Sintering Properties Research Articles

The mechanical and dielectric properties of high-density Ti-doped MgAl2O4 ceramic prepared by non-hydrolytic sol-gel combined with mechanochemical method

The synthesis of MgAl2O4 requires high calcination temperatures which generally result in larger grain sizes and smaller specific surface areas. These factors pose challenges in achieving high-density MgAl2O4 ceramic. This study introduces an innovative approach that has successfully sintered MgAl2O4 ceramic at 1500 ℃ with MgAl2O4 powder prepared using a Non-Hydrolytic Sol-Gel (NHSG) method combined with a mechanochemical method. The sintered MgAl2O4 ceramic with 2 wt% TiCl4 doping displays an apparent porosity of only 0.09 %, a flexural strength of 183 MPa, a relative permittivity of 8.7, a quality factor of 77000 GHz, and a frequency temperature coefficient of −59.4 ppm/℃. The introduction of titanium ions causes lattice distortion and cationic vacancies, which promotes sintering and improves the mechanical and dielectric properties of the resulting ceramic. This study demonstrates the effectiveness of NHSG combined with the mechanochemical method in preparing MgAl2O4 ceramic with enhanced sintering properties.

Adaptability analysis of H2-rich gas injection and sintered ore performance with different raw material ratios

As a source substitution technology that reduces pollutants emission and optimizes sinter properties, H2-rich gas injection-assisted iron ore sintering holds significant practical value. This study analyzed the adaptability of this technology to different ore blend ratios and basicity levels by comparing sintering indexes, pore structure, mineral phase composition, and metallurgical performance before and after H2-rich gas injection. The carbon emission reduction following H2-rich gas injection was calculated. The results indicate that increasing the proportion of high-silica, low-alumina ore (Ore-A) and basicity, along with H2-rich gas injection, can effectively enhance sinter yield and quality, but shrink the pore structure of sinter. Under H2-rich gas injection conditions, decreasing Ore-A ratios and increasing basicity can augment SFCA phase formation and mineral phase uniformity, thereby improving the anti-pulverization ability and reductivity of the sinter. H2-rich gas injection presents better adaptability to sintered ore with lower Ore-A ratio and basicity, which can achieve greater improvements in the sintering indexes, RDI, and RI. For a 265 m2 sinter plant producing sinter with 18 wt.% Ore-A and 2.0 basicity, annual CO2 emissions can be reduced by approximately 40,000 t.

Facile Synthesis, Sintering, and Optical Properties of Single-Nanometer-Scale SnO2 Particles with a Pyrrolidone Derivative for Photovoltaic Applications

We investigate the preparation of mesoscopic SnO2 nanoparticulate films using a Sn(IV) hydrate salt combined with a liquid pyrrolidone derivative to form a homogeneous precursor mixture for functional SnO2 nanomaterials. We demonstrate that N-methyl-2-pyrrolidone (NMP) plays a crucial role in forming uniform SnO2 films by both stabilizing the hydrolysis products of Sn(IV) sources and acting as a base liquid during nanoparticle growth. The hydrolysis of Sn(IV) was controlled by adjusting the reaction temperature to as low as 110 °C for 48 h. High-resolution TEM analysis revealed that highly crystalline SnO2 nanoparticles, approximately 3–5 nm in size, were formed. The SnO2 nanoparticles were deposited onto F-doped SnO2 glass and converted into dense particle films through heat treatments at 400 °C and 500 °C. This pyrrolidone-based nanoparticle synthesis enabled the production of not only crystallized SnO2 but also transparent and uniform films, most importantly by controlling the slow hydrolysis of Sn(IV) and polycondensation only with those two chemicals. These findings offer valuable insights for developing stable and uniform electron transport layers of SnO2 in mesoscopic solar cells, such as perovskite solar cells.

Sintering and Tribological Properties of Ti3SiC2-TiSix Composite Sintered by High-Pressure High-Temperature Technology.

