Amorphous Core Research Articles

Effect of WEDM Electrical Parameters on Micro-morphology and Magnetic Properties of Stacked Amorphous Iron Cores

Effect of WEDM Electrical Parameters on Micro-morphology and Magnetic Properties of Stacked Amorphous Iron Cores

Local adaptive insulation in amorphous powder cores with low core loss and high DC bias via ultrasonic rheomolding

Amorphous powder cores are promising components for next-generation power electronics. However, they present inherent challenges of internal air gaps and stresses during cold compaction, which significantly deteriorate soft magnetic properties. Here, we report the formation of a local adaptive insulation structure of biconcave lens in amorphous powder cores by ultrasonic rheomolding. Consequently, compared with conventional cold-compacted powder cores, the ultrasonic rheomolded powder cores offer significant simultaneous improvements in the permeability from 31.3–32.4 to 41.8–43.3 and the direct-current bias performance from 69.4–69.7% to 87.4–87.8% (7960 A/m), thereby overcoming the trade-off between permeability and direct-current bias performance. In particular, their core losses are as low as 13.73–15.45 kW/m3, approximately one twentieth of that of the cold-compacted powder cores (282.84–304.03 kW/m3) at a magnetic field of 100 mT and 100 kHz. The biconcave-lens insulation structure can effectively buffer the impact of high mechanical stress on the magnetization of magnetic powder particles, allowing for the ultrasonic rheomolded powder cores to maintain better magnetization efficiency and consequently resulting in excellent soft magnetic properties under the cooperative effect of very low internal stresses and low porosity. The ultrasonic rheomolded powder cores can be used as alternative core components in next generation miniaturized power electronics.

FeSiBCuNbZr amorphous composites decorated with SiO2 and TiO2(B) (bronze phase TiO2) for efficient electromagnetic wave absorption

The application of Fe-based amorphous microspheres in high-performance electromagnetic wave absorbing materials is significantly limited by a single loss mechanism. Utilizing interfacial engineering and magnetic-dielectric synergistic effect is a viable approach to enhance microwave absorption. In this work, FeSiBCuNbZr amorphous microspheres were synthesized using single copper roller melt-spinning method and ball mill method. The finding reveals that the incorporation of SiO2 and TiO2(B) (bronze phase TiO2) shells notably enhances polarization loss and conductive loss. FeSiBCuNbZr@SiO2@TiO2(B) amorphous composites exhibited a minimum reflection loss value of −64.89 dB at a thickness of 2.17 mm and an effective absorption bandwidth (EAB) of 8.08 GHz covering 9–18 GHz at a thickness of 1.9 mm. The exceptional wave absorption performance is ascribed to the combined effect of magnetic loss in the FeSiBCuNbZr amorphous core and dielectric loss from the double-shell structure, while maintaining favorable impedance matching. This work provides a new core–shell FeSiBCuNbZr amorphous composites for efficient electromagnetic wave absorption.

Electroless Deposition of Noble Metals on Rod-Shape Plant Viruses in Various Aqueous Metal Precursor Solutions.

