Pulsed laser deposition of AlMgB14 thin films

Hard, wear-resistant coatings of thin film borides based on AlMgB14 have the potential to be applied industrially to improve the tool life of cutting tools and pump vanes and may account for several million dollars in savings as a result of reduced wear on these parts. Past work with this material has shown that it can have a hardness of up to 45GPa and be fabricated into thin films with a similar hardness using pulsed laser deposition. These films have already been shown to be promising for industrial applications. Cutting tools coated with AlMgB14 used to mill titanium alloys have been shown to substantially reduce the wear on the cutting tool and extend its cutting life. However, little research into the thin film fabrication process using pulsed laser deposition to make AlMgB14 has been conducted. In this work, research was conducted into methods to optimize the deposition parameters for the AlMgB14 films. Processing methods to eliminate large particles on the surface of the AlMgB14 films, produce films that were at least 1μm thick, reduce the surface roughness of the films, and improve the adhesion of the thin films were investigated. Use of a femtosecond laser source rather than a nanosecond laser source was found to be effective in eliminating large particles considered detrimental to wear reduction properties from the films. Films produced with the femtosecond laser were also found to be deposited at a rate 100 times faster than those produced with the nanosecond laser. However, films produced with the femtosecond laser developed a relatively high RMS surface roughness around 55nm. Attempts to decrease the surface roughness were largely unsuccessful. Neither increasing the surface temperature of the substrate during deposition nor using a double pulse to ablate the material was found to be extremely successful to reduce the surface roughness. Finally, the adhesion of the thin films to M2 tool steel substrates, assessed using the Rockwell C indentation adhesion test, was found to be substantially improved by the deposition of a titanium interlayer, but unaffected by increasing the temperature of the substrates. The titanium was found to improve the adhesion strength of the films because it reacted with both the steel and the AlMgB14 compound to form new compounds. Ultimately, it was concluded that the films with the best properties were produced with a femtosecond pulsed laser and were deposited on top of a titanium interlayer to improve the thin film adhesion

Nanoscale Mechanical Switching of Ferroelectric Polarization Via Flexoelectricity

Flexoelectric coefficient is a fourth-rank tensor arising from the coupling between strain gradient and electric polarization and thus exists in all crystals. It is generally ignored for macroscopic crystals due to its small magnitude. However, at the nanoscale, flexoelectric contributions may become significant and can potentially be utilized for device applications. Using the phase-field method, we study the mechanical switching of electric polarization in ferroelectric thin films by a strain gradient created via an atomic force microscope tip. Our simulation results show good agreement with existing experimental observations. We examine the competition between the piezoelectric and flexoelectric effects and provide an understanding of the role of flexoelectricity in the polarization switching. Also, by changing the pressure and film thickness, we reveal that the flexoelectric field at the film bottom can be used as a criterion to determine whether domain switching may happen under a mechanical force

THE HERMENEUTICAL RECEPTION OF THE CHARACTER OF JORGE DE BURGOS IN UMBERTO ECO\u27S NOVEL "THE NAME OF THE ROSE"

U članku se analiziraju modaliteti Ecova intertekstualnog prisvajanja fikcionalne osobe J.L. Borgesa i pojedinih književnih metafora koje se razvijaju u njegovim pripovijetkama u izgradnji hermeneutičke recepcije lika Jorgea iz Burgosa, glavnog negativca romana Ime ruže Umberta Eca. Dok je prvi aspekt dostatno obrađen u kritičkoj literaturi o Imenu ruže, drugi je ostao zanemaren u nekim bitnim aspektima. Analiza ideoloških i hermeneutičkih aspekata njegovog lika u Ecovu romanu otkriva da u izgradnji ne samo njegova etičkog i teološkog habitusa nego i razvitku glavnog narativnog tijeka romana, čiji je on pokretač, veliku ulogu igraju dvostruko kodirane metafore koje Borges razvija u svojim pripovijetkama Teolozi i Tri tumačenja Jude. U članku se analizira njihova uloga u spomenutim Borgesovim novelama i njihov intertekstualni odjek u Imenu ruže koji se pronalazi na idejnoj i kompozicijsko-pripovjednoj razini. Temeljna Borgesova metafora \u27svi su ljudi jedan čovjek\u27 razrađuje se u romanu raznim figurama ponavljanja, a unutar te primarne metafore značajna je metaforika Jude koju Borges razvija u noveli Tri tumačenja Jude. Analiza hermeneutičke recepcije Jorgeova lika otkriva presudnu ulogu te metafore u njenoj iozgradnji.This article analyses the modalities of Umberto Eco\u27s intertextual adoption of J. L. Borges\u27 \u27fictional person\u27 and the specific literary metaphors Borges developed and used in his short stories when building the hermeneutical reception of the character of Jorge de Burgos, the villain of Eco\u27s novel The Name of the Rose. While the critical literature on The Name of the Rose has devoted considerable attention to the former, the latter has remained neglected in some crucial aspects. The analysis of ideological and hermeneutic aspects of his character in Eco\u27s novel revealed that, in creating his ethical and theological habitus and even in the development of the novel\u27s main narrative, a significant role was played by double coded metaphors developed by Borges in his short stories The Theologians and Three Versions of Judas. This article analyses their role in the aforementioned short stories by Borges and their intertextual resonance in The Name of the Rose visible both, on the level of ideas and the compositional-narrative level. The basic Borges\u27 metaphor, "Whatever one man does, it is as if all men did it", was developed in the novel with the help of various figures of repetition. Within that primary metaphor, an important place is held by the metaphorics of Judas developed by Borges in Three Versions of Judas. Analysis of the hermeneutical reception of Jorge\u27s character has revealed the crucial role of that metaphor in its creation

