Jinwei Gao - Academia.edu (original) (raw)
Papers by Jinwei Gao
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Chemical Physics, 2006
Mes 2 B[p-4,4 0 -biphenyl-Nph(1-naphthyl)] (BNPB) is a new light-emitting materials being capable... more Mes 2 B[p-4,4 0 -biphenyl-Nph(1-naphthyl)] (BNPB) is a new light-emitting materials being capable of transporting both holes and electrons. In this work, a series of new compounds whose structures were similar to that of BNPB, were designed and calculated. The total energies, HOMO and LUMO energies, the ionization potential (I p ) and electron affinity (E a ) of these compounds in neutral, cationic and anionic states were obtained based on the optimized geometrical structures. The absorption spectrum of these compounds have been also calculated by TD-DFT(B3LYP) methods with 6-31G(d) basis set. The calculation indicated that all of compounds 1-5 are multifunctional materials as well as BNPB, the I p and E a of compounds 1-5 with electron donating substituents decrease while those of compounds 1-5 with electron withdrawing substituents increase. The different bands of absorption can be obtained by changing the substituents in the benzene rings connected with both nitrogen atom and boron atom.
Density functional theory calculations have been carried out for monomers of polymers at the B3LY... more Density functional theory calculations have been carried out for monomers of polymers at the B3LYP/6-31G(d) level. The quantum chemical descriptors of the calculated results, which are the molecular average polarizability, the most positive net atomic charge on hydrogen atoms in a molecule, the energy of the lowest unoccupied molecular orbital, and the molecular dipole moment, have been used to predict the cohesive energy of polymers with the structure (C1H2C2R3R4). A general quantitative structure–property relationship model, with a correlation coefficient of R = 0.986 and a standard error of s = 2636 J/mol, has been built by multiple linear regression analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 409–415, 2006
Quantitative structure -property relationships (QSPR) for glass translation temperatures (T g), d... more Quantitative structure -property relationships (QSPR) for glass translation temperatures (T g), density (ρ) and indices of refraction (n) of the polyamides have been determined. All descriptors are calculated from molecular structures at the B3LYP/6-31G(d) level. These QSPR models are generated by two methods: multiple linear regression (MLR) and error back-propagation artificial neural networks (BPANN). The model obtained by MLR is used for the calculations of T g (R training=0.9074, SDtraining=22.4687, R test=0.8898, SDtest=23.2417), ρ (R training=0.9474, SDtraining=0.0422, R test=0.8928, SD test=0.0422), n (R training=0.9298, SDtraining=0.0204, R test=0.9095, SDtest=0.0274). The model obtained by BPANN is used for the calculations of T g (R training=0.9273, SDtraining=14.8988, R test=0.8989, SDtest=16.4396), ρ (R training=0.9523, SDtraining=0.0466, R test=0.9014, SDtest=0.0512), n (R training=0.9401, SDtraining=0.0131, R test=0.9445, SDtest=0.0179). These results demonstrate that the MLR and BPANN methods can be used to predict T g, ρ and n. The more accurate predicted results are obtained from BPANN. Figure: Experimental vs. calculated n with cross-validation method (BPANN) for the training set of 53 polyamides and the test set of 14 polyamides. Figure Experimental vs. calculated n with cross-validation method (BPANN) for the training set of 53 polyamides and the test set of 14 polyamides
A set of molecular descriptors, such as hb, alk, Eint, Qii, QH and nN, which are obtained directl... more A set of molecular descriptors, such as hb, alk, Eint, Qii, QH and nN, which are obtained directly from polymeric repeating unit structures, are used to predict the solubility parameter (δ) of polymers and generate a quantitative structure-property relationship (QSPR) model, with the standard error s of 0.75 (J/cc)0.5 for the training set of 51 polymers and the standard error s of 1.01 (J/cc)0.5 for the test set of 46 polymers. The calculated results show that the QSPR model is easier to apply and has better predictive capability than the existing models.
