Mutual Mixing Research Articles

Broad metal ion and plasma beams techniques TAMEK for material surface modification

This paper reviews the development of vacuum arc metal ion sources and their application for material surface modification. The versatile, compact (high-voltage power supply and ion gun are located in the 70 × 40 × 25 cm 3 space) vacuum arc source TAMEK operated in frequency-pulsed mode is capable of generating a large spot area of 300–2000 cm 2 metal ion beams for ion implantation E i < 200 keV, d D i/d t < 10 16 ion/cm 2/min, or deposition d H/d t < 50–200 nm/min. If desired, metal ion implantation, deposition, or metal ion beam assisted deposition (IBAD) can be performed without switching off the source. The TAMEK source considerably improves IBAD treatment by means of alternation of the ion implantation and ion deposition and provides coatings both on metals and dielectric materials with deeper mutual mixing at low target temperature and simple surface preparation before treatment. TAMEK-M sources operated in pulsed t=1–5 μs mode, U accel <100 kV, I i<5 kA are used for increasing microhardness in subsurface layers up to 150 μm in depth after several pulses with an energy input into the surface d W=2–5 J/cm 2 This permits the TAMEK-M source to be used for the treatment of precision and small size products, e.g. drills with diameter smaller than 1–3 mm. TAMEK sources can be successfully used in conventional fields of ion implantation and physical vapor deposition, and some TAMEK applications for treatment of metals, ceramics, glass, polymers are also shown, e.g. tools, construction materials, electrical contacts and electrodes, mirrors, etc.

Interpolymer complexes and miscible blends of poly( p-vinyl phenol) and poly(ethylene imine)

Interpolymer complexation between poly( p-vinyl phenol) (PVPh) and poly(ethylene imine) (PEI) in various solvents was studied. By mutual mixing of solutions of PVPh and PEI, precipitates of PVPh/PEI complexes were prepared from methanol, ethanol, cyclohexanone, N,N-dimethylformamide and N,N-dimethylacetamide. However, only polymer blends were obtained from N-methyl-2-pyrrolidone (NMP). It has been found that solvent molecules also participate in hydrogen-bonding interactions, either as donors or acceptors, with a component polymer; the nature of the solvent assumes a profound influence on the degree of the interpolymer association. The glass transition ( T g ) behavior of the complexes and the blends were studied by DSC. Both the complex and the blend showed one composition-dependent T g , indicating its single-phase nature, and the PVPh/PEI blends prepared by casting from NMP are miscible over the entire composition range. The complexes showed higher T g s in comparison with those of the blends having the same compositions and positive deviations of T g were observed for the complexes, suggesting that the strength of the interactions between the components in the complex is much higher than that in the blend. FT-IR study revealed that there are hydrogen-bonding interactions between hydroxyl groups of PVPh and N—H groups of PEI in the blends cast from NMP and that the average strength of the hydrogen bond between the hydroxyl groups of PVPh and the N—H groups of PEI in the blend is much higher than that between hydroxyl groups in pure PVPh. A fluorescence study confirmed that there are stronger interactions between PVPh and PEI in ethanol than in NMP. The interpolymer complexation of PVPh with PEI in ethanol reduces the possibility of the formation of excimer between the structural units of PVPh.

The Mutual Mixing Effect in the LB Films of Merocyanine Dyes

The mutual mixing effect in the LB films of four kinds of merocyanine dyes have been investigated by optical absorption and fluorescence measurements. In single component films, DSe, DS and 6-methyl DS (6Me-DS) can form J-like aggregates but not for DO. In [6Me-DS]-[DO] system, a sharp J-band peak linearly shifts to the longer wavelength for the replacement of 6Me-DS by DO. In [DS]-[DO] system, [DS]:[DO]=1:1 film shows a both sharp J-band absorption and fluorescence peak. The behavior are understood by the formation of the ‘solid solution’ for [6Me-DS]-[DO] and the ‘intermolecular compound’ for [DS]-[DO]. Furthermore, the spectrum of [DO]-[DSe] system shows the presence of the ‘phase separation’. These results would relate to an interesting problem, what we may call a ‘2-dimensional phase diagram’ in J-aggregates.

