Crystals In Temperature Range Research Articles

Fabrication of highly b-oriented MFI zeolite film over broad temperature window

Despite that oriented MFI zeolite films exhibit significant prospects for a wide range of applications due to microstructural superiority, their precise orientation control entails rigorous demands on reaction conditions (e.g., reaction temperature). In this work, we achieved facile synthesis of continuous b-oriented MFI zeolite films with few twins over a wide crystallization temperature range of 30–210 °C through adopting NH4F-mediated gel as nutrient during epitaxial growth. Both ammonium ions and fluorine ions were found crucial for enhancing the gel reactivity, endowing epitaxial growth with higher crystallization rates; moreover, the above morphology could be maintained even under fluctuating temperature conditions during film processing, thereby showing great potential for their bath production in a facile and reproducible manner.

Synthesis of trehalose-grafted poly(ester amide) with potential ice recrystallization inhibition activity

The ice recrystallization inhibition (IRI) activity of a macromolecular cryoprotectant is of great significance for applications in cryopreservation of biosamples. Herein, in order to create a possibly biodegradable trehalose-modified polymer, thiol-monosubstituted trehalose was synthesized by a simplified method, and then tethered to allylated-based poly(ester amide) (PEA) via thiol-ene click reaction. The synthesized PEA-g-trehalose (PEA-g-Tre) was able to inhibit ice recrystallization by 55% at 10 mg mL−1 compared to PBS control, superior to poly(ethylene glycol). Differential scanning calorimetry results showed that PEA-g-Tre exhibited a significantly higher glass transition temperature at 92.4 °C than PEA at 33.5 °C, and had a narrowed ice crystallization temperature range due to introduction of trehalose. Raman spectroscopy indicated that the IRI activity of PEA-g-Tre was attributed to the presence of trehalose residues in the side groups, which disrupted the regular arrangement of freezable water molecules. It is suggested that modification by trehalose can give rise to the IRI activity of the polymer through adsorption and diffusion mechanism with water, and thiol-ene reaction provides a feasible way for preparing polymeric cryoprotectants containing trehalose.

Effects of shear-induced crystallization on the complex viscosity of lamellar-structured concentrated surfactant solutions.

Material relationships at low temperatures were determined for concentrated surfactant solutions using a combination of rheological experiments, cross-polarized microscopy, calorimetry, and small angle X-ray scattering. A lamellar structured 70 wt% solution of sodium laureth sulfate in water was used as a model system. At cold temperatures (5 °C and 10 °C), the formation of surfactant crystals resulted in extremely high viscosity. The bulk flow behavior of multi-lamellar vesicles (20 °C) and focal conic defects (90 °C) in the lamellar phase was similar. Shear-induced crystallization at temperatures higher than the equilibrium crystallization temperature range resulted in an unusual complex viscosity peak. The effects of processing-relevant parameters including temperature, cooling time, and applied shear were investigated. Knowledge of key low-temperature structure-property-processing relationships for concentrated feedstocks is essential for the sustainable design and manufacturing of surfactant-based consumer products for applications such as cold-water laundry.

Microstructure and properties of Al−2Mg−0.5Mn alloy with narrow crystallization temperature range realized by adding trace elements

The wide crystallization temperature range of Al−Mg alloys is a key factor for the surface defect formation during continuous casting and rolling process. To reduce the crystallization temperature range of the alloy, the influences of trace Zn, Si, Zr and Ti elements on the microstructure and properties of Al−2Mg−0.5Mn alloy were investigated. The X-ray photoelectron spectroscopy, atomic force microscopy, scanning and transmission electron microscopy were used for microstructural characterization. The Ti and Zr additions could refine the grain size and improve the strength of the Al−Mg−Mn alloy by forming Al3Ti and Al3Zr in the alloy, while the crystallization temperature ranges of these alloys were wider. It was revealed that Zn and Si additions could form new secondary phases with Mg in the alloy, thus reducing the actual Mg content during later eutectic solidification process. Therefore, the crystallization temperature range of Al−2Mg−0.5Mn−0.2Zn−0.2Si alloy was narrower than that of Al−2Mg−0.5Mn alloy. The mechanical properties and corrosion resistance of Al−2Mg−0.5Mn alloy were also improved by the additions of Zn and Si.

