Papers by Keyword: Spark Plasma Sintering (SPS)

Abstract: The structural features of multilayered "metal - intermetallic" composite materials based on nickel and aluminum, obtained by SPS method have been investigated in this paper. The effect of sintering temperature on phase composition of the intermetallic layers was studied. The influence of intermetallic layers phase composition on the mechanical properties of the composites was estimated.

Abstract: Particularities of the multilayered “Ti – Al₃Ti” composites structure formation were investigated. Spark plasma sintering of Ti and Al plates in cylindrical molds at the temperature of 830 ^оС and pressure of 3 kN during 5 minutes was found to be the most efficient technology of formation of materials with intermetallic layers. The regime described above allows fabricating material with high-quality intermetallic layers and with microhardness level up to 3800 MPa.

Abstract: In this paper structure and mechanical properties of Ni₃Al intermetallic compound was studied. The materials was fabricated according to different schemes, which combined mechanical alloying of Ni and Al powders, self-propagating high temperature synthesis (SHS) and spark plasma sintering (SPS). Relative density of all sintered samples was ~ 97 %. Microhardness of the sintered materials ranged from 6100 to 6300 MPa. SPS of 86.71 % wt. Ni and 13.29 % wt. Ni powder at 1100 °C led to formation of material with the highest level of tensile strength equal to 400 MPa.

Abstract: High density graphite and silicon carbide powder (alpha phase) were used to obtain joints by Spark Plasma Sintering (SPS) technique. The joining of C/SiC was performed both by direct bonding (DB) and with the aid of a ceramic powder mixture (SiC+5%wt.B₄C) as intermediary joining material. The joints were performed in vacuum at 1900°C under 30 MPa with a dwell time of 3 minutes. The interface structures of the obtained joints were characterized from the structural and mechanical point of view. XRD analysis of both joints have shown only the presence of crystalline phases of SiC and C while the crystalline phase of B₄C was not detected due to its low content (5 wt.%) with a higher degree of amorphization of 9.1% for the junction with interlayer than that of the corresponding junction obtained by DB (5.5%). Interface compositional analyses and SEM images have shown that the process of diffusion bonding was the mechanism both for joining by DB and with a SiC+5wt%B₄C interlayer. The Vickers microhardness and Young Modulus values measured by nanoindentation evidenciated a strong increase of HV values (11 – 14 GPa) at interface for the junction with SiC+B₄C intermediate layer and, as expected, the highest stiffness (180-197 GPa).

Abstract: Wet mechanical alloying (MA) were used to prepare amorphous soft magnetic Fe₇₅Si₂₀B₅ (at.%) powders starting from elemental powders of Fe, Si and B. The structural, morphological and magnetic properties of the powders were investigated. It was found that wet MA leads to the amorphisation of the alloy after 40 hours of wet milling using benzene (C₆H₆) as process control agent (PCA). The influence of the wet MA process on the saturation magnetization of the powders was investigated. Amorphous powder of Fe₇₅Si₂₀B₅ (at.%) obtained by wet MA route was used to prepare compacts by spark plasma sintering (SPS). The chosen sintering temperature was 800, 850 and 900 oC. Toroidal samples of Fe₇₅Si₂₀B₅ (at.%) were investigated in DC and AC magnetization regime and their magnetic properties were correlated with sintering parameters, compacts density and phases evolution during sintering.

Abstract: Multiferroics are interesting materials which present more than one ferroic property and have a great potential for practical applications [,,]. In addition, the coupling of magnetic and electric properties, the magnetoelectric effect (ME), offers news possibilities to applications [2,]. The magnetoelectric effect can be observed in single-phase materials like LuFe₂O₄, BiFeO₃, etc. [1,] or in composites like PMN-PT/CFO, BaTiO₃/CoFe₂O₄, etc. The ME composites have advantages over single-phase materials. They are easier to fabricate, less expensive, and have a wider range of working temperatures than single-phase materials []. However, some parameters that enhance the ME response need to be optimized. These parameters are the composition, the microstructure (grain size, grain orientation) and sintering parameters [6]. Thus, this work attempts to create a synthesis protocol to prepare the ME composite PMN-PT/CFO by Spark Plasma Sintering (SPS) keeping the average grain size as small as possible.

Abstract: Silica (SiO₂) nanolayer was coated on silicon carbide (SiC) powder by rotary chemical vapor deposition (RCVD). The SiC/SiO₂ composite were consolidated by spark plasma sintering (SPS) at 1923 K using the SiO₂ coated SiC powder. The relative density and hardness of the SiC/SiO₂ composites increased with increasing SiO₂ content, and were 97% and 17 GPa, respectively, at SiO₂ content of 22 mass%. The relative density and hardness of a composite consolidated using the mixture powders of SiC and SiO₂ (22 mass%) at 1923 K were 81% and 8 GPa, respectively.

Abstract: Electric current assisted sintering (ECAS) has been used for sintering of nitride ceramic powders. It was mainly used for fabrication of fine-grained silicon nitride ceramics with high plasticity at high-temperatures, because high heating rate of ECAS was effective for densification without grain growth. Recent trend of silicon nitride ceramics sintered by ECAS are for wear resistance, corrosion resistance, or high toughness. Application of silicon nitride ceramics is expanding and the ECAS is helpful for improving the properties. The ECAS is used for sintering of aluminum nitride ceramics, recently. Aluminum nitride powder could be densified without sintering additive by ECAS, but some kinds of sintering additives are effective for densification and improvement of thermal conductivity.

Abstract: Porous Al with controlled pore size was prepared by the spacer method including spark plasma sintering and the dissolution of space-holding NaCl particles. The NaCl of the controlled pore size (particle diameter control range of 5˰ڌm~20˰ڌm) were prepared by precipitation method. The effects of sintering condition such as the sintering electric current intensity, voltage and the size, morphology and content of NaCl powder on the porosity and size of porous Al are investigated. The porous Al with higher porosity of 69.41% and smaller pore size of 5 ڌm was obtained.

Abstract: WC-Co-cBN composites were consolidated by SPS at 1373 to 1673 K under a moderate pressure of 100 MPa. The addition of cBN increased the starting and finishing temperature of shrinkage and decreased the relative density of WC-Co. The relative density of WC-(10-20 vol%) cBN composites was about 97-100% at 1573 K and decreased with increasing the sintering temperature to 1673 K due to the phase transformation of cBN to hBN. The highest hardness and fracture toughness of WC-Co-20 vol% cBN composite sintered at 1573 K were 23.2 GPa and 8.0 MP m^1/2, respectively.