Increasing Particle Diameter Research Articles

Study on the effects of the shot peening intensity on the microstructure, friction and wear properties of high-strength steel

The microstructure, hardness, residual stress, and friction and wear properties of 25CrNi2MoV steel with different particle diameters during shot peening strengthening were studied. Studies have shown that a grain refinement layer appeared on the surface of the material after shot peening. The shot peening intensity increased with increasing particle diameter; a greater shot peening intensity corresponded to a greater surface hardness of the material, the maximum hardness was 592 HV0.2, and the residual compressive stress on the material surface was 725 MPa. A shot peening finite element model was established to accurately predict the residual stresses in the samples after shot peening. The prediction errors were 1.4–7.9%. The finite element model indicates that the maximum residual stress occurs in the subsurface layer. After shot peening, the wear resistance of the sample significantly improved, and the amount of wear significantly decreased. Therefore, shot peening can significantly improve the mechanical properties and wear resistance of high-strength steel, which increases the service life of parts.

Effect of oxygen contents on morphology, nanostructure, and its formation of soot in laminar coflow ethylene-ammonia diffusion flames

Oxygen content plays a crucial role in influencing the characteristics and formation processes of soot particles. This study explores the effects of varying oxygen levels on the morphology, nanostructure, and formation of soot particles in laminar coflow ethylene-ammonia diffusion flames using a combination of experimental analysis, model development, and numerical simulation. Initially, the impact of oxygen concentration on morphology and nanostructure of particles is examined experimentally. Subsequently, a novel C2H4-NH3-PAHs kinetic model, incorporating cross-reactions between C3\\A1-A3 and HCN, is developed and validated through parameters such as ignition delay, laminar flame speed, and species concentrations. The new model is then used to analyze the effects of different oxygen concentrations on soot formation and nitrogen-containing PAHs in ethylene-ammonia flames. The findings show that a decrease in oxygen concentration results in an increase in the average diameter of primary particles, a reduction in fringe separation distance and fringe length, and an increase in fringe tortuosity. Additionally, lower oxygen concentrations are found to slightly reduce PAH formation and significantly decrease the surface growth rate via the HACA mechanism, leading to reduced soot formation. Furthermore, the primary nitrogen-containing PAHs identified are 2-benzonitrile and 2-naphthonitrile, followed by pyrrolyl and cyanophenanthrene, with lower oxygen concentrations diminishing the formation of these nitrogen-containing PAHs.

Effects of major air pollutants on cognitive function in middle-aged and elderly adults: Panel data evidence from China Health and Retirement Longitudinal Study.

Although numerous studies have discussed about the impact of air pollution on cognitive function, a consensus has yet to be reached, necessitating further exploration of their relationship. The aim of this study is to reveal the effects of major air pollutants on cognitive function in Chinese middle-aged and older adults, while considering the lagged effects of pollution. Panel data were constructed by integrating the air pollutants concentration (particulate matter diameter ≤1 µm (μm) (PM1), PM2.5, PM10, nitrogen dioxide (NO2), and ozone (O3)) among 28 provinces in China and the personal characteristics from China Health and Retirement Longitudinal Study participants during the period of 2011-2015. To explore the effects of single pollutants and their interactions on cognitive function, panel linear regression using ordinary least squares method was employed, and first-order lag effects (two-year interval) of air pollution were introduced into the models. Our study revealed that, after adjusting for confounding factors, higher levels of particulate matter (PM1, coefficient (Coef.) = -0.093, P = 0.001; PM2.5, Coef. = -0.051, P = 0.001; PM10, Coef. = -0.030, P = 0.001) and NO2 (Coef. = -0.094, P = 0.006) were associated with lower cognitive function scores among the participants. Moreover, the interaction between the five major pollutants exhibited a negative effect on cognitive function(Coef. = -2.89, P = 0.004). PM1, PM2.5, PM10 have detrimental effects on the cognitive function of middle-aged and elderly adults in China, where increasing particle diameter correlates with a less negative impacts, providing theoretical underpinnings for the formulation of environmental protection policies.

