Search

This study introduces a stable, water-based graphene nanoplatelets (GNPs) nanofluid as a sustainable cutting fluid for grinding Ti-6Al-4V alloy under minimum quantity lubrication (MQL). Using ethanol and sodium deoxycholate (SDOC) surfactant, the dispersion stability of GNPs in water was remarkably extended from 1 h to 57 days. This novel nanofluid formulation enhances wettability, thermal conductivity, and tribological properties. Grinding tests showed a 0.35 mg/mL water-GNPs concentration reduced grinding forces by 74.44 % and 33.37 % compared to dry and conventional flood lubrication, respectively, while improving surface roughness. Raman spectroscopy confirmed graphene's presence on the machined surface, highlighting the potential of water-GNPs nanofluids as an eco-friendly alternative to traditional metalworking fluids, enhancing sustainability in manufacturing. [ABSTRACT FROM AUTHOR]

Abstract Metallic implant materials are biomaterials that have experienced major development over the last fifty years, yet some demands posed to them have not been addressed. For the osseointegration process and the outcome of endosseous implantation, it is crucial to reduce the stress shielding effect and achieve sufficient biocompatibility. Powder metallurgy (PM) was utilized in this study to fabricate a new type of titanium (Ti) + magnesium (Mg) bioactive composite to enable stress-shielding reduction and obtain better biocompatibility compared with that of the traditional Ti and Ti alloys used for dental implants. Such composites are produced by well-known cost-effective and widely used PM methods, which eliminate the need for complex and costly Ti casting used in traditional implant production. The relation between the microstructure and mechanical properties of as-extruded Ti + (0–24) vol% Mg composites was investigated with respect to the Mg content. The microstructure of the composites consisted of a biodegradable Mg component in the form of filaments, elongated along the direction of extrusion, which were embedded within a permanent, bioinert Ti matrix. As the Mg content was increased, the discrete filaments became interconnected with each other and formed a continuous Mg network. Young's modulus (E) of the composites was reduced to 81 GPa, while other tensile mechanical properties were maintained at the values required for a dental implant material. The corrosion behavior of the Ti + Mg composites was studied during immersion in a Hank's balanced salt solution (HBSS) for up to 21 days. The elution of Mg pores formed at former Mg sites led to a further decrease of E to 74 GPa. The studied compositions showed that a new Ti + Mg metallic composite should be promising for load-bearing applications in endosseous dental implants in the future. [ABSTRACT FROM AUTHOR]

• Characteristics of milled surface of carbon fiber-reinforced polyetheretherketone were predicted. • Fractal dimension and surface roughness were predicted as functions of cutting speed, cutting width, feed per tooth, and orientation of fibers. • A hybrid machine learning model was developed. • Adaptive network-based fuzzy inference system was optimized by a gazelle optimizer. • The developed model was compared with other well-established models. Motivated by the nonlinear behavior of composite materials under different machining operations, this work aims at developing an optimized artificial intelligence model to predict milled surface characteristics of carbon fiber-reinforced polyetheretherketone (CFRPEEK). The milling operations were carried out under high-speed dry-cutting conditions. The developed model was employed to predict fractal dimension and surface roughness as functions of cutting speed, cutting width, feed per tooth, and orientation of fibers. The model is composed of an adaptive network-based fuzzy inference system (ANFIS) optimized by a gazelle optimizer (GO). The performance of the model was compared with five other optimized ANFIS models. ANFIS-GO showed outperformance compared with other models to predict milled surface characteristics. The root-mean-square deviation and determination coefficient of predicted data by ANFIS-GO compared with experimental ones are 0.002 and 0.911 for fractal dimension and 0.129 and 0.998 for surface roughness, respectively. [ABSTRACT FROM AUTHOR]

This article presents the outcomes of a recent study carried out among engineering professionals and academics in Egypt to propose a criteria-based energy efficiency rating system for existing buildings. It discusses the use of a multiple criteria decision making technique, namely the Analytic Hierarchy Process (AHP), for developing the weights of the proposed rating system criteria, and generally reviews the use of AHP to develop building energy rating systems. While the AHP approach of criteria weighting was applied in other countries, the present study distinctively applied it to developing a proposed rating system for existing buildings in Egypt. In this study, nine energy rating criteria were identified by thoroughly comparing and analyzing internationally established green building / sustainability rating systems for existing buildings such as LEED, BREEAM, Green Globes, Energy Star, IGBC and Pearl rating system for Estidama. A survey was then conducted to collect the opinions of Egyptian engineering professionals regarding the relative priority of the identified criteria, and to determine, according to the opinions of participants, which criteria are mandatory and which are optional for existing buildings seeking to become ‘greener’. Using AHP, weights were developed for the optional criteria, representing their relative importance. Based on the performed analysis, the resulting rating criteria are: one mandatory prerequisite, which is the Minimum Energy Performance, and eight optional credits with descending relative weights, which are: Use of Renewable Energy Sources, Building Envelope Efficiency Strategies, Use of Energy Efficient Appliances and Equipment, Building Systems Automation and Controllability, Eco-friendly Refrigerants & Fire Suppression Systems, Operation and Maintenance Practices, Metering and Sub-metering of Building, zones and systems and finally Building-related Transportation Impact. [ABSTRACT FROM AUTHOR]