ИДЕНТИФИКАЦИЯ ПРОДУКТОВ КРИСТАЛЛИЗАЦИИ СТЕКОЛ ДЛЯ ПРОИЗВОДСТВА СТЕКЛОВОЛОКНА, ПОЛУЧЕННЫХ НА ОСНОВЕ ТЕХНОГЕННЫХ ОТХОДОВ ТЭЦ

Achieving technological sovereignty in the field of production of composite materials today requires a rapid increase in production volumes of special-purpose glass fibers. At the same time, scientific solutions in this area must be effective, both from a technological and economic point of view. The article presents research results that form an idea of the possibility of using technogenic waste from thermal power plants in the industrial production of electrical insulating and high-modulus glass fibers. Since the technological efficiency of fiber formation is largely determined by the tendency of melts to crystallize, most of the research was aimed at studying the crystallization process, determining the temperature range of crystallization and identifying the nature of crystallization products. It has been established that in the temperature range of 1100-1200°C the crystallization products are represented by diopside and anorthite, which, with increasing temperature, undergo amorphization and subsequent dissolution in the glass phase. In glass S, the products of crystallization in the temperature range 1200-1300°C are represented by minerals of the continuous isomorphic series albite-anorthite and an insignificant content of ferruginous minerals - magnetite, hematite or goethite. The data obtained will make it possible to develop rational parameters for the process of forming glass fibers or methods for suppressing such an undesirable phenomenon for technology as crystallization in the molding range.

Study on improving the fluidity of Ti2AlNb alloy

In this paper, the effects of main elements like Al, Nb and trace elements like Fe, Mo, W, Co, B and Si on the fluidity of Ti–22Al–25Nb alloy were investigated. The alloy composition which is beneficial to improve the fluidity was selected by calculating the thermal property parameters affecting the fluidity of the alloy through thermodynamic software, numerical simulation test of the fluidity of the alloy and verification test of the fluidity of the preferred alloy. Finally, the improvement mechanism of the alloy fluidity was discussed. Results showed that the appropriate reduction of Nb element was better than Al element for the improvement of fluidity. The addition of trace Fe, B and Si elements was beneficial to the improvement of fluidity, the improvement effect of B element was the best, while the addition of trace Mo, W, and Co was not conducive to the improvement of fluidity. The cessation mechanism of Ti2AlNb alloy is the cessation mechanism of the alloy with a wide crystallization temperature range. The composition which was the most beneficial to improve the fluidity was Ti–22Al–24Nb-0.1B. The main reasons for the improvement of the fluidity were that on the one hand, reducing 1 at% Nb and adding 0.1 at% B not only increased the superheat and crystallization latent heat but also reduced the melt viscosity and thermal conductivity, thus improving the fluidity. And on the other hand, the TiB phase refined the grains, and the fine grains prevented the dendrites from growing into a well-developed dendritic network, inhibited the adverse effect of the increase in the width of the solidification zone on the fluidity, and further improved the fluidity.

Crystallization behavior of CMAS + sea salt mixture and its effect on the mixture penetration into thermal barrier coatings

When aero-engines are operated in dusty and near-sea environments, thermal barrier coatings (TBCs) are threatened by coupling corrosion of calcium-magnesium-alumina-silicate (CMAS) and sea salt. Investigating the crystallization behavior of CMAS + sea salt that affects the melt penetration into TBCs is the key to seeking protection methods against coupling corrosion. In this study, the crystallization temperature range and crystalline products of CMAS + sea salt were investigated. The results indicated that the crystallinity of CMAS + sea salt is affected by temperature. CMAS, CMAS+5SS (95 wt% CMAS + 5 wt% sea salt), and CMAS+10SS (90 wt% CMAS + 10 wt% sea salt) were crystalized initially at 1000 °C, but the crystallinity was low. At 1100 °C, more crystallization occurred, with diopside (CaMgSi2O6), akermanite (Ca2MgSi2O7), and anorthite (CaAl2Si2O8) being precipitated. With the temperature increasing to 1200 °C, wollastonite (CaSiO3) instead of akermanite was precipitated in both CMAS and CMAS+5SS samples, while the CMAS+10SS sample became almost amorphous glass with little crystallization indicating that higher sea salt content narrows the crystallization temperature range. Moreover, at the appropriate crystallization temperature (1100 °C), the addition of sea salt in CMAS played a depolymerization role and promoted discrete precipitation of dendritic akermanite, which reduced the crystalline layer compactness increasing the threat of mixture penetration into TBCs.

