Sintering Technique Research Articles

Morphological and structural evaluation of spark plasma sintered calcium silicate ceramics

AbstractCalcium silicate ceramics were successfully prepared at various temperatures by spark plasma sintering technique (SPS) using two different compositions, and their morphological and structural characteristics were thoroughly analyzed and compared by scanning electron microscope, X‐ray diffraction, and apparent density measurements. The effect of the sintering method and temperature on microstructural properties has also been studied. The sintered samples prepared by SPS through a heat input of 800°C showed the highest densification as results 800°C was suggested as optimum sintering temperature. Different phases presented in pseudo‐wollastonite, wollastonite, and triclinic Ca3(SiO4)O have been observed in the case of 50C50C with lowest porosity and highest density 2.6 g/cm3, whereas the composition 10C90S resulted in a fully amorphous material presented in granular microstructure with density of 1.7 g/cm3.

Effect of Different Metal Bonding Agents on Shear Bond Strength of Ceramic to Direct Metal Laser Sintering

Introduction: laser sinter Cobalt Chromium metal replacing traditional casting processes of dental alloys for metal ceramic restorations, appropriate bonding of ceramic to metal is an important factor for long survival time. Twenty laser sinter cubic metal 10 mm for each sides was fabricated by software designing and CAD\CAM direct metal laser sintering technique. The twenty cubics were classified according to the type of metal to ceramic bonding agents into two groups (n=10), Ceram bond apply for group A and Crea alloy bond for group B. Samples fabricated using custom made silicon index was used to act as standardized mold for metal bond application and porcelain buildup. Instron with chisel indenter and special holding device were involve to measure the strength of bond for ceramic to laser sinter metal. The mean shear bond load of group A (688.8N) was significantly higher than that of group B (303.2N). Application of Ceram bond to metal laser sinter produces more bond strength when compare to usage of Crea bond material.

Bioactive potassium and sodium niobate (K0.5Na0.5)NbO3 synthesized by solid‐state reaction and sol–gel methods

AbstractThis study proposes an innovative approach in the quest for piezoelectric materials, aiming to replace lead‐based ceramics (PZTs), known for their high toxicity. Potassium sodium niobate (KNN) compounds were chosen as a promising alternative. While the synthesis of KNN via solid‐state reaction (SSR) is common, maintaining the correct stoichiometry is challenging. In this work, we employed sol–gel (SG) and SSR methods for synthesis, combined with both conventional sintering techniques and spark plasma sintering. Comprehensive analyses were conducted, including crystal structure, microstructure, density, and piezoelectric properties, as well as bioactivity tests, among others. The results revealed that KNN samples exhibited remarkable piezoelectricity, coupled with surprising bioactivity, demonstrating good cell viability and resorption in a biological medium. Thoughtful selection of synthesis methods and variations in the sintering process were crucial in achieving high densification rates, enabling the investigation of the interplay between density and piezoelectric properties. Additionally, the application of polarization prior to immersion in a biological medium stimulated apatite precipitation. This indicates the promising application of these compounds as bioceramic devices.

Effects of Mechanical Milling and FAST Sintering on Mg Powders: Microstructural Analysis and Mechanical Properties

This study investigates the sintering mechanism of commercially pure Magnesium (Mg) using the Field Assisted Sintering Technique (FAST). FSEM and XRD analysis identified four distinct bonding and sintering mechanisms influenced by particle geometry, residual stress, and microstructure developed through mechanical milling. XRD analysis demonstrated variations in crystallite size and lattice micro-strain with increasing milling time. The combination of mechanical milling and FAST exhibited significant effects on the microstructural and mechanical properties of Mg powders, with the Mg36 sample displaying promising strength and hardness.

Very strong levitation force and stability achieved with a large MgB2 superconductor disc

This rapid communication highlights a remarkable achievement obtained with a 120 mm diameter large cylindrical MgB2 bulk: the measurement of magnetic levitation forces up to 700 N at 20 K, levitation being stable up to levitation forces exceeding 400 N. The investigated sample, which has one of the largest dimensions reported in the literature, was fabricated using the unconventional spark plasma sintering technique. This method is known as one of the most efficient methods for producing dense MgB2 samples. This breakthrough holds significant potential for advancing high-performance levitation systems and superconducting applications, including high-speed transportation systems and magnetic bearings.

