Chemical Composition Of Substrate Research Articles

Investigation Of Coastalock Performance On A Breakwater With Porous Core

Hard stabilization methods have traditionally been employed to mitigate coastal erosion. Concrete armour is widely used due to its high level of dependence, robustness, ease of production and cost effectiveness (Cooke et al., 2020; Pikey and Cooper, 2012). It is inevitable that coastline ‘armouring’ will continue to rise because of the growing human population and urbanization, desire for and value of coastal property, opposed to predicted climate change (Chapman and Underwood, 2011). The environmental impact of such 'armouring' on coastal systems can be detrimental, resulting in a degradation or destruction of habitats and the loss of ecologically trivial species (Gittman et al., 2015). The CoastalockTM, a single-layer armour unit, aims to blend coastal protection with marine habitat creation. This armour unit is designed to mimic inter- and sub-tidal habitats, with chemical composition of substrate and micro and macro features that provide niches for various species. The key feature of CoastalockTM is the cavity that is integrated into the design, that caters to diverse marine life needs depending on its orientation (ECOncrete Tech Ltd., 2019). CoastalockTM's hydraulic performance is under research. Preliminary tests conducted in the Hydraulic Engineering Laboratory (HEL) of the Technical University of Delft (TUD) on a 2V:3H impermeable slope in deep water conditions highlighted that with tight placement of the units significant pressure gradients across the top layer led to damage. The introduction of spacings between units for enhanced permeability improved stability significantly (Gutiérrez et al., 2023). A redesign of the unit was proposed incorporating protrusions to enforce the spacings between the blocks (Molenkamp, 2022). This research focuses on evaluating the influence of a porous core on the hydraulic performance of a CoastalockTM armour layer, specifically assessing its stability, overtopping, and reflection on a 2V:3H breakwater slope in deep water conditions—from the toe to just below the crest. A pivotal aspect of this research is the investigation of the impact of protrusions on the hydraulic performance. Furthermore, the study explores the influence of different toe configurations, aiming to comprehend the vulnerability of the armour layer to sliding. Toe scour falls outside the scope of this study.

Methane yield response to pretreatment is dependent on substrate chemical composition: a meta-analysis on anaerobic digestion systems

Proper pretreatment of organic residues prior to anaerobic digestion (AD) can maximize global biogas production from varying sources without increasing the amount of digestate, contributing to global decarbonization goals. However, the efficiency of pretreatments applied on varying organic streams is poorly assessed. Thus, we performed a meta-analysis on AD studies to evaluate the efficiencies of pretreatments with respect to biogas production measured as methane yield. Based on 1374 observations our analysis shows that pretreatment efficiency is dependent on substrate chemical dominance. Grouping substrates by chemical composition e.g., lignocellulosic-, protein- and lipid-rich dominance helps to highlight the appropriate choice of pretreatment that supports maximum substrate degradation and more efficient conversion to biogas. Methane yield can undergo an impactful increase compared to untreated controls if proper pretreatment of substrates of a given chemical dominance is applied. Non-significant or even adverse effects on AD are, however, observed when the substrate chemical dominance is disregarded.

Active screen plasma nitriding of Fe-24Mn-2Al-0.45C TWIP steel: Microstructure evolution and a synergistic selective oxidation mechanism

In this study, Fe-24Mn-2Al-0.45C twinning-induced plasticity (TWIP) steel was investigated after active screen plasma nitriding (ASPN) at 350–480 °C. Up to 450 °C, the ASPN-treated TWIP steel showed a double-layered structure, with a topmost Fe4N-type γ’ layer and an underlying interstitial solid solution. The underlying nitrogen interstitial solid solution obtained on ASPN-treated TWIP steel can be identified as γN(i), being expanded austenite with small lattice expansions at low nitrogen (and carbon) absorption levels. However, the 480 °C ASPN-treated TWIP steel surface is composed of an unexpected MnO-containing ferritic topmost layer and a thick underlying γN(i) layer, which corresponds to a hardness-depth profile different to those obtained at 350–480 °C. Hence, we propose and elucidate a selective oxidation mechanism (that occurred alongside nitrogen inward diffusion) on TWIP steel during ASPN treatment, which can be attributed to (a) an elevated treatment temperature that allowed Mn migration, (b) a processing atmosphere with low oxygen partial pressure, and (c) a high-Mn substrate chemical composition with low Al/Mn (or Si/Mn) ratio.

