Showing papers on "Crystal growth published in 2017"
TL;DR: The coercivity of cube-like Fe3O4 NPs increased to a maximum of 190 Oe at the critical size, which suggests strong exchange interactions during spin alignment, and sphere-like NPs have lower magnetic coercivity and remanence values, which is caused by the different orientations of their polycrystalline structure.
Abstract: Highly crystalline single-domain magnetite Fe3O4 nanoparticles (NPs) are important, not only for fundamental understanding of magnetic behaviour, but also for their considerable potential applications in biomedicine and industry. Fe3O4 NPs with sizes of 10–300 nm were systematically investigated to reveal the fundamental relationship between the crystal domain structure and the magnetic properties. The examined Fe3O4 NPs were prepared under well-controlled crystal growth conditions using a large-scale liquid precipitation method. The crystallite size of cube-like NPs estimated from X-ray diffraction pattern increased linearly as the particle size (estimated by transmission electron microscopy) increased from 10 to 64.7 nm, which indicates that the NPs have a single-domain structure. This was further confirmed by the uniform lattice fringes. The critical size of approximately 76 nm was obtained by correlating particle size with both crystallite size and magnetic coercivity; this was reported for the first time in this study. The coercivity of cube-like Fe3O4 NPs increased to a maximum of 190 Oe at the critical size, which suggests strong exchange interactions during spin alignment. Compared with cube-like NPs, sphere-like NPs have lower magnetic coercivity and remanence values, which is caused by the different orientations of their polycrystalline structure.
426 citations
TL;DR: A dopant compensation in alloyed OIHP single crystals is reported to overcome limitations of device noise and charge collection, enabling γ-ray spectrum collection at room temperature.
Abstract: Organic–inorganic halide perovskites (OIHPs) bring an unprecedented opportunity for radiation detection with their defect-tolerance nature, large mobility–lifetime product, and simple crystal growth from solution. Here we report a dopant compensation in alloyed OIHP single crystals to overcome limitations of device noise and charge collection, enabling γ-ray spectrum collection at room temperature. CH3NH3PbBr3 and CH3NH3PbCl3 are found to be p-type and n-type doped, respectively, whereas dopant-compensated CH3NH3PbBr2.94Cl0.06 alloy has over tenfold improved bulk resistivity of 3.6 × 109 Ω cm. Alloying also increases the hole mobility to 560 cm2 V−1 s−1, yielding a high mobility–lifetime product of 1.8 × 10−2 cm2 V−1. The use of a guard ring electrode in the detector reduces the crystal surface leakage current and device dark current. A distinguishable 137Cs energy spectrum with comparable or better resolution than standard scintillator detectors is collected under a small electric field of 1.8 V mm−1 at room temperature. Hybrid organic–inorganic perovskite single crystals with optimized combination of Cl and Br ions are used to fabricate γ-ray detectors operating at room temperature and competing with the performance of sodium iodide scintillators.
426 citations
TL;DR: It is shown that utilizing the below-bandgap absorption of perovskite single crystals can narrow down their effective optical bandgap without changing the composition, resulting in an efficiency of 17.8% for single crystal perovSKite solar cells.
Abstract: The efficiency of perovskite solar cells has surged in the past few years, while the bandgaps of current perovskite materials for record efficiencies are much larger than the optimal value, which makes the efficiency far lower than the Shockley-Queisser efficiency limit. Here we show that utilizing the below-bandgap absorption of perovskite single crystals can narrow down their effective optical bandgap without changing the composition. Thin methylammonium lead triiodide single crystals with tuned thickness of tens of micrometers are directly grown on hole-transport-layer covered substrates by a hydrophobic interface confined lateral crystal growth method. The spectral response of the methylammonium lead triiodide single crystal solar cells is extended to 820 nm, 20 nm broader than the corresponding polycrystalline thin-film solar cells. The open-circuit voltage and fill factor are not sacrificed, resulting in an efficiency of 17.8% for single crystal perovskite solar cells.
415 citations
TL;DR: In this article, the design and hydrothermal crystal growth of double perovskite Cs2AgInCl6 was investigated in detail, including crystal structure, morphology related to the crystal growth habit, band structure, optical properties, and stability.
