One-step Sintering Method Research Articles

Changing the polar order using different sintering methods

In this study, solid solution ceramics (1–x)Bi0.5K0.5TiO3–xBi0.2Sr0.7TiO3 (x = 0.1, 0.15 and 0.2, abbreviated as BKST1 for a one-step sintering method and as BKST2 for a two-step sintering method) were prepared using two different sintering methods. The BKST1 ceramics exhibited an average cubic structure, while the BKST2 ceramics had tetragonal distortions. As the Bi0.2Sr0.7TiO3 content increased, spontaneous relaxor-ferroelectric transition disappeared in the BKST1 ceramics owing to the formation of the polar nanoregions (PNRs). The compositions developed using the two-step sintering method exhibited a noticeable dielectric anomaly with respect to spontaneous relaxor-ferroelectric transitions. Double ferroelectric hysteresis loops appeared near the ergodic relaxor-ferroelectric (or non-ergodic relaxor) transition points. The relationship between the piezoelectric coefficient (d33) and compositions suggested that 0.15BKST1 exhibited the optimum piezoelectric properties (d33, 128 pC/N). The 0.15BKST ceramic developed using the one-step sintering method had a low depolarisation temperature (~176 °C in 0.15BKST1 compared to ~227 °C in 0.15BKST2). The improved piezoelectric properties were attributed to the electrical field-induced transformation from PNRs to the long-range ferroelectric ordering as evidenced by the poling effects on the XRD patterns and dielectric behaviours.

Phosphor-in-glass with full-visible-spectrum emission based on ultra-low melting Sn-F-P-O glass pumped by NUV LED chips

Herein, the phosphor-in-glass (PiG) with full-visible-spectrum emission has been successfully fabricated by incorporating SrSi2O2N2: Eu2+ (SSON:Eu) and CaAlSiN3: Eu2+ (CASN:Eu) phosphors in ultra-low melting Sn-F-P-O glass using one-step sintering method. The Sn2+ ions show intense blue-green emission characteristics under the excitation of NUV chips, which are highly dependent on its coordination environment in Sn-F-P-O glass. Then, it was investigated in detail for the first time that fluoride from Sn-F-P-O glass substrate migrates and gathers around the embedded phosphors, which is closely related to the emission performance of Sn2+ activators in the PiG. Furthermore, the mechanism of enhancing the PL intensity of Sn2+ ions by embedded phosphors is proposed. As a result, the PiG with full-visible-spectrum emission can be achieved under 370 nm excitation. Importantly, the PiG pumped by NUV LED chips shows excellent-quality white-light with high CRI (Ra = 91) and lower CCT (4993 K). The WLED based on this PiG has been demonstrated as a promising candidate for solid warm light source in the future because of the excellent optoelectronic performance and easy-preparation process.

Binary V–Mo sulfides grown on CNTs with morphological and electronic modulation for enhanced hydrogen evolution

Binary V–Mo sulfides on carbon nanotubes with superior electrocatalytic water splitting performance in acid media are successfully synthesized by a facile one-step sintering method.

Microstructure, phase transformation and mechanical property of porous NiMnGa alloys prepared by one-step sintering

This article investigated microstructure, martensitic transformation and mechanical property of porous NiMnGa alloys fabricated by one-step sintering method using Mg powder as a pore former. The overall pore size was decreased with decreasing Mg content due to the reduction of aggregation tendency of Mg particles. Residual Mg existed mainly in the pore wall (interfacial areas between NiMnGa and Mg) due to interfacial reactions. The porous alloys with different porosity exhibited one-step martensitic transformation with close transformation temperatures and the temperature of martensitic transformation was lower for the porous alloys than the original NiMnGa powder. The porous NiMnGa alloys exhibited a low compressive strength and ductility due to the existence of pores. The porous NiMnGa alloys with continuous pore wall structure could be a better candidate than NiMnGa particles to form composites with ductile matrix.

