Small-sized Particles Research Articles

Osteogenic activity of a micro/nano hierarchical nano-hydroxyapatite coating on zirconium alloy

Micro/nano hierarchical structures and nano-sized hydroxyapatite (nHA) have been proven to play a critical role in promoting osseointegration. However, still, it is a challenge to prepare tightly adherent nHA coatings with micro/nano hierarchical structure, and the correlation between the physicochemical properties of hydroxyapatite (HA) and osteoblasts (OBs) activity at different stages is unclear yet. In this study, the grain refinement of large-sized HA generated by traditional microarc oxidation-hydrothermal treatment was achieved through a simple method of adding Ca/P (Ca2+ and PO43−) to hydrothermal reaction, and micro/nano hierarchical nHA coatings with different crystallinities and grain sizes were prepared on Zr16Nb12Ti alloy. Further, the OBs responses on these coatings were investigated in proliferation and differentiation stages, respectively. It was found that small-sized HA particles provide more integrin-binding sites, which are important for the adhesion and proliferation stages of OBs. The high ion release resulting from the low crystallinity of HA is a crucial condition for promoting OBs differentiation. However, amorphous HA coatings with excessively low crystallinity exhibit poor osteogenic activity due to their inferior cell adhesion activity. Finally, a micro/nano hierarchical nHA coating with appropriate crystallinity was prepared through a simple method, demonstrating excellent osteogenic activity, and providing new strategies for biomimetic coatings research.

Characteristics of microplastics in sediment of the Vaal River, South Africa: implications on bioavailability and toxicity

The aim of this study was to examine the physical characteristics and chemical composition of microplastics in sediments of the Vaal River, South Africa. Microplastics were detected in all samples, with abundance ranging from 29.12 to 1095.89 particles/kg dw. The physical identification of microplastics revealed dominance of small-sized particles of less than 0.5 mm, which accounted for 31.75% of the total microplastics detected in all samples. Fragments and fibres were significantly abundant compared to pellets, representing 63% and 35%, respectively. Microplastics were observed in different colours, among which blue, white and green were the most dominant. Raman analyses of microplastics showed the presence of high density polyethylene, low density polyethylene, polyurethane foam, polypropylene, polyethylene co-vinyl acetate, and poly(ethylene-co-1-hexene). Additionally, two pigments (vine black and smalt), one dye (saffron), three minerals (orthoclase, carbon, and microcline), and one additive (cis-13-docosanol) were also identified. The dominance of fragments and fibres, with the clear signs of fragmentation implied that microplastics in the Vaal River are mostly from secondary sources. The study reported the first data on microplastic pollution and characteristics in sediments of the Vaal River, thus, providing a benchmark and reference platform for relevant formulation and decision-making regarding this essential water source.

Effects of Simulated Reclaimed Water on Soil Particle Sizes and Cd Adsorption and Migration in Soils at Smelting Sites.

This work studied the vertical migration characteristics of Cd in soil profiles from a zinc smelting site under the influence of simulated reclaimed water containing NaCl and Na2SO4. The isothermal adsorption curves of Cd in the soils of miscellaneous fill and weathered slate well fitted the Freundlich and Langmuir models, with R2 ranging from 0.991 to 0.998. The maximum adsorption capacity of Cd in the soils decreased significantly under the salt ion treatments with NaCl and Na2SO4. After leaching, the Cd concentrations in the leachates and Cd contents in the subsoil layers of 10-60cm followed the order NaCl treatment > Na2SO4 treatment > CK (p < 0.05), suggesting that the salt ions promoted the vertical migration of exogenous Cd. The proportion of coarse particles (> 0.02mm) decreased, while that of fine particles (< 0.02mm) increased under salt ion treatments (p < 0.05). The morphological characterization indicated that salt ions accelerated the erosion and fragmentation of coarse particles to form fine particles. The use of reclaimed water to flush smelting sites may increase the risk of Cd migration with small-sized soil particles from the soil to groundwater.

