质子化氮化碳的制备及其复合材料的光催化性能

分别采用硫酸、盐酸和硝酸对尿素热解得到的体相块状石墨相氮化碳(g-C_3N_4)进行质子化改性,超声剥离得到氮化碳纳米片,考察3种质子化氮化碳纳米片对亚甲基蓝染料的光催化降解性能,利用XRD、FT-IR、SEM、BET、UV-DRS、UV-VIS等对其结构、形貌、比表面积、禁带宽度进行分析。结果表明,硫酸改性后的g-C_3N_4比表面积最大(60. 9 m~2·g~(-1)),亚甲基蓝降解效果最好,降解率为46. 7%,相比于体相块状g-C_3N_4的29. 2%提高了17. 5个百分点。以硫酸质子化改性的g-C_3N_4为前驱体,采用搅拌法制备得到质子化g-C_3N_4/石墨烯复合材料,其光催化降解亚甲基蓝的降解率为81. 7%,较硫酸质子化g-C_3N_4提高了35. 0个百分点。     

Microstructure and mechanical properties of stainless steel clad plate joints produced by TIG and MAG hybrid welding

Abstract

This paper investigated the microstructure and mechanical properties of Q235/304 stainless steel clad plate welding seam produced by hybrid welding of tungsten inert gas welding (TIG) and metal active gas arc welding (MAG). The results showed that the dual phases containing ferrite and austenite appeared in the stainless steel covering welding (SSCW), while the partial martensite phases appeared in the carbon steel backing welding (CSBW), which is attributed to the dilution behavior of Ni and Cr elements from stainless steel to the Q235 steel results into the movement of the CCT curve to the right side and the decrease of critical martensite formation cooling rate. The CSBW possesses the highest microhardness value in the weld metal due to the existence of the martensite zone. The impact tests were carried out and the results showed that the Charpy absorbed energy of weldments (81?J) is almost equal to that of base clad plate (83?J). The SSCW layer possesses the ductile fracture characteristics accompanying many dimples. However, in the CSBW layer, some cleavage fracture characteristics are presented in the radiation zone while many dimples are located in the fibrous zone, revealing a complex combination of brittle and ductile fracture behavior, which is due to the existence of martensite zone, different stress states and crack propagation velocity.

• Highlights

• Hybrid (TIG, MAG) welding is suitable for welding stainless steel clad plate;

• The martensite formation in CSBW is related to dilution and diffusion of Cr and Ni;

• Partial martensite transformation can strengthen and toughen the welding seam.

     

Effect of shielding rates on upward flame spread over extruded polystyrene foam in vertical channel and heat transfer mechanism

Fire hazard of extruded polystyrene (XPS) thermal insulation materials has aroused public concern. In order to develop flame spread theory and the guideline for fire risk assessment of XPS, an experimental study on upward flame spread behavior and heat transfer mechanism of XPS in a vertical channel with different frontal shielding rates was conducted. Maximum temperature at the place 2 cm from XPS surface and at the center of channel first increase and then decrease as the shielding rate rises. The former is higher than the latter. Experimental value of average flame height rises as the shielding rate increases. A model for predicting the flame height is built, and the predicted results are consistent with the experimental results. Moreover, the relation between flame height and pyrolysis height under different shielding rates is obtained. The flame spread rate rises as the shielding rate increases. A prediction model of flame spread rate is established, and its prediction results are more accurate compared with those from previous models. The model also predicts that radiative heat transfer is the dominant heat transfer mode, accounting for 93% of the total heat transfer. This work is beneficial for fire risk assessment and fire safety design of building façade.     

The APOA5-rs662799 Polymorphism Is a Determinant of Dyslipidemia in Vietnamese Primary School Children

Apolipoprotein A-V encoded by apolipoprotein 5 (APOA5) gene plays an important role in lipid metabolism, especially in the regulation of plasma triglycerol levels. The study aimed to evaluate the association of the APOA5-rs662799 polymorphism with dyslipidemia in Vietnamese children and the potential modification of obesity-related traits (body mass index, waist circumference, hip circumference, and waist-to-hip ratio) on this association. A case–control study was conducted with a total of 154 dyslipidemia cases and 389 controls at the age of 6 to 10 recruited at 31 primary schools in Hanoi city of Vietnam. Genotype for APOA5-rs662799 polymorphism was determined by the restriction fragment length polymorphism analysis. The association of APOA5-rs662799 polymorphism with dyslipidemia adjusting for age, sex, residence, and obesity-related traits was analyzed by binary logistic regression analysis. The results showed that in comparison with T/T and T/C carriers, the C/C carriers had a higher concentration of serum TAG in cases (p =0.049). Carriers of the C allele (C/C + T/C) had higher risk for developing dyslipidemia and hypertriglyceridemia than subjects with T/T genotype (odds ratio, OR = 1.7, p =0.0062 and OR = 1.6, p = 0.026, respectively). The association remained significant after adjusting for age, gender, residence, and obesity status (OR = 1.75, p = 0.006 and OR = 1.53, p = 0.049, respectively) or other obesity-related traits. The study suggested that the APOA5-rs662799 polymorphism may be a determinant of dyslipidemia and hypertriglyceridemia in Vietnamese children, independent of obesity-related traits.     