Abstract: The discovery of lead-free double perovskites provides a feasible way of searching for air-stable and environmentally benign solar cell absorbers. Herein we report the design and hydrothermal crystal growth of double perovskite Cs2AgInCl6. The crystal structure, morphology related to the crystal growth habit, band structure, optical properties, and stability are investigated in detail. This perovskite crystallized in a cubic unit cell with the space group Fm3m and is composed of [AgCl6] and [InCl6] octahedra alternating in a ordered rock-salt structure, and the as-obtained crystal size is dependent on the hydrothermal reaction time. Cs2AgInCl6 is a direct gap semiconductor with a wide band gap of 3.23 eV obtained experimentally and 3.33 eV obtained by DFT calculation. This theoretically predicted and experimentally confirmed optical gap is a prototype of the band gaps that are direct and optically allowed except at the single high-symmetry k-point, which didn't raise interest before but have potential applications in future technologies. Cs2AgInCl6 material with excellent moisture, light and heat stability shows great potential for photovoltaic and other optoelectronic applications via further band gap engineering.
274 citations
TL;DR: This work reports a one-step approach that exploits heteroepitaxial growth for the rapid fabrication of oriented polycrystalline MOF films on the centimetre scale and demonstrates that an anisotropic crystalline morphology can translate to a functional property.
Abstract: Heteroepitaxial growth using aligned crystalline substrates allows extended metal–organic framework crystal growth oriented relative to the substrate
252 citations
TL;DR: Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show that the CsPbBr3 epitaxial thin film has a slow charge carrier recombination rate, low surface recombination velocity, and low defect density of 1012 cm-3, which are comparable to those of cesium lead bromide perovskite single crystals.
Abstract: High-quality metal halide perovskite single crystals have low defect densities and excellent photophysical properties, yet thin films are the most sought after material geometry for optoelectronic devices. Perovskite single-crystal thin films (SCTFs) would be highly desirable for high-performance devices, but their growth remains challenging, particularly for inorganic metal halide perovskites. Herein, we report the facile vapor-phase epitaxial growth of cesium lead bromide perovskite (CsPbBr3) continuous SCTFs with controllable micrometer thickness, as well as nanoplate arrays, on traditional oxide perovskite SrTiO3(100) substrates. Heteroepitaxial single-crystal growth is enabled by the serendipitous incommensurate lattice match between these two perovskites, and overcoming the limitation of island-forming Volmer–Weber crystal growth is critical for growing large-area continuous thin films. Time-resolved photoluminescence, transient reflection spectroscopy, and electrical transport measurements show tha...
191 citations
TL;DR: A combined experimental and computational investigation on the precipitation of CaCO3 in dilute aqueous solutions shows that all steps in this process can be explained according to classical concepts of crystal nucleation and growth, and that long-standing physical concepts of nucleation can describe multistep, multiphase growth mechanisms.
Abstract: Understanding and controlling nucleation is important for many crystallization applications. Calcium carbonate (CaCO3) is often used as a model system to investigate nucleation mechanisms. Despite its great importance in geology, biology, and many industrial applications, CaCO3 nucleation is still a topic of intense discussion, with new pathways for its growth from ions in solution proposed in recent years. These new pathways include the so-called nonclassical nucleation mechanism via the assembly of thermodynamically stable prenucleation clusters, as well as the formation of a dense liquid precursor phase via liquid–liquid phase separation. Here, we present results from a combined experimental and computational investigation on the precipitation of CaCO3 in dilute aqueous solutions. We propose that a dense liquid phase (containing 4–7 H2O per CaCO3 unit) forms in supersaturated solutions through the association of ions and ion pairs without significant participation of larger ion clusters. This liquid acts as the precursor for the formation of solid CaCO3 in the form of vaterite, which grows via a net transfer of ions from solution according to z Ca2+ + z CO32− → z CaCO3. The results show that all steps in this process can be explained according to classical concepts of crystal nucleation and growth, and that long-standing physical concepts of nucleation can describe multistep, multiphase growth mechanisms.
166 citations
TL;DR: In this paper, the formation process for the regular decahedron BiVO4 crystals prepared by a convenient hydrothermal method was investigated, and the phase was transformed from tetragonal zircon type to monoclinic sheelite type.
