High-temperature Sintering Process Research Articles

Microstructure and Abrasive Wear Resistance of Deposited Materials of the Ni–Cr–B–Si System with Inclusions of Dispersed Phases

We study the microstructure of deposited coatings formed by a composite material based on PG-10N-01 self-fluxing alloy and modified with a mechanically activated composite material obtained as a result of the self-propagating high-temperature sintering process. By the X-ray phase diffraction analysis, in the structure of the coating, we detect the presence of titanium diboride (TiB2), nickel boride (Ni3B), titanium oxide (TiO), and iron oxide (Fe3O4) inclusions distributed over the nickel matrix. It is demonstrated that the modifying addition promotes not only the refinement of structure in the course of electric-arc deposition but also the elevation of the levels of hardness and microhardness of the deposited layer and a 1.5-fold increase in the abrasive wear resistance as compared with the wear resistance of PG-10N-01 alloy.

Effect of the crystal alignment and grain size on the thermoelectric properties of Bi0.4Sb1.6Te3 sintered materials

Sintered polycrystalline Bi0.4Sb1.6Te3 thermoelectric materials with various degrees of crystal alignment and grain sizes were prepared by pulse-current sintering under cyclic uniaxial pressure at sintering temperatures of 350–425 °C for holding times of 0–60 min to clarify the relationship between the microstructure and the thermoelectric properties. The degree of crystal alignment was enhanced with an increase of both the sintering temperature and holding time, and grain growth was also confirmed in the high temperature or long-time sintering process. The thermoelectric properties were measured perpendicular to the pressing direction, which corresponds to the crystal alignment direction. The electrical resistivity decreased and the thermal conductivity slightly increased with increasing sintering temperature and holding time. As a result, the figures of merit of the crystal-aligned samples sintered at high temperatures or for long holding times tended to reach 0.9–1 with large power factors because of the small electrical resistivity. The relationships between the quantified microstructure parameters and thermoelectric properties are discussed. The electrical resistivity decreased with increasing degree of crystal alignment and it saturated at a certain degree of crystal alignment, indicating that perfect crystal alignment is not necessary to obtain the lower limit of the electrical resistivity. Conversely, no significant change of the lattice thermal conductivity was observed in the grain size range 0.6–9.7 μm. This means that the lattice thermal conductivity of crystal aligned Bi0.4Sb1.6Te3 is almost independent of the degree of crystal alignment and grain size in the measured range.

Achieving High-Performance Perovskite Photovoltaic by Morphology Engineering of Low-Temperature Processed Zn-Doped TiO2 Electron Transport Layer.

Perovskite solar cells (PSCs) have become one of the most promising renewable energy converting devices. However, in order to reach a sufficiently high power conversion efficiency (PCE), the PSCs typically require a high-temperature sintering process to prepare mesostructured TiO2 as an efficient electron transport layer (ETL), which prohibits the PSCs from commercialization in the future. This work investigates a low-temperature synthesis of TiO2 nanocrystals and introduces a two-fluid spray coating process to produce a nanostructured ETL for the following deposition of perovskite layer. The temperature during the whole deposition process can be maintained under 150 °C. Compared to the typical planar TiO2 layer, the perovskite layer fabricated on a nanostructured TiO2 layer shows uniform compactness, preferred orientation, and high crystallinity, leading to reproducible and promising device performance. The detail mechanisms are revealed by the contact angle test, morphology characterization, grazing incident wide angle X-Ray scattering measurement, and space charge limited currents analysis. Finally, optimized device performance can be achieved through adequate Zn doping in the TiO2 layer, demonstrating an average PCE of 19.87% with champion PCE of 21.36%. The efficiency can maintain over 80% of its original value after 3000 h storage in ambient atmosphere. This study suggests a promising approach to offer high-efficiency PSCs using the low-temperature process.

Highly efficient preparation of Ce0.8Sm0.2O2-δ–SrCo0.9Nb0.1O3-δ dual-phase four-channel hollow fiber membrane via one-step thermal processing approach

Fabricating dual-phase hollow-fiber membranes via a one-step thermal processing (OSTP) approach is challenging, because of complex sintering kinetics and the subsequent impacts on membrane morphology, phase stability, and permeation properties. In this study, we have demonstrated that Ce0.8Sm0.2O2-δ-SrCo0.9Nb0.1O3-δ (SDC-SCN) four-channel hollow fiber membrane can be manufactured via a single high-temperature sintering process, by using metal oxides and carbonates directly as membrane materials (sources of metal ions). It has been found that use of a low ramping rate reduces grain sizes, increases grain and forming cobalt oxide nanoparticles, a key step to promoting surface exchange process followed by enhancing oxygen permeation. While the grain boundary interface region can be limited to approximately 20–30 nm. At 1173 K oxygen permeation of the SDC-SCN four-channel hollow fiber membrane was measured at approximately 1.2 mL cm−2·min−1 using helium as the sweep gas. Meanwhile, the dual-phase membrane shows a good tolerance to carbon dioxide, with the oxygen permeation flux fully recovered after long-term exposure to carbon dioxide (more than 100 h). This will enable further application of the OSTP approach for preparing dual-phase multi-channel hollow fiber membranes for applications of oxyfuel combustion, catalytic membrane reactors and carbon dioxide capture.

Synthesis and characterization of high ionic-conductive sodium beta-alumina solid electrolyte derived from boehmite

In this work, sodium beta-alumina solid electrolytes with high β″-Al2O3 content and high density are synthesized through solid-state reaction method employing boehmite as alumina sources. The influences of sodium oxide dosage on the phase component, texture structure, and ionic conductivity as well as the application performances in sodium ions battery for the synthesized beta-alumina electrolytes are investigated in detail. High β″-Al2O3 content of 94.6% and density of 97.8% are obtained for the electrolyte sinters through adding suitable excess of Na2O content, owing to the compensation of Na loss and the formation of molten state during the high-temperature sintering process. High ion conductivity of 1.16 × 10−2 S/cm at 350 °C is recorded for the beta-alumina electrolyte sinters, resulting from its high β″-Al2O3 content and density. The resultant beta-alumina electrolyte applied in Na3V2(PO4)3/Na battery delivers an initial discharge capacity of 80.5 mAh g−1 at 0.5 C and a high capacity retention of 79.25% after 100 cycles.

Low-Temperature Processed TiOx Electron Transport Layer for Efficient Planar Perovskite Solar Cells.

The most frequently used n-type electron transport layer (ETL) in high-efficiency perovskite solar cells (PSCs) is based on titanium oxide (TiO2) films, involving a high-temperature sintering (>450 °C) process. In this work, a dense, uniform, and pinhole-free compact titanium dioxide (TiOx) film was prepared via a facile chemical bath deposition process at a low temperature (80 °C), and was applied as a high-quality ETL for efficient planar PSCs. We tested and compared as-deposited substrates sintered at low temperatures (< 150 °C) and high temperatures (> 450 °C), as well as their corresponding photovoltaic properties. PSCs with a high-temperature treated TiO2 compact layer (CL) exhibited power conversion efficiencies (PCEs) as high as 15.50%, which was close to those of PSCs with low-temperature treated TiOx (14.51%). This indicates that low-temperature treated TiOx can be a potential ETL candidate for planar PSCs. In summary, this work reports on the fabrication of low-temperature processed PSCs, and can be of interest for the design and fabrication of future low-cost and flexible solar modules.

Biomedical applications of copper-impregnated bioactive glass

Bioactive glass (BG) is generally reckoned as an active constituent that both bonds with skeleton and connects with cartilage. This active material often releases the active ions in a controlled fashion via degradation, which is of particular interest in clinical medicine. However, monodispersed bioactive glass without modification still exists limitations, e.g., aggregation or lower activities both in vitro and in vivo . Owing to its unique morphology, distinctive cell uptake process, excellent degradation and biomineralization ability, as well as certain high biosafety, functionalized bioactive glass plays a key role in diverse biomedical applications such as bioimaging, gene/drug delivery and wound healing, facilitating the self-repair and regeneration of tissues. The interesting physicochemical properties of bioactive glass can be adjusted by appropriately selecting active ions, especially metal ions, as impregnated components to alter original bridging oxygen (BO) network to non-bridging oxygen (NBO) structure. In terms of the difference in matrix, bioactive glass is generally devided into three types, i.e., silicate, borate, and phosphate-based architectures. As a universal element in human physiological fluids, copper ions can also be impregnated in the structure of bioactive glass, in which these species not only affect the signal pathway and metabolic activity, but also serve as essential cofactors for many enzymes. After the ion exchange with the surrounding fluidic environment, copper ions can be precisely released at the desired site, minimizing the adverse effects. On the one hand, the impregnated copper ions inhibit the activity of osteoclast and stimulate the generation and aggregation of collagens, which significantly impact on the formation and healing of skeleton and cartilage. On the other hand, these copper species not only upregulate the expresssion of fibroblast growth factor (FGF)-2 and hypoxia inducible factor (HIF)-1α, but also enhance the production of endothelial nitric oxide synthase, subsequently promoting the proliferation and migration of human endothelial cells. In addition, the doped copper species are capable of bonding with mercapto, imidazole, carboxyl and amine, among others, to make changes in the membrane structure, including permeability augmentation and membrane transport dysfunction, indicating efficient antibacterial ability. Besides, hyperthermia process appears due to the photothermal effect after the irridation of near-infrared. In another case, copper ions participate in Fenton-like reaction under the acidic microenvironment of tumors, converting glutathione to oxidized glutathione, catalyzing the generation of reactive oxygen species (ROS), thus leading to the damage of mitochondria, ultimately inducing the apoptosis of cancer cells. Currently, it is required to achieve clinical translation from laboratory outcomes. Despite of a series of advantegeous features, the biomedical applications of copper-impregnated bioactive glass are still facing great challenges. To further facilitate the superiority of this prospective field, the developmental proposals are systemically discussed in this review. Further, critical discussions on effectively solving the aggregation caused by high-temperature sintering process and the denaturation induced by organic solvent utilization are emphasized. Moreover, the encapsulation mechanisms of certain molecules and compensate for the dificient exertion in cancer therapeutics are elaborated, providing an innovative and uninvasive platform in the field of prosperous biomedicine.

TiO2 Mesocrystals Processed at Low Temperature as the Electron-Transport Material in Perovskite Solar Cells.

TiO2 is the most widely used material for preparing the electron-transporting layer (ETL) in perovskite solar cells (PSCs). However, it requires a high-temperature sintering process. Moreover, the intrinsic defects and low electron mobility of TiO2 ETLs cause instability and hysteresis effects in PSCs. In this study, a mesoporous film composed of anatase TiO2 mesocrystals was facilely fabricated by a low-temperature route and then used as an ETL in PSCs for the first time. A satisfactory efficiency of 20.26 % can be achieved through delicate control of the entire device fabrication procedure. The optimal device, with an area of 1 cm2 , achieves an efficiency of 17.07 %. In comparison to the common TiO2 ETLs, those composed of TiO2 mesocrystals show the enhanced electron extraction and suppression of charge accumulation at the perovskite/ETL interface, resulting in improved photovoltaic performance and reduced hysteresis.

Sintering behaviour of Nb–16Si–25Ti–8Hf–2Cr–2Al alloy powder fabricated by a hydrogenation–dehydrogenation method

The present study investigated the sintering behaviour of Nb–16Si–25Ti–8Hf–2Cr–2Al alloy powders. The alloy powders were produced using ahydrogenation–dehydrogenation method and featured an irregular morphology. Powders sintered at 1500°C and 1600°C exhibited pores in their microstructures, while powders sintered at 1700°C for 4 h were fully densified and poreless. The cast ingot and powders were composed of three phases: Nbss, Nb5Si3, and Nb3Si. However, the Nb3Si phase was not observed, while HfO2 oxides formed in the sintered compact. The hafnium and oxygen reacted to form an HfO2 oxide during the high-temperature sintering process. From the result of the thermodynamic calculation, Hf oxide formed after sintering because Hf has the highest driving force for oxidation among the elements constituting the alloy.

Enhancement of the Biological and Mechanical Performances of Sintered Hydroxyapatite by Multiple Ions Doping

In the present work, hydroxyapatite nanoparticles (HA) doped with Mg2+, Sr2+ and Zn2+ ions are developed by wet neutralization method and then sintered at 1250 °C to obtain bulk consolidated materials. Physicochemical and microstructural analyses show that the presence of ion doping in the HA structure induced the formation of betaTCP as secondary phase, during the sintering process, and we found that this effect is depending on the solubility and stability of the various doping ions in the hydroxyapatite lattice itself. We also found that the formation of betaTCP as secondary phase, in turn, confines the grain growth of HA induced by the high temperature sintering process, thus leading to a strong increase of the flexural strength of the bulk materials, according to Hall-Petch-like law. Furthermore, we found that the doping ions enter also in the structure of the betaTCP phase; besides the grain growth confinement, also the solubility and ion release ability of the final materials were enhanced. In addition to ameliorate the mechanical performance, the described phenomena also activate multiple bio-functionalities: i) ability to up-regulate various genes involved in the osteogenesis, as obtained by human adipose stem cells culture and evaluated by array technology; ii) enhanced resistance to the adhesion and proliferation of gram+ and gram- bacterial strains. Hence, our results open a perspective for the use of sintered multiple ion-doped HA to develop ceramic bio-devices such as plates, screws or other osteosynthesis media, with enhanced strength, osteointegrability and ability to prevent post-surgical infections.

Effect of Co Leaching on the Vertical Turning Lathe Wear Properties of Polycrystalline Diamond Compact Manufactured by High Temperature and High Pressure Sintering Process

Polycrystalline diamond compact (PDC) has excellent wear resistance, high impact resistance, superior fatigue properties, and has been used in the oil and gas drilling industries. This study investigated the effect of Co leaching on the microstructure, vertical turning lathe (VTL) wear properties of PDCs manufactured by high-temperature and high-pressure (HTHP) sintering. The VTL wear test has the advantage of simulating the actual oil drilling environment by using granite as the workpiece. PDC sintered material that did not receive Co leaching was named HTHP sintered PDC-A, and the material subjected to Co leaching was called Co-leached PDC-B in this study. As a result of XRD analysis of both PDCs, diamond and WC peaks were detected, and only the HTHP sintered PDC-A exhibited some Co peaks. In the HTHP sintered PDC-A, the binder WC and Co were evenly distributed at the diamond interface. However, in the Co-leached PDC-B, some empty spaces were observed at the diamond interface. The HTHP sintered PDCA exhibited a similar or slightly higher VTL wear resistance than the Co-leached PDC-B, but only in the short sliding distance. In the long sliding distance after 9 km, Co-leached PDC-B showed significantly superior wear resistance compared to the HTHP sintered PDC-A. The HTHP sintered PDC-A exhibited both abrasive and adhesive wear behaviors, while the Co-leached PDC-B showed only abrasive wear. Based on the above results, the VTL wear mechanism of PDCs, and ways of improving wear resistance were also discussed.

Mineral transition and formation mechanism of calcium aluminate compounds in CaO-Al2O3-Na2O system during high-temperature sintering

The mineral transition and formation mechanism of calcium aluminate compounds in CaO-Al2O3-Na2O system during the high-temperature sintering process were systematically investigated using DSC-TG, XRD, SEM-EDS, FTIR, and Raman spectra, and the crystal structure of Na4Ca3(AlO2)10 was also simulated by Material Studio software. The results indicated that the minerals formed during the sintering process included Na4Ca3(AlO2)10, CaOAl2O3, and 12CaO·7Al2O3, and the content of Na4Ca3(AlO2)10 could reach 92wt% when sintered at 1200°C for 30 min. The main formation stage of Na4Ca3(AlO2)10 occurred at temperatures from 970 to 1100°C, and the content could reach 82wt% when the reaction temperature increased to 1100°C. The crystal system of Na4Ca3(AlO2)10 was tetragonal, and the cells preferred to grow along crystal planes (110) and (210). The formation of Na4Ca3(AlO2)10 was an exothermic reaction that followed a secondary reaction model, and its activation energy was 223.97 kJ/mol.

Production of silicon carbide reinforced molybdenum disilicide composites using high-pressure sintering

Studying the mechanical and thermal properties as well as the relationship between microstructure evolution and strengthening mechanisms is crucial for obtaining superior high-temperature refractory molybdenum disilicide-silicon carbide composites. In this study, molybdenum disilicide and silicon carbide powders with different volume ratios were used to fabricate molybdenum disilicide-silicon carbide composites via high pressure and high temperature at 5.5 GPa/1773 K. The introduction of the second phase improved the materials' mechanical properties. Transmission electron microscopy demonstrated that severe plastic deformation generated numerous micro-defects and grain refinement during the high pressure sintering process. The second phase enhancement also improved the samples’ performances. Under high pressure and high temperature sintering process, the thermal and mechanical properties of the materials increased dramatically, including a well Vickers hardness (~20.6 GPa), fracture toughness (~10.3 MPa·m1/2) and thermal stability (>1673 K).

Optimizational orange emitting behavior of Li2Na1-xBP2O8:xPr solid solutions under an short-wave ultraviolet irradiation

Li2Na1-xBP2O8:xPr3+ (x = 0–0.04 mol) solid solutions were synthesized by a high temperature sintering process. The crystalline phase, microstructure, chemical state of constituent element, and luminescence were performed. Excited by the short-wave ultraviolet light originating from 4f2 → 4f15d1 of Pr3+, an orange emitting behavior (3P0 → 3F3 of Pr3+, 673 nm) was proposed. The relationship between the doping Pr3+ concentration and the orange emitting behavior was analyzed. Concentration quenching occurs due to electric dipole – dipole interaction. All work revealed that the title solid solution is a selected material for solid state illumination and lighting.

Tuning the surface of LiNi0.8Co0.1Mn0.1O2 primary particle with lithium boron oxide toward stable cycling

The interfacial and structural instability of Ni-rich ternary cathode materials impedes its practical application in lithium ion battery with high energy density. Herein, a thin coating layer of lithium borate (~9.5 nm), which is confirmed robustly by the surface characterization techniques including TEM, FE-EPMA, and TOF-SIMS, forms onto the primary particles of LiNi0.8Co0.1Mn0.1O2 via H3BO3 treatment followed by sintering process. During the high-temperature sintering process, the boron dopes into the crystal structure of LiNi0.8Co0.1Mn0.1O2, which increases the interslab of transition metal layer and minimizes the Li+/Ni2+ cation mixing as evidenced by XRD results. Benefited from the stable glassy lithium borate coating and enhanced structural stability, LiNi0.8Co0.1Mn0.1O2 treated with 0.8 mol% H3BO3 delivered much improved cycling stability, especially the high-temperature performance. It achieves a capacity retention of 83.0% (25 °C) and 77.3% (50 °C) after 200 cycles at 200 mA g−1, respectively. This bi-functional modification effects originated from a simple wet coating method with H3BO3 solution may provide a guidance in practical application of Ni-rich cathode materials.

A well-designed CoTiO3 coating for uncovering and manipulating interfacial compatibility between LiCoO2 and Li1.3Al0.3Ti1.7(PO4)3 in high temperature zone

The unexpected chemical reaction between LiCoO2 (LCO) and Li1.3Al0.3Ti1.7(PO4)3 (LATP) in high temperature sintering process was studied by a well-designed stoichiometric ratio method. The species, content, color, interface morphology, element distribution and electrode impedance were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Various electrochemical analyses such as charge/discharge, cycle life test and electrochemical impedance spectroscopy (EIS) were conducted to evaluate the cell performance. Based on the understanding of the interaction between the cathode material (LCO) and the ceramic electrolyte (LATP), the four key steps involved in the reaction mechanism were discussed in detail. We found that the high-temperature chemical reactions between LCO and LATP could be well suppressed by introducing CoTiO3 as an efficient inhibition coating. High-density solid-state electrodes were prepared at high temperature, which exhibited high electrochemical performance in LCO-LATP-LiIn solid-state batteries.

A Review of Geopolymer Based Metakaolin Membrane as an Effective Adsorbent for Waste Water Treatment.

Geopolymer-based products help eco-accommodating sources of materials such as metakaolin, slag or fly ash. This review explores the blend configuration to generate geopolymer-based metakaolin membrane metakaolin and to evaluate the impact of a range of geopolymer-based metakaolin sintering temperatures at a temperature of 50 °C, 60 °C, 70 °C and 80 °C. As the quick development of a modern culture contributes to a large increase in interest in water, adsorption is taken closer to examined waste water extraction of the adsorption and repulsion of a metakaolin membrane geopolymer. Membrane waste water treatment is chosen to explore simple and inorganic membrane preparation techniques that have long help lives and low production costs. Reviews for geopolymer-based metakaolin membrane were therefore synthesized via a suspension that depends on the quick solidification method of high temperature suspension geopolymer slurries that were used as an adsorbent for treating waste water. Porous geopolymeric spheres have developed a homogenous structure with the aid of electron microscopy and Brunauer Emmett Teller (BET) investigations.Since permeable materials are regularly adsorbents, this examination has analyzed the adsorption by membrane geopolymers of heavy metals. This finding will advance the formation of improved wastewater treatment systems and along these lines give an elective answer for ecological harm brought about by substantial metal contaminations. Along these lines, molar (SiO2/Na2O) ratio of metakaolin and sodium silicate are fundamental in assembling a sort of geopolymer-based inorganic membrane which does not require a high temperature sintering process. Adsorption and dismissal consolidated can be utilized for wastewater auxiliary electrical plating forms not exclusively to proficiently wipe out center and low groupings of overwhelming metals in wastewater yet in addition to wipe out little sub-atomic contaminants in wastewater.

Synthesis and luminescence characteristics of Mg2Al4Si5O18:Eu2+ and nitrided Mg2Al4Si5O18:Eu2+ phosphors

Mg2Al4Si5O18:Eu2+ and nitrided Mg2Al4Si5O18:Eu2+ phosphors were synthesized through a high temperature sintering process. The luminescence characteristics of Mg2Al4Si5O18:Eu2+ phosphors and influence of nitridation on their luminescence characteristics were investigated. The XRD results demonstrate that the Eu2+ or N3− doping does not change the phase of Mg2Al4Si5O18 host. Under excitation at 365 nm, Mg2Al4Si5O18:Eu2+ phosphors exhibit emission band locating at blue light region. The introduction of N3− results in the reduction of Eu2+ emission intensity and redshift of Eu2+ emission spectrum. Meanwhile, the introduced N3− enhances the thermal stability and prolongs lifetime of Mg2Al4Si5O18:Eu2+ phosphors. On the basis of luminescence characteristics of Mg2Al4Si5O18:Eu2+ and nitrided Mg2Al4Si5O18:Eu2+, the influence of introduced N3− on luminescence was confirmed.

Surface Engineering of Low-Temperature Processed Mesoporous TiO2 via Oxygen Plasma for Flexible Perovskite Solar Cells.

A major problem in the application of mesoporous TiO2 as an electron transport layer for flexible perovskite solar cells is that a high-temperature sintering process is required to remove organic additives from the TiO2 layer. A facile oxygen plasma process is herein demonstrated to fabricate mesoporous-structured perovskite solar cells with significant photovoltaic performance at low temperatures. When the low-temperature processed TiO2 layer is modified via oxygen plasma, the organic additives in the TiO2 layer that hinder the charge transport process are successfully decomposed. The oxygen plasma treatment improves the wettability and infiltration of the perovskite layer and also passivates the oxygen vacancy related traps in TiO2. Hence, the oxygen plasma treatment evidently enhances charge extraction and transport, thereby improving photovoltaic performance and decreasing hysteresis.

On‐Demand Printing of Wearable Thermotherapy Pad

Thermotherapy is an effective method for pain relief, recovery from injury, and general healthcare. The ordinary heat pad used for thermotherapy at home is not usually tailored to the individual but supplied in a few different pre-fixed sizes and shapes for mass marketing. A customized wearable heat pad often requires expert support. Herein, an instant, custom-fit, and on-demand heat pad for thermotherapy is demonstrated. The heater is directly printed using silver nanoparticle ink on an off-the-shelf medical grade tape by inkjet technology. By coating the tape with silica nanoparticles as ink-absorbing layer and chloride ions as chemical sintering agent, stable heater patterns are printed without the need for subsequent high temperature sintering process. A 3D scanner is used to acquire body information, and a customized heater is produced using the information. The printed heat pad is attached to the shoulder and the effect of thermotherapy is verified objectively through electroencephalography and subjectively through survey. This printed heat pad produced by simple and low-cost fabrication provides wearable medical devices for personal thermotherapy.