Low-temperature Sintering Technology Research Articles

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.

Constructing phonon transport bridges via low-temperature sintering in Diamond@Ag/EP composite to achieve efficient 3D networks structure

The rapid advancement of integrated circuits and electronic devices presents challenges to traditional epoxy molding compound (EMC), necessitating the demand for highly thermally conductive yet electrically insulating composites to address the “hotspot issues” in high-power chips. Here, a low-temperature sintering technology based on metal–organic decomposition is developed to fabricate a three-dimensional interconnected networks structure composite (3D-Diamond@Ag/EP). The in-situ decomposition of the silver amine complex on the surface of the Diamond@Ag hybrid filler forms nano-silver bridges, which facilitate the successful construction of the three-dimensional networks structure. When the Ag reaches 4.0 vol%, the thermal conductivity of the composite (reaches 6.42 W/m·K) breaks out of the low numerical blockade of the epoxy resin (0.18 W/m·K), while maintaining excellent insulation performance. It is noteworthy that the great improvement of thermal conductivity is achieved by the synergistic effect of sufficient thermal pathways and minimizing interfacial thermal resistance along these paths. Moreover, this work obtained composite exhibits other excellent thermal characteristics. It provided a practical route to produce high thermal conductivity polymer-based composites with electrical insulation for heat management in modern electronic devices.

Promoted electrochemical performance of one-step sintered intermediate temperature solid oxide fuel cells using nanoscale electrodes

Solid oxide fuel cells (SOFCs) require simple cell fabrication procedure and reduced sintering temperature to improve system economics and durability. In this work, we propose a one-step low temperature (950 °C vs. conventional ≥1300 °C) sintering technology to prepare doped ceria electrolyte-based SOFCs by adding 3 mol% of Li2O sintering aid. Super low temperature sintering grants the direct application of nanoporous Ni-based cermet anode and hierarchical SrNb0.1Fe0.9O3 cathode with improved catalytic activities, which improves SOFC efficiency. The ionic conductivity of the electrolyte and catalytic activities of electrodes are systematically investigated by the electrochemical impedance spectroscopy technique and analyzed by the distribution of relaxation time method. These electrolyte-supported SOFCs exhibit an OCV value of 1.01 V at 500 °C and a peak power density of 291 mW cm−2 at 700 °C as well as sufficient stability for 50 h. Our results demonstrate a reliable and affordable method for manufacturing high-performance SOFCs.

Continuous degradation of plasticizer bisphenol A by catalytic Cu(FexAl2-x)O4@sediment ceramic membranes combined with peroxymonosulfate activation

The Cu(FexAl2-x)O4-embeded sediment ceramic membranes (CuFeAl@SCMs) were fabricated by the low-temperature sintering technology and further employed in a dead-end filtration device for continuous bisphenol A (BPA) degradation with peroxymonosulfate (PMS) activation. Results showed that using river sediment as precursor decreased the fabrication temperature for ceramic membranes (900 °C). The Al-doping Cu(FexAl2-x)O4 spinel solid solution was the predominant product phase, and the membrane with 42 wt% spinel content (CuFeAl@SCM-42) exhibited the highest BPA degradation efficiency (98.3%). SO4∙- and ∙OH were identified as the involved and primary reactive oxygen species (ROS). The density functional theory (DFT) calculations illustrated the forming mechanisms of SO4∙- and ∙OH. Furthermore, the DFT results confirmed that Al doping could enhance the adsorption energy and the electron transfer rate between the spinel and PMS, which encouraged PMS activation for BPA degradation. The outstanding performance of BPA degradation was observed in different pH, PMS content, transmembrane pressure, anions, natural organic matter (NOM) and water matrices, which revealed the excellent practicability, stability and recyclability of the prepared CuFeAl@SCM-42 in complex water environment. Therefore, this study demonstrated the possibility of using dredged river sediment to fabricate the superior catalytic ceramic membranes for wastewater treatment under a low-temperature sintering scheme.

