Globular Morphology Research Articles

Micro- and Nanoparticulate Hydroxyapatite Powders as Fillers in Polyacrylate Bone Cement-A Comparative Study.

Acrylate polymer-based bone cements constitute the most popular bonding agents used in regenerative surgery. Due to their inferior biocompatibility, however, these materials are often enriched with ceramic additives including hydroxyapatite (HAp). The aim of this paper was to perform a comparative study of the acrylate cements filled with different content (3–21%) of nano- and microscale hydroxyapatite. The work concerns a comparison of times and temperatures of the cross-linking reaction, as well as morphology, glass transition temperature, and principal mechanical properties of the resulting composites. Before being used as a filler, both HAp forms were subjected to an in-depth characterization of their morphology, specific surface area, pore size distribution, and wettability as well as chemical composition and structure. For that purpose, such analytical techniques as scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, tensiometry, Brunauer–Emmett–Teller surface area analysis, differential scanning calorimetry, Shore D hardness test, and Charpy impact test were used. The results indicated a drop of cross-linking temperature and an extension of setting time with the addition of µHAp. The µHAp-filled acrylate composites were characterized by a globular surface morphology, higher glass transition temperature, and lower hardness and impact strength compared to nHAp-filled materials. This relationship was evident at higher nHAp concentrations.

Room temperature ionic liquid assisted rapid synthesis of amorphous Se nanoparticles: Their prolonged stabilization and antioxidant studies

Considering the meticulous synthetic procedures as well as rapid phase transformation of amorphous-Selenium (α-Se) nanoparticles, herein, an attempt has been made by employing a highly facile and rapid approach to sort out such issues. An imidazolium-based room temperature ionic liquid (RTIL) was used in the synthetic protocol, wherein it played the role of a solvent, a reducing agent as well as a stabilizing agent. The synthesis was carried out in purely ambient conditions, while Se nanoparticles formation was over within 10 min of the reaction. The appearance of brick-red color indicated the formation of α-Se nanoparticles, which was further confirmed by various techniques such as XRD, Raman mapping and TEM. The electron based microscopic studies revealed the average size of the nanoparticles as 34 ± 5 nm with globular morphology. An important aspect of this work is that the α-Se nanoparticles were stable for more than 1 month, as compared to a few minutes-to-days, known hitherto. The phase stability of the nanoparticles has been explained taking into account of the structural and the fluidic aspects of the RTIL. Besides, these nanoparticles exhibited fairly good antioxidant properties, which have been discussed by comparing with standard antioxidant.

Study on Heat Transfer Performance and Anti-Fouling Mechanism of Ternary Ni-W-P Coating

Since the formation of fouling reduces heat transfer efficiency and causes energy loss, anti-fouling is desirable and may be achieved by coating. In this work, a nickel-tungsten-phosphorus (Ni-W-P) coating was prepared on the mild steel (1015) substrate using electroless plating by varying sodium tungstate concentration to improve its anti-fouling property. Surface morphology, microstructure, fouling behavior, and heat transfer performance of coatings were further reported. Also, the reaction path, transition state, and energy gradient change of calcite, aragonite, and vaterite were also calculated. During the deposition process, as the W and P elements were solids dissolved in the Ni crystal cell, the content of Ni element was obviously higher than that of the other two elements. Globular morphology was evenly covered on the surface. Consequently, the thermal conductivity of ternary Ni-W-P coating decreases from 8.48 W/m·K to 8.19 W/m·K with the increase of W content. Additionally, it goes up to 8.93 W/m·K with the increase of heat source temperature 343 K. Oxidation products are always accompanied by deposits of calcite-phase CaCO3 fouling. Due to the low surface energy of Ni-W-P coating, Ca2+ and [CO3]2− are prone to cross the transition state with a low energy barrier of 0.10 eV, resulting in the more formation of aragonite-phase CaCO3 fouling on ternary Ni-W-P coating. Nevertheless, because of the interaction of high surface energy and oxidation products on the bare matrix or Ni-W-P coating with superior W content, free Ca2+ and [CO3]2− can be easy to nucleate into calcite. As time goes on, the heat transfer efficiency of material with Ni-W-P coating is superior to the bare surface.

