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| '''Magnonics''' is an emerging field of modern [[magnetism]], which can be considered a sub-field of modern [[solid state physics]].<ref>Kruglyak V.V, Demokritov S.O, Grundler D Magnonics J. Phys. D Appl. Phys. 43 264001 (2010), {{doi|10.1088/0022-3727/43/26/264001}}</ref> Magnonics combines waves and magnetism, its main aim is to investigate the behaviour of [[spin waves]] in nano-structure elements. In essence, spin waves are a propagating re-ordering of the [[magnetisation]] in a material and arise from the [[precession]] of [[magnetic moment]]s. Magnetic moments arise from the orbital and [[spin (physics)|spin]] moments of the electron, most often it is this spin moment that contributes to the net magnetic moment. | | The '''OMEGA''' process (''only mono ethylene glycol advanced process'') is a process of the [[Royal Dutch Shell]] to produce [[ethylene glycol | Mono-ethylenlglycol]] from [[ethylene oxide]], [[carbon dioxide]] as [[catalyst]] and water with high [[selectivity]]. |
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| Following the success of the modern [[hard disk]], there is much current interest in future magnetic [[data storage]] and using spin waves for things such as 'magnonic' logic and data storage. Similarly, [[spintronics]] looks to utilize the inherent 'spin' degree of freedom to complement the already successful charge property of the electron used in contemporary [[electronics]]. Modern magnetism is concerned with furthering the understanding of the behaviour of the magnetisation on very small (sub-micrometre) length scales and very fast (sub-nanosecond) timescales and how this can be applied to improving existing or generating new technologies and computing concepts.
| | == Process == |
| | The traditional process of [[monoethylene glycol]] (MEG) production is by reaction of ethylene oxide with water. The product of the first reaction stage, MEG, reacts with ethylene oxide on to [[di-|diethylene glycol]] and [[triethylene glycol]], which makes a [[distillation]] work-up necessary. The selectivity to MEG is about 90%. |
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| A magnonic crystal is a magnetic [[metamaterial]] with alternating magnetic properties. Like conventional metamaterials, their properties arise from geometrical structuring, rather than their bandstructure or composition directly. Small spatial inhomogeneities create an effective macroscopic behaviour, leading to properties not readily found in nature. By alternating parameters such as the [[relative permeability]] or saturation magnetisation, there exists the possibility to tailor 'magnonic' [[bandgap]]s in the material. By tuning the size of this bandgap, only spin wave modes able to cross the bandgap would be able to propagate through the media, leading to selective propagation of certain spin wave frequencies.
| | In the OMEGA process, the ethylene oxide is first converted with [[carbon dioxide]] (CO<sub>2</sub>) to [[ethylene carbonate]] to then react with water in a second step to selectively produce [[monoethylene glycol]]. The carbon dioxide is released in this step again and can be fed back into the process circuit. The carbon dioxide comes in part from the ethylene oxide production, where a part of the [[ethylene]] is completely [[oxidation|oxidized]]. |
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| ==Theory==
| | (1) <math>{C_2H_4O + CO_2 \longrightarrow C_3H_4O_3}</math> |
| Spin waves can propagate in magnetic media with magnetic ordering such [[ferromagnet]]s and [[antiferromagnet]]s. The frequencies of the precession of the magnetisation depend on the material and its magnetic parameters, in general precession frequencies are in the microwave from 1–100 GHz, exchange resonances in particular materials can even see frequencies up to several THz. This higher precession frequency opens new possibilities for analogue and digital signal processing.
