Changes In Crystal Morphology Research Articles

Distinct impacts of natural organic matter and colloidal particles on gypsum crystallization

Gypsum scaling via crystallization is a major obstacle limiting the applications of membrane-based technologies and heat exchangers in engineered systems. Herein, we perform the first comparative investigation on the impacts of natural organic matter (Suwannee River humic acid, SRHA) and colloidal particles on the gypsum crystallization process in terms of induction time and crystal morphology. Results show that the presence of SRHA significantly increases the induction time of gypsum crystallization. Specifically, at a solution saturation index of 4.92, the induction time increases 6.5-fold in the presence of 6 mg/L SRHA, compared to the case without SRHA. SRHA also alters the morphology of the formed calcium sulfate crystals, resulting in a polygon-like shape, differing from the characteristic needle-like shape of gypsum in the absence of additives. These changes in crystal morphology are attributed to the adsorption of SRHA on the gypsum crystal surface, blocking the active sites for gypsum growth. In contrast, in the presence of colloidal particles, the observed induction time of gypsum crystallization either decreases or increases, depending on the competitive interplay between the enhancement effect in the nucleation step and the inhibition effect in the subsequent crystal growth step. Furthermore, the formed gypsum crystals in the presence of colloidal particles exhibit a needle-like morphology similar to the crystals formed in the absence of any additives. Our study provides fundamental understanding of gypsum crystallization in feedwaters containing natural organic matter and colloidal particles, highlighting the importance of feedwater composition in gypsum scaling.

Effect of polyethylene glycol additives on the polymorph and crystal habit of carbamazepine

The effect of polyethylene glycol (PEG) with different molecular weights on carbamazepine (CBZ) crystallization was investigated by experiments and molecular dynamics (MD) simulations. The influence of PEG on the crystal morphology and solvent-mediated phase transition of CBZ was studied. It was found that PEG inhibited the CBZ III nucleation and CBZ II transition. The crystal morphology changes significantly from needle to rod when adding PEG with a molecular weight greater than 1500. MD simulations show that the binding energy sequence between the additive and the crystal surface is: Eb(1 –1 –1) > Eb(2 –2 1) > Eb(2 –1 0), which explains the suppression of axial crystal growth. The results provide a possible method to stabilize the metastable crystal form of CBZ and improve crystal morphology.

Unfolding the Role of B Site-Selective Doping of Aliovalent Cations on Enhancing Sacrificial Visible Light-Induced Photocatalytic H2 and O2 Evolution over BaTaO2N

The doping of foreign cations and anions is one of the effective strategies for engineering defects and modulating the optical, electronic, and surface properties that directly govern the photocatalytic O2 and H2 evolution reactions. BaTaO2N (BTON) is a promising 600 nm-class photocatalyst because of its absorption of visible light up to 660 nm, small band gap (Eg = 1.9 eV), appropriate valence band-edge position for oxygen evolution, good stability under light irradiation in concentrated alkaline solutions, and nontoxicity. Although the photocatalytic and photoelectrochemical water-splitting efficiencies of BaTaO2N have been progressively improved, it is still far from the requirements set for practical applications. Here, we employ a 5% B site-selective doping of aliovalent metal cations (Al3+, Ga3+, Mg2+, Sc3+, and Zr4+) to enhance sacrificial visible light-induced photocatalytic H2 and O2 evolution over BaTaO2N. The results of physicochemical characterizations reveal that no significant change in crystal structure, crystal morphology, and optical absorption edge is observed upon cation doping. Therefore, the difference observed in O2 and H2 evolution during the photocatalytic reactions over pristine and doped BaTaO2N photocatalysts is explained by examining optical, electronic, and surface properties. Also, molecular dynamics (MD) is used to gain insights into the respective effect of cation doping on adsorption energy of water molecules and formed intermediates (H* for H2 evolution and HO*, O*, and HOO* for O2 evolution) on the BaTaO2N surfaces terminated with TaO6, TaN6, and TaO4N2 octahedra. Finally, the experimental reaction rates for H2 and O2 evolution are correlated well using a linear energy–performance relationship, elucidating the doping and surface-termination trends observed in the BaTaO2N photocatalysts.

