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Cao, Z., Osorio, N. G., Cai, X., Feng, P. & Akhtar, F. (2020). Carbon-reinforced MgCl2 composites with high structural stability as robust ammonia carriers for selective catalytic reduction system. Journal of Environmental Chemical Engineering, 8(1), Article ID 103384.
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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2020 (English)In: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437, Vol. 8, no 1, article id 103384Article in journal (Refereed) Published
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, 2020
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)000515128500034 ()2-s2.0-85077208374 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-01-10 (johcin)

Available from: 2019-12-10 Created: 2019-12-10 Last updated: 2020-04-16Bibliographically approved
Narang, K. & Akhtar, F. (2020). Freeze Granulated Zeolites X and A for Biogas Upgrading. Molecules, 25(6), Article ID 1378.
Open this publication in new window or tab >>Freeze Granulated Zeolites X and A for Biogas Upgrading
2020 (English)In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 25, no 6, article id 1378Article in journal (Refereed) Published
Abstract [en]

Biogas is a potential renewable energy resource that can reduce the current energy dependency on fossil fuels. The major limitation of utilizing biogas fully in the various applications is the presence of a significant volume fraction of carbon dioxide in biogas. Here, we used adsorption-driven CO2 separation using the most prominent adsorbents, NaX (faujasite) and CaA (Linde Type A) zeolites. The NaX and CaA zeolites were structured into hierarchically porous granules using a low-cost freeze granulation technique to achieve better mass transfer kinetics. The freeze granulation processing parameters and the rheological properties of suspensions were optimized to obtain homogenous granules of NaX and CaA zeolites 2–3 mm in diameter with macroporosity of 77.9% and 68.6%, respectively. The NaX and CaA granules kept their individual morphologies, crystallinities with a CO2 uptake of 5.8 mmol/g and 4 mmol/g, respectively. The CO2 separation performance and the kinetic behavior were estimated by breakthrough experiments, where the NaX zeolite showed a 16% higher CO2 uptake rate than CaA granules with a high mass transfer coefficient, 1.3 m/s, compared to commercial granules, suggesting that freeze-granulated zeolites could be used to improve adsorption kinetics and reduce cycle time for biogas upgrading in the adsorption swing technology.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
freeze granulation, zeolite NaX, zeolite CaA, gas separation, carbon dioxide capture
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-78308 (URN)10.3390/molecules25061378 (DOI)000530248700121 ()32197376 (PubMedID)2-s2.0-85082067921 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-04-02 (alebob)

Available from: 2020-04-02 Created: 2020-04-02 Last updated: 2020-05-28Bibliographically approved
Alvi, S., Saeidi, K. & Akhtar, F. (2020). High temperature tribology and wear of selective laser melted (SLM) 316L stainless steel. Wear, 448-449, Article ID 203228.
Open this publication in new window or tab >>High temperature tribology and wear of selective laser melted (SLM) 316L stainless steel
2020 (English)In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 448-449, article id 203228Article in journal (Refereed) Published
Abstract [en]

High temperature wear behaviour of selective laser melted (SLM) 316L stainless steel (SS) was studied to elucidate the influence of characteristic microstructure of SLM 316L SS on the wear properties. The wear tests were conducted from room temperature (RT) to 600 °C using ball-on-disc setup with alumina counter ball. The effect of temperature on the wear rate and the underlying mechanisms were evaluated and compared with conventional 316 SS. The RT coefficient of friction (COF) and wear rate of SLM 316L SS and conventional 316 SS were 0.5 and 4.6 ± 0.4 x 10−4 mm3/Nm and 0.7 and 4.5 ± 0.1 x 10−4 mm3/Nm, respectively. The wear rate of conventional 316 SS slightly decreased with increasing temperature from 4.5 ± 0.1 x 10−4 mm3/Nm at RT to 3.2 ± 0.1 x 10−4 mm3/Nm at 300 °C, followed by increasing to 4.9 ± 0.4 x 10−4 mm3/Nm at 400 °C, while the wear rate of SLM 316L SS was twofold lower with 2.3 ± 0.6 x 10−4 mm3/Nm at 300 °C and 2.7 ± 0.3 x 10−4 mm3/Nm at 400 °C. The wear rate at 600 °C was found to be comparable between SLM 316L SS and conventional 316 SS with a wear rate of 6.4 ± 0.7 x 10−4 mm3/Nm and 6.6 ± 0.6 x 10−4 mm3/Nm, respectively. The lower wear rate in SLM 316L SS at higher temperatures of 300 °C and 400 °C was due to its stable hierarchical microstructure, cellular subgrains, formation of stable oxide glaze and higher hardness. Moreover, the cross-sectional microscopy of wear track after 600 °C wear tests showed that the deformation zone below the wear track in SLM 316L SS was 10–15 μm compared to 30–40 μm for conventional 316 SS. The two folds low wear rate of the SLM 316L SS at 300 °C and 400 °C compared to conventional 316 SS could potentially render it for usage in applications where high temperature wear resistant SS are needed.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Selective laser melting, Stainless steel, High temperature wear, Microstructure
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-77860 (URN)10.1016/j.wear.2020.203228 (DOI)000520091000008 ()2-s2.0-85079400326 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-02-25 (alebob)