Different nitrogen conditions regulating extracellular polymeric substances and erosion resistance of sewer sediment: Mechanism of microbial metabolism and molecular response

Nitrogen biotransformation plays a vital role in the metabolism of microbial communities in sewers. Extracellular polymeric substances (EPS) secreted by microbial communities can form gel-like sewer sediments, causing clogging of the sewer. However, knowledge on the effects of varying nitrogen conditions on the erosion resistance of sewer sediments and EPS produced by sewer microorganisms is limited. In this study, two typical organic/inorganic nitrogen ratios of sewage were reproduced in simulated sewer reactors, i.e., 3/7 (R1 group) and 7/3 (R2 group). Higher organic nitrogen (ON) concentrations were found to increase the critical erosion shear stress by 26.43%; this was ascribed to increased particle diameter, weakened electrostatic repulsion of sediments and stimulated EPS secretion in the R2 group. The protein and polysaccharide contents of the R2 group were 48.84% and 34.25% higher than those of the R1 group, respectively, which was supported by increased gene abundances for aromatic amino acid synthesis, general secretory pathways of protein, and synthesis of precursors and polysaccharides. Tightly-bound EPS in R2 group exhibited increased contents of hydrophobic protein secondary structures and intermolecular hydrogen bonds, thereby promoting the formation of gel-like sediment structures with enhanced erosion resistance. However, the microbial diversity and the abundance of key genes involved in EPS generation and secretion (e.g., tyrB, yajC, secB, gumF, and gumH) obviously decreased in the R1 group. Moreover, high ON concentrations increased microbial diversity and enhanced microbial glycolysis, tricarboxylic acid cycle and ammonium assimilation. This study reveals the formation mechanisms of EPS in sewer sediments under different nitrogen conditions and their effects on sediment erosion resistance, which contributed to improved sewer system operation and sewer sediment control.

Autoignition of premixed hydrogen/air mixtures with uniformly dispersed carbon particles

The autoignition of a stoichiometric hydrogen/air mixture laden with uniformly distributed coal char particles is simulated with the Eulerian-Lagrangian approach under isochoric conditions. A zero-dimensional model is adopted to assess the effects of gas temperature, pressure, particle diameter, and concentration on ignition dynamics. Increasing the initial temperature reduces the ignition time and maximum heat release rate of the homogeneous reactions, while the parameters for particle reactions stabilize after reaching a critical temperature. Initial pressure exhibits a non-monotonic influence on gas phase ignition, with higher pressures promoting particle autoignition. An increase in particle diameter decreases the ignition time for the homogeneous reaction, approaching that of particle-free conditions. Meanwhile, particle ignition time first decreases and then linearly increases. Increasing particle concentration reduces the interphase disparities of ignition times, while the two-phase ignition times rapidly rise after exceeding the critical concentration. Moreover, pre-ignition temperature equilibrium (PTE) significantly impacts the ignition parameters and processes. PTE results in a minimal ignition time disparity between the gas and particles, with coal char particles markedly influencing hydrogen ignition. Failure to reach PTE leads to significant two-phase ignition time differences, with negligible impact from the solid phase on gas phase ignition. The particle effect ratio, δ, is introduced to evaluate these effects. Notably, the evolution variations in ignition time and heat release rate are determined by the existence of the PTE under corresponding initial conditions. The findings of this study are crucial for developing strategies to mitigate explosion hazards and enhance the performance of detonation propulsion systems using hybrid fuels.

Basic hydrodynamics of a pilot-scale liquid-solid inverse fluidized bed

A pilot-scale liquid-solid inverse fluidized bed (LSIFB) with 0.33 m in inner diameter and 3.0 m in height was designed and installed. Basic hydrodynamics were investigated experimentally using particles with different diameters and densities. The minimum fluidization velocity increases with the increase of particle diameter and the decrease of particle density and is independent of particle loading. Forty eight sets of data on minimum fluidization velocities from the investigation combined with the literature were collected and summarized to establish an empirical equation by modifying the Wen and Yu equation. The modified equation can predict effectively the minimum fluidization velocity across a wide range of Archimedes number. The bed expansion ratio increases with liquid velocity and particle density but decreases with the increase of particle diameter. Based on the bed expansion characteristics, an empirical equation was proposed by correlating Archimedes number and Reynolds number to predict successfully the bed expansion.

