Maximum Roughness Research Articles

Optimization of composite extrusion modeling process parameters for 3D printing of low-alloy steel AISI 8740 using metal injection moulding feedstock

Composite Extrusion Modeling (CEM) is an advanced material extrusion additive manufacturing technique for low-cost rapid production of complex parts. In this work, a conventional Metal Injection Moulding (MIM) feedstock is used for 3D printing of low alloy-steel AISI 8740 via CEM. This steel is widely used in aircraft, aerospace, and MIM industries. However, it has, so far, not been processed using CEM-based 3D printing. The influence of four printing parameters, extrusion multiplier, extrusion temperature, nozzle velocity, and layer thickness on green density and surface roughness was explored following the feedstock's investigation. Full-factorial and face-centered response designs were utilized to study the influence of printing parameters and their optimization to achieve maximum green density and minimum surface roughness. The optimized parameters were found to be an extrusion multiplier of 107.6 %, extrusion temperature of 180 °C, nozzle velocity of 20 mm/s and layer thickness of 0.050 mm through a multiple response optimization process. The dense green part with relative densities of ≥ 98 % was achieved with minimum surface roughness of Ra = (2.3 ± 0.1) μm and Rz = (16.1 ± 1.1) μm. Moreover, a scanning electron microscope was utilized to study the surfaces of green parts. The parts printed with optimized printing parameters showed the best quality with minimized printing voids and smooth extrusion.

Fabrication of Bioinspired Micro/Nano-Textured Surfaces Through Scalable Roll Coating Manufacturing

Abstract Bio-inspired, micro/nanotextured surfaces have a variety of applications including superhydrophobicity, self-cleaning, anti-icing, antibiofouling, and drag reduction. In this paper, a template-free and scalable roll coating process is studied for fabrication of micro/nanoscale topographies surfaces. These micro/nanoscale structures are generated with viscoelastic polymer nanocomposites and derived by controlling ribbing instabilities in forward roll coating. The relationship between process conditions and surface topography is studied in terms of shear rate, capillary number, and surface roughness parameters (e.g., Wenzel factor and the density of peaks). For a given shear rate, the sample roughness increased with a higher capillary number until a threshold point. Similarly, for a given capillary number, the roughness increased up to a threshold range associated with shear rate. A peak density coefficient (PDC) model is proposed to relate capillary number and shear rate to surface roughness. The optimum range of the shear rate and the capillary number was found to be 40–60 s−1 and 4.5 × 105–6 × 105, respectively. This resulted in a maximum Wenzel roughness factor of 1.91, a peak density of 3.94 × 104 (1/mm2), and a water contact angle (WCA) of 128 deg.

Performance evaluation of electro-spark eroded high-volume fraction of Cr-Fe-Ni superalloy

Current research aims to execute a viability study of electro-spark erosion technique to process Inconel 690, a high-volume fraction of Cr-Fe-Ni superalloy (∼32% Cr). The Box-Behnken design of response surface methodology with varying processing conditions is used to execute the experimental trails. Process performance is examined in terms of material removal rate and surface topography. The surface conditions of the processed surface are studied using scanning electron microscopy. The tool wear character and tribological behavior of the processed surface are also scrutinized to check the post-process consequences. The study explores the formation of oxide layers, craters, spherical droplets, and micro-cracks on the surface processed at Ton: 118 mu; Toff: 45 mu; Ip: 130 mu; Sv: 50 V ( parametrical settings for maximum material removal rate), and at Ton: 118 mu; Toff: 30 mu; Ip: 220 mu; Sv: 50 V ( parametrical settings for maximum surface roughness) attributing a deteriorating surface quality. The maximum material removal rate of 9.38 mm3/min and minimum surface roughness of 0.47 μm are achieved. A significant improvement of approximately 20 HV in micro-hardness is detected owing to the formation of a recast layer on the processed surface. Consequently, a noticeable improvement is observed in the wear resistance of the processed surface.

