Elemental Chemical Composition Research Articles

A brief overview of X-ray photoelectron spectroscopy characterization of thin films

Preparation and characterization of nanostructured thin films have been reported by many researchers. X-ray photoelectron spectroscopy (XPS) method has been used over few decades in different fields such as superconductor, semiconductor, metallurgy and catalysis. In this work, elemental oxidation state, electronic state, chemical structure and chemical composition were investigated for metal sulfide, metal selenide, metal oxide and metal telluride films. Evaluation of binding energy for the obtained samples was reported. XPS spectra showed that annealing treatment has a very strong effect on the composition of the films. The elemental oxidation state and electronic state were strongly dependent on the specific experimental conditions.

Design and implementation of control system for electroplating wastewater treatment by photovoltaic energy sinusoidal alternating current coagulation technology

A novel photovoltaic energy-sinusoidal alternating current coagulation (PE-SACC) system was proposed for the removal of heavy metal ions (HMs) in electroplating wastewater. A response surface methodology was used to study the combined effect of two factors on removal efficiency (Re) and energy consumption (EEC), and the optimal process parameters were obtained. The morphology, surface element content, crystal structure, and chemical composition of the flocs generated during the electrocoagulation (EC) process were characterized using SEM, EDS, XRD, FTIR, and XPS techniques. The intra-particle diffusion model was used to describe the adsorption behavior of HMs (Cu2+, Zn2+ and Ni2+) by flocs. Finally, the removal mechanism of HMs by SACC technology and its application in actual wastewater treatment were discussed in detail. The results revealed that when c0(Ni2+) = c0(Zn2+) = c0(Cu2+) = 50 mg·dm−3, cCl− = 100 mg·dm−3, pH0 = 10, j = 1.3 A·m−2, t = 85 min, the Re(Cu2+), Re(Zn2+) and Re(Ni2+) were 99.3%, 99.1%, and 98.4%, respectively, and the EEC was 0.105 kWh·m−3. Compared with the traditional direct current coagulation (DCC), EEC, electrode consumption, and sludge production in SACC mode were reduced by 37.1%, 62.2%, and 66.6%, respectively. The PE-SACC system achieved ultra-low cost treatment of heavy metal electroplating wastewater. The adsorption process included surface adsorption, pore adsorption, and adsorption equilibrium. The mechanisms for the removal of HMs included cathode reduction, alkaline precipitation, and adsorption. In the actual wastewater treatment process, the removal efficiency of HMs could still be maintained above 99%, and the effluent met the national discharge standard (GB 31574–2015). This study presented an economically and environmentally sustainable approach for the evolution and industrial utilization of novel electrocoagulation technologies.

Chemical elemental composition of Elodea canadensis Michx. 1791. and its use for the assessment of anthropogenic pollution of the littoral of Lake Baikal

The ICP-MS method was used to study chemical elemental composition of the invasive species Elodea canadensis Michx. at Lake Baikal littoral sites with different degree of anthropogenic load. It is found out that dominant macroelements in E. canadensis are K > Ca > Na > P > Mg > S > Cl, dominant microelements are Fe, Mn > Si, Sr > Al, Ba, Zn > Br, B. The content of Ca, Sr, Mg, B and Si in E. canadensis samples are characterized by the least variability, and Na, P, Cl, K, V, Ni, Cu, Zn, As, Se, Br, Rb, Cd, I, Pb contents are more variable. The maximal heterogeneity in distribution is characteristic for lithophilous elements (Be, Al, Ti, Cr, Mn, Y, Zr, Nb, REE (rare earth), Hf, Ta, W, Th) as well as for Fe, Co, Sn, Sb, Bi. Maximal contents of Na, Cl, K and P associated with income of household waste waters into the near-shore zone is found in Elodea samples collected in Frolikha vent and at littoral sites adjacent to such populated areas as Gremyachinsk, Maksimikha, Nizhneangarsk. The elevated level of Zn, Cd, Pb is characteristic as well for the samples collected at the littoral sites with a high anthropogenic charge (Listvyanka settl., Bugul’deyka, Nizhneangarsk, Maksimikha village and Gremyachinsk).

