One-step Sintering Research Articles

Glass-ceramics synthesis using the collaborative smelting slag of spent automotive catalyst and copper-bearing electroplating sludge

This paper studied the glass-ceramics preparation from the collaborative smelting slag of spent automotive catalyst (SAC) and copper-bearing electroplating sludge (CBES) by the one-step sintering method without additional nucleating agents. The crystallization mechanism, including nucleation and crystal growth steps, was investigated by DSC, XRD and FETEM-EDS. The crystallization process during heat treatment could be summarized as follows: Fe3+ ions will congregate firstly in a small range on the surface and inside of the originally homogeneous amorphous matrix, and then gradually crystallize and transform into stable hematite (Fe2O3) crystal nuclei. Augite and gehlenite as the main two crystalline phases grow around hematite (Fe2O3) epitaxially. Additionally, the surface crystallization dominates the overall process based on the crystallization kinetics calculation. The optimum sintering temperatures of glass-ceramics preparation were researched according to the physicochemical properties analysis. When the sintering temperatures are 850℃−875℃, the density, water absorption, Vickers hardness, flexible strength, acid and alkali resistance of glass-ceramics products are 2.8–2.9 g/cm3, 0.08%–0.09%, 6.5–6.7 GPa, 98–115 MPa, 96.6%–96.9% and 98.5%–99.6%, respectively. Toxicity characteristic leaching procedure (TCLP) test shows that the material can be taken as non-hazardous. This work realizes resource utilization and detoxification of the co-smelting slag of SAC and CBES.

Versatile phosphor-in-glass based on Sn–F–P–O matrix with ultra-high color rendering for white LEDs/LDs

White light with excellent color rendering property has been highly required for comfortable and healthy illumination. A facile strategy to achieve high color rendering index (Ra >90) in practical applications is using near ultraviolet chips as excitation sources combined with RGB phosphors. However, achieving high color rendering with both blue chips and near-ultraviolet (NUV) chips for commercial phosphors dispersed in phosphor-in-glass (PiGs) materials is still a big challenge. In this work, the PiG based on the ultra-low melting point Sn–F–P–O glass with commercial green (Lu3Al5O12:Ce3+) and red (SrxCa1-xAlSiN3:Eu2+) phosphors has been successfully fabricated by one-step sintering method. The phase identification and distribution of monochromatic red phosphor in glass (R-PiG) and green phosphor in glass (G-PiG) were investigated in detail. The Sn2+ ions in Sn–F–P–O matrix show the intense blue emission bands centered at 420 nm under the excitation of NUV chips (365 nm). Notably, the polychromatic red/green phosphor in glasses (R/G-PiGs) are versatile and exhibited excellent color rendering (Ra = 93, Ra = 95, Ra = 92, respectively) properties excited by both blue chips, NUV chips and laser diodes (WLD). The working temperature of R/G-PiGs is stable at ∼33 °C and ∼55 °C when employed in WLEDs/WLDs (1 W), which greatly prevented the phenomenon of “thermal quenching” for the phosphors caused by high temperature. Thus, the versatile R/G-PiG with ultra-high color rendering and excellent thermal properties indicates its promising application in high-power white LEDs/LDs.

Engineering of cobalt-free Ni-rich cathode material by dual-element modification to enable 4.5 V-class high-energy-density lithium-ion batteries

Ni-rich Co-free cathodes have attracted extensive attention for high-energy–density lithium ion batteries (LIBs). However, structural and interfacial instability in these cathodes accelerates capacity degradation under high-voltage operation. Herein, Ni-rich Co-free In/Sn dual-element modified cathode (InSn-LiNi0.85Mn0.09Al0.06O2, InSn-NMA85) was synthesized through a one-step sintering strategy. Dual-element doping along with the in-situ induced LiInO2 interphase synergistically prolongs the cycle life of the Ni-rich Co-free cathode under high voltage (≥4.5 V) as well as high temperature (≥45 °C). Comprehensive characterizations combined with DFT calculation confirm that In/Sn dual-element modification effectively increases Li+/Ni2+ mixing energy and oxygen release energy, stabilizes the lattice structure, and improves the electrochemical performance. Meanwhile, in-situ formed coating of LiInO2 effectively protects the cathode from redundant cathode-electrolyte side reactions, preserves the layered phase, and further inhibits the generation of microcracks after cycles. The modified cathode maintains superior capacity retention of ∼ 100 % and ∼ 90 % within the voltage range of 2.7–4.5 V at 30 °C and 45 °C, respectively, after 100 cycles. The modification strategy enables the Ni-rich Co-free layered NMA85 cathode to deliver comparable battery performance with NCM and NCA cathodes, which provides promising approaches for the application of Ni-rich Co-free cathode in 4.5 V-class high-energy–density LIBs.

