Low Si Research Articles

Synthesis and Characterization of DOPO Modified Tetraglycidyl Eugenol Cyclic Siloxane Resins Cured with Tannic Acid

AbstractIn this work, a tetra glycidyl eugenol cyclic siloxane resin (TGED4) is synthesized, then further modified with 9,10‐dihydro‐9‐oxa‐10‐phosphaphenathrene‐10‐oxide (DOPO) to produce Si and P epoxy resins. After blending with diglycidyl ether of bisphenol A (DGEBA) and curing with tannic acid (TA), high performance, fire‐retardant polymer networks are created. Near infrared spectroscopy (NIR) confirms the networks are highly cured and have low extractable content, while dynamic mechanical thermal analysis (DMTA) displays a lower Tg and heterogeneous network with increasing DOPO. The networks display a maximum improvement in flexural modulus, strength, and strain to failure of 20.6%, 55.5%, and 78.8% respectively, and at 65.4 MPa strength and 2.8 GPa modulus are comparable to high‐performance networks. Thermogravimetric analysis (TGA) shows that increasing P reduces thermal stability, but contributes to higher char yield despite lower Si. The fire retardancy improve markedly measured via limiting oxygen index (LOI), increasing from 26.5% to a maximum of 35.5%, while V‐0 behavior is readily achieved at the lowest DOPO content. Cone colorimetry further reduces peak heat release rate (PHHR) and total heat release rate (THHR) by 28% and 42%. This work presents hybrid bio‐derived epoxy resins with excellent fire retardancy and good mechanical properties.

Effects of Silicon Concentration and Synthesis Duration on Lignin Structure: A Spectroscopic and Microscopic Study.

Silicon (Si) is a highly abundant mineral in Earth's crust. It plays a vital role in plant growth, providing mechanical support, enhancing grain yield, facilitating mineral nutrition, and aiding stress response mechanisms. The intricate relationship between silicification and lignin chemistry significantly impacts cell wall structure. Yet, the precise influence of Si on lignin synthesis remains elusive. This study investigated the interaction between Si and lignin model compounds during invitro synthesis. Employing spectroscopic and microscopic analyses, we delineated how Si concentrations modulate lignin polymerization dynamics, particularly affecting molecular conformation and aggregation behavior over time. Fluctuations in the polymer structure are directly related to both the synthesis time and the concentration of silica. Our results demonstrate that lower Si concentrations promote the aggregation of lignin oligomers into larger particles, while higher concentrations increase the possibility of oligomer repulsion, thus preventing particle growth. These findings elucidate the intricate interplay between Si and lignin, which is crucial for understanding plant cell wall structure and stress resilience. Moreover, the results provide insights for developing lignin-silica materials with increasing applications in industry and medicine.

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.

Peculiarities of Plant Mineral Composition in Semi-Desert Conditions

Plant–soil interactions in semi-desert conditions elicit the development of plant-specific adaptation strategies, including selective accumulation of macro- and microelements. Using an ICP-MS analysis of 12 plant species belonging to Asteraceae, Fabaceae, Poaceae, Ephedraceae, Amarantaceae, and Lamiaceae families of the Baskunchak Nature Reserve, remarkable species differences in accumulation of 22 macro- and microelements were recorded. The most common Artemisia species and Poaceae representatives belong to two different groups of plants with high content of Na, K, Zn, Cu, V and high antioxidant status and low Si typical for the former group and the opposite characteristics for the latter one. The mentioned phenomenon indicates two diverse powerful adaptation mechanisms based on the antioxidant defense and Si protection, respectively. The high frequency of remarkable levels of Se in plants with BCF exceeding 1 (Glycyrrhiza aspera, Phlomis pungens, Tanacetum nullifolium, Helichrysum nogaicum, and Jurinea ewersmannii), Zn in all species except Poa angustifolia, and Cu in the Asteraceae plants Phlomis pungens and Krascheninnikovia ceratoides suggests the significance of these elements in plant tolerance to environmental stresses. Plant–soil positive correlations were recorded for Sr (r = 0.866; p < 0.001); plant Sr, Fe, Co, Pb levels and soil salinity (r = 0.763, p < 0.001; r = 0.606, p < 0.03; r = 0.627, p < 0.02; r = 0.548, p < 0.05, respectively); and Cr only for Asteraceae species (r = 0.986, p < 0.001). The results obtained in this research may be used in plant adaptability evaluation in conditions of environmental stress.

