Drop In Strength Research Articles

Effect of solvothermal-treated polyethylene on the mechanical properties of sandcrete blocks and concrete

In building construction, seepage and dampness in walls present serious problems since they can cause structural failures and damage in both residential and commercial contexts. Finding more affordable options is necessary as mitigating these problems frequently requires expensive fixes. This study aims to evaluate the effects of solvothermal-treated polyethylene added at concentrations ranging from 0 to 1.0% on the mechanical properties of concrete and sandcrete blocks. In addition to assessing the workability, split tensile strength, and compressive strength of concrete samples at different levels of the polyethylene (PE) inclusion, the study looked into the water absorption capacity, density, and compressive strength of sandcrete blocks. The blocks’ compressive strength and water absorption capacity reduced as the amount of polyethylene additives rose, although there was a slight increase in the density. These changes remain well within the Nigerian Industrial Standards’ specified limits. Hardened concrete shows a drop in density, compressive strength, and split tensile strength with increasing polyethylene content, while fresh concrete's workability decreases as the percentage increases. 0.4% incorporation of the treated polyethylene achieved the target strength of 20 N/mm2 while Sandcrete blocks with up to 1% of the solvothermal treated polyethylene had compressive strengths more than the 2.5 N/mm2 minimum required for non-load-bearing walls. About 61% reduction in water absorption was achieved in 48 h by the blocks, presenting a promising and cost-effective solution for seepage-related issues in building construction.

The effect of freeze-thaw cycles and sulfuric acid attack separately on the compressive strength and microstructure of 3D-printed air-entrained concrete

3D-printed concrete (3DPC) is a promising technique for constructing structures and intricate designs. To ensure the successful performance of these structures throughout their service life, it is essential to understand their long-term properties and durability. While the use of air-entraining additives can enhance the durability of concrete against freeze-thaw cycles, investigating their impact on other properties is crucial. This study examines the effect of freeze-thaw cycles and sulfuric acid attack on the durability of 3D-printed concrete containing air-entraining additives. The results indicate that, in addition to improving resistance to freeze-thaw cycles, air-entraining additives also increases resistance to sulfuric acid attack. The drop in compressive strength of the samples containing air-entrained additive (0.08–0.12 % AEA) is 1.4–5.3 % less than the control samples against the freezing and thawing cycles. Examining the mechanisms of action of these invasive agents also shows this. Creating intentional voids to reduce the internal pressure of water expansion during freezing and reducing the number and width of possible microcracks are the dominant mechanisms of air-entraining additives against freeze-thaw cycles. Besides, their performance mechanisms during acid attacks are somewhat similar. Analysis of elements created in the matrix of the samples after acid attack indicates a decrease in calcium concentration and an increase in silica concentration. Among the observed reactions, the second reaction prevails, leading to the breakdown of the C-S-H structure into gypsum and silica hydroxide. This phenomenon is associated with changes in acid concentration. However, the presence of air bubbles causes surplus plate-like Calcium hydroxide crystals resulting from the elevated cement content in printed mixes to form within these bubbles, making them susceptible to damage and fracture during freeze-thaw and acid attacks.

Cause Analysis and Improvement Measures for Superheated Platen Tubes Failure of a 580 t/h CFB Boiler

Superheaters are crucial components of boilers operating under high temperatures and pressures. Understanding potential damages, especially in components like superheaters, is essential for enhancing boiler, turbine, and overall power plant productivity. This paper highlights a study for the failure investigation of platen superheater tube in Unit 2 of a 2x150 MW coal-fired power plant in South Sumatra. Various tests including chemical composition, hardness, tensile, metallography, SEM fracture surface examination, and XRD compound analysis were conducted to assess the failure of the platen superheater tube. The investigation revealed that the failure of platen superheater tube was initiated by the plugging of the tube elbow due to deposits and ashes adhering to the tube's interior. This obstruction prevented saturated steam flow inside the tube, leading to overheating and a subsequent drop in mechanical strength. Overheating was confirmed by the presence of spheroid particles in the ferrite matrix. Prolonged overheating resulted in the formation of microvoids, leading to creep failure and crack formation in the tube. Following improvements made during Unit 2 maintenance outage, which involved adding refractory material inside the furnace on the platen superheater panel, positive results were observed. The platen superheater tubes, which previously exceeded temperature limits, now operate within normal range temperatures. This improvement also reduced spray water consumption and significantly increased boiler efficiency from 83.19% to 83.54%.