Nanoemulsions containing oil and aqueous extract of green coffee beans with antioxidant and antimicrobial activities

Coffee has bioactive compounds with protective effect against free radicals and antifungal and antibacterial activities that are beneficial to the health skin. This work aims to provide scientific evidence that nanoemulsions developed with oil and green coffee extract have antioxidant and antimicrobial effects. Nanoemulsions were prepared by spontaneous emulsification method using different concentrations of components (oil, extract and tensoactive) in order to optimize the preparation of formulations. The nanoemulsions presented globular morphology, negative charges, monodispersity and size around 200 nm. Two nanoemulsions, namely F7 and F16, presented characteristics of size and concentration of tensoactives more suitable for investigation regarding their antioxidant and antibacterial activities. The later assay was performed against standard strains of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli at different nanoemulsion concentrations. The formulations proved to be inhibitors of free radicals and showed excelent antibacterial activity, demonstrating their potential for cosmetic and therapeutic applications.

The possibility of enhanced hydrogen embrittlement resistance of medium-Mn steels by addition of micro-alloying elements

In the present study, we elucidated the possibility of improvement in H embrittlement (HE) resistance of micro-alloyed medium-Mn steels by MC carbides formation. The Fe-6Mn-0.08C (wt%) steel was used as a base material, and the different amount of Nb, Ti, and V was added to form MC carbides. All steels exhibited the nano-sized globular morphology with dual-phase of α ferrite plus γR retained austenite, and the phase fraction was almost identical regardless of steel compositions. The steels showed an almost similar grain size of γR phase, regardless of composition. However, the micro-alloyed steel revealed the smaller size of α phase relative to base steel owing to MC carbides precipitation in the α phase. The micro-alloyed steel exhibited higher strength and lower ductility compared to the base material due to precipitation hardening and fine grain size of α. Considering HE resistance, we realized that the addition of the micro-alloying element resulted in a trivial effect on the medium-Mn steels, because MC carbides in the α phase could not act as influential trap sites of diffusible H. Most of the H atoms were preferentially trapped in the γR phase, and the H-enriched γR phase caused H-assisted nano crack when it transformed to strain-induced martensite. After that, the nano crack developed to the intergranular crack, leading to premature fracture.

Application of multi-phase-field lattice Boltzmann method to semi-solid deformation

Mechanisms of semi-solid deformation are crucial for reducing solidification defects. In this study, a multi-phase-field lattice Boltzmann (MPF-LB) model, which can simulate growth of multiple dendrites with liquid flow, solid motion and collision, is applied to semi-solid deformation. An elastic contact is introduced to the MPF-LB model to consider collision of two grains. The semi-solid deformation with globular morphology is simulated in the two-dimension by the MPF-LB method. Through the simulations, high potential of the MPF-LB model as the evaluation method of semi-solid deformation is confirmed.

Synthesis, Characterization, and Study of NO2Gas Sensing Behavior of CSA Doped PANi-Ta2O5Nanocomposite

Polyaniline in its emeraldine salt form was obtained by chemical oxidative polymerization of aniline monomer. PANi thus obtained was mixed with tantalum pentoxide (Ta2O5) nano powder in 50 wt% to get PANi-Ta2O5 nanocomposite. The nanocomposite was further mixed with Camphor Sulphonic Acid (CSA) with concentrations of 20wt%, 30wt% and 40wt% respectively for solid-state doping. All the samples were characterized by FESEM, TEM, XRD, FTIR and UV-Vis spectroscopy. Thin film sensor device was developed taking each of the samples as the sensing material to study the gas sensing properties towards NO2 gas at room temperature. The CSA doped nanocomposite possessed highly aggregated globular morphology that led to high surface area. Doping of CSA notably favored the gas sensing process. PANi-Ta2O5-CSA40wt% exhibited the best performance with sensor response above 80% towards 500 ppm NO2, a faster response time of 55 seconds and a recovery time of 160 seconds. The device showed good repeatability and high selectivity to NO2. The sensor response was studied under 38%, 57% and 65% relative humidity conditions respectively and it was found to remain stable under different humidity levels.