Preparation and characterization of heteroepitaxial Zn2SnO4 single crystalline films prepared on MgO (100) substrates

Zinc stannate (Zn₂SnO₄) films were deposited on MgO (100) substrates by pulsed laser deposition, and Zn₂SnO₄ monocrystalline films were obtained by postannealing process. The structures, surface morphologies, and optical properties of the Zn₂SnO₄ films annealed at different temperatures were investigated in detail. Crystal structure analyses showed that the film annealed at 800°C was single crystal Zn₂SnO₄ with an inverse-spinel structure. The heteroepitaxial mechanism was further clarified by a schematic diagram, and the epitaxial relationships between the film and substrate were Zn₂SnO₄ (400) || MgO (200) with Zn₂SnO₄ [001] || MgO [001]. The obtained Zn₂SnO₄ films exhibited excellent transparency. The optical band gap of the 800°C-annealed Zn₂SnO₄ film was about 3.97 eV. The extinction coefficients and refractive indexes of the Zn₂SnO₄ films annealed at different temperatures as a function of wavelength were analyzed in detail.     

Photocatalytic degradation and heat reflectance recovery of waterborne acrylic polymer/ZnO nanocomposite coating

This work aims to clarify the photocatalytic degradation mechanism and heat reflectance recovery performance of waterborne acrylic polymer/ZnO nanocomposite coating. To fabricate the nanocomposite coating, ZnO nanoparticles (nano-ZnO) were dispersed into acrylic polymer matrix at the various concentrations from 1 to 6% (by total weight of resin solids). The photocatalytic degradation of nanocomposite coating under ultraviolet (UV) light irradiation has been investigated by monitoring its weight loss and chemical/microstructural/morphological changes. As the topcoat layer, its heat reflectance recovery has been evaluated under UV/condensation exposure by using an artificial dirty mixture of 85 wt% nanoclay, 10 wt% silica particles (1–5 μm), 1 wt% carbon black, and 2 wt% engine oil. After 108-cycle UV/condensation exposure, infrared spectra and weight loss analysis indicated that the maximal degradation for nanocomposite coating is observed at 1 wt% nano-ZnO. On the other hand, after 96 hr of UV light exposure, the nanocomposite coating with1 wt% nano-ZnO could restore effectively the reflective index of solar-heat reflectance coating (from 58.45 to 80.78%). Finally, the photodegradation mechanism of this waterborne acrylic polymer coating has been proposed as the UV-induced formation of CC CO conjugated double bonds. As a result, its self-cleaning phenomenon can be achieved as the recovery of heat reflectance.     

Live-Cell Copper-Induced Fluorescence Quenching of the Flavin-Binding Fluorescent Protein CreiLOV

CreiLOV is a flavin-binding fluorescent protein derived from the blue-light photoreceptor protein family that contains light-oxygen-voltage (LOV) sensing domains. Flavin-binding fluorescent proteins represent a promising foundation for new fluorescent reporters and biosensors that can address limitations of the well-established green fluorescent protein (GFP) family. Flavin-binding fluorescent proteins are smaller than GFPs, are stable over a wider pH range, offer rapid chromophore incorporation, and are oxygen-independent so can be applied to live anaerobic organisms. Among the flavin-binding fluorescent proteins, CreiLOV has a high quantum yield and excellent photophysical properties, making it promising for cellular applications. Here, we investigated the suitability of CreiLOV as an intensity- and fluorescence-lifetime-based metal sensor. CreiLOV selectively binds copper(II) over other biologically relevant metals with low-micromolar affinity, resulting in fluorescence quenching and a decrease in the fluorescence lifetime that can be observed in cuvettes and live bacterial cells.     

Advanced Surface of Fibrous Activated Carbon Immobilized with FeO/TiO2 for Photocatalytic Evolution of Hydrogen under Visible Light

FeO-doped TiO₂ nanoparticle photocatalysts were immobilized onto the surface of fibrous activated carbon (ACF) via a sol-gel process. As an adsorbent and photocatalyst, FeO-TiO₂ on immobilized ACFs (FeO-TiO₂/ACF) greatly improved the photocatalysis rate of hydrogen production as compared with pure TiO₂ and ACF-TiO₂ under UV irradiation and visible light. The addition of ACFs surface significantly reduced the photogenerated pairs of electrons-hole recombination, thereby promoting the photocatalysis action of doped photo-metal oxides of FeO-TiO₂. Co-doping of FeO onto the lattice of the TiO₂ approach can improve the absorption activity of visible light through photo-metal oxide of TiO₂ and further enhance hydrogen production under visible light. The photocatalytic fabrics (FeO-TiO₂/ACF) were effortlessly split out from the experimental solution for re-utilization and exhibited high stability even after five complete regeneration cycles.     

Effect of Supports and Promoters on the Performance of Ni-Based Catalysts in Ethanol Steam Reforming

Ethanol steam reforming (ESR) is one of the potential processes to convert ethanol into valuable products. Hydrogen produced from ESR is considered as green energy for the future and can be an excellent alternative to fossil fuels with the aim of mitigating the greenhouse gas effect. The ESR process has been well studied, using transition metals as catalysts coupled with both acidic and basic oxides as supports. Among various reported transition metals, Ni is an inexpensive material with activity comparable to that of noble metals, showing promising ethanol conversion and hydrogen yields. Additionally, different promoters and supports were utilized to enhance the hydrogen yield and the catalyst stability. This review summarizes and discusses the influences of the supports and promoters of Ni-based catalysts on the ESR process.