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Publications (10 of 16) Show all publications
Wang, B. & Kari, L. (2020). One dimensional constitutive model of isotropic magneto-sensitive rubber under shear deformation with amplitude, frequency and magnetic dependency. In: IOP Conference Series: Materials Science and Engineering. Paper presented at 2020 The 3rd International Conference on Smart Materials Applications 13-16 January 2020, Seoul, South Korea (pp. 012002). IOP Publishing, 855(1)
Open this publication in new window or tab >>One dimensional constitutive model of isotropic magneto-sensitive rubber under shear deformation with amplitude, frequency and magnetic dependency
2020 (English)In: IOP Conference Series: Materials Science and Engineering, IOP Publishing , 2020, Vol. 855, no 1, p. 012002-Conference paper, Published paper (Refereed)
Abstract [en]

Modelling the amplitude, frequency and magnetic dependency of magneto-sensitive (MS) rubber in one dimensional case under shear deformation is proposed in this paper. MS rubber is a kind of smart materials which mainly consists of magnetizable particles and rubber matrix. The modulus of MS rubber changes rapidly after the applying of magnetic field which is referred as the magnetic dependency of MS rubber. Besides the magnetic dependency, there is an amplitude and frequency dependency of MS rubber. Specifically, the shear modulus of MS rubber under larger strain magnitude is smaller than the corresponding modulus under small strain and the shear modulus of MS rubber increases with increasing of frequency. A one-dimensional constitutive model consists of a fractional derivative element in parallel with a nonlinear kinematic elastoplastic model to depict the amplitude, frequency and magnetic dependency of MS rubber is developed in this paper. After comparison with the test result, it found that with eight parameters the amplitude, frequency and magnetic dependency can be depict precisely by the model developed. It is helpful for the predicting the dynamic behaviours of MS rubber-based vibration devices in the design phase and promotes MS rubber's application in sound and vibration area.

Place, publisher, year, edition, pages
IOP Publishing, 2020
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-301695 (URN)10.1088/1757-899X/855/1/012002 (DOI)2-s2.0-85086369118 (Scopus ID)
Conference
2020 The 3rd International Conference on Smart Materials Applications 13-16 January 2020, Seoul, South Korea
Note

QC 20210917

Available from: 2021-09-17 Created: 2021-09-17 Last updated: 2023-03-02Bibliographically approved
Li, X., Bai, Y., Wang, B. & Su, Y. J. (2015). Water adsorption induced in-plane domain switching on BaTiO3 surface. Journal of Applied Physics, 118(9), Article ID 094104.
Open this publication in new window or tab >>Water adsorption induced in-plane domain switching on BaTiO3 surface
2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 9, article id 094104Article in journal (Refereed) Published
Abstract [en]

In this study, the influences of the adsorption of water molecules on the changes in the atomic and electric structures of BaTiO3 surface were investigated using ab initio calculation. Water molecules are molecularly and dissociatively adsorbed on the BaTiO3 surface, which makes electrons transfer from water molecules to the BaTiO3 surface. The redistribution of electrons in the BaTiO3 surface layers weakens the Ba-O interactions and strengthens the Ti-O interactions, so that the Ti atom shifts in TiO2 plane, i.e., an in-plane domain switching. The adsorption of water molecules on BaTiO3 surfaces also results in a reduction in the surface rumpling.

Place, publisher, year, edition, pages
AIP Publishing, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-174225 (URN)10.1063/1.4930035 (DOI)000360926500016 ()2-s2.0-84940990111 (Scopus ID)
Note

QC 20151016

Available from: 2015-10-16 Created: 2015-10-02 Last updated: 2023-08-17Bibliographically approved
Wang, B., Århammar, C., Jiang, X., Arauji, C. M. & Ahuja, R. (2014). A Comparison Between Hybrid Functional, GW Approach and the Bethe Salpether Equation: Optical Properties of High Pressure Phases of TiO2. Science of Advanced Materials, 6(6), 1170-1178
Open this publication in new window or tab >>A Comparison Between Hybrid Functional, GW Approach and the Bethe Salpether Equation: Optical Properties of High Pressure Phases of TiO2
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2014 (English)In: Science of Advanced Materials, ISSN 1947-2935, E-ISSN 1947-2943, Vol. 6, no 6, p. 1170-1178Article in journal (Refereed) Published
Abstract [en]

Titanium dioxide has good corrosion resistance in aqueous solutions and is a good candidate for photoelectrodes. The limitation of the anatase phase of TiO2 is its large band gap. High pressure phases of TiO2 like fluorite, pyrite and cotunnite may possess a more suitable band gap than the well known atmospheric phases. In this paper, the electronic properties of high pressure phases of TuO(2), fluorite, pyrite and cotunnite, have been investigated by hybrid functional and GW methods. Our calculations suggest that the band gap of fluorite and pyrite phases have optimal band gaps to absorb visible light for photocatalysis to decompose water. The imaginary part of the dielectric function has also been calculated for fluorite, pyrite, cotunnite and anatase phases using the Bethe-Salpether (BSE) method. The dielectric function calculated by BSE for the anatase phase agrees well with experiment and with previous studies, using the same level of theory. Therefore we expect that we are also able to predict the optical properties of the high pressure phases of TiO2 by the BSE method. The spatial properties and the localization character of excitons in these high pressure phases were investigated and discussed in terms of photoconversion efficiency.