Experimental study on fabrication, biocompatibility and mechanical characterization of polyhydroxybutyrate-ball clay bionanocomposites for bone tissue engineering

The poly (3-hydroxybutyrate) (PHB)/ball clay nanocomposites (B1-B10) were synthesized using solvent casting method with different weight percentage of ball clay in PHB matrix. Scanning electron microscope (SEM) showed maximum root mean square roughness (188.73 μm) for 10% ball clay loading. Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) showed establishment of intercalated structure and formation of hydrogen bond between ball clay and PHB matrix. Contact angle values (67.3 - 51.3°) exhibited that the nanocomposites (B1-B10) are more hydrophilic than neat PHB (70.30°). Thermogravimetric (TGA) and differential scanning calorimetry (DSC) revealed maximum Tmax (278 °C) and Tm (175 °C) for the nanocomposite B10 (PHB/PEG/ball clay: 80%/10%/10%). Maximum tensile strength (38.21 ± 0.15 MPa) and Young’s modulus (1.74 ± 0.016 GPa) was observed for B10 nanocomposite. The values of protein adsorption, platelet adhesion, PT, APTT and complement activation for B10 nanocomposites were 165 ± 2 μg/cm2, 72 ± 3 × 109 platelets/cm2, 23 ± 1 s, 44 ± 2 s, 102 ± 2 mg/dL and 631 ± 3 mg/dL, respectively. Hydroxyapatite formation was also observed for nanocomposite (B10) in in vitro simulated body fluid (SBF) study. Finally, the nanocomposite (B10) showed no harmful effect on MG-63 cells, indicating that they are physiologically safe.

Silica-Embedded Polyurea Microspheres with Rough Surface for Matte Leather Finishing

A type of polyurea microspheres with rough surfaces and different sizes (1-12 μm), which was used for waterborne polyurethane matte leather coating, were prepared by precipitation polymerization in H 2 O/acetonitrile system, using isophorone diisocyanate as polymerized monomer, 2,4-diaminobenzenesulfonic acid sodium salt as hydrophilic monomer and nano-SiO 2 as surface roughener. The effect of the loading of isophorone diisocyanate and 2,4-diaminobenzenesulfonic acid sodium salt, the volume ratio of H 2 O/acetonitrile and the addition stage of nano-SiO 2 on the particle size and surface roughness were investigated so as to achieve the excellent matte effect of the coating. The results indicated that the adding of hydrophilic monomer can reduce the particle size of microspheres and improve its re-dispersibility in water, while the increase of the proportion of acetonitrile in the mixed solvent and the loading of polymerized monomer can enlarge the size of the polyurea microspheres. As surface roughener, with the increase of nano-SiO 2 loading, the surface roughness and the particle size of microspheres increase. When nano-SiO 2 is added at the stage of the reaction system getting turbid, the maximum surface roughness of polyurea microspheres can be achieved. Polyurea microspheres with particle size (1-2 μm) and high surface roughness have better matting effect, and the gloss of the prepared waterborne polyurethane coating can be adjusted to less than 1.6° (60°-incident Angle).

Optimization of compositional manipulation for hydroxyapatite modified with boron oxide and graphene oxide for medical applications

Bone tissue engineering is the most used technology in recent years for repairing damaged bones. A novel heterogeneous biomaterial is prepared and studied to be suggested as a promising bone substitute biomaterial, based on three different nanoparticles: hydroxyapatite (HAP), boron oxide (B2O3), and graphene oxide (GO) a triple nanocomposite is designed HAP/B2O3/GO. This hybrid scaffold is analyzed with XRD to examine the crystalline structure of HAP/B2O3/GO and shows its crystal planes. Moreover, the interaction between the three nanoparticles and their distinctive active functional groups is illustrated with FTIR analysis. Further, TEM micrographs demonstrate the structural alteration and the uniform incorporation of HAP and B2O3 into GO sheets with an average length of 30 nm and diameter of 6 nm for HAP, and a size of 8 mm for B2O3. Furthermore, SEM micrographs reveal the porous structure of HAP/B2O3/GO with a grain size of 5–10 nm. The maximum roughness average value is obtained by HAP/B2O3/GO which is 11.04 nm. Besides, HAP/B2O3/GO nanocomposite shows the highest cell viability value of 96.1 ± 1.2%. The bacterial toxicity of HAP/B2O3/GO is confirmed with the obtained inhibition zone against Escherichia coli and Staphylococcus aureus of 15.7 ± 1.1 mm and 16.2 ± 0.8 mm respectively. In addition, the hardness of the triple composite is improved showing a maximum value of 3.7 ± 0.3 GPa. Distinctly, the addition of B2O3 to HAP and GO nanosheets alter the morphological properties and enhances the roughness parameters of HAP/B2O3/GO. Besides, HAP/B2O3/GO shows improved porosity, cell viability, and biodegradability. Hence, studying HAP/B2O3/GO nanocomposite with different scans and analyses reveals its porous integrated structure and shows an excellent antibacterial property, so that HAP/B2O3/GO composite can be suggested as a promising bone substitute biomaterial.