Modeling of the kinetics of polymorphic isothermal crystallization of poly(l-lactide) subjected to uniaxial molecular orientation

Kinetic model of polymorphic crystallization of uniaxially oriented amorphous poly(l-lactide) under isothermal conditions is formulated basing on the Hoffman-Lauritzen theory. Entire ranges of the crystallization temperatures and amorphous orientation factor are considered. The inverse transformation half-times of the amorphous phase to the individual polymorphs, between the unstable α’ and stable α polymorphs, as well as of the overall crystallization are discussed. The kinetic effects are assigned to the decrease in the amorphous phase entropy caused by deformation and orientation of the flexible chain macromolecules.The model predicts that crystallization to the stable α form is controlled by the rate of transformation of the amorphous phase to α’. Concentration of heterogeneous nuclei typical for commercial polymer is assumed and in this case the role of homogeneous nucleation in the transformation kinetics is negligible. The role of homogeneous nucleation at different hypothetical concentrations of heterogeneous nuclei is estimated vs. the Hermans amorphous orientation factor and crystallization temperature. Ranges of domination of heterogeneous and homogeneous nucleation are predicted as dependent on the heterogeneous nuclei concentration.The increase of the overall oriented crystallization rate is predicted for the entire crystallization temperature range as resulting from the increase of the amorphous-to-α′ transformation rate at increasing amorphous orientation. The model provides a view on the mechanisms for possible control of the development of α’/α composition by adjusting the crystallization time vs. orientation and temperature.

Synchronous formation of the ‘forearc’ Bay of Islands ophiolite and its basal high-temperature metamorphic sole constrained by U–Pb zircon ages

The welded metamorphic sole at the base of the Bay of Islands Ophiolite Complex (BOIC) in the Northern Appalachians of Newfoundland shows a typical inverted pressure-temperature (P-T) metamorphic gradient from HT-MP granulite to LT-LP greenschist facies. It incorporates mafic volcanic/plutonic protoliths mixed with pelagic, hemi-pelagic and coarser epiclastic sedimentary protoliths. New LA-ICP-MS U–Pb concordia ages, trace elements, and Ti-in-zircon geothermometry for ∼250 zircon analyses from three metabasites of the upper HT sole amphibolites with N-MORB-like protoliths are reported. Two samples collected within meters of the ophiolite peridotite-sole contact of the Blow Me Down Mountain and North Arm Mountain massifs yielded the oldest comparable concordia ages of 487.7±2.6 Ma and 489.1±3.1 Ma, respectively, that are both within error of the igneous age of 488.3±1.5 Ma of the directly overlying BOIC ophiolite, which formed at a supra-subduction zone (SSZ) forearc spreading center. A third slightly younger age of 484.2±2.4 Ma was obtained for an upper HT amphibolite sample with similar phase assemblages but collected ∼30 m below the peridotite contact of the Table Mountain massif. Zircon crystals analyzed have similar size and morphologies, subparallel rare earth element (REE) variation patterns, and steep heavy REE-enrichments ((Lu/Gd)cn >20), significant positive Ce anomalies (dominantly >5) and slight positive to dominantly negative Eu anomalies (1.2 – 0.4). Zircon shows Th/U mean values of 0.37 – 0.48 with little to no rim to core variation. Minimum Ti-in-zircon mean crystallization temperatures range from ∼764 – 787 °C. These neocrystallized zircon crystals appear to be derived from thin leucosomes within the three amphibolites. Two other samples also from the upper HT sole show evidence of inherited detrital zircon with core dates spanning the Cambrian Notre Dame Arc through older Laurentian-like basement and rift age ranges.Subcretion of the sole took place below a hot forearc asthenospheric wedge, that is, a consequence of the newly-formed BOIC forearc spreading center extending from the back arc to a triple junction along the westward- (or paleo-northward) verging trench of the Notre Dame arc. The early HT sole formation age at ca. 489–488 Ma is long prior to initiation of obduction at ca. 470 Ma and long after initiation of subduction beneath the paleo-northward verging Notre Dame peri-Laurentian arc at ca. 514 Ma. This indicates Newfoundland sole ages of the BOIC and St. Anthony Complex are correlated with the age of SSZ spreading, but not necessarily subduction initiation because previously existing and self-sustaining subduction was ongoing. Sole ages are then not correlated with the younger age of obduction-related orogenic events (e.g., proposed Taconic I and II) in the Newfoundland Appalachians.