The Ti3SiC2TiSix ceramic composite was synthesized in situ from a mixture of 3Ti:1.5Si:1.2C powders under pressures ranging from 2 to 5 GPa and temperatures of 1150 °C to 1400 °C. At medium and high temperatures (4-5 GPa and 1400 °C), Ti3SiC2 dissolves into the cubic TiC phase. SEM analysis revealed that the high-pressure-produced multilayer structure of Ti3SiC2 remained intact. The friction properties of Ti3SiC2-TiSix composites combined with copper and aluminum were studied under both dry and lubricated conditions. After the break-in period, the Ti3SiC2-TiSix/Al combination exhibited the lowest friction coefficient: approximately 0.2. In dry-sliding conditions, the friction coefficient varies between 0.5 and 0.8. The wear mechanisms for Ti3SiC2-TiSix composites paired with aluminum primarily involve pear groove wear and adhesive wear during dry friction. Irregularly shaped aluminum balls accumulate in the pear grooves and adhere to each other. With increasing sintering pressure, the average friction coefficient of Ti3SiC2-TiSix composites against Cu ball pairs first increases and then decreases. The wear rate of the samples did not vary significantly as the sintering pressure increased, whereas the wear rate of Cu balls decreased with increasing sintering pressure. The adhesive wear of the Ti3SiC2-TiSix composite with its Cu counterpart is stronger than that of the Al counterpart. Abrasive chips of Cu balls appeared in flake form and adhered to the contact interface.

The effect of BaO addition on the sintering properties and grain growth behavior of CaZrO3 ceramics

The effect of BaO addition on the sintering properties and grain growth behavior of CaZrO3 ceramics

Microstructures evolution and properties of titanium vacuum sintering on metal injection molding 316 stainless steel via dip coating process

Enhancing the surface coating of 316 L stainless steel, fabricated via metal injection molding, is crucial for its application in cost-effective, mass-produced components. This study investigated the titanium coating on 316 L stainless steel to address its limitations in mechanical performance. Titanium was coated on the 316 L stainless steel via a dip coating process, followed by vacuum sintering at temperatures of 1100 °C, 1150 °C, and 1200 °C. The optimal mechanical properties were achieved with a 100 μm thick coating sintered at 1200 °C, which exhibited uniformity and good bonding strength. The microstructure results demonstrated an average yield strength of 342.63 MPa and a polarization impedance of 968.48 Ω·cm2. Electron probe microanalysis confirmed the uniform diffusion of titanium into the stainless steel substrate, forming intermetallic phases such as Fe2Ti and NiTi. In addition, this study conducted a heat treatment process for the as-coated specimens. It was found that annealing at 750 °C for 4 h oil quenched and a 550 °C three-hour aging treatment the polarization impedance increases to 1243.3 Ω·cm2 without compromising the yield strength. These findings indicate that the titanizing process enhances the mechanical properties of 316 L stainless steel, making it more suitable for demanding applications.

Low‐dielectric‐loss ZnZrNb2O8 ceramics combined with H3BO3 for low‐temperature co‐fired ceramics applications

AbstractH3BO3 was used as the sintering additive to enable Zn0.997Cu0.003ZrNb2O8 ceramics to accomplish low‐temperature sintering and outstanding microwave dielectric performances. Composite ceramics were created using typical solid‐state processes. The effects of added H3BO3 on the sintering behavior, microstructural characteristics, vibrational properties, and microwave dielectric performances of Zn0.997Cu0.003ZrNb2O8 + x wt% H3BO3 (2 x 8) ceramics have been systematically investigated by means of X‐ray diffraction, Raman scattering spectroscopy, scanning electron microscopy, and complex chemical bond theory. The results of relative density and microscopic morphology demonstrated that the application of an adequate quantity of H3BO3 additive can significantly enhance sintering properties. The doped H3BO3 alters the inter‐ionic interactions so that the structural features become intrinsic to the microwave dielectric performances. The particularly satisfactory microwave dielectric performances ( = 10.61, = 33 980 GHz, and = ‐45.10 ppm/°C) were detected in x = 6 ceramic specimens sintered at 950°C, which would make it promising for use in modern low temperature co‐fired ceramics technology.

Enhancement of sintering and mechanical properties of alumina-rich Al2O3-MgO-CaO refractory composite by doping La2O3

Ceramics or refractories prepared in the Al2O3-rich corner of the Al2O3-MgO-CaO system show excellent high-temperature mechanical properties and chemical stability because of the presence of spinel (MgAl2O4) and calcium hexaluminate (CaAl12O19). However, the densification of these two crystals usually requires high firing temperatures due to their poor sinterability. To address this issue, La2O3-doped MgAl2O4-CaAl4O7-CaAl12O19 refractory composites were designed, and the influence of the doping level on the densification, microstructure, and mechanical properties of the composite was investigated. It was found that the doped La3+ was predominantly dissolved in the CA6 grains by replacing Ca2+, forming uniform solid solutions regardless of doping concentration. This reaction significantly accelerates ion diffusion and CA2 grain growth. Besides, it reduces the aspect ratio of CA6 crystals, weakening the negative effect of the elongated grains on mass transfer and sintering. As a result, the relative density increases from 79.5 % to 95.1 % after sintering at 1600 °C with doping only 0.5 wt% La2O3 into the composite, producing a uniform and dense microstructure with regular angular grains. The above effects result in a significant improvement in flexural strength and fracture toughness (increasing by 61 % and 57 %, respectively). Moreover, the La2O3-doped refractory composite achieves a decline of the high-temperature creep rate by one order of magnitude at 1600 °C.

