Low Si Content Research Articles

Study on the difference of composition between traditional and modern lime used in the restoration of Qufu San Kong Ancient Architectural

In recent years, a decline in the binding strength and frost resistance of lime binder used in the restoration of the Qufu San Kong ancient architectural complex in Shandong Province has been observed, which has significantly affected the quality of restoration. In this study, lime binder samples were collected from the Kuiwen Pavilion roof, limestone samples in the vicinity of the Confucius Temple, and modern industrial quicklime from various provinces in China. Analytical methods including X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy were employed. Results indicate that the local limestone in Qufu contains impurities such as Si or Mg. XRD patterns reveal that the main phase of the Kuiwen Pavilion roof lime binder samples is calcite. Using FTIR and Scanning Electron Microscope- Energy Dispersive Spectrometer (SEM-EDS), the presence of hydrated calcium silicate (C-S-H) gel is identified in the samples. This suggests that the traditional quicklime-production process in Qufu yields a multiphase composite system. Modern industrial quicklime, aged for two months, showed no presence of C-S-H gel in the FTIR spectra and SEM-EDS results, indicating that it is a comparatively pure system primarily comprising CaO. The study suggests that traditional quicklime-production processes typically involve burning limestone with higher Si content, leading to the generation of a significant amount of dicalcium silicate. Additionally, the use of high-ash coal as fuel introduces reactive silicon dioxide into the quicklime product. These factors contribute to the formation of C-S-H gel in hydrated lime. The presence of C-S-H gel enhances lime binder properties such as binding strength and frost resistance. Modern quicklime production, which selects limestone with lower Si content and employs low-ash coal as fuel, aims to minimize or avoid the formation of C-S-H gel in hydrated lime. High-purity CaO quicklime products align with the principles of modern fine processing; however, they compromise the binding strength and durability of lime binder required for traditional architectural restoration.

Geochronological and geochemical constraints on the multistage magmatic processes of the Lianhuashan batholith, South China: Implications for the petrogenesis and polymetallic mineralization

The Lianhuashan batholith, which is a composite pluton located in the middle part of a world-class giant tungsten (W) polymetallic belt of South China, hosts a huge reserve of more than 50000 t of W. Despite this great economic significance, the petrogenesis of each phases of the Lianhuashan batholith, as well as its temporal and genetic relationships to the W polymetallic mineralization, is still unclear. To address these questions, we conducted a comprehensive study for the Lianhuashan batholith, including LA-ICP-MS zircon U-Pb dating, whole-rock geochemical and in-situ mineral trace element analyses. Different from previous studies, four main granitic phases (G1 to G4) were identified. The biotite granite (G1) formed from 168.6 to 165.3 Ma, has the lowest Si content and high Al and Fe contents, and is significantly depleted in Ba, Sr, Ti, P, and Nb whereas enriched in U, Hf, Zr, and Y contents. In contrast, the two-mica granite (G2) and fine-grained muscovite granite (G3), formed from 162.8 to 160.5 Ma, exhibit similar characteristics including enrichment in La, Y, Hf, Th, U, and depletion in Ba, Sr, and P. The porphyritic granite (G4) is the latest magmatic phase and formed at 158.3 Ma. It is characterized by high K, Si, Th, U, Zr, Hf contents but low Al, Fe, Sr, P, and Ti contents. These features support that four main phases of the Lianhuashan batholith belong to S-type granites that experienced significant fractional crystallization, and display reduced and low temperature features. Combined with previously published studies, we suggest that the Lianhuashan batholith formed in an intraplate extensional setting triggered by the high-angle rollback subduction of the paleo-Pacific plate. The three early phases (i.e., G1–G3) are in turn more oxidized and are responsible for the transition from Sn- to W-dominated mineralization. In contrast, the G4 granite, characterized by lower oxygen fugacity, is resposible for Pb-Zn-Ag-U polymetallic mineralization.

