Effect Of Sintering Additives Research Articles

Effects of sintering additives and sintering methods on the mechanical, antimicrobial and optical properties of Si3N4 bioceramics

Si3N4 bioceramics were fabricated using GPS and SPS method with MgO-RE2O3 (RE = La, Nd, Gd, Ho and Lu) sintering additives. The effect of sintering methods and sintering additives on the grain growth, mechanical, antimicrobial properties and color of Si3N4 bioceramics were studied. Samples sintered with GPS are composed of β-Si3N4 and samples sintered with SPS are composed of α-Si3N4 and β-Si3N4. The growth of β-Si3N4 grains in samples sintered with GPS are more adequate. Samples sintered with GPS exhibit a S. aureus inactivation rate up to 98% and a bright color appearance with a hardness of about 13 GPa and a fracture toughness up to 7.5 MPa m1/2, suitable for dental implants. And samples sintered with SPS exhibit a hardness of about 17 GPa and a fracture toughness about 6 MPa m1/2.

High luminous efficiency and high saturation threshold in highly transparent LuAG:Ce phosphor ceramics for laser diodes lighting.

Lu3Al5O12:Ce (LuAG:Ce) phosphor ceramics (PCs) with the excellent thermal stability and high saturation threshold are considered as the best green-fluorescent converters for high-power laser diodes (LDs) lighting. In this study, the effects of sintering additives and sintering processes on the transmittance and microstructure of LuAG:Ce PCs were systematically studied, and the luminescence performance of ceramics with different transmittance was compared. LuAG:Ce PCs with the transmittance of 80% (@800 nm, 1.5 mm) were obtained by using 0.1 wt.% MgO and 0.5 wt.% TEOS as sintering additives, combined with optimized vacuum pre-sintering and hot isostatic pressing. Compared to the non-HIP samples, the transmittance had increased by 11%. The microstructure of ceramics indicated that high transparency was closely related to the decrease in intergranular pores. Notably, the luminous efficiency of 253 lm/W and its saturation thresholds of > 46 W/mm2 were obtained simultaneously in green-emitting LDs devices. Moreover, under 3W laser irradiation, highly transparent ceramics had the low surface temperature of 66.4 °C, indicating the good heat dissipation performance. The observed high luminous efficiency and high saturation threshold of LuAG:Ce PCs were attributed to fewer pores and oxygen vacancies. Therefore, this work proves that highly transparent LuAG:Ce PCs are promising green-fluorescent converters for high-power LDs lighting.

Effect of sintering additives on fabrication of silica porous glass structure

Effect of sintering additives on fabrication of silica porous glass structure

Effects of sintering additives on dielectric breakdown strength of sintered reaction-bonded silicon nitride

We prepared sintered reaction-bonded silicon nitride (Si3N4) by using various lanthanide oxides and magnesia for sintering additives and evaluated their effects on the microstructure and dielectric breakdown strength (DBS). Both the microstructure and DBS varied by the types of the sintering additives, and artificial intelligence (AI) based determination was conducted for the DBS to separate the effect of microstructural factors from that of sintering additives. The results indicated that the DBS values varied mainly by the former effect. The microstructures of Si3N4 with Eu2O3 and La2O3 contained a large number of pores, leading to lowered DBS; on the contrary, those with Tm2O3 and Y2O3 possessed dense microstructures with large-elongated grains, showing higher DBS. On the other hand, the Si3N4 with Yb2O3 showed lower DBS than what AI-determined from the microstructures because the additive forms grain boundary phase with a low electrical resistance.

An insight into sintering mechanisms of silicon carbide nanoparticles with additives using MD simulation

The effect of sintering additives on the sintering of SiC nanoparticles is studied by MD simulation. A new potential function is developed based on the lattice size theory. The Al-Si-C element system, Ti-Si-C element system, and V-Si-C element system are simulated and compared. MD simulation can be used to select the sintering additives of SiC ceramics and Al is better by atomic diffusion analysis. The nanoparticle sintering evolution processes with/without aluminum are studied in detail and compared with the typical sintering experimental results. The sintering mechanisms of nanoparticles are quantitatively analyzed by sintering neck growth, energy evolution, and atomic diffusion. The results show that it is beneficial for selecting an appropriate temperature to obtain the highest sintering promotion effect with additives. Kinds of sintering mechanisms are summarized and in good agreement with the traditional sintering theory. The results here are helpful to understand the sintering underlying mechanism of SiC ceramics.

