Phase Morphology Research Articles

Molybdenum oxide catalyzed low temperature preparation of mullite whisker from silica-alumina gel slag

Catalyzed by MoO3, mullite whiskers were synthesized through a molten salt method. This study comprehensively explored the impact of reaction temperature, MoO3 mass fraction, and calcination temperature on the morphology of mullite whiskers. Employing analytical techniques such as XRD and SEM, the phase composition and morphology of the samples were meticulously scrutinized. The results unveiled that at a MoO3 mass fraction of 7–8% (molar fraction) and a calcination temperature of 800 °C, mullite whiskers demonstrated a heightened level of purity. Building on these observations, the study delved into the mechanistic underpinnings of MoO3 as a catalyst in mullite whisker synthesis. It is proved that the metal oxides contained in the silica-alumina glue slag can also form a local liquid phase at low temperatures, reducing the viscosity of the reaction system and liquefaction temperature. The addition of molybdenum oxide makes the reaction process of mullite whisker growth shorter. At the same time, the addition of molybdenum oxide can effectively reduce the viscosity of the reaction system, thus lowering the reaction temperature and increasing the reaction efficiency. In addition molybdenum oxide can be used as a templating agent to induce the growth of mullite whiskers along specific crystal planes. Compared with aluminum fluoride catalysis, molybdenum oxide does not produce the hazardous gas HF, the sublimated molybdenum oxide gas can be recycled, and the molybdenum oxide attached to the whiskers can also be dissolved in water. These theories provide experience in the large-scale preparation of mullite whiskers.

Operando study of the dynamic evolution of multiple Fe-rich intermetallics of an Al recycled alloy in solidification by synchrotron X-ray and machine learning

Using synchrotron X-ray diffraction, tomography and machine-learning enabled phase segmentation strategy, we have studied under operando conditions the nucleation, co-growth and dynamic interplays among the dendritic and multiple intermetallic phases of a typical recycled Al alloy (Al5Cu1.5Fe1Si, wt.%) in solidification with and without ultrasound. The research has revealed and elucidated the underlying mechanisms that drive the formation of the very complex and convoluted Fe-rich phases with rhombic dodecahedron and 3D skeleton networks (the so-called Chinese-script type morphology). Through statistical microstructural analyses and numerical modelling of the ultrasound melt processing, the research has demonstrated that a short period of ultrasound processing of just 7 s in the liquid state is able to reduce the average size of the α-Al dendrites and the Fe-containing intermetallic phases by ∼5 times compared to the cases without ultrasound. For the first time, this work has revealed fully the nucleation and growth dynamics of the convoluted morphology of the Fe-containing intermetallic phases in 4D domain. The research has also demonstrated clearly the beneficial effects of applying ultrasound to control the Fe phases' morphology in recycled Al alloys and it is one of the most effective and green processing strategies.

Impact of Ground Granulated Blast Furnace Slag on Calcium Leaching of Low-Heat Portland Cement Paste.

Low-heat Portland cement and ground granulated blast furnace slag are widely used for the preparation of hydraulic concrete. Nevertheless, the effect and mechanism of corrosion on low-heat Portland cement paste mixed with ground granulated blast furnace slag need to be further explored. This paper investigated the impact of ground granulated blast furnace slag on the calcium leaching of low-heat Portland cement paste by evaluating its mass loss, porosity, leaching depth, compressive strength, and Vickers hardness, and comparing it with the leaching performance of ordinary Portland cement paste. Furthermore, the phase composition and morphology of low-heat Portland cement paste containing ground granulated blast furnace slag were analyzed by X-ray diffraction, mercury intrusion porosimetry, and scanning electron microscopy. The results indicate that, after 180 days of soaking in ammonium chloride solution, the mass loss rate, growth rate of porosity, leaching depth, and compressive strength loss rate of low-heat Portland cement paste were 8.0%, 43.6%, 9.1 mm, and 27.7%, respectively, while those of ordinary Portland cement paste were 7.4%, 37.8%, 8.4 mm, and 30.1%, indicating that low-heat Portland cement paste is slightly more damaging than ordinary Portland cement. The addition of ground granulated blast furnace slag could significantly improve the leaching resistance of low-heat Portland cement. For instance, after adding 20% ground granulated blast furnace slag, the above test values were 2.4%, 28.5%, 5.6 mm, and 20.8%, respectively. The reason for this is that ground granulated blast furnace slag has the potential to reduce the porosity of low-heat Portland cement paste, and it can also undergo the secondary hydration reaction with its hydration product Ca(OH)2 to enhance the paste structure. Considering the cost performance, the suitable dosage of low-heat Portland cement paste for satisfactory leaching resistance is about 20%.