Characterization and Classification of Some Soils Formed on Ophiolitc Rocks in Al-Bassit Region /Northwestern Syria

The aim of this study is to characterize and classify soils formed from ophiolitic rocks (mafic and ultramafic) by determining their morphological, physical and chemical properties, petrographic and elemental composition studies. The profiles were prepared under forest vegetation (pines) and described based on the referenced methods in Al-Bassit region (NW Syria) between the coordinates: N: 35° 41` - N: 35° 57`, E: 35° 42` - E: 36° 05`, which belongs to Mediterranean climate regime. Samples were collected from horizons of all profiles and some physical and chemical analyses were performed in addition to petrographic and Chemical composition studies. The horizons were of the form A (Mollic)-Cr-R in profile P1, and A (Mollic)-BW-C- in the profile P2, and of the form A ((Mollic)-C1-Cr2- in the profile P3. They were ordered as: A(Ochric)-C1-C2 in the profile P4. The fires that took place in the region affected the characteristics of surface horizons of some soils, such as the percentage of organic matter, structure, and the degree of soil interaction .The ultramafic derived soils in the P1 profile contained a high level of clay, while the percentage of sand increased in mafic derived soil P2, P4. The soil contained high levels of exchangeable Ca+2 and Mg+2, likely because they are in the structure of the rock. Carbonates are in low levels and are absent in some horizons, this is due to the composition of the parent material. The soil classification for studied profiles show that the profiles (P1, P2, P3) classified as Mollisols and the Profile P4 as Entisols.

Perinatal foodborne titanium dioxide exposure-mediated dysbiosis predisposes mice to develop colitis through life

BackgroundPerinatal exposure to titanium dioxide (TiO2), as a foodborne particle, may influence the intestinal barrier function and the susceptibility to develop inflammatory bowel diseases (IBD) later in life. Here, we investigate the impact of perinatal foodborne TiO2 exposure on the intestinal mucosal function and the susceptibility to develop IBD-associated colitis. Pregnant and lactating mother mice were exposed to TiO2 until pups weaning and the gut microbiota and intestinal barrier function of their offspring was assessed at day 30 post-birth (weaning) and at adult age (50 days). Epigenetic marks was studied by DNA methylation profile measuring the level of 5-methyl-2′-deoxycytosine (5-Me-dC) in DNA from colic epithelial cells. The susceptibility to develop IBD has been monitored using dextran-sulfate sodium (DSS)-induced colitis model. Germ-free mice were used to define whether microbial transfer influence the mucosal homeostasis and subsequent exacerbation of DSS-induced colitis.ResultsIn pregnant and lactating mice, foodborne TiO2 was able to translocate across the host barriers including gut, placenta and mammary gland to reach embryos and pups, respectively. This passage modified the chemical element composition of foetus, and spleen and liver of mothers and their offspring. We showed that perinatal exposure to TiO2 early in life alters the gut microbiota composition, increases the intestinal epithelial permeability and enhances the colonic cytokines and myosin light chain kinase expression. Moreover, perinatal exposure to TiO2 also modifies the abilities of intestinal stem cells to survive, grow and generate a functional epithelium. Maternal TiO2 exposure increases the susceptibility of offspring mice to develop severe DSS-induced colitis later in life. Finally, transfer of TiO2-induced microbiota dysbiosis to pregnant germ-free mice affects the homeostasis of the intestinal mucosal barrier early in life and confers an increased susceptibility to develop colitis in adult offspring.ConclusionsOur findings indicate that foodborne TiO2 consumption during the perinatal period has negative long-lasting consequences on the development of the intestinal mucosal barrier toward higher colitis susceptibility. This demonstrates to which extent environmental factors influence the microbial-host interplay and impact the long-term mucosal homeostasis.