Conventional machining lubricants pose environmental hazards and increase production costs. This study addresses this challenge by investigating nanodiamond composite (NDC) coatings deposited on WC–Co substrates as a lubricant-free alternative for sustainable machining. The NDC films show superior hardness (65 GPa) compared to the substrate (22 GPa) and enhanced adhesion (HF2). The NDC's unique self-lubrication results in a low and stable friction coefficient (COF ≤ 0.095) and exceptional wear resistance (7.45 × 10−8 mm3/N·m) in dry tesing against Al 2 O 3 counter-body. Compared to CVD diamond, NDC coatings show a 47.8 % reduction in COF and a 31.65 % enhancement in wear resistance, promoting environmentally friendly machining practices. • Eco-friendly CAPD deposits 10 μm thick NDC films on WC−Co at 3.5 μm/h rate. • High-performance NDC films boast 65 GPa hardness and 688 GPa Young's modulus. • NDC films show superior adhesion compared to CVD diamond (HF2 vs. HF6). • NDC maintains stable, low friction (0.095 CoF) against Al 2 O 3 in dry conditions. • NDC films exhibit wear resistance (7.45 × 10−8 mm3/N·m) for harsh environments • NDC coatings reduce COF by 47.8 % and enhance wear resistance by 31.65 % vs diamond. [ABSTRACT FROM AUTHOR]

Conventional cutting fluids cannot fit the principles of green manufacturing in terms of cost, energy-saving, environmental and health impacts. Therefore, it is planned to develop high-performance cutting fluids based on biodegradable, health-friendly nanofluids that exhibit sufficient lubrication and cooling properties. Palm oil-based nanofluid containing different percentages of graphene nanoplatelets (GNPs) were prepared and evaluated utilizing the Minimal quantity lubrication (MQL) mode. The cutting, tribological and microstructure tests revealed that GNPs with the content percentage of 0.1 wt% decreased the specific grinding energy by 91.78% compared to dry cutting. Furthermore, the palm oil/0.1 wt% GNPs based nanofluid could lessen the specific cutting energy by 80.25% compared to commercially high-performance Acculube LB2000 because of the sharp reduction in the friction coefficient. Image 1 • The proposed nanofluid saved the energy by 91.78% compared to dry cutting. • The proposed nanofluid saved the specific energy by 80.25% compared to LB2000. • Cutting force is decreased by the action of palm oil-GNPs/MQL lubrication strategy. • The surface quality is improved by palm oil-GNPs/MQL lubrication strategy. • The friction coefficient of the sliding tribo-pairs is reduced by the nanofluid. [ABSTRACT FROM AUTHOR]

Fused silica is a material of great importance in the field of precision optical equipment due to its excellent optical properties, e.g. photolithography, laser fusion devices, etc. However, the material's inherent hardness and brittleness render it a challenging material to process. Therefore, an enhanced precision lapping technique was proposed, i.e., a synergistic integration of mechanical and mechanochemical lapping processes. Firstly, a synergistic lapping tool with an outer layer of porous diamond abrasive and an inner layer of CeO 2 abrasive was fabricated by hot press forming method. The reduction of layer thickness due to abrasion and detachment of the porous diamond abrasive layer was analyzed, and the lapping mechanism of porous diamond on fused silica materials was revealed. The surface creation mechanism of the CeO 2 abrasive layer on fused silica material was analyzed by molecular dynamics simulation and the results were validated by enhanced precision lapping experiment. The results demonstrated that the surface atoms of fused silica are removed in a 'remote disordered' manner by conventional diamond abrasive grains, whereas the surface atoms of fused silica are removed in a 'proximally ordered' manner by the fine porous diamond abrasive grains through the micro-multi-flute cutting. Consequently, the grinding of a porous diamond abrasive layer can significantly reduce the processing damage, with the surface roughness of the lapping Ra reaching 199 nm. The lapping of CeO 2 induces the formation of an oxygen bridge on the surface of fused silica, which then produces bending vibration. This is followed by the adsorption and diffusion of oxygen atoms, which form the -Ce-O-Si intermediate with the oxygen atoms shared with the fused silica. This process results in the formation of CeSiO 3 and CaSiO 3 compounds. The final surface quality with a surface roughness of Ra 21 nm was obtained by mechanochemical lapping of the cerium oxide abrasive layer. The single mechanical-mechanochemical composite ultra-precision lapping process provides technical support for the efficient and low-damage processing of hard and brittle components. [ABSTRACT FROM AUTHOR]

