Aluminum Dihydrogen Phosphate Research Articles

3D-Printing Functional Ceramic for One-Step Fabrication of Pd/C Catalytic Reactor

Catalysts are widely used in the chemical industry because of their environmental friendliness and low energy consumption. However, integrated fabrication of catalytic reactors (CRs) remains challenging. In this study, we propose the integrated manufacturing of a palladium-carbon (Pd/C) CR for the first time. The outer shell ink comprises Al2O3 powder and aluminum dihydrogen phosphate (AP), whereas the inner core ink consists of activated carbon powder, AP, and polymethylmethacrylate (PMMA). By integrating with the coaxial 3D printing strategy, the Pd/C CR can be freeform-designed with different core thicknesses, lengths, and shapes (W-type, L-type, and U-type). Based on this, a CR with excellent catalytic properties was further developed by loading palladium (Pd) particles. Typically, the resultant Pd/C CR with a length of 2.5 cm exhibits a catalytic efficiency of up to 97.6% after 60 min. This method of preparing Pd/C CR using coaxial 3D printing combines multimaterial 3D printing, integrated molding, and complex biomimetic structure fabrication. This offers a feasible and cost-effective solution that uses a simple fabrication process.

A green inorganic binder for material extrusion of ultra-low shrinkage and relatively high strength metakaolin ceramics at low sintering temperature

Ultra-low shrinkage and relatively high strength metakaolin ceramics printed by material extrusion were innovatively fabricated using inorganic aluminum dihydrogen phosphate (Al(H2PO4)3) as a binder and low sintering temperature. The optical microscopy, scanning electron microscopy (SEM), electronic vernier caliper, three-point bending test, Archimedes method and X-ray diffraction (XRD) were used to measure and evaluate the surface morphology, microstructure, dimensional shrinkage, flexural strength, porosity and phase composition of the printed ceramics sintered at different temperatures. The results showed that when the mass ratio of metakaolin, Al(H2PO4)3 and deionized water was 17:6:2, the rheological characteristic of the purely green inorganic ceramic slurry was very suitable for material extrusion additive manufacturing, and the corresponding printed ceramic green bodies possessed high-quality formability. The ceramic samples sintered at 750 °C possessed the best whiteness, the lowest shrinkage (<2%), relatively high flexural strength (9.02 MPa). As the sintering temperature increased, Al(H2PO4)3 transformed to aluminum metaphosphate Al(PO3)3, and then decomposed into aluminum phosphate (AlPO4) and phosphorus pentoxide gas (P2O5), which caused pores and reduced strength, and alumina oxide (Al2O3) and silicon oxide (SiO2) in metakaolin gradually transformed to mullite and cristobalite with more stable structure and higher strength.

Discussion on the applicability and mechanism of phosphate-based geopolymers used for cadmium and cadmium-lead heavy metals solidification/stabilization

Lead (Pb2+) and cadmium (Cd2+) are common heavy metal pollution, which is harmful to humans and animals. However, the diffusion rate of heavy metal ions moves faster in acidic environment, there are a large number of acidic heavy metal polluted soil in China, but the conventional binders are not effective to deal with them. Phosphate-based geopolymers (PGEOs) are acidic materials, and have excellence mechanical properties in acidic environment and solidification/stabilization (S/S) effect on Pb2+, but the applicability of PGEOs to Cd, Pb and Cd composite pollution is not clear. Therefore, this study discusses the applicability of PGEOs fabricated from fly ash (FA) and aluminum dihydrogen phosphate (ADP) as activator for S/S treatment of Cd, Pb-Cd composite pollution. Results show that the influence of Cd2+ and Pb2+ on the compressive strength of PGEOs was inconsistent, as the Cd2+ content raised, the compressive strength reduced slightly at 7 and 14 days, but it did not change basically at 28 days. However, the compressive strength rose firstly and then declined with an increase in Pb-Cd content when partial Pb2+ was used to replace Cd2+. The compressive strength of PGEOs with a Pb-Cd content of 0.6 % reached maximum (11.45 MPa), exceeding the compressive strength of PGEOs containing Cd2+. Moreover, the PGEOs presents an excellent stabilization effect on Pb2+, but poor effect on Cd2+. The Pb2+ leaching concentration meet the hazardous solid waste identification criteria (<5 mg/L), but the Cd2+ leaching is high and is more than 1 mg/L. Furthermore, the compressive strength of PGEOs had a good correlation with pH and EC. The S/S mechanism of PGEOs for Pb2+, Cd2+ includes physical adsorption, encapsulation, and chemical precipitation. However, Pb2+ involved in the geopolymerization process, while Cd2+ can not participate in the structure formation, so the PGEOs have a poor S/S effect. Therefore, it needs to be further improved when using PGEOs to stabilize acidic Cd2+ contaminated soil.

