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Zhang, H., Hedman, D., Feng, P., Han, G. & Akhtar, F. (2019). A high entropy B4(HfMo2TaTi)C and SiC ceramic composite. In: : . Paper presented at XVI ECerS CONFERENCE.
Open this publication in new window or tab >>A high entropy B4(HfMo2TaTi)C and SiC ceramic composite
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2019 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Refractory carbides HfC, Mo2C, TiC, TaC, B4C, and SiC were mixed with a molar ratio of 2:1:2:2:1:2 to fabricate multicomponent ceramic composite by pulsed current processing (PCP). From the starting materials that consist of face-centered cubic (FCC), hexagonal and rhombohedral crystal structures, the investigated carbide system is reported to form a single phase B4(HfMo2TaTi)C high-entropy ceramic (HEC) with SiC. The HEC phase contains uniform distribution of constitutional elements Hf, Mo, Ta, Ti, B and C, according to Energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) results.

The fabricated HEC phase displays a hexagonal crystal structure, with a high average lattice distortion of 8.26% (Figure 1). The HCP structure was observed by X-ray diffraction and selected area diffraction in transmission electron microscopy (TEM). Density-functional theory (DFT) optimization suggested that the hexagonal crystal structure has alternating layers of metal atoms and carbon/boron atoms, i.e. metal atoms of Hf, Mo, Ta and Ti were distributed on the (0001) plane in the hexagonal lattice, while the carbon/boron atoms formed hexagonal 2D grids on the (0002) plane in the hexagonal unit cell. Despite of the vast differences in the crystal structures and lattice parameters among the utilized carbides, the formation of the unique hexagonal lattice structure of B4HfMo2TaTi)C can be a result of independent diffusion of the metal and nonmetal atoms. The sintered HEC ceramic composite exhibits excellent oxidation resistance at mediate temperature, 900 ºC for 50h, and elevated temperature, 2000 ºC for 20 s. Nanoindentation test shows that the HEC phase has a high hardness of 35 GPa. The remarkable improvement compared to the theoretical hardness value estimated based on the rule of mixtures (23 GPa) was contributed by the severe lattice distortion in the hexagonal structure.

National Category
Materials Engineering
Identifiers
urn:nbn:se:ltu:diva-74894 (URN)
Conference
XVI ECerS CONFERENCE
Available from: 2019-06-24 Created: 2019-06-24 Last updated: 2019-06-24
Zhang, H., Hedman, D., Feng, P., Han, G. & Akhtar, F. (2019). A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite. Dalton Transactions, 48(16), 5161-5167
Open this publication in new window or tab >>A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite
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2019 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 16, p. 5161-5167Article in journal (Refereed) Published
Abstract [en]

A multicomponent composite of refractory carbides, B4C, HfC, Mo2C, TaC, TiC and SiC, of rhombohedral, face-centered cubic (FCC) and hexagonal crystal structures is reported to form a single phase B4(HfMo2TaTi)C ceramic with SiC. The independent diffusion of the metal and nonmetal atoms led to a unique hexagonal lattice structure of the B4(HfMo2TaTi)C ceramic with alternating layers of metal atoms and C/B atoms. In addition, the classical differences in the crystal structures and lattice parameters among the utilized carbides were overcome. Electron microscopy, X-ray diffraction and calculations using density functional theory (DFT) confirmed the formation of a single phase B4(HfMo2TaTi)C ceramic with a hexagonal close-packed (HCP) crystal structure. The DFT based crystal structure prediction suggests that the metal atoms of Hf, Mo, Ta and Ti are distributed on the (0001) plane in the HCP lattice, while the carbon/boron atoms form hexagonal 2D grids on the (0002) plane in the HCP unit cell. The nanoindentation of the high-entropy phase showed hardness values of 35 GPa compared to the theoretical hardness value estimated based on the rule of mixtures (23 GPa). The higher hardness was contributed by the solid solution strengthening effect in the multicomponent hexagonal structure. The addition of SiC as the secondary phase in the sintered material tailored the microstructure of the composite and offered oxidation resistance to the high-entropy ceramic composite at high temperatures.