Background: Without clear evidence, selecting among the existing immunotherapeutic options for warts remains challenging.Objective: Through network meta-analyses, we aimed to evaluate the comparative efficacy of different intralesional immunotherapeutic modalities.Methods: We included randomized controlled trials comparing intralesional immunotherapeutic modalities to cryotherapy, placebo, or imiquimod. All outcomes were presented as odds ratios (ORs) with 95% confidence intervals. Both conventional and network meta-analyses (with a frequentist approach) were conducted on R software. The P-score was used to rank different treatments.Results: Network meta-analysis of 17 randomized controlled trials (1676 patients) showed that PPD (purified protein derivative vaccine, OR 39.56), MMR (measles, mumps, rubella vaccine, OR 17.46) and interferon β (OR 15.55) had the highest efficacy in terms of complete recovery at the primary site compared with placebo. Regarding complete recovery at the distant site, autoinoculation (OR 79.95), PPD (OR 42.95), and MMR (OR 15.39) were all statistically superior to placebo. According to the P-score, MMR was more effective than other modalities in reducing the recurrence rate at the same site.Limitations: Relatively small sample size in some comparisons and variability in baseline characteristics.Conclusion: PPD and MMR were the most effective in achieving complete primary and distant recovery (along with autoinoculation for distant recovery) and reducing the recurrence rate at the same site compared with cryotherapy and other immunotherapeutic modalities. [ABSTRACT FROM AUTHOR]

The calcium fluoride (CaF 2) component has excellent light transmission and a high laser damage threshold in the UV band, and thus is a potentially ideal material for high-power laser facility. However, the low-damage surface is difficult to attain via the existing processing technologies due to its brittleness, especially the dissociation property of the (111) surface. We innovatively propose H 2 O(g) plasma-assisted porous diamond abrasive lapping technology to achieve low-damage and high-precision surface processing of CaF 2 component, which means that the CaF 2 component is modified first and then the softened modified layer is removed by the porous diamond abrasive lapping. The H 2 O(g) plasma modification mechanism was elucidated through a combination of molecular dynamics simulation and experiment and comparison with H 2 O(g) plasma etching. The modification layer including an oxide layer and a phase change layer was produced by adjusting the plasma processing process (power of 25 W and H 2 O(g) content of 10 ml). Then the modified CaF 2 component was lapped by the porous diamond abrasive tool on the ductile domain layer which is more than the modified layer and less than the sum of the modified layer and plastic domain. When the lapping process parameters were 200 rpm platen rotation speed and 20 N lapping pressure, a surface accuracy of 15.34 nm PV, 2.29 nm RMS (φ1 mm) was obtained. This study provides technical support for the low-damage processing of CaF 2 component. [ABSTRACT FROM AUTHOR]

This study investigates Nanofluid Minimum Quantity Lubrication (NMQL) efficiency in grinding hard-to-cut materials by incorporating graphene and Al 2 O 3 nano-additives into oleic acid-based nanofluids. Varied concentrations and ratios were examined, analyzing thermal conductivity, viscosity, and contact angle. NMQL assessment covered grinding force, specific grinding energy, temperature, surface quality, wear rate, and friction coefficient. Hybrid nanofluids displayed superior lubrication. At 1 wt% nano additives concentration, minimum specific grinding energies, friction coefficients, and friction test temperature increments were reduced by 73.92 %, 46.57 %, and 65.69 %, respectively in comparison with dry conditions. Optimal surface quality for ZrO 2 and Ti-6Al-4V workpieces emerged at 2 wt% and 3 wt% nano additives concentrations, reducing surface roughness by 60.53 % and 48.66 %, respectively compared to dry cutting. • The Incorporation of nanoparticles improved the thermal conductivity, viscosity, and contact angle of the fluid. • GNPs outperformed Al 2 O 3 in terms of grinding force and grinding temperature reduction. • The Al 2 O 3 /GNPs hybrid nanofluid outperformed the single-phase Al 2 O 3 and GNPs nanofluids. [ABSTRACT FROM AUTHOR]

The micro-grinding of complex meso/micro-components of hard and brittle materials have attracted much attention in recent years. However, little related knowledge was accumulated, and there is a lack of quantitative evaluation of edge chipping damage, which is a major drawback. A theoretical model was established to further analyze the material removal mechanism under the action of single grain, considering the pressure phase transition, dislocation nucleation, and crack growth. An evaluation factor Fr of edge chipping damage was proposed to provide a reference for evaluating micro-grinding quality. Besides, the theoretical results were verified using the nano-scratch test. The experimental results proved that the proposed evaluation factor was an efficient tool to describe and predict micro-grinding quality. [Display omitted] • The micro-grinding mechanism of silicon was analyzed through scratching experiment. • The model was established based on phase transformation-dislocation theory. • The evaluation factor was proposed to determine the edge chipping damage. • The micro-grinding process was optimized through the evaluation factor. [ABSTRACT FROM AUTHOR]