The challenge of synthesizing noble metal nanostructures sustainably has encouraged researchers to explore biological routes for nanostructure production, such as biotemplating. Plant viruses with rod-shape morphology, such as tobacco mosaic virus (TMV) and barley stripe mosaic virus (BSMV), offer promising biotemplates to produce metal nanorods. TMV and BSMV can be incubated in aqueous metal precursor solutions to mineralize metals on the coat proteins (CPs) of the viruses. Previous studies have primarily examined palladium (Pd) mineralization on TMV and BSMV using Na2PdCl4 as the Pd precursor. There is limited scientific literature on the effect of using alternative Pd precursor solutions besides Na2PdCl4 such as K2PdCl4 and PdCl2 to mineralize Pd on TMV and BSMV. Past attempts at mineralizing other noble metals such as platinum (Pt) and gold (Au) required an initial layer of Pd to be deposited on the TMV and BSMV biotemplates. In this study, we aimed to expand the understanding of using alternative Pd precursor solutions to mineralize Pd on TMV and BSMV. Additionally, the deposition of Pt and Au onto TMV and BSMV without the need for an initial Pd mineralization layer was achieved using alternative Pt and Au precursors, including K2PtCl4 and AuCl3, respectively. Pd, Pt, and Au were successfully deposited on TMV and BSMV by incubation in aqueous solutions of Na2PdCl4, K2PdCl4, PdCl2, K2PtCl4, and AuCl3. Kinetic studies were also conducted using ultraviolet-visible (UV-vis) spectroscopy to examine the rates at which Pd, Pt, and Au precursor ions were reduced during the mineralization process, mimicking their adsorption onto TMV and BSMV CPs. BSMV adsorbed noble metal precursor ions faster than TMV as determined by UV-vis spectroscopy. While palladium nanorods (PdNRs) offer high electrical conductivity desirable for electronic applications, Pd-coated TMV and BSMV may face limitations due to their organic cores, potentially compromising conductivity. To address this, one approach is to convert the organic core into conductive amorphous carbon through thermal annealing. In this study, in situ transmission electron microscopy was utilized to thermally anneal Pd-TMV2Cys, thereby transforming them into PdNRs with amorphous carbon cores.

Wire-arc directed energy deposition of oxide-modified H13 steel: Microstructural characterization and mechanical properties

The preparation of H13 steel using wire-arc directed energy deposition has broad application prospects; however, the high hardenability of H13 steel makes it prone to forming cold cracks during deposition, thus limiting its further applications. Fortunately, the oxide metallurgy technology holds promise in addressing this issue. Specifically, nano oxides have the capability to refine the grain and facilitate the formation of intracrystalline ferrite, ultimately resulting in an improvement in steel's toughness and subsequently mitigating its propensity towards cold cracking. In this study, H13 steel wires, incorporating Al-Si-Ti composite oxides, were used to deposit part (W-O-H13) with excellent performance and no cold cracks. Owing to the special thermal cycling during wire-arc directed energy deposition, a periodic build unit was formed that could be roughly divided into three zones, namely, fine grain, columnar grain, and heat-affected zones. The microstructure of the parts contained lath martensite, high-alloy martensite, and ferrite. After arc exposure, the oxide formed a complex core-shell structure, with vanadium carbide (VC) encapsulating the amorphous oxide core. Moreover, the oxide particles refine the grain structure and induce the formation of ferrite, thereby enhancing the toughness of the part and further improving its strength and wear resistance. The low mismatch between the VC thin layer wrapping the oxide and ferrite was a crucial factor in the conductive ferrite phase transformation. Additionally, the elemental segregation caused by the rapid cooling rate ultimately led to the formation of high-alloy martensite having a maximum hardness of 5.32 GPa. The results reveal that the average tensile strength of W-O-H13 steel in the X, Y, and Z directions is improved by 21.0 %, 20.3 %, and 14.3 % respectively, compared to the parts fabricated solely from H13 steel wire without the addition of oxide (W-H13). Additionally, the impact toughness of W-O-H13 steel surpasses W-H13 steel in all three directions, achieving an average of 33, 27, and 28 J/cm2 respectively in the X, Y, and Z axes. In comparison to W-H13, the impact toughness of W-O-H13 has witnessed a substantial increase ranging from 10 % to 30 %. Furthermore, the wear resistance of W-O-H13 steel significantly surpasses that of W-H13 steel, particularly under high-temperature wear conditions. Specifically, the average wear volume of W-O-H13 steel at temperatures ranging from 400 to 600 °C is merely 0.163 and 0.224 mm³, representing only 30 % and 40 % of the wear volume exhibited by W-H13 steel under the same wear conditions.

Design of a high‐frequency transformer based on amorphous cut cores for insulation breakdown testing

AbstractInnovative test methods are required to keep up with the increased demand for insulation materials which can withstand the high‐frequency square‐wave voltages generated by power‐electronic equipment. Test systems using high‐voltage, high‐frequency transformers have proven versatile and easy to realise. The authors investigate the application of amorphous cut cores in such transformers. Analytical and numerical models for the transformer and its frequency response are developed, aiding the design process. An amorphous core‐based transformer is designed for 8 kVpk output at 100 kHz and compared to two previous designs based on ferrite cores. The frequency and pulse response, as well as the high‐voltage and thermal performance, are evaluated. The comparison shows that while the low parasitics of the amorphous‐based transformer allow for superior frequency response, they are unsuitable for long‐duration tests with high pulse repetition frequencies (25–100 kHz) due to increased core losses. The partial discharge inception and flashover voltage are comparable to the ferrite‐based transformers.