Linking the soil carbon pool management index to ecoenzymatic stoichiometry and organic carbon functional groups in abandoned land under climate change

Ongoing, multifaceted climate change impacts soil carbon (C) dynamics, with serious possible consequences on terrestrial C cycling. Using a three-year manipulative experiment in abandoned land on the Loess Plateau of China, we examined the effects of in situ warming and altered precipitation (ranging from 50% reduction to 50% increases in precipitation) on different fractions of the soil organic C (SOC), the C pool management index (CPMI), ecoenzymatic stoichiometry, and SOC functional groups. Our results showed that SOC, readily oxidizable organic C, dissolved organic C, particulate organic C, and microbial biomass C exhibited an increasing trend with increasing precipitation, whereas warming had no significant effect. This response pattern also led to an increase in the CPMI with increasing precipitation. The ecoenzymatic vector model indicated that microbial C limitation decreased with increasing precipitation. In addition, the proportion of labile poly-alcoholic C and aliphatic C increased with precipitation gradient, while recalcitrant aromatic C and carboxylic C decreased. The CPMI correlated negatively with microbial C limitation and positively with labile SOC functional groups. Structural equation modeling and relative importance analyses further indicated that microbial C-limitation and labile SOC functional groups are important factors mediating the CPMI but have opposite effects. Overall, these findings considerably advance our understanding of the links between the soil CPMI and both microbial elemental limitations and SOC chemical composition, providing new insight for the accurate prediction of soil C dynamics under changing environments.

Artificial intelligence for enhanced flotation monitoring in the mining industry: A ConvLSTM-based approach

In the mining industry, accurate monitoring of the elemental composition in the flotation froth is crucial for efficient minerals separation. The hybrid deep learning algorithms offer powerful computational intelligence for real-time monitoring of froth quality in flotation processes. This soft sensor tool can provide valuable information for process control, including predictions of the elemental chemical composition. In this study, we propose a novel approach based on a Convolutional Long Short-Term Memory (ConvLSTM) neural network for real-time monitoring of chemical composition grades in flotation froth. The proposed model effectively extracts spatial and temporal patterns from video data, providing a better understanding of the dynamic behavior of the froth surface in flotation processes. Our proposed approach includes a deployment architecture that enables real-time monitoring of elemental concentrate grades, allowing for the adjustment of flotation parameters for accurate process efficiency.The results of our study show that The proposed approach is accurate, with a mean absolute error (MAE) of 4.52 in the cleaners of the zinc differential flotation circuit. The use of the ConvLSTM neural network provides an accurate and reliable model for monitoring the flotation froth quality. The proposed approach has the potential to improve the operational performance and efficiency of complex polymetallic flotation circuits in mineral processing. Additionally, we propose a deployment architecture in the industrial scale of a differential flotation circuit. This architecture offers advantages such as portability, scalability, consistency, and isolation for efficient use for the flotation monitoring. This study demonstrates the potential of using a deployed deep learning model to provide a practical and efficient solution for real-time monitoring of flotation froth quality in the mining industry. This approach can be used to optimize the flotation process and increase productivity, potentially leading to significant flotation performances improvement and cost saving for mining companies.

Purple soil inheritance and source of parent rock material and tectonic background in the Sichuan Basin, China

ABSTRACT The parent rock inheritance of the purple soils in the Sichuan Basin is evident, and this is due to factors that are directly related to the parent rocks’ characteristics. Fundamentally, the nature of purple soils is determined by the lithology, chemical composition, weathering, and soil formation of parent rocks, whereas the provenance, and tectonic context of rocks during their diagenesis have a significant influence on their rock attributes. In this study, rocks from four sedimentary layers of the Cretaceous and Jurassic eras – k1c, J3p, J3s, J2s in the Sichuan Basin – as well as the overlying soils were examined, and experimental determinations of the samples’ physical characteristics and chemical elemental composition were made to confirm the parent rock inheritance of purple soils. The essential weathering indices ICV, CIAcorr, WIP, and Na/K were used to study the weathering characteristics of the rocks and soils, and the A-CN-K ternary diagram was used to assess the weathering trends of the rocks. The findings demonstrate that purple soil exhibits significant parent rock inheritance due to its rapid physical soil formation process and weak chemical weathering process. That the rocks of the four sedimentary layers in the study area have all reached a moderate degree of weathering, their original source components are quartzose sedimentary which may have been derived from feldspar source rocks. The tectonic background of the source rocks may be mainly continental arc and active continental margin environment, there may be an oceanic arc tectonic environment.