Prediction of Progressive Erosion Characteristics of Centrifugal Pump Blades Based on Dynamic Boundaries

Abstract The conventional method of fixed boundaries for predicting erosion inadequately reflects the erosion characteristics of centrifugal pumps under realistic operating conditions. In this research, we employ the dynamic boundary method, considering the influence of changes in wall morphology due to erosion on the flow field. We utilize the Euler-Lagrange approach and the E/CRC erosion model, incorporating a dynamic boundary geometry reconstruction strategy, to predict the erosion characteristics of the IS80-50-315 single-stage single-suction centrifugal pump. Solid-liquid two-phase flow calculations are conducted on the pump to predict erosion characteristics under varied operating conditions. The results show that the dynamic boundary-based progressive erosion prediction method realistically forecasts the erosion characteristics of the overflow wall and captures the evolution of blade morphology with erosion time. Erosion intensity on the blade suction surface significantly surpasses that on the pressure surface, guided by particle distribution characteristics in the centrifugal pump flow channel. Particle diameter primarily influences the erosion position of centrifugal pump blades; smaller particles induce erosion in the middle region of the blade, while an increase in particle diameter shifts the severe erosion position towards the impeller outlet direction. At a consistent particle diameter, higher particle concentrations correspond to elevated erosion rates in the blade area. We establish a relationship between the blade mass loss rate and erosion time during 2500 hours of pump operation at the design condition, introducing the blade mass loss rate for convenient assessment and prediction of blade damage in the centrifugal pump.

Effect of powder feeding rate and size on critical velocity and mechanical properties of cold sprayed Al2O3/2024 deposit

The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites (Al2O3/2024) are complicated by the addition of ceramic particles. The effects of different feeding rates and particle diameters on critical velocity and mechanical properties were studied by numerical simulation and experiment. The results indicate that as the powder feeding rate increases, the impact velocity of gas and particles gradually decreases, and the temperature of gas and particles increases, resulting in an increase in the difference between particle impact velocity and critical velocity. The highest tensile strength of the deposit is achieved at a powder feeding rate of 1 r/min, which is 343 MPa. As the powder feeding rate increases, the performance of the deposits decreases, but it significantly saves time and cost. As the particle diameter increases, the impact temperature first increases and then decreases, resulting in the critical velocity first decreasing and then increasing, and the mechanical performance first increasing and then decreasing. To some extent, the best performance of the deposit is achieved when the size of the metal particle is close to that of the ceramic particle.

Visual study of hydrate particles agglomeration and rolling characteristic in gas-oil-water phase using a flow loop

Natural gas hydrate blockage always leads to safety problems in oil and gas transportation pipelines. It is important to look for the characteristic of hydrate blockage process. The hydrate blockage was visually investigated under gas-oil-water multi-phase flow conditions in a flow loop in this study. The change of pressure drop with water conversion rate variations were detected. The hydrate particle movements were also observed in the visual pipes at different liquid loadings and water cuts. It was found that the hydrate particles may agglomerate and deposit with an obvious rolling process in low water cut conditions. The oil phase will accelerate particles agglomeration in the contact interface of oil, gas and water, and form a large number of flocculent hydrates. A theoretical hydrate particle rolling model was conducted to analysis the experiment results, and the hydrate particle velocity increases first and then decreases with the increase of particle diameter due to the comprehensive influence of van der Waals force and drag force. The results also confirmed the maximum of the pressure drop increased when the liquid loading increased. However, the hydrate formation and blockage speed also slow down due to small component of the gas phase in high liquid loading. In addition, comparing with 20 % and 80 % water cut, 50 % water cut has the fastest hydrate formation speed in different experimental conditions. Furthermore, the maximum water conversion rate increased with have a higher water cut. More hydrate will form in the condition, which will lead to the decrease of flow velocity in the pipeline.

Numerical investigation of particle behavior and erosion wear in a centrifugal pump using coarse-grained Discrete Element Method

Erosion wear presents a significant challenge in the operation of hydrodynamic systems, particularly in centrifugal pumps. To address this issue, this study employs the coarse-grained Discrete Element Method (CGDEM) coupled with Computational Fluid Dynamics (CFD) to predict erosion wear areas and elucidate particle behavior dynamics. The simulation considers spherical solid particles (brown corundum) with diameters ranging from 0.3 mm to 1 mm and volume fractions of 15% and 5%. The flow field is calculated using the Navier-Stokes equations and the shear-stress-transport (SST) k-ω model. Particle movement is tracked using Newton’s second law, considering drag and gravitational forces. Results indicate that the highest turbulent kinetic energy (TKE) occurs at a flow rate of Q = 15 m3/h. Moreover, the pressure reduces slightly when the flow rate increases, although flow velocity might increase with volumetric discharge. Additionally, increased particle diameter leads to greater erosion wear, particularly on blade leading edges, the volute tongue area, and the volute casing belly region. As particle mass concentration intensifies, wear rates on the volute wall and inner hub edge also increase. The study’s robustness is demonstrated through alignment between experimental and numerical data. This investigation offers valuable insights into erosion dynamics in centrifugal pumps, crucial for enhancing operational efficiency and mitigating erosion-induced challenges in these critical systems.

