Sintering Technology Research Articles

A Novel Sapphire@PiGF@Sapphire Color Converter with High Luminescence Saturation Threshold for Laser Lighting

AbstractNext‐generation high‐brightness laser lighting confronts a key challenge in preparing static color‐converting materials with remarkable luminescence saturation. Herein, a novel architecture of transmissive Y3Al5O12: Ce3+ (YAG) phosphor‐in‐glass film (PiGF) with double‐sided sapphires, i.e., a sandwich structured sapphire@PiGF@sapphire (S@PiGF@S) composite, is designed and fabricated by a thermocompression sintering technology. This kind of material can tolerate high laser power density (LPD) for the efficient double‐sided thermal channels and the high‐energy laser spot away from the PiGF emitting layer. As a consequence, the optimized S@PiGF@S color converter yields white light with a high luminous flux (LF) of 7602 lm at a record luminescence saturation threshold of 46.47 W·mm−2 benefiting from its low working temperature of merely 284 °C, which is 6.3 times that of traditional PiGF@sapphire color converter (1205 lm@10.89 W·mm−2). These findings verify that the developed S@PiGF@S color converter enables preferably optical‐thermal performances for promising applications in high‐brightness laser lighting.

Highly Robust, Pressureless Silver Sinter-Bonding Technology Using PMMA Combustion for Power Semiconductor Applications

This study presents the development of a highly robust, pressureless, and void-free silver sinter-bonding technology for power semiconductor packaging. A bimodal silver paste containing silver nanoparticles and sub-micron particles was used, with polymethyl methacrylate (PMMA) as an additive to provide additional thermal energy during sintering. This enabled rapid sintering and the formation of a dense, void-free bonding joint. The effects of sintering temperature and PMMA content on shear strength and microstructure were systematically investigated. The results showed that the shear strength increased with rising sintering temperatures, achieving a maximum of 41 MPa at 300 °C, with minimal void formation due to enhanced particle necking facilitated by PMMA combustion. However, at 350 °C, the shear strength decreased to 35 MPa due to cracks and voids at the copper substrate–copper oxide interface caused by thermal expansion mismatch. The optimal PMMA content was found to be 5 wt.%, balancing sufficient thermal energy and void reduction. This pressureless sintering technology demonstrates significant potential for high-reliability applications in power semiconductor modules operating under high-temperature and high-stress conditions.

Study on the fabrication and mechanical properties of SiCp/SiC gradient lattice structure based on selective laser sintering technology

ABSTRACT Conventional uniform lattice structures are subject to non-uniform loads or concentrated loads alternating back and forth during service, which can no longer meet the refinement requirements. In this paper, SiCp/SiC gradient lattice structures are prepared by selective laser sintering (SLS) technology and polymer impregnation pyrolysis (PIP) process, and compression standard specimens with different tilt angles are prepared according to the structural model by changing the printing direction, to analyze the influence of the anisotropic properties of the materials due to the SLS molding technology on the load-bearing behaviour of the core rod, and to further study the mechanical properties of the gradient lattice structures and the Failure behaviour. The results show that: with the increase of the angle of printing direction, the compression performance of the densification specimen decreases gradually; the compression strength of the gradient lattice structure is 13.95 MPa. During compression, the core rods with tilt angles of 60° and 75° mainly exhibit shear failure and crushing failure, respectively. The theoretical and simulated compression strengths were 16.08 and 16.32 MPa, respectively. This paper provides a new insight into the research and application of gradient lattice structures.

3D-Printed Shape Memory and Piezoelectric Bifunctional Thermoplastic Polyurethane/Polyvinylidene Fluoride Porous Composite Scaffold for Bone Regeneration.

