Dispersion behavior and thermal conductivity characteristics of Al2O3–H2O nanofluids

Dongsheng Zhu,Xinfang Li,Nan Wang,Xianju Wang,Jinwei Gao,Hua Li 한국물리학회 2009 Current Applied Physics Vol.9 No.1

Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typically of 1–100 nm suspended in base fluids. In this study, Al2O3–H2O nanofluids were synthesized, their dispersion behaviors and thermal conductivity in water were investigated under different pH values and different sodium dodecylbenzenesulfonate (SDBS) concentration. The sedimentation kinetics was determined by examining the absorbency of particle in solution. The zeta potential and particle size of the particles were measured and the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to calculate attractive and repulsive potentials. The thermal conductivity was measured by a hot disk thermal constants analyser. The results showed that the stability and thermal conductivity enhancements of Al2O3–H2O nanofluids are highly dependent on pH values and different SDBS dispersant concentration of nano-suspensions, with an optimal pH value and SDBS concentration for the best dispersion behavior and the highest thermal conductivity. The absolute value of zeta potential and the absorbency of nano-Al2O3 suspensions with SDBS dispersant are higher at pH 8.0. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The Al2O3–H2O nanofluids with an ounce of Al2O3 have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al2O3 nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%. Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typically of 1–100 nm suspended in base fluids. In this study, Al2O3–H2O nanofluids were synthesized, their dispersion behaviors and thermal conductivity in water were investigated under different pH values and different sodium dodecylbenzenesulfonate (SDBS) concentration. The sedimentation kinetics was determined by examining the absorbency of particle in solution. The zeta potential and particle size of the particles were measured and the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to calculate attractive and repulsive potentials. The thermal conductivity was measured by a hot disk thermal constants analyser. The results showed that the stability and thermal conductivity enhancements of Al2O3–H2O nanofluids are highly dependent on pH values and different SDBS dispersant concentration of nano-suspensions, with an optimal pH value and SDBS concentration for the best dispersion behavior and the highest thermal conductivity. The absolute value of zeta potential and the absorbency of nano-Al2O3 suspensions with SDBS dispersant are higher at pH 8.0. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The Al2O3–H2O nanofluids with an ounce of Al2O3 have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al2O3 nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%.

Hardness and microstructure of interstitial free steels in the early stage of high-pressure torsion

Song, Yuepeng,Wang, Wenke,Gao, Dongsheng,Yoon, Eun Yoo,Lee, Dong Jun,Lee, Chong Soo,Kim, Hyoung Seop Springer-Verlag 2013 JOURNAL OF MATERIALS SCIENCE - Vol.48 No.13

Analysis of Stress States in Compression Stage of High Pressure Torsion Using Slab Analysis Method and Finite Element Method

Wenke Wang,Yuepeng Song,Dongsheng Gao,Eun Yoo Yoon,이동준,이종수,김형섭 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.5

High pressure torsion (HPT) is useful for achieving substantial grain refinement to ultrafine grained/nanocrystalline states in bulk metallic solids. Most publications that analyzed the HPT process used experimental and numerical simulation approaches, whereas theoretical stress analyses for the HPT process are rare. Because of the key role of compression stage for the deformation of HPT, this paper aims to conduct a theoretical analysis and to establish a practical formula for stress and forming parameters of HPT process using the slab analysis method. Three equations were obtained via equations derivation to describe the normal stress states corresponding to the three zones of plastic deformation for HPT process as stick zone, drag zone and slip zone. As to the compression stage of HPT, the stress distribution results using the finite element method agree well with those using the slab analysis method. There are drag and stick zones on the contact surface of the HPT sample, as verified by the finite element method (FEM) and slab analysis method.

Finite Element Analysis of the Effect of Friction in High Pressure Torsion

Yuepeng Song,Wenke Wang,Dongsheng Gao,Eun Yoo Yoon,이동준,김형섭 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.3

High pressure torsion (HPT) is one of the most important techniques among various methods that createsevere plastic deformation in the production of bulk materials with nano/ultrafine grained microstructures. Since the driving force in deforming the workpiece in HPT is surface friction, understanding of the frictioneffect is critical for successful application of HPT. In this study, the friction effect in HPT was analyzed usingthe finite element method. The distribution of effective strain on the contact surface of the HPT samplesunder different friction conditions was investigated. The friction force influenced the effective strain morein the middle and edge regions than in the central region. The condition for the minimum friction factor thatcould achieve a sticking condition between the surfaces of the dies, and the samples in the middle and edgeregions, was investigated. There was a critical friction coefficient in which the effective strain varies sharplywith an increasing friction coefficient.

Computer Simulation and Verification of Adiabatic Temperature and Apparent Activity Energy of the NiO/Al Aluminothermic System

Song, Yuepeng,Zhu, Yanmin,Gao, Dongsheng,Guo, Jing,Kim, Hyoung Seop The Korean Powder Metallurgy Institute 2013 한국분말재료학회지 (KPMI) Vol.20 No.5

Recently, self-propagating high-temperature synthesis (SHS), related to metallic and ceramic powder interactions, has attracted huge interest from more and more researchers, because it can provide an attractive, energy-efficient approach to the synthesis of simple and complex materials. The adiabatic temperature $T_{ad}$ and apparent activation energy analysis of different thermit systems plays an important role in thermodynamic studies on combustion synthesis. After establishing and verifying a mathematic calculation program for predicting adiabatic temperatures, based on the thermodynamic theory of combustion synthesis systems, the adiabatic temperatures of the NiO/Al aluminothermic system during self-propagating high-temperature synthesis were investigated. The effect of a diluting agent additive fraction on combustion velocity was studied. According to the simulation and experimental results, the apparent activation energy was estimated using the Arrhenius diagram of $ln(v/T_{ad}){\sim}/T_{ad}$ based on the combustion equation given by Merzhanov et al. When the temperature exceeds the boiling point of aluminum (2,790 K), the apparent activation energy of the NiO/Al aluminothermic system is $64{\pm}14$ kJ/mol. In contrast, below 2,790 K, the apparent activation energy is $189{\pm}15$ kJ/mol. The process of combustion contributed to the mass-transference of aluminum reactant of the burning compacts. The reliability of the simulation results was experimentally verified.

Effect of Revolution on Inhomogeneous Deformation of IF Steel in High Pressure Torsion

Song, Yuepeng,Chen, Miaomiao,Xu, Baoyan,Gao, Dongsheng,Kim, Hyoung Seop 'Scientific Research Publishing, Inc.' 2016 Materials sciences and applications Vol.7 No.11

Synthesis of stable nanoparticles at harsh environment using the synergistic effect of surfactants blend

Ehsan Nourafkan,Maryam Asachi,Zhongliang Hu,Hui Gao,Dongsheng Wen 한국공업화학회 2018 Journal of Industrial and Engineering Chemistry Vol.64 No.-

Synthesis of nanoparticles (NPs) that can withstand high temperature and high salinity (HT-HS) is a big challenge in the research community. A novel strategy to synthesize stable nanoparticles under harsh environment (HT-HS) is proposed in this work by using the synergistic effect of a surfactant mixture. Long-term stable iron oxide nanoparticles at HT-HS conditions were produced and stabilized by two different surfactant classes, i.e. sulfonate surfactant for high temperature resistance and ethoxylated alcohol surfactant for high salinity resistance. The results prove that the new strategy could be used for production of stable NPs which is suitable for enhanced oil recovery application.

Synthesis of stable iron oxide nanoparticle dispersions in high ionic media

Ehsan Nourafkan,Maryam Asachi,Hui Gao,Ghulum Raza,Dongsheng Wen 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.50 No.-

A novel one-pot method was developed in this work to synthesize and disperse nanoparticles in a binarybasefluid. As an example, stable magnetite iron oxide (Fe3O4) dispersions, i.e., nanofluids, were producedin a high ionic media of binary lithium bromide-water using a microemulsion-mediated method. Theeffects of temperature and precursor concentration on morphology and size distribution of producednanoparticles were evaluated. An effective steric repulsion force was provided by the surfacefunctionalization of nanoparticles during the phase transfer, supported by the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The formed nanoparticles exhibited a superior stability againstagglomeration in the presence of high concentrations of lithium bromide, i.e., from 20 to 50 wt.%, whichmake them good candidates for a range of novel applications.