Comparative optimization of densified system of ultra-fine particles (DSP) and Horsfield filling toward UHPC fabrication

Using small size particle as secondary filler to fill in the gap between cement particles according to either DSP or Horsfield filling theory will optimize the packing structure, thereby enhancing the properties of UHPC. However, there are key differences between the two theories regarding to the ratio between the particle size of cement and secondary filler, making it questionable to improve the performance of UHPC. Herein, we developed DSP guided UHPC and Horsfield inspired UHPC via the use of silica fume and fly ash microsphere, respectively, we compared and evaluated the packing structure and corresponding performance. We found that less well-known method Horsfield filling theory contributed to the overall best performers of UHPC compared with that of DSP inspired UHPC. 1H NMR spectra and wet packing density calculation results demonstrated that Horsfield packing contributed to a more homogeneous and denser microstructure, and significantly reduced autogenous shrinkage, cost, and energy burden compared with that of DSP-modified UHPC. We also found that typical DSP fell far short of its theoretical state due to SF agglomeration. This study explores the potential of Horsfield packing in optimizing the packing structure of UHPC, providing an economical option for enhancing the performance of concrete.

Microstructure evolution, interface and mechanical properties of SiCp/2A14 joint during laser keyhole welding

Welding problems have restricted the applications of lightweight SiCp/Al composites in aerospace. In this work, the controllability of the keyhole mode, nucleation mechanism, and mechanical properties of the laser-welding process are studied in detail. The extrusion effect formed by the open keyhole pushes SiC particles to the bottom of the molten pool. To observe the nucleation and growth mechanism of the Al4C3 of keyhole laser-welded SiC/2A14Al composites, the dissolution–precipitation behavior of the SiC particles and growth behavior of the Al4C3 tip were observed. Owing to its high chemical properties, Al4C3 mainly begins nucleating from the open edges of the SiC particles and its formation is mainly distributed along the direction of Al grains. Al4C3 was the main crack source and propagation path while the small-sized SiC particles hindered the crack propagation. This work innovatively regulates the keyhole mode to achieve ‘small damage breakdown’ laser welding, greatly reducing the volume fraction of Al4C3. It also provides new insight into fusion welding of SiC particle-reinforced Al matrix composites.

Microstructure and mechanical performances of novel multi-phase refractory high entropy alloys in Ti-Zr-V-Mo fabricated by vacuum arc melting

In this work, four novel refractory high entropy alloys (RHEAs) of the Ti-Zr-V-Mo system have been developed and characterized by experiments. Except for the RHEA of Ti0.5ZrVMo with phase constituents of bcc + pm-3n + Laves (C15 type), the phase constituents in the as-solidified condition of all the other three RHEAs can be denoted as bcc1 + bcc2 + Laves (C15 type). All four alloys exhibited typical dendrite morphology with coarse dendrites and thin inter-dendritic regions. Besides, there were certain small-sized precipitated particles dispersed in the inter-dendrite matrix. In TiZrV3Mo, bcc structured solid solution phases of (TiMoV) and (TiZrV) as well as one C15 Laves phase of (MoV) Zr were confirmed. The equiatomic RHEA of TiZrVMo exhibited a yield strength of 1323.0 MPa, compressive strength of 1521.9 MPa and a compressive strain of 4.5%, also with double bcc structured solid solution phases of (TiMo) and (TiZr) as well as the Laves precipitate of Zr0.5Ti0.5Mo2. The multi-phase RHEAs with solid solutions and minor precipitates with excellent performances by deformation incompatibility between phases, provide a certain reference for the composition design and the industrial development of RHEAs in practical applications.

Triboelectrostatic separation of coal gasification fine ash based on different mineralogical characteristics

Unburned carbon particles in coal gasification fine ash can be recycled as fuel for further combustion and ash particles are highly valuable for utilization, which can only be of secondary utilization if the two are separated. Due to the small size of gasification fine ash particles, triboelectrostatic separation has more technological advantages than traditional flotation. In this study, a first attempt has been made to separate carbon and ash particles from coal gasification fine ash by triboelectrostatic separation. It aims to investigate the feasibility of the method and to study how different mineralogical characteristics affect triboelectrostatic separation. Herein, proximate analysis, X-ray fluorescence spectroscopy analysis and X-ray diffraction analysis were adopted to investigate the fundamental nature of raw ash. The triboelectrostatic separation experiments under single conditions were conducted. Carbon enriched products with loss on ignition of 37.45% and ash enriched products with that of 10.32% were obtained whose yield was 29.81% and 32.98%, respectively. Results demonstrated the feasibility of the dry technology to separate residual carbon and ash particles in coal gasification fine ash. Furthermore, triboelectrostatic separation of coal gasification fine ash was significantly affected by differences in particle size and microtopography. Particles of small size were firstly adsorbed by plates in the high voltage electric field. The charge capacity of flake and blocky carbon particles was stronger than that of bonded and flocculated carbon particles allowing them easier to be separated.