Strongly acidic lead contaminated soil solidification/stabilization using metakaolin-modified fly ash phosphoric-based geopolymer

The existing binders are difficult to be compatible with the acidic environment of acidic heavy metal contaminated soil, it is hard to repair acidic heavy metal contaminated soil. In this study, a modified acid phosphorus-based geopolymer (MAPG) binder suitable for the solidification/stabilization (S/S) treatment of acidic heavy metal Pb2+ contaminated soil was fabricated using aluminum dihydrogen phosphate (ADP) as activator, fly ash and metakaolin (MK) as raw materials. The influences of liquid–solid ratio (L/S), MK content, ADP concentration, curing age and leaching environment on the compressive strength, toxic leaching, resistivity, pH and EC of MAPG stabilized acidic Pb2+ contaminated soil were studied. Meantime, the X-ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, and mercury intrusion (MIP) experiments were used to study the chemical properties and microscopic performance of MAPG treated acidic Pb2+ contaminated soil. The results showed that the MAPG binder prepared from MK had an excellent S/S effect on the acidic Pb2+ contaminated soil, and the MAPG binders had good compatibility with the acidic environment. The compressive strength of each group of MAPG stabilized soil could meet the strength standard (>350 kPa) for solid waste landfill and Pb2+ leaching concentration is < 5 mg/L for toxicity identification criteria after 7 days of curing. With an increase in curing age, the strength of stabilized acidic contaminated soil decreased slightly, but the strength still met the requirements of landfill strength standard after 28 days of curing. In three different leaching environments, the Pb2+ leaching decreased with an increase in curing age. Microscopic analysis showed that the main crystalline compounds in stabilized contaminated soil were potassium feldspar, Berlinite and lead phosphate compounds, and their contents were related to L/S, MK content, ADP concentration, and curing time. Potassium feldspar, berlinite, and lead phosphate compounds could not only fill pores, but also had physisorption, encapsulation and chemical precipitation effects on Pb2+. The study could provide an economical, environmental friendly and efficient binder for the remediation of acidic Pb2+ contaminated soil, but the further investigation into the long-term effectiveness of the MAPG binder or its applicability to other types of contaminated soil is also needed.

MODIFICATION OF SODIUM HUMATE WITH ALUMINUM DIHYDROPHOSPHATE DEPENDING ON TIME AND THE RATIO OF SOLID AND LIQUID PHASES

Due to their high chemical activity, humic compounds participate in various reactions. A large number of functional groups opens up wide possibilities for the humic compounds chemical modification. Most studies on the modification of humic substances are focused on studying the structure of humic substances, as well as on the factors influencing the completeness of the release of one humic substances fraction. The purpose of the work is to study the patterns of modification processes of sodium humate with aluminum dihydrogen phosphate, to determine the composition and properties of the resulting organomineral composite materials. Methods. Chemical analysis, infrared spectroscopy, X-ray analysis. Results and discussion. The composition and properties of organo-mineral composite materials obtained by conversion of sodium humate with aluminum dihydrogen phosphate have been determined. With an increase in the S:L ratio from 1:0.5 to 1:1.5, the yield of humic compounds increases from 15.62 to 21.92%, and the amount of phosphorus and nitrogen, on the contrary, the S:L=1:1.5 decreases, that is, the amount of phosphorus decreases from 37.51 to 32.19%, and the amount of nitrogen decreases from 1.78 to 1.11%. This is due to the improvement of diffusion conditions by reducing the medium viscosity and increasing the rate of primary components interaction. And the reduction in the amount of nitrogen occurs due to a decrease in ammonia consumption due to the humic substances neutralizing ability. Conclusion. It has been shown that the conversion of humic compounds with aluminum dihydrogen phosphate leads to a change in its composition and properties; the resulting products are enriched with phosphorus and nitrogen, and have good physicochemical and physicomechanical properties. After the macromolecules of humic compounds modification with aluminum dihydrogen phosphate, the number of oxygen-containing functional groups increases as a result of which the ion-exchange, complexing, sorption, detoxification and growth-stimulating properties is observed.