Calcined colemanite as an additive for iron ore sintering process

During sintering process, iron ores, fluxes and coke are agglomerated into a desirable blast furnace feed. The degrading iron ore quality and environmental norms has forced sinter producers to look for additives which can improve the sintering process efficiency. For the current work, use of calcined colemanite as an additive was studied by adding it from 0% to 4% within the sinter raw blend through lab-scale pot trials. During the sintering process, calcined colemanite forms a Calcium Borosilicate (Ca11B2Si4O22) phase at temperature above 400 °C which latter gets dissociated within the liquid melt thus increasing the liquid slag formation. Increasing calcined colemanite up to 2% increases tumbler index from 56.27% to 61.67%, decreasing thereafter to 55.33% at 4% of calcined colemanite. The sinter yield (+5 mm) is also found to be maximum of 89.39% at 2% of calcined colemanite. An increase in calcined colemanite from 0% to 4% increases sintering time from 20 to 26 min, decreasing the overall sinter productivity from 2.35 to 1.99 t/m2/h. Before integrating calcined colemanite within the sintering process at plant scale, its cost and efficacy must be considered. An alternate approach can be combining it with an organic binder where the two can complement each other in providing the required sinter properties.

Simultaneous effect of microwave sintering and TiO2 addition on sinterability, mechanical properties, and scratch resistance of zirconia toughened alumina ceramics

This paper delves into the transformative impact of varying titanium dioxide (TiO2) content on the sinterability, physical, and mechanical properties, as well as scratch behavior, of zirconia-toughened alumina (ZTA) ceramic composites. By adjusting TiO2 content from 0 wt% to 5 wt% and employing advanced microwave sintering at 1150 °C, the study aims to lower the sintering temperature of ZTA. Microwave sintering, known for its efficiency and rapid processing, enables significant enhancements in material properties at reduced temperatures. Notably, incorporating TiO2 into ZTA yields remarkable improvements in physical and mechanical attributes, with the optimal TiO2 content determined to be 3 wt%. At this concentration, the composite achieves exceptional properties: a relative density of ∼99 %, microhardness of ∼2002 HV, and an indentation fracture toughness of ∼6.13 MPa m0.5. These enhancements represent increases of over 120 % in hardness and 61 % in toughness compared to TiO2-free ZTA. Additionally, the highest scratch resistance is observed at 3 wt% TiO2, evidenced by a minimal scratch depth of ∼7.53 μm. However, exceeding the 3 wt% solubility limit results in the formation of secondary phases, such as tialite (Al2TiO5) and zirconium titanate (ZrTiO4), which degrade the composite's properties. This research underscores the potential of TiO2 doping and microwave sintering to elevate the performance of ZTA ceramics, offering a pathway to superior materials for advanced applications.

Sintering, microstructure and mechanical properties of anorthite-based ceramics prepared from iron-extracted steel slag

Steel slag is a promising source of ceramic materials, but it causes a waste of iron resources and inferior ceramic performance because the slag contains over 30 % iron oxides. To deal with this problem, we proposed a two-step utilization process for steel slag, including iron extraction by smelting reduction and ceramics preparation from residual slag. In this work, the effect of the reduced slag addition on phase constituents, microstructure, and properties of this novel ceramic was studied. The major crystalline phase is anorthite for all the ceramics. Although abundant liquid is expected theoretically in conventional ceramics at 1175 °C, it did not achieve vitrification until 1250 °C. The slag addition plays different roles in sintering under various slag contents. After introducing 15 wt% slag, the sintering and pore elimination are accelerated significantly because of the slag’s fluxing effect although the ceramic shows no change in the theoretical liquid content. The ceramics have no advantage in producing liquids with further increasing the slag content. Therefore, limited densification is observed with 30 wt% slag addition owing to the lack of liquid phase. Fortunately, solid solution diopside is largely generated in the anorthite matrix with 45 wt% slag addition, greatly enhancing the ion diffusion and grain growth. This effect contributes to a highly dense and uniform sintered structure with small rounded pores at 1175 °C, at which its flexural strength increases by 92 % compared to the conventional ones. However, a higher slag addition in the ceramic should be avoided to ensure satisfactory structure integrity.

