Melt Components Research Articles

Створення низькотеплопровідних полімерних нанокомпозитів для внутрішніх газовідвідних стволів димових труб котелень

Methods and results of experimental studies of thermophysical, structural and mechanical properties of low-heat-conducting polymer nanocomposites, oriented to use for gas ducts and chimneys of boiler installations, as well as various other gas and water communications are presented. In this work, on the basis of the performed set of methodological studies regarding the analysis of the legitimacy of using different models of heat conductivity for predicting the heat-conducting properties of these composites, the possibility of using for this prediction a number of models of the theory of the effective medium and the theory of percolation is considered. The analysis of thermophysical properties, structural characteristics and Young's modulus of low-heat-conductivity polymer nanocomposites based on polyethylene and polypropylene is carried out. Using these nanocomposites as an example, the achievement of a significant increase in their Young's modulus in comparison with unfilled polymers with a relatively small increase in heat conductivity is demonstrated. To obtain nanocomposites, we used a method based on mixing the components in a polymer melt using an extruder and then shaping the composite into the required shape by hot pressing. The method of differential scanning calorimetry was used to determine Young's modulus. On the basis of the studies carried out, the possibility of obtaining low-heat-conducting polymer nanocomposites with improved mechanical characteristics has been shown. In particular, it was shown that for nanocomposites based on polyethylene or polypropylene filled with CNTs (carbon nanotubes) or nanodispersed aerosil particles, with a mass fraction of the latter up to 2%, the following takes place a relatively insignificant increase in heat conductivity coefficients and a significant increase in the modulus of elasticity in tension. The research data also made it possible to obtain for the developed nanocomposites the temperature dependences of their specific mass heat capacity and, on this basis, to analyze the regularities of changes in the structural characteristics of these materials.

Constraints on deep, CO2-rich degassing at arc volcanoes from solubility experiments on hydrous basaltic andesite of Pavlof Volcano, Alaska Peninsula, at 300 to 1200 MPa

Abstract The solubility of CO2 in hydrous basaltic andesite was examined in fO2-controlled experiments at a temperature of 1125 °C and pressures between 310–1200 MPa. Concentrations of dissolved H2O and CO2 in experimental glasses were determined by ion microprobe calibrated on a subset of run glasses analyzed by high-temperature vacuum manometry. Assuming that the solubility of H2O in mafic melt is relatively well known, estimates of XH2Ofluid and PH2Ofluid in the saturating fluid were modeled, and by difference, values for XCO2fluid and PCO2fluid were obtained (XCO2 ~0.5–0.9); fCO2 could be then calculated from the fluid composition, temperature, and pressure. Dissolved H2O over a range of 2.3–5.5 wt% had no unequivocal influence on the dissolution of CO2 at the pressures and fluid compositions examined. For these H2O concentrations, dissolved CO2 increases with fCO2 following an empirical power-law relation: dissolved CO2 (ppmw) = 14.9−3.5+4.5[fCO2 (MPa)]0.7±0.03. The highest-pressure results plot farthest from this equation but are within its 1 standard-error uncertainty envelope. We compare our experimental data with three recent CO2-H2O solubility models: Papale et al. (2006); Iacono-Marziano et al. (2012); and Ghiorso and Gualda (2015). The Papale et al. (2006) and Iacono-Marizano et al. (2012) models give similar results, both over-predicting the solubility of CO2 in a melt of the Pavlof basaltic andesite composition across the fCO2 range, whereas the Ghiorso and Gualda (2015) model under-predicts CO2 solubility. All three solubility models would indicate a strong enhancement of CO2 solubility with increasing dissolved H2O not apparent in our results. We also examine our results in the context of previous high-pressure CO2 solubility experiments on basaltic melts. Dissolved CO2 correlates positively with mole fraction (Na+K+Ca)/Al across a compositional spectrum of trachybasalt-alkali basalt-tholeiite-icelandite-basaltic andesite. Shortcomings of current solubility models for a widespread arc magma type indicate that our understanding of degassing in the deep crust and uppermost mantle remains semi-quantitative. Experimental studies systematically varying concentrations of melt components (Mg, Ca, Na, K, Al, Si) may be necessary to identify solubility reactions, quantify their equilibrium constants, and thereby build an accurate and generally applicable solubility model.

