Ra Values Research Articles

Antioxidant and Antimicrobial Activity of Citrus Limetta

One of the most common fruit crops grown in tropical and subtropical areas is Citrus limetta. Upon processing, about40-47% percent of the fruit's non-edible mass is discarded as waste that impacts the environment. The aromatic compounds calledessential oils (EOs) are concentrated in oil glands found in leaves, flowers, and fruit peels. The study's primary objective was toevaluate the biological activity of fresh and heated peels extracted essential oil from Citrus limetta (CLEO). The study emphasizedthe determination of bioactive compounds from the CLEO antioxidant and antimicrobial activity assessment. CLEO's main volatilecomponent was D-Limonene in both oils, with RA (%) values of 44.14 and 77.50 in fresh and heated peel oil, respectively. Theantioxidant activity was comparable to the standard used for ascorbic. The activity (%) reached its highest (83±1.53%) at theconcentration of of100μL/mL for fresh peel oil, which is higher than the heated peel oil. Comparative antimicrobial activity wasdetermined to assess the effects of CLEO against ten bacterial pathogens, which implies that seven pathogens were significantlysensitive against heated oil. The current findings suggest that CLEO could be an impressive natural source with significant potentialto show good biological activity in both fresh and treated forms. A complex composition with approximately 20 components inCitrus limetta essential oil has been scientifically proven beneficial in aromatherapy, medications, beverages, food color enhancers,and aromatic-nature infusions for personal health care.

A Surface Topographical Analysis of Lithium Disilicate Ceramics Pretreated With Rose Bengal, Er:YAG Laser, and Ceramic Primer on Bond Integrity, Surface Roughness, and Bond Failure to Composite Resin

To evaluate adhesive bond integrity and surface roughness (Ra) of LDS ceramics following various surface modification treatments. Forty LDS ceramic disks were manufactured and allocated into distinct groups according to the pretreatment procedure. Group 1 samples were treated with HF (hydrofluoric acid) and S (silane). Group 2 uses RBe (Rose Bengal photosensitizer) S. Group 3 utilizes SECP (self-etch ceramic primer), while Group 4 employs Er:YAG laser. The Ra, shear bond strength (SBS), and surface topography of the conditioned LDS ceramic were evaluated. The bonding of all LDS ceramics was assessed with a universal testing machine. Debonded samples were analyzed using a stereomicroscope. The Ra and bond integrity values were assessed through the utilization of a two-way ANOVA, followed by Tukey post hoc testing. The samples prepared with HF+S displayed the highest Ra and bond values. However, group 2 (RBe+S) exhibited the least bond strength. There were no notable disparities in the results regarding the strength of the bonds among group 1, group 3 (SECP), and group 4 (Er:YAG laser+S). Er:YAG and SECP show promise as potential substitutes for hydrofluoric acid (HFA) in conditioning LDS ceramics, yielding satisfactory bond scores by positively altering the surface morphology.

Evaluation of Surface Roughness of Acrylic Denture Bases Polished Using Algishine, a Novel Polishing Material: An In Vitro Study.

Introduction Surface roughness (Ra) significantly impacts the aesthetic and functional qualities of dental prosthetics. Traditional polishing involves pumice, a material routinely used in dental practice. This study introduces Algishine as a potential cost-effective eco-friendly alternative. Materials and methods A 3D design software (Geomagic) created a Standard Tesselation Language (STL) file of 10 mm x 10 mm x 2 mm. 30 STL file outputs were generated. The output was milled in wax. This was then flasked and processed. 30 acrylic resin specimens were fabricated and divided into two groups. Group A was polished using traditional pumice, and Group B was polished using Algishine. The Ra of each sample was measured using surface profilometry, with three readings per sample averaged for each group. Results Kruskal-Wallis test was performed to compare the two groups with the pre-testing samples, which showed p<0.05; indicating that there was a significant difference between the two groups. The average Ra value for unpolished acrylic was 7.105, while the specimens polished with pumice showed an Ra value of 2.218; specimens polished with novel materialAlgishine showed an Ra value of 1.743. This illustrates that Algishine achieves surface smoothness significantly superior to commonly used polishing agent andpumice. Discussion The results of our study demonstrate that Algishine, a novel polishing material derived from recycled alginate, effectively reduces the Ra of acrylic resin. This finding has significant implications, both clinically and environmentally. The primary clinical benefit of a smoother acrylic resin surface is the enhanced aesthetic appearance and increased patient comfort. A polished surface reduces plaque accumulation, thereby decreasing the risk of oral infections and improving the longevity of the dental prosthesis. The results show that Algishine achieves surface smoothness comparable to or better than pumice indicating that it can maintain, if not enhance, these clinical outcomes. Dental professionals can confidently use Algishine, knowing it meets the high standards required for patient care. Conclusion Algishine effectively reduces the Ra of acrylic resin, suggesting it is a viable, eco-friendly alternative to traditional pumice for dental polishing procedures. This indicates potential benefits in maintaining clinical outcomes while promoting environmental sustainability.

