HF Concentration Research Articles

Ultrahigh temperature ablation resistant HfB2-SiC composites: From liquid SiHfCB precursor synthesis to light weight bulk preparation and characterization

The current generation of ultrahigh temperature ceramic precursors typically encounters obstacles in achieving high ceramic yields (<40 wt.%) due to the challenges in integrating significant amounts of boron, which hampers their conversion into boride-based ultrahigh temperature ceramics. To tackle these challenges, a serious of pioneering liquid multi-component hafnium-containing ceramic SiHfCB precursors (with different Hf/Si ratios) have been developed. These novel precursors are featured with stable molecular structure and high ceramic yield which were successfully created through a novel one-pot polymerization process. They present in liquid form and their structure is characterized by C-C bonds forming its main chain with branched chains of O-Si-O, Si-O-Hf, Si-O-B, and B-O-Hf which have untapped advantages including uniform component dispersion, and excellent fluidity. The ceramic yield of SiHfCB precursor with Hf/Si of 0.2 is remarkably up to 68.6 wt.% at 1500 °C, and their Hf content exceeded 50 wt.%. Of particular interest, the pyrolyzed product HfB2-SiC nanopowders derived from the SiHfCB precursor with Hf/Si of 0.2, consist of nanopowders in the 40–60 nm range with a density of 5.23 g cm−3. Remarkably, this material demonstrates exceptional performance in ultrahigh temperature oxygen-containing environments at 2500 °C, showing near-zero ablation with a linear ablation rate of just 2.5 × 10−4 mm s−1. Post-ablation analysis of the microstructure reveals that the formation of a lava-like HfO2 and HfO2-SiO2 oxide layer effectively blocks oxygen penetration and provides excellent oxidation resistance. The innovative SiHfCB hafnium-containing ceramic precursor offers a groundbreaking solution for the preparation of lightweight ultrahigh-temperature ceramics. This development is poised to provide robust technical support for the use of ultrahigh temperature ceramics in non-ablative thermal protective systems, particularly in the construction of hypersonic vehicles, where ultrahigh temperature resilience is crucial.

Formation mechanisms of Fe-dominated versus Fe polymetallic deposits in the West Tianshan, NW China: A magnetite perspective

The West Tianshan in the Central Asian Orogenic Belt is one of important Fe belts in China, where many submarine volcanogenic iron-oxide deposits constitute the Awulale metallogenic belt. The Dunde deposit is a Fe-Zn-Au deposit, whereas Chagangnuoer, Zhibo, and Beizhan are Fe-dominated deposits. To examine the factors controlling the formation of Fe polymetallic deposits, the texture and chemical composition of magnetite from the Dunde deposit were studied in detail and compared with those of other deposits in the same belt. The Dunde deposit magnetite can be divided into Mag-1, Mag-2, and Mag-3, which correspond to stages of retrograde, sulfide, and carbonate stages, respectively. They have experienced oxy-exsolution and coupled dissolution and reprecipitation (CDR), forming multiple generations of magnetite. The exsolution of gahnite in Mag-1 and 10 times higher Zr, Hf, Sc, Ta, Nb, Mn, and Zn contents in the all stages of magnetite than those of Fe-dominated deposits, indicating the Dunde magnetite was crystallized from high-temperature, high-salinity, Fe-Zn-rich fluids. The similar chalcophile element contents in host volcanic rocks between Dunde and other deposits indicate host volcanic rocks are not the reason for Zn enrichment in Dunde. The higher Mg + Mn and Si + Al contents in Dunde magnetite than magnetite of other deposits indicate stronger fluid-rock interaction. Extensive CDR texture in Mag-1 and Mag-2 and lower Zn in secondary magnetite indicate that Zn leached from Zn-rich magnetite may have also contributed to the formation of sphalerite in sulfide stage. Our study has demonstrated that high-temperature, high-salinity, Fe- and Zn-rich primary fluids, a higher degree of fluid-rock interaction, and repeated fluid infiltration are key factors controlling the formation of Fe-Zn polymetallic deposits, such as the Dunde deposit in West Tianshan.

Exploring Heusler superconducting properties for Ni2ZrAl and Ni2ZrGa Heusler compounds: First principal insight

This paper presents a theoretical study of structural, mechanical, electronic, vibrational and superconducting properties of full Heusler compounds Ni2ZrZ (Z= Al and Ga) using the norm conserving pseudo potential within the framework of Density Functional Theory (DFT) and Density Functional Perturbation Theory (DFPT). Our finding reveal that the non-magnetic L21 phase structure is energetically more stable for both compounds. The band structure shows that these compounds have a metallic behavior with a saddle point (Van Hove Singularity) at L-point. Elastic and vibrational properties analysis confirm the mechanical and dynamical stability of our studied compounds. The Ni2ZrAl and Ni2ZrGa exhibit BCS weak coupling superconductivity with critical temperatures of 1.78 K and 2.68 K, respectively. The study extends to explore the impact of Hf concentrations, providing valuable insights into the superconducting properties of Ni2Zr(1-x)HfxGa alloys.

