Dissolution-precipitation Mechanism Research Articles

PMMA light channels facilitate the additive manufacturing of complex-structured SiC reflector mirrors

The rapid manufacturing of lightweight SiC reflector mirrors has always posed a formidable challenge. We have successfully solved the problem of SiC slurry’s difficulty in vat photopolymerization by using highly transparent organic particles to construct the light channels for the first time. Through the integration of digital light processing with reaction sintering, we manufactured complex-structured SiC/Si reflector mirrors. Utilizing the light channels constructed with PMMA, ultraviolet light can effectively penetrate SiC slurry, thereby significantly enhancing the curing depth. During subsequent reaction sintering, PMMA particles induce the formation of numerous spherical silicon through dissolution-precipitation mechanism, alleviating stress concentration in the matrix and enhancing the flexural strength of SiC/Si ceramics. The method achieves significantly higher curing depth for SiC slurry and greater flexural strength for ceramic compared to similar materials. Extending the success above further, we have demonstrated their potential as high-quality products for practical applications.

Hydrothermal mineral replacement in the apatite-rhabdophane-monazite system: Experiments, reaction mechanisms and geological implications

Apatite, rhabdophane and monazite are actinide- and rare-earth element (REE)-bearing phosphate minerals with diverse geoscientific applications. However, their mineral-fluid reaction mechanisms below 200 °C are understudied. Insufficient understanding as to how these minerals behave during hydrothermal alteration impedes useful interpretations of REE-U-Th mobilisation in regolith profiles, diagenetic environments and low-temperature hydrothermal systems. This work experimentally investigates the replacement of apatite by rhabdophane in a Ce-doped acidic fluid at 30 °C, and of rhabdophane by monazite in REE-barren acidic fluids at 180 °C. Rhabdophane replaced apatite via the coupled dissolution-precipitation mechanism, forming nanoscale prisms clustered into spherulitic aggregates. Interstitial voids that formed between rhabdophane and apatite indicate how rhabdophane precipitation was the rate-limiting step. Void widths varied in response to apatite's anisotropic dissolution; rapid dissolution parallel to the c-axis formed the widest voids (50–125 μm) and thickest rhabdophane layers (20–50 μm), while slow dissolution perpendicular to the c-axis formed narrower voids (< 1 μm) and thinner layers (< 5 μm). At 180 °C, monazite also replaced rhabdophane via the dissolution-precipitation mechanism. Replacement rates increased with increasing phosphate concentrations, implying that monazite precipitation was the rate-limiting step. However, microscale rhabdophane aggregates were pseudomorphically preserved. This is attributed to the shared orientation of rhabdophane prisms (not pseudomorphically preserved) and their intergranular boundaries which, as microreactors, guided monazite precipitation. Both replacement reactions were accompanied by a loss of U to solution, which is attributed to the stabilisation of uranyl-phosphate complexes under acidic conditions. Results indicate that: 1) anisotropic dissolution can govern the extent of rate coupling between dissolution and precipitation during mineral replacement; 2) the pseudomorphic replacement of mineral aggregates can occur when precipitation is the rate-limiting step; 3) rhabdophane is a feasible (and perhaps necessary) metastable precursor to authigenic monazite precipitation in low temperature hydrothermal systems; 4) highly porous aggregates of both rhabdophane and monazite generate insufficient EPMA totals, such that they cannot be differentiated by EPMA alone, and; 5) phosphate complexes can mobilise U under certain hydrothermal conditions, with implications for geochronology, nuclear waste management and the formation of REE deposits.

An electron backscatter diffraction study of monazite: Linking the time-deformation path