Thermal Stability and Thermal Fatigue Resistance Improvement of New High Toughness 5% Cr Hot Working Die Steel

This work developed a new high toughness 5% Cr martensitic hot working die steel (GYDCK-20), which exhibits better thermal stability and thermal fatigue resistance than AISI H13 steel. The concrete study involves: conducting on the evolution of microstructures and mechanical properties of two steels during the 60-hour holding process at 600°C, as well as the thermal fatigue behavior under the cyclic heating-water quenching conditions. The experimental results showed that in the case of ensuring the same initial hardness of two steels (43-43.5 HRC), GYDCK-20 emerged better thermal stability and superior toughness after 60-hour holding process at 600°C. After thermal cycling was increased from 1000 to 2000 times, the average crack length growth rate of GYDCK-20 was 31.8% lower than that of H13 and the maximum crack width growth rate was 35.1% lower than that of H13. It was found that thermal fatigue cracking was dominated by transgranular propagation at lower cycle numbers, while more inclined to propagate along the grain boundaries at higher cycle numbers. The higher toughness of GYDCK-20 steel promotes the dispersion of thermal stress, thereby enhancing the thermal fatigue resistance. It is mainly attributed to the lower V content of GYDCK-20 steel, which reduces the density of large-sized MC primary carbides. On the other hand, the lower Si content promotes the dissolution of cementite particles, and the secondary carbides precipitate in a smaller and uniformly distributed form, which hinders the propagation of thermal fatigue cracks, while also delays the coarsening of the fatigue-adverse phase M23C6 carbides.

Applicability of Waste from Al Industry toward Dephosphorization of Hot Metal in Primary Steel Making

Managing industrial waste is a global challenge. Red mud is a byproduct of the aluminum industry posing serious concerns. The presence of FeO and CaO in red mud makes it a potential DeP flux. Red mud has been utilized as a DeP flux in previous studies, but these studies deal with low Si content and no P2O5 content in the red mud. However, certain steel makers have high initial Si content (0.6–0.7 wt%) in the hot metal, and with increasing demand for low P steel, new dephosphorization fluxes need to be explored. Addressing this gap, this study investigates red mud's potential as a flux for dephosphorization in hot metal with elevated Si levels. Conducting slag–metal equilibrium experiments at 1350 °C, using red mud‐based fluxes, the research achieves a 40% dephosphorization degree under optimized conditions of double deslagging and fluxing. Analysis via wet chemical methods and inductively coupled plasma mass spectrometry confirms the effectiveness of the approach. Furthermore, thermodynamic calculations highlight the influence of O2 partial pressure and Si content on dephosphorization efficacy. Through laboratory experiments and theoretical insights, this study provides a valuable roadmap for leveraging red mud as a sustainable flux in hot metal dephosphorization processes, contributing to both waste management and steel production efficiency.

Silica Accumulation in Potato (Solanum tuberosum L.) Plants and Implications for Potato Yield Performance-Results from Field Experiments in Northeast Germany.

The potato is the most important non-cereal food crop, and thus improving potato growth and yield is the focus of agricultural researchers and practitioners worldwide. Several studies reported beneficial effects of silicon (Si) fertilization on potato performance, although plant species from the family Solanaceae are generally considered to be non-Si-accumulating. We used results from two field experiments in the temperate zone to gain insight into silica accumulation in potato plants, as well as corresponding long-term potato yield performance. We found relatively low Si contents in potato leaves and roots (up to 0.08% and 0.3% in the dry mass, respectively) and negligible Si contents in potato tuber skin and tuber flesh for plants grown in soils with different concentrations of plant-available Si (field experiment 1). Moreover, potato yield was not correlated to plant-available Si concentrations in soils in the long term (1965-2015, field experiment 2). Based on our results, we ascribe the beneficial effects of Si fertilization on potato growth and yield performance reported in previous studies mainly to antifungal/osmotic effects of foliar-applied Si fertilizers and to changes in physicochemical soil properties (e.g., enhanced phosphorus availability and water-holding capacity) caused by soil-applied Si fertilizers.