Apatite geochronology and chemistry of Luanchuan granitoids in the East Qinling Orogen, China: Implications for petrogenesis, metallogenesis and exploration

The Luanchuan granitoids in the East Qinling Orogen, Central China host multiple genetic types of Mo-W-Pb-Zn-Ag polymetallic deposits. Here we present results from systematic geochronological and geochemical investigations on apatite with a view to gain insights into the petrogenesis, metallogenesis and potential for mineral exploration. We analyzed 388 apatite grains from eight Late Mesozoic granitic plutons in the Luanchuan ore district. Apatite U–Pb geochronology yields 206Pb/238U mean ages in the range of 151.5–102.3 Ma, representing the crystallization ages. Through integrating our results with those from previous studies on the multi-stage magmatism (160–130 Ma; 111–108 Ma) and metallogeny (150–139 Ma; 138–135 Ma; 114 Ma), the newly obtained apatite ages can be correlated with coeval magmatic and metallogenetic events of this ore district. In comparison, except for the Nannihu pluton which is ca. 19 Ma younger than the corresponding zircon U–Pb ages, the other studied plutons show almost consistent apatite and zircon U–Pb ages within error ranges, suggesting rapid post magmatic cooling below ~450 °C in response to shallow emplacement. Apatite chemistry displays ΣREE concentrations in the range of 2379–15,925 ppm, characterized by rather high LREE concentrations, depleted to flat HREE profiles and distinctive negative Eu anomalies, suggesting crust-mantle mixing in the magma source prior to apatite crystallization, which incorporated different degrees of sediment melting and slab melting components triggered by the subducted Paleo-Pacific slab-derived fluids. In conjunction with element concentrations and ratios (e.g., Sr, Mn, Cl, Y, La/Y, Eu/Eu*, (Sm/Nd)N, (La/Sm)N, (Eu/Eu*)N, (Ce/Ce*)N, (La/Yb)N) in apatite, the Luanchuan granitoids are classified as moderately oxidized and mineralized I-type granites. We suggest that the Huangbeiling pluton and other igneous rocks in its vicinity likely have relatively higher potential for future W-Mo/Mo-W exploration, and that different degrees of magmatic differentiation might have generated the porphyry-skarn Mo–W deposit in the Yuku ore field. Moreover, our study also demonstrates that the apatite REE concentrations and ratios can be used as potential indicators for mineral exploration.

A mechanism theory of dissolution profile of oxide particles in oxide melt

AbstractThe shape origin and variation of oxide dissolution profile in the oxide melt is for the first time explained with a mechanism of diffusion‐distance‐controlled dissolution (DDD). A novel analytical model is derived to present this theory. The profile shape is governed by the diffusion distance of the dissolved components in the oxide melt. The viscosity gradient at the boundary of the diffusion region provides the driving force for the profile variation. Both temperature and initial viscosity of oxide melt are the key factors determining the oxide dissolution kinetics. This theory can be applied to describe diffusion‐limited particle dissolution in a general system.

Features of structure formation of dispersively filled with microcomposites with a polypropylene matrix

Backgrounds. The regularities of the structure formation of polymer microcomposite materials during their cooling from the melt are established. Objective. The aim of the work is to study the crystallization features of microcomposites based on a polypropylene matrix with a filler in the form of aluminum microparticles.Methods. The research technique includes two stages: the experimental receipt of crystallization exotherms and, based on them, the theoretical determination of the main characteristics of the structure formation process.Results. The patterns of composites crystallization were studied in a wide range of changes in the melt cooling rate and the mass fraction of filler for microcomposites obtained by two methods, the first of which is based on mixing the components in dry form, the second – in the polymer melt. An analysis of the structure formation mechanisms of the studied composites at the nucleation stage and at the stage of structures formation in the melt volume is made.Conclusions. It is shown that at the first of the indicated stages, a planar and volumetric crystallization mechanism is realized with some prevalence of the volumetric one. At the second stage, when using the method of producing composites, based on the mixing of components in a dry form, a tense matrix mechanism takes place; when implementing the method of mixing components in a polymer melt, the structure formation mechanism depends on the mass fraction of the filler.