Selective oxidation of aluminium in Mo(Al,Si)2

Mo(AlxSi1-x)2 alloy with x in the range of 0.35–0.65 were prepared by a one-step spark plasma sintering. To study the exclusive formation of an α-Al2O3 scale, oxidation experiments were conducted in low and high oxygen partial pressure ambient at 1373 K; viz.: 10−14 and 0.21 atm. The oxidation kinetics follows a parabolic rate law after a transient period. A counter-diffusion process of O and Al along grain boundaries of Al2O3 scale is responsible for the equiaxed and columnar grain growth based on a two-layered microstructure. The formation of a dense equiaxed α-Al2O3 layer contributes to excellent oxidation resistance.

Effect of Two-Step Sintering on Properties of Alumina Ceramics Containing Waste Alumina Powder.

This study aims to evaluate the recycling potential of solid waste alumina powder (WAP) by utilization of the two-step sintering (TSS) process. For the study, WAP was collected as an industrial scrap after the machining process for the formation of green alumina compacts. The alumina samples were prepared according to the slip casting method by preparing suspensions containing commercial alumina with 0.8 μm average particle size and by adding up to 20 dwb. % (i.e., expressed on a dry weight basis) of WAP with 3.4 μm average particle size. The samples were sintered at optimized TSS conditions and compared with conventional one-step sintering (OSS) by conducting morphological analyses. The average grain size (AGS) was determined from the obtained field emission scanning electron microscopy (FESEM) images, while the sample porosity was calculated based on apparent densities. The obtained micrographs after TSS implementation revealed a partially textured microstructure. Furthermore, a comparison of the mechanical properties of alumina samples lacking or containing 20 dwb. % of WAP obtained after sintering is presented. The indentation fracture toughness (~3.2 MPa m1/2) and Vickers hardness data (~14.5 GPa) showed a positive effect of adding WAP to alumina samples. The slightly improved mechanical properties of ceramic samples containing waste alumina are a consequence of lower porosity, which is due to the remaining sintering additives in WAP. The collected results demonstrate the possibility of using TSS for sintering ceramic materials that contain WAP.

Binder derived semi-conductive graphite/alumina composites via novel one-step pulsed electric current sintering

Semi-conductive graphite/Al2O3 ceramic composites were successfully fabricated via a novel and facile approach by pulsed electric current sintering of binder embedded Al2O3 powders, which were prepared by a simple ball-milling assisted mixing of Al2O3 powder with polyvinyl alcohol solution. By altering the sintering conditions with respects to temperature and pressure controlling and concentration of binder, relative density, and microstructure of fabricated graphite/Al2O3 ceramic composites, and the electrical properties were schematically investigated in this study. The fabricated graphite/Al2O3 ceramic composites exhibit superior semi-conductive properties. Moreover, the carrier type in fabricated semi-conductive graphite/Al2O3 composites was successfully modified by adding polycarboxylic acid as a dispersant in binder embedded Al2O3 powders. The contents in this work present a new strategy for the design and development of functional ceramic composites.

Optimized strength and conductivity of multi-scale copper alloy/metallic glass composites tuned by a one-step spark plasma sintering (SPS) process

A superiority in interfacial bonding is favorable to fabricate high-strength conductive composites for electrical contact applications. In the present work, high strength and high conductivity multi-scale metallic glass composites (including micron-scale CuZrAl metallic glass reinforcement, hundred-nanometer-scale CuCrZr crystalline grain matrix, and nano-scale precipitated phase) were fabricated by a one-step spark plasma sintering (SPS). The strength and conductivity of the bulk copper matrix metallic glass composites (BCMGCs) were enhanced simultaneously with the increase in the sintering pressure of the SPS. The excellent performance is attributed to the improved interfacial bonding between the metallic glass reinforcement and the copper alloy matrix due to the high pressure assisted by temperature and pulsed current. In particular, the precipitation of nanoprecipitates at the interface further reduces the interfacial resistance and improves the mechanical properties of the composites. This work broadens the horizon for the selection and optimization of reinforcements and manufacturing processes for high-performance electrical contact materials (ECMs).