Real-time study of the interplay between phase formation and stress evolution at the W1−xSix/a−Si interface

Nanoscale W1−xSix layers with different Si content were deposited by magnetron sputtering on amorphous silicon layers. The structure and stress evolution during deposition were monitored and in real time. Thus, it was possible to disentangle different origins of stress built-up (interface formation, phase formation, grain growth, and texture) on the nanoscale. It was found that the bcc phase with a composition-dependent texture forms at low Si content (less than 10% Si), but only above a critical thickness. At intermediate Si content (13.9% and 16.5% Si), or low Si content and low thicknesses (≲4.5 nm), the β phase with A15 structure and coexisting phases (bcc or amorphous) form, while a single, amorphous phase is observed at high Si content (≳22% Si). An A15 formation driven by impurities (O,C,N) was excluded by combined x-ray photoelectron spectroscopy and x-ray diffraction measurements on a second sample series. calculations of substitutional bcc and A15 W1−xSix alloys support the formation of A15 at higher Si content. The A15-containing interlayer should be taken into account when discussing the superconductivity of W/Si multilayers. The stress evolution during deposition of W1−xSix was correlated with the microstructure evolution, and compared to similar observations for Mo1−xSix. Due to the crystalline phase (bcc/A15) and bcc texture ([111] and [110]) competition, the structure formation of W1−xSix shows a higher complexity. This explains the wide range of stress states (from tensile to compressive) observed after deposition of W1−xSix. Nanoscale W-Si based stress-compensation layers could be employed for tailoring the stress state of nonepitaxial semiconductor devices. Published by the American Physical Society 2024

Effect of Si additions on microstructure and properties of TiZrHfNbSix high-entropy alloys as potential biomaterials

High-entropy alloys (HEAs) have emerged as promising biomaterials owing to their favorable mechanical properties and resistance to corrosion. This investigation focuses on the impact of incorporating Si on the microstructure and properties of TiZrHfNbSix HEAs. The inclusion of Si leads to the formation of complex compositional silicides, showing multiple structures as the Si content varies. At low Si content, the BCC-silicide eutectic structure blocks the expansion of the shear zone during the deformation process, accounting for the increase in strength. The TiZrHfNbSi0.25 alloy presents a balanced combination of yield strength (∼1129 MPa) and plasticity (∼17 %). Additionally, TiZrHfNbSi0.5 exhibited optimal corrosion resistance in Hank's balanced salt solution (Icorr = 1.713 × 10−7 A cm−2, Ecorr = −0.327 V, 310 K) owing to the reduction in the number of protocells brought about by Si. The remarkable properties of TiZrHfNbSix HEAs renders it a highly promising option for application of silicide reinforcement in biomedical materials.

Exploring the effect of Si content in Cr coating on its microstructure and properties

Four CrSi coatings with varying Si content ranging from 2 at.% to 9 at.% were deposited on the both surface of Zr-4 substrate. This study systematically investigated the effect of Si content on microstructure, mechanical properties, corrosion resistance and high-temperature oxidation resistance. Due to the lower Si content, only the Cr phase was detected in the CrSi coating, with Si existing in solid-solution. Therefore, all CrSi coatings exhibited good mechanical and hydrophobic properties. The addition of Si in the Cr coating significantly reduces the surface roughness compared with Cr coating. During the long-term autoclave test (30-day, 60-day and 90-day) at 320 °C and 11.3 MPa, CrSi coatings demonstrated superior corrosion resistance attributed to the effective inhibition of further Si dissolution by the dense and continuous Cr2O3 layer forming on the surface. Additionally, after exposure to high-temperature oxidation at 1200 °C for 30 min, all CrSi coatings protect the substrate from oxidation. However, only the Cr0.91Si0.09 coating internally formed a dense and continuous in-situ Zr2Si diffusion barrier layer, which effectively reduce the Cr/Zr inter-diffusion, and sufficient Si prevent the outwards diffusion of Cr by forming Cr3Si boundary. The corrosion and oxidation mechanism have been studied in detail.