Additive friction stir deposition of Al 6061-B4C composites: Process parameters, microstructure and property correlation

Al 6061-B4C metal matrix composites were fabricated using a novel solid state additive manufacturing technique of additive friction stir deposition (AFSD). Incorporation of B4C particles into the deposit was achieved by employing hollow Al 6061 feed stock filled with B4C powder and three different AFSD tool rotational speeds (200, 300 and 400 rpm). Fabricated deposits exhibited remarkable metallurgical bonding across the substrate/deposit interface and interlayer interfaces for all tool rotational speeds, indicating a wider fabrication window. A physics based pseudo-thermo mechanical model was employed to evaluate the thermo-kinetic conditions experienced by the depositing material to correlate with the microstructural observations. Deposited layers exhibited refinement of grains to ∼10 μm from the corresponding coarse grain structure of feedstock (136 μm). The regions near the B4C particles were observed to have finer grains (<2 μm) signifying particle stimulated nucleation. Although considerable loss in the tensile properties (60 % drop in yield strength) was observed in the AFSD deposits due to the associated dissolution of β’’ precipitates, subsequent heat treatment restored the tensile properties to the level of as received material (∼290 MPa). The thermo-kinetic conditions (temperature in excess of 500 °C and strain rates in excess of 250 s−1) experienced by the builds under higher AFSD tool rotational speeds (300 and 400 rpm) appeared to result in refinement of Al–Fe–Si based secondary intermetallic precipitates/dispersoids leading to the observed higher stability of their microstructure during the subsequent post AFSD heat treatment. Samples AFSD fabricated with a lower tool rotational speed of 200 rpm, however, exhibited significant grain growth on account of relatively larger secondary precipitates/dispersoids.

A green binder for cold weather applications: enhancing mechanical performance of alkali-activated slag through modulus, alkali dosage, and Portland cement substitution

Below 5 °C, Portland cement (PC) experiences delayed hydration, slowing strength development, making it unsuitable for winter. Alkali-activated slag (AAS) emerges as a viable alternative with continuous hydration in low-temperature conditions. The effect of the activator nature on the performance of AAS cured at normal temperatures is well known, but further studies are required for low-temperature conditions. This study investigates the synergistic impact of activator modulus (1.2 and 1.5), alkali dosage (5, 7, and 9%), and PC substitution rates (0, 10, and 20%), on low-temperature cured AAS properties. Eighteen mixtures were prepared and cured at 2 °C. Compression and ultrasonic pulse velocity tests were conducted after 7, 28, and 90 days. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy analyses were performed to examine the microstructure of the samples. Elevating alkali dosage enhanced early age strength but resulted in a drop in 90-day strength. Simultaneous increases in modulus and PC substitution rate reduced strength due to shrinkage-induced crack formation. Optimal mixture design options included using 10% PC in the 1.2 modulus and omitting PC when the 1.5 modulus was selected. Despite low temperatures, the use of PC significantly accelerated the setting time. Altering modulus and alkali dosage caused a considerable change in the intensity of the peaks in the FTIR spectrum. The findings indicate that AAS shows promise when adjusting the mixture design for temperatures below 5 °C, which are unfavorable for the hydration of PC.

Investigation on submerged friction stir welding of AZ31B magnesium alloy under the influence of rotation speed

In this study, submerged friction stir welding (SFSW) was performed to weld 6 mm thick AZ31B Mg alloy plates, aiming to explore the impact of rotation speed on microstructure and tensile behavior. The water medium was used to submerge the samples. The SFSW was conducted at three different speeds (815, 960, and 1200 rpm), to assess the impact of rotation speed on SFSWed joint performance. As the rotation speed increased from 815 to 960 rpm, tensile strength increased plateauing over a range of the rotation speed. However, a significant drop in tensile strength occurred at 1200 rpm due to the formation of void defects. The SZ exhibits a size and width increment in the lower part with increasing rotation speed. The hardness of the stir zone (SZ) gradually rose with increasing rotation speed from 815 to 960 rpm. Fracture locations were observed in the thermal-mechanically affected zone (TMAZ) adjacent to the SZ at a rotation speed of 815 rpm, and in the heat-affected zone (HAZ) adjacent to the TMAZ at a rotation speed of 960 rpm. The joint welded at 1200 rpm fractured within the SZ. This study offers valuable insights into the welding and joining field, particularly regarding their mechanical characteristics.