Rational design of polyelectrolyte complexes based on bevacizumab and gellan gum with a surface modified with chitosan

Bevacizumab (BVZ) is an anti-angiogenic monoclonal antibody used to treat diseases such as various types of cancer. However, its parenteral administration causes several side effects and oral administration is limited due to the integrity of these macromolecules in the face of the extreme conditions of the gastrointestinal tract. To overcome these limitations, the study of drug delivery systems becomes a promising strategy to increase the efficiency of BVZ therapeutic delivery. Therefore, it is important that drug delivery systems are meticulously designed and that their physicochemical properties are understood. The objective of the present study was to develop nanoparticles through polyelectrolytic complexation between polysaccharides and polyampholytes, without the use of organic solvents, and to evaluate the influence of pH and molecular weight on particle formation. Different proportions of polymers were tested to obtain the nanoparticles, exhibiting average diameters in the range of 222.6–412.1 nm, zeta potential of −16.3 to −40 mV, and polydispersity index of ∼0.16–0.53. Complexation with chitosan promoted charge inversion (> +40 mV), in addition to increasing particle diameter and association efficiency, ranging from 29 % to approximately 60 %.

Synergistic Effect of Microconvex Texture and Particle Medium on the Tribological Property of the Rubber Sliding Interface.

In this study, we examined how surface topography and particle medium interact to affect the tribological performance of rubber sliding interfaces, uncovering the mechanisms of particle lubrication under various conditions. We found that microtextured surfaces, created using a mold transfer method, modestly reduced the friction coefficient of rubber under both dry and lubricated states, primarily by altering the real contact area. Additionally, the presence of different microconvex textures on the surface topography significantly influenced rubber's tribological properties. Our three-dimensional morphological analysis revealed that microtextured rubber surfaces with higher Sa, Sku, and Sal and lower Str values consistently showed lower friction coefficients during sliding. The friction mechanism was attributed to the combined effects of the material properties, surface topography, and contact area. With the addition of a particle medium, the dry friction coefficient of the rubber interface decreased but exhibited an initial increase, followed by a decrease with increasing particle diameter. When particles were mixed with a water-based cutting fluid, the concentration, diameter, and wettability of the particles significantly impacted the tribological properties due to the synergistic effects of surface topography and particle lubrication. This work enhances our understanding of tribological control for viscoelastic materials through surface design, providing a theoretical basis for the tribological optimization of rubber surfaces.

Measurement and theoretical analysis of effective thermal conductivity of lanthanum pentanickel powder beds for hydrogen storage in different particle sizes and bed porosities

Particle diameter and bed porosity change due to the expansion and contraction of metal hydride particles during hydrogen absorption and desorption, which leads to variations in the effective thermal conductivity of metal hydride beds. Therefore, the effective thermal conductivity of the metal hydride beds under different bed porosities and particle diameters must be measured for the design of metal hydride-based hydrogen storage tanks. In this study, the effective thermal conductivities of four kinds of lanthanum pentanickel (LaNi5) powder beds with different bed porosities and particle diameters were measured in various gas atmospheres with gas pressure varying from 0.1 to 4.0 MPa. The volume mean diameters of the four kinds of LaNi5 powders equal 335.2, 196.4, 147.7, and 23.7 μm, respectively. Subsequently, the effects of bed porosity and particle diameter on the effective thermal conductivities were analyzed through the modified Zehner–Schlünder–Damköhler model considering the Smoluchowski effect. Experimental results show that particle diameter and bed porosity influence markedly the effective thermal conductivity of lanthanum pentanickel (LaNi5) powder beds. However, the findings of theoretical analysis based on the modified Zehner–Schlünder–Damköhler model reveal the considerably weaker effect of particle diameter on the effective thermal conductivity under identical bed porosity compared with the measurement results. Such a finding was observed because the variation in particle diameter inevitably changed bed porosity during the effective thermal conductivity measurement, which also affected the effective thermal conductivity of the beds. In addition, decreasing bed porosity and increasing particle diameter can remarkably improve the heat transport via the gas–solid mixture pathway, which improved the effective thermal conductivity of the beds and thus explained the experimental results.