Low Temperature Epitaxy Processes for Contact Resistivity Reduction

With the continued scaling of CMOS logic devices the contact resistivity at the semiconductor/silicide interface has become a limiting factor for device performance. High active dopant concentration at this interface is critical to realizing low contact resistance, and ion implantation is conventionally used to achieve this. We have previously reported [1] that contact cavity shaping to increase the contact area can be used to decrease the contact resistivity. This etching process produces convex (111) facets from a (100) starting surface in the source-drain volume, thereby increasing the contact area. The etched-recess shape can be varied from a “U” to a “V” as seen in figures 1(b) through (d). The ρc for these shapes was measured after integrating a 385°C SiGe:B in the recessed layer on TLM structures decreases with increasing (111) facet-length and for the longest facet length a ρc = 8.0 x10-10 Ωcm-2, where the implant + anneal control sample had ρc = 1.5x10-9 Ωcm-2. On FinFET structures the cavity shaping + low temp SiGe:B achieved a ρc = 5.2 x10-10 Ωcm-2 compared to the implant + anneal control of ρc = 1.5x10-9 Ωcm-2 as shown in figures 1(e) and (f).Cavity shaping can be a helpful knob to improve contact resistance, however thermal budget and integration constraints necessitate that the epitaxial growth of these layers are at temperatures ≤ 400°C. These low growth temperatures can be beneficial to dopant activation, however the growth rate and selectivity are negatively impacted. Next generation contact epitaxy processes will integrate etch cavity shaping with novel deposition chemistries to surmount these challenges. For PMOS SiGe:B deposition acceptable growth rates are more easily realized due to the intrinsic growth rate benefit from Ge and B incorporation, as well as the higher reactivity of Ge precursors compared to their Si analogs. However maintaining selective deposition requires large flows of HCl which decrease the growth rate and the boron concentration. We have employed an alternative Cl-containing precursor to maintain selectivity during Si0.5Ge0.5:B deposition at temperatures as low as 350°C, with a growth rate of 13 Å/min. Whereas to achieve selectivity with HCl at this temperature results in a growth rate of 6 Å/min. Figures 2(a) through (d) show a patterned wafer images with and without the addition of this precursor at 350°C.The situation for NMOS Si:P deposition is more difficult, as PH3 does not increase the growth rate as drastically as GeH4 or B2H6 do, and the gas-phase reactivity of conventional Si-hydrides and hydrochlorides is quite low. Higher-order silanes such as Si3H8 and Si4H10 can be used however the cost of these precursors is high and their efficiency at 400°C is typically between 0.01% and 1%. Ideally a phosphorus doping precursor, which is ostensibly used at lower flow rates, could enhance the growth rate similar to the effect of B2H6 in the growth of p-type materials. The other major concern for low temperature Si:P deposition processes is the selectivity to dielectric surfaces. A fully selective process in unlikely for Si:P at these temperatures and etch-back cycles will be required to remove the materials which nucleate on the dielectric surfaces. It is therefore desired to identify a P precursor with higher intrinsic selectivity than Si2H6-PH3 and/or Si3H8-PH3 processes.Here we present a Si2H6-based process in which the P dopant precursor (PDOP-1) is engineered to enhance the epitaxial growth rate and delay the nucleation of material on the dielectric surface. Figure 3(a) compares the growth rate vs. temperature for a Si2H6-PH3 process and Si2H6-PDOP-1. The growth rate of the PH3 process falls-off rapidly below 400°C, whereas a measurable epitaxial growth rate is maintained down to ~ 385°C in the PDOP-1 process. We find that for equivalent growth conditions and %P that PDOP-1 can increase the growth rate by 60-80% relative to PH3 processes. In figure 3(b) the amorphous growth rate on SiO2 is plotted vs time for a Si2H6-PH3 benchmark and Si2H6-PDOP. From this plot we have determined a nucleation delay of ~ 90 seconds for PDOP-1, whereas the benchmark PH3 does not exhibit a nucleation delay. This behavior is further explored in figure 4 where we have deposited SiP non-selectively on a simple patterned wafer using Si2H6-PH3, Si3H8-PH3, and Si2H6-PDOP1. We have used the epi to amorphous thickness ratio as metric for the intrinsic selectivity of each process. Based on these results the intrinsic selectivity is improved to 4:1 using PDOP-1, from 2:1 and 3:1 for the, Si3H8-PH3 and Si2H6-PH3 benchmarks, respectively.[1] N. Breil et. al. IEEE Symposium on VLSI Technology, 2023 Figure 1