Sketching feasibility of additively manufactured different size gradient conventional hollow capsular shells (HCSs) by selective laser sintering (SLS): From design to applications

Additive manufacturing (AM) is widely used to fabricate 3D printed objects from Computer-aided Design (CAD) prepared using the SolidWorks CAD modelling software. Different printing techniques are used to fabricate desired 3D objects; among all these techniques, it is widely accepted that SLS is one of the most effective methods of 3D printing for fabricating drug-loaded solid oral dosage forms (SODFs) in bulk quantities using the single-step process. Different SODFs, such as pills, miniprintlets, dual miniprintlets, and tablets, were fabricated with different sizes and shapes. In this study, for the first time, we introduce SLS-mediated hollow capsular shells (HCSs) with the help of the SLS 3D printing technique. This work aimed to explore the sinterability and feasibility of sketching HCSs using the SLS-mediated sintering technique with different marketed sizes of capsules ranging from 000 to 5. Here, we have utilized Kolliphor P 188 (KP 188) and Kollidon SR (KSR) in a 1:1 ratio as a matrix-forming agent and 1% charcoal as a laser absorption-enhancing material. In accordance with the CAD models, we have fabricated the gradient conventional different sizes of HCSs ranging from 000 to 5 using the constant printing parameters and composition. Fabricated all biobased HCSs were subjected to the assessment of mechanistic and physicochemical parameters using varied analytical tools. In the current study, tartrazine dye is used to assess the release pattern from HCSs, which resulted in the modified release pattern. The adapted approach will be the futuristic approach to replace animal-based gelatin capsules with pharmaceutical-grade polymer-based HCSs with a modified release with optimum mechanical strength.

Characterization of LaFeO3 Dielectric Ceramics Produced by Spark Plasma Sintering.

Commercially available LaFeO3 powder was processed using the spark plasma sintering (SPS) technique. The results of the dielectric measurement showed high permittivity, but this was strongly frequency-dependent and was also accompanied by a high loss tangent. The chemical purity of the powder and changes induced by the SPS process influenced the stability of the dielectric parameters of the bulk compacts. A microstructure with a homogeneous grain size and a certain porosity was produced. The microhardness of the sintered LaFeO3 was rather high, about 8.3 GPa. All the results are in reasonable agreement with the literature related to the production of LaFeO3 using different techniques. At frequencies as low as 100 Hz, the material behaved like a colossal permittivity ceramic, but this character was lost with the increasing frequency. On the other hand, it exhibited persistent DC photoconductivity after illumination with a standard bulb.

Densification, microstructure, and nanomechanical evaluation of pulsed electric sintered zirconia-silicon nitride reinforced Ti-6Al-4 V alloy

In this study, the influence of silicon nitride (Si3N4) and zirconia (ZrO2) ceramics was examined on the titanium alloy using the pulsed electric current sintering technique to investigate the microstructural behavior, densification, and nanomechanical properties of these composites. Si3N4 and ZrO2 were dispersed in Ti-6Al-4 V at a functional pressure of 50 MPa, a sintering temperature of 1200 °C, a heating rate of 100 °C/min, and a holding time of 10 min. The ternary composite samples were prepared viz, Cs1 (Ti6Al4V-3 vol.% Si3N4-15 vol.% ZrO2), Cs2 (Ti6Al4V-3 vol.% Si3N4-10 vol.% ZrO2), and Cs3 (Ti6Al4V-3 vol.% Si3N4-5 vol.% ZrO2). The bulk morphology of the composites was studied using scanning electron microscopy (SEM) equipped with EDS, and the phase contents were identified with an X-ray diffractometer (XRD). The relative density results for the tri-composites showed that the Cs1 sample recorded the highest at 99.94%, producing a fully dense sintered composite. However, there was a drop in the relative density of composites Cs2 and Cs3, recording 97.73% and 97.11%, respectively, comparable to the unreinforced Ti-6Al-4 V alloy with 98.65%. The nanoindentation examination conducted for the trio-composites showed linear mechanical responses/improvement, with Vickers hardness, from 589.31 to 865.70 MPa; nano hardness, from 6.466 to 9.441 GPa, and elastic modulus, from 113.52 to 185.95 GPa.