Fabrication of 4 at.% La3+ ion doped (TbxLu0.96−x)2O3 transparent ceramics by using NC-PLSH technology and characterisation of their magneto-optical properties

Nanocrystalline powders and pressureless sintering (NC-PLSH) were used in a H2 atmosphere to fabricate 4 at.% La3+ doped (TbxLu0.96−x)2O3 magneto-optical transparent ceramics. La3+ was utilised as a sintering aid, and Lu3+ was used as a phase stabiliser. A component of the (TbxLu0.96−xLa0.04)2O3 magneto-optical material was designed and investigated based on powder sinterability and green compact sintering. Transparent (TbxLu0.96−xLa0.04)2O3 ceramics were obtained by using a one-step sintering process in H2 atmosphere, without the need for subsequent hot isostatic pressing. The in-line transmittance of the as-polished 4 at.% La3+:(Tb0.8Lu0.16)2O3 ceramic was 79% at 1400 nm. The measured Verdet constant at wavelengths of 633 nm and 1064 nm was 354 rad/(T·m) and 100.2 rad/(T·m), respectively. The required length of the (Tb0.8Lu0.16La0.04)2O3 ceramics was 63% less than that of Tb3Ga5O12 ceramics.

Internal and external bifunctional vanadium-modification strategy for LiNi0.80Co0.15Al0.05O2 cathode materials

LiNi0.80Co0.15Al0.05O2 (NCA) is widely used in Li-ion batteries due to its high reversible capacity and energy density. However, residual Li on the exterior of NCA suffers severe side reactions with air during preparation process, which destroy the surface of cathode material and cause irreversible capacity loss. This performance degradation has remained an issue that needs to be solved. Herein, a bifunctional modification strategy consisting of V doping and coating with Li3VO4 is reported to address this issue. V-doped and Li3VO4-coated NCA (VNCA) cathode materials were obtained using solid-phase method through one-step sintering. External Li3VO4 coating layer formed from the consumption of surface residual Li prevents the occurrence of interfacial adverse reactions. Furthermore, V doping stabilizes lattice structure. Obtained cathode material can improve the stability and rate capability of Li-ion batteries. 100-cycle cycle retention rate of VNCA coated with 2-M% Li3VO4 at 1C is 89.32%, which is significantly higher than that of NCA (67%). Additionally, specific discharge capacity of VNCA at 10C (145.6 mAh·g−1) is considerably higher than that of NCA (129.8 mAh·g−1).

High-rate and durable sulfide-based all-solid-state lithium battery with in situ Li2O buffering

Sulfide electrolytes (SEs)-based all-solid-state lithium batteries (ASSLBs) are advantageous over traditional lithium-ion batteries (LIBs) because of high energy density and safety. Unfortunately, the commercialization of SEs-based ASSLBs is presently hindered by interfacial instability between SEs and active materials, sluggish dynamics and poor cycling performance. Here we report, for the first time, a stable and conductive Li2O buffering coating for Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) in ASSLBs using SEs of Li6PS5Cl via a facile one-step sintering. We show using judiciously combined computation and experiment that Li2O buffering improves the stability of NCM811 and significantly boosts transfer of Li+. Via tuning the thickness of the Li2O buffer, we demonstrate the high initial discharge capacity of 189.66 mAh g − 1 (0.1C) and rate capability of 61.71 mAh g − 1 (3C), together with outstanding long-term cycling performance of ∼ 2600 cycles at 1C with capacity retention of 81.47%, and Coulombic efficiency of 99.9%. We conclude that conductive Li2O buffering can be used to obviate interfacial instability between SEs and active materials and to boost dynamics and cycling performance. Findings will be of immediate benefit to a range of researchers in design for high-performance ASSLBs for practical application and commercialization.