On the mechanism of Si-promoted destabilization of TiCx particles in Al alloys

TiCx is an excellent composite strengthening particle and grain refiner for Al alloys. However, the stability of TiCx is poor when solute Si exists in Al alloy melts, which significantly depresses its strengthening and grain refining effects. In this work, the destabilization mechanisms of the TiCx particles in Al-Si alloy melt with a composition of Al-7Si-7.5TiC were explored via experiments, first-principles calculations and thermodynamic calculations. The experimental results show that Si atoms diffuse into TiCx and Ti atoms are released into the Al melt to form a Ti-rich transition zone during the insulation of TiCx in Al-Si melt, and the TiAlySiz and Al4C3 phases are solidified in the Ti-rich zone and at Ti-rich zone/TiCx interface, respectively. The first principles calculations show that the low formation energy of C vacancies facilitates the rapid diffusion of Si atoms in TiCx, while the doping of Si atoms reduces the energy barrier of diffusion of Ti atoms in TiCx and promotes the formation of Ti-rich zones. The thermodynamic calculations show that the wide crystallization temperature range of the destabilized product TiAlySiz phase is the key to continuous decomposition of TiCx particles. In addition, the driving force of the main destabilization reaction of TiCx in the Al-Si alloys is about 44 times higher than that in the Al alloys without Si addition. This indicates that the presence of solute Si remarkably promotes the subsequent decomposition process of TiCx in the Al-Si alloy melts.

Compositional variation and Sn isotope fractionation of cassiterite during magmatic-hydrothermal processes

Cassiterite (SnO2) precipitates over a wide physicochemical range during magmatic-hydrothermal processes. Significant variations in chemical and Sn isotopic compositions of cassiterite have been increasingly reported from hydrothermal deposits worldwide. However, the mechanisms responsible for such notable changes in cassiterite geochemistry remain to be fully addressed. Toward this end, we investigated the chemical and Sn isotopic compositions of distinct generations of cassiterite from a highly-evolved magmatic-hydrothermal-metallogenic system (Xianghualing Sn polymetallic deposit, South China). Cassiterite is widespread in the albite granite, greisen, skarn, and sulfide ore of this deposit, covering most of the known cassiterite-bearing rock/ore types. Based on distinct morphologies and mineral paragenesis, three generations of the Xianghualing cassiterite are identified: (1) Cst 1 occurs in albite granite and greisen; (2) Cst 2 occurs in skarn; and (3) Cst 3 is present in sulfide ore. A lattice strain model indicates that inter-element compositional differences of cassiterite are dual-controlled by cassiterite element partition coefficients and melt/fluid compositions for sufficient and deficient elements, respectively. The variations in Zr, Hf, Nb, and Ta elements in cassiterite are recognized as thermo-indicators of the melt/fluid physicochemical conditions. Their concentrations are influenced by pre- and syn-precipitated Zr-Hf-Nb-Ta-enriched minerals that have a wide crystallization temperature range. Due to differentiations of multiple cationic valences, concentrations and interelement ratios of Sb, Fe, V, and U can be utilized to monitor the relative melt/fluid redox state of different cassiterite generations. Tin stable isotopic compositions are notably fractionated in the Xianghualing cassiterite samples, with δamuSn values relative to standard NIST 3161a ranging from −0.16‰ to 0.19‰. By comparison with compiled Sn isotopes of other hydrothermal deposits, kinetic disequilibrium fractionation is proposed as the main control on cassiterite Sn isotopes fractionation. A Rayleigh fractionation model generates fractionation factors of 1.00010–1.00025, consistent with fractionation factors predicted by first principles calculations (1.00013 to 1.00037). Thus, progressive precipitation of Sn-enriched minerals due to the change of physicochemical conditions during magmatic-hydrothermal processes will cause lighter Sn isotopic compositions in residual melt/fluid. This study highlights that cassiterite chemical and Sn stable isotopes are novel indicators to magmatic-hydrothermal processes.

