Reactive Sintering Method Research Articles

Effect of Y2O3 content on densification, microstructure and mechanical properties of reaction sintered magnesium aluminate spinel

Dense magnesium aluminate (MgAl2O4) spinels were developed via single-stage solid-state reaction sintering method at 1550–1650oC using combinations of varied commercial grade reactants-three different sources of alumina and two different sources of magnesia. The effect of Y2O3 doping in the concentration range of 1–4 wt % on different spinel batches was studied. Y2O3 addition was found to favour the densification of all the spinels at all dopant concentrations and maximum densification was found for the 2 wt % Y2O3 containing spinel batches. Phase analysis of the Y2O3 containing batches revealed the presence of yttrium aluminum garnet (YAG, Y3Al5O12) at all the sintering temperatures. Owing to similar crystal structure isotropic configuration of YAG (cubic) as that of spinel (cubic), Y2O3 doping was found to favour densification of spinel. Microstructural investigation revealed that Y2O3 containing batches have a controlled grain structure as compared to the without additive batches. Also, 2 wt % Y2O3 containing spinel batches sintered at 1650oC revealed better mechanical properties such as cold modulus of rupture and strength retainment after thermal shock than that of the undoped spinel batches.

Ce3+, Pr3+ Co-Doped Lu3Al5O12 Single Crystals and Ceramics: A Comparative Study.

Ce3+, Pr3+ co-doped Lu3Al5O12 (Ce, Pr:LuAG) single crystals and ceramics were prepared using the optical floating zone (OFZ) and reactive vacuum sintering methods, respectively. The microstructure, photo- (λex = 450 nm), and radio-luminescence (under X-ray excitation) performance, as well as scintillation light yield (LY, under γ-ray, 137Cs source) of both materials, were investigated and compared. Ce, Pr:LuAG ceramics had an in-line transmittance of approximately 20% in the visible light range, while the analogous crystals were more transparent (~65%). The X-ray excited luminescent (XEL) spectra showed the characteristic Ce 3+ and Pr3+ emissions located at 310 nm, 380 nm, and 510 nm. The highest LY of the Ce, Pr:LuAG ceramics reached 34,112 pho/MeV at 2 μs time gate, which is higher than that of a single crystal. The ratio of LY values (LY2/LY0.75) between shaping times of 0.75 μs and 2 μs indicated a faster scintillation decay of ceramics regarding single crystals. It was ascribed to the lower effective concentration of luminescent activators in single crystals because of the coefficient segregation effect.

Scanning pulsed laser ablation in liquids: An alternative route to obtaining biocompatible YbFe nanoparticles as multiplatform contrast agents for combined MRI and CT imaging

Ytterbium ferrites are being used in many promising applications, such as visible-light photocatalysis, solar cells, magnetooptic devices, electro-magnetic equipment, etc., due to their fantastic ferroelectric and ferromagnetic properties. However, despite their good magnetic and radiopaque features, the use of ytterbium ferrites as multiplatform contrast agents in magnetic resonance imaging (MRI) and X-ray computed tomography (CT) is still under-developed. This is mainly due to difficulties in obtaining stable and biocompatible aqueous colloidal dispersions of ytterbium ferrite nanoparticles. In order to overcome this limitation, this work explores an eco-friendly method to directly synthesize such dispersions by liquid-assisted pulsed laser ablation of ytterbium ferrite massive targets. First, orthorhombic bulk YbFeO3 targets were obtained by a reaction-sintering method. Then, colloidal dispersions of nanoparticles were produced directly in both distilled water and ethanol by irradiating the bulk YbFeO3 targets with high-power infrared nanosecond lasers pulses. A battery of techniques has been used to characterize the as synthesized YbFeO3 targets and colloidal dispersions of YbFe nanoparticles to determine their composition, structure, magnetic properties, X-ray attenuation potentials, and colloidal properties. Moreover, the biocompatibility of the systems was also analysed by MTT cell viability assay. Results indicated that the use of distilled water as ablation medium yields colloidal dispersions consisted mainly of paramagnetic ytterbium ferrite nanoparticles. Contrarily, the use of ethanol as solvent leads to colloidal dispersions of polycrystalline nanoparticles with both ferromagnetic and paramagnetic behaviour, due to the coexistence, in each nanoparticle, of ytterbium ferrite, ytterbium oxide, and iron oxide crystalline phases. Both colloidal dispersions exhibit also high biocompatibility and suitable X-ray attenuation properties. Moreover, they show bio-safe hydrodynamic sizes (lower than 200 nm) with acceptable overall hydrodynamic polydispersity index values (under 0.4), being stable in water for several weeks. These results pave the way for the future evaluation of Yb–Fe based nanoparticles as multiplatform contrast agents in multimodal MRI and CT imaging.

Effects of Y2O3 and LiAl5O8 on the Microstructure and Optical Properties of Reactively Sintered AlON Based Transparent Ceramics.

Sintering aid was very crucial to influence the microstructure and thus the optical property of the sintered optical ceramics. The purpose of this work was to explain the difference between the sintering aids of Li+ and Y3+ on Al23O27N5 (AlON) ceramic via reaction sintering method. The effects of LiAl5O8 (LA) and Y2O3 on the sintering of Al2O3-AlN system were carefully compared, in terms of X-ray diffraction (XRD), microstructure, density, X-ray photoelectron spectroscopy (XPS) and optical transmittance. According to the XPS and XRD lattice analysis, the chemical structure of the materials was not obviously affected by different dopants. We firstly reported that, there was obvious volume expansion in the Y3+ dopped AlON ceramics, which was responsible for the low transparency of the ceramics. Obvious enhancements were achieved using Li+ aids from the results that Li: AlONs showing a higher transparency and less optical defects. A higher LA content (20 wt%) was effective to remove pores and thus obtain a higher transmittance (~86.8% at ~3.5 μm). Thus, pores were the main contributions to the property difference between the dopant samples. The importance of sintering aids should be carefully realized for the reaction sintering fabrication of AlON based ceramics towards high transparency.

Synthesis, microstructure, and formation mechanism of a potential neutron shielding material: WAlB

• Dense, predominately single-phase samples of WAlB were synthesized using a reactive hot press sintering method for the first time. • DFT calculations and Rietveld analysis of WAlB indicate that WAlB most likely forms via a topotatic transformation reaction, by the intercalation of Al layers into WB crystal structure. • The calculated linear attenuation coefficients for different energy gamma-rays imply WAlB has a high gamma-ray shielding capacity.

Mg-Fe-Al-O spinel: Preparation and application as a heterogeneous photo-Fenton catalyst for degrading Rhodamine B.

It is an urgent need to develop new environmentally friendly spinel ferrites with high catalytic efficiency. In this work, a series of Mg-Fe-Al-O spinels with different ratios of Mg/Al were successfully synthesized by the reaction sintering method and were used as a heterogeneous photo-Fenton catalyst for degradation of Rhodamine B (RhB). The effect of different ratios of Mg/Al on the properties of Mg-Fe-Al-O spinel was characterized and analyzed through a range of advanced characterization techniques and DFT calculations. The influence factors on the photo-Fenton reaction catalyzed by Mg-Fe-Al-O spinels were systematically investigated. The results showed that the prepared Mg-Fe-Al-O spinels had larger lattice parameters, wider bandgap, and stronger magnetism, with the Mg content increased. Among them, Mg-9 (Mg0.88Fe1.88Al0.23O4) had the best catalytic performance in the photo-Fenton reaction. The degradation efficiency of RhB reached 98.45%, and the TOC removal efficiency was 83.47%. The elemental valence and PDOS of Mg-9 (Mg0.88Fe1.88Al0.23O4) spinels were closer to MgFe2O4. The photo-generated holes could directly oxidize water and hydroxyl to generate reactive oxygen species ·OH, improving the catalytic activity.

Defect Regulation of Terbium-Doped Y2Zr2O7 Transparent Ceramic for Wide-Range Multimode Tunable Light-Shielding Windows.

In the most promising new window materials, the light-blocking property of the state-of-the-art transparent polycrystalline ceramics is still located in the UV range, which undoubtedly limits their applications. Herein, a transparent Y2Zr2O7:Tb (YZO:Tb) ceramic for light-shielding windows was prepared by a solid-state reaction and vacuum sintering method. Two simple and efficient routes, with doping concentrations varying and air-annealing temperatures regulating, were developed for the first time to control the content of defect clusters [TbY4+-O2--TbY4+] and [TbY4+-e•], enabling the optical cutoff waveband of these ceramics spanning from UV and BV to green light. These defect clusters generated from an air-annealing process were proposed for the relevant reaction mechanisms concerning light erasure behavior. The controllably tailoring of optical cutoff wavelength from Tb single-doped YZO ceramics, adjusted by defect clusters, may open a novel door to develop lanthanide-doped transparent ceramics for wide-range tunable light-shielding windows.

On the structural characteristics of 45S5-xSFO bioglass-ceramic composites for medical applications

Bioactive ferromagnetic glass-ceramics composites have been prepared through the combination of the quenching and solid-state reaction (SSR) sintering methods, viewing their integration in biomedical applications. The material under study consists of a glassy system with the chemical formula (94-2x)SiO2−xNa2O−xCaO-6P2O5, which acts as host-matrix for the magnetic phase (strontium ferrite). The samples were obtained by a modified incorporation technique, where the magnetic phase, previously synthetized by the SSR method, was added to the glass-matrix in desired proportions. The physical properties were investigated considering the analysis of the X-ray diffraction as well as Raman spectroscopy techniques, both performed at room temperature. Results revealed the formation of partially crystallized bioglass-ceramics, with a strong influence of the magnetic phase on the crystallization kinetics, which suggests the obtained bioactive composites promising materials for clinical treatments.

Study of the dielectric relaxation mechanisms in KNbO3-based electro-ceramics

Electro-ceramics based on the KNbO3 ferroelectric system were synthesized from the solid-state reaction sintering method. In particular, the electrical properties have been investigated at room temperature in the (1−x)KNbO3−xBaNi1/2Nb1/2O3−δ (KBNN) solid-solution. The dielectric relaxation mechanisms have been analyzed as a function of the oxygen vacancy (δ) concentration and the frequency dispersion of the complex dielectric permittivity was analyzed in a wide frequency range. The obtained results were discussed within the framework of the current models reported in the literature for the dielectric relaxation processes.

Performance enhancement of perovskite solar cells based on a CdO-quantum dot/TiO2-nanocrystal array electron transport layer

An oriented TiO2 nanocrystal array (TiO2-NA) shows a unique electron extraction capability for perovskite solar cells (PSCs) due to it having fewer grain boundaries and high crystallinity for effective charge collection. Based on these advantages, we prepared PSCs based on TiO2-NA mesoporous film (mp-film), and chose CdO quantum dots (QDs) as the modifier of the TiO2-NA mp-film. The diameter of a single TiO2-NA and the TiO2-NA gap were controlled by controlling the hydrothermal reaction time. The CdO-QDs/TiO2-NA mp-film, as the electron transporting layer (ETL), was prepared by successive ionic layer adsorption and the reaction-sintering method. In this work, oxidation state CdO QDs were first used as the modifier in the ETL of the PSC. We gradually optimized the CdO/TiO2-NA mp-film by controlling the hydrothermal reaction time of TiO2-NA to improve PSC performance. Infiltration of the perovskite absorber–submicrometer-thick rutile TiO2-NA mp-films with Spiro-MeOTAD yielded a strikingly high photoelectric conversion efficiency of 11.94% under AM 1.5G illumination. The dependence of photovoltaic performance and interfacial electronic behavior on the length of the CdO/TiO2-NA was also investigated.

Development of Ti2AlN MAX phase/cellulose acetate nanocomposite membrane for removal of dye, protein and lead ions

To our knowledge, this study was carried out because there is no other study using Ti2AlN MAX phase material as an inorganic additive to improve the performance of the cellulose acetate (CA) membrane. In this research, the effect of titanium aluminum nitride (Ti2AlN) MAX phase on the performance of CA polymeric membrane was investigated. In the first step, the Ti2AlN MAX phase was synthesized via the reactive sintering method and characterized. The Successful synthesis of the MAX phase with high purity in the hexagonal crystalline structure was confirmed with the XRD pattern. The prepared MAX phase was used as a hydrophilic inorganic additive to improve the performance of the CA membrane. An improvement in hydrophilicity of the CA membranes was observed by incorporating the MAX phase into the matrix of membranes. The nanocomposite membrane containing optimum content of MAX phase (0.75 wt%) showed a threefold increase in permeability during filtration of pure water and dye solutions. In addition, the optimum nanocomposite membrane exhibited an improved flux recovery ratio of 92.7 % with a high removal efficiency of 70.7 % for reactive black 5, 93.5 % for reactive red 120, and >98 % for bovine serum albumin. Finally, the rejection of different salts was investigated, and the optimum nanocomposite showed high rejection for lead ions (97 %) with moderate rejection for Na2SO4 (>55 %) and NaCl (>30 %). The results of this research demonstrated the high potential of MAX phase-based materials for improving polymeric membranes.

Effect of Sn Content on the Pore Structures of Porous Ni-Sn Alloys Produced by Reactive Synthesis Sintering Method

Effect of Sn Content on the Pore Structures of Porous Ni-Sn Alloys Produced by Reactive Synthesis Sintering Method

Tailoring Li2Si2O5 rod-like particles and their simultaneously strengthening and toughening effects on lithium disilicate glass-ceramics

To achieve high performance of glass-ceramics, it is urgent to open a new path to enhance the mechanical properties. In this study, Li2Si2O5 rods were successfully synthesized by a modified two-step solid-state reaction sintering method. The rod aspect ratio could be controlled by adjusting the second stage sintering time. The evolution process of such Li2Si2O5 rods and their possible formation mechanism were put forward. For the first time, the Li2Si2O5 rods were used to strengthen and toughen the homologous Li2Si2O5 glass-ceramic in a typical quaternary Li2O-SiO2-K2O-La2O3 system, which indicates a high flexural strength and toughness of 315±24 MPa and 2.42±0.6 MPa·m1/2, respectively. In this glass-ceramic, the microstructure features a densely stagger network formed by the elongated rods and smaller Li2Si2O5 crystals in the glass matrix, contributing to the improvement of mechanical properties. The results demonstrate that Li2Si2O5 rods could be an excellent candidate for strengthening and toughening glass-ceramics.

A Microwave Dielectric Ceramic with Ultra-low Dielectric Constant Prepared by Reaction Sintering Method

A Microwave Dielectric Ceramic with Ultra-low Dielectric Constant Prepared by Reaction Sintering Method

A novel MoSi2-rich coating on the SiC-Si coated C/C composites for the preparation and antioxidative properties at 1773 K and 1973 K

To provide a long-term oxidative protection for C/C composites at elevated temperatures, we designed and fabricated a novel MoSi2-rich oxidation protective coating on the surface of SiC-Si coated C/C composites by a combined method of powder reactive sintering and molten silicon infiltration. The phase composition, microstructure and oxidation protective performance of the coating were investigated. The results show that as-prepared MoSi2-rich coating had a dense structure with multiphase mosaic. After oxidation for 581 h at 1773 K in air, the mass loss of the coated specimen was only 1.83%. Particularly, the composite coating can effectively prevent C/C substrate from oxidation for more than 200 h at 1973 K in air, indicating that it possessed outstanding antioxidative capacity due to the rapid formation of the dense SiO2 glass layer in a long-term high-temperature atmosphere.

Fabrication of porous gehlenite coating on Al2O3-ZrO2-SiC composite ceramics and its in vitro biological activities.

Porous gehlenite coatings on Al2O3-ZrO2-SiC composite ceramics were prepared by electro-spraying technique combined with reactive sintering method. The influences of gehlenite coating on the mechanical property of the ceramics and biological activity of the coating were investigated. The results indicated that the gehlenite coating has limited influences on flexural strength and fracture toughness of the ceramics, and the coating has elastic modulus of 82GPa, hardness of 2.2 GPa, and adhesive strength of 1512mN, suggesting its potential application in load-bearing ceramic implants. Simulated body fluid soaking test, CCK-8 and alkaline phosphatase activity assay demonstrated that the porous gehlenite coating has strong mineralization ability, which promotes proliferation and differentiation of MC3T3-E1 cells. These excellent biological performances can be attributed to the synergistic effect of the porous surface of the coating and its release of Ca2+ and Si4+.

Ultrasound-assisted catalytic activation of peroxydisulfate on Ti3GeC2 MAX phase for efficient removal of hazardous pollutants