Physical stimulations such as mechanical and electric stimulation can continuously work on bone defect locations to maintain and enhance cell activity, and it has become a hotspot for research in the field of bone repair. Herein, bifunctional porous composite scaffolds with shape memory and piezoelectric functions were fabricated using thermoplastic polyurethane (TPU) and poly(vinylidene fluoride) through triply periodic minimal surfaces design and selective laser sintering technology. Thereinto, the shape fixity ratio and recovery ratio of the composite scaffold reached 98.6% and 81.2%, respectively, showing excellent shape memory functions. More importantly, its piezoelectric coefficient (d33 = 2.47 pC/N) is close to the piezoelectric constant of bone tissue (d33 = 0.7-2.3 pC/N), and the voltage released during the compression process can reach 0.5 V. Furthermore, cyclic compression experiments showed that the strength of composite scaffold was up to 8.3 times compared with the TPU scaffold. Besides, the composite scaffold showed excellent cytocompatibility. In conclusion, the composite scaffold is expected to continuously generate mechanical and electric stimulation due to shape memory and piezoelectric function, respectively, which provide an effective strategy for bone repair.

Blacklight sintering of BaZrO3-based proton conductors

Acceptor-doped BaZrO3, a ceramic proton conductor, is well researched for use in solid oxide fuel cells due to its proton conductivity and chemical stability. A major drawback of the material is the difficulty of sintering as it requires high sintering temperatures and long heating times (> 1600 °C, 24 h). An emerging sintering technology to mitigate this challenge is blacklight sintering, which uses a high-powered blue or UV light source to heat ceramics extremely fast leading to short sintering times and reduced energy demand. In this work, BaZr0.8Y0.2O3-δ (BZY20) and BaZr0.8Y0.1Sc0.1O3-δ (BZY10Sc10) were blacklight-sintered with a high-power blue laser in under four minutes. Even though the resulting samples have a gradient from large to small grains and structurally disordered grain boundaries, the proton conductivity is comparable to conventionally sintered samples. Hence, blacklight sintering is a promising technology with the potential to sinter BaZrO3 much faster, while saving energy.

Study on the laser sintering process of veined red snail/polylactic acid composite powder

Drawing on the composition of shells and the microstructure of cross-laminated sheets, laser sintering technology was used to prepare laser-sintered fabrications of veined red snail powder as an inorganic material and polylactic acid (PLA) as an organic material. The process was optimized using the response surface method based on one-way experiments by adding veined red snail powder. At a 13.27 W laser power, 1.2 m/s scanning rate, 0.17 mm scanning spacing, and 0.23 mm delamination thickness, the bending strength of the veined red conch powder/PLA composite powder parts reached 8.53 ± 0.15 MPa, with an error of only 1.7% from the model’s predicted value. Under these process conditions, the characterization of laser-sintered parts with 0, 5, 10, 15, 20, and 25 wt% veined red snail powder revealed that parts with 15 wt% exhibited optimal mechanical properties, showing a 155.9% improvement over pure PLA parts.

Investigating on the Tribological Behavior of Binderless WC Matrix Composite

The purpose of this study was to investigate the dry friction and wear behavior of WC-4.3wt.%MgO-2wt.%ZrO2 (WM2Z) composite. WM2Z composite prepared by high-energy ball milling and spark plasma sintering (SPS) technology exhibited excellent comprehensive mechanical properties and dense microstructure. Dry friction test results indicated that the increase of sliding speed will lead to the decrease of friction coefficient, while at the same sliding speed, the extension of sliding time has no significant effect on the friction coefficient. The wear volume increased proportionally with the sliding time, while the wear rate stabilized after reaching a certain duration. The wear mechanism was mainly slight abrasive wear. Additionally, some oxidation occurred on both the WM2Z composite and the Si3N4 ball during friction, forming an oxide film that contributed to the reduction of the friction coefficient. The novelty of this study lies in the first systematic investigation of the effects of sliding speed and time on the wear performance of WM2Z composite, and the revelation that in high-speed sliding environments, even with shorter sliding times, the material experiences faster wear. This discovery emphasizes the important role of sliding speed in the wear process and provides new insights into understanding the wear mechanism of materials in practical applications. This study not only enriches the friction and wear theory of binderless WC matrix composites, but also provides important experimental data and theoretical support for the design and application of related materials, laying a solid foundation for wear resistance optimization and industrial applications.