Mechanical and microstructure characterisation of 2.5D C/C-SiC composites applied for the brake disc of high-speed train

Carbon fibre reinforced silicon carbide (C/C-SiC) composite materials have attracted increasing attention in brake system of high-speed trains, due to their low density, high specific strength, thermal stability, and frictional wear performance. This study aims to explore the mechanical properties of the 2.5D C/C-SiC composites, in order to characterise its potential application to the friction braking system of high-speed trains. To comprehensively evaluate the mechanical performance of the 2.5D C/C-SiC composites, the chemical vapor infiltration (CVI) method was adopted to prepare novel samples with high densification and low content of residual Si. The mechanical properties and failure mechanisms of the composites were investigated under various loading conditions, including tension, compression, bending, and shear tests. The experimental results indicated that the 2.5D C/C-SiC composites exhibited superior mechanical properties, with average in-plane tensile strength, compressive strength, bending strength, and interlaminar shear strength reaching 127.67 MPa, 326.92 MPa, 355.74 MPa, and 9.77 MPa, respectively, which are 2–8 times higher than the mechanical properties of C/C-SiC composites in existing publications. Under different loading conditions, the composites demonstrated characteristics of ductile fracture, pseudo-plastic compression fracture, pseudo-plastic bending fracture, and brittle shear fracture. Both high fibre content and the formation of SiC structure were advantageous for enhancing the load-bearing performance of C/C-SiC composites. The outstanding mechanical properties of the 2.5D C/C-SiC composite render the brake disc highly resistant to deformation and cracking under high stress, thereby enhancing its durability and establishing it as the ideal material for the next generation of high-speed train brake discs.

Extremely enhanced friction and wear performance of hydrogen-free DLC film at elevated temperatures via Si doping

Hydrogen-free diamond-like carbon (DLC) films have garnered significant attention as a highly efficient solid lubrication material, but poor high-temperature lubrication and wear resistance limit their further application. Here, silicon-doped DLC (Si-DLC) films with different Si contents were deposited using a superimposed HiPIMS-DCMS deposition system to improve their high-temperature lubrication and wear resistance performance. The influence of Si content on the microstructure, mechanical and high-temperature friction and wear behavior of Si-DLC films was investigated. The results showed that Si-DLC films had a dense structure and nanoscale smooth surface. The Si doping enhanced the adhesion strength and relieved the residual stress of Si-DLC films, but decreased the hardness and Young's modulus. Meanwhile, Raman and XPS spectroscopy revealed significant local structural changes in Si-doped DLC films. Furthermore, the results showed that DLC films doped with low Si content displayed excellent tribological performance at elevated temperatures due to the graphite lubricating layer on the surface of wear marks. Specifically, Si-DLC film with 3.31 at% Si had an ultra-low average friction coefficient of 0.04 at 450 °C and still provided effective lubrication at temperatures up to 500 °C. In contrast, pure DLC film failed to lubricate at 450 °C due to the severe graphitization transition and Si-DLC film with 17.47 at% Si quickly failed to lubricate at 200 °C due to the SiC and SiO2. This work sheds light for the high-temperature application of DLC films doped with low Si content by superimposed HiPIMS-DCMS deposition system.

Multi-scale experimental study on the failure mechanism of high-strength bolts under highly mineralized environment

High-strength bolts have become indispensable support materials in geotechnical engineering, but the incidence of safety accidents caused by bolt fractures under complex geological conditions is increasing. To address this challenge, this study focuses on a typical roadway in the Xinjulong coal mine, employing a combination of mechanical performance testing, microscopic and macroscopic analyses to investigate the failure mechanism of bolt breakage. The research indicates that the cracks in the failed bolts underground exhibit subcritical patterns, with the presence of oxides and Cl elements, and multiple intergranular fractures internally, consistent with the characteristics of stress corrosion failure. Additionally, inherent defects in the bolts are also a primary cause of failure. For instance, for type A bolts, the levels of P and S elements significantly exceed the normative requirements, forming inclusions, while the low content of elements like Si and V leads to reduced plasticity, toughness, and corrosion resistance. Furthermore, the excessive pitch in type A bolts leads to stress concentration and cracking under complex loads. The study concludes that the synergistic effect of stress corrosion cracking and inherent flaws in bolts are the main causes of failure. Therefore, it is recommended to enhance the reliability and safety of bolt support by optimizing the bolt shape and developing anti-corrosion bolts, thereby achieving long-term stability in underground engineering.