Comparative study on the preparation of phosphate-based geopolymers using different activators

Fly ash has the potential to be used as the precursor in the acid-activated geopolymer preparation, fly ash can react with phosphorus-containing activators to form geopolymers, but different types of activators present different activation effects on fly ash. In this study, common liquid phosphoric acid (PA), liquid aluminum dihydrogen phosphate (ADP), solid sodium dihydrogen phosphate (SDP) and solid potassium dihydrogen phosphate (PDP) are used as a single-component or composite activators and fly ash as raw material to prepare phosphate-based geopolymers (PGEOs). The effect of different activators on setting time, pH, electrical conductivity (EC) and compressive strength of PGEOs were assessed. Moreover, the activation mechanism of different activators on fly ash was revealed by using X-ray diffraction, Fourier transform infrared spectroscopy, Mercury Intrusion Porosimetry, X-ray Photoelectron Spectroscopy and Scanning Electron Microscopy-Energy Dispersive Spectroscopy. The results showed that geopolymer prepared using ADP exhibited the highest compressive strength among the different activators, but combining ADP and PA would prolong setting time. However, the unreacted SDP and PDP particles were detected in geopolymers activated by PA+SDP and PA+SDP composite activator due to insufficient geopolymerization. Nonetheless, combining PDP or SDP with PA as composite activator is more effective than the single-component PDP or SDP activator in improving compressive strength. The pH values of the geopolymers increased with the curing time while EC showed a decreasing trend which was independent of the activator type. AlPO4 phase was found in all samples, and Al-containing phases are the main strength-given component of PGEOs.

High temperature performance of high magnesium nickel slag based geopolymers with different P/Al molar ratios prepared by acidic activator

This study uses high magnesium nickel slag (HMNS) directly as a raw material, to prepare high-temperature-resistant HMNS silico-aluminophosphate geopolymer (HMNSGP) activated by different types of acid activators including Al(H2PO4)3, H3PO4 and KH2PO4. By using characterization techniques such as XRD, FTIR, SEM-EDS, and MIP, the micro-properties, pore structure, and reaction mechanism of HMNSGP were investigated. The high temperature resistance of HMNSGP was evaluated by comparing compressive experiments before and after high temperature and TG-DSC. The results showed that the best samples were prepared using aluminium dihydrogen phosphate (ADP) at a P/Al molar ratio of 0.6. At room temperature, the main phases geopolymerized of the sample are crystalline products (Newberyite) and amorphous hydrated products (-Si-O-P-O-Si-, -Al-O-P-O-, -Si-O-Al-O-Si- and -P-O-Mg-). At 1200 °C, HMNSGP can still maintain its integrity, and its compressive strength can be increased to 48.4 MPa. The HMNSGP prepared using H3PO4 has the same hydration products as the optimal samples, but the lower amount of gel phase causes spallation at high temperatures. Besides primary phases geopolymerized with ADP as activator, the KH2PO4 sample includes crystalline products (K-struvite). However, this phase decomposes at 207 °C, affecting its high-temperature resistance while a significant volume shrinkage occurs at 1200 °C. In summary, using ADP with a P/Al molar ratio of 0.6 can directly prepare HMNS into an environmentally friendly refractory geopolymer material, the compressive strength shows stable growth after being exposed to 1200 °C. This results suggested that HMNSGP prepared with ADP can be used for structural applications, laying the foundation for future replacement of refractory cement.

Preparation and High-Temperature Resistance Properties of Phenolic Resin/Phosphate Hybrid Coatings.

