Amorphous Crystallization Research Articles

Critical point of jamming transition in two-dimensional monodisperse systems.

The existence of amorphous packings in two-dimensional monodisperse system is a classical unsolved problem. We get the energy minimum state by the energy minimization method of enthalpy under constant pressure conditions. Firstly, we find that there are two peaks in the experiment, which demonstrate the interesting features of the coexistence of crystals and amorphous crystals. And then, we confirm the critical point of jamming transition of the two-dimensional monodisperse is [Formula: see text]. Finally, we prove that the jamming scaling is still satisfied in two-dimensional monodispersed system: [Formula: see text] and vanishes as [Formula: see text], and the boson peak shifts to lower frequencies for less compressed systems.

Thermal behavior of PLA plasticized by commercial and cardanol-derived plasticizers and the effect on the mechanical properties

This paper is aimed at studying the thermal properties of poly(lactic acid), PLA with different plasticizers. Plasticized PLA was obtained by mixing and extruding PLA with 20 mass% of neat cardanol, epoxidized cardanol acetate (ECA) and poly(ethylene glycol) (PEG) 400. The glass transition of completely amorphous samples, melting and crystallization behavior of plasticized PLA were analyzed by differential scanning calorimetry. Results obtained show that, below Tg, a higher enthalpy relaxation occurs for PLA plasticized by cardanol derivatives. This is indicative of a faster mobility of PLA chains below Tg, when cardanol derivatives are used as plasticizers. On the other hand, an opposite behavior was observed for the crystallization studies. In facts, a much faster crystallization was found for PLA plasticized by PEG, which in turn indicates a much higher mobility of PLA chains above Tg compared to PLA plasticized by cardanol derivatives. Mechanical properties obtained on completely amorphous samples show that PLA plasticized by ECA is characterized by lower modulus, which is indicative of a more efficient plasticization. On the other hand, the thicker crystals formed during crystallization of PLA plasticized by ECA involve a more relevant increase in the modulus in semicrystalline samples.

Rapid fabrication of large-scale structurally colored PS@SiO2 films with enhanced self-cleaning capability

Structural colors are widespread in myriads of natural living organisms measuring from tens to hundreds of nanometers. In recent years, amorphous photonic crystal films have received extensive attention due to their stable color rendering properties. However, the internal structure of the films is easy to be contaminated by liquid. Thus, self-cleaning performance has been considered as one of the main obstacles to the practical application of artificial structural colored films. In order to solve the issues, we used heptadecafluoro-1,1,2,2-tetrahydrodacyl trimethoxysilane to modify the structural colored films. The results demonstrated that the modified colored films showed super-hydrophobic (contact angle > 160°) and high oleophobic (contact angle > 150°) properties. The rapid production of water-resistant and oil-resistant structural color coatings by spraying is significant for expanding their application in outdoor conditions (e.g., acid–base, alkali base, pollution) for a long time.

Archaeometry of fire aided limnosilicite mining in the Avas-Tűzköves (Miskolc, NE-Hungary) Paleolithic silica source

ABSTRACT This paper communicates new results on fire aided limnosilicte mining in a Hungarian paleolithic site. The beneficial effect of temperature on material fragmentation and chipping was proved by laboratory experiments, with samples fired at 260°C and 360°C. Mineralogical transformations which lead to fragmentation are triggered by heating and were characterized by analytical methods in detail. The raw material is nanocrystalline quartz dominant silicolite with amorphous silica, moganite and traces of goethite and tridymite, identical to length-fast chalcedony. X-ray diffraction revealed the recrystallization of amorphous silica into quartz, accompanied by H2O loss measured by thermogravimetry. Using attenuated total reflectance Fourier-transformed infrared spectroscopy, both H2O and OH content, their loss by heating and recrystallization was evidenced. Scanning electron microscopy on chipped surfaces revealed the disappearance of the fibrous texture, promoting the knappability of the material. The main factors influencing fire-aided mining and/or processing were identified as H2O pressure, amorphous silica crystallization as a result of H2O and OH removal from the silanol groups and change in quartz crystallite morphology.

Experimental observation of two-stage crystallization of Ge2Sb2Te5 amorphous thin films under the influence of a pulsed laser

The nature of crystallization in telluride based phase change memory materials is being actively discussed, and we present new experimental results on the effect of a pulsed laser treatment on the amorphous thin film crystallization of composition Ge2Sb2Te5 (GST225). It is shown that there are two ways of crystalline phase formation under femtosecond pulses excitation. At the moderate value of laser fluence, crystalline fraction forms inside the solid amorphous phase. This process is apparently two-stage, and this leads to formation of fine-grained polycrystalline material. The second way of crystallization proceeds at higher levels of the laser fluence, closer to the beam axis. In this case, larger grains are produced closer to the beam axis, and eventually no new nuclei can be formed due to high cooling velocity leading to inhibition of nucleation. The article also presents the results on the effect of the substrate type (metallic or oxide) and film thickness on crystallization, which is due to the light penetration depth and reflection from the film-substrate interface.

Remineralization potential of GC Tooth Mousse and GC Tooth Mousse plus on initial caries like lesion of primary Teeth – An in-vitro comparative evaluation

Aim: Teeth are constantly going through cycles of demineralization and remineralization. The ultimate goal of clinical intervention is the preservation of tooth structure and the prevention of lesion progression to the point where restoration is required. Thus promoting remineralization is the ultimate goal of clinical prevention of caries lesion. The present in vitro study aimed to investigate the efficacy of GC Tooth Mousse (CPP-ACP) and GC Tooth Mousse Plus (CPP-ACP)F on artificial enamel caries in primary human teeth.
 
 Methods and Material: Sixty freshly extracted human primary anterior teeth were used in this study.
 The root portion of 60 primary anterior teeth was separated from the crown portion at the cemento-enamel junction (CEJ)
 Teeth samples were divided into 3 Groups (n=20 each). Group 1 as a control group, Group 2 GC Tooth Mousse, and Group 3 Tooth Mousse Plus containing dentifrices were used. Samples were subjected to 10 days of pH cycling protocol.
 The changes were analyzed using Vickers Hardness Testing Machine and SEM.
 
 Pre and post groups were compared by paired t-test. Independent groups were compared by one-way analysis of variance.
 
 Result: 
 Micro-morphological observations of the enamel surfaces with SEM :
 Group 1 the enamel scanning showed shallow depressions and fine porosities within these depressions, Group 2 showed numerous granular particles and amorphous crystals which were arranged on the enamel surface. Smooth, homogeneous surface, and no irregularities were seen in Group 3.
 Surface Microhardness Evaluation
 After treatment, the mean hardness Group III was the highest followed by Group II and Group I (i.e. Group I < Group II < Group III).
 
 Conclusion: GC Tooth Mousse Plus showed a statistically significant amount of remineralization.

Symmetry and Asymmetry in Quasicrystals or Amorphous Materials

Quasicrystals (QCs) are long-range ordered materials with a symmetry incompatible with translation invariance. Accordingly, QCs exhibit high-quality diffraction patterns containing a collection of discrete Bragg reflections. Notwithstanding this, it is still common to read in the recent literature that these materials occupy an intermediate position between amorphous materials and periodic crystals. This misleading terminology can be understood as probably arising from the use of models and notions borrowed from the amorphous solid’s conceptual framework (such us tunneling states, weak interference effects, variable range hopping, or spin glass) in order to explain certain physical properties observed in QCs. On the other hand, the absence of a general, full-fledged theory of quasiperiodic systems certainly makes it difficult to clearly distinguish the features related to short-range order atomic arrangements from those stemming from long-range order correlations.

Ir-oxide mediated surface restructure and corresponding impacts on durability of bimetallic NiOx@Pd nanocatalysts in oxygen reduction reaction

With proper conjunctions between inter/intra-particle domains, the activity and durability of heterogeneous nanocatalysts (NCs) can be substantially improved by more than an order. In this study, tri-metallic NCs comprising an Ir-clusters decorated unconformable Pd-shell over amorphous NiOx core crystal underneath (namely NPI) are developed for oxygen reduction reaction (ORR) in alkaline medium (0.1 M KOH). Results for NPI NCs with different extents of Ir decoration (1 and 14 wt%) are compared for clarifying the configuration effects corresponding to ORR performance. For the optimum case with an Ir loading of ∼1.0 wt%, the mass activity (MA) is 2066.8 mAmg−1. This value is ∼31-folds increased as compared to that of commercial J.M.-Pt/C catalyst (20 wt% Pt) at 0.85 V vs RHE (67.1 mA mg−1). Moreover, as prepared NPI-0025 NC exhibits nearly 100% stability when operated up to 21 k accelerated degradation test (ADT) cycles. By cross-referencing results of physical structure inspections and electrochemical analysis, we reveal that such a high ORR performance could be attributed to the incorporation of Ir atoms in defect sites of Ni–Pd interfaces. These Ir atoms facilitate the O2 splitting by electronegativity differences to the adjacent sites, therefore, improves the ORR performance of NPI NCs.