Mineralogy and geochemistry of rare metal (Zr-Nb-Hf-Ta-REE-Ga) coals of the seam XXX of the Izykh Coalfield, Minusinsk Basin, Russia: Implications for more widespread rare metal mineralization in North Asia

This study focuses a comprehensive mineralogical and geochemical study of rare-metal (Zr-Nb-Hf-Ta-REE-Ga) mineralization in the Permian coal seam XXX-XXXa of the Izykh Coalfield, Minusinsk Basin, southern Siberia. A link is demonstrated between the accumulation of rare metals in the coal with a volcanogenic rock parting up to 45 cm thick separating the coal seams. The floor of seam XXX is also characterized by the presence of pyroclastic material, which affects the level of accumulation of rare elements in the coal of the seam. Coals and intra-seam rock partings in seam XXX-XXXa have abnormally high concentrations of Zr, Nb, Hf, Ta, REE and Ga. In coal ash samples, the contents of some elements are highly evaluated, e.g., 1.4% Zr, 0.26% Nb, 164 ppm Hf, 17.9 ppm Ta, 0.8% REE, 0.13% Y, and 226 ppm Ga. The concentration of rare elements is higher in the coal and coal ash of the XXX coal seam than in the XXXa coal seam. The accumulation of anomalous concentrations of Zr-Nb-Hf-Ta-REE and Ga is mostly specific for the rock parting between the XXX and XXXa seams, as well as for the coals in contact with this parting. Zirconium, Nb, Y, and REE form more contrasting halos near the parting compared to Ta, Hf, and Ga. This is explained by the different mobility of the elements under weathering and diagenetic conditions. Other ore elements are concentrated to a greater extent in the coal in the near-contact zone, as well as at a distance from the partings. Ore material is concentrated primarily in the fine-dispersed mineral phase represented mainly by Zr-Nb-Ti-Fe oxides, complex Nb-Zr-P silicates, and REY-bearing phosphates (monazite, xenotime). Volcanogenic pyroclastics of acidic and alkaline composition (rhyolite-pantellerite) influenced the accumulation of rare metals in coal. Volcanic ash, transported from a distant source, served as the raw material for the formation of the rock interlayer in coal. The composition of this volcanic ash is believed to correspond to a pantelleritic tuff. These findings are comparable to those reached in earlier work on the altered ash in the coal seam XI of the Kuznetsk Coal Basin, which has similar geochemical features and is also of Permian age. Complex Zr-Nb-Hf-Ta-REE-Ga mineralization in the coals of the Kuznetsk and Minusinsk basins, associated with volcanogenic pyroclastics, indicates a wide manifestation of active acid and alkaline volcanism during the formation of coal deposits and the possibility of identifying similar mineralization in Permian coals of East and North Asia.

Effects of Zr and Hf on superelasticity, shape memory effect and microstructure of β-type (Ti–Zr–Hf)–Nb–Sn multi-principal element alloys with low magnetic susceptibility

(Ti–Zr–Hf)(97−x)–xNb–3Sn (Ti:(Zr + Hf) = 1:1) alloys were designed for biomedical superelastic alloys with magnetic resonance imaging (MRI) compatibility. The effects of Zr and Hf on constituent phases, superelasticity, shape memory effect and magnetic susceptibility were clarified. The specific Nb content for superelasticity and shape memory effect was also explored. It was found that the (Ti–Zr)–6.5Nb–3Sn alloy exhibited a superelastic recovery strain of 5.2 % with lower magnetic susceptibility compared to conventional Ti–Ni and Ti–Nb alloys. The magnetic susceptibility decreased with increasing Hf content. The (Ti–Hf)–9Nb–3Sn alloy showed a superelastic recovery strain of 0.9 % and very low magnetic susceptibility less than half of that of the conventional alloys. Based on the lattice parameters of these alloys, it was found that these alloys exhibited larger transformation lattice strain between a β phase and an α” phase than those of the Ti–Nb alloys, suggesting high potential to exhibit a large superelastic recovery strain. According to orientation analyses of constituting grains, the larger superelastic recovery strain in the (Ti–Zr)–6.5Nb–3Sn alloy than that of the (Ti–Hf)–9Nb–3Sn alloy is considered to be caused by a strong recrystallization texture of {001}β <110>β. By optimization of heat-treatment temperature, superelastic recovery strain of 3.6 % was achieved in the (Ti–0.5Zr–0.5Hf)–7.5Nb–3Sn alloy.