Thermodynamic Modeling of Phase Diagrams of Binary and Ternary Oxide Systems Belonging to the FeO–MgO–MnO–Al2O3 System

Thermodynamic modeling of phase diagrams of the FeO–MnO, MnO–MgO, MnO–Al2O3, FeO–MgO–MnO, FeO–MnO–Al2O3, and MgO–MnO–Al2O3 systems was carried out. The energy parameters of the theories of regular ionic solutions and subregular ionic solutions used in the simulation were determined. The calculation method used in this work allowed us to estimate the enthalpy (170,000 J/mol) and entropy [49.56 J/(mol·K)] of formation of galaxite MnAl2O4 from the oxide melt components.

Methodology of mass-exchange processes calculation in steel SA-20A alloying by nitrogen during blow through bottom tuyeres

To alloy steel by nitrogen, any material containing nitrogen in necessary amount and being capable to dissolve in the liquid metal, can be used. Methods of alloying by nitrogen, based on melt blowing through by gaseous nitrogen are known. However to carry out this process it is necessary to have a qualitative estimation of nitrogen behavior at various stages of steelmaking process. It is also necessary to have reliable data on the nitrogen assimilation speed and conditions of its interaction with other melt components. Therefore, elaboration of a methodology of estimation of nitrogen assimilability under conditions of blowing through with stirring and thermo-dynamic conditions of vanadium nitrides formation in the steel SA-20A is rather actual. In the course of methodology elaboration, equilibrium nitrogen concentration was determined accounting parameters of interaction, calculation of stirring power and nitrogen assimilability under set conditions of blowing through were accomplished. Besides, calculations were accomplished on average effective “bubble” coefficient of mass-transfer of nitrogen to liquid steel; duration of blow through by nitrogen under conditions of stirring and thermo-dynamic conditions of VN nitrides formation under equilibrium and industry conditions. The effect of mass-transfer speed on the nitrogen assimilability by steel was shown. It was determined, that blow through parameters and first of all, gaseous nitrogen consumption are determined by a number of bubbles and the area of their surface. Results of the elaborated methodology testing presented. The necessity of specifying the methodology of estimation of gas bubbles evolution in the process of their moving during the bottom blow through justified. Comparison of the obtained data with the industrial data were confirmed by the sufficiency of nitrogen concentration in steel SA-20A for realization of the nitride hardening process.

Hf-O isotope systematics of zircons from the Taitao granitoids: Implications for slab-melting material

Slab-melting is considered to have played an important role in the formation of continental crust. The combination of oxygen (O) and hafnium (Hf) isotope signatures can provide key information relating to the melting components during slab-melting. To reveal the melting components, we used SIMS and LA-ICP-MS to determine O isotope ratios at 220 spots and Hf isotope ratios at 61 spots in zircons from five plutons in the Taitao Peninsula, where slab-melting occurred at ca. 4–5 Ma. In addition, we measured whole-rock HfO isotope ratios in 11 rocks that were intruded by the granitoids. The zircon δ18O values of the Seno Hoppner pluton (5.37 ± 0.44‰) are identical to those of mantle-equilibrated zircons, whereas those of the other four plutons are relatively high (6.09–6.53‰). The ɛHf(t) values of zircons in the granitoids are negatively correlated with δ18O, and they fell along the mixing line between a juvenile component and sedimentary rocks. Therefore, the HfO profiles can be attributed to mixing of juvenile granitoid magma and the sedimentary rocks, the amount of which was likely minimal in the Seno Hoppner pluton. As such, the δ18O values of the Seno Hoppner pluton could best reflect the juvenile component. In view of the δ18O variation in whole-rock samples of the Taitao ophiolite, the melting of hydrothermally altered basalt and dolerite is considered responsible for the juvenile magma generation. This further implies that juvenile granitoid magmas can be generated by the melting of the upper half of subducted oceanic crusts.

Ureilite meteorites provide a new model of early planetesimal formation and destruction

Ureilite meteorites are ultramafic rocks derived from parts of the depleted silicate mantle of their parent planetesimal. We used Monte Carlo modelling to explain the observed array of oxygen isotopes and major element chemistry shown by bulk ureilites, after restoration of their missing core and silicate melt components. Despite using a wide range of primitive nebular material, our modelling shows that only a combination of proxy material resembling Allende-type FeO-rich and MgO-rich chondrules, can account for the ureilite oxygen isotope trend and the reconstructed ureilite major element chemistry. Our model predicts formation of a radial gradient in major elements and oxygen isotopes within the planetesimal, with a more Mg-rich silicate interior and a more Fe-rich silicate exterior. Temperatures recorded by ureilites were not high enough to form a magma ocean but were sufficiently high to form a metallic core and silicate melts. The ureilite parent planetesimal was then disrupted by impact. Re-accretion of the outer layers of more Fe-rich silicate material, at the expense of the more MgO-rich material and the core, explains the observed distribution of bulk rock and mineral compositions.

