Калориметрический анализ в качестве инструмента для изучения процесса термического упрочнения сплава БрО15Н5

Общеизвестно, что медные сплавы не обладают высокими прочностными свойствами. Для повышения прочностных характеристик существует ряд способов. Одним из таких способов является термическое упрочнение. При термическом упрочнении прочность возрастает в результате дисперсионного твердения после закалки и старения. Этот вывод подтверждается большим количеством работ [1-5] связанных с упрочнением меди и ее сплавов. Цель данной работы заключается в выборе режимов для термического упрочнения бронзы БрО15Н5, используя калоритмический анализ

High coercive Field and Film Stress for epitaxial Monolayers of Fe on W(110)

Elastic and magnetic properties of ultra-thin iron films on tungsten(110) are investigated. In situ film stress measurements during growth show stress values of 25 GPa per deposited monolayer. Our experiments indicate that the tremendous film stress triggers the formation of a misfit dislocation network at a coverage of 1.5 monolayers. The effect of the film stress and its spatial variation on the magnetic behavior are discussed. We find an high coercivity of order 0.3 T for 1.5 monolayer thick films. A model is presented that explains the high coercivity in terms of strong domain wall pinning

Stress and structure of Ni monolayers on W(110): The importance of lattice mismatch

The combination of in situ stress measurements, low-energy electron diffraction, and scanning tunneling microscopy reveals the intimate relation between film structure and film stress for epitaxial growth of Ni on W(110) in the monolayer range. In contradiction to lattice mismatch considerations, we measure tremendous compressive stress in the pseudomorphic Ni film, where tensile film stress is expected from strain arguments. Surface stress of the film-substrate composite is proposed to be much more relevant for the description of film stress in the submonolayer range than lattice mismatch arguments are

Hydrogen-induced ferromagnetism in two-dimensional Pt dichalcogenides

Electronic, structural, and magnetic properties of Pt dichalcogenide monolayers are investigated using firstprinciple calculations.We find that hydrogenation lifts the spin degeneracy in narrow antibonding Pt 5d subband electrons and transforms the nonmagnetic semiconductors PtX2 (X = S,Se,Te) into ferromagnetic metals, PtX2-1H; neither strain nor thin-film edges are necessary to support the transition. The trend towards ferromagnetism is most pronounced for X = S, decreasing with increasing atomic weight of the chalcogens

Diffusion-controlled on-surface synthesis of graphene nanoribbon heterojunctions

We report a new diffusion-controlled on-surface synthesis approach for graphene nanoribbons (GNR) consisting of two types of precursor molecules, which exploits distinct differences in the surface mobilities of the precursors. This approach is a step towards a more controlled fabrication of complex GNR heterostructures and should be applicable to the on-surface synthesis of a variety of GNR heterojunctions

Film Stress and Domain Wall Pinning in Sesquilayer Iron Films on W(110)

We present an in situ investigation of the correlation between elastic and magnetic properties of monolayer iron films on W(110). Sesquilayers, consisting of two-monolayer patches on a nearly ideal monolayer film, exhibit anomalous elastic properties and a strikingly high in-plane coercivity of order 0.3 T. The sesquilayer coercivity maximum is explained by a novel domain wall pinning mechanism, based on an enhanced exchange interaction in the two monolayer thick patches. This rather unique behavior is restricted to (110) surfaces but does not occur on (100) and (111) thin films

Length scales of interactions in magnetic, dielectric, and mechanical nanocomposites

It is investigated how figures of merits of nanocomposites are affected by structural and interaction length scales, Aside from macroscopic effects without characteristic lengths scales and atomic-scale quantum-mechanical interactions there are nanoscale interactions that reflect a competition between different energy contributions. We consider three systems, namely dielectric media, carbon-black reinforced rubbers and magnetic composites. In all cases, it is relatively easy to determine effective materials constants, which do not involve specific length scales. Nucleation and breakdown phenomena tend to occur on a nanoscale and yield a logarithmic dependence of figures of merit on the macroscopic system size. Essential system-specific differences arise because figures of merits are generally nonlinear energy integrals. Furthermore, different physical interactions yield different length scales. For example, the interaction in magnetic hardsoft composites reflects the competition between relativistic anisotropy and nonrelativistic exchange interactions, but such hierarchies of interactions are more difficult to establish in mechanical polymer composites and dielectric

Magnetic anisotropy of deposited transition metal clusters

We present results of magnetic torque calculations using the fully relativistic spin-polarized Korringa-Kohn-Rostoker approach applied to small Co and Fe clusters deposited on the Pt(111) surface. From the magnetic torque one can derive amongst others the magnetic anisotropy energy (MAE). It was found that this approach is numerically much more stable and also computationally less demanding than using the magnetic force theorem that allows to calculate the MAE directly. Although structural relaxation effects were not included our results correspond reasonably well to recent experimental data

Site selective adsorption of the spin crossover complex Fe(phen)\u3csub\u3e2\u3c/sub\u3e(NCS)\u3csub\u3e2\u3c/sub\u3e on Au(111)

The iron(II) spin crossover complex Fe(1,10-phenanthroline)2(NCS)2, dubbed Fe-phen, has been studied with scanning tunneling microscopy, after adsorption on the \u27herringbone\u27 reconstructed surface of Au(111) for sub-monolayer coverages. The Fe-phen molecules attach, through their NCS-groups, to the Au atoms of the fcc domains of the reconstructed surface only, thereby lifting the herringbone reconstruction. The molecules stack to form 1D chains, which run along the Au[110] directions. Neighboring Fe-phen molecules are separated by approximately 2.65 nm, corresponding to 9 atomic spacings in this direction. The molecular axis, defined by the two phenanthroline groups, is aligned perpendicular to the chain axis, along the Au [221] direction, thereby bridging over 5 atomic spacings, in this direction. Experimental evidence suggests that the molecular spins are locked in a mixed state in the sub-monolayer regime at temperatures between 100 K and 300 K

Temperature Dependence of the Surface Anisotropy of Fe Ultrathin Films on Cu(001)

We report an experimental approach to separate temperature dependent reversible and irreversible contributions to the perpendicular magnetic anisotropy of Fe films grown at low temperatures on Cu(001) substrates. The surface anisotropy KS(T) is found to decrease linearly with temperature, causing a thermally induced spin reorientation into the plane. The irreversible shift of the spin reorientation transition and the coercivity of the iron films are directly correlated to the increasing Fe island size during annealing. The increased coercivity is discussed in terms of domain wall energy inhomogeneities provided by the islands