Fire resistance of light wood frame walls sheathed with innovative gypsum-particle composite: Experimental investigations

Gypsum board (GB) is used as a fire-resistant component of light wood frame (LWF) walls for its excellent fire resistance, but cracking and separation cause LWF failure due to water release at high temperature. In this study, eight mesoscale LWF walls were tested to determine the effects of an innovative gypsum-particle composite (IGP) on fire resistance, according to the ISO 834 standard. Three LWF walls were burned until failure for determination of fire endurance. Five LWF walls were heated for 0, 20, and 30 min during a standard fire and followed by lateral load resistance testing. Scanning electron microscopy was used to analyze microscopic changes of crystal morphology in GB and IGP after various periods in fire. The results indicated that the temperature in walls sheathed with IGP or double-layer GB consistently increased more slowly than single-layer GB during fire testing. The fire endurance of IGP-wall was 50.9 min, which was 12.9% higher compared to GB-wall and met the demands of a non-load-bearing exterior wall and partition wall on both sides of an evacuation route in timber structures. The fire endurance of the wall sheathed with two-layer GB was 55.7 min. The length of needle-like crystals in GB tended to be shorter in fire tests due to the release of chemically bound water, leading to cracks at high temperature. The residual morphology of IGP exhibited as intact after the same duration fire tests, compared to GB. The residual maximum load (Ppeak), elastic shear stiffness (Ke), and ductility (D) of IGP-wall heated for 20 min during standard fire were reduced by 10, 35, and 18%, but were also 6, 75, and 53% more compared to GB-wall. Under a 30 min duration exposure, the Ppeak, Ke, and D of IGP-wall were 1.15, 1.74, and 1.48 times that of GB-wall, respectively. IGP was capable of beneficially substituting for GB in LWF wall.

Thermally induced polymorphic transformation of Hexanitrohexaazaisowurtzitane (CL-20)

To investigate the polymorphic transformation and crystal morphology changes of ε-CL-20 under different thermal stimuli, isothermal and non-isothermal experiments were conducted using a hot stage microscope and in-situ X-ray powder diffraction. It was found that the ε- and γ- phases coexisted at 120 °C (9.727 wt% γ-CL-20), and the ε→γ phase transformation occurred between 115 and 120 °C and reached completion at 130 °C. The ε-CL-20 expanded isotropically in the temperature range of 25 to 115 °C. About a quarter of the ε-CL-20 transformed after being heated at 120 °C for 12 h, whereas almost all of ε-CL-20 transformed after being heated at 150 °C for 12 h. Under the microscope, the expansion of crystal volume, changes of crystal morphology, and phenomena of decomposition were observed during heating. Molecular dynamics simulation and Rietveld refinement were conducted to verify the experimental results. A solid-solid phase transition mechanism is presented.

Defects of diamond crystal structure as an indicator of crystallogenesis

Based on the study of a representative collections of diamonds from diamondiferous formations of the Urals and deposits of the Arkhangelsk and Yakutian diamond provinces, we established patterns of zonal and sectoral distribution of crystal structure defects in crystals of different morphological types, identified the specifics of crystals formed at different stages of crystallogenesis and performed a comprehensive analysis of constitutional and population diversity of diamonds in different formations. We identified three stages in the crystallogenesis cycle, which correspond to normal and tangential mechanisms of growth and the stage of changing crystal habit shape. At the stage of changing crystal habit shape, insufficient carbon supersaturation obstructs normal growth mechanism, and the facets develop from existing surfaces. Due to the absent stage of growth layer nucleation, formation of new {111} surfaces occurs much faster compared to tangential growth mechanism. This effect allows to explain the absence of cuboids with highly transformed nitrogen defects at the A-B1 stage: they have all been refaceted by a regenerative mechanism. Based on the revealed patterns, a model of diamond crystallogenesis was developed, which takes into account the regularities of growth evolution, thermal history and morphological diversity of the crystals. The model implies the possibility of a multiply repetitive crystallization cycle and the existence of an intermediate chamber; it allows to explain the sequence of changes in morphology and defect-impurity composition of crystals, as well as a combination of constitutional and population diversity of diamonds from different geological formations.

