Crystallization Events Research Articles

Phase transformation, thermal behavior, and magnetic study of new (FeSiBP)100-XCuX glassy alloys obtained by melt-spinning in air

In the current work, a new variation of the FeSiBPCu system with good glass forming ability and soft magnetic properties was developed and investigated. The effect of copper addition on the FeSiBP base alloy was studied in the system (Fe0.77Si0.08B0.1P0.05)100-xCux with x = 0, 0.25, 0.5, 0.75 and 1.0 at%. Microstructural evolution upon the annealing process was evaluated by XRD and TEM, revealing the formation of α-Fe(Si), Fe2B and Fe3(B,P) crystalline phases. VSM allowed to determine that the combination of chemical composition and microstructure with the best soft magnetic properties after the annealing corresponds with the alloy with 0.75% Cu. In addition, activation energy for glass transition and the first crystallization event were calculated using the Kissinger method. The research findings demonstrated that maintaining the relationship between the main elements, it is possible to keep the good glass forming ability with the possibility of developing a nanocrystalline structure with soft magnetic performance.Graphical abstract

Integrated U-Pb and Hf zircon and whole-rock Nd isotopes studies of Devonian granitic rocks from Sierra de San Luis (Sierras Pampeanas, Argentina): Petrogenetic implications

Previous geochronological data indicate a protracted Devonian magmatic activity developed in the Sierra de San Luis, Sierras Pampeanas of Argentina, with three major crystallization events: 393±3, 384±2, and 377±2 Ma. Previously reported whole-rock Sm-Nd isotopes data define two average distinctive εNdt values: -1.37 and -3.47, and they are consistent with new data presented here. The first signature is assumed for a parental magma with dominant metasomatized subcontinental lithospheric mantle (SCLM) source, whereas the second signature could represent a parental magma derived of a lower continental crust source hybridized with magmas of the first signature. Notably, the new zircon Hf isotopes performed on the same zircon domains that were previously dated, indicate that the contribution of the source was variable over time. In situ Hf in zircon is relevant to evaluate the compositional evolution of the Devonian granitic magmas in the Sierra de San Luis, since the high variability of the εHft values recorded in zircons indicate that the calculated εNdt values for the samples can only be interpreted as a final picture of the petrogenetic process. Zircon Hf isotopes data suggest that the zircon crystallized from a magma with variable composition, recording two major events, yielding two εHft signatures: (1) -3.54 and (2) -6.85. A third composition, yield a less representative εHft value of -5.44, and represent a εHft signature (3).

Effects of Cooling Rate and Emulsifier Combination on the Colloidal Stability of Crystalline Dispersions Stabilized by Phospholipids and β-Lactoglobulin

A lot of applications for (semi-)crystalline triacylglycerol (TAG)-in-water dispersions exist in the life science and pharmaceutical industries. Unfortunately, during storage, these dispersions are often prone to changes in particle size due to unforeseen crystallization and recrystallization events. This results in the alterations of important product properties, such as viscosity and mouthfeel, or the premature release of encapsulated material. In this study, we investigated the effects and interplay of formulation, i.e., emulsifier combination, and processing parameters, i.e., cooling rate, on the colloidal stability of dispersed TAGs and aimed to improve their colloidal stability. We chose phospholipids (PLs) and β-lactoglobulin (β-lg) as the emulsifiers for our model systems, which are commonly applied in many food systems. When dispersions were characterized directly after cooling, we obtained smaller particles and narrower size distributions after fast cooling. Over the course of eleven weeks, the creaming behavior, particle size, melting behavior and polymorphism were characterized. The dispersions stabilized with solely β-lg exhibited a slight increase in particle size, whereas a decrease in size was found when PLs were added. Our results indicate that mass transport phenomena between TAG droplets and particles took place during storage. This migration of TAG molecules changed the composition and size distribution of the dispersed phase, especially at higher PL concentration (0.1 wt%). In our case, this could be prevented by using a lower concentration of PLs, i.e., 0.05 wt%.

Magnetite Mineralization inside Cross-Linked Protein Crystals.