Investigation on electrical conductivity and surface distribution of work function of C12A7 electride

In this work, a polycrystalline C12A7 electride target was prepared by one-step sintering method using a graphite crucible. X-rays diffraction confirmed the presence of the C12A7 phase. In the meanwhile, a carbon phase was founded in the target and this situation was never reported before. It can be considered that there is a little carbon left in the C12A7 crystal. The electrical and emission properties of carbon doped C12A7 electride were explored. In terms of the electrical characteristics, the electrical resistance measured by a four-pin resistance meter at 300 K is relatively large, which is similar to semiconductors, indicating a low-level electron concentration of about 1.0 × 1018 cm−3. For the emission performance, a Scanning Kelvin Probe was used to measure the surface distribution of work function. The result shows that the surface work function is relatively stable with a floating about ± 0.03 eV of the average value 3.7 eV. The work function is also smaller, although it is higher than other pure C12A7 electrides, making it has a great prospect in optoelectronics devices.

Facile liquid-assisted one-step sintering synthesis of superfine L10-FePt nanoparticles.

A liquid-assisted one-step sintering method was proposed for the synthesis of L10-FePt superfine nanoparticles. The liquid assisted Fe and Pt precursors were homogeneously deposited on NaCl media, which facilitated the nucleation rates, obviously reduced the particle size and promoted the orderly transformation. Through optimizing the sintering parameters, superfine L10-FePt nanoparticles (about 7 nm, TEM) with coercivity as high as 2.29 T were obtained. This research highlights the feasibility of synthesizing L10-FePt nanoparticles with superfine sizes and ultra-high coercivity.

Preparation of a High-Performance Porous Ceramic Membrane by a Two-Step Coating Method and One-Step Sintering

Hole defects and uneven membrane thicknesses can lead to poor performance, especially in the separation stability of ceramic membranes. This paper uses a one-step sintering method, which avoids hole defects and uneven membrane thicknesses, for the preparation of high-performance and defect-free ceramic membranes. For this purpose, two kinds of ceramic membrane slurry with high or low viscosities were prepared by alumina particles, as raw materials. Both the effects of the two coating process with a one-step coating method for low-viscosity slurry, and the two-step coating method with a high viscosity flush after a low viscosity coating, on the surface properties of a ceramic membrane, were studied in detail. The result shows that the properties of ceramic membranes can be improved by a two-step coating method, with a high viscosity flush after a low viscosity coating, A high-performance and defect-free ceramic membrane was obtained by one-step sintering at 1450 °C for 2 hr with 7 wt % solid content and a coating time of 11 s.

Composite Cathode Material Using Spark Plasma Sintering for Bulk-Type Hybrid Solid-State Batteries

A Composite cathode without polymer binder was prepared by a one-step sintering method employing spark plasma sintering (SPS) of laminated LiCoO2 and Li3BO3 pellets. The amorphous Li3BO3 solid electrolyte melted during the sintering process. For better characterization of the composite cathode, a liquid electrolyte was used in the battery test. However, the active material was mainly in the all-solid-state environment. The specific capacity of the composite cathode was found to be dependent on its thickness. The 0.2 mm thick composite cathode showed a high specific discharge capacity of 99 mAh g −1 at 0.5 C rate, excellent cycling performance over 10 cycles, and good rate capability of about 93.2 mAh g −1 with 94% retention capacity. In addition, the composite cathode showed an initial discharge capacity of 0.25 mAh g −1. The discharge capacity after 3 cycles under the all-solid-state condition was 0.22 mAh g −1. The SEM and TEM results showed that the melted Li3BO3 solid electrolyte synthesized by the SPS process produced Li+ ion transport pathways, which reduced the grain boundary resistance. Hence, this composite cathode consisting of LiCoO2 as the cathode, amorphous Li3BO3 as the solid electrolyte, and MWCNT as the electric conductor is a promising material for all-solid-state batteries and bulk-type hybrid solid-state batteries.

Mechanical and microstructural characterization of W–Cu FGM fabricated by one-step sintering method through PM route

Five layer W-Cu functionally graded material (FGM) for components in nuclear fusion application was fabricated by a one-step resistance sintering process, known as spark plasma sintering (SPS). In this study effect of sintering temperature (Ts) on physical, mechanical and surface property was investigated. Detailed microstructural study revealed that the graded structure of the composite layers with varying composition from 0 to 100 wt% W and Cu in opposite directions could be well densified after the SPS process. It also indicates that the fine microstructure within functionally graded layers can be maintained because of short sintering time. The sample sintered at 1050°C shows more than 90% theoretical density, hardness greater than 239±5 Hv and excellent surface scratch resistance. The result demonstrates that SPS is promising and more suitable process for fabrication of W-Cu FGM.