Monazite, (Ce,REE)PO4, is a common accessory mineral used to quantify the timing and duration of tectono-metamorphic processes in (poly)metamorphosed orogenic terranes. As monazite frequently yields a spread of dates, there can be ambiguity linking age domains to specific metamorphic reactions and/or deformation events. This study aims to: (1) discern the effect of deformation on the monazite crystal structure; (2) understand how dynamic recrystallisation and dissolution-precipitation mechanisms are recorded by microtexture and/or the distribution and concentration of elements and isotopes within the monazite; and (3) assess the usefulness of microtextural imaging for the interpretation of complex petrochronological datasets.Monazites are analysed from several different geological settings including, the Himalaya (India), Western Gneiss Region (Norway), Snake Range (Nevada, USA), and Madagascar. Here, combined laser-ablation split stream isotopic (U-Th/Pb) and trace element analysis and Electron Backscatter Diffraction (EBSD) are used to investigate links between monazite (re)crystallisation/precipitation mechanisms, microtextures, age and trace-element distribution in individual grains. The studied monazite display a variety of microtexture including (001)[100] and (120)[120] (deformation) twins, micron-scale lattice rotation, and sub-grain boundaries.Observed monazite microtextures are interpreted to have formed during ductile deformation. Microtextures typically coincide with geochemically distinct, younger monazite, suggesting that crystallographic defects focus coupled dissolution-precipitation mechanisms during deformation and metamorphism. Crystallographic defects (including twins and sub-grains) are interpreted to be significant pathways for fluid, enabling coupled dissolution-precipitation of chemically distinct monazite during ductile deformation and metamorphism. This study highlights the power of combining traditional petrochronology approaches with microtextural imaging to better link monazite ages to specific deformation events.

Utilization of Eggshell Waste Calcite as a Sorbent for Rare Earth Element Recovery.

The green energy transition requires rare earth elements (REE) for the permanent magnets used in electric cars and wind turbines. REE extraction and beneficiation are chemically intensive and highly damaging to the environment. We investigated the use of eggshell waste as a sustainable alternative sorbent for the capture and separation of REE from aqueous solutions. Hen eggshell calcite was placed in multi-REE (La, Nd, Dy) solutions at 25 to 205 °C for up to 3 months. A pervasive diffusion of the REE inside the eggshell calcite was observed along pathways formed by the intracrystalline organic matrix and calcite crystal boundaries. At 90 °C, kozoite (REECO3OH, orthorhombic) spherulites precipitate on the surface of the dissolving calcite. At 165 and 205 °C, an interface-coupled dissolution-precipitation mechanism is observed, resulting in the complete dissolution of the calcite shell and its pseudomorphic replacement by polycrystalline kozoite. At 205 °C, kozoite is slowly replaced by hydroxylbastnäsite (REECO3OH, hexagonal), the stable form of the rare earth hydroxycarbonate polymorphs. Our results demonstrate two potential applications of eggshell waste for the uptake of rare earth elements in solution: at low temperatures, as a mixed organic-inorganic adsorbent and absorbent, given sufficient sorption time; and at higher temperatures, as an efficient sacrificial template for the precipitation of rare earth hydroxycarbonates.

Fluid–Melt–Rock Interaction during the Transition from Magmatism to HT-UHT-Granulite- and Amphibolite-Facies Metamorphism in the Ediacaran Adrar–Suttuf Metamafic Complex, NW Margin of the West African Craton (Southern Morocco)

Abstract Underplated mafic intrusions ponded at the base of the lower continental crust in extensional settings can experience ultra-high-temperature (UHT) granulite-facies metamorphism during tens of My due to slow cooling rates. These intrusions are also the source of heat and carbonic fluids for regional high-temperature (HT) granulite-facies metamorphism in the continental crust. This work analyses the fluid–melt–rock interaction processes that occurred during the magmatic to HT-UHT-granulite- and amphibolite-facies metamorphic evolution of high-grade mafic rocks from the Eastern Ediacaran Adrar–Suttuf Metamafic Complex (EASMC) of the Oulad Dlim Massif (West African Craton Margin, Southern Morocco). P–T conditions were determined using Ti-in-amphibole thermometry, two-pyroxene and amphibole–plagioclase thermobarometry, and phase diagram calculations. The thermobarometric study reveals the presence of tectonically juxtaposed lower- and mid-crustal blocks in EASMC that experienced decompression-cooling paths from, respectively, UHT and HT granulite-facies conditions at ca. 1.2 ± 0.28 GPa and 975 ± 50°C, and ca. 0.82 ± 0.15 GPa and 894 ± 50°C, to amphibole-facies conditions at ca. 0.28 ± 0.28 GPa and 787 ± 45°C (precision reported for the calibrations at 1 s level). An age for the magmatic to UHT granulite-facies metamorphic transition of 604 Ma was constrained from published SHRIMP Th–U–Pb zircon ages of the igneous protoliths. An amphibole 40Ar–39Ar cooling age of 499 ± 8 Ma (precision at 2 s level) was obtained for the lower-crustal blocks. Amphibole 40Ar–39Ar closure temperatures of 520–555°C were obtained for an age range of 604–499 Ma and an average constant cooling rate of 4.2°C/My, suggesting that the lower-crustal blocks cooled down to the greenschist–amphibolite facies transition in ca. 100 My. During the high-temperature stage, interstitial hydrous melts assisted textural maturation of the rock matrix and caused incongruent dissolution melting of olivine and pyroxenes, and, probably, development of An-rich spikes at the grain rims of plagioclase, and local segregation of pargasite into veins. Subsequent infiltration of reactive hydrous metamorphic fluids along mineral grain boundaries during cooling down to amphibolite-facies conditions promoted mineral replacements by coupled dissolution-precipitation mechanisms and metasomatism. Ubiquitous dolomite grains, with, in some cases, evidence for significant textural maturation, appear in the granoblastic aggregates of the high-grade mafic rocks. However, calculated phase relationships reveal that dolomite could not coexist with H2O–CO2 fluids at HT-UHT granulite- and low-medium P amphibolite-facies conditions. Therefore, it is proposed that it may have been generated from another CO2-bearing phase, such as an immiscible carbonatitic melt exsolved from the parental mafic magma, and preserved during cooling due to the prevalence of fluid-absent conditions in the granoblastic matrix containing dolomite. The lower-crustal mafic intrusions from EASMC can represent an example of a source of heat for granulitisation of the mid crust, but a sink for carbon due to the apparent stability of dolomite under fluid-absent conditions.

