Milled Samples Research Articles

Effect of Mechanical Surface Treatment on Shear Bond Strength of Orthodontic Brackets to 3D Printed and Milled CAD/CAM Provisional Materials: An In Vitro Study

The aim of the study is to assess the impact of mechanical surface treatments on the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensional (3D) printed and milled CAD/CAM provisional materials. Sixty cylindrical samples were fabricated for each provisional material. Samples were treated with one of the following surface treatments: aluminum oxide airborne particle abrasion, diamond bur rotary instrument roughening, and phosphoric acid etching (control). Stainless steel brackets were bonded to the samples, and then SBS was tested using a universal testing machine. SEM and digital microscopy were utilized to examine the bonding interface and the failure modes. Two-way ANOVA, one-way ANOVA, Tukey’s HSD, and independent sample t-tests were used for statistical analysis. Results revealed significant differences in SBS between 3D printed and milled samples and significant differences in SBS among most surface treatments, with rotary instrument roughening resulting in the highest values for 3D printed, while airborne particle abrasion leading for milled samples. Digital microscopy indicated that more adhesive remained on 3D-printed samples. SEM analysis revealed varying surface roughness across treatments. Based on the findings of this study, it can be concluded that different surface treatments improve the bonding of orthodontic brackets to provisional crowns.

Nanocrystalline/Amorphous Tuning of Al-Fe-Nb (Mn) Alloy Powders Produced via High-Energy Ball Milling.

The demand for advanced Al-based alloys with tailored structural and magnetic properties has intensified for applications requiring a high thermal stability and performance under challenging conditions. This study investigated the phase evolution, magnetic properties, thermal stability, and microstructural changes in the Al-based alloys Al82Fe16Nb2 and Al82Fe14Nb2Mn2, synthesized via mechanical alloying (MA), using stearic acid as a process control agent. The X-ray diffraction results indicated that Al82Fe16Nb2 achieved a β-phase solid solution with 13-14 nm crystallite sizes after 5 h of milling, reaching an amorphous state after 10 h. In contrast, Al82Fe14Nb2Mn2 formed a partially amorphous structure within 10 h, with enhanced stability with additional milling. Magnetic measurements indicated that both alloys possessed soft magnetic behavior under shorter milling times (1-5 h) and transitioned to hard magnetic behavior as amorphization progressed. This phenomenon was associated with a decrease in saturation magnetization (Ms) and an increase in coercivity (Hc) due to structural disorder and residual stresses. Thermal stability analyses on 10 h milled samples conducted via differential scanning calorimetry showed exothermic peaks between 300 and 800 °C, corresponding to phase transformations upon heating. Post-annealing analyses at 550 °C demonstrated the presence of phases including Al, β-phase solid solutions, Al₁3Fe₄, and residual amorphous regions. At 600 °C, the Al3Nb phase emerged as the β-phase, and the amorphous content decreased, while annealing at 700 °C fully decomposed the amorphous phases into stable crystalline forms. Microstructural analyses demonstrated a consistent reduction in and homogenization of particle sizes, with particles decreasing to 1-3 μm in diameter after 10 h. Altogether, these findings highlight MA's effectiveness in tuning the microstructure and magnetic properties of Al-Fe-Nb (Mn) alloys, making these materials suitable for applications requiring a high thermal stability and tailored magnetic responses.

Comparative Analysis of Modern 3D-Printed Hybrid Resin-Ceramic Materials for Indirect Restorations: An In Vitro Study.

The study investigated the impact of aging on surface roughness, color stability, and biocompatibility of hybrid resin-ceramic materials. A total of 225 specimens were produced from three three-dimensional (3D)-printed (HarzLabs Dental Sand Pro (HL), BEGO VarseoSmile Crown plus (BV), Voco V-Print c&b temp (VV)) and one milled material (Voco Grandio Blocs (VG)). Specimens were grouped into untreated, polished, and glazed surfaces. 5000 thermal cycles simulated aging. Surface roughness and color stability were analyzed, and surface topography was observed using scanning electron microscopy (SEM). Biocompatibility was evaluated with L929 cells. Surface roughness differed significantly between untreated and other groups, with no changes before and after artificial aging. Untreated milled samples were significantly smoother than 3D-printed ones. SEM analysis revealed roughest surfaces in untreated 3D-printed specimens. Polished and glazed specimens were smoother than untreated ones. Color values showed significant differences between untreated and treated/aged groups. No material showed cytotoxicity. In summary, untreated VG was smoother than 3D-printed materials, but polishing and glazing reduced roughness to levels comparable to VG. Surface treatments induced color changes, with glazing causing more changes than polishing. Aging affected color stability and biocompatibility but not surface roughness. All materials showed acceptable color changes and good biocompatibility.

