V. Mamedov

Bio: V. Mamedov is an academic researcher. The author has contributed to research in topics: Spark plasma sintering & Sintering. The author has an hindex of 1, co-authored 1 publications receiving 269 citations.

Spark plasma sintering as advanced PM sintering method

Abstract: A short overview of works on spark plasma sintering (SPS) is given in the present paper. SPS is a newly developed rapid sintering technique with a great potential for achieving fast densification results with minimal grain growth in a short sintering time. It is proven by obtained experimental data that enhanced sinterability of powders subjected to SPS mainly associated with particle surface activation and increased diffusion rates on the contact zones caused by applied pulse current. Application of rapid heating results in bypassing of low temperature regions where surface transport controlled sintering is dominant. This preserves the powder surface area to temperature levels where bulk transport is significant. However, the nature of activation effects, especially in its regards to acceleration of diffusion processes, is not clearly established. A lot of research work reports about the occurrence of plasma during the application of pulse current. However, the appearance of thermal plasma during...

1000 at 1000: The effect of electric field and pressure on the synthesis and consolidation of materials: a review of the spark plasma sintering method.

Abstract: The use of electric current to activate the consolidation and reaction-sintering of materials is reviewed with special emphasis of the spark plasma sintering method. The method has been used extensively over the past decade with results showing clear benefits over conventional methods. The review critically examines the important features of this method and their individual roles in the observed enhancement of the consolidation process and the properties of the resulting materials.

Consolidation/synthesis of materials by electric current activated/assisted sintering

Abstract: This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Neck Formation and Self-Adjusting Mechanism of Neck Growth of Conducting Powders in Spark Plasma Sintering

Abstract: By using spherical Cu powders as the conducting sintering material, the microstructures of sintered powder particles at different stages in the process of spark plasma sintering (SPS) have been investigated. Theoretical analyses are proposed to quantify the effects of the pulsed direct current on the neck formation and the neck growth of conducting powders. It is found that there is a considerable inhomogeneous distribution of the temperature increase from the particle-contacting surface to the center of the particle when the pulsed current passes through. The temperature at the particle-contacting surface may reach the boiling point of the material, which results in neck formation at relatively low-sintering temperatures through a process of local melting and rapid solidification. The neck growth depends on the local distribution of the current intensity, which is determined by the competition between the neck cross-sectional area and the electrical resistivity increasing with the temperature. Accordingly, we propose that the coarsening of necks follows a "self-adjusting" mechanism, which is likely to be the essential reason for the homogeneous distributions of neck sizes and sizes of fine grains formed in the neck zones during the SPS process.

High-entropy ceramics: Review of principles, production and applications

Abstract: High-entropy ceramics with five or more cations have recently attracted significant attention due to their superior properties for various structural and functional applications. Although the multi-component ceramics have been of interest for several decades, the concept of high-entropy ceramics was defined in 2004 by producing the first high-entropy nitride films. Following the introduction of the entropy stabilization concept, significant efforts were started to increase the entropy, minimize the Gibbs free energy and achieve stable single-phase high-entropy ceramics. High-entropy oxides, nitrides, carbides, borides and hydrides are currently the most popular high-entropy ceramics due to their potential for various applications, while the study of other ceramics, such as silicides, sulfides, fluorides, phosphides, phosphates, oxynitrides, carbonitrides and borocarbonitrides, is also growing fast. In this paper, the progress regarding high-entropy ceramics is reviewed from both experimental and theoretical points of view. Different aspects including the history, principles, compositions, crystal structure, theoretical/empirical design (via density functional theory, molecular dynamics simulation, machine learning, CALPHAD and descriptors), production methods and properties are thoroughly reviewed. The paper specifically attempts to answer how these materials with remarkable structures and properties can be used in future applications.

Microstructure and mechanical properties of ZrB2–MoSi2 ceramic composites produced by different sintering techniques

Abstract: Ceramic composites in the system ZrB 2 –(15–20 vol% MoSi 2 ) were produced by different densification techniques: pressureless sintering, hot-pressing and spark plasma sintering. Regardless of the sintering technique, the addition of 15–20 vol% MoSi 2 was beneficial for the densification of these composites. Nearly fully dense materials (98–99%) were obtained at 1750–1800 °C by the pressure-assisted techniques and at 1850 °C by pressureless sintering. All the microstructures were very fine, with mean ZrB 2 grain sizes between 1.4 and 2.5 μm. Vickers hardness, fracture toughness, Young's modulus and CTEs were similar for all the materials produced. The room temperature flexural strength varied between 500 and 700 MPa. At 1200 and 1500 °C, the highest values of flexural strength were obtained for the pressureless sintered material (655 and 500 MPa, respectively). The high-temperature flexural strength of the hot-pressed and spark plasma sintered samples was negatively affected by residual silica pockets.