Strength Values Research Articles

PENGARUH PENAMBAHAN SERAT BAMBU PADA PEMBUATAN PAVING BLOCK TERHADAP KUAT TEKAN

Bamboo is widely used for various forms of building construction, such as houses, as roofs, columns and foundations. Apart from that, the remainder of its use will become waste. One of the building materials that is often used is paving blocks as an alternative ground surface cover that can be used for road pavement, parking lots, pedestrians, parks, etc. The aim of this research was to determine the effect of adding bamboo fiber with variation of 1%, 3%, and 5% on the compressive strength of paving blocks. The method used in this research is the experimental method. Primary data consists of material testing results and paving block compressive strength. Research was conducted at the Structures and Materials Laboratory, Departement of Civil and Mining Engineering, Ketapang State Polytechnic. From the results of the compressive strength testing of paving blocks that have been carried out, the highest average value of compressive strength of paving blocks with a variation of 1% is 320.01 kg/cm2 which corresponds to the quality concrete C used for home garage pavement, pedestrian circulation, and parking lot.

Mechanical properties of Al–Si alloy/Si3N4 interpenetrating phase composite based on a preform fabricated at 1200 °C

Interpenetrating phase composites with three-dimensional co-continuous architecture are promising materials for advanced structural applications due to their excellent combination of properties. In this work, a novel and low-cost Al–Si alloy/Si3N4 IPC was fabricated via squeeze infiltration of Al11Si alloy melt into a porous Si3N4 preform manufactured at a low temperature of 1200 °C using H3PO4 as pore-former and binder. Microstructures of IPC show a good infiltration quality and strong interfacial bonding between metal and ceramic phases without any intermediate reaction products. The fabricated IPC exhibited significantly higher specific hardness and stiffness than the Al11Si alloy. Moreover, an excellent damage tolerance, a substantial increase in compressive strength of 420 %, flexural strength of 168 %, and a significant reduction in wear rate of 95 % in the IPC was achieved with respect to Al11Si. The flexural strength and fracture toughness values of the fabricated IPC compare well to values of Al alloy/Si3N4 IPCs reported in the literature, despite being processed using a porous Si3N4 preform fabricated at a much lower temperature.

Preparation and characterization of intelligent and active bi-layer film based on carrageenan/pectin for monitoring freshness of salmon

This work aimed to develop and characterize a novel bi-layer film (BIF) for monitoring the freshness of salmon. The indicator layer consists of carrageenan (Car), pectin (PEC) and purple sweet potato anthocyanin (PSPA), and the antibacterial layer consists of Car and magnolol (Mag). The results showed that the Car/Mag2 had the optimal water resistance: the static water contact angle of 80.36 ± 0.92°, moisture content of 31.38 ± 0.86 %, swelling degree of 92.96 ± 0.46 %, and water solubility of 40.08 ± 1.17 %, and showed excellent antibacterial properties against E. coli and S. aureus with antibacterial rate of 86.13 % ± 0.10 % and 97.53 % ± 0.02 %, respectively. Then BIFs with different PSPA concentration were tested. The morphology, mechanical and water vapor properties (WVP) of the BIFs were studied, and its application in salmon preservation was evaluated. The mechanical properties and WVP test results showed that the BIF0.2 had the optimal Tensile strength (TS) and WVP values. The BIFs showed distinguishable color changes between the pH ranges of 3–10. The shelf life of salmon packaged by BIF0.2 was prolonged by 2 days. Moreover, the BIF0.2 was able to effectively monitor salmon freshness. In conclusion, the BIF has great potential for monitoring salmon meat freshness.