Visible-light-enhanced photocatalytic activity of BaTiO3/γ-Al2O3 composite photocatalysts for photodegradation of tetracycline hydrochloride

A polyacrylamide gel method combined with low temperature sintering technology was developed for fabrication of BaTiO3/γ-Al2O3 composite photocatalysts, which exhibits excellent photocatalytic activity for the degradation of tetracycline hydrochloride (TC-HCl) under simulated sunlight irradiation. The effects of BaTiO3/γ-Al2O3 mass percentages, drug concentrations and pH values on the photocatalytic activity of BaTiO3/γ-Al2O3 composite photocatalysts were investigated. The optimum BaTiO3/γ-Al2O3 mass percentage, drug concentration and pH value are 5 wt%, 50 mg/L, and 6.77, respectively. The maximum photocatalytic degradation rate of BaTiO3/(5 wt%) γ-Al2O3 composite photocatalysts for the degradation of TC-HCl was approximately 16.81 times that of γ-Al2O3. The trapping experiments and reactive oxygen species production experiments proved that reactive hole and hydroxyl radical played major role in drug degradation. The photocatalytic activity enhancement of the BaTiO3/γ-Al2O3 composite photocatalysts came from the defect states in alumina and the interfacial defects between barium titanate and alumina and the high charge transfer and separation efficiency, which resulted from the type II band arrangement structure of BaTiO3/γ-Al2O3. The above results reveal that there is a significant potential application for the BaTiO3/γ-Al2O3 composite as a photocatalyst in the photo-degradation of drugs under simulated sunlight irradiation.

Selective removal of antibiotics over MgAl2O4/C3N4/YMnO3 photocatalysts: Performance prediction and mechanism insight

AbstractA simple polyacrylamide gel method combined with low temperature sintering technology has been used to synthesize the C–O functional groups grafted MgAl2O4/C3N4/YMnO3 (MAO–CN–YMO) heterojunction photocatalysts with enhanced visible‐light‐induced photodegradation toward oxytetracycline hydrochloride (OTC‐HCl). A variety of characterization methods are used to gain insight into the phase purity, crystal structure, microstructure, functional group information, elemental composition, surface defect, light response capability, and photocatalytic activity of the as‐synthesized samples. The influences of the mass ratios of mCN/mYMO, mCN/mMAO, and mMAO/(mCN + mYMO) in CN–YMO, CN–MAO, and MAO–CN–YMO heterojunction photocatalysts on the photocatalytic activity for the degradation of OTC‐HCl was also discussed, and the optimal mass ratio of mMAO/(mCN + mYMO) is identified as 15 wt%. The photocatalytic experiments confirmed that the MAO–CN–YMO heterojunction photocatalysts had high selectivity for the degradation of antibiotics. The prediction of the photocatalytic activity of the MAO–CN–YMO heterojunction photocatalysts for the degradation of OTC‐HCl was made by a variety of intelligent algorithm models. The results of the whale optimization algorithm are highly consistent with the experimental results. Combined with the energy band theory and the characterization results of high‐performance liquid chromatography–tandem mass spectrometry, the free radicals in the reaction solution preferentially attacked the –CH3, –NCH2, and –OH of OTC‐HCl during the degradation of OTC‐HCl by MAO–CN–YMO heterostructure photocatalysts, and then attack –C=O and –C=O–NH2, and finally perform ring‐opening reaction to degrade OTC‐HCl into nontoxic and harmless products of small molecules such as CO2, H2O, and NH4+. This work provides a new idea for the development of novel double p–n junction MAO–CN–YMO heterojunction photocatalysts for antibiotic degradation and the prediction of photocatalytic activity of multiple heterojunction photocatalysts by intelligent algorithms.