Reparation of porous Ti-Cu alloy by one-step sintering method and application of hydrogen evolution reaction

• The porous Ti-Cu alloy catalyst was synthesized by the one-step sintering method. • The introduction of Mo metal significantly improves the HER performance. • The first-principles approach gives the experiment a detailed interpretation of the atomic orbital hierarchy. In this paper, Ti-Cu porous alloy electrocatalysts were synthesized by simple mechanical alloying combined with a one-step sintering method, and the positive effects of milling time, sintering temperature, and sintering time on HER were explored. The results show that the Ti 2 Cu 3 porous alloy catalyst after ball milling has excellent electrocatalytic activity. After the introduction of transition metal Mo, the overpotential of ball-milled Mo-Ti 2 Cu 3 -600 electrocatalyst is 133 mV, and the corresponding Tafel slope is 97.37 mV·dec −1 , second only to commercial Pt/C catalyst. At the same time, the first principle was used to reveal the interaction of electrons in catalysis. The effective mass of the ternary alloy containing Mo is 0.19 m 0 , and the original alloy catalyst is 0.28 m 0 . It can be found that the introduction of Mo atoms improves the carrier migration efficiency, which has a high promotion effect on the catalytic performance of the original alloy. The reaction energy barrier is also reduced from 0.584 eV to 0.051 eV, which greatly improves the reaction process. Such a simple one-step sintering method can also obtain excellent electrocatalysts, which provides a new design idea for short-process processing of excellent electrocatalysts and has broad application prospects.

Structure and electrochemical property of single-crystal α-MoO3 microbelts synthesized by a solid-state reaction

In this paper, we report the simple and cost-effective synthesis of α-MoO3 microbelts with side lengths on the centimeter or millimeter scale by one-step sintering using MoO3 powder. Transparent and flat microbelts revealing (0k0) plane facets cleaved preferentially along the [001] direction are formed without the use of supporting substances in air. Atomic force microscopy and high-resolution transmission electron microscopy analyses confirm that a single-crystal microbelt composed of stacked bunches of α-MoO3 sheets is synthesized. The effect of the synthesis conditions on the structure and size of the α-MoO3 microbelts is systematically investigated by varying the residual time during sintering and the amount of the source powder. Finally, we demonstrate the electrochemical properties of the single-crystal α-MoO3 microbelt in an acidic solution; the microbelt exhibits a variation in transmittance with the application of a potential, implying that it is electrochromic and possesses ion-storage capacity, making it promising for application in supercapacitors. Our study proposes a novel and facile method for the large-scale preparation of α-MoO3 microbelts, which will open up new avenues in the field of electrochemical devices.

The effects of pre-sintering temperature and La2O3 addition on sinterability and corrosion resistance of stoichiometric magnesium aluminate spinel

In this study, effects of pre-sintering temperature and subsequent La2O3 addition on the densification of magnesium aluminate spinel (MgAl2O4) were investigated. Further, the role of La2O3 was evaluated in terms of sintering/mechanical properties and corrosion resistance. Results reveal that two-step sintering achieves higher relative density than one-step pressureless sintering (from 70.21% to 83.86%) because it avoids volume expansion effect of MgAl2O4, but high pre-sintering temperature leads to a decrease in the activity of the raw material (for post-sintering). Subsequent experimental data show that the introduction of La2O3 endows the sample with greater relative density (from 91.24% to 95.65%), which is attributed to the formation of LaAlO3 and defect activation effect caused by stoichiometric mismatch. Besides, corrosion resistance of MgAl2O4 gets improved due to the formation of 2CaO·4La2O3·6SiO2, CaO·2Al2O3, and CaO·6Al2O3.