Preparation and characterization of intelligent and active bi-layer film based on carrageenan/pectin for monitoring freshness of salmon

This work aimed to develop and characterize a novel bi-layer film (BIF) for monitoring the freshness of salmon. The indicator layer consists of carrageenan (Car), pectin (PEC) and purple sweet potato anthocyanin (PSPA), and the antibacterial layer consists of Car and magnolol (Mag). The results showed that the Car/Mag2 had the optimal water resistance: the static water contact angle of 80.36 ± 0.92 °, moisture content of 31.38 ± 0.86 %, swelling degree of 92.96 ± 0.46 %, and water solubility of 40.08 ± 1.17 %, and showed excellent antibacterial properties against E. coli and S. aureus with antibacterial rate of 86.13 % ± 0.10 % and 97.53 % ± 0.02 %, respectively. Then BIFs with different PSPA concentration were tested. The morphology, mechanical and water vapor properties (WVP) of the BIFs were studied, and its application in salmon preservation was evaluated. The mechanical properties and WVP test results showed that the BIF0.2 had the optimal Tensile strength (TS) and WVP values. The BIFs showed distinguishable color changes between the pH ranges of 3–10. The shelf life of salmon packaged by BIF0.2 was prolonged by 2 days. Moreover, the BIF0.2 was able to effectively monitor salmon freshness. In conclusion, the BIF has great potential for monitoring salmon meat freshness.

Comprehensive analysis of mechanical properties, wear, and corrosion behavior of AA7075-T6 alloy subjected to cryogenic treatment for aviation and defense applications

It is important that the parts to be used in the aviation and defense industry have high wear, fatigue and corrosion resistance. AA7075-T6 alloys are increasingly used in every field due to their advantageous physical and mechanical properties. However, some of the materials of this alloy types exhibit excellent fatigue strength and ductility, but their surface hardness and surface roughness after processing may be poor. For this reason, the wear resistance of AA7075-T6 aluminum alloy expected to be improved in order to increase their corrosion resistance properties. In this work, cryogenic treatment was applied to AA7075-T6 alloy and the mechanical characteristics, wear and corrosion behaviors of these samples were examined. As a result of the experiments, it was determined that cryogenic treatment improved the wear behavior of AA7075-T6 alloy. The untreated sample was found to have the highest wear rate, whereas the sample with deep cryogenic treatment (DCT) had the lowest wear rate. The hardness of the DCT process increased by 5.79 %, according to macro hardness measurements, making the AA7075-T6 alloy harder from 80.16 HRB to 84.8. The SEM images revealed that, the shallow cryogenic and deep cryogenic operations had substantial effects on the microstructure by modifying the size and distribution of precipitates in the AA7075-T6 alloy. In addition, tensile and hardness tests were carried out to assess the mechanical characteristics of the samples. Accordingly, the maximum tensile strength and hardness values were obtained in the deep cryogenically treated sample. The tensile strength of the DCT sample was approximately 544.18 MPa, a considerable 11.5 % increase above the untreated sample's 488.07 MPa strength. In potentiodynamic polarization testing, the DCT treated sample was determined to have the maximum corrosion resistance. Among the materials tested, the DCT sample showed the strongest corrosion resistance, with a corrosion potential of −0.689 V and a corrosion rate of 0.021 mm/year. Wear rate analysis revealed that DCT samples experienced the least material loss, demonstrating improved abrasion resistance. Enhanced hardness and the formation of stable oxide tribo-layers contributed to these superior wear characteristic.

Synergistic improvement of strength and ductility by high magnetic field assisted intercritical annealing in lightweight medium Mn steel

The microstructures and mechanical properties of lightweight medium Mn steels were studied by high magnetic field (HMF) assisted intercritical annealing process (HMF-IA). The results show that the volume fraction of retained austenite increased and reached the maximum value of 56.2% when the magnetic flux density (MFD) was 10 T at first and then decreased with the increase of MFD. The application of 10 T HMF promoted the diffusion ability of carbon atoms into austenite by magnetic stress-driven dislocation movement and increased the volume fraction and grain size of austenite. HMF also played a critical role in dislocation movement and element partitioning during the IA process. Due to the wide range of bimodal size distribution of austenite after the HMF-IA process, stronger transformation induced plasticity effect and twin induced plasticity effect happened in the process of plastic deformation. For the sample annealed under 10 T, comparing with the sample annealed without HMF, the product of strength and elongation value increased from 45.7 GPa·% to 55.1 GPa·%. Additionally, it also kept a persistent high strain hardening. The present study provides a new understanding of the role of HMF in adjusting the relationship between microstructure and mechanical properties during the annealing process and opens up a new path for designing industrial medium Mn steel with low cost, high performance and simple process.