Thin Films Based on Cobalt Phthalocyanine:C60 Fullerene:ZnO Hybrid Nanocomposite Obtained by Laser Evaporation.

Matrix-assisted pulsed laser evaporation (MAPLE) was used to deposit hybrid nanocomposite thin films based on cobalt phthalocyanine (CoPc), C60 fullerene and ZnO nanoparticles. The inorganic nanoparticles, with a size of about 20 nm, having the structural and optical properties characteristic of ZnO, were chemically synthesized by a simple precipitation method. Furthermore, ZnO nanoparticles were dispersed in a dimethyl sulfoxide solution in which CoPc and C60 had been dissolved, ready for the freezing MAPLE target. The effect of the concentration of ZnO nanoparticles on the structural, morphological, optical and electrical properties of the CoPc:C60:ZnO hybrid nanocomposite layers deposited by MAPLE was evaluated. The infrared spectra of the hybrid nanocomposite films confirm that the CoPc and C60 preserve their chemical structure during the laser deposition process. The CoPc optical signature is recognized in the ultraviolet–visible (UV–Vis) spectra of the obtained layers, these being dominated by the absorption bands associated to this organic compound while the ZnO optical fingerprint is identified in the photoluminescence spectra of the prepared layers, these disclosing the emission bands linked to this inorganic semiconductor. The hybrid nanocomposite layers exhibit globular morphology, which is typical for the thin films deposited by MAPLE. Current-voltage (J-V) characteristics of the structures developed on CoPc:C60:ZnO layers reveal that the addition of an appropriate amount of ZnO nanoparticles in the CoPc:C60 mixture leads to a more efficient charge transfer between the organic and inorganic components. Due to their photovoltaic effect, structures featuring such hybrid nanocomposite thin films deposited by MAPLE can have potential applications in the field of photovoltaic devices.

Electrodeposition of Ni-W-P alloy

Influence of sodium hypophosphite admixture to electrolyte for deposition of Ni-W alloy on the coating composition, morphology, structure and microhardness is investigated. Antisymbatic dependence of tungsten and phosphorus content in Ni-W and Ni-W-P alloys on the sodium hypophosphite concentration in the electrolyte is observed, namely, at higher sodium hypophosphite concentration in the electrolyte solution the coatings are become poorer in tungsten whereas phosphorus content is increased. Phosphorus incorporation into the alloy leads to globular morphology of the surface of coatings. The minimal roughness was obtained at high hypophosphite concentrations in the electrolyte (7.5 and 10 g/L). As-deposited Ni-W and Ni-W-P alloys possess nanocrystalline structure manifested in broad X-ray diffraction peaks. Addition of 2.5…5 g/L of hypophosphite markedly weakens Ni reflections (200) and (220), the (111) peaks becomes broader. In addition, a Ni3P phase is appeared in the coatings. Thermal treatment in vacuum at 400 °С induces growth of nickel crystallites. Microhardness of as-deposited coatings is weakly dependent on sodium hypophosphite concentration in the electrolyte and is in the range 3.8…4.2 GPa. Thermal treatment of Ni-W-P alloys at 400 °С during 1 h increases microhardness up to 5.9…8.8 GPa.

Ultrafine Fe-Fe2Ti eutectics by directed energy deposition: Insights into microstructure formation based on experimental techniques and phase field modelling

We investigated the Fe-Fe2Ti eutectic microstructure obtained by Directed Energy Deposition (DED) with a hypereutectic composition of Fe-17.6 at.% Ti. Ultrafine lamellar spacings as low as 200 nm were achieved, features which otherwise can only be obtained in thin specimens, e.g. by suction casting. However, at interlayer boundaries (ILBs) a globular morphology of the primary Fe2Ti phase is observed with halos of the Fe phase. For the given DED conditions the crystalline structure is thus discontinuous across the ILBs. Both 2D and 3D analysis methods were used to quantify the microstructure, including high resolution synchrotron holographic X-ray computed tomography (HXCT). The generic behaviour of eutectic systems under conditions that qualitatively correspond to those of laser additive manufacturing was explored by phase-field modelling for selected nucleation scenarios and alloy compositions spanning from eutectic to hyper-eutectic. While providing valuable insights into microstructure formation, the simulations point out the need to further deepen our understanding about melting under additive manufacturing conditions in order to implement suitable nucleation and / or free growth models. The simulations also show that globular ILBs can be prevented when using exactly eutectic alloy compositions.

