Microstructure and mechanical properties of 8YSZ ceramics by liquid-phase sintering with CuO-TiO_2 addition

The 8% （mass fraction） yttrium-partially-stabilized zirconia （8YSZ） ceramic was fabricated via liquid phase sintering at 1 200-1 400℃ by adding different mass ratios of CuO-16.7%TiO2 （molar fraction） as sintering aid. Relative density, microstructure, Vickers hardness and bending strength as a function of sintering temperature and additive content were investigated. The experiment results show that liquid phase sintering at low temperature can be realized through adding CUO-16.7% TiO2 to 8YSZ. The Vickers hardness and bending strength of samples with sintering aid are generally much higher than those of samples without sintering aid for all sintering temperatures, and increase with the increase of sintering temperature. When the addition content of CUO-16.7% TiO2 is beyond 0.5%, the relative density, Vickers hardness and bending strength decrease with the increase of the mass ratio of sintering aid. Low additions of sintering aid are beneficial to aiding densification; high additions of sintering aid are detrimental to the sintered properties mainly due to greater amounts of pores generated by the volatilization of oxygen with the eutectic reaction between copper oxide and titanium dioxide. It is found that the fine grain size and high relative density are two main reasons of the high bending strength and Vickers hardness of the materials.

Mineral-phase evolution and sintering behavior of MO–SiO_2–Al_2O_3–B_2O_3 (M = Ca,Ba) glass-ceramics by low-temperature liquid-phase sintering

In this work, network former SiO_2 and network intermediate Al_2O_3 were introduced into typical low-melting binary compositions CaO·B_2O_3, CaO·2B_2O_3, and BaO·B_2O_3 via an aqueous solid-state suspension milling route. Accordingly, multiple-phase aluminosilicate glass-ceramics were directly obtained via liquid-phase sintering at temperatures below 950°C. On the basis of liquid-phase sintering theory, mineral-phase evolutions and glass-phase formations were systematically investigated in a wide MO–SiO_2–Al_2O_3–B_2O_3(M = Ca, Ba) composition range. The results indicate that major mineral phases of the aluminosilicate glass-ceramics are Al_(20)B_4O_(36), CaAl_2Si_2O_8, and BaAl_2Si_2O_8 and that the glass-ceramic materials are characterized by dense microstructures and excellent dielectric properties.

Combining cold sintering and Bi_(2)O_(3)-Activated liquid-phase sintering to fabricate high-conductivity Mg-doped NASICON at reduced temperatures

The cold sintering process(CSP)and Bi_(2)O_(3)-activated liquid-phase sintering(LPS)are combined to densify Mg-doped NASICON(Na_(3.256)Mg_(0.128)Zr_(1.872)Si_(2)PO_(12))to achieve high densities and conductivities at reduced temperatures.As an example,a cold-sintered specimen with the addition of 1.1wt%Bi_(2)O_(3)sintering additive achieved a high conductivity of 0.91 mS/cm(with~96%relative density)after annealing at 1000℃;this conductivity is>70%higher than that of a cold-sintered specimen without adding the Bi_(2)O_(3)sintering additive,and it is>700%of the conductivity of a dry-pressed counterpart with the same amount of Bi_(2)O_(3)added,all of which are subjected to the same heating profile.The highest conductivity achieved in this study via combining CSP and Bi_(2)O_(3)-activated LSP is>1.5 mS/cm.This study suggests an opportunity to combine the new CSP with the traditional LPS to sinter solid electrolytes to achieve high densities and conductivities at reduced temperatures.This combined CSP-LPS approach can be extended to a broad range of other materials to fabricate the“thermally fragile”solid electrolytes or solid-state battery systems,where reducing the processing temperature is often desirable.

Liquid-phase sintering enabling mixed ionic-electronic interphases and free-standing composite cathode architecture toward high energy solid-state battery