DC conductivity mechanism in La0.7Sr0.3MnO3 (LSMO)-ZnO nanocomposites

La0.7Sr0.3MnO3 (LSMO)-ZnO nanocomposites with varying concentrations of ZnO have been synthesized using the solution combustion method. A bimodal particle size distribution has been formed in all the samples. The crystallite size increases in the composites as compared to LSMO. The study on electrical resistivity reveals that LSMO exhibits a metal-to-insulator transition at 359 K, while the inclusion of ZnO suppresses the metallic behavior in the composites and increases the resistivity. Transport behavior of the samples in metallic and semiconducting regions has been explained with a known polynomial equation and a two-channel conduction model obeying the small polaron hopping mechanism, respectively. A very low activation energy in the range of 10–12 meV is observed due to smaller-sized particles. The presence of ZnO drives the hopping mechanism from adiabatic in LSMO to become non-adiabatic in the composites and enhances the maximum temperature coefficient of resistance. 80% LSMO-20% ZnO (by weight ratio) composite shows a maximum TCR of −29.81%/K at 248 K, which makes it a potential candidate for several applications in sensing devices. The Curie temperature of the material decreases with the increase in ZnO content in the sample. The results of this study also confirm the existence of correlation between the electrical and magnetic properties of LSMO.

Facile cubic Nd doped MnO nanostructure synthesis as effective electrocatalyst for oxygen evolution reaction

Development of an effective electrocatalyst for the electrochemical water splitting to store electrical energy as H2 fuel and improve sluggish oxygen evolution reaction (OER) is the need of the time. For H2 production and making it more accessible, developing a low-cost fabrication method for an efficient OER catalyst with characteristics including a large surface area, an abundance of active sites, and exceptional stability is necessary. In this study, neodymium-doped manganese oxide (Nd-MnO) with a larger specific surface area (32.6 m2/g), small size particles (84 nm), and most crucially high concentration of oxygen vacancies fabricated via a simple solution reduction method using NaBH4 as a reductant. Nd-MnO has an overpotential of 394 mV and a Tafel slope value of 84 mV/dec reaching 10 mA/cm2, superior to RuO2 and MnO. The potential results of the Nd-MnO are due to a unique structure consisting of nanocubes that may enhance OH ion mass diffusion/transport and offer a large number of active sites for catalysis of OER, as well as oxygen vacancies which are also validated by DFT that may enhance the electronic conductivity and provide H2O adsorption on the surface of neighboring Mn3+ sites.

Photocatalytic Systems Based on ZnO Produced by Supercritical Antisolvent for Ceftriaxone Degradation

Emerging contaminants are a significant issue in the environment. Photocatalysis is proposed as a solution for the degradation of pollutants contained in wastewater. In this work, ZnO-based photocatalysts have been produced and tested for the photocatalytic degradation of an antibiotic; specifically, ceftriaxone has been used as a model contaminant. Moreover, there is particular interest in combining small-size ZnO particles and β-cyclodextrin (β-CD), creating a hybrid photocatalyst. Zinc acetate (ZnAc) (subsequently calcinated into ZnO) and β-CD particles with a mean diameter of 0.086 and 0.38 µm, respectively, were obtained using the supercritical antisolvent process (SAS). The produced photocatalysts include combinations of commercial and micronized particles of ZnO and β-CD and commercial and micronized ZnO. All the samples were characterized through UV–Vis diffuse reflectance spectroscopy (DRS), and the band gap values were calculated. Raman and FT-IR measurements confirmed the presence of ZnO and the existence of functional groups due to the β-cyclodextrin and ZnO combination in the hybrid photocatalysts. Wide-angle X-ray diffraction patterns proved that wurtzite is the main crystalline phase for all hybrid photocatalytic systems. In the photocatalytic degradation tests, it was observed that all the photocatalytic systems exhibited 100% removal efficiency within a few minutes. However, the commercial ZnO/micronized β-CD hybrid system is the photocatalyst that shows the best performance; in fact, when using this hybrid system, ceftriaxone was entirely degraded in 1 min.

Tough and lightweight polyimide/cellulose nanofiber aerogels with hierarchical porous structures as an efficient air purifier

With the increasing severity of health problems caused by air pollution, the demand for high-quality air filtration aerogel materials is increasing. Aerogels with a hierarchical porous structure are beneficial for filtering dangerous small-sized particles, especially for the removal of nanoparticles in the air. In this study, composite nanofibrous aerogels with clear hierarchical porous structures were successfully prepared by the introduction of cellulose nanofibers (CNF) into a polyimide nanofiber (PINF) system by self-assembly and freeze-drying technology. Notably, solvent-induced crystallization was used to improve the pore structures of the nanofiber aerogels. The resulting aerogel samples exhibited an extremely low density and a hierarchical porous structure. More importantly, the samples exhibited high filtration efficiency (99.69% for PM0.3) and a low pressure drop (230 Pa) at a lower base weight, rendering them promising air filtration materials for the applications in more complex environments.

Promotion of catalytic performance of Pd/Al2O3 for o-xylene oxidation by morphological control

Pd/Al2O3 catalysts with different support morphologies (nanoflake, nanorod, nanobeam) were prepared and tested for o-xylene oxidation, and characterized by BET, XRD, TEM, XPS, NMR, CO-TPR-MS, H2-TPR and in-situ DRIFTS. The results indicated that the morphology has a strong effect on the dispersion of Pd species and the oxidation capacity of the catalysts. Compared with nanorod and nanobeam, the nanoflake morphology provides more surface defect sites, penta-coordinated Al3+ and surface OH species. Such sites (defect sites, AlP sites and OH species) enabled the immobilization of Pd to form Pd metal particles of small size, resulting in high Pd dispersion with primary exposure of Pd(100) facets possessing more defect sites for the adsorption. The OH species were also the adsorption sites. Both of them are conducive to the reactivity of adsorbed o-xylene. Moreover, the OH species on Pd/Al2O3 represented activated oxygen, indicating that o-xylene can be oxidized by OH directly. It means that these small Pd particles with more active surface OH species are responsible for the excellent catalytic performance of Pd/Al2O3-NF. Its o-xylene oxidation activity is much better than that of other Pd-based catalyst previously reported. Consequently, morphology control can manipulate Pd particle size and surface OH species to effectively improve the catalytic performance of Pd/Al2O3.

Unusual size effect of spinel Co0.5Fe0.5Al2O4 supported Pt catalysts on the selective hydrogenation of cinnamaldehyde

Pt/Co0.5Fe0.5Al2O4 catalysts with the average Pt particle size of 1.6–3.4 nm were prepared and applied to the selective hydrogenation of cinnamaldehyde (CAL). Not only the TOF was promoted from 0.19 to 2.70 s−1, but also the selectivity to cinnamyl alcohol (COL) was improved from 68% to 94%, with the increase of Pt particle size. Stronger interaction occurred between Co0.5Fe0.5Al2O4 and smaller-sized Pt particles, resulting in electron-deficient Pt particles, so that CO and CC bond could be activated simultaneously. However, electron-rich Pt species existed on Pt/Co0.5Fe0.5Al2O4 with larger Pt size, which is beneficial for the preferential activation of CO bond.

Compressive strength prediction of crumb rubber mortar based on mesoscale model

A mesoscale model was developed to study the compressive performance of crumb rubber mortar (CRM). The internal structure of CRM was considered as a three-phase composite consisting of rubber, mortar, and interfacial transition zone (ITZ). The effects of ITZ, rubber aggregate distribution, mortar matrix strength, rubber aggregate shape, and treating rubber as pores on the compressive strength of CRM were studied. The influence of the presence of ITZ on the compressive strength of CRM was lower than 2 % and was negligible.The location of rubber particles has an effect on the strength of CRM. The use of small-sized rubber particles resulted in a more uniform internal structure of the CRM samples and less variation in strength among different samples. Adding rubber reduces the compressive strength of mortar, and the strength reduction rate is mainly affected by the rubber content. Rubber particles can be equivalent to pores to analyze their influence on the compressive strength and failure mode of CRM. The stress concentration that occurs around the position of the rubber particles is a major factor that causes the strength of CRM to decrease. A prediction formula was presented to calculate the compressive strength of CRM, which agreed well with the experimental results.

