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Semicrystalline polymers under nanoconfinement show distinct structural and thermomechanical properties compared to their bulk counterparts. Despite extensive research on semicrystalline polymers under nanoconfinement, the nanoconfinement effect on the local crystallization process and the unique structural evolution of such polymers have not been fully understood. In this study, we unveil such effects by using coarse-grained molecular dynamics simulations to study the crystallization process of a model semicrystalline polymer—polyvinyl alcohol (PVA)—under different levels of nanoconfinement induced by nanoparticles that are represented implicitly. We quantify in detail the evolution of the degree of crystallinity ( X C ) of PVA and examine distinct crystalline regions from simulation results. The results show that nanoconfinement can promote the crystallization process, especially at the early stage, and the interfaces between nanoparticles and polymer can function as crystallite nucleation sites. In general, the final X C of PVA increases with the levels of nanoconfinement. Further, nanoconfined cases show region-dependent X C with higher and earlier increase of X C in regions closer to the interfaces. By tracking region-dependent X C evolution, our results indicate that nanoconfinement can lead to a heterogenous crystallization process with a second-stage crystallite nucleation in regions further away from the interfaces. In addition, our results show that even under very high cooling rates, the nanoconfinement still promotes the crystallization of PVA. This study provides important insights into the underlying mechanisms for the intricate interplay between nanoconfinement and the crystallization behaviors of semicrystalline polymer, with the potential to guide the design and characterization of semicrystalline polymer-based nanocomposites. [ABSTRACT FROM AUTHOR]

Semicrystalline polymers under nanoconfinement show distinct structural and thermomechanical properties compared to their bulk counterparts. Despite extensive research on semicrystalline polymers under nanoconfinement, the nanoconfinement effect on the local crystallization process and the unique structural evolution of such polymers have not been fully understood. In this study, we unveil such effects by using coarse-grained molecular dynamics simulations to study the crystallization process of a model semicrystalline polymer—polyvinyl alcohol (PVA)—under different levels of nanoconfinement induced by nanoparticles that are represented implicitly. We quantify in detail the evolution of the degree of crystallinity (XC) of PVA and examine distinct crystalline regions from simulation results. The results show that nanoconfinement can promote the crystallization process, especially at the early stage, and the interfaces between nanoparticles and polymer can function as crystallite nucleation sites. In general, the final XC of PVA increases with the levels of nanoconfinement. Further, nanoconfined cases show region-dependent XC with higher and earlier increase of XC in regions closer to the interfaces. By tracking region-dependent XC evolution, our results indicate that nanoconfinement can lead to a heterogenous crystallization process with a second-stage crystallite nucleation in regions further away from the interfaces. In addition, our results show that even under very high cooling rates, the nanoconfinement still promotes the crystallization of PVA. This study provides important insights into the underlying mechanisms for the intricate interplay between nanoconfinement and the crystallization behaviors of semicrystalline polymer, with the potential to guide the design and characterization of semicrystalline polymer-based nanocomposites.

Heterogeneous crystallization is a common occurrence during the formation of solid wastes. It leads to the encapsulation of valuable/hazardous metals within the primary phase, presenting significant challenges for waste treatment and metal recovery. Herein, we proposed a novel method involving the in-situ formation of a competitive substrate during the precipitation of jarosite waste, which is an essential process for removing iron in zinc hydrometallurgy. We observed that the in-situ-formed competitive substrate effectively inhibits the heterogeneous crystallization of jarosite on the surface of anglesite, a lead-rich phase present in the jarosite waste. As a result, the iron content on the anglesite surface decreases from 34.8% to 1.65%. The competitive substrate was identified as schwertmannite, characterized by its loose structure and large surface area. Furthermore, we have elucidated a novel mechanism underlying this inhibition of heterogeneous crystallization, which involves the local supersaturation of jarosite caused by the release of ferric and sulfate ions from the competitive substrate. The local supersaturation promotes the preferential heterogeneous crystallization of jarosite on the competitive substrate. Interestingly, during the formation of jarosite, the competitive substrate gradually vanished through a dissolution-recrystallization process following the Ostwald rule, where a metastable phase slowly transitions to a stable phase. This effectively precluded the introduction of impurities and reduced waste volume. The goal of this study is to provide fresh insights into the mechanism of heterogeneous crystallization control, and to offer practical crystallization strategies conducive to metal separation and recovery from solid waste in industries. [Display omitted] [ABSTRACT FROM AUTHOR]