Numerical simulation for β/α transformation of Ti–6Al–4V alloy using a lattice Boltzmann - Cellular automata method

This paper considers the beta/alpha transformation of Ti–6Al–4V alloy using a lattice Boltzmann method (LBM) – cellular automata (CA) coupled method in terms of microstructural evolution during phase transformation. Particularly, the effects of the cooling rate on microstructures such as beta grain size, alpha colony size, and alpha lath thickness were examined as well as the overall morphologies. The LBM and CA were used to implement the diffusion of alloy components and phase transformation, respectively. Additionally, the thermodynamic and kinetic data for simulating the ternary alloy system were obtained from CALPHAD software to utilize the equilibrium phase diagram calculations. The initial states of the beta grain and its composition fields affect the processing of beta/alpha phase transformation and the final alpha + beta phase morphologies. Validation of the proposed method was conducted to compare the simulation results with experimental trends for microstructures of Ti–6Al–4V from the literature. The error in prediction of microstructural morphologies were 20% in the average alpha thickness with deviation of up to 5 μm.

Part-scale microstructure prediction for laser powder bed fusion Ti-6Al-4V using a hybrid mechanistic and machine learning model

Laser powder bed fusion (LPBF) Ti-6Al-4V is widely studied for use in structural applications in aerospace and medical industries, but mechanical anisotropy and microstructural inhomogeneity prohibits its wider adoption. Although successful microstructure prediction models have been developed, a remaining challenge is their limited integration across length/time scales and validation by experimental studies. This work proposes a physics-augmented machine learning surrogate model to unite predictions of LPBF temperature, β phase morphology and texture, and α/α’ formation into a single framework that is calibrated and validated with experiments. First, a phase field (PF) model of the martensitic β→α’ transformation is developed and calibrated using data from in-situ synchrotron cyclic heating/cooling studies quantifying the variation of α phase fraction with time. In parallel, an established finite difference-Monte Carlo (FDMC) model predicts the part-scale temperature profile and β grain formation during solidification. A dataset is developed using LPBF cyclic temperature descriptors from the FDMC model as inputs and corresponding α/α’ phase fraction and width from the PF model as outputs. Five machine learning (ML) regression models are tested and optimized, having mean absolute error in testing ≤ 4 %, and the k-nearest neighbors (KNN) model is selected as the best performing. The KNN model is called at the nodal level during post-processing of the FDMC model to replace and downscale the response of the PF model. The combined agility and accuracy of the hybrid FDMC-ML model enables part-scale microstructure predictions that can be further used for property predictions to accelerate AM process optimization.