Trace Element and Isotopic Evidence for Recycled Lithosphere from Basalts from 48 to 53°E, Southwest Indian Ridge

AbstractMantle source heterogeneity and magmatic processes have been widely studied beneath most parts of the Southwest Indian Ridge (SWIR). But less is known from the newly recovered mid-ocean ridge basalts from the Dragon Bone Amagmatic Segment (53°E, SWIR) and the adjacent magmatically robust Dragon Flag Segment. Fresh basalt glasses from the Dragon Bone Segment are clearly more enriched in isotopic composition than the adjacent Dragon Flag basalts, but the trace element ratios of the Dragon Flag basalts are more extreme compared with average mid-ocean ridge basalts (MORB) than the Dragon Bone basalts. Their geochemical differences can be explained only by source differences rather than by variations in degree of melting of a roughly similar source. The Dragon Flag basalts are influenced by an arc-like mantle component as evidenced by enrichment in fluid-mobile over fluid-immobile elements. However, the sub-ridge mantle at the Dragon Flag Segment is depleted in melt component compared with a normal MORB source owing to previous melting in the subarc. This fluid-metasomatized, subarc depleted mantle is entrained beneath the Dragon Flag Segment. In comparison, for the Dragon Bone axial basalts, their Pb isotopic compositions and their slight enrichment in Ba, Nb, Ta, K, La, Sr and Zr and depletion in Pb and Ti concentrations show resemblance to the Ejeda–Bekily dikes of Madagascar. Also, Dragon Bone Sr and Nd isotopic compositions together with the Ce/Pb, La/Nb and La/Th ratios can be modeled by mixing the most isotopically depleted Dragon Flag basalts with a composition within the range of the Ejeda–Bekily dikes. It is therefore proposed that the Dragon Bone axial basalts, similar to the Ejeda–Bekily dikes, are sourced from subcontinental lithospheric Archean mantle beneath Gondwana, pulled from beneath the Madagascar Plateau. The recycling of the residual subarc mantle and the subcontinental lithospheric mantle could be related to either the breakup of Gondwana or the formation and accretion of Neoproterozoic island arc terranes during the collapse of the Mozambique Ocean, and is now present beneath the ridge.

Thermodynamics of nitrogen solubility in nickel-based alloys at plasma-arc remelting

Heat-resistant nickel-based alloys are widely used in the domestic aircraft industry, rocket engineering, and instrument making. Increasing the basic mechanical and operational characteristics of the metal is achieved mainly by alloying the base with various elements such as rhenium, ruthenium, hafnium, etc. However, increasing the operational properties can also be achieved by metal nitriding, as a result of which interstitial solid solutions are formed (finely dispersed nitrides), which increase the strength of the alloy. The work is devoted to the study of nitriding process of nickel-based complex alloys. Various options of the interaction of nitrogen with the melt are considered under conditions of open melting and processing with low-temperature nitrogen-containing plasma. The use of plasma-arc remelting allows one to obtain various types of gas in form of atoms, ions and molecules in plasma. The first two forms are much more active than molecular nitrogen, which leads to super-equilibrium concentrations in the alloy. A thermodynamic analysis of nitrogen solubility in a nickel-based melt was performed during open melting and under plasma-arc remelting. The nitrogen solubility in model EP741NP alloy was calculated depending on the partial pressure of nitrogen above the melt surface and in the plasma-forming gas. It was shown that treatment of the melt with nitrogen-containing plasma makes it possible to obtain higher content of nitrogen in the alloy. In this work, temperature of the metal in the zone of contact with plasma arc was estimated using the technique according to which the evaporation of the melt components from the arc spot area occurs when the metal boiling point is reached.