Density functional theory (DFT) calculations are carried out for polyvinyls repeating units at th... more Density functional theory (DFT) calculations are carried out for polyvinyls repeating units at the B3LYP/6-31G(d) level, and the calculated results of E T , E int , C v , S, Q ii , m, a and q K are used to predict V (298 K), P s , F d , R LL , c, H vsum , U R and U H . Multiple linear stepwise regression analysis is used to generate eight more physically meaningful quantitative structure-property relationship models having correlation coefficient R of 0.996 for V (298 K), 0.998 for P s , 0.997 for F d , 0.997 for R LL , 0.997 for c, 0.992 for H vsum , 0.992 for U R and 0.991 for U H , and the conclusions are in consistence with theoretical analysis. Investigated results indicate QSPR models given here are easy to apply and have good predictive capability. q Polymer 46 (2005) 9443-9451 www.elsevier.com/locate/polymer 0032-3861/$ -see front matter q
Quantitative structure–property relationships (QSPR) for the melting point of the polyamides have... more Quantitative structure–property relationships (QSPR) for the melting point of the polyamides have been determined. All descriptors were calculated from molecular structures at the B3LYP/6–31G(d) level and a QSPR model was generated by multiple linear regression (MLR). The important molecular descriptors for polyamide melting-point temperatures (T m) are the number of benzene rings in the backbone chain, the proportion of methylene and acylamino in the backbone chain, the total molecular energy and the atomic charge for the oxygen atom in the acylamino group. The MLR determination coefficient (r 2) and the standard error of estimation for the model are 0.865 and 21.34 K, respectively. In addition to the nonlinear regression technique, error back-propagation artificial neural networks (BPANN) was used to study the relationships between molecular structures and melting-point temperatures. It is concluded that melting-point temperatures for polyamides can be described by molecular chain rigidity and interchain attractive interactions. The more accurate predicted results were obtained from BPANN. Figure Experimental vs calculated Tm using BPANN
Macromolecular Theory and Simulations, 2006
![Research paper thumbnail of Theoretical Investigations on Donor-acceptor Conjugated Copolymers Based on Naphtho [1, 2-c: 5, 6-c] bis [1, 2, 5] thiadiazole for Organic Solar Cell Applications](https://attachments.academia-assets.com/47823147/thumbnails/1.jpg)
](Conjugated polymers with donor−acceptor architectures have been successfully applied in bulk hete... more Conjugated polymers with donor−acceptor architectures have been successfully applied in bulk heterojunction solar cell devices. Tuning the electron-withdrawing capability in donor−acceptor (D−A) conjugated polymers allows for design of new polymers with enhanced electrical and optical properties. In this paper, a series of D−A copolymers, PBDFDTBT (P1a), PBDTDTBT (P2a), PNDTDTBT (P3a), and PQDTDTBT (P4a), were selected and theoretically investigated using PBE0/6-311G** and TD-PBE0/6-311G**//PBE0/6-311G** methods. The calculated results agree well with the available experimental data of HOMO energy levels and band gaps. We further designed and studied four novel copolymers, P1b, P2b, P3b, and P4b, by substituting the 2,1,3-benzothiadiazole (BT) unit in P1a−P4a with a stronger unit of naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole (NT), respectively. Compared with P1a−P4a, the newly designed polymers of P1b−P4b show better performance with the smaller band gaps and lower HOMO energy levels. The PCEs of ∼5%, ∼7%, ∼7%, and ∼7% for P1b−P4b, predicted by Scharber diagrams, are much higher than those of P1a−P4a when used in combination with PCBM. These results clearly reveal that tuning the electron-withdrawing capability in D−A conjugated polymers is an effective way to improve the electrical and optical properties and the efficiency of the photovoltaic device.