Abstract: Precise control of the morphology and crystalline structure of semiconductor-based photocatalyst is crucial for improving the efficiency of solar energy conversion system. In this work, taking BiVO4 semiconductor photocatalyst as an example, we investigated the formation process for the regular decahedron BiVO4 crystals prepared by a convenient hydrothermal method and found that the synthesis is undergoing a dissolution–recrystallization process, concomitantly, the phase was transformed from tetragonal zircon type to monoclinic sheelite-type. By controlling the kinetics of crystal growth for BiVO4 through regulating acidity of the reaction solution, we rationally tune the morphology of monoclinic BiVO4 from regular decahedron crystals to short rod-like particles, particularly precisely modulate the proportion of {010}/{011} facets for the decahedron BiVO4. By tuning the crystalline phase and morphologies of BiVO4 crystal, we found that the photocatalytic water oxidation activity for the well-defined BiVO4...
147 citations
TL;DR: A facile roll-printing method based on transfer of a perovskite ink solution via a patterned rolling mould to a heated substrate, where the solution crystallizes instantly with the immediate evaporation of the solvent, for the fabrication of large-scale, single-crystal CH3NH3PbI3 perovkite thin films.
Abstract: We report a facile roll-printing method, geometrically confined lateral crystal growth, for the fabrication of large-scale, single-crystal CH3NH3PbI3 perovskite thin films. Geometrically confined lateral crystal growth is based on transfer of a perovskite ink solution via a patterned rolling mould to a heated substrate, where the solution crystallizes instantly with the immediate evaporation of the solvent. The striking feature of this method is that the instant crystallization of the feeding solution under geometrical confinement leads to the unidirectional lateral growth of single-crystal perovskites. Here, we fabricated single-crystal perovskites in the form of a patterned thin film (3 × 3 inch) with a high carrier mobility of 45.64 cm2 V−1 s−1. We also used these single-crystal perovskite thin films to construct solar cells with a lateral configuration. Their active-area power conversion efficiency shows a highest value of 4.83%, which exceeds the literature efficiency values of lateral perovskite solar cells. Wafer-scale deposition of uniform metal halide perovskite single-crystals is a step towards commercialisation. Using geometrically-confined lateral crystal growth, Leeet al., report patterned thin films of highly-aligned single-crystals and achieve lateral solar cells with efficiencies up to 4.83%.
146 citations
TL;DR: In this paper, the authors examine the underlying physical processes that determine growth rates and structure formation of ice crystals from liquid water and from water vapor, focusing on the underlying molecular attachment kinetics on faceted surfaces and large scale diffusion processes.
Abstract: We examine ice crystallization from liquid water and from water vapor, focusing on the underlying physical processes that determine growth rates and structure formation. Ice crystal growth is largely controlled by a combination of molecular attachment kinetics on faceted surfaces and large-scale diffusion processes, yielding a remarkably rich phenomenology of solidification behaviors under different conditions. Layer nucleation plays an especially important role, with nucleation rates determined primarily by step energies on faceted ice/water and ice/vapor interfaces. The measured step energies depend strongly on temperature and other factors, and it appears promising that molecular dynamics simulations could soon be used in conjunction with experiments to better understand the energetics of these terrace steps. On larger scales, computational techniques have recently demonstrated the ability to accurately model the diffusion-limited growth of complex structures that are both faceted and branched. Together with proper boundary conditions determined by surface attachment kinetics, this opens a path to fully reproducing the variety of complex structures that commonly arise during ice crystal growth.
118 citations
TL;DR: In this article, the NH4PbI3-based phase transformation is realized by simply adding NH4I additive, in order to simultaneously control perovskite nucleation and crystal growth.
Abstract: The NH4PbI3-based phase transformation is realized by simply adding NH4I additive, in order to simultaneously control perovskite nucleation and crystal growth. Regarding the nucleation process, the NH4+ with small ionic radius preferentially diffuses into the [PbI6]4− octahedral layer to form NH4PbI3, which compensates the lack of CH3NH3I (MAI) precipitation. The generation of NH4PbI3 intermediate phase results in extra heterogeneous nucleation sites and reduces the defects derived from the absence of MA+. Regarding the crystal growth process, the cation exchange process between MA+ and NH4+, instead of the MAs directly entering, successfully retards the crystal growth. Such NH4PbI3 consumption process slows down the crystal growth, which effectively improves the perovskite quality with lowered defect density. The cooperation of these two effects eventually leads to the high-quality perovskite with enlarged grain size, prolonged photoluminescence lifetime, lowered defect density, and increased carrier concentration, as well as the finally enhanced photovoltaic performance. Moreover, NH3 as a byproduct further facilitates the proposed transformation process and no external residue remains even without any post-treatment. Such methodology of introducing a novel phase transformation to simultaneously control nucleation and crystal growth processes is of universal significance for further devotion in the foreseeable perovskite solar cells (PSCs) evolution.