TiO2-hBN nanocomposite coating with excellent wear and corrosion resistance on Ti6Al4V alloy prepared by plasma electrolytic oxidation

Hexagonal boron nitride (hBN) is recognized for its promising application prospects in anti-friction and corrosion resistance due to its self-lubrication and excellent impermeability to gases and liquids. In this study, the TiO2-hBN nanocomposite coatings are prepared via the liquid plasma-assisted particle deposition sintering (LPDS) technology, enabling compact and uniform growth of hBN on the Ti6Al4V surface. Results indicate that the dense and stable plasma at the coating/electrolyte interface facilitates the deposition and sintering of hBN particles, effectively filling surface defects and achieving a coating density of 86.7 %. The friction coefficient of the TiO2-hBN nanocomposite coating significantly decreases from 0.54 (titanium alloy) to 0.28, remaining stable even after 2000 sliding cycles. Compared to the substrate, the wear rate (4.3 × 10−4 mm3N−1 m−1) of nanocomposite coating drops by 70.8 %, which is primarily attributed to the self-lubricating property of hBN, reducing the frictional shear stress. Moreover, the TiO2-hBN nanocomposite coating also has excellent corrosion resistance due to the hBN sheet filling internal defects and inhibiting the corrosion reaction. All these merits render the LPDS technology competitive in expanding the severe service conditions of titanium alloys in aerospace and marine engineering equipment.

Interfacial microstructure and synergistic enhancement mechanism of symmetric gradient SiCp-reinforced aluminum matrix sandwich structure

Inspired by the biological sandwich structure to achieve excellent mechanical properties with both high strength and high ductility, the symmetric gradient silicon carbide particles (SiCp) reinforced aluminum (Al) composites, consisting of 10% SiCp/Al-3% SiCp/Al-Al-3% SiCp/Al-10% SiCp/Al, was fabricated using spark plasma sintering technology. The flat interface was achieved through hot rolling, significantly improving the bonding of interlayers. The differences in SiCp content among layers led to distinct evolution patterns in microstructure. In the pure Al layer, a notable continuous recrystallization mechanism was observed, while in the 3% SiCp/Al and 10% SiCp/Al layers, the recrystallization mechanism was nucleation-growth. The transmission electron microscope results indicated that the hindrance of dislocation motion at the interlayer interface and SiCp-Al interface enhanced the dislocation density, thereby improving its plastic deformation capability. On the other hand, the deflection and passivation of cracks at the interlayer interface significantly improves toughness. The differences intragranular strain among layers were most pronounced at the interlayer interfaces, leading to them becoming the stress concentration zone. Uncoordinated plastic deformation leads to sequential failure of layers, vertical cracks first occurred in the 10% SiCp/Al layer, then propagated towards the interlayer interface and the 3% SiCp/Al layer, respectively.

Flash sintering glass–ceramic treatment of Sr-contaminated soil waste

Effective disposal of radioactive waste is crucial for safe development of nuclear energy. In this study, flash sintering technology is used for the first time to quickly solidify simulated Sr-contaminated soil waste. The waste can be converted into a glass–ceramic phase by heating the waste at 1100 °C for 1 min during flash sintering. The phase evolution during flash sintering as a function of density and amorphous fraction was systematically investigated. Additionally, the microstructural evolution of the matrices and the leaching behavior of simulated waste elements (e.g., Sr) were evaluated. This study explores the feasibility of using flash sintering for treating radioactive contamination waste.

Preparation of spherical Gd2Zr2O7 powders by RF induction thermal plasma process

Spherical Gd2Zr2O7 (GZO) powders with a uniform particle size distribution are successfully prepared using a novel industrial approach, which combines spray-drying process and thermal plasma sintering technology together. In this, GZO powders with pyrochlore structure as the main phase are first synthesized via a solid-state reactive route using a mixture of the milled Gd2O3 powders and ZrO2 powders as starting materials. The influence of sintering temperature on the microstructure of prepared powders is researched. Then, GZO granules are prepared after wet-grinding and spray-drying process, which exhibit a spherical shape with the average particle size of 46.5 μm. RF induction thermal plasma is finally used to sinter the granulated particles, and the influence of feeding rate on the properties of spherical powders is investigated. The apparent density of plasma sintered GZO spherical powders is increased from 1.53 g/cm3 to 2.29 g/cm3 when the feeding rate of granulated powders is 80 g/min, and further increased up to 3.90 g/cm3 when the feeding rate is 15 g/min. Such powders are in potential demand for plasma sprayed coatings and additive manufacturing techniques, and the successful synthesis of spherical GZO powders may guide the way toward the preparation of many other spherical rare earth zirconates powders.