Energy and environmental problems have raised great concerns in recent years. The conversion of s... more Energy and environmental problems have raised great concerns in recent years. The conversion of sunlight to electricity is one of the promising ways to solve the energy and environmental problems. The most widely used devices for solar energy harvesting are single crystalline silicon (c-Si) solar cells, with a worldwide installed capacity of over 60 GW, [ 1 ] which can convert solar energy directly into electricity. The conversion effi ciency of solar cells can be improved by boosting light trapping in the cell, and assuring a very high conductivity and transparency of the window electrodes. Several approaches have been developed for improving light trapping: making pyramidal surface textures or other micro-/ nanostructures, [2][3] scattering light with metallic nanoparticles, depositing an anti-refl ection coating (ARC), and fabricating plasmonic metallic structures, and for improving electrode conductivity: metallic grids or conducting oxide fi lms are often applied. For example, commercial c-Si solar cells often adopt a pyramidally textured Si surface covered by an ARC, displaying a high absorbance of ∼ 95%; Ag fi nger electrodes by screen printing are used to get a good conductivity. Light absorbance often compromises electrical conductivity in commercial c-Si solar cells. On a large area device, a screen printed solar cell may have shading losses as high as 10 to 15%.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
We demonstrate through simulations and experiments that a perforated metallic film, with subwavel... more We demonstrate through simulations and experiments that a perforated metallic film, with subwavelength perforation dimensions and spacing, deposited on a substrate with a sufficiently large dielectric constant, can develop a broad-band frequency window where the transmittance of light into the substrate becomes essentially equal to that in the film absence. We show that the location of this broad-band extraordinary optical transmission window can be engineered in a wide frequency range (from IR to UV), by varying the geometry and the material of the perforated film as well as the dielectric constant of the substrate. This effect could be useful in the development of transparent conducting electrodes for various photonic and photovoltaic devices. V C 2013 American Institute of Physics. [http://dx.
We theoretically designed four new A-A-D-A-A type electron donors by side-by-side combination of ... more We theoretically designed four new A-A-D-A-A type electron donors by side-by-side combination of strong electron-withdrawing groups. The electronic structures and optical absorption spectra of donors were calculated using density functional theory (DFT) and time-dependent DFT (TDDFT) at the 6-31G ⁄ level, respectively. The results show that the calculations are in good agreement with the experiments on electronic structures and optical spectra. The designed molecules exhibit good properties with low band gap, low LUMO energy level, and broad light absorption. Moreover, the estimated solar cell efficiency is up to $10% when these donors are used in combination with PCBM as an acceptor.
ABSTRACT Dispersion and stability of Cu nano-suspensions with dispersant is the important base fo... more ABSTRACT Dispersion and stability of Cu nano-suspensions with dispersant is the important base for the study of rheology and heat transfer enhancement of the suspensions. This paper presented a procedure for preparing a nanofluid which was a suspension consisting of nanophase powders and a base liquids. By means of the procedure, Cu-H2O nanofluids with and without dispersant were prepared, whose sedimentation photographs were given to illustrate the stability and evenness of suspension with dispersant. Dispersion and stability of Cu nanoparticles in water were studied under different pH values and the concentration of hexadecyl trimethyl ammonium bromide (CATB) dispersant by the method of zeta potential and absorbency. The results show that zeta potential has very corresponding relation with absorbency, and the higher absolute value of zeta potential and absorbency are, the better dispersion and stability in system is. The absolute value of zeta potential is higher at pH 9.5. CATB can significantly increase the absolute value of the zeta potential of the particle surfaces by electrostatic repulsions, which leads to the enhancement of the stability of the Cu suspensions. The optimizing concentration for CATB in the 0.1% copper nano-suspensions is 0.05%, which has the best disperse results.
Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typi... more 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, Al 2 O 3 -H 2 O 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 Al 2 O 3 -H 2 O 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-Al 2 O 3 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 Al 2 O 3 -H 2 O nanofluids with an ounce of Al 2 O 3 have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al 2 O 3 nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%.
Nanofluids have been attractive for the last few years with the enormous potential to improve the... more Nanofluids have been attractive for the last few years with the enormous potential to improve the efficiency of heat transfer fluids. This work focuses on the effect of pH and sodium dodecylbenzenesulfonate (SDBS) surfactant on the thermal conductivity of nanofluids. The thermal conductivity was measured by a Hot Disk Thermal Constants Anlyser. The results showed that the thermal conductivity enhancements of Cu-H 2 O nanofluids are highly dependent on the weight fraction of nanoparticle, pH values and SDBS surfactant concentration of nano-suspensions. The Cu-H 2 O nanofluids with an ounce of Cu have noticeably higher thermal conductivity than the base fluid without nanoparticles, For Cu nanoparticles at a weight fraction of 0.001 (0.1 wt%), thermal conductivity was enhanced by up to 10.7%, with an optimal pH value and SDBS concentration for the highest thermal conductivity. Therefore, the combined treatment with both the pH and chemical surfactant is recommended to improve the thermal conductivity for practical applications of nanofluid.