Sintered and unsintered pressed fly ash geopolymer: A comprehensive study on structural transformation in nitric and sulfuric acid

Acidic attacks contribute to the degradation of cementitious materials, diminishing the structural service life and increasing the requirement for maintenance of the structure. To address the limited understanding of the impact of the sintering process on the acid resistance of pressed geopolymer, an investigation and comparison of the acid resistance of room-cured (RPG) and sintered (SPG) pressed geopolymer was performed. Specimens were immersed in 3 % and 8 % nitric (HNO3) and sulfuric (H2SO4) acids for 7 and 28 days. Despite the higher sorptivity, SPG demonstrated better mechanical strength retention than that of RPG. Specifically, the compressive strength of SPG after 3 % of HNO3 immersion for 28 days increased (+14.2 %), surpassing the control specimen, while RPG experienced a 14.5 % strength drop. The strength increment in SPG was due to the further geopolymerization during acid immersion. In RPG, a new crystalline phase of NaNO3 was observed after immersion in 8 % HNO3 for 28 days. In contrast, SPG showed no evidence of NaNO3 formation, indicating lower reactivity with HNO3 compared to RPG. Additionally, both RPG and SPG exhibited gypsum formation after immersion in H2SO4. The presence of gypsum induced crack formation in RPG, whereas SPG, with its intensive cross-linked structure, effectively compensated for gypsum expansion, preventing crack formation. This finding is crucial for practical applications where exposure to aggressive acids is a concern, as it provides a method to enhance the acid resistance of geopolymer structures.

Performance of Zero-Slump Concrete Made with Recycled Concrete Aggregate

Abstract Concrete with no slump that is typically used for prefabrication is known as zero slump concrete (ZSC). ZSC is sensitive to mixture proportion. Since coarse aggregate makes up the majority of the concrete volume, recycling concrete aggregates will be a great choice for reducing the amount of concrete waste. Therefore, the purpose of this paper is to analyze the impact of using coarse recycled concrete aggregate (RCA) in ZSC properties. Five mixes were manufactured, each with a different percentage of coarse RCA (0%, 25%, 50%, 75%, and 100%). Compressive strength, flexural strength, ultrasonic pulse velocity (UPV), dry bulk density, and water absorption of recycled aggregate ZSC were conducted at 7, 28 and 90 days. Experiments revealed that the inclusion of coarse RCA in ZSC degraded the quality of manufactured concrete. At 90 days, in comparison to the control mix, the minor drop was at 25% coarse RCA incorporation, which resulted in a 6.2%, 4.1%, 2%, and 2.4% drop in compressive strength, flexural strength, UPV, and dry bulk density, respectively, while there was a 24.4% increase in water absorption. The highest drop of recycled aggregate ZSC at 100% incorporation resulted in a 41.7%, 19.1%, 8.6%, and 7.6% drop in compressive strength, flexural strength, UPV, and dry bulk density, respectively, while there was a 158.8% increase in water absorption.

Functional Performance and Tendon Morphology After Operative or Nonoperative Treatment of Achilles Tendon Ruptures.

While controversy remains as to the relative benefit of operative (OM) versus non-operative management (NOM) of Achilles tendon (AT) ruptures (ATR), few studies have examined the effect on high impact maneuvers such as jumping and hopping. The purpose of this study was to determine if functional performance including strength, jumping, and hopping outcomes differed between OM and NOM of acute ATR. The secondary objective was to assess the degree of association between AT morphology and performance outcomes. Retrospective cohort with a single prospective evaluation. All patients were treated at an institutional secondary care center. Eligible participants (n=12 OM; 12 NOM) who were treated with OM or NOM of ATR within three weeks of injury were evaluated a minimum 20 months following ATR. AT length, thickness and gastrocnemius muscle thickness were assessed with B-mode ultrasound. Isokinetic plantar flexor strength, hop tests and countermovement and drop jumps were completed. Two-way ANOVAS were completed on all tests with unilateral values, independent t-tests were used for bilateral outcomes, and linear regressions were completed to assess the relationship between normalized AT length and performance. Affected limb AT was elongated and thickened (p\<0.01), gastrocnemius was atrophied (p\< 0.01) and angle-specific plantar flexor torque was reduced at 120°/s when measured at 20° plantar flexion (p = 0.028). Single leg drop vertical jump was higher in OM (p = 0.015) with no difference for hop and jump tests. AT length was related to plantar flexor torque but had no relationship with hopping performance. Hop test performance was maintained despite plantarflexion weakness, gastrocnemius atrophy, and AT elongation. This may be the result of compensatory movement patterns. AT length holds limited explanatory power in plantar flexor strength, although this relationship should be evaluated further. Level III.

Influence of Extra-Short Extra-Fine Steel Fibers on Mechanical Properties of Self-Compacting Concrete with Single-Doped Fly Ash

This study assesses the influence of extra-short extra-fine steel fibers on the performance of self-compacting concrete (SCC) modified with fly ash. Replacing standard steel fