Al2 O3 Research Articles

Corrosion of phosphate added high-chrome refractory materials in an entrained-flow gasifier

Durability of the refractory liner located in an entrained-flow gasifier is one of the main factors affecting the efficiency and cost of gasification process. This study investigates the corrosion mechanism of phosphate added high-chrome refractories in a commercial entrained-flow gasifier and the effect of phosphate additives on the improvement of service life combining thermodynamic simulation calculations. The microstructures, chemical compositions, and mineral phases of the corroded samples were analyzed by scanning electron microscopy (SEM and EDS) and X-ray powder diffraction (XRD). The results demonstrated that chemical corrosion mainly occurred at the slag-matrix interface and the junction of aggregates and matrix regions. Complex spinel solid solutions were formed at the slag-refractory interface. Phosphate additives decomposed into gaseous products (such as O2, P2O3) and diffused into the interior of refractories at or close to the slag-refractory interface, not only causing an oxidizing environment but also increasing the phosphate contents in the interior of refractories. Phosphate additives in the infiltration layer occupied the gaps between crystal grains of (Cr, Al)2O3 solid solutions, reduced the infiltration of silicate phases, and absorbed Ca and Na in the slag, which subsequently increased the viscosity of the slag.

Numerical study of simultaneous transport of heat and mass transfer in Maxwell hybrid nanofluid in the presence of Soret and Dufour effects

The article aims to investigate the influence of copper (Cu) and a combination of copper (Cu) and aluminum oxide (Al2O3) on the simultaneous transfer of heat and mass in sodium alginate liquid moving over a circular pipe. This transport activity is modeled by the use of conservation laws with correlations for physical quantities of Cu, Al2 O3, and sodium alginate. Through cylindrical coordinates formulation, the set of partial differential equations is obtained. These models are solved numerically by the finite element method (FEM). The relaxation time associated with momentum diffusion in Maxwell fluid plays role in controlling the viscous region. Moreover, momentum relaxation time in Cu/sodium alginate is strong than that in Cu–Al2O3/sodium alginate. It is noticed from simulations that particles of Cu/ sodium alginate have a greater velocity than the velocity of Cu–Al2O3/sodium alginate. Therefore, distortion of magnetic lines by the flow of Cu/sodium alginate is more than the distortion of magnetic lines by the flow of Cu–Al2O3/sodium alginate. The rise in the thermal conductivity of sodium alginate due to simultaneous dispersion of Cu and Al2O3 is more than the rise in thermal conductivity of sodium alginate. Thus for maximum HT, the simultaneous dispersion of Cu and Al2O3 in sodium alginate is recommended.

Lower Cretaceous Clay in Anti-Lebanon Mountains, Syria And Their Importance in Ceramic Manufacturing

Lower Cretaceous rocks are exposed only in the mountain regions of Syria, such as the Anti Lebanon mountain on the western side of Damascus. The lower cretaceous sequences are made up of different rocks. The upper and middle parts of the section are composed mainly of carbonate sediments and less frequently gypsum and anhydrite. The lower beds are mainly composed of sandstone, conglomerate and clay. Clay samples were collected from the study area, which is located about 45 km west of the city of Damascus, near the border village of Kfer Yabous and to the left of the Damascus -Beirut International Road, within the lower Cretaceous upper Aptian deposits. The properties of clay were carried out by X-ray diffraction (XRD) and, X-ray fluorescence (XRF) and Thermal Analysis (DTA-TG-DSC) techniques. The studied clay samples are mainly composed of kaolinite, quartz, mica-illite and same feldspar. Chemical analysis shows a content of SiO2 that varies from 46.06 to 73 % and Al2 O3 between 14.55 and 26.56 %. Total content of staining oxides (Fe2 O3 + TiO2 ) is between 4.3 and 12.5 %. The physical properties were determined by studying their behavior before and after firing. They showed low bending strength values (22.5 kg/cm²) after drying, and after firing at 1180°C (about 247 kg/cm²). Water absorption value at 1180 °C was about 10 %. The coefficient thermal expansion coefficient (CTE) at 1140°C was 2,137 x 10-5 All obtained results confirm the suitability of this clay for the ceramic industry