Place, publisher, year, edition, pages
Royal Society of Medicine Press, 2019
National Category
Materials Engineering Ceramics Composite Science and Engineering Other Physics Topics
Research subject
Engineering Materials; Applied Physics
Identifiers
urn:nbn:se:ltu:diva-72953 (URN)10.1039/C8DT04555K (DOI)000465328200037 ()30778490 (PubMedID)2-s2.0-85064521555 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-08-20 (johcin)

Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-08-20Bibliographically approved
Alvi, S. A., Ghamgosar, P., Rigoni, F., Vomiero, A. & Akhtar, F. (2019). Adaptive nanolaminate coating by atomic layer deposition. Thin Solid Films, 692, Article ID 137631.
Open this publication in new window or tab >>Adaptive nanolaminate coating by atomic layer deposition
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2019 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 692, article id 137631Article in journal (Refereed) Published
Abstract [en]

Atomic layer deposition (ALD) was used to deposit ZnO/Al2O3/V2O5 nanolaminate coatings to demonstrate a coating system with temperature adaptive frictional behaviour. The nanolaminate coating exhibited excellent conformity and crack-free coating of thickness 110 nm over Inconel 718 substrate. The ALD trilayer coating showed a hardness and elastic modulus of 12 GPa and 193 GPa, respectively. High-temperature tribology of the nanolaminate trilayer was tested against steel ball in dry sliding condition at 25 °C (room temperature, RT), 200 °C, 300 °C, and 400 °C. It was found that the nanolaminate coating showed a low coefficient of friction (COF) and wear rate at RT and 300 °C. The trilayer coating was found intact and stable at all temperatures during the friction tests. The adaptability of nanolaminate coating with the temperature was verified by performing the cyclic friction test at 300 °C and RT. The low COF and wear rate had been attributed to the (100) and (002) basal plane sliding of ZnO top layer, and the interlayer sliding of weakly bonded planes parallel to (001) plane in V2O5 bottom layer. Furthermore, even after the removal of ZnO coating during the tribotest, the bottom V2O5 layer coating stabilized the COF and wear rate at RT and 300 °C.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Atomic layer deposition, Nanolaminate coating, Tribology, High temperature, Adaptive coating
National Category
Other Physics Topics Other Materials Engineering
Research subject
Experimental Physics; Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-76604 (URN)10.1016/j.tsf.2019.137631 (DOI)2-s2.0-85075506757 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-12-09 (johcin)

Available from: 2019-11-04 Created: 2019-11-04 Last updated: 2019-12-09Bibliographically approved
Saeidi, K., Alvi, S., Lofaj, F., Petkov, V. I. & Akhtar, F. (2019). Advanced Mechanical Strength in Post Heat Treated SLM 2507 at Room and High Temperature Promoted by Hard/Ductile Sigma Precipitates. Metals, 9(2), Article ID 199.
Open this publication in new window or tab >>Advanced Mechanical Strength in Post Heat Treated SLM 2507 at Room and High Temperature Promoted by Hard/Ductile Sigma Precipitates
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2019 (English)In: Metals, E-ISSN 2075-4701, Vol. 9, no 2, article id 199Article in journal (Refereed) Published
Abstract [en]

Duplex stainless steel, 71 wt.% austenite, 13 wt.% ferrite and 16 wt.% sigma, was made upon heat treating of fully ferritic as-built selective laser melted (SLM) 2507 stainless steel at 1200 °C. Formation of sigma phase in the heat treated SLM 2507 was investigated using optical microscopy and scanning electron microscopy (SEM). The heat treated SLM 2507 demonstrated a yield strength of 686 MPa, ultimate tensile strength of 920 MPa and an elongation of 1.8% at room temperature with a brittle fracture morphology. Precipitation of sigma phase during heat treatment and slow cooling improved the mechanical and wear properties at high temperatures (1200 °C and 800 °C, respectively). The tensile strength and elongation of the heat treated SLM 2507 was measured 400 MPa and 20% as compared to casted duplex steel with 19 MPa and 30% elongation at 1200 °C. The 20 times higher mechanical strength as compared to casted duplex steel was attributed to sigma precipitates. Tribological behaviour of heat treated duplex SLM 2507 containing sigma at 800 °C showed very low wear rate of 4.5 × 10−5 mm3/mN compared to casted duplex steel with 1.6 × 10−4 mm3/mN.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
selective laser melting, duplex stainless steel, heat treatment, mechanical properties
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-73183 (URN)10.3390/met9020199 (DOI)000460764700090 ()2-s2.0-85062367956 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-03-13 (johcin)