Effects of thermal treatment on air-dried density, color change, average surface roughness, and sound absorption capacity of Scots pine

This study was conducted to investigate some characteristics of thermally treated Scots pine (Pinus sylvestris L.) wood specimens such as air-dried density, color change, average surface roughness, and sound absorption capacity. Heat treatment of Scots pine wood was performed at atmospheric pressure at 140, 160, 180, and 200 °C for 2 h. As a result, the air-dried density values of the thermally treated wood decreased as the temperature of the thermal treatment increased. With the increase of thermal treatment temperature, an increase in total color change values was detected on the surfaces of the samples and the color of the samples became darker. The average surface roughness (Ra) value of samples improved due to thermal treatment conditions and the highest value was determined in thermally treated samples at 200 °C as 3.59 μm. At 140 °C the value of maximum sound absorption coefficient was observed to be 0.48 at 2500 Hz and the highest sound transmission loss value, which was 36.7 dB, was measured at 6300 Hz and at 200 °C.

Non-Oberbeck–Boussinesq effects on a differentially heated vertical cavity with high-Prandtl number fluid

This study explores the non-Oberbeck–Boussinesq (NOB) effects on hydrodynamics and heat transport in two-dimensional glycerol-filled differentially heated vertical cavity (DHVC). The simulations span Rayleigh numbers (Ra) from 2×103 to 5×109 and temperature difference (Δθ̃) up to 50 K at a Prandtl number (Pr) of 2547. We showed the emergence of stratified flow structures, delineated the NOB effects on temperature distribution symmetry, and analyzed the scaling behaviors of the Nusselt number (Nu), Reynolds number (Re), and thermal boundary layer (BL) thicknesses (λ¯hθ and λ¯cθ) against Ra. For Ra≥3×105, the stratification number (S) shows reduced sensitivity to changes in Ra, stabilizing around 0.5. Additionally, the center temperature (θcen) appears to be unaffected by Ra and increases linearly with Δθ̃ for Ra&amp;gt;106, satisfying θcen≈2.99×10−3K−1Δθ̃. Our results also revealed that Nu∼Raγ Nu and Re∼RaγRe with 0.2649≤γ Nu≤0.2654 and 0.3633≤γ Re≤0.3643, respectively, where γ Nu and γ Re exhibit a monotonic decrease as NOB effects intensify. For all investigated Ra values, NuNOB/NuOB&amp;lt;1 and ReNOB/ReOB&amp;gt;1 hold consistently, with deviations from OB predictions capped at 6.38% and 2.63% for Ra≥108, respectively. The analysis of thermal BL thickness reveals distinct scaling behaviors, characterized by λ¯h,cθ∼Raγ λ¯ h, c, with scaling exponents ranging from −0.2690 to −0.2669 for both OB and NOB scenarios. Notably, it reveals a divergence from water-based DHVC trends, showing linear decreases in the hot wall's scaling exponent and increases for the cold wall.

Incorporated Au/Se nanoparticles into HPMC/CMC blend for enhancing structural, optical and morphological properties: Hybrid nanocomposites for optoelectronic applications