Thermodynamic Modeling of Phase Equilibria in the FeO-MgO-Al<sub>2</sub>O<sub>3</sub> System

Thermodynamic modeling of coordinates of phase diagrams’ liquidus lines of the FeO–MgO, FeO–Al2O3, MgO–Al2O3 systems and coordinates of phase diagram’s liquidus surface of the FeO–MgO–Al2O3 system has been carried out. In the course of work, a thermodynamic model which describes activity of oxide melt had been selected for each of the systems; energy parameters of the model have been determined. Regions of thermodynamic stability of solid phases which are at equilibrium with the oxide melt have been determined. Results of the modeling have been compared with experimental data existing in the literature. Modeling technique has also allowed evaluating enthalpies and entropies of FeAl2O4 and MgAl2O4 compounds’ formation out of components of the oxide melt. The obtained results are of interest for steelmaking industry processes when determining the melt temperature of a slag containing oxides of iron, magnesium and aluminum.

EFFECT OF PARTICLE REFRACTORY CHEMICAL COMPOUNDS ON METAL TRANSFER IN THE ARC IN SURFACING COMPOSITE WIRE

It is shown that the introduction of micro-sized particles of refractory compounds TiB, ZrB, CeO in the composition of the filler of the composite wire (CW) contributes to an increase in the quality of mass transfer of metal in the welding arc. It was found that under the influence of particles of the considered components, melting components of the CW filler, heterogeneous in terms of thermophysical properties, are more actively formed into a metal drop, and its overheating decreases. This helps to improve the quality of transfer of the electrode metal in the welding arc and to increase the conversion factors of alloying elements into the weld metal.

Dissolution kinetics of arbitrarily-shaped alumina in oxide melt: An integration of phase-field modelling and real-time observation study

Abstract A feasibility study of utilizing a phase-field model considering the convection effect is performed in this work to investigate the dissolution kinetics of arbitrarily-shaped alumina particle in the oxide melt. The established model has been benchmarked by high temperature confocal laser scanning microscope (HT-CLSM) to observe the polycrystalline sapphire dissolution in multicomponent oxide melt. The effects of alumina morphology and temperature on the dissolution kinetics were studied quantitatively. It is for the first time found that the dissolution of irregular alumina particle in oxide melt shows a double-fold smooth anisotropy behavior. The dissolution rate of alumina particle is governed by the interface interactions rather than the self-diffusion of dissolved component in oxide melt. Increasing the temperature, the interfacial mobility coefficient increases, and the effect of alumina particle shape on the dissolution rate decreases. The temperature variation has a minor influence on the shape evolution of alumina during dissolution process. The convection intensity affects both the dissolution rate and shape evolution of alumina particle. An increased convection intensity increases the dissolution rate. As the convection partially affects the contact area of alumina particle with oxide melt, a decreased alumina particle curvature increases the dissolution rate. When the convection affects the whole contact area of alumina particle with oxide melt, the contact area plays an important role on the dissolution rate. The obtained methodology can be applied to investigate a general dissolution phenomenon in the high temperature oxide melt in materials science.

MATHEMATICAL MODELING OF THE DISTRIBUTION OF ARGON IN A TUNDISH WITH A MOLTEN METAL DURING FILLING

The article is devoted to the mathematical description of the process of filling an intermediate ladle (tundish) with argon, which is blown into the melt stream falling from the steel casting ladle, which is common at metallurgical plants. Metallurgical plants use an intermediate ladle to reliably supply a continuous casting machine for the melt. Also important for the tundish is the removal of non-metallic inclusions using argon. The good distribution of argon bubbles in the tundish significantly influences the removal of unwanted melt components such as hydrogen and nitrogen. Given the need for gas to escape, the melt speed in the intermediate ladle should be sufficiently low, especially near outflow holes, where melt needs to be homogeneous and slow for a high–quality casting. Conducting experiments during the operation of a metallurgical plant is undesirable, costly and is accompanied by difficulties associated with high temperature and opacity of the melt. Therefore, the experiments are often carried out in laboratories on the so-called cold models, where the melt is replaced by water, argon – by air, and the tundish – by the transparent container of the rectangular shape under the conditions of similarity. Despite the obvious advantages of such cold modeling, today most experiments are still conducted on mathematical models, which are a much cheaper and low-erroneous way of predicting the development of a given process under different conditions. Mathematical modeling of melt motion helps to select the optimal geometry of the tundish, as well as the required amount of argon and usefulness of barriers on a way of melt streams. The article proposes to use the convection-diffusion equation for the argon field and the Navier-Stokes equations – for the velocity field. The numerical solution using finite volume method is well tested and provides sufficient accuracy. In addition, this method is easily parallelized to speed up computing on modern multi-core processors. A graphical user interface software application allows you to display the status of the system on the screen for further review and adoption decisions.