Crystallization in confined spaces is a widespread process in nature that also has important implications for the stability and durability of many man-made materials. It has been reported that confinement can alter essential crystallization events, such as nucleation and growth and, thus, have an impact on crystal size, polymorphism, morphology, and stability. Therefore, the study of nucleation in confined spaces can help us understand similar events that occur in nature, such as biomineralization, design new methods to control crystallization, and expand our knowledge in the field of crystallography. Although the fundamental interest is clear, basic models at the laboratory scale are scarce mainly due to the difficulty in obtaining well-defined confined spaces allowing a simultaneous study of the mineralization process outside and inside the cavities. Herein, we have studied magnetite precipitation in the channels of cross-linked protein crystals (CLPCs) with different channel pore sizes, as a model of crystallization in confined spaces. Our results show that nucleation of an Fe-rich phase occurs inside the protein channels in all cases, but, by a combination of chemical and physical effects, the channel diameter of CLPCs exerted a precise control on the size and stability of those Fe-rich nanoparticles. The small diameters of protein channels restrain the growth of metastable intermediates to around 2 nm and stabilize them over time. At larger pore diameters, recrystallization of the Fe-rich precursors into more stable phases was observed. This study highlights the impact that crystallization in confined spaces can have on the physicochemical properties of the resulting crystals and shows that CLPCs can be interesting substrates to study this process.

Zircon xenocrysts obscured the zircon date for the lower Koras Group, southern Africa

Abstract The Koras Group is a bimodal volcanosedimentary group located in post-tectonic grabens in a foreland thrust complex in the Kaaien Terrane of the Mesoproterozoic Namaqua-Natal Province of southern Africa. It contains two sequences of mafic and felsic volcanic rocks with an unconformity between them, only the lower sequence being slightly folded. The Koras Group was long regarded as having formed at the end of the 1 210 to 1 000 Ma Namaqua Orogeny, because it lacks the severe deformation and metamorphism of the underlying rocks, with igneous minerals preserved in many samples. Following years of unsuccessful attempts to precisely date the volcanic rocks, the first two ion probe U-Pb zircon studies both reported ages of ~1 172 Ma for the Swartkopsleegte Formation felsic lava in the slightly folded lower sequence (based on relatively few dated zircons) and ~1 100 Ma for the Leeuwdraai Formation rhyolite in the undeformed upper sequence. Thus a major 70 m.y. hiatus seemed apparent between the lower and upper sequences despite their similar geochemistry and rift-related setting. This gave rise to models which envisaged the Kaaien Terrane being unaffected by the syn- to late-tectonic deformation, migmatisation and granite intrusions, documented between 1 200 and 1 150 Ma in the adjoining Namaqua-Natal terranes to the west. A high-pressure (10 kbar) metamorphic event, recognised in the Kaaien Terrane basement just south of hardly-deformed Koras Group exposures and dated at 1 150 Ma, is inconsistent with such models. A re-investigation and microbeam dating campaign on the Koras Group confirms the 1 101 ± 2 Ma (n = 6) age for felsic volcanic rocks of the upper sequence, but establishes a new reliable age of 1 114 ± 4 Ma for the lower one (n = 2). The 1 170 ages obtained in the earlier two studies were revisited and are now considered to reflect the age of zircon xenocrysts from the source rocks, which dominate the zircon population of some Swartkopsleegte Formation samples. Several criteria to distinguish autocrystic (magmatic) from antecrystic (age-overlappping xenocrystic) data points were investigated. One sample had high Th levels in only the younger zircons, but histograms of sufficiently precise 207Pb/206Pb ages provided the main criterion. Calculations of zircon crystallisation temperature intervals were not useful in predicting the abundance or proportions of magmatic and antecryst zircons. A multi-episode model of magmatic generation and crystallisation events is probably appropriate. In cases when felsic volcanic samples yield few zircons, care must be taken to avoid the problem exposed in this study. The Koras Group sediments have similar detrital zircon U/Pb age distributions to those of the Rehoboth Basement Inlier. This supports the concept that the Kaaien Terrane originated as the southern part of the Rehoboth Province.