TL;DR: In this article, a bulk β-Ga2O3 single crystal with a width of 1 inch was grown by using an optimized edge-defined film-fed growth (EFG) method under Ar plus 50% CO2 atmosphere.
TL;DR: In this paper, 2-pyridylthiourea can not only promote the conversion of 2-D PbI2 to tetragonal CH3NH3PbI3 crystals, but also improve the quality of the perovskite absorber layer via enhancing the uniformity and the size of the crystal grains.
Abstract: Here, we report a rapid and simple process to prepare perovskite solar cells in ambient air by adding 2-pyridylthiourea in the precursor solution. 2-Pyridylthiourea can not only promote the conversion of 2-D PbI2 to tetragonal CH3NH3PbI3 crystals, but also improve the quality of the perovskite absorber layer via enhancing the uniformity and the size of the crystal grains. The perovskite solar cells with the addition of 2-pyridylthiourea at a concentration of 0.5 mg mL−1 exhibited a remarkable overall power conversion efficiency (PCE) of 18.2%, which is among the highest PCE of CH3NH3PbI3-based devices fabricated in ambient air. It also showed an 18% increase and less hysteresis compared with the cells without additives. Importantly, the devices with 2-pyridylthiourea show relatively better stability compared to reference devices when aged under ambient air of 55 ± 5% relative humidity in the dark and under 65 °C after 30 days. The presented results clearly show that 2-pyridylthiourea can be an additive candidate for tuning the morphology of perovskite thin films, which may be a new direction for large-scale production of PSCs.
TL;DR: Experimental findings on homogeneous crystal nucleation in polymers are summarized, showing that polymer nucleation is homogeneous at such temperatures as near and even below the glass transition temperature.
Abstract: The pathway of crystal nucleation significantly influences the structure and properties of semi-crystalline polymers. Crystal nucleation is normally heterogeneous at low supercooling, and homogeneous at high supercooling, of the polymer melt. Homogeneous nucleation in bulk polymers has been, so far, hardly accessible experimentally, and was even doubted to occur at all. This topical review summarizes experimental findings on homogeneous crystal nucleation in polymers. Recently developed fast scanning calorimetry, with cooling and heating rates up to 106 K s-1, allows for detailed investigations of nucleation near and even below the glass transition temperature, including analysis of nuclei stability. As for other materials, the maximum homogeneous nucleation rate for polymers is located close to the glass transition temperature. In the experiments discussed here, it is shown that polymer nucleation is homogeneous at such temperatures. Homogeneous nucleation in polymers is discussed in the framework of the classical nucleation theory. The majority of our observations are consistent with the theory. The discrepancies may guide further research, particularly experiments to progress theoretical development. Progress in the understanding of homogeneous nucleation is much needed, since most of the modelling approaches dealing with polymer crystallization exclusively consider homogeneous nucleation. This is also the basis for advancing theoretical approaches to the much more complex phenomena governing heterogeneous nucleation.
TL;DR: A general approach to understanding and, in theory, predicting the growth of a wide range of crystal types, including the incorporation of defect structures, by simultaneous molecular-scale simulation of crystal habit and surface topology using a unified kinetic three-dimensional partition model.