Evaluation of Cashew Nut Shell Liquid Borate Ester as Pour Point Depressant for Flow Assurance of Waxy Crude Oil

The development of chemical solutions to wax problems by modifying renewable natural products is an innovative response to the need for cheaper, eco-friendly pour point depressants for waxy crude oil flow improvement. Natural cashew-nut shell liquid (CNSL) was extracted from shells of Anacardium occidentale and derivatized into the borate ester. Pour point of oil doped with 500ppm CNSL borate ester was reduced by -24oC. The effect of borate ester addition on wax morphology was studied by cross-polarized microscopy. Analysis of micrographs using ImageJ software showed a decrease in Feret diameter, aspect ratio, and boundary fractal dimension of wax crystals in doped oil and increased crystal circularity and solidity, indicating the evolution of smaller, rounder, regular structures with smoother, even surfaces. At 10oC, oil shear stress and dynamic viscosity were reduced by 27.6% and 24.6%, respectively. Pour point depressant and flow improvement effects of additive were related to changes in crystal morphology.

Pour point depression and flow improvement of waxy crude oil using polyethylene glycol esters of cashew nut shell liquid

Wax crystallization and deposition is a major flow assurance problem in production and transportation of waxy crude oil. Conventional flow improvers are mainly high molecular weight synthetic polymers, many of which are eco-toxic. Bio-based flow improvers derived from natural products are promising as inexpensive, eco-friendly alternatives to existing products. In this study, natural cashew nut shell liquid (CNSL) extracted from waste shells of Anacardium occidentale was esterified with polyethylene glycol (PEG). CNSL derivative reduced the pour point of waxy crude oil by 12 °C at 1000 ppm. The effects of CNSL derivatives on wax crystal morphology and micro-structure were studied by cross-polarized microscopy. Micrographs were processed and analyzed with ImageJ software. Addition of CNSL derivatives to oil resulted in changes in wax crystal morphology and micro-structure evidenced by a reduction in average crystal Feret diameter and aspect ratio and increase in boundary fractal dimension, indicative of formation of increasing number of smaller, rounder crystals. Effect of the additives on flow properties of the waxy oil was determined using a co-axial cylinder rotational viscometer. Dynamic viscosity of oil at shear rate of 17 s−1 was reduced by 79.7–90.5%. CNSL-PEG esters show good prospects as low-cost additives for production, storage and pipeline transportation of waxy crude oil.

Changes in Crystal Phase, Morphology, and Flexural Strength of As-Sintered Translucent Monolithic Zirconia Ceramic Modified by Femtosecond Laser

Conventional bonding technology suitable for silica-based ceramics is not applicable to zirconia, due to its polycrystalline phase composition, chemical stability, and acid corrosion resistance. The development of an effective treatment to improve its surface roughness and mechanical properties remains an unresolved problem. Therefore, to solve this problem, this in vitro study evaluated the changes in surface morphology and flexural strength of translucent monolithic zirconia surfaces treated with femtosecond laser technology. As-sintered translucent zirconia specimens were subjected to airborne particle abrasion and femtosecond laser treatments, while control group specimens received no treatment. After treatment, the roughness and morphology of the treated zirconia surfaces were examined. The flexural strength and X-ray diffraction of the treated specimens were measured and analyzed. Statistical inferential analysis included one-way analysis of variance at a set significance level of 5%. The surface roughness after femtosecond laser treatment was significantly improved when compared with the control group and the group that received the airborne particle abrasion treatment (p < 0.05). In comparison with the airborne particle abrasion group, the flexural strength of the group that received the femtosecond laser treatment was significantly improved (p < 0.05). The femtosecond laser approach using appropriate parameters enhanced the roughness of the zirconia without reducing its flexural strength; therefore, this approach offers potential for the treatment of zirconia surfaces.

Dichroic Calcite Reveals the Pathway from Additive Binding to Occlusion

Organic additives play key roles in controlling the precipitation of calcium carbonate in the environment, industry, and biology, where they can direct polymorphism, alter crystal morphologies, and sometimes even become occluded, modifying bulk properties. However, significant questions remain regarding the pathway from adsorption on crystal surfaces to occlusion. Here, the optical properties of calcite crystals grown in the presence of the dye Congo red are used to characterize the organization of the additives within the crystal. Complemented by the analysis of surface adsorption through in situ atomic force microscopy (AFM), molecular simulations, and changes in crystal morphologies, we show that the occluded dye molecules are randomly oriented under fast growth conditions, but that slow growth engenders ordering of the dye within islands, whose orientation is determined by the dye/terrace interaction free energy. The islands are subsequently overgrown such that their internal structure is preserved. These results reveal that the occlusion of organic macromolecules into calcite can be understood by thermodynamics operating at the adsorption stage. This new insight will ultimately enable the design of additives to give specific material properties.