The present study employed a solution-casting approach to fabricate a hybrid polymer system using hydroxypropyl methylcellulose and sodium carboxymethyl cellulose (HPMC/CMC) with different weight percentages of gold/selenium (Au/Se) nanoparticles (50:50). The chemical reaction between the components of the nanocomposites was studied using Fourier transform infrared, X-ray diffraction, and UV/visible spectroscopic analyses, which indicated the prevalence of the amorphous areas. AFM and FESEM were used to check the homogeneity in addition to the morphology of the current samples. The optical energy gap was reduced because the resulting nanocomposite films mostly included amorphous areas rather than crystalline ones. The HPMC/CMC samples were carefully analysed for their band gap metallization criterion (Mc), optical conductivity, and refractive indices. The optical characteristics of the sample were improved, and the Urbach energy (Eurb) reached a new level of 2.045 eV for the film filled with 5 wt% of Au/Se NPs (HCAuSe-5), up from 0.415 eV for the pure HPMC/CMC blend. EDS mapping confirmed the successful incorporation of the (Au/Se) nanoparticles into the HPMC/CMC matrices. The roughness parameters, including surface kurtosis, surface skewness, root mean square, and average roughness, were calculated. The samples with 3 and 4 wt% of the nanofillers had a Rku value of 2.787243 and 2.87752, respectively, which got the best rough nature, lowered the Ra value, improved the contact characteristics, and made it more useful in high-tech applications, particularly in optoelectronics.

EXPERIMENTAL INVESTIGATION ON ONE-WAY ABRASIVE FLOW MACHINING ON HOT WORK STEEL

Abrasive flow machining (AFM) is a process where a semi-solid abrasive-laden media is forced to flow through the internal passages of a workpiece under pressure. In high-resolution work, increased accuracy and faster smooth surface polishing work with the developed motorized AFM prototype. This research presents the effect of the clearance of specimen tools for surface roughness (Ra) of SKD 61 (AISI H13) hot work steel related to AFM. This research experimented with half-spherical specimens. AFM experiments are performed to identify the improved surface roughness when applied to the polishing specimens. Specimens were prepared by being turned, hardened, and polished with sandpaper from number P180 to P1200 and measured with an original value of Ra compared with the final value of Ra at the end of the process. The experimental prototype uses a unidirectional motor drive system different from previously developed machines. The process parameters are as follows: a pressure (p) of 1, 2, and 3 bar, cycle time (t) of 10, 15, and 20 min., an abrasive particle size (Al2O3) of 5.0 μm in Silicon Oil (50 % concentration by weight), hardness of specimens 45±2 HRC, etc. The experimental results show that under these conditions, the average surface roughness of specimens was decreased from an original value of Ra 0.057 to 0.042 μm. The greatest response surface (RSM) was obtained at a pressure of 3 bar and a time of 20 minutes. The result allows for better precision control and further development in industrial applications.

A Comparative Study of Dry Turning Performance of 4340 Alloy Steel with As-Received and Cryogenically Treated Coated Cermet Cutting Tools

Cryogenic treatment has been shown to significantly improve the cutting performance of inserts. Alloy steel grade 4340, renowned for its high impact and abrasion resistance, has extensive application in aircraft landing and high-power transmission gears. In this study, a comparative characterization (microhardness and XRD profile) and dry turning performance evaluation (turned surface roughness and insert wear) of alloy steel grade 4340 were performed using as-received and cryogenically treated coated cermet cutting inserts. The turning operation was carried out with various cutting velocities ( 55, 90, and 150 m/min) and a constant feed and cutting depth (0.111 mm/rev and 1 mm) under dry cutting conditions. The cryogenically treated insert obtained A reduced Ra value compared to untreated conditions at all cutting speeds. In addition, Ra value was reduced to a maximum of 29%. A lower level of insert wear and chip particle deposition at the cutting point was observed with cryo-treated inserts. Finally, it was revealed that the better machining characteristics in terms of reduced Ra values and insert wear with cryo-treated conditions were due to the enhanced wear resistance over the untreated conditions.

Simulation and experimental study for enhancing surface integrity of micro-slots processed on Nimonic-263 super alloy via electrochemical machining