Keywords
High Pressure, Titanium Dioxide, Hybrid Functional, GW, BSE
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-145886 (URN)10.1166/sam.2014.1883 (DOI)000337268100012 ()2-s2.0-84904627960 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20140603

Available from: 2014-06-03 Created: 2014-06-03 Last updated: 2024-03-18Bibliographically approved
Wang, B. (2014). Electronic Structure and Optical Properties of Solar Energy Materials. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Electronic Structure and Optical Properties of Solar Energy Materials
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, we have studied the electronic and optical properties of solar energy m-terials. The studies are performed in the framework of density functional theory (DFT), GW, Bethe-Salpeter equation (BSE) approaches and Kinetic Monte Carlo (KMC). We present four sets of results. In the first part, we report our results on the band gap engineering issues for BiNbO4and NaTaO3, both of which are good photocatalysts. The band gap tuning is required for these materials in order to achieve the maximum solar to hydrogen conversion efficiency. The most common method for the band gap reduction is an introduction of foreign elements. The mono-doping in the system generates electrons or holes states near band edges, which reduce the efficiency of photocatalytic process. Co-doping with anion and cation or anion and anion can provide a clean band gap. We have shown that further band gap reduction can be achieved by double-hole mediated coupling between two anionic dopants. In the second part, the structure and optical properties of (CdSxSe1x)42nanoclusters have been studied. Within this study, the structures of the (CdS)42, (CdSe)42, Cd42Se32S10, Cd42Se22S20, and Cd42Se10S32 clusters have been determined using the simulated annealing method. Factors influencing the band gap value have been analyzed. We show that the gap is most significantly reduced when strongly under coordinated atoms are present on the surface of the nanoclusters. In addition, the band gap depends on the S concentration as well as on the distribution of the S and Se atoms in the clusters. We present the optical absorption spectra calculated with BSE and random phase approximation (RPA) methods based on the GW corrected quasiparticle energies. In the third part, we have employed the state-of-art computational methods to investigate the electronic structure and optical properties of TiO2high pressure polymorphs. GW and BSE methods have been used in these calculations. Our calculations suggest that the band gap of fluorite and pyrite phases have optimal values for the photocatalytic process of decomposing water in the visible light range. In the fourth part we have built a kinetic model of the first water monolayer growth on TiO2(110) using the kinetic Monte Carlo (KMC) method based on parameters describing water diffusion and dissociation obtained from first principle calculations. Our simulations reproduce the experimental trends and rationalize these observations in terms of a competition between different elementary processes. At high temperatures our simulation shows that the structure is well equilibrated, while at lower temperatures adsorbed water molecules are trapped in hydrogen-bonded chains around pairs of hydroxyl groups, causing the observed higher number of molecularly adsorbed species at lower temperature.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. p. viii, 82
Keywords
GW, Bethe-Salpeter equation, Kinetic Monte Carlo, Density Functional Theory
National Category
Condensed Matter Physics
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-145625 (URN)978-91-7595-190-4 (ISBN)
Public defence
2014-06-13, FB53, AlbaNova, Roslagstullsbacken, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20140603

Available from: 2014-06-03 Created: 2014-05-23 Last updated: 2022-09-13Bibliographically approved
Wang, B., Nisar, J., Almeida, C. G., Santos Mascarenhas, A. J., Silva, L. A., Francis David, D. G., . . . da Silva, A. F. (2014). Optical and electronic properties of nanosized BiTaO4 and BiNbO4 photocatalysts: Experiment and theory. Physica status solidi. B, Basic research, 251(5), 1034-1039
Open this publication in new window or tab >>Optical and electronic properties of nanosized BiTaO4 and BiNbO4 photocatalysts: Experiment and theory
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2014 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 251, no 5, p. 1034-1039Article in journal (Refereed) Published
Abstract [en]

Nanosized BiTaO4 and BiNbO4 were prepared by the citrate method. The electronic and optical properties of BiTaO4 and BiNbO4 have been investigated by means of photo-acoustic spectroscopy (PAS), X-ray photo-electron spectroscopy (XPS), and first-principles calculations based on density functional theory. The measured valence band (from XPS) of both materials agreed well with the theoretical findings. It was also found that the calculated optical properties such as dynamical dielectric function and optical absorption spectra are in good agreement with the experimental findings. According to the absorption spectra, the absorption edges of BiNbO4 and BiTaO4 are located at 370 and 330nm, respectively. Both phases have the ability to harvest UV light and relatively high surface area to volume ratio and can be used as UV/visible light-driven photocatalysts.

