nS Particles Research Articles

Influence of nanosilica and chain extender on the mechanical behavior of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) blends

AbstractThe effect of incorporating different percentages of hydrophobic and hydrophilic nanosilica (HPB and HPL NS) particles and chain extender (CE) on the mechanical behavior of poly(lactic acid)/poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) blends was evaluated. The mechanical behavior of the samples was explained using different theoretical models. Microscopic studies showed that adding both types of NS particles and CE led to more uneven surfaces for blends. Also, no obvious aggregations were observed in both blend nanocomposites, and both kinds of NS particles were mainly present in the PBAT phase. Except for the blend containing 1 phr HPB NS particles, which revealed a continuous morphology, all the PLA/PBAT blends containing both types of NS particles indicated a droplet‐matrix morphology. The more the NS content, the more uniform the PBAT distribution. Adding CE in the blends improved Young's modulus, yield strength, and elongation‐at‐break to a particular loading of CE (2 phr), while these properties were diminished after introducing more CE. Also, the most improvements in the yield strength (45%) and Young's modulus (35%) were seen for the PLA/PBAT (75/25 w/w) containing 2 phr CE and 5 phr HPL NS particles. Besides, a good agreement was observed for experimental values and theoretical models for all samples.

SiO nanoparticle modified CFRP composites effecting on mechanical and vibration damping properties

AbstractSiO nanoparticle inclusion effects on vibration‐damping and mechanical properties of carbon fiber reinforced plastic composites (CFRP) were experimentally investigated by incorporating the NS particles into the epoxy resin system. The nanoparticles in the SiO form were incorporated into the epoxy resin at different ratios (0.5%, 1%, 1.5%, 2%, and 3%) in weight to produce the modified CFRP samples. In addition, the effects of cutout with two different types (edgewise semicircular and central circular) on the vibration response of SiO modified CFRP test samples were determined for different SiO particle incorporation ratios. In this way, variation of both mechanical and vibration properties was experimentally determined in terms of cutout weakening of the composite in the middle while incorporating the SiO particle modification of the CFRP composites. It was seen from this study that the incorporation SiO nanoparticles into CFRP composites were provided the increasing trend in the vibration‐damping and mechanical properties and the highest mechanical and vibration properties were obtained for the addition of 1.5 wt% SiO nanoparticles. On the other hand, further SiO nanoparticle addition, more than 1.5–2 wt%, decreased in mechanical and vibration properties of the composite test samples.Highlights SiO nanoparticle effects on mechanical properties of CFRP composite laminates. SiO nanoparticle effects on vibration damping of CFRP composite laminates. Central cutout effects on vibration characteristics of CFRP composite laminates. Fracture characteristics of CFRP composite laminates with SiO nanoparticle incorporation.

Eco-friendly nanosilica-filled lubricant for fatliquoring leather

The present work focused on the synthesis and characterization of two different nanosilica (named NS-1 and NS-2) particles for use with lubricant in fatliquoring leather. NS-1 was prepared in a base-catalyzed reaction at room temperature via a sol-gel-based eco-friendly approach, while NS-2 was synthesized using the bi-functional silane coupling agents in an acid-catalyzed medium at 60 °C. After the NS particles in different contents are added separately to the lubricant (coded NSL-1 and NSL-2), they were applied to leather as a nanosilica-filled lubricant for fatliquoring leather. NS-1 particles with an amorphous and spherical-shaped structure had better thermal stability (at 700–900 °C), a smaller particle size of 150 nm, and particle size distribution, and good wettability properties due to its lower contact angle of 29° than NS-2 particles. NSL-1 containing 10% uniform nanosilica particles was determined to provide well isolation and inter-fibrillar opening in fibrous structures by the SEM analysis. Compared to the others, NS-1- filled lubricant gave a good lubrication effect and exhibited enhancing better and strong the fibrous network structure of the leather consisting of very thin and tight collagen fibers. Also, the leathers treated with NS-1- filled lubricant showed that they can be exhibited better tensile strength, percentage extension, good touching, and fat uptake. The prepared NS particle via a greener sol-gel approach proved a filling effect on the leather and can be used for application in the leather industry as a lubrication agent due to their good properties.