Impact of earthworms on soil Si availability and wheat Si concentration in low- and high-Si soils

Silicon (Si) is a beneficial element known to increase growth and the stress resistance of plants, including resistance against drought. However, as with many other elements, only a small fraction of Si in soils is available for plant uptake. Plant-available Si originates either from the weathering of soil minerals or from the dissolution of phytoliths in plant litter. It is known that soil fauna plays a role in both processes that contribute to the availability of Si in the soil. However, very little is known about the interactions between the weathering of soil minerals and the dissolution of Si by earthworms from phytoliths and subsequent Si uptake by plants. In greenhouse pot experiments, this study investigated the effect of an epigeic earthworm species (Dendrobaena veneta) on Si availability and uptake by wheat (Triticum aestivum) grown in soils with high or low Si availability. In addition, Si-rich plant litter (wheat straw) was added to the topsoil in some treatments. The addition of plant litter significantly increased the available Si in the soil. Plant litter addition was positively correlated with the Si concentration in wheat in low-Si soil, but not in high-Si soil. Earthworms increased Si availability in soil and casts of the low-Si soil and partly of the high-Si soil, but not Si uptake by wheat. These results suggest that earthworms play an important role in regulating the Si status of soils and may influence Si uptake by plants, especially in soils with initially low Si content and when earthworm population densities are high.

The composition of apatite in the Archean Siilinjärvi glimmerite-carbonatite complex in eastern Finland

We present a geochemical dataset and cathodoluminescence images of apatite from the Neoarchean (2610 Ma) glimmerite-carbonatite rocks from the Siilinjärvi complex, Eastern Finland. The subhedral, tapered prismatic grains are compositionally fluorapatite, with limited substitution of Ca by Sr, Na and low REE and Si contents. The Sr/Y ratios are among the highest in a global apatite comparison, comparable to those from other calcite carbonatites, dolomite carbonatites, and phoscorites. Some grains show evidence of late- or post-magmatic interaction with a carbonatite magma or a hydrothermal fluid, resulting in REE-rich overgrowth rims or recrystallized grains with abundant fluid inclusions. We interpret the high Sr/Y ratios combined with low REE contents and depleted heavy REE+Y to represent crystallization from a mantle-derived carbonatite parental magma. We show that the Siilinjärvi apatite is chemically heterogeneous but with a limited range in compositions. There are noticeable compositional differences on all spatial scales from micrometer to tens of meters, i.e., within a single crystal, between crystals in a sample, between samples and the two individual sampling locations. We conclude that the intra-crystal geochemical variability in apatite is a suitable tracer of the magmatic and post-magmatic evolution of carbonatite complexes.

Effects of diamond as a main carbon source on the fabrication and mechanical properties of reaction-bonded SiC

RBSC with a low residual Si less than 5 vol% was fabricated using SiC–C preform with diamond as a main carbon source by a conventional reaction sintering process at the temperature range between 1500 °C and 1800 °C. The diamond content in the SiC–C preform varied from 10 wt% to 17 wt%. The diamond as the main carbon source used in SiC–C preform effectively minimized the residual Si in RBSC by increasing the reaction of diamond due to the enhanced Si melt infiltration even in SiC–C preform with high carbon content. The Si melt infiltration should be performed above 1600 °C for the complete reaction of diamond particles with size of 0.5 μm because of the relatively low dissolution rate of diamond in Si melt. The flexural strength of RBSC with residual Si content less than 7 vol% exceeded 400 MPa. The flexural strength of RBSC was increased with decreasing residual Si content, but sharply decreased by the residual carbon accompanying pores in RBSC. RBSC with low residual Si content displayed moderate flexural strengths around 200 MPa even above Si melt temperature because of the formation of continuous SiC structure in RBSC by the enhanced grain growth of SiC. Vickers hardness of RBSC was steadily increased from 17.7 GPa to 24.6 GPa with decreasing residual Si.

