Phase change composite bimorphs

A bilayer composite thin-film beam structure is described. The structure incorporates a bulk phase change material as small inclusions in one layer of a bimorph. The structure, also referred to as a “phase change composite bimorph” or “PCBM”, curls abruptly, and reversibly, at a phase transition temperature. Large curling and effective expansion coefficients are demonstrated. The PCBMs may be employed in various self-assembly mechanisms and actuators.Published versio

Monatomic phase change memory

Phase change memory has been developed into a mature technology capable of storing information in a fast and non-volatile way, with potential for neuromorphic computing applications. However, its future impact in electronics depends crucially on how the materials at the core of this technology adapt to the requirements arising from continued scaling towards higher device densities. A common strategy to finetune the properties of phase change memory materials, reaching reasonable thermal stability in optical data storage, relies on mixing precise amounts of different dopants, resulting often in quaternary or even more complicated compounds. Here we show how the simplest material imaginable, a single element (in this case, antimony), can become a valid alternative when confined in extremely small volumes. This compositional simplification eliminates problems related to unwanted deviations from the optimized stoichiometry in the switching volume, which become increasingly pressing when devices are aggressively miniaturized. Removing compositional optimization issues may allow one to capitalize on nanosize effects in information storage

Phase-change chalcogenide glass metamaterial

Combining metamaterials with functional media brings a new dimension to their performance. Here we demonstrate substantial resonance frequency tuning in a photonic metamaterial hybridized with an electrically/optically switchable chalcogenide glass. The transition between amorphous and crystalline forms brings about a 10% shift in the near-infrared resonance wavelength of an asymmetric split-ring array, providing transmission modulation functionality with a contrast ratio of 4:1 in a device of sub-wavelength thickness.Comment: 3 pages, 3 figure

MIA HALL’S BEHAVIOUR CHANGE IN GAYLE FORMAN’S IF I STAY

This final project analysis Gayle Forman’s novel entitled: If I Stay. The purpose of this final project is to analysis the behaviour change of the main character, Mia Hall. The study uses psychological approach and library research to analyse the behaviour change of the main character. Mia experiences three phases of behaviour change: unfreezing phase, movement phase and refreezing phase of Mia. Mia changes her behaviour and the social environment affect Mia’s behaviour change. Mia’s change is planned change. However, Mia decides not to change her behaviour permanentl

Phase change material in automated window shades

The purpose of this report is to detail the development process for a phase change material window shading system, which stores solar thermal energy and later releases it indoors to provide nighttime space heating. To do this, wax-filled louvers with thermally absorptive front faces were developed and outfitted with a control system, which utilized historical weather data to orient the louvers to specific solar azimuthal angles, thus maximizing the thermal absorption. The system was tested against other common window treatments in a pair of thermally comparable testing structures, and was found to provide energy savings as high as 50%

Phase-Change Control of Interlayer Exchange Coupling

Changing the interlayer exchange coupling between magnetic layers in-situ is a key issue of spintronics, as it allows for the optimization of properties that are desirable for applications, including magnetic sensing and memory. In this paper, we utilize the phase change material VO2 as a spacer layer to regulate the interlayer exchange coupling between ferromagnetic layers with perpendicular magnetic anisotropy. The successful growth of ultra-thin (several nanometres) VO2 films is realized by sputtering at room temperature, which further enables the fabrication of [Pt/Co]2/VO2/[Co/Pt]2 multilayers with distinct interfaces. Such a magnetic multilayer exhibits an evolution from antiferromagnetic coupling to ferromagnetic coupling as the VO2 undergoes a phase change. The underlying mechanism originates from the change in the electronic structure of the spacer layer from an insulating to a metallic state. As a demonstration of phase change spintronics, this work may reveal the great potential of material innovations for next-generation spintronics

Phase-change materials handbook

Handbook describes relationship between phase-change materials and more conventional thermal control techniques and discusses materials' space and terrestrial applications. Material properties of most promising phase-change materials and purposes and uses of metallic filler materials in phase-change material composites are provided

Phase change indicators for subambient temperatures

Evaluation of organic compounds for temperature indicators for subambient temperature

Somatic embryogenesis and phase change in trees

The advantages of clonai plantations are obvious for a lot of tree species. Somatic embryogenesis is a clonai propagation method with the greatest potential for achieving this goal, especially if combined to genetic engineering. However, more than for other vegetative propagation techniques, the practical use of somatic embryogenesis remains strongly impeded by the genetic identity and the physiological age of the mature selected trees to be cloned. So far, somatic embryogenesis has been successfully obtained from mature individuals only for a very limited number of broad-leaved or deciduous species using as primary explants leaves in a proper physiological condition and also sporophytic tissues from the reproductive organs. It is currently still limited to the embryonic phase of the ageing process for many evergreen coniferous species of high industrial impact. Shoot apical meristems owing to their key role in phase change warrant special consideration for attempting to clone mature trees by somatic embryogenesis. If direct induction from in situ collections is still hazardous in the absence of reliable indicators for the more responsive physiological stage, preconditioning in vitro procedures are worth considering when attempting to succeed in somatic embryogenesis from mature trees. These in vitro techniques include serial microcutting in subcultures as well as meristem culture and micrografting. With these techniques meaningful results have been obtained for different tree species in terms of rejuvenation. If some are limited to in vitro conditions, others are more unequivocal. (Résumé d'auteur

Photochemically Induced Phase Change in Monolayer Molybdenum Disulfide.

Monolayer transition metal dichalcogenide (TMDs) are promising candidates for two-dimensional (2D) ultrathin, flexible, low-power, and transparent electronics and optoelectronics. However, the performance of TMD-based devices is still limited by the relatively low carrier mobility and the large contact resistance between the semiconducting 2D channel material and the contact metal electrodes. Phase-engineering in monolayer TMDs showed great promise in enabling the fabrication of high-quality hetero-phase structures with controlled carrier mobilities and heterojunction materials with reduced contact resistance. However, to date, general methods to induce phase-change in monolayer TMDs either employ highly-hostile organometallic compounds, or have limited compatibility with large-scale, cost-effective device fabrication. In this paper, we report a new photochemical method to induce semiconductor to metallic phase transition in monolayer MoS2 in a benign chemical environment, through a bench-top, cost-effective solution phase process that is compatible with large-scale device fabrication. It was demonstrated that photoelectrons produced by the band-gap absorption of monolayer MoS2 have enough chemical potential to activate the phase transition in the presence of an electron-donating solvent. This novel photochemical phase-transition mechanism advances our fundamental understanding of the phase transformation in 2D transition metal dichalcogenides (TMDs), and will open new revenues in the fabrication of atomically-thick metal-semiconductor heterostructures for improved carrier mobility and reduced contact resistance in TMD-based electronic and optoelectronic devices