Farid Akhtar

• PhD in Materials Science and Engineering
• Professor at Luleå University of Technology

In this work, the capabilities of plasma‐assisted centrifugal atomization for the fabrication of spherical powders of Ti‐V‐Zr‐Nb‐Mo‐Hf‐Ta‐W refractory high‐entropy alloys (R‐HEAs) are thoroughly studied. Atomization in the transient regime by direct droplet formation is investigated through batch processing by simultaneous melting, alloying, and at...

The advancement of modern 3D printing technologies has opened the possibilities to fabricate different spectrums of materials using these technologies. Binder jetting 3D printing is a shaping-debinding-sintering-based Additive manufacturing process that selectively fabricates the parts in a layer-by-layer fashion using the local imprinting of polym...

The oxygen evolution reaction (OER) is known as a kinetics barrier in electrochemical water splitting. Developing stabilized non-precious metal-based catalysts is crucial for the wide application of electrolytic water splitting in oxygen production. Porous Co-based intermetallics function as promising non-noble metal catalysts for OER. Porous nanog...

Employing alloy anodes based on Si, Ge, Sn, etc. can increase the energy density of lithium-ion batteries (LIBs) by their high gravimetric capacity. ¹ Their large volumetric expansion during lithiation, however, leads to cracks and solid electrolyte interphase (SEI) breakdown, followed by pulverization. ² Alloy engineering, creating composite alloy...

An entropy-stabilized multicomponent ultrahigh-temperature ceramic (UHTC) coating, (Ti0.25V0.25Zr0.25Hf0.25)B2, on a graphite substrate was in-situ sintered by spark plasma sintering (SPS) from constituent transition metal diboride powders. The (Ti0.25V0.25Zr0.25Hf0.25)B2 coating had a hardness of 31.2±2.1 GPa and resisted 36.9 GPa of stress before...

One often proposed route to improved energy density for lithium‐ion batteries is to use alloy anodes, such as silicon, able to store large amounts of lithium. Mechanical instability caused by the large expansion and contraction associated with (de)lithiation, and hence bad cyclability, has, however, so far hindered progress. As proof‐of‐concept of...

Ni–Al–Cr alloys in the β phase (B2–NiAl) region exhibit remarkable stability and mechanical property. Through thermal explosion (TE) reaction, Ni–Al–Cr intermetallic compounds with high porosity can be obtained. In this study, the focus lies on analyzing the macroscopic morphology, microstructure, phase distribution, TE behaviour, and the mechanica...

Mesoporous silica particles (MSPs) can be used as food additives, clinically for therapeutic applications, or as oral delivery vehicles. It has also been discussed to be used for a number of novel applications including treatment for diabetes and obesity. However, a major question for their possible usage has been if these particles persist structu...

The aim of this study was to investigate the effect on high temperature of mechanical properties of adding Al2O3 particles to polycrystalline Mo(Si,Al)2. Mo(Si,Al)2-Al2O3 composites, containing 0–25 wt% Al2O3 particles have been compression tested at 1300 °C, and the microstructure after deformation was studied using electron backscatter diffractio...

By their unique compositions and microstructures, recently developed high-entropy materials (HEMs) exhibit outstanding properties and performance above the threshold of traditional materials. Wear- and erosion-resistant materials are of significant interest for different applications, such as industrial devices, aerospace materials, and military eq...

Calcium chloride (CaCl2) impregnated zeolite A and strontium chloride (SrCl2) impregnated zeolite A and X composite granules were evaluated as ammonia sorbents for automotive selective catalytic reduction systems. The SrCl2-impregnated zeolite A granules showed a 14% increase in ammonia uptake capacity (8.39 mmol g-1) compared to zeolite A granules...

Entropy stabilized multicomponent alloys offer remarkable mechanical properties and thermal stability rendering these alloys for high-temperature protective films. A novel septenary CrMnFeHfTiTaV complex concentrated alloy (CCA) film was deposited using magnetron sputtering on 304 stainless steel (SS) and silicon substrates. The phase evolution, na...

Metal‐organic frameworks (MOFs) are hybrid porous crystalline networks with tunable chemical and structural properties. However, their excellent potential is limited in practical applications due to their hard‐to‐shape powder form, making it challenging to assemble MOFs into macroscopic composites with mechanical integrity. While a binder matrix en...