Crystal chemistry and formation of authigenic chlorite: Influence on tight sandstone reservoir in the Yanchang formation, Ordos Basin, China

Authigenic chlorite is a crucial diagenetic cement that significant impacts tight sandstone reservoirs. The occurrence, crystal chemistry, formation and influences on reservoirs of different authigenic chlorite types were studied in the Yanchang Formation tight sandstones from the Ordos Basin. This study identified two primary types of chlorites: alteration chlorite and autochthonous authigenic chlorite. The alteration chlorite, characterizing by high Fe, Mg, Ti and AlIV contents and low Si and AlVI contents, originated from biotite during diagenesis. The autochthonous authigenic chlorite can be further classified into grain-coating, pore-lining, and pore-filling chlorite. The grain-coating chlorite features thin layers and limited crystal form. During the syndiagenetic stage, Fe2+ and Mg2+ carried by water adsorbed onto the particle surfaces. Additionally, the grain-coating chlorite contains relatively high K content due to the hydrolysis of biotite during the eodiagenetic A stage. The pore-lining chlorite formed during the prolonged eodiagenetic B stage. The biotite and abundant intermediate-basic magmatic fragments released Fe2+ and Mg2+, contributing to the widespread development of euhedral pore-lining chlorite. Notably, the pore-lining chlorite displayed elemental composition variations from the grain edge to the pore center, with increased Fe, Mg and AlIV, and decreased K and AlVI. The pore-filling chlorite formed locally resulted from Fe2+ and Mg2+ crystallization due to the hydrolysis of intermediate-basic magmatic rocks and the dissolution early formed chlorite. The pore-filling chlorite contains the most Fe, Mg and Mn contents and the least K content. Overall, authigenic chlorite acts as a "double-edged sword" in tight sandstone reservoir. The grain-coating and grain-lining chlorite enhance the mechanical strength, resist compaction, and inhibit quartz overgrowth, while pore-filling chlorite trends to obstruct pore throats and break reservoir quality. This study provides valuable insights into the detailed control factors influencing reservoir quality and can serve as a reference for further research.

Volcanic and climatic impacts on silicon abundance in shale: Implications for the expansion of Permo-Carboniferous terrestrial plants in North China

Silicon (Si) is known as an important regulator of the global carbon cycle via its effect on silicate weathering in continents and phytoplankton productivity in the oceans. It is also beneficial to plants by improving their resistance to biotic and abiotic stresses. Detailed analysis of geological record of Si in sediments underpins our understanding of ecosystem evolution over geological time. Here, we unravel the mystery of low Si content in Permo-Carboniferous shales from the central North China and link the terrestrial Si fluxes to the thriving forest ecosystems at that time. Provenance fluctuations as indicated by Zr/TiO2 are well explained by episodic volcanic input which are identified by elevated Zr/TiO2 and lowered V/Al2O3 and Cr/Al2O3. CIA and Ga/Rb and K2O/Al2O3 ratios imply cyclic changes of climate in an overall warm and humid condition. The covariation between the volcanic indicators and climatic proxies indicates that the volcanism forced the climate cycles. Despite the felsic sources (high Zr/TiO2 and Th/Sc ratios and low Zr/Sc ratios), the Si-poor shales are universal in Permo-Carboniferous across the North China Block. The enhanced continental weathering of mineral silicates and the hydrolysis of volcanic materials released silica into the environment and led to the eventual deposition of Si-poor shales. The shales lacking in Si tend to have larger TOC contents except for the most distal shales. It implies that the sufficient supply of dissolved-Si in environments may benefit the expansion of terrestrial plants in Permo-Carboniferous and therefore the accumulation of organic matter in the shales. This work provides new insight into feedback linking volcanism, climates, terrestrial dissolved silica flux, and terrestrial ecosystems in Permo-Carboniferous North China Block.