Microscopic and Small-/Wide-Angle Microbeam X-ray Analyses on Dendritic Crystals in Poly(butylene succinate)

A unique composite dendritic spherulite is detected in a specific crystallization temperature range (Tc = 60–78 °C), whose assembly is probed using microscopy techniques and powerful synchrotron X-ray microbeam analyses. Composite dendritic spherulites composed of feather-like and fern-like branches in poly(butylene succinate) (PBSu) crystallized with poly(ethylene oxide) diluent are analyzed on top surface morphologies correlating with interior-dissected assembly, concurrently through polarized-light optical microscopy, scanning electron microscopy, and synchrotron-radiation X-ray microbeam analysis. The feather-like branch is composed of fully edge-on crystal plates, while the fern-like branch is composed of flat-on crystal plates. These branches originate from a common nucleus with different growth rates. For the first time, the dendritic PBSu spherulite serves as a convenient model for understanding the mechanisms how edge-on and flat-on crystal orientations can alternate not only in a serial mode to form ring bands but also in a parallel mode to form straight dendrites. Morphology evidence and detailed microbeam techniques collectively prove that these discontinuous lamellar plates discretely and gradually tilt and bend to transform from a vertical to a horizontal crystal plate with a corresponding alteration in birefringence.

Crystal structure, electrical and magnetic properties of anion-deficient perovskite-like Ba3SmFe2O7.5

Anion-deficient perovskite-like Ba3SmFe2O7.5 was prepared using a glycerol–nitrate synthesis. Using high-temperature X-ray diffraction in situ a crystal structure transition temperature range 800 and 840 °C was established. These results were further confirmed by high-temperature dilatometric analysis. The average thermal expansion coefficient (TEC) of Ba3SmFe2O7.5 is about 12.8 × 10−6 K−1 between 25 °C and 800 °C. Magnetic experiments proved an excellent phase purity of the oxide and reveal that Fe3+ ions stay in high and intermediate spin states in a ratio of 75% and 25% respectively.

Influence of Cr Doping on Structural, Optical, and Photovoltaic Properties of BiFeO3 Synthesized by Sol-Gel Method

In this work, pure BiFeO3 and samples doped with different concentrations of chromium were synthesized to improve the optical properties and efficiency of solar cells based on BiFeO3. The sol-gel method was used for synthesis due to its ability to produce nanostructured materials with high purity and good homogeneity, as well as the possibility of controlling the size and shape of the resulting particles. The samples were characterized by different analytical techniques. Thermal analysis results indicate that the dopant increases the weight loss of the sample from 61 to 81%, with an increase in the exothermal in the nucleation and crystallization temperature range. The X-ray diffraction patterns and UV-visible spectra show a dependence of the crystallite size and bandgap with respect to the amount of Cr dopant, decreasing from 168 to 73 nm and from 2.14 to 1.92 eV, respectively. Scanning electron microscopy images display a decreasing grain size as a result of an increasing amount of dopant. The I-V analysis results show a 1% Cr-doped BiFeO3 photovoltaic device exhibits enhanced photovoltaic performance with higher photocurrent and 4.17 times greater energy conversion efficiency compared with a pure BiFeO3 photovoltaic device. For their behavior, Cr-doped BiFeO3-based photoelectrodes are very promising materials for photovoltaic devices.