Experimental investigation of the coupled effects of bedding planes and flaws on fracture evolution of soft bedded rocks based on 3D printing and DIC technologies

Bedded rocks are a typical geological formation with significant implications for understanding tectonic evolution, rock engineering, and geological hazard mitigation. This study introduces a novel method for fabricating bedded rocks using 3D printing (3DP) technology. By comparing the mechanical anisotropic properties and failure modes of 3DP bedded rocks with natural bedded rocks, we validate the feasibility of this approach. Compression tests are conducted on 3DP bedded rocks containing a single flaw to investigate the coupled effects of bedding planes and flaws on the mechanical properties. Digital image correlation (DIC) is employed for full-field deformation measurement during loading, enabling the study of deformation and crack evolution patterns. The results indicate that bedding planes dominate the brittleness of 3DP bedded rocks containing a single flaw. Significant plastic characteristics and prolonged nonlinear deformation stages are observed when the bedding angle (α) is between 0° and 45°, while brittleness becomes apparent beyond 45°. Both strength and elastic modulus are decided by bedding planes and initial flaws. By comparing stress–strain curves and rate of effective variance change (REVC)-strain curves, crack initiation can be quantitatively identified, revealing a linear correlation between strength and stress values at crack initiation points. The bedding plane also dominates crack propagation and failure modes: when α ≤ 30°, cracks propagate through the bedding, indicating tensile failure; when 45° ≤ α＜90°, cracks propagate along the bedding, indicating tensile-shear or shear failure; and when α = 90°, cracks propagate along bedding planes, indicating tensile failure. The findings of this study provide insights for explaining and predicting failure modes in engineering projects involving bedded rock formations, such as slopes, tunnels, and coal mines.

Effect of nonthermal atmospheric plasma application at different time intervals on the dentinal shear bond strength pretreated with 2% chlorhexidine as cavity disinfectant: An in vitro study

Context: Effective use of nonthermal atmospheric plasma (NTAP) to strengthen adhesive–dentin interfacial bonding while disinfecting with chlorhexidine (CHX). Aim: NTAP application at different time intervals on the dentinal shear bond strength (SBS) after pretreatment with 2% CHX as a cavity disinfectant. Settings and Design: The design of the study was an in vitro study. Materials and Methods: Forty permanent mandibular teeth were collected (n = 40) and the occlusal surfaces were flattened. For, all the specimens 37% phosphoric acid etching was done followed by pretreatment with 2% CHX as cavity disinfectant for 5 s. According to the surface treatment, divided into four groups of n = 10. Group I (Control): No NTAP pretreatment was done. Group II: NTAP pretreatment done for 15 s. Group III: NTAP pretreatment done for 30 s. Group IV: NTAP pretreatment done for 45 s. Later, all the specimens were treated with a bonding agent, incremental build-up of composite resin on the dentin surface was done and evaluation of SBS was done. Analyzed using One-way analysis of variance with a post hoc Tukey’s test (P < 0.05). Results: Two percent CHX pretreatment as cavity disinfectant followed by NTAP application for 30 s (Group III) exhibited greater values compared to the control group (Group I). Conclusion: Two percent CHX pretreatment as cavity disinfectant followed by NTAP pretreatment for 30 s was found to exhibit better bond strength values compared to 15 s as well as 45 s.

Strengthening mechanisms for microstructures containing unimodal and bimodal γ′ precipitates in ATI 718Plus

