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The wettability of nanofluid is a key factor affecting oil recovery and fluid heat transfer. However, the traditional wettability measurement method consisting in determining the contact angle enables to assess the wettability at a solid–liquid contact point only and not within the continuous detection range. Therefore, in this work, a lateral friction detection system is used to continuously measure the wettability of hydroxylated multi-walled carbon nanotubes/deionized water (MWCNT-OH/DIW) nanofluids on polydimethylsiloxane surfaces. Specifically, MWCNT-OH/DIW nanofluids with various mass fractions are configured, and different surfactants are introduced to regulate the dispersion in deionized water. The results reveal that the surface tension and contact angle decrease simultaneously with the increase in MWCNT-OH/DIW mass fraction. Meanwhile, this change also causes an increase in the lateral friction at the nanofluid/PDMS interface. Furthermore, both sodium dodecyl sulfate and cetyltrimethylammonium bromide (CTAB) as surfactants can effectively reduce its surface tension. Notably, when CTAB is added, the maximum static friction (132.62 μN) exceeds that of SDS (113.13 μN). Therefore, the proposed method opens up new prospects in wettability detection of nanofluids. [ABSTRACT FROM AUTHOR]

Corundum‐mullite composite ceramics appropriate for application in solar heat transmission pipelines were fabricated by the addition of Tm2O3 and sintered at atmospheric pressure. The results demonstrated that with the introduction of Tm2O3 (1–7 wt.%), the physical and mechanical properties, corrosion resistance, and thermal shock resistance of the composite ceramics were significantly enhanced. The sintered sample AT5 (with 5 wt.% of Tm2O3 added) showed the best overall performance at 1550°C. The residual bending strength remained higher than 186 MPa after corrosion with 20 wt.% H2SO4 solution and 10 wt.% sodium hydroxide solution. The reaction of Tm2O3 with the Al2O3–SiO2 system produced the Tm2O3–Al2O3–SiO2 liquid phase. This liquid phase eliminated the pores through viscous flow, resulting in a dense microstructure. Furthermore, more mullite and dithulium disilicate were generated after thermal shock cycles, and their inhibition of crack deflection and extension allowed the composite ceramics to achieve excellent thermal shock resistance (residual bending strength as high as 199 MPa). The prepared corundum‐mullite composite ceramics have a good potential for application in solar heat transmission pipelines. [ABSTRACT FROM AUTHOR]

Coal gasification fine slag (CGFS) is a by-product of gasification process of gasification beds that pollutes the environment. To make the utilization of CGF more efficient, poly (vinyl chloride) (PVC)/CGFS composites were prepared via a melt blending process, and their mechanical and thermal properties were investigated. In order to dig deeper into the decomposition mechanism, the thermal degradation kinetics were systematically analyzed by drawing non-isothermal heat maps based on the Flynn-Wall-Ozawa, Friedman, and Kissinger model-free methods. According to the results, the properties of all tests vary significantly with CGFS content. In particular, at a the CGFS content of 20 phr, the tensile strength (tensile modulus) and flexural strength (flexural modulus) of CGFS-20 were 13.5% (47.8%) and 13.9% (41.6%) higher, respectively, than those of conventional CGFS-0 composites. However, the impact strength decreases with the increase of CGFS content. At the same time, the addition of CGFS suppresses the mass conversion rate and improves the thermal stability of PVC composites at high temperature, and the final residual mass reaches 31%, which is 12.7% higher than that of pure PVC. The kinetic analysis of thermal decomposition shows that CGFS promotes the initial degradation of the composites reduces the activation energy of the reaction, and at the same time endows them with higher thermal stability in the high-temperature phase. [ABSTRACT FROM AUTHOR]

Mullite ceramics were fabricated by reaction sintering using bauxite and kaolin as raw materials and Al(OH)3 as an additive. Enhanced mullite ceramic performance was achieved by optimizing sintering temperature and amount of added Al(OH)3. Results show that higher amount of Al(OH)3 led to increased mullite content. Furthermore, scanning electron microscopy results revealed better interfacial bonding due to interlocking structures of columnar mullite at high sintering temperatures (≥ 1500 °C) in samples prepared with the addition of Al(OH)3. This led to significant improvement in bulk density and mechanical strength of mullite ceramics. Thus, compared with samples prepared without Al(OH)3, the addition of Al(OH)3 was beneficial to formation, growth, and development of mullite. The optimum bulk density of 2.75 g/cm3 was achieved with apparent porosity of 0.79%, and the highest flexural strength of 129.25 MPa was achieved in samples with 12 wt.% Al(OH)3 after sintering at 1550 °C for 3 h. [ABSTRACT FROM AUTHOR]

Herein, a 3D SERS substrate based on nickel foam (NF) and silver nanoparticles (AgNPs/NF 3D SERS) was synthesized using vacuum-assisted thermal evaporation deposition. The performance of the AgNPs/NF 3D SERS substrate was investigated using rhodamine 6G (R6G) as a probe molecule at different AgNP deposition levels. The highest sensitivity of the substrate with a limit of detection (LOD) of 10−9 M and an enhancement factor (EF) of 1.56 × 106 was achieved when the optimal amount of AgNPs was reached. Moreover, the use of R6G at 10−6 M concentration as the probe molecule ensured the relative standard deviation (RSD) of 9.2% for the AgNPs/NF 3D SERS substrate, and its SERS performance hardly decreased after 30 days of placement at room temperature, which evidenced that the prepared SERS substrate had favorable stability and repeatability. Finally, the substrate was used to analyze carbendazim in deionized and river water in two different environments. The results revealed that the LOD of CBZ was as low as 10−7 M under both conditions, and there was a good linear relationship between the CBZ concentration and the SERS signal intensity (R2 = 0.955 and 0.927, respectively), which demonstrated the great potential of AgNPs/NF 3D SERS substrates for pesticide residue identification in practical analysis. [ABSTRACT FROM AUTHOR]

Wettability is an important factor that influences surfactant oil displacement efficiency, where surfactant solutions wet rock surfaces better and have lower interfacial tensions with crude oil, thus enhancing the oil recovery rate. Therefore, understanding the wetting of rock surfaces and selecting suitable surfactant solutions are essential for enhanced oil recovery. In this paper, a self-built system to measure the lateral friction at solid and liquid interfaces was established, and the effects of different types and concentrations of inorganic salt additives on the dynamic wettability of the surfactant solution on the solid surface were studied. A rough silica surface was used to simulate the reservoir environment, and methylene chloride was used as the simulation oil. The experimental results show that when the concentration of sodium dodecyl sulfonate is lower than the critical micelle concentration, the inorganic salt additives (NaCl, Na2SO4, and KCl) affect the surface tension, contact angle, and lateral friction of the solution. As the concentration of the inorganic salt additives increased, the surface tension and contact angle of the solution continuously decreased, the lateral friction of the solution on the simulated silica surface increased, and the wettability of the surfactant solution on the solid surface improved. [ABSTRACT FROM AUTHOR]