Effect of Gas Nitriding on Interface Adhesion and Surface Damage of CL60 Railway Wheels under Rolling Contact Conditions

The influence of surface gas nitriding on wheel/rail rolling contact fatigue and wear behavior of CL60 wheel was studied on a new rolling contact fatigue/wear tester (JD-DRCF/M). The failure mechanisms of the wheel/rail surface after the gas nitriding and without gas nitriding on the wheel surface were compared and analyzed. The results show that the wheel with gas nitriding could form a dense and hard white bright layer which was approximately 25 μm thick and a diffusion layer which was approximately 70 μm thick on the wheel surface. Thus, the gas nitriding on the railway wheel not only significantly improved the wear resistance on the surface of the wheel, but also effectively reduced the wear of the rail; the results show that the material loss reduced by 58.05% and 10.77%, respectively. After the wheel surface was subjected to gas nitriding, the adhesive coefficient between the wheel/rail was reduced by 11.7% in dry conditions, and was reduced by 18.4% in water media, but even so, the wheel with gas nitriding still could keep a satisfactory adhesive coefficient between the wheel/rail systems, which can prevent the occurrence of phenomena such as wheel-slip. In short, the gas nitriding on the wheel surface can effectively reduce the wear, and improve the rolling contact fatigue resistance of the wheel/rail system. This study enlarges the application field of gas nitriding and provides a new method for the surface protection of railway wheels in heavy-duty transportation

The enhancement roles of sulfate on the adsorption of sodium dodecylsulfate by calcium-based layered double hydroxide: microstructure and thermal behaviors

As a commonly used surfactant, sodium dodecyl sulfate (SDS) usually coexists with inorganic anions in the industrial wastewater. These anions have a significant influence on SDS removal, indirectly threatening the environment. It is important to understand the relationship between the adsorption of SDS and inorganic anions. In this study, calcium-based layered double hydroxide (CaAl-LDH-Cl) as an efficient adsorbent was synthesized for investigating the effect of SO on SDS removal. The SDS adsorption capacities were enhanced to 3.21 and 4.21 mmol g in the presence of SO with low/high SDS concentration, respectively. The phenomenon and mechanism were confirmed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Scanning electron microscopy (SEM). Anionic exchange played a dominant role in the adsorption of SDS onto CaAl-LDH-Cl at DS/SO < 2, while both anion exchange and precipitation occurred when DS/SO exceeded 2. Moreover, the thermal analysis (TG-DTA) was employed to further reveal the interaction mechanism. The results showed the highest total mass loss and the lowest loss temperature of interlayer water in the sulfate coexist system, confirming the enhancement of SDS adsorption amount in the presence of SO

A Pragmatic and High-Performance Radiative Cooling Coating with Near-Ideal Selective Emissive Spectrum for Passive Cooling

Radiative cooling is a passive cooling technology that can cool a space without any external energy by reflecting sunlight and radiating heat to the universe. Current reported radiative cooling techniques can present good outside test results, however, manufacturing an efficient radiative material which can be applied to the market for large-scale application is still a huge challenge. Here, an effective radiative cooling coating with a near-ideal selective emissive spectrum is prepared based on the molecular vibrations of SiOx, mica, rare earth silicate, and molybdate functional nanoparticles. The radiative cooling coating can theoretically cool 45 &deg;C below the ambient temperature in the nighttime. Polyethylene terephthalate (PET) aluminized film was selected as the coating substrate for its flexibility, low cost, and extensive production. As opposed to the usual investigations that measure the substrate temperature, the radiative cooling coating was made into a cubic box to test its space cooling performance on a rooftop. Results showed that a temperature reduction of 4 &plusmn; 0.5 &deg;C was obtained in the nighttime and 1 &plusmn; 0.2 &deg;C was achieved in the daytime. Furthermore, the radiative cooling coating is resistant to weathering, fouling, and ultraviolet radiation, and is capable of self-cleaning due to its hydrophobicity. This practical coating may have a significant impact on global energy consumption

Efficient Synthesis of Liquid Fuel Intermediates from Furfural and Levulinic Acid via Aldol Condensation over Hierarchical MFI Zeolite Catalyst