Effects of solid isolation medium on the microstructure and magnetic properties of one-step sintered L10-FePtCu nanoparticles

To explore a more efficient process parameter for controlling the microstructure and magnetic properties of liquid-phase assisted one-step sintering method, the effects of isolation medium size and uniformity on L10-FePtCu NPs have been studied. The grain size (d) of L10-FePtCu NPs has been refined by decreasing the average size of solid isolation mediums (D), and the relationship can be approximated as d= 6.60 × D1/3 − 9.14. The disorder-order transition of the L10 phase has been inhibited by decreasing the medium size, however, it has been facilitated by increasing the medium size uniformity. The ordering degree, coercive force, and magnetic energy product of L10-FePtCu NPs reach the highest when using the middle sized and best uniformity NaCl mediums (about 8 µm). This research indicates that controlling the interface between the solid isolation mediums and the precursors is an effective strategy to tune the microstructure and magnetic properties of one-step sintered highly ordered L10 phase NPs.

Improvement of electrochemical performance and structural stability of LiNi0.83Co0.12Mn0.05O2 at high-voltage by La and Ti modification

The large-scale commercialization of Ni-rich LiNi1−x-yCoxMnyO2 is hindered by the rapid capacity decay, which is caused by structural instability, interface side reaction, and surface phase transition. In this study, the Ni-rich cathode is modified with Ti and La through a one-step sintering method. Ti and part La diffuse into the cathode particles, and the rest of La is coated on the surface of the particles in the form of La4NiLiO8. The La and Ti modified cathodes show excellent cycling performance even at a high cut-off voltage of 4.5 V. The modified cathode has an initial capacity of 195.5 mAh g−1 and capacity retention of 87% after 200 cycles. The rate performance is also improved, and the capacity at 5 C reaches 178.3 mAh g−1. The improved cycling performance is attributed to the modification of La and Ti, which avoids structural degradation and maintains the mechanical integrity of the cathode particles during cycling. The improvement in rate performance is attributed to the fact that the Li+ diffusion coefficient is increased due to the modification.

One-step synthesis of t-ZrO2 from Zircon using magnesium-calcium minerals as stabilizers

Stabling crystal structure at room temperature is a classic problem in the study of Zirconium dioxide (ZrO2). However, there are few investigations on making tetragonal zirconia (t-ZrO2) in one step at a low cost. In this research, t-ZrO2 is synthesized using a one-step high-temperature solid-state sintering technique with magnesite, dolomite, and limestone as stabilizers and zircon as the raw material. The most suitable stabilizers and reaction conditions are determined, and the mechanism of zirconia structure stabilization is explored. The findings suggest that magnesite has the lowest effect as a crystal structure stabilizer, whereas dolomite and limestone are pretty close, but dolomite introduces more impurities. The ideal reaction conditions were 60% mol limestone at 1500 °C. The stabilization mechanism is zirconia gap correction, according to XRD and EPR data. The characterization of the SEM demonstrates that the heat treatment temperature and stabilizer had little effect on the morphology of t-ZrO2. When limestone was introduced throughout the process, EDS data revealed that some amorphous silicon-calcium compounds occurred in the product. The focus of follow-up work will be on how to lessen the impact in this area. This research offers vital reference value for reducing the cost of the synthetic t-ZrO2 process.

Investigation into the viability of the properties of porous glass-ceramics produced from granite dust and maize cob for use in thermal insulation of external walls of residential buildings

Given the enormous need for cost-effective wall insulation materials in the developing countries and Nigeria specifically, this study, explores the viability of porous glass-ceramics production from granite dust and maize cob using one-step sintering technology. The chemical compositions of the locally sourced materials used including granite dust, ball clay and maize cob were obtained using XRF. 300µm of granite dust and ball clay as well as 425µm of maize cob powder were used. Different amount of granite dust and maize cob powder were mixed with constant amount of a mixture of NaOH and Na2SiO3 in three different groupings to formulate the porous glass-ceramics samples. The formulated samples were uniaxially pressed at 10MPa and sintered in a gas kiln at 850oC for 3 hours. The sintered samples were subjected to experimental tests. The results showed water absorption, apparent porosity, bulk density, compressive strength and thermal conductivity of 25.6%–46.7%, 43.5%–75%, 1.45g/cm3 –1.9g/cm3, 0.7MPa–9.7MPa and 0.11W/m.K–0.53W/m.K respectively. The mineralogical properties of the sintered samples were obtained using XRD. The results indicated a viable material for use in thermal insulation of residential buildings.