Spark plasma sintered TiB2-SiC UHTC derived from B4C and stoichiometric intermetallic phases from Ti-Si system

Previously conducted studies determined that the reactive sintering of B4C and stoichiometric additions of TiSi2 or Ti5Si3 intermetallics created a dense TiB2-SiC double-phase system that could be classified as ultra-high temperature ceramics (UHTC). In this work, a spark plasma sintering (SPS) technique was used to improve the sintering process and thus further reduce the obtaining temperature and improve the final microstructure and mechanical properties of the proposed, double-phase TiB2-SiC UHTC systems. To evaluate the effects of the experiment, a comprehensive study of phase composition, microstructure and mechanical properties was added. As a result, minimal sintering temperatures were further reduced from 1420 - 1650 ºC to a range of 1200–1400 ºC. Among the prepared composites those sintered at 1400 ºC achieved the best properties. The prepared composites maintained high hardness (up to 24.85 GPa), high tensile strength (up to 309 GPa), relatively high fracture toughness (up to 4.80 MPa∙m1/2) and relatively low density, all of which characterized TiB2-SiC UHTC systems.

Mechanical properties and water vapour corrosion behaviour of Al x CoCrFeNi high-entropy alloys.

Al x CoCrFeNi (x = 0.1, 0.5 and 1) high-entropy alloys (HEAs) were prepared using a spark plasma sintering (SPS) technique combined with aerosol powder. Their microstructure and phase constituents were characterized using an X-ray diffractometer and SEM, and their tensile properties, hardness and compactness were tested. The results show that the crystal structure of the Al x CoCrFeNi HEAs changed significantly with the Al content, from the original single face-centered cubic FCC phase (Al0.1CoCrFeNi) to an FCC + BCC structure (Al0.5CoCrFeNi), and then to FCC + BCC + sigma (σ) phase structures (AlCoCrFeNi). Chemical composition analysis showed that the crystal structure transformation was related to the segregation caused by the increased Al content. The hardness of the Al x CoCrFeNi HEAs increases with increasing Al content, and the hardness of AlCoCrFeNi reaches a maximum of 507.3 HV. The tensile properties of the alloy show a trend of first increasing and then decreasing with increasing Al content, and the yield strength, ultimate tensile strength and elongation of the Al0.5CoCrFeNi alloy reach maximum values of 527.4 MP, 943.3 MPa and 28.2%, respectively. The fracture mechanism of the Al0.1CoCrFeNi and Al0.5CoCrFeNi alloys is typical ductile fracture, while that of the AlCoCrFeNi alloy is cleavage fracture. The compactness of the alloy increases with the Al content. The samples were also subjected to high-temperature water vapour corrosion, and corrosion products such as Al3Fe5O12, CoCr2O4 and NiCr2O4 were found in the Al0.1 and Al0.5 alloys, whereas no oxide peaks were detected using XRD for the Al1 alloy. It was also presumed that a very thin alumina film was generated on the surface of the Al1 alloy, preventing the oxidation of the sample, in combination with the analysis of SEM, EDS and XPS behaviour.

The role of internal architecture in producing high-strength 3D printed cobalt-chromium objects.

The objectives of the current study were to estimate the influence of self-reinforced hollow structures with a graded density on the dimensional accuracy, weight, and mechanical properties of Co-Cr objects printed with the direct metal laser sintering (DMLS) technique. Sixty-five dog-bone samples were manufactured to evaluate the dimensional accuracy of printing, weight, and tensile properties of DMLS printed Co-Cr. They were divided into Group 1 (control) (n = 5), Group 2, 3, and 4 with incorporated hollow structures based on (spherical, elliptical, and diamond) shapes; they were subdivided into subgroups (n = 5) according to the volumetric reduction (10%, 15%, 20% and 25%). Radiographic imaging and microscopic analysis of the fractographs were conducted to validate the created geometries; the dimensional accuracy, weight, yield tensile strength, and modulus of elasticity were calculated. The data were estimated by one-way ANOVA and Duncan's tests at P < .05. The accuracy test showed an insignificant difference in the x, y, z directions in all printed groups. The weight was significantly reduced proportionally to the reduced volume fraction. The yield strength and elastic modulus of the control group and Group 2 at 10% volume reduction were comparable and significantly higher than the other subgroups. The printing accuracy was not affected by the presence or type of the hollow geometry. The weight of Group 2 at 10% reduction was significantly lower than that of the control group. The yield strength and elastic modulus of the Group 2 at a 10% reduction showed means equivalent to the compact objects and were significantly higher than other subgroups.