An insight into the thermal processability of highly bioactive borosilicate glasses through kinetic approach

AbstractThe paucity of crystallization resistant bioactive glasses with desired biological functions stands as a bottleneck toward the fabrication of various biomedical constructs such as amorphous coatings, scaffolds, and fibers for advanced tissue engineering applications. In this context, a series of borosilicate‐based bioactive glasses with a range of compositions: (53.88 − x)SiO2–21.7Na2O–21.7CaO–1.7P2O5–xB2O3 (mol%) where x = 0, 13.47, 22.45, 31.43, and 40.41 were prepared to address such limitation. The glasses were primarily investigated for their potential to be processed into amorphous scaffolds through evaluation of crystallization kinetics, sintering behavior, and viscosity–temperature dependence. The inclusion of B2O3 gradually reduces the activation energy of crystallization (Ea), according to the prediction from different kinetic models, whereas Friedman's model‐free method unraveled the variation in Ea as crystallization progresses. The crystallization event is further elucidated by obtaining the Avrami parameter (n) and dimensionality (m) through Matusita–Sakka equation. The optimization of the sintering schedule for amorphous scaffold preparation was accomplished by exploiting isothermal prediction from Avrami–Erofeev model. Moreover, viscosity–temperature relationship for the studied glasses was established to identify the processing window for drawing and sintering. This study proposes a comprehensive approach adopting theoretical models to elucidate suitable high‐temperature process parameters of bioactive glasses avoiding devitrification.

Crystallization sequence of an (Al86Ni9La5)98Si2 amorphous alloy under continuous heating

Based on isochronal phase transformation kinetics, the crystallization sequence of (Al86Ni9La5)98Si2 amorphous alloy was fcc-Al→fcc-Al→Al3Ni+La3Al11+unidentified phases at a heating rate > 5 K/min; while the crystallization sequence changed to fcc-Al→Al3Ni+La3Al11+unidentified phases→fcc-Al at a heating rate < 5 K/min. However, the last two crystallization events were kinked rather than reversed in sequence even if the heating rate decreased from 160 to 1 K/min in experiments. This inconsistency illustrated that the crystallization sequence associated with the two crystallization events can hardly be profiled sophisticatedly by their individual thermal analyzed kinetics, and here was attributed to two bifurcate originations: the prerequisite conditions for the formation of Al3Ni, La3Al11, and unidentified phases was actually the precipitation of the second stage fcc-Al, and the monotonous Al can hardly be existed independently in the amorphous state.

Thermal analysis and non-isothermal crystallization kinetics of Ag–Ga2Te3–SnTe telluride glasses

In this paper, the microstructure evolutions and crystallization kinetics of the newly developed Agx-[(Ga2Te3)34(SnTe)66]100−x (x = 6, 8 and 10%) telluride glasses were comprehensively investigated under non-isothermal conditions. The microscopic structure of the investigated samples were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM) and the selected area electron diffraction (SAED). The crystalline products were identified as the SnTe phase (primary crystalline phase) and Ga6SnTe10 phase. The exothermic crystallization process for any investigated samples was actually on the envelope of two overlapped peaks and could be assigned to the first crystallization event of SnTe precipitation and followed by the second crystallization event of Ga6SnTe10 phase. The crystallization mechanism and activation energies were estimated by Matusita–Sakka model under continuous heating based on the differential scanning calorimeter (DSC). For the first crystallization event, the Avrami exponent n values for each of the three investigated samples was approximately 3, suggesting the crystallization occurred through the two-dimensional growth with increasing number of nucleation. The values of n for the second crystallization event of Ga6SnTe10 phase were close to 4, indicating three-dimensional growth with a increasing number of nuclei. The activation energy Ec for both the first and second crystallization events was gradually decreased as the Ag content increased.

Understanding crystallization in undoped and nitrogen doped GeTe thin films using substrate curvature measurements

Herein, we study the crystallization of undoped and nitrogen doped amorphous GeTe thin films (slightly rich in Ge) obtained by sputtering using substrate curvature measurements to understand the underlying mechanisms controlling stress evolution in the film throughout the phase transformation. At temperatures below crystallization temperature, amorphous films showed stress relaxation and the stress gradually became tensile with annealing time. The GeTe samples show a two-step crystallization wherein amorphous GeTe crystallized first (at the crystallization temperature Tx) followed by crystallization of excess Ge (Ge precipitation) at -Tx+50 °C. Upon GeTe crystallization, a sharp increase in the tensile stress is explained using a coalescence mechanism. This interpretation resolves the issue of the discrepancy between the measured stress buildup reported by several authors and the predicted stress jump from elastic accommodation of density change. The precipitation of excess Ge (from amorphous to crystalline) along grain boundaries in GeTe leads to compressive stress build-up. Nitrogen doping affects both the GeTe and Ge crystallization events leading to lesser tensile and compressive stress. The models for stress relaxation in the amorphous phase, stress build-up due to GeTe, and excess Ge crystallization are discussed.