Soft machining-induced surface and edge chipping damage in pre-crystalized lithium silicate glass ceramics

Soft machining is a key procedure in fabrication of high-strength lithium-based silicate glass ceramic (LS) restorations. This paper reports on the diamond machining-induced surface and edge chipping damage in two pre-crystalized LS materials: pre-crystallized lithium metasilicate/orthophosphate glass ceramic (Pre-LS, IPS e.max CAD) and pre-crystallized zirconia-containing lithium metasilicate glass ceramic (Pre-ZLS, Vita Suprinity). Indentation techniques were used to measure the material mechanical properties. Soft machining was conducted using a robotic controlled apparatus mimicking dental CAD/CAM machining processes at different removal rates and enabling in-process force measurement. Machined surface roughness was assessed using 3D confocal optical profilometry in terms of the average and maximum surface heights. Scanning electron microscopy was used to assess diamond tool and machined surface and edge morphology. Soft machining of both materials was dominated by brittle fracture mixed with localized ductile flow. However, the higher brittleness index of Pre-ZLS than Pre-LS yielded higher degrees of machining-induced conchoidal fractures in Pre-ZLS in comparison with irregular fractures in Pre-LS. Thus, much larger surface roughness and deeper edge chipping damage were produced in Pre-ZLS than Pre-LS. Machining forces for Pre-ZLS were significantly smaller than Pre-LS, due to the lower machinability index associated with a complex relation of the mechanical properties as well as less debris adhesion for Pre-ZLS than Pre-LS. Further, increased material removal rates resulted in significantly increased machining forces, maximum surface roughness and fracture, and edge chipping damage in both Pre-ZLS and Pre-LS materials. Therefore, optimization of soft machining processes needs to be practiced to achieve accepted surface and edge quality at balanced removal rates.

Fabrication of high-performance nanofiltration membranes by using sulfated cellulose nanofibril as the intermediate support layer

The preparation of high-performance nanofiltration membranes with high permeability and selectivity is a big challenge. Herein, we proposed a novel composite nanofiltration membrane used sulfated cellulose nanofibril (SCNF) to prepare the intermediate support layer. Three SCNFs with different amounts of surface charge was prepared by deep eutectic solvent pretreatment and mechanical treatment. The composite nanofiltration membrane was fabricated with three layers, and physicochemical properties and separation performance of composite nanofiltration were analyzed. The results showed that with the increase of the amount of surface charge of the intermediate support layer of SCNF, the roughness and absolute value of surface zeta potential of the composite nanofiltration membrane all increased, the maximum roughness value was 112 nm, while the absolute value of surface zeta potential was 85 mV. The decreasing of water contact angle indicated that hydrophilicity of composite nanofiltration membrane enhanced. The membrane exhibited high Na2SO4 rejection above 98% and water permeability above 30 L/m2/h under 2 bars. Moreover, the optimal membrane of PES/H-SCNF/PIP-TMC showed the rejection order was Na2SO4 (98.91%) > Mg2SO4 (78.42%) > MgCI2 (49.80%) > NaCI (21.23%) > CaCI2 (12.31%). These outstanding separation characters endowed the membranes with a great prospect in the process of desalination for future application.