Polycrystalline Mo(Si,Al) with C40 crystal structure was deformed in compression with a strain rate of 10−4 s−1 at 1300 °C. The specimens were deformed to a strain of 10%–15% and showed maximum stresses around 150 MPa prior to pronounced softening. No crack formation or significant increase in porosity could be observed. Post-test microstructure an...

Polluted water resources, particularly those polluted with industrial effluents' dyes, are carcinogenic and hence pose a severe threat to sustainable and longstanding worldwide development. Meanwhile, adsorption is a promising process for polluted/wastewater treatment. In particular, activated carbon (AC) is popular among various wastewater treatme...

The inception of high‐entropy alloy promises to push the boundaries for new alloy design with unprecedented properties. This work reports entropy stabilisation of an octonary refractory, HfMoNbTaTiVWZr, high‐entropy thin film metallic glass, and derived nitride films. The thin film metallic glass exhibited exceptional ductility of ≈60% strain witho...

Hardness is defined as the resistance of a material to localized plastic deformation. Owing to their non-destructive nature, static indentation hardness tests are widely used in industry. Hardness testing is particularly useful for the mechanical characterization of materials that cannot be tested otherwise, e.g. powdered materials. In this study,...

Industrial spent MoSi2-based materials were used to fabricate oxidation-resistant coatings on molybdenum via slurry painting in air. The microstructure, phase constituent and high-temperature oxidation behaviors of the coatings at 1500 °C were explored. The results show that the bonding layer is generated in the coatings after sintering, which stre...

High-entropy/multicomponent alloy (HEA/MCA) has received significant research attention in the last decade. There is a dearth of data-driven works dedicated to assessing and visualizing the HEA/MCA literature from a global perspective. To this end, we present the first bibliometric literature analysis of more than 3500 HEA/MCA articles, published b...

High-entropy materials have attracted considerable interest due to their unique, improved properties and large configurational entropy. Out of these, high-en-tropy ceramics (HECs) are of particular interest since the independent solubility of cations and anions results in increased configurational entropy. However, most HEC research considers only...

Polyacrylonitrile (PAN) nanofibers were prepared by electrospinning and coated with zeolitic imidazolate framework-8 (ZIF-8) by a phase conversion growth method and investigated for CO2 capture. The PAN nanofibers were pre-treated with NaOH, and further coated with zinc hydroxide, which was subsequently converted into ZIF-8 by the addition of 2-met...

A hydrophobic CO 2 physisorbent Most materials for carbon dioxide (CO 2 ) capture of fossil fuel combustion, such as amines, rely on strong chemisorption interactions that are highly selective but can incur a large energy penalty to release CO 2 . Lin et al . show that a zinc-based metal organic framework material can physisorb CO 2 and incurs a lo...

Transition metal borides have a unique combination of high melting point and high chemical stability and are suitable for high temperature applications (>2000 °C). A metastable dual-phase boride (Ti0.25V0.25Zr0.25Hf0.25)B2 with distinct two hexagonal phases and with an intermediate entropy formation ability of 87.9 (eV/atom)⁻¹ as calculated via the...

A novel refractory multicomponent boron-carbide coating of 300 nm thickness, HfMoTaTi-BC, was deposited on carbon-carbon composites (CCC). The coating showed a face-centred cubic (FCC) structure of lattice parameter of 0.4429 nm with an average crystallite size of 5 nm. The FCC coating transformed from single-phase solid solution into multiple cera...

In article number 2008505, Farid Akhtar and Zhejian Cao design a novel porous strontium chloride (SrCl2) scaffolded by graphene networks as ammonia carriers. The optimized porous SrCl2‐reduced graphene oxide (rGO) composite demonstrates extraordinary structural stability and rapid kinetics for ammonia absorption and desorption, offering a robust st...

High-entropy materials are promising for high-temperature applications. In order to achieve high-temperature wear resistance, a novel high-entropy alloy based composite, (CrMnFeHf)7.14(TiTaV)23.81, was designed and consolidated by spark plasma sintering at 1320 ℃ following thermodynamic simulations using the CALPHAD method. The microstructure of th...

Industrial spent MoSi2-based materials and HfO2 were recycled as raw materials to fabricate MoSi2-HfO2 composite coating by spark plasma sintering (SPS). The microstructural evolution of the coatings was characterized and the 1500 °C oxidation behavior was explored. Cracks penetrated through the MoSi2 coating while no cracks can be found in the HfO...

