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Dong, H., Zhao, Z. & Wang, C. (2019). Effect of powder characteristics on the thermal conductivity and mechanical properties of Si 3 N 4 ceramics sintered by Spark plasma sintering. Journal of materials science. Materials in electronics, 30(8), 7590-7599
Open this publication in new window or tab >>Effect of powder characteristics on the thermal conductivity and mechanical properties of Si 3 N 4 ceramics sintered by Spark plasma sintering
2019 (English)In: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 30, no 8, p. 7590-7599Article in journal (Refereed) Published
Abstract [en]

The effect of powder characteristics on the thermal conductivity and mechanical properties of silicon nitride (Si 3 N 4 ) ceramics were investigated systematically by using two α-Si 3 N 4 powders as raw materials and using MgSiN 2 or MgO + Y 2 O 3 as sintering additives. The Si 3 N 4 ceramics with a higher density were obtained by α-Si 3 N 4 powders with lower oxygen content and impurities and using none-oxide sintering additive MgSiN 2 . The α–β phase transformation completely taken place in all the specimen at 1750 °C. The specimens sintered by powders with lower levels of oxygen and impurities show higher mechanical properties than other specimens. The Y 2 O 3 and MgO sintering additives lead to higher flexural strength and fracture toughness than MgSiN 2 . The Vickers’ hardness is just the opposite. The thermal conductivity value of powders with lower oxygen content is higher than that of the materials prepared by the other type of powder at the same conditions. The effects of the Si 3 N 4 particle size, native oxygen and impurities on the thermal conductivity of resultant materials were discussed in detail. This work demonstrates that the improvement in thermal conductivity of Si 3 N 4 can be obtained by using none-oxide sintering additive MgSiN 2 and the Si 3 N 4 powder with lower oxygen content, and impurities.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2019
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-251829 (URN)10.1007/s10854-019-01074-w (DOI)000467637200041 ()2-s2.0-85064720981 (Scopus ID)
Note

QC 20190523

Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-06-11Bibliographically approved
Zheng, D., Wei, G., Xu, L., Guo, Q., Hu, J., Sha, N. & Zhao, Z. (2019). LaNi x Fe 1- x O 3 (0 ≤ x ≤1) as photothermal catalysts for hydrocarbon fuels production from CO 2 and H 2 O. Journal of Photochemistry and Photobiology A: Chemistry, 377, 182-189
Open this publication in new window or tab >>LaNi x Fe 1- x O 3 (0 ≤ x ≤1) as photothermal catalysts for hydrocarbon fuels production from CO 2 and H 2 O
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2019 (English)In: Journal of Photochemistry and Photobiology A: Chemistry, ISSN 1010-6030, E-ISSN 1873-2666, Vol. 377, p. 182-189Article in journal (Refereed) Published
Abstract [en]

LaNi x Fe 1- x O 3 perovskite compounds (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were successfully synthesized by a sol-gel combustion method. The crystal structure, morphology, BET surface area, oxygen vacancies, band gap and catalytic properties of the catalyst were characterized in detail. The results showed that LaNi 0.4 Fe 0.6 O 3 compound exhibits the best photothermal catalytic performance. Under the same catalytic conditions (350 ℃ + Vis-light), CH 4 and CH 3 OH yields are about 3.5 and 4.0 times, 1.8 and 2.1 times of that of LaFeO 3 and LaNiO 3 . It was found that all the solid solutions possesses better catalytic properties than the pure end compounds. The doping of Ni lead to a significant modification with the quantity of oxygen vacancies and band gaps. These findings may further broaden the materials scope for photothermal conversion of CO 2 and H 2 O. © 2019 Elsevier B.V.

Place, publisher, year, edition, pages
Elsevier B.V., 2019
Keywords
CO 2 reduction, LaFeO 3, LaNiO 3, Photothermal catalysis
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-252527 (URN)10.1016/j.jphotochem.2019.03.045 (DOI)000468714500021 ()2-s2.0-85063933526 (Scopus ID)
Note

QC 20190610

Available from: 2019-06-10 Created: 2019-06-10 Last updated: 2019-06-11Bibliographically approved
Wei, G., Zheng, D., Xu, L., Guo, Q., Hu, J., Sha, N. & Zhao, Z. (2019). Photothermal catalytic activity and mechanism of LaNixCo1-xO3(0 <= x <= 1) perovskites for CO2 reduction to CH4 and CH3OH with H2O. MATERIALS RESEARCH EXPRESS, 6(8), Article ID 086221.
Open this publication in new window or tab >>Photothermal catalytic activity and mechanism of LaNixCo1-xO3(0 <= x <= 1) perovskites for CO2 reduction to CH4 and CH3OH with H2O
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2019 (English)In: MATERIALS RESEARCH EXPRESS, ISSN 2053-1591, Vol. 6, no 8, article id 086221Article in journal (Refereed) Published
Abstract [en]