Exploring the impact of synergistic dual-additive electrolytes on 5 V-class LiNi0·5Mn1·5O4 cathodes

Tris (trimethylsilyl) phosphate (TMSP) and tris(2,2,2-trifluoroethyl) phosphate (TTFP) was added to carbonate solvent-based electrolytes as dual-additives to enhance the performance of LiNi0·5Mn1·5O4 (LNMO). The X-ray photoelectron spectroscopy results revealed that both TMSP with high oxidation ability and TTFP with high oxidation resistance participated in the formation of cathode–electrolyte interphase (CEI) films. Electrochemical impedance spectroscopy confirmed that the constructed CEI films had excellent electronic insulation and ionic conductivity, reducing the interfacial impedance of the LNMO electrode, and improving the electrochemical performance of LNMO/Li half-cells and LNMO/Li4Ti5O12 full-cells. As measured by the nuclear magnetic resonance, the incorporation of TMSP and TTFP significantly reduced the HF content in the electrolytes. Therefore, both LNMO/Li half-cells (500 cycles with 95.7% capacity retention) and LNMO/Li4Ti5O12 full-cells (200 cycles with 79.9% capacity retention) displayed higher cycling stabilities at 5 C owing to the synergistic effect of TMSP and TTFP. In comparison, capacity retentions of ∼76.5% after 500 cycles and ∼37.2% after 200 cycles were respectively achieved for the LNMO/Li half-cells and LNMO/Li4Ti5O12 full-cells with the standard electrolyte at 5 C. This study provides strong evidence that additive combinations can improve the electrochemical performance of high-energy and high-voltage cathode materials.

Trace Elements Distribution in the k7 Seam of the Karaganda Coal Basin, Kazakhstan

We investigated the distribution patterns and evaluated the average contents of trace elements in the k7 seam of the Karaganda coal basin in Central Kazakhstan. This paper presents the results of studying the geochemistry of 34 elements in 85 samples of the k7 seam. The study employed a suite of advanced high-resolution analytical methods, including atomic emission spectrometry with inductively coupled plasma (ICP–OES) and mass spectrometry with inductively coupled plasma (ICP–MS), along with their processing and interpretation. It was determined that the concentrations of trace elements in the k7 seam are primarily associated with lithophile elements, revealing high concentrations of Li, V, Sc, Zr, Hf, and Ba. Additionally, increased concentrations of Nb, Ta, Se, Te, Ag, and Th were observed compared to the coal Clarke. Specific Nb(Ta)–Zr(Hf)–Li mineralization accompanied by a group of associated metals (Ba, V, Sc, etc.) was identified. The study revealed lateral and vertical heterogeneity of the rare elements’ distributions in coals, attributed to the formation dynamics of the coal basin. A correlation between Li and Al2O3 with a less positive relationship with K2O suggests the affinity of certain elements (Li, Ta, Nb, and Ba) to kaolinite. Clay layers showed increased radioactivity, with Th—13.2 ppm and U—2.6 ppm, indicating the possible presence of volcanogenic pyroclastic rocks characterized by radioactivity. Taken together, these data reveal the features of the rock composition of the source area, which is considered a mineralization source. According to geochemical data, it was found that the source area mainly consists of igneous felsic rocks, indicating that the formation occurred under conditions of a volcanic arc. This study’s novelty lies in estimating the average trace elements in the k7 seam, with elevated concentrations of certain elements that suggest promising prospects for industrial extraction from coals and coal wastes. These findings offer insights into considering coal as a potential source of raw material for rare metal production, guiding the industrial processing of key elements within coal. The potential extraction of metals from coal deposits, including from dumps, holds significance for industrial and commercial technologies, as processing critical coal elements can reduce disposal costs and mitigate their environmental impact.

Geochemistry and origin of the Late Carboniferous ultramafic, mafic, and felsic plutonic rocks (NW Iran)