Synthesis and Characterization of BaTiO3/TiO2 Heterojunction Photocatalyst for Novel Application in Photocatalytic Degradation of TBBPA under Simulated Sunlight Irradiation

AbstractThe polyacrylamide gel method combined with low temperature sintering technology (PGMCLTST) have been used to synthesize the BaTiO3/TiO2 heterojunction photocatalysts. The BaTiO3/TiO2 heterojunction photocatalyst only contains tetragonal BaTiO3, rutile TiO2 and anatase TiO2, without any other impurities. Based on a variety of characterization, it was confirmed that a special heterojunction was formed between BaTiO3 and TiO2, and there were a large number of interface defects or oxygen defects in the samples. The BaTiO3/10 wt % TiO2 heterojunction photocatalysts have high photocatalytic activity for the degradation of tetrabromobisphenol A (TBBPA) under simulated sunlight irradiation. The interfacial defects enhance the transfer and separation efficiency of charge carriers in BaTiO3/TiO2 heterojunction photocatalysts. This technique provides a new idea for the application of BaTiO3/TiO2 heterojunction photocatalysts and other heterojunction photocatalysts in the degradation of persistent organic pollutants (POPs).

Skillfully grafted C O functional group to enhance the adsorption/photocatalytic mechanism of YMnO3/MgAl2O4 heterojunction photocatalysts

The YMnO3 with different manganese salts includes MnSO4·H2O, MnCO3 and C4H6MnO4·4H2O and YMnO3/MgAl2O4 heterojunction photocatalysts (YMO/MAO) with different mass percentage of MgAl2O4 were synthesized by a simple wet chemistry method combined with low temperature sintering technology. The effects of manganese salts on the structure, functional groups, morphology, charge states and optical properties of YMnO3 phase were studied in detail. The pure YMnO3 with the uniformity of particles can be obtained when only C4H6MnO4·4H2O is used as manganese source. The results confirmed that the YMO/MAO heterojunction was constructed by one step low-temperature sintering technique. The YMnO3/wt 10 % MgAl2O4 photocatalyst exhibits high optical absorption coefficient and highest adsorption capacity of 122.86 mg/g and degradation percentage of 98.98 % for the degradation of Congo red (CR), 86.16 % for the degradation of tetracycline hydrochloride (TC) and 72.51 % for the degradation of tetrabromo bisphenol A (TBBPA). The hydroxyl and superoxide radicals dominated the photocatalytic reaction process of YMO/MAO for the degradation of CR, TC and TBBPA. The present work pioneers the potential application of YMO/MAO grafted by CO functional group as dyes, antibiotics and persistent organic pollutants (POPS) adsorption / degradation catalyst and further provides technical reference for the synthesis of others heterojunction photocatalysts.

Degradation Behavior of High Power Semiconductor Modules by Low-Temperature Sintering Technology

This paper presents a degradation behavior of high-power semiconductor modules, i.e., IGBT, with sintered silver by power cycle test and thermal cycle test. The electrical characteristics, such as on-state voltage drop, thermal resistance and leakage current, were studied. For power cycle test, the IGBT module still has an acceptable electrical performance after the 30 K power cycles. No noticeable changes can be found in the die-attach layer, while the DBC-attach layer begins to fail after 30 K power cycles. For the thermal cycling test, the electrical characteristics of the IGBT module were only tested within the first 300 cycles because the Al2O3 DBC substrate failed first before the failure of the bonding layers. Finally, finite element methods (FEM) were used to analyze thermal and mechanical stress distribution and failure mechanism of the bonding layers.

Double heterojunction CQDs/CeO2/BaFe12O19 magnetic separation photocatalysts: Construction, structural characterization, dye and POPs removal, and the interrelationships between magnetism and photocatalysis

This novel double heterojunction carbon quantum dots (CQDs)/CeO2/BaFe12O19 magnetic separation photocatalysts (CCBFOMSPs) were successfully prepared via a polyacrylamide gel method and low temperature sintering technology combined with a hydrothermal method. The CQDs components in CCBFOMSPs were identified by neutron powder diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. The charge carriers could transfer and separation between the valence state components (CeO2 and BaFe12O19) and CQDs facilely, inhibiting the recombination of electron-hole pairs significantly by Hall effect. The photocatalytic activity of CCBFOMSPs for the degradation of mixed dyes include methyl orange (MO), rhodamine B (RhB) and methylene blue (MB) and tetrabromobisphenol A (TBBPA) were remarkably improved by regulating the electromagnetic interaction between the BaFe12O19 contents and the photo-generated electrons. Capturing experiment showed that the active species of hole (hVB+), hydroxyl radical (•OH) and superoxide radical (•O2−) played dominant roles in mixed dyes degradation. Attractively, the effect shed new light on wide applications of the double heterojunction magnetic separation photocatalysts.