FORMULATION DEVELOPMENT AND CHARACTERIZATION OF LYOPHILIZED FEBUXOSTAT NANOSUSPENSION

Objective: The study aims to prepare and evaluate febuxostat nanosuspension to improve oral bioavailability. Methods: Febuxostat nanosuspension was prepared by the solvent-antisolvent method, followed by a lyophilization technique using PVP K-30 as a stabilizer and sodium lauryl sulfate as a surfactant. Drug content, differential scanning calorimetry, powder x-ray diffraction, Fourier transform infrared spectroscopy, and in vitro dissolution studies were used to characterize the nanosuspension. Results: The results of the characterization studies indicated the formation of nanosuspension. The lyophilized FXT NS particle size is 2170.2 nm, the PDI value is 0.63, the negative zeta potential is 1.6 mV, and the drug content is 19.02%. Functional characterization studies demonstrated that the particle size reduced due to the interaction between the stabilizer and surfactant. Conclusion: It can be concluded that the prepared febuxostat nanosuspension enhances the aqueous solubility of FXT and improves its oral bioavailability.

Effect of Nanoreduction on Functional and Structural Properties of Resistant-Starch from Lotus Stem

This study characterizes the resistant starch (RS) and ball milled RS nanoparticles extracted from the stem of Nelunmbo nucifera, an underutilized aquatic plant. Starch (NS) was extracted from lotus stem and subjected to enzymatic digestion to isolate naturally present RS. The RS nanoparticles were produced via planetary ball milling carried out for 30 min (RS30), 60 min (RS60), and 90 min (RS90). The samples so obtained were characterized using dynamic light scattering (DLS), scanning electron microscopy (SEM), light microscopy, Fourier transform infra-spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and differential scanning colorimeter (DSC). DLS revealed a hydrodynamic diameter of 12.05 μm, 6.7 μm, 543.11 nm, 378.65 and 123.12 nm, and a zeta potential of −12.63, −22.15, −28.79, −35.08, and −27.42 mV for NS, RS, RS30, RS60, and RS90, respectively. SEM displayed oval and smooth NS particles, irregular RS particles, and small and disintegrated RS nanoparticles. RS nanoparticles had significantly higher apparent amylose content, resistant starch content, hydration properties, light transmittance, freeze thaw stability, and viscoelasticity than RS and NS. Also, the expected glycemic index of RS was significantly lower (p < 0.05) than that of NS, whereas nanoreduction elevated the glycemic index values of RS. Thus, lotus stem shows potential to be a source for RS, which could be used as wall material in growing functional and pharmaceutical industries.

Flow ability of cemented pastefill material that contains nano-silica particles

No investigations have been performed on the rheological characteristics of cemented paste backfill (CPB) that contains nano-silica (nS) particles, although the addition of nS to CPB has been regarded as a promising approach to enhance the strength and strength gain rate of CPB at an early age. The present papers present the results of an experimental study on the impact of nano-silica (nS) on the rheological characteristics of CPB. It is found that the nanoparticles considerably impact the rheological properties of CPB, and thus alter its flow ability. The yield stress and viscosity of the CPB specimens incorporating nS are higher than that of the samples without nS. However, the magnitude of this effect is dependent on the binder type, curing time and water content. The findings described and discussed in this manuscript will support the development of the nano-CPB technology and its successful application in underground mine backfill operations.