Physicochemical Assessment, Pyrolysis and Thermal Characterization of Albizia Zygia Tree Sawdust

Standard methods were used to obtain proximate and ultimate parameters of Albizia zygia tree sawdust. The HHV of 16.01 MJ/ Kg, H/C of 0.127, O/C of 0.96, high volatile matter of 87.85 wt.% and low ash content of 1.55 wt.% Albizia zygia sawdust makes it a good biofuel. Its empirical formula from elemental ratios combination is CH0.127 O0.96 N0.057 . There were insignificant volumes of oxides of nitrogen and sulphur produced during its pyrolysis since %N & %S are relatively low (2.63 & 0) wt.% respectively. Its TG/DTG profile showed devolatilization of sawdust began at 230 o C and the pyrolysis temperature was in the range of 420- 600 o C. Its fixed bed pyrolysis recorded maximum value of bio-oil at 450 o C. FTIR analysis confirmed the presence of oxygenated compounds in the sawdust and its crude bio-oil. The analysis of the obtained bio-oil using GC-FID showed that significant quantity of -OH compounds were produced from the sawdust through pyrolysis though the obtained quantity is not economical. Sintering and slagging-fouling indicators such as; [Na2 O + K2 O] / [SiO2 ]= 0.0695 showed (unlikely sintering inclination); Base/Acid=0.438 (low ash deposition tendency); [SiO2 ]/([Al2 O3 ]=5.44 & [Fe2 O3 ] / [CaO]=0.28 (low ash deposition tendencies respectively); slagging viscosity index= 68.58 (low slagging tendency); %(SiO2 )=55.18 (high); Babcock (Rs)= 4.38x 10-5 & Fouling indices (Fu)= 1.68x10-2 (low deposition tendencies); Total alkalis (TA) =0.0097 ( Low fouling tendency). It can be projected that improvement on pyrolysis process parameters and pre-treatment of sawdust can be used to achieve higher yield of bio-oil then consequently leading to higher quantity of alcohol compounds.

Evolution of Hierarchically Porous Nickel Alumina Catalysts Studied by X-Ray Ptychography.

The synthesis of hierarchically porous materials usually requires complex experimental procedures, often based around extensive trial and error approaches. One common synthesis strategy is the sol–gel method, although the relation between synthesis parameters, material structure and function has not been widely explored. Here, in situ 2D hard X‐ray ptychography (XRP) and 3D ptychographic X‐ray computed tomography (PXCT) are applied to monitor the development of hierarchical porosity in Ni/Al2O3 and Al2O3 catalysts with connected meso‐ and macropore networks. In situ XRP allows to follow textural changes of a dried gel Ni/Al2O3 sample as a function of temperature during calcination, activation and CO2 methanation reaction. Complementary PXCT studies on dried gel particles of Ni/Al2O3 and Al2O3 provide quantitative information on pore structure, size distribution, and shape with 3D spatial resolution approaching 50 nm, while identical particles are imaged ex situ before and after calcination. The X‐ray imaging results are correlated with N2‐sorption, Hg porosimetry and He pycnometry pore characterization. Hard X‐ray nanotomography is highlighted to derive fine structural details including tortuosity, branching nodes, and closed pores, which are relevant in understanding transport phenomena during chemical reactions. XRP and PXCT are enabling technologies to understand complex synthesis pathways of porous materials.

Evaluation of Microshear Bond Strength of Four Different CAD-CAM Polymer-Infiltrated Ceramic Materials after Thermocycling.

