Yijun Shi

Facile synthesis of mesoporous carbon nanocomposites from natural biomass for efficient dye adsorption and selective heavy metal removal

Mesoporous carbon with embedded iron carbide nanoparticles was successfully synthesized via a facile impregnation–carbonization method. A green biomass resource, cotton fabric, was used as a carbon precursor and an iron precursor was implanted to create mesopores through a catalytic graphitization reaction. The pore structure of the nanocomposites can be tuned by adjusting the iron precursor loadings and the embedded iron carbide nanoparticles serve as an active component for magnetic separation after adsorption. The microstructure of the nanocomposites was carefully investigated by various characterization techniques including electron microscopy, X-ray diffraction, surface analyzer, magnetic property analyzer and etc. The newly created mesopores are demonstrated as a critical component to enhance the adsorption capacity of organic dyes and embedded iron carbide nanoparticles are responsible for the selective removal of heavy metal ions (Zn2+, Cu2+, Ni2+, Cr6+ and Pb2+). Isotherm adsorption, kinetic study at three different temperatures (25, 45 and 65 °C) and cycling retention tests were performed to understand the adsorptive behavior of the nanocomposites with organic dyes (methylene blue and methyl orange). Together with the preferable removal of more toxic heavy metal species (Cr6+ and Pb2+), these mesoporous nanocomposites show promising applications in pollutant removal from water. The facile material preparation allows convenient scale-up manufacturing with low cost and minimum environmental impact.

Comparative Study of Tribological Properties of Different Fibers Reinforced PTFE/PEEK Composites at Elevated Temperatures

The friction and wear properties of PTFE/PEEK composites filled with potassium titanate whisker (PTW) or short carbon fiber (CF) at elevated temperatures (160, 180, 200, 220, and 240°C), different loads (100 and 200 N), and various sliding velocities (0.7 and 1.4 m/s) were investigated in this article. The results show that the friction coefficient of PTW/PTFE/PEEK composites is more stable and 30% lower than that of CF/PTFE/PEEK composites at various sliding conditions. Moreover, it is found that the wear rate of PTW-filled PTFE/PEEK composites is only 10 to 40% that of CF/PTFE/PEEK composites. The wear rate of PTW/PTFE/PEEK composites is only 20% of CF/PTFE/PEEK composites at 200 N, 1.4 m/s, and 240°C. Scanning electron microscopy (SEM) study reveals that PTW can reduce the adhesive wear of PTFE/PEEK composites.

Non-corrosive and Biomaterials Protic Ionic Liquids with High Lubricating Performance

Achieving non-corrosive and green ionic liquids is a big challenge for the tribologist. A kind of biomaterials-based protic ionic liquids (PILs) was synthesized in this paper. Rapeseed oil, group 1 mineral oil and one commercially available fully formulated gear oil were as used reference to study the property of the synthesized PILs. The copper strip standard corrosion test was employed to study the anti-corrosion property. The boundary lubrication and elastohydrodynamic lubrication performance of the lubricants was studied on an Optimol SRV-III oscillating friction and wear tester, and a WAM (model 11) ball-on-disk test rig, respectively. The lubricating mechanism of the synthesized PILs was also discussed in this paper.

Non-corrosive green lubricants: strengthened lignin–[choline][amino acid] ionic liquids interaction via reciprocal hydrogen bonding

A series of novel green lubricants with dissolved lignin in [choline][amino acid] ([CH][AA]) ionic liquids (ILs) have been synthesized in this work. The effect of lignin on the thermal and tribological properties of the lignin/[CH][AA] lubricants was systematically investigated by means of thermogravimetric analysis, differential scanning calorimetry, and a friction and wear tester. The lignin in [CH][AA] has been demonstrated to be an effective additive to improve thermal stability, reduce the wear rates and stabilize the friction coefficients of lignin/[CH][AA] lubricants. Density function theory calculations on the electronic structure of [CH][AA] ILs reveal the atomic natural charge of ILs and their hydrogen bonding capability with lignin. Moreover, these green lubricants show excellent anti-corrosive properties against commercial aluminum and iron boards. The strong physical adsorption of [CH][AA] ILs onto the steel surface and the reciprocal hydrogen bonding between [CH][AA] ILs and lignin synergistically contribute to the enhanced lubrication film strength and thus the tribological properties of these new lubricants. This work provides a new perspective on utilizing complete bio-products in advanced tribological lubrication systems. In addition, this will open a new application venue for lignin to improve product value in lignocellulosic biomass utilization.

Ionic Grease Lubricants: Protic [Triethanolamine][Oleic Acid] and Aprotic [Choline][Oleic Acid].

Ionic liquid lubricants or lubricant additives have been studied intensively over past decades. However, ionic grease serving as lubricant has rarely been investigated so far. In this work, novel protic [triethanolamine][oleic acid] and aprotic [choline][oleic acid] ionic greases are successfully synthesized. These ionic greases can be directly used as lubricants without adding thickeners or other additives. Their distinct thermal and rheological properties are investigated and are well-correlated to their tribological properties. It is revealed that aprotic ionic grease shows superior temperature- and pressure-tolerant lubrication properties over those of protic ionic grease. The lubrication mechanism is studied, and it reveals that strong physical adsorption of ionic grease onto friction surface plays a dominating role for promoted lubrication instead of tribo-chemical film formation.