The influence of γ′ precipitate size distribution on the deformation mechanisms under tensile loading in ATI 718Plus was studied. A set of aging treatments within the temperature range of 720 °C–900 °C was performed on solution-treated samples to obtain various γ′ precipitate size distributions. Unimodal and bimodal γ′ precipitate size distributions were achieved through single-step and two-step aging sequences, respectively, and such microstructures were tensile tested to failure to assess their yield strength, ultimate tensile strength, and elongation-to-failure. Some of the tensile samples were interrupted after achieving 3–4 % plastic strain, and the deformed microstructures were examined using transmission electron microscopy to investigate the γ′ precipitate-dislocation interactions. For the unimodal γ′ precipitate size distribution samples with the smaller γ′ precipitates (radius ∼ 7 nm), dislocations sheared through the precipitates. Both dislocation loops and paired dislocations were observed for the microstructures containing larger γ′ precipitates (radius ∼ 24 nm). The microstructure containing a bimodal γ′ precipitate size distribution, which included average γ′ precipitate radii of ∼6 nm and ∼28 nm, exhibited shearing as the dominant deformation mechanism, and this microstructure exhibited the highest strength values. The experimental observations were rationalized based on the theoretically-calculated critical resolved shear stress values for shearing and looping and a modified model for predicting the yield strength for bimodal microstructures was introduced.

Comparative evaluations of shear bond strength of mineral trioxide aggregate, Biodentine, and calcium-enriched mixture to bulk-fill flowable composite using three different adhesive systems: An in vitro study

Objective: The objective of the study was to assess the shear bond strength of bulk-fill flowable composite resin smart dentin replacement plus when bonded to mineral trioxide aggregate (MTA)-angelus, biodentine, and calcium-enriched mixture (CEM) at two different aging periods (15 min and 72 h) using three distinct adhesive systems. In addition, the study identified the specific modes of failure (adhesive, cohesive, or mixed) using a stereomicroscope and scanning electron microscope. Materials and Methods: One hundred and twenty-six cylindrical acrylic blocks used in the study were sorted into three groups based on the bioactive substance used to fill the 3-mm diameter and 3-mm high hole in the center of each block. The groups were MTA, Biodentine, and CEM. The specimens were then divided into subgroups based on the aging interval (15 min and 72 h) of the bioactive material and the adhesive system used (two-step total-etch, two-step self-etch [SE], and one-step SE) while bonding to the restorative bulk-fill flowable composite. The shear bond strength values were measured with a universal testing machine, and the data were analyzed using two-way and one-way analysis of variance, followed by a post hoc test. The specimens were assessed under stereomicroscope and scanning electron microscope to characterize the mode of bond failure (cohesive, adhesive, or mixed). Results: The study showed that the type of adhesive system and the time of bonding affected the shear bond strength of bulk-fill composite to the pulp capping agents (P < 0.05). For MTA, the highest bond strength was observed with two-step SE group at 15 min (18.16 ± 2.97 MPa) (P < 0.05). CEM exhibited the highest bond strength with two-step SE group at 72 h intervals (8.77 ± 1.76) (P < 0.05). The highest bond strength for biodentine group was observed with total-etch group (8.54 ± 1.35 Mpa) and two-step SE (8.19 ± 1.94 Mpa) bonded at 72 h interval (P < 0.05). The majority of the samples in the MTA group (29/42) and CEM group (20/42) showed a cohesive fracture, whereas Biodentine group (22/42) had an adhesive fracture in most of its samples. Conclusion: MTA demonstrated the highest bond strength with two-step SE group at 15 min, and CEM exhibited the highest bond strength with two-step SE groups at 72 h interval. For biodentine group, the type of adhesive used did not impact the bond strength values.

Validity and reliability of the modified sphygmomanometer test for assessing upper limb and trunk muscle strength in adolescents

The Modified Sphygmomanometer Test (MST) is a method for assessing muscle strength that offers objective measures similar to those of a portable dynamometer, while also being cost-effective. However, previous studies have not investigated the measurement properties of the MST in adolescents. Thus, the objectives of the study were (1) to examine the concurrent criterion validity, test-retest and interrater reliability of the Modified Sphygmomanometer Test (TMS) for assessing muscle strength in adolescents, (2) to calculate the Standard Error of Measurement (EPM) and the smallest real difference (SRD) of muscle strength values; and (3) analyze the different forms of operationalization and their influence on the results obtained. Fifty-two adolescents (mean age: 16.5 ± 0.70 years) participated in the study. Muscle strength of the upper limbs (UL) and trunk was assessed using the MST and portable dynamometers. The Spearman test was used to determine concurrent criterion validity and the intraclass correlation coefficient (ICC) was used to assess reliability (α = 0.05). To analyze the stability of the measurements (SEM and SRD), the 95% test-retest confidence interval (CI) and inter-rater reliability were considered for all data collected. ANOVA was performed to explore different methods of operationalizing the MST. Criterion validity, test-retest reliability and moderate to very high inter-rater reliability (0.61≤r ≤ 0.94; p < 0.001; 0.63≤ICC≤0.97; p < 0.001) were found for the groups assessed muscles and different forms of operationalization, with no statistically significant differences between the different operationalization approaches. Therefore, the MST demonstrated adequate measurement properties for assessing muscle strength in adolescents.