Abstract An aluminum material stabilized with a 1.6 vol% of nanometric Al 2 O 3 dispersoids, named HITEMAL, was fabricated by hot extrusion of a fine atomized Al powder. The Al 2 O 3 dispersoids stemmed from a native Al 2 O 3 films on an aluminum powder surface. An extruded rod of the material was then cold-deformed out into a thin wire by rotatory swaging, hydro extrusion and rolling. Such severely deformed HITEMAL was studied as a prospective outer sheath stabilizer material for MgB 2 core superconductor wires. An emphasis was put on the effect of annealing realized at various temperatures close to the melting point of Al, which is typically applied to form an in-situ MgB 2 superconductive core, on the mechanical and electrical properties of the HITEMAL wire. A systematic investigation was performed of changes to a severely deformed Al grain structure and Al 2 O 3 dispersoids upon annealing the as-deformed wire from 595 to 655 °C for 30 min. Mechanical and electrical properties of the wire were measured at room and cryogenic temperatures. The results showed that the ultrafine-grained Al + 1.6 vol% Al 2 O 3 wire exhibited advantageous properties, and surface integrity after annealing up to 642 °C. It is thus a lightweight material of choice for outer sheaths of MgB 2 superconductors. Graphical abstract Unlabelled Image Highlights • Al wire fabricated from a fine Al powder was studied as outer sheath material for lightweight MgB 2 superconductors. • The effect of annealing realized at 595-655 °C on microstructure, mechanical and electrical properties was investigated. • The as-rolled wire showed ultrafine-grained Al structure with 1.6% of nanometric Al 2 O 3 dispersoids dispersed in Al matrix. • The Al 2 O 3 dispersoids effectively stabilized Al grain structure during annealing, and only minor Al grain growth occurred. • Wires annealed up to 642 °C showed attractive strength and electrical resistivity at room and cryogenic temperatures. [ABSTRACT FROM AUTHOR]

Multilayer graphene (MLG) shows an attractive prospect for the demanding engineering applications. This paper reports the mechanical and tribological properties of MLG reinforced Ni 3 Al matrix composites (NMCs) under dry sliding at varying sliding speed. The hardness and elastic modulus of the NMCs are significantly influenced with MLG content. It is found that the hardness and elastic modulus of the NMCs are found to be increased by increasing MLG content up to 1.0 wt.%, while decreased when MLG content is above 1.0 wt.%. Tribological experiments suggest that MLG can dramatically improve the wear resistance and decrease the friction coefficient of the NMCs. Such marked improvement of wear resistance is attributed to the reinforcing mechanisms of MLG, such as crack deflection and pull-out, and reduction of friction coefficient is related to the formation of a tribofilm on the sliding contact surface. [ABSTRACT FROM AUTHOR]

• A mechanical model of monocrystalline silicon modified-substrate layer structure based on two-dimensional green's function was established. • The correctness of the mechanical model is proved by the nanoindentation-scratch experiment combined with the phase transition of monocrystalline silicon. • Using this mechanical model to draw the stress component contour diagram and interface stress distribution diagram of monocrystalline silicon modified-substrate layer structure, the internal stress state of the material when the surface is stressed is obtained. It provides a reference for the formulation of process parameters of chemical mechanical micro-grinding process. The application and demand of monocrystalline silicon components are becoming more and more urgent for many advanced applications like solar cells. Chemical-mechanical micro-grinding is one of the effective methods for processing such components. However, the theory of chemical-mechanical micro-grinding of monocrystalline silicon has not been fully established, and the mechanism of material removal is still unclear. In this paper, the monocrystalline surface is modified by catalytic modification, resulting in a modified-substrate layer region. A model is proposed to study and analyze force conditions based on Green's function for modified-substrate layer region under the action of normal force and tangential force. The nanoindentation, XPS, and Raman spectroscopy have been done to verify the theoretical model and explore the phase change process of monocrystalline silicon. The results showed that the established mechanical model can predict the stress distribution at the interface between the surface modification layer of the monocrystalline silicon material and the substrate layer. Furthermore, the internal stress distribution of the surface of the monocrystalline silicon material that has undergone surface chemical modification under load can be obtained. Therefore, the recent paper provides a theoretical basis for the optimization of the process of chemical-mechanical micro-grinding of monocrystalline silicon. [Display omitted] [ABSTRACT FROM AUTHOR]