Investigation and multi-objective optimization of monocrystalline silicon wafering using wire electro-discharge machining

Monocrystalline silicon wafers are widely used as the primary material for solar cell production in the photovoltaic industry, owing to their high efficiency and sleeker aesthetic. Wafering is the primary process towards wafer production. The existing wafering processes have limitations of cracking, chipping, and high kerf loss, arising the need for cost-efficient and precise methods to produce wafers. In the present experimental work, an attempt has been made to explore the potential of Wire Electro-discharge Machining (WEDM) for wafer production and to gain an understanding of the effects caused by pulse on time (Ton), pulse off time (Toff), peak current (Ip), wire tension (WT), and wire feed rate (WFR) during the wafering process to achieve the optimal parametric setting for attaining maximum wafering speed and minimum surface roughness. The work material used was P-type monocrystalline silicon. Wafers thickness of 250 μm was produced, avoiding edge chipping. The experimentation was planned according to the face-centered central composite design. The obtained results were statistically analyzed, and response surface methodology (RSM) was used to model the wafering speed and surface roughness. From the analysis of experimental results, it was noticed that at the higher level of Ton and Ip, a maximum wafering speed of 2.574 mm/min was attained. In contrast, the minimum surface roughness of 1.57 μm was achieved at the lower level of Ton and Ip. The most significant process variables that influence the wafering speed and surface roughness are the Ton, Toff, and Ip. Micrographs of the wafer surface reveal the presence of micro craters, but there was no evidence of micro-cracks. The multi-objective optimization of the responses was done using the desirability approach, and the optimized values of wafering speed and surface roughness attained were 0.989 mm/min and 1.57 μm, respectively.

Parametric Optimization of Material Removal Rate of EDM (AISI-4147) by using Taguchi Approach

Electric discharge machine is a non-conventional machining. In which there is no contact between tool and work piece. By EDM process machining of hard material components that are difficult to machine such as heat treated tool steels, ceramics, composites, carbides, heat resistance steel which are used in die and mould producing industries, aero space and nuclear industries. EDM is a non-contact type technique of material removal and in this spark is used to remove the material from the work piece. Since the EDM is an attractive means of making tool and dies with high accuracy in dimension and surface finish quality of micro scale parts. The present experimental research studies the process parameters that are influencing the machining concert and its productivity. A collective approach is used for the optimization in parameters and performance characteristics which are based on Taguchi method. The experiments are based on Taguchi‟s L9 orthogonal array. The reaction graph and reaction table of each near of machining constraints are took from Taguchi method to select the optimum levels of machining factors. In the work, the machining parameters for thesis are current, pulse on time and pulse off time, which are optimized for minimum tool wear rate (TWR), maximum material removal rate (MRR) and minimum surface roughness during electro discharge machining of AISI 4147. Analysis of Variance is also used to find out variable affecting the various responses mentioned above.

Dependence of Creep Strain and Fatigue Behavior on Surface Characteristics of Resistive Strain Gauges.

Creep behavior and fatigue life are important performance indexes that affect the long-term stability of resistive strain gauges. The resistive strain gauges, fabricated with wet etching and resistance trimming, present micro-morphology such as textures and uneven edges on the surface and side-wall profile of sensitive grids. This paper observed the micro-morphology of the sensitive grids by microscope and analyzed its range of geometric dimensions. A sine function was used to establish equivalent geometric models for the surface textures and side-wall profile. Based on time hardening theory and the S–N curve, the dependence of micro-morphology of metal resistive strain gauges on creep behavior and fatigue life was studied. The results indicate that the roughness of micro-morphology has an influence on creep behavior and fatigue life. The surface textures and side-wall profile lead to the increase of creep strain and the decrease of fatigue life in varying degrees. When 60% of the ultimate stress of the strain gauges is loaded, the average creep strain in steady-state calculated by the maximum roughness of the side-wall profile reaches up to 6.95 times that of the perfect flat surface. Under the condition of loading 70% of the ultimate stress and the same roughness, the fatigue life led by side-wall profile could be reduced to 1/25 of the textured surface. The obtained achievements promote an understanding for optimizing the fabrication process of resistive strain gauges as well as developing high-precision and long-life force sensors.