Polystyrene microplastics with different sizes induce the apoptosis and necroptosis in liver through the PTEN/PI3K/AKT/autophagy axis

The production of plastics worldwide has been instrumental in the progress of modern society, while the increasing accumulation of plastics castoff in oceans, soils and anywhere else has become a major pressure source on environmental sustainability and animal health. Meanwhile, from a biological perspective, our understanding of the toxicological fingerprints of plastics, especially microplastics (MPs), is still poor. Here, we reported a phenomenon of hepatotoxicity dominated by MPs in the form of polystyrene (PS), was observed in mice model systems and cellular assays. Apoptosis and necroptosis related to the size of particles were seen upon PS-MPs introduction, as revealed by transmission electron microscopy, fluorescence microscopy, flow cytometry, and quantitative analysis of signaling pathways in vivo and vitro. Collectively, the current study demonstrated that the levels of liver cell injury caused by PS-MPs were negatively correlated with the particle diameters. Small-sized particles (1–10 μm) induced cell death primarily as necroptosis whereas the large-sized particles (50–100 μm) mainly induced apoptosis, which was directly accomplished by PTEN/PI3K/AKT signaling axis and its targeted autophagy flux. More interestingly, inhibition of autophagy not only alleviated PS-MPs-triggered cell death, but also changed the form of death injury to a certain extent. This uncovered crosstalk relationship opens up a new avenue for investigating the biological and toxicological effects of MPs, and may provide important insights for preventing and limiting of health hazards from MPs.

Influence of Deposition Time on Titanium Nitride (TiN) Thin Film Coating Synthesis Using Chemical Vapour Deposition

Titanium nitride (TiN) thin film coatings were grown over silicon (p-type) substrate using the atmospheric pressure chemical vapour deposition (APCVD) technique. The synthesis process was carried out to evaluate the effect of deposition time on the physical and mechanical characteristics of TiN coating. Thin films grown over Si substrate were further characterised to evaluate the morphological properties, surface roughness and mechanical properties using a scanning electrode microscope (SEM), atomic force microscopy (AFM) and nanoindentation, respectively. EDS equipped with SEM showed the presence of Ti and N elements in considerable amounts. TiN morphology obtained from the SEM test showed small-sized particles on the surface along with cracks and pores. AFM results revealed that by increasing the deposition time, the surface roughness of the coating also increased. The nanomechanical properties such as nanohardness (H) and Young’s modulus (E), etc., evaluated using the nanoindentation technique showed that higher deposition time led to an increase in H and E. Overall, it was observed that deposition time plays a vital role in the TiN coating deposition using the CVD technique.

High-loading magnetic nanocrystals well-dispersed onto carbon nanosheet honeycombs as ultralight and broadband microwave absorbers

Homogenously and densely dispersing small-sized magnetic particles into hierarchically porous carbon matrices is essential yet challenging for high-performance carbon-based microwave absorbers with balanced impedance matching and strong attenuation ability. Herein, we propose a general and scalable strategy by direct pyrolysis of solid polyvinylpyrrolidone (PVP) dissolved with metal (i.e., Fe, Co, and Ni) nitrates to prepare carbonaceous-magnetic hybrid absorbers. Benefiting from coordination interactions of carbonyl group-rich PVP molecules toward metal ions and the thermal foaming effect of PVP, the optimized CoNi-based composite material possesses a honeycomb-like architecture built by ultrathin (<2 nm) carbon nanosheets embedded with a high-loading (>50 wt%) of ultrafine CoNi alloy nanocrystals (an average size of ∼20 nm). Such structural characteristics endow the absorber with an ultralow tap density of 87.0 mg cm−3 and excellent microwave absorption performance with a superior reflection loss of −51.4 dB at a thickness of 2.6 mm and an effective absorption bandwidth of 7.2 GHz (10.5−17.7 GHz). Moreover, this synthesis methodology is universally applicable and can easily be extended to prepare carbon honeycomb composite absorbers decorated with other magnetic nanocrystals.