[
Chemical Physics, 2006
Mes 2 B[p-4,4 0 -biphenyl-Nph(1-naphthyl)] (BNPB) is a new light-emitting materials being capable... more Mes 2 B[p-4,4 0 -biphenyl-Nph(1-naphthyl)] (BNPB) is a new light-emitting materials being capable of transporting both holes and electrons. In this work, a series of new compounds whose structures were similar to that of BNPB, were designed and calculated. The total energies, HOMO and LUMO energies, the ionization potential (I p ) and electron affinity (E a ) of these compounds in neutral, cationic and anionic states were obtained based on the optimized geometrical structures. The absorption spectrum of these compounds have been also calculated by TD-DFT(B3LYP) methods with 6-31G(d) basis set. The calculation indicated that all of compounds 1-5 are multifunctional materials as well as BNPB, the I p and E a of compounds 1-5 with electron donating substituents decrease while those of compounds 1-5 with electron withdrawing substituents increase. The different bands of absorption can be obtained by changing the substituents in the benzene rings connected with both nitrogen atom and boron atom.
Density functional theory calculations have been carried out for monomers of polymers at the B3LY... more Density functional theory calculations have been carried out for monomers of polymers at the B3LYP/6-31G(d) level. The quantum chemical descriptors of the calculated results, which are the molecular average polarizability, the most positive net atomic charge on hydrogen atoms in a molecule, the energy of the lowest unoccupied molecular orbital, and the molecular dipole moment, have been used to predict the cohesive energy of polymers with the structure (C1H2C2R3R4). A general quantitative structure–property relationship model, with a correlation coefficient of R = 0.986 and a standard error of s = 2636 J/mol, has been built by multiple linear regression analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 409–415, 2006
Quantitative structure -property relationships (QSPR) for glass translation temperatures (T g), d... more Quantitative structure -property relationships (QSPR) for glass translation temperatures (T g), density (ρ) and indices of refraction (n) of the polyamides have been determined. All descriptors are calculated from molecular structures at the B3LYP/6-31G(d) level. These QSPR models are generated by two methods: multiple linear regression (MLR) and error back-propagation artificial neural networks (BPANN). The model obtained by MLR is used for the calculations of T g (R training=0.9074, SDtraining=22.4687, R test=0.8898, SDtest=23.2417), ρ (R training=0.9474, SDtraining=0.0422, R test=0.8928, SD test=0.0422), n (R training=0.9298, SDtraining=0.0204, R test=0.9095, SDtest=0.0274). The model obtained by BPANN is used for the calculations of T g (R training=0.9273, SDtraining=14.8988, R test=0.8989, SDtest=16.4396), ρ (R training=0.9523, SDtraining=0.0466, R test=0.9014, SDtest=0.0512), n (R training=0.9401, SDtraining=0.0131, R test=0.9445, SDtest=0.0179). These results demonstrate that the MLR and BPANN methods can be used to predict T g, ρ and n. The more accurate predicted results are obtained from BPANN. Figure: Experimental vs. calculated n with cross-validation method (BPANN) for the training set of 53 polyamides and the test set of 14 polyamides. Figure Experimental vs. calculated n with cross-validation method (BPANN) for the training set of 53 polyamides and the test set of 14 polyamides
A set of molecular descriptors, such as hb, alk, Eint, Qii, QH and nN, which are obtained directl... more A set of molecular descriptors, such as hb, alk, Eint, Qii, QH and nN, which are obtained directly from polymeric repeating unit structures, are used to predict the solubility parameter (δ) of polymers and generate a quantitative structure-property relationship (QSPR) model, with the standard error s of 0.75 (J/cc)0.5 for the training set of 51 polymers and the standard error s of 1.01 (J/cc)0.5 for the test set of 46 polymers. The calculated results show that the QSPR model is easier to apply and has better predictive capability than the existing models.