In this study, a novel fabrication method was used to synthesize phenolic resin/phosphate hybrid coatings using aluminum dihydrogen phosphate (Al(H2PO4)3, hereafter denoted as Al), SC101 silica sol (Si) as the primary film-forming agent, and phenolic resin (PF) as the organic matrix. This approach culminated in the formation of Al+Si+PF organo-inorganic hybrid coatings. Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) results confirmed the successful integration of hybrid structures within these coatings. The crystalline structure of the coatings post-cured at various temperatures was elucidated using X-ray diffraction (XRD). Additionally, the surface and cross-sectional morphologies were meticulously analyzed using scanning electron microscopy (SEM), offering insights into the microstructural properties of the coatings. The coatings' porosities under diverse thermal and temporal regimes were quantitatively evaluated using advanced image processing techniques, revealing a significant reduction in porosity to a minimum of 5.88% following a thermal oxidation process at 600 °C for 10 h. The antioxidant efficacy of the phosphate coatings was rigorously assessed through cyclic oxidation tests, which revealed their outstanding performance. Specifically, at 300 °C across 300 h of cyclic oxidation, the weight losses recorded for phosphate varnish and the phenolic resin-infused phosphate coatings were 0.15 mg·cm-2 and 0.09 mg·cm-2, respectively. Furthermore, at 600 °C and over an identical period, the weight reduction was noted as 0.21 mg·cm-2 for phosphate varnish and 0.085 mg·cm-2 for the hybrid coatings, thereby substantiating the superior antioxidation capabilities of the phenolic resin hybrid coatings in comparison to the pure phosphate varnish.

Rapid, Direct Fabrication of Thermochromic Ceramic Composite Sensors via Flash Lamp Annealing

An inorganic, high‐temperature (≈600 °C) thermochromic sensor is synthesized from a chemically bonded ceramic composite. The ceramic composite is composed of thermochromic 10 wt% chromium‐doped alumina (Cr:Al2O3) powder blended with a low‐reacting temperature (around 250 °C) phosphate binder, Al(H2PO4)3, (aluminum dihydrogen phosphate [ADP]). Cr‐doped alumina exhibits thermochromism at high temperatures, typically around 500–600 °C. Previously, infrared (IR) irradiation has been used to successfully convert ADP to an aluminum phosphate (AlPO4) ceramic phase that can bind ceramic components together. Here, an ultrahigh‐power (tens of kilowatts per square centimeter) flash lamp annealing (FLA) system is evaluated as an alternative photonic heating process to rapidly transform ADP to this ceramic. While IR lamps require 30 min to fully transform the ADP binder, FLA processes require less than 1 min and provide more dense microstructures, opening opportunities to additively manufacture ceramic components without the need for a post‐processing heating step. Final ceramics exhibit reversible thermochromic behavior, transitioning from pink to dark gray as the temperature increases from 25 to 600 °C. Here, the ability to use this technology to fabricate a temperature warning system for heated objects that are not yet emitting significant visible black‐body radiation is demonstrated.

Coaxial 3D printed Al2O3 ceramic continuous-flow fixed-bed reactor with bionic core-shell structure

Continuous-flow fixed-bed reactors (CFBR) have attracted considerable attention owing to their high efficiency and low energy consumption; however, the integrated fabrication of CFBR with core-shell structures remains a great challenge at present. Herein, a facile coaxial three-dimensional (3D) printing strategy was developed for the first time to rapidly and efficiently construct a CFBR with Al2O3 powder and aluminum dihydrogen phosphate (AP) as the outer shell ink, and Al2O3 powder, AP, and polymethyl methacrylate as the inner core ink that is extruded through a customized coaxial needle. Coaxial 3D printing realizes the integral fabrication of ceramic shells and inner porous ceramic carriers. CFBR with an outer wall thickness of 1.2 mm, core diameter of 3.7 mm, and variable length were fabricated, which were enabled with excellent catalytic properties by simply impregnating precious metal particles. The catalytic efficiencies for the reducing of 4-nitrophenol (4-NP) in the 3-cm-length Pd/CFBR, Pt/CFBR, and Ag/CFBR were found 96.9 %, 97.4 %, and 93 % after 10 min, respectively. Combining integrated fabrication, rapid prototyping, and complex architecture formation, coaxial 3D printing provides a novel strategy for directly integrating multifunctional CFBR.