Strontium chloride (SrCl2) as ammonia (NH3) carriers has been widely exploited due to its high ammonia uptake capacity and low energy penalty for ammonia release. However, the dramatic volume swing during absorption–desorption cycles, from SrCl2 to Sr(NH3)8Cl2 to SrCl2, imposes a challenge to structure SrCl2 for ammonia storage applications. Herein...

Mechanism of MFI film growth from seed crystals and evolution of defects during the film growth were investigated. The hydrothermal growth of colloidal silicalite-1 crystals of 50 nm on silicon substrate was used to reveal the MFI film formation mechanism at different time intervals using high resolution-transmission electron microscopy (HR-TEM) an...

Spent MoSi2 and MoB were used as raw materials to prepare multilayer MoSi2/MoB coating on molybdenum by the two‐step method of slurry deposition and spark plasma sintering. The results showed dense MoSi2/MoB coating after sintering while penetrated cracks appeared in MoSi2 coating due to coefficient of thermal expansion mismatch between the Mo subs...

Freeze-casting is a powerful consolidation technique for the fabrication of highly porous and layered-hybrid materials, including ceramic-metal composites, and porous scaffolds for catalysis, bone substitutes and high-performance membranes. The aqueous suspensions to be freeze-casted usually contain dense particles facilitating macroporous, layered...

Due to the high exothermic characteristic of NiAl during the reaction synthesis process from Ni–Al elemental powders, the NiAl intermetallic melts frequently, and the specimens are difficult to maintain their original shape, which leads to the inhomogeneity of the pore size and morphology. To tackle this problem, porous NiAl intermetallic monolith...

Three examples of porous ceramics in energy applications are described: catalysts, solid oxide cells (SOCs) and porous separation membranes. Ceramics offer properties, such as high temperature stability, chemical durability, conductivity, mechanical strength and abrasive resistance, which make these materials attractive for high performance applica...

Ammonia is one of the most common reductants for the automotive selective catalytic reduction (SCR) system owing to its high NO2 reduction (deNOx) efficiency. However, ammonia carriers for the SCR system have sluggishly evolved to achieve rapid ammonia dosing. In this study, the MOFs [M2(adc)2(dabco)] (M = Co, Ni, Cu, Zn) were synthesized and chara...

The phase stability, compressive strength, and tribology of tungsten alloy containing low activation elements, W0.5(TaTiVCr)0.5, at elevated temperature up to 1400 °C were investigated. The spark plasma sintered W0.5(TaTiVCr)0.5 alloy showed body centered cubic (BCC) structure, which was stable up to 1400 °C using in-situ high temperature XRD analy...

Electron beam powder bed fusion (EBPBF) is a beneficial processing route to fabricate Ti6Al4V alloy for aerospace applications due to its relatively low lead time and the possibility of topology optimization. The dry sliding wear behavior of EBPBF-Ti6Al4V against steel- and alumina-counterballs from room temperature (RT) to 500 °C was investigated...

Ultra-high temperature ceramic composites have been widely investigated due to their improved sinterability and superior mechanical properties compared to monolithic ceramics. In this work, high-entropy boron-carbide ceramic/SiC composites with different SiC content were synthesized from multicomponent carbides HfC, Mo2C, TaC, TiC, B4C, and SiC in...

Development of high entropy alloys (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 targ...

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, Na...

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 t...

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, whe...

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 m...

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...

To recycle elemental molybdenum from waste molybdenum disilicide (MoSi2) heating elements, the MoSi2 was first disintegrated to MoO3 and SiO2 powders in air at a pest oxidation temperature of 500 °C. X-ray diffraction (XRD) patterns confirmed the completion of the pest oxidation reaction. The mixture of MoO3 and SiO2 powders were heated to 950 °C i...

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...

Martensitic 420 stainless steel was successfully fabricated by Selective laser melting (SLM) with >99% relative density and high mechanical strength of 1670 MPa, yield strength of 600 MPa and elongation of 3.5%. X-ray diffraction (XRD) and scanning electron microscopy disclosed that the microstructure of SLM 420 consisted of colonies of 0.5–1 μm si...

The effect of type of sacrificial template on the processing and properties of porous alumina ceramics was investigated. Two templates, I) hollow pre‐expanded polymer spheres (Expancel) and II) dense glassy carbon, were used to prepare porous alumina ceramics by gel‐casting. The results showed that the burnout of sacrificial expandable polymer micr...

Correction for ‘A high-entropy B 4 (HfMo 2 TaTi)C and SiC ceramic composite’ by Hanzhu Zhang et al. , Dalton Trans. , 2019, DOI: 10.1039/c8dt04555k.

