Impact of quenched random fields on the ferroelectric-to-relaxor crossover in the solid solution (1−x)BaTiO3−xDyFeO3

Lead-based perovskite relaxor ferroelectrics are widely used as materials for numerous applications due to their extraordinary dielectric, piezoelectric, and electrostrictive properties. While the mechanisms of relaxor behavior are disputable, the importance of quenched (static) random electric fields created at nanoscale by the disordered heterovalent cations has been well recognized. Meanwhile, an increasing amount of scientific and technological efforts has been concentrated on lead-free perovskites, in particular, solid solutions of classical ferroelectric BaTiO 3 (BT), which better meet ecological requirements. Among BT-based solutions the homovalent systems are elaborately studied where strong random electric fields are absent, while the solubility limit of heterovalent solutions is typically too low to fully reveal the peculiarities of relaxor behavior. In this paper, we prepare a perovskite solid solution system (1 − x )Ba 2 + Ti 4 + O 3 − x Dy 3 + Fe 3 + O 3 (0 x 0 . 3) and study it as a model heterovalent lead-free system. We determine crystal structure, ferroelectric, and dielectric properties of ceramics in a wide range of temperatures and concentrations, construct a phase diagram, and find and analyze the concentration-induced crossover from normal ferroelectric to relaxor behavior. We demonstrate that quenched random electric fields of moderate strength promote the ferroelectric-to-relaxor crossover, but do not change qualitatively the peculiarities of relaxor behavior, while strong enough fields destroy the relaxor state, so that the material becomes an ordinary linear dielectric. The experimental results are compared with the predictions of known theories of relaxor ferroelectricity

Governing effects of melt viscosity on fire performances of polylactide and its fire-retardant systems

Extreme flammability of polylactide (PLA) has restricted its real-world applications. Traditional research only focuses on developing new effective fire retardants for PLA without considering the effect of melt viscosity on its fire performances. To fill the knowledge gap, a series of PLA matrices of varied melt flow index (MFI) with and without fire retardants are chosen to examine how melt viscosity affects its fire performances. Our results show that the MFI has a governing impact on fire performances of pure PLA and its fire-retardant systems if the samples are placed vertically during fire testing. PLA with higher MFI values achieves higher limiting oxygen index (LOI) values, and a lower loading level of fire retardants is required for PLA to pass a UL-94 V-0 rating. This work unveils the correlation between melt viscosity and their fire performance and offers a practical guidance for creating flame retardant PLA to extend its applications

Synthesis and Characterization of Ferroelectric and Antiferroelectric Complex Perovskite Systems

Single crystals of Pb(Sc1/2Nb1/2)O3 (PSN) were grown by a high-temperature solution method using (PbO + B2O3) as flux. X-ray diffraction (XRD) indicates a pure perovskite phase without B-site ordering. Polarized light microscopy shows that the crystals are of rhombohedral symmetry at room temperature and become cubic at 112 oC on heating which is the Curie temperature (TC). A relaxor-to-ferroelectric phase transition is confirmed by dielectric spectroscopy. Frequency-dependent permittivity is also observed, revealing relaxor behavior. Poling the crystal at room temperature does not change TC but suppresses the permittivity. A typical ferroelectric hysteresis loop is obtained at room temperature, indicating the ferroelectric nature of the PSN crystal.A new antiferroelectric solid solution ceramics of (1-x)PbZrO3-xPb(Zn1/2W1/2)O3 [(1-x)PZ-xPZnW, with x = 0 - 10%] has been prepared by conventional solid state reaction method. XRD reveals the perovskite structure of the (1-x)PZ-xPZnW ceramics. TC decreases when the percentage of PZnW increases. Meanwhile, another transition related to the transformation from antiferroelectric (AFE) to an intermediate ferroelectric (FE) phase was observed and its transition temperature (TAFE-FE) decreases from 213 oC for x = 0 to 58 oC for x = 0.10. A typical FE hysteresis loop was obtained, indicating the FE nature of the intermediate phase.The 0.97PbZrO3-0.03Pb(Zn1/2W1/2)O3 (97%PZ-3%PZnW) ceramic was used to study the intermediate FE phase. The temperature dependence of dielectric permittivity was studied. TC on cooling and heating are both 212 oC, indicating a second-order phase transition. Another phase transition below TC was observed, from the AFE phase at room temperature to an intermediate phase at higher temperature. This transition shows thermal hysteresis on cooling and heating, representing a first-order phase transition. Within the temperature range of the intermediate phase, ferroelectric hysteresis loops were displayed and a non-centrosymmetric structure was revealed by second harmonic generation, which indicates the FE nature for the intermediate phase. High resolution XRD and the subsequent refinement results show that the intermediate FE phase is rhombohedral (R3m) and the AFE phase is orthorhombic (Pbam). A phase diagram of the (1-x)PbZrO3-xPb(Zn1/2W1/2)O3 solid solution has been established

DEV induce autophagy via the endoplasmic reticulum stress related unfolded protein response.