Universal and Stable Slippery Coatings: Chemical Combination Induced Adhesive-Lubricant Cooperation.

Liquid lubricant of low affinity makes slippery coatings widely used in lubricating, anti-biofouling, anti-icing, fluid guiding, and drag reduction. Two critical challenges, however, remain in the practical application of slippery coatings consisting of liquid lubricants: (1) universality regardless of roughness and chemical composition of substrates, (2) stability of surface lubricity against evaporation. Herein, a chemical method is reported to create a universal and stable slippery lubricant-adhesive cooperated coating (SLACC) through acid catalyzed dehydration reaction between the phenolic hydroxyl of polydopamine (PDA), with universal (for challenge-1) and strong (for challenge-2) adhesion properties, and liquid-like polydimethylsiloxane (PDMS), with lubricant properties. Through overlying PDMS on PDA, a spatial gradient interpenetration of chemical combined PDA and PDMS leaving lubricant PDMS at the outermost of coating is achieved. This structure contributes to the following performances of SLACC: nearly universality suitable for 100 different abiotic or biotic substrates and stability sustainable for long-term usages, UV radiating, refrigerating, hot air drying, freeze drying, knife scratch and abrasion. This proposed strategy is envisioned anti-fouling from plane to tube and exhibits drag reduction in confined space.

Impact of temperature on corrosion behavior of austenitic stainless steels in solar salt for CSP application: An electrochemical study

The compatibility between solar salt and structure materials is still a key issue in concentrated solar power (CSP) technology. The corrosivity of solar salt is significantly dependent on temperature. In this work, the temperature effect on the corrosion of 304 and 316L stainless steels (SS) in solar salt was studied at 500, 565, and 600 °C using electrochemical methods. Results indicate that higher values of i corr and corrosion rate (CR) are found for both 304 and 316L SS at higher temperatures. EIS results demonstrate that corrosion process of 304 SS in solar salt at 500 and 565 °C is controlled by ions transportation through the oxide layer. At 600 °C, however, the Warburg impedance is observed due to the porous and Cr 2 O 3 -free oxide layers formed on the surface of the sample exposed in molten solar salt for 138 h. Comparatively, the ions transportation through the oxide layer is always the rate-controlling process for 316L SS at each temperature. Protective oxide layer containing Cr 2 O 3 is formed on 316L SS even at 600 °C. Moreover, the formation of Cr-rich nitride underneath the oxide/substrate interface depends on the temperature of melt and chemical composition of substrate. • Electrochemical corrosion behaviors of 304 and 316L SS in temperature range of 500–600 °C are studied. • Higher i corr of 304 SS than that of 316L SS is observed at each temperature. • Formation of Cr-rich nitride depends on temperature and types of steel. • Cr 2 O 3 -free oxide layer forms on 304 SS at 600 °C, inducing Warburg impedance. • Cr 2 O 3 exists in protective oxide scale of 316L SS in the studied temperature range.

Kinetics of the UNS S32750 Super Duplex Stainless Steel Low-Temperature Plasma Nitriding

This work reports an experimental investigation on the thermodynamic and kinetic view-point of the nitrided layer growth behavior, carried out separately at ferrite and austenite phase grains, for the UNS S32750 super duplex stainless steel (SDSS). For this purpose, and motivated by the DSSs distinct behavior showing formation of two- or single-phase nitrided layers, which apparently depend on the steel substrate chemical composition, two series of treatment were studied here, one varying the nitriding temperature on the 300-450 °C range for 4 h time, and other one varying the time on the 2-8 h range at 350 °C. Microstructural characterization of studied layers by means of SEM and EDS analysis, XRD and microhardness measurements showed precipitation-free nitrogen-expanded austenite layer formation on both steel phases for all samples treated up to 400 °C. The nitriding kinetics study showed that the layer thickness on both steel phases is proportional to the square root of the treatment time and follows an Arrhenius law for the studied treatment temperatures. The nitrogen diffusion activation energy, separately determined from the layer growth on each steel phase, was 115±3.2 and 120±5.4 kJmol-1, for austenite and ferrite grains, respectively.

