Hydrothermal synthesis of copper zirconium phosphate hydrate [Cu(OH)2Zr(HPO4)2·2H2O] and an investigation of its lubrication properties in grease

Preparation of Zirconium Hydrogen Phosphate Coatings on Sandblasted/Acid-Etched Titanium for Enhancing Its Osteoinductivity and Friction/Corrosion Resistance

Background

Sandblasted/acid-etched titanium (SLA-Ti) implants are widely used for dental implant restoration in edentulous patients. However, the poor osteoinductivity and the large amount of Ti particles/ions released due to friction or corrosion will affect its long-term success rate.

Purpose

Various zirconium hydrogen phosphate (ZrP) coatings were prepared on SLA-Ti surface to enhance its friction/corrosion resistance and osteoinduction.

Methods

The mixture of ZrCl₄ and H₃PO₄ was first coated on SLA-Ti and then calcined at 450°C for 5 min to form ZrP coatings. In addition to a series of physiochemical characterization such as morphology, roughness, wettability, and chemical composition, their capability of anti-friction and anti-corrosion were further evaluated by friction-wear test and by potential scanning. The viability and osteogenic differentiation of MC3T3-E1 cells on different substrates were investigated via MTT, mineralization and PCR assays.

Results

The characterization results showed that there were no significant changes in the morphology, roughness and wettability of ZrP-modified samples (SLA-ZrP0.5 and SLA-ZrP0.7) compared with SLA group. The results of electrochemical corrosion displayed that both SLA-ZrP0.5 and SLA-ZrP0.7 (especially the latter) had better corrosion resistance than SLA in normal saline and serum-containing medium. SLA-ZrP0.7 also exhibited the best friction resistance and great potential to enhance the spreading, proliferation and osteogenic differentiation of MC3T3-E1 cells.

Conclusion

We determined that SLA-ZrP0.7 had excellent comprehensive properties including anti-corrosion, anti-friction and osteoinduction, which made it have a promising clinical application in dental implant restoration.

Photodynamic effect of Zirconium phosphate biocompatible nano-bilayers containing methylene blue on cancer and normal cells

Pharmaceutical applications of methylene blue, especially as photosensitizer, have been limited due to its rapid enzymatic reduction in the biological systems. In this study nano-platelet zirconium phosphate was synthesized and its biocompatibility was evaluated. The synthesized material was considered as drug delivery vehicle for methylene blue to enhance the photodynamic therapy efficacy in human breast cancer cells. Zirconium phosphate-methylene blue nano-hybrids were characterized by X-Ray Powder Diffraction (XRPD), Scanning Electron Microscopy (SEM), and Thermo gravimetric Analysis (TGA). Biocompatibility of synthesized nano materials were studied on Hu02 human fibroblast normal cell and MDA-MB-231 human breast cancer cell. The results clarified that ZrP-MB nanoparticles could decrease the dark toxicity of free methylene blue. Photodynamic therapy using zirconium phosphate-methylene blue on MDA-MB-231 human breast cancer was evaluated by MTT assay, colony forming ability assay, AO/EB dual staining and flow cytometry detection of apoptosis. The results suggest that zirconium phosphate-methylene blue nano-hybrids significantly enhance photodynamic therapy efficacy probably via apoptosis cell death mechanism against human breast cancer cells. According to the results, zirconium phosphate nanoparticles could be suggested as a promising nano-carrier for photosensitizer delivery in photodynamic therapy.

In Situ Green Synthesis of the New Sandwichlike Nanostructure of Mn3O4/Graphene as Lubricant Additives

Nanoparticles and two-dimensional (2D) nanosheets are well-investigated as lubricant additives, which can significantly reduce frictional energy consumption. However, the tribological properties of the additives will deteriorate because of the occurrence of aggregation in the lubricant and the difficulty in entering the frictional contact area. In the present work, the new sandwichlike nanostructure of Mn₃O₄ nanoparticles and graphene nanosheets (Mn₃O₄@G) has been developed by an in situ green synthesis method; i.e., the impurities of Mn²⁺ ions in crude graphite oxide as the precursor are directly transferred into Mn₃O₄ precipitate between the graphene sheets. The graphene has a lamellar structure without folds and wrinkles, and the Mn₃O₄ nanoparticles are not only uniformly anchored on the graphene surfaces but also intercalated in the layers of the graphene nanosheets. The Mn₃O₄@G exhibits excellent tribological properties and high stability because of a synergistic lubrication effect between the graphene nanosheets and the Mn₃O₄ nanoparticles. Even at an ultralow concentration (0.075 wt %) and a high temperature of 125 °C, the friction coefficient and the wear depth have been reduced by 75% and 97% compared with base oil, respectively. The synthesis method and the Mn₃O₄@G nanocomposite have significant potential in various tribological applications for saving energy.

Rapid selection of environmentally friendly layered alkaline-earth metal phosphates as solid lubricants using crystallographic data

Lubricating technologies are essential for saving energy and identifying effective, environmentally friendly layered materials that meet the demands of solid lubricants is an important direction. Herein, we probed the relationships between load-carrying capacity and crystal structure. The results showed that increasing the sliding resistance of interlayers using corrugated layers increased the load-carrying capacity of layered solid lubricants. This finding expands on the traditional lubrication mechanism of layered materials. Following the rules, rapid selection of layered potassium magnesium and calcium phosphates (K-LMP and K-LCP) as effective solid lubricants was achieved using crystallographic data and strict filtering criteria. In order to prepare materials suitable for lubrication, the synthesis of K-LMP and K-LCP was optimised. These materials could be utilised in the food, textile or marine machinery industries in the future. The developed method could successfully guide the synthesis of application-oriented materials.

Lubrication Performance of α-Zirconium Phosphates as an Anti-Wear Additive in Vegetable Oil-Based Anhydrous Calcium Grease

Vegetable oil has significant potential as a base oil, and substitute for mineral oil in grease formulation due to its biodegradability, low toxicity and excellent lubrication. This paper studied the development of vegetable oil-based greases with α-Zr(HPO4)2·H2O (α-ZrP) as an additive, exploring base oil influence in tribological behavior. The results demonstrated that the addition of α-ZrP in vegetable-based greases is beneficial to anti-wear property. α-ZrP particles exhibit good performance in anti-wear, friction-reduction and load-carrying capacity, and its tribological performances are better than the normally used molybdenum disulfide and graphite additives. Owing to its superior tribological properties as a vegetable oil-based grease additive, α-ZrP holds great potential for use in environmentally friendly applications in the future.

Tribological Investigation of Layered Zirconium Phosphate in Anhydrous Calcium Grease

The tribological properties of α-zirconium phosphate particles as an additive in anhydrous calcium grease were studied by using an Optimol SRV-V oscillating reciprocating tester and a four-ball tester. Fortunately, α-Zr(HPO4)·H2O (α-ZrP) grease exhibits excellent properties in anti-friction and wear-resistant, load-carrying capacity, and extreme pressure properties. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and 3D analysis show that α-ZrP particles appear to form a protective film allowing increased load capacity and operating frequency of the rubbed pairs. Meanwhile, α-ZrP particles can provide low friction coefficient and wear loss during a long-term test.