Density functional theory (DFT) calculations are carried out for polyvinyls repeating units at th... more Density functional theory (DFT) calculations are carried out for polyvinyls repeating units at the B3LYP/6-31G(d) level, and the calculated results of E T , E int , C v , S, Q ii , m, a and q K are used to predict V (298 K), P s , F d , R LL , c, H vsum , U R and U H . Multiple linear stepwise regression analysis is used to generate eight more physically meaningful quantitative structure-property relationship models having correlation coefficient R of 0.996 for V (298 K), 0.998 for P s , 0.997 for F d , 0.997 for R LL , 0.997 for c, 0.992 for H vsum , 0.992 for U R and 0.991 for U H , and the conclusions are in consistence with theoretical analysis. Investigated results indicate QSPR models given here are easy to apply and have good predictive capability. q Polymer 46 (2005) 9443-9451 www.elsevier.com/locate/polymer 0032-3861/$ -see front matter q
Quantitative structure–property relationships (QSPR) for the melting point of the polyamides have... more Quantitative structure–property relationships (QSPR) for the melting point of the polyamides have been determined. All descriptors were calculated from molecular structures at the B3LYP/6–31G(d) level and a QSPR model was generated by multiple linear regression (MLR). The important molecular descriptors for polyamide melting-point temperatures (T m) are the number of benzene rings in the backbone chain, the proportion of methylene and acylamino in the backbone chain, the total molecular energy and the atomic charge for the oxygen atom in the acylamino group. The MLR determination coefficient (r 2) and the standard error of estimation for the model are 0.865 and 21.34 K, respectively. In addition to the nonlinear regression technique, error back-propagation artificial neural networks (BPANN) was used to study the relationships between molecular structures and melting-point temperatures. It is concluded that melting-point temperatures for polyamides can be described by molecular chain rigidity and interchain attractive interactions. The more accurate predicted results were obtained from BPANN. Figure Experimental vs calculated Tm using BPANN
Macromolecular Theory and Simulations, 2006
Conjugated polymers with donor−acceptor architectures have been successfully applied in bulk hete... more Conjugated polymers with donor−acceptor architectures have been successfully applied in bulk heterojunction solar cell devices. Tuning the electron-withdrawing capability in donor−acceptor (D−A) conjugated polymers allows for design of new polymers with enhanced electrical and optical properties. In this paper, a series of D−A copolymers, PBDFDTBT (P1a), PBDTDTBT (P2a), PNDTDTBT (P3a), and PQDTDTBT (P4a), were selected and theoretically investigated using PBE0/6-311G** and TD-PBE0/6-311G**//PBE0/6-311G** methods. The calculated results agree well with the available experimental data of HOMO energy levels and band gaps. We further designed and studied four novel copolymers, P1b, P2b, P3b, and P4b, by substituting the 2,1,3-benzothiadiazole (BT) unit in P1a−P4a with a stronger unit of naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole (NT), respectively. Compared with P1a−P4a, the newly designed polymers of P1b−P4b show better performance with the smaller band gaps and lower HOMO energy levels. The PCEs of ∼5%, ∼7%, ∼7%, and ∼7% for P1b−P4b, predicted by Scharber diagrams, are much higher than those of P1a−P4a when used in combination with PCBM. These results clearly reveal that tuning the electron-withdrawing capability in D−A conjugated polymers is an effective way to improve the electrical and optical properties and the efficiency of the photovoltaic device.
Energy and environmental problems have raised great concerns in recent years. The conversion of s... more Energy and environmental problems have raised great concerns in recent years. The conversion of sunlight to electricity is one of the promising ways to solve the energy and environmental problems. The most widely used devices for solar energy harvesting are single crystalline silicon (c-Si) solar cells, with a worldwide installed capacity of over 60 GW, [ 1 ] which can convert solar energy directly into electricity. The conversion effi ciency of solar cells can be improved by boosting light trapping in the cell, and assuring a very high conductivity and transparency of the window electrodes. Several approaches have been developed for improving light trapping: making pyramidal surface textures or other micro-/ nanostructures, [2][3] scattering light with metallic nanoparticles, depositing an anti-refl ection coating (ARC), and fabricating plasmonic metallic structures, and for improving electrode conductivity: metallic grids or conducting oxide fi lms are often applied. For example, commercial c-Si solar cells often adopt a pyramidally textured Si surface covered by an ARC, displaying a high absorbance of ∼ 95%; Ag fi nger electrodes by screen printing are used to get a good conductivity. Light absorbance often compromises electrical conductivity in commercial c-Si solar cells. On a large area device, a screen printed solar cell may have shading losses as high as 10 to 15%.