Compressive Strengths of Cube vs. Cored Specimens of Cement Stabilized Rammed Earth Compared with ANOVA

Cement-stabilized rammed earth (CSRE) is a variation of the traditional rammed earth building material, which has been used since ancient times, strengthened by the addition of a stabilizer in the form of Portland cement. This article compares the compressive strength of CSRE determined from specimens cored from structural walls and those molded in the laboratory. Both types of specimens underwent a 120-day curing period. The tests were conducted on specimens with various grain sizes and cement content. An analysis of variance (ANOVA) was performed on the obtained results to determine whether it is possible to establish a conversion factor between the compressive strength values obtained from laboratory-molded cubic samples and those from cored samples extracted from the CSRE structure. The study revealed that the compressive strength of CSRE increases significantly over the curing period, with substantial strength gains observed up to 120 days. The results indicated no statistically significant difference in the mean unconfined compressive strength (UCS) between cubic and cored specimens for certain mixtures, suggesting that a shape coefficient factor may not be necessary for calculating CSRE compressive strength in laboratory settings. However, for other mixtures, normal distribution was not confirmed. These findings have implications for the standardization and practical application of CSRE in construction, highlighting the need for longer curing periods to achieve optimal strength and the potential to simplify testing protocols.

Repairing Al7075 surface using cold spray technology with different metal/ceramic powders

Cold spray process is essentially a coating technique as well as used in repair applications. This method is a low-temperature solid-state process. In this study, the damaged surface of Al7075 was repaired by low pressure cold spray method with Ni-Zn-Al2O3, Al-Zn-Al2O3, Al-Al2O3, Ni-Al2O3, and Zn-Al2O3 metal/ceramic feedstock powders. Microstructure examination, microhardness measurements, tribological experiments, and tensile tests were conducted on the repaired samples and compared with Al7075. The repaired regions exhibited a composite microstructure characterized by the presence of Al2O3 ceramic particles with high hardness dispersed within a metal matrix composed of Al, Ni, Zn, NiZn, and AlZn. This composite structure was attributed to the interlocking mechanism of cold spray. The highest hardness value was measured in the repaired area using Ni-Al2O3, which is approximately 1.28 times higher than that of Al7075 alloy. According to the dry sliding test, the wear performance of all repaired specimens was superior to that of Al7075. The wear resistance of samples repaired with Ni-Al2O3 and Ni-Zn-Al2O3 increased approximately 7.1 and 5.8 times, respectively, compared to Al7075. The specimens repaired with Ni-Zn-Al2O3 feedstock powder showed the most similar results in tensile and yield strength values to Al7075 to the tensile test.