A marine incursion during the onset of T-OAE in Sichuan Basin, China: Evidence from green clay minerals and carbonate concretions

A high-amplitude global sea level rose rapidly during the early Toarcian (Early Jurassic), making the transgression deposits potential stratigraphic correlation markers of marine and terrestrial successions. Green clay minerals (i.e., glauconite and chamosite), carbonate concretions, and geochemical database associated with the early Toarcian global transgression are archived in the Lower Jurassic Da'anzhai Member (the Early Toarcian age) in the Sichuan Basin of China, a mega lake along the Tethys Ocean. The fine-grained glauconites with high Al and low Si contents suggested that they were transported from offshore to the lake by marine incursion and were oxidized during the transport processes. The green authigenic chamosite cement and redeposited chamosite grains with high Mg/Fe and low Al/Si ratios were diagenetically transformed from berthierine formed in the brackish water caused by marine incursion. The chemically impure siderite concretions with low 87Sr/86Sr ratios and high δ13C values suggested that the lake water and sediment pore waters were mixed with seawater. Coeval calcareous concretions have low 87Sr/86Sr ratios and high δ13C values, indicating the mixing of lake water with seawater. Combining the stratigraphic low 87Sr/86Sr values, we suggested that there was a marine incursion into the Sichuan Basin. According to the organic carbon isotopic stratigraphy correlation, the marine incursion occurred during the onset of T-OAE. The rapid and high-amplitude global sea-level rise may have caused this marine incursion.

Effect of Si content on the thermal stability and oxidation resistance of arc-deposited TiAlSiN films with cubic structure

Recently, TiAlSiN thin films have attracted increasing research interest due to their potential to have simultaneously enhanced hardness, thermal stability, and oxidation resistance compared with Si-free TiAlN films. Previous studies have revealed that a relatively low Si content (2.1–6.0 at.% Si) is essential for the phase stability and hardness of TiAlSiN thin films. Despite the optimum Si content for the hardness of TiAlSiN thin films being proposed, a systematical study concerning the optimum Si content for tailored phase stability, thermal stability, and oxidation resistance of TiAlSiN thin films is still missing. Here, we arc-deposited Ti1-x-zAlxSizN thin films (x = ~0.45, 0.01 ≤ z ≤ 0.08), and investigated the dependence of their structure, mechanical properties, thermal stability, and oxidation resistance on Si content. XRD analysis reveals the transformation from single-phase cubic structure for z ≤ 0.06 to a cubic-wurtzite dual-phase structure for z = 0.08. Increasing the Si content of cubic-structured Ti1-x-zAlxSizN thin films conduces a continuous increase of hardness (H) from 29.3 ± 0.5 GPa for z = 0.01 up to 37.3 ± 0.7 GPa for z = 0.06, whereas the w-AlN formation leads to a drop of H to 32.8 ± 0.6 GPa for z = 0.08. Furthermore, enhancing the Si content from z = 0.01 to z = 0.06 continuously improves film thermal stability, where the Ti0.48Al0.46Si0.06N film presents the highest hardness values within the whole studied temperature range (as-deposited, 800–1200 °C). All Ti1-x-zAlxSizN films undergo age-hardening, with peak H of 33.3 ± 1.0 GPa at 1000 °C for z = 0.01, 35.0 ± 0.6 GPa at 1100 °C for z = 0.02, 35.4 ± 0.5 GPa at 1100 °C for z = 0.03, 40.2 ± 0.7 GPa at 1200 °C for z = 0.06, and 37.8 ± 0.6 GPa at 1100 °C for z = 0.08. Additionally, the oxidation resistance of Ti1-x-zAlxSizN films at 800–1000 °C is improved with increasing Si content, due to the suppressed transformation of anatase-to-rutile TiO2 and the promoted formation of a top dense oxide scale. After oxidation at 900 °C for 15 h, the Ti0.54Al0.45Si0.01N film has been completely oxidized, whereas Ti0.53Al0.45Si0.02N, Ti0.51Al0.46Si0.03N, Ti0.48Al0.46Si0.06N and Ti0.45Al0.47Si0.08N films exhibit oxide scales of ~1.7, ~1.4, ~1.2 and ~0.9 μm, respectively. Overall, we propose z = 0.06 as the optimum Si content for the over-rounded performance of Ti1-x-zAlxSizN thin films.