Bond strength between corroded steel and recycled aggregate concrete incorporating nano silica

Limited information related to the application of nano silica in recycled aggregate concretes has been available in the literature. However, investigations on the effect of nano silica on the bond performance of reinforcement embedment length in recycled aggregate concrete have not been conducted yet. Therefore, the present study aimed at investigating the bond strength for recycled aggregate concretes incorporating nano silica under different levels of corrosive environments. The experimental work consisted of testing 180 pull-out specimens prepared from different mixtures. The main parameters studied were the amount of recycled aggregate (i.e. 0%, 25%, 50% and 100%), nano silica (1.5% and 3%), embedment length (5 and 13Ø) as well as reinforcement diameter (12 and 20 mm). Different levels of corrosion were electrochemically induced by applying impressed voltage technique for 2, 5, 10 and 15 days. Finally, the experimental results were compared with the existing models.Experimental results showed that the bond performance between un-corroded steel and RCA concrete slightly reduced, while a significant degradation was observed after being exposed to corrosive conditions, in comparison to normal concrete. On the other hand, the use of a small quantity of NS (1.5%) showed between 8 and 21% bond enhancement with both normal and RCA concretes under normal conditions. However, much better influence was observed with the increase of corrosion periods, reflecting the improvement in corrosion resistance. NS particles showed a more effective role with RCA concretes rather than conventional concretes in terms of enhancing bond and corrosion resistance. Therefore, it was superbly effective in recovering the poor performance in bond for RCA concretes. By doubling the content of NS (3%), the bond resistance slightly enhanced for non-corroded samples, while its influence becomes more pronounced with increasing RCA content as well as exposure time to corrosion.

Optimization of Low-Carbon Footprint Quaternary and Quinary (37% Fly Ash) Cementitious Nanocomposites with Polycarboxylate or Aqueous Nanosilica Particles

The dispersion medium of nano-SiO2 (nS) particles can have a significant effect on the properties of nanoparticles themselves and consequently on the cement binders it will be added to. In this paper, nS particles dispersed in (a) polycarboxylate or (b) water were added to a low-carbon footprint reference binder containing 43% Portland cement (PC), 20% limestone powder (LS), and 37% fly ash (FA) by mass of binder. Eight quaternary binders containing nS, PC, LS, and FA and eight quinary binders comprising nS, PC, LS, FA, and silica fume (μS) were investigated. nS was added at 0.1%, 0.2%, 0.5%, or 1.0% by mass of binder as a replacement of LS for the quaternary binders and at 0.5% or 1.0% for the quinary binders. The nanoparticles were examined via transmission and X-ray scanning electron microscopy (TEM/SEM/EDX). For the pastes, compressive strength tests and thermal gravimetric analyses (TGAs) were performed at days 1, 7, 28, and 56, all testified to additional pozzolanic activity and additional C–S–H production. X-ray diffraction analyses and backscattered scanning electron imaging carried out on specific formulations also confirmed this finding at days 1, 28, and 56. Notwithstanding the additional pozzolanic reactivity, nS particles could not mitigate the delayed hydration of the reference paste in the early ages. In such complex formulations, the hydration products seem to create a wrapping around the FA particles delaying their activation at early ages. At later ages, the 0.5% nS addition provided strength, microstructural, and hydration improvements. The polycarboxylate/nS particles provided more pronounced strength improvements at 0.5% addition, possibly due to their superplasticizing effect. Lastly, a tabulated literature review on the thermal decomposition ranges of the hydration products of cementitious nanocomposites is also presented.

Localized Nanoscale Heating Leads to Ultrafast Hydrogel Volume-Phase Transition.

The rate of the volume-phase transition for stimuli-responsive hydrogel particles ranging in size from millimeters to nanometers is limited by the rate of water transport, which is proportional to the surface area of the particle. Here, we hypothesized that the rate of volume-phase transition could be accelerated if the stimulus is geometrically controlled from the inside out, thus facilitating outward water ejection. To test this concept, we applied transient absorption spectroscopy, laser temperature-jump spectroscopy, and finite-element analysis modeling to characterize the dynamics of the volume-phase transition of hydrogel particles with a gold nanorod core. Our results demonstrate that the nanoscale heating of the hydrogel particle core led to an ultrafast, 60 ns particle collapse, which is 2-3 orders of magnitude faster than the response generated from conventional heating. This is the fastest recorded response time of a hydrogel material, thus opening potential applications for such stimuli-responsive materials.