To evaluate the bond strength of three monolithic hybrid ceramics/resin nanoceramics and a zirconia-reinforced lithium silicate to resin cement after thermocycling. Using four materials, including Vita Enamic (VITA Zahnfabrik), Lava Ultimate (3M ESPE), Crystal Ultra (Digital Dental), and Vita Suprinity (VITA Zahnfabrik), 64 specimens were prepared with dimensions of 4 mm × 3 mm × 1.5 mm. Vita Suprinity samples were sintered at 840°C for 8 min. After polishing and cleaning all the samples in each group (n = 16), they were subjected to their recommended surface treatment: 10% hydrofluoric acid for Vita Enamic (60s) and Vita Suprinity (20s); air abrasion of Lava Ultimate and Crystal Ultra with 50 u Al2 O3 particles. Then, tygon tubes were filled with dual cure resin cement (Panavia F2.0), cured and then subjected to thermal cycling (2000 cycles; 5-55°C). The microshear bond strength was measured using microtensile testing machine. The data were analyzed using Welch and Games-Howell tests (α = 0.05). The mode of failure was also evaluated using a stereomicroscope. The highest and the lowest mean microshear bond strength belonged to the Crystal Ultra (7.71 ± 1.54 MPa) and Vita Suprinity (4.73 ± 1.87 MPa) groups, respectively. The differences between groups were significant and Crystal Ultra had higher bond strength in comparison to all three materials (p < 0.05). Hybrid ceramics showed higher bond strength to resin cements in comparison to resin nanoceramics and zirconia-reinforced lithium silicate materials.

Determining the influence of ultra-dispersed aluminum nitride impurities on the structure and physical-mechanical properties of tool ceramics

This paper considers features related to manufacturing the chromium oxide-based tool material. The process involved ultra-dispersed powders made of aluminum nitride. It has been established that the destruction of chromium oxide at high sintering temperatures is prevented through the reaction sintering of chromium oxide (Cr2O3) and aluminum nitride (AlN). It was established that the structure of the composite depends both on the temperature and the duration of hot pressing. Thermodynamic calculations of the interaction between Cr2O3 and AlN showed that this interaction begins at a temperature of 1,300 °C. In contrast to hot pressing in the air, no СrN and Сr2N compounds were formed in a vacuum. With increasing temperature, the content of Al2O3 in solid solution becomes maximum at a temperature of 1,700 °C in the case of hot pressing in the air while in vacuum the content of Al2O3 remains unchanged within the entire temperature range of 1,300–1,700 °C. When increasing the time of hot pressing to 30 minutes, the size of individual grains reaches 10 μm. It has been shown that in the sintering process involving Cr2O3 and AlN, the plasma-chemical synthesis produces the solid solution (Cr, Al)2O3 at the interphase boundary, which improves the mechanical properties of the material. The influence exerted on the quality of the machined surface of tempered hard steel when machining by the devised tool material based on chromium oxide with an optimal admixture of 15 wt % of ultra-dispersed aluminum nitride powder was investigated. It was determined that the quality of the machined hard steel surface improved compared to standard imported tool plates. It was established that the resulting tool material, in addition to relatively high strength and crack resistance, also demonstrates high thermal conductivity, which favorably affects the quality of the machined steel surface, given that lubricants and coolants are not used during the cutting process.

Promoting the Performance of 2D Material Photodetectors by Dielectric Engineering.

Low light absorption and limited carrier lifetime are two limiting factors hampering the further breakthrough of the performance of 2D materials (2DMs)-based photodetectors. This study proposes an ingenious dielectric engineering strategy toward boosting the photosensitivity. Periodic dielectric structures (PDSs), including SiO2 /h-BN, SiO2 /Al2 O3 , and SiO2 /SrTiO3 (STO), are exploited to couple with 2D photosensitive channels (denoted as PDS-2DMs). The responsivity, external quantum efficiency, and detectivity of an optimized SiO2 /STO(300nm) -WSe2 photodetector reach 89081 A W-1 , 2.7 × 107 %, and 1.8 × 1013 Jones, respectively. These performance metrics are orders of magnitude higher than a pristine WSe2 photodetector, enabling reliable sub-1 pW weak light detection. Based on systematic characterizations and first-principle calculations, such dramatic performance improvement is associated with the promoted direct bandgap transition, reduced exciton binding energy, and PDS-induced periodic intramolecular built-in electric field across the atomically thin channels, which efficiently separates the photoexcited electron-hole pairs. More inspiringly, this strategy is also successfully exploited to 2D WS2 photodetectors, demonstrating broad applicability. As a whole, this work promises an exceptional avenue to ameliorate 2DM photodetectors and opens up a new horizon "dielectric optoelectronics," simultaneously highlighting the role of dielectric environment during analyzing the fundamentals of 2DM devices.