Tuning the solubility of polysulfides for constructing practical lithium-sulfur battery

Li-S batteries are regarded as one of the most promising candidates for next-generation battery systems with high energy density and low cost. However, the dissolution-precipitation reaction mechanism of the sulfur (S) cathode enhances the kinetics of the redox processes of the insulating sulfur, which also arouses the notorious shuttle effect, leading to serious loss of S species and corrosion of Li anode. To get a balance between the shuttle restraining and the kinetic property, a combined strategy of electrolyte regulation and cathode modification is proposed via introducing 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoroprpyl ether (HFE) instead of 1,2-dimethoxyethane (DME), and SeS7 instead of S8. The introduction of HFE tunes the solvation structure of the LiTFSI and the dissolution of intermediate polysulfides with Se doping (LiPSSes), and optimize the interface stability of the Li anode simultaneously. The minor Se substitution compensates the decrease in kinetic due to the decreased solubility of LiPSs. In this way, the Li-SeS7 batteries deliver a reversible capacity of 1062 and 1037 mAh g−1 with 2.0 and 5.5 mg SeS7 cm−2 loading condition, respectively. Besides, an electrolyte–electrode loading model is established to explain the relationship between the optimal electrolyte and cathode loading. It makes more sense to guide the electrolyte design for practical Li-S batteries.

Clean-up of divalent cobalt ions by massive sequestration in a low-cost calcium silicate hydrate material

Cobalt is a critical resource in industrial economies for the manufacture of electric-vehicle batteries, alloys, magnets, and catalysts, but has acute supply-chain risks and poses a threat to the environment. Large-scale sequestration of cobalt in low-cost materials under mild conditions opens a path to cobalt recycling, recovery and environmental clean-up. We describe such sequestration of cobalt by a widely available commercial calcium silicate material containing the mineral xonotlite. Xonotlite rapidly and spontaneously takes up 40 percent of its weight of cobalt under ambient conditions of temperature and pressure and reduces dissolved cobalt concentrations to low parts per million. A new Sharp Front experimental design is used to obtain kinetic and chemical information. Sequestration occurs by a coupled dissolution-precipitation replacement mechanism. The cobalt silicate reaction product is largely amorphous but has phyllosilicate features.

Bio-based anode material production for lithium–ion batteries through catalytic graphitization of biochar: the deployment of hybrid catalysts

Producing sustainable anode materials for lithium-ion batteries (LIBs) through catalytic graphitization of renewable biomass has gained significant attention. However, the technology is in its early stages due to the bio-graphite's comparatively low electrochemical performance in LIBs. This study aims to develop a process for producing LIB anode materials using a hybrid catalyst to enhance battery performance, along with readily available market biochar as the raw material. Results indicate that a trimetallic hybrid catalyst (Ni, Fe, and Mn in a 1:1:1 ratio) is superior to single or bimetallic catalysts in converting biochar to bio-graphite. The bio-graphite produced under this catalyst exhibits an 89.28% degree of graphitization and a 73.95% conversion rate. High-resolution transmission electron microscopy (HRTEM) reveals the dissolution–precipitation mechanism involved in catalytic graphitization. Electrochemical performance evaluation showed that the trimetallic hybrid catalyst yielded bio-graphite with better electrochemical performances than those obtained through single or bimetallic hybrid catalysts, including a good reversible capacity of about 293 mAh g−1 at a current density of 20 mA/g and a stable cycle performance with a capacity retention of over 98% after 100 cycles. This study proves the synergistic efficacy of different metals in catalytic graphitization, impacting both graphite crystalline structure and electrochemical performance.