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
We demonstrate through simulations and experiments that a perforated metallic film, with subwavel... more We demonstrate through simulations and experiments that a perforated metallic film, with subwavelength perforation dimensions and spacing, deposited on a substrate with a sufficiently large dielectric constant, can develop a broad-band frequency window where the transmittance of light into the substrate becomes essentially equal to that in the film absence. We show that the location of this broad-band extraordinary optical transmission window can be engineered in a wide frequency range (from IR to UV), by varying the geometry and the material of the perforated film as well as the dielectric constant of the substrate. This effect could be useful in the development of transparent conducting electrodes for various photonic and photovoltaic devices. V C 2013 American Institute of Physics. [http://dx.
We theoretically designed four new A-A-D-A-A type electron donors by side-by-side combination of ... more We theoretically designed four new A-A-D-A-A type electron donors by side-by-side combination of strong electron-withdrawing groups. The electronic structures and optical absorption spectra of donors were calculated using density functional theory (DFT) and time-dependent DFT (TDDFT) at the 6-31G ⁄ level, respectively. The results show that the calculations are in good agreement with the experiments on electronic structures and optical spectra. The designed molecules exhibit good properties with low band gap, low LUMO energy level, and broad light absorption. Moreover, the estimated solar cell efficiency is up to $10% when these donors are used in combination with PCBM as an acceptor.
ABSTRACT Dispersion and stability of Cu nano-suspensions with dispersant is the important base fo... more ABSTRACT Dispersion and stability of Cu nano-suspensions with dispersant is the important base for the study of rheology and heat transfer enhancement of the suspensions. This paper presented a procedure for preparing a nanofluid which was a suspension consisting of nanophase powders and a base liquids. By means of the procedure, Cu-H2O nanofluids with and without dispersant were prepared, whose sedimentation photographs were given to illustrate the stability and evenness of suspension with dispersant. Dispersion and stability of Cu nanoparticles in water were studied under different pH values and the concentration of hexadecyl trimethyl ammonium bromide (CATB) dispersant by the method of zeta potential and absorbency. The results show that zeta potential has very corresponding relation with absorbency, and the higher absolute value of zeta potential and absorbency are, the better dispersion and stability in system is. The absolute value of zeta potential is higher at pH 9.5. CATB can significantly increase the absolute value of the zeta potential of the particle surfaces by electrostatic repulsions, which leads to the enhancement of the stability of the Cu suspensions. The optimizing concentration for CATB in the 0.1% copper nano-suspensions is 0.05%, which has the best disperse results.
Nanofluid is a kind of new engineering material consisting of solid nanoparticles with sizes typi... more 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, Al 2 O 3 -H 2 O 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 Al 2 O 3 -H 2 O 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-Al 2 O 3 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 Al 2 O 3 -H 2 O nanofluids with an ounce of Al 2 O 3 have noticeably higher thermal conductivity than the base fluid without nanoparticles, for Al 2 O 3 nanoparticles at a weight fraction of 0.0015 (0.15 wt%), thermal conductivity was enhanced by up to 10.1%.
Nanofluids have been attractive for the last few years with the enormous potential to improve the... more Nanofluids have been attractive for the last few years with the enormous potential to improve the efficiency of heat transfer fluids. This work focuses on the effect of pH and sodium dodecylbenzenesulfonate (SDBS) surfactant on the thermal conductivity of nanofluids. The thermal conductivity was measured by a Hot Disk Thermal Constants Anlyser. The results showed that the thermal conductivity enhancements of Cu-H 2 O nanofluids are highly dependent on the weight fraction of nanoparticle, pH values and SDBS surfactant concentration of nano-suspensions. The Cu-H 2 O nanofluids with an ounce of Cu have noticeably higher thermal conductivity than the base fluid without nanoparticles, For Cu nanoparticles at a weight fraction of 0.001 (0.1 wt%), thermal conductivity was enhanced by up to 10.7%, with an optimal pH value and SDBS concentration for the highest thermal conductivity. Therefore, the combined treatment with both the pH and chemical surfactant is recommended to improve the thermal conductivity for practical applications of nanofluid.