The Late Carboniferous Gharabagh-Mamkan-Mingol plutonic complex (GMMP) consists of a variety of ultramafic, mafic, felsic intrusive rocks, including the 325–315 Ma Gharabagh gabbroic, granitic, and monzonitic rocks and Mamkan-Mingol 320–315 Ma massive appinites (hornblende-rich gabbros) and 300–295 Ma layered mafic-ultramafic (gabbro, appinitic gabbro, and appinite) rocks in the northwestern Sanandaj-Sirjan zone, Iran. The relationships between various rock types in the plutonic complex are unknown. To address these issues, we conducted a detailed petrologic and geochemical study of the complex, and its country rocks.The abundance of major and trace elements and isotopic ratios of 87/86Sr (0.70379–0.70428) and 143/144Nd (0.51228–0.51245) systems showed that the Gharabagh gabbros formed from a metasomatized amphibole-bearing spinel lherzolite from an ancient subduction-modified mantle source with OIB characteristics including high contents of light rare earth elements (LREEs), Ti, Nb, Ta, and Ba, as well as low concentrations of Sr, Hf, and Zr. The geochemical data show that monzonites had high concentrations of LREEs, Ba, U, K, Hand Zr, and the low contents of Th, Nb, Ta, Sr, P, and HREEs and Eu-positive anomalies and originated from the melting of the continental crustal base in the subducted mantle wedge. The granites are similar to monzonites, with their difference being in the high concentrations of Th and Eu-negative anomalies. Combining petrographic, petrological, geochemical, and isotopic data suggests that Gharabagh plutonic rocks were formed as a result of Paleo-Tethys slab break-off, and slab sinking, during trans-tensional collision between the Central Iranian microplate and Gondwanaland during the Late Carboniferous. As a result of this event, decompression melting began in the upwelling mantle, coeval with the formation of the pull-apart basin, during major strike-slip faulting, leading to a hydrous mafic melt with about 10–12% partial melting.The Mamkan-Mingol massive and layered masses have a tholeiitic affinity. The Mamkan-Mingol rocks are characterized by different trace element patterns, especially in the concentrations of REEs and high field strength elements (HFSEs) such as Nb, Ta, Hf, Zr, and P and large-ion lithophile elements (LILEs) such as Th, U, Sr, K, Rb, and Ba. The massive and layered rocks mostly show a variably developed negative anomaly in HFSEs, and widely varying ratios of (La/Yb)n (1.0–5.2). Massive appinites and layered gabbros of GMMP originated due to different partial melting in the upwelling zone of metasomatized OIB-like amphibole-bearing spinel lherzolite and a less hydrous- to dry upwelling mantle zone, respectively, in an environment associated with the initiation of rifting, where the remnants of the Paleo-Tethys subducted slab plunges deep into the mantle. Contrasting Nd isotopic ranges are present between the massive appinites (ɛNd = +0.39) and different types of mafic-ultramafic rocks in layered outcrops (ɛNd = +1.12 to +2.07) of the complex. Based on the geochemical and isotopic (ratios of Sr, Nd, and Pb) data, we suggest that variations in of contribution of slab-derived fluids or crustal components in the primary melt caused the generation of massive appinites and different types of layered gabbros.

Palynostratigraphy and Bayesian age stratigraphic model of new CA-ID-TIMS zircon ages from the Walloon Coal Measures, Surat Basin, Australia

The Surat Basin hosts significant coal and coal seam gas resources. New high-precision CA-TIMS U/Pb zircon ages from tuffs and Bayesian age stratigraphic models are combined with palynology from fine-grained sedimentary rocks and zircon trace elements to provide further chronostratigraphic and biostratigraphic constrains on the Walloon Coal Measures in the eastern margin of the Surat Basin and infer the palaeoenvironment and tectonic setting. The tuff ages range from 165.88 ± 0.11 Ma to 158.84 ± 0.05 Ma, with those from the stratigraphically lower Taroom Coal Measures ranging from 165.88 ± 0.11 to 163.05 ± 0.08 Ma and Juandah Coal Measures ranging from 159.91 ± 0.04 to 158.84 ± 0.05 Ma. This corroborates that the lower part of the Walloon Coal Measures is Callovian and the upper part is Oxfordian. The palynology results from mudstones show that all samples are dominated by microfossils of spore-pollen with conifers being the most abundant. Our samples fall within Price’s (1997) stratigraphic zonation of APJ4.2 and APJ4.3. Posterior ages for palynology samples were estimated through Bayesian age stratigraphic modelling using stratigraphic depths and U-Pb zircon ages. The palaeoenvironment in the eastern portion of the basin is inferred to be predominantly fluvial, with spores and pollen derived from fresh water or terrestrial plants. Higher concentrations of green algae in one sample suggest that at times the water was somewhat stagnant. The zircons were derived from predominantly intermediate magmas, as indicated by the generally low Ti, Ta, and Nb values. The tectonic environment that the zircons were derived from was most likely a continental subduction zone due to their high U/Yb, low Nb/Yb and relatively low Hf concentrations. These new data support previous conclusions of the Surat Basin palaeoenvironment, contribute to the ongoing discussion about the tectonic setting of the basin and add new regional age marker horizons.