Optical Properties of Multilayered Staggered SiGe Nanodots Depending on Si Spacer Growth Temperature

Introduction Uniformly ordered SiGe nanodot (ND) has the potential for optoelectronic device application. By engineering Si surface morphology, heteroepitaxial SiGe layer thickness distribution can be controlled by self-ordering [1]. The self-ordering is an attractive phenomenon for fabricating a vertically ordered stack of SiGe ND fabrication. Yamamoto et al. have successfully fabricated the SiGe staggered NDs by controlling the balance between the surface energy and the residual strain of the Si spacer [2]. We have evaluated the strain state, the optical characteristics, and the band structure of the SiGe staggered and dot-on-dot NDs by Raman and PL (Photoluminescence) spectroscopy, and clarified that the strain state not only in the SiGe NDs but also in the Si spacer affects the emission energy [3]. The surface energy can be controlled by the growth temperature of the Si spacer, and it is expected to modify the dot shape and size. Indeed, the cross-sectional transmission electron microscopy (TEM) observations show that the lower Si spacer growth temperature results in a smaller dot size. However, it has not been sufficiently clarified the effect of the strain induced in NDs and the optical properties of the multilayered staggered NDs realized by the difference in the Si spacer growth temperature. Therefore, we investigated the strain and the luminescence properties of those multilayered staggered SiGe NDs by Raman and PL spectroscopy. Experiment The staggered NDs (designated structure: {Si0.6Ge0.4 NDs /50 nm Si spacer} × 10 cycles) on the Si spacer with the growth temperature of 625, 650, 675, 700, and 725℃ were prepared, which were fabricated on the Si substrate by a reduced pressure chemical vapor deposition. Figure 1 shows the cross-sectional TEM images of the staggered NDs on the Si spacers grown at 625 and 675℃. These samples were evaluated by Raman and low-temperature PL spectroscopy. The Raman spectrometer has a 2,000 mm focal length and a high resolution of approximately 0.1 cm-1. A diode-pumped solid-state (DPSS) laser with a wavelength of 532 nm and a beam diameter of approximately 1 µm as the excitation source was used. The PL measurement setup was equipped with a spectrometer which contains an InGaAs diode array detector, with a measurable wavelength range between 0.9 and 1.7 μm. This spectrometer can control the sample stage temperature between 4 and 300 K with a helium compressor and a heater device. A He-Cd laser with a wavelength of 325 nm and a DPSS laser with a wavelength of 532 nm, here the beam diameters of approximately 50 µm, were utilized as the excitation source. The relatively wide slit of 100 µm enabled obtaining a high PL intensity with the wavelength resolution of approximately 4 nm. Results and Discussion Raman spectrum of the SiGe NDs on the Si spacer grown at the temperature of 625℃ is shown in Fig. 2. The Raman peaks of the Si-Si mode derived from Si spacers and SiGe NDs were observed around 520 cm-1 and 510 cm-1, respectively. Figure 3 shows the Raman shift of Si-Si mode from the SiGe NDs on the Si spacers grown at 625, 650, 675, 700, and 725℃. The large compressive strain seems to be induced in the staggered SiGe NDs compared to the strain-free Raman shift of the single crystalline Si0.6Ge0.4 [4], and the higher growth temperature of the Si spacer leads to stronger compressive strain. Figure 4 shows the PL spectra derived from the SiGe NDs on the Si spacers grown at 625, 650, 675, 700, and 725℃. As shown in Fig. 4, we confirmed the TO-phonon-assist line derived from the Si spacer, transverse-optical (TO)-phonon-assist line, and Non-phonon (NP) line related to SiGe NDs. All staggered NDs show stronger SiGe-derived PL, compared to the TO-phonon-assist line derived from Si spacers. The transition energy of the TO-phonon-assist line derived from SiGe NDs indicates that the higher growth temperature for the Si spacer leads to a wider bandgap. This behavior of the transition energy might be caused by the strain in the SiGe NDs and/or the Si spacers. In conclusion, lower Si spacer growth temperature leads to a smaller size of the SiGe NDs and the red-shift of the luminescence due to the strain state of SiGe NDs and/or Si spacer in the staggered structure.