The Replacement of Celestine (SrSO4) by Strontianite (SrCO3) in Aqueous Solution Studied In Situ and in Real Time Using Fluid-Cell Raman Spectroscopy

The replacement of celestine (SrSO4) by strontianite (SrCO3) has extensively been studied over the past few decades. It also represents an ideal reaction to in situ study the kinetic and fundamental mechanistic details of mineral replacement reactions in aqueous solutions via fluid-cell Raman spectroscopy. This technique allows us to study the reaction process in real time by continuously analysing the solution or by imaging the solid–liquid interface where the reaction takes place and while the replacement process is ongoing. Two sets of experiments were conducted, the first of which was carried out with celestine powder and an equimolar Na2CO3 solution in a heated fluid cell between 30 and 60 °C. The progress of the reaction was followed by Raman spectroscopic in situ measurements of the solution. Another experiment was performed with a polished cuboid cut from a single celestine crystal and a 1 M Na2CO3 solution in a fluid cell at room temperature (21 °C). In this experiment, the reaction was studied in situ, spatially resolved, and in real time. The results of both types of experiments revealed that the replacement occurs via a coupled dissolution–precipitation mechanism and that the evolution of the solution composition cannot fully be explained by a single rate law derived from a shrinking core model. By applying the model-independent time-to-a-given-fraction method, three kinetic regimes could be identified and the associated activation energies quantified.

Dissolution-precipitation hydration mechanism of steel slag based on ion exchange of a layered alkali-activator

This paper provided a new alkali activator for steel slag cementitious material - layered sodium disilicate (LSD), and focused on its dissolution-precipitation mechanism based on ion exchange capacity of LSD. The results showed that LSD could act as an effective activator for steel slag and the higher compressive strength of pastes (S3(14.9 MPa) and S10(22.3 MPa) increased by 222% and 332% respectively) were achieved and a matrix with much denser pore structure was formed. The pore solution analysis indicated LSD could play a role as ions transporter to facilitate the dissolution of steel slag (mainly C2S and C3S). Analysis of the hydration products showed that the addition of LSD increased the formation of C-S-H gels, CaCO3 and Mg(OH)2, but reduced the content of hydrotalcite-like phase. In addition, TEM and FTIR analysis indicated that the laminar C-S-H gel generated from LSD-activated steel slag had a higher SiO2 and Al content and a higher degree of silicate chain polymerization.

In operando study of gypsum crystal growth through in-cell environmental SEM

Thanks to their setting ability, hydraulic binder materials (e.g., cements, plasters) are used for a wide variety of applications (e.g., construction, medical). The setting reaction occurs through a dissolution–precipitation mechanism during which initial particles dissolve releasing ionic species from which new crystals precipitate. The development of such a microstructure governs the final properties of the material and are thus of uttermost interest.In this paper, the in operando study of the precipitation of gypsum crystals from the dissolution of bassanite particles using a specific cell for scanning electron microscope (SEM) observation is presented. Image analysis based on segmentation enabled to give quantitative results on the growth of crystals at global and local scales. Single crystal facets are indexed based on crystallography and literature results, which enables the quantification of crystal growth rates for the indexed crystallographic planes. Different growth regimes are identified; they are attributed to the transition from unfavored to the most favored crystal facets known for gypsum. The {111} and {110} planes were the fastest growing planes, whereas the {120} and {010} planes were the most stable and grew slowly.