Understanding the metal-mold interfacial reactions during directional solidification of superalloys using Al2O3-rich ceramic mold

This study investigates the reactions occurring at the metal-mold interface during directional solidification of Ni-based superalloys, exerting a significant influence on both the surface quality and the desired composition of the alloy. The origin and nature of these reactions are systematically investigated by integrating thermodynamics and microstructural evolution of the alloy. It was observed that Hf from the melt reacts with the Al2O3-based ceramic mold, leading to the formation of HfO2 at the interface. This compound adheres to the surface of the ingot and also infiltrates into the melt near the interface. In order to validate these findings, an exploration of four alternative Ni-based superalloys, both with and without Hf content, was conducted, revealing an absence of comparable reactions at the interface in Hf-free alloys. Additionally, it was explored that the interface formed due to the metal-mold reaction may serve as a preferential nucleation site for MC-type carbides in C-containing Ni-based superalloys. This study concludes that the Hf content is the primary determinant influencing reactions at the metal-mold interface.

Chemical etching optimization of 3D printed α-Al2O3 monoliths to enhance the catalytic applications

Direct Ink Writing has been demonstrated to be a promising route to produce ceramic catalysts with complex geometries and enhanced catalytic performances. To increase the catalytic performances, chemical etching can be conducted to get an interconnected and hierarchical porous structure, to increase the surface area and the contact time of the reactants. In this work, DIW alpha (α)-Al2O3 catalysts were chemically etched with hydrofluoric acid (HF). Several combinations of acid concentrations and etching times were studied to find the optimal etching condition. For HF concentration of 5, 20 and 40 wt%, the optimal etching time was 48, 24 and 5 h, respectively, being 40 wt% the concentration that shows the greatest increase of surface porosity (of around 5%). HF etching can produce an interconnected porosity on 3DP α-Al2O3, but it does not yield improvement in catalytic performances when the content of fluor (F) is higher than 10 at% since it produces parasite reactions.

Magmatic–hydrothermal stage recorded by mica zonation and Nb–Ta–W–Sn mineralization: New insight into the genesis of highly evolved Songshugang Nb–Ta deposit (Jiangxi, SE China)

The role of magmatic and hydrothermal processes in niobium-tantalum mineralization is still controversial and has been limited by a lack of mineralogical records in the evolving magmatic–hydrothermal system. Micas as essential rock-forming minerals and comprise the amount of elements (especially rare-metal elements), become one of the ideal indicator. The Songshugang rare-metal granite (RMG) located in the southern part of Jiangxi Province, China, is renowned as the largest tantalum reservoir in South China. The albite–topaz–K-feldspar granite is the major granite, with layers of pegmatite, topaz-K-feldspar granite, and greisen overlay on it. It is the typical highly evolved peraluminous with low phosphorous RMGs (PLP-type) according to geochemistry. The Songshugang pluton preserves analogical characters in topaz-albite-K feldspar granites and topaz-K feldspar granite, and partly reserves in greisen. Detailed petrographic, mineralogy, and chemical composition study of zoned mica and accessory Nb–Ta minerals suggest that zinnwaldite and Nb-Ta oxides have experienced magmatic fractionation with gradually decrease of K/Rb and Nb/Ta ratio in prismatic zinnwaldite and columbite-(Fe). The leap of Rb (Rb2O up to 4.08 wt%) and Ta (Ta# up to 0.29) at the rim of zinnwaldite and columbite is likely attributed to supersaturation. Afterwards the overgrowth of Rb-deficit zinnwaldite (0.56–0.72 wt% Rb2O) is coeval with the Ta-highest wodginite, taking place during the magmatic-hydrothermal transition associated with a fluid-melt interaction in hydrosaline melt. The ascent of fluxing elements contributes to the formation of hydrothermal zinnwaldite and cassiterite through greisenization. The systemic coupling mineralization of zinnwaldite and Nb–Ta oxides altogether record the both the melt-driven and fluid-driven processes in highly evolved Songshugang deposit that is critical for rare-metal mineralization. The Songshugang displays a great similarity to the typical PLP RMGs Cínovec cupola in geochemistry, which are metaluminous to peraluminous, containing low phosphorous, intermediate REE, Zr, Hf, and Th content. But Songshugang has experienced strong supersaturation; the latter is more akin to highly evolved melts alike Yichun or Beauvoir. The strong supersaturation and crystallization demonstrate its discrepant mineralization mechanism in Songshugang RMGs.