Duck enteritis virus (DEV) can infect ducks, geese, and many other poultry species and leads to acute, septic and highly fatal infectious disease. Autophagy is an evolutionarily ancient pathway that plays an important role in many viral infections. We previously reported that DEV infection induces autophagy for its own benefit, but how this occurs remains unclear. In this study, endoplasmic reticulum (ER) stress was triggered by DEV infection, as demonstrated by the increased expression of the ER stress marker glucose-regulated protein 78 (GRP78) and the dilated morphology of the ER. Pathways associated with the unfolded protein response (UPR), including the PKR-like ER protein kinase (PERK) and inositol-requiring enzyme 1 (IRE1) pathways, but not the activating transcription factor 6 (ATF6) pathway, were activated in DEV-infected duck embryo fibroblast (DEF) cells. In addition, the knockdown of both PERK and IRE1 by small interfering RNAs (siRNAs) reduced the level of LC3-II and viral yields, which suggested that the PERK-eukaryotic initiation factor 2α (eIF2α) and IRE1-x-box protein1 (XBP1) pathways may contribute to DEV-induced autophagy. Collectively, these data offer new insight into the mechanisms of DEV -induced autophagy through activation of the ER stress-related UPR pathway

One-step and green synthesis of a bio-based high-efficiency flame retardant for poly (lactic acid)

The synthesis of bio-based high-efficiency flame retardants in accordance with green and facile method is critical yet very challenging for bioplastics, e.g., poly (lactic acid) (PLA). In this study, a bio-based flame retardant named as PF is synthesized by the reaction between phytic acid (PA) and furfurylamine (FA) in water. PF improves the flame retardancy of PLA at low addition. For instance, PLA composite containing only 2 wt% PF passes a UL-94 V-0 classification, and that containing 4 wt% PF exhibits a limiting oxygen index (LOI) of 28.5%, which is 46.2% higher than that of pure PLA. PF slightly reduces the peak heat release rate (PHRR) and total heat release (THR) of PLA in cone calorimeter test (CCT). In detail, 4 wt% PF reduces the PHRR from 362.2 kW/m2 to 332.7 kW/m2 by 8%. Additionally, PLA/PF composite is comparable to the neat PLA in terms of mechanical properties and thermal stability when a UL-94 V-0 rating is achieved. The flame-retardant mechanism analyses demonstrate that PF takes action in both gaseous and condensed phases. It is proposed that PF accelerates the generation of melting droplets to take away heat, suppresses the release of combustible gases and improves the compactness of char layer during combustion. This study provides a green and facile strategy to create bio-based high-efficiency flame retardants for the preparation of fire-safe bioplastics holding a promising future in the industry

Sulfonated Block Ionomers Enable Transparent, Fire-Resistant, Tough yet Strong Polycarbonate

Polycarbonate (PC) features high transparency and balanced mechanical properties, and thus is being growingly used for producing many high-end products, e.g., construction facades, sensors and 5G equipment. For these applications, PC is required to combine satisfactory fire retardancy and great toughness while retain its mechanical strength and optical transparency. However, existing either fire retardants or toughening agents fail to enable PC to achieve such a required performance portfolio due to their improper molecular designs. To overcome this challenge, we, herein, rationally design a series of sulfonated ionomeric fire retardants (sSEBS-M, M = Na+, Zn2+, Ce3+) by sulfonating and neutralizing styrene-ethylene-butylene-styrene (SEBS). The sSEBS-M can be well-dispersed within the PC matrix with phase domain sizes less than 500 nm. Chemical structures of sSEBS-M and their dispersion within the polymer matrix strongly correlate to their comprehensive performances in PC. Among three sSEBS-M ionomers, sSEBS-Ce endows PC with better comprehensive performances. With 1.5 wt% of sSEBS-Ce, the final PC achieves a high limiting oxygen index of 33.5% and a desired UL-94 V-0 rating, in addition to a 53% reduction in peak heat release rate and a comparable transparency to virgin PC. Moreover, its impact toughness and ductility are enhanced by 40% and 116% with tensile strength well-preserved. The integrated performance portfolios are superior to previous counterparts. This work offers a novel strategy for the design of multifunctional ionomer-based fire retardants for creating high-performance PC and reveals its structure-composition-property relationship in PC, which will enable PC to realize its practical applications in above-mentioned industries