Abstract: A general simulation approach that can replicate, and in theory predict, the growth of a wide range of crystal types, including porous, molecular and ionic crystals, is demonstrated. Understanding crystal growth is essential for controlling functionality in modern materials. Michael Anderson et al. describe a simulation approach to predicting crystal growth that can replicate, and in theory predict, the fine details of surface structure and habit for a wide range of crystal types, including porous crystalline materials, metal–organic frameworks and ionic crystals. The method is based on Monte Carlo simulations of 'units of growth'—space-filling tiles or Voronoi polyhedra, depending on the nature of the crystal. This is a coarse-grained alternative to the computationally intensive and sometimes intractable problem of simulating individual atomic positions. The approach replicates the surface structure of experimentally grown crystals that incorporate growth modifiers or common defects, and those grown out of equilibrium, and could be applicable across a variety of crystal systems, the authors say. Understanding and predicting crystal growth is fundamental to the control of functionality in modern materials. Despite investigations for more than one hundred years1,2,3,4,5, it is only recently that the molecular intricacies of these processes have been revealed by scanning probe microscopy6,7,8. To organize and understand this large amount of new information, new rules for crystal growth need to be developed and tested. However, because of the complexity and variety of different crystal systems, attempts to understand crystal growth in detail have so far relied on developing models that are usually applicable to only one system9,10,11. Such models cannot be used to achieve the wide scope of understanding that is required to create a unified model across crystal types and crystal structures. Here we describe a general approach to understanding and, in theory, predicting the growth of a wide range of crystal types, including the incorporation of defect structures, by simultaneous molecular-scale simulation of crystal habit and surface topology using a unified kinetic three-dimensional partition model. This entails dividing the structure into ‘natural tiles’ or Voronoi polyhedra that are metastable and, consequently, temporally persistent. As such, these units are then suitable for re-construction of the crystal via a Monte Carlo algorithm. We demonstrate our approach by predicting the crystal growth of a diverse set of crystal types, including zeolites, metal–organic frameworks, calcite, urea and l-cystine.
TL;DR: In this paper, the quiescent crystallization behaviors of three PLA grades were studied with polarized optical microscopy and small-angle light-scattering experiments, and two growth rate regimes, which were attributed to α and α′ crystallization with a transition around 120 °C, were observed.
Abstract: The crystallization behavior of poly(lactic acid) (PLA) has been studied extensively, and this has resulted in different reported values for the nucleation densities (Ns) and crystal growth rates (Gs) for similar grades. These inconsistencies may be magnified when they are used in subsequent modeling studies. Therefore, the quiescent crystallization behaviors of three PLA grades were studied with polarized optical microscopy and small-angle light-scattering experiments. The Gs and Ns were determined at several isothermal crystallization temperatures with a device that provided near-instantaneous cooling to the isothermal crystallization temperature. Two growth rate regimes, which were attributed to α and α′ crystallization with a transition around 120 °C, were observed. Avrami analysis revealed that the poly(l-lactic acid) homopolymer crystal growth was three-dimensional and was unaffected by the presence of stereocomplex PLA. The PLA copolymer crystals had a transition from an initial sheaflike conformation to three-dimensional growth. Furthermore, the lamellar twisting of the homopolymer was observed at the isothermal crystallization temperature around 144 °C. These findings can be used for future modeling studies to predict material behavior in various industrial processes. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44566.
TL;DR: Using a typical SLM condition and Co-Cr-Mo alloys, microstructures of tracks were characterized in this paper, where epitaxial growth has been found to have two possible crystallographic orientations of : either a continuation of the same orientation as in previous track or a change of 90° to another orientation.
Abstract: Modes of solidification during selective laser melting (SLM) of metallic alloys, including Co–Cr–Mo alloy, are still not fully understood. This understanding is important in SLM to achieve acceptable properties and part reliability. Using a typical SLM condition and Co–Cr–Mo alloys, microstructures of tracks were characterized in this study. As is commonly observed, solidification starts from epitaxial growth in the boundary of melt track. Cells were found to grow immediately from the melt boundary, without forming a planar zone. This is explained by the growth velocity being sufficiently high that planar growth condition is not favorable. Epitaxial growth has been found to have two possible crystallographic orientations of : either a continuation of the same orientation as in previous track or a change of 90° to another orientation. The selection is in response to scan direction-dependent heat flux direction. The crystal growth direction in relation to heat flux direction also explains that a grain (a group of cells) after epitaxial growth could either stop or continue to the track surface. No equiaxed grains were observed, and this can be explained by the continuation of cellular growth in the whole track.
TL;DR: In this article, the growth mechanisms of primary Cu6Sn5 are studied in Sn-Cu alloys and solder joints by combining EBSD, FIB-tomography and synchrotron radiography.