The compatible performance of three-dimensional SiO2–ZnO amorphous photonic crystals in adjustable structural color and low infrared emissivity

In high temperature environments, most low-emissivity coatings show monotonous and dull colors which make the visible-infrared compatible stealth still challenging. To achieve a wide range of color selection, in this work, three-dimensional (3D) SiO2–ZnO amorphous photonic crystals (APCs) are manufactured by electrodepositing Zn2+ into 3D SiO2 APCs, investigating the compatibility of adjustable structural color and low emissivity. A variety of structural colors could be easily obtained by modulating the diameter of SiO2 nanospheres. In addition, the experimental parameters of spin-coating counts and electrodeposited time are studied to optimize the compatible performance of color and infrared emissivity. The results indicate that the doped ZnO effectively reduces the infrared emissivity in 3–5 μm waveband without changing the structural color of SiO2 APCs. However, excess electrodeposited time of ZnO would cause the structural color faded gradually because of the increased refractive index and destroyed periodical structure. The adequate spin-coating counts is helpful for the bright structural color, but excess spin-coating counts would induce more defects in periodic structure and result in more absorption in 3–5 μm waveband. When the spin-coating counts and electrodeposition content of Zn2+ in the SiO2 APCs are properly modulated in this study, the SiO2–ZnO APCs can exhibit a good compatibility in desired structural color and low infrared emissivity (~0.4), as well as excellent thermal stability. This study provides a new approach for the design of multi-spectrum compatible stealth materials.

Femtosecond Laser Annealing of Multilayer Thin-Film Structures Based on Amorphous Germanium and Silicon

The processes of femtosecond laser annealing of thin-film multilayer structures based on amorphous silicon and germanium produced by plasma-chemical deposition on a glass substrate have been studied. The formation of periodic structures on the surface of irradiated films has been detected by the scanning electron microscopy method. Analysis of Raman spectra has shown that amorphous germanium crystallizes and a mixing of germanium and silicon layers depending on the pulse energy density occurs in the absence of amorphous silicon layers crystallization as a result of exposure to femtosecond laser pulses.

Strain dependent evolution of structure and stress in propylene-based elastomer during stress relaxation

The stress relaxation behaviors of propylene-based elastomer with pure α form were investigated at 30 °C at various pre-stretched strains by means of in situ wide angle X-ray diffraction techniques. The stress decreased rapidly at the beginning of relaxation process and then showed a slow decay independent of pre-stretched strains. This decrease in stress during relaxation was accompanied by an obvious increase in the orientational degree and the crystallinity. However, the processes of increasing the crystallinity depended strongly on the imposed strain. At small strain (εH 0.17), besides the transition of some oriented amorphous phase into oriented crystals, a fraction of unoriented amorphous phase transformed into unoriented crystals. At medium strains (εH 0.76 and 1.28), a fraction of unoriented amorphous and unoriented crystals transformed to oriented crystals. A very small fraction of unoriented amorphous phase transformed into unoriented mesomorphic phase. At large strains (εH 1.63 and 1.85), a fraction of oriented amorphous phase transformed to oriented crystals. The different network with varied fraction of amorphous and crystalline phases accounted for the distinct transformation processes at different pre-stretched strains. Especially at medium strains, the “appropriately stretched” high elastic network was formed so that higher portion of stress remained after the relaxation. Furthermore, it was found that crystallization during stress relaxation provides an alternative route for lowering the macroscopic stress by reducing the effective number of network chain segments in unit volume.