A water-tolerant, basic, and hierarchical MFI zeolite catalyst was synthesized and applied in the aldol condensation reaction between biomass-derived furfural and levulinic acid. The results showed that the addition of poly(diallyl dimethylammonium chloride) significantly affected the textural and acid-base properties of hierarchical zeolite, which subsequently influenced the catalytic performance of hierarchical zeolite. In the aqueous phase, potassium-modified, hierarchical MFI zeolite (K/H-MFI-n) was more active for aldol condensation between furfural and levulinic acid than the potassium-modified, conventional MFI zeolite (K/MFI). This was ascribed to higher basic sites density and improved diffusion limitation of K/H-MFI-n. A 70.6% yield of aldol condensation product was achieved with a complete conversion of furfural at 100 degrees C for 9 h by K/H-MFI-0.6. However, only 27.4% yield of aldol condensation product with 55.1% furfural conversion was obtained by K/MFI at the same condition. Two major isomeric aldol products, beta-furfurylidenelevulinic acid and delta-furfurylidenelevulinic acid (beta-FDLA and delta-FDLA), were obtained after acidification. K/H-MFI-n displayed an enhanced selectivity (54.9%) to delta-FDLA, owing to the stronger basicity of K/H-MFI-n. However, K/MFI showed a preferred selectivity to beta-FDLA (42.7%), owing to the dominant Lewis acidity. Recyclability research showed that the catalytic performance of potassium-modified, hierarchical MFI zeolite was acceptable after five runs

Preparation of two different crystal structures of cerous phosphate as solid acid catalysts: their different catalytic performance in the aldol condensation reaction between furfural and acetone

Liquid fuel intermediates can be produced via aldol condensation reactions through furan aldehydes and ketones driven from biomass. It was found that cerous phosphate (CP) with two different crystal structures (hexagonal and monoclinic structure), which was tailored by different hydrothermal temperature (120 degrees C for the hexagonal structure and 180 degrees C for the monoclinic structure) and calcination temperature (900 degrees C for the monoclinic structure) as a solid acid catalyst, exhibit high catalytic performance in aldol condensation between furfural and acetone. The CP with hexagonal structure gave 89.1% conversion of furfural with 42% yield of 4-(2-furyl)-3-buten-2-one (FAc) and 17.5% of yield of 1,5-di-2-furanyl-1,4-pentadien-3-one (F2Ac), much higher than CP with monoclinic structure. However, both furfural conversion and aldol product yield increased from 82.3% to 96% and from 50.5% to 68.4%, respectively, for CP with the monoclinic structure after calcination owing to the higher amount of acid of catalyst after calcination but decreased continuously for CP with hexagonal structure after calcination because of its rapidly reduced BET surface area and total pore volume. The results indicated that calcination affects significantly the physical-chemical properties of CP catalysts, which influence subsequently the catalytic performance in the aldol condensation reaction. Recycling experiments showed that the catalytic performance after five number runs for CP with monoclinic structure after calcination was acceptable but was not ideal for CP with hexagonal structure owing to its poor hydrothermal stability

Metabolic Study of Tetra-PEG-Based Hydrogel after Pelvic Implantation in Rats

In vivo metabolism of polyethylene glycol (PEG) hydrogels has rarely been studied. In this study, we prepared a chemically crosslinked hydrogel formulation using 14C-labeled tetra-armed poly (ethylene glycol) succinimidyl succinate (Tetra-PEG-SS) and 3H-labeled crosslinking agent for implantation into the pelvis of Sprague-Dawley (SD) rats. This radioactive labeling technique was used to investigate the radioactivity excretion rates in of feces and urine, the blood exposure time curve, and the radioactivity recovery rate in each tissue over time. We showed that the primary excretion route of the hydrogel was via urine (3H: about 86.4%, 14C: about 90.0%), with fewer portion through feces (3H: about 6.922%, 14C: about 8.16%). The hydrogel metabolites exhibited the highest distribution in the kidney, followed by the jejunal contents; The 3H and 14C radioactivity exposures in the remaining tissues were low. We also showed that the 3H and 14C radioactivity recovery rates in the blood were usually low (−1 at 12 h after implantation), even though, in theory, the hydrogel could be absorbed into the blood through the adjacent tissues. By using a combination of HPLC-MS/MS and offline radioactivity counting method, we established that the tetra-PEG-based hydrogel was mainly metabolized to lower-order PEG polymers and other low-molecular-weight substances in vivo