Effects of sintering additives on defect chemistry and hydration of BaZr0.4Ce0.4(Y,Yb)0.2O3−δ proton conducting electrolytes

The effects of NiO, ZnO, and CuO sintering additives (0.5, 1.0, or 2.0 wt%) on the sintering behaviour, effective acceptor concentration, and hydration thermodynamics are examined for BaZr0.4Ce0.4Y0.1Yb0.1O3−δ and BaZr0.4Ce0.4Y0.2O3−δ proton conducting electrolytes. Thermogravimetry of hydration shows that the sintering additives – except for 0.5 wt% CuO – lead to a decrease in the effective acceptor concentration, and the decrease per mole sintering additive is the largest for NiO. The absence of typical secondary phases such as BaY2NiO5 and the homogeneous distribution of Ni determined from elemental mapping imply that sintering additives dissolve into the perovskite lattice. Exsolution of metallic Ni and Cu upon reduction leads to a substantial recovery of the effective acceptor concentration. Subsequent oxidation is accompanied by a repeated decrease in the effective acceptor concentration as the sintering additives appear to re-dissolve. Defect chemical reactions are proposed to explain the observed results and these are supported by energetics from first principles calculations. Overall, NiO has the highest positive impact on densification and grain growth, and a relatively small amount of 0.5 wt% NiO or CuO is preferable to optimise both sintering and hydration.

Effects of MgO-RE2O3 and SiO2-RE2O3 (RE = La, Nd, Gd, Ho and Lu) complex sintering additives on the phase composition, microstructure and mechanical properties of dual-phase Si3N4 ceramics

Dual-phase (α+β)-Si3N4 ceramics with MgO-RE2O3 and SiO2-RE2O3 (RE = La, Nd, Gd, Ho and Lu) complex sintering additives were prepared by SPS at 1650 and 1700 °C. The effect of sintering additives on the phase transition, microstructure evolution and mechanical properties of the Si3N4 ceramics were studied. For the MgO-RE2O3 samples, as the RE radius increased, the phase transition was decelerated, the percentage of rod-like grains and fracture toughness decreased and the hardness showed a hill-shape curve. It is proposed that the effect of RE radius is connected with the segregation behavior of RE cations on the surface of Si3N4 grains. For the SiO2-RE2O3 samples, as the RE radius increased, the phase transition was accelerated and the percentage of rod-like grains increased. It is suggested that the effect of RE radius is related with the liquid phase viscosity and nitrogen solubility.

Effect of sintering additives on the properties of alumina toughened zirconia (ATZ)

The effect of small amounts of copper oxide, manganese oxide, and stainless steel as sintering additives on the sintering behavior and mechanical properties of Alumina Toughened Zirconia (ATZ, 3Y-TZP with 20 wt% Al2O3) ceramic composites were evaluated and contrasted with that of undoped ATZ by using microwave sintering (MW) method. Green bodies were sintered at 1250°C, 1350°C, and 1500°C using a holding time of 5 min., with a heating rate of 30°C /min. In general, all ATZ samples exhibited a similar trend, as the results showed that the relative density and mechanical properties increased with increasing sintering temperature regardless of the addition of dopants. It was found that the addition of 0.2 wt% CuO, 0.5 wt% MnO2, and 0.2 wt% SS were beneficial in enhancing the densification and improving the mechanical properties of ATZ without inducing grain coarsening. The ATZ composite samples' relative density, tetragonal phase stability, microstructural evolution, Vickers hardness, and fracture toughness were revealed. The addition of 0.2 wt% CuO was the most beneficial in improving the properties of ATZ at a low sintering temperature of 1250°C since the sample obtained the highest relative density of 97%, Vickers hardness of 13.2GPa and fracture toughness of 6.5 MPa m1/2. In contrast, the undoped ATZ required a high sintering temperature to achieve comparable results to the doped samples. The ANOVA analysis revealed that the CuO-doped ATZ sample exhibited the highest significance and was the most suitable in improving both hardness (H) and fracture toughness (KIc) across all temperature conditions. This study also proved that the microwave sintering technique promotes the densification and mechanical properties of ceramic composites compared to the conventional sintering technique.Graphical abstract

