Composite Dielectrics BaTiO3–Fe Consolidated via Field‐Assisted Sintering Technology

Field assisted sintering technology (FAST), also known as spark plasma sintering (SPS), is increasingly utilised to process powders/particulates of engineering alloys and metal-based composite materials. FAST is currently extensively used at laboratory scale by research institutes and universities as a rapid and cost‑effective process to consolidate powders. This includes investigating new alloy compositions and material combinations, improving established materials’ properties, and consolidating materials considered challenging/impossible through conventional sintering techniques. FAST is gaining traction for industrial applications with possible benefits as an alternative to hot isostatic pressing or conventional melt-wrought processing. FAST preform complexity is improving and near-net-shape components are becoming a possibility. Demonstrator components for the aerospace and automotive sectors, including aeroengine blades, brake callipers and rocker arms, have been produced from titanium alloy powders. FAST has also been demonstrated as an effective intermediate step for consolidating a range of feedstocks, including recycled materials, into shaped billets that can be further processed to refine shape and/or properties. Hybrid processes such as FAST‑forge and FAST‑DB have been developed that can produce affordable titanium components with forged properties. This paper presents the current status, emerging developments, and challenges of FAST for titanium-based powders and particulates.

On the surface integrity of machined aero-engine grade Ni-based superalloy billets produced by the field-assisted sintering technology (FAST) route

Influence of processing on the microstructural evolution and multiscale hardness in titanium carbonitrides (TiCN) produced via field assisted sintering technology

Influence of the interface strength on the mechanical properties of discontinuous tungsten fiber-reinforced tungsten composites produced by field assisted sintering technology

This paper highlights the thermal properties of copper–diamond composites fabricated by field assisted sintering technology. The samples were fabricated using a matrix of copper alloyed with silver and zirconium. Previous reports have shown that these samples possess high thermal conductivity. This work examines the thermal conductivity of the samples after being subjected to thermal cycling. Coefficient of thermal expansion is also reported in this work.

Honey has become a main target of adulteration due to its important nutrient commodity of high price and in short supply. It can include illegal adulteration as well as overheating by adding water and sugar syrups. For this purpose, the dielectric assessment kit (DAK) which offers measurements of high precision dielectric attributes such as dielectric permittivity,penetration depth, conductivity and loss tangent over a wide frequency range has been used. Dielectric parameters of pure yellow standard honey (A) and their adulterated samples with moisture levels from 17.5 % to 31.2 % were measured with coaxial-line probe from 600 to 6000 MHz at 25–55 ℃. Influence of water content and temperature on dielectric properties(dielectric constant, loss tangent, electrical conductivity and penetration depth) of various honey brands B, C and D were also investigated. Temperature and moisture content have a substantial impact on honey's dielectric properties over the complete frequency range. It was observed that the dielectric constant and dielectric conductivity of honey brand named C were related to that of the pure honey sample A, although the values for various parameters of C and D were drastically different from A. Results show that the 915 MHz frequency is more appropriate for microwave heating of honey than the 2450 MHz frequency due to its deeper penetration depth. Finally overheating and water content of honey directly affects its dielectric parameters and their measurements can be used in quality assessment for degraded honey detection.

The Nb3+ ion substituted Sr hexaferrites (SrNbxFe12−xO19 (x = 0.00–0.08) hexaferrites (HFs)) were fabricated via a citrate-assisted sol-gel approach. X-ray powder diffractometer analysis affirmed the pureness of all products. The crystallite sizes of the products which were estimated from Scherrer equation were in the 36–40 nm range. The chemical component of the samples was proved by Energy-dispersive X-ray spectroscopy (EDX) and Elemental mapping. The hexagonal morphology of all products was confirmed by Field Emission Scanning Electron Microscopy (FE-SEM). The electrical conduction mechanisms and dielectric properties of a variety of Nb3+ions-substituted SrNbxFe12−xO19 HFs were investigated by a complex impedance system. Dielectric parameters such as conductivity, dielectric constant, dielectric loss, dielectric tangent loss and complex modulus, were studied at temperatures up to 120 °C in a frequency range varying from 1.0 Hz to 3.0 MHz for several Nb ratios. The frequency dependence of the conductivity was found to comply with the power law with diverse exponents at all frequencies studied here. Subsequently, incremental tendencies in dc conductivity with temperature indicate that the substituted Sr-HFs leads to a semiconductor-semimetal like behavior. This could be attributable to a feature of conduction mechanism which is based on the tunneling processes. Additionally, the dielectric dispersion pattern was also explained by Maxwell–Wagner polarization in accordance with the Koop’s phenomenological theory.

A novel, two-step, solid-state method to produce complex geometry titanium parts was investigated by combining Cold Isostatic Pressing (CIP) with Field Assisted Sintering Technology (FAST). Hydride-dehydride powders of commercially pure titanium and Ti-6Al-4V were CIP’ed into shaped compacts using silicone moulds, then further consolidated using FAST, with ZrO2 powder as a secondary pressing media. The final parts retained the complex features from the CIP moulds but were compressed in the pressing axis. Densities >99% were achieved, with optimised FAST processing parameters required for the different alloys. High hardness and fine equiaxed microstructures were observed at the edges of the parts, suggesting oxygen transfer from the ZrO2 pressing media had occurred, with more investigation needed to better understand and prevent this. Despite this, the CIP-FAST process route has been demonstrated to be a fast, low-cost and material-efficient option to produce a wide variety of complex titanium parts.