Phase stability and microstructural properties of high entropy alloy reinforced aluminium matrix composites consolidated via spark plasma sintering

Spark plasma sintering (SPS) technique was employed in the consolidation of Cr20Mn20Ni20Cu20Nb10Co10 high entropy alloy (HEA) reinforced aluminium matrix composites. Phase stability and prediction expressions were used in the determination of the powder combination for the HEA. The microstructural analysis showed that an interdiffusion layer was formed between the aluminium matrix and the HEA particles in the sintered composites. Further investigation of the composites by X-ray diffraction (XRD) showed that in addition to the Al matrix phase present, other new phases (BCC, FCC and other intermetallics) were formed as a result of the reaction between the Al matrix and the atoms precipitated from the added HEA during sintering. The density of the HEA-reinforced Al matrix composites decreases with an increase in the wt.% of HEA from 98.6 % for pure aluminium to 98.1 % for the reinforced alloy with 10 % HEA, while the microhardness increases with an increase in the wt.% of the HEA from 35 HV for pure aluminium to 96.0 HV for the alloy reinforced with 10 % HEA.

Influence of sintering temperature on Ti6Al4V-Si3N4-ZrO2 ternary composites prepared by spark plasma sintering

In this study, Ti6Al4V-ZrO2-Si3N4 ternary composites were fabricated using a novel spark plasma sintering technique at different temperatures between 950-1200 °C, the pressure of 50 MPa, sintering rate of 100 °C/min, and a holding time of 10 min to determine the effect of sintering temperature on the consolidated composites. The microstructures of the fabricated composites were examined by the scanning electron microscope (SEM-EDX). The distinct phases and the nano-mechanical properties of the composite were determined by the X-ray diffractometer and nanoindenter. The results show a non-linear response. At elevated temperatures from the composite sample, CT1-950 °C to the composite sample, CT2-1100 °C, the densification, and nanomechanical properties experienced an increase, and when the temperature is elevated to 1200 °C, composite CT3 declines in values. However, the relative density of all fabricated composites was above 95%, which suggests an overall good densification via the spark plasma sintering technique. The ternary composite fabricated at 1100 °C, (CT2) attained maximum values of Vickers hardness, elastic modulus, and nano hardness at 7380 MPa, 177.91 GPa, and 60.06 GPa, respectively, while composite CT3 declines at 1200 °C.

Investigation of microstructural, mechanical and tribological properties of NiTi/nB4C metal matrix composites produced by spark plasma sintering

In this paper, it was aimed to improve the microstructure, mechanical and tribological properties of composite samples according to the alloy by adding 0.25%, 0.5% and 1% nano B4C to NiTi shape memory alloy. A 3D ball mixer device was used to prepare composite powders and the samples were produced by Spark Plasma Sintering technique. FE-SEM/EDS and XRD were used for microstructure and phase characterization, nanoindentation to determine mechanical properties, and pin-on disc wear device to determine wear properties. It was determined that with the increase in the reinforcement ratio added to the NiTi alloy, nB4C ceramic particles settled at the grain boundaries and the hardness value of the 1% nB4C (334 HV) sample with the highest hardness increased significantly by 30% unreinforced NiTi alloy (264 HV).

Enhanced thermoelectric properties of p-type α-SrSi2 nanostructured by melt spinning

A melt spinning technique followed by spark plasma sintering technique was used to synthesize nanostructured SrSi2 alloys with high homogeneity and density (>99 %). The impact of the wheel speed on the microstructure of the ribbons was investigated and shows the presence of nanostructures. After sintering, typical grain size between ∼140 and ∼400 nm was obtained. We show that they permit to decrease strongly the lattice thermal conductivity. The ZT values of these melt-spun alloys are about two times higher than in our bulk material. We finally show that this short step process could be of strong interest for further development.

Effect of full melt temperature sintering and semi-melt heat preservation sintering on microstructure and mechanical properties of Ti3SiC2/Cu composites

The influence of sintering parameters on the microstructure, phase composition and mechanical property of the Ti3SiC2/Cu composites sintered by spark plasma sintering technique was investigated and the related sintering mechanism was clarified in detail. Results indicated that during the heating process, one part of the high energy adsorbed by the composites let Cu melt and fill the gaps inside the composites. Meanwhile, there’s different molten condition about Cu duel to different heating temperature that cause Cu fill in the most space between Ti3SiC2 particles. The other part of the energy caused to the local high temperature, contributing for the chemical reaction and the formation of TiCx and Cu3Si. Therefore, at the same heating rate, the composites showed better mechanical property and higher density with a longer heating time. The heating stage played an important role in the change of the mechanical property, microstructure and volume of the composites. During the holding stage, because the amount of the reactants significantly decreased, the related chemical reaction got slow and the energy needed during this stage was lower than that during the heating stage. And the particle of Ti3SiC2 need more time for moving to the space of Cu. Therefore, the higher the holding temperature, the more significant was the diffusion of the phases. The more uniform the phases, the higher was the density. When heating temperature (higher than holding temperature) cause Cu complete melt and holding temperature keep the Cu in semi-melt, there will be a more effective sintering method.