Keywords
electronic structure, niobates, optical absorption, photocatalysis, tantalates, water splitting
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-147056 (URN)10.1002/pssb.201350265 (DOI)000335983000017 ()2-s2.0-84899965238 (Scopus ID)
Funder
Swedish Research CouncilFormas
Note

QC 20140624

Available from: 2014-06-24 Created: 2014-06-23 Last updated: 2024-03-18Bibliographically approved
Wang, B. & Skorodumova, N. (2014). Structure and optical properties of (CdSxSe1-x) 42 nanoclusters. Physical Chemistry, Chemical Physics - PCCP, 16(27), 13956-13963
Open this publication in new window or tab >>Structure and optical properties of (CdSxSe1-x) 42 nanoclusters
2014 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 27, p. 13956-13963Article in journal (Refereed) Published
Abstract [en]

The structures of the (CdS)(42), (CdSe)(42), Cd42Se32S10, Cd42Se22S20, and Cd42Se10S32 clusters have been determined using the simulated annealing method. Factors influencing the band gap value have been analysed. We show that the gap is most significantly reduced when strongly under coordinated atoms are present on the surface of the nanoclusters. In addition, the band gap depends on the S concentration as well as on the distribution of the S and Se atoms in the clusters. We present the optical absorption spectra calculated with BSE and RPA methods based on the GW corrected quasiparticle energies. Strong electron-hole coupling is observed for all the clusters, shifting the calculated RPA onset of optical absorption to lower energies. The absorption edge is shifted to higher photon energies as S concentration increases. The calculated energy separation of the first bright exciton and first dark exciton increases with S concentration.

Keywords
Light-Emitting-Diodes, Cdse Quantum Dots, Initio Molecular-Dynamics, Augmented-Wave Method, Binding-Energy, Solar-Cells, Band-Gaps, In-Vivo, Semiconductor, Nanocrystals
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-145887 (URN)10.1039/c4cp01008f (DOI)000338116700047 ()24898415 (PubMedID)2-s2.0-84902668581 (Scopus ID)
Note

QC 20140808. Updated from manuscript to article in journal.

Available from: 2014-06-03 Created: 2014-06-03 Last updated: 2024-03-18Bibliographically approved
Wang, B., Lilja, M., Ma, T., Soerensen, J., Steckel, H., Ahuja, R. & Stromme, M. (2014). Theoretical and experimental study of the incorporation of tobramycin and strontium-ions into hydroxyapatite by means of co-precipitation. Applied Surface Science, 314, 376-383
Open this publication in new window or tab >>Theoretical and experimental study of the incorporation of tobramycin and strontium-ions into hydroxyapatite by means of co-precipitation
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2014 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 314, p. 376-383Article in journal (Refereed) Published
Abstract [en]

Antibiotic incorporation into hydroxyapatite (HA) coatings by co-precipitation and the impact of bone relevant doping elements on the adsorption kinetics are investigated from both theoretical and experimental points of view. Tobramycin interactions with bioactive TiO2 and HA surfaces are analyzed using density functional theory. According to the calculations, the drug molecule has larger adsorption energy than the Ca+ ion on both surfaces under study in Phosphate Buffered Saline (PBS). The results support the experimental observations that HA nucleation and growth are strongly limited on TiO2 surfaces in the presence of clinically relevant antibiotic concentrations in PBS. The drug molecule is more likely to adopt parallel arrangement onto the HA surface, as the adsorption energy of such arrangement is higher compared to a perpendicular one. Strontium substitution of the HA surface is found to results in a weaker drug-surface interaction, and leads also to a decrease in coating thickness. However, the presence of strontium gives rise to a coating morphology with enhanced drug incorporation capacity and slower antibiotic release compared to non-substituted, co-precipitated counterparts. Our theoretical calculation results were found to be in excellent agreement with experimental data and provide a powerful tool to understand the interaction mechanism between drug and different surface chemistries necessary for development of future versatile orthopedic and dental implant surfaces.

