Influence of Low-pH Beverages on the Two-Body Wear of CAD/CAM Monolithic Materials

The aim of this in vitro study is to evaluate the effect of different acidic media on volumetric wear and surface roughness of CAD/CAM monolithic materials. Forty-eight rectangular specimens were prepared using different CAD/CAM monolithic materials: nanohybrid composite (Grandio Blocks, Voco), resin-based composite (Cerasmart, GC), lithium disilicate (E-Max, Ivoclar), and high-translucency zirconia (Katana STML, Kuraray Noritake). After storage in distilled water at 37 °C for two days, the specimens were tested using a chewing machine with a stainless-steel ball as an antagonist (49N loads, 250,000 cycles). Testing was performed using distilled water, Coca-Cola, and Red Bull as abrasive media. Wear and surface roughness analyses of the CAD/CAM materials were performed using a 3D profilometer and analyzed with two-way analysis of variance and post hoc pairwise comparison procedures. Worn surfaces were examined using scanning electron microscopy. Resin-based materials suffered higher volumetric wear than ceramics (p = 0.00001). Water induced significantly less volumetric wear than the other tested solutions (p = 0.0014), independent of the material tested. High-translucency zirconia showed less surface roughness than all the other materials tested. The selection of monolithic CAD/CAM materials to restore worn dentition due to erosive processes could impact restorative therapy stability over time. Resin-based materials seem to be more influenced by the acidic environment when subjected to a two-body wear test.

A Recyclable, Metal-Free Mechanochemical Approach for the Oxidation of Alcohols to Carboxylic Acids

The oxidation of primary alcohols under mechanochemical conditions in a Spex8000M Mixer/Mill was investigated. To facilitate ease of separation and recyclability, a polystyrene-bound version of a TEMPO catalyst was employed. When paired with Oxone® in a stainless-steel vial with a stainless-steel ball, several primary alcohols were successfully oxidized to the corresponding carboxylic acids. The product was isolated using gravity filtration, which also allowed for the polystyrene-bound TEMPO catalyst to be recovered and reused in subsequent oxidation reactions. Furthermore, it was demonstrated that the size and steric hindrance of the primary alcohol does not hinder the rate of the reaction. Finally, the aldehyde was selectively obtained from a primary alcohol under ball milling conditions by using a combination of non-supported TEMPO with a copper vial and copper ball.

Application of Polishing AISI 316L Stainless Steel Ball Bearing with A Magnetic Abrasive Finishing Process: A Review

Advanced machining process telah terbukti dalam teknologi proses rekayasa untuk surface finishing dan proses material removal, atau dengan proses traditional finishing: fase fundamental, unrestrained, dan permintaan tinggi dalam fase tenaga kerja selama produksi. Finishing abrasif magnetik, pada polishing dalam proses non-konvensional mampu menyelesaikan dengan presisi dengan proses pemesinan yang dikontrol oleh medan magnet dan itu tidak berlaku untuk beberapa proses kompleks di mana teknik penyelesaian konvensional dapat dengan mudah diterapkan. Makalah ini mengulas teknik praktis untuk memoles bantalan AISI 316L ST Ball dengan proses finishing abrasif magnetik untuk menyelesaikan desain permukaan bola eksternal. Parameter input yang berbeda dari proses ditinjau seperti kecepatan elektromagnetik, arus dan tegangan langsung yang diinduksi, kepadatan fluks magnetik, jumlah ukuran partikel abrasif, lingkungan kerja, dan bahan benda kerja. Input yang terjadi untuk proses finishing bantalan bola stainless steel dapat memvalidasi kinerja laju material removal rate dan surface roughness.

UHMWPE Nanocomposite Coatings Reinforced with Alumina (Al2O3) Nanoparticles for Tribological Applications

Due to a growing demand for protecting metallic components from wear and tear, polymer coatings are being extensively researched and developed as one of the most effective and efficient solutions to reduce friction and wear in demanding tribological applications. The present study focuses on developing a polymer nanocomposite coating of ultra-high molecular polyethylene (UHMWPE) reinforced with different loadings (0.5, 3, 5, and 10 wt %) of alumina to protect steel surfaces. Wear tests were conducted on the coated samples using a tribometer with a ball-on-disk configuration, sliding against a 440C hardened stainless steel ball as a counterface to evaluate the wear life and the load-bearing capacity of the developed coatings. Micro-indentation, energy dispersive X-ray spectroscopy, scanning electron microscopy, and optical profilometry techniques were used to characterize the coatings in terms of hardness, dispersion of the nanofillers, morphology, and wear mechanisms, respectively. Results showed that the UHMWPE nanocomposite coating reinforced with 3 wt % and 5 wt % of alumina did not fail, even until 250,000 cycles at a normal load of 12 N and a linear speed of 0.1 m/s, showing a significant improvement in wear resistance as compared to the pristine UHMWPE coating.

Tribological properties of graphene oxide sheets as water-based lubricant additive

Purpose The purpose of this paper is to investigate the tribological performance of graphene oxide (GO) sheets as water-based lubricant additive when ultra-high molecular weight polyethylene (UHMWPE) plates slid against 316L stainless steel ball using a reciprocating tribometre. Design/methodology/approach The factors influencing the tribological performance were considered, including the viscosity of the GO dispersion, normal load, sliding velocity and the roughness of UHMWPE. The surface microstructure and properties of UHMWPE were studied by means of scanning electron microscopy, laser confocal microscopy, Raman spectroscopy and contact angle measurements. Findings The results revealed that the GO dispersion reduced friction and sliding-wear. The surface images of the wear UHMWPE plates indicated that GO sheets were prone to adsorption on the surface and form a thin physical tribofilms at the substrate. Originality/value Based on the experimental findings for the evolution of the microstructure morphology and the development of subsurface cracks, less debris and cracking can be observed in the UHMWPE plates lubricated by GO dispersion.

Influence of Thermal Stress on Simulated Localized and Generalized Wear of Nanofilled Resin Composites

SUMMARY Objective: This study investigated the influence of thermal stress on the simulated localized and generalized wear of nanofilled resin composites. Methods: Six nanofilled resin composites were evaluated and then subjected to a wear challenge of 400,000 cycles in a Leinfelder-Suzuki (Alabama) wear simulation device after 24 hours of water storage (24-hour group) and 24 hours of water storage and 10,000 thermal cycles (TC group). Simulated localized wear was generated using a stainless-steel ball bearing, and simulated generalized wear was generated using a flat-ended stainless-steel cylinder. Wear testing was accomplished in a water slurry of polymethyl methacrylate beads. Simulated localized and generalized wear was determined using a noncontact profilometer (Proscan 2100) in conjunction with Proscan and AnSur 3D software. Results: Wear was significantly different (p<0.05) among the resin composites for both simulated localized and generalized wear of either the 24-hour group or the TC group. The simulated localized wear of the TC group was significantly greater than that of the 24-hour group; however, the simulated generalized wear of most of the resin composites of the TC group was not significantly different from that of the 24-hour group. Conclusion: The simulated localized and generalized wear of nanofilled resin composites is material dependent. The simulated localized wear of nanofilled resin composites appears to be influenced by thermal stress, whereas this effect is not as apparent in simulated generalized wear testing.