Carbon Dots in Enantioselective Sensing.

Chirality has a crucial effect on clinical, chemical and biological research since most bioactive compounds are chiral in the natural world. It is thus important to evaluate the enantiomeric ratio (or the enantiopurity) of the selected chiral analytes. To this purpose, fluorescence and electrochemical sensors, in which a chiral modifier is present, are reported in the literature. In this review, fluorescence and electrochemical sensors for enantiorecognition, in which chiral carbon dots (CDs) are used, are reported. Chiral CDs are a novel zero-dimensional carbon-based nanomaterial with a graphitic or amorphous carbon core and a chiral surface. They are nanoparticles with a high surface-to-volume ratio and good conductivity. Moreover, they have the advantages of good biocompatibility, multi-color emission, good conductivity and easy surface functionalization. Their exploitation in enantioselective sensing is the object of this review, in which several examples of fluorescent and electrochemical sensors, containing chiral CDs, are analyzed and discussed. A brief introduction to the most common synthetic procedures of chiral CDs is also reported, evidencing strengths and weaknesses. Finally, consideration concerning the potential challenges and future opportunities for the application of chiral CDs to the enantioselective sensing world are outlined.

Preparation of low-loss amorphous soft magnetic powder cores by joint coating of resin and ZnO nanoparticles

Preparation of low-loss amorphous soft magnetic powder cores by joint coating of resin and ZnO nanoparticles

Accurate calculation of losses in amorphous alloy cores based on a dynamic Jiles-Atheron model under wide frequency and variable temperature operating conditions

The stator core of the high-speed amorphous alloy permanent magnet synchronous motor(HSAAPMSM）experiences significant temperature fluctuations due to exposure to a high-frequency alternating magnetic field. We introduce the dynamic Jiles-Atheron(J-A) model under wide frequency and variable temperature operating conditions to achieve accurate modeling for stator core loss. In contrast to previous modeling techniques, this approach does not rely on amount of experience data and laborious parameter identifications. The adaptive chaotic dung beetle optimization algorithm is applied to improve the effectiveness of parameter identification. The temperature-dependent static J-A model is modified into a dynamic J-A model by combining the field separation approach with the Riemann-Liouville (R-L) fractional derivative theory to enable the model's application under high-frequency operating circumstances. Finally, the model described in this study is verified through experimentation and can be used to precisely calculate the loss of amorphous alloy cores.

Amorphous Core Distribution Transformer with Improved Efficiency and Low Loss for Power Sector Application

The amorphous transformer (AMTD) is an energy-efficient transformer that minimizes both airborne pollutants and the amount of energy required to create power. This research investigates the use of amorphous material in transformer construction rather than the usual silicon steel core. It outperforms silicon steel in terms of magmatic characteristics. Because of its high resistivity and low thickness, adopting amorphous as a transformer core instead of a traditional transformer can eliminate 70% of transformer no load losses. When deciding which transform to install and use in the electrical network, the total prices of silicon steel and amorphous steel are considered. The total owed cost (TOC) of any specific transformer is calculated by discounting future transformer losses (losses from both load and no load) to present value and leveling them across the transformer's lifetime. The characteristics of amorphous and conventional electrical cold-rolled grain-oriented(CRGO) materials were evaluated. Amorphous metal is a special type of alloy with an irregular molecular arrangement rather than a well-organized crystalline structure. Amorphous metal can be utilized for the transformer core to increase transformer efficiency. The material's increased magnetic characteristics and physical dimensions lead to much lower hysteresis and eddy current losses. Using amorphous metal cores can minimize transformer core loss by more than60 percent. High power-density transformers are in high demand in many applications where weight and available space are severely constrained, such as power electronics. While electromagnetic device weights and sizes normally decrease at higher frequencies, core loss may increase considerably.