Multifunctional Separator Allows Stable Cycling of Potassium Metal Anodes and of Potassium Metal Batteries.

This is the first report of a multifunctional separator for potassium-metal batteries (KMBs). Double-coated tape-cast microscale AlF3 on polypropylene (AlF3 @PP) yields state-of-the-art electrochemical performance: symmetric cells are stable after 1000 cycles (2000 h) at 0.5mA cm-2 and 0.5 mAh cm-2 , with 0.042V overpotential. Stability is maintained at 5.0mA cm-2 for 600 cycles (240 h), with 0.138V overpotential. Postcycled plated surface is dendrite-free, while stripped surface contains smooth solid electrolyte interphase (SEI). Conventional PP cells fail rapidly, with dendrites at plating, and "dead metal" and SEI clumps at stripping. Potassium hexacyanoferrate(III) cathode KMBs with AlF3 @PP display enhanced capacity retention (91% at 100 cycles vs 58%). AlF3 partially reacts with K to form an artificial SEI containing KF, AlF3 , and Al2 O3 phases. The AlF3 @PP promotes complete electrolyte wetting and enhances uptake, improves ion conductivity, and increases ion transference number. The higher of K+ transference number is ascribed to the strong interaction between AlF3 and FSI- anions, as revealed through 19 F NMR. The enhancement in wetting and performance is general, being demonstrated with ester- and ether-based solvents, with K-, Na-, or Li- salts, and with different commercial separators. In full batteries, AlF3 prevents Fe crossover and cycling-induced cathode pulverization.

Influence of alumina ratio on reactions at the surface of alite crystals during cooling.

Microstructural features of industrial Portland cement clinker samples are presented to illustrate the influence of the clinker melt chemistry on the reactions taking place on the surfaces of alite crystals during cooling at high temperatures. While clinker melts rich in Al2 O3 are usually undersaturated with respect to CaO, leading to corrosion of alite crystals and formation of secondary belite, clinker melts rich in Fe2 O3 are oversaturated with respect to CaO. This leads to a final growth step of alite during cooling, as long as the clinker temperature is still in the stability field of alite (>1250°C). In the first case, the microstructural features of the alite surface permits conclusions on the length of the precooling zone in the rotary kiln, which is closely connected to the flame shape. In the latter case, such conclusions cannot be drawn.

Effects of Al addition on high temperature oxidation behavior of 16Cr ODS steel

To reveal the effects of Al addition on the oxidation mechanisms of 16Cr ODS steel, high temperature oxidation at 1000 °C of 16Cr and 16Cr-3Al ODS steels with the same Cr content were investigated. After oxidation, the weight gain of the 16Cr ODS steel was relatively higher than that of the 16Cr-3Al ODS steel. The 16Cr ODS steel had triple oxide layers of an outer FeCr2O4 layer, an intermediate Cr2O3 layer, and an inner SiO2 layer, while the 16Cr-3Al ODS steel had double oxide layers of an outer (Cr, Al)2O3 layer and an inner Al2O3 layer. The oxidation mechanisms of both ODS steels were explored through thermodynamic calculations, and the significant improvement in oxidation resistance of the 16Cr-3Al ODS steel compared to 16Cr ODS steel was attributed to the lower diffusion rate of O in Al2O3 than in Cr2O3. The existence form of oxide particles in the oxide layers was illustrated. These findings offer new strategies for enhancement in oxidation resistance of structural materials used in high temperature environment.