ABSTRACT The potential of micro electrochemical slotting is significant due to its adaptability and usefulness across diverse manufacturing applications. This technique holds potential, particularly for handling advanced engineering materials like superalloys, with a focus on applications requiring high strength, i.e., micro-cutting for gas-turbine parts, biomedical applications, etc. With this view, this article has been attempted to explore the influence of various considered machining factors, namely as; applied potential difference, tool feed rate (TFR), pulse supply, and modes of tool insulation on the performance measures, i.e. material removal rate (MRR) and surface roughness (Ra) while attempting micro-slotting in Nimonic-263 superalloy work samples. The entire experimentation was conducted on the in-house fabricated 3-axis micro-electrochemical setup designed for performing various complex machining operations at a miniature scale. Furthermore, this study has also been focused toward investigating the impact of varying the electrical conductivity by employing different tool materials (i.e. copper and SS304) on the process characteristics measured. The observed effects of the tool electrode’s conductivity have also been expressed and supported by performing the simulation for electric field distribution using COMSOL Multiphysics software. The experimental results have revealed that the process input variables remarkably influence MRR and Ra, mainly applied voltage and TFR. The best values of MRR and Ra attained with SS304 and copper tool electrodes were 1.521 mg/min and 0.721 mg/min, and 0.038 µm and 0.029 µm, correspondingly. The microstructure analysis has further been conducted on machined micro-slotted work samples that provided detailed insights into various surface integrity aspects, which are essential for microdevice applications.

Effect of postpolymerization time and atmosphere on surface properties and biofilm formation in additively manufactured resins for definitive restorations

ObjectivesTo investigate how postpolymerization time (PPT) and atmosphere (PPA) influence the surface properties, protein adsorption, and microbial adhesion of two types of additively manufactured (AM) resins used for definitive restorations. MethodsTwo different types of commercially available AM resins for definitive restorations (UR and CR) were used to create disk-shaped specimens. These specimens were divided into eight groups based on resin type (UR and CR), PPT (standard or extended), and PPA (air or nitrogen). After postpolymerization, the surface roughness (Ra and Sa) and surface free energy (SFE) of all specimens were measured. The study also evaluated protein adsorption, microbial attachment, and cytotoxicity. A non-parametric factorial analysis of variance with post-hoc analyses was conducted, using a significance level (α) of 0.05. ResultsThe Ra and Sa values for CR were higher than those for UR, regardless of PPT or PPA (P < 0.05). For UR, SFE was higher with extended PPT compared to standard PPT. CR had higher SFE than UR under standard PPT. The interaction between PPT and PPA had a significant effect on protein adsorption (P < 0.05). When PPT was standard, nitrogen significantly increased protein adsorption compared to air. The interaction between resin type and PPA, and between resin type and PPT, significantly affected microbial adhesion (P < 0.05). The changes in PPT or PPA did not affect the cytotoxicity of either AM resin. ConclusionSurface properties, protein adsorption, and microbial attachment were influenced by the interactions among PPT, PPA, and resin type. These factors can have implications for resin-based definitive restorations. Clinical significancesClinicians should understand the impact of PPT and PPA on the surface properties of AM resins for definitive restorations, particularly regarding protein adsorption and microbial adhesion. Additionally, the type of AM resin (based on chemical composition) could affect its biological properties.

PECVD technology deposition of high hardness a-C:H films on micro-drill surfaces: Substrate bias voltage effects

The plasma enhanced chemical vapor deposition (PECVD) technique was utilized to produce hydrogenated amorphous carbon (a-C:H) films. The overall structure of the films consists of a Cr/WC transition layer, a WC/a-C:H transition layer, and an a-C:H functional layer. The study investigated the effects of substrate bias voltages (SBVs) of −580 V, −660 V, −740 V, −820 V, and −900 V on the microstructure, mechanical, and tribological properties of a-C:H films. The findings indicate that different SBVs influence the ionic energy during the deposition of a-C:H films, consequently affecting the film growth. In this case, when the SBV is -820 V, C+ with sufficient energy will penetrate beneath the initial layer in the form of shallow injection. Therefore, compared to other experimental groups, the a-C:H films prepared under this condition have the lowest Ra value (0.42 nm), the highest sp3 CC bond content (39.88 %), the maximum hardness (31.6 GPa), the lowest friction coefficient (0.052), and the smallest wear rate (7.48 × 10−8 mm3/(N·m)), demonstrating significantly better mechanical and tribological properties. The a-C:H films, prepared at different SBVs, are deposited on micro-drill surfaces for hole drilling tests. The experimental results indicate that a-C:H films prepared at SBV of −820 V exhibit the satisfactory drilling performance due to the better mechanical and tribological properties. This is evident not only in the minimal surface wear of the film micro-drill after different drilling quantities but also by the satisfactory quality of the corresponding machined holes. The a-C:H film micro-drill prepared at SBV of −820 V exhibited larger process capability index (CPK) values for the machined holes at 500, 1000, and 2000 hole numbers of 5.449, 3.693, and 3.263 respectively. During the 2000th drill on the printed circuit board (PCB) surface, the hole wall roughness (Rz) and nail head values of the machined hole were measured to be 10.6 μm and 1.3, respectively.