A series of LaNixCo1-xO3 perovskites were synthesized by sol-gel combustion method, the photothermal catalysis of CO2 and H2O into CH4 and CH3OH was investigated systematically. The crystal structure, surface area, oxygen vacancies, band structures and catalytic performance of LaNixCo1-xO3 perovskites were characterized thoroughly in order to understand the design principle of the material for such a photothermal catalysis of CO2 and H2O. With the change of x value, the best catalytic performance was achieved at x = 0.4 and the accumulated yield of CH4 and CH3OH can reach 678.57, 20.83 mu molg(-1) in 6 h, which were 3.4 and 3.8, 1.9 and 2.2 times of that of two end composition, LaCoO3 and LaNiO3 under the same condition. For LaNi0.4Co0.6O3, the surface area reached a maximum concentration of oxygen vacancy while the band gap reached a minimum of 1.42 eV. It is evident that the formation of solid solution between LaMO3 (M = transition metals) compounds can be a general strategy for the new catalyst design.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
photothermal catalysis, CO2 reduction, LaNiO3, LaCoO3
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-261041 (URN)10.1088/2053-1591/ab2965 (DOI)000484535300001 ()2-s2.0-85069704682 (Scopus ID)
Note

QC 20191002

Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-10-02Bibliographically approved
Ren, Y., Zheng, D., Liu, L., Guo, Q., Sha, N. & Zhao, Z. (2018). 3DOM-NiFe2O4 as an effective catalyst for turning CO2 and H2O into fuel (CH4). Journal of Sol-Gel Science and Technology, 88(3), 489-496
Open this publication in new window or tab >>3DOM-NiFe2O4 as an effective catalyst for turning CO2 and H2O into fuel (CH4)
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2018 (English)In: Journal of Sol-Gel Science and Technology, ISSN 0928-0707, E-ISSN 1573-4846, Vol. 88, no 3, p. 489-496Article, review/survey (Refereed) Published
Abstract [en]

Three-dimensional ordered macroporous NiFe2O4 (3DOM-NFO) powder was synthesized through the direct templating method combined with the sol-gel combustion technique. Polymethyl methacrylate (PMMA) spheres with different sizes were used as the hard templates. In order to understand the effect of PMMA spheres mean size on the structure and catalytic activity of synthesized 3DOM-NFO, the detailed characterization of the material was carried out by XRD, SEM, BET, XPS, UV-VIS, and DRS techniques. Direct hydrogeneration production of CH4 from CO2 and H2O was used to evaluate the catalysis performance of 3DOM-NFOs. The production of CH4 evolution can reach 1040.8mol/g at 350 degrees C and ambient pressure when 300nm template was used. It was concluded that the specific surface area and moderate concentration of oxygen vacancies are the crucial factors affecting the catalysis properties. Reasonably high turnover number of 0.244 and high CH4 conversion efficiency of 0.897% were obtained in this study. 3DOM-NFO can be a promising catalyst for hydrocarbon fuel production by directly using CO2 and H2O as the safe and cheap feedstocks. [GRAPHICS] .

Place, publisher, year, edition, pages
SPRINGER, 2018
Keywords
NiFe2O4, Templating method, Sol-gel combustion, Oxygen vacancies, Hydrogeneration
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-239986 (URN)10.1007/s10971-018-4816-6 (DOI)000450652400001 ()2-s2.0-85055997372 (Scopus ID)
Note

QC 20181211

Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-11Bibliographically approved
Cheng, Z. & Zhao, Z. (2018). Ink-jet printed BNT thin films with improved ferroelectric properties via annealing in wet air. Ceramics International, 44(9), 10700-10707
Open this publication in new window or tab >>Ink-jet printed BNT thin films with improved ferroelectric properties via annealing in wet air
2018 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 44, no 9, p. 10700-10707Article in journal (Refereed) Published
Abstract [en]