The study of the structure and mechanical properties of T and K + Al + N + Ti steels after casting and hot plastic deformation (HPD)

Purpose. To perform comparative studies of structural features and mechanical properties of test steel for railway wheels with microalloy complex Al + N + Ti and known steel for high-strength railway wheels of brand T, microalloyed with vanadium.&#x0D; Methodology. Microstructural, micro-X-ray spectral and X-ray phase analyzes were used to determine the structural state of the alloys.&#x0D; Results. Comparative analysis of the structure and mechanical properties of steels for high-strength railway wheels of brand T and K + Al + N + Ti. It is shown that in K + Al + N + Ti steel after crystallization the structure becomes finer-grained and increase in the volume fraction of perlite was observed in comparison with steel of T brand. It was found that the HPD leads to the decrease in the volume fraction and size of oxides, and in aluminum oxides Al2O3 there is a partial replacement of aluminum atoms by iron and titanium atoms.&#x0D; Originality. It is shown that the reduction of vanadium content in steel and complex alloying with aluminum, titanium and nitrogen leads to the formation of the finer-grained structure and increase in the volume fraction of fine perlite. In the microstructure of K + Al + N + Ti steel, the formation of oxides, nitrides and carbonitrides was observed, which were located along the grain boundaries and in the body of the perlite grain.&#x0D; It was shown for the first time that HPD leads to the fact that in the inclusions of aluminum oxides Al2 O3 the partial replacement of aluminum atoms by atoms of iron or titanium, with the formation of oxides of Fe2(Al)O3 and (Al, Ti)2O 3, take place.&#x0D; Practical value. The use of complex alloying of steel leads to improvement of mechanical properties: increase in toughness at the high level of hardness and strength of steel grade K + Al + N + Ti in comparison with steel of brand T.&#x0D;

Denture base adaptation, retention, and mechanical properties of BioHPP versus nano-alumina-modified polyamide resins.

Background. Continuous development of denture base materials has led to the introduction of innovative alternatives to polymethyl methacrylate. The present study aimed to evaluate the mechanical properties, adaptation, and retention of alumina nanoparticles (Al2O3 NPs) modified polyamide resin versus BioHPP (high-performance polymer) denture base materials. Methods. Four groups of specimens, one control (group I) (unmodified polyamide) and two groups (groups II and III) (2.5 and 5 wt% Al2O3 NP-modified polyamide, respectively) versus BioHPP specimen group (group IV), were tested for surface microhardness and flexural strength. Complete dentures fabricated from 5 wt% Al2O3 NP-modified polyamide resin and BioHPP were used to evaluate denture base adaptation and retention. Results. The higher concentration in the alumina NP-modified polyamide group (5 wt%) demonstrated significantly higher flexural strength values and insignificantly higher hardness values than the lower concentration (2.5 wt%). There was a significant increase in the BioHPP group in both flexural strength and surface hardness compared to all polyamide groups. A statistically insignificant difference was observed between the two denture base materials regarding mean misfit values of the calculated total tissue surface area and four of the total seven evaluated areas. Satisfactory and comparable retention values were observed for both denture base materials. Conclusion. BioHPP and Al2O3 NP-modified polyamide resin could be used as a promising alternative denture base material with good adaptation, retention, and mechanical properties.

Oxide Nanoclusters on Ti3 C2 MXenes to Deactivate Defects for Enhanced Lithium Ion Storage Performance.

The commercialization of MXenes as anodes for lithium-ion batteries is largely impeded by low initial coulombic efficiency (ICE) and unfavorable cycling stability, which are closely associated with defects such as Ti vacancies (VTi ) in Ti3 C2 MXenes. Herein, an effective strategy is developed to deactivate VTi defects by in situ growing Al2 O3 nanoclusters on MXenes to alleviate the irreversible electrolyte decomposition and Li dendrites formation trend induced by defects, improving ICE and cycling stability. Furthermore, it is revealed that excessively lithiophilic VTi defects would impede Li ions diffusion due to their strong adsorption, leading to a locally nonuniform Li flux to these "hot spots," setting scene for the formation of Li dendrites. The Al2 O3 nanoclusters anchored on VTi sites can not only improve Li diffusion kinetics but also promote the homogeneous solid electrolyte interphase formation with small charge transfer resistance, achieving uniform Li deposition in a smaller overpotential without formation of Li dendrites. As expected, Ti3 C2 @Al2 O3 -11 electrode delivers a high ICE of 76.6% and an outstanding specific capacity of 285.5mAhg-1 after 500 cycles, which is much higher than that of pristine Ti3 C2 sample. This work sheds light on modulating defects for high-performance energy storage materials.