The tetracyclines removal by MgAl layered double oxide in the presence of phosphate or nitrate: Behaviors and mechanism exploration

Pollution of tetracyclines (TCs) in swine wastewater has been a critical concern worldwide. Notably, multiple anions (e.g. PO , NO ) coexist in the actual environments, which could significantly influence the TCs removal. In the current study, MgAl layered double oxide (MgAl-LDO) was adopted for investigating the TC removal performance with/without PO or NO . In all systems, the adsorption performance exhibited two different approaches between low and high TC concentrations. In the single system, pseudo-second-order and the Freundlich model fitted well to the equilibrium adsorption data when TC concentration was below 125 mg·L, while the pseudo-first-order and the linear model could describe the removal process at high TC concentration (>125 mg·L). The maximum adsorption capacity was 83.56 mg·g. In the co-existing system, the adsorption capacity was slightly enhanced when TC concentration below 150 mg·L however was inhibited at high concentration (>150 mg·L). Combined with the characterization analyses, the interaction mechanism at low concentration was primarily surface adsorption on reconstructed LDH from LDO in the TC-alone system. It is worth mention that both PO and NO facilitated the formation of LDH via rehydration of LDO which enhanced surface adsorption in the co-existing system. At high TC concentration, the formation of tetracycline-metal complexes played a dominant role in TC removal in the single system, whereas diminished complexation in the binary system led to the decreased TC removal. This study provides a theoretical and practical guidance for MgAl-LDO on the efficient remediation of actual tetracyclines wastewater

Partition and Fate of Phthalate Acid Esters (PAEs) in a Full-Scale Horizontal Subsurface Flow Constructed Wetland Treating Polluted River Water

When used as highly produced chemicals and widely used plasticizers, Phthalate acid esters (PAEs) have potential risks to human life and the environment. In this study, to assess the distribution and fate of PAEs, specifically inside a full-scale horizontal subsurface flow constructed wetland, four PAEs including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), and bis (2-ethylhexyl) phthalate (DEHP) were investigated. In effluent, PAEs concentration decreased 19.32% (DMP), 19.18% (DEP), 19.40% (DBP), and 48.56% (DEHP), respectively. Within the wetland, PAEs partitioned in water (0.18&ndash;1.12 &mu;g/L, 35.38&ndash;64.92%), soil (0.44&ndash;5.08 &mu;g/g, 1.02&ndash;31.33%), plant (0.68&ndash;48.6 &mu;g/g, 0.85&ndash;36.54%), air and biological transformation (2.72&ndash;33.21%). The results indicated that soil and plant adsorption contributed to the majority of PAE removal, digesting DMP (19.32%), DEP (19.18%), DBP (19.40%), and DEHP (48.56%) in constructed wetlands. Moreover, the adsorption was affected by both octanol/water partition coefficient (Kow) and transpiration stream concentration factors (TSCF). This work, for the first time, revealed the partition and fate of PAEs in constructed wetlands to the best of our knowledge

Voltage-Dependent Emission Varying from Blue to Orange&ndash;Red from a Nondoped Organic Light-Emitting Diode with a Single Emitter

Organic light-emitting diodes (OLEDs) with tunable emission colors, especially white OLEDs, have rarely been observed with a single emitter in a single emissive layer. In this paper, we report a new compound featuring a D&ndash;A&ndash;D structure, 9,9&prime;-(pyrimidine-2,5-diylbis(2,1-phenylene))bis(3,6-di-tert-butyl-9H-carbazole) (PDPC). A nondoped OLED using this compound as a single emitter exhibits unique voltage-dependent dual emission. The emission colors range from blue to orange&ndash;red with an increase in voltage, during which white electroluminescence with a Commission Internationale De L&rsquo;Eclairage (CIE) coordinate of (0.35, 0.29) and a color render index (CRI) value of 93 was observed. A comparative study revealed that the dual emission simultaneously originates from the monomers and excimers of the emitter. This study provides insight into understanding the multimer-excited mechanism and developing novel color-tunable OLEDs