In this work, an ink-jet printing process based on the sol-gel route was applied to prepare lead-free ferroelectric Na0.5Bi0.5TiO3(BNT) thin films for the first time. Dense and crack-free films with perovskite structure were obtained from a modified precursor solution through multiple printing and pyrolysis processes. The ferroelectric, dielectric and electrical properties were significantly affected by the annealing temperature and atmosphere. The film annealed at 670 °C in wet air showed a high remnant polarization of 24.7 μC/cm2 with a low coercive field of 263 kV/cm, the dielectric constant and loss were 185 and 0.1 at 10 kHz, respectively. It was found that wet air was an alternative to reduce oxygen vacancies and enhance properties of ferroelectric films, which can be explained by the defect chemical reaction between water and oxygen vacancies. X-ray photoelectron spectroscopy(XPS) confirmed the decrease of oxygen vacancies after annealing with water presence, with a formation of Ohmic conduction mechanism dominated by charged hydroxyl groups.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Bismuth sodium titanate, Ferroelectric thin films, Ink-jet printing, Oxygen vacancies
National Category
Ceramics
Identifiers
urn:nbn:se:kth:diva-227542 (URN)10.1016/j.ceramint.2018.03.104 (DOI)000431470200087 ()2-s2.0-85044007827 (Scopus ID)
Note

QC 20180521

Available from: 2018-05-21 Created: 2018-05-21 Last updated: 2019-09-20Bibliographically approved
Stuer, M., Carry, C. P., Bowen, P. & Zhao, Z. (2017). Comparison of apparent activation energies for densification of alumina powders by pulsed electric current sintering (spark plasma sintering) and conventional sintering-toward applications for transparent polycrystalline alumina. Journal of Materials Research, 32(17), 3309-3318
Open this publication in new window or tab >>Comparison of apparent activation energies for densification of alumina powders by pulsed electric current sintering (spark plasma sintering) and conventional sintering-toward applications for transparent polycrystalline alumina
2017 (English)In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 32, no 17, p. 3309-3318Article in journal (Refereed) Published
Abstract [en]

In the quest for high real in-line transmittances for transparent polycrystalline alumina (PCA), we need defect free processing. One of the biggest advances in producing high density defect free ceramics over recent years has been the advent of spark plasma sintering (SPS) or pulsed electric current sintering. The production of PCA with high transmittances >60% has been demonstrated, but the mechanisms behind this fast, pressure aided sintering method are still much debated. Here, we investigate the sintering of doped a-alumina powders using traditional and pulsed electric current dilatometry. We demonstrate that at the final sintering stage, there is no major difference in the sintering mechanisms between conventional sintering and SPS sintering. High densification rates occurring in SPS are shown to be related to powder reorientation at the very early sintering stage and viscous-flow dominated densification in the intermediate sintering cycle. This paper clarifies what parameters in the processing-sintering domain have to be improved for even higher real in-line transmittances for PCA.

Place, publisher, year, edition, pages
CAMBRIDGE UNIV PRESS, 2017
National Category
Ceramics
Identifiers
urn:nbn:se:kth:diva-217064 (URN)10.1557/jmr.2017.119 (DOI)000412720300012 ()2-s2.0-85018412888 (Scopus ID)
Note

QC 20171123

Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2017-11-23Bibliographically approved
Aimable, A., Doubi, H. G., Stuer, M., Zhao, Z. & Bowen, P. (2017). Synthesis and Sintering of ZnO Nanopowders. TECHNOLOGIES, 5(2), Article ID 28.
Open this publication in new window or tab >>Synthesis and Sintering of ZnO Nanopowders
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2017 (English)In: TECHNOLOGIES, ISSN 2227-7080, Vol. 5, no 2, article id 28Article in journal (Refereed) Published
Abstract [en]

Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulating their development: sufficient low-cost, high throughput synthesis methods which lead to a production with well-defined and reproducible properties; and for ceramics specifically, the conservation of the powders' nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv(50)similar to 60 nm, easily redispersable) by using a continuous Segmented Flow Tubular Reactor (SFTR), which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a "scale-out" concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 degrees C and 1100 degrees C, and Spark Plasma Sintering (SPS) at 900 degrees C. The performance of the synthesized nanopowder was compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 min at 900 degrees C, while also limiting the grain growth, thus leading to a nanostructured material.

Place, publisher, year, edition, pages
MDPI AG, 2017
Keywords
ZnO, ceramic nanopowders, Segmented Flow Tubular Reactor (SFTR), Spark Plasma Sintering (SPS)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-211026 (URN)10.3390/technologies5020028 (DOI)000404135500007 ()
Note

QC 20170712

Available from: 2017-07-12 Created: 2017-07-12 Last updated: 2017-07-12Bibliographically approved
Bu, J., Jönsson, P. G. & Zhao, Z. (2016). Electrical conductivities of translucent BaZr(X)Ce0.8-XY0.2O3-delta (x=0.5, 0.6, 0.7) ceramics. Scripta Materialia, 115, 87-90
Open this publication in new window or tab >>Electrical conductivities of translucent BaZr(X)Ce0.8-XY0.2O3-delta (x=0.5, 0.6, 0.7) ceramics
2016 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 115, p. 87-90Article in journal (Refereed) Published
Abstract [en]