A novel flexible, layered, recoverable SiO2 fiber skeleton and aerogel composites material prepared by papermaking process

The anisotropic ceramic fiber skeleton and its aerogel composite materials have important applications in the fields of high temperature insulation and aerospace. However, the traditional ceramic fiber skeleton has been limited in its application due to the complexity of its preparation process. Here, referencing the traditional papermaking technology, a flexible and recoverable SiO2 fiber skeleton with anisotropic layered structure was prepared through papermaking process and low-temperature sintering (170 °C) technology. Complete heteromorphic skeleton could be prepared by this simple process. On this basis, we impregnated the fiber skeleton with silica aerogel to further improve the composite properties of the pure fiber block. Compared with SiO2 fiber skeleton, the SiO2 aerogel/fiber skeleton composite exhibited lower thermal conductivity (0.023 W/(m·k)), higher compressive strength (2.19 MPa) and excellent high temperature thermal insulation. The recoverable and excellent thermal insulation properties of anisotropic layered composite materials provide an effective way for the manufacture of low-cost aerogel composite materials. At the same time, it has potential application value in high-temperature thermal insulation materials.

Synthesis of novel CQDs/CeO2/SrFe12O19 magnetic separation photocatalysts and synergic adsorption-photocatalytic degradation effect for methylene blue dye removal

A novel carbon quantum dots decorated n-n type CeO2/SrFe12O19 (CQDs/CeO2/SrFe12O19) magnetic separation photocatalyst was successfully synthesized via a hydrothermal method and gamma-ray assisted polyacrylamide gel method combined with low temperature sintering technology. To study the feasibility of CQDs/CeO2/SrFe12O19 magnetic separation photocatalyst as an adsorbent and photocatalyst to remove methylene blue (MB) dye, a series of heterostructure construction, adsorption and photocatalytic experiments were carried out. When compared with pristine CeO2, CQDs/CeO2 or SrFe12O19/CeO2, the CQDs/CeO2/SrFe12O19 magnetic separation photocatalyst exhibit a higher efficiency towards adsorption and photocatalytic degradation of MB dye molecule under simulated sunlight irradiation. The present work suggests that the CQDs/CeO2/SrFe12O19 magnetic separation photocatalyst have rapid magnetic separation, simple synthetic process, high optical absorption coefficient, excellent adsorption capacity, high photocatalytic activity, higher stability and reusability, which shows potential application for removing the organic pollutants in wastewater.

Bonding of Large Substrates by Silver Sintering and Characterization of the Interface Thermal Resistance

Low-temperature silver sintering technology, which has been proven to be a promising die-attach solution, was extended to bonding large substrates. Strong bonding strengths for substrates with a dimension of greater than 25 mm × 50 mm were achieved by sintering a nanosilver paste at temperatures below 270 °C under a pressure of less than 5 MPa. To characterize the thermal performance of the substrate-attach interface, we applied a transient thermal technique with cumulative structure function analysis. Using self-heating and the temperature-sensitive threshold voltage of a power device, we measured the transient thermal responses of the device placed at various locations on the bonded structures. Each transient thermal response was used to determine the cumulative structure function, which represents the relationship between cumulative thermal capacitance and cumulative thermal resistance from the device junction to the ambient environment. Two-dimensional maps corresponding to interface thermal resistance were obtained from structure function plots. We found that for well-bonded substrates, the average specific thermal resistance contributed by the sintered silver interface was between 5.20 and 5.78 mm2K/W with a variation of 4.7%–6.0%.