| | : <small> Ethylene oxide reacts with carbon dioxide to ethylene carbonate</small>. |
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| Spin waves themselves have [[group velocity|group velocities]] on the order of a few km per second. The [[damping]] of spin waves in a magnetic material also causes the amplitude of the spin wave to decay with distance, meaning the distance freely propagating spin waves can travel is usually only several 10's of μm. The damping of the dynamical magnetisation is accounted for phenomenologically by the Gilbert damping constant in the [[Landau-Lifshitz-Gilbert equation]] (LLG equation), the energy loss mechanism itself is not completely understood, but is known to arise microscopically from [[magnon]]-magnon [[scattering]], magnon-[[phonon]] scattering and losses due to [[eddy currents]]. The Landau-Lifshitz-Gilbert equation is the [[equation of motion|'equation of motion']] for the magnetisation. All of the properties of the magnetic systems such as the applied bias field, the sample's exchange, anisotropy and dipolar fields are described in terms of an 'effective' magnetic field that enters the Landau–Lifshitz–Gilbert equation. The study of damping in magnetic systems is an ongoing modern research topic.
| | (2) <math>{C_3H_4O_3 + H_2O \longrightarrow HO{-}C_2H_4{-}OH + CO_2}</math> |
| The LL equation was introduced in 1935 by Landau and Lifshitz to model the precessional motion of [[magnetization]] <math>\mathbf{M}</math> in a solid with an effective magnetic field <math>\mathbf{H}_\mathrm{eff}</math> and with damping.<ref>{{citation|authorlink1=Lev Landau|authorlink2=Evgeny Lifshitz|first=L.D. |last=Landau|first2= E.M.|last2= Lifshitz|title= Theory of the dispersion of magnetic permeability in ferromagnetic bodies|journal= Phys. Z. Sowietunion|volume= 8, 153 |year=1935}}</ref> Later, Gilbert modified the damping term, which in the limit of small damping yields identical results. The LLG equation is,
| | : <small> ethylene carbonate reacts with water to (mono) ethylene glycol and carbon dioxide </small>. |
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| :<math>\frac{\partial \textbf m}{\partial t}\, =\, -\gamma \,\textbf m\times \textbf{H}_{\mathrm{eff}}\, +\, \alpha\,\textbf m\times\frac{\partial \textbf m}{\partial t}\,.\qquad </math>
| | The selectivity to MEG is approximately 99.5%. |
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| The constant <math>\alpha</math> is the Gilbert phenomenological damping parameter and depends on the solid, and <math>\gamma</math> is the electron [[gyromagnetic ratio]]. Here <math>\textbf m={\textbf M}/{\mathrm M_S}\,.</math>
| | MEG is mainly used for the production [[polyethylene terephthalate]] and is also used a [[corrosion inhibitor]] in refrigerants. |
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| Research in magnetism, like the rest of modern science, is conducted with a symbiosis of theoretical and experimental approaches. Both approaches go hand-in-hand, experiments test the predictions of theory and theory provides explanations and predictions of new experiments. The theoretical side focuses on numerical modelling and simulations, so called [[micromagnetics|micromagnetic modelling]]. Programs such as OOMMF or NMAG are micromagnetic solvers that numerically solve the LLG equation with appropriate boundary conditions. Prior to the start of the simulation, magnetic parameters of the sample and the initial groundstate magnetisation and bias field details are stated.
| | A large-scale plant with 750,000 tonnes annual capacity was put in operation in 2009. <ref> [http://marketpublishers.de/lists/6226/news.html shell starts up MEG plant in Singapore]</ref> |
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| ==Experiment== | | == References == |
| Experimentally, there are many techniques that exist to study magnetic phenomena, each with its own limitations and advantages. The experimental techniques can be distinguished by being [[time-domain]] (optical and field pumped TR-MOKE), field-domain ([[Ferromagnetic resonance]] (FMR)) and [[frequency-domain]] techniques (Brillouin light scattering (BLS), Vector Network Analyser Ferromagnetic resonance (VNA-FMR)). Time-domain techniques allow the temporal evolution of the magnetisation to be traced indirectly by recording the [[polarization (waves)|polarisation]] response of the sample. The magnetisation can be inferred by the so-called 'Kerr' rotation. Field-domain techniques such as FMR tickle the magnetisation with a CW microwave field. By measuring the absorption of the microwave radiation through the sample, as an external magnetic field is swept provides information about magnetic resonances in the sample. Importantly, the frequency at which the magnetisation precesses depends on the strength of the applied magnetic field. As the external field strength is increased, so does the precession frequency. Frequency-domain techniques such as VNA-FMR, examine the magnetic response due to excitation by an RF current, the frequency of the current is swept through the GHz range and the amplitude of either the transmitted or reflected current can be measured.