Application of phosphomolybdate/tungsten disulfide composites in the adsorption and photocatalytic degradation of dyeing wastewater

Water pollution from dye wastewater is a major problem. As an indirect semiconductor, tungsten disulfide has a large specific surface area to adsorb dyes, and can absorb energy to degrade dye molecules under visible light. Furthermore, polyoxometalates reduce the energy gap of the photocatalyst and inhibit the recombination of photogenerated electrons and holes. Here, a novel phosphomolybdate/tungsten disulfide composite was constructed firstly via a solvothermal method to load phosphomolybdic acid onto few-layer-thick disulfide nanosheets. The chemical structure, morphology, porosity, phase, and element composition of the composite phosphomolybdate/tungsten disulfide were characterized. The absorption performance and photocatalysis of the complexes was tested. The adsorption capacity of phosphomolybdate/tungsten composites for dyes has an increasing trend with the increase in phosphomolybdate loading until the loading reaches 80%. The material can selectively adsorb malachite green and methylene blue, with a selectivity factor as high as 4.28 in the mixed solution of methyl orange/malachite green. But it has better photocatalytic effect on methyl orange than malachite green and methylene blue. The material can degrade 98% of methyl orange in 90 min. Our results indicate that the adsorption capacity and photocatalysis of phosphomolybdate/tungsten disulfide composites are significantly enhanced compared with tungsten disulfide. This work creatively combined tungsten disulfide with oxidative polyoxometalates which provide novel insights into the design of low-cost photocatalytic materials and adsorption materials for dyeing wastewater.

Assessing quality and beneficial uses of Sargassum compost

Sargassum spp. (specifically Sargassum fluitans and S. natans), one of the dominant forms of marine macroalgae (seaweed) found on the beaches of Florida, is washing up on the shores throughout the Caribbean in record quantities. Currently, a common management option is to haul and dispose of beached Sargassum in local landfills, potentially wasting a valuable renewable resource. The objective of this study was to determine whether composting represents a feasible alternative to managing Sargassum inundations through measurements and comparisons to eleven guidelines. Specifically, we assessed the characteristics of the compost [physical–chemical parameters (temperature, moisture content, pH, and conductivity), nutrient ratios (C:N), elemental composition, bacteria levels, and ability to sustain plant growth] in both small- and large scale experiments. Results show that although nutrient concentration ratios were not within the standards outlined by the U.S. Composting Council (USCC), the Sargassum compost was able to sustain the growth of radishes (Raphanus sativus L., var. Champion). Trace metal concentrations in the compost product were within five regulatory guidelines evaluated, except for arsenic (As) (6.64–26.5 mg/kg), which exceeded one of the five (the Florida Soil Cleanup Target Level for residential use). Bacteria levels were consistent with regulatory guidelines for compost produced in large-scale outdoor experiments but not for the small-scale set conducted in enclosed tumblers. Overall results support that Sargassum compost can be beneficially used for fill and some farming applications.

Less Energetic Routes for the Production of SiOx Films from Tris(dimethylamino)silane by Plasma Enhanced Atomic Layer Deposition

SiOx films, frequently derived from amino silane precursors, have found several applications with high added value. Although frequently used, the deposition of coatings from Tris(dimethyl amino) silane (TDMAS) has been reported to demand considerable amounts of energy, mainly due to the difficulty of oxidizing such compounds. As is well known, Plasma-enhanced atomic layer deposition (PEALD) is able to improve the oxidation efficiency, even under low processing temperatures. Owing to this, PEALD can be considered a very promising technique for the deposition of SiOx coatings. In this work, the deposition of silicon oxide films using TDMAS at 150 °C has been investigated. The effect of the plasma oxidation time (6 to 18 s) and atmosphere composition (pure O2 or O2 + Ar) on the chemical structure, elemental composition, and chemical bonding state of the films has also been evaluated. Increasing the plasma oxidation time in pure O2 resulted in a larger proportion of retained C (Si-CH3), whereas N was preserved in the structure (Si-N). On the other hand, the formation of SiOx films from TDMAS is favored in shorter oxidation times and O2 + Ar plasmas.