Microstructure Evolution and Creep Properties of AZ61 Magnesium Matrix Composites Reinforced with Bimodal-Sized SiC Particles

In the scope of this exploration, AZ61 magnesium matrix composites fortified with bimodal size SiC particles were synthesized using ultrasonic-assisted mixing in the semi-solid state, which exhibited optimal grain refinement and exceptional creep resistance. We examined the impact of bimodal SiC particles on the microscopic structure and creep deformation of the resulting composites. Our findings indicated that incorporating bimodal SiC particles resulted in the refinement of the matrix grains and alteration of the morphology of the Mg17Al12 phase. Furthermore, the micron-sized SiC particles exhibited a typical necklace-like particle distribution around the grain boundaries of the bimodal SiC particle/AZ61 composites, while the nano-sized SiC particles were mainly located around the micron-sized particles. As the volumetric percentage of micron SiC particles increased, the quantity of nano-sized particle clusters diminished noticeably. Creep analysis at 200 °C and 50 MPa revealed that the creep life of M−6+N−1 composite was increased by 111.9% compared to the AZ61 alloy. Additionally, the M−6+N−1 combination exhibited a significantly lower steady-state creep rate compared to the matrix alloy, with a reduction of approximately 11 times. These results indicate that the bimodal SiC particle/AZ61 composites have superior creep resistance, which is a consequence of the grain refinement and grain boundary pinning effects of SiC particles.

Temperature dependences of phase composition, densification, and thermal/chemical stability of Sr0.5Zr2(PO4)3-Nd0.5Sm0.5PO4 composite ceramics for nuclear waste form

A kind of Sr0.5Zr2(PO4)3-Nd0.5Sm0.5PO4 (hereinafter SrZP-Nd0.5Sm0.5PO4) composite ceramics was prepared through a one-step microwave sintering technique, where Sr, Nd, Sm were simulated for fission products and minor actinides (MA). The crystal structure and morphology of constituent phases were systematically characterized by XRD, TEM, and SEM techniques. The temperature dependent phase analysis results of SrZP-Nd0.5Sm0.5PO4 composite ceramics illustrate that with evaluating temperature monazite structure formed primarily, and the SrZP phase formed subsequently. With the temperature rising further, the monazite phase finally transformed into Nd0.5Sm0.5PO4 monazite solid solution. XRD refinement and TEM measurements are used to verify the crystal structures of the as-prepared SrZP and Nd0.5Sm0.5PO4 phases in the composite ceramics. The dependence of densification behaviors on temperature shows that the distinct densification of the SrZP-Nd0.5Sm0.5PO4 composite ceramics occurs in the temperature range of 950 °C to 1000 °C, and the relative density reaches 97.7 % at 1050 °C. TG-DSC tests show that the SrZP-Nd0.5Sm0.5PO4 composite ceramics exhibit excellent thermal stability at high temperatures. And SrZP-Nd0.5Sm0.5PO4 composite ceramics possess outstanding chemical stability, whose normalized leaching rate of Sr, Nd, and Sm is 10−4 g·m−2·d−1, 10−7 g·m−2·d−1, and 10−7 g·m−2·d−1 order of magnitude, respectively.

A double transition metal MXene/S-scheme heterojunction composite with improved photoelectrochemical and photocatalytic properties

Herein, a novel double transition metal MXene (DTMXene) S-scheme photocatalyst was constructed with potential application in mineralization of organic pollutants found in water. The fabrication of the DTMXene heterojunction photocatalyst (Ce2S3/WO3@TiVCTx) was achieved through an ultrasonication and calcination approach. The highly conductive DTMXene (TiVC), was incorporated into an S-scheme heterojunction to maximize the separation of the charge kinetics, subsequently enhancing the photocatalytic properties. The phase structure, morphology, photoelectrochemical, and optical properties of the synthesized materials were characterized and confirmed by spectroscopic, microscopic, and photoelectrochemical techniques. The DTMXene-based heterojunction photocatalyst showed a significant increase in optical and electrochemical properties compared to the pristine materials of the 7 wt%-Ce2S3/WO3@TiVC-7 wt% ternary composite exhibiting excellent photoelectrochemical properties, including a weak PL emission intensity and a decreased EIS resistance, indicating efficient separation and transfer of photogenerated charge carriers. A significant improvement of the photocatalytic and electrochemical properties is attributed to the excellent conductive nature of the DTMXene, which facilitates the separation of the photogenerated charge carriers. This work therefore gives a novel approach to the fabrication of a reliable DTMXene-based photocatalyst with enhanced potential in environmental remediation, hydrogen evolution, and energy storage.