Geochemical proxies of the gryphon breccia of mud volcanoes in East Azerbaijan: regularities in the distribution of chemical elements and spatial characteristics of sedimentation

The paper is devoted to the study of the patterns of distribution of major oxides and trace elements in the gryphon breccia of 12 active mud volcanoes located in various oil and gas regions (Absheron, Gobustan and Lower Kura) of Azerbaijan. Interpretations of the chemical elements found in gryphon breccia samples have allowed the composition of their source rocks, sedimentation conditions, and sedimentation areas to be determined. Purpose. The main goal of the study is to conduct geochemical studies of gryphon breccias belonging to various oil and gas regions, determine spatial patterns, achieve their explanation, and at the same time determine the conditions for the deposition of mud sediments. Methods. The chemical composition of mud volcanic breccia samples was analyzed using an “S8 TIGER Series 2” spectrometer and an “Agilent 7700 Series ICP-MS” mass spectrometer. Based on the results obtained, in addition to identifying patterns in the areas, modern approaches based on geochemical interpretation were used to explain them. The results on the genesis of breccias are consistent with the results of the published literature on the development of geodynamic and paleobasin conditions in the region. Results. Samples with the lowest Si content are characteristic of the Lower Kura mud volcanoes, where the youngest (Quaternary) deposits are recorded. In samples from these mud volcanoes, relatively high contents of Mg and P are also noticeable. High contents of Ca are characteristic of volcanoes located near the Caspian Sea. These mud volcanoes are also rich in trace elements such as Li, Ga, Rb, Zr, Mo, Cs, Pr, Tl, Pb, Th, U and others, but depleted in Ni, Sr, Ba and etc. Conclusions. Plagioclase-rich source rocks and oxygen-dominated paleobasin environments played a key role in the formation of breccia deposits belonging to the mud volcanoes of Azerbaijan. Geochemical proxies make it possible to link the paleobasin conditions of the formation of the gryphon breccia of the most mud volcanoes of South and Central Gobustan with the continental setting, especially in comparison with some volcanoes of the Lower Kura, as well as Gobustan and Absheron, located on the shores of the Caspian Sea and relatively close to it. The breccias of mud volcanoes located at a relatively large distance from the modern sea boundary and in the steepest northern part of the Lower Kura are associated with marine conditions, as are breccias of mud volcanoes located in the south of this tectonic zone (subjected to intense subsidence) and at a short distance from the Caspian Sea, may be due to geological factors.

Microstructure and properties of Al–Si functionally graded materials for electronic packaging

Two- and three-layer Al–Si functionally graded materials (FGMs) for electronic packaging were prepared by spray deposition. The results show that dense microstructure and good interlayer bonding are obtained in the FGMs. The flexural strength of the three-layer FGMs is higher than that of the two-layer FGMs, and the flexural strength in the H–L direction with high Si content layer as the bearing surface is higher than that in the L–H direction with low Si content layer as the bearing surface. The thermal conductivity of all the FGMs exceeds 140 W/(m·K), and the coefficient of thermal expansion (CTE) shows no significant difference. After thermal shock treatment, more and larger cracks are found in the two-layer FGM than in the three-layer FGMs. This phenomenon is due to the high thermal stress at the interfaces and the tendency of large Si particles to rupture as a result of stress concentration.