Influence of Various Desensitizing Mouthrinses and Simulated Toothbrushing on Surface Roughness and Microhardness of Tetric N-Ceram Bulk-Fill Resin Composite: An In Vitro Study and Scanning Electron Microscope Analysis.

Bulk-filled composite resins are popularly used for posterior restorations due to various advantages. Routine oral hygiene measures like toothbrushing and the use of various mouthrinses can influence the mechanical properties of composite resins. Desensitizing mouthrinses are widely used as well, to manage dentinal hypersensitivity. Studies on the influence of desensitizing mouthrinses on bulk-filled composites are limited. Hence, the objective of the present in vitro study was to evaluate the influence of toothbrushing and various desensitizing mouthrinses on the surface roughness and microhardness of Tetric N-Ceram bulk-fill composite resin. Fifty Tetric N-Ceram bulk-fill composite resin disks were prepared and were randomly divided into five groups (n = 10). Group 1 (Control): no toothbrushing and no mouthrinse; Group 2: toothbrushing only; Group 3: toothbrushing + HiOra-K mouthrinse; Group 4: toothbrushing + Listerine Sensitive mouthrinse; and Group 5: toothbrushing + Shy-OR mouthrinse. The specimens were brushed with a soft bristle brush using a toothpaste slurry and immersed in respective mouthrinse twice daily for 1 month. The mean surface roughness (average roughness) and microhardness (Vickers Pyramid number) values were determined and the data were tabulated. Data were analyzed using one-way analysis of variance, Post-hoc Tukey test, and Pearson correlation test. A p-value less than 0.05 was considered statistically significant. Specimens treated with HiOra-K mouthrinse exhibited maximum surface roughness (p < 0.05) and specimens treated with Listerine Sensitive exhibited the least microhardness (p < 0.05). A weak negative correlation was found between surface roughness and microhardness for groups 1, 2, and 5, while a weak positive correlation was found for groups 3 and 4. It is suggested that desensitizing mouthrinses containing alcohol or essential oils can lead to increased surface roughness and reduction in microhardness of bulk-fill composites, which could have an undesirable effect on their clinical performance.

Effect of the reversal of the layer thickness ratio in the CrN/CrCN multilayer coating on cavitation-induced degradation

CrN/CrCN multilayer coatings with reversal ratios of layer thickness (1:2 and 2:1) and uncoated 1.4021 steel substrate were tested against cavitation erosion. Mechanical properties of the coatings were investigated. The CrN/CrCN coating with a layer thickness ratio of 2:1 (CrN_2–1 coating) had higher hardness, H, Young's modulus, E, and adhesion, i.e. LC2 force (the friction force in a scratch test at which the coating is completely removed) than the CrN/CrCN coating with a layer thickness ratio of 1:2 (CrN_1–2 coating). However, the CrN_2–1 coating had lower stiffness (the H/E and H3/E2 ratios) and LC1 force (the friction force at which the first coating failure occurs). Cavitation tests were carried out using a tunnel with a system of barricade exciters. Both coatings improved cavitation erosion resistance. The erosion rate of all tested materials started with the highest erosion rates which then decreased. After the cavitation tests, the erosion rate of 1.4021 steel was 50% higher than the erosion rate of the CrN 1–2 coating and 122% greater than the erosion rate of the CrN_2–1 coating. The H·LC2/E parameter better than the H/E ratio correlated with the volume loss of the tested coatings in cavitation erosion tests. Deep cracks and pits, and the dense network of cracks were the reason for the higher roughness of uncoated steel compared to coated steel. The maximum Ra roughness parameter of 1.4021 steel was from 60% to about 100% bigger than those obtained for coatings. Thicker layers of CrN in the multilayer CrN/CrCN coating led to a reduction in the density and size of pits due to a higher ability to absorb the impact energy compared to the coating with the thicker CrCN layers.