Mechanism of action of various terpenes and phenylpropanoids against Escherichia coli and Staphylococcus aureus.

Foodborne, disease-causing microorganisms are increasingly resistant to commercial antibiotics. Thus, there is a need for the development of new agents capable of acting efficiently in the control of these pathogens. Terpenoids and phenylpropanoids stand out for having high biological activity and a broad spectrum of action. The objectives of this study were to evaluate the antibacterial potential of limonene, β-citronellol, carvone, carvacrol, eugenol and trans-cinnamaldehyde and to investigate the mechanism of activity of these compounds against the bacteria Escherichia coli and Staphylococcus aureus. The terpene and phenylpropanoid compoundswere purchased and their antibacterial potential was assessed by macrodilution. The mechanism of action was verified by tests of potassium ion efflux, salt tolerance, extravasation of cellular contents, absorption of crystal violet and morphological changes analyzed by electron microscopy. Bacteriostatic and bactericidal effects caused by the compounds carvone, carvacrol, eugenol and transcinemaldehyde were observed in both species; antibacterial activity against only S. aureus was observed for β-citronelol and limonene. Reduced salt tolerance was found for strains of E. coli treated with carvacrol and S. aureus treated with β-citronelol. There was extravasation of cellular materials induced by treatments with carvone, carvacrol, eugenol and trans-cinnamaldehyde in both microorganisms. The absorption of crystal violet increased for E. coli after incubation with each treatment. Deleterious effects and morphological changes were observed. Therefore, the monoterpenes and phenylpropanoids under study are potentially applicable for antimicrobial use against E. coli and S. aureus, and the mechanism of action involves changes in membrane permeability without cell lysis.

In vitro evaluation of cytotoxic effects of di (2-ethylhexyl) phthalate (DEHP) produced by Bacillus velezensis strain RP137 isolated from Persian Gulf

Phthalates are widely used in polymer science and have potential toxicity related to their chemical structures. However, lots of evidence indicate that phthalate derivatives are undoubtedly produced as secondary metabolites by organisms, including plants, animals, and microorganisms. In the present study, Bacillus velezensis strain RP137 was cultured under optimized conditions. Its biomass was extracted with ethyl acetate with one fraction showing cytotoxic properties. A pure compound was isolated from the active fraction using combined silica gel and LH20 size exclusion column chromatography. Structural evaluation including FT-IR, 1H NMR, 13C NMR, HR-MS and CHN analysis identified the purified compound as di(2-ethylhexyl)phthalate (DEHP) with the formula C24H38O4 and the molecular weight of 389.29 Da. The microorganism-derived (stereospecific) DEHP was strongly reduced the proliferation and induced cytotoxic effects on various eukaryotic cell lines in compare to the synthetic racemic mixture of the compound when assessed by MTT assay. Furthermore, crystal violet assay and morphological changes confirmed the cytotoxic effect of DEHP. Interestingly, non-malignant SV40-immortalized fibroblast cells were less affected by the purified DEHP. Further evaluation on the antibacterial activity of DEHP documented no effect toward Gram-positive (S. aureus) and Gram-negative (E. coli and P. aeruginosa) pathogens even at a high concentration of 100 μM. In conclusion, existence of DEHP as byproduct of microorganism's metabolism can seriously be considered as a warning to human health.

Phase formation and structural evolution of multicomponent (CrFeCo)1-yNy films

The Cantor alloy (CoCrFeMnNi) and its variants, in bulk as well as thin films, have been extensively studied. They are known to exhibit cubic crystal structures and thermodynamic stability regardless of their complex chemical composition. Therefore, they may find use as hard, wear-resistant, corrosion and oxidation-resistant coatings. The addition of light elements, such as nitrogen, is known to help improve these properties further through processes such as amorphization and nitride compound formation. Here, we investigate the ternary CrFeCo system to study the effects of nitrogen addition. (CrFeCo) 1-y N y multicomponent thin films are grown on silicon substrates by DC magnetron sputtering. Changes in crystal structure, morphology, mechanical and electrical properties with gradual increases of nitrogen in the film are described and discussed. Increased addition of nitrogen from 14 at.% to 28 at.% in the film leads to a transformation from an fcc to a bcc crystal structure, affects both the mechanical and electrical properties. XPS analysis shows the tendency of nitrogen to bond with Cr over other metals. The films display hardness values between 7 and 11 GPa with resistivities values ranging between 28 and 165 μΩ cm. • Multicomponent (CrFeCo)Ny coatings deposited by reactive magnetron sputtering • Effect of nitrogen content on structure, morphology and composition was studied. • Phase formation and evolution with changes in nitrogen content • Mechanical and electrical properties of (CrFeCo)Ny thin films