First-principles study on the structure, mechanical and thermodynamic properties of (Ti, Hf, Nb, Ta)C high-entropy carbide ceramics

High-entropy carbide ceramics (HECCs) have demonstrated extraordinary properties and broad application potential. However, the action mechanisms of metallic elements on the properties have not been understood in depth. In this study, the structural stability and the mechanical and thermodynamic properties of (Ti, Hf, Nb, Ta)C HECCs across a broad composition spectrum were systematically analyzed based on the density functional theory and Debye–Grüneisen model. The crystal structure was constructed and validated through experimental testing. The mechanical properties such as elastic moduli, ductility, hardness, and Poisson's and Pugh's ratios were calculated. Furthermore, the temperature dependence of bulk moduli, thermal expansion coefficients, and heat capacities of the HECCs were investigated. To interpret the elastic and toughening mechanisms of non-equiatomic HECCs, the electronic structures were investigated. The results indicate that the HECCs with a single solid solution phase of the FCC rock-salt structure are thermodynamically stable. The HECCs containing higher Nb and Ta contents have greater strength and stiffness, and those containing higher Ti and Hf contents exhibit greater hardness and brittleness than the equiatomic HECC. In addition, non-equiatomic HECCs containing higher Nb and Ta contents have larger bulk moduli and lower linear thermal expansion coefficients, which can be attributed to the stronger covalent interaction among metallic elements and carbon. This study is expected to have an impact on designing ideal HECCs for high-temperature applications under extreme environments.

Effects of thermal disposal of oil-water residues on operation heating plant boiler

Industrial zones are often the source of specifically polluted waters, depending on type of industry. These waters are usually not in the limits for outtake into public sewers and it is necessary to dispose them externally or build-up technologies for their pre-treatment. The article is about the real case of an industrial. A separate sewage network is built for oily water. Solid impurities are separated from the oily water and oily water is treated by evaporation technology. The evaporator produces two types of products - condensate and concentrate. Condensate is a water with high organic content, and it is necessary to purified it by a chemical treatment plant in next step. Evaporator technology remove from water the most of metal content and significantly decrease organic and water content in concentrate. Concentrate is oily stream with lower water content. Water content in concentrate decreased in next technology steps to ca. 40-50 %. The final product is certificated technological fuel, and its final elimination is in the heating plant fluidized bed boiler. The article is detailed focused on the influence of concentrate combustion. A local temperature increases around 10-15 °C extending across the combustion chamber was confirmed. There was also an increase in HF concentration in flue gas. CO concentrations were higher in the first moments of combustion, but the control system responded by increasing the combustion air supply, and CO concentrations were finally lower at the level of 3 mg·m-3. During combustion, there was no provable increase in concentrations of NOX or other substances, and the co-combustion did not have a significant effect on the operation of the boiler, so this way was evaluated like technically and economically effective.

Effect of Hf addition on structural transformation and aging stability of Cu–15Ni–8Sn alloy

The Cu–15Ni–8Sn-xHf (wt.%, x = 0–0.6) alloys were prepared by vacuum melting, and the effect of Hf on the micro-structure of as-cast, as-solution-treated and as-aged alloys was systematically investigated, as well as the alloy aging stability. The Hf addition provided a significant role on refining the solidification structure and reducing the micro-segregation degree, and it also made γ-D03 phases more likely to form in needlelike-shape rather than lamellar-shape. With the presence of more Hf atoms, their existence form was accordingly changed from solid solute atoms to nano-scale precipitation phases and then to micron-scale segregation phase. A small content of Hf (0.1 wt%) could effectively improve the aging stability by inhibiting the growth of γ-D03. Once its content reached or exceeded 0.3 wt%, the harmful discontinuous precipitation was completely inhibited, and the common lamellar-shape γ-D03 locating around the grain boundary was no longer formed. Even the alloy failed at higher temperatures, it could only be carried out through the continuous precipitation method, namely the generation of needlelike-shape γ-D03 uniformly in the matrix. The appropriate Hf addition was capable of extending the alloy aging window, and the hardness of Cu–15Ni–8Sn-0.3Hf alloy could still exceed 360 HV even after 48 h aging.

Nanoscale-doped dual-channel for improved performance and reliability of Hf: IGTO / a-IGTO thin film transistor