Collective Variables for Crystallization Simulations-from Early Developments to Recent Advances.

Crystallization is an important physicochemical process which has relevance in material science, biology, and the environment. Decades of experimental and theoretical efforts have been made to understand this fundamental symmetry-breaking transition. While experiments provide equilibrium structures and shapes of crystals, they are limited to unraveling how molecules aggregate to form crystal nuclei that subsequently transform into bulk crystals. Computer simulations, mainly molecular dynamics (MD), can provide such microscopic details during the early stage of a crystallization event. Crystallization is a rare event that takes place in time scales much longer than a typical equilibrium MD simulation can sample. This inadequate sampling of the MD method can be easily circumvented by the use of enhanced sampling (ES) simulations. In most of the ES methods, the fluctuations of a system's slow degrees of freedom, called collective variables (CVs), are enhanced by applying a bias potential. This transforms the system from one state to the other within a short time scale. The most crucial part of such CV-based ES methods is to find suitable CVs, which often needs intuition and several trial-and-error optimization steps. Over the years, a plethora of CVs has been developed and applied in the study of crystallization. In this review, we provide a brief overview of CVs that have been developed and used in ES simulations to study crystallization from melt or solution. These CVs can be categorized mainly into four types: (i) spherical particle-based, (ii) molecular template-based, (iii) physical property-based, and (iv) CVs obtained from dimensionality reduction techniques. We present the context-based evolution of CVs, discuss the current challenges, and propose future directions to further develop effective CVs for the study of crystallization of complex systems.

Triple and Quadruple Surface Pattern Memories in Nanoimprinted Polymer Blends

Trigger-responsive surfaces with multiple surface properties have wide-ranging application potential from surfaces with trigger-responsive fluid flow to cell culture to optical effects; such surfaces can be achieved through surface morphological changes. Although multiple shape-memory effects are successful in bulk polymers, there is limited programing and recovery of multiple surface memories due to the challenges in fabricating multiple surface topographies with good controllability. Here, we report the synergy between the polymer blend formulation and the thermal nanoimprinting process to achieve multiple microtopography memories. A series of immiscible blends consisting of poly(caprolactone) (PCL) and polyethylene (PE) with distinct thermal transitions governed by distinct crystallization events were augmented with improved elasticity through preferential cross-linking in the polymer blend. The effect of preferential cross-linking by dicumyl peroxide on the elastic property of the PCL/PE has been found to be nonlinearly dependent on the blend composition. This approach enabled triple and quadruple surface pattern fixity and recovery in nanoimprinted PCL/PE blends. Specifically, we demonstrated the recovery of a micropillar structure (diameter: 20 μm and height: 10 μm) from a hierarchical micrograting topography (width: 2 μm and height: 2 μm) when exposed to a thermal stimulus at 60 °C for 180 s. Furthermore, we also demonstrated the recovery of a deformed micrograting followed by a secondary recovery of the micropillar structure.

The Origin of Lattice Rotation during Dendritic Crystallization of Clinopyroxene

AbstractUnderstanding dendritic crystallization is key to obtaining petrological information about rapid crystallization events. Clinopyroxene dendrites from a basaltic rock fulgurite from Nagpur, India, exhibit curved branches with corresponding lattice rotation that exceeds 180° for some branches. This paper combines crystallographic orientation mapping with microstructural observations and compositional information to determine the dendrites’ 3-D morphology and their bending mechanism. Dendrites exhibit a network of branches in the (010) plane, following either {001}* (normal to {001} planes, strong lattice curvature) or &amp;lt; 10–1 &amp;gt; (weak lattice curvature). Three or more orders of branches are observed in the (010) plane, alternating between {001}* and &amp;lt; 10–1&amp;gt;. Side branches with weak lattice curvature extend sub-perpendicular to the (010) plane, following either {021}* (sprouting from {001}* branches) or &amp;lt; 12–1 &amp;gt; (from &amp;lt;10–1 &amp;gt; branches) and defining curved ‘ribbons’ containing their respective central branch. All branches rotate about [010], with a consistent rotation sense regardless of elongation direction in sample or crystal coordinates. Bending must therefore be caused by local asymmetric thermal and compositional fields in the melt, generated by dendritic growth itself, not by sample-scale compositional, thermal or mechanical gradients. The most likely cause of bending is asymmetric distribution of melt supersaturation around branch tips, related to unequal growth rates perpendicular to different facets. Lattice rotation is inferred to occur via preferential incorporation of high densities of [001] (100) edge dislocations of one sign. High inferred dislocation densities imply that the preservation of bent dendrites requires rapid quenching. Higher inferred degree of undercooling (based on microstructural observations) correlates with greater lattice curvature. Bent dendrites can thus potentially be used to deliver information about spatial variations in degree of undercooling and place limits on the history of a sample after dendritic crystallization. Finally, finding lattice rotation exclusively about [010] is a new criterion to identify cryptic dendritic growth stages in euhedral crystals.