Available from: 2019-03-13 Created: 2019-03-13 Last updated: 2019-04-12Bibliographically approved
Cao, Z., Osorio, N. G., Cai, X., Feng, P. & Akhtar, F. (2019). Carbon-reinforced MgCl2 composites with high structural stability as robust ammonia carriers for selective catalytic reduction system. Journal of Environmental Chemical Engineering
Open this publication in new window or tab >>Carbon-reinforced MgCl2 composites with high structural stability as robust ammonia carriers for selective catalytic reduction system
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2019 (English)In: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437Article in journal (Refereed) Epub ahead of print
Abstract [en]

Novel carbon-MgCl2 composites were designed as robust ammonia carriers for selective catalytic reduction (SCR) system, with graphite (Gt) and graphene nanoplatelets aggregates (GNA) as additives to MgCl2. The cylindrically pelletized composites manifested high structural stability above the melting temperature of MgCl2 with 95 % mass retention, whereas the pure MgCl2 pellets completely lost their structural integrity. With the support of carbon additives, molten MgCl2 in the composites was isolated and retained the sample-to-holder angle of 90°, contrary to pure MgCl2 of 5.7° contact angle at 1073 K. Furthermore, the composites demonstrated rapid ammonia sorption and desorption kinetics, due to the enhanced surface area and creation of additional microporosity. Our results demonstrated that 20 wt.% GNA-80 wt.% MgCl2 (GNA20) composite presented 83 % faster kinetics in ammonia sorption and 73% faster in the first-2-minutes of desorption compared to the pure MgCl2. The enhancement of both structural stability and sorption kinetics makes the GNA20 composite a robust ammonia carrier.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
magnesium chlorideammoniacarbon compositestructural integritykinetics
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-77127 (URN)10.1016/j.jece.2019.103584 (DOI)
Available from: 2019-12-10 Created: 2019-12-10 Last updated: 2019-12-10
Zhang, H., Hedman, D., Feng, P., Han, G. & Akhtar, F. (2019). Correction: A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite. Dalton Transactions, 48(19), 6647-6647
Open this publication in new window or tab >>Correction: A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite
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2019 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 19, p. 6647-6647Article in journal (Refereed) Published
Abstract [en]

The authors regret that there is an error in writing the crystal structure in the article. The authors would like to address as follows:

The presented XRD and TEM results revealed a hexagonal crystal structure. The following analyses including the identification of the lattice parameters and the DFT calculation were based on a hexagonal lattice. Therefore, the HCP (hexagonal close-packed) structure mentioned in the article should be regarded as a hexagonal structure. The HCP term used in the introduction, where the article from Joshua Gild et al. was cited, should also be regarded as hexagonal AlB2 structure.

The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.

Place, publisher, year, edition, pages
Royal Society of Medicine Press, 2019
National Category
Materials Engineering Ceramics Composite Science and Engineering Other Physics Topics
Research subject
Engineering Materials; Applied Physics
Identifiers
urn:nbn:se:ltu:diva-74978 (URN)10.1039/C9DT90099C (DOI)000472451000039 ()2-s2.0-85065896417 (Scopus ID)
Note

Coorection to: A high-entropy B 4 (HfMo 2 TaTi)C and SiC ceramic composite

(2019) Dalton Transactions, 48 (16), pp. 5161-5167.DOI:10.1039/c8dt04555k

Available from: 2019-06-25 Created: 2019-06-25 Last updated: 2019-08-15Bibliographically approved
Hooshmand, S., Nordin, J. & Akhtar, F. (2019). Development of Ceramic Foams Containing Platinum Nanoparticles as the Catalyst. In: : . Paper presented at 10th EEIGM International Conference on Advanced Materials Research.
Open this publication in new window or tab >>Development of Ceramic Foams Containing Platinum Nanoparticles as the Catalyst
2019 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