The importance of promising composites in modern materials science is constantly increasing. The use of various fillers or additives is associated with their influence not only on the defining properties of the composite, but also on physical and mechanical characteristics of the material. In this case, the distribution of the additive and its wetting with a polymer play an important role. The problem highlighted in this article is the influence of different copper-containing fillers (copper (II) sulphate powder, micro-sized copper (II) oxide powder, and nano-structured copper (II) oxide-based hollow microspheres) on the technological and physical–mechanical properties of the composites based on polylactic acid (PLA). The hollow microspheres of copper (II) oxide have been obtained by ultrasonic spray atomization via pyrolysis of copper (II) nitrate. The structure of the copper-based additives has been studied using X-ray diffraction, scanning electron microscopy, and static light scattering. For the PLA-composites, scanning electron microscopy, differential scanning calorimetry, stress-strain properties testing, and density analysis have been performed. The plasticizing effect of polycaprolactone and polyethylene glycol has been studied for the highly filled PLA/CuSO4 composite. The samples of PLA with over 2 wt.% of CuO microspheres have a full volume-filling and percolation structure of the additive's particles. Due to the regular spherical shape of the particles and a lower specific volume, CuO hollow microspheres are uniformly distributed in the PLA matrix acting as a structuring and reinforcing modifier. Differential scanning analysis showed heterogeneous crystallization on CuO particles with an increase in the degree of crystallinity and the melting point of the polymer. It has been shown that the pre-masterbatching technology and adding plasticizers to obtain PLA composites contribute minimizing defects and enhance mechanical properties. [ABSTRACT FROM AUTHOR]

Electrochemically induced crystallization is a promising method for removing and recovering P from wastewater but may be hindered by intrinsic limitations, e.g., high energy consumption and cost. To overcome such limitations, a dual-electrode electrochemically induced crystallization process (DEIC) was proposed using an electrochemical reactor equipped with an iron anode and a stainless-steel cathode. Results showed that > 95% P removal was achieved in 20 hours at the experimental conditions of current density = 0.2 mA/cm2, pH = 6.5, Ca2+ = 5.4 mM, and P concentration = 6.5 mM. The specific energy consumption was calculated as 0.82 kWh/kg P, which is much lower than the reported results (7 – 65 kWh/kg P). According to the XRD and SEM-EDS analysis, P removal was achieved in the form of vivianite (Fe 3 (PO 4) 2.8 H 2 O) and CaP crystallization, induced by the releases of Fe2+ and OH– at the anode and cathode, respectively. Vivianite was found to be deposited at the anode with high purity and a regular plane structure. The DFT calculation confirmed that the control of vivianite growth in a plane shape is thermodynamically feasible. Lastly, the economic analysis showed that the operational cost of DEIC (1.07 USD/kg P) was lower than that of conventional chemical precipitation (1.3 – 1.8 USD/kg P), suggesting that the DEIC process could be a viable method to achieve P removal and recovery. [Display omitted] • A dual-electrode electrochemical method was first applied for P removal. • Extreme low energy consumption for P removal was achieved. • High-purity vivianite deposited on anode but not increased working voltage. • High current conditions hindered the growth of vivianite crystals. [ABSTRACT FROM AUTHOR]

Flat‐on lamellar crystals are crucial for gas‐barrier polymer films. The formation of this lamellar crystalline structure with chains perpendicular to the substrate is currently understood as the result of confined crystallization, e.g., in block copolymers and ultrathin polymer films. In this paper, it is demonstrated that these flat‐on lamellar crystals of various thermoplastic polymers may form on stainless steel and silicon wafer surfaces without the presence of confined crystallization. Atomic force microscopy, high‐resolution scanning electron microscopy, and polarized light hot‐stage microscopy are used to characterize the formation of the lamellar crystals. Further results show that the surface physicochemical properties of the substrates strongly influence the formation of these lamellar crystals. A hypothesis, based on the heterogeneous crystallization theory, is proposed to explain the formation of such flat‐on lamellar crystals. These results are crucial for a fundamental understanding of the formation of lamellar crystals and may provide a new approach to fabricate such structures. [ABSTRACT FROM AUTHOR]