Amorphous oxide semiconductors are widely used in the backplane thin film transistors (TFTs) of displays and are extensively researched as materials for next-generation memory devices. However, they face reliability degradation due to stress factors such as thermal, bias, and light exposure. To mitigate these issues, extensive research is focused on improvements, including doping, enhancing crystallinity, and applying pre-and post-treatments. This study investigates the significantly improved reliability and electrical properties of amorphous indium gallium tin oxide (a-IGTO) TFTs by adopting a dual-channel configuration through simultaneous co-sputtering of HfO2 and IGTO targets. The device fabrication involved co-sputtering HfO2 and IGTO at the gate oxide interface, followed by depositing an IGTO-only layer, rather than doping the entire channel material. The effect of varying Hf concentration was evaluated by applying different HfO2 sputtering powers. Optimal hafnium doping reduced the threshold voltage of the a-IGTO TFT from −0.85V to 0.15V compared to the pristine a-IGTO TFT, while enhancing the field-effect mobility (μFE). Furthermore, the Hf-doped device exhibited improved stability, with a reduced threshold voltage shift (ΔVth) under positive (+15 V) and negative(-15 V) bias stress at 3000s, decreasing from 11.5 V to 4.8 V, and 4.7 V–1.1 V, respectively. This study proposes a novel device fabrication method to enhance the reliability of amorphous oxide semiconductor, addressing their inherent stress-related issues.

Composition-dependent structure and bandgaps in HfxZr1−xO2 thin films

ZrO2 as a wide-bandgap semiconductor with high dielectric constant and ferroelectric properties has been extensively studied. To explore the impact of chemical doping on the structure and optical performance of ZrO2, HfxZr1−xO2 (x = 0, 0.25, 0.5, 0.75, 1) thin films were prepared through pulsed laser deposition. X-ray diffraction reveals that the orthorhombic phase (o) (111) gradually transforms into the monoclinic phase (m) (−111) with the increase in Hf content from 0 to 1. Furthermore, optical property analysis demonstrates an increase in the optical bandgap from 5.17 to 5.68 eV with the increase in Hf doping content. Density functional theory calculations and x-ray photoelectron spectroscopy suggest that the widening of the bandgap in HZO films is associated with the hybridization of Zr 4d and Hf 5d orbitals.

Trace Silicon Determination in Biological Samples by Inductively Coupled Plasma Mass Spectrometry (ICP-MS): Insight into the Volatility of Silicon Species in Hydrofluoric Acid Digests for Optimal Sample Preparation and Introduction to ICP-MS

A method for the determination of trace levels of silicon from biological materials by inductively coupled plasma mass spectrometry (ICP-MS) has been developed. The volatility of water-soluble silicon species, hexafluorosilicic acid (H2SiF6), and sodium metasilicate (Na2SiO3) was investigated by evaporating respective solutions (50 µg/mL silicon) in HNO3), nitric acid + hydrochloric acid (HNO3 + HCl), and nitric acid + hydrochloric acid + hydrofluoric acid (HNO3 + HCl + HF) at 120 °C on a hot-block to near dryness. The loss of silicon from H2SiF6 solutions was substantial (&gt;99%) regardless of the digestion medium. Losses were also substantial (&gt;98%) for metasilicate solutions heated in HNO3 + HCl + HF, while no significant loss occurred in HNO3 or HNO3 + HCl. These results show that H2SiF6 species were highly volatile and potential losses could confound accuracy at trace level determinations by ICP-MS if digestates prepared in HF are heated to eliminate HF. Among the various matrices comprising major elements, sodium appeared to be effective in reducing silicon loss from H2SiF6 solutions. Excess sodium chloride (NaCl) matrix provided better stability, improving silicon recoveries by up to about 80% in evaporated HF digestates of soil and mine waste samples, but losses could not be fully prevented. To safely remove excess acids and circumvent the adverse effects of excess HF (e.g., risk of high Si background signals), a two-step digestion scheme was adopted for the preparation of biological samples containing trace silicon levels. A closed-vessel digestion was performed either in 4 mL of concentrated HNO3 and 1 mL of concentrated HCl or 4 mL of concentrated HNO3, 1 mL of concentrated HCl and 1 mL of concentrated HClO4 on a hot plate at 140 °C. Digestates were then evaporated to incipient dryness at 120 °C to remove the acids. A second closed-vessel digestion was carried out to dissolve silicates in 0.5 mL of concentrated HNO3 and 0.5 mL of concentrated HF at 130 °C. After digestion, digestates were diluted to 10 mL. The solution containing about 5% HNO3 and 5% HF was directly analyzed by ICP-MS equipped with an HF-inert sample introduction system. The limit of detection was about 110 µg/L for 28Si when using the Kinetic Energy Discrimination (KED) mode. The method was used to determine silicon in various plant and tissue certified reference materials. Data were acquired for 28Si using KED and standard (STD) modes, and 74Ge and 103Rh as internal standard elements. There was not any significant difference between the accuracy and precision of the results obtained with 74Ge and 103Rh within the same measurement mode. Precision, calculated as relative standard deviation for four replicate analyses, varied from 5.3 (tomato leaves) to 21% (peach leaves) for plant and from 2.2 (oyster tissue) to 33% (bovine liver) for tissue SRM/CRMs. Poor precision was attributed to material heterogeneity and the large particle size distribution. An analysis of lung tissue samples from those with occupational exposure to silica dust revealed that tissues possessed substantial levels of water-soluble silicates, but the most silicon was present in the particulate matter fraction.