Synthesis of Type A Zeolite from Rice Husk Ash and Its Application as a Builder on Effervescent Tablet Form Detergent

Abstract The application of phosphate compounds as a builder in a detergent formulation created eutrophication that encouraged industry to produce more eco-friendly detergents. To overcome that problem, phosphate can be substituted by zeolit that is more effective in cleaning and also biodegradable. In this study, zeolite was synthesized from rice husk ash using a melting method followed by hydrothermal processes. Effervescent detergent tablets were prepared with the following formulations: 3 formulations containing zeolite (F1–F3), 3 formulations containing sodium tripolyphosphate (STPP: P1–P3) and 1 control formulation. The synthesized zeolit was analysed by XRD (X-Ray Diffraction), FTIR (Fourier-Transform Infrared Spectroscopy), SEM (Scanning Electron Microscopy) and cation exchange capacity (CEC). Furthermore, all detergent formulas were characterized for flowability, compressibility, compatibility, disintegration time, pH, cleaning action and biodegradability. The results of FTIR, XRD and SEM characterization showed that the synthesized zeolite was an amorphous type-A crystal and the predominance of the amorphous phase with a cubic structure and CEC value of 95.71 cmol(+) kg−1. In this study the formulation F1 with 15-% zeolite was found to be the best formulation with granule flow rate parameters of 13.6 g/s, stationary angle of 22.0°, compressibility of 16.6-%, detergent tablet hardness accounted to 0.81 kgf/cm2, crushed time of tablet detergent of 1.5 min, pH 6.7, and biodegradability value of 70.3-% in BOD5 test. A higher concentration of zeolite provided a better cleaning effect of the detergent tablets.

Thermal behavior of complex model with the cellulose II and amorphous chain

To investigate the thermal behavior of complex model with amorphous region and crystallization region of cellulose II, the structures and properties of cellulose II, amorphous chain and their combined models were studied by molecular dynamics simulation. The results showed that the amorphous chain is more susceptible to temperature than the cellulose II. It can form anti-parallel structure similar to cellulose II at high temperature. In the complex model, one end of the amorphous chain is fixed to form hydrogen bonds with the cellulose II, and the other end is not. At 300[Formula: see text]K, the free part of amorphous chain is approximately perpendicular to the axial direction of the cellulose II. When the temperature increases, the free part of amorphous chain adheres to the surface of cellulose II. The free part of amorphous chain did not form hydrogen bond with the cellulose II. The formation of amorphous chain and surface of the cellulose II is a zipper process at 450[Formula: see text]K. Furthermore, water molecules penetrate into the inter-space of the amorphous and crystalline regions. The probability of hydrogen bonds between water molecules and the complex model was less than 8.21% which explains why cellulose is insoluble in water. These conclusions provide a guiding significance for the dissolution mechanism of cellulose.

Effect of Fly Ash Based Geopolymer Reinforced Low Density Polyethylene (LDPE) Composite

Composite is commonly used today attributed to the distinctive characteristics that can be acquired from the mixture of the components in them. However, as time passes on, our globe is heading towards providing green technology for the sector to use environmentally friendly methods. In this study, Fly Ash geopolymer is used as filler, in the production of LDPE / FA composite, to be inserted in a low-density polyethylene matrix. To enhance bonding between the fly ash filler and the LDPE matrix, alkali activator therapy with the use of sodium hydroxide and sodium silicate at the molarity of NaOH is in range of 12M and the ratio for fly ash to alkali activator is about 2.0. In this research properties of these composites are investigate using tensile test, morphology analysis, thermal properties and infrared spectrum analysis, FTIR. The result found that the tensile strength and modulus of elasticity of the composite increased with increasing of filler loading but the percentage of elongation decrease due to filler loading increase while fly ash filler show the interfacial adhesion on LDPE matrix as evidenced by images of scanning electron microscopy (SEM) and this also proved by FTIR spectra explain that LDPE/FA charged with SiO which is fly ash composed with silica. Moreover, thermal properties explain that fly ash interface reaction which can change to amorphous crystallization during the temperature increase.