Interface-coupled PbSO4 dissolution and PbS precipitation and its effect on sulfidization flotation of anglesite

Anglesite sulfidization mechanism was systematically investigated using flotation tests, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), Raman spectroscopy, and ultraviolet− visible diffuse reflectance spectroscopy (UV−Vis DRS). The activation effect of sodium sulfide on anglesite flotation was demonstrated by the flotation tests; however, sodium sulfide concentration must be properly controlled to avoid excessive sulfide ions causing flotation depression. The results of XPS, Raman, and UV−Vis DRS revealed that PbSO4 was replaced by PbS during anglesite treatment with a sodium sulfide aqueous solution. FESEM imaging shows the dissolution of PbSO4 and the precipitation of PbS nanoparticles during sulfidization. Thus, it can be suggested that the reaction of anglesite with a sodium sulfide aqueous solutionproceeds via an interface-coupled dissolution–precipitation mechanism: upon contact with a sodium sulfide aqueous solution, anglesite dissolution releases Pb2+ and SO42– into the fluid boundary layer, which becomes oversaturated with respect to PbS phase; then the PbS nanoparticles nucleate and grow on the surface of anglesite. The PbS nanoparticles grown on anglesite can improve the floatability of anglesite.

Water-assisted densification and broadband dielectric response of cold-sintered CaCu3Ti4O12-SnF2 composites

Miniaturization of electronic devices is one of the great challenges faced by the scientific and engineering community; hence extensive research has focused on novel materials, devices and technologies to implement the same. Calcium copper titanate (CCTO), a unique electro-ceramic material with a complex perovskite structure and reasonably high temperature-stable relative permittivity, is a potential candidate for the miniaturization of capacitors. In the present work, cold sintering is used to synthesize xCCTO–(1 – x)SnF2 (x = 0.5–0.8 vol fraction) composites at ultra-low temperature (<150 °C) in 30 min at a pressure of 500 MPa, which has not been reported earlier. The effect of the liquid phase (water) on the densification and microstructure of these composites is also investigated. X-ray diffraction (XRD) analysis confirms the co-existence of CCTO and SnF2 phases in the composites. As the volume fraction of SnF2 increases in the presence of the liquid phase, an evolution of microstructure showing the enhancement in densification is observed. A high relative density (>90%) is obtained for SnF2-based, cold-sintered systems, which can be due to the melting of SnF2, thus forming a liquid phase during cold sintering that enhances the dissolution-precipitation mechanism. Microstructural studies reveal that a certain amount of SnF2 and water enhances the densification in the composite through dissolution–precipitation followed by melting of SnF2. The relative permittivity (εr), dielectric loss (tan δ) and micro-hardness of the xCCTO-(1 – x) SnF2 composite increase from 21.6 to 25.3, from 0.026 to 0.039 and from 3.6 to 5.1 GPa, respectively, with increasing SnF2 content. Further, a comparison of sintering temperature, relative permittivity, dielectric loss and micro-hardness of this system reveals that the 0.8CCTO–0.2SnF2 composite cold-sintered at 150 °C achieves moderate relative permittivity (25.3 at 950 MHz), low dielectric loss (0.039 at 950 MHz) and good micro-hardness (3.6 GPa).

Ultrasound-induced interinhibitive dissolution-precipitation evolution and significantly improved mechanical properties of Kovar/SnSb10 assembly

Ultrasound-assisted Kovar/SnSb10 assemblies are promising candidates for high-precision electronic devices; however, limited research has been conducted on the effect of ultrasonication on its interfacial evolution and mechanical properties. In this study, the microstructure evolution, orientation relationships (ORs), interinhibitive dissolution-precipitation mechanism, and mechanical properties of a Kovar/SnSb10 assembly with/without ultrasonication were systematically investigated. The morphology of the intermetallics (IMCs) evolved from a newly-formed, lash-type to a block-type morphology with an increasing reflow duration, and dentation-type IMCs appeared after ultrasonication. The interfacial IMC without ultrasonication mainly contained FeSn2 and a minority of Ni3Sn2, whereas the strong disturbance caused by ultrasound led to the formation of FeSn in the peripheral FeSn3 and NiSn IMCs. Furthermore, high-resolution transmission electron microscopy (HRTEM) analysis revealed that the ORs of IMC/solder and IMC/Kovar transformed from coherent and semi-coherent to incoherent relationships after ultrasonic treatment. The ORs of the IMC/solder growth front after ultrasonication were [0 1¯ 1]Sn∥[1 1 0]FeSn3, (0 1 1)Sn∥(0 0 1¯)FeSn3 and [0 1¯ 1]Sn∥[5¯ 1 0]NiSn, (0 1 1)Sn∥(0 1¯ 0)NiSn. Additionally, 60 s ultrasonic treatment promoted the growth of IMCs, and increased the ultimate shear strength by approximately 20 MPa, despite the emergence of incoherent interfaces. This phenomenon was primarily attributed to the dispersion strengthening effect of the abundant ultrasound-induced nano-Ni3Sn2 precipitates. This study substantiates the feasibility of ultrasonication-assisted Kovar/SnSb10 assemblies and introduces a novel concept for low-cost, high-efficiency, and high-performance packaging.