Intelligent Matching Method for College Dormitory Roommates: Chameleon Algorithm Based on Optimized Partitioning

A chameleon algorithm based on optimized partitioning was studied to solve the intelligent matching problem of college dormitory roommates. Using quantitative research methods, data on personal preferences and lifestyle habits of college students were collected, and the K-center object chameleon algorithm was used for data analysis and roommate matching. Test the algorithm performance on the BBC dataset, compare clustering quality indicators such as entropy, purity, and RI value, and verify the effectiveness of the algorithm. This algorithm can accurately assign students to their respective dormitories, avoiding overlapping situations and achieving excellent matching results. In terms of matching accuracy and running time, the K-center object chameleon algorithm shows superior performance compared to other algorithms. In terms of clustering quality evaluation, comparisons were made from three dimensions: entropy value, purity, and RI value. The experimental results show that the closer the entropy value is to 0, the closer the purity and RI value are to 1, and the better the matching effect. This result further validates the effectiveness of the algorithm in the intelligent matching problem of college dormitory roommates. The matching accuracy of this algorithm on the BBC dataset reached 98.82%, showing better clustering quality than other algorithms in terms of entropy, purity, and RI values. The entropy value approached 0, while the purity and RI values approached 1, verifying the efficiency of matching quality. The chameleon algorithm based on optimized partitioning proposed in the study has shown excellent performance in intelligent matching of college dormitory roommates, with the characteristics of high-precision matching and fast running time. It has important practical significance for improving the quality of life and learning efficiency of college dormitory students, and provides new research methods and ideas for related fields.

Effect of surface treatment strategies on bond strength of additively and subtractively manufactured hybrid materials for permanent crowns

ObjectivesThe purpose of this study is to evaluate the bond strength of different computer-aided design / computer-aided manufacturing (CAD/CAM) hybrid ceramic materials following different pretreatments.MethodsA total of 306 CAD/CAM hybrid material specimens were manufactured, n = 102 for each material (VarseoSmile Crownplus [VSCP] by 3D-printing; Vita Enamic [VE] and Grandio Blocs [GB] by milling). Each material was randomly divided into six groups regarding different pretreatment strategies: control, silane, sandblasting (50 μm aluminum oxide particles), sandblasting + silane, etching (9% hydrofluorics acid), etching + silane. Subsequently, surface roughness (Ra) values, surface free energy (SFE) were measured. Each specimen was bonded with a dual-cured adhesive composite. Half of the specimens were subjected to thermocycling (5000 cycles, 5–55 °C). The shear bond strength (SBS) test was performed. Data were analyzed by using a two-way analysis of variance, independent t-test, and Mann-Whitney-U-test (α = 0.05).ResultsMaterial type (p = 0.001), pretreatment strategy (p < 0.001), and the interaction (p < 0.001) all had significant effects on Ra value. However, only etching on VSCP and VE surface increased SFE value significantly. Regarding SBS value, no significant difference was found among the three materials (p = 0.937), while the pretreatment strategy significantly influenced SBS (p < 0.05). Etching on VSCP specimens showed the lowest mean value among all groups, while sandblasting and silane result in higher SBS for all test materials.ConclusionsThe bond strength of CAD/CAM hybrid ceramic materials for milling and 3D-printing was comparable. Sandblasting and silane coupling were suitable for both millable and printable materials, while hydrofluoric etching should not be recommended for CAD/CAM hybrid ceramic materials.Clinical relevanceSince comparable evidence between 3D-printable and millable CAD/CAM dental hybrid materials is scarce, the present study gives clear guidance for pretreatment planning on different materials.