A study on nanosilica- and microsilica-added concretes under different transport mechanisms

This paper presents the relative performance of nanosilica (nS)- and microsilica (mS)-added concrete with reference to durability under different transport mechanisms such as absorption, sorption, diffusion and migration. The concrete for this study was made with optimum quantities of mS and nS, which were determined based on maximum strength efficiency factor. The results showed that nS-added concrete exhibited superior durability properties compared to mS-added concrete under the above transport mechanisms, even at lower cement replacement. The beneficial effects of nS on the pore refinement of concrete were observed through the latter's high resistance to water absorption, sorptivity, chloride penetration and corrosion susceptibility. The relatively higher rapid chloride permeability and lower concrete resistivity of nS added concrete were attributed to the possible static surface charge of nS particles. The scanning electron microscopic image showed a compact and dense microstructure of nS-added concrete with increased finer-sized calcium–silicate–hydrate, reduced calcium hydroxide contents, and compact interfacial transitional zones.

Polycarboxylate/nanosilica-modified quaternary cement formulations – enhancements and limitations

The effect of polycarboxylate/nanosilica (nS) particles in quaternary cement formulations comprising Portland cement (PC), limestone powder (LS) and fly ash (FA) was investigated for the first time. The reference formulation contained 60% PC, 20% LS and 20% FA by mass of binder in an effort to minimise clinker and maximise the other constituents. nS particles were characterised by way of transmission and X-ray scanning electron microscopy (SEM). The nS was added at 0·3 or 0·6% by mass as a partial replacement for PC and different water-to-binder (w/b) ratios were explored. Compressive strength tests and thermal gravimetric analyses (TGA) performed at day 7, 28 and 56 testified to pozzolanic behaviour. Results suggest a mechanism of ‘de-activation’ of some FA particles with age. A new ratio: (compressive strength in MPa)/(calcium hydroxide content detected by TGA) was introduced, correlating microscale characteristics (hydration products) and macroscale performance (delivered compressive strengths). Back-scattered SEM images confirmed the calcium–silicate–hydrate (C–S–H) network formation, the presence of reacted/unreacted FA particles and the availability of calcium hydroxide for delayed hydration reactions. Tests on mortars also confirmed the enhancement offered by nS addition. The lower bound nS addition was determined to be 0·6% by mass of binder for pastes and 0·5% for mortars.

Plasmonic Effect of Gold Nanostars in Highly Efficient Organic and Perovskite Solar Cells.

Herein, a novel strategy is presented for enhancing light absorption by incorporating gold nanostars (Au NSs) into both the active layer of organic solar cells (OSCs) and the rear-contact hole transport layer of perovskite solar cells (PSCs). We demonstrate that the power conversion efficiencies of OSCs and PSCs with embedded Au NSs are improved by 6 and 14%, respectively. We find that pegylated Au NSs are greatly dispersable in a chlorobenzene solvent, which enabled complete blending of Au NSs with the active layer. The plasmonic contributions and accelerated charge transfer are believed to improve the short-circuit current density and the fill factor. This study demonstrates the roles of plasmonic nanoparticles in the improved optical absorption, where the improvement in OSCs was attributed to surface plasmon resonance (SPR) and in PSCs was attributed to both SPR and the backscattering effect. Additionally, devices including Au NSs exhibited a better charge separation/transfer, reduced charge recombination rate, and efficient charge transport. This work provides a comprehensive understanding of the roles of plasmonic Au NS particles in OSCs and PSCs, including an insightful approach for the further development of high-performance optoelectronic devices.

Effects of nano-silica on the gas permeability, durability and mechanical properties of high-strength lightweight concrete

This study presents an experimental investigation on the effect of nano-silica (nS) on the gas permeability, durability and mechanical properties of high strength lightweight concrete (HSLWC). In order to expose the effects of nS on the performance of concrete, the lightweight coarse aggregate (LWA) has been fabricated through cold bonded method by the pelletization process by mixing 10% of cement with 90% of fly ash (FA). Then, the utilization of HSLWCs has been finished off by volumetric substitution of normal coarse aggregate with 5 different levels, namely (0%, 10%, 20%, 30% and 40%) with and without nS at a constant water/binder ratio of 0.35 and a constant ratio of 20% of FA. The concrete has been tested at the age of 28 and 90days for splitting tensile strength, sorptivity index, gas permeability and compressive strength as well as 3 and 7days for compressive strength. It has been observed that the increase in the replacement of lightweight coarse aggregate affecting the strength and permeability properties negatively. On the other hand, the results indicate that the addition of 3% nS to HSLWCs reduce the negative properties of lightweight coarse aggregate and leads to remarkable increase in mechanical properties while the sorptivity and gas permeability values have been decreased up to 25% and 40% respectively, when the values compared with the same replacement levels of LWAs. Moreover, it has been found that nS particles have better results on normal concrete compared to the LWCs.

