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Iron-based specimens with boronized layers were prepared by boriding at 800 ℃, 900 ℃ and 1000 ℃ for 3, 5, and 7 hours, respectively. The thickness, microstructure, surface roughness, friction, and wear performance were studied. Results showed that the process parameters such as temperature, the time of boriding have remarkable impact on the thickness of the boronized layer. Dual-phase was generated at 1000 ℃ which lead to increased brittleness, lower surface hardness, and decreased adhesion to the substrate. Compared with specimens boronized at 1000 ℃ and 800 ℃, the surface structure of the boronized layer of specimens boronized at 900 ℃ is denser and uniform, the wear track is not damaged. The average friction coefficient and mass loss by wear of specimens boronized at 900 °C are smaller than that of boronized at 1000 ℃ and 800 ℃, indicating that specimens borided at 900 ℃ behave excellent friction and wear performance.

Dark fermentation (DF) is a promising technology for biohydrogen production. Low efficiency of biohydrogen production is a bottleneck of the scale-up prospects for DF. Additives have been extensively studied to improve the biohydrogen production efficiency. Among of them, iron-based additives present a promising application potential due to their demonstrated significant enhancement of DF efficiency and among the low-cost bioactive agents. However, current reviews mainly examined the effects of nano-materials on DF and an in-depth analysis of enhancing mechanisms with addition of iron-based additives in DF is still lacking. To this end, this article comprehensively reviewed and evaluated the effects of iron-based additives on DF. Further, the potential mechanisms, including altering metabolic pathways, improving activities of microbes and enzymes, promoting electron delivery, and enriching hydrogen-producing bacteria, were discussed. Lastly, prospects and challenges of iron-based additives for subsequent research and large-scale application for DF were summarized.

In this study, effective and easily accessible cheap catalysts that assist converting heavy oil residue to lighter products with high yield are investigated. Hydrocracking experiments were carried out in a 10 ml stainless steel bomb-type reactor with up and down stirrer at 200 times of reciprocation per minute. The catalyst mixture provided the minimum coke yield was investigated. FeSO4.H2O, the binary mixtures of FeSO4.H2O with metal oxides (Fe2O3, Al2O3, CaO, SiO2) and the mixtures Fe2O3, Al2O3 and SiO2 with elementary sulphur were used as catalyst. Experiments were conducted at 425 0C for 90 minutes with the initial pressure 100 bar H2. The amount of coke, liquid products and C5- gas products were calculated for each experiment. Gel Permeation Chromatography (GPC), Nuclear Magnetic Resonance (1H NMR) and elemental analysis were used for Iranian heavy oil residue. Differential Scanning Calorimeter (DSC) was used to analyze the catalyst. According to the results, minimum coke yield is achieved by FeSO4.H2O+SiO2 catalyst. Although minimum coke yield achieved with FeSO4.H2O+SiO2, middle distillate containing toluene soluble fraction (TSF) was maximized with Fe2O3+Al2O3+Sulphur catalyst mixture. In addition, the product selectivity in the reactions with the least coke formation showed selectivity in the direction of the formation of gas and light products, not in the direction of liquid product formation.

Corrosion of the steel products is one of the significant challenges which is managed by coating with Al-Zn-based alloys. The Galvalume alloy (Al-55%, 43.5%-Zn, Si-1.5%) is coated on steel strips via a hot-dipping process. The dissolution of iron (Fe) from steel strips and the formation of Fe-based intermetallic particles is an inevitable phenomenon during the hot-dip coating process. These intermetallic particles are a primary source of massive bottom dross build-up in the coating pot and metal spot defects in the coated steel products. Therefore, it is important to investigate the formation of Fe-based intermetallic particles. In this study, Fe-based intermetallic particles are produced via the powder metallurgy route. High energy ball milling was used for mechanical alloying of aluminum (Al), iron (Fe), silicon (Si), and zinc (Zn) powders. Optimized ball milling conditions were identified after a series of trials. After cold pressing, the mechanically alloyed samples (pellets) were sintered at various conditions in a high vacuum sintering furnace. The X-ray diffraction (XRD) and scanning electron microscope (SEM) equipped with energy-dispersive X-ray diffraction (EDS) were used for the analysis of raw material, mechanically alloyed powders, and sintered pellets. It is concluded that the mechanical alloying of 6h and cold pressing at 9 tons for 30 min is sufficient to produce a dense compact material. It was found that Fe-based intermetallic particles were successfully fabricated which were α-AlFeSi. However, intermetallic particles similar to those found in the bottom dross of the coating pot are difficult to fabricate through the powder metallurgy route due to the volatilization of Zn during the sintering process.