Hierarchically Porous Silica Membrane as Separator for High-Performance Lithium-Ion Batteries.

Commercial polymeric separators in lithium-ion batteries (LIBs) typically suffer from limited porosity, low electrolyte wettability, and poor thermal and mechanical stability, which can degrade the battery performance especially at high current densities. Here, the design of hierarchically porous, ultralight silica membranes as separator for high-performance LIBs is reported through the assembly of hollow mesoporous silica (HMS) particles on the cathode surface. The rich mesopores and large cavity of individual HMS particles provide low-tortuosity pathways for ionic transport, while simultaneously serving as electrolyte reservoir to further boost the electrochemical kinetics. Moreover, benefiting from their inorganic and hierarchically porous nature, such HMS separators display better electrolyte affinity, thermal stability, and mechanical strength than commercial polypropylene (PP) separators. As a demonstration, LIBs with a LiFePO4 cathode coated with HMS separators exhibit exceptional rate capability and cycling stability, outperforming LIBs with PP and Al2 O3 -modified PP separators as well as separators made of solid silica particles.

Electrically and Optically Controllable p-n Junction Memtransistor Based on an Al2 O3 Encapsulated 2D Te/ReS2 van der Waals Heterostructure.

The exploration of memtransistors as a combination of a memristor and a transistor has recently attracted intensive attention because it offers a promising candidate for next-generation multilevel nonvolatile memories and synaptic devices. However, the present state-of-the-art memtransistors, which are based on a single material, such as MoS2 or perovskite, exhibit a relatively low switching ratio, require extremely high electric fields to modulate bistable resistance states and do not perform multifunctional operations. Here, the realization of an electrically and optically controllable p-n junction memtransistor using an Al2 O3 encapsulated 2D Te/ReS2 van der Waals heterostructure is reported. The hybrid memtransistor shows a reversible bipolar resistance switching behavior between a low resistance state and a high resistance state with a high switching ratio up to 106 at a low operating voltage (<10V), high cycling endurance, and long retention time. Moreover, multiple resistance states are achieved by applying different bias voltages, gate voltages, or light powers. In addition, logical operations, including the inverter and AND/OR gates, and synaptic activities are performed by controlling the optical and electrical inputs. The work offers a novel strategy for the reliable fabrication of p-n junction memtransistors for multifunctional devices and neuromorphic applications.

Simultaneously Blocking Chemical Crosstalk and Internal Short Circuit via Gel-Stretching Derived Nanoporous Non-Shrinkage Separator for Safe Lithium-Ion Batteries.

The separator, an ionic permeable and electronic insulating membrane between cathode and anode, plays a crucial role in the electrochemical and safety performance of batteries. However, commercial polyolefin separators not only suffer from inevitable thermal shrinkage at elevated temperature, but also fail to inhibit the hidden chemical crosstalk of reactive gases such as O2 , leading to often reported thermal runaway (TR) and hence preventing large-scale implementation of high-energy-density lithium-ion batteries. Herein, a nanoporous non-shrinkage separator (GS-PI) is fabricated via a novel gel-stretching orientation approach to eliminate TR. In situ synchrotron small angle X-ray scattering during heating clearly shows that the as-prepared thin GS-PI separator exhibits superior mechanical tolerance at high temperature, thus effectively preventing internal short circuit. Meanwhile, the unique nanoporous structure design further blocks chemical crosstalk and the associated exothermic reactions. Accelerating rate calorimetry tests reveal that the practical 1 Ah LiNi0.6 Co0.2 Mn0.2 O2 (NCM622)/graphite pouch cell using GS-PI nanoporous separator show a maximum temperature rise (dT/dtmax ) of only 3.7°C s-1 compared to 131.6°C s-1 in the case of Al2 O3 @PE macroporous separator. Moreover, despite the reduced pore size, the GS-PI separator demonstrates better cycling stability than conventional Al2 O3 @PE separator at high temperature without sacrificing specific capacity and rate capability.