The enhanced separation effect of synthesized hydroxyapatite incorporated with ethylenediamine-tetramethylene phosphonic acid for Zn2+ and Co2+ ions and the deep insight into mechanism

Hydroxyapatite (HAP) incorporated with ethylenediaminetetramethylene phosphonic acid (EDTMP) was prepared and used for the separation of the toxic Zn2+ and Co2+ heavy metal ions in an aqueous solution. When the doping amount of EDTMP was 20%, the adsorption capacity of 20ED-HAP composite for Zn2+ and Co2+ reached 229.5 mg/g and 162.4 mg/g, which was 11.0 times and 11.8 times that of synthesized HAP in the absence of EDTMP. The effects of different concentrations of common coexisting ions such as Na+, K+, Ca2+, and Mg2+ were explored, and the removal rate of Co2+ or Zn2+ in a simulated actual water environment was also investigated. The removal of cobalt ions by EDTMP-HAP complex included ion exchange and surface complexation mechanisms. In addition to the above two mechanisms, the separation of zinc ions involved the dissolution precipitation mechanism with the formation of CaZn2(PO4)2·2H2O. Moreover, the affinity between EDTMP and HAP was revealed via Independent Gradient Model based on the Hirshfeld partition of molecular density (IGMH) and Hirshfeld surface analysis. Meanwhile, the interaction mechanism between EDTMP and Co2+ or Zn2+ was explored in depth through Multiwfn wavefunction analysis. The prepared adsorbent could be used as a low-cost potential adsorbent for toxic Zn2+ and Co2+ ions.

Corrosion of glaze in the marine environment: study on the green-glazed pottery from the Southern Song “Nanhai I” shipwreck (1127–1279 A.D.)

The “Nanhai I” shipwreck is an important discovery in the underwater archaeology of China, and many ceramics have been unearthed. These ceramics are important material artifacts of China’s “Maritime Silk Road” and have considerable significance for the study of foreign trade in the Southern Song Dynasty (1127–1279 A.D.). However, these ceramics have been buried in a marine environment for approximately 800 years and have all been corroded to varying degrees, with green-glazed pottery being the most severely corroded. In this study, the chemical compositions of five samples of green-glazed pottery and the corrosion morphology and mechanism of a representative sample were analyzed by optical microscopy, scanning electron microscopy-energy dispersive X‐ray spectrometry (SEM–EDS), Raman spectroscopy, and X-ray diffraction (XRD). Results: The green glaze is a low-temperature silica-aluminum oxide-lead oxide (SiO2-Al2O3-PbO) glaze with copper ions (Cu2+) as the main colorant. The corrosion morphology is characterized by alternating silicon (Si)- and lead (Pb)-rich layers, a sharp reaction interface between the Si-rich layer and the pristine glaze, and a relatively high porosity of the Si-rich gel layer, which is formed by the accumulation of spherical hydrated silica colloidal particles. These features suggest that the glaze was corroded through an interface-coupled dissolution–precipitation mechanism and that the properties of the gel pores controlled the reaction kinetics. Fluctuations in the solution properties at the reaction interface produced the complex morphology of the gel layer, whereas changes in the dryness and humidity of the environment are not essential factors. The samples have been corroding in the marine environment for nearly a thousand years, and explorations of the corrosion morphology and mechanism could provide reference information on the corrosion of various ancient ceramics and glasses and a basis for scientific conservation of these objects.

