Prestressing of compression springs

A scheme of force variation during the compression of a spring in both elastic and elastic-plastic state is presented. For the elastic state it has been found that equivalent load increments occur with equivalent deflection increments. In the elastic-plastic state equivalent load increments correspond to higher deflection increments. Prestressing the spring increases the range of the elastic deformation of a spring. Equations for the determination of torsional moment during prestressing and relationships of total non-dilatational strain versus elastic strain and radii of elastic zone are also presented. The effect of characteristic spring dimensions and non-dilatational strain on spring deflection has been determined. A nomogram for the determination of the resultant equivalent strain as a function of external load, also considering residual stress distribution, has as well been elaborated.     

Comparative study of self-assembling of multilayers using reactive sputter deposition and mass selective ion beam deposition

While experimenting with the growth of metal-containing amorphous carbon (a-c:Me) thin films using two different growth processes, self-assembled multilayered structures were observed. One of the processes is a reactive magnetron sputter deposition process. The other process is a mass selective ion beam deposition process. Despite of the differences in the growth method and the growth condition, self-assembled multilayered thin films, consisting of alternating dark layer and bright layer, were obtained in both processes. Based on the consideration of energy for atomic diffusion in the thin films, the growth mechanism is discussed.     

Effect of transfer on droplet size in liquid-liquid dispersions

Mean droplet diameter of the dispersed phase in pulsed plate extraction columns was measured for binary and ternary systems. A change in the droplet size in the presence of solute, dependent on such factors as the direction of mass transfer, droplet size in the binary system, radio of diffusion coefficients, viscosity of the continuous phase, interfacial tension and driving force for extraction was observed. Two new empirical correlations of mean droplet sizes in mass transfer conditions are proposed. These correlations have been successfully applied to other extraction columns.     

Performance and stability of poly(phenylene vinylene) based polymer light emitting diodes with caesium carbonate cathode

We have studied the phenomena resulting from the combination of a hole-conducting poly(phenylene vinylene) (PPV) based light emitting polymer with a highly efficient electron injection layer of caesium carbonate (Cs₂CO₃) in light emitting diodes. A strong dependence between the thickness of the applied Cs₂CO₃ and the electro-optical performance of the diodes is detected and already with ultrathin Cs₂CO₃ layers high efficiency diodes are achieved. The Cs₂CO₃ is shown to diffuse into the polymer layer leading to an increased electron density but also quenching of both electro and photoluminescence when the amount of applied Cs₂CO₃ is increased. During electrical stressing the electron density decreases assumably through degradation of the n-doping and quenching Cs₂CO₃ species inducing an unusual increasing luminescence behavior.     

High‐TC Interfacial Ferromagnetism in SrMnO3/LaMnO3 Superlattices

Heterostructures of strongly correlated oxides demonstrate various intriguing and potentially useful interfacial phenomena. LaMnO₃/SrMnO₃ superlattices are presented showcasing a new high‐temperature ferromagnetic phase with Curie temperature, T_C ≈360 K, caused by electron transfer from the surface of the LaMnO₃ donor layer into the neighboring SrMnO₃ acceptor layer. As a result, the SrMnO₃ (top)/LaMnO₃ (bottom) interface shows an enhancement of the magnetization as depth‐profiled by polarized neutron reflectometry. The length scale of charge transfer, λ_TF ≈2 unit cells, is obtained from in situ growth monitoring by optical ellipsometry, supported by optical simulations, and further confirmed by high resolution electron microscopy and spectroscopy. A model of the inhomogeneous distribution of electron density in LaMnO₃/SrMnO₃ layers along the growth direction is concluded to account for a complex interplay between ferromagnetic and antiferromagnetic layers in superlattices.     

A mathematical model of mixing of particulate solids

A mathematical model of mixing of particulate solids accompanied by segregation is presented. The model has been constructed on the assumption of diffusional mechanisms of both phenomena occurring when the mixing takes place, i.e. homogenisation and segregation. For the mechanism of diffusional segregation a “Law of Diffusional Segregation” has been formulated, analogous to Fick's Second Law. The model has been solved for a two-component system mixed radially in a horizontal rotating drum mixer. A solution has been obtained in the form of the dependence of the concentration of the key component upon the time and position. After introducing the statistical definition of the degree of mixing, based on the concentration standard deviation in the system, a rate equation has been obtained.     

Experimental studies of power consumption for agitated vessels equipped with non-standard baffles and high-speed agitator

The influence of the geometrical parameters of non-standard baffles on power consumption has been investigated for agitated vessels equipped with a high speed agitator (Rushton disc turbine, pitched-blade turbine or propeller) The following geometrical parameters of the baffles have been tested: number J, width B, length L and distance p between the lower edge of the baffle and the bottom of the vessel. Measurements were carried out according to a second-order rotatable design of experiment, using the strain gauge technique. The results of the experiments have been approximated in the form of equations.     

Self-organized formation of layered carbon–copper nanocomposite films by ion deposition

The quasi-simultaneous deposition of low energy-mass-selected C⁺ and metal⁺ ions leads to the formation of metal–carbon nanocomposites. In the case of C⁺ and Cu⁺ deposition, a homogeneous distribution of small copper clusters in an amorphous carbon matrix is expected. However, at a certain C⁺/Cu⁺ fluence ratio and energy range, alternately metal-rich and metal-deficient layers in an amorphous carbon matrix with periods in the nm range develop have been observed. The metal-rich layers consist of densely distributed crystalline Cu particles while the metal-deficient layers are amorphous and contain only few and small Cu clusters. The formation of multilayers can be described by an interplay of sputtering, surface segregation, ion induced diffusion, and the stability of small clusters against ion bombardment. This formation has been investigated for the a-C:Cu system with respect to the ion energy and the C⁺/Cu⁺ fluence ratio. The sputter coefficient S_M = r_f S_CCu + S_CuCu is the parameter to switch between layer growth (S_M < 1) and homogeneous cluster distribution (S_M > 1).