Co-hydrolysis of TEOS and DDS to obtain a modified hydrophobic SiO2 insulation layer for FeSiBC amorphous magnetic powder core with low energy loss

The hysteresis effect and eddy currents caused by alternating magnetic fields greatly impede the improvement of the working efficiency and performance stability of soft magnetic powder cores. In this work, modified hydrophobic SiO2 nanoparticles were prepared by tetraethyl orthosilicate (TEOS) and dimethyl-diethoxy-silane (DDS) as co-precursors through sol–gel methods. The effect of different proportions of DDS and TEOS on the amorphous magnetic powder cores performance was studied. It was demonstrated that the insulation layer in DDS and TEOS co-precursors hydrolyzed composite powders exhibited more uniform distribution compared with TEOS hydrolyzed alone counterpart. The introduction of methyl groups reduced the accumulation of hydrolysis intermediates on the surface of FeSiBC powders. Furthermore, the addition of DDS reduced eddy current loss significantly with a low hysteresis loss. The total energy loss of the DDS and TEOS co-hydrolysis powder core were reduced by 16.1 % and 7.7 % at 1 MHz, 0.05 T compared to the uncoated powder core and the TEOS hydrolysis alone counterpart, respectively. The presented results provide insights into improving the application range and energy utilization efficiency for the magnetic powder cores.

Easy Synthetic Access to High‐Melting Sulfurated Copolymers and their Self‐Assembling Diblock Copolymers from Phenylisothiocyanate and Oxetane

AbstractAlthough sulfurated polymers promise unique properties, their controlled synthesis, particularly when it comes to complex and functional architectures, remains challenging. Here, we show that the copolymerization of oxetane and phenyl isothiocyanate selectively yields polythioimidocarbonates as a new class of sulfur containing polymers, with narrow molecular weight distributions (Mn=5–80 kg/mol with Đ≤1.2; Mn,max=124 kg/mol) and high melting points of up to 181 °C. The method tolerates different substituent patterns on both the oxetane and the isothiocyanate. Self‐nucleation experiments reveal that π‐stacking of phenyl substituents, the presence of unsubstituted polymer backbones, and the kinetically controlled linkage selectivity are key factors in maximising melting points. The increased tolerance to macro‐chain transfer agents and the controlled propagation allows the synthesis of double crystalline and amphiphilic diblock copolymers, which can be assembled into micellar‐ and worm‐like structures with amorphous cores in water. In contrast, crystallization driven self‐assembly in ethanol gives cylindrical micelles or platelets.

Easy Synthetic Access to High-Melting Sulfurated Copolymers and their Self-Assembling Diblock Copolymers from Phenylisothiocyanate and Oxetane.

Although sulfurated polymers promise unique properties, their controlled synthesis, particularly when it comes to complex and functional architectures, remains challenging. Here, we show that the copolymerization of oxetane and phenyl isothiocyanate selectively yields polythioimidocarbonates as a new class of sulfur containing polymers, with narrow molecular weight distributions (Mn=5-80 kg/mol with Đ≤1.2; Mn,max=124 kg/mol) and high melting points of up to 181 °C. The method tolerates different substituent patterns on both the oxetane and the isothiocyanate. Self-nucleation experiments reveal that π-stacking of phenyl substituents, the presence of unsubstituted polymer backbones, and the kinetically controlled linkage selectivity are key factors in maximising melting points. The increased tolerance to macro-chain transfer agents and the controlled propagation allows the synthesis of double crystalline and amphiphilic diblock copolymers, which can be assembled into micellar- and worm-like structures with amorphous cores in water. In contrast, crystallization driven self-assembly in ethanol gives cylindrical micelles or platelets.

Gas-Phase Structures of [Au21(SR)14]- and [Au17(SR)10]- with Eight Electrons: Can They Support an Icosahedral Au13 Core?