Effects of reactive dissolution of orthopyroxene in producing incompatible element depleted melts and refractory mantle residues during early fore-arc spreading: constraints from ophiolites in eastern Mediterranean

Compositional variations of peridotites from the Cretaceous ophiolites in southern Turkey and Northern Cyprus are presented to document the nature of partial melting and possible effects of reactive dissolution of primary mantle phases during fore-arc spreading. The peridotites overall exhibit a range of 187Os/188Os ratios from 0.1171 to 0.1266 and appear to represent a mantle region that preserves a record of ancient melt depletion. The samples are depleted in 187Os/188Os compared to the ambient oceanic upper mantle (187Os/188Os ~0.127), suggesting that they are representatives of a shallow fore-arc mantle where transport of radiogenic 187Os during slab dehydration was limited. Chemical variations of primary mantle minerals indicate that the peridotites are the residues of moderate to high degrees (>16%) of partial melting and have experienced significant modal and chemical compositional modification through interaction with oxidizing hydrous basaltic melts. Interacting melts, which appear to be similar in composition to primitive arc tholeiite, are likely to have originated from sub-lithospheric lower part of the mantle wedge during early stages of fore-arc spreading and migrated upward to react with variably depleted harzburgites to induce further melting in the overlying lithospheric mantle through open-system reactive flow. This second stage melting resulted in (1) common occurrence of reactive harzburgites and dunites by incongruent melting of orthopyroxene and crystallization of olivine through interaction with olivine saturated melt; and (2) local development of refertilized peridotites by shallower melt impregnation that involves interaction with olivine + clinopyroxene saturated melt. The dissolution of orthopyroxene caused the reacting melt to be enriched in silica and diluted in incompatible elements which led to the production of the final melts similar in composition to fore arc basalt and boninite. Involvement of compositionally variable mantle and melt components with different rates of melt influx therefore appears to explain the generation of fore-arc crust with a range of diverse rock suites including temporally and spatially associated arc tholeiites and boninites with significant depletion in incompatible elements.

Concentrations of Te, As, Bi, Sb and Se in the Marginal Zone of the Bushveld Complex: Evidence for crustal contamination and the nature of the magma that formed the Merensky Reef

The association of platinum-group elements (PGE) and the chalcophile elements Te, As, Bi, Sb and Sn (TABS) has been extensively documented in several magmatic sulfide deposits over the past years. However, understanding the roles of TABS during the formation of magmatic sulfide deposits partially depends on constraining the concentration of TABS on the liquids from which they crystallized. This study presents the distribution of TABS (apart from Sn) in rocks of the Marginal Zone of the Bushveld Complex. These rocks record the composition of the parental magmas from which the Bushveld Complex have crystallized. The major and trace elements of the marginal rocks have been modelled as mixtures of komatiite, continental crust and a plagioclase-rich residuum. Similar mixtures are required to model the TABS in the marginal rocks, with the continental crust component contributing a large part of the As, Sb and Bi budgets in these melts. The concentrations of the TABS in the Merensky Reef can be modelled as a mixture of two of the magma types present in the Marginal Zone (the B-1 and B-2). The modelling also reveals that the distributions of Se, Te and Bi in the reef are essentially controlled by the presence of sulfide minerals, whereas As and Sb distributions are controlled by both sulfide minerals and melt component. This is because Se, Te and Bi are moderately to strongly chalcophile elements, but As and Sb are only slightly chalcophile elements. Thus, whole-rock As and Sb concentrations are not upgraded by the formation of the sulfide minerals, and may still be used to trace crustal contamination.