The Dispersion of Lead in Hypoeutectic Aluminium-Silicon Alloys by Spray Forming Process and their Characterization

The present paper describes the Lead dispersion in hypoeutectic Aluminium-Silicon alloys and their microstructural characteristics. The homogeneous dispersion of Lead (Pb) in Aluminium-Silicon alloys (Al-6Si+Pb (=0, 10, 15, 20, 25)) were fabricated by using of spray forming technique (also known as spray casting or spray deposition) in the form of near-net shape disc. The microstructural characterization has been done for different location of spray formed disc by using optical microscopy (OM), Scanning electron microscopy (SEM) and X-Ray Diffraction (XRD) respectively. The results of the optical image were exhibited the equiaxed and globular grain morphology of primary Aluminium with the homogeneous dispersion of extremely fine and malleable particles of Lead and spherical particles of silicon in α–Aluminium matrix. The dispersed Lead has seen clearly in the SEM images of spray formed Aluminium-Silicon alloys and result of XRD pattern confirmed the phases of Aluminium-Silicon and Lead. The grain size of Aluminium has been analyzed by intercept line method. The lattice parameter and lattice strain have been calculated with the help of the XRD pattern to determine the effect of Lead dispersion on Al-Si alloy.

Influence of cooling rate on microstructure development of AlSi9MgMn alloy

Aluminum alloys are widely applied in automotive, aircraft, food, and building industries. Multicomponent technical AlSi9MgMn alloy is primarily intended for high cooling rate technology. Controlled addition of alloying elements such as iron and manganese as well as magnesium can improve mechanical and technological properties of the final casting depending on the cooling conditions during solidification. The aim of this investigation is the characterization of AlSi9MgMn alloy microstructure and mechanical properties at lower cooling rates than those for which this alloy was primarily developed. Thermodynamic calculation and thermal analyses revealed solidification sequence in correlation to the microstructure investigation as follows: development of primary dendrite network, precipitation of high temperature Al15(Mn,Fe)3Si2 and Al5FeSi phases, main eutectic reaction, precipitation of intermetallic Al8Mg3FeSi6 phase, and Mg2Si as a final solidifying phase. Influence of microstructure features investigation and cooling rate reveals significant Al15(Mn,Fe)3Si2 morphology change from Chinese script morphology at low, irregular broken Chinese script morphology at medium, and globular morphology at high cooling rate. High manganese content in AlSi9MgMn alloy together with high cooling rate enables the increase of Fe+Mn total amount in the intermetallic Al15(Mn,Fe)3Si2 phase and encourage favourable morphology development, all resulting in enhanced mechanical properties in as-cast state.

Corrosion protection of AZ91D magnesium alloy by a duplex coating

A duplex coating was formed under potentiostatic conditions on magnesium alloy AZ91D in order to improve its corrosion resistance in a simulated physiological environment. The first layer was formed by anodization at low potentials in molybdate solution. The outer layer was a PPy film electrosynthesized in sodium salicylate solution. The conditions of the formation were determined to obtain a layer with globular morphology. The bilayer was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The corrosion protection properties of the coatings were examined in Ringer solution by monitoring the open circuit potential (OCP), polarization techniques, and electrochemical impedance spectroscopy (EIS). The obtained results showed that the bilayer improves the corrosion resistance of the substrate. Moreover, the duplex coating presented better anticorrosive properties than a single PPy film. Afterwards, the bilayer was modified by cementation of silver ions from a solution containing AgNO3. The modified electrode exhibited good antibacterial properties.

A spectroscopic and molecular dynamics study on the aggregation process of a long-acting lipidated therapeutic peptide: the case of semaglutide.

The aggregation properties of semaglutide, a lipidated peptide drug agonist of the Glucagon-like peptide 1 receptor recently approved for the treatment of type 2 diabetes, have been investigated by spectroscopic techniques (UV-Vis absorption, steady-state and time-resolved fluorescence, and electronic circular dichroism) and molecular dynamics simulations. We show that in the micromolar concentration region, in aqueous solution, semaglutide is present as monomeric and dimeric species, with a characteristic monomer-to-dimer transition occurring at around 20 μM. The lipid chain stabilizes a globular morphology of the monomer and dimer species, giving rise to a locally well-defined polar outer surface where the lipid and peptide portions are packed to each other. At very long times, these peptide clusters nucleate the growth of larger aggregates characterized by blue luminescence and a β-sheet arrangement of the peptide chains. The understanding of the oligomerization and aggregation potential of peptide candidates is key for the development of long acting and stable drugs.

Effect of microstructure on Ti3Al precipitation during ageing of Ti-6Al-4V alloy

The aim of the present work is to explore the age-hardening potential of Ti-6Al-4V (Ti-64) alloy with variation of the starting microstructure, with attention to the precipitation of nano-sized Ti3Al phase, as influenced by microstructural features. The alloy was either solution-treated or deformed by compression at temperatures above and below its β-transus to produce microstructures comprising martensitic, lamellar and globular α morphologies, as well as the existence or absence of β phase, and subsequently submitted to ageing treatments at 400°C/8h using in situ x-ray diffraction. Precipitated fractions of Ti3Al were obtained via Rietveld refinement and aged microstructures were characterized by micro-hardness measurements. Results show that α2 precipitation is favored by a globular morphology of α and hindered by a martensitic α morphology, and suggest that the presence of β phase also has as influence on precipitation.

Photocatalytic activity of electric-arc furnace flue dusts

Two electric-arc furnace flue dusts, a waste generated during the steel production process, were characterized and their photocatalytic activity was assessed. Chemical composition by X-ray fluorescence (XRF) analysis identified that both dusts were principally formed by iron, zinc and chromium oxides. Structural characterization carried out by X-ray diffraction patterns (XRD), and micro-Raman measurements demonstrated that ZnFe2O4 (zinc ferrite), FeCr2O4 (chromite) and ZnO (zincite) are present in both waste dusts as majority phases. Scanning electron microscopy (SEM) images showed that both dusts are formed by nanoparticles with a globular and octahedral morphology characteristic of the type of flue dusts formation and the obtained phases. Cathodoluminescence (CL) spectra show the characteristics bands of spinel structure (ZnFe2O4) and Fe3+ emission. X-ray photoelectron spectroscopy (XPS) measurements indicate that Fe ions could be present in 2+ and 3+ oxidation state in the spinel structure, while zinc and chromium ions are in 2+ and 3+, respectively. In addition, the photocatalytic experiments demonstrated that the analyzed samples could be useful as photocatalyzed showing a degradation percentage above 75 %.

Surface modification of Ti6Al4V by forming hybrid self-assembled monolayers and its effect on collagen-I adsorption, osteoblast adhesion and integrin expression

Silanization is a widely explored chemical technique to modify surfaces for tailoring physio-chemical properties like surface chemistry and wettability but its impact on bio-interfaces interaction i.e. protein adsorption and cellular responses is not well understood. This work focusses on modulating surface properties of Ti6Al4V to study their behavior towards collagen-I (Col-I) adsorption and subsequently on osteoblast adhesion and integrin expression. The moderate hydrophobic Ti6Al4V surfaces (θ = 78 ± 3°) were prepared by forming hybrid self-assembled monolayers (SAMs), which contain both hydrophobic and hydrophilic moieties on the same SAM molecule and were characterized using different techniques. The experimental adsorbed amounts of Col-1 were compared with the predicted ones using the Gibbs equation, which were overestimated but linearly related. AFM and secondary structure analyses of the adsorbed Col-I revealed globular morphology with significant change only in helical content. Cells adhered to hybrid surface pre-adsorbed with Col-1 exhibited better cell adhesion (~100%) and spreading area (1127 µm2) as compared to cells adhered to hybrid surface without (adhesion of 69% and cell area of 509 µm2) and with (adhesion of 94% and cell area of 908 µm2) FBS in cell culture media. Further, integrin expression was analyzed using ELISA based integrin assay to elucidate the cellular adhesion. We observed higher expression of α1 and α2 integrins on surfaces with pre-adsorbed Col-I and were correlated with the increase in nuclei area indicating α1 and α2 mediated cell adhesion promoted the cell proliferation. Overall, cell-surface interactions were improved on hybrid surfaces with pre-adsorbed Col-I, which designated the potential applications of the modified Ti6Al4V especially in metallic orthopedic implants.