Crystallization of Aluminum droplet at low undercooling: homogeneous nucleation approach

Crystallization in an undercooled Aluminum (Al) droplet occurs via the formation of crystalline nuclei by homogeneous or heterogeneous nucleation and successive growth of nuclei. Clusters of a new phase appear in the system due to fluctuations and after reaching a critical size grow up to microscopic size. Crystallization event at low undercooling 6.4°C of 9.91 mg in compact Al sample was detected using isothermal differential scanning calorimetry (DSC) after several tenths of minutes. In this case, standard analysis based on Johnson-Mehl-Avrami-Kolmogorov (JMAK) model is not appropriate as Avrami parameter n obtained by fitting of DSC data is too low (n ≤ 1 and thus the dimensionality of the system d = n – 1 ≤ 0). Al growth rate is extremely high and that is why we presume that the time delay of crystallization, detected by DSC, is slightly higher than nucleation time delay. A homogeneous nucleation model is applied to determine the basic characteristics of nucleation: the size distribution of nuclei, nucleation rate, total number of nuclei and crystallization fraction at the nucleation process. The number of atoms in a liquid Aluminum droplet decreases with time as the formation of a new crystalline phase occurs. As a consequence, a decrease in stationary nucleation occurs. It is shown that decrease in the number of atoms in a liquid Al droplet is predominantly caused by formation of subcritical clusters.

Thermal stability and crystallization behavior of Al86Ni9Y5 amorphous alloys with different Si addition

In this paper, a series of (Al 86 Ni 9 Y 5 ) 100- x Si x ( x = 0, 1, 2, 3, 4, 5) amorphous ribbons were prepared to study the effect of Si addition on the crystallization behavior. The amorphous microstructure of Al 86 Ni 9 Y 5 base alloy is essentially heterogeneous. When it is subjected to annealing, primary α-Al nanocrystals first precipitate in the Al-rich regions and then regrow in the residual amorphous matrix at a far higher temperature, resulting in two separate primary crystallization events, called as abnormal crystallization. Addition of Si to the base alloy principally enhances the chemical heterogeneity, due to which more α-Al crystals precipitates with a lower onset temperature and crystallization activation energy. Meanwhile this abnormal crystallization of α-Al is promoted when x ≤ 3. The largest temperature interval between two crystallization peaks of α-Al is up to 154 K. As more Si is added, however, the crystallization of Al 3 Ni and Al 3 Y is advanced, causing the vanishment of the abnormal crystallization. The strong interaction between different species of solute atoms and the existence of free Al atoms are responsible for the occurrence of the abnormal crystallization. • Abnormal crystallization of α-Al occurs in Al 86 Ni 9 Y 5 but not in Al 86 Ni 9 La 5 amorphous alloy. • Addition of 1–3 at.% Si enhances the abnormal crystallization in Al 86 Ni 9 Y 5 amorphous alloy. • Severe chemical heterogeneity is essential for the abnormal crystallization. • Strong interaction between solute atoms promotes the abnormal crystallization.