Hydrometallurgical processing of ash and slag waste

This work assesses the possibility of hydrometallurgical processing of ash and slag waste in order to extract rare and rare earth elements. The ash and slag waste from the Chita CHPP-2 combined heat and power plant was used as a research object. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to determine the elemental chemical composition of coal combustion products. To preconcentrate rare and rare earth elements, magnetic separators were used to isolate the -0.5+0.3 mm and -0.3+0.1 mm grain size fractions of ash and slag waste. The leaching of rare and rare earth elements from the studied samples was investigated using sulfuric, hydrochloric, and nitric acids, as well as an aqua regia solution, in combination with simultaneous ultrasonic exposure. It was determined that electromagnetic separation of the -0.5+0.3 mm and -0.3+0.1 mm grain size fractions of ash and slag waste significantly concentrates rare and rare earth elements in the magnetic fraction, including titanium (up to 25%), zircon (up to 33%), yttrium (up to 50%), lanthanum (up to 150%), and cerium (up to 5%). It was determined that an increase in the duration of ultrasonic treatment during the leaching of metals from ash and slag waste with sulfuric acid resulted in a uniform 7.25-fold increase in gallium content (from 0.008 to 0.058 g/dm3). Additionally, when decomposed with aqua regia, a 3-fold concentration of the same element was observed (from 0.008 to 0.024 g/cm3), while ultrasonic treatment offered only a slight increase in concentration. When leaching with sulfuric acid (the duration of ultrasonic exposure is 5 minutes), a 4-fold increase in the rubidium content was observed (from 0.108 to 0.457 mg/dm3). Therefore, the most effective method for extracting rare and rare earth elements from the ash and slag waste of Chita CHPP-2 involves acid leaching combined with electromagnetic separation and ultrasonic pulp leaching.

Current development of V.I. Vernadsky's biogeochemical ideas

The essence and development of a new scientific direction in geochemistry and biology – biogeochemistry, created by V.I. Vernadsky, are considered. The special attention is focused on the concepts - living matter, biogenic migration of chemical elements, chemical elemental composition of organisms and its ecological significance. The analysis of the development of the functions of the biosphere (ecological, concentration, information) is given. The differentiation of the chemical elemental composition of organisms in the conditions of man-made of the biosphere is shown. The role of biogeochemistry in the development of biotechnology and the formation of biogeochemical indication of the ecological state of biosphere taxon is presented. The analysis of the achievements of biogeochemistry and existing problems is given.

Chromium Disarmament from Veritable Tanneries Sewer Water Utilizing Carbonic Rice Straw as a Sorbent: Optimization and Carbonic Rice Straw Characteristics

This exploration focuses on the removal of chromium from actual tannery wastewater, collected from the HARBY TANNERY factory in Rubiki (Badr City), using an economical sorbent made from activated carbon derived from rice straw (CRS). The CRS sorbent is activated using H3PO4. The experiment aims to assess the impact of various parameters, including chromium initial concentration, sorbent dosage, treatment time, agitation velocity (rpm), sorbent particle size, and solution pH, on chromium removal from tannery wastewater. Structural, morphological, and electronic distinctive of raw and treated CRS, as well as carbonized CRS, were analyzed using FTIR, SEM, and TEM techniques. XRF analysis was conducted to investigate the chemical elemental composition of carbonized CRS before and after sorption. Zeta potential measurement was performed to assess the electrical charges of particles present in a suspension. The adsorption data was tested for both Langmuir and Freundlich adsorption isotherms, and most of the factors suggested that it follows the Langmuir adsorption isotherm with an R2 value of 99.67%. Additionally, adsorption kinetics were performed to identify the reaction order, which exhibited that sorption pursued pseudo-second-order kinetics with a rate constant (k) of 0.0658 g/mg g/min, a high correlation factor (R2) of 99.76%, and an estimated equilibrium chromium ion adsorption capacity (qe) of 1.597 mg/g, which closely matched the experimental data (1.4835 mg/g). The improved surface morphology and increased surface area of CRS resulted in approximately 98.9% chromium removal. Mechanism studies confirmed that intraparticle diffusion is not the sole rate-controlling step, and Boyd’s model demonstrated that film diffusion limited the rate of chromium adsorption. The desorption of chromium from the carbonized rice straw surface could be achieved by up to 96.4% of the sorbed amount by raising the solution pH to 10, indicating the potential reusability of carbonized rice straw for additional adsorption cycles. Finally, a statistical regression analysis and least square multivariate analysis were used to establish a correlation for predicting efficiency, yielding an R2 value of 97.54%.