The oval-shaped tubes are the valuable product for using to transport the clean gas and high-purity solutions in the field of aerospace, semiconductor, LCD, and medical industries. However, due to their complex shape, it could significantly difficult to improve their inner surface quality by the conventional processes. In this study, the application of Al2O3/iron-based composite abrasives on magnetic abrasive finishing (MAF) process was used to finish the inner surface of oval-shaped SUS 316L tubes. Their inner surface was finished by a mixture of magnetic abrasive tools of Al2O3/iron-based composite abrasives with Fe powders, and light oil. An artificial neural network (ANN) model was used to predict the results of MAF process and then was compared with the actual test. It is found that the results predicted by the ANN model have significant agreement with the actual test results. The correlation coefficient (R2) for both training and testing of surface roughness on span and rise portion is larger than 0.92, and RMSE values for both cases are extremely small (less than 0.01). The actual test results showed that the inner surface of oval-shaped SUS 316L tube was smoothly improved from 0.24 μm to 0.05 μm and 0.04 μm on the rise and span portion, respectively. The application of Al2O3/iron-based composite abrasives on MAF process is an efficient method for inner surface finishing of the oval-shaped tubes.

Water solvent plays an important role in catalytic water oxidation to dioxygen, in particular in the O-O bond formation process. In this work, we revisit the mechanism of O-O bond formation catalyzed by a mononuclear iron catalyst [Cl-FeIII(dpa)-Cl]+, in a DFT-based molecular dynamics (DFT-MD) study that incorporates explicit solvent and thermal fluctuations. Two possible mechanisms for the crucial O-O bond formation, namely water nucleophilic attack (WNA) and nitrate nucleophilic attack (NNA) on the high-valent Fe-V-oxo moiety, were considered and found to have similar barriers (15 kcal/mol vs 16 kcal/mol). Comparison with static DFT calculations demonstrated the important role of water solvent molecules, especially for the NNA pathway. For this mechanism, the interaction of the negatively-charged nitrate with solvent molecules is substantial, giving rise to a free energy barrier increase of 7.7 kcal/mol compared with static DFT calculations. The study suggests that for molecular water-oxidation catalysts, the local aqueous solvation structure and its thermal fluctuations plays a significant role in the crucial O-O bond formation step. The study also elucidates the role of the nitrate ion as a co-catalyst, a notion that may serve as a potential design rule for developing improved water oxidation catalysts.

Chemical looping reforming (CLR) is a recent trend for syngas production, which has several merits compared to the conventional manner. One of the most important issues for CLR is to find low-cost material as oxygen carriers, so iron is a promising candidate. This paper contributes to testing the thermodynamic ability of iron-based oxygen carrier for chemical looping reforming of ethanol (CLRE). Iron thermodynamically investigated in temperature 100–1300 °C and excess oxygen number (Φ) 0–4. It was found that the temperature and Φ have an apparent effect on the gaseous composition produced from the process. Increases in temperature within the range of 100–1300 °C enhanced syngas generated and reduced coke formation and CH4. Whereas, increased Φ, particularly at higher temperatures, had also enhanced syngas production as well as reduced coke formation. However, increasing Φ for values beyond one had decreased syngas and not significantly reduced coke deposition. Moreover, an experimental investigation was carried out in a fixed bed reactor for more in-depth verification of iron ability as an oxygen carrier through using magnetite ore (mainly Fe3O4). It found that the effect of temperature on syngas production was consistent with that calculated thermodynamically, as syngas increased with raising the temperature through the CLRE.