Study on the mechanism of potassium fluoride, magnesium fluoride and calcium fluoride on the crystal morphology and sintering performance of fluorapatite functional glass-ceramics

Fluorapatite glass-ceramics were prepared at lower temperatures by atmospheric pressure sintering method using KF, MgF2 and CaF2 as additives, respectively. Using XRD, SEM and mechanical property test to justify the effect of different fluorides on the sintering properties of fluorapatite composites. The results show that fluoride can be used as nucleating agent, react with wollastonite and phosphate glass to crystallize rod-like fluorapatite phase during heat treatment. The crystallization mechanism of fluorine-containing glass-ceramics was analyzed by crystallization thermodynamics and crystallization kinetics. KF with lower melting point is beneficial to promote the crystallization reaction and improve the morphology stability of the glass ceramic composite, but the volatile gas released during the reaction will affect the mechanical properties of it, resulting in a flexural strength of only 11.81 MPa at 900 °C. For the samples supplemented with MgF2 and CaF2, because of the formation of polycrystalline phase systems, the flexural strength of the composite at 900 °C increases to 62.79 and 52.6 MPa, respectively.

Effect of increasing the proportion of high-alumina iron ore on structures and properties of sinter produced in iron ore blending sintering process

Effect of increasing the proportion of high-alumina iron ore on structures and properties of sinter produced in iron ore blending sintering process

Study on the microstructure, recrystallization, and mechanical properties of hot-press sintered (TiC + B4C)/6061Al composites during hot rolling

Hot rolling is a vital secondary processing technique for aluminum matrix composites. To explore the forming mechanism of (TiC+B4C)/6061Al composites during hot rolling, the 6061Al and (TiC+B4C)/6061Al composites were fabricated via vacuum hot-press sintering followed by hot rolling. The results show that reinforcing particles changed the distribution of Si and resulted in the in-situ generation of SiC in hot-rolled (TiC+B4C)/6061Al composites. During hot rolling, reinforcing particles inhibited the elongation and refined the size of Al grains, and contributed to further enhancing the hardness and strength of hot-rolled 6061Al. With the hot rolling reduction rate increasing, the hardness and strength of hot-rolled (TiC+B4C)/6061Al composites improved, and the refinement effect of reinforcing particles intensified. Both reinforcing particles and hot rolling exhibited effects on the recrystallization behavior of 6061Al during hot rolling, primarily through particle induced nucleation mechanism and strain induced grain boundary migration mechanism. Remarkably, the strength achieved by hot-rolled (TiC+B4C)/6061Al composites at a 20% hot rolling reduction rate rivals that of hot-rolled 6061Al at an 80% hot rolling reduction rate, while still preserving high plasticity. Hot-rolled (TiC+B4C)/6061Al composites predominantly exhibited the ductile fracture of aluminum matrix and cleavage fracture of particles, and the ductile fracture characteristics gradually weakened with the hot rolling reduction rate increasing. The dislocation increment strengthening mechanism contributed the most to the strength improvement of hot-rolled (TiC+B4C)/6061Al composites. This study can provide valuable insights into aluminum matrix composites.

Effects of NiO addition on the microstructural evolution and performance of sintered magnesia aggregates

This study introduces a novel approach to enhance the properties of sintered magnesium oxide (MgO) aggregates by incorporating nickel oxide (NiO) powder as a solid-solution modification additive. The addition of NiO improves the densification of the specimens and promotes grain growth through the activation of sintering via the solid-solution reaction of MgO–NiO at high temperatures. The formation of the (Mg, Ni)O solid-solution structure enhances the strength of the specimens, while gradually reducing thermal conductivity. However, excessive addition of NiO (>6 mol%) adversely affects the sintering properties of the specimens due to limited diffusive mass transfer rate during sintering and the Zener effect, resulting in diminished grain size and strength. Although thermal conductivity is not significantly affected, at 1000 °C, one specimen (MN-6) demonstrates a 61.03 % decrease in thermal conductivity compared to a specimen without NiO addition. These findings suggest that the incorporation of a moderate amount of NiO enhances the corrosion resistance of the cement clinker of the specimens primarily by increasing densification, grain size, and high-temperature contact angle.