Conductive Fusion Technology Advanced Die Attach Materials for High Power Applications

Abstract High power semiconductor applications require a die attach material with high thermal conductivity to efficiently release the heat generated from these devices. Current die attach solutions such as eutectic solders and high thermal conductive silver epoxies and sintered silver adhesives have been industry standards, however may fall short in performance for high temperature or high stress applications. This presentation will focus on development of a reinforced, sintered silver die attach solution for high power semiconductor applications with focus on a pressure-less, low temperature sintering technology that offers high reliability for high temperature (250°C) applications. The electronic, optoelectronic, and semiconductor industries have the need for high performance adhesives, in particular, high power devices require low-stress, high thermal conductivity, thermally stable, and moisture resistant adhesives for the manufacture of high reliability devices. This paper introduces a new reinforced sintered silver adhesive based on the “resin-free” Conductive Fusion Technology. The high performance adhesive offers a robust solution for high temperature, high reliability applications. Conductive Fusion Technology consists of a high thermal conductivity silver component blended with a non-conductive, low-modulus powder component. The non-conductive powder component comprises an organically modified inorganic material that exhibits excellent thermal stability at temperatures exceeding 250°C. Properties of the sintered silver adhesive, such as storage modulus, can be modified by varying the content of the non-conductive component.

Structure and properties of (K0.5Na0.5)0.98Ag0.02Nb0.96Ta0.04O3 piezoelectric ceramics doped by CuO

Low-temperature sintering technology can control the volatilization of sodium and potassium ions during high-temperature preparation to obtain excellent physical properties of ceramics. In this research, we used the traditional ceramic preparation technology. KNN-based lead-free piezoelectric ceramics were prepared for the first time at home and abroad by using CuO and Na2O as collective additives under low sintering temperature (1020 °C) conditions. X-ray diffraction, scanning electron microscopy, and other modern test analyses show that KNANTC ceramics can form a pure perovskite structure of tetragonal phase in the total research range when 0.01 mol Na2O is used as a supplement to the A position of KNN piezoelectric ceramics. A moderate amount of CuO doping can simultaneously enhance liquid-phase sintering, promote grain growth, improve the density of ceramics, and achieve excellent electrical properties. The test results of KNANTC piezoelectric ceramics show good electrical properties when x = 0.035, that is, d33 = 343 pC/N, kp = 49%, er = 1382, tan δ = 1.1%, Pr = 24.9 µC/cm2, EC = 1.92 kV/mm, and Tc = 306 °C. These results indicate that KNANTC-x is a promising lead-free piezoelectric ceramic material that can gradually replace the traditional PZT-based piezoelectric ceramics in the future.

Low-Temperature Sintering of Stereocomplex-Type Polylactide Nascent Powder: Effect of Crystallinity

Stereocomplex (SC) crystallization between high-molecular-weight poly(l-lactide) (PLLA) and poly(d-lactide) (PDLA) provides a promising route to substantially improve the properties of polylactide (PLA), but conventional melt processing of the SC-type PLA (SC-PLA) is nearly impossible primarily due to the poor crystallization memory effect as well as serious thermal degradation after complete melting of SC crystallites with high melting temperatures of above 220 °C. Recently, we reported an innovative low-temperature (180–210 °C) sintering technology for fabricating SC-PLA products from its nascent powder. Unfortunately, its practical application has been significantly hindered by an extremely high pressure of 1 GPa, which must be utilized to ensure good surface wetting of the densified powder particles. With this challenge in mind, herein, the role of powder crystallinity in the low-temperature sintering has been investigated. Interestingly, we first demonstrate that depressing powder crystallinity is fa...

Operational characteristics of loop heat pipes with porous copper fiber sintered sheet as wick

Porous copper fiber sintered sheets (PCFSS) as wick are fabricated for loop heat pipes (LHP) using low-temperature solid-phase sintering technology and smooth and rough copper fiber as the manufacturing material. The operational characteristics of LHP with varied wick surface morphologies and filling ratios are analyzed. This study focuses on evaluating the following characteristics: thermal resistance characteristics under increasing and decreasing heat load patterns, evaporator surface thermal homogeneity, thermal inertia, and limit operational characteristics. Experimental results demonstrated that LHP with rough PCFSS exhibited lower thermal resistance. As compared to decreasing heat load conditions, relatively lower thermal resistance of LHP under increasing heat load conditions was obtained. The evaporator surface thermal homogeneity yielded improvement with rough PCFSS and increased filling ratio. A larger thermal inertia of LHP was observed when the low filling ratio was applied, and it will be improved when the filling ratio was increased and the smaller heat load variation intensity was selected. When rough PCFSS wick with 70% porosity and a deionized water filling ratio of 30% were selected, the LHP was able to effectively operate under 5–200W heat load conditions and yielded prompt response to heat load variation.

Ultrahigh-performance electrospun polylactide membranes with excellent oil/water separation ability via interfacial stereocomplex crystallization

A low-temperature sintering technology is devised to fabricate electrospun sc-PLA membranes with superior mechanical strength and unprecedented separation performanceviaforming sc crystallites between adjacent fibers.

Thermal performance of loop heat pipe with porous copper fiber sintered sheet as wick structure

Novel porous copper fiber sintered sheets (PCFSSs), with both single and composite porosities, were fabricated by the low-temperature solid-phase sintering technology. Subsequently, a new type of loop heat pipe (LHP) was constructed with the PCFSS as its wick structure. Results show that the capillary suction height is increased with porosity decreasing from 90% to 60%. With the single-porosity PCFSS, the evaporator wall temperature and the thermal resistance gradually decrease with the decreasing porosity. Compared to a single-porosity PCFSS, the LHP with a composite-porosity PCFSS as its wick structure shows a lower evaporator wall temperature and thermal resistance, and its start-up time reduces slightly because of the enhanced heat transfer and reduced back heat leak. The lowest evaporator wall temperature and minimum thermal resistance are obtained with the 70%+60% composite-porosity PCFSS, while the larger porosity is closer to the heat source. When the evaporator temperature is controlled to remain less than 100°C, the proposed LHPs tolerate a maximum heat load of 200W, with thermal resistance of 0.047°C/W.

Evaluation of Thermal Cycling Reliability of Sintered Nanosilver Versus Soldered Joints by Curvature Measurement

Low-temperature silver sintering technology is emerging as a lead-free die-attach solution to significantly improve the heat dissipation and reliability packaging of power devices and modules die attached by solder alloys. With the recent introduction of nanosilver materials, which dramatically simplify the bonding process by lowering the required pressure down to a few megapascals, the silver sintering die-attach solution is poised for wide use in the manufacture of electronic products. In this paper, the thermomechanical reliability of sintered-silver joints was studied in comparison with soldered joints of two lead-free solders, SN100C and SAC305. Die-attach samples were fabricated by bonding 10 mm × 10 mm silicon mechanical chips to silver-metalized copper blocks and direct-bond copper (DBC) substrates according to the respective heating profiles of a nanosilver paste and the two solders. The die-attach samples were thermally cycled between -40 °C and +125 °C. The bonding reliability was evaluated by measuring the bending curvatures of the cycled samples and examining the cross sections of the samples under an electron microscope. Bending of the bonded structures, which is the result of mismatched coefficients of thermal expansion between silicon and copper or DBC, offered a nondestructive method for monitoring the integrity of the bond line. The bending curvatures of all of the die-attach samples decreased rapidly after they were thermally cycled. Most of the drop in curvature can be attributed to stress relaxation in the bonding materials without bond-line cracking. However, in the samples on copper blocks, after 800 cycles, the curvatures of the soldered samples decreased to near 0 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> , but those of the silver-sintered samples still had about 30% of the original curvatures. Scanning electron microscopy images showed that the joints of the soldered samples with near 0 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> curvature had been cracked almost all the way through, but the joints of the sintered samples were still intact. These results demonstrate that the sintered-silver joints are more reliable than the soldered joints.