The development of an air-stable iron(III)-based precatalyst for the Suzuki−Miyaura cross-coupling reaction of alkyl halides and unactivated aryl boronic esters is reported. Despite benefits to cost and toxicity, the proclivity of iron(II)-based complexes to undergo deactivation via oxidation or hydrolysis is a limiting factor for their widespread use in cross-coupling reactions compared to palladium-based or nickel-based complexes. The new octahedral iron(III) complex demonstrates long-term stability on the benchtop as assessed by a combination of (1)H NMR spectroscopy, Mössbauer spectroscopy, and its sustained catalytic activity after exposure to air. The improved stability of the iron-based catalyst facilitates an improved protocol in which Suzuki−Miyaura cross-coupling reactions of valuable substrates can be assembled without the use of a glovebox and access a diverse scope of products similar to reactions assembled in the glovebox with iron(II)-based catalysts.

Iron-based phosphates have attracted considerable attention as cathode materials for sodium-ion batteries by virtue of their natural abundance, low cost, and nontoxicity. A significant challenge of...

Low-pressure powder injection moulding (LPIM) is a cost-effective manufacturing technology used to fabricate complex-shaped parts with high mechanical properties at low- or high-volume production. ...

Machining quality and productivity of superalloys are limited due to their poor machinability, and fewer studies have focused on the cutting of iron-based superalloys. In this study, the cutting performance of coated and uncoated carbide tools in high-speed dry turning iron-based superalloy GH2132 was investigated by performing a series of cutting experiments. The experimental results indicated that cutting temperature and cutting forces increased, while tool life decreased with the increase in the cutting speed from 30 to 100 m/min. Under relatively low cutting speeds, flank face wear was dominated by abrasion and adhesion, while rake face wear mainly involved built-up edge (BUE), built-up layer (BUL), adhesion, and breakage near the depth of cut. Under higher cutting speed, adhesion wear was more serious on the flank face, and peeling off of the coatings and substrate occurred on the rake face. Owing to the protective effect of (Ti, Al)N + TiN coating, the coated tools exhibited better wear resistance and thus longer tool life, in particular, under higher cutting speeds. Analysis of the tool wear gap in the horizontal direction indicates that better dimensional accuracy could be obtained when coated tools are used. In dry turning of GH2132 with carbide tools, a favorable surface finish could be obtained. The surface roughness roughly showed a tendency to first decrease and then increase with the increase in average flank wear. The coated tools should be avoided to machine GH2132 at higher cutting speed due to the poor surface finish.

Since the initial identification of the iron-based superconductors (IBS) in 2008, numerous studies had focused on how to improve critical current density. However, the research of quench behaviors for iron-based multi-filamentary tapes was rarely reported. It is important to understand quench behaviors, and two main parameters should be examined carefully, i.e., normal zone propagation velocity (NZPV) and minimum quench energy (MQE). In this paper, a two-dimensional quench model integrating the stationary electrodynamics equations and heat conduction equation was proposed to study the quench propagation of iron-based Sr/Ba0.6K0.4Fe2As2 (Sr/Ba122) tape in different transport currents and temperatures. MQEs and NPZVs of IBS tape were calculated by the quench model, and the results were well complied with experimentally results which verified the correctness of the proposed quench model. In addition, since iron-based superconducting coils for high magnetic field application were operating in liquid helium mostly, an experiment was performed to study the quench behaviors of Ba122 tape in liquid helium, for the purpose of understanding the stability of the iron-based superconductor and designing quench protection systems of IBS coils reliably.