Prediction of exploration targets based on integrated analyses of source rock and simulated hydrocarbon migration direction: a case study from the gentle slope of Shulu Sag, Bohai Bay Basin, northern China

Changqing Ren,Fugui He,Xianzhi Gao,Dongsheng Wu,Wenli Yao,Jianzhang Tian,Huiping Guo,Yuanxin Huang,Li Wang,Han Feng,Junwei Li 한국지질과학협의회 2019 Geosciences Journal Vol.23 No.6

The Shulu Sag which is a rifted sag with NNE trend is located in the south of Jizhong Depression, Bohai Bay Basin, northern China. The gentle slope and three troughs are situated in the west and east of the sag, respectively. Both of the lower part of Shasan Member (Es3x) and the lower part of Shayi Member (Es1x) act as source rocks in this sag. Researches on the type, quantity, quality and thermal maturity of the respective organic matter have been conducted using Rock-Eval pyrolysis data. Type II is the dominant kerogen in Es1x of all troughs. However, Type II1 and III is the dominant kerogen in Es3x of Middle-Southern and Northern trough, respectively. TOC (total organic carbon) and pyrolysis S2 (hydrocarbon) values suggest that the Es1x source rocks in Middle-Southern and Northern trough are fair to good and poor to fair generative potential of hydrocarbon, separately. The Es3x source rocks in Middle-Southern and Northern trough possess fair to excellent and poor to fair generative potential of hydrocarbon, individually. Tmax (pyrolysis temperature at maximum S2) values indicate that most of Es3x samples are thermally mature, but all Es1x samples are thermally immature. Under large scale condition, the hydrocarbon secondary migration in the upper part of Shasan Member (Es3s), Shaer Member (Es2) and the upper part of Shayi Member (Es1s) have been simulated using fluid potential model with Arcgis 9.3 software. The simulation results reveal the direction of hydrocarbon secondary migration and the distribution of hydrocarbon migration-accumulation units (HMAUS), and also suggest that the hydrocarbon migration direction is obviously controlled by nose-like structure belts where most of hydrocarbons accumulate. That shows high reliability because they are consistent with the hydrocarbon exploration result in this area. On the basis of integrated analyses of source rocks and hydrocarbon migration direction, the following five areas in the gentle slope are identified to be the preferred hydrocarbon accumulation area: Taijiazhuang area, northern and southern Xicaogu area, as well as northern and southern Leijiazhuang area. It is considerably helpful to reduce the risk in hydrocarbon exploration of Shulu Sag.

Effects of Friction and Anvil Design on Plastic Deformation during the Compression Stage of High-Pressure Torsion

( Yuepeng Song ),( Miaomiao Chen ),( Baoyan Xu ),( Dongsheng Gao ),( Jing Guo ),( Lingfeng Xu ),( Zheng Wang ),( Hyoung Seop Kim ) 대한금속재료학회(구 대한금속학회) 2016 대한금속·재료학회지 Vol.54 No.11

Herein, we report the results of our investigation on the effect of friction and anvil design on the heterogeneous plastic-deformation characteristics of copper during the compressive stage of high-pressure torsion (HPT), using the finite element method. The results indicate that the friction and anvil geometry play important roles in the homogeneity of the deformation. These variables affect the heterogeneous level of strain in the HPT compressed disks, as well as the flash in the disk edge region. The heterogeneous plastic deformation of the disks becomes more severe with the increasing depth of the cavity, as anvil angle and friction coefficient increase. However, the homogeneity increases with increases in the wall angle. The length of flash and the area of the dead metal zone increase with the depth of the cavity, while they decrease at a wall angle of 180°. (Received March 17, 2016; Accepted May 25, 2016)