TL;DR: It is reported that citric acid (CA) and chloride anion, working together, modulate crystal growth of CH3NH3PbI3, producing sub-mm-sized cuboid crystals-a morphology more suitable for close packing in a thin film than the commonly observed elongated dodecahedral morphology.
Abstract: Solar cells made of lead perovskite crystals have attracted much attention for their high performance, but far less attention as a subject of crystal engineering. Here, we report that citric acid (CA) and chloride anion, working together, modulate crystal growth of CH3NH3PbI3, producing sub-mm-sized cuboid crystals—a morphology more suitable for close packing in a thin film than the commonly observed elongated dodecahedral morphology. By using a 15 wt % CA-doped precursor solution, we formed a single layer of large, flat, and oriented cuboid crystals with minimum crystal domain boundaries and maximum contact with neighboring layers, and fabricated an archetypal inverted-structured device of 4 mm2 area, which showed, reproducibly and with little hysteresis, 16.75% power conversion efficiency (PCE), 26% higher than the PCE obtained for a polycrystalline film made without CA doping. Under weaker irradiation of a 1 cm2 device, the PCE improved from 14.52% (one sun) to 20.4% (0.087 suns). Under illumination wi...
TL;DR: In this article, the authors reported a highly anisotropic proton-conductive 2D metal-organic framework (MOF) with definite crystal structures showing single-crystal transformation between the anhydrate and trihydrate (1·3H2O) phases, where hydrogen bonded chains consisted of well defined lattice water molecules and hydroxyl functional groups of the Htzehp2-ligand array inside the 2D interlayer spaces along the crystallographic a-axis.
Abstract: Proton conductivity research on single crystals is essential to elucidate their conduction mechanism and guide the unidirectional crystal growth to improve the performance of electrolyte materials. Herein, we report a highly anisotropic proton-conductive 2D metal–organic framework (MOF) [Cu2(Htzehp)2(4,4′-bipy)]·3H2O (1·3H2O, H3tzehp = N-[2-(1H-tetrazol-5-yl)ethyl]-l-hydroxyproline) with definite crystal structures showing single-crystal to single-crystal transformation between the anhydrate (1) and trihydrate (1·3H2O) phases. The hydrogen bonded chains consisted of well-defined lattice water molecules and hydroxyl functional groups of the Htzehp2– ligand array inside the 2D interlayer spaces along the crystallographic a-axis ([100] direction) in 1·3H2O. Temperature- and humidity-dependent proton conductivity was achieved along the [100] and [010] directions, respectively. The anisotropic proton conductivity of σ[100]/σ[010] in a single crystal of 1·3H2O was as high as 2 orders of magnitude. The highest p...
TL;DR: In this article, antimony telluride (Sb2Te3) thin films were directly deposited on polyimide substrate and the crystalline structures and morphologies of the thin films are analyzed, and the mechanism of crystal growth influenced by sputtering pressure was discussed.
TL;DR: This study investigates the low-temperature solid-phase crystallization (SPC) of Ge on a glass substrate, focusing on the precursor conditions, to form SPC-Ge with a hole mobility of 340 cm2/Vs, the highest value among semiconductor thin films grown on insulators at low temperature (<900 °C).
Abstract: High-carrier mobility semiconductors on insulators are essential for fabricating advanced thin-film transistors, allowing for three-dimensional integrated circuits or high-performance mobile terminals. We investigate the low-temperature (375–450 °C) solid-phase crystallization (SPC) of Ge on a glass substrate, focusing on the precursor conditions. The substrate temperature during the precursor deposition, T
d, ranged from 50 to 200 °C. According to the atomic density of the precursor and the T
d dependent SPC properties, the precursor conditions were determined by three regimes: the low-density regime (T
d < 100 °C), high-density regime (100 ≤ T
d ≤ 125 °C), and nucleation regime (T
d > 125 °C). The use of the precursor in the narrow high-density regime enabled us to form SPC-Ge with a hole mobility of 340 cm2/Vs, the highest value among semiconductor thin films grown on insulators at low temperature (<900 °C). The origins of the high hole mobility were determined to be both a large grain size (5 µm) and a low energy barrier height (6.4 meV) for the grain boundary. The findings from and knowledge gained in this study, that is, the influence of the precursor conditions on subsequent crystal growth, will be universal and applicable to various materials.