Population and deactivation of lowest lying barium levels by collisions with He, Ar, Xe and Ba ground state atoms

Excitation transfer between the barium low lying excited states 6s6p 3 P 1 0 , 6s5d 1 D 2 and 6s5d 3 D J by collisions with He,Ar,Xe and Ba has been investigated. The population densities in all levels involved were probed by absorption or by fluorescence usingcw lasers. The depopulation cross sections of the Ba3 P 1 0 state by collisions with noble gases were found to be σHe(3 P 1 0 )=5.5·10−16 cm2, σAr(3 P 1 0 )=4.6·10−16 cm2, and σXe(3 P 1 0 )=1.7·10−16 cm2. For Ar, the collisional depopulation of the3 P 1 0 level is exclusively due to the transition to the1 D 2 state. Under the assumption that the3 D J metastable states are populated collisionally by1 D 2 →3 D J transfer only, we have deduced the upper limit for the corresponding cross section σ 13 Ar =1.5·10−18 cm2. From the Ba1 D 2 and Ba3 D J steady-state diffusion distributions, collisional relaxation rates of the1 D 2 and3 D J levels were evaluated. The collisional relaxation rates by Ar and Ba yielded total cross sections for the depopulation of metastable levels: σAr(1 D 2)=1.5·10−17 cm2, σBa(1 D 2)℞1·10−13 cm2, σAr(3 D J)=7·10−21 cm2, and σBa(3 D J)=1·10−15 cm2. Furthermore, it was found that the main contribution of the collisional depopulation of the1 D 2 state by Ar is related to back transfer to the3 P 0 state, whereas the deactivation of the3 D J metastable state is due to back transfer to the1 D 2 state. Taking into account other cross sections reported in literature we can conclude that collisional deactivation of both metastable levels by Ba ground state atoms can be attributed to their mutual collisional mixing.

Unpredictability in some nonchaotic dynamical systems.

We study properties of decay of the correlations for a class of smooth observables and mutual mixing for a class of subsets, with various rates ranging from the power-law to the exponential rate, in simple deterministic nonstrongly chaotic dynamical systems on the torus ${T}^{2}$. In fact, these systems are ergodic, have zero $K\ensuremath{-}S$ entropy and an absolutely continuous part in their spectrum, and display divergence of trajectories with a power-law rate. We show that they generate time series which are unpredictable in the sense of the statistical theory of prediction.

Iron-metal multilayers studied by Mössbauer spectroscopy, RBS and X-ray diffraction

Fe/M (M = Ag, Zn and Sn) multilayers prepared by a vacuum evaporation method are studied by Mossbauer spectroscopy (MS), Rutherford backscattering spectroscopy (RBS) and X-ray diffraction (XRD). For the case of an M = Ag multilayer, MS reveals that Fe in the multilayer remains as anα-phase down to the layer thickness of 10 nm. This result is in agreement with the RBS result that Fe and Ag form a completely discrete layer structure without any mutual mixing. For the case of M = Zn and Sn, RBS reveals that a considerable mixing has taken place between Fe and Sn during the specimen preparation. MS on Fe/Sn specimens with different layer thickness shows that an alloy phase of about 5 nm thickness is formed at the interface. Structural as well as magnetic properties of the alloy phase are discussed based on MS at different temperatures and on reported results of the intermetallic compound FeSn.

The microstructure and superconducting properties of melt-processed YBCO samples containing RE-211 particles

The melt-processed YBCO containing rare-earth 211-particles (Yb 2BaCuO 5) were synthesized with or without Pt-doping. A mixing of Yb and Y in the 211-phase occurs immediately after the incongruent melting of the 123-phase and proceeds during solidification. However, Pt-doping is found to suppress substantially the coalescence of the 211-particles and a mutual mixing of Y and Yb during the slow solidification process.