One-step synthesis of hierarchically porous carbons for high-performance electric double layer supercapacitors

With plenty of unique porous structure at micro-/nano scale, hierarchically porous carbons (HPCs) are promising for usage in advanced electric double layer supercapacitors (EDLCs) as the electrode materials. However, wide-range adoption of HPC for practical application is largely shadowed by its extremely complex synthesis process with considerably low production efficiency. Herein we reported a simple template-free, one-step sintering method, to massively produce the HPCs for high-performance EDLCs. Resorting to the 3D structure modification of the wide pore size distribution, high surface area of HPCs (up to 3000 m2 g−1) was achieved. By using 1 M Na2SO4 as electrolyte, the as-fabricated HPCs based EDLCs can be operated reversibly over a wide voltage window of 1.6 V with superior specific capacitance of 240 F g−1 under a current density of 0.5 A g−1. In the meanwhile, the EDLCs exhibit excellent rate capability (high power density of 16 kW kg−1 at 10.2 Wh kg−1) and long-term cycling stability with 9% loss of its initial capacitance after 2000 cycles. This output performance distinguished itself among most of the carbon-based EDLCs with neutral aqueous electrolyte. Thus, the template-free one-step sintering method produced HPCs for EDLCs represents a new approach for high-performance energy storage.

Fabrication of porous attapulgite hollow fiber membranes for liquid filtration

Attapulgite (ATP) hollow fiber membranes with a mesh-like structure layer were prepared via a combined phase-inversion and one-step sintering method. A finger/sponge mixed structure in the membrane cross-section was obtained. The change of ATP chemical structure enhanced the membrane mechanical strength and had few effects on the general physical morphology. High permeate fluxes indicated that the ATP hollow fiber membrane is an attractive alternative as a liquid microfiltration membrane.

六方晶U型フェライトBa4Me2Fe36O60 (Me=Co, Ni, Mg)の作製プロセスの確立および磁気特性

We have established the preparation process of hexagonal U-type ferrites Ba4Me2Fe36O60 (Me=Co, Ni, Mg) and investigated their crystal structure and magnetic properties. The U-type ferrite single phase was not fabricated by using a conventional ceramic synthesis process which comprises two-steps: calcination and sintering. We have found that the U-type ferrites single phase can be obtained by a one-step sintering method that skips the calcination process. The single phase of the U-type ferrite was formed at a very narrow temperature at about 1250°C. The values of saturation magnetization and the Curie temperature of Co2U ferrite were higher than those of Co2Z ferrite. Initial permeability of Co2U ferrite has a higher value than those of Ni2U and Mg2U ferrites. The U-type ferrite has a great potential for high frequency magnetic materials.

Pore size control of Al 2O 3 ceramics using two-step sintering

Porous Al 2O 3 ceramics were prepared using a two-step sintering method. Green bodies were prepared using the slip cast method. The average pore size and porosity of the obtained samples were, respectively, 73 nm and 42%. The porosities and the average pore size of the samples prepared using a one-step sintering method decreased concomitantly with increasing sintering temperature. The porosity was mostly constant at temperatures higher than 1300 °C. The T 1 and T 2 temperatures were set, respectively as 1150 °C and 1000 °C for two-step sintering tests. Under these conditions, the pore size was controllable by sintering time without porosity change. The average pore size of the obtained samples was 61–76 nm without porosity change.

Preparation and Magnetic Properties of X-type Hexaferrites with Transition Metal Elements

The conventional synthesis of ferrite compounds consists of two-steps sintering processes. The first process is calcination to produce precursor of a desired ceramic object, and the second is to obtain the desired object.However, it was difficult to prepare X-type hexaferrite (Ba2Me2+2Fe28O46: Me2X, Me=Co, Ni, Cu, Zn) samples by this method. Two-steps sintering of these samples resulted in formation of spinel, M and W-type ferrite phases.We have found that Me2X can be obtained by a one-step sintering method that skipped the calcination process. When this method is applied, the temperature range of Me2X formation was very narrow and about 1250°C.We measured the saturation magnetization at 2 K and room temperature, and examined the Curie temperatures of Me2X samples produced by this method. These magnetic properties for Me2X samples relatively resemble those of MeFe2O4 spinel ferrites, which suggests that Me2+ cations are distributed in spinel blocks in the Me2X crystal structure.