Herein, Ti3GeC2 MAX phase was synthesized using the reactive sintering method and characterized via various techniques. The X-ray diffraction pattern confirmed the successful synthesis of the MAX phase in the hexagonal crystal structure with high purity. Based on the field-emission scanning electron microscopy and high-resolution transmission electron microscopy analysis, layered morphology with the compacted structure was observed. The catalytic activity of the MAX phase was evaluated for activation of peroxydisulfate (PDS) under ultrasound (US) irradiation. Ti3GeC2 MAX phase (0.2 g/L) with a bandgap of 1.72 eV demonstrated high capability to activate 0.15 mmol/L of PDS under US irradiation, resulting in 94.7% removal efficiency within 80 min of reaction time. The removal of diverse types of pollutants such as dimethyl phthalate, hydroxychloroquine, and mefenamic acid confirmed the high performance of the Ti3GeC2/PDS/US ternary system. The quenching tests indicated that both radical and non-radical pathways are involved in the degradation process, and O2•−, O•H, SO4•−, and O21 were recognized as critical species. In addition, a probable degradation mechanism was proposed. The results provide a promising perspective for the application of MAX phase-based materials in the ternary catalyst/oxidant/US systems for the efficient treatment of organic contaminants. To the best of our knowledge, the present work is the first effort to make use of the Ti3GeC2 MAX phase as a desirable catalyst for the removal of organic pollutants applying the catalyst/PDS/US ternary system.

Ce3+‐Doped Yttrium Aluminum Garnet Transparent Ceramics for High‐Resolution X‐Ray Imaging

AbstractScintillators, as the core materials for X‐ray imaging, have received great attention in radiation detection, security inspection, and biomedical applications. However, the current single crystal and thin film scintillators have encountered several issues, such as high cost, insufficient stability, and uneven distribution, which undoubtedly limit the development of high‐quality X‐ray imaging. Herein, the Y3Al5O12:Ce3+ (YAG:Ce3+) transparent ceramics (TCs), which presented a high transmittance of 82% and a steady‐state light yield of 24 600 photons MeV−1, are prepared by the vacuum solid‐state reactive sintering method. The fabricated YAG:Ce3+ TCs exhibit X‐ray imaging with an excellent spatial resolution (≈34.7 lp mm−1). Moreover, because of the structural stability of YAG:Ce3+ TCs, long‐term stable work under X‐ray irradiation is realized successfully. This work indicates that the TC scintillators provide a new opportunity for the development of high‐quality X‐ray imaging.

Obtaining and Study Smart Composites in the B<sub>4</sub>C-SiC-Si-Al-Al<sub>2</sub>O<sub>3</sub>—Carbon Fiber System

Goal: To obtain SIALON containing composites by reactive sintering method in SiC-B4C-Si-Al-Al2O3 system. Using this method of synthesis, it became possible to obtain composites with different percentages of SIALON. Our task was also to study the phase composition in the SiC-B4C-Si-Al-Al2O3 system. Method: The obtained mass was grounded in an attritor and the consolidated composite was obtained by hot pressing at 1800°C, 40 minutes, delaying at final temperature for 8 min. under 30 MPa pressure. To study the phase composition of the composites, we conducted an X-ray structural analysis on the DRON-3 device, and to study the microstructure, we conducted research on an optical microscope and a raster electron microscope “Nanolab 7” of the company “OPTON”. The values of the electrical parameters of the study composites were calculated on the basis of the obtained “lgp-t” dependence. Result: In SiC-B4C-Si-Al-Al2O3 system we obtained composites with a matrix composed of: β-SIALON, silicon carbide, corundum and nanoparticles of boron nitride. Conclusion: The phase composition of the obtained composite provides high physical-technical and performance properties of these composites. Compression strength—2187 MPA, Bending strength—285 MPa, Thermal expansion coefficient a20-700-3.8 × 10-60 C.

Fabrication of (Zr,Ti)B2–ZrN–BN composites through reactive spark plasma sintering of ZrB2 and TiN

Mechanical properties and sintering behavior of additive-free and TiN-doped ZrB2 ceramics were studied. Reactive spark plasma sintering method was applied for manufacturing of ceramics at 1850 °C for 6 min under 40 MPa. The impact of TiN addition on the microstructure evaluation, densification, and mechanical feathers was investigated. A porous monolithic ZrB2 with a relative density of 76.5 % was manufactured, while the introduction of 5 wt% TiN resulted in enhancement of relative density to 93.1 %. The formation of (Zr,Ti)B2 solid solution and in-situ h-BN and ZrN phases was proven by microstructural assessments and X-ray diffractometry. Minimizing the grain growth and improving the densification, as the results of TiN addition, led to enhancement in mechanical properties. The values of bending strength, fracture toughness, and Vickers hardness boosted from 187.6 MPa, 1.9 MPa.m½, and 10.1 GPa for additive-free ZrB2 to 606.5 MPa, 4.5 MPa.m½, and 18.8 GPa for (Zr,Ti)B2–ZrN–BN composite.