Electron-microscopic study of the mutual mixing of components in the tantalum - uranium system with neutron irradiation

It is well known that certain combinations of metals are characterized by an almost complete lack of mutual solubility. However, the formation of alloys from such metals is possible as a result of radiational mixing, which in some cases gives rise to an effective technology but in others leads to undesirable consequences, for example, impaired functioning of reactor fuel elements. Consequently, intensive physical and technological studies of radiational mixing are under way. Binary systems in which one of the components is feasible are of particular interest. A powerful experimental approach to the study of radiational mixing is provided by transmission electron microscopy, complemented by diffractional analysis of the structure and x-ray microanalysis of the chemical composition, as well as microprobe autoionic microscopy. In studying the mutual mixing of uranium and tantalum under fast-neutron irradiation, the goal is to elucidate whether it is possible, in principle, to form a tantalum-uranium alloy with a uranium content exceeding the limit of solubility given by the stat diagrams. Results obtained by transmission electron microscopy are considered in the present work.

Thermodynamic study of poly(N-vinyl caprolactam) hydration at temperatures close to lower critical solution temperature

The lower critical solution temperature of aqueous solutions of poly(N-vinyl caprolactam) falls in the 305–307 K range and depends on the molecular weight of the polymer. The thermodynamic functions of mixing at 298 K have been calculated from measurements of vapor pressures and heats of dissolution and dilution. Partial Gibbs energy, partial enthalpy, and partial entropy of mixing were negative over the entire range of composition. Increasing temperature resulted in a decrease in the exothermal character of mixing. Excessive heat capacity values, calculated from the dependencies of enthalpy of mixing on temperature, were positive over the entire composition range. Heat capacity of dilute solutions was measured at 298 K and partial heat capacity of poly(N-vinyl caprolactam) at infinite dilution was shown to be positive. The data obtained point out the hydrophilic and hydrophobic hydration of poly(N-vinyl caprolactam) in aqueous solutions. Hydrophobic hydration dominates at temperatures close to binodal curve. As a result, the mutual mixing of the polymer with water is decreased and phase separation takes place.

Development and relaxation of the interface in binary polymer mixtures

The mutual mixing, and hence the dvelopment with time of the interface between two chemically different polymeric species, may be dominated by enthalpic rather than entropic considerations. Two extreme cases are described. The first is accelerated interdiffusion, that occurs when the polymers have a large mutual attraction, and results in remarkable concentration profiles across the interface. At the oxtreme is suppressed interdiffusion, where two partially miscible polymers are in contact. The interface in this case tends to an equilibrium width, that varies with time quite differently than for the case of free interdiffusion.

Observations of some atmospheric electrical parameters in the surface layer

Measurements of atmospheric potential gradient, conductivity of both polarities and space charge are reported for Pune (18°32′N, 73°51′E, 559 m above msl). Observations show negative excursions of potential gradient at night, frequent observations of excess values of one polarity of conductivity and the presence of very high values of space charge of either polarity at night. Results are discussed in terms of a lower thin layer of positive space charge due to the electrode effect and an upper layer of negative space charge due to radioactive elements and their emanations close to ground and mutual mixing of these two layers under different meteorological conditions.

Formation of detonation coatings applied on an iron base

The results of x-ray diffraction analysis indicate a complex multiphase composition of the areas adjoining the zone of contact of the coating with the base related to occurrence of the α → γ and γ → α-structural transformations. Mutual mixing of the materials of the coating and base in the liquid phase leads to alloying and stabilization of the high temperature modification of iron (γ-Fe) and cobalt (Β-Co).

Collective and two-particle excitations in78Se

Excited states in78Se have been studied up to spin (12)ℏ at about 5.8 MeV in the76Ge(α, 2n) reaction using in-beamγ-ray spectroscopy. Mean lifetimes could be determined for 27 of the 33 levels observed by applying Doppler shift and pulsed-beam timing methods. According to theB(E2) values most of the levels have been grouped into collective bands. Irregularities in the level spacings of the yrast band above spin 6ℏ are interpreted to be due to the interaction of the ground state band withg 9/2 two-proton and two-neutron excitations. The mutual mixing of these configurations is reflected by strongM 1 transitions between the mixed states. The interaction strengths between the configurations involved have been estimated from three-band mixing calculations.

Geology and geochemistry of Huronian rhyolites and low-Ti continental tholeiites from the Thessalon region, central Ontario

Bimodal volcanism associated with early phases of Huronian rifting in central Ontario, dated about 2450 Ma, produced low-Ti tholeiitic basalts and two varieties of crustally derived calc-alkaline rhyolite. Early tholeiites are characteristically highly evolved, have Mg* values from 30 to 50, and display pronounced enrichment in large-ion lithophile elements (LILE) and light rare-earth element (LREE) in comparison with modern oceanic basalts, fractionated heavy rare-earth element (HREE) patterns, and low Ti, Zr, P, Nb, Ba, and K abundances. Ti/Zr ratios rise progressively in early basalts and associated basaltic andesite fractionates from about 35 in early flows to 55 in central units. Late basalts also carry enriched LILE and LREE, but, in contrast to early types, have average Mg* values greater than 50 and lower rare-earth element (REE) abundances with flat HREE patterns. They also display negative Ba, Nb, and P anomalies on chondrite-normalized distribution diagrams, but lack low K, Zr, and Ti contents. Their Ti/Zr ratios of about 80 approach chondritic levels. Melting models suggest the differences are explained by lower degrees of fusion (as low as 10%) in a hydrated, LILE- and LREE-enriched peridotite during generation of the early basalts, leaving a residue containing appreciable garnet, amphibole, Ti oxides, zircon, and apatite.Erupted simultaneously with the basalts were two distinctive rhyolite types: (1) a low-LILE, high-LREE group (25% of analysed specimens), derived by −20% melting of granulitic siliceous tonalitic gneiss, presumably at deep crustal levels, and (2) a high-LILE, low-LREE group (75%), derived, probably at shallower levels, by ≤ 30% melting in granitic rocks with pegmatitic or leucogranitic compositions. Mutual magma mixing of basalts and rhyolites during early stages of volcanism produced abundant hybrid andesites, but the frequency of contamination is much lower in later units.Hypothetical subcontinental source compositions, calculated from the Raleigh equation, suggest that the Huronian mantle had already undergone a complex history. Low Ba, Nb, P, Ti, and depleted HREE abundances compared with abundances for modern oceanic basalts suggest that a basaltic melt had already been withdrawn from this source during Archean time. Subsequently, an episode of hydrous metasomatism enriched the source in LILE and LREE. The latter event resulted from (1) subcontinental mantle metasomatism by previous Archean subduction, (2) mantle metasomatism during the terminal Archean Kenoran Orogeny, or (3) a wave of hydrous metasomatism accompanying Huronian mantle convection immediately preceding volcanism.

Small‐angle X‐ray scattering of polyethylene‐polypropylene blends

AbstractSAXS investigations of PE, PP and PE‐PP blends were performed. The locations of the long period peaks of the blends and the pure components were compared. It was shown that mutual mixing of the polymers does not considerably affect their fine structure. The analysis of the SAXS patterns of thermally treated samples confirms the assumption that PE and PP are independent components of the blends.

SAXS and WAXS investigation of polyamide‐6 modified with methacrylic acid

AbstractWAXS and SAXS investigations of polyamide‐6 modified with poly(methacrylic acid) were performed. At small concentrations of PMAA in the blend mutual mixing of the components in the amorphous phase of PA‐6 is observed. At higher concentrations of PMAA distinct domains of the latter exist in the amorphous phase of PA‐6. Swelling of PA‐6 in methacrylic acid solution results in a γ‐α‐phase transition in the crystalline regions of PA‐6.