Structure Investigation of highly porous bioceramics based on biogenic hydroxyapatite with graphene oxide coating

Highly porous bioceramics (porosity equal to 93–94 %) based on biogenic hydroxyapatite and sodiumborosilicate glass (40wt% of glass) was prepared by foam replication method at 700 °C and coated by graphene oxide using CVD method. Obtained bioceramics samples were studied by SEM, XRD and Raman spectroscopy. Phase composition, morphology, skeleton density, porosity and compression strength were evaluated. It was shown that biogenic hydroxyapatite in highly-porous bioceramics composition is stable and keeps hydroxyapatite phase without secondary phase formation after sintering with sodiumborosilicate glass as well as after application of CVD method for graphene oxide coating. Formation of graphene oxide for coated bioceramics was confirmed by XRD, SEM and Raman spectroscopy. Significant effect of graphene oxide coating on the porosity and skeleton density was not detected due to thin layer and low content of graphene oxide, but it allows 30 % increasing the compression strength of highly porous bioceramics.

A HRTEM-EDS-SAED Study of Precipitates in Mg-Zn-Zr Alloy

In this study, aging heat treatment was performed on extruded Mg-Zn-Zr alloy. Aging was performed on as-extruded samples at 180°C for 1-2-4-8 and 24 hours. Microhardness tests were made to obtain the aging curve. Detailed transmission electron microscopy (TEM) examinations such as selected area electron diffraction (SAED), energy dispersive spectrometry (EDS), and high resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure, second phases, and precipitates. Size, type, and morphologies of second phases and precipitates were studied aided by advanced transmission electron microscopy techniques. With the help of hardness test results peak aged condition was found to be 8 hour aging. TEM examinations were detailed for the 8-hour aged sample. It was observed that the precipitates responsible for age hardening were MgZn2. Moreover, the majority of these precipitates were β’1 phase.

Regulating the microstructure and mechanical properties of Al-Cu-Li alloys via optimizing Cu/Li ratio and homogenization

The effect of homogenization process on the microstructure evolution and mechanical properties of Al-Cu-Li alloys with various Cu/Li ratios (ranging from 2.4 to 3.7) are studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and synchrotron radiation X-ray computed tomography (SR-CT) analysis. The results show that with the increase in the Cu/Li ratio, the volume fraction of the secondary phase (fv) in the as-cast alloys gradually increases, and the morphology of the secondary phases transforms from spherical-like to chain-like. For the single-step homogenization (SSH), the fv decreases with increasing homogenization temperature and time. The 510 ℃ /24 h is identified as the optimal SSH regime due to the alloys exhibiting a lower fv and a shorter SSH time than other SSH regimes. Interestingly, the alloys processed by double-step homogenization (DSH) exhibit a lower fv compared with the SSH process. The residual secondary phases consist of a small number of regular block-Al2Cu, dispersed Al20Cu2Mn3 phase and spherical-like Zr-rich phase after SSH and DSH. Furthermore, according to the results of diffusion kinetics analysis, the secondary phases can be dissolved completely into the matrix after homogenization treatment at 510 °C for 22.9 h. Therefore, the 450 ℃ / 12 h+510 ℃ / 24 h (DSH-24) is determined as the optimal homogenization regime. After DSH, a large number of spherical-like GP-Li and Al3Li nanoparticles are precipitated during natural aging. The critical resolved shear stress calculation model suggests that the Al-4.1Cu-1.3Li alloy with a Cu/Li ratio as 3.2 possess high yield strength. The Al-4.1Cu-1.3Li alloy processed by DSH-24 exhibits excellent mechanical properties, with yield strength of 299 MPa, ultimate tensile strength of 449 MPa, and elongation of 18.8 %. This study provides a foundation for the development of high-performance Al-Li alloys.