A new exhalation-assisted aerosol delivery method for nasal administration

Nasal administration can be used to treat not only local and systemic diseases but also central nervous system diseases. However, the delivery efficiency to the target site needs to be improved. In this paper, a new exhalation-assisted aerosol delivery method (EDM) for nasal administration is proposed. Numerical simulation model validated by experiments was applied to investigate the transport phenomenon of aerosol drugs in the nasal cavity. The effects of aerosol particle diameter and expiratory flow rate on delivery efficiency were investigated. The results show that exhalation flow prevents small-sized particles from entering the larynx and lower respiratory tract, so it will reduce drug wastage and side effects. Moreover, the delivery efficiency of EDM was compared with bi-direction nasal delivery method (BDM) to confirm that the proposed method has an advantage. A slight exhalation flow during aerosol administration can achieve higher delivery efficiency to the turbinate compared with BDM for small particles. There exists an optimum expiratory flow rate for a specific particle size that maximizes the delivery efficiency of the turbinate. The EDM has the advantages of more uniform drug distribution and higher delivery efficiency, it may be more promising for the treatment of central nervous system diseases, local diseases, and systemic diseases in the future.

Lipoprotein Particle Profiles Associated with Telomere Length and Telomerase Complex Components.

Telomere length (TL) is a well-known marker of age-related diseases. Oxidative stress and inflammation increase the rate of telomere shortening, triggering cellular senescence. Although lipoproteins could have anti-inflammatory and proinflammatory functional properties, the relationship between lipoprotein particles with TL and telomerase activity-related genes has not been investigated much. In this study, we assessed the associations of lipoprotein subfractions with telomere length, TERT, and WRAP53 expression in a total of 54 pre-diabetic subjects from the EPIRDEM study. We regressed TL, TERT, and WRAP53 on 12 lipoprotein subclasses, employing a Gaussian linear regression method with Lasso penalty to determine a lipoprotein profile associated with telomere-related parameters. The covariates included age, sex, body mass index (BMI), dyslipidemia, statin consumption, and physical activity leisure time. We identified a lipoprotein profile composed of four lipoprotein subfractions associated with TL (Pearson r = 0.347, p-value = 0.010), two lipoprotein subfractions associated with TERT expression (Pearson r = 0.316, p-value = 0.020), and five lipoprotein subfractions associated with WRAP53 expression (Pearson r = 0.379, p-value =0.005). After adjusting for known confounding factors, most lipoprotein profiles maintained the association with TL, TERT, and WRAP53. Overall, medium and small-sized HDL particles were associated with shorter telomeres and lower expression of TERT and WRAP53. Large HDL particles were associated with longer telomere and lower expression of WRAP53, but not with TERT. Our results suggest that the lipoprotein profiles are associated with telomere length, TERT, and WRAP53 expression and should be considered when assessing the risk of chronic diseases.

A Heuristic Approach for Predicting the Geometrical Packing of Cementitious Paste to Reduce CO2 Emissions in Reinforced Concrete Production

In recent years, a number of researchers have adopted the wet packing (WP) approach to design different types of concrete mixes. Particle grading is a key to the optimization of the wet compactness density; for that reason, all empty spaces that exist in between large-size particles need to be completely filled with particles of smaller size. Previously-conducted studies in this field have been focused on measuring the particle size distribution’s packing density (PD) of the of granular matrices is the purpose of investigating how to increase the PD of cementitious materials. Thus, literature lacks models capable of predicting the optimal PD value. The current study collected and analyzed 216 datasets in order to construct a model for accurate prediction of PD. The main datasets were organized into two categories: modeling datasets and validation datasets. To configure the model in the best way, a hybrid gravitational search algorithm-artificial neural network (GSA-ANN) was also developed in this study. The findings confirmed ANN as an effective alternative for measuring the ultimate PD of cementitious pastes. ANN provided high levels of accuracy, practicality, and effectiveness in the process of predicting the PD value. Based on the final results, the implementation of the hybrid GSA-ANN technique causes a significant decrease in the number of tests conducted on experimental samples, which results in not only saving time and money, but also reducing the CO2 emission volume.