Synthesis and study of the properties of zirconium dioxide powders with different yttrium content

As part of the study, the influence of yttrium content on the properties of particles during controlled precipitation and after thermal treatment was investigated. Precipitation was carried out at a constant pH of 5 from nitric acid solutions, where the concentration of zirconium was 1 mole/dm3 and the yttrium content ranged from 0 to 30 % based on their oxides. The drying and calcination temperatures of the precipitates were 40 °C and 1000 °C, respectively. It was shown that with a yttrium content of up to 15 %, there was a consistent increase in the average diameter of zirconium hydroxide particles during deposition. When the yttrium concentration was increased to 30 %, the average particle size increased during the first 10 minutes of deposition, followed by a gradual decrease. The largest particle diameter was observed in the specimen with 7 % yttrium. In all cases, the formation of spherical aggregates was observed. With an increasing yttrium content, the boundaries between particles became smoother, and the degree of co-deposition of yttrium during synthesis decreased from 80 % to 60 %. Depending on the yttrium concentration, different modifications of stabilized zirconium dioxide powders were obtained: tetragonal ZrO2 for 2–7 % yttrium, and cubic ZrO2 for 15–30 % yttrium. Therefore, the results obtained during the study can be useful for the development of technology for the production of powdered materials for various applications.

Impact of urban tree arrangement on pedestrian exposure to the size-fractional particulate matter in a city boulevard

Trees act as natural filters that mitigate roadside air pollution. However, the filtration impact of different tree arrangements on traffic pollutants with different particle diameters has rarely been analysed in real street canyon environments. To quantify how roadside tree arrangements impact pedestrian exposure to particle number concentrations (PNCs) of different diameters (0.25–32 μm), in situ field measurements were carried out in a boulevard-type street canyon in the city of Xi'an, China. This study analysed the experimental data of PNCs collected along segments of a pedestrian lane under four typical tree arrangements: open space without trees, a sparse-spaced tree arrangement, a medium-spaced tree arrangement, and a dense-spaced tree arrangement in a street canyon. Our results reveal that the effect of tree arrangement on PNCs depended on the particle diameter. In general, trees can significantly reduce coarse PNC (particles with diameters >2.5 μm) but not the fine PNC. Quantitative analysis showed that a medium-spaced tree arrangement, in which tree crowns are adjacent to each other but do not overlap, is the most capable of reducing PNC, followed by a sparse-spaced tree arrangement, while a the dense-spaced tree arrangement has the least impact. The attenuation effect of trees on the PNCs increased with increasing particle diameter. Moreover, the presence of trees altered the local microclimate, which also affected how exposure to PNCs changed. Our empirical findings further highlight the complexity of how trees affect particulate pollutants in street canyons and provide timely insights for enhancing tree-planning management in cities from the perspective of air quality improvement.

Study of the behavior of dust particles in helium turbines considering the effects of particle deposition and resuspension

The deposition of graphite dust poses significant challenges to the helium turbines in high-temperature gas-cooled reactors. In this study, FLUENT, a Computational Fluid Dynamics (CFD) program was used with a discrete-phase model and a random-walk model to calculate the trajectories of particles (assumed spherical). Considering the interactions between particles and the wall as well as the resuspension effect of the fluid, a particle-deposition model was established and coupled to the flow-field calculations of blades with film cooling using user-defined functions. The influence of different deposition models, particle diameters, and blowing ratios on deposition were investigated. The results show rebounding and resuspending particles significantly affect the particle-deposition rate and its distribution. With increasing particle diameter, the deposition rate initially increases and then decreases. The influence of blowing ratio on deposition is complex; as the blowing ratio is increased, the deposition rate of small particles increases, while that of large particles decreases.

Solid–Liquid Two-Phase Flowmeter Flow-Passage Wall Erosion Evolution Characteristics and Calibration of Measurement Accuracy

Solid–liquid two-phase flowmeters are widely used in critical sectors, such as petrochemicals, energy, manufacturing, the environment, and various other fields. They are indispensable devices for measuring flow. Currently, research has primarily focused on gas–liquid two-phase flow within the flowmeter, giving limited attention to the impact of solid phases. In practical applications, crude oil frequently contains solid particles and other impurities, leading to equipment deformation and a subsequent reduction in measuring accuracy. This paper investigates how particle dynamic parameters affect the erosion evolution characteristics of flowmeters operating in solid–liquid two-phase conditions, employing the dynamic boundary erosion prediction method. The results indicate that the erosion range and peak erosion position on the overcurrent wall of the solid–liquid two-phase flowmeter vary with different particle dynamic parameters. Erosion mainly occurs at the contraction section of the solid–liquid two-phase flowmeter. When the particle inflow velocity increases, the erosion range shows no significant change, but the peak erosion position shifts to the right, primarily due to the evolution of the erosion process. With an increase in particle diameter, the erosion range expands along the inlet direction due to turbulent diffusion, as particles with lower kinetic energy exhibit better followability. There is no significant change in the erosion range and peak erosion position with an increase in particle volume fraction and particle sphericity. With a particle inflow velocity of 8.4 m/s, the maximum erosion depth reaches 750 μm. In contrast, at a particle sphericity of 0.58, the minimum erosion depth is 251 μm. Furthermore, a particle volume fraction of 0.5 results in a maximum flow coefficient increase of 1.99 × 10−3.