Preparation and Electrothermal Transport Behavior of Sn8[(Ga2Te3)34(SnTe)66]92 Bulk Glass.

High-conductivity tellurium-based glasses were anticipated to be the attractive candidates in chalcogenide glass systems on account of their distinctive characteristics and extensive application prospects. In this paper, the high-density (>96%) Sn8[(Ga2Te3)34(SnTe)66]92 bulk glass with the density of 5.5917 g/cm3 was successfully prepared by spark plasma sintering (SPS) technology at 460 K, using a 5 min dwell time and 450 MPa pressure. The room-temperature thermal conductivity of Sn8 bulk materials significantly decreased from 1.476 W m-1∙K-1 in the crystalline sample to 0.179 W m-1∙K-1 in the glass, and the Seebeck coefficient obviously increased from 35 μV∙K-1 in to 286 μV∙K-1, indicating that the glass transition of tellurium-based semiconductors could optimize the thermal conductivity and Seebeck coefficient of the materials. Compared to the conventional tellurium-based glassy systems, the fabricated Sn8 bulk glass presented a high room-temperature conductivity (σ = 6.2 S∙m-1) and a large glass transition temperature (Tg = 488 K), which was expected to be a promising thermoelectric material.

Microwave Hybrid Sintering and Soldering of Cu-Cr-W Composite Material for Reactive Power Breakers.

Over 60% of reported failures for reactive power compensation systems are given for damage to electrical circuit breaker contacts. This paper presents a study on the development of microwave technology for sintering of W-Cu-Cr alloys at 1012 °C for 65 min using 623.38 W microwave power, as well as microwave joining at 231 °C of the W-Cu-Cr composite material on body contact using 475 W microwave power for 55 s. The joined components were subjected to mechanical and electrical tests in accordance with ICE standards to validate the applied technology. Tests of connection-disconnection of the electrical contacts were carried out in accordance with the maximum number of disconnections allowed by the manufacturer (2 cycles/min): 25 s rest time and 5 s operating time under load. The components of the electrical contact after 111237 switches were analyzed under a microscope revealing a reduction of the damaged area by 27% compared with the original contact.

A Saw Blade Drill Bit with Reduced Heat Loss

We adopt microwave sintering technology prepared a low-cobalt Fe-Co-Cu diamond saw blade bit. The bit can achieve densification sintering which meets the index of diamond saw blade heads. Furthermore, the use of microwave non-pressure sintering significantly shortens the total sintering time and saves more than 20% energy. This environmentally friendly saw blade head can stimulate the development of the sawing industry and would be vastly used in the field of high and new technologies.

Effect of Mo addition on microstructure and mechanical properties of Cu-12.5Ni-5Sn alloy

Cu-12.5Ni-5Sn-xMo (x=0, 0.5, 1.0, 1.5 wt%) alloys were prepared using Spark Plasma Sintering (SPS) technology. The effect of Mo addition on the microstructure and mechanical properties of Cu-12.5Ni-5Sn alloy was investigated. The results indicate that adding trace amounts of Mo significantly refines the grain structure of Cu-12.5Ni-5Sn alloy, attributed to the formation of Mo-rich phases. Mo addition also inhibited the growth of discontinuous precipitation (DP) after aging treatment, reducing the DP volume fraction from approximately 25 % to 6 %. This effect is attributed to the precipitation of micron-sized Mo-rich phases at grain boundaries, which inhibit DP nucleation and growth by occupying γ-phase nucleation sites and pinning grain boundaries, thus impeding grain boundary diffusion. In addition, the interlamellar spacing of the discontinuous precipitation increases and the growth rate of lamellae decreases with increasing Mo content. Furthermore, an optimized combination of hardness (310 HB) and yield strength (586 MPa) was achieved in the Cu-12.5Ni-5Sn-1.0Mo alloy after aging treatment.