Solid-state batteries(SSBs)will potentially offer increased energy density and,more importantly,improved safety for next generation lithium-ion(Li-ion)batteries.One enabling technology is solid-state composite cathodes with high operating voltage and area capacity.Current composite cathode manufacturing technologies,however,suffer from large interfacial resistance and low active mass loading that with excessive amounts of polymer electrolytes and conductive additives.Here,we report a liquidphase sintering technology that offers mixed ionic-electronic interphases and free-standing electrode architecture design,which eventually contribute to high area capacity.A small amount(~4 wt.%)of lithium hydroxide(LiOH)and boric acid(H_(3)BO_(3))with low melting point are utilized as sintering additives that infiltrate into single-crystal Ni-rich LiNi_(0.8)Mn_(0.1)Co_(0.1)(NMC811)particles at a moderately elevated temperature(~350℃)in a liquid state,which not only enable intimate physical contact but also promote the densification process.In addition,the liquid-phase additives react and transform to ionic-conductive lithium boron oxide,together with the indium tin oxide(ITO)nanoparticle coating,mixed ionic-electronic interphases of composite cathode are successfully fabricated.Furthermore,the liquid-phase sintering performed at high-temperature(~800℃)also enables the fabrication of highly dense and thick composite cathodes with a novel free-standing architecture.The promising performance characteristics of such composite cathodes,for example,delivering an area capacity above 8 mAh·cm^(−2) within a wide voltage window up to 4.4 V,open new opportunities for SSBs with a high energy density of 500 Wh·kg^(−1) for safer portable electronic and electrical transport.

Solution-processed n-type Bi_2Te_(3-x)Se_x nanocomposites with enhanced thermoelectric performance via liquid-phase sintering

The much slower progress in enhancing the thermoelectric performance of n-type Bi2Te3 than that of p-type Bi2Te3 based materials in the past decade hinders the widespread use in power generation and refrigeration. Here, a facile bottom-up solution-synthesis with spark plasma sintering(SPS) process has been developed to build n-type Bi2Te3-xSex bulk nanocomposites, which substantially improves the power factor and decreases the lattice thermal conductivity by tuning the interface scattering of phonons and electrons. The stoichiometric composition in ternary Bi2Te3-xSex nanocomposites is also tuned to optimize the carrier concentration and lattice thermal conductivity. The optimized bulk nanocomposite Bi2Te2.7Se0.3 exhibits a ZT of 1.1 at^371 K, which is comparable to the corresponding commercially available ingots. Our results demonstrate the great potential of the solution-processed n-type Bi2Te3-xSex nanocomposites for cost-effective thermoelectric applications.

Microstructural evolution and mechanical properties of h-BN composite ceramics with Y2O3-AlN addition by liquid-phase sintering

Hexagonal boron nitride(h-BN)composite ceramics were prepared by hot pressing with the addition of Y2O3 and AlN.The effects of different Y2O3–AlN contents on microstructural evolution,mechanical properties and thermal diffusion coefficients of h-BN composite ceramics were investigated.The results indicate that Y2O3–AlN forms a liquid phase during the sintering process achieving a good wettability with h-BN grains.In pure h-BN ceramic and h-BN composite ceramic with 40 wt%Y2O3–AlN,the h-BN grains grow well when controlled through solid-phase and liquid-phase diffusion,respectively.With the increase in Y2O3–AlN content,mechanical properties and thermal diffusion coefficients of h-BN composite ceramics first decrease and then increase,and the properties of h-BN composite ceramic with 10 wt%Y2O3–AlN are the inflection points.Such properties are highly related to the phase compositions,porosity and microstructure.

Spark Plasma Sintering of Mg-based Alloys:Microstructure,Mechanical Properties,Corrosion Behavior,and Tribological Performance

Within the past ten years,spark plasma sintering(SPS)has become an increasingly popular process for Mg manufacturing.In the SPS process,interparticle diffusion of compressed particles is rapidly achieved due to the concept of Joule heating.Compared to traditional and additive manufacturing(AM)techniques,SPS gives unique control of the structural and microstructural features of Mg components.By doing so,their mechanical,tribological,and corrosion properties can be tailored.Although great advancements in this field have been made,these pieces of knowledge are scattered and have not been contextualized into a single work.The motivation of this work is to address this scientific gap and to provide a groundwork for understanding the basics of SPS manufacturing for Mg.To do so,the existing body of SPS Mg literature was first surveyed,with a focus on their structural formation and degradation mechanisms.It was found that successful Mg SPS fabrication highly depended on the processing temperature,particle size,and particle crystallinity.The addition of metal and ceramic composites also affected their microstructural features due to the Zener pinning effect.In degradative environments,their performance depends on their structural features and whether they have secondary phased composites.In industrial applications,SPS'd Mg was found to have great potential in biomedical,hydrogen storage,battery,automotive,and recycling sectors.The prospects to advance the field include using Mg as a doping agent for crystallite size refinement and using bulk metallic Mg-based glass powders for amorphous SPS components.Despite these findings,the interactions of multi-composites on the processing-structure-property relationships of SPS Mg is not well understood.In total,this work will provide a useful direction in the SPS field and serve as a milestone for future Mg-based SPS manufacturing.