Kaolinite plastic binder in mortars: Rheological and mechanical properties

Portland cement and hydrated lime-based mortars are widely used in civil construction for covering and laying walls, sealing or structural restoration. However, the binders used in the production of mortar are produced in a way that is harmful to the environment, highlighting the need for alternative binders. In this work, the use of kaolinite plastic binder in mortars was evaluated, replacing hydrated lime with the material at levels of 0%, 50% and 100%. The importance of this study is to evaluate the feasibility of using an alternative binder in Portland cement and hydrated lime-based mortars. Fresh state properties were evaluated, such as consistency, squeeze flow and density in the fresh state; in addition to properties in the hardened state, such as compressive strength, water absorption, x-ray diffraction (XRD) and scanning electron microscopy (SEM). The characterization results of kaolinite plastic binder (D10 = 0.00009 mm and D60 = 0.0004 mm) show that the material has a particle size closer to hydrated lime (D10 = 0.00001 mm and D60 = 0.0004 mm), than Portland cement and quartz sand, evidenced by parameters D10 and D60. Additionally, the kaolinite plastic binder presents moderate pozzolanicity, indicating the feasibility of being used in this type of application. The workability tests show that kaolinite plastic binder has the potential to improve the workability of the mortar. In dynamic tests (consistency) it was observed that the 100% kaolinite plastic binder composition is viable as it promotes an increase in spread from 253 to 265 mm. In static tests (squeeze flow) the composition with 50% kaolinite plastic binder showed the best spreading results, with values of 10.7 mm, while the compositions containing 0% and 100% showed spreading of 8.97 and 7.40 mm, respectively. This demonstrates the potential for using kaolinite plastic binder in mortars. The hardened state results, such as compressive strength and water absorption, were also satisfactory. Although the compressive strength values showed a reduction with the use of kaolinite plastic binder, the values reached 7.5 MPa after 28 days, which is compatible with the proposed application. Finally, it was observed from the results of XRD and SEM that the kaolinite plastic binder shows adhesion with the hydration products of the Portland cement in the mortar, promoting a reduction in ettringite and portlandite due to its moderate pozzolanicity. Based on these results, it is possible to conclude that kaolinite plastic binder is a viable substitute for hydrated lime in mortars.

Comparative evaluations of shear bond strength of mineral trioxide aggregate, Biodentine, and calcium-enriched mixture to bulk-fill flowable composite using three different adhesive systems: An in vitro study

Objective: The objective of the study was to assess the shear bond strength of bulk-fill flowable composite resin smart dentin replacement plus when bonded to mineral trioxide aggregate (MTA)-angelus, biodentine, and calcium-enriched mixture (CEM) at two different aging periods (15 min and 72 h) using three distinct adhesive systems. In addition, the study identified the specific modes of failure (adhesive, cohesive, or mixed) using a stereomicroscope and scanning electron microscope. Materials and Methods: One hundred and twenty-six cylindrical acrylic blocks used in the study were sorted into three groups based on the bioactive substance used to fill the 3-mm diameter and 3-mm high hole in the center of each block. The groups were MTA, Biodentine, and CEM. The specimens were then divided into subgroups based on the aging interval (15 min and 72 h) of the bioactive material and the adhesive system used (two-step total-etch, two-step self-etch [SE], and one-step SE) while bonding to the restorative bulk-fill flowable composite. The shear bond strength values were measured with a universal testing machine, and the data were analyzed using two-way and one-way analysis of variance, followed by a post hoc test. The specimens were assessed under stereomicroscope and scanning electron microscope to characterize the mode of bond failure (cohesive, adhesive, or mixed). Results: The study showed that the type of adhesive system and the time of bonding affected the shear bond strength of bulk-fill composite to the pulp capping agents (P &lt; 0.05). For MTA, the highest bond strength was observed with two-step SE group at 15 min (18.16 ± 2.97 MPa) (P &lt; 0.05). CEM exhibited the highest bond strength with two-step SE group at 72 h intervals (8.77 ± 1.76) (P &lt; 0.05). The highest bond strength for biodentine group was observed with total-etch group (8.54 ± 1.35 Mpa) and two-step SE (8.19 ± 1.94 Mpa) bonded at 72 h interval (P &lt; 0.05). The majority of the samples in the MTA group (29/42) and CEM group (20/42) showed a cohesive fracture, whereas Biodentine group (22/42) had an adhesive fracture in most of its samples. Conclusion: MTA demonstrated the highest bond strength with two-step SE group at 15 min, and CEM exhibited the highest bond strength with two-step SE groups at 72 h interval. For biodentine group, the type of adhesive used did not impact the bond strength values.