Characterization of Iron – Based Partial Pre - Alloyed Powders as Matrix Materials for Diamond Tools

Fe-Cu-Co is a structural component used in applications requiring both high strength and high hardness. A diamond cutting tool with iron -based (Fe -53%, Cu – 28%, Co -17%, P– 1% &amp; Ni -1%) pre-alloyed powders was prepared in the laboratory using powder metallurgy technique. Commercially available pure powders were combined to create the alloys, which were then roll compacted into bars and right away hot processed into fully dense alloy bars. Solid state sintering technique is used to manufacture composite material as it gives less defectives, more accurate than casting and excellent dimensional control. During sintering process metal powders are blended in ball milling and are compacted on hot press machine by applying heat and pressure simultaneously at different elevated temperatures. The sintered specimens are subjected to hardness, impact, density and porosity tests along with fractography study. From experimental observations it is found that material has high hardness than the steel, which can withstand mechanical vibrations, high impact strength and high toughness. According to experimental results it is most suitable for cutting applications, and there is a possibility to add diamond crystals in this tool, to strengthen hardness helping to cut the rocks.

Comparative Evaluation of the Marginal and internal adaptation of Metal Copings Fabricated using Conventional Casting, Computer aided Design/ Computer aided Milling and direct Metal Laser Sintering techniques: An invitro study

Comparative Evaluation of the Marginal and internal adaptation of Metal Copings Fabricated using Conventional Casting, Computer aided Design/ Computer aided Milling and direct Metal Laser Sintering techniques: An invitro study

Effects of adding carbonyl Fe or Mn–Zn ferrite powders to fibre-based soft magnetic composites prepared via hybrid cold sintering/spark plasma sintering

This manuscript presents the preparation and characterisation of fibres-based soft magnetic composites that incorporates a secondary magnetic phase such as carbonyl Fe and Mn–Zn ferrite nanopowder. Amorphous Fe77.7Si7.5B15 at.% fibres were coated with a dielectric layer of ZnO via thermal evaporation. SEM-EDX investigations revealed that the thermal evaporation technique leads to a complete coating of the fibres with a ZnO coating having a thickness of 150–250 nm as demonstrated via STEM-EDX analysis. The hybrid cold sintering/spark plasma sintering technique was used for the first time for the preparation of soft magnetic composites. Substituting 10 wt% of ZnO with carbonyl Fe resulted in an increase in the saturation magnetisation of the composite from 0.61 T to 0.7 T. In contrast, substituting it with Mn–Zn ferrite led to a decrease in saturation magnetisation from 0.61 T to 0.5 T. The coercivity of the composites increased when ZnO was partially substituted with Fe or Mn–Zn ferrite, rising from 16.9 A/m to 22.7 A/m and 36.8 A/m, respectively. AC magnetic characterization revealed that the relative permeability of the composites remains constant across the entire frequency range tested for all composites. However, the introduction of carbonyl Fe or Mn–Zn ferrite led to a reduction in the relative permeability values of the composites from 1310 to 1200 and 890, respectively. The core losses of the composites were also influenced by the secondary magnetic phase used. The use of Mn–Zn ferrite or carbonyl Fe resulted in a significant increase in the hysteresis losses of the composites. When carbonyl Fe was used for partial substitution of ZnO, a substantial increase of the eddy currents losses of the composites was noted.

Dry tribological behaviour of microwave-assisted sintered AA2024 matrix hybrid composites reinforced by TiC/B4C/nano-graphite particles

Abstract This study aimed to produce hybrid composites with a AA2024 matrix reinforced by TiC/B4C/nano-graphite through a microwave-assisted sintering technique at 560 °C for 60 min. The nano-graphite ratio in the produced composite samples was kept constant as 1 wt.%. TiC and B4C were used in equal ratios at 2, 6 and 10 % by weight total to determine their effects on tribological properties. Wear tests were conducted under three different loads: 3, 5 and 10 N. In the hybrid composites produced, an inverse correlation was observed between the increase in reinforcement ratio and sinterability, while a direct correlation relationship was found in hardness and wear resistance. Compared to the sample containing 2 % TiC/B4C in total by weight, a ∼50 % increase in Brinell hardness and a 52–68 % decrease in wear rate was obtained in the sample containing 10 % TiC/B4C. As the reinforcement ratio increased, tribofilm formation increased, and abrasive wear was replaced by mild-oxidative wear type.