Petrological and geochemical characteristics of the Low- and High-Hf Nam Meng dioritoid, northwest Vietnam: Implication for the mantle partial melting, mixing, and magmatic differentiation

This paper investigated the petrological, elemental, and isotope geochemical characteristics of the Nam Meng dioritoid to clarify the magma source and process. The Nam Meng massif comprises large amounts of dioritoids (gabbro-diorite and quartz diorite) and lesser amounts of granitoids (granodiorite and granite). The Nam Meng gabbro-diorite is a porphyritic texture with fine-grained plagioclase, amphibole, K-feldspar, and phenocryst biotite. The Nam Meng quartz diorite comprises coarse-grained plagioclase, amphibole, biotite, quartz, and K-feldspar. The Nam Meng gabbro-diorite contains higher plagioclase and lower biotite and quartz than the Nam Meng quartz diorite. The variation in petrography and mineralogy with the negative correlation between SiO2 contents with Al2O3, MgO, Al2O3 + MgO, T-Fe2O3, and CaO contents suggest a magmatic differentiation process. All the Nam Meng dioritoids have low ACNK (mostly less than 1.0), total alkaline (Na2O + K2O ≤ 6 wt.%) with Na2O/K2O ≥ 1, and negative anomalies of Ta, Nb, and Ti. Combined with the U-Pb zircon age of 290 Ma (Hieu et al. (2017), the Nam Meng dioritoid is thought to be an I-type granitic rock formed in the subduction stage of the Indosinian amalgamation event. The low La/Yb ratios (1.14-3.21) suggest that the mantle wedge that was melted to form the Nam Meng magma had a spinel peridotite composition. The εNd (290 Ma) of the Nam Meng dioritoid is close to bulk earth silicate at 290 Ma (-4.43 to 2.34). The 87Sr/86Sr (290 Ma) of the Nam Meng dioritoid varies in a wide range from low to intermediate (0.6987 to 0.7088), and the calculated Nd model age of the Nam Meng dioritoid is 1,258 ± 47 Ma. The Sr and Nd isotope data suggest that the Nam Meng spinel peridotite was a result of mixing between an ancient ocean crust, EM1, and EM2 that occurred in a paleo-subduction zone at Meso-Neoproterozoic Rodinia supercycle. The Hf contents of the low-Hf and high-Hf Nam Meng dioritoid series are 0.38-1.02 and 2.60-8.08, respectively. The LILE/Hf and HSFE/Hf ratios in the low-Hf Nam Meng dioritoids are high and have a strongly negative correlation with Hf. On the other hand, those ratios in the high-Hf Nam Meng dioritoids are low and have a weakly negative correlation with Hf. The Hf contents positively correlate with the degree of partial melting of the mantle wedge in the subduction zone. Therefore, the low Hf, high LILE/Hf, and HSFE/Hf ratios of the Nam Meng dioritoids could be derived from a low degree of partial melting of the mantle wedge. In contrast, the high Hf, low LILE/Hf, and HSFE/Hf ratios of the Nam Meng dioritoids could be produced by a high degree of partial melting of the mantle wedge.

Understanding the contributions of F–, HF, and HF2– to the etching of SiO2 and unveiling the reaction kinetics to represent etching behavior of SiO2 up to pH 5

Understanding of the silicon dioxide (SiO2) etching mechanism in hydrofluoric acid (HF) solutions is important in semiconductor manufacturing processes. A study on the previous SiO2 etching mechanism claimed that only difluoride (HF2–) participated in SiO2 etching. However, in this study, it was observed that the etching of SiO2 occurred in the HF solution, where difluoride barely existed. Hence, a new SiO2 etching mechanism and reaction rate were proposed. Various concentrations of HF and ammonium fluoride (NH4F) under varying pH conditions were used to etch SiO2, leading to an SiO2 etching rate of 510[F–] + 610[HF] + 2890[HF2–] (Å/min). HF2– was the primary contributor to SiO2 etching; however, unlike the previous SiO2 etching mechanism, the effects of F– and HF on the etching of SiO2 were included in the rate of SiO2 etching. The SiO2 etching rate, considering the reactions between various fluorine species with varying SiO2 surface states, effectively represented the SiO2 etching behavior under various conditions over a broader pH range, up to pH 5. Controlling the ratio of the fluorine species, F–, HF, and HF2–, our etching model could also be extended to the selective etching of SiO2.