Fractionated crystallization and fractionated melting behaviors of poly(ethylene glycol) induced by poly(lactide) stereocomplex in their block copolymers and blends

Stereocomplexation has been an effective way to improve the physical properties of block copolymers or blends. However, the effect of stereocomplexation on the confined and fractionated crystallization of other crystallizable block has not been comprehensively investigated so far. In this work, we used poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) as stereocomplexable higher melting component and studied the confined crystallization and melting behaviors of poly(ethylene glycol) (PEG) in their block copolymers and blends. Unexpectedly, marked fractionated crystallization and fractionated melting behaviors of PEG component occurred during the two-step crystallization process, because of the constrained effect of the early formed stereocomplex (SC) crystals. The fractionated crystallization and melting behaviors were further facilitated with decreasing the isothermal crystallization temperatures of PLLA and PDLA (Tic,PLA). As revealed by polarized optical microscopy (POM), the increase of Tic,PLA favors the transformation of PEG component from the interlamellar to interspherulitic regions due to the reduced nucleation density of PLA. We proposed that fractionated crystallization and fractionated melting behaviors of PEG impacted by SC crystals were attributed to PEG component dispersed in and out interlamellar regions of PLA matrix. Moreover, small-angle X-ray scattering (SAXS) results indicated that two scattering peaks were identified for copolymers after two-step crystallization process, one consisted of mixed PEG and PLA lamellae and the other contained almost pure PEG lamellae originated from the crystallization of PEG dispersed in interfibriller/interspherulitic regions. This study has shed light on the unique fractionated crystallization and fractionated melting behaviors of the lower melting component in polymer systems with the higher melting component preferentially co-crystallized into SC crystals.

SPINMELT-2.0: Simulation of Spinel–Melt Equilibrium in Basaltic Systems under Pressures up to 15 Kbar: III. The Effects of Major Components in the Melt on the Chrome-Spinel Stability and a Possible Solution of the Problem of Origin of Chromitites

The effect of variations in the fo, fa, en, fs, di, an and ab components in high-Mg basaltic melts on the topology of the spinel liquidus was quantified by conducting simulations with the new SPINMELT-2.0 model for the spinel–melt equilibrium. It has been established that enrichment of the melt in pyroxene components leads to an increase, and conversely, enrichment in plagioclase and olivine components, to a decrease in the solubility of chromite. This effect can be important at the gravitational compaction of cumulates accompanied by the extraction of intercumulus melt and its infiltration upward. In this case, it is reasonable to expect sequential reequilibration of the infiltrating melt with cumulate piles of different composition. This suggests that Cr-spinel can be transferred and concentrated again during the postcumulus solidification stage of layered intrusions. The concentrating process involves Cr-spinel extraction into the melt enriched in pyroxene components and the subsequent redeposition of the mineral during when this melt reacts with the feldspar-rich matrix of proto-anorthosite layers or horizons enriched in olivine. Some of these layers and horizons may be produced by additional injections of more primitive magma. The realism of the proposed mechanism is evident from the well-known spatial relations between the chromite layers with anorthosites and dunite–harzburgites of the Bushveld complex.

Effect of straining flow on growth of columnar crystal in ternary undercooled melt

As an important microstructure, columnar crystal growth technology, especially the growth technology of single columnar crystal plays an important role in improving the performances of semiconductor, optical devices and other related products. In many practical applications, because the alloy is composed of multi-component and there is inevitably flow in the melt, it is necessary to study the growth of columnar crystals in multi-component melt with flow separately. The growth of columnar crystal in a ternary undercooled melt subjected to straining flow under non-isothermal conditions is studied, and the approximate analytical expression for growth morphology of columnar crystal is given by using asymptotic method. It can be seen from the expression that straining flow is an important reason for irregular columnar crystal. When analyzing the effect of straining flow on the growth of columnar crystal in ternary melt, it is found that the incoming flow accelerates the growth velocity of the interface, while the outgoing straining flow reduces the growth velocity of the interface, namely, the straining flow makes the interface of columnar crystal deformed. At the same time, it is found that the interface deformation becomes more intense with the increase of flow velocity. The above conclusion can also be applied to the effect of straining flow on the interface morphology of columnar crystal in pure melt and binary melt. The comparison of the effects of straining flow on the interface of columnar crystal among pure melt, binary melt and ternary melt, shows that the interface morphology of columnar crystal in dilute alloy melt is more affected by straining flow than in the pure melt, but the more components are more easily affected by flow. However, the number of components in melt is not a decisive factor for the change of interface morphology of the columnar crystal, but the constitutional undercooling is an important factor for determining the interface morphology of multicomponent alloy. According to the conclusion of this paper, the influence of straining flow on the interface morphology of columnar crystal growth can be quantitatively predicted, which provides the necessary theoretical guidance in accurately controlling the interface morphology in the future.