Effect of Li2CO3–Bi2O3 doping on the low-temperature sintering, structure, and dielectric and mechanical properties of MgO–TiO2(w) ceramics

Dense MgO–12% TiO2(w) ceramics containing 12 wt% TiO2, which were doped with Li2CO3–Bi2O3 composite sintering aids, were prepared at a low sintering temperature of 950 °C in this study. The effects of sintering additives on the sintering characteristics, phase composition, microstructure, and dielectric and mechanical properties of the ceramic samples were systematically investigated, and the influences of their phase composition and microstructure on the dielectric and mechanical properties were examined. The introduction of sintering aids produced a new Bi4Ti3O12 phase in the sample structure, while the residual Bi2O3 mixed with the newly formed Mg2TiO4 and Bi4Ti3O12 phases distributed at MgO grain boundaries formed a structure surrounding MgO grains. This structure filled the pores in the ceramic sample, which increased its density and enhanced the mechanical properties. At a Li2CO3–Bi2O3 content of 15 wt%, the density, flexural strength, and Vickers hardness of the ceramic samples reached their maximum values of 3.4 g/cm3, 218.9 MPa, and 778.7 HV, respectively. However, the further increase in the Li2CO3–Bi2O3 content deteriorated their dielectric properties although the dielectric constant and dielectric loss remained below 13.4 and 2.1 × 10−3, respectively. The findings of this work indicate that Li2CO3–Bi2O3 sintering aids can significantly lower the sintering temperature of MgO–12% TiO2(w) ceramics and control their dielectric and mechanical properties through microstructural changes.

Sintering Aid Strategy for Promoting Oxygen Reduction Reaction on High-Performance Double-Layer LaNi0.6Fe0.4O3-δ Composite Electrode for Devices Based on Solid-State Membranes.

Strontium and cobalt-free LaNi0.6Fe0.4O3-δ is considered one of the most promising electrodes for solid-state electrochemical devices. LaNi0.6Fe0.4O3-δ has high electrical conductivity, a suitable thermal expansion coefficient, satisfactory tolerance to chromium poisoning, and chemical compatibility with zirconia-based electrolytes. The disadvantage of LaNi0.6Fe0.4O3-δ is its low oxygen-ion conductivity. In order to increase the oxygen-ion conductivity, a complex oxide based on a doped ceria is added to the LaNi0.6Fe0.4O3-δ. However, this leads to a decrease in the conductivity of the electrode. In this case, a two-layer electrode with a functional composite layer and a collector layer with the addition of sintering additives should be used. In this study, the effect of sintering additives (Bi0.75Y0.25O2-δ and CuO) in the collector layer on the performance of LaNi0.6Fe0.4O3-δ-based highly active electrodes in contact with the most common solid-state membranes (Zr0.84Sc0.16O2-δ, Ce0.8Sm0.2O2-δ, La0.85Sr0.15Ga0.85Mg0.15O3-δ, La10(SiO4)6O3-δ, and BaCe0.89Gd0.1Cu0.01O3-δ) was investigated. It was shown that LaNi0.6Fe0.4O3-δ has good chemical compatibility with the abovementioned membranes. The best electrochemical activity (polarization resistance about 0.02 Ohm cm2 at 800 °C) was obtained for the electrode with 5 wt.% Bi0.75Y0.25O1.5 and 2 wt.% CuO in the collector layer.

Effect of sintering additives on Y2O3 ceramic: Synthesis, structural, morphological, and optical properties investigations

Solid-state ceramic lasers have a wide range of applications in industrial, medical, and military applications. This research work presents the fabrication of vacuum sintered Y2O3 ceramics synthesized using co-precipitation method. The impact of sintering additives such as La2O3 and ZrO2 were examined on the structural and morphological traits of Y2O3. The development of pure cubic phases is revealed by X-ray diffraction studies. Williamson-Hall method is used to determine the crystallite size and micro-strain. The incorporation of La3+ and Zr4+ are confirmed through FTIR spectra. The optical characteristics are investigated through UV–VIS spectroscopy. The addition of La3+ and Zr4+ additives increases the densification of Y2O3 ceramic pellets and improves their sintering behavior. The effect of sintering additives on grain size and elemental composition were examined using scanning electron microscopy and energy dispersive spectroscopy.

