Impact of disintegrants on the structure and disintegration of hydroxypropyl methylcellulose-based amorphous solid dispersion tablets.

Cronobacter sakazakii is a major pathogen that contaminates infant milk powder, which usually attaches to abiotic surfaces in the form of biofilms and causes diseases. However, few in-depth studies have been conducted on the properties of biofilms formed on different abiotic surfaces. Therefore, this study explored the characteristics of biofilm formation by C. sakazakii on commonly used food contact surfaces, including stainless steel (SS), glass (GS), poly(phenylene sulfone) resin (PPSU), and soft silicone (SSI), with a focus on the biofilm formation ability and the biofilms' functional, structural, and compositional properties. Correlation analysis was used to confirm the leading factors affecting C. sakazakii biofilm formation, including surface hardness and stiffness, cell length, and extracellular nucleic acid content. Finally, proteomic analysis revealed menaquinone biosynthesis, amino acid metabolism, SOS response, and transport systems as being crucial for C. sakazakii biofilm formation. This study provides valuable insights for a deeper understanding of the bacterium's biofilm formation.

Compact carbonate stones are widely used in architectural heritage for their aesthetic value and cultural significance, yet their long-term durability in saline environments remains insufficiently understood, particularly when assessed using standard salt crystallization tests developed primarily for porous lithotypes. This study investigates salt-induced deterioration in Portoro limestone, a compact ornamental carbonate extensively employed in historic architecture, considering four commercial varieties representative of heritage applications. Salt crystallization tests were performed using saturated sodium sulphate (Na2SO4) and sodium chloride (NaCl) solutions following the relevant European standard procedure, with the protocol extended to 45 cycles to capture delayed deterioration processes. Both untreated specimens and samples subjected to controlled thermal pre-conditioning at 300 °C and 500 °C were tested to activate latent microstructural weaknesses. Material decay was assessed through mass variation, porosity changes, surface observations, Leeb rebound hardness and ultrasonic pulse velocity measurements. Results demonstrate that deterioration is primarily controlled by salt type and microstructural characteristics rather than by total porosity. Sodium sulphate induced severe internal damage and abrupt structural failure associated with mirabilite crystallization, often following a prolonged phase of apparent stability. In contrast, sodium chloride causes mainly superficial effects with negligible mechanical impact. Thermal pre-conditioning accelerated damage development, while non-destructive techniques revealed internal deterioration well before visible damage occurred. These findings indicate that standard crystallization tests may be inadequate for low-porosity stones and that extended-cycle approaches provide a more reliable framework for durability assessment in saline environments.

The objective of this work is to study the laser quenching process of AISI P20 + S mould steel, focusing on improving surface hardness and wear resistance. AISI P20 + S steel was laser-quenched using temperatures of 1000°C and 1200°C, and laser beam overlap rates of 10% and 25%. The as-received and laser quenched steel was characterized by optical microscopy, scanning electron microscopy, and X-ray diffraction. After laser quenching, nanoindentation and pin-on-disk tests were performed to determine hardness profiles and assess wear resistance, respectively. The hardness at the surface more than doubled compared to the hardness of the untreated steel, confirming the formation of martensite. The 1000°C laser quenching resulted in a depth lower than 700μm, with a surface hardness close to 8 GPa. At 1200°C, the depth increased to nearly 1400μm, and the hardness reached 8-9 GPa, although the thicker oxide layer formed during the laser treatment led to an increase in the wear coefficient and volume. Due to the detachment of oxide layers, the main wear mechanism observed was adhesive. The work carried out confirmed the potential of laser quenching in the surface hardening of mould steels.

ABSTRACT Severe rail wear, particularly side wear on the outer rail of small‐radius curves in metro lines, remains a critical challenge. Moreover, the effect of track factors on the evolution of rail wear remains unclear. To further study the wear mechanisms of small‐radius curved tracks and propose effective mitigation measures, this paper examines the factors that influence rail wear on curved tracks and takes the sensitivity analysis of key parameters on rail wear. This paper establishes a vehicle dynamics model and a rail wear prediction model. The Jendel wheel wear model is employed to analyse the evolution of rail wear. The effects of superelevation, rail profiles, rail cant, rail surface hardness, gauge widening, and curve radius on rail wear were analysed. Rail profile, rail surface hardness, gauge widening, and curve radius significantly affect rail wear. Using CHN60N rail profiles reduces side wear in the outer rail but increases vertical wear on the outer rail. Higher rail surface hardness decreases rail wear. The curve radius has the greatest influence on side wear, with a wear depth variation range of 4.1 mm and a variation sensitivity of 178.5%. The rail profile has the least influence on side wear, with a wear depth variation range of only 0.1 mm and a variation sensitivity of 3%. This paper provides a theoretical foundation for wear mitigation strategies.

Abstract Low-frequency vibration (LFV) assisted metal plastic forming technique has potential since it reduces the interfacial friction and reinforces the surface quality while bearing great loading. In this study, the surface performance of Ti45Nb titanium alloy during low-frequency vibration assisted upsetting (LFVAU) process is investigated. The friction coefficient is calibrated through a comparison between the experimental and simulated barreling degrees under different friction states. The interfacial friction between the specimen and the tool is remarkably decreased through superimposing the oscillation and the reduction is enhanced by increasing the vibration frequency and amplitude. Due to the improvement in lubrication condition and plastic deformability, the surface asperities are flattened and the surface roughness Ra decreases from 2.26 μm to 1.63 μm, with a reduction amont of 27.88%, thus improving the surface quality. The material deformation at the surface is strengthened and the grains are refined when applying the LFV. The surface hardness the LFVAU specimen increases to 230.6 HV, which is 20.98% higher than that of the quasi static upsetting (QSU) specimen. The study shows that the LFV can improve the surface performance of the metallic material, which is of great benefit to the industrial production in aerospace and automobile fields.

The wear performance of BG801 bearing steel under elevated-temperature conditions exerts a decisive influence on the service life and operational reliability of aero-engine bearings. In this study, the vacuum low-pressure carburizing heat treatment technology was employed to perform surface carburization on BG801 bearing steel, and the effect of carburization on the frictional properties of this steel was explored over a temperature range of 25 °C to 400 °C. The results indicate that with the increase in temperature, the friction coefficients of both the uncarburized specimens (hereinafter referred to as BG801-NC) and carburized specimens (hereinafter referred to as BG801-C) are maintained in the range of 0.5~0.8. Compared with BG801-NC, the wear rate of BG801-C is reduced by approximately 50% and exhibits an overall variation tendency of increasing first and then decreasing. At elevated temperatures, BG801-C presents superior wear resistance, which is attributed to the formation of a martensite-carbide composite strengthened layer on the surface of the bearing steel after carburizing treatment, a microstructure that remarkably enhances the surface hardness and wear resistance of the steel. Moreover, the carburized layer also diminishes the thickness of the plastic deformation layer during the friction process, thereby further suppressing the extension of wear damage.

ABSTRACT This study reports the fabrication and characterisation of Al7075-based nano-sized chromium oxide (Cr₂O₃) and iron oxide (Fe₂O₃) particle-reinforced metal matrix composites by the squeeze casting technique. The main aim of the research was to analyse the effect of double ceramic oxide reinforcement at different weight percentages – 3, 5 and 7 wt-% on the microstructural, mechanical, and tribological properties of the composite material against the unreinforced base Al7075 alloy. Squeeze casting was utilised to provide high-density defect-free castings through pressure application during solidification. Microstructural observations indicated even particle distribution and grain refinement in smaller and moderate levels of reinforcement, whereas SEM fractography indicated a shift in fracture mode from ductile towards brittle with increased reinforcement. Tensile strength and hardness were significantly enhanced with increased reinforcement, with the 5 wt-% showing the best performance. The wear rate was considerably reduced with reinforcement owing to enhanced surface hardness and the development of protective tribolayers. The 7 wt-% reinforcement, there was no significant improvement in properties owing to particle agglomeration and slight porosity increase. The results establish that hybrid Cr₂O₃ and Fe₂O₃ reinforcement enhances load-carrying and wear properties of Al7075 with negligible sacrifice in ductility and density.

The impact of microcrystalline cellulose (MCC) on the mechanical, physicochemical, and tribological properties of hemp fabric–reinforced epoxy (HF/Ep) hybrid composites is examined in this work. Different MCC contents were used to construct the composites (0 wt% (M0), 3 wt% (M1), 6 wt% (M2), and 9 wt% (M3)). Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), hardness, impact strength, and three-body abrasive wear testing were used to assess the impacts of MCC integration. The results showed that MCC greatly improved the composites’ toughness and hardness, with impact strength improving by about 83% and Shore D hardness rising from 83 (M0) to 89 (M3). While XRD patterns showed increased crystallinity with increasing MCC content, FTIR examination verified enhanced interfacial contacts between the MCC, hemp fibers, and epoxy matrix. Wear loss was significantly reduced in three-body abrasive wear tests, especially for the M2 composition, which reached a maximum reduction of about 68.6% under extreme loading conditions. Increased surface hardness, greater load transfer, efficient crack deflection, and the development of a protective tribolayer during abrasion were all identified as contributing factors to the improved wear performance. These findings show that the structure-property-wear correlations of HF/Ep composites may be successfully tailored by controlled MCC incorporation, making them appropriate for wear-resistant, lightweight engineering applications.

The purpose of this study is to clarify the mechanical properties of the expanded austenite (S phase) formed in austenitic stainless steel (ASS). A small thin rolled plate of SUS304 with 0.5 mm thickness was used as test sample. The test sample was nitrided by active screen plasma nitriding (ASPN) at low processing temperature of 400 °C and 450 °C during 4 hrs. processing time. S phase was formed on the surface of the test sample. The surface hardness of ASPN sample was higher than that of untreated sample. Furthermore, tensile tests and fracture surface observations revealed that the tensile strength was also improved compared to untreated samples.

Conventional plasma nitriding can induce defects due to direct plasma formation on the surface of the treated material. To address this issue, the screen-assisted direct current plasma nitriding (S-DCPN) method was developed, which generates plasma on both the sample and a surrounding screen, thereby reducing such defects. In this study, S-DCPN was applied to ferritic stainless steel (SUS430) using austenitic stainless steel (SUS304) as the screen material. Treatments were performed at 633 K for 15 hours under gas pressures of 200 and 600 Pa, with varying gas compositions of 75 % N 2 – 25 % H 2 , 50 % N 2 – 50 % H 2 , and 25 % N 2 – 75 % H 2 . To evaluate the effects of gas composition and pressure, a range of analyses was conducted, including X-ray diffraction (XRD), cross-sectional microstructural observations, glow discharge optical emission spectrometry (GD-OES), hardness testing, and corrosion testing. The results revealed the formation of the α N phase, a supersaturated solid solution of nitrogen in ferrite, under all conditions. Nitrogen diffusion and surface hardness increased with higher hydrogen content, and corrosion resistance was notably enhanced under the 25 % N 2 – 75 % H 2 condition. These findings demonstrate the effectiveness of S-DCPN in improving the surface properties of ferritic stainless steel while maintaining or enhancing corrosion resistance.

Changes in the cytocompatibility, surface hardness, and surface topography of 3-dimensional-printed clear aligners after clinical use.

Two- and three-body wear of BPA-free resin composites.

This study investigates how four cooling media SAE 40 oil, palm oil, waste palm oil and water affect the surface hardness and impact toughness of pack carburizing quenching ASTM A36 steel. While conventional quenching practices rely on petroleum based oils or water, the use of waste palm oil as an alternative cooling medium has not been widely investigated. The carburizing media is a mixture of charcoal powder and BaCO3 as energizer. It was conducted at 900 °C with a soaking time for 2-6 h, followed by quenching in each cooling media. The results indicate that both hardness and toughness are strongly dependent on the cooling media. Water produced the highest hardness, reaching up to 616 HV at 6 h, but caused a substantial reduction in impact toughness approximately 60% lower than the oil based cooling media. Waste palm oil generated slightly lower hardness yet provided a more desirable hardness and toughness balance due to its more moderate cooling rate. Palm oil yielded intermediate hardness and toughness, while SAE 40 oil resulted in the lowest hardness but the highest toughness. Significantly, waste palm oil produced a balanced hardening response, offering higher toughness than water and a stronger hardening effect than palm oil and SAE 40 oil, suggesting its potential as a sustainable, technically advantageous option. This work is novel in establishing waste palm oil as a viable, eco friendly cooling media that can improve the functional reliability of pack carburizing quenching ASTM A36 steel components.

Development of resin-modified glass ionomer functionalized with polyvalent metals and cyclic phosphates: Evaluation of mechanical properties, fluoride release, antibiofilm activity and cytotoxicity.

Interfacial structures on the nanoscale are crucial for a wide field of applications ranging from biological membranes in life sciences through organic solar cells and industrial coatings in soft matter to hard matter structures. The latter include thin film coatings and materials such as magnetic nanoparticles and topological structures like magnetic skyrmions. Advancing such application rests on the ability to reveal structures at hidden interfaces at different length scales. Techniques like scanning probe microscopy provide information about surface structures and topology with high precision, but are limited to the probe interacting with the surface. The high penetration power of neutrons, their sensitivity to light elements and the capability to probe magnetic structures makes grazing incidence small-angle neutron scattering (GISANS) a valuable, but yet underexploited, tool for organic materials and condensed matter systems and, in particular, to study buried interfaces. Together with specular and off specular neutron reflectometry, interfacial structures on length scales from a few nanometres up to micrometres can be revealed. Apart from giving a comprehensive introduction to the GISANS technique, we will highlight the importance of interfacial layer structures in different fields and how recent developments in the surface techniques have revealed common features in a range of systems. This includes the formation, structure, and topology of the interfaces of and between materials, which are controlled by the same fundamental molecular and colloidal forces.

This study investigates the tribological properties of 17-4PH martensitic stainless steel modified by plasma-based low-energy nitrogen ion implantation to enhance its surface hardness and wear resistance. The steel was nitrided at temperatures of 350 °C, 450 °C, and 550 °C for 4 h, and the resultant layers were characterized with respect to microstructure, hardness, and composition. Tribological tests were performed using a ball-on-disk tribometer under dry sliding conditions against an Si3N4 ceramic ball, with normal loads of 2-8 N and sliding speeds of 0.15-0.60 m/s. The results demonstrate that the nitrided layer thickness increased from 11 μm to 27 μm and the surface nitrogen concentration rose from 29.7 at.% to 33.1 at.% with increasing temperature, accompanied by an increase in nanocrystallite size from 2 nm to 15 nm and enhanced hardness from 13.51 GPa to 15.66 GPa. All nitrided layers exhibited significantly improved wear resistance relative to the unmodified steel. The layer nitrided at 450 °C demonstrated optimal performance due to a refined nanostructure and minor CrN that enhance plastic deformation resistance and facilitate oxide film formation. While, the 350 °C treated layer exhibits diminished thickness and reduced hardness, and the 550 °C treatment induces excessive CrN precipitation and micro-cracking, consequently compromising both toughness and wear resistance.

This work investigates the effect of pre-nitriding treatment before vacuum carburizing on the carburizing efficiency of 20CrMnTi steel. The results show that pre-nitrocarburizing significantly enhances the vacuum carburizing efficiency of 20CrMnTi steel, refines the microstructure of the carburized layer's martensite, and promotes the precipitation of carbides. At the same carburized layer depth, the hardness and carbon content of the pre-nitrocarburized samples are significantly higher than those of the samples without pre-nitriding. Specifically, the effective hardening depth and surface hardness increase by approximately 0.15 mm and 75 HV, respectively. These improvements are attributed to the formation of loose and porous nanoscale nitride particles on the surface during the pre-nitrocarburizing process, which significantly increases the surface roughness and porosity. This surface morphology facilitates the adsorption and inward diffusion of carbon atoms during the carburizing process. This study provides some inspiration for pretreatment techniques to improve the efficiency of vacuum carburizing.

This study presents the fabrication and optimization of eco-efficient epoxy composites reinforced with ground natural stone fillers, namely pebble, sandstone, and marble, at loadings of up to 15.6 wt.%. Low content of a bio-based modifier, modified castor oil (MCO ≈ 0.5 wt.%), is incorporated to improve filler dispersion, processing behavior, and matrix-filler interfacial compatibility. The composites are designed to enhance mechanical, thermal, and dielectric performance using low-cost, abundant, and environmentally sustainable constituents. An experimental optimization approach is employed to evaluate and optimize bulk density, Shore D hardness, thermal conductivity, dielectric constant, and tensile strength. The results demonstrate that pebble-reinforced composites exhibit the highest tensile strength (≈30 MPa) and surface hardness (≈82 Shore D), which are attributed to the angular morphology and high intrinsic rigidity of pebble particles. Marble-filled systems show superior thermal stability, with residual mass increasing from approximately 2.5 wt.% for neat epoxy to over 11 wt.% at 550 °C, owing to the thermally stable calcium carbonate phase. In contrast, sandstone-reinforced composites exhibit the lowest dielectric constant (≈3.2), indicating enhanced electrical insulation capability. Fourier-transform infrared spectroscopy (FTIR) results confirm that the epoxy network structure is preserved upon filler incorporation, while MCO promotes improved interfacial interactions through physical interactions. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) reveal enhanced thermal resistance, reduced microvoid formation, and improved filler-matrix adhesion at optimal filler contents of approximately 3.5 wt.%.

The object of this study is a medium-carbon gear steel commonly used for sprockets and gears in mechanical drive systems. The problem to be solved in this study is the limited understanding of the integrated effect of austenitizing temperature, sprocket rotation speed, and quenching medium on surface hardness and microstructural evolution, that makes parameter selection of flame hardening in industry does not optimum. The experiments were conducted by heating the medium-carbon gear steel into austenitizing temperatures of 850°C and 900°C, rotation speeds of 1503 rpm and 1977 rpm, and using water and oil as quenching medium. Specimens were evaluated by using Rockwell hardness tester (B scale) and optical microscopy. The result of this study reveals that the highest surface hardness of 120.08 HRB is achieved at austenitizing temperature of 900°C, rotation speed of 1503 rpm, and quenched by using water. This is also supported by the result of microstructural observations which show very fine martensite. The surface hardening is most affected by quenching medium, while rotation speed has no significant effect on the hardness enhancement. At austenitizing temperature of 900°C, the steel has been in austenite phase, so the increasing rotation speed reduces hardness due to excessive heat input and austenite grain coarsening. The distinctive feature of these results lies in the identification of interaction mechanisms between thermal exposure time and cooling rate. The findings can be practically applied to medium-carbon gear steel components subjected to controlled flame hardening with continuous rotation at speeds of 1503–1977 rpm, followed by water or oil quenching, particularly in small- and medium-scale industrial heat treatment of gears and sprockets