Impact of Er,Cr:YSGG Laser, Sandblast, and Acid Etching Surface Modification on Surface Topography of Biodental Titanium Implants.

Introduction: Several techniques have been used to modify the surface of commercially pure titanium (CPTi) implants to improve osseointegration using lasers, sandblasts, sandblasts with acid etching, and other modalities. For implant-osseointegration, surface features like chemical composition of a surface, topography, and surface energy are essential. The present comparative study aimed to compare the impact of Er,Cr:YSGG laser, sandblasting, and acid etching implant surface modifications on the surface topography, roughness, and element chemical composition of the Ti dental implant. Methods: Thirty CPTi dental implants were divided into three groups according to the surface modification (n=10 for each group): Group A: Sandblasting with acid etching (SLActive), group B: Sandblasting, and group C: Er,Cr:YSGG laser surface modifications. The modified surfaces were analyzed using scanning electron microscopy (SEM), profilometer, and energy dispersive x-ray spectrometry (EDS). Results: One-way analysis of variance (ANOVA) showed that there were significant differences in the mean values of average roughness (Ra) of the three groups (P<0.05). Tukey's post hoc test showed that the average roughness (Ra) of laser-surface modification (group C) of the implant had the highest mean value (2.30 µm) among the different groups, while sandblasted surface modification (group B) of the implant had the lowest mean value (1.39 µm). The SLActive (group A) sandblast with acid etching had a mean value of 1.63 µm. SEM analysis showed that significantly modified surface topographies and different element concentrations were found within all modified groups. Conclusion: The Er,Cr:YSGG laser irradiation increased the implant surface roughness value after implant surface modification, compared to sandblasts and sandblasts with acid etching application. The observations for the SEM-EDS analysis revealed several elements with different concentrations, which were affected by the physical-chemical characteristics of the surface modification techniques. The SEM analysis showed a significant modification in implant surface topographies of the tested groups.

From desert dust to ongoing soil formation in the mountainous areas of the south Levant

Mediterranean soils of the south Levant have been investigated and described during the past several decades, especially brown-reddish mountain soils, but certain issues, such as the role of desert dust as a parent material, remain unresolved. This study aims to quantify the role of desert dust in the formation of the mountain soils of the south Levant area, examine the environmental factors that affect the soil formation processes, and evaluate their time of formation. This is done by sampling and analyzing soil sites along two west-east transects across the Judea and Samaria mountains that encompass the transition from the Mediterranean to the semiarid climate. The new database includes the bulk mineralogical and chemical compositions of major oxides and trace elements, particle size distributions, and basic soil’s parameters. Although the range of calcite content in the soils studied is large (>1 % to 60 %), all soil types have similar grain size distributions of three modes: 45–55 μm mode within the coarse silt fraction, 20–25 μm mode within the fine silt fraction, and a clay mode. Local (Jerusalem) dust, collected near the sampled soils, is distinguished from desert dust by a lower quartz content and lower concentrations of SiO2, TiO2, Th, and Zr, suggesting that the local dust is a mixture of remote desert dust and local sources. The soils on the eastern side of the Judean Mountains, under a semiarid climate, are dominated by the coarse silt mode, and their compositions reflect a higher contribution of desert dust and weaker pedogenic processes. The pedogenic formation of smectites turns the clay fraction into the main grain size mode in the leached soils of the western side, under higher precipitation and denser vegetation. The almost identical compositions found for two adjacent soils on limestone and on chert demonstrate that dust is almost the exclusive parent material for soils presently forming on hard sedimentary rocks. This, other chemical parameters, and additional field observations indicate no relation between soils and bedrock or visible karstic activity at present. Accordingly, soil formation in the mountainous areas of the south Levant is a result of ongoing dust accumulation and transformation since the last major erosion event in the early Holocene.