Development of Ti3SiC2 MAX phase tubular structures for solar receiver applications

Solar receiver tubes are key components of concentrating solar-thermal power (CSP) systems that harvest solar energy. For better efficiency, the Gen3 CSP receivers, which collect heat into a heat transfer fluid, require a temperature exceeding 700 °C during operation and need to perform under extreme conditions of high temperature and high thermal stress. Operators are seeking CSP designs using new high-temperature structural materials with high thermal conductivity and high creep resistance to achieve a design life of 30 years and thus help recover the plant capital cost sooner. MAX phase materials, which consist of an early transition metal element, an A-group element, and carbon or nitrogen, are expected to exhibit high creep resistance as well as high fracture toughness. In this paper, we describe fabricating both (1) dense Ti3SiC2 MAX phase disks and (2) short-length tubes using field-assisted sintering technology (FAST). First, the disk samples that we fabricated are fully dense and contain ≈90 % Ti3SiC2 MAX phase materials and ≈10 % TiC phase materials. We determined a flexure strength of 519 ± 32 MPa by conducting a four-point bending test at room temperature with rectangular bar samples of ≈100 % density. The thermal conductivity of the Ti3SiC2 MAX phase samples, measured by light-flashing analysis, decreases linearly from a value of 41 W·m−1·K−1 at room temperature to a value of 36 W·m−1·K−1 at 650 °C. A solar reflectance measurement of the Ti3SiC2 MAX phase revealed that, temperature increases from 400 to 1400 °C, thermal emittance increases from 0.39 to 0.49, while selectivity decreases from 1.8 to 1.4, respectively. Whereas the surface oxidized MAX phase samples after 100 h exposure to air at 1000 °C exhibit that of SiC.Next, we discuss fabrication of the crack-free Ti3SiC2 MAX phase tubular structures accomplished by using FAST processing in graphite bedding. A Ti3SiC2 MAX phase content of > 95 % with traceable ≈3% remaining TiC phase and ≈15 % porosity were demonstrated after high-temperature annealing. An average fracture strength of ≈250 MPa was determined with Ti3SiC2 MAX phase tubes of ≈85 % density by diametral compression testing at room temperature. Our work demonstrated that using FAST processing to produce Ti3SiC2 MAX phase tubular structures for CSP receiver applications is a viable approach.

New phase-construction phosphors ceramics for warm-white solid-state lighting: Orange-yellow-emitting (Lu,Gd)3(Sc,Al)5O12: Ce3+

Phosphor-converted white light-emitting diodes (pc-wLEDs) and phosphor-converted white laser diodes (pc-wLDs) are extensively utilized in lighting applications, with their quality and reliability heavily dependent on color converters. Recent progress in all-inorganic color converters, particularly phosphor ceramics (PCs), have markedly enhanced performance. However, due to the difficulty of managing emissive components, achieving warm white light with substantial red emission still remains challenging. In this work, a series of pure-phase Ce3+-activated garnet-structured solid-solution PCs, (Lu,Gd)3(Sc,Al)5O12: Ce (LGSAG: Ce), were fabricated using vacuum sintering technology for the first time. Through systematic analysis, it can be revealed that the addition of Gd3+ leads to a red shift in emission through changes in crystal-field splitting, whereas the inclusion of Sc3+ primarily focuses on improving the microstructure of the developed PCs. Particularly, the pc-wLED constructed from typical LGSAG: Ce PC generated significantly warmer light with a correlated color temperature (CCT) of 2916 K, compared to the 9557 K from LuAG: Ce PC. Meanwhile, under 40.0 W (15.7 W/mm2) blue laser excitation, the maximum luminous flux and luminescence efficiency of one typical LGSAG: Ce PG are 1172 lm and 29.3 lm/W, respectively. Therefore, the developed LGSAG: Ce PCs can show notable potential as color converters for future high-power warm-white solid-state lighting applications.

A Highly Sensitive NiO Flexible Temperature Sensor Prepared by Low-Temperature Sintering Electrohydrodynamic Direct Writing.