Solubility and magnetic properties of Ag−Co−Si alloy synthesized by mechanical alloying and annealing

AbstractThis present work concerns the effect of ternary addition of non‐metallic and diamagnetic silicon on the metastable solubility of the immiscible silver‐cobalt system during the course of ball milling, annealing of the ball milled samples and the corresponding magnetic properties. It should be noted that silicon has a smaller goldsmidt radius (111 pm) than silver (144 pm) and silicon+4 has more valence electrons than silver+1. Keeping the objectives of the current study in mind, silicon may thus be considered as an option for ternary addition, in contrast to metallic components. An attempt has been made to examine the phase changes that occurred in the 50 silver‐40 cobalt‐10 silicon (atom percent) system during ball milling and the subsequent isothermal annealing of the ball milled product. Phase evolution during mechanical alloying and isothermal annealing is identified by means of x‐ray diffraction, differential thermal analysis, high resolution transmission electron microscopy and magnetic measurements. The addition of silicon facilitates cobalt‘s formation of a metastable alloy with copper after 50 hours of ball milling. Annealing significantly improves the magnetic characteristics of materials that have been ball milled; the optimal combination of magnetic properties was obtained after an hour of annealing at 550 °C.

Implications of crystal disorder on the solid-state stability of Olanzapine

Mechanical perturbations of drug during solid pharmaceutical processing like milling can often generate crystal disorder posing serious implications to drug's stability. While physical changes like amorphization, recrystallization, polymorphism of the disordered drugs are extensively studied and reported in the literature, the propensities and inter-dependencies of recrystallization and degradation propensities of disordered drugs have seldom received deep attention. Previous investigations from our lab have explored some of these interplays, aiming to develop predictive stability models. As a follow-up, the implication of crystal disorder on the oxidative instability of Olanzapine (OLA) during accelerated storage is investigated in this work. Cryo-milling OLA at varied time intervals generated different extents of crystal disorder. The milled samples were characterized using calorimetry and infrared (IR) spectroscopy to examine the physical state, while their degradation was evaluated using ultra-performance liquid chromatographic methods. An X-ray amorphous OLA sample was generated by melt-cooling, and used as an amorphous reference. The crystallinity of the cryo-milled samples was quantified using a partial least square regression model based on ATR-FTIR spectroscopic data. The cryo-milled samples were exposed to different accelerated stability conditions along with crystalline (unmilled) and quench cooled (amorphous) samples, serving as controls. At periodic intervals, samples were removed from the stability storage, and analyzed using ATR-FTIR and UPLC methods to quantify the crystallinity- and degradation extents. A positive relation was witnessed between the initial degree of crystallinity and degradation kinetics of the disordered OLA samples during stability storage indicating a strong dependency of degradation on the disorder contents for such disordered solids. The results obtained in this study can potentially explain consequences of inter-batch variations of drugs during stability storage, in addition to enabling de-risking strategies towards eliminating solid drug instabilities in product development.

Evaluation of Antifungal Activity of Oil Extracted from Two Varieties of Tomato Seeds against Fungal organisms Causing Rot in Tomato Fruits