On the fabrication and mechanical properties of Si3N4 ceramics with low content sintering additives

AbstractSi3N4 ceramics were prepared by hot pressing (HP) and spark plasma sintering (SPS) methods using low content (5 mol%) Al2O3–RE2O3(RE = Y, Yb, and La)–SiO2/TiN as sintering additives/secondary additives. The effects of sintering additives and sintering methods on the composition, microstructures, and mechanical properties (hardness and fracture toughness) were investigated. The results show that fully density Si3N4 ceramics could be fabricated by rational tailoring of sintering additives and sintering method, and TiN secondary additive could promote the density during HP and SPS. Besides, SN‐AYS‐SPS possesses the most competitive mechanical properties among all the as‐prepared ceramics with the Vickers hardness as 17.31 ± .43 GPa and fracture toughness as 11.07 ± .48 MPa m1/2.

Effect of sintering additives on the densification and dielectric properties of Sr0.5Ba0.5Nb2O6 ceramics synthesized by a soft-chemistry method

Nano-crystalline Sr0.5Ba0.5Nb2O6 powders with addition of LiNbO3 or LiF as sintering additives were prepared by a soft-chemistry synthesis using polyethylene glycol. Calcination at 600 ​°C results in nanocrystalline powders (dcryst. ​≈ ​30 ​nm) which were sintered between 1000 and 1300 ​°C to ceramic bodies. By addition of 10 and 20 ​mol% LiNbO3, the sintering temperature was reduced by about 200 ​K and the activation energy of the initial stage of sintering decreases from 386 to 271 ​kJ ​mol−1. The sintering aid improves the grain growth and dense ceramic bodies were obtained after sintering at 1125 ​°C for 1 ​h. A higher LiNbO3 content favors the formation of a pillar-like microstructure. XRD patterns of ceramics sintered above 1000 ​°C show only reflections of the Sr0.5Ba0.5Nb2O6 phase indicating an incorporation of LiNbO3 in the Sr0.5Ba0.5Nb2O6 structure. Dielectric measurements reveal a diffuse phase transition and a relaxor-like behavior. The phase transition temperature (Tm) depends on the sintering conditions and is between 117 and 127 ​°C for 10 ​mol% LiNbO3, which is very close to pure Sr0.5Ba0.5Nb2O6, while addition of 20 ​mol% shifts Tm to around 200 ​°C and the transition becomes slightly more diffuse. The optical band gap of the samples is ​≈ ​3.3 ​eV and depends slightly on the sintering conditions. We also tried LiF as sintering aid, but this leads to the formation of considerable amounts of secondary phases in the ceramics and relative densities of only 82%.

Effect of Sintering Additives on the Sintering and Spectral-Luminescent Characteristics of Quaternary GYAGG:Ce Scintillation Ceramics

Effect of Sintering Additives on the Sintering and Spectral-Luminescent Characteristics of Quaternary GYAGG:Ce Scintillation Ceramics

Effects of Sintering Additives on Microstructure and Mechanical Properties of Hot-Pressed α-SiC Ceramics

Effects of Sintering Additives on Microstructure and Mechanical Properties of Hot-Pressed α-SiC Ceramics