Positive and negative effects of graphite flake and monolayer graphene oxide templates on protein crystallization

Heterogeneous template-induced nucleation is a promising way to regulate protein crystallization events and could be employed for purification processes and crystallographic studies. Protein crystallization process with graphite and graphene oxide, as heterogeneous templates, were investigated. More than 640 hanging drops with different concentrations of Lysozyme (30, 50, 70, 100 mg/mL) and NaCl (0.7, 0.9, 1.1, 1.3, 1.5 M) were crystallised at 4 °C with or without graphite/graphene oxide templates. The induction times and crystallization process were observed under the microscope. The lysozyme in the solutions with graphite flakes nucleated faster under all the conditions than the lysozyme with equal experimental conditions without templates. The crystals preferred to grow around the edge of graphite flakes than on the flat surfaces. In the droplets with monolayer graphene oxide, more crystals appeared around graphene oxide particles, and the faster or slower nucleation processes with templates were dependent on the lysozyme and NaCl concentrations. Graphene oxide templates strongly inhibited nucleation at high lysozyme concentrations but promoted nucleation at low lysozyme concentrations. Both heterogeneous templates changed the crystal morphology and the crystallization kinetics. More crystals were observed in the solution with graphite templatesthan with graphene oxide templates and without any template.

Crystallization behavior of uranium glass-ceramic matrix under simulated self-irradiation conditions

The study of irradiation stability for radioactive waste matrices is essential for efficient long-term waste management. The uranium-contaminated soil was vitrified using microwave technology in the current study, and the irradiation response mechanism was examined using 0.5 MeV He2+ ions to approximately imitate self-irradiation. The results demonstrate that the glass matrices with differing uranium contents showed various irradiation response mechanisms. The stability of the matrix with lower uranium content (0 and 500 μg/g) may be slightly impacted by the ions irradiation, as one may see a crystallization behavior for the matrix with 50,000 μg/g uranium after being irradiated to He2+ ions at a fluence of 1 × 1017 ions/cm2. The crystalline phase (SiO2) was identified via phase investigations and microscopic studies. As a result of the crystallization event, the Vickers hardness of the matrix decreased from 6.88 GPa to 6.77 GPa after irradiation. Additionally, the un-irradiated matrix containing 50,000 μg/g of uranium had a uranium leaching rate of 3.2 × 10−5 g·m−2·d−1 at 28 days. The leaching rate for the irradiated matrix under the identical experimental conditions is 5.4 × 10−5 g·m−2·d−1, demonstrating that the crystallization behavior affects the chemical stability.

Electron localization in recrystallized models of the Ge2Sb2Te5 phase-change memory material

Understanding the relation between the structural disorder in the atomic geometry of the recrystallized state of phase-change memory materials and the localized states in the electronic structure is necessary not only for technological advances, but also essential to achieve a fundamental understanding of these materials. In this computational study, hybrid density-functional theory simulations are employed to ascertain the impact of antisite defects on the spatial localization of the electronic states in the bottom of the conduction band in recrystallized models of the prototypical phase-change material ${\mathrm{Ge}}_{2}{\mathrm{Sb}}_{2}{\mathrm{Te}}_{5}$. $\mathrm{Te}\text{\ensuremath{-}}\mathrm{Te}$ homopolar bonds are the local defective atomic environments mainly responsible for the electron localization of the conduction-band-edge states in the simulated structures, while $\mathrm{Sb}\text{\ensuremath{-}}\mathrm{Te}$ chains can also induce spatial localization. Unoccupied defect-related electronic states can emerge in the band gap during a crystallization event, while $\mathrm{Sb}\text{\ensuremath{-}}\mathrm{Sb}$ homopolar bonds have been identified in the defect environment of a deep localized state.

Surmounting the thermal processing limits: Patterning TiZrCuPdSn bulk metallic glass even with nanocrystallization

Ni-free Ti-based bulk metallic glasses (BMGs) are promising for biomedical applications, thanks to their excellent biocompatibility and high corrosion resistance. BMGs can be shaped and patterned by viscous flow deformation using thermoplastic net-shaping. This work presents a novel strategy for thermoplastic net-shaping of Ti40Zr10Cu34Pd14Sn2 BMG. Instead of operating for a short time slightly above the glass transition temperature to avoid crystallization, the proposed method accepts the formation of nanocrystals and makes use of the lower viscosity of the supercooled liquid when processing above the glass transition temperature. Following this approach, Ti40Zr10Cu34Pd14Sn2 BMG is deformed from a rod to a thin disk, and patterns scaling from 5 μm to 300 μm are successfully created on the Ti-BMG surfaces, demonstrating the potential to create complex features for functional materials. Furthermore, after the thermoplastic net-shaping treatment, the Vickers hardness increases by 6% while the corrosion and passivation current density decrease by an order of magnitude. This work reveals that the BMGs can still be deformed and patterned via the thermoplastic net-shaping technique if the first crystallization event of the BMG systems is the formation of nanocrystals. Most importantly, this work reveals the possibility of processing a broad family of mediocre glass-forming systems and semi-crystalline composites via thermoplastic net-shaping.