Pressure-induced absorption spectra change in alkali halide phosphors: mutual mixing between excited states

An apparatus has been developed which permits optical measurements up to 30 kbar at 1.5K using a piston-cylinder-type high-pressure cell. Using this apparatus, studies of the hydrostatic pressure effects of absorption spectra of KI and KBr doped with Tl+ or In+ have been made up to 10 kbar. Under high pressure, a mutual mixing occurs due to the electron-lattice interaction between the excited states corresponding to the A, B, C and D absorption bands, even at low temperatures, resulting in the give-and-take of the absorption intensity between these absorption bands. To explain the mutual mixing, the pressure dependence of the electron-lattice coupling is taken into account. The pressure variation of the A band shape is also discussed in connection with the pressure dependence of the electron-lattice coupling constants.

Thermal self-ignition of previously unmixed gases

Because of the complexity of the problem, studies of thermal selfignition of systems with previously unmixed components have been performed only recently. The present study examines the process of self-ignition of previously unmixed gases A/sub 1/ and A/sub 2/, which can enter into an irreversible chemical reaction. The formulation of the problem in the planar case is considered, and equations describing the processes of diffusion, thermal conductivity and chemical reaction for Arrhenius kinetics are derived. The induction period for thermal explosion can be determined approximately. The ignition process begins with mutual diffusion mixing of the two components. At some time, the width of the zone in which chemical reaction occurs reaches a critical value, permitting consideration of the process in two stages: diffusion mixing and thermal self-heating. Solution of the equations shows that unmixed gases self-ignite over a time period of the same magnitude as do mixed gases. Equations solved with a numerical method show that ignition occurs in a narrow region, whereupon the combustion front propagates to both sides of the ignition plane.

Measurements of interacting turbulent shear layers in a duct

Measurements have been made of the turbulent flow in a rectangular duct of aspect ratio 12:1 at a Reynolds number (based on duct height h) using conditional-sampling techniques. The lower boundary layer was heated in the entry region, and the fluctuating output of a resistance thermometer was used to distinguish ‘hot’ and ‘cold’ fluid. Thus separate velocity-fluctuation statistics could be obtained for fluid from the upper and lower boundary layers, even after the two layers had merged. The measurements suggest that the interaction region near the centre-line consists of a continuously contorting interface between the ‘hot’ and ‘cold’ layers, shaped by the eruption of large eddies across the centre-line from either side of the duct and surprisingly little affected by the inevitable fine-scale mixing.In the mean, this time-sharing between ‘hot’ and ‘cold’ fluid gives the impression of two superposed turbulence fields whose mean-square intensities add to give the total intensity. Exact superposition (which cannot take place in a nonlinear system) would imply that one layer had the same turbulent intensity profiles as an isolated boundary layer spreading into a non-turbulent free stream with the same mean velocity profile as the duct flow. The centre-line interaction grows in strength with increasing distance downstream until a steady rate of mutual eddy intrusion and fine-scale mixing is achieved, when the flow is commonly called ‘fully developed’. It is concluded that superposition (timesharing) is a physically reasonable first approximation for use in turbulence models for interacting shear layers: it is argued that better approximations could be obtained if necessary by correlating departures from superposition (i.e. changes in turbulence structure) by means of one or more interaction parameters.

The radial spread and the number of rivulets in a trickle bed

the column. Although the coefficients of radial spread following from the two models do not differ appreciably the agreement between the experiment and the theoretical distribution given by the generalized model improves by 50 - 60%. The scatter of the experiment about the theoretical distribution of the tracer provided an estimate of the number of liquid rivulets trickling down the packing and their mutual mixing. The results suggest that under very low densities of wetting the number of rivulets is given by the geometry of the packing, e.g. by the number of elements of packing appearing sectioned in a horizontal cross section of the column. At a relatively low density of wetting mutual mixing of the rivulets occurs and intensifies with increasing flow rate of liquid. As more realistic for description of liquid distribution in random packings appear the two-dimensional models which, in contrast to one-dimensional ones, account also for possible non-uniformities in the radial profile. This paper deals with the me­ thod of evaluating the coefficient of radial spread and the character of liquid distri­ bution in the packing. The method using a tracer was chosen for experiments. To eva­ luate the data the well-known model assuming uniform flow of liquid was used as well as a generalized model accounting for possible non-uniformities of the flow of li­ quid carrying the tracer due to the gradual build-up of the wall flow.