The effect of the preparation method of asphalt waste foam ceramic loaded Pd/Ce-P-Al2O3 coatings on their properties

Asphalt waste-based foam ceramics were prepared by organic foam impregnation, followed by ultrasound-assisted impregnation and calcination to deposit 3-5 wt.% Pd/Ce-P-Al2O3 active coatings. The results show that γ-Al2O3 as an aluminum source provides a higher specific surface area and facilitates the dispersion of the catalytic components, so that low-temperature conversion of CO can be achieved, but the coating uniformity, stability, and the ability to modify the defects on ceramic surfaces are lower than those of the aluminum nitrate calcination products. Aluminum dihydrogen phosphate as a P source could rapidly convert 60% of CO, but the performance decreased at a later stage, while phosphoric acid as a P source could achieve the complete conversion of CO at a lower temperature. The mechanical properties of the samples with the addition of aluminum dihydrogen phosphate and aluminum nitrate baked products were better, which was 0.6 MPa higher than the uncoated foam ceramics.

Research on structural strengthening technology for regenerative denitration catalysts.

The cost of replacing failed selective catalytic reduction (SCR) catalysts and their disposal as hazardous solid waste is high. If failed catalysts are recovered and regenerated into new SCR denitration catalysts, the cost of flue gas denitration can be effectively reduced. However, regenerated SCR catalysts have relatively low structural strength and activity and cannot yet form an effective replacement. In this study, aluminum dihydrogen phosphate, aluminum nitrate, and aluminum sulfate were used as structural strengthening agents in the regeneration of SCR catalysts, and over-impregnation, drumming-assisted impregnation, and ultrasonic-assisted preparation techniques were compared. The corresponding regenerated SCR catalysts were then prepared and analyzed for compressive strength, wear strength, H2-TPR, NH3-TPD, and in situ IR. Factors influencing the structural strength, physical properties, and catalytic activity of the regenerated catalysts were investigated. The best results were obtained as follows: compressive strength of 4.57 MPa, wear rate of 0.088% kg-1, and denitration of 58% after 10 min of drumming-assisted impregnation in an aluminum sulfate solution with a concentration of 16%. Based on this, a synergistic method for catalyst activity and structural strengthening was explored to support the design of better SCR catalysts for regeneration.

Enhancement mechanical properties of phosphoric-based geopolymer using aluminum dihydrogen phosphate

Phosphoric acid-based geopolymer (PGEO) is a acidic material, but the low strength and poor stability for the geopolymer synthesized with using fly ash limits its application and development. In this article, the aluminum dihydrogen phosphate (ADP) was introduced to form a composite activator to strengthen the mechanical strength of PGEOs synthesized from fly ash, and its hydration heat, workability, compressive strength, electrical conductivity (EC), and pHs were investigated, also the chemical and microscopic mechanism were also revealed. The results show that the geopolymerization heat was reduced after incorporating ADP activator. The workability were affected by the ADP content, the introduced ADP activator could improve the strength and long-term stability of PGEOs, and no compressive strength loss was found for the prepared geopolymer. The compressive strength reduced with EC raised with pH and, the Al–P existed in Al[OSi(P)]4 environment, and the geopolymer matrix composed of amorphous gels and crystalline compounds.

A green phosphate-based geopolymer adsorbent or binder with high specific surface area for environmental applications

High water content mud has complex chemical composition and high water content, making it difficult to be directly utilized in engineering. However, its high clay content, small particle size, and large specific surface area may make it possible to prepare a adsorbent or binder with high specific surface area for environmental applications. This study attempts to prepare a phosphate-based geopolymer (PGEOs) adsorbent or binder with high specific surface area using aluminum dihydrogen phosphate as the activator, high water content mud powder and fly ash as raw materials. The microstructure of PGEO was invsetigated using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and N2 adsorption/desorption experiments. The results showed that the PGEOs belong to mesoporous materials, and has the maximum strength (9.06 MPa) at 28 days when the mud powder content was 10 %. Moreover, the specific surface area of the PGEO increased significantly with an increase in mud powder content, at 7 days of curing, when the mud powder content increases to 50 %, and the specific surface area increased from 42.074 m 2/g to 311.660 m2/g. which are significantly higher than many existing adsorbents. Therefore, the PGEOs prepared with mud powder and fly ash has great potential in pollutant adsorption and solidification/stabilization treatment in future.