A parametric study of the microstructural evolution of an advanced Ni-based superalloy powder when consolidated using Field Assisted Sintering Technology, compared to a hot isostatic pressing benchmark

Dielectric investigations on metal (Ni and Cu) tetrahydroxy phenyl porphyrins in PMMA polymer matrix

With the development and progress of the city, people’s research on outdoor sculpture has gone deeper, and the field of material research has been raised to the field of spiritual culture. Tang Sancai is beautiful in color and wonderful in shape, such that when ceramics are used in outdoor environmental sculpture art, except for its performance, its appearance and tone must also be taken into consideration. Even when ferroelectric ceramics are used in outdoor sculptures, changing their shapes and taking into account their colors can be done invisibly only by passing through an electromagnetic field. Ferroelectric ceramics are generally divided into insulating, dielectric, piezoelectric, magnetic, semiconductor, transparent, and infrared sensor ceramics. This article integrates the manufacturing method of ferroelectric ceramics into outdoor environmental sculpture art. First of all, this article describes the ferroelectric ceramics and outdoor environmental sculptures, explains the method of preparing ferroelectric ceramics from barium titanate nanoparticles, and explains the pyroelectric inverse process of the electric card effect principle of electric ceramic materials, the thermodynamics of Maxwell’s relationship, and the thermodynamics of Landau’s phenomenological theory. The elasticity of the system is calculated, and the preparation of tetragonal barium titanate ferroelectric ceramics prepared by hydrothermal nanoparticles and SBT/Cu ferroelectric ceramic composites prepared by nanoparticle metallurgy is explained. In the plasma discharge mode, the optimal temperature for sintering the composite material is obtained. Then through experiments, research on the preparation and performance of the high dielectric constant BTnf-Ag/PVDF ferroelectric ceramic nanocomposite and its application in environmental sculptures are demonstrated. Compared with the two ancient BTnf/PVDF composite materials, the barium titanate fiber prepared by electrostatic spinning shows that the BTnf-Ag/PVDF composite material has a higher dielectric constant, and the dielectric loss is not too high. The 41.8vol% BTnf-Ag composite material has a dielectric constant of 82.6BTnf/PVDF, but the composite material’s dielectric constant is only 62.4, an increase of 32%. The dielectric loss of the 41.8vol% BTnf-Ag composite material is 0.053, and the dielectric loss constant of the BTnf/PVDF composite material is 0.049; the dielectric loss is reduced by 8% year-on-year. Ferroelectric ceramic composites prepared by adding silver ions have ideal dielectric properties and enhanced energy storage density.

Optimized processing of high density ternary hafnium-tantalum carbides via field assisted sintering technology for transition into hypersonic applications

Synthesis and dielectric investigations of bismuth sulfide particles filled PVA: Polypyrrole core-shell nanocomposites

This paper presents the technology of powder sintering by the spark plasma sintering method, also known as the field assisted sintering technique. The mechanisms, compared to other sintering techniques, advantages of this system, applied modifications and the history of the development of this technique are presented. Spark Plasma Sintering (SPS) uses uniaxial pressing and pulses of electric current. The direct flow of current through the sintered material allows high heating rates to be reached. This has a positive effect on material compaction and prevents the grain growth of sintered compact. The SPS mechanism is based on high-energy spark discharges. A low-voltage current pulse increases the kinetics of diffusion processes. The SPS temperature is up to 500 °C lower than the sintering temperature using conventional methods. The phenomena that occur during sintering with the Field Assisted Sintering Technology (FAST)/SPS method give great results for consolidating all types of materials, including those which are nonconductive. This method is used, among others, in relation to metals, alloys and ceramics, including advanced and ultra-high-temperature ceramics. Due to the good results and universality of this method, in recent years it has been developed and often used in research institutions, but also in industry.

This study examines the radiation-dependent dielectric properties of an Au/(Co/Zn)-doped PVA/n-Si MPS-type Schottky structure (SS). Capacitance/conductance-voltage (C/(G/ω)−V) measurements were taken at 1 MHz frequency before and after 22 kGy radiation application on the 1st, 3rd, 5th, 10th, 20th, and 30th days. The dielectric constant (ε') and dielectric loss (ε'') parameters were calculated using the impedance/admittance spectroscopy method. The results indicate that the most significant difference occurred on the first day after irradiation. In the subsequent days, particularly on the 30th day, the values closely approached those of the unirradiated sample (U.S). Similar results were obtained for loss tangent (tan(δ)), ac-conductivity (σac), and the complex electric modulus (M*), including both the real (M') and imaginary (M'') parts. The results indicate that the sample is mainly affected by the transient effects of radiation, but there are also permanent radiation effects present. The results show that the polarisation mechanism, which is a crucial factor in dielectric properties, can be explained by the Maxwell–Wagner dispersion model based on Koop’s theory. The study concluded that the Au/(Co/Zn)-doped PVA/n-Si MPS-type SS can be safely and accurately used as a rectifier contact even after exposure to 22 kGy radiation.