Quaternary high-entropy ceramic (HEC) composite was synthesized from HfC, Mo2C, TaC, and TiC in pulsed current processing. A high-entropy solid solution that contained all principal elements along with a minor amount of a Ta-rich phase was observed in the microstructure. The high entropy phase and Ta-rich phase displayed a face-centered cubic (FCC)...

An equiatomic high entropy alloy (HEA) CuMoTaWV was designed for room temperature to high temperature wear applications using spark plasma sintering of elemental powder mixture at 1400 °C. The sintered solid solution showed uniform distribution of elements in a BCC high entropy alloy phase along with V rich solid solution phase with an average hard...

A multicomponent composite of refractory carbides, B4C, HfC, Mo2C, TaC, TiC and SiC, of a 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(HfMo2Ta...

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 SL...

Electronic Supplementary Information: A high-entropy B4(HfMo2TaTi)C and SiC ceramic composite

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...

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 63...

Overcoming the brittleness of metal organic frameworks (MOFs) is a challenge for industrial applications. To increase the mechanical strength, MOFs have been blended with polymers to form composites. However, this also brings challenges such as, integration and integrity of MOF in the composite which can hamper the selectivity of gas separations. I...

Partially ion-exchanged zeolites A and X binderless granules were evaluated for CO2 separation from CH4. The CO2 adsorption capacity and CO2-over-CH4 selectivity of binderless zeolites A and X granules were optimized by partial exchange of cations with K⁺ and Cs⁺, while retaining the mechanical strength of 1.3 MPa and 2 MPa, respectively. Single ga...

Shaped porous ceramics have proven to be the most adapted materials for several industrial applications, both at low and high temperatures. Recent research has been focused on developing shaping techniques, allowing for a better control over the total porosity and the pores characteristics. In this study, macroporous alumina foams were fabricated b...

Structured laminated diatomite monoliths with superior mechanical properties were prepared by controlled freeze‐casting of the aqueous suspensions of diatomite powders for wastewater treatment. The directional freezing of suspensions with solids loading of 25, 30, and 37 wt % at cooling from 0.5 to 5 K/min resulted in the formation of lamellar pore...

Abstract Polymer derived ceramic (PDC) composite coatings were deposited on AISI 304 substrates using siloxane based preceramic polymer polymethlysilsquioxane (PMS) and ZrSi2 as active filler or Ag as passive filler. The tribological performance of the composite coatings was evaluated at room temperature and moderately high temperatures (150 °C, 20...

A high-porosity CuAl-based intermetallic compound with composition Cu-50 at.% Al has been successfully prepared by thermal explosion (TE) using NaCl as space holder. The results showed that the NaCl particles were completely removed from the green compact by water leaching. The temperature of the specimen during the TE and the evolution of the poro...

Open-cell Fe-Al intermetallic foams were successfully prepared by a simple and energy-saving thermal explosion (TE) process. The effects of the Fe/Al molar ratio (Fe-(40–50) at. pct Al) and thermal treatment temperature on the TE temperature profile, phase composition, pore characteristics, and oxidation resistance of the prepared foams were invest...

Stainless steel 316 L prepared by laser melting consisted of a hierarchical austenitic microstructure with micrometre-sized (10–25 µm) grains containing fine 1 µm subgrains with a cellular structure. At high-temperature thermal treatments (greater than or equal to 1100°C), merging and growth of the 1 µm subgrains into bigger subgrains restricted th...

The high porosity of FeAl/Al2O3 composites was successfully prepared via a low-energy consumption method of thermal explosion (TE) in vacuum from reactant mixtures of Fe, Al and Fe2O3. The temperature profiles, phase compositions, microstructure, porosity and pore size of the products were investigated. The TE reactions were ignited between 639 and...

The synthesis of flat tablet-shaped ZSM-5 crystals from a gel using metakaolin as aluminosilicate source and n-butyl amine as structure directing agent was investigated. The evolution inside the solid phase was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, thermogravimetry and mass spectrometry. A...

By complexing a bent phosphonate monoester ligand with cobalt(II), coupled with in situ ester hydrolysis, coordination microspheres (CALS=CALgary Sphere) are formed whereas the use of the phosphonic acid directly resulted in a sheet-like structure. Manipulation of the synthetic conditions gave spheres with different sizes, mechanical stabilities, a...