THE INFLUENCE OF ABUTMENT SURFACE TREATMENT ON PULL-OFF BOND STRENGTH BETWEEN (5)YTTRIA STABILIZED ZIRCONIA CROWN AND TITANIUM IMPLANT ABUTMENT

ABSTRACT Aim: The objective of this research was to evaluate the effect of mechanical method and energetic method of surface treatments for Ti-abutment base (Ti-Base, Dentium/Korea) on the pull-off bond strength with (5)Y-TZP crown. Materials and Methods: : Forty titanium implant abutments were used in this study and randomly assigned to four groups (n = 10 for each group) according surface treatment methods of titanium abutment: group (1) act as control without surface treatment for Ti-abutment, group (2) bur surface treatment of Ti-abutment, group (3) sandblast (50-µm aluminum oxide) surface treatment for Ti-abutment, group (4) plasma surface treatment for Ti-abutment. Then, forty implant analogs were placed in the center of acrylic mold. After that abutment was tightened on the each analog with (35 N/cm) torque . Forty (5)Y-TZP crowns fabricated by CAD/CAM system that had special design with occlusal O-hole cemented to all abutments using Allcem dual-cure resin cement. All specimens were then subjected to thermos-cycling with (5000) cycles. With a universal testing machine record pull-off bond strength for all samples, Collected data were analyzed using a one-way analysis of variance at a significance level of (p &lt; 0.01) . Results:, The bur treated abutment (group 2) group showed the highest bond strength values, followed by sandblast treated abutment (group 3) and plasma treated abutment (group 4). Control group was the lowest value of tensile strength. Conclusion: Surface treatments of Ti-abutment had observed effect on pull-off (tensile bond strength) between Ti-abutment and (5)Y-TZP crown Bur and sandblast cause roughness of surface and increase bond strength , plasma cause reactive surface for increasing tensile bond strength.

In English

Biopolymer matrices has been synthesized on the basis of ED-20 epoxy resin and soybean oil (SbO) bearing cyclocarbonate and epoxy groups. Mono(cyanoethyl)diethylenetriamine (UP) and tris(2-hydroxyethyl)amine (TEA) were used as hardeners. Chemical structure, mechanical properties, thermo-oxidative resistance of the samples and their changes after contact with distilled water, alkaline or acidic environment were studied. By means of ATR-FTIR the possible formation of H-NIPU (hybrid non-isocyanate polyurethane) fragments between cyclocarbonate groups of SbO and amino groups of the hardener was demonstrated. Influence of the curing mode and the type of hardener on water absorption, chemical and thermal oxidation resistance of the developed biopolymer matrices was thoroughly investigated. UP-based biopolymer matrices showed water and alkali resistance similar to the ones of neat epoxy polymers, while TEA-based biopolymer matrices showed better resistance to the acidic medium. The thermo-oxidative stability of the chosen samples was revealed by the TGA method in an air atmosphere. It was demonstrated that epoxy polymer cured with TEA hardener were more stable than the one cured with UP hardener. The similar dependence is observed for biopolymer matrices based on TEA hardener. At the same time, the curing mode has almost no effect on ultimate tensile strength value of the samples with ED-20/UP composition. However, the addition of functionalized SbO to the epoxy matrix cured with both TEA and UP hardeners increases the ultimate tensile strength values regardless of the type of oil functionalization. As expected, all biopolymer matrices exhibited higher ultimate tensile strength compared with unmodified epoxy polymers, which provides the possibility of their further application to obtain multi-layered bioplastics.

Fabrication of Novel Nanofiber Patch Containing BoerhaviaDiffusa Extract for Wound Healing Application Using Response Surface Methodology

In this study, we successfully prepared a Boerhavia diffusa extract-loaded nanofiber wound dressing using the electrospinning method, optimizing the process through a 3x2 factorial design. The optimized nanofiber, denoted as BRNF7, exhibited excellent characteristics, including an entrapment efficiency of 85.12% and a drug loading of 9%. Furthermore, the swelling index was measured at 86.6, demonstrating its potential as an effective wound dressing material. Characterization of the BRNF7 nanofiber revealed promising results, as FTIR spectra exhibited all the expected peaks, while XRD analysis indicated a highly crystalline structure with intense peaks. DSC thermograms displayed a characteristic peak at 133.42°C, corresponding to Boerhavia diffusa extract. Thermal analysis, as indicated by TGA thermograms, showed that the nanofiber gradually decomposed at a higher temperature range, signifying its thermal stability. Wound dressing various parameter included as the film thickness ranged from 0.069 to 0.074 mm, and all films exhibited excellent folding endurance, ensuring flexibility. Moisture interaction studies demonstrated good physical stability of the film under high humidity conditions and maintained integrity under dry conditions. The films exhibited a moisture absorption range of 3.8% to 4.6% and a moisture loss range of 3.2% to 4.7%. Tensile strength values ranged from 2.14 to 2.85 kg/cm², and the percentage of drug content was uniform between 90.15% and 92.11%.Furthermore, our Boerhavia diffusa extract-loaded Nanofibrous dressing displayed notable antibacterial activity against various pathogens and exhibited promising wound-healing effects, making it a potential candidate for advanced wound care. This study provides a comprehensive assessment of the BRNF7 nanofiber, emphasizing its potential in biomedical applications.