Investigation on sintering and deformation strengthening of Mo-Cu alloy

Mo-Swt%Cu nanocomposite powders were fabricated by mechanical alloying, and full density alloy was obtained via liquid-phase sintering and post-treatment process. The microstructure of Mo-8wt%Cu alloy was investigated by scanning elec-tron microscope （SEM） , and the effects of process parameters on relative density, tensile strength and elongation were stud-ied. The results indicate that the relative density of Mo-Cu alloy is 98. 6% after sintering at 1 250℃ for 30 min, and its micro-structure is composite network The full density of Mo-Cu alloy can be obtained when specimens are treated through deforma-tion strengthening process of rotating forging and hydrostatic extrusion The tensile strength and elongation rate are 576 MPa and 5. 8% ,respectively, when hydrostatic extrusion deformation degree is 40%.

Phase-Field Simulation of Sintering Process:A Review

Sintering,a well-established technique in powder metallurgy,plays a critical role in the processing of high melting point materials.A comprehensive understanding of structural changes during the sintering process is essential for effective product assessment.The phase-field method stands out for its unique ability to simulate these structural transformations.Despite its widespread application,there is a notable absence of literature reviews focused on its usage in sintering simulations.Therefore,this paper addresses this gap by reviewing the latest advancements in phase-field sintering models,covering approaches based on energy,grand potential,and entropy increase.The characteristics of various models are extensively discussed,with a specific emphasis on energy-based models incorporating considerations such as interface energy anisotropy,tensor-form diffusion mechanisms,and various forms of rigid particle motion during sintering.Furthermore,the paper offers a concise summary of phase-field sintering models that integrate with other physical fields,including stress/strain fields,viscous flow,temperature field,and external electric fields.In conclusion,the paper provides a succinct overview of the entire content and delineates potential avenues for future research.

Effect of sintering temperature and holding time on structure and properties of Li_(1.5)Ga_(0.5)Ti_(1.5)(PO_4)_(3)electrolyte with fast ionic conductivity

Li_(1.5)Ga_(0.5)Ti_(1.5)PO_(4))_(3)(LGTP)is recognized as a promising solid electrolyte material for lithium ions.In this work,LGTP solid electrolyte materials were prepared under different process conditions to explore the effects of sintering temperature and holding time on relative density,phase composition,microstructure,bulk conductivity,and total conductivity.In the impedance test under frequency of 1-10^(6) Hz,the bulk conductivity of the samples increased with increasing sintering temperature,and the total conductivity first increased and then decreased.SEM results showed that the average grain size in the ceramics was controlled by the sintering temperature,which increased from(0.54±0.01)μm to(1.21±0.01)μm when the temperature changed from 750 to 950°C.The relative density of the ceramics increased and then decreased with increasing temperature as the porosity increased.The holding time had little effect on the grain size growth or sample density,but an extended holding time resulted in crack generation that served to reduce the conductivity of the solid electrolyte.

Spark Plasma Sintering of Boron Carbide Using Ti_(3)SiC_(2) as a Sintering Additive

Boron carbide has unique properties for wide application possibilities;however,poor sinterability limits its applications.One approach to overcome this limitation is the addition of secondary phases into boron carbide.Boron carbide based composite ceramics are produced by the direct addition of secondary phases into the structure or via reactive sintering using a sintering additive.The present study investigated the effect of Ti_(3)SiC_(2) addition to boron carbide by reactive spark plasma sintering in the range of 1700-1900℃.Ti_(3)SiC_(2) phase decomposed at high temperatures and reacted with B4C to form secondary phases of TiB2 and SiC.The results demonstrated that the increase of Ti_(3)SiC_(2) addition(up to 15 vol%)effectively promoted the densification of B4C and yielded higher hardness.However,as the amount of Ti_(3)SiC_(2) increased further,the formation of microstructural inhomogeneity and agglomeration of secondary phases caused a decrease in hardness.