Improving photostriction of KNN-based ceramics by MnO2 additive and polarization

The effects of sintering additives on photostriction properties have been rarely reported and the polarization effect of KNN-based ceramics on the photostriction characteristics remains uncertain. In the present work, a highly feasible approach has been adopted to obtain improved photostrictive coefficient (α = 2.4 × 10−9 m2/W) for KNN-based ceramics by adding appropriate amount (x = 0.5 wt%) of MnO2 as sintering additives into 0.97(K0.5Na0.5)NbO3-0.03(La0.51Na0.49)(Zr0.54Ni0.46)O3 (97KNN-3LNNZ) ceramics. The appropriate amount of MnO2 (x ≤ 0.5 wt%) in the ceramics does not alter the inherent multi-phase structure and results in uniform grain growth of the ceramics. The ferroelectricity and piezoelectricity can be optimized by the “softening” effect of Mn2+ and Mn3+ in KNN-based ceramics. The addition of MnO2 increases energy band gap and also optimizes the optical absorption properties in the near-infrared band. 97KNN-3LNNZ+0.5 wt% MnO2 ceramics show optimum overall performance. In addition to this, for x = 0.5 wt% sample, the power-dependent Raman spectra of ceramics measured before and after the electrical poling shows that the prior E-field poling can enhance the red shift corresponding to F2g bending vibration mode. Subsequently, there are changes in bond angle of elements induced by light in oxygen octahedron. These phenomena play active roles in getting a deep understanding of the underlying mechanisms of photostriction for ferroelectric ceramics.

The Effects of Sintering Additives on the Sintering of 3Y-TZP Ceramic

The influence of 0.5 wt.% of manganese oxide (MnO2) addition as dopant into 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) were studied in comparison to undoped 3Y-TZP using different sintering profiles. Samples were sintered at 1200°C, 1300°C and 1400°C with holding time of 1 min, 12 min, 2 hours and 20 hours all for single step sintering. The optimal sintering profiles are A4 and C2 where 3Y-TZP doped with 0.5% wt. MnO2 sintered at 1400°C for 12 minutes and 1200 °C for 20 hours respectively. At these sintering parameters, the MnO2 doped 3Y-TZP sample exhibited relative density of ~97%, Vicker’s Hardness value of ~13 GPa, Fracture toughness value of ~4 MPam1/2 and Young’s modulus of ~210 GPa.

Effects of sintering additives on hot corrosion behavior of γ-Y2Si2O7 ceramics in Na2SO4+V2O5 molten salt

Dense γ-Y2Si2O7 ceramics were prepared by moulding and sintering of pure γ-Y2Si2O7 powders synthesized by adding various additives. Effects of sintering additives on hot corrosion behavior of γ-Y2Si2O7 ceramics in Na2SO4 + V2O5 molten salts were systematically investigated. Chemical kinetics of corrosion process was also calculated to illuminate the influence of different additives on chemical stability. Results showed that corrosion reaction started at grain boundary due to the loose microscopic network. When the intercrystalline glass phase was completely etched, the molten salts began to contact Y2Si2O7, forming NaY9Si6O26 and YVO4. Compared with Li2O and MgO, intercrystalline glass phase formed by Al2O3 additive had the most compact microscopic network structure, leading to the best chemical stability. Apparent activation energy for hot corrosion reaction of γ-Y2Si2O7 ceramics in pure Na2SO4, Na2SO4 + 5 wt% V2O5, Na2SO4 + 10 wt% V2O5, Na2SO4 + 15 wt% V2O5 molten salts was calculated to be 408.16, 373.60, 310.62, and 249.63 kJ/mol, respectively.

Comparison of hydrothermal corrosion behavior of SiC with Al2O3 and Al2O3 + Y2O3 sintering additives

AbstractFully dense SiC bulks with Al2O3 and Al2O3 + Y2O3 sintering additives were prepared by spark plasma sintering and the effect of sintering additives on the hydrothermal corrosion behavior of SiC bulks was investigated in the static autoclave at 400°C/10.3 MPa. The SiC specimen with Al2O3 sintering additive exhibited a higher weight loss and followed a linear law. However, the SiC specimen with Al2O3 + Y2O3 additive exhibited a lower weight loss and followed a parabolic law, indicating that the corrosion kinetic and mechanism were different for these two SiC bulks. Further examination revealed that, a deposited layer was formed on the surface of SiC specimen with Al2O3 + Y2O3 sintering additive after corrosion, which can effectively protect the SiC specimen from further corrosion, and thereby improved the corrosion resistance of the SiC specimen with Al2O3 + Y2O3 sintering additive.

Effects of Sintering Additives on the Thermal and Mechanical Properties of AlN by Pressureless Sintering

Effects of Sintering Additives on the Thermal and Mechanical Properties of AlN by Pressureless Sintering