Effect of Nanosilica on the Fresh Properties of Cement-Based Grouting Material in the Portland-Sulphoaluminate Composite System

The effect of NS particle size and content on the fresh properties of the grouting material based on the portland-sulphoaluminate composite system was analyzed. The experimental results indicated that air content increased and apparent density decreased, with increased NS content, but the NS particle sizes have minimal effect on the air content and apparent density. The setting time of mortar was significantly shortened, with increased NS content; however, NS particle sizes had little influence on the setting time. The effect of fluidity on the mortars adding NS with particle size of 30 nm is larger than NS with particle sizes of 15 and 50 nm and the fluidity decreased with increased NS content, but the fluidity of mortars with the particle sizes of 15 and 50 nm is almost not affected by the NS content. XRD analysis shows that the formation of ettringite was promoted and the process of hydration reaction of cement was accelerated with the addition of NS. At the microscopic level, the interfacial transition zone (ITZ) of the grouting material became denser and the formation of C-S-H gel was promoted after adding NS.

The effect of nanosilica addition on flowability, strength and transport properties of ultra high performance concrete

The experimental study herein presented was conducted aiming to evaluate the influence of nanosilica (nS) addition on properties of ultra-high performance concrete (UHPC). Thermo gravimetric analysis results indicated that nS consumes much more Ca(OH)2 as compared to silica fume, specifically at the early ages. Mercury intrusion porosimetry measurements proved that the addition of nS particles leads to reduction of capillary pores. Scanning electron microscope observation revealed that the inclusion of nS can also efficiently improve the interfacial transition zone between the aggregates and the binding paste. The addition of nS also resulted in an enhancement in compressive strength as well as in transport properties of UHPC. The optimum amount of cement replacement by nS in cement paste to achieve the best performance was 3 wt.%. However, the improper dispersion of nS was found as a deterrent factor to introduce higher percentage of nS into the cement paste.

Exploring the potential of siloxane surface modified nano-SiO2 to improve the Portland cement pastes hydration properties

This paper investigates the potential of siloxane surface modified nano-SiO2 as an admixture capable of modifying heat development and microstructure densification of Portland cement pastes. Two different types of siloxanes were grafted on nano-SiO2 (nS) particles. Calorimetric measurements of Portland cement pastes with 0.3 w/b ratio show that the siloxane functional group clearly interferes on the early age reactions of cement pastes with 0.1 or 0.5 by weight of functionalized nS. In situ soft X-ray transmission microscope images of nS/Ca(OH)2 solutions demonstrate that siloxane cover the nS surface and that the treatment allowed nS particles to last longer on a calcium hydroxide saturated solution before forming C–S–H. The possible reasons of this behavior are discussed, including the matrix densification and C–S–H nano-structure filling. The results indicate a potential use of this hybrid to improve the nanostructure of the cement paste matrix.