Boosting thermoelectric efficiency of Ag_(2)Se through cold sintering process with Ag nano-precipitate formation

Silver selenide(Ag_(2)Se)stands out as a promising thermoelectric(TE)material,particularly for applications near room temper-atures.This research presents a novel approach for the fabrication of bulk Ag_(2)Se samples at a relatively low temperature(170℃)using the cold sintering process(CSP)with AgNO_(3)solution as a transient liquid agent.The effect of AgNO_(3)addition during CSP on the micro-structure and TE properties was investigated.The results from phase,composition and microstructure analyses showed that the introduc-tion of AgNO_(3)solution induced the formation of Ag nano-precipitates within the Ag_(2)Se matrix.Although the nano-precipitates do not af-fect the phase and crystal structure of orthorhombicβ-Ag_(2)Se,they suppressed crystal growth,leading to reduced crystallite sizes.The samples containing Ag nano-precipitates also exhibited high porosity and low bulk density.Consequently,these effects contributed to sig-nificantly enhanced electrical conductivity and a slight decrease in the Seebeck coefficient when small Ag concentrations were incorpor-ated.This resulted in an improved average power factor from~1540μW·m^(−1)·K^(−2)for pure Ag_(2)Se to~1670μW·m^(−1)·K^(−2)for Ag_(2)Se with additional Ag precipitates.However,excessive Ag addition had a detrimental effect on the power factor.Furthermore,thermal conductiv-ity was effectively suppressed in Ag_(2)Se fabricated using AgNO_(3)-assisted CSP,attributed to enhanced phonon scattering at crystal inter-faces,pores,and Ag nano-precipitates.The highest figure-of-merit(zT)of 0.92 at 300 K was achieved for the Ag_(2)Se with 0.5wt%Ag dur-ing CSP fabrication,equivalent to>20%improvement compared to the controlled Ag_(2)Se without extra Ag solution.Thus,the process outlined in this study presents an effective strategy to tailor the microstructure of bulk Ag_(2)Se and enhance its TE performance at room temperature.

Effect of Sintering Temperature on the Microstructure and Mechanical Properties of Nanocrystalline Cemented Carbide

WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property test.The results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.

Fabrication of YAG:Ce^(3+) and YAG:Ce^(3+),Sc^(3+) Phosphors by Spark Plasma Sintering Technique

In this study,a single-doped phosphors yttrium aluminum garnet(Y_(3)Al_(5)O_(12),YAG):Ce^(3+),single-doped YAG:Sc^(3+),and double-doped phosphors YAG:Ce^(3+),Sc^(3+) were prepared by spark plasma sintering(SPS)(lower than 1 200℃).The characteristics of synthesized phosphors were determined using scanning electron microscopy(SEM),X-ray diffraction(XRD),and fluorescence spectroscopy.During SPS,the lattice structure of YAG was maintained by the added Ce^(3+) and Sc^(3+).The emission wavelength of YAG:Ce^(3+) prepared from SPS(425-700 nm) was wider compared to that of YAG:Ce^(3+) prepared from high-temperature solid-state reaction(HSSR)(500-700 nm).The incorporation of low-dose Sc^(3+) in YAG:Ce^(3+) moved the emission peak towards the short wavelength.

Spark plasma sintering of tungsten-based WTaVCr refractory high entropy alloys for nuclear fusion applications

W-based WTaVCr refractory high entropy alloys (RHEA) may be novel and promising candidate materials for plasma facing components in the first wall and diverter in fusion reactors. This alloy has been developed by a powder metallurgy process combining mechanical alloying and spark plasma sintering (SPS). The SPSed samples contained two phases, in which the matrix is RHEA with a body-centered cubic structure, while the oxide phase was most likely Ta2VO6through a combined analysis of X-ray diffraction (XRD),energy-dispersive spectroscopy (EDS), and selected area electron diffraction (SAED). The higher oxygen affinity of Ta and V may explain the preferential formation of their oxide phases based on thermodynamic calculations. Electron backscatter diffraction (EBSD) revealed an average grain size of 6.2μm. WTaVCr RHEA showed a peak compressive strength of 2997 MPa at room temperature and much higher micro-and nano-hardness than W and other W-based RHEAs in the literature. Their high Rockwell hardness can be retained to at least 1000°C.