Effect of Ultrasonic Treatment on Grain Structure, Eutectic Phase and Mechanical Properties of an Al–6.2 wt% Cu Alloy

The microstructural modification of eutectic phase is a crucial factor for the mechanical properties strengthening of the Al–Cu binary alloy. In this paper, Al–6.2% Cu melts were subjected to ultrasonic treatment from 710 or 660 °C with different durations. The microstructural evolutions of primary α-Al grains and α-Al + θ-Al2Cu eutectic phase under ultrasonication were investigated based on the nucleation and growth behavior. Results indicated that with the increase of ultrasonic processing time, the growth of dendritic or petaloid grains were completely suppressed and noticeable refinement to globular morphology were observed for α-Al grains. Meanwhile, broad lamella-like eutectic structure transformed to debris or even particles with continuous ultrasonication. Accordingly, the area fraction, average length and width of coarsening eutectic lamellas were dramatically reduced. In addition, the decrease of coarsening eutectic phase rather than the refinement of α-Al grains was found to be the main contributor to the enhancement of mechanical properties for Al–6.2% Cu alloy. The mechanisms underlying the transformation of eutectic phase under ultrasonic treatment was also interpreted based on the experimental results.

Peptide-Decorated Ultrasmall Superparamagnetic Nanoparticles as Active Targeting MRI Contrast Agents for Ovarian Tumors

Magnetic resonance imaging (MRI) is widely applied in medical research and diagnosis, and a MRI contrast medium plays a crucial role in improving the sensitivity of detection. Ultrasmall superparamagnetic iron oxides (USPIOs) exhibit the potential as a T2 enhancement contrast medium for MRI due to their excellent magnetic response performance; however, to endow them with specific tumor targetability, long-term circulation performance has always been a hot topic in this field. In this study, a well-designed procedure of chemical coprecipitation, surface modification, and peptide grafting was applied to prepare the active tumor-targeting USPIOs@F127-WSG, in which Pluronic F127 (F127) and the peptide WSGPGVWGASVK (peptide-WSG) were selected as the template agent and the ovarian tumor-targeting ligand, respectively. The results showed that single USPIOs@F127-WSG particles were Fe3O4 nanoparticles regulated by the confinement effect of F127 micelles with a uniform globular morphology and size (∼9 nm), and peptide-WSG was grafted for their tumor targetability. USPIOs@F127-WSG particles presented superparamagnetic behavior with high T2 relaxivity (r2 = 278.15 mM-1 s-1) and in vitro targetability for SKOV-3 cells due to the special binding between peptide-WSG and specific receptors of SKOV-3. The test results in vivo verified the targetability of USPIOs@F127-WSG by their specific aggregation in the tumor regions, leading to the T2-weighted MRI contrast enhancement. These outstanding properties indicate that USPIOs@F127-WSG have great potential to be applied as the active tumor-targeting contrast agent for MRI.

Palladium Supported on Carbon Nanoglobules as a Promising Catalyst for Selective Hydrogenation of Nitroarenes

The catalysts 1 wt% palladium supported on carbon nanoglobules (CNGs) were shown to be highly active in the liquid-phase hydrogenation of various nitroarenes and provided nearly 100% selectivity to aromatic amines at complete conversion under mild conditions (323 K, 0.5 MPa, 1 h). The catalytic activity (in terms of turnover frequency and substrate conversion) and selectivity depend on the kind of CNGs support, catalyst preparation method and the reaction conditions (solvent nature). The Pd/CNGs catalyst can be repeatedly used while maintaining the same catalytic performance. The excellent performances of Pd/CNGs catalysts can be due to the globular morphology of the supports as well as the absence of micropores and pronounced surface defects.