Rockwell Science Center for the purpose of nondestructively inspecting metallic and composite structures. The laser-based ultrasound (LBU) system was initially developed to inspect large-area composite airframe structures, including the automated inspection of integrally stiffened and complexly curved composite structures. Furthermore the benefits offered by LBU, such as its noncontacting nature and ability to operate at elevated temperatures, have extended its usefulness to a wide range of applications—for example, in situ process monitoring where the capability to monitor a fabrication process or possibly inspect a part while still in a mold or autoclave could lead to significant cost benefits. Two manufacturing techniques that have shown promise and are presently under investigation are resin-transfer molding and compression molding. Since both of these processes typically occur at elevated temperatures, the noncontacting nature of LBU makes it an ideal candidate for an in situ sensor. More recently, measurement of the case depth in ground vehicle components has been investigated. This article describes current research that uses the LBU technique to determine surface hardness in steel-axle shafts.

In-situ electrical-resistivity measurements in the high-voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 68-69
Author(s):  
W. E. King
Keyword(s):  
Electrical Resistivity ◽  
Electron Microscope ◽  
High Voltage ◽  
Resistivity Measurements ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Wide Range ◽  
Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

Site specific agricultural soil management with the use of new technologies

2013 ◽  
Vol 16 (1) ◽  
pp. 59-67
Keyword(s):  
New Technologies ◽  
Digital Interface ◽  
Appropriate Treatment ◽  
Wide Range ◽  
Soil Variation ◽  
Soil Information ◽  
Remote Sensing Techniques ◽  
Agricultural Areas

<p>The Soil Science Institute of Thessaloniki produces new digitized Soil Maps that provide a useful electronic database for the spatial representation of the soil variation within a region, based on in situ soil sampling, laboratory analyses, GIS techniques and plant nutrition mathematical models, coupled with the local land cadastre. The novelty of these studies is that local agronomists have immediate access to a wide range of soil information by clicking on a field parcel shown in this digital interface and, therefore, can suggest an appropriate treatment (e.g. liming, manure incorporation, desalination, application of proper type and quantity of fertilizer) depending on the field conditions and cultivated crops. A specific case study is presented in the current work with regards to the construction of the digitized Soil Map of the regional unit of Kastoria. The potential of this map can easily be realized by the fact that the mapping of the physicochemical properties of the soils in this region provided delineation zones for differential fertilization management. An experiment was also conducted using remote sensing techniques for the enhancement of the fertilization advisory software database, which is a component of the digitized map, and the optimization of nitrogen management in agricultural areas.</p>

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