Crystallization of Sodium Bicarbonate in the Presence of Trace Amounts of HPMA

AbstractThe effect of trace amounts of hydrolytic polymaleic anhydride (HPMA) on the crystallization of sodium bicarbonate (NaHCO3) has been investigated by molecular simulation and experimental methods. Cooling crystallization experiments show that the trace HPMA molecule effectively promotes the formation of larger NaHCO3 crystals. Besides, the crystal morphology changes from needle‐like to flake‐like. The determination of the metastable zone width of NaHCO3 and Atomic Force Microscopy (AFM) observation confirmed that the spontaneous nucleation processes are suppressed. Molecule simulation was used to explore the interaction of HPMA molecule and different crystal faces of NaHCO3. It was found that the binding energy between HPMA and NaHCO3 surface is greater than the corresponding attachment energy of NaHCO3 surface. The electrostatic interaction energy between double‐bonded oxygen on the HPMA molecule and the Na+ of the NaHCO3 crystal plane plays a dominant role in the additive molecule‘s adsorption on the NaHCO3 crystal surface. This work suggests that HPMA could serve as an inhibitor of nucleation and impact NaHCO3 crystallization.

Understanding Crystal Cleavability and Physical Properties of Crystal Surfaces Using in Silico Simulation.

In the drug formulation process, compound dissolution rate and wettability may be improved by grinding. However, there is no method to understand the effects of the wettability of the crystal facets of the ground product. Here, acetylsalicylic acid (ASA) was used to evaluate the changes in crystal morphology and dissolution rate by jet milling using powder X-ray diffraction and in silico simulation. Several cleavage facets were observed in cube crystals, and the (0 0 2) facet was observed in plate crystals. Furthermore, the dissolution rate of the ground samples per unit area decreased with the cleavage of the (1 0 0) and (0 0 2) facets. The polar surface energy of the ground sample decreased with increasing grinding pressure. The simulation results showed that the absolute attachment energy of the (1 0 0) and (0 0 2) facets was lower than that of the other crystal facets. Moreover, atoms with low polarity were present on the crystal surface of (0 0 2). The wettability and dissolution rate of the (0 0 2) facet were worse than those of the (1 0 0) facet. It was suggested that the dissolution rate of the ground sample was affected by the wettability of the crystal facet caused by the cleavage. The cleavability and wettability may be understood by simulation.

Non-digesting strategy for efficient bioconversion of cassava to bioethanol via mechanical activation and metal salts pretreatment

This study focused on the development of an efficient technology for bioconversion of cassava to bioethanol without high temperature digesting. Mechanical activation (MA, ball milling)-metal salt (MA-MS) technology was applied to pretreat cassava flour, leading to significant changes in crystal structure, morphology, and viscosity. The destruction of stable structure of cassava flour induced by MA-MS pretreatment increased the accessibility of glucoamylase to starch granules from surface to interior, which contributed to direct and efficient saccharification of cassava flour without digesting. The decrease in viscosity of slurry and the use of metal salt as nutrient for yeast (Saccharomyces cerevisiae) had favorable effect on fermentation process. The combination of MA and MgSO4 exhibited outstanding synergistic interaction. The ethanol concentration and conversion efficiency of MA-MgSO4 pretreated cassava flour achieved 13.64 vol% and 93.4% under optimum conditions (addition amount of MgSO4 = 6 wt%, MA time = 75 min, dosage of glucoamylase = 200 U/g cassava, and dosage of Saccharomyces cerevisiae = 0.3 wt%). MA-MS pretreatment significantly enhanced the saccharification and fermentation processes for efficient bioconversion of cassava to bioethanol by non-digesting strategy.