In the study for this contribution, production of in situ synthesized TiB2 particles in iron-based composite coatings using four different submerged arc welding powders (fluxes) containing increasing amounts of ferrotitanium and ferroboron with S1 welding wire, were targeted. For this purpose, coating deposition was carried out to improve the hardness and wear properties of the AISI 1020 steel surfaces using hybrid submerged arc welding. In hybrid submerged arc welding, the welding pool is protected by both welding powders and an argon gas atmosphere. To examine the composite coatings, visual, chemical, microstructural analyses and hardness and wear tests were carried out. With the use of increasing amounts of ferrotitanium and ferroboron in the welding powders, it was observed that the microstructure of the coatings changed in terms of TiB2 particle geometries such as rectangular and hexagonal; volume fractions of TiB2 particles in the coating microstructures increased; hardness values of coatings were enhanced from 34 HRC to 41 HRC; the wear resistance of the coatings improved, and worn surface images of the coatings caused by the counter body changed from continuous with deep scratches to discontinuous with fine scratches and crater cavities.

The effect of Sb doping at As-chain site of the recently discovered 112 (i.e., CaFeAs2) iron based superconductors is studied with density functional theory based ab-initio electronic structure calculation. Our electronic structure calculation shows that there is an enhancement of As partial density of states in Sb doped 112 compounds. Thus, there exist possibility of enhanced superconductivity in Sb and rare earth co-doped 112 superconductors. Further our first principles calculation also reveals the fact that enhancement in As partial density of states for Sb doping in different rare earth doped 112 compounds is also different.

In this study, a chemical reaction process was designed to prepare the endogenous conversion coating on a smooth and clean amorphous alloy surface, solving the problem of non-wetting of the interfa...

With unique physicochemical properties and biological effects, magnetic nanomaterials (MNMs) play a crucial role in the biomedical field. In particular, magnetic iron oxide nanoparticles (MIONPs) are approved by the United States Food and Drug Administration (FDA) for clinical applications at present due to their low toxicity, biocompatibility, and biodegradability. Despite the unarguable effectiveness, massive space for improving such materials’ performance still needs to be filled. Recently, many efforts have been devoted to improving the preparation methods based on the materials’ biosafety. Besides, researchers have successfully regulated the performance of magnetic nanoparticles (MNPs) by changing their sizes, morphologies, compositions; or by aggregating as-synthesized MNPs in an orderly arrangement to meet various clinical requirements. The rise of cloud computing and artificial intelligence techniques provides novel ways for fast material characterization, automated data analysis, and mechanism demonstration. In this review, we summarized the studies that focused on the preparation routes and performance regulations of high-quality MNPs, and their special properties applied in biomedical detection, diagnosis, and treatment. At the same time, the future development of MNMs was also discussed.

Iron is a favored catalyst for Fischer-Tropsch (FT) synthesis, the production of hydrocarbons from synthesis gas. Zeolites are common catalysts for hydrocarbon processing. Here we review iron-based...

Zirconium is used as an alloying element owing to its ability to form carbides, nitrides, oxides, and other intermetallic compounds. Zirconium alloying has the high efficacy in increasing the oxida...

In the last few years I have noticed more and more papers addressing power electronics and reliability. These papers are, as I have noticed, all coming from academia. Now there is even a university re - search center focused on power electronics reliability — the Center Of Reliable Power Electronics (CORPE) at the University of Aalborg in Denmark. I admit that I have been a bit put off by this. As someone who has spent his entire career in industry, my reaction has been "What do these university folks think they know about reliability that industry has not already solved?" The author concludes that he is now glad to see university research on power electronics reliability even though I suspect industry is actually way ahead but unable to publish their results due to business confidentiality needs. Anything that can help move us ahead is welcome. As power electronics becomes more and more central to our lives, reliability, service life, and availability will become increasingly important. While we can never achieve perfect reliability and availability, we can strive to make our semiconductor based power electronics as reliable and long lived as the copper and iron based electronics they will be replacing.