A Comprehensive Review of Nano-sized Silica’s Effects on Plant Growth, Molecular Responses, and Biochemical Changes

Silicon (Si) is a tetravalent metalloid and second most abundant on earth approximately 28%. Slags were used in agriculture as a silica fertilizer (10–28% Si); which improvise degraded crop soils, as well as crop growth and disease resistance. Si improves abiotic stress in crop lodging, UV tolerance, improves water uptakes and blocking the NaCl toxicity was observed in Gramineae family. It showed tolerance to biotic stress in terms of physical strengthening of plants against microbial infestation and activation of defensive enzymes such as peroxidase, polyphenol oxidase, lipoxygenase, phenylalanine ammonia lyase. There was an enhanced vegetative growth and germination percentage in varied vegetable crops with 100 to 500ppm range of silica nanoparticles. The plants available Si (H4SiO4) form in soil solution ranges about 0.1 to 0.6 mM and it get absorbed from roots via xylem to shoot containing a specialized cell surface protein called as Nod26-like major intrinsic protein (NIP) of aquaporin family. The list of total genes responsible for uptake of silica form are Low silica genes (Lsi1, Lsi2, Lsi3, Lsi6) and Si efflux transporter genes (SIET3, SIET4, SIET5). The nano-sized silica have been proven to be more validated impact on genes responsiveness via morpho-physiological parameter relationship. It is concluding that, use of silica in commercial crops have deep root to influence the genes and a bright future in its crop growth development aspects.

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.

Genetic Signatures: CD44 Single-Nucleotide Polymorphisms Affect Cell Surface Expression and Elevate Risk in Head and Neck Squamous Cell Carcinoma.

This study aimed to investigate the impact of single-nucleotide polymorphisms (SNPs) in the CD44 gene, specifically in the 3'UTR region (rs13347) and intronic region (rs187115), on the cell surface expression of CD44 protein and the risk of development of head and neck squamous cell carcinoma (HNSCC). The study involved analysis of 85 samples and 85 healthy controls. Immunohistochemistry (IHC) and flow cytometry were used to assess cell surface protein expression using CD44 antibody. DNA from formalin-fixed paraffin-embedded tissue sections was isolated and amplified using targeted primers. Sanger sequencing of the resultant amplified products was performed to determine the genotypes of the CD44 rs13347 and rs187115 SNPs. GTEx and RegulomeDB were queried to evaluate the genotypic effects of these variants on target gene expression and regulation. A comparison between patients with HNSCC and healthy controls revealed a significant association between CD44 rs13347 and an increased risk of HNSCC in all the analyzed models, especially the TT genotype showed a significantly higher risk with an odds ratio of 8.69 (95% CI, 2.35 to 32.09; P = .0003). However, no significant association was found between CD44 rs187115 and HNSCC in any of the models analyzed (all P > .05). Other notable findings included significant associations between CD44 rs13347 genotype and age (P = .031), number of CD44-positive tumor cells (P = .049), CD44 staining intensity (SI; P = .039), and CD44 immunoreactivity score (IRS) status (P = .019). The T allele and homozygous TT genotype of CD44 rs13347 SNP were associated with increased susceptibility to HNSCC and decreased proportion of CD44-positive tumor cells, low SI, and reduced IRS.