STRENGTHENING OF THE SURFACE BY FRICTION

The study is devoted to the application of the method of surface hardening by friction Object of study - the process of surface hardening by friction.Subject of study - samples of 65G steel the method allows achieving high values of hardness, strength and wear resistance of materials in a short time and at much lower cost compared to other processing methods. The aim and objectives of the study are to investigate the nature of surface hardening of steel samples by friction. To achieve this goal, the following tasks are envisaged: manufacturing samples from 65G steel in the form of plates, preliminary heat treatment of samples for their maximum thermal hardening, hardening of the surface of samples by friction, analysis of the microstructure and microhardness of each sample, comparison of the microstructure, microhardness and depth of hardening of these samples, conclusions on the influence of processing factors on the hardening result. Based on the experimental data obtained, we constructed graphs of microhardness changes in the cross-section of the samples and studied the microstructures. It can be seen that after friction treatment, a layer with a modified structure is formed in the surface of the samples. The microhardness of the surface is significantly higher (approximately 2 times) than the microhardness of the main part in the samples. Metallographic analysis has shown that the layer formed in the samples has a martensitic structure characterized by a higher degree of dispersion and microhardness compared to the martensitic structure obtained during the previous heat treatment. Changes in the microstructure and microhardness of the samples that were surface hardened using different processing modes were compared. Certain differences in the characteristics of their hardened «white» layers were found. It is also shown that the hardened «white» layer is located along the entire length of the surface in the samples and is continuous and homogeneous.

Жароміцні інтерметалідні сплави та особливості їх легування

The work considers the prerequisites for the development of creep-resistant and heat-resistant alloys, based on intermetallics, taking into account the optimal combination of their physical and mechanical properties, as well as structural characteristics. It is shown that there is a sufficient number of intermetallics, which have a density lower than iron-based alloys, which, in combination with high melting temperatures and heat resistance, makes them promising materials for aerospace application, in particular, for gas turbine engine parts manufacturing. The most suitable creep-resistant and heat-resistant intermetallics can be called aluminides and silicides of titanium, nickel and molybdenum. For these compounds, it is possible to combine high values of specific strength with alloying-favorable types of crystal lattice. One of the most important and common creep-resistant alloys based on intermetallics is Ni3Al with FCC lattice. For this material, complex optimized alloying is the main way to increase creep resistance. The heat resistance of such alloys is significantly increased by applying ceramic coatings. Titanium aluminides Ti3Al and TiAl mainly have only a low density among the advantages. Their fragility at room temperatures and tendency to superplasticity at high temperatures significantly limits their application. The impact of disadvantages may be reduced by applying thermomechanical processing of such materials, which aims to change their structure. Alloying titanium aluminides with a large amount of niobium was chosen as a solution that significantly reduced marked week sides of Ti-Al intermetallic alloys. As a result, this led to the creation of a new alloy based on intermetallic Ti2AlNb with a high set of operational characteristics. Mo-Si and Mo-Si-B can be considered as one of the most perfect systems for creating heat-resistant intermetallic alloys. They combine an acceptable density, high creep and heat resistance, which can be additionally increased by reinforcing with ceramic particles. Keywords: intermetallic-based alloys, creep resistance, alloying, Ni-Al, Ti-Al, Mo-Si, Mo-Si-B.