Bio-Based, Self-Healing, Recyclable, Reconfigurable Multifunctional Polymers with Both One-Way and Two-Way Shape Memory Properties

Shape memory polymers (SMPs) have attracted wide attention over the past few decades due to their fantastic applications in modern life. Nevertheless, excellent self-healing properties, recyclability, solid-state plasticity, and reversible shape-switching ability are necessary but can rarely be satisfied in one material. Herein, we report multifunctional SMPs by constructing a dynamic boronic ester bond cross-linking network using sustainable Eucommia ulmoides gum as a raw material. Thanks to the crystallization and wide melting temperature range, these kinds of SMPs have thermal-triggered one-way shape memory performance and show two-way shape memory properties, whether under constant stress or stress-free conditions. Owing to the dynamic nature of the boronic ester bond, it exhibits good self-healing properties (near 100% at 80 °C), shape reconfigurability, and chemical recyclability. In addition, by incorporating multiwalled carbon nanotubes, the formed composite is responsive to 808 nm near-infrared light. Its applications are further exploited, including photoresponsive actuators, vascular stents, and light-driven switches. This paper provides a simple way for fabricating multifunctional SMPs, and the as-prepared materials have potential applications in diverse fields, such as biomedicine, intelligent sensing, and soft robotics.

Jeziorny Method Should Be Avoided in Avrami Analysis of Nonisothermal Crystallization.

The Jeziorny method treats nonisothermal crystallization data by replacing the variable temperature (T) values with the corresponding values of time and substituting them into the isothermal Avrami plot, ln[-ln(1 - α)] vs. lnt. For isothermal data, the slope of this plot is the Avrami exponent, n and the intercept is the rate constant, kA. This does not hold for nonisothermal data. Theoretical analysis suggests that in the case of nonisothermal data the intercept cannot be interpreted as kA, and its "correction" by dividing over the temperature change rate β is devoid of any meaning. In turn, the slope cannot be interpreted as n. It is demonstrated that the slope changes with time and its value depends not only on n but also on the temperature, temperature range, and activation energy of crystallization. Generally, the value of the slope is likely to markedly exceed the n value. The theoretical results are confirmed by analysis of simulated data. Overall, the Jeziorny method as well as other techniques that substitute nonisothermal data into the isothermal Avrami plot should be avoided as invalid and useless for any reasonable Avrami analysis. It is noted that n can be estimated from the nonlinear plot of ln[-ln(1 - α)] vs. T.

Effects of Mg contents on microstructures and second phases of as-cast Al–Zn–Mg–Cu alloys

The effects of Mg content on the microstructures and second phases of the as-cast Al–Zn–Mg–Cu alloys were investigated. The results show that the nonequilibrium eutectic structure consists of α(Al), Al7Cu2Fe, η(MgZn2) and T(AlCuMgZn) intermetallic compounds. The alloys with the highest Mg content generate nonequilibrium eutectic structures. The maximum value of nonequilibrium eutectic structures is 10.13 ± 0.62%. As the Mg content increases, the number of tertiary dendrites in the α(Al) matrix increases significantly, and more Mg can be dissolved into the Al- matrix. In addition, as the Mg content increases, the crystallization temperature range decreases from 169.8 K to 157.3 K. When the Mg content is higher than 2.6 wt%, the microstructure evolution of the Al–Zn–Mg–Cu aluminum alloy is as follows: Liq. → Liq. + α(Al) → Liq. + α(Al) + Al7Cu2Fe → α(Al) + Al7Cu2Fe + η(MgZn2) + T(AlCuMgZn). These results play a certain role in promoting the basic research of Al–Zn–Mg–Cu aluminum alloys with high Mg content.

Self-assembly kinetics of short-chain glucan aggregates (SCGA)

Self-assembly (formation and crystallization) kinetics of short-chain glucan aggregates (SCGAs) prepared at isothermal conditions (4, 20, 40, and 60℃) with or without nucleation (4℃, 1 h) were investigated. The fastest formation and crystallization rates of SCGA were observed when short-chain glucan was stored at 4℃ and 20℃, respectively. SCGA was not formed at 60℃. However, nucleation resulted in SCGA forming-ability at 60℃. Moreover, nucleation increased the yield in all temperature conditions. SCGA with nucleation decreased the crystal melting transition temperature range. All SCGAs had nanosized particles (<500 nm) with B-type crystal patterns regardless of temperature and nucleation. Consequently, self-assembly temperature and presence of nucleation step could change the physicochemical characteristics of SCGA, and manipulation of the nucleation step is expected to be an effective method to increase the yield of SCGA and produce SCGA at high temperature.