La-modified SBA-15/H2O2 systems for the microwave assisted oxidation of organosolv beech wood lignin

In this manuscript, the inuence of organosolv beech wood lignin (LOB) on its oxidative conver- sion to high added-value phenolic aldehydes is discussed. Environmental friendly and low-cost H 2 O 2 was used as the oxygen atom donor. � e catalyst was prepared by immobilizing Lanthanum com- pounds onto the periodic mesoporous channels of siliceous SBA-15. � e activity of the La/SBA-15 was investigated towards oxidation of LOB in the presence of hydrogen peroxide as oxidant with microwave irradiation. Considering the characteristics of LOB, an unexpected low syringaldehyde concentration at 10min of reaction time (1.47 g/L, corresponding to 15.66% yield) was obtained; the other major product was vanillin at 25min (0.78 g/L, i.e., 9.94% yield). � e high reactivity of syringyl nuclei may be pointed out as the main reason for the faster production and degradation of syringaldehyde in oxida- tion. Other low molecular weight phenolic products were found: vanillic acid, syringic acid and minor quantities of aceto-derivatives. � e prole of products concentration with the reaction time of catalytic oxidation with microwave irradiation are shown and discussed with reference to the investigated lignin features. � e mechanism of the microwave catalytic oxidation for LOB under alkaline conditions was proposed.

LA-CONTAINING SBA-15/H2O2 SYSTEMS FOR THE MICROWAVE ASSISTED OXIDATION OF A LIGNIN MODEL PHENOLIC MONOMER

A convenient and efficient application of heterogeneous Lanthanum-containing SBA-15 systems for the microwave assisted oxidation of a lignin model phenolic monomer, 3-methoxy- 4-hydroxybenzyl alcohol, is reported. Environmental friendly and low-cost H2O2 was used as the oxygen atom donor. The catalyst was prepared by immobilizing Lanthanum species on to the periodic mesoporous channels of siliceous SBA-15. Powder X-ray diffraction data and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) revealed that the host retains its hexagonal mesoporous structure after immobilization and most of the lanthanum species are better dispersed in the calcined materials. The surface area and pore size of La/SBA-15 was considerably decreased indicating the intrapore confinement of the Lanthanum species. The activity of the La/SBA-15 was investigated in the oxidation of 3-methoxy-4-hydroxybenzyl alcohol in the presence of hydrogen peroxide as oxidant. 68% conversion of 3-methoxy-4-hydroxybenzyl alcohol to vanillin or other undetectable by-products was obtained after 30 min of reaction under 200W microwave irradiation, compared to a poor 25% degradation after 24 h under conventional heating. The possibility of recycling the catalyst was studied.

Grafting heteroelement-rich groups on graphene oxide: Tuning polarity and molecular interaction with bio-ionic liquid for enhanced lubrication

Two different heteroelement-rich molecules have been successfully grafted on graphene oxide (GO) sheets which were then used as lubricant additives in bio-ionic liquid. The grafting was processed with reactions between GO sheets and synthesized heteroelement-rich molecules (Imidazol-1-yl phosphonic dichloride and 1H-1,2,4-triazol-1-yl phosphonic dichloride, respectively). The modified GO (m-GO) was added into [Choline][Proline] ([CH][P]) bio-ionic liquid, and has been demonstrated effective additive in promoting lubrication. Different characterization techniques have been utilized to study the reaction between GO and the two modifiers. The effect of molecular structure of the modifiers on the rheological and tribological properties of m-GO/[CH][P] lubricants was systematically investigated. Both theoretical calculation and experimental results demonstrated that the introduced heteroelement-rich groups are beneficial to increase the robustness of lubrication film by intensified hydrogen bonding and enhance the lubricant/friction surface adhesion by increased polarity of the m-GO. As a result, the interfacial lubrication could be significantly improved by these newly developed m-GO/[CH][P] lubricants.

Linear Complementarity Framework for 3D Steady-State Rolling Contact Problems Including Creepages with Isotropic and Anisotropic Friction for Circular Hertzian Contact

ABSTRACT In this article, the problem of 3D steady-state rolling contacts with dry friction for circular Hertzian contacts is formulated mathematically as a linear complementarity problem (LCP). The complementarity variables are the traction and the relative slip of contact regions, in which a polyhedral friction law is employed. The present work uses the general expressions describing the surface deformations due to uniform traction over a rectangular area on an elastic half-space to derive the influence coefficient matrix for rolling contact problems. Three possible creepage types—that is, longitudinal, lateral, and spin creepage—are considered in this work. Firstly, the numerical results are verified against the existing numerical solutions and good agreement has been found. Secondly, the anisotropic friction is studied by the verified approach. Some numerical examples are provided to illustrate the current LCP method for both isotropic and anisotropic friction in which the combined effects of the three kinds of creepage on the traction distribution are shown.

A Complementarity Problem–Based Solution Procedure for 2D Steady-State Rolling Contacts with Dry Friction

ABSTRACT The problem of steady-state rolling contact between two cylinders with dry friction was formulated into standard linear complementarity problems (LCPs) using the explicit physical definition. For normal contacts, the complementarity variables are the normal pressure and the gap. For the tangential contact, the traction distribution and relative slip are the variables obtained by solving the LCP. The frictional behavior is assumed to be governed by the Coulomb friction law, and LCP formulations of both similar elastic (Carter problem) and dissimilar elastic rolling contacts are presented in this work. Good agreement was found between the current LCP approach and publicly available software for both the rolling contact of similar elastic and dissimilar elastic cylinders. Moreover, the surface roughness was taken into account in this article by the verified approach. The results show the initial slope of the traction-relative creepage curve decreases as the surface roughness increases.