A prototypical thiolate (RS)-protected gold cluster [Au25(SR)18]- has high stability due to specific geometric and electronic structures: an icosahedral (Ih) Au13 core with a closed electronic shell containing eight electrons is completely protected by six units of Au2(SR)3. Nevertheless, collisional excitation of [Au25(SR)18]- in a vacuum induces the sequential release of Au4(SR)4 to form [Au21(SR)14]- and [Au17(SR)10]- both containing eight electrons. To answer a naive question of whether these fragments bear an Ih Au13(8e) core, the geometrical structures of [Au21(SC3H7)14]- and [Au17(SC3H7)10]- in the gas phase were examined by the combination of anion photoelectron spectroscopy and density functional theory (DFT) calculation of simplified models of [Au21(SCH3)14]- and [Au17(SCH3)10]-. We concluded that [Au21(SC3H7)14]- retains a slightly distorted Ih Au13(8e) core, while [Au17(SC3H7)10]- has an amorphous Au13 core composed of triangular Au3, tetrahedral Au4, and prolate Au7 units. DFT calculations on putative species [Au19(SCH3)12]- and [Au18(SCH3)11]- suggested that the Ih Au13(8e) core undergoes dramatic structural deformation due to mechanical stress from μ2 ligation of only one RS.

A multidimensional integrated micro three-component fluxgate sensor based on microelectromechanical system technology

In this paper, a miniature three-component fluxgate sensor with U-shaped structure is fabricated by the multidimensional integration technology. We manufacture a batch of single axis solenoid fluxgate chips based on Micro Electromechanical System （MEMS） technology, which possesses the Co-based amorphous ribbon core and solenoid excitation-detection coil. According to multidimensional integration theory, a full integrated three-component fluxgate sensors is achieved through orthogonal linking of printed circuit board （PCB） substrates and bonding between single axis fluxgate chip and substrate. The chips used in the X-Y-Z axis have a sensitivity of 1947 V/T, 1951 V/T, and 1949 V/T, and noise power spectral density of 0.061 nT√Hz@1HZ, 0.077 nT√Hz@1HZ, and 0.087 nT√Hz@1HZ, and time-drift peaks of 21 nT, 17.4 nT, and 14.8 nT, respectively. The linear range of three chips is 0–70μT. After least square error correction, the peak-to-peak value of the in-situ total magnetic field decreases from 2.4 μT to 0.22 μT.

Calculation of electromagnetic force and temperature distribution of amorphous transformers in different operating modes by finite element method

The study used the Finite element method (FEM) by ANSYS 3D software to calculate the distribution of electromagnetic force (EMF) and temperature on the high voltage and low voltage windings (HLVWs) of the amorphous steel core 3 phase transformer (ASCT) which has a power of 1000kVA –22/0.4kV under different load cases: No load, full load and short circuit (SC). The obtained results show the exact temperature distribution and location where the highest temperature is found on the HLVWs of ASCT. From the analysis of the temperature distribution on the HLVWs, it is shown that when the transformer falls into an SC fault, it causes the greatest EMF and thermodynamic force, causing extremely heavy consequences for the transformers. The obtained results help designers, manufacturers, and operators have the most suitable options to improve strength of SC and increase the life of the transformer.

Heterogeneous-Structured Molybdenum Diboride as a Novel and Promising Anode for Lithium-Ion Batteries.

With the development of electric vehicles, exploiting anode materials with high capacity and fast charging capability is an urgent requirement for lithium-ion batteries (LIBs). Borophene, with the merits of high capacity, high electronic conductivity and fast diffusion kinetics, holds great potential as anode for LIBs. However, it is difficult to fabricate for the intrinsic electron-deficiency of boron atom. Herein, heterogeneous-structured MoB2 (h-MoB2) with amorphous shell and crystalline core, is prepared by solid phase molten salt method. As demonstrated, crystalline core can encapsulate the honeycomb borophene within two adjacent Mo atoms, and amorphous shell can accommodate more lithium ions to strengthen the lithium storage capacity and diffusion kinetics. According to theoretical calculations, the lithium adsorption energy in MoB2 is about -2.7 eV, and the lithium diffusion energy barrier in MoB2 is calculated to be 0.199 eV, guaranteeing the enhanced adsorption capability and fast diffusion kinetic behavior of Li+ ions. As a result, h-MoB2 anode presents high capacity of 798 mAh g-1 at 0.1 A g-1, excellent rate performance of 183 mAh g-1 at 5 A g-1 and long-term cyclic stability for 1200 cycles. This work may inspire ideas for the fabrication of borophene analogs and two-dimensional metal borides.