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

Influence of Si on the Elevated-Temperature Mechanical and Creep Properties of Al–Cu 224 Cast Alloys during Thermal Exposure

The influence of Si content (0.1–0.8 wt.%) on the development of precipitation microstructures and the resultant mechanical and creep properties during thermal exposure, up to 1000 h at 300 °C, in Al–Cu 224 cast alloys, was systematically investigated. The room and elevated temperature yield strength (YS) increased with increasing Si content under the T7 condition, which was attributed to the fact that the Si promoted the precipitation of fine θ′. However, Si increased the coarsening of θ′ during thermal exposure at 300 °C, and the alloys with low Si exhibited a higher YS and creep resistance at elevated temperatures than high Si alloys. The mechanical strength and creep resistance were mainly controlled by the precipitation strengthening of the predominant θ′ phase. Because of the high mechanical strength and creep resistance of the 0.1Si alloy during long-term thermal exposure, the Si level in Al–Cu alloys should be maintained at a low level of 0.1 wt.% for high-temperature applications. The strengthening mechanisms were quantitatively analyzed, based on the characteristics of the precipitate. The predicted YS values under different exposure conditions agreed well with the experimentally measured values.

Effect of the addition of Ni and Cu on solidification microstructure evolution of Al-5Si-0.5Mg alloys

AbstractTo develop new high-performance hypoeutectic Al–Si–Mg alloys at elevated temperatures, it is often necessary to add alloying elements of Cu and Ni. The high-temperature strength of the most used Al–Si–Mg–Cu–Ni alloy depends on a load transfer from the α-Al matrix to the intermetallic compounds. However, there is still a lack of detailed investigation on the effects of the combined addition of Ni and Cu on the solidification microstructure evolution of Al–Si–Mg base alloys with a lower Si concentration. This investigation specifically addresses the effects of the addition of Cu or Cu and Ni on the solidification microstructure evolution of the Al–5Si–0.5Mg alloy. It was found that when Al–5Si–0.5Mg is alloyed with Cu or Cu and Ni, the solidus temperature decreases, while the freezing range of the Al–5Si–0.5Mg alloy increases. With the addition of Cu and even small amounts of Ni, the phases Al7Cu4Ni and Al5Cu2Mg8Si6 were predicted by TC simulations and also observed by SEM. With a higher Ni content, Al3Ni and Al3Ni2 also solidify. More importantly, the presence of Cu and Ni can partition into the α-AlSiFeMn phase and change the size and morphology of the α-AlSiFeMn phase. This investigation provides a helpful hint to the development of the high-performance Al–Si–Mg–Cu–Ni alloys with a simultaneous improvement of the thermal conductivity and mechanical properties.

Molecular forecasting of domoic acid during a pervasive toxic diatom bloom

In 2015, the largest recorded harmful algal bloom (HAB) occurred in the Northeast Pacific, causing nearly 100 million dollars in damages to fisheries and killing many protected marine mammals. Dominated by the toxic diatom Pseudo-nitzschia australis, this bloom produced high levels of the neurotoxin domoic acid (DA). Through molecular and transcriptional characterization of 52 near-weekly phytoplankton net-tow samples collected at a bloom hotspot in Monterey Bay, California, we identified active transcription of known DA biosynthesis (dab) genes from the three identified toxigenic species, including P. australis as the primary origin of toxicity. Elevated expression of silicon transporters (sit1) during the bloom supports the previously hypothesized role of dissolved silica (Si) exhaustion in contributing to bloom physiology and toxicity. We find that coexpression of the dabA and sit1 genes serves as a robust predictor of DA one week in advance, potentially enabling the forecasting of DA-producing HABs. We additionally present evidence that low levels of iron could have colimited the diatom population along with low Si. Iron limitation represents an overlooked driver of both toxin production and ecological success of the low-iron-adapted Pseudo-nitzschia genus during the 2015 bloom, and increasing pervasiveness of iron limitation may fuel the escalating magnitude and frequency of toxic Pseudo-nitzschia blooms globally. Our results advance understanding of bloom physiology underlying toxin production, bloom prediction, and the impact of global change on toxic blooms.

