1,134 research outputs found
Manipulation of electronic and magnetic properties of MC (M=Hf, Nb, Sc, Ta, Ti, V, Zr) monolayer by applying mechanical strains
Tuning the electronic and magnetic properties of a material through strain
engineering is an effective strategy to enhance the performance of electronic
and spintronic devices. Recently synthesized two-dimensional transition metal
carbides MC (M=Hf, Nb, Sc, Ta, Ti, V, Zr), known as MXenes, has aroused
increasingly attentions in nanoelectronic technology due to their unusual
properties. In this paper, first-principles calculations based on density
functional theory are carried out to investigate the electronic and magnetic
properties of MC subjected to biaxial symmetric mechanical strains. At the
strain-free state, all these MXenes exhibit no spontaneous magnetism except for
TiC and ZrC which show a magnetic moment of 1.92 and 1.25 /unit,
respectively. As the tensile strain increases, the magnetic moments of MXenes
are greatly enhanced and a transition from nonmagnetism to ferromagnetism is
observed for those nonmagnetic MXenes at zero strains. The most distinct
transition is found in HfC, in which the magnetic moment is elevated to 1.5
/unit at a strain of 15%. We further show that the magnetic properties
of HfC are attributed to the band shift mainly composed of Hf(5) states.
This strain-tunable magnetism can be utilized to design future spintronics
based on MXenes
Monte-Carlo-Simulation-Based, Product-Quality-Focused Analysis Of Nanocoating Curing And Post Curing Process
ABSTRACT
MONTE CARLO SIMULATION BASED
PRODUCT QUALITY ANALYSIS OF
POLYMER COATING CURING AND POST CURING
By
Jianming Zhao
May 2017
Advisor:Dr. Yinlun Huang
Major: Chemical Engineering
Degree: Master of Science
To achieve better property of polymer coatings, different categories of nanoparticles are applied before coating’s curing process. However, one of the adverse effects is the change of final property, which leads the difficulty of product quality control. Using mathematical modeling method can actually improve the cost and time to get a prediction of product quality. Still now, different series of models are developed for various purposes. For example, Monte-Carlo simulation suits short-term usage prediction; kinetics simulation suits long-term usage prediction; potential energy simulation suits to model microcosmic particle’s energy change.
To solve the difficulty of quality control, Monte-Carlo simulation is used to provide relatively accurate data under given conditions. A series of models are redesigned, based on those developed by Xiao et al. (2009, 2010). From the simulation data, a visualized conversion and final Young’s modulus change can be clearly seen.
In this thesis, a linear plot of the general curing process is gained. Monte Carlo simulation methodology is a new method to describe the conversion change. The post-curing process is also simulated, with the contrast of the real data from Yari (2014), the post-curing process and principle can be explained. The effect of the nanoparticle can also be gained in this work. Additionally, with the work of this thesis, people can control the product quality more easily
Electric-field induced dipole blockade with Rydberg atoms
High resolution laser Stark excitation of np (60 < n < 85) Rydberg states of
ultra-cold cesium atoms shows an efficient blockade of the excitation
attributed to long-range dipole-dipole interaction. The dipole blockade effect
is observed as a quenching of the Rydberg excitation depending on the value of
the dipole moment induced by the external electric field. Effects of eventual
ions which could match the dipole blockade effect are discussed in detail but
are ruled out for our experimental conditions. Analytic and Monte-Carlo
simulations of the excitation of an ensemble of interacting Rydberg atoms agree
with the experiments indicates a major role of the nearest neighboring Rydberg
atom.Comment: 4 page
Dipole blockade through Rydberg Forster resonance energy transfer
High resolution laser excitation of np Rydberg states of cesium atoms shows a
dipole blockade at F\"{o}rster resonances corresponding to the resonant
dipole-dipole energy transfer of the np + np → ns + (n + 1)s reaction.
The dipole-dipole interaction can be tuned on and off by the Stark effect, and
such a process observed for relatively low n (25 − 41) is promising for
quantum gate devices. Both Penning ionization and saturation in the laser
excitation can limit the range of observation of the dipole blockadeComment: number of pages:
Gas adsorption on MoS2 monolayer from first-principles calculations
First-principles calculations within density functional theory (DFT) have
been carried out to investigate the adsorption of various gas molecules
including CO, CO2, NH3, NO and NO2 on MoS2 monolayer in order to fully exploit
the gas sensing capabilities of MoS2. By including van der Waals (vdW)
interactions between gas molecules and MoS2, we find that only NO and NO2 can
bind strongly to MoS2 sheet with large adsorption energies, which is in line
with experimental observations. The charge transfer and the variation of
electronic structures are discussed in view of the density of states and
molecular orbitals of the gas molecules. Our results thus provide a theoretical
basis for the potential applications of MoS2 monolayer in gas sensing and give
an explanation for recent experimental findings.Comment: 15 pages, 5 figure
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