Effects of Diamond on the Mechanical Properties and Thermal Conductivity of Si_(3)N_(4)Composites Fabricated Using Spark Plasma Sintering

Micrometer-sized diamonds were incorporated into silicon nitride(Si_(3)N_(4))matrix to manufacture high-performance Si_(3)N_(4)-based composites using spark plasma sintering at 1500℃under 50 MPa.The effects of the diamond content on the phase composition,microstructure,mechanical properties and thermal conductivity of the composites were investigated.The results showed that the addition of diamond could effectively improve the hardness of the material.The thermal conductivity of Si_(3)N_(4)increased to 52.97 W/m·k at the maximum with the addition of 15 wt%diamond,which was 27.5%higher than that of the monolithic Si_(3)N_(4).At this point,the fracture toughness was 7.54 MPa·m^(1/2).Due to the addition of diamond,the composite material generated a new substance,MgSiN2,which effectively combined Si_(3)N_(4)with diamond.MgSiN2 might improve the hardness and thermal conductivity of the materials.

Computational Analysis of Selective Laser Sintering of Inconel 625

A two-dimensional multi-physics finite element model is developed to simulate the Selective Laser Sintering(SLS)process using Inconel 625 powders.The validity of the developed model is first assessed by comparing its results with experimental data.Various factors such as phase transition,recoil pressure,surface tension,and theMarangoni force are considered.The study’s findings underscore that the morphology and thermal-fluid dynamics of the molten pool in the SLS process are predominantly shaped by the influence of the Marangoni force and recoil pressure acting on its surface.The recoil pressure at the front of the laser spot rises exponentially with temperature,making the liquid metal move downward,and creating a depression at the pool’s head.It also causes particles to splash from the pool’s rear edge.The study explores the influence of the backward Marangoni force,where hightemperature liquid flows from the front to the rear of the molten pool,creating a vortex and moving the pool in the rear.Process parameters like laser intensity,scan speed,and spot size were analyzed.The findings indicate that higher laser power lower scanning speed and laser beam spot size lead to increased width and depth of the molten pool.

Feasibility Analysis of the Sintering Flue Gas Oxidation Method for Denitrification Technology Route

With the vigorous development of China’s iron and steel industry and the introduction of ultra-low emission policies, the emission of pollutants such as SO2 and NOx has received unprecedented attention. At present, the commonly used denitrification methods include selective catalytic reduction (SCR), active coke, etc. As a newly developed denitrification technology, oxidation denitrification is not widely used, and the technical level is mixed, and there might be problems such as yellow smoke, secondary pollution and ozone escape in the practical application. In this paper, problems existing in the denitrification process of sintering flue gas oxidation are analyzed, and a 320 m2 sintering machine is taken as an example. Comparing the denitrification technology of sintering industry, it could be seen that the denitrification technology route of oxidation method has low pollution, low cost and high comprehensive environmental benefits, and has greatly potential development.

Microstructure and properties of liquid-phase sintered tungsten heavy alloys by using ultra-fine tungsten powders

The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size of 3 μm) were investigated respectively. Commercial tungsten powders (original tungsten powders) were mechanically milled in a high-energy attritor mill for 35 h. Ultra-fine tungsten powders and commercial Ni, Fe powders were consolidated into green compacts by using CIP method and liquid-phase sintering at 1 465 ℃ for 30 min in the dissociated ammonia atmosphere. Liquid-phase sintered tungsten heavy alloys using ultra-fine tungsten powders exhibit full densification (above 99% in relative density) and higher strength and elongation compared with conventional liquid-phase sintered alloys using original tungsten powders due to lower sintering temperature at 1 465 ℃ and short sintering time. The mechanical properties of sintered tungsten heavy alloy are found to be mainly dependent on the particles size of raw tungsten powders and liquid-phase sintering temperature.

Effect of basicity on sintering behavior of low-titanium vanadium-titanium magnetite

Basicity has an important effect on the sinter quality, especially for low-titanium vanadium-titanium sinter. The effect of basieity on sintering behavior of low-titanium vanadium-titanium mixture, and the transference and distribution of element in sintering process were researched by sinter pot test, mineralogical analysis, scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS） analysis. The results show that CaO preferentially reacts with TiO2, generating pervoskite, so that the total liquid phase content of the sinter is low. There is an increase in the perovskite concentration of the sinter with the basicity ranging from 1.9：1 to 2.7：1. With increasing the basicity, the calcium ferrite content increases slightly and then rises rapidly, while the silicate content decreases and the metallurgical property of the sinter is improved. As for the distribution of these elements in the sinter, Ti occurs mainly in perovskite, V occurs mainly in silicate, and Fe occurs mainly in magnetite and hematite. The most abundant occurrence of Ca and Si occurs in silicate and perovskite. With increasing the basicity, the contents of A1 and Mg increase in calcium ferrite, while they decrease in other minerals.