The exhaust gases contribute significantly to global warming, but without a catalytic converter, exhaust gases would be even more polluting. Therefore, having a catalytic metal such as platinum nanoparticles on the surface of the pore walls in ceramic foams is a practical way to remove particulate matters and to have an effective catalytic converter in one. The porous structure of the foam filters the particulate matters and the high specific surface area of the Pt nanoparticles in the pores speed up the reactions. The role of platinum is to oxidize carbon monoxide (CO) and hydrocarbons (HC) to form carbon dioxide (CO2) and water vapor (H2O). In this study, The Pt nanoparticles were coated on the surface of the thermally expandable microspheres (Expancel). The Energy-dispersive X-ray spectroscopy (EDS) and Ultraviolet-visible spectroscopy (UV-Vis) confirmed the successful adsorption of Pt on the Expancel surface. In the next step, alumina foams prepared by the gel-casting technique using Pt-coated Expancels as the sacrificial template. The EDS confirmed the successful transfer of the Pt nanoparticles to the pore walls of the foam. The morphology and the porosity of the foams were studied using SEM and X-ray microtomography. Moreover, the compressive strength of the prepared sample in form of the green body, debinded and sintered was measured.  The results showed a promising way to design ceramic-based bi-functional foams for eliminating dust and converting harmful gases to nontoxic gases simultaneously.

National Category
Ceramics
Identifiers
urn:nbn:se:ltu:diva-74639 (URN)
Conference
10th EEIGM International Conference on Advanced Materials Research
Available from: 2019-06-17 Created: 2019-06-17 Last updated: 2019-06-17
Wenjing, Z., Narang, K., Salcedo, A. J., Dou, Y., Simonsen, S. B., Sørensen, M. G., . . . Kaiser, A. (2019). Electrospun nanofiber materials for energy and environmental applications. In: : . Paper presented at 10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, China (pp. 6723-6724). Elsevier, 158
Open this publication in new window or tab >>Electrospun nanofiber materials for energy and environmental applications
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2019 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Electrospinning is the one of the most versatile techniques to design nanofiber materials with numerous applications in the fields of energy conversion, catalytic chemistry, liquid and gas filtration.1 By electrospinning, complex structures can be designed from a rich variety of materials including polymers, metals, ceramics and composite, with the ability to control composition, morphology and secondary structure and tailor performance and functionality for specific applications. Moreover, with recent developments in the design of electrospinning equipment and availability of industrial-scale electrospinning technologies with production rates of several thousands of square meters per day new opportunities for electrospinning are imminent. With this, the advanced research on materials performed in our labs is getting closer to the commercialization of new products for applications in fields of energy and environment.

An overview will be given on electrospinning activities at DTU Energy that address the sizable challenges in energy and environmental applications by electrospinning: 1. Electrospun perovskite oxide nanofiber electrode for use in solid oxide fuel cells. In this application, a (La0.6Sr0.4)0.99CoO3-δ cathode was shaped into 3-dimensional thin-film by so-gel assisted electrospinning method combined with calcination and sintering; 2. Electrospun nanofiber materials for gas adsorption. Both the advantages and challenges of using electrospun nanofiber materials will be discussed, in terms of electrochemical performance, surface area, packing efficiency and mechanical stability.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-73870 (URN)10.1016/j.egypro.2019.01.016 (DOI)
Conference
10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, China
Available from: 2019-05-07 Created: 2019-05-07 Last updated: 2019-06-14Bibliographically approved
Jiao, X., Feng, P., Wang, J., Ren, X. & Akhtar, F. (2019). Exothermic behavior and thermodynamic analysis for the formation of porous TiAl3 intermetallics sintering with different heating rates. Journal of Alloys and Compounds, 811, Article ID 152056.
Open this publication in new window or tab >>Exothermic behavior and thermodynamic analysis for the formation of porous TiAl3 intermetallics sintering with different heating rates
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2019 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 811, article id 152056Article in journal (Refereed) Published
Abstract [en]