Fabrication of carbon fiber reinforced aluminum matrix composites by inorganic binders

Infiltration is an important issue for unidirectional carbon fiber-reinforced aluminum matrix (CF/Al) composites. In the present study, aluminum dihydrogen phosphate (ADP) and silica sol were used to prepare CF preforms, then CF/Al composites were prepared by simulated horizontal continuous casting. The results showed that silica sol significantly affects the curing process of ADP. When the content of silica sol is 50 % and heated at 500 °C, the product transformed from Al(PO3)3 (cubic system) to an amorphous phase with good thermostability. The mixture binder can fully fill the gaps between CFs, leading to a dense CF preform. The obtained CF/Al composite has a good bonding interface between Al and CFs, without pores or crack defects, and thus shows an obvious enhancement in tensile strength of 64.9 MPa, which is 34.6 % improved compared with that of CPAl. The CF/Al composites also maintained a good electrical conductivity of 56.9 % IACS, similar to that of CPAl.

Analysis of the properties of chemically bound phosphate ceramics (CBPCs) produced from metakaolin with various acid phosphates

In this study, chemically bound phosphate ceramics (CBPCs), a type of geopolymer, were synthesized by reacting metakaolin (MK) with acidic solutions of phosphoric acid (PA), potassium dihydrogen phosphate (KDP), calcium dihydrogen phosphate (CDP), and aluminum dihydrogen phosphate (ADP). The obtained CBPCs were characterized using thermal analysis (DTA-TG), X-ray diffraction, dilatometry, and scanning electron microscopy and by their real density, porosity, water absorption, and compressive strength. The analyses revealed that the used acid phosphate type strongly influenced the properties of the resulting CBPCs. The best compressive strength results were found in CBPCs obtained using ADP, with an average value of 34.50 MPa and average porosity of 23.21%. For CBPCs obtained from PA, CDP, and KDP, the average compressive strength values were 14.18, 8.17, and 2.84 MPa, respectively; their average porosities were 18.79%, 36.23%, and 37.90%, respectively. The results demonstrate that CBPCs produced with MK can be cured at room temperature and that CBPCs obtained with ADP have higher compressive strength values than these of the other acids.

Surface adsorption strategy enables bright green light-emitting Cs4PbBr6 nanocrystals@Al(H2PO4)3 phosphor for solid-state lighting

Inorganic phosphate materials possess intriguing structural features which facilitate the smooth nucleation-growth and adsorption of light-emitting perovskite nanocrystals onto its surface. However, finding a suitable phosphate material and a proper method for growing halide perovskite (HP) nanocrystals (NCs) onto the surface of it is a tedious task due to the soft ionic nature of HPNCs. In this work, the spherical composite structures of Cs4PbBr6 NCs@AlP [AlP = aluminium dihydrogen phosphate, Al(H2PO4)3] are developed via nucleation and growth of Cs4PbBr6 NCs on the surface of AlP. The inherent adsorption capability of AlP opens up the possibility of adsorption of CsBr and PbBr2 on the large area surface of AlP, facilitating the nucleation-growth of Cs4PbBr6 NCs on the surface of bulk AlP. The synthesized Cs4PbBr6 NCs@AlP composite exhibits brighter green emission and enhanced humid stability than the bare one. As-a-proof of concept, we demonstrate intensive green LED fabricated by combining the synthesized phosphor, Cs4PbBr6 NCs@AlP with near-ultraviolet InGaN chip (λem = 395 nm). This work paves a new way for synthesizing spherical composite having long-term stability for optoelectronic devices.

Industrial-scale fabrication of FeSiCr magnetic powder cores with high magnetic permeability and low loss