Evaluation of Relation between Friction Coefficient and Oil Film Thickness of Ground Gear

Matsumoto's equation, which determines the ratio of the friction coefficient between boundary lubrication and fluid lubrication by the ratio of the maximum height roughness and minimum oil film thickness, is often used to predict the friction coefficient on gear tooth surfaces. Recently, however, several papers using gears with highly smoothed tooth surfaces have reported discrepancies between the measured friction coefficient of tooth surface and Matsumoto's equation. It seems that the problem of how to determine the boundary lubrication friction coefficient lies behind these discrepancies. In this paper, the coefficient of tooth friction is determined under a wide range of lubrication conditions using ground spur gears, and the experimental results are compared with the calculation results of Matsumoto's equation to reevaluate the relationship between the two. The friction coefficient of boundary lubrication was found to vary with surface roughness of tooth surface.

A Comparative Analysis of Surface Characteristics of Enamel after Conventional Acid Etching and Er,Cr:YSSG Laser Irradiation.

BackgroundTo evaluate the influence of Erbium, Chromium:Yttrium-Scandium-Gallium-Garnet (Er,Cr:YSGG) laser irradiation (2W 15Hz, 2W 25Hz) on Penetration Depth, Surface Roughness, Surface Morphology and Etching Pattern of enamel and to compare it with conventional acid etching. Material and MethodsSixty sound human premolars extracted for orthodontic reasons were used for this study. Penetration Depth and Surface Roughness between Acid Etched and Laser Etched Enamel were evaluated using Non-contact 3D- Profilometer .Surface Morphology and the Etching Pattern were evaluated using Field Emission - Scanning Electron Microscope. ResultsOn comparing the maximum depth and surface roughness values among all the three groups, highest was found in the acid-etched group, followed by the 2W 15Hz laser–etched group and the least was with the 2W 25Hz laser–etched group. The laser etching of enamel surface with an Er,Cr:YSGG laser system showed Type 3 etching pattern, whereas acid etched surface showed Type 1 etching pattern as described by Silverstone (1974). ConclusionsEr,Cr:YSGG laser irradiation produces favourable etching pattern and micro-irregularities that are suitable for resin penetration. Moreover, due to its decreased surface roughness and penetration depth, laser etching can significantly decrease the probability of formation of white spot lesions which is proved to be the potential disadvantage of conventional acid etching. Hence, laser etching can be preferred over the conventional phosphoric acid etching for orthodontic bonding. Key words:Laser, Er,Cr:YSGG, Surface Roughness, Etching Pattern,Penetration Depth,SEM, Laboratory Research, Acid etching.

Influence of surface roughness of die sinking EDM on mold releasability in compression molding of thermosetting phenol resin

Improvement in metal mold characteristics such as wear resistance, corrosion resistance and mold releasability is essential for plastic molding. In this study, factors of the mold releasability were investigated by quantitative evaluations of adhesion forces between the processed metal mold surfaces and the molded resins in compression molding of thermosetting phenol resin. Die sinking EDM was employed as the processed surfaces of the metal molds. As the mold releasability tests, the molded thermosetting phenol resin onto the EDMed surface was pulled up in the perpendicular direction from the surface. Consequently, the mold releasability could be quantitatively evaluated by measuring a maximum tensile load which means a mold release force when the molded resin is separated from the EDMed surface.Several workpieces with different surface roughness as the EDMed surfaces were prepared by varying discharge currents and pulse durations. As a result of investigations on relationships between surface roughness parameters and measured mold release forces, the mold release forces tended to increase as maximum height roughness RZ and average length RSm of the surface roughness parameters increase. On the other hand, the mold release forces tended to decrease as peak count RPc increases. Accordingly, it is considered that anchor effects become higher with increase of undulation on the EDMed surfaces. Therefore, the undulation is one of the factors affecting the mold releasability, and it would be possible to improve the mold releasability by reducing the undulations on the EDMed surfaces with EDM conditions.

Surface and Wear Investigation on Microwave Sintered Nitinol Composite

The present research of the article is used to describe the microwave sintering of nitinol composite and its surface topography analysis by atomic microscopy (AFM). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) technique is used to analyze the characterization and alloying composition of the composite. Silicon carbide is the reinforcing particle between nickel and titanium. Wear test is conducted to investigate the worn surface morphology of the sintered specimen. The synthesized composite has exceptional material properties such as ultimate tensile strength of 1020MPa, 16% of elongation to fracture, 7.51 g/cc of density and hardness of 310 HV. Low wear rate of 0.01 mg/m is perceived at minimum load and minimum sintering time. Surface roughness is varied from 22.87 to 54.05nm at different sintering time. Maximum roughness height of 327.6 nm is observed in the surface profile of the composite.