Enhancing magnetic drug targeting efficiency through computational analysis: Investigating Particle-RBC interaction and non-newtonian blood behavior

Cancer stands as a foremost global mortality determinant, characterized by a persistent deficit in therapeutic modalities capable of reliably and efficiently conveying anti-cancer pharmaceutical agents to profound tissue loci. Within this context, magnetic drug targeting (MDT) has emerged as an innovative approach to cancer management, offering the promise of minimal adverse effects. Accordingly, the current investigation endeavors to evaluate the capture efficacy (CE) of drug-loaded nanoparticles under the influence of an external magnetic field. To this end, a cylindrical neodymium magnet (NdFeB) is employed as the magnetic source. The finite element method (FEM) was utilized to solve the governing equations. The effect of several parameters, including particle diameter, drag force, blood properties, magnetic field intensity, blood’s non-Newtonian behavior, and particle-RBC interaction on the CE of nanoparticles has been investigated. Simultaneous effect of interaction forces and non-Newtonian behavior of blood on the capturing nanoparticles at the tumor site is considered as the novelty of the present work. Taking into account these two parameters will provide more realistic results. Finding showed that the magnetic field intensity and particles’ diameter positively affect the nanoparticles’ CE. For example, by increasing particle diameter from 250 nm to 1500 nm, the CE is increased from 22 % to 53 %, respectively. In addition, it was revealed that consideration of the particle-red blood cell (RBC) interaction, on average, causes a decrease in the CE of nanoparticles by up to 20 %. Regarding the non-Newtonian behavior of blood, it was found that considering blood as non-Newtonian fluid would decrease, on average, 25 % of CE of nanoparticles compared to Newtonian fluid. Results revealed that simultaneous considering the non-Newtonian behavior of blood and interaction forces significantly affect the CE of nanoparticles.

FORMULAS FOR CALCULATING THE STATIONARY WAVE VELOCITY AND IGNITION TEMPERATURE IN FILTRATION COMBUSTION OF HYDROGEN-AIR MIXTURE

We present formulas for calculating the steady-state wave velocity and ignition temperature during filtration combustion of a hydrogen-air mixture in an inert porous medium. According to the obtained formula, the ignition temperature rises smoothly with the increase of the mixture blowing velocity, and decreases with the increase of the porous medium particle diameter. The calculated wave velocities increase with the increase of the mixture inlet velocity and pass into other velocity regimes.

Zn complexed on hybrid manganese doped cobalt ferrite nanoparticles covered by silica as a catalyst in the synthesis of 2-amino-4H-pyran and N- arylquinoline derivatives

In the present work, Zn complexed on hybrid manganese doped cobalt ferrite nanoparticles covered by silica were synthesized. These MNPs were characterized using different techniques including Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), Field emission‐scanning electron micro-scope (FE-SEM), Energy‐dispersive X‐ray spectroscopy (EDS), Vibration sample magnetometer (VSM), Inductively coupled plasma atomic emission spectroscopy (ICP), Zeta potential and Thermogravimetric analysis (TGA). FE-SEM Images showed uniform spherical shape with rough surfaces and an aggregation in structure of MNPs. A decrease in Ms is visible in VSM analysis due to the increase in particle diameter as a result of loading the organic coating on the surface of the magnetic nanoparticles. According to TGA analysis, the synthesized MNPs have good stability up to 125 °C. The ICP analysis indicates the presence of 0.13 mmol/g zinc on the surface of loaded MNPs. The effect of these prepared MNPs as a catalyst was studied in the synthesis of 2-amino-4H-pyran and N- arylquinoline derivatives. This method provides excellent yield of products with short reaction time, simple purification and easy separation of the catalyst. Furthermore, the reusability of the catalyst during five periods was not associated with a significant decrease in its activity.