Evaluation of the antifungal activity of oil extracted from two varieties of tomato seeds against fungal organisms causing rot in tomato fruits was carried out in Makurdi. The presence of decay caused by Fungi on tomatoes results in postharvest losses. Riogrande and Roma VF tomato seeds were washed, dried at 50˚C for 3 days in an oven, and milled. With the aid of a soxhlet extractor, using n-Hexane at 40-60°C for 6 hours, oil was extracted from the milled samples. Analysis of the oil revealed that oil is stable, translucent, and highly penetrating. A portion of tomatoes showing signs and symptoms of rot were detached, sterilized, and placed in a medium of Potato Dextrose Agar for one week for fungal growth. Fungi growths were identified macroscopically and microscopically and matched with standards. Fungi such as Curvularia affinis, Aspergillus flavus, Aspergillus niger, and Penicillium waksmanii were isolated. The pour plate method was used for fungi growth in the presence of the oil extracted. At days 3-7, the Riogrande seed oil media inhibit the growth of the isolated fungi with Aspergillus niger having the highest inhibition ranging from 1.333 to 1.733 mm and the Roma seed oil media inhibit the growth of Curvularia affinis with the highest inhibition ranging from 1.266 to 1.950 mm and while the control ranged from 3.533 to 8.100 mm. The results showed that numerous fungi are involved in rot of tomatoes and the extracted oil contains phytochemicals that are responsible for inhibiting fungal growth in the plates.

Investigation of the Influence of Copovidone Properties and Hot-Melt Extrusion Process on Level of Impurities, In Vitro Release, and Stability of an Amorphous Solid Dispersion Product.

Hot-melt extrusion (HME) is a widely used method for creating amorphous solid dispersions (ASDs) of poorly soluble drug substances, where the drug is molecularly dispersed in a solid polymer matrix. This study examines the impact of three different copovidone excipients, their reactive impurity levels, HME barrel temperature, and the distribution of colloidal silicon dioxide (SiO2) on impurity levels, stability, and drug release of ASDs and their tablets. Initial peroxide levels were higher in Kollidon VA 64 (KVA64) and Plasdone S630 (PS630) compared to Plasdone S630 Ultra (PS630U), leading to greater oxidative degradation of the drug in fresh ASD tablets. However, stability testing (50 °C, closed container, 50 °C/30% RH, open conditions) showed lower oxidative degradation impurities in ASD tablets prepared at higher barrel temperatures, likely due to greater peroxide degradation. Plasdone S630 is suitable for ASDs with drugs prone to oxidative degradation, while standard purity grades may benefit drugs susceptible to free radical degradation, as they generate fewer free radicals post-HME. ASD tablets exhibited greater physical stability than milled extrudate samples, likely due to reduced exposure to stability conditions within the tablet matrix. Including SiO2 in the extrudate composition resulted in greater physical stability of the ASD system in the tablet; however, it negatively affected chemical stability, promoting greater oxidative degradation and hydroxylation of the drug substance. No impact of the distribution of SiO2 on drug release was observed. The study also confirmed the congruent release of copovidone, the drug substance, and Tween 80 using flow NMR coupled with in-line UV/vis. This research highlights the critical roles of peroxide levels and SiO2 in influencing the dissolution and physical and chemical stability of ASDs. The findings provide valuable insights for developing stable and effective pharmaceutical formulations, emphasizing the importance of controlling reactive impurities and excipient characteristics in ASD products prepared by using HME.

High Milling Time Influence on the Phase Stability and Electrical Properties of Fe50Mn35Sn15 Heusler Alloy Obtained by Mechanical Alloying.

Fe50Mn35Sn15 Heusler alloy, obtained by mechanical alloying, was subjected to larger milling times in the range of 30-50 h to study the phase stability and morphology. X-ray diffraction studies have shown that the milled samples crystallise in a disordered A2 structure. The A2 structure was found to be stable in the milling range studied, contrary to the computation studies performed on this composition. Using Rietveld refinements, the lattice parameter, mean crystallite size, and lattice strain were computed. The nature of the obtained phases by milling was found to be nanocrystalline with values below 50 nm. A linear increase rate of 0.00713 (h-1) was computed for lattice strain as the milling time increased. As the milling time increases, the lattice parameter of the cubic Heusler was found to have a decreasing behaviour, reaching 2.9517 Å at 50 h of milling. The morphological and elemental distribution-characterised by scanning electron microscopy and energy-dispersive X-ray spectroscopy-evidenced Mn and Sn phase clustering. As the milling time increased, the morphology of the sample was found to change. The Mn and Sn cluster size was quantified by elemental line profile. Electrical resistivity evolution with milling time was analysed, showing a peak for 40 h of milling time.