Highly Efficient Fabricating Amorphous Photonic Crystals Using Less Polar Solvents and the Wettability‐Based Information Storage and Recognition

AbstractFacile and efficient fabrication of amorphous photonic crystals (APCs) with uniform and angle independent structural colors is highly desired due to their unique applications in non‐iridescent colors‐based displays, pigments, and sensors. Here, a solvent‐assisted colloidal assembly approach is reported to fabricate APCs with uniform and angle‐independent structural colors by the self‐assembly of polydopamine‐embedded silica particles in pentanol. The surface charge of the particle mediated by the polarity of solvent is demonstrated to be the key to control the particle arrangements and the angle dependency of the structural colors, which makes the fabrication more efficient, simple, and convenient compared to previous methods. Owing to the amorphous structures, the APCs show unique sensitivity to the variation of the refractive index contrast. Based on this unique sensitivity of APCs, an information storage‐recognition system is established by constructing different wettability between the information and background region. The information integrated with the color, the number, and the site of APCs of the system can be stored and recognized at dry and wetting state, respectively, and the switching of the storage‐recognition process is fully reversible. These findings provide new insights into the design, fabrication, and application of materials with non‐iridescent structural colors.

Two Birds with One Stone: Manipulating Colloids Assembled into Amorphous and Ordered Photonic Crystals and Their Combinations for Coding–Decoding

Photonic crystals, including amorphous and ordered photonic crystals (APCs and OPCs), show wide applications in color displays, sensors, and pigments. The fabrication of APCs and OPCs by one method...

The Interlayer Effects of Nitrogen Implantation in the TiN/N<sub>2</sub>- Film Synthesis on the NAK80 Steel

Nitrogen ions with an energy of 200keV were used for the investigation of the interlayer effects of nitrogen implantation in the TiN/N2-film synthesis on the NAK80 steel. The nitrogen ion plasmas formed a broad ion mixing area at the interface between TiN film and NAK80 substrate. The measured hardness indicates the well mixing of TiN film into the NAK80 substrate, which may have an effect on increasing the adhesion of the deposited film. The chemical components and micro-hardness of the filmed surface were measured. The micro-hardness of Rockwell C-scale (HRC) was increased from 40 to 61 after the films of TiN/N2 were synthesized on the NAK80 substrate, the increased micro-hardness is attributed to the metallurgical phase change and formation of amorphous crystal due to the nitrogen implantation.

Unraveling the effects of linker substitution on structural, electronic and optical properties of amorphous zeolitic imidazolate frameworks-62 (a-ZIF-62) glasses: a DFT study

Zeolitic imidazolate frameworks (ZIFs), as one sub-family of metal–organic frameworks (MOFs), are a new class of glass formers. Among them, one termed as ZIF-62 [Zn(Im)2−x(bIm)x], has great glass-forming ability compared with other ZIFs. Yet very few reports provide us with information about this glass from the computational point of view. In order to explore and have a deeper understanding of the effects of mixing organic ligands on the fundamental properties, we systematically investigate the electronic, intrinsic bonding and optical properties of amorphous ZIF-62 (a-ZIF-62) glass with density functional theory (DFT) calculation. Here we construct six amorphous ZIF-62 (a-ZIF-62) models with the ratio of bIm/(Im + bIm) ranging from 0 to 33.5%. These models are constructed based on a near perfect continuous random network model with over one thousand atoms originated from silica glass. They all keep a short range order but lack a long range order. As the concentration of bIm increases, our results show that the internal cohesion of a-ZIF-62 increases, indicating a strong network connectivity. Especially, for the first time we reveal that an obvious mid-band emerges in the conduction band due to the addition of bIm ligands. This further leads to alternation in the dielectric function. The calculated refractive index increases with an increase in the content of bIm ligands, which agrees well with the experimental results. The present results help us have a deeper understanding of the linker ratio effects on the various properties of amorphous ZIF glass and shed light on other ways to tune the properties of amorphous ZIF glass.

Локальная структура аморфных и кристаллических пленок Ge-=SUB=-2-=/SUB=-Sb-=SUB=-2-=/SUB=-Te-=SUB=-5-=/SUB=-

The Mössbauer spectroscopy data on the 119Sn, 121Sb and 125Te isotopes have showed that the structure of germanium atoms local surrounding changes as a result of Ge2Sb2Te5 amorphous films crystallization (tetrahedral symmetry changes to octahedral), while the environment of antimony and tellurium atoms does not change, and for antimony atoms it is close to that in the Sb2Te3 compound.

Amorphous colloidal photonic crystals assembled by mesoporous silica particles for thin layer chromatography with high separation efficiency and colorimetric recognition

A mesoporous SiO2 amorphous photonic crystal film was used to develop new thin-layer chromatography with high separation efficiency and simplified recognition.