The electrical conductivities of translucent BaZr0.5Ce0.3Y0.2O3-delta (x = 0.5, BZCY532), BaZr0.6Ce0.2Y0.2O3-delta (x = 0.6, BZCY622) and BaZr0.7Ce0.1Y0.2O3-delta(x = 0.7, BZCY712) proton conductors were investigated systematically in different atmospheres and also at different oxygen partial pressures. The obtained results indicate that translucent BZCY532, BZCY622 and BZCY712 ceramics are pure oxygen-ion and proton conductors without unfavorable electronic conduction. In addition, they represent promising proton conductors to be used as intermediate temperature solid oxide fuel cell electrolytes.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Spark plasma sintering, Fuel cell materials, Solid electrolytes, Ionic conductors, Solid oxide fuel cells
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-184013 (URN)10.1016/j.scriptamat.2016.01.009 (DOI)000370893800020 ()2-s2.0-84960509988 (Scopus ID)50 (Local ID)50 (Archive number)50 (OAI)
Note

QC 20160324

Available from: 2016-03-24 Created: 2016-03-22 Last updated: 2017-11-30Bibliographically approved
Wang, L., Wang, Y., Cheng, Y., Liu, Z., Guo, Q., Ha, M. N. & Zhao, Z. (2016). Hydrogen-treated mesoporous WO3 as a reducing agent of CO2 to fuels (CH4 and CH3OH) with enhanced photothermal catalytic performance. Journal of Materials Chemistry A, 4(14), 5314-5322
Open this publication in new window or tab >>Hydrogen-treated mesoporous WO3 as a reducing agent of CO2 to fuels (CH4 and CH3OH) with enhanced photothermal catalytic performance
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2016 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 14, p. 5314-5322Article in journal (Refereed) Published
Abstract [en]

A series of mesoporous WO3 catalysts were facilely synthesized by a hydrothermal method using mesoporous silica KIT-6 as a hard template and silicotungstic acid as a precursor. All the catalysts possess a well-defined mesoporous structure with interconnected networks. Oxygen-deficient mesoporous WO3 (m-WO3-x) was prepared by hydrogenation treatment at different temperatures with improved photothermal coupling performance. Moreover, the as-prepared catalysts exhibit selectivity toward CH4 evolution under visible-light only irradiation. Then, under photothermal conditions, the results show that the concentration of oxygen vacancies of m-WO3 has a great influence on its catalytic performance. The CH4 evolution rate reached 25.77 mu mol g (1), which is about 22 times that of mesoporous WO3 (1.17 mu mol g(-1)) under the same conditions, and a moderate concentration of oxygen vacancies is necessary to achieve selectivity for the conversion of CO2 into CH4. A mechanism of the catalytic reduction of CO2 over m-WO3-x is proposed, in which the initial oxygen vacancies function as an excellent electron transfer mediator and decompose CO2 into its elements (C/CO). These findings may further broaden the scope for photothermal chemical conversion and provide new insights into the oxygen nonstoichiometry strategy for the development of CO2 reduction.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-185675 (URN)10.1039/c5ta10180h (DOI)000373119500038 ()2-s2.0-84962119081 (Scopus ID)
Note

QC 20160426

Available from: 2016-04-26 Created: 2016-04-25 Last updated: 2017-11-30Bibliographically approved
Zhu, F., Li, C., Ha, M. N., Liu, Z., Guo, Q. & Zhao, Z. (2016). Molten-salt synthesis of Cu-SrTiO3/TiO2 nanotube heterostructures for photocatalytic water splitting. Journal of Materials Science, 51(9), 4639-4649
Open this publication in new window or tab >>Molten-salt synthesis of Cu-SrTiO3/TiO2 nanotube heterostructures for photocatalytic water splitting
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2016 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 51, no 9, p. 4639-4649Article in journal (Refereed) Published
Abstract [en]

A series of Cu-loaded SrTiO3/TiO2 nanotube heterostructures were synthesized by a facile molten salts method and an impregnation-calcination method. Through adjusting the molar ratio of Sr/Ti, the photocatalytic performance of the samples changed regularly. When Sr/Ti = 0.2, the catalyst showed the highest performance in water splitting and the H-2 generation amount was 0.597 mmol under UV irradiation for 8 h. The enhanced performance of Cu-loaded SrTiO3/TiO2 nanotubes could be attributed to the heterostructures, the small crystallite size, and the reduced band gap inside them.

National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-183599 (URN)10.1007/s10853-016-9779-9 (DOI)000370342100044 ()2-s2.0-84957017516 (Scopus ID)
Note

QC 20160319

Available from: 2016-03-19 Created: 2016-03-18 Last updated: 2017-11-30Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-3060-9987

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