The effect of PEO parameters on the properties of biodegradable Mg alloys: a review

This paper comprehensively reviews recent research carried out in the field of preparation of bioactive coatings on magnesium (Mg)–aluminum (Al)–zinc (Zn) alloys by using the plasma electrolytic oxidation (PEO) method and investigation of factors affecting it. Magnesium–aluminum–zinc alloys (AZ grades) have been developed for use as biodegradation materials because the addition of aluminum and zinc as alloying elements can ameliorate their mechanical properties and increase corrosion resistance over those of pure magnesium alone without decrement in biocompatibility. Among the common methods for improvement of biodegradation, corrosion resistance and biocompatibility of magnesium alloys, surface modification techniques have been more effective. PEO is a relatively novel surface modification technique that provides excellent wear- and corrosion-resistant coatings on lightweight metals, in particular on magnesium and its alloys. The processing parameters of PEO, such as pulse frequencies, applied voltages, oxidation time, electrolyte concentrations and substrate chemical composition, are some of the major factors that determine the quality of the coatings in terms of corrosion resistance and bioactivity in body fluid solutions. Considering the fact that comprehensive review articles on the effect of PEO parameters on the properties of magnesium alloys have not been published in recent years, the aim of the present text is to provide an understanding of all aspects of these process parameters.

Nanoporous Anodic Aluminum-Iron Oxide with a Tunable Band Gap Formed on the FeAl3 Intermetallic Phase.

Nanostructured anodic oxide layers on an FeAl3 intermetallic alloy was prepared by two-step anodization in 20 wt.% H2SO4 at 0 °C. The obtained anodic oxide coating was subjected to phase and chemical composition analysis using XPS and XRD techniques. An analysis of the band gap of individual coatings was also performed. The applied parameters of the anodization process were determined, enabling the formation of a nanostructured coating on the FeAl3 intermetallic alloy. Tests were carried out on samples produced at a voltage between 10 V and 22.5 V in 2.5 V steps. The produced coatings were subjected to an annealing process at 900 °C for 2 h in an argon protective atmosphere. Moreover, the influence of the substrate chemical composition on the chemical and phase composition of the anodic oxide are discussed. Band gaps of 2.37 eV at 22.5 V and 2.64 eV at 10 V were obtained directly after the anodizing process. After applying the heat treatment, band gap values of 2.10 eV at 22.5 Vand 2.48 eV for the coating produced at 10 V were obtained.

Carbon derived from silicon carbide fibers, a comparative study

SiC-based fibers, eleven in total, derived from polycarbosilane pyrolysis and belonging to the three different generations, were fully converted into microporous carbon after selective etching of silicon atoms under pure chlorine flow at intermediate temperatures (550–850 °C). In this work, relationship between as-received fibers and their subsequent carbide-derived carbon (CDC) properties, pore structure oxidation resistance and mechanical properties, was investigated. The resulting carbon is microporous or micro-mesoporous with equivalent specific surface area exceeding 1000 m2 g−1 and pore size distribution (PSD) related to the substrate chemical composition and microstructure of former fibers. Oxidation kinetics were found to depend on this PSD. The former sp2 carbon free network of fibers remained unaffected by the chlorination. Its amount and percolation were respectively correlated to Young modulus and tensile strength of CDC. This carbon thus displays a nano-composite-like behavior with a former etched carbide matrix (transformed SiC and SiCO) and carbon free reinforcement. The results demonstrate CDC allows the control over pore size and mechanical properties by selecting an appropriate multiphasic substrate, combining etched and non-etched compounds.

Microbial Synthesis and Characterization of Biodegradable Polyester Copolymers from Burkholderia Cepacia and Cupriavidus Necator Strains Using Crude Glycerol as Substrate

Abstract Polymers are materials of pronounced importance in the modern world, since they are massively present in everyday life, especially in the form of packaging. However, most of these materials are derived from non-renewable sources and their disposal generates large volumes of waste, which is extremely damaging to natural environments. In this context, microbial biopolymers appear as a powerful alternative in the substitution of several applications of synthetic plastics, causing less harm to the environment, as they are biodegradable and produced from renewable sources. In this study, evaluation and characterization of polyhydroxyalkanoates (PHAs) produced by Cupriavidus necator (IPT 026 and IPT 027) and Burkholderia cepacia (IPT 119 and IPT 400), using crude glycerol as substrate, were carried out (crude glycerol 15 g L-1, pH 7.0, 150 rpm, 72h). The substrate chemical composition was determined and all microorganisms tested were able to utilize it to synthesize PHA. C. necator IPT 026 exhibited the highest polymer production (1.52 ± 0.03 g L-1). B. cepacia strains produced low crystallinity PHA. All polyesters synthesized exhibited long chain length polymers with low polydispersity and initial thermal degradation temperatures superior to 300°C. The microorganism strains and the substrate composition highly affected PHAs synthesis, composition and thermochemical characteristics.