An interesting phase transition in polyamide 6/nitrile rubber blend induced by temperature and pressure and its effect on tribological performance

AbstractThe preparation of high‐performance rubber‐plastic blending elastomers has always been a research hotspot in the field of petroleum equipment. The two‐phase separation structure of the blend determines the macroscopic properties of the materials. It is of great significance to deeply explore the influence of processing technology on the two‐phase separation structure. In this paper, polyamide 6 (PA6)/nitrile rubber blends were prepared via the melt–compounding method. To meet the requirements of oil production and oil transport equipment, we investigated systematically the mechanical properties of the specimens exposed to different environments. The oil resistance and high‐temperature resistance of the blends were enhanced considerably with the addition of PA6. The temperature and pressure fields induced a novel transition from particle into fibrous phase based on Ostwald's ripening. However, this brand new transformation showed no benefits to the improvement of the frictional performance. Meanwhile, the relationship between aggregate structure and mechanical performance was demonstrated from the aspects of crystallization behavior and phase morphology.

Effect of Heat Treatment on Structure Evolution and Mechanical Property Strengthening of Low-Cobalt Nickel-Based Superalloy

In this paper, the microstructure of an alloy was regulated by means of strengthening solution aging, and microstructure observation and composition analysis were carried out by means of an optical microscope and X-ray diffractometer. Combined with the Vickers hardness tester, electronic universal testing machine and high-temperature persistent creep testing machine, the mechanical properties and high-temperature properties of the alloy were tested, and the strengthening mechanism of the alloy was explored. The results showed that the dendritic morphology and structure of the alloy decreased with an increase in temperature during the solution process, and the γ′ phase morphology also changed with the solution temperature: oval → cross → cubic. The γ′ phase after solid solution at 1295 °C was closest to the cubic form. Therefore, it is believed that the 1295 °C solution treatment had the best effect. In the aging process, the uniform cubic degree of γ′ phase distribution was the highest at 1090 °C. On the basis of fixed aging temperature (1090 °C), it was found that the volume fraction of the γ′ phase increased significantly after 8 h. The γ′ phase, which was closest to the cubic form, had the largest proportion of precipitation, and the volume fraction increased to 70.3%. The minimum carbide volume was 1.0%. The hardness of the alloy reached 435.8 HV; the yield strength increased to 280.1 MPa; and the durability of the alloy under the conditions of 1000 °C/230 MPa and 870 °C/655 MPa was 99.7 h and 42.7 h, respectively, which achieved the purpose of alloy design.

Microstructure evolution and mechanical properties of Fe–Cr–B alloys with varying Mo additions

The continuously net-like morphology of borides accounts for the poor toughness of Fe–Cr–B wear-resistant alloys. To effectively modify the morphology of Fe2B, Mo element has been introduced in Fe–Cr–B alloys, and the microstructure evolution and mechanical properties have been systematically investigated. The results show Fe–Cr–B alloys are mainly composed of martensite, M2B, M23(B, C)6 and lamellar M3B2 after Mo addition. With the increase of Mo addition, the content of M3B2 increases gradually while that of M23(B, C)6 increases firstly and then decreases. Consequently, the net-like structure of M2B can be effectively broken to acquire the isolated bulk-like morphology, which is mainly attributed to the growth inhibition effect of lamellar structure M3B2. In addition, the hardness varies depending on the volume fraction of borides. However, the fracture toughness of Fe–Cr–B alloy can be dramatically improved by 34.3% with Mo addition increasing from 1 to 4%. Grain morphology modification of M2B plays the predominant role in the toughness improvement because the crack propagation path can be blocked. Furthermore, the lamellar M3B2 structure can effectively hinder the cracking propagation so as to improve the alloy's fracture toughness. Mo addition has been proved to be an effective way to modify the grain morphology of M2B hard phase.