An experimentally validated model for quiescent multiphase primary and secondary crystallization phenomena in PP with low content of ethylene comonomer

While crystallization behavior of isotactic polypropylene homopolymers had been subject to a wide range of experimental and modeling studies, this is not the case for propylene-ethylene random copolymers (PPR). This class of polymers offers up to now significant challenges, both from an experimental as well as a modeling perspective. The ethylene incorporation in the propylene chains, as well as the distribution of this comonomer, has a marked effect on the crystallization kinetics. Moreover, the presence of these defects causes a clear separation between primary crystallization (i.e. space filling) and subsequent secondary crystallization (increase of crystallinity in filled space) within the spherulitic skeletons, particularly subsequent at high primary crystallization temperatures. In this work, the underlying mechanism is first quantified by means of a combination of in-situ WAXD and SAXS experiments, as well as ex-situ WAXD experiments and calorimetric measurements. Based on these experiments an extended model framework is presented, capable of predicting multiphase non-isothermal crystallization kinetics as well as the final crystallinity as a function of the applied thermal conditions relevant for processing. The chemical composition distribution (CCD) of the ethylene comonomer serves as critical input to parameterize the model. Optical microscopy- and DSC experiments are used for parameterization of the primary crystallization model. The model developed in this study is, in principle, applicable to all polypropylenes, ranging from homo-polymers to random copolymers with variable comonomer content and/or CCD but, so far, only applied and validated on one PPR. To validate the model and the parameters for a given PPR, several non-isothermal and isothermal experiments (the latter followed by subsequent cooling) are conducted over a wide range of crystallization temperatures and cooling rates. The good match between experiments and model predictions demonstrates the power of the newly developed framework. The final crystallinity, the amount of α - and γ -phase, and the ratio between primary and secondary crystallization can be predicted as a function of the time-temperature history. To the best knowledge of the authors, it is the first time that such a direct connection with the CCD is incorporated in a crystallization model. Consequently, the model offers a new tool to bridge the gap between chemical structure and resulting product properties, which now has come one step closer for PPR systems. • Isothermal and cooling experiments reveal primary and secondary crystallization behavior of PPR. • Primary crystallization is modeled via formation of α-skeletons, in which γ-phase co-crystallizes. • Incorporated multi-phase secondary crystallization to predict final phase composition. • Final crystallinity from the introduction of a crystallizable fraction and kinetic maximum. • Direct link between chemical composition distribution and crystallization kinetics.

Investigation of the effect of the slag system of coated electrodes on the efficiency of metal inoculation of a welding bath of low-carbon steel

Welded joints are subject to increased requirements for structural condition, as well as a complex of mechanical and special properties. A promising way to regulate the structure of the deposited metal directly in the welding process is its inoculation with ultrafine refractory components. This article presents the results of a study of the structure and mechanical properties of metal deposited with electrodes with basic and rutile coatings containing 5% ultrafine titanium monocarbide powder. It is shown that the addition of ultrafine TIC powder to the electrode coating of the basic type leads to a decrease in the average cross-sectional area of crystallites in the deposited metal by 5 times, from 73000 - 74000 &mu;m2 to 14,000 - 15,000 &mu;m2&nbsp;and an increase in the shape factor by 1,5 times, from 0,27 to 0,46. The addition of TiC to the rutile-type electrode coating leads to a decrease in the average cross-sectional area of crystallites in the deposited metal by 12-13 times, from 163000 - 164000 &mu;m2 to 11000 to 12000 &mu;m2&nbsp;and an increase in the shape factor by 2 times, from 0,28 to 0,57. It is established that the effect of inoculation is manifested when using both basic-type coatings and rutile-type coatings. This is due to the fact that the viscosity of liquid welding slags in the crystallization temperature range of a steel welding bath is at the same level of 0,15 &ndash; 0,2 Pa&middot;s, and remains so in the flesh up to temperatures of 1325 - 1350 &deg;С, both for basic and rutile slag systems, and equally affects the process of assimilation of ultrafine refractory particles by the metal of the welding bath. It is shown that, despite the inoculation of the metal of the welding bath with refractory particles and the realization of the effect of volumetric crystallization, the final shape of the crystallites depends on the temperature gradient when the heat of the bath is removed into the base metal.The work was carried out within the framework of state support for young Russian&nbsp;scientists &mdash; grant of the President of the Russian Federation (No. MK-3849.2021.4).