Thin, binder-less zeolite NaX laminates, with thicknesses ranging between 310 to 750 μm and widths exceeding 50 mm and biaxial tensile strength in excess of 3 MPa, were produced by pulsed current processing. The NaX laminates displayed a high CO2 adsorption capacity and high binary CO2-over-N2 and CO2-over-CH4 selectivity, suitable for CO2 capture...

Porous TiAl3 intermetallics were fabricated through vacuum reactive sintering from Ti–75Al at.% elemental powder mixture. The phase compositions, expansion behaviors, pore characteristics and microstructure evolution of TiAl3 intermetallics were investigated, and the pore formation mechanism was also proposed. It was found that the actual temperatu...

Porous hydrogel copolymers of acrylamide (AAM) and acrylic acid (AAC) were structured in the form of monoliths and granules. AAM-co-AAC porous copolymer monoliths were synthesized using high internal phase emulsion (HIPE) as template and photopolymerization. For granulation, photopolymerization was used for the fabrication of the AAM-co-AAC hydroge...

Mo, Si and B4C powders were used to fabricate 0.4MoB-0.1SiC-xMoSi2 composites by self-propagating high-temperature synthesis (SHS) and hot pressing (HP). The effects of MoSi2 content (x=1, 0.75, 0.5 and 0.25) on phase composition, microstructure and properties of the composites were investigated. The results showed that the 0.4MoB-0.1SiC-xMoSi2 com...

In-situ processing of tungsten aluminide and tungsten reinforced aluminium matrix composites from elemental tungsten (W) and aluminium (Al) was investigated by thermal analysis and pulsed current processing (PCP). The formation mechanism of tungsten aluminides in 80 at.% Al-20 at.% W system was controlled by atomic diffusion. The particle size of W...

Porous monoliths of MoO3 nanoplates were synthesized from ammonium molybdate (AHM) by freeze-casting and subsequent thermal treatment from 300 to 600 °C. Pure orthorhombic MoO3 phase was obtained at thermal treatment temperature of 400 °C and above. MoO3 monoliths thermally treated at 400 °C displayed bimodal pore structure, including large pore ch...

Porous mullite materials with high porosity of 71.8–88.2% were prepared by foaming of coal gangue/Al2O3/starch composite slurry and subsequent pore structure stabilization using starch consolidation and sintering. Coal gangue was recycled to prepare porous mullite foams. Starch was used as gellant, replacing commonly used poisonous chemical and exp...

TiAl-based porous materials were synthesized by a novel process of thermal explosion (TE) reaction. The effect of heating rate on expansion behavior of powder assemblies, phase compositions and pore structures were investigated. Results showed that the actual temperature of specimen increased rapidly from 655-661 °C (furnace temperature) to 1018–11...

Spark plasma sintered zirconia (3Y-TZP) specimens have been produced of 140 nm 372 nm and 753 nm grain sizes by sintering at 1250 °C, 1450 °C and 1600°C, respectively. The sintered zirconia specimens were grinded using a diamond grinding disc with an average diamond particle size of about 60 µm, under a pressure of 0.9 MPa. The influence of grindin...

Hierarchically porous Cu with controlled pore characteristics and mechanical properties were fabricated from CuO powders and NaCl as template. NaCl particles were removed by dissolution from the pre-sintered CuO pellet using deionized water. CuO was decomposed to Cu during sintering at 900 °C in vacuum and resulted in porous Cu with bimodal pores....

Natural abundance solid-state multinuclear ((13) C, (15) N and (29) Si) cross-polarization magic-angle-spinning NMR was used to study structures of three block copolymers based on polyamide and dimethylsiloxane and two polyamides, one of which including ferrocene in its structure. Assignment of most of the resonance lines in (13) C, (15) N and (29)...

Hierarchically porous mullite foams were fabricated from coal-series kaolin and Al2O3 slurries by freeze-casting using tert-butyl alcohol (TBA) and water as templates. TBA developed unidirectionally aligned pore channels along the freezing direction and water developed lamellar pores. The total porosity (60.2–83.4%), density (0.49–1.23 g/cm3) and m...

The effect of 10wt%VC addition on the friction and sliding wear response of WC-12wt%Co cemented carbides produced by spark plasma sintering (SPS) was studied. The SPS of WC-12wt%Co alloys with and without 10wt% VC, at 1100 °C and 1130 °C respectively, yielded dense materials with minimal porosity. No eta phase was found in any of the alloys. The WC...