Assessment of droplet self-shaping and crystallization during temperature fluctuations exceeding the melting temperature of the dispersed phase

Oil-in-water emulsions with crystalline dispersed phase are widely used formulations in life sciences. Ideally, during cooling each droplet crystallizes in its original size and shape set by chosen process parameters. Recently it was shown, that droplets may spontaneously break their shape symmetry crystallizing in non-spherical shape, which strongly depends on the surfactant molecular structure and cooling profile. In this contribution, we focus on the assessment of droplet self-shaping, crystallization and melting behavior during repeated cooling and heating cycles, and the influence of small changes in the temperature-time profile on these processes. These temperature cycles are typical conditions to which crystalline dispersions are subjected during storage and transport. Shape changes and crystallization of n-hexadecane droplets stabilized with the surfactants Brij® S20 and Tween® 60 were investigated by means of a thermo-optical method. In both model systems, self-shaping was observed during the first cooling cycle. Subsequent melting of particles led to the breakup of droplets into smaller, sub-micrometer droplets due to self-emulsification. When a second cooling step followed directly after melting at 20 and 22 °C, spontaneous self-shaping was again observed for n-hexadecane droplets stabilized with Brij® S20, while droplets stabilized with Tween® 60 crystallized in spherical shape. However, these samples showed self-shaping of droplets, when given longer times at 22 °C (incubation of 1 h) or being heated to the bulk Tween® 60 melting temperature (∼ 24 °C) before the second cooling step. During cooling of pure 1 wt% Tween® 60 solutions, crystal precipitation was observed to a great extent. Thus, the concentration of free surfactant molecules drops and may be too low to induce self-shaping of droplets. In 1 wt% Brij® S20 solutions, crystal precipitation was much less pronounced, probably leaving enough free molecules to induce self-shaping. In the case of Tween® 60, enough time after reheating and/or a high enough temperature is needed to melt the surfactant crystal precipitates and re-disperse the molecules to provide enough surfactants at the oil-water-interface for self-shaping during the second cooling scan. These results show, that the droplet crystallization and self-shaping behavior can greatly vary between different formulations, even when the surfactants are very similar in their molecular structure. Additionally, small changes in the temperature-time profile in the formulations’ lifetime have a distinctive influence on resulting particle size and morphology. The melting behavior of the dispersed phase, and crystallization and melting events of surfactants may have a distinctive influence on the particle size and morphology, and thus dispersion characteristics.

GeoBioMed perspectives on kidney stone recurrence from the reactive surface area of SWL-derived particles

Shock wave lithotripsy (SWL) is an effective and commonly applied clinical treatment for human kidney stones. Yet the success of SWL is counterbalanced by the risk of retained fragments causing recurrent stone formation, which may require retreatment. This study has applied GeoBioMed experimental and analytical approaches to determine the size frequency distribution, fracture patterns, and reactive surface area of SWL-derived particles within the context of their original crystal growth structure (crystalline architecture) as revealed by confocal autofluorescence (CAF) and super-resolution autofluorescence (SRAF) microscopy. Multiple calcium oxalate (CaOx) stones were removed from a Mayo Clinic patient using standard percutaneous nephrolithotomy (PCNL) and shock pulse lithotripsy (SPL). This produced approximately 4–12 mm-diameter PCNL-derived fragments that were experimentally treated ex vivo with SWL to form hundreds of smaller particles. Fractures propagated through the crystalline architecture of PCNL-derived fragments in a variety of geometric orientations to form rectangular, pointed, concentrically spalled, and irregular SWL-derived particles. Size frequency distributions ranged from fine silt (4–8 μm) to very fine pebbles (2–4 mm), according to the Wentworth grain size scale, with a mean size of fine sand (125–250 μm). Importantly, these SWL-derived particles are smaller than the 3–4 mm-diameter detection limit of clinical computed tomography (CT) techniques and can be retained on internal kidney membrane surfaces. This creates clinically undetectable crystallization seed points with extremely high reactive surface areas, which dramatically enhance the multiple events of crystallization and dissolution (diagenetic phase transitions) that may lead to the high rates of CaOx kidney stone recurrence after SWL treatment.