Development of PLGA-based itraconazole injectable nanospheres for sustained release

PurposeItraconazole (ITZ) is a synthetic triazole antifungal agent, which is widely used for treatment and prevention of fungal infections. The purpose of this study is to develop ITZ-loaded poly(lactic-co-glycolic acid) (PLGA) nanospheres (PLGA-ITZ-NS) as a new sustained-release formulation for intravenous ITZ administration.Materials and methodsPLGA-ITZ-NS were prepared by a nanoprecipitation method and optimized by modifying the surfactant poloxamer 188 concentration and PLGA:ITZ ratio. Their physicochemical properties, including size, zeta potential, external morphology and encapsulation efficiency, were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM) and high performance liquid chromatography (HPLC). The effect of the different selected lyoprotectants with various concentrations on NS particles size and surface charge were also assessed. Rapid and sensitive HPLC and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods were developed to determine ITZ concentrations in formulation and in rat plasma, respectively. Pharmacokinetics of the optimum PLGA-ITZ-NS formulation was compared with the former commercial Sporanox® injection formulation using rats as the animal model. Noncompartmental pharmacokinetic parameters were obtained by WinNonlin® software.ResultsOptimal PLGA-ITZ-NS had a mean particle size of about 200 nm with a high homogeneity (polydispersity index ≈0.2), favorable zeta potential (approximately −20 to −30 mV) and encapsulation efficiency (72%). In addition, 2% w/v sucrose was selected as a lyoprotectant for NS freeze-drying. The newly developed LC-MS/MS assay was validated and found to be accurate and precise. The in vivo study showed that the NS formulation has a similar systemic bioavailability to Sporanox® while providing a sustained plasma level (> 100 ng/mL) for up to 24 hours after intravenous administration.ConclusionOur newly developed PLGA-ITZ-NS has shown great sustained release and comparable bioavailability with Sporanox®, therefore having the potential to be an alternative injectable formulation of ITZ.

Thermal Cycle Reliability of Glass/Ceramic Composite Gas Sealing Materials

We have developed glass/ceramic composite seals composed of glass precursors (NS particles) and ceramic precursors (S particles). The composite seals exhibited low gas permeability at room temperature −650°C, irrespective of the fusion profiles. However, short-term fusion led to the formation of pores in the seals and the pores in the seals depressed the thermal cycle durability. As for the NS/S composite ratios, the addition of S particles obviously improved the thermal cycle durability, but excess addition will bring about delamination at the seal/substrate interface. Appropriate NS/S ratios as well as an adequate fusion profile would result in composite seals with high strength and adhesion.

Effect of nano-silica on rheology and fresh properties of cement pastes and mortars

Amorphous nano-silica (nS) particles (0–2.5 wt%) by cement were incorporated in cement pastes and mortars, and their effect on the fresh state behaviour was analysed. Rheological tests showed that after 75 min from the mixing start, the mortar having 2.5 wt% nS shows insufficient flowability to allow its continuous monitoring in a Viskomat PC viscometer. The influence of nS content was better observed on yield stress when compared with plastic viscosity values (the first increased about 66.5% while the latter just increased 3.6%). With nS addition, spread, setting time and the moment to reach the maximum temperature decreased 33%, 60% and 51.3%, respectively, when compared with samples without nS. X-ray diffraction showed presence of calcium hydroxide after 9 h in the sample with 2.5 wt% nS. The air content increased 79% and apparent density decreased 2.4% when nS was added.

Bonding phase of amorphous silicate gas-tight seals for electrode-supported SOFCs

Electrode-supported SOFCs exhibit highly electrochemical performance but they require gas-tight sealing between porous electrodes. Conventional sealing materials can sufficiently seal with dense materials such as ceramics and metals, but the sealing materials were much penetrated into porous electrodes and excess penetration caused severe gas-leakage. We have prepared insulating flexible sheets to realize gas-tight sealing against porous SOFC electrodes during fusion at 800°C. Amorphous Na2O-SiO2 spherical particles (NS particles) and amorphous SiO2 particles (S particle) were synthesized by sol-gel method, and thick sheets containing NS and S particles were obtained by tape-casting method. Porous La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) ceramics were used as a porous electrode to investigate penetration of sealing materials and identification of bonding phases. Fusion of the sheet against porous LSCF at 800°C resulted in gas-tight sealing and the formation of NaLa9(SiO4)6O2 (NLSO) phase. The formation of NLSO phase was controlled by the addition of S particles. TEC of NLSO did not show anomalous profiles which often result in severe cracks and are shown for some glasses at glass transition temperatures. Therefore, the NLSO phase would be valuable as the bonding phase between LSCF and glass seals.