FeSiCr magnetic powders is the key raw material for inductive components such as molding choke and power factor correction (PFC) inductors. In this paper, the industrial-scale insulation coating process of high-performance FeSiCr soft magnetic powder cores (SMPCs) were studied by using mature and environmentally friendly silica sol (SiO2), aluminum dihydrogen phosphate solution (AHP), glass powders (GP), and phosphoric acid (PA) as insulators and water-soluble sodium silicate (NSO) as an inorganic binder, respectively. A comprehensive analysis of the SEM, EDS, and XPS results showed that the surface insulation layer uniformity of the four coating powders is poor due to the irregular morphology of the FeSiCr powder, with the glass powder having the worst coating uniformity due to partial agglomeration occurring in mechanical mixing. The four coated powders all had high saturation magnetization (173.1–176.5 emu∙g−1), in which the chemical reaction of FeSiCr in the phosphoric acid coating process consumed Fe atoms, resulting in the lowest Ms of the powders in the several coating processes. At the corresponding optimum heat treatment temperature, the FeSiCr@SiO2 @NSO SMPCs had the highest permeability of 96.1, while the FeSiCr@PA@NSO SMPCs had the lowest at 75.5, due to the phosphoric acid consuming part of the ferromagnetic material and the loose porous structure of the phosphate layer further reducing the density of SMPCs. The total losses of the four powder cores are low (228.9–259.2 mW·cm−3, 100 Gs, 1000 kHz), while loss separation and experiments with different pressing tonnages showed that the eddy current losses of SMPCs was higher than the hysteresis losses, which was caused by the irregular morphology of FeSiCr powders. The FeSiCr@SiO2 @NSO SMPCs exhibit optimum corrosion resistance due to the uniform coating of the SiO2 nano-insulating layer on the powders surface as a result of the strong bonding of the silica sol with FeSiCr. As can be seen, FeSiCr@SiO2 @NSO SMPCs prepared using silica sols have very high saturation magnetization, very high permeability, low core loss, and good corrosion resistance compared to the other three insulation processes and can be industrially produced on a large scale, offering great application prospects in the field of high current and high frequency.

Industrial-scale fabrication of amorphous magnetic powder cores with excellent high-frequency magnetic properties: Optimization for kinds and content of insulating agents

Based on the powder metallurgy method, FeBSiC amorphous powders were produced by a novel gas-water combined atomization process and were co-coated by five kinds of insulating agents (polyamide, aluminum dihydrogen phosphate, calcium phosphate, zinc phosphate and hydrochloric acid) and epoxy resins. The content of each insulating agents was optimized to improve the magnetic properties of the amorphous magnetic powder cores (AMPCs). The results showed that the FeBSiC powders showed extremely high saturation magnetization (171.1 emu·g–1) and low coercivity (6.11 Oe), which could provide excellent raw materials for AMPCs. Among the five insulating agents, the polyamide-coated AMPCs had the worst electrical insulating effect and magnetic properties. Although the AMPCs coated with aluminum dihydrogen, zinc phosphate, calcium phosphate and hydrochloric acid all exhibited low eddy current losses, only the AMPCs coated with calcium phosphate exhibited extremely low hysteresis losses. As the calcium phosphate content increased, the density and resistance of the AMPCs both increased and then decreased, and the core losses decreased and then increased. When the calcium phosphate content was 0.5 wt.%, the FeBSiC@ calcium phosphate + epoxy resins core-shell structured AMPCs had high permeability of 28.1 ± 0.3, high DC bias% of 96.1 ± 0.2 at a DC magnetic field of 5671.5 A·m–1, and low core loss of 18.0 ± 0.8 kW·m–3 at 100 kHz and 0.02 T, which showed excellent magnetic properties at high frequency and confirmed to the current development trend of miniaturization, high-frequency and high-efficiency in electrical and electronic fields.

Organic-inorganic in-situ hybrid aluminum dihydrogen phosphate binder for enhancing tribocorrosion resistance of ceramic coatings

Aluminum dihydrogen phosphate (AP) is modified through organic-inorganic in-situ hybridization and employed as a binder to prepare the chemically bonded phosphate ceramic coatings on AISI 304 L stainless steel. The chemical structure of the hybrid AP binder, mechanical properties and tribocorrosion behavior of the hybrid AP coatings (HAPC) are investigated. The results demonstrate that AP is successfully hybridized with methyltriethoxysilane (MTES) and a chemical structure with P-O-Si as the framework is created. The hybrid AP as a binder improves the hydrophobicity, cohesion and bonding strength of ceramic coatings. In addition, the corrosion current density and total material volume loss of HAPC are lower than those of pure AP coatings, whether under pure corrosion or tribocorrosion. In tribocorrosion experiments, the pure mechanical wear and the wear induced by corrosion dominate the total volume loss of the coating. The filamentous substances generated inside the HAPC enhance the pull-out resistance of the alumina particles and the cohesion of coatings, which can reduce the purely mechanical wear behavior. Besides, the filamentous substances can also fill the holes and cracks inside the coating, extending or blocking the diffusion path of the corrosive medium, which can significantly reduce the friction behavior generated by corrosion induction. Based on these two aspects, the hybrid AP binder effectively enhances the tribocorrosion resistance of ceramic coatings.