Monitoring & healing dual channel system designed for continuous glucose monitoring decorated with high-efficient self-healing CuO nanoflakes glucose catalytic electrode

Continuous glucose monitoring (CGM) system provides diabetics with an extremely attractive alternative in controlling blood glucose level. Compared with enzymatic and noble meal-based electrode, copper-based electrode presents a better stability and anti-interference property, which is more suitable to be applied in CGM system for long-term working. The investigation of the failure behavior of copper-based electrode is of vital importance for the application in CGM system. In this paper, the damaged mechanism of copper-based electrode was investigated by analyzing the variation of structure and catalytic properties of CuO nanoflakes (NFs) electrode after long-term working. The results indicated that the main reason for the failure of CuO NFs electrode was structure damage. Copper anodization is an effective electrochemical method to construct the nanostructured film in situ and was used to repair the damaged structure. Based on the damaged mechanism of the copper-based catalytic electrode and the dissolution-precipitation mechanism of copper anodization, a monitoring & healing dual channel (M&H) system decorated with highly efficient self-healing CuO NFs electrode was designed for CGM system. The M&H system enable the monitoring and healing process to be achieved by only adjusting the working potential in the same supporting electrolyte (0.1 M NaOH aqueous), which greatly facilitates glucose measurement and has instructive significance for engineering applications in commercial glucose sensors.

Preparation of nanometer zirconia by hydrothermal method: Influence of temperature and mechanism

Monoclinic (m-ZrO2) and tetragonal zirconia (t-ZrO2) nanoparticles with average grain size of 22.8 nm were synthesized by hydrothermal method using zirconium oxychloride octahydrate (ZrOCl2·8H2O), urea (CO(NH2)2) and deionized water as zirconium source, precipitant, and solvent, respectively. The effects of CO(NH2)2 hydrolysis rate, hydrothermal temperature, and time on the crystal structure, morphology, and grain size were studied. The structure, morphology, grain size, and crystal phase of zirconium oxide (ZrO2) were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Thermogravimetry (TG-DTA), and Fourier Transform Infrared spectroscopy (FT-IR). The results show that the formation mechanisms of different crystal forms can be controlled by the average pH value. The hydrolysis rate of CO(NH2)2 was relatively slow at 120 °C, resulting in a slower rate of OH− production. The lower average pH value favors the formation of m-ZrO2 through the dissolution precipitation mechanism. With the increase of crystallization temperature, the hydrolysis rate of CO(NH2)2 is accelerated, and the average pH value of the solution is increased, which is conducive to the structural rearrangement of [Zr(OH)8(H2O)16]8+ precursor to form tetragonal phase. In addition, the number of defect sites is directly proportional to the crystallization temperature. Extension of crystallization time helps the generation of ZrO2 crystals by polycondensation and directional growth.

New insights into the evolution of TiB whisker and TiC particle during selective laser melting of titanium matrix composites

In-situ TiB, TiC, and (TiB + TiC) reinforced titanium matrix composites were prepared by selective laser melting. We focused on clarifying the evolution mechanism of in-situ TiB whisker and TiC particle. Detailed microstructural characterization and phase diagram analysis revealed that the TiC particles were formed through a dissolution-precipitation mechanism, and the TiB whiskers were predominantly a reaction product. In the hybrid reinforced composite, the reaction product TiB whisker clusters acted as nucleation sites for TiC particles, thereby altering their distribution status. Compressive testing demonstrated that TiB whiskers exhibited a stronger strengthening effect than TiC particles, related to their different spatial distributions. Overall, our findings provide valuable insights into the evolution mechanism of TiB whisker and TiC particle during selective laser melting of titanium matrix composites and have important implications for their design and optimization.

Cold Sintering Process for a BaTiO3/Poly(vinylidene difluoride) Ceramic-Polymer Composite: Evaluation of the Structural and Microwave Dielectric Properties.

The sintering process is essential to transforming particular material into dense ceramics. Although several sintering techniques have emerged over the past few years, the process is still performed at high temperatures. The alternative cold sintering process (CSP) is a potential strategy for producing an advance high dielectric permittivity and enables densification at low temperature. In this process, the CSP technique has been applied to successfully prepare the BaTiO3/poly(vinylidene difluoride) (PVDF) nanocomposite. The inorganic material of the BaTiO3/PVDF nanocomposite was confirmed by various physical characterizations, and the densification studies were performed using a semiautomated press, indicating a dissolution-precipitation mechanism. When a uniaxial pressure of 350 MPa was applied, with transient liquid could be sintered at 190 °C, and a relative density of 94.8%. The nanocomposite exhibits an excellent dielectric properties like εr = 71.1 and tan δ = 0.04 with frequency range at 1 GHz for various dwelling times and maximize the electrical resistivity. The BaTiO3/PVDF composite indicating a breakthrough opportunity toward an increase of the high dielectric constant will be significantly impacted by cold sintering. It enables innovative materials design and integrated devices to advance modern electronic industry applications.