TL;DR: In this paper, a simple expression of macroscopic crystallization stress (MCS), depending on the microscopic crystallization pressure and the amount of precipitated crystal, was presented and the model was calibrated through experimental study on the deformation behavior of soil combined with phase change during freezing.
TL;DR: A promising approach of using pristine and modified CNCs to control the crystallization of biodegradable aliphatic polyesters is offered, indicating that nucleation is dominant during PHB crystallization, instead of crystal growth.
TL;DR: A class of one-dimensional hollow microstructure is described, which was formed by a kinetically controlled crystal growth process and which modulates light intensity across the microrods as a result of interference arising from light scattering and reflection by the inner walls.
Abstract: A class of one-dimensional hollow microstructure is described, which was formed by a kinetically controlled crystal growth process. A hexagonal-phase NaYbF4 microrod comprising isolated holes along the longitudinal axis was synthesized by a one-pot hydrothermal method with the assistance of citrate ligands. The structural void feature modulates light intensity across the microrods as a result of interference arising from light scattering and reflection by the inner walls. A single crystal comprising a structural void was doped with upconverting lanthanide ions. Upon near-infrared excitation of the doped crystal spatially resolvable optical codes were produced.
TL;DR: In this article, the organic single crystal of piperazinium bis(4-hydroxybenzenesulphonate) (P4HBS) was grown by slow evaporation solution (SEST) at room temperature.
TL;DR: The crystal size was found to significantly affect the switching characteristics, in particular the gate opening pressure in nitrogen adsorption isotherms at 77 K for this highly porous and flexible network.
Abstract: Controlled nucleation in a micromixer and further crystal growth were used to synthesize Ni2(2,6-ndc)2dabco (2,6-ndc – 2,6-naphthalenedicarboxylate, dabco – 1,4-diazabicyclo[2.2.2]octane), also termed DUT-8(Ni) (DUT = Dresden University of Technology), with narrow particle size distribution in a range of a few nm to several μm. The crystal size was found to significantly affect the switching characteristics, in particular the gate opening pressure in nitrogen adsorption isotherms at 77 K for this highly porous and flexible network. Below a critical size of about 500 nm, a type Ia isotherm typical of rigid MOFs is observed, while above approximately 1000 nm a pronounced gating behaviour is detected, starting at p/p0 = 0.2. With increasing crystal size this transition gate becomes steeper indicating a more uniform distribution of activation energies within the crystal ensemble. At an intermediate size (500–1000 nm), the DUT-8(Ni) crystals close during activation but cannot be reopened by nitrogen at 77 K possibly indicating monodomain switching.
TL;DR: In this paper, the effects of molar mass and optical purity on the kinetics of primary crystal nucleation and growth of poly(l-lactic acid are discussed, as well as the relationship between the conditions of melt solidification and the crystallization process.
Abstract: Prediction of the supermolecular structure and properties of poly(l-lactic acid) requires in-depth knowledge of the relation between the conditions of melt solidification and the crystallization process. Crystallization involves primary crystal nucleation, which then is followed by crystal growth. Both processes require chain segment mobility at different length scales, and exhibit different temperature and cooling-rate dependencies, as described in this review. Following an introduction to polymer crystallization and general information about crystallization of poly(l-lactic acid), data are presented on the kinetics of primary crystal nucleation, covering a wide range of temperatures. Crystal nuclei formation in the glassy state requires completion of the glass relaxation process, as shown by enthalpy relaxation experiments. Discussion of the nucleation behavior is then followed by information about crystal growth rates, which reveal a bimodal temperature dependence as a result of the specific α′/α-crystal polymorphism. Throughout this review, the effects of molar mass and optical purity on the kinetics of nucleation and growth of crystals are discussed.
TL;DR: In this paper, a series of nonpolar antisolvents (chlorobenzene, bromobenzenene, iodobenzenes and toluene) were used to assist in the formation of smooth and crystalline CH3NH3PbI3 thin films by a one-step spin-coating method.
TL;DR: In this article, a hydroxide co-precipitation method was used to synthesize transition metal hydroxides (Ni1/3Co 1/3Mn1/ 3Mn/3(OH)2), which is the precursor for layer-structured LiNi1.