Comparative study on material properties of ancient fired clay bricks of China

The city wall is a military defense building of an ancient city and a unique landscape architecture of a modern country that has extremely important historical, artistic, and scientific values. Most ancient Chinese walls were built of bricks and have been severely damaged and degraded by environmental and human influences. To protect these historical building monuments, it is necessary to determine scientifically the material properties of the bricks used in the ancient walls. In this study, the physical and mechanical properties, chemical element composition, mineral composition, micromorphology, and pore structure of 20 ancient fired clay bricks from four different regions, including white and blue wall bricks from Nanjing, blue wall bricks from Xi'an and Linqing, and the Great Wall bricks from Beijing, were compared using various modern analysis and testing methods. The results show that talc could be one of the raw materials to produce white bricks and the firing temperature of some white bricks could exceed 1200 ℃. The ancient blue bricks were mainly composed of quartz and feldspar, whereas the ancient white bricks were mainly composed of quartz and long prismatic and rod-like enstatite. The solid density and compressive strength of the white bricks were higher than that of the blue bricks. The proportion of pores larger than 10 µm in all ancient bricks is less than 10%. The pores smaller than 0.1 µm is less than 6% at higher firing temperatures. The results of this study can provide scientific guidance for the restoration and conservation of fired clay bricks of ancient city wall.

New insights into the surface features of SKD61 steel at heat-treated and non-heat-treated states as processed by powder-mixed EDM

In this paper, the two states of SKD61 steel include heat-treated (HT) and non-heat-treated (NHT), were processed by powder-mixed electrical discharge machining (PMEDM) using tungsten compound powder. Several machined surface properties were investigated by methods such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), 3D Laser Scanning Microscope, and X-ray diffraction (XRD). In both states, their surfaces were changed in chemical composition and content of elements (CCCE), and tungsten carbide phase (W2C) was created. In comparison with the HT state, some surface features of NHT specimens, such as: the percentage of micro-crack acreage per surface (PCAS) is better improved, the penetration of the W element into surfaces and the intensity of the tungsten carbide phase are larger, the distribution of C and W elements on the surface is a more even, and the surface topography has more uniformity and flatness.

Friction films analysis and tribological properties of composite antifriction self-lubricating material based on nickel alloy

Abstract This article analyzes the composition and distribution of chemical elements in friction films and their effect on the tribological properties of the self-lubricating, high-temperature antifriction composite based on EP975 powder nickel alloy with CaF2 solid lubricant. Analysis of the chemical elements by energy-dispersive spectroscopy (EDS) showed their uniform distribution, on both the composite’s surface and the counterface’s surface. The alloying elements’ uniform distribution leads to a uniform distribution of the corresponding phases and structural elements in the antifriction film. This ensures high tribological properties at high temperatures. Analysis of the material’s tribological properties, by means of metallographic and micro-X-ray research confirmed the correctness of the technology for producing the composite. Solid lubricant CaF2, alloying elements, and their corresponding phases form the continuous antiscoring film. The film influences the antifriction properties formation during the friction process and provides a self-lubricating mode under the action of high temperature and oxygen. Antiscoring, self-lubricating CaF2 films minimize wear of the friction pairs and defend the contact surfaces against intensive wear. The dense antifriction films have smooth microtopography, which stabilizes the high-temperature friction unit operation. Thus, the self-lubrication mode is realized for a long exploitation time. Tribological properties analysis allowed us to determine the ranges of rational exploitation modes for the material being studied: a load up to 5.0 MPa, a slide speed from 0.3 to 1.0 m/s, a temperature up to 800°C, in the air. The results obtained opened the opportunity to control the antifriction film formation and the composite’s tribological properties by the choice of the initial ingredients while taking into account the operating conditions.

Sources of Material for Surface Bottom Sediments in Some Regions of the Nordic Seas (According to Geochemical Data)

The mineral, bulk chemical (main rock-forming oxides) composition and systematics of rare-earth elements, Sc, Cr, Zr and Th of surface bottom sediments taken in a number of cruises of the R/V Akademik Mstislav Keldysh in the Nordic Seas (Mona, Knipovich, Kolbeinsey and Aegir ridges, the basins of the Norwegian and Greenland seas, the continental slope of Svalbard, the western continental margin of the Barents Sea, etc.) are considered to determine the sources of fine-grained material of bottom sediments. If for coastal sediments the primary influence of terrigenous drift is obvious, then seaward sediments are affected by “relatively war-mer” Atlantic waters, leading to their dilution with calcium carbonate, the main producers of which are planktonic foraminifers. It is concluded that the source of fine-grained aluminosiliciclastics for most of the studied samples were both acidic and basic igneous rocks (volcanic rocks of Iceland) in different proportions.