Investigating electrical and magnetic properties of spark plasma sintered (FeCoNi)75Cu25−xSix high entropy alloys

Investigating electrical and magnetic properties of spark plasma sintered (FeCoNi)75Cu25−xSix high entropy alloys

The Role of Dehydrogenation Conditions on Sinterability and Magnetic Properties of Fine NdFeB Powders Consolidated With Hydrogen-Containing Sintering

The Role of Dehydrogenation Conditions on Sinterability and Magnetic Properties of Fine NdFeB Powders Consolidated With Hydrogen-Containing Sintering

Synthesis and property enhancement of Ti-Si/SiC composites by reactive infiltration for semiconductor applications

Poor machinability and limited electrical conductivity present significant challenges for silicon carbide (SiC) composites used in the semiconductor industry. In this study, Ti-Si/SiC composites were synthesized by liquid infiltration of a Ti-Si eutectic alloy, using SiC and Carbon black as raw materials. The reactive sintering mechanism and properties of Ti-Si/SiC composites were investigated using the reactive infiltration sintering process. The relative density of Ti-Si/SiC composites reached 98.43 % at 1600 °C. The results indicate that continuous infiltration of the Ti-Si eutectic alloy and dissolution-reprecipitation are critical for synthesizing Ti-Si/SiC composites. The coefficient of thermal expansion for the composites is 5.16 × 10−6 °C−1. Remarkably, the exponential increase in electrical conductivity with rising temperature strongly supports the enhanced conductive properties of this composite semiconductor. The Ti-Si/SiC composites exhibit maximum flexural strength, indentation modulus, and hardness values of 310.4 MPa, 434.1 GPa, and 29.4 GPa, respectively. This research aims to advance the application of high-performance Ti-Si/SiC materials in semiconductor technology.

Effects of novel carbon sources additives on the solid-state sintering behavior and properties of SiC ceramics

To enhance the density of SiC and improve the purity of the SiC, carbon is frequently used as a sintering additive. SiC ceramics were prepared in this study by using various carbon sources (graphitic carbon microsphere, carbon black, and flake graphite) combined with B4C through spark plasma sintering (SPS) at temperatures ranging from 1800 °C to 1900 °C. Among the above carbon sources, the graphitic carbon microspheres were created by hydrothermal carbonization combined with catalytic graphitization. The influence of the carbon sources on the phase compositions, microstructure, physical properties, and oxidation resistance of the SiC specimens was investigated. The findings revealed that the SiC specimens prepared with graphitic carbon microsphere had a smaller crystallite size than those prepared with other kinds of carbon. The SiC specimens prepared with graphitic carbon microsphere displayed high relative density, hardness, fracture toughness, and remarkable oxidation resistance. This was attributed to the lower oxygen content, better dispersion, and higher chemical reactivity of graphitic carbon spheres. In terms of the oxidation resistance of SiC specimens, factors such as purity (residual carbon) and porosity were found to have a more significant impact than grain size. In general, the use of carbon sources with high reactivity and good dispersion is an effective method in preparing SiC ceramics.

Enhancing Bioactivity and Mechanical Properties of Nano-Hydroxyapatite Derived from Oyster Shells through Hydrothermal Synthesis.

Nano-hydroxyapatite (nHA) demonstrates favorable biological activity, cell adhesion, cell proliferation, and osteoconductivity, making it highly valuable in biomedicine. It is extensively used as a bone substitute and in bone transplantation within the dental and orthopedic fields. This study employed oyster shells as a calcium source to synthesize nHA at 150 °C with various hydrothermal reaction durations (10 min, 1 h, 6 h, and 12 h). As a control, HA synthesized via a wet precipitation method for 1 h at room temperature was utilized. Subsequent material analyses, including XRD, FE-SEM, FTIR, and ICP-MS, were conducted, followed by comprehensive evaluations of the bioactivity, cell attachment, cell proliferation, and sintering properties of the synthesized nHA. The results indicated that nHA synthesized through the hydrothermal reaction produced nanoscale crystals, with the aspect ratio of nHA particles increasing with the duration of hydrothermal treatment. Notably, rod-like nHA particles became prominent with hydrothermal durations exceeding 6 h. nHA particles derived from oyster shells contained carbonate and trace elements (Na, Mg, K, and Sr), similar to constituents found in human hard tissue such as bone and teeth. The immersion of nHA synthesized at 150 °C for 1 h (HT2) in simulated body fluid (SBF) for 28 d led to the formation of a bone-like apatite layer on the surface, indicating the excellent bioactivity of the synthesized nHA. The cell culture results revealed superior cell attachment and proliferation for nHA (HT2). Following the sequential formation and sintering at 1200 °C for 4 h, HT2 ceramics exhibited enhanced microhardness (5.65 GPa) and fracture toughness (1.23 MPa·m0.5), surpassing those of human tooth enamel.