Construction and validation of parametric models to predict radium sorption in soils

Elucidating the factors affecting the transfer of naturally occurring radionuclides (NOR) between environmental compartments is a key part of the assessment of ecosystem's exposure to naturally occurring radionuclide materials (NORM). For that, the sorption and desorption solid-liquid distribution coefficients (Kd) of radium (Ra) were quantified in a collection of 31 soil samples with contrasting edaphic properties under controlled conditions in laboratory batch experiments. Ra sorption was demonstrated to be moderate to high, with Kd (Ra) values ranging from 102 to 103 L kg−1. Ra sorbed was mostly irreversible, as evidenced by desorption percentages lower than 2 %. An exploratory analysis with partial least squares (PLS) regression identified the soil properties that correlated with Kd (Ra) and discarded those that were not relevant for describing Kd variability. A dataset of the sorption Kd (Ra) values and associated soil properties was built from our own data and from the literature after performing an in-depth review of similar Ra sorption studies. For the first time, Kd (Ra) parametric prediction models were constructed using univariate linear regression (ULR) and multivariate linear regression (MLR). Ra sorption in soils was mostly explained by the soil properties directly or indirectly related to the available exchange sites, such as the levels of water-soluble and exchangeable Ca and Mg as well as the pH of the contact solution. The most promising models explained around 80 % of the Kd (Ra) data variance, only needing Kd (Ca + Mg) or additional soil descriptors such as pH, Mn content, and the specific surface area. The validation of the proposed models confirmed that Kd (Ra) can be predicted with only a few soil properties that can be characterised in routine analysis. Thus, the proposed models could be used to estimate the interaction of Ra in soils in risk assessment.

Are Ecological Risk Indices for Trace Metals Relevant for Characterizing Polluted Substrates in the Katangese Copperbelt (DR Congo) and for Assessment of the Performance of Remediation Trials?

This study aims to contribute to the characterization of Katangese Copperbelt’s (DR Congo) mining wastes and soils polluted with trace metals, using pollution indices and direct concentration measurements. This study also evaluated the use of these indices in assessing the success of remediation projects. Data from previous studies and samples collected from six types of discharge and one polluted soil were used to address the first objective. Soil and plant samples were collected at Kipushi and Penga Penga for the second objective. The results reveal very high concentrations of As, Cd, Co, Cu, Mn, Pb, and Zn in all mine tailings and polluted soils, compared with local references. The degree of contamination (DC) values (from 72 to 5440) and potential ecological risk (RI) values (from 549 to 162,091) indicate very high-risk situations associated with polluted discharges and soils. Regarding revegetation trials, the results show lower concentrations and RIs in tree rhizospheres compared with unamended areas at both sites. However, trace metal concentrations are higher in tree rhizospheres compared with local references, and RI values are in the considerable risk range for Penga Penga (RI = 533) and in the very high range (&gt;1500) for Kipushi. Bioconcentration factor values are below 1, indicating low accumulation in roots, wood, and leaves, and low risk of contamination of the trophic chain. In this context, it seems that the pollution indices used are suitable for characterizing pollution and prioritization for remediation. However, their seems unsuitable for assessing the effectiveness of phytotechnology processes based on metal stabilization. Direct plant performance measurements combined with direct measurements of metals in substrates and plants to assess transfer and efficiency are more appropriate.

Analysis of the Surface Roughness of Different Denture Teeth Materials: A Quantitative In-Vitro Study.

The surface roughness of denture teeth materials significantly influences their clinical performance and patient satisfaction. Understanding the variations in surface roughness among different materials is crucial for optimizing denture fabrication processes. In this quantitative in-vitro study, three commonly used denture teeth materials, namely acrylic resin, composite resin, and porcelain, were evaluated for surface roughness. Twenty samples of each material were prepared and subjected to profilometric analysis. The surface roughness parameters Ra and Rz were measured using a contact profilometer. Statistical analysis was performed to compare the surface roughness among the different materials. The mean surface roughness (Ra) values were found to be 0.32 μm for acrylic resin, 0.25 μm for composite resin, and 0.18 μm for porcelain. Similarly, the mean Rz values were 2.45 μm for acrylic resin, 1.98 μm for composite resin, and 1.62 μm for porcelain. Statistical analysis revealed significant differences in surface roughness among the three materials (P < 0.05). Porcelain denture teeth exhibited the smoothest surface, followed by composite resin and acrylic resin. These findings suggest that material selection plays a crucial role in determining the surface roughness of denture teeth. Porcelain may offer superior aesthetics and reduced plaque accumulation compared with acrylic and composite resin materials. Clinicians should consider these differences when choosing denture materials to achieve optimal clinical outcomes and patient satisfaction.