The effect of different substrates on the growth of six cultivated mushroom species and composition of macro and trace elements in their fruiting bodies

There is an ongoing interest in the production of mushrooms as food, and with their consumption on the rise, there is a need to establish different safety measures. In the present study, six mushroom species (Agrocybe cylindracea, Clitocybe maxima, Flammulina velutipes, Ganoderma lucidum, Lentinula edodes and Pleurotus eryngii) were cultivated on two commonly used substrates (A—based on alder and beech sawdust; B—based on oak sawdust and flax shives). The aims were to determine their growth and the accumulation of 70 elements in their fruiting bodies, 33 of which were detected in all analysed samples and were used for statistical evaluation. Cultivation of C. maxima, G. lucidum and L. edodes resulted in higher yield and mineral content when substrate A was used, cultivation of A. cylindracea and F. velutipes yielded better results on substrate B, P. eryngii cultivation outcomes were similar for both substrates. L. edodes was found to have a high affinity to accumulate Cd, C. maxima can bioconcentrate Al and Ni, Ganoderma lucidum—Pb, while F. velutipes—Hg. The study indicated that the chemical composition of substrates could affect both the yield and the level of various toxic and nutritional elements.

Characterization of Borided DIN X165CrMoV12 Steel

In the present study, characterization properties of borides formed on DIN X165CrMoV12 steel have been investigated. Boriding was performed in a solid medium consisting of Ekabor-II powders at 1073 and 1273K for 4 h. The boride layer was characterized by optical microscopy, X-ray diffraction technique and the micro-Vickers hardness tester. X-ray diffraction analysis of boride layers on the surface of the steels revealed the existence of FexBy and CrxBy compounds. Depending on the chemical composition of substrates, the boride layer thickness on the surface of the DIN X165CrMoV12 steel was found to be 32.75 μm and 78.92 μm at 1073 and 1173K for 4 h, respectively. The hardness of the boride compounds formed on the surface of the DIN X165CrMoV12 steel ranged from 1638 to 1892 HV 0,1 , whereas Vickers hardness values of the untreated steel DIN X165CrMoV12 was 432 HV0,1.

Determination of the Efficiency and Kinetics of Biogas Production from Energy Crops through Nitrogen Fertilization Levels and Cutting Frequency

The efficiency and kinetics of methane fermentation were evaluated for six energy crops when cultivated at three different nitrogen (N) fertilization levels, specifically, maize, sorghum, sunflower, triticale, reed canary grass (RCG), and Virginia mallow (VM). In the case of the perennials, RCG and VM, the impacts of individual swath and cutting frequency were examined. A new model for predicting the methane yield based on the substrate chemical composition was developed and validated. A raised N fertilization dose increased the biogas, methane yield, and the specific rate of their production. The highest increase in methane yield was observed in VM from 145 to 197 dm3 kg-1 of volatile solids (VS) due to a 15% rise in biodegradability. This resulted from a decrease in the lignin content and favorable changes in the lignin to structural carbohydrates ratio. Moreover, in the case of perennials, more efficient biogas production was observed for the biomass collected at an earlier stage. The results in this investigation are important for the production of high-quality biomass for biogas plants, without competition for arable land areas with food and feed production.

From Mountains to Plains: Ecological Structure of the South Ural (Russia) Fen Vegetation

This study focuses on comparing the driving ecological factors and community diversity of fen vegetation from the plain part of the South Ural region with those of the mountain fen vegetation, previously described by us (Ivchenko and Znamenskiy Russian Journal of Ecology 47:453–459, 2016), by means of vegetation data clustering and gradient analysis. The indicator values by several authors (H Ellenberg, E Landolt, LG Ramensky, DN Tsyganov) and WorldClim bioclimatic variables were used to determine the ecological meaning of the gradients. We found that the main gradient for both plain and mountain fen vegetation is the “poor-rich fen” gradient, which depends on local substrate chemical composition. The second gradient is associated with moisture, which tends to increase consistently both from mountains towards plains and across plains from peneplain towards West Siberian Lowland. The moisture gradient proved to be unrelated to precipitation, which increase linearly from plains towards mountains. The community diversity in the mountain part is higher than in the plain part. The fen vegetation of plains and mountains overlap in ordination space but a half of the types described for mountain fen vegetation do not occur on plains, while two types of plain fen vegetation from the West Siberian Lowland are absent on mountains.