Porous TiAl3 intermetallcis are of great interest due to its excellent properties and widely applied in filtering apparatus, separation material and catalyst carrier. In this study, interconnected pore-structures have been synthesized by diffusion or thermal explosion (TE) reaction sintering with different heating rates. The thermal characteristics such as temperature-time curves, exothermic change and visual images indicate that the sample experienced a significant TE reaction at higher heating rates. Results shown that the sample was ignited at 672 °C and then rapidly increased to combustion temperature of 1169, 1110 and 933 °C in tens of seconds with the heating rate of 15, 10 and 5 °C∙min−1 respectively. Meanwhile, TE represented the uniformity of volume combustion, instantaneous reaction and rapid cooling to furnace temperature, the amount of heat released during TE reaction dropped from 1303 to 963 J g−1. This indicates that the entire sintering process was controlled by TE and the pre-diffusion reaction before the melting temperature of Al atom, which would affect the subsequent combustion reaction. Thermodynamic data explained that the reaction mechanism is mainly step-controlled diffusion reaction at a low heating rate (1 °C∙min−1), while the energy gradually accumulated and thermal explosion (TE) reaction become obvious with the increasing of heating rate (from 2 to 15 °C∙min−1).

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Intermetallics, Diffusion, Kinetics, Microstructure, Thermal analysis
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-75824 (URN)10.1016/j.jallcom.2019.152056 (DOI)000487657000072 ()2-s2.0-85071535926 (Scopus ID)
Note

Validerad;2019;Nivå 2;2019-09-03 (johcin)

Available from: 2019-09-03 Created: 2019-09-03 Last updated: 2019-10-18Bibliographically approved
Liu, Y., Cai, X., Sun, Z., Zhang, H., Akhtar, F., Czujko, T. & Feng, P. (2019). Fabrication and Characterization of Highly Porous FeAl‐Based Intermetallics by Thermal Explosion Reaction. Paper presented at 2nd International Conference and Exhibition on Light Materials − Science and Technology(LightMAT2017), September 8-10, 2017, Bremen, Germany. Advanced Engineering Materials, 21(4), Article ID 1801110.
Open this publication in new window or tab >>Fabrication and Characterization of Highly Porous FeAl‐Based Intermetallics by Thermal Explosion Reaction
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2019 (English)In: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 21, no 4, article id 1801110Article in journal (Refereed) Published
Abstract [en]

Porous FeAl-based intermetallics with different nominal compositions ranging from Fe–40 at% Al to Fe–60 at% Al are prepared by a novel process of thermal explosion (TE) mode. The results show that the Al content significantly affects the combustion behavior of the specimens, the ignition temperature of the Fe–Al intermetallics varies from 641 to 633 °C and the combustion temperature from 978 to 1179 °C. The porous materials exhibit uniform pore structures with porosities and average pore sizes of 52–61% and 20–25 µm, respectively. The TE reaction is the dominant pore formation mechanism regardless of the alloy composition. However, differences in the porosity and average pore size are observed depending on the Al content. The compressive strength of porous Fe–Al intermetallics is in the range of 23–34 MPa, duly applied as filters. Additionally, a surface alumina layer is formed at the early stage and both of the oxidation process and the sulfidation process follows the familiar parabolic rate law in the given atmosphere, exhibiting excellent resistance to oxidation and sulfidation. These results suggest that the porous Fe–Al intermetallics are promising materials for applications in harsh environments with a high-temperature sulfide-bearing atmosphere, such as in the coal chemical industry.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
FeAl intermetallics, microstructure, porous material, properties, thermal explosion
National Category
Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-72765 (URN)10.1002/adem.201801110 (DOI)2-s2.0-85060210181 (Scopus ID)
Conference
2nd International Conference and Exhibition on Light Materials − Science and Technology(LightMAT2017), September 8-10, 2017, Bremen, Germany
Note

Konferensartikel i tidskrift

Available from: 2019-02-01 Created: 2019-02-01 Last updated: 2019-06-26Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4888-6237

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