Hydrocarbons, Hydrogen, and Organic Acids Generation by Ball Milling and Batch Incubation of Sedimentary Rocks

Pulverized rock samples are widely used in laboratory experiments, e.g., to assess microbial or abiotic processes in batch incubation tests. However, it is unclear if ball-milled samples accurately reflect in-situ conditions and if observed processes are affected by by-products artificially generated during the sample preparation procedure. As such, this study examined the effects of dry ball milling on the release of gases, which include C1-C4 hydrocarbons, carbon dioxide (CO2), hydrogen (H2), and low molecular weight organic acids (LMWOAs) from different sedimentary rocks. The experiments involved pulverization using a gas-tight zirconium oxide planetary ball mill followed by wet and dry batch incubation and thermal desorption up to 200 o C. During milling, all sedimentary rocks, except a low organic carbon sandstone sample, yielded methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), H2, CO2, and unsaturated hydrocarbons, e.g., ethene (C2H4). Sandstones only yielded H2, CH4, and CO2. Stable carbon isotope signatures of these products are similar to thermogenic gases. The gases were also detected in subsequent wet incubation experiments (after gases from milling had been removed). Additionally, formate, acetate, and citrate, were detected in all samples except for sandstone. Pyruvate, malate, and succinate were also detected in some samples. Thermal desorption products of powdered limestone, shale, and pyrite concretion samples included organic acids, such as acetate and formate, which were higher in milled samples than in crushed particles (∼1 mm). The original geological thermal maturity of the studied sedimentary rock samples was low (below “oil window”) and, thus, considerably below “gas window”, suggesting that most of the detected gases were generated during ball milling. H2 generated during ball milling may be derived from the reduction of water from fluid inclusion or phyllosilicates, involving the formation of reactive mineral surfaces or radicals. Notably, the concentrations of gaseous hydrocarbons derived from milling are relatively high and comparable to “wet” gases. At the same time, these data indicate that substantial amounts of gases and LWMOAs might be artificially generated during laboratory batch experiments with milled samples. Hence, ball milled rock samples must be used with caution if assessing (bio-)geochemical processes for natural environments.

Crystal structure of asphaltene under mechanical stress of ball milling

This work aims to investigate the structural behaviour of asphaltene under mechanical stress using ball milling. Asphaltene samples were collected and separated from Kuwait export crude using n-heptane and subsequently ball milled for up to 24 h. X-ray diffraction was used to provide an insight into asphaltene macrostructure properties, which subsequently utilised to determine crystallite parameters. The results showed that the mechanical stress has a great influence on these structural parameters, with an increase of the aromatic sheet's inter-layer distance from 3.6 Å to 3.9 Å. While the height of stacked aromatic sheets per cluster and the number of stacked aromatic sheets per cluster decreased from 24.6 Å to 9.3 Å and 8 to 3.2, respectively. A significant increment in the aromaticity value was also observed after the ball milling experimentations, indicating mechanical stress induces cyclisation and aromatisation. The XRD profiles of the higher milling time samples reveals a high background intensity. This suggests a formation and/or increasing the proportion of highly disordered materials. In addition, the effects magnitude on asphaltene crystal parameters between the mechanical stress against heat stress was compared. The results showed core structural parameters are more sensitive to mechanical stress over heat stress.

Physicochemical and nutritional quality of pigmented rice and bran: Influence of milling and cooking

Pigmented rice bran is under-researched for human nutrition. This study investigated milling and cooking effects on the physicochemical and nutritional quality of pigmented and non-pigmented rice. Raw rice properties, cooking behavior and nutritional in-vitro quality were evaluated. Samples were cooked following a “risotto” preparation method. Bran removal by milling reduced kernel dimension (15%) and hardness (8%). Pigmented rice had higher total phenolic content (TPC; >41%) and higher antioxidant activity (AOA; >24%) than Carnaroli but milling significantly (p ≤ 0.05) reduced them. The bran was fractionated and (re)added during rice cooking as a new strategy to preserve nutritional compounds at their best. Compared with brown rice, milled samples exhibited greater geometric expansion and shorter cooking times (>47%), confirming that removal of the outer layer facilitated water penetration. Cooking affected the TPC differently depending on the rice variety (e.g., -15.5% for Violet and +7.8% for Orange brown samples). The incorporation of rice bran during cooking improved the “risotto” color and its nutritional value (TPC > 53% and AOA > 60%). Results evidenced the impact of different processing methods on rice quality, suggesting the potential use of rice co-product (i.e., bran) as new ingredient for healthier and more sustainable foods.

Evaluation of tribo-mechanical measurements and thermal expansion of Cu-based nanocomposites reinforced by high strength hybrid ceramics

It is known that Copper’s (Cu) electrical conductivity makes it a desirable material for use in industry. Due to poor properties such as hardness, thermal expansion, and corrosion resistance, its applications are limited. This manuscript solves these problems while maintaining no breakdown in electrical conductivity. In this study, high-strength ceramics (SiC nanoparticles and graphene nanosheets) were used as reinforcements in the manufacture of Cu-based hybrid nanocomposites using powder metallurgy technique. X-ray diffraction analysis (XRD) was used to investigate phase composition and crystal size of the milled powders. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM), respectively examined the microstructure of the prepared powder powders and sintered nanocomposites. Then, various properties of the sintered samples are measured, including physical, electrical and thermal properties and wear resistance. The obtained XRD technique and TEM images showed decreases in the crystal and particle size of milled samples reaching up to 14.08 and 28.30 nm, respectively for the sample contained 8 vol. % SiC + 0.8 vol. % graphene (SG8). A surprising improvement in the mechanical properties of up to 809.15, 341.84 MPa and 336.56 GPa for microhardness, strength and longitudinal modulus for the sample containing the highest reinforcements, achieving an improvement of up to 122, 61.37 and 41 percent compared to the Cu matrix. Moreover, there was a noticeable improvement in the coefficient of thermal expansion (CTE) and wear rate values of the samples by increasing the percentages of hybrid reinforcements in the examined sintered nanocomposite samples. The Sample SG8 recorded the lowest value, decreasing by about 50.2 and 76.5% compared to the SG1 sample. Finally, adding reinforcements to the Cu matrix had a negative effect on the relative density and electrical conductivity, and the lowest values was 92.94% and8.59 × 106 S/m, respectively for the SG sample.

Influence of Feedstock Particle Size on the Certain Determination of Chlorine and Bromine in Pyrolysis Oils from Waste Electrical and Electronic Equipment Plastics.

Rejected streams emerging from waste sorting and recycling plants are still capable of being valorized by unconventional recycling routes. This is the case of the plastic-rich fraction generated after the treatment of waste electrical and electronic equipment (WEEE). However, the material complexity of this stream supposes a handicap when it comes to obtaining repetitive results in laboratory-scale recycling processes. This work aims to highlight the influence that the pretreatment (mainly particle size reduction) of a real WEEE plastic-rich stream has on the variability of the concentration of halogens (representative pollutants) in the oils obtained from its recycling via pyrolysis. The pretreatment steps were based on the standards of the European Committee for Standardization (ECN) for the analysis of waste samples. Four samples were studied: the WEEE plastics as received; two milled samples (2 and 1 mm particle size) derived from the original one; and a simulated sample composed of virgin polymers. All the samples were treated under the same conditions: 500 °C reaction temperature, 15 °C min-1 heating rate, 30 min dwell time, and a 1 L min-1 nitrogen purge flow. The oils obtained in, at least, two pyrolysis tests performed on the same sample were deeply characterized, and the results were compared. The oils derived from the "as-received" sample showed an unacceptable relative standard deviation (RSD, ∼42%) in the chlorine concentration. The sample milled to 2 mm reduced the RSD on the concentration of chlorine in the oils down to 8%, while no enhancement in the results was observed for the further milled sample. The other two major pyrolysis fractions were also characterized, showing an overall enhancement in the RSD of the analysis of the main components of the gases, while no improvement in the solids pollutants' characterization was achieved.