Discriminating between Seasonal and Chemical Variation in Extracellular Enzyme Activities within Two Italian Beech Forests by Means of Multilevel Models

Enzymes play a key-role in organic matter dynamics and strong scientific attention has been given to them lately, especially to their response to climate and substrate chemical composition. Accordingly, in this study, we investigated the effects of chemical composition and seasons on extracellular enzyme activities (laccase, peroxidase, cellulase, chitinase, acid phosphomonoesterase, and dehydrogenase) by means of multilevel models within two Italian mountain beech forests. We used chemical variables as the fixed part in the model, season as random variation and layers (decomposition continuum for leaf litter and 0–5, 5–15, 15–30, and 30–40 cm for soil) as nested factors within the two forests. Our results showed that seasonal changes explained a higher amount of variance in enzyme activities compared to substrate chemistry in leaf litter, whereas chemical variation had a stronger impact on soil. Moreover, the effect of seasonality and chemistry was in general larger than the differences between forest sites, soils, and litter layers.

Silk Fibroin–Substrate Interactions at Heterogeneous Nanocomposite Interfaces

Silk fibroin adsorption at the heterogeneous hydrophobic–hydrophilic surface of graphene oxide (GO) with different degrees of oxidation is addressed experimentally and theoretically. Samples are prepared using various spin‐assisted deposition conditions relevant to assembly of laminated nanocomposites from graphene‐based components, and compared with silicon dioxide (SiO2) as a benchmark substrate. Secondary structure of silk backbones changes as a function of silk fibroin concentration, substrate chemical composition, and deposition dynamics are assessed and compared with molecular dynamic simulations. It is observed that protofibrils form at low concentrations while variance in the deposition speed has little effect on silk secondary structure and morphology. However, balance of nonbonded interactions between electrostatic and van der Waals contributions can lead to silk secondary structure retention on the GO surface. Molecular dynamics simulations of silk fibroin at different surfaces show that strong van der Waals interactions play a pivotal role in losing and disrupting secondary structure on graphene and SiO2 surfaces. Fine tuning silk fibroin structure on heterogeneous graphene‐based surfaces paves the way toward development of biomolecular reinforcement for biopolymer–graphene laminated nanocomposites.

The chemical composition and in vitro digestibility evaluation of almond tree (Prunus dulcis D. A. Webb syn. Prunus amygdalus; var. Shokoufeh) leaves versus hulls and green versus dry leaves as feed for ruminants

The current study aimed to evaluate the chemical composition and in vitro digestibility of almond tree (Prunus dulcis D. A. Webb syn. Prunus amygdalus; var. Shokoufeh) leaves versus hulls, and green versus dry leaves as feed for ruminants. The fresh green almond hulls (GAH) and leaves (GAL) were harvested and spread under a shade to dry. Dry almond leaves (DAL) were collected from under the trees where as dry almond hulls (DAH) were collected 4 weeks after harvesting the fresh samples. The chemical composition of substrates was determined using standard approaches and the metabolisable energy (ME), in vitro dry matter (DMD) and in vitro organic matter (OMD) digestibility were measured using the in vitro gas production (GP) technique. The GAL contained 81 g crude protein (CP) kg−1 DM while DAH contained 103 g CP kg−1 DM. The CP was higher (P = 0.0003) in dry (leaves and hulls) than in green (leaves and hulls) samples. The ash content ranged from 99.2 to 181.5 g kg−1 DM in DAH and DAL, respectively, (P = 0.0041). The ether extract content ranged from 27 for DAH to 65 g kg−1 for DAL (P = 0.0018). The acid detergent fibre and neutral detergent fibre content ranged from 185 to 304 and 444 to 620 g kg−1 DM (P = 0.04), for GAL and DAH, respectively. The DAH had the highest (P = 0.0001) GP24 and GP96. The DAH had the highest (P = 0.0001) potential GP (i.e., b), while the GP rate was highest for GAL and GAH (P = 0.034), ME was highest for DAH (P = 0.0001), and in vitro OMD was highest for DAH (P = 0.0001). The highest DMD (P = 0.0001) values were obtained with DAH followed by GAL, DAL and GAH, respectively. It can be concluded that almond hulls and leaves have a good nutritional potential to cover the maintenance nutrient requirements of small ruminants. Almond hulls and leaves can also be used as supplement to low quality mature pasture and/or crop residues. However, more studies are warranted to better characterize these feeds in in vivo animal feeding trials.