Solvent-driven crystal-crystal transformation and morphology change in a 2D layered inorganic POM-based framework.

In this paper, a pure 2D inorganic POM-based framework underwent a single crystal to single crystal conversion when soaked in organic solvents that are miscible with water, forming a more densely packed identical framework accompanying the formation of nanowires. The change in morphology is closely related to the surface tension of water, and the lower surface tension achieved by dehydration promotes the formation of nanowires, which is revealed by SXRD, PXRD, SEM, TGA and electrochemical impedance spectroscopy (EIS).

Obtaining High‐Paraffin‐Content Oil Depressants

AbstractA depressor action composition was prepared for lowering the pour point of high‐paraffin oils based on butanol and cotton soap stock fatty acids (FA), mainly a C16–C18 distillate fraction. The possibility of using cotton soap stock FA for their esterification with butyl alcohol and ester production based on them is shown. A scheme for preparing the depressor action reagent “BEG‐1” based on the esterified FA, monoethanolamine, and cotton soap stock is proposed. When the BEG was introduced into the samples of high‐paraffin oil taken directly from the group metering device, a decrease in the paraffin crystal size and shape was observed, i.e. their almost complete dissolution, which was accompanied by a change in the viscosity of the samples. Compositions having high surface‐active properties, thermodynamic resistance, and stability were prepared. The paraffin crystal morphology, crystal structure, and shape change were studied. The data obtained are of value for the pipeline transport of hydrocarbons, as the use of the proposed depressor action reagent for high‐paraffin oils can significantly reduce the viscosity of the oil in the pipeline, helping to reduce the energy costs associated with heating the oil for its pumping.

Na+/Mg2+ interactions on membrane distillation permeation flux and crystallization performance during high saline solution treatment

Membrane distillation crystallization (MDC) was an effective method for saline solution treatment to simultaneously recovery pure water and salt products. In MDC process, an important topic was the influence of ionic interactions produced by complex salt solution on MDC performance. We processed a typical ternary saturated solution (Na+/Mg2+//Cl-–H2O) with MDC to investigate the influence of different Na+/Mg2+ ratios on membrane distillation permeation flux and crystal morphology from the perspective of experiment and molecular dynamics simulation. From the simulation results, it was demonstrated that increasing magnesium ions could modify the hydration structure of the cations and influence the diffusion coefficient of the hydrated ions in the solution. The reduced free water and diffusion ability led to the changes in permeation flux and crystal morphology. The crystals with different morphologies could be produced by adjusting the ratio of Na+/Mg2+ and MDC temperature. In addition, selective solvent (ethanol) wash approach was developed to further improve the separation performance and reveal the effect of Mg2+ on NaCl crystal growth.

On the crosslinking temperature dependence of charge transport behavior in XLPE film deduced from surface potential decay measurements

The effect of crosslinking temperature on charge transport behavior in crosslinked polyethylene (XLPE) film has been investigated by means of surface potential decay measurements. 200 μm-thick XLPE specimens were prepared by hot-molding low density polyethylene (LDPE) by adding dicumyl peroxide (DCP) as crosslinking agent and phenolic antioxidant with temperatures ranging from 150 to 180 °C. Surface potentials on corona-charged samples were monitored by using a Kelvin type probe equipped with an electrostatic voltmeter, based on which trap distribution, effective charge mobility and field dependent conductivity were estimated. Fourier Transform Infrared (FTIR) spectrum and Differential Scanning Calorimeter (DSC) analysis were employed to examine the change in chemical structure and crystal morphology of test samples. Results obtained show that the charge transport dynamics is cross-linking temperature and polarity dependent. With the rise of the crosslinking temperature, the mobility of positive charge increases monotonously from 1.05 × 10−16 m2V−1s−1 to 5.42 × 10−15 m2V−1s−1, whereas the mobility of negative charge shows a fall-and-rise tendency that a minimum value of 1 × 10−16 m2V−1s−1 appears at 160 °C. A single trap center for electron is observed at any test sample. However, as regards to hole, a double-trap-center feature tends to appear as the temperature exceeds 160 °C. Moreover, with the increase of the crosslinking temperature, the conductivity of sample becomes field dependent. It is suggested that the variation of charge transport behavior should be ascribed to the presence of by-products as well as the crystallinity change caused by the temperature.