Enhanced electric conductivity at ferroelectric vortex cores in BiFeO3

In many large ensembles, the property of the system as a whole cannot be understood from studying the individual entities alone ¿ these ensembles can be made up by neurons in the brain, transport users in traffic networks or data packages in the Internet. The past decade has seen important progress in our fundamental understanding of what such seemingly disparate 'complex systems' have in common; some of these advances are surveyed here

Pulsed laser deposition of AlMgB14 thin films

Hard, wear-resistant coatings of thin film borides based on AlMgB14 have the potential to be applied industrially to improve the tool life of cutting tools and pump vanes and may account for several million dollars in savings as a result of reduced wear on these parts. Past work with this material has shown that it can have a hardness of up to 45GPa and be fabricated into thin films with a similar hardness using pulsed laser deposition. These films have already been shown to be promising for industrial applications. Cutting tools coated with AlMgB14 used to mill titanium alloys have been shown to substantially reduce the wear on the cutting tool and extend its cutting life. However, little research into the thin film fabrication process using pulsed laser deposition to make AlMgB14 has been conducted. In this work, research was conducted into methods to optimize the deposition parameters for the AlMgB14 films. Processing methods to eliminate large particles on the surface of the AlMgB14 films, produce films that were at least 1μm thick, reduce the surface roughness of the films, and improve the adhesion of the thin films were investigated. Use of a femtosecond laser source rather than a nanosecond laser source was found to be effective in eliminating large particles considered detrimental to wear reduction properties from the films. Films produced with the femtosecond laser were also found to be deposited at a rate 100 times faster than those produced with the nanosecond laser. However, films produced with the femtosecond laser developed a relatively high RMS surface roughness around 55nm. Attempts to decrease the surface roughness were largely unsuccessful. Neither increasing the surface temperature of the substrate during deposition nor using a double pulse to ablate the material was found to be extremely successful to reduce the surface roughness. Finally, the adhesion of the thin films to M2 tool steel substrates, assessed using the Rockwell C indentation adhesion test, was found to be substantially improved by the deposition of a titanium interlayer, but unaffected by increasing the temperature of the substrates. The titanium was found to improve the adhesion strength of the films because it reacted with both the steel and the AlMgB14 compound to form new compounds. Ultimately, it was concluded that the films with the best properties were produced with a femtosecond pulsed laser and were deposited on top of a titanium interlayer to improve the thin film adhesion.</p

Giant Resistive Switching via Control of Ferroelectric Charged Domain Walls

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134223/1/adma201600160.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134223/2/adma201600160-sup-0001-S1.pd

ARTICLE Atomic-scale mechanisms of ferroelastic domain-wall-mediated ferroelectric switching

Polarization switching in ferroelectric thin films occurs via nucleation and growth of 180°d omains through a highly inhomogeneous process in which the kinetics are largely controlled by defects, interfaces and pre-existing domain walls. Here we present the first real-time, atomic-scale observations and phase-field simulations of domain switching dominated by pre-existing, but immobile, ferroelastic domains in Pb(Zr 0.2 Ti 0.8 )O 3 thin films. Our observations reveal a novel hindering effect, which occurs via the formation of a transient layer with a thickness of several unit cells at an otherwise charged interface between a ferroelastic domain and a switched domain. This transient layer possesses a low-magnitude polarization, with a dipole glass structure, resembling the dead layer. The present study provides an atomic level explanation of the hindering of ferroelectric domain motion by ferroelastic domains. Hindering can be overcome either by applying a higher bias or by removing the as-grown ferroelastic domains in fabricated nanostructures

Direct Observation of Asymmetric Domain Wall Motion in A Ferroelectric Capacitor using In-situ TEM

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Stability of polar vortex lattice in ferroelectric superlattices

A novel mesoscale state comprising of an ordered polar vortex lattice has been demonstrated in ferroelectric superlattices of PbTiO3/SrTiO3. Here, we employ phase-field simulations, analytical theory, and experimental observations to evaluate thermodynamic conditions and geometric length scales that are critical for the formation of such exotic vortex states. We show that the stability of these vortex lattices involves an intimate competition between long-range electrostatic, long-range elastic, and short-range polarization gradient-related interactions leading to both an upper and a lower bound to the length scale at which these states can be observed. We found that the critical length is related to the intrinsic domain wall width, which could serve as a simple intuitive design rule for the discovery of novel ultrafine topological structures in ferroic systems