Keywords
Hydroxyapatite, Tobramycin, Co-precipitation, Strontium, Antibiotic release, Adsorption energy
National Category
Materials Engineering Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-153252 (URN)10.1016/j.apsusc.2014.06.193 (DOI)000341464100051 ()2-s2.0-84906690737 (Scopus ID)
Note

QC 20141009

Available from: 2014-10-09 Created: 2014-10-03 Last updated: 2024-03-18Bibliographically approved
Li, X., Wang, B., Zhang, T.-Y. & Su, Y. (2014). Water Adsorption and Dissociation on BaTiO3 Single-Crystal Surfaces. The Journal of Physical Chemistry C, 118(29), 15910-15918
Open this publication in new window or tab >>Water Adsorption and Dissociation on BaTiO3 Single-Crystal Surfaces
2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 29, p. 15910-15918Article in journal (Refereed) Published
Abstract [en]

Experimental and theoretical studies of water-molecule adsorption on BaTiO3 single-crystal surfaces are presented in this paper. The Fourier transform infrared spectrum shows that there are three types of energy-nonequivalent active modes for water-molecule adsorption on the in-plane-polarized BaTiO3(100) surface. The X-ray photoelectron spectroscopic results illustrate hydroxyl group on the surface, thereby indicating that the adsorbed water molecules are dissociated. The first-principles calculations of the 1/4-, 1/2-, and 1-monolayer water coverage demonstrate that H bonds are formed between the hydrogen of water and the surface oxygen of BaTiO3 and between the hydrogen of hydroxyl and the surface oxygen of BaTiO3, and the difference in the water adsorption behavior on the BaO- and TiO2-terminated surfaces. The calculation results are in good agreement with the experimental observations.

Keywords
Barium-Titanate, Humidity, XPS
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-149503 (URN)10.1021/jp5051386 (DOI)000339540700039 ()2-s2.0-84904994747 (Scopus ID)
Note

QC 20140822

Available from: 2014-08-22 Created: 2014-08-22 Last updated: 2022-06-23Bibliographically approved
Wang, B., Kanhere, P. D., Chen, Z., Nisar, J., Pathak, B. & Ahuja, R. (2013). Anion-Doped NaTaO3 for Visible Light Photocatalysis. The Journal of Physical Chemistry C, 117(44), 22518-22524
Open this publication in new window or tab >>Anion-Doped NaTaO3 for Visible Light Photocatalysis
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2013 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 44, p. 22518-22524Article in journal (Refereed) Published
Abstract [en]

In this paper, we have employed DFT and HSE06 methods to study the doping effects on the NaTaO3 photocatalyst. N, S, C, and P monodoping and N-N, C-S, P-P, and N-P codoping have been studied. The redopants' formation energies have been calculated, and we find S monodoping is energetically more favorable than any other elemental doping. The mechanism of anion doping on the electronic properties of NaTaO3 is discussed. We find the band gap reduces significantly if we dope with anionic elements whose p orbital energy is higher than the O 2p orbitals. N and S can shift the valence band edge upward without losing the ability to split water into H-2 and O-2. Double-hole-mediated codoping can decrease the band gap significantly. On the basis of our calculations, codoping with N-N, C-S, and P-P could absorb visible light. However, they can only decompose water into H-2 when the valence band edge is above the water oxidation level.

Keywords
Initio Molecular-Dynamics, Augmented-Wave Method, Hydrogen Evolution, Water, H-2, Lanthanum, Exchange, Solids, O-2
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-137471 (URN)10.1021/jp407025r (DOI)000326845400007 ()2-s2.0-84889841428 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20131217

Available from: 2013-12-17 Created: 2013-12-13 Last updated: 2024-03-18Bibliographically approved
Nisar, J., Wang, B., Araújo, C. M., da Silva, A. F., Kang, T. W. & Ahuja, R. (2012). Band gap engineering by anion doping in the photocatalyst BiTaO4: First principle calculations. International journal of hydrogen energy, 37(4), 3014-3018
Open this publication in new window or tab >>Band gap engineering by anion doping in the photocatalyst BiTaO4: First principle calculations
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2012 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, no 4, p. 3014-3018Article in journal (Refereed) Published
Abstract [en]

We have shown the effect of mono and co-doping of non-metallic anion atoms on the electronic structure in BiTaO4 using the first-principles method. It can improve the photocatalytic efficiency for hydrogen production in the presence of visible sunlight. It is found that the band gap of BiTaO4 has been reduced significantly up to 54% with different nonmetallic doping. Electronic structure analysis shows that the doping of nitrogen is able to reduce the band gap of BiTaO4 due to the impurity N 2p state at the upper edge of the valence band. In case of C or C-S doped BiTaO4, double occupied (filled) states have been observed deep inside the band gap of BiTaO4. The large reduction of band gap has been achieved, which increases the visible light absorption. These results indicate that the doping of non-metallic element in BiTaO4 is a promising candidate for the photocatalyst due to its reasonable band gap.

Keywords
Band gap engineering, Photocatalysis, Anionic doping in BiTaO4
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-93949 (URN)10.1016/j.ijhydene.2011.11.068 (DOI)000301615100004 ()2-s2.0-84856587728 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20120503Available from: 2012-05-03 Created: 2012-05-03 Last updated: 2024-03-18Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7321-8594

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