Flexible temperature sensors have diverse applications and a great potential in the field of temperature monitoring, including healthcare, smart homes and the automotive industry. However, the current flexible temperature sensor preparation generally suffers from process complexity, which limits its development and application. In this paper, a nickel oxide (NiO) flexible temperature sensor based on a low-temperature sintering technology is introduced. The prepared NiO flexible temperature sensor has a high-resolution temperature measurement performance and good stability, including temperature detection over a wide temperature range of (25 to 70 °C) and a high sensitivity performance (of a maximum TCR of -5.194%°C-1 and a thermal constant of 3938 K). The rapid response time of this temperature sensor was measured to be 2 s at 27-50 °C, which ensures the accuracy and reliability of the measurement. The NiO flexible temperature sensor prepared by electrohydrodynamic direct writing has a stable performance and good flexibility in complex environments. The temperature sensor can be used to monitor the temperature status of the equipment and prevent failure or damage caused by overheating.

A Chemotherapy-Photothermal synergistic system in bifunctional bone Scaffold: Tumor therapy and bone repair

Bone defect repair and tumor recurrence are the main challenges in the postoperative treatment of bone tumors. The incorporation of zoledronate (ZOL) into scaffolds presents a promising approach, attributed to its osteogenic and anti-tumor properties. However, there are still some unfavorable factors that make it difficult to eradicate tumor cells at the surgical site, including drug rapid release, the insufficient anti-tumor efficacy of ZOL and the multidrug resistance of chemotherapy. Herein, a novel nano drug delivery platform mesoporous silicon-coated graphene oxide (GO/MSN) and ZOL loaded nanoparticle (GO/MSN-ZOL) were developed. Then PLLA/ GO/MSN-ZOL scaffold that integrates photothermal therapy (PTT) and chemotherapy was fabricated using poly (L-lactic acid) as raw materials by selective laser sintering (SLS) technology. The GO not only imparted scaffold with photothermal properties for localized tumor cell ablation but also significantly enhanced its anti-tumor efficacy through synergistic effects in combination with chemotherapy. The mesoporous structure and large specific surface area of MSN contribute to the sustained release of ZOL. Additionally, GO could promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), which in combine with ZOL’s osteoclast inhibition, enhances the bone repair capacity. This study offers a straightforward and promising strategy for treating tumor-related bone defects.

FeSiBCCr bulk metallic glasses with excellent soft magnetic properties prepared using spark plasma sintering technology

Fe-based amorphous alloys have received much attention in the fields of electronics and electrical due to their excellent soft magnetic properties at high frequency. However, the controllable preparation of large-sized Fe-based bulk metallic glasses (BMGs) still faces numerous challenges. In this study, FeSiBCCr amorphous powders prepared by gas-water combined atomization were used as raw materials, and FeSiBCCr BMGs were prepared through spark plasma sintering (SPS) at different pressures. The microstructure, phase and magnetic properties of the compacts were systematically characterized using SEM, XRD, TEM, DSC, and VSM. The results showed that when the sintering pressure was 50 MPa, the slow densification process dominated by particle rearrangement at the initial densification process made the internal contact resistance of the compacts larger. This led to macroscopic inhomogeneous physical fields and severe local overheating during the later stages of sintering, causing the precipitation of α-(Fe, Si) and Fe3B phases. Although the material exhibited a relatively high saturation magnetization (Bs) of 1.08 ± 0.01 T, the low density and amorphous fraction resulted in a high coercivity (Hc) of 1060.8 ± 37.8 A·m-1. When the sintering pressure was increased to 250 MPa, the degree of particle densification significantly improved, and the temperature inhomogeneity was markedly suppressed due to reduced internal resistance. Thus, the prepared FeSiBCCr BMGs exhibited an extremely high density of 6.66 ± 0.06 g·cm-3 and excellent soft magnetic properties with Bs of 1.23 ± 0.01 T and Hc of 18.8 ± 1.8 A·m-1. This indicated that the FeSiBCCr BMGs prepared in this study exhibited broad application prospects in efficient electromagnetic conversion and advanced electronic devices.