This paper presents a one-step method that significantly simplifies the biomass carbonization preparation with Fe0 as active catalyst. The catalyst activity was compared to that of the catalyst pre...

In this study, we demonstrate the synthesis of an Fe78Si9B10P3 amorphous alloy by three pathways: mechanical alloying, melt-spinning and a combination of melt-spinning and ball milling. Microstructure, thermal stability and soft magnetic properties of the melt-spun and mechanically alloyed powders are comparatively studied. Ball milling of previously melt-spun samples led to an amorphous powder with an average particle size of ~2.4 μm after 20 hrs of milling. Mechanical alloying of elemental Fe-Si-B-P powders in a planetary ball mill for up to 100 hrs led only to a partial amorphisation of powder with a median particle size of ~1.3 μm. Differential thermal analysis of the amorphous ribbon revealed that the amorphous phase was stable up to ~520 °C, at which the crystallization process occurred. The melt spun ribbons exhibited excellent soft ferromagnetic behavior, including high saturation magnetization (Ms) of ~171 emu/g and a low coercivity (Hc) of ~2.8 Oe. In the 20 hrs milled ribbons, due to a probable partial anisotropy which induced by ball milling stress, the Ms value decreased slightly to ~161 emu/g but the Hc increased to ~38 Oe. The mechanically alloyed samples present a relatively lower Ms of ~154 emu/g and higher Hc of ~43 Oe. It is to be noted that the milling of ribbons is usually inevitable due to their technological restrictions in use.

Iron-based metal–organic frameworks (Fe-MOFs) have captured considerable attention owing to their intriguing structural architectures, excellent stability, durability, and function. Fe-MOFs are ant...

The promotional effects of sodium on Fe5C2 catalysts for CO2 hydrogenation were systematically investigated by a synergistic combination of density functional theory (DFT) calculations and experime...

In this study, phytic acid (PA) surface treatment was used to prepare iron-based soft magnetic composites (SMCs). The composition and microstructure of the SMCs were analyzed to assess changes in the magnetic properties. As the treatment time increased, the insulating layer on the powder surface gradually thickened, changing the internal morphology and conductive path of the annular samples after compacting. The changes in the magnetic properties and core loss were attributed to the increased resistivity and enhancement of the magnetic dilution effect. The optimal soft magnetic performance (μm = 389, Pt = 235.1 mW/g measured at 100 kHz and 50 mT) was obtained by adjusting the processing time. This reduces the loss by 52.96% compared to the untreated sample and improves the application potential of soft magnetic composites at medium and high frequencies.

Studies of a powder used as a modifier obtained from solid-alloy waste, such as tungsten carbide (drill balls), are presented. Dispersion, particle morphology and phase analysis of the powder were studied. The powder obtained from solid-alloy waste is a phase – it is tungsten carbide WC, it consists of nanoobjects of various shapes (nanoparticles, nanoplastics) up to 100 nm in size, with a slight presence of agglomerates up to 250 nm in size. The influence of tungsten carbide nanopowder as a modifier on the mechanical properties (strength and hardness) of PK70D3 iron-based powder structural steel has been studied. For the study, two different modes of preparation of powder alloy have been used with the use of one-stage and two-stage sintering. The influence of additive nanopowder of tungsten carbide on the mechanical properties of structural alloy powder based on iron PK70D3 has been defined: strength increases by more than 23% (in single-stage sintering), by more than 28% (in double-sintering), hardness decreases by more than 6% in single-stage sintering and increases by more than 26% with two stages of sintering, compared to the initial alloy. It has been shown that samples, obtained using double sintering with a tungsten nanopowder modifier (2.5%), have higher values of strength (more than 80%) and hardness (more than 13%), compared to modified samples, obtained by single-stage sintering technology. Thus, the modification of a 2.5 % nanoprobe of tungsten carbide, a widely used structural powder alloy based on iron PC70D3 allows for a significant change in mechanical properties. The use of powder alloys in double sintering technology provides the material hardness and the strength increase.