• Homogeneous and heterogeneous CaCO 3 precipitation were distinguished using magnetite as seeds. • Increasing SI preferentially promoted heterogeneous crystallization at low SI, but homogeneous at high SI. • High seed dosage and small seed particle size facilitate heterogeneous crystallization. • Heterogeneous nuclei adhered to seed surfaces, exhibiting better settleability than homogeneous ones. Homogeneous and heterogeneous crystallization of CaCO 3 simultaneously occur in seed-induced crystallization during water softening, while suppressing homogeneous crystallization is necessary due to the production of fine particulates that poorly precipitate. However, homogeneous crystallization is difficult to distinguish from heterogeneous crystallization. Consequently, a central focus in improving water softening is understanding their competing activities. In this study, a novel method for distinguishing homogeneous and heterogeneous calcium carbonate crystallization is described that utilizes magnetite as seed particles. Results showed that saturation index (SI) was the primary driver of both homogeneous and heterogeneous crystallizations. Heterogeneous crystallization was preferentially promoted at low SI, while homogeneous crystallization was promoted at high SI. The highest suppression effect to homogeneous crystallization occurred at SI of about 1.01. Seed dosage and mean particle size were the primary parameters related to the competition of the crystallization types. Higher seed dosage and smaller seed particle sizes promoted heterogeneous crystallization and suppressed homogeneous crystallization. Due to the good adaptability of heterogeneous crystallization at low SI, the absorption of CO 2 from the air into the solutions also improved the efficiency of hardness removal. The introduction of seed particles did not change crystalline product phases, with calcite being the only observed phase and possessing rhombohedral forms with highly regular and smooth edges. Water softening pilot test results showed that SI of 1.5 was more favorite for CaCO 3 layer formation on seed surface and hardness removal in comparison with SI of 1.0 and 2.0. Overall, the results from this study demonstrate that the introduction of seed particles is a promising approach to suppress the homogeneous crystallization of CaCO 3. Moreover, these results can serve as a framework for improved seed-induced crystallization during water softening. [Display omitted] [ABSTRACT FROM AUTHOR]

This article discusses the effects of surfacing with the introduction of mechanical vibrations into the material using shot blasting. It does not require a rigid attachment of the vibrating system to the base material, and vibrations are introduced as a result of supplying energy of collision of the shot with the parent material. The effect of introducing mechanical vibrations through shot blasting during welding of P235GH steel on the structure and hardness of obtained structures was described. Comparative results of tests revealing the basic differences in the structural structure and hardness of reached welds without shot blasting and with its participation were presented. As a result of the conducted research, differences in the structural structure of the welds were shown and it was shown that shot blasting is an effective and alternative method of introducing mechanical vibrations supporting welding processes.

This study investigates crystallization, melting and glass transition of Li- and Ca-12-hydroxystearate greases in relation to the pour point of the corresponding oils. The base oils for the greases are mineral oil, polyalphaolefin, alkylated naphthalene, propylene glycol, and trimellitate. For the mineral oil-based greases the crystallization temperature Tc increases and the melting temperature Tm decreases upon addition of thickener. The pour point of the mineral oil then is 3 K below Tc and does not properly define the lowest application temperature for mineral oil (MO) based greases. Both thickeners induce a small increase of the glass transition temperature (1–3 K) of the synthetic oils polyalphaolefin, alkylated naphthalene, propylene glycol. The pour point of the base oils correlates well with the onset of the glass transition in the corresponding grease indicated by a sharp increase in grease viscosity. Pure trimellitate with unbranched alkyl chains does not crystallize upon cooling but shows noticeable supercooling and cold crystallization. As the percentage of thickener in corresponding greases increases, more oil crystallizes upon cooling 20 K above the crystallization temperature of the trimellitate without thickener (−44 °C). Here, the thickener changes the crystallization behavior from homogeneous to heterogeneous and thus acts as a crystallization nucleus. The pour point of the base oil does not provide information on the temperature below which the greases stiffen significantly due to crystallization.

A general model is proposed in order to describe the growth of a deposit by heterogeneous reactions. The hydrodynamics in the fluid is described by a multicomponent transport model for ionic species diluted in a solvent and heat transfer is taken into account in both liquid and solid domains. The boundary condition at the interface where the reaction takes place is described thoroughly. It involves the reaction kinetics and gives access to the velocity of the interface, ie, the mass rate of the solid deposit. The model is then applied to the case of barite crystallization in a heat exchanger. The liquid phase is therefore composed of two ionic species Ba2+ and SO42− diluted in water. The solid phase is modelled as a homogeneous barite deposit. The fully dynamic CFD simulation of the model is made using Comsol Multiphysics, in a cylindrical pipe. The solid growth is analyzed over time and space in terms of the relevant variables of the model. [ABSTRACT FROM AUTHOR]

A study has been performed, in which the crystallization and optical properties of glass of the stoichiometric composition of lithium disilicate 33.5LiO · 66.5SiO mol % has been studied on the same samples of photostructured glass with additives of the photosensitive gold impurity of 0.03 and 0.003 wt % above 100%. It was shown that the same amount of the crystal phase in glass with different amounts of the photosensitive gold impurity can be obtained by varying the X-ray irradiation time. The position of the surface plasmon resonance does not change. [ABSTRACT FROM AUTHOR]

Using polymeric surfaces is a novel way to control crystallization. However, the mechanism is still ambiguous. In the present study, chitosan (CS) films that were doped with different molecules were employed to investigate the impact of surface chemistry on the heterogeneous crystallization behavior of acetaminophen (APAP). Crystal growth rate and crystallization kinetic measurements of APAP on various substrates were performed. Fourier transform infrared spectroscopy was used to probe intermolecular interactions between APAP and CS films. The results were interpreted with the aid of molecular simulations. It was found that substrates with more hydrogen bonding groups that could interact with APAP promoted its crystallization. [ABSTRACT FROM AUTHOR]