The Potential Dual Role of H2.0-like Homeobox in the Tumorgenesis and Development of Colorectal Cancer and Its Prognostic Value

Background. H2.0-like homeobox (HLX) is highly expressed in several hematopoietic malignancies. However, the role of HLX in the carcinogenesis and progression of colorectal cancer (CRC) patients has rarely been reported. Methods. In this study, the data were collected from The Cancer Genome Atlas and Gene Expression Omnibus databases. The diagnostic value of HLX was analyzed by the R package “pROC.” The overall survival was estimated using the “survival” and “survminer” packages. A nomogram was established to predict 1-, 3-, and 5-year overall survival of CRC patients. The CIBERSORT software was employed to calculate the relative proportions of 22 immune cells. Results. HLX expression was downregulated in CRC patients. Remarkably, HLX expression was increased with stage (stage I–stage III) of CRC, and the CRC patients with high HLX expression exhibited a poor prognosis. The promoter methylation level of HLX was prominently increased in CRC samples compared to paracancerous samples. We also found that the six miRNAs target HLX genes, leading to its downregulation, and HLX expression had a negative correlation with its downstream target gene BRI3BP in both CRC and normal samples. Finally, we found that the 12 immune infiltrating cells were observably different between high and low HLX expression groups. The HLX had a significant positive correlation with 8 immune checkpoints (PD-1 (PDCD1), CTLA4, PDL-1 (CD274), PDL-2 (PDCD1LG2), CD80, CD86, LAG3, and TIGIT) expressions. Conclusion. HLX probably played a carcinostasis role in the early stages of CRC but exhibited a cancer-promoting effect in the advanced stages. Meanwhile, HLX could serve as a reliable prognostic indicator for CRC

Recent advances in fire-retardant rigid polyurethane foam

Driven by global environmental concerns, many efforts have been made to develop halogen-free flame retardants for rigid polyurethane foam (RPUF). These environmentally benign flame retardants are mainly divided into (i) reactive, (ii) additive, and (iii) coating types. The last decade has witnessed great progress of these three strategies, which enhance the fire safety of RPUF and maintain even improve the thermal insulation properties. This comprehensive review focuses on the up-to-date design of the reactive, additive, and coating flame retardants, and their effects on flame retardancy and thermal conductivity of RPUF. Moreover, the practical applications of the as-prepared flame-retardant RPUFs are highlighted. Finally, key challenges associated with these three kinds of flame retardants are discussed and future research opportunities are also proposed

A hyperbranched P/N/B-containing oligomer as multifunctional flame retardant for epoxy resins

Flame-retardant epoxy resins (EPs) with superior optical, mechanical and dielectric properties are highly desired in high-tech industries. In this work, a multifunctional hyperbranched additive (BDHDP) was synthesized for EPs. Our results showed that BDHDP catalyzed the curing of epoxy resin because of its tertiary amine and hydroxyl groups. At a low addition level (<3.0 wt%), BDHDP increased the glass-transition temperature and maintained the optical transmittance of epoxy thermoset. Meanwhile, BDHDP improved the mechanical strength and toughness, and reduced the dielectric constant and loss of EP because of the rigid phosphaphenanthrene groups and intra-molecular cavities. Moreover, BDHDP reduced the heat release and smoke generation during the EP combustion. Adding 1.5 wt% of BDHDP led to a UL-94 V-0 rating, and reduced the total smoke production by 16.4%. Hence, this study offers an effective method to create transparent EP thermosets with outstanding mechanical, dielectric and fire-retardant properties via incorporating a P/N/B-containing hyperbranched oligomer

A Novel Synergistic Flame Retardant of Hexaphenoxycyclotriphosphazene for Epoxy Resin

Hexaphenoxycyclotriphosphazene (HPCP) is a common flame retardant for epoxy resin (EP). To improve the thermostability and fire safety of HPCP-containing EP, we combined UiO66-NH2 (a kind of metal-organic frame, MOF) with halloysite nanotubes (HNTs) by hydrothermal reaction to create a novel synergistic flame retardant (H-U) of HPCP for EP. For the EP containing HPCP and H-U, the initial decomposition temperature (T5%) and the temperature of maximum decomposition rate (Tmax) increased by 11 and 17 °C under nitrogen atmosphere compared with those of the EP containing only HPCP. Meanwhile, the EP containing HPCP and H-U exhibited better tensile and flexural properties due to the addition of rigid nanoparticles. Notably, the EP containing HPCP and H-U reached a V-0 rating in UL-94 test and a limited oxygen index (LOI) of 35.2%. However, with the introduction of H-U, the flame retardant performances of EP composites were weakened in the cone calorimeter test, which was probably due to the decreased height of intumescent residual char