Tremendous research works including nanofabrication techniques and crystal defect preparation approaches have been applied to enhance the capacitance of bulk materials. However, a comprehensive understanding of active sites in the reaction process is an enigma for all researchers. This work reported an environmentally friendly system with a basic polymerized ferric sulfate (BPFS) electrolyte and electroactive graphite electrode, which achieved high area capacitance and showed the different characteristics of active sites. This enhanced energy storage system shows the evidence that carbon materials are electrochemically activated as a result that active groups could react with iron groups in aqueous solutions. A high area specific capacitance of 12 F cm-2(1255 F g-1) is obtained in a mixed BPFS at 5 mV s-1 in a potential window of 2.1 V in a three-electrode cell. In an aqueous solution capacitor, a capacity of 4.8 F cm-2 at 30 mA from 0 V to 1.5 V is achieved at room temperature. It has the potential to develop a low-cost, high energy storage, and high safety system, which can be a lead-acid battery substitute.

Metal-organic frameworks (MOFs) are crystalline materials comprising metal centers and organic linkers that feature structural rigidity and functional flexibility. These attractive materials offer large surface areas, high porosity, and good chemical stability; they have shown promise in chemistry (H2 separation and catalysis), magnetism, and optics. They have also shown potential for drug delivery following the demonstration in 2006 that chromium-based MOFs can be loaded with ibuprofen. Since then, iron-based MOFs (Fe-MOFs) have been shown to offer high drug loading and excellent biocompatibility. The present review focuses on the synthesis and surface modifications of Fe-MOFs as well as their applications in drug delivery and biomedicine.

Iron can be found in all mammalian cells and is of critical significance to diverse cellular activities within human bodies. Widespread applications and the underlying chemical and biological funda...

The correlation between valence electrons per atom (ev/a) and the characteristic transition temperatures of quaternary and quinary Fe-based shape memory alloys (SMAs) is investigated. Regression equations relating their transformation temperatures (Ms, As) to composition and ev/a are obtained. On adding alloying elements to the SMAs, their transformation temperatures get altered and this is correlated to their ev/a ratio. Three distinct trends between the ev/a ratio and transformation temperatures are found. The correlation between the transformation hysteresis and the atom diameter of the alloying elements is also analysed.

A micromechanical analysis under large deformations for iron-based composites is introduced to predict the deformation behavior of iron (Fe)-copper (Cu) composites. In particular, pure Fe, pure Cu, Fe-17 wt. $$\%$$ Cu, and Fe-83 wt. $$\%$$ Cu are studied. In Fe-Cu composites, Cu is a soft-phase material. Hence, it undergoes a large deformation. Fe being the hard phase material shows elevated stresses. Because of the heterogeneity in the microstructure of Fe-Cu composites, the micromechanical model enables the capture of the flow behavior of Fe-Cu polycrystals. Both Fe and Cu constituents are rate-dependent elasto-viscoplastic materials. Hence, they are formulated in the framework of large deformations. The reliability of the prediction of flow behavior is investigated by comparing the numerical model (Taylor approach) and experiments.