Negative thermal expansion performance of (NaMg)xCr2-x(MoO4)3 (0≤x≤1) ceramics

Cr2Mo3O12 ceramics show negative thermal expansion (NTE) in a narrow high-temperature range due to the phase transition around 385 °C. To widen its NTE temperature range, a series of (NaMg)3+ co-doped Cr2Mo3O12 ceramics has been synthesized via a solid reaction process in this work. The effects of double cation (NaMg)3+ co-doping on the phase composition, morphology, phase transformation, and thermal expansion performance of Cr2Mo3O12 ceramics were studied using XRD, Raman, XPS, SEM, and TMA. Results indicate that double cation (NaMg)3+ can partially substitute Cr3+ in Cr2Mo3O12, which causes a phase transition from monoclinic Cr2Mo3O12 to hexagonal (NaMg)xCr2-xMo3O12. The single-phase (NaMg)xCr2-xMo3O12 ceramics with hexagonal structure is obtained when x = 0.5. (NaMg)3+ co-doping promotes the growth of grains and the density of hexagonal (NaMg)0·5Cr1·5Mo3O12 ceramics. (NaMg)3+ co-doping also successfully eliminates the temperature-induced phase transition of Cr2Mo3O12 at 385 °C. Hexagonal (NaMg)0·5Cr1·5Mo3O12 ceramics presents a better NTE with a coefficient of thermal expansion (CTE) of −3.97 × 10−6 °C−1 over a larger temperature range from 30 °C to 700 °C.

Development of δ-Bi2O3/Bi2SiO5 heterostructures based on biogenic silica for photocatalytic treatment from organic pollutants

ABSTRACT δ-Bi2O3/Bi2SiO5 heterostructural photocatalysts with different contents of bismuth in samples (X-Bi-Si, where X = 10–60% Bi2O3) were prepared by the facile sol–gel method using bismuth nitrate and biogenic silica from rice husk biomass as precursors. FT-IR, scanning electron microscope, XRD, energy-dispersive X-ray fluorescence, and UV–Vis methods were systematically used to characterize the as-obtained materials. The photodegradation of methyl orange (MO) in neutral aqueous solutions (pH (6.8)) under UV irradiation was studied to evaluate their photocatalytic activities. The phase composition, morphology, and photocatalytic activity of the samples depended on the content of bismuth oxide in the samples. The maximum degree of MO degradation was 45% for 50-Bi-Si samples containing photoactive δ-Bi2O3 and Bi2SiO5 phases.

Construction of loading g-C3N4/TiO2 on waste cotton-based activated carbon S-scheme heterojunction for enhanced photocatalytic degradation of microplastics: Performance, DFT calculation and mechanism study

In order to achieve the degradation of polyethylene microplastics (PE) in wastewater. The g-C3N4/TiO2/WCT-AC composite photocatalytic materials were prepared by mixed high-temperature thermal polymerization method with the g-C3N4 and the waste cotton based activated carbon (WCT-AC) loaded TiO2 as precursors. The phase morphology, elemental composition, morphology and photochemical properties of the g-C3N4/TiO2/WCT-AC were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), ultraviolet–visible diffuse reflectance spectrum (UV–vis DRS) and photo luminescence (PL). The results of UV–vis DRS and PL showed that the combination of the g-C3N4 and the TiO2/WCT-AC improved the absorption in the visible region, broadened the spectral response range, and the formation of heterojunctions enabled efficient photoelectron-hole separation and improved the photocatalytic activity. Under visible light irradiation for 200 h, catalyst dosage 50 mg, and system pH = 7.0, the highest removal rate of the g-C3N4/TiO2/WCT-AC for PE microplastics reached 67.58 %, and it still showed excellent stability after 5 cycles. The active groups such as ·O2−, ·OH and h+ produced in the g-C3N4/TiO2/WCT-AC system under visible light excitation realized the degradation of PE microplastics. The whole process is a complex oxidation bond breaking process, and the degradation of PE microplastics by g-C3N4/TiO2/WCT-AC follows the S-type charge transfer mechanism.