| | {{Reflist}} |
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| Modern [[ultrafast laser]]s allow femtosecond (fs) temporal resolution for time-domain techniques, such tools are now standard in laboratory environments. Based on the [[MOKE|magneto-optical Kerr effect]], TR-MOKE is a pump-probe technique where a pulsed laser source illuminates the sample with two separate laser beams. The 'pump' beam is designed to excite or perturb the sample from equilibrium, it is very intense designed to create highly non-equilibrium conditions within the sample material, exciting the electron, and thereby subsequently the phonon and the spin system. Spin-wave states at high energy are excited and subsequently populate the lower lying states during their relaxation path's. A much weaker beam called a 'probe' beam is spatially overlapped with the pump beam on the magnonic material's surface. The probe beam is passed along a delay line, which is a mechanical way of increasing the probe path length. By increasing the probe path length, it becomes delayed with respect to the pump beam and arrives at a later time on the sample surface. Time-resolution is built in the experiment by changing the delay distance. As the delay line position is stepped, the reflected beam properties are measured. The measured Kerr rotation is proportional to the dynamic magnetisation as the spin-waves propagate in the media. The temporal resolution is limited by the temporal width of the laser pulse only. This allows to connect ultrafast optics with a local spin-wave excitation and contact free detection in magnonic metamaterials, [[photomagnonics]].<ref>B. Lenk, H. Ulrichs, F. Garbs, M. Münzenberg, The building blocks of magnonics, Physics Reports 507, 107-136 (2011), {{doi|10.1016/j.physrep.2011.06.003}}or arXiv:cond-mat/1101.0479v2</ref><ref>{{cite journal|last=Nikitov|first=Sergey|coauthors=Tailhades, Tsai|title=Spin waves in periodic magnetic structures—magnonic crystals|journal=Journal of Magnetism and Magnetic Materials|date=3|year=2001|month=November|volume=236|issue=3|pages=320–330|doi=10.1016/S0304-8853(01)00470-X|bibcode = 2001JMMM..236..320N }}</ref>
| | ==External links== |
| | * [http://www.shell.com/static/globalsolutions-en/downloads/knowledge_centre/pres_speeches_papers/2006/techpersptv_eijsberg.pdf description of Shell OMEGA process] |
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| ==References==
| | [[Category:Chemical processes]] |
| {{Reflist}}
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| [[Category:Magnetic ordering]] | | [[de:OMEGA-Prozess]] |
The OMEGA process (only mono ethylene glycol advanced process) is a process of the Royal Dutch Shell to produce Mono-ethylenlglycol from ethylene oxide, carbon dioxide as catalyst and water with high selectivity.
Process
The traditional process of monoethylene glycol (MEG) production is by reaction of ethylene oxide with water. The product of the first reaction stage, MEG, reacts with ethylene oxide on to diethylene glycol and triethylene glycol, which makes a distillation work-up necessary. The selectivity to MEG is about 90%.
In the OMEGA process, the ethylene oxide is first converted with carbon dioxide (CO2) to ethylene carbonate to then react with water in a second step to selectively produce monoethylene glycol. The carbon dioxide is released in this step again and can be fed back into the process circuit. The carbon dioxide comes in part from the ethylene oxide production, where a part of the ethylene is completely oxidized.
(1)
- Ethylene oxide reacts with carbon dioxide to ethylene carbonate.
(2)
- ethylene carbonate reacts with water to (mono) ethylene glycol and carbon dioxide .
The selectivity to MEG is approximately 99.5%.
MEG is mainly used for the production polyethylene terephthalate and is also used a corrosion inhibitor in refrigerants.
A large-scale plant with 750,000 tonnes annual capacity was put in operation in 2009. [1]
References
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
External links
de:OMEGA-Prozess