It is shown that the phase heterogeneity of SiO-NaO-AlO glass has a liquation and crystallization nature, the balance between which is determined by the conditions of their synthesis. An increase in the aluminum oxide content decreases the number of liquation and crystallization sites, and also the linear sizes of the crystalline formations without eliminating the phase separation due to the liquation. The area of metastable immiscibility in the SiO-NaO-AlO system, which is determined by scanning electron microscopy, is probably wider than the area detected by the optical methods. [ABSTRACT FROM AUTHOR]

This study investigates crystallization, melting and glass transition of Li- and Ca-12-hydroxystearate greases in relation to the pour point of the corresponding oils. The base oils for the greases are mineral oil, polyalphaolefin, alkylated naphthalene, propylene glycol, and trimellitate. For the mineral oil-based greases the crystallization temperature Tc increases and the melting temperature Tm decreases upon addition of thickener. The pour point of the mineral oil then is 3 K below Tc and does not properly define the lowest application temperature for mineral oil (MO) based greases. Both thickeners induce a small increase of the glass transition temperature (1–3 K) of the synthetic oils polyalphaolefin, alkylated naphthalene, propylene glycol. The pour point of the base oils correlates well with the onset of the glass transition in the corresponding grease indicated by a sharp increase in grease viscosity. Pure trimellitate with unbranched alkyl chains does not crystallize upon cooling but shows noticeable supercooling and cold crystallization. As the percentage of thickener in corresponding greases increases, more oil crystallizes upon cooling 20 K above the crystallization temperature of the trimellitate without thickener (−44 °C). Here, the thickener changes the crystallization behavior from homogeneous to heterogeneous and thus acts as a crystallization nucleus. The pour point of the base oil does not provide information on the temperature below which the greases stiffen significantly due to crystallization. [ABSTRACT FROM AUTHOR]

Crystallization near structured substrates is explored by extensive Brownian dynamics computer simulations of two-dimensional equimolar binary colloidal suspensions. The particles are interacting via repulsive dipole-dipole forces. The two species have different (big and small) dipole moments which are tunable by an external magnetic field. A quench is realized by a sudden drastic increase of the magnetic field which formally corresponds to a quench to zero temperature. The structured walls are modelled by fixed particles on an alternating binary equimolar square lattice which is cut along the (10) direction. Two situations are studied and compared where the outermost layer of fixed particles either consists of big or of small dipolar particles. Both of these structures favour local crystallites which pick up the square symmetry of the substrate. After the quench the equilibrium state is an alternating square lattice which coincides exactly with that imposed by the external wall. The relaxation behaviour following the quench is explored. The amount of local crystallites with triangular and square symmetry is monitored as a function of time for different initial temperatures. It is found that the number and structure of crystallites near the walls strongly depend on the wall pattern. Even though local square structures are favoured energetically and the equilibrium state is an alternating square lattice, the number of triangular crystallites close to the wall which has outermost fixed small particles is significantly higher than in the unconfined case. The actual number of triangular clusters depends on the depth of the quench. This effect is not contained in classical nucleation theory. [ABSTRACT FROM AUTHOR]

Abstract: To grow protein crystals is not an easy task; moreover, if we need to grow protein crystals with controlled shape, size, and size distribution, depending on their application, the mission becomes even harder. Membrane crystallization has been recognized as an interesting tool for growing protein crystals with enhanced crystallization kinetics, both in static and in forced solution flow configuration, without detrimental effects on crystal quality. In the present work, we have studied the membrane crystallization process of benzamidine inhibited trypsin from bovine pancreas (BPT), with ammonium sulphate (dissolved in Tris–HCl buffer, 0.1M, pH 8.5), as precipitant agent. We have demonstrated that, by using the membrane crystallization technique, BPT crystals can be obtained in 24–48h, in static configuration, and in 4–7 days, in a forced solution flow system, depending on the experimental conditions. Furthermore, the kinetics of BPT crystallization have been modulated, to control the morphological characteristics of the crystals produced, by an accurate selection of the operative parameters involved in the process. The active membrane surface and the flow rate of extraction solvent in quiescent configuration, and the solution velocity in forced convection solution experiments, were the parameters investigated. In this respect, membrane crystallization techniques have been assessed as an interesting way for growing proteins, and more specifically enzyme crystals, with high control on the final properties of the crystalline material produced, with potential fundamental implication in the field of structural biology and biotechnology. [Copyright &y& Elsevier]