Effects of drawing speed on microstructure and properties of Cu-Ni-Si alloy clad AA8030 alloy composites prepared by continuous casting composite technology

The Cu-Ni-Si alloy clad AA8030 alloy rod was prepared by continuous casting composite technology with gradient-varying drawing speeds, and the influences of drawing speed on the casting quality and microstructure of Cu-Ni-Si alloy clad AA8030 alloy rod were systematically studied. The drawing speed at which satisfactory continuous casting quality could be obtained was 90–120 mm/min. Meanwhile, axial columnar grains favorable for subsequent plastic processing were obtained, although the angle between columnar grains and axial direction increased with the increases of drawing speed. Moreover, with the drawing speed increasing from 90 mm/min to 120 mm/min, the thickness of composite interfacial layers was significantly increased, and the morphology of interfacial phases was gradually changed. The Cu-Ni-Si alloy cladding layer was cut from the composite to perform solution and aging experiments. The results showed that the solid solution effect of the as-cast Cu-Ni-Si alloy was consistent with that of the solution-treated Cu-Ni-Si alloy because of the rapid cooling characteristics of continuous casting composite technology, which solved the problem that the composite rod could not be solution treated as a whole due to the lower melting point of the Al core.

Stepwise crystallization method combining isotactic polypropylene-based plastic waste film to prepare high-performance polypropylene random copolymer

Upcycling of waste plastic film is increasingly important at the background of energy shortage and environmental crisis. However, direct reuse of the waste plastics as reworked material inevitably downgrades the mechanical properties. Herein, a stepwise crystallization method was used to enable the recycling of waste isotactic polypropylene (iPP) film value-added in iPP-based homocomposites. In detail, the effect of β-nucleating agent (β-NA) and iPP on crystallization behaviors of polypropylene random copolymer (PPR) was investigated at first. The stepwise crystallization procedure was further introduced to promote the β-crystallization of PPR/iPP/β-NA composites in which the crystal structures, polymorph compositions and phase morphologies were systematically researched. At last, impact behaviors of PPR/iPP/β-NA composites were characterized and a penitential toughening mechanism was proposed. It was found that the stepwise crystallization boosted β-crystallization and growth of rubbery phase during the isothermal procedure, resulting in an increase of relative β-crystal content and low temperature impact toughness from 0 % and 2.02 kJ/m2 of neat PPR to 33.4 % and 3.06 kJ/m2 of PPR/iPP/β-NA composites. This work provides a simple, implementable, and effective method for the recycling of waste iPP films and the low-temperature toughening of PPR.

NIR-II luminescence and temperature sensing properties based on double perovskite La2MgTiO6: Yb3+/Er3+/Ho3+ phosphor

The near-infrared-II (NIR-II) fluorescence thermometer based on rare earth-doped double perovskite is rarely. Herein, Er3+-Ho3+ and Yb3+ co-doped lead-free double perovskite La2MgTiO6 (LMTO) phosphors were synthesized by a conventional high temperature solid phase method. The phase purity and morphology of the samples were analyzed using XRD and FE-SEM. The NIR-II luminescence properties of LMTO: Er3+-Ho3+-Yb3+ phosphors were systematically investigated under laser irradiation at 980 nm. A NIR-II fluorescence thermometer was also designed based on non-thermal coupled energy levels originated from the 4I13/2 energy level of Er3+ and the 5I6 energy level of Ho3+. The maximum value of relative sensitivity (Sr) was 0.54 % at 513 K. Compared to visible thermometers (LMTO: Er3+-Yb3+ and LMTO: Ho3+-Yb3+), the NIR-II thermometers offer better temperature measurement capability and penetration depth. All the experimental results show that the NIR-II thermometer with a wider range and higher sensitivity has been realized, which puts forward a new idea for the design and optimization of NIR-II thermometers.