Preparation of hollow carbon nanospheres from oxidation of spent tyre oil‐derived carbon black in air

AbstractHollow carbon nanospheres (HCNS) were prepared from carbon black (CB) derived from spent tyre pyrolysis oil. The pristine CB produced by partial oxidation of the pyrolysis oil in a drop tube furnace was subsequently oxidised in air in a fixed bed reactor to yield HCNS. The effect of oxidation temperature (300 to 700°C) and time (1 to 8 h) on the burn‐off (Bt) of the sample over the duration (t) of oxidation and average reaction rate (Rt) was assessed. The BET surface area and pore volume and the nanostructure of the HCNS samples obtained were characterised using N2 adsorption–desorption and high‐resolution transmission electron microscope (HRTEM) techniques, respectively. Higher temperature and longer oxidation time led to higher Bt. As Bt increased, the BET surface area and pore volume initially increased linearly due to the removal of the amorphous core and then decreased because of the collapse of the shell of the carbon nanostructure. At Bt of ~56%, the maximum BET surface area and pore volume of the HCNS were 383.2 m2 g−1 and 0.39 cm3 g−1, respectively, compared to ~19.5 m2 g−1 and 0.033 cm3 g−1 of the pristine CB. The HRTEM images indicate that the change in BET surface area corresponds to the formation of the HCNS, as the core of the CB particle was preferentially consumed to create a hollow structure. The formation of HCNS follows an internal oxidation model, which is characterised by rapid core consumption and relatively slow shell consumption.

Effects of cores types on non-solvent displacement nonaqueous precipitation synthesis of core-shell structured materials: A case study on effects of carbon sources on C@ZrSiO4 preparation

Effects of cores types on non-solvent displacement nonaqueous precipitation synthesis of core-shell structured materials were investigated via taking case study on effects of carbon sources on C@ZrSiO4 preparation. The influencing mechanism of carbon sources was investigated via XRD, FE-SEM, TEM and the CIELAB colorimeter. The results show that the optimized carbon source for non-solvent displacement nonaqueous precipitation synthesis of C@ZrSiO4 is amorphous and isolated spheroid-like carbon source. Neither layer-structured particle nor sheet-like particle can be effectively encapsulated through non-solvent displacement nonaqueous precipitation method. The shell layer is difficult to be effectively encapsulated on the edges of the around of corresponding particle. In comparison with the higher crystallinity core, the amorphous core is more favorable for encapsulation. The core materials selection principles discovered in this work are expected to be widely referred in the preparation of other core-shell structural materials.

Fabrication of FeSiBCr/wollastonite amorphous soft magnetic powder cores with low loss and high-quality factor

In this paper, the best magnetic properties of FeSiBCr/wollastonite soft magnetic composites were explored by adjusting the content of wollastonite powder and annea- ling temperature. FeSiBCr/wollastonite soft magnetic composites with low loss and high quality factor were successfully prepared by adding micron-sized wollastonite po-wder into amorphous magnetic powder. Wollastonite was used as the insulating coating material of amorphous magnetic powder for the first time, which showed good performance in reducing the loss of magnetic powder. The loss change of FeSiBCr/wollastonite magnetic powder cores was studied by B-H analyzer and loss separation analysis model. The results show that the total loss (Pcv) of FeSiBCr/woll- astonite composite cores is lower than that of the pure FeSiBCr cores. With the incre- ase of wollastonite powder content and annealing temperature, the total loss of FeSiBCr/wollastonite composite powder cores shows a trend of first decreasing and then increasing. The composite powder cores containing 0.8 wt% wollastonite powder was heat treated at 678 K for 1 hour under the protection of nitrogen, and its magnetic properties were the best, with a permeability of 28.93 and a loss of 196.2 mW/cm3( f =1 MHz and Bm =20 mT). Wollastonite is a new coating material, which has a good effect of reducing loss. At the same time, this work also provides a new scheme for reducing the total loss of soft magnetic powder cores.