Investigation of Adhesion and Tribological Behavior of Borided AISI 310 Stainless Steel

In the present study, the effects of the boriding process on adhesion and tribological properties of AISI 310 steel were investigated. Boriding was performed in a solid medium consisting of Ekabor-II powders at 1123 and 1323K for 2 and 6 h. The boride layer was characterized by optical microscopy, the X-ray diffraction technique and the micro-Vickers hardness tester. The X-ray diffraction analysis of the boride layers on the surface of the steels revealed the existence of FexBy, CrxBy and NixBy compounds. Depending on the chemical composition of substrates, the boride layer thickness on the surface of the AISI 310 steel was found to be 56.74 μm. The hardness of the boride compounds formed on the surface of the AISI 310 steel ranged from 1658 to 2284 HV0,1, whereas the Vickers hardness value of the untreated steel AISI 310 was 276 HV0,1. The wear tests were carried out in a ball-disc arrangement under a dry friction condition at room temperature with an applied load of 10N and with a sliding speed of 0.3 m/s, at a sliding distance of 1000m. The wear surfaces of the steel were analyzed using an SEM microscopy and X-ray energy dispersive spectroscopy EDS. It was observed that the wear rate of unborided and borided AISI 310 steel ranged from 4.57 to 71.42 mm3/Nm.

Diffusion kinetics and characterization of borided AISI D6 steel

In this study, the case properties and diffusion kinetics of AISI D6 steel borided in Ekabor-II powder were investigated by conducting a series of experiments at temperatures of 1123, 1223 and 1323 K for 2, 4 and 8 h. The boride layer was characterized by optical microscopy, X-ray diffraction technique and microVickers hardness tester. X-ray diffraction analysis of boride layers on the surface of the steels revealed the existence of FeB, Fe2B, CrB and Cr2B compounds. Depending on the chemical composition of substrates and boriding time, the boride layer thickness on the surface of the steel ranged from 13.54 μm and 164.42 μm. The hardness of the boride compounds formed on the surface of the steels ranged from 1672 to 2118 HV0.05, whereas Vickers hardness values of the untreated the steels was 584 HV0.05. The activation energies (Q) of the borided steel were 180.359 kJ/mol. The growth kinetics of the boride layers forming on the AISI D6 steel and the thickness of boride layers were also investigated.

The characterization of the coating formed by Microarc oxidation on binary Al–Mn alloys

In this study, effects of Mn content on behavior and properties of Microarc Oxidation (MAO) coatings produced on binary Al–Mn alloys and pure Al were investigated. Al–Mn alloys containing 1, 2, 4, 8 at.% Mn and pure aluminum produced using induction furnace under controlled atmosphere were coated in an alkaline electrolytic solution for 120 min. Surface roughness, thickness, microhardness, phase composition, microstructure and chemical composition of coatings were characterized by profilometry, Eddy Current test, microhardness measurement, XRD, SEM and SEM–EDS. All coatings composed of three regions: thin transition layer, dense inner region and porous loose outer region. Granular precipitates of α-Al2O3 were observed through dense inner region of coatings. With increasing Mn content, coating thickness increased from 111 μm to 169 μm. All coatings, regardless of substrate chemical composition, contained Al6Si2O13, γ-Al2O3, α-Al2O3 and considerable amount of amorphous phases. Increasing amount of Mn suppressed α-Al2O3 formation. It was seen that surface roughness and porosity formation tends to increase whereas the coating hardness tend to decrease with increasing Mn content. The coatings produced on Al–Mn alloys contained Mn along with Al, Si, O. The amount of Mn in the coatings increases with increase of Mn content in the substrates.