Accessing the Frank-Kasper Phase of Block Copolymer in the Fuzzy Colloid Regime

The discovery of Frank-Kasper (FK) phase in block copolymer (bcp) has prompted the progress of the field of soft quasicrystals. In principle, the formation of FK phase from the supercooled liquid phase of the bcp micelles should involve the mass transport of constituent molecules to transform the unimodal distribution of micelle size into the multimodal distribution prescribed by the volume asymmetry of the Voronoi cells in the FK phase. Here we present a new regime in which the Laves C14 phase of bcp developed below the glass transition temperature of the micelle core, where the mass transport was inhibited by the immobile block chains forming the core. The bcp micelle comprising a glassy core and a soft corona resembles the fuzzy colloid and the strong van der Waals attraction between the cores directs their organization into C14 phase to minimize the interparticle interaction energy under the metastable condition.

Atomic ordering and coercive force of nanocrystalline Fe-Co alloy films

In single crystal films of the Fe0,5Co0,5 alloys grown by the method of vacuum condensation, a metastable condition may be received that is similar to the completely disordering condition. Approximately during ten days after the condensation in the film at the room temperature the short range and then long range atomic ordering is developed. Simultaneously the changes of magnetic anisotropy, electroresistance and coercive force of the films were investigated. This investigations show that the appearance of the shot range atomic ordering increases the electroresistance of films and the long range atomic ordering reduces it. The dependence of coercive force from time to time at room temperature atomic ordering films Fe0,5Co0,5 alloys, and Fe0,75Co0,25. Found that the biggest change Hc (double) is observed in single-crystal films when changing mechanism of magnetization reverse. Most is a consequence of the changes to the crystallographic anisotropy.

Influence of Phase Composition on Properties of Corundum-Zirconium Ceramic

The results of the analysis of influence of the phase composition of corundum-zirconium ceramic on its properties are presented in this paper. It was established that the most perspective ceramic has composition 0,6 (ZrО2 + 3M% Y2O3) – 0,4 Аl2О3. High strength properties of this composition are determined by the presence of compressive stresses and the opportunity of retaining of tetragonal grains ZrО2 in a metastable condition at low temperatures.

Nanocrystalline Diamond Films Prepared with Different Diamond Seeding Processes of 4 Nm and 0.25 Μm Diamond Powders

The growth of diamond films in metastable condition occurs in two steps: nucleation and growth of crystals. Studies have shown that the nucleation process is the most critical step and essential to optimize the properties of the diamond, but its understanding is still very limited. Furthermore, the nucleation process is directly related to the pretreatment applied to the surface of the substrate: cleaning the surface and seeding. When the substrate is silicon, it is cleaned with acetone and scratching with diamond particles dispersed in a suitable solvent followed by ultrasonic agitation (nucleation rate = 109part/cm2). However, research has demonstrated that the use of diamond nanoparticles (ND) prepared with the use of a powerful ultrasound (750W) provides nucleation density much higher (1012part/cm2) compared to that processed with larger size particles. This work demonstrates that diamond films prepared with ND different solutions exhibit differences in relation to diamond films prepared using diamond particle dispersed in an organic solvent. Morphological analysis and the quality of the films were evaluated by Scanning Electron Microscopy, Optical Perfilometry and Raman Scattering Spectroscopy.

Change in Film Thickness Profile of Perfluoropolyethers During Dewetting

The physical spacing between a magnetic head and a disk surface has been decreasing in order to achieve the higher recording density for hard disk drives (HDD), and a new head/disk system, such as the contact type, has been proposed in recent years. However, a molecularly-thin PFPE film dewets due to intermolecular forces particularly when the polar interaction is predominant which results in the formation of microdroplets. It was reported that the microdroplets on the disk surface attacked the magnetic head, caused a fluctuation in the physical spacing and made the flying head unstable. Therefore, the precise investigation of the dewetting at head disk interfaces (HDI) is fundamentally needed. The substrates evaluated in this study were 2.5inch glass disks used for HDD. These glass disks are comprised of a magnetic layer and diamond-like carbon (DLC) overcoat, of which the DLC thickness is about 3nm, and have a textured pattern on the surface. PFPE Zdol diluted with HFE-7100DL was coated on the disk surface by a dip-coating method. The change in the film thickness profile was investigated using an ellipsometer for the film under an unstable or metastable condition. It was found from the observation of the unstable film that the development of microdroplets indicates the movement of PFPE molecules through the under layer. For the metastable condition, the surface texture triggered the dewetting and affected the formation of microdroplets. In the “thicknesses spectrum”, a sharp peak was seen at about 7.8nm immediately after the dip-coating, but before the occurrence of dewetting. The peak at 7.8nm easily disappeared and another peak at about 1.6nm appeared instead. This means that the 7.8nm thickness film was unstable and moved to a more stable state. It is noted that the microdroplets were formed by this instability, and the 1.6 nm thickness corresponded to that of the dewetted area.

Chromosomes attain a metaphase position on half-spindles in the absence of an opposing spindle pole

To examine the relative roles of chromosomes, spindle poles and microtubules in the formation of the metaphase spindle and metakinesis, I have experimentally placed an extra centrosome-free pronucleus close to a forming bipolar spindle in a living cell. The chromosomes from the extra nucleus induce the formation of an extra half-spindle from one pole of the otherwise normal bipolar spindle with chromosomes positioned at the putative metaphase plate. I conclude that chromosomes determine the location of half-spindles by sustaining a higher than normal density of microtubules. These results are surprising for two reasons: first, because previous in vivo experiments in tissue culture cells show that mono-oriented chromosomes with functional attachments to spindle microtubules do not support half-spindle formation but oscillate unstably or move to one spindle pole. Additionally, the generally accepted view is that chromosomes attain a metastable condition at the metaphase plate as a result of a balance between forces directed to opposite spindle poles. However, our observation that chromosomes on extra half-spindles attain a metastable position in the absence of an opposing spindle pole, suggests that Ostergren's model does not account for metakinesis in sea urchin embryos.

Elemental Sulfur as a Plasticizer for Polysulfide Polymers and Other Polymers

So-called elastic sulfur obtained by quick-quenching molten sulfur from a temperature of 250° C to a temperature of about −10° C is really a mixture of polymeric sulfur and monomeric S8 sulfur, the latter in a metastable condition, Quick-quenched sulfur is elastic because of the plasticizing effect of the liquid S8 sulfur on the polymeric sulfur. In this publication we show that large concentrations of S8 can exist dissolved in a liquid condition in other polymers where it also acts as a plasticizer. In many cases these compositions appear completely stable, i.e., there is no tendency for the dissolved sulfur to crystallize out. The best example is crosslinked polyethylene tetrasulfide polymers. These polymers can retain 40 per cent of dissolved sulfur in the form of liquid S8 over indefinitely long periods of time. We prove that the sulfur is in its elemental form by quantitative extraction with CS2. The specific volume of the dissolved sulfur shows it is in a liquid condition. The mechanical properties of the sulfur plasticized crosslinked polymers are just what would be expected from this type of structure. Preliminary information concerning sulfur in other polymers is presented.