Nanoparticle-mediated photothermal therapy (PTT) has shown promising capability for tumor therapy through the high local temperature at the tumor site generated by a photothermal agent (PTA) under visible or near-infrared (NIR) irradiation. Improving the accumulation of PTA at the tumor site is crucial to achieving effective photothermal treatment. Here, we developed temperature-activatable engineered neutrophils (Ne) by combining indocyanine green (ICG)-loaded magnetic silica NIR-sensitive nanoparticles (NSNP), which provide the potential for dual-targeted photothermal therapy. The combined effect of neutrophil targeting and magnetic targeting increased the accumulation of PTA at the tumor site. According to magnetic resonance imaging (MRI), the retention of intravenous injected NSNP-incorporated neutrophils within the tumor site was markedly augmented as compared to free NSNP. Furthermore, when irradiated by NIR, NSNP could cause a high local temperature at the tumor site and the thermal stimulation of neutrophils. The heat can kill tumor cells directly, and also lead to the death of neutrophils, upon which active substances with tumor-killing efficacy will be released to kill residual tumor cells and thus reduce tumor recurrence. Thereby, our therapy achieved the elimination of malignancy in the mouse model of the pancreatic tumor without recurrence. Given that all materials used in this system have been approved for use in humans, the transition of this treatment method to clinical application is plausible.

Iron based catalysts have been widely used in CO2 hydrogenation reactions and the phase transformaiton during the hydrogenation has been noticed. Herein, iron oxide was observed to be in-situ carburized into Fe3C, and Fe3C was identified as the active and stable phase during the reverse water gas shift (RWGS) reaction. Factors such as reduction degree of iron oxide and reaction temperatures were revealed to affect the phase transformation from iron oxide to Fe3C. The feed gas ratio of H2/CO2 showed a decisive effect on the in-situ formation of Fe3C and an optimized ratio of 2 was crucial to avoid the excessive oxidation or reduction of carbide. Ex-situ synthesized Fe3C via CO carbonization performed an inferior catalytic performance compared with the in-situ generated Fe3C due to the unexpected but inescapable carbon deposition

The performance and cost of electrocatalysts play an important role in the development and application prospects of energy conversion technology. Single-atom catalysts (SACs) have constituted a new frontier in the field of catalytic science in recent years. As a non-precious metal, iron (Fe)-SACs show great potential in the field of electrocatalysis, which is comparable to or even better than the performance of precious metal catalysts. However, a robust, generic synthetic strategy toward atomically dispersed Fe catalysts is still lacking, which is still a formidable challenge to maintain the dispersion of Fe atoms at high temperatures and to obtain high catalytic activity. In this review, the latest progress in the synthesis of Fe-SACs is introduced and summarized, and the electrochemical applications of Fe-SACs are further summarized and discussed. Herein, the relationship between the structural characteristics and performance of Fe-SACs is further introduced and discussed. Finally, the existing problems and development prospects of Fe-SACs are discussed.

The distribution of microhardness in cylindrical samples formed from industrial iron-based powders and not subjected to sintering is experimentally studied. This distribution is described by a simple mathematical model. It is shown that the measured hardness has a significant correlation with the strength. Microhardness is correlated with the local strength. Because, during the subsequent sintering and heat treatment of the powder sample, phase transformations occur within the individual grains, the microhardness distribution that occurs before the sample is sintered will remain after sintering. The technology of microhardness equalization in the sample at the stage of its forming, before sintering, is described.

Enhancement of anaerobic digestion is vital for substrate solubilization and increased biogas production at a reduced cost. The use of several iron-based additives has proven effective in improving overall bio-digester performance during anaerobic digestion sludge. This study evaluates different iron-based additives for the selection of the best additive from the alternatives using a multi-attribute decision making (MADM) approach. The weights of the attributes were computed with the entropy weight technique and the ranking of the alternatives were performed using order preference by similarity to ideal solution (TOPSIS) method. Five attributes and thirteen frequently used alternatives were selected for evaluation. The result showed that additive cost and dosages were assigned the highest weight of 62.37 % and 27.46 %, respectively. Based on the performance scores of 99.15 %, 20 mg/L of Fe3O4 nanoparticles (Fe3O4 NPs-20) ranked best (number 1) among considered alternatives for enhancement of anaerobic digestion of sludge. The outcome of this evaluation agrees with previous experimental results and suggests that the choice of an effective iron-based additive should be based on its biogas enhancement potential and cost-effectiveness (low dosage requirement and low price).