Effect of aqueous graphite dispersion on alumina-zircon suspension

H. Majidian,T. EBADZADEH 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.3

The effect of two dispersants (Glydol N1055 and kx9009) on high solids content graphite suspensions were characterized by rheological behavior, sedimentation test and zeta potential. Only the Glydol N1055 dispersant was effective for the wettability of graphite, and kx9009 dispersant being superior to Glydol for graphite suspension as a result of a greater zeta potential and lower viscosity or sedimentation behavior. Alumina-zircon-graphite suspensions were prepared using alumina and zircon powders and graphite dispersion. These suspensions had shear-thinning behavior and could be dispersed using the Dolapix CE-64 dispersant (0.5 wt.%) as well as Glydol (4 wt.%) and kx9009 (0.3 wt.%). Graphite dispersions displayed no sedimentation when alumina-zircon powders and Dolapix were added.

CH4 reforming with CO2 for syngas production over nickel catalysts supported on mesoporous nanostructured γ-Al2O3

Nasrollah Majidian,Mehran Rezaei,Narges Habibi 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.7

Nanostructured γ-Al2O3 with high surface area and mesoporous structure was synthesized by sol-gel methodand employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared sampleswere characterized by XRD, BET, TPR, TPH, SEM and TPO techniques. The BET analysis showed a high surfacearea of 204m2g−1 and a narrow pore-size distribution centered at a diameter of 5.5 nm for catalyst support. The resultsrevealed that an increase in nickel loading from 5 to 15 wt% decreased the surface area of catalyst from 182 to 160m2g−1. In addition, the catalytic results showed an increase in methane conversion with increase in nickel content. TPOanalysis revealed that the coke deposition increased with increasing in nickel loading, and the catalyst with 15 wt%of nickel showed the highest degree of carbon formation. SEM and TPH analyses confirmed the formation of whiskertype carbon over the spent catalysts. Increasing CO2/CH4 ratio increased the methane conversion. The BET analysisof spent catalysts indicated that the mesoporous structure of catalysts still remained after reaction.

Stability properties of alumina-zircon-SiC suspensions by adsorption of Dolapix onto the particles

H. Majidian 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.3

The dispersing behavior of alumina-zircon-SiC concentrated suspensions (up to a solids volume fraction of 50%) in aqueous media was monitored by zeta potential analyses, the amount of adsorbed dispersant on the surfaces and the slip casting rate as a function of SiC addition and dispersant concentration (Dolapix CE-64). The dispersant content for optimum dispersion was found to be 0.5 wt. %. The adsorbed amount of Dolapix was measured by titration and the FTIR method. Results showed that the amount of Dolapix adsorption on alumina surfaces was found to be more than the other phases (zircon and SiC). As the calculation of the Peclet number showed the stability behavior of an alumina-zircon suspension was increased by the addition of SiC particles up to 20 vol. %. Also the adsorption of Dolapix and the slip casting rate were found to decrease by increasing the SiC content. A high green density (about 63%) was obtained by the slip casting of optimum slips.

Frequency and critical fluid velocity analysis of pipes reinforced with FG-CNTs conveying internal flows

Ghaitani, M.,Majidian, A. Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.24 No.3

This paper addresses vibration and instability of embedded functionally graded (FG)-carbon nanotubes (CNTs)-reinforced pipes conveying viscous fluid. The surrounding elastic medium is modeled by temperature-dependent orthotropic Pasternak medium. Flugge shell model is applied for mathematical modeling of structure. Based on energy method and Hamilton's principal, the motion equations are derived. Differential quadrature method (GDQM) is applied for obtaining the frequency and critical fluid velocity of system. The effects of different parameters such as volume percent of CNTs, elastic medium, boundary condition and geometrical parameters are discussed.

Frequency and critical fluid velocity analysis of pipes reinforced with FG-CNTs conveying internal flows

M.M. Ghaitani,A. Majidian 한국풍공학회 2017 Wind and Structures, An International Journal (WAS Vol.24 No.3

This paper addresses vibration and instability of embedded functionally graded (FG)-carbon nanotubes (CNTs)-reinforced pipes conveying viscous fluid. The surrounding elastic medium is modeled by temperature-dependent orthotropic Pasternak medium. Flugge shell model is applied for mathematical modeling of structure. Based on energy method and Hamilton’s principal, the motion equations are derived. Differential quadrature method (GDQM) is applied for obtaining the frequency and critical fluid velocity of system. The effects of different parameters such as volume percent of CNTs, elastic medium, boundary condition and geometrical parameters are discussed.

2D numerical modelling of soil-nailed structures for seismic improvement

Panah, Ali Komak,Majidian, Sina Techno-Press 2013 Geomechanics & engineering Vol.5 No.1

An important issue in the design of soil-nailing systems, as long-term retaining walls, is to assess their stability during seismic events. As such, this study is aimed at simulating the dynamic behavior and failure pattern of nailed structures using two series of numerical analyses, namely dynamic time history and pseudo-static. These numerical simulations are performed using the Finite Difference Method (FDM). In order to consider the actual response of a soil-nailed structure, nonlinear soil behaviour, soil-structure interaction effects, bending resistance of structural elements and construction sequences have been considered in the analyses. The obtained results revealed the efficiency of both analysis methods in simulating the seismic failure mechanism. The predicted failure pattern consists of two sliding blocks enclosed by three slip surfaces, whereby the bottom nails act as anchors and the other nails hold a semi-rigid soil mass. Moreover, it was realized that an increase in the length of the lowest nails is the most effective method to improve seismic stability of soil-nailed structures. Therefore, it is recommended to first estimate the nails pattern for static condition with the minimum required static safety factor. Then, the required seismic stability can be obtained through an increase in the length of the lowest nails. Moreover, placement of additional long nails among lowest nails in existing nailed structures can be considered as a simple retrofitting technique in seismic prone areas.