Boosting the High Performance of BiFeO3-BaTiO3 Lead-Free Piezoelectric Ceramics: One-Step Preparation and Reaction Mechanisms.

One of the notorious problems in BiFeO3-based piezoelectric ceramics is how to limit the formation of Bi25FeO39 and Bi2Fe4O9 impurities to achieve excellent piezoelectric performance. In this study, a one-step preparation technology, namely, excluding PVA, calcining, and sintering are completed in one step, instead of three steps in the ordinary sintering method, is developed to prepare BiFeO3-xBaTiO3 (BF-xBT) ceramics. The significance of this one-step method is that the thermodynamically unstable region of BiFeO3 is successfully avoided based on the Gibbs free energy of BiFeO3, Bi25FeO39, and Bi2Fe4O9. Benefiting from preventing the formation of Bi25FeO39 and Bi2Fe4O9 impurities, the resultant ceramics show dense structures, macroscopic stripe domains, and a small number of island domains and display saturated P-E curves, sharp I-V characteristics, butterfly-shape S-E loops, and good piezoelectric properties (d33 = 174-199 pC/N; TC = 494-513 °C). By analyzing X-ray diffraction patterns of BF-xBT (0 ≤ x ≤ 1) powders at different calcination temperatures (Tcal), the different reaction mechanisms between 750 °C ≤ Tcal ≤ 900 °C and 950 °C ≤ Tcal ≤ 1000 °C are revealed. When 750 °C ≤ Tcal ≤ 900 °C, Bi3+ diffuses into Fe2O3 particles to form BiFeO3 and Bi25FeO39 and then reacts with BaTiO3; in this temperature range, the formed Bi25FeO39 is hard to eliminate. At 950 °C ≤ Tcal ≤ 1000 °C, Bi3+ and Fe ions simultaneously diffuse into BaTiO3 to form BF-xBT, which is beneficial to preventing the formation of Bi25FeO39 and the improvement of performance.

Effect of in-situ synthesized TiB2 on microstructure and mechanical property of Al/TiB2-SiC interpenetrating phase composites

ABSTRACT Al/TiB2-SiC composites were prepared based on TiB2-SiC porous ceramic preforms. The advantages of this work were characterized by the in-situ synthesized TiB2 in porous ceramic preforms which directly formed interconnected pores as well as TiB2-SiC ceramic skeletons during the one-step ceramic sintering. By controlling in-situ synthesized TiB2 volume fraction, it is possible to tailor TiB2-SiC preform structures so as to determine the structures and mechanical properties of Al/TiB2-SiC composites. The porous ceramic preforms with 20 vol% TiB2 addition achieved the highest porosity, the biggest pore size, but the lowest flexural strength. Al/TiB2-SiC composite with 20 vol% TiB2 addition showed the optimum mechanical properties. The improvement of mechanical properties of Al/TiB2-SiC composites was mainly ascribed to TiB2 additions as well as dense composite structures which were fully infiltrated with Al. This special interpenetrating structural feature and TiB2 addition also constituted an improved toughness through complex crack patterns such as branching, bridging, and deflection.

Synthesis of KVPO4F/Carbon Porous Single Crystalline Nanoplates for High-Rate Potassium-Ion Batteries.

With high theoretical capacity and operating voltage, KVPO4F is a potential high energy density cathode material for potassium-ion batteries. However, its performance is usually limited by F loss, poor electronic conductivity, and unsteady electrode/electrolyte interface. Herein, a simple one-step sintering process is developed, where vanadium-oxalate-phosphite/phosphate frameworks and fluorinated polymer are used to synthesize carbon-coated KVPO4F nanoplates. It is found that the V-F-C bond generated by fluorinated-polymer-derived carbon at the interface of KVPO4F/C nanoplates diminishes the F loss, as well as enhances K-ions migration ability and the electronic conductivity of KVPO4F. The as-synthesized KVPO4F/C cathode delivers a reversible capacity of 106.5 mAh g-1 at 0.2 C, a high working voltage of 4.28 V, and a rate capability with capacity of 73.8 mAh g-1 at the ultrahigh current density of 100 C. In addition, a KVPO4F/C//soft carbon full cell exhibits a high energy density of 235.5 Wh kg-1.