nanoparticle agglomeration
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Pharmaceutics ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1581
Author(s):  
Nasser Alhajj ◽  
Idanawati Naharudin ◽  
Paolo Colombo ◽  
Eride Quarta ◽  
Tin Wui Wong

Pulmonary delivery of chitosan nanoparticles is met with nanoparticle agglomeration and exhalation. Admixing lactose-based microparticles (surface area-weighted diameter~5 μm) with nanoparticles mutually reduces particle agglomeration through surface adsorption phenomenon. Lactose-polyethylene glycol (PEG) microparticles with different sizes, morphologies and crystallinities were prepared by a spray drying method using varying PEG molecular weights and ethanol contents. The chitosan nanoparticles were similarly prepared. In vitro inhalation performance and peripheral lung deposition of chitosan nanoparticles were enhanced through co-blending with larger lactose-PEG microparticles with reduced specific surface area. These microparticles had reduced inter-microparticle interaction, thereby promoting microparticle–nanoparticle interaction and facilitating nanoparticles flow into peripheral lung.


2021 ◽  
Vol 10 (3) ◽  
pp. 420-430
Author(s):  
Mohammed A. Y. A. Bakier ◽  
Keisuke Suzuki ◽  
Panart Khajornrungruang

The materials used in base fluids and nanoparticles are varied. One- and two-step manufacturing processes are used to create stable and highly conductive nanofluids. Both methods for making nanoparticle suspensions suffer from nanoparticle agglomeration, which is a major problem in any technique that uses nanopowders. As a result, the key to substantial surface finishing at planarization treatments and increase in the thermal characteristics of nanofluids is the production and suspension of almost non-agglomerated or monodispersed nanoparticles in liquids. This unfavorable aggregation is a major problem in nanopowder technology. Primary material constituents agglomerate rapidly overcoming the stable situation, and nanoparticle agglomerates set out in liquids, making it difficult to create nanofluids using two-step techniques. This research looks at the link between nanoparticle agglomeration during slurry flow and Material Removal Rate (MRR) during chemical mechanical polishing (CMP). The reciprocal relationship between MRR and the shear force exerted by the slurry flow was qualitatively elucidated by the researchers for the theoretical investigation. However, the present manipulation is focused on quantifying the shear stress exerted by nanoparticles floating in the slurry. As a result, the MRR-aggregation model is established based on the relationship between MRR and shear force. The experiment is being carried out to support this idea. The experimental results of aggregation and shear forces have been conducted by some recent studies. However, the extension to the real CMP is very promising for accomplishing a precise style of the removal mechanism and surface finishing criterion as well.


Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3882
Author(s):  
Georgios A. Kelesidis ◽  
M. Reza Kholghy

Nanoparticle agglomeration in the transition regime (e.g. at high pressures or low temperatures) is commonly simulated by population balance models for volume-equivalent spheres or agglomerates with a constant fractal-like structure. However, neglecting the fractal-like morphology of agglomerates or their evolving structure during coagulation results in an underestimation or overestimation of the mean mobility diameter, dm, by up to 93 or 49%, repectively. Here, a monodisperse population balance model (MPBM) is interfaced with robust relations derived by mesoscale discrete element modeling (DEM) that account for the realistic agglomerate structure and size distribution during coagulation in the transition regime. For example, the DEM-derived collision frequency, β, for polydisperse agglomerates is 82 ± 35% larger than that of monodisperse ones and in excellent agreement with measurements of flame-made TiO2 nanoparticles. Therefore, the number density, NAg, mean, dm, and volume-equivalent diameter, dv, estimated here by coupling the MPBM with this β and power laws for the evolving agglomerate morphology are on par with those obtained by DEM during the coagulation of monodisperse and polydisperse primary particles at pressures between 1 and 5 bar. Most importantly, the MPBM-derived NAg, dm, and dv are in excellent agreement with the data for soot coagulation during low temperature sampling. As a result, the computationally affordable MPBM derived here accounting for the realistic nanoparticle agglomerate structure can be readily interfaced with computational fluid dynamics in order to accurately simulate nanoparticle agglomeration at high pressures or low temperatures that are present in engines or during sampling and atmospheric aging.


2021 ◽  
Vol 58 (2) ◽  
pp. 80-90
Author(s):  
Branislava Petronijevic Sarcev ◽  
Danka Labus Zlatanovic ◽  
Miroslav Hadnadjev ◽  
Branka Pilic ◽  
Ivan Sarcev ◽  
...  

The aim of this work was to find the influence of the addition of low amount of hydrophilic and hydrophobic TiO2 nanoparticles on compressive strength, microhardness and rheological properties of flowable dental composite material. Specimens were prepared by adding 0.05; 0.2 and 1 wt. % of hydrophilic and hydrophobic 20 nm TiO2 nanoparticles. These specimens were compared to non-modified control specimens in compressive strength and microhardness. Furthermore, their rheological properties were determined. The optimal nanoparticle loading was 0.2 % hydrophobic TiO2, resulting in significantly higher compressive strength and microhardness than those of the control specimen group. Mechanical properties of flowable composites reinforced with hydrophilic and hydrophobic TiO2 at higher loadings are lower than those of control specimens, which is the result of nanoparticle agglomeration. TiO2 nanoparticles addition resulted in the decrease in viscosity in all specimens except for the specimewn with 1% hydrophilic TiO2 nanoparticles. In accordance to the obtained results, hydrophobic nanoparticle addition results in a more resistant and durable material, combined with an increased flowability compared to a non-modified composite.


Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3463
Author(s):  
Yangyiwei Yang ◽  
Carlos Doñate-Buendía ◽  
Timileyin David Oyedeji ◽  
Bilal Gökce ◽  
Bai-Xiang Xu

The control of nanoparticle agglomeration during the fabrication of oxide dispersion strengthened steels is a key factor in maximizing their mechanical and high temperature reinforcement properties. However, the characterization of the nanoparticle evolution during processing represents a challenge due to the lack of experimental methodologies that allow in situ evaluation during laser powder bed fusion (LPBF) of nanoparticle-additivated steel powders. To address this problem, a simulation scheme is proposed to trace the drift and the interactions of the nanoparticles in the melt pool by joint heat-melt-microstructure–coupled phase-field simulation with nanoparticle kinematics. Van der Waals attraction and electrostatic repulsion with screened-Coulomb potential are explicitly employed to model the interactions with assumptions made based on reported experimental evidence. Numerical simulations have been conducted for LPBF of oxide nanoparticle-additivated PM2000 powder considering various factors, including the nanoparticle composition and size distribution. The obtained results provide a statistical and graphical demonstration of the temporal and spatial variations of the traced nanoparticles, showing ∼55% of the nanoparticles within the generated grains, and a smaller fraction of ∼30% in the pores, ∼13% on the surface, and ∼2% on the grain boundaries. To prove the methodology and compare it with experimental observations, the simulations are performed for LPBF of a 0.005 wt % yttrium oxide nanoparticle-additivated PM2000 powder and the final degree of nanoparticle agglomeration and distribution are analyzed with respect to a series of geometric and material parameters.


Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 692
Author(s):  
Helen Uchenna Modekwe ◽  
Messai Adenew Mamo ◽  
Kapil Moothi ◽  
Michael Olawale Daramola

The role of the effect of the support on the reactivity of heterogeneous catalysts cannot be over-emphasized. Therefore, the study documented in this article investigated the effect of different metal oxide supports (MgO, CaO and TiO2) and mixed oxide supports (CaTiO3) on the performance of a bimetallic NiMo catalyst prepared via the sol–gel method during the catalytic growth of carbon nanotubes (CNTs) from waste polypropylene (PP). Waste PP was pyrolyzed at 700 °C in a single-stage chemical vapor deposition reactor and off-gas was utilized in-situ as a cheap carbon feedstock for the growth of CNTs under similar conditions for all the prepared NiMo catalysts (supported and unsupported). The structures of the prepared catalysts and deposited carbon were extensively characterized using X-ray diffraction (XRD), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), etc. The catalytic performance of NiMo supported and unsupported catalysts was evaluated in terms of the yield, purity, and morphology of synthesized CNTs. The results revealed that the stabilizing role of supports is fundamental in preventing nanoparticle agglomeration and aggregation, thereby resulting in improved yield and quality of CNTs. Supported NiMo catalysts produced better aligned graphitic and high-quality CNTs. The NiMo/CaTiO3 catalyst produced the highest carbon of 40.0%, while unsupported NiMo produced low-quality CNTs with the lowest carbon yield of 18.4%. Therefore, the type of catalyst support and overall stability of catalytic materials play significant roles in the yield and quality of CNTs produced from waste PP.


2020 ◽  
pp. 002199832097374
Author(s):  
MJ Mahmoodi ◽  
MK Hassanzadeh-Aghdam ◽  
M Safi

A multi-step homogenization approach is presented to predict the off-axis creep response of hybrid polymer matrix composites (HPMCs) reinforced with unidirectional carbon fibers and silica nanoparticles. The first step deals with evaluating the viscoelastic properties of silica nanoparticle-polymer nanocomposite using the Mori-Tanaka micromechanical model. Two essential features affecting the behavior, including silica nanoparticle agglomeration and interphase region generated due to the interaction between the nanoparticle and polymer are taken into account. In the second step, the off-axis viscoelastic behavior of HPMCs is extracted from the homogenized nanocomposite and carbon fiber properties using a unit cell-based micromechanical model. Some comparative studies between the predictions and available experiment are directed to verify the homogenization process. All the model predictions are in good agreement with the experimental data. The results indicate that with increasing the fiber off-axis angle from 0° to 90°, the presence of silica nanoparticles leads to a reduction in the HPMC creep compliance. Also, the proposed multi-step homogenization approach is applied to investigate the effects of volume fraction, size and agglomeration degree of silica nanoparticles; thickness and material properties of the interphase region; and off-axis angle and volume fraction of the carbon fiber on the HPMC creep response.


Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5164
Author(s):  
Dengwu Jiao ◽  
Karel Lesage ◽  
Mert Yucel Yardimci ◽  
Khadija El Cheikh ◽  
Caijun Shi ◽  
...  

Understanding the influence of magnetic fields on the rheological behavior of flowing cement paste is of great importance to achieve active rheology control during concrete pumping. In this study, the rheological properties of cementitious paste with water-to-cement (w/c) ratio of 0.4 and nano-Fe3O4 content of 3% are first measured under magnetic field. Experimental results show that the shear stress of the cementitious paste under an external magnetic field of 0.5 T is lower than that obtained without magnetic field. After the rheological test, obvious nanoparticle agglomeration and bleeding are observed on the interface between the cementitious paste and the upper rotating plate, and results indicate that this behavior is induced by the high magnetic field strength and high-rate shearing. Subsequently, the hypothesis about the underlying mechanisms of nanoparticles migration in cementitious paste is illustrated. The distribution of the nanoparticles in the cementitious paste between parallel plates is examined by the magnetic properties of the powder as determined by a vibrating sample magnetometer. It is revealed that the magnetization of cementitious powders at different sections and layers provides a solid verification of the hypothesis.


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