The effect of nanoparticle in reduction of critical fluid velocity in pipes conveying fluid

Ghaitani, M.M.,Majidian, A.,Shokri, V. Techno-Press 2020 Advances in concrete construction Vol.9 No.1

This paper deal with the critical fluid velocity response of nanocomposite pipe conveying fluid based on numerical method. The pressure of fluid is obtained based on perturbation method. The motion equations are derived based on classical shell theory, energy method and Hamilton's principle. The shell is reinforced by nanoparticles and the distribution of them are functionally graded (FG). The mixture rule is applied for obtaining the equivalent material properties of the structure. Differential quadrature method (DQM) is utilized for solution of the motion equations in order to obtain the critical fluid velocity. The effects of different parameters such asCNT nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios and internal fluid are presented on the critical fluid velocity response structure. The results show that with increasing the CNT nanoparticles, the critical fluid velocity is increased. In addition, FGX distribution of nanoparticles is the best choice for reinforcement.

Facile preparation of bentonite/nano-gamma alumina composite as a cost-effective adsorbent for Ca2+ removal from aqueous solutions

Saeide Pourshadlou,Iman Mobasherpour,Huodsa Majidian,Esmaeil Salahi 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.127 No.-

Desalination and removing elements such as calcium from aqueous solutions is very important to improvewater quality. In this study, bentonite/nano c-alumina composites were utilized as a low-cost adsorbent forcalcium removal from aqueous solutions. To investigate the adsorption process, several experiments wereconducted, including initial calcium concentration, adsorbent dosage, pH, contact time, and the c-aluminacontent in the composite. Increasing c-alumina amounts in the composite by more than 1% had the reverseeffect due to agglomeration. The increase in specific surface area for bentonite-1wt% c-alumina compared tobentonite is mainly due to the addition of c-alumina. The calcium adsorption capasity increased from0.5 mg/g to 1.15 mg/g when the initial ion concentration was raised from 60 ppm to 100 ppm. The adsorptioncapacity of 1.15 mg/g and removal % of 23 with were obtained for optimal initial concentration of100 ppm, adsorbent dosage of 20 g.l1, and composite percentage of bentonite/1 wt% c-alumina. Theadsorption mechanism was studied by the Langmuir, Freundlich, and Dubinin-Radushkevich isothermmodels, and the adsorption data was fitted better by the Freundlich model. The Dubinin-Radushkevich isothermrevealed the physical nature of the adsorption. Conclusively, the bentonite-1wt% c-aluminananocomposite had better results than the raw bentonite.

Dynamic analysis of laminated nanocomposite pipes under the effect of turbulent in viscoelastic medium

M.M. Ghaitani, A,A. Majidian,V. Shokri 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.30 No.2

In this paper, critical fluid velocity and frequency of laminated pipe conveying fluid are presented. Each layer of the pipe is reinforced by functionally graded carbon nanotubes (FG-CNTs). The internal fluid is assumed turbulent and the induced forces are calculated by momentum equations. The pipe is resting on viscoelastic foundation with spring, shear and damping constants. The motion equations are derived based on classical shell theory and energy method. Differential quadrature method (DQM) is used for solution and obtaining the critical fluid velocity. The effects of volume percent and distribution of CNT, boundary condition, lamina layer number, length to radius ration of pipe, viscoelastic medium and fluid velocity are shown on the critical fluid velocity. Results show that with increasing the lamina layer number, the critical fluid velocity increases.

Simultaneous biosorption of nickel and cadmium by the brown algae Cystoseria indica characterized by isotherm and kinetic models

Mohammad Khajavian,David A. Wood,Ahmad Hallajsani,Nasrollah Majidian 한국응용생명화학회 2019 Applied Biological Chemistry (Appl Biol Chem) Vol.62 No.6

Biosorption is an effective way of extracting heavy metal ions from aqueous solutions of various compositions. The brown algae, Cystoseria indica, when treated with sodium chloride, demonstrates significant capacity to extract cadmium and nickel, simultaneously, from aqueous solutions. The batch system was running over wide ranges of initial metal ion concentrations (5–150 mg/L), pH (2–6), adsorbent mass (1–4 g/L), and contact times (20–300 min), at a temperature of 25 °C. The results obtained when applying the system in these conditions exhibit higher removal capacities for cadmium than nickel. The optimal conditions of the biosorption process were found as the adsorbent mass of 1 g/L, initial concentration of adsorbates of 100 mg/L and pH of 6. The equilibrium data obtained are better described by the extended-Freundlich isotherm for nickel and cadmium. The maximum biosorption of nickel and cadmium in binary-metal-component system were 18.17 and 55.34 mg/g, respectively. The kinetic data derived from these experiments were evaluated with pseudo-first-order, pseudo-second-order and intra-particle-diffusion kinetic models. Kinetic examination of the equilibrium data derived from these models suggest that the adsorption of nickel and cadmium both follow the intra-particle-diffusion kinetic model.