Effect of some industrialized acidic beverages on the roughness of pit and fissure sealants: an in vitro study.

This study evaluated in vitro the roughness of the pit and fissure sealants (PFS) after immersion in some industrialized acidic beverages. 120 discs (5 mm diameter and 2 mm thick) of 4 commercial brands (3M, Ivoclar, Ultradent, and VOCO) were immersed in 1.5 mL of 3 different industrialized acid beverages (soft drink, apple juice, and fermented milk) and incubated at 37 ºC for 15 and 30 days. Surface roughness (Ra and Rz) was measured at the beginning (0), 15 (1), and 30 days (2) after immersion, using a profilometer, under the standard ISO 4287-1997. Data were analyzed with one-way analysis of variance (One-way ANOVA) and repeated measures analysis of variance (Repeated measures ANOVA) test (p < 0.05). Ultradent and VOCO had the higher baseline surface roughness values, while 3M presented the lower baseline values (p > 0.05). After 15 and 30 days of immersion, the 3M group still showed the minimum values of surface roughness (p < 0.05). In addition, the maximum roughness values were seen in group UC (Ultradent/Coca-Cola) (p < 0.05). The surface roughness of the PFS increased according to the period of immersion in some industrialized acidic beverages. This increase was specific to each commercial brand. Therefore, the 3M PFS presented the best performance before and after immersion in the beverages.

Microstructure, morphology and physicochemical properties of nanocomposites containing hydroxyapatite/vivianite/graphene oxide for biomedical applications.

Designing a nanocomposite that accumulates biocompatibility and antimicrobial behaviour is an essential requirement for biomedical applications. Hydroxyapatite (HAP), graphene oxide, and vivianite in one ternary nanocomposite with three phases and shapes led to an increase in cell viability to 97.6% ± 4 for the osteoblast cells in vitro. The obtained nanocomposites were investigated for their structural features using X-ray diffraction, while the microstructure features were analyzed using a scanning electron microscope (SEM) and a transmission electron microscope. The analysis showed a decrease in the crystal size to 13 nm, while the HAP grains reached 30 nm. The elongated shape of vivianite reached 200 nm on SEM micrographs. The monoclinic and hexagonal crystal systems of HAP and vivianite were presented in the ternary nanocomposite. The maximum roughness peak height reached 236.1 nm for the ternary nanocomposite from 203.3 nm, while the maximum height of the roughness parameter reached 440.7 nm for the di-nanocomposite of HAP/graphene oxide from 419.7 nm. The corrosion current density reached 0.004 μA/cm2 . The ferrous (Fe2+ ) and calcium (Ca2+ ) ions released were measured and confirmed. Therefore, the morphology of the nanocomposites affected bacterial activity. This was estimated as an inhibition zone and reached 14.5 ± 0.9 and 13.4 ± 1.1 mm for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) after 24 h. The increase in viability and the antibacterial activity refer to the compatibility of the nanocomposite in different medical applications.

An experimental investigation of viscosity of a newly developed natural polymer-based media for abrasive flow machining (AFM) of 3D printed ABS parts

Abrasive Flow Machining (AFM) is the method of finishing complex surfaces and internal channels with the help of extrusion pressure and abrasive-laden viscoelastic polymer media. This paper is based on developing a new AFM media using a natural waste polymer as a base material. In the article, a natural polymer media viz. rice husk ash-based media has been developed, and subsequently, rheological analysis has been done, and experimentation has been performed on Anton-paar® rheometer to optimize the viscosity of these newly developed AFM media. In this research study, the hollow elliptical shape of ABS (acrylonitrile-butadiene-styrene) material was manufactured using the FDM technique and then finished with a one-way AFM machine. This paper examined the parametric dependencies of AFM process parameters on finishing FDM printed hollow elliptical parts. The improved surface roughness of the FDM printed hollow elliptical parts has been investigated relating to the AFM process parameters. The maximum surface roughness has been achieved by 95.98%.