The Yanshanian Uranium Mineralization Age and Its Geological Significance in the Dashigou Carbonatite-Type Mo-REE-U Deposit, East Qinling Orogen, China

The Dashigou deposit is one of the most representative carbonatite-type Mo-REE deposits in the East Qinling metallogenic belt of China, with a molybdenum resource of more than 180 kt and a rare earth resource of 37.8 kt. Recent exploration has revealed a considerable scale of uranium mineralization within this deposit. Therefore, this study conducted detailed mineralogical and EPMA U-Th-Pb chemical dating on the uranium mineralization in the Dashigou deposit. The results indicate that the U-ore body in the Dashigou deposit mainly consists in carbonatite veins, and principally as anhedral, mesh-like uraninite. The mineral assemblage is characterized by uraninite + rutile + bastnasite + parisite or brannerite. The uraninite displays geochemical compositions of high Y and Ce and low Si, Ti, and Mg. The EPMA U-Th-Pb chemical dating is 144 ± 3.1 Ma, representing the Yanshanian uranium mineralization age in the region. The newly discovered uranium mineralization age indicates that the deposit experienced a uranium remobilization event during the Cretaceous and was formed in an intracontinental orogenic and extensional environment post-collision orogeny.

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.

A near-infrared metastructure to realizing polarization conversion and sensing based on the electromagnetic induced reflection

A multifunctional metastructure (MS) working in the near-infrared band is proposed that achieves linear to circular polarization conversion (LTCPC) and electromagnetically induced reflection (EIR). In addition, due to the use of reflected electric fields to overcome the influences of near-infrared band thermal radiation, MS has a good multifunctional sensing detection. The given MS is composed of a four-layer stacked structure. From the substrate to the top layer (along the +z-direction), it consists of silver, a silicon dioxide layer, and two layers of silicon (Si) resonators. Each layer of the Si resonator has four holes created by rotation. By breaking the symmetry of the upper and lower Si layers of MS, the deviation of the rotation angle of the upper and lower holes is introduced, so the MS achieved a near-infrared EIR with an ultrahigh quality factor (Q-factor). Under electromagnetic wave incidence, at 187.89 THz, the Q-factor of MS's reflection peak reaches 2441.25. Due to the unique shapes of the two resonator layers' holes, the axial ratio (AR) is less than 3 dB between 187.844 THz and 187.871 THz, realizing LTCPC. Utilizing the relationship between the optimal polarization conversion frequency point (the frequency corresponding to the lowest AR) and the environmental refractive index, the MS can be used for detecting cancer cells with a sensing sensitivity (S) of 37.24 THz/RIU (36.06 THz/RIU). By introducing the alcohol into the MS, the refractive index of the alcohol to be measured. MS achieved the detection function of the alcohol solution volume fraction, with an S reaching 33.32 THz/RIU, and a figure of merit as high as 154.202. Finally, the related parameters and polarization angle are discussed. The effects of different parameters on EIR and AR also are analyzed. The innovation of this paper lies in the realization of EIR, and a method to improve the Q-factor of near-infrared EIR by rotating the structure is proposed. The combination of a high Q-factor and polarization conversion overcomes the disadvantage that both are difficult to achieve together, and the EIR is easier to detect than the electromagnetically induced transparency. The design also has potential applications in biomedical sensors and industrial production.

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.

Intensity Analysis Method of Acoustic Emission Signals for the Damage Monitoring of Post-Tensioned Concrete Beams.

Acoustic emission (AE) is well suited for the real-time monitoring and detection of damage in reinforced concrete structures. In this study, loading/unloading cycles up to failure were applied on three different full-scale beams, each with varying defect morphologies. An intensity analysis method was employed to assess the damage sensitivities of the defective structures under stress conditions. Specifically, the calm ratio, load ratio, severity, and historical index were identified as statistical parameters that can provide global information on the damage level. Consequently, they can be easily used as damage evolution indexes for reinforced concrete structures. Correlations between these parameters were investigated to better discriminate between their potentials and identify critical levels that might not be evident using parametric analysis. The AEI chart helps locate damaging areas, aiding focused repairs. For defected beams with broken strands, at low load, HI and SI fall in zone B (damage detected). At cycles 4 and 6, with significant deflection, they fall into a critical zone, E (severe damage). Comparing post-tensioned beams revealed defects correlating with damage susceptibility. B3 beams with diffused defects displayed high activity at higher loads. Applying a load-calm ratio chart, initial minor damage worsened progressively. Severe damage was prominent in defective B2 and B3 beams, reaching zone 3. The variation in the acquired parameters over time can then be considered as an affordable and reliable indicator of damage progression.