An AIE-Active Ultrathin Polymeric Self-Assembled Monolayer Sensor for Trace Volatile Explosive Detection.

This work has prepared polymeric self-assembled monolayer (SAM) sensors for the detection of trace volatile nitroaromatic compound (NAC) explosives by fluorescence quenching. A typical aggregation-induced emission (AIE) luminogen 1,1,2,2-tetraphenylethene (TPE) polymerizes into PTPE to increase the fluorescence intensity in the SAMs, and the phosphoric acid acts as the anchor group to form stable covalent bonds with the Al2 O3 substrate. This design takes advantage of the high sensitivity and good stability of SAMs, and high fluorescence intensity, and "wire effect" of the conjugated polymers. The polymeric SAM sensors are prepared on the Al2 O3 silicon wafer and testing paper. Both of them show good response speed, reversibility, selectivity, and sensitivity. The detection limits down to 0.07, 0.35, and 4.11ppm for TNT, DNB, and NB, respectively, are achieved on the inorganic testing paper. Furthermore, due to the higher fluorescence intensity by interlacing and overlapping of fibers, the detection of the paper can be distinguished by naked eyes even with a low-power handheld UV lamp, which provides an experimental basis for the development of cheap and easy trace NAC explosive sensors.

Remarkable Black-Phase Robustness of CsPbI3 Nanocrystals Sealed in Solid SiO2 /AlOx Sub-Micron Particles.

This work combines the high-temperature sintering method and atomic layer deposition (ALD) technique, and yields SiO2 /AlOx -sealed γ-CsPbI3 nanocrystals (NCs). The black-phase CsPbI3 NCs, scattered and encapsulated firmly in solid SiO2 sub-micron particles, maintain in black phases against water soaking, ultraviolet irradiation, and heating, exhibiting remarkable phase stability. A new phase-transition route, from γ via β to α phase without transferring into δ phase, has been discovered upon temperature increasing. The phase stability is ascribed to the high pressure exerted by the rigid SiO2 encapsulations, and its condensed amorphous structures that prevent the permeation of H2 O molecules. Nanoscale coating of Al2 O3 thin films, which are deposited on the surface of the CsPbI3 -SiO2 by ALD, enhances the protection against O2 infiltration, greatly elevating the high-temperature stability of CsPbI3 NCs sealed inside, as the samples remain bright after 1-hannealing in air at 400 °C. These fabrication and encapsulation techniques effectively prevent the formation of δ-CsPbI3 under harsh environment, bringing the high-pressure preservation of black-phase CsPbI3 from laboratory to industry toward potential applications in both photovoltaic and fluorescentareas.

Fundamental understanding on the microstructure and corrosion resistance of Cr-(Cr, Al)2O3 composite coatings in-situ synthetized by reactive plasma spraying

Three composite coatings were prepared with Al-Cr2O3-Al2O3 composite powders feedstocks by in-situ reactive plasma spraying, and the microstructures and corrosion resistances were studied. The results show that the CAC-1 coating is the hypoeutectic microstructure consisting of large-size Cr particles and the eutectic structure, the CAC-2 coating presents a typical eutectic microstructure [nano-Cr + (Cr, Al)2O3], and the CAC-3 coating is the hypereutectic microstructure which is composed of (Cr, Al)2O3 solid solution and eutectic structure. The corrosion resistance of the coating is closely related to the microstructure and defects of the coating. The surface of the nano-Cr particles in the CAC-2 coating can form a stable Cr(OH)3 film, which hinders the further contact with the electrolyte, thereby improving the corrosion resistance of the coating itself. In addition, the uniform and dense microstructure also leads to the least coating defects, further improving the corrosion resistance of the coating. While the surface product film of large-size Cr particles in the CAC-1 coating cannot exist stably, causing the Cr to continue to dissolve until it peels off. The coating itself has the highest porosity, so the coating has the worst corrosion resistance. The CAC-3 coating mainly exhibits the characteristics of ceramic coating due to the limited eutectic structure contained. Due to the unevenness of the microstructure, the coating has more defects, resulting in lower corrosion resistance than the CAC-2 coating.