Available from: 2020-02-25 Created: 2020-02-25 Last updated: 2020-04-09Bibliographically approved
Zhang, W., Narang, K., Simonsen, S. B., Vinkel, N. M., Gudik-Sørensen, M., Han, L., . . . Kaiser, A. (2020). Highly Structured Nanofiber Zeolite Materials for Biogas Upgrading. Energy Technology, 8(1), Article ID 1900781.
Open this publication in new window or tab >>Highly Structured Nanofiber Zeolite Materials for Biogas Upgrading
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2020 (English)In: Energy Technology, E-ISSN 2194-4296, Vol. 8, no 1, article id 1900781Article in journal (Refereed) Published
Abstract [en]

Hierarchical zeolite composite nanofibers are designed using an electrospinning technique with post‐carbonization processing to form mechanically strong pellets for biogas upgrading. A ZSM‐5 nanopowder (zeolite) and a polyvinylpyrrolidone (PVP) polymer are electrospun to form ZSM/PVP composite nanofibers, which are transformed into a ZSM and carbon composite nanofiber (ZSM/C) by a two‐step heat treatment. The ZSM/C nanofibers show a 30.4% increase in Brunauer–Emmett–Teller (BET) surface area compared with the non‐structured ZSM‐5 nanopowder. Using ideal adsorbed solution theory, CO2‐over‐CH4 selectivity of 20 and CO2 uptake of 2.15 mmolg−1 at 293 K at 1 bar for ZSM/C nanofibers are obtained. For the efficient use of adsorbents in pressure swing adsorption operation, the nanofibers are structured into ZSM/C pellets that offer a maximum tensile strength of 6.46 MPa to withstand pressure swings. In the breakthrough tests, the CO2 uptake of the pellets reach 3.18 mmolg−1 at 293 K at 4 bar after 5 breakthrough adsorption–desorption cycles, with a much higher mass transfer coefficient of 1.24 ms−1 and CO2 uptake rate of 2.4 mg of CO2 g−1s−1, as compared with other structured zeolite adsorbents.

Place, publisher, year, edition, pages
John Wiley & Sons, 2020
Keywords
adsorbent materials, biogas upgrading, electrospinning, zeolites
National Category
Other Materials Engineering
Research subject
Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-76434 (URN)10.1002/ente.201900781 (DOI)000488168800001 ()
Note

Validerad;2020;Nivå 2;2020-01-28 (johcin)

Available from: 2019-10-18 Created: 2019-10-18 Last updated: 2020-01-28Bibliographically approved
Alvi, S., Jarzabek, D. M., Gilzad Kohan, M., Hedman, D., Jenczyk, P., Natile, M. M., . . . Akhtar, F. (2020). Synthesis and Mechanical Characterization of a CuMoTaWV High-Entropy Film by Magnetron Sputtering. ACS Applied Materials and Interfaces, 12(18), 21070-21079
Open this publication in new window or tab >>Synthesis and Mechanical Characterization of a CuMoTaWV High-Entropy Film by Magnetron Sputtering
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2020 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 12, no 18, p. 21070-21079Article in journal (Refereed) Published
Abstract [en]

Development of high-entropy alloy (HEA) films is a promising and cost-effective way to incorporate these materials of superior properties in harsh environments. In this work, a refractory high-entropy alloy (RHEA) film of equimolar CuMoTaWV was deposited on silicon and 304 stainless-steel substrates using DC-magnetron sputtering. A sputtering target was developed by partial sintering of an equimolar powder mixture of Cu, Mo, Ta, W, and V using spark plasma sintering. The target was used to sputter a nanocrystalline RHEA film with a thickness of ∼900 nm and an average grain size of 18 nm. X-ray diffraction of the film revealed a body-centered cubic solid solution with preferred orientation in the (110) directional plane. The nanocrystalline nature of the RHEA film resulted in a hardness of 19 ± 2.3 GPa and an elastic modulus of 259 ± 19.2 GPa. A high compressive strength of 10 ± 0.8 GPa was obtained in nanopillar compression due to solid solution hardening and grain boundary strengthening. The adhesion between the RHEA film and 304 stainless-steel substrates was increased on annealing. For the wear test against the E52100 alloy steel (Grade 25, 700–880 HV) at 1 N load, the RHEA film showed an average coefficient of friction (COF) and wear rate of 0.25 (RT) and 1.5 (300 °C), and 6.4 × 10–6 mm3/N m (RT) and 2.5 × 10–5 mm3/N m (300 °C), respectively. The COF was found to be 2 times lower at RT and wear rate 102 times lower at RT and 300 °C than those of 304 stainless steel. This study may lead to the processing of high-entropy alloy films for large-scale industrial applications.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2020
Keywords
high-entropy alloys, magnetron sputtering, spark plasma sintering, mechanical properties, wear
National Category
Other Materials Engineering Other Physics Topics
Research subject
Experimental Physics; Engineering Materials; Applied Physics
Identifiers
urn:nbn:se:ltu:diva-78868 (URN)10.1021/acsami.0c02156 (DOI)32290645 (PubMedID)2-s2.0-85084379557 (Scopus ID)
Note

Validerad;2020;Nivå 2;2020-05-12 (alebob)

Available from: 2020-05-12 Created: 2020-05-12 Last updated: 2020-05-18Bibliographically approved
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: 2020-04-03Bibliographically 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)000499678700001 ()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: 2019-12-20Bibliographically 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
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: 2020-04-03Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-4888-6237

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