Effect of Process Parameters on the Roughness and Wetting Characteristics of SS304 Surfaces Using Electrolytic and Plasma Electrolytic Polishing Techniques

Metallic parts manufactured by conventional machining and additive manufacturing techniques possess poor surface quality and require post-processing operations before their end-use. Many methods exist for the post-processing of parts with free-form surfaces. In this study, two of the most used polishing techniques, electrolytic polishing (EP) and plasma electrolytic polishing (PeP), were investigated to understand the morphology of the resultant surface after both techniques. Pilot experiments suggested that an aqueous solution of ammonium sulphate is the most effective electrolyte for both the polishing techniques in terms of the lowest achievable value of average surface roughness ( Ra ). A systematic investigation of the electrolyte concentration, applied voltage, and polishing time revealed an identical dependence on all these process parameters: First, a decrease and then an increase in Ra. A minimum Ra of 0.63 μm and 0.49 μm were achieved with EP and PeP, respectively. Samples polished by PeP possess high gloss with negligible changes to the shape and form of the samples. Furthermore, static contact angle measurements with water revealed that surfaces treated with PeP showed higher hydrophilicity compared to those polished with EP. This can be attributed to the lower Ra value achieved with PeP.

Effect of femtosecond laser induced surface patterns on the flexural strength of monolithic zirconia.

To investigate how patterns generated by femtosecond (fs) laser and femtosecond laser power affect the surface roughness (Ra) and biaxial flexural strength (BFS) of monolithic zirconia. Eighty disk-shaped zirconia specimens were divided into eight subgroups (n = 10): Control (C), airborne-particle abrasion (APA), 400 mW fs laser (spiral [SP(400)], square [SQ(400)], circular [CI(400)]), and 700 mW fs laser ([SP(700)], [SQ(700)], [CI(700)]). Ra values were calculated by using a surface profilometer. One additional specimen per group was analyzed with scanning electron microscopy and x-ray diffractometry. BFS values were obtained by using the piston-on-3-ball test. One-way ANOVA and either Tukey's HSD (BFS) or Tamhane's T2 (Ra) tests were used to evaluate data (α = 0.05). Regardless of the pattern and power, fs laser groups had higher Ra than C and APA, while SP groups had lower Ra than CI and SQ groups (p ≤ 0.004). For each pattern, Ra increased with higher laser power (p < 0.001), while the laser power did not affect the BFS (p ≥ 0.793). CI and SQ groups had lower BFS than the other groups (p ≤ 0.040), whereas SP groups had similar BFS to C and APA (p ≥ 0.430). Fs laser microstructuring with spiral surface pattern increased the Ra without jeopardizing the BFS of zirconia. Thus, this treatment might be an option to roughen tested zirconia.

D-shaped photonic crystal fiber based on surface plasmon resonance for low refractive index applications

Here, a fresh D-type photonic crystal fiber has been developed by us, relying on the surface plasmon resonance effect. Differing from conventional D-type photonic crystal fiber, this model coats gold film on an open-loop channel for excitation. Through the finite element method analysis, this sensor exhibits an effective scope of 1.20–1.30 for the refractive index of analyte. As the RI of the analyte rises, the loss peak within the spectrum gradually intensifies and then remains stable. At an RI value of 1.30, achieving a resolution of 9.52 × 10−6 RIU, this sensor exhibits excellent performance with a maximum sensitivity of 10,500 nm/RIU. Its simple structure adds to its overall appeal. The outstanding sensing performance demonstrates enhanced competitiveness in sectors with lower refractive indices. Farther, to enhance the sensor's sensing capabilities, we conducted an analysis of how structural parameters impact the resonance spectrum with the goal of optimization.

An Experimental Investigation of Cutting Condition Influences on Hard Milling of AISI D2 Tool Steel

The presented work aims to study the effects of cutting speed, feed rate and depth of cut on surface roughness Ra in hard milling of AISI D2 steel (58 ÷ 60 HRC) using carbide inserts. A factorial experimental design was used to evaluate the influence of input variables. The obtained results indicated that feed rate causes the most significant effect on surface roughness, whereas cutting speed and depth of cut have little influence. The interaction effects between cutting speed and depth of cut as well as between feed rate and depth of cut have the significant influences on surface roughness Ra. Moreover, the cutting speed of 92 ÷ 100 m/min, feed rate of 0.1 ÷ 0.11 mm/tooth, and cutting depth of 0.1 ÷ 0.12 mm should be recommended for reaching the smaller surface roughness Ra values, which play an important role for further studies on hard milling process.