The Effect of the Incorporation of a 3D-Printed Titanium Framework on the Mechanical Properties CAD/CAM Denture Base Materials

Background: Complete dentures should withstand occlusal forces and wear. However, over time, dentures can suffer fatigue and develop cracks, chipping, and fractures. Conventional methods for the fabrication of complete dentures involve injection molding, thermal curing, and the use of microwaves with polymethyl methacrylate (PMMA)-based materials. These methods have served well for many years. More recently, the incorporation of computer-aided design and computer-aided manufacturing (CAD/CAM) to fabricate complete dentures has been shown to enhance the dentures’ mechanical properties, including resistance to wear and impact strength. This study aims to investigate the mechanical properties and fracture types of CAD/CAM denture base materials (both milled and printed) as compared to a novel proprietary method that embeds a 3D-printed framework within PMMA-milled blocks. The null hypothesis is that incorporating a 3D-printed framework does not affect the mechanical properties of milled PMMA blocks. Methods: Three groups of bars were fabricated using CAD/CAM methods: printed (P), milled (M), and milled with a 3D-printed metallic framework reinforcement (M + F). A three-point bending test evaluated deformation, followed by an impact fracture test for fracture toughness. A descriptive fractographic analysis assessed the fracture characteristics. A statistical analysis using a paired t-test compared the differences between the groups. Results: The P group showed more elastic deformation than the M and M + F groups (p < 0.05). The M + F group achieved a higher fracture toughness as compared to the M and P groups (p < 0.05). Conclusions: Within the limitations of this experimental study, the null hypothesis can be rejected. Milled samples with an embedded 3D-printed titanium framework possess higher resistance to impact than milled samples without frameworks, and printed samples and milled samples with embedded 3d-printed titanium frameworks present increased flexural strength and lower elastic deformation as compared to milled samples without frameworks and printed samples.

A Comparative Evaluation of Powder Characteristics of Recycled Material from Bronze Grinding Chips for Additive Manufacturing.

In the manufacturing process of ship propellers, large quantities of grinding chips are generated. These grinding chips result from the finishing of the blade surfaces after the primary casting process of the propeller. The aim of this study was to investigate and compare different preparation processes used to produce chip powders with sufficient powder quality for the additive manufacturing process of directed energy deposition. The preparation of the samples was performed through different sieving, milling and re-melting processes. For the characterization of the prepared samples, powder analysis according to relevant industry standards was carried out. It was found that the re-melting processes result in superior powder quality for additive manufacturing in terms of particle size, morphology, and flowability. For some characteristics, the powder exhibits even better properties than those of commercial powders. Furthermore, the powder properties of the milled samples demonstrate a promising potential for use in additive manufacturing.

Influence of Long Milling Time on the Electrical Resistivity of Nanocrystalline Ni2MnSn Heusler Alloy Obtained by Mechanosynthesis.

A Ni2MnSn Heusler alloy was obtained as a single B2 phase after 12 h of mechanical milling. The influence of prolonged milling on the phase stability was analysed for milling times up to 50 h, related to mean crystallite size, lattice strain, and electrical resistivity. The nature of the powders in the milled range was found to be nanocrystalline, with a mean crystallite size of about 33 ± 2 nm. An evaluation of the internal stresses induced by milling was performed, a linear behaviour was found, and a coefficient of the internal stress increase with milling time was proposed. Particle size distributions of milled samples were analysed, and the morphology of the powders was visualised by scanning electron microscopy. The elemental distribution of milled samples was quantified by energy-dispersive X-ray spectroscopy. Electrical resistivity measurements were performed on compacted samples, and their behaviour with milling time was analysed.

Analysis of Gingival Fibroblasts Behaviour in the Presence of 3D-Printed versus Milled Methacrylate-Based Dental Resins-Do We Have a Winner?

Computer-aided design and computer-aided manufacturing (CAD/CAM) techniques are based on either subtractive (milling prefabricated blocks) or additive (3D printing) methods, and both are used for obtaining dentistry materials. Our in vitro study aimed to investigate the behavior of human gingival fibroblasts exposed to methacrylate (MA)-based CAD/CAM milled samples in comparison with that of MA-based 3D-printed samples to better elucidate the mechanisms of cell adaptability and survival. The proliferation of human gingival fibroblasts was measured after 2 and 24 h of incubation in the presence of these samples using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and the membrane integrity was assessed through the lactate dehydrogenase release. The level of reactive oxygen species, expression of autophagy-related protein LC3B-I, and detection of GSH and caspase 3/7 were evaluated by fluorescence staining. The MMP-2 levels were measured using a Milliplex MAP kit. The incubation with MA-based 3D-printed samples significantly reduced the viability, by 16% and 28% from control after 2 and 24 h, respectively. There was a 25% and 55% decrease in the GSH level from control after 24 h of incubation with the CAD/CAM milled and 3D-printed samples, respectively. In addition, higher levels of LC3B-I and MMP-2 were obtained after 24 h of incubation with the MA-based 3D samples compared to the CAD/CAM milled ones. Therefore, our results outline that the MA-CAD/CAM milled samples displayed good biocompatibility during 24-h exposure, while MA-3D resins are proper for short-term utilization (less than 24 h).

Evaluation of Deviations for Horizontal Thin Walls Determined by Optical and Contact Methods for Milled Samples of Nickel Alloy Inconel 625

The aerospace industry is imposing increasingly strict dimensional tolerances, which is forcing continuous development in component manufacturing. Ensuring tight dimensional tolerances is difficult for thin-walled structures due to their reduced stiffness, which are increasingly used in the aerospace industry, where titanium alloys and nickel alloys, among others, dominate. Developments in this area are causing a search for machining conditions that provide sufficient quality characteristics including dimensional and shape accuracy. We discuss, herewith, thin wall deformations in the horizontal orientation of Inconel 625 nickel alloy samples in cross-sections perpendicular and parallel to the direction of tool feed motion. We measured dimensional and shape accuracy using a 3D optical scanner and also using a coordinate measuring machine to correlate these results. We compared the results obtained by the two methods and obtained the maximum discrepancy of the results equal to around 8%. Samples made with adaptive cylindrical milling had similar values of thin wall deviations, with the smallest deviations observed for the sample made with the tool for high-performance machining using adaptive cylindrical milling.

Decisive role of preparation technique on the structural, electrical and magnetic properties of vanadium doped ZnO nanoparticles

1% vanadium doped ZnO powders have been successfully synthesized via two different preparation techniques viz., glycine assisted combustion method and mechanical attrition method to understand their impact on the structure-property relation. X-ray Diffraction study validates the Wurtzite phase formation of ZnO with hexagonal structure. X-ray diffraction peak discloses the marked role of size and strain component. Evidently, the shift of lattice strain with the preparation techniques from compressive to tensile nature show the importance of structure property relations in the ZnO compounds. SEM micrographs depict the formation of densely populated nanograins with networking like structures which is characteristics of combustion synthesized product whereas as top down approach exhibits the presence of coarse grains amidst the broken sea of fine particles. Selected area electron diffraction (SAED) images display ring and bright circular spot pattern with changes in method of preparation, which further clarifies the distinct nature of investigated ZnO:V particles. Vibrational spectral study gives clear evidence on the structural disorder as deduced from the changes associated with longitudinal optical mode phonon scattering. Interestingly, the UV spectral study divulges the increment in optical band gap as well as a strong visible light absorption (about 30 %) for milled ZnO:V over their chemically prepared counterparts. Photoluminescence spectra of milled V doped ZnO upheld the structural disorder taken place with the suppression of Near Band Edge (NBE) transition and the shifting of broad asymmetric defect emission band towards the lower wavelength regime. Impedance study enlightens the crucial role of synthesis method with 5 times enhanced grain boundary resistance along with suppression of grain contribution in the milled samples. Magnetic study highlights the remarkable distinction of preparation route which alters the ferromagnetic ordering in the combustion synthesized samples to conventional diamagnetic signature of the host ZnO in the milled samples.

ТЕХНОЛОГИЧЕСКИЕ МЕТОДЫ УВЕЛИЧЕНИЯ ДОЛГОВЕЧНОСТИ КОЛЕС ПАССАЖИРСКОГО ЖЕЛЕЗНОДОРОЖНОГО ВАГОНА

The cut of passenger cars due to wear damage to the rolling surface of the wheelset in 2022 is considered. It is found out that the most typical damage is a shelled tread. An analysis of the methods for restoring the rolling profile of wheels showed that the wheel milling with an end mill can be used as a promising one. To assess the effectiveness of the method, metallographic and tribological studies of wheel samples subjected to turning and milling are compared. According to the study results, it is found that when machining samples of wheel steel by end milling, their wear resistance is 22% higher, compared with samples machined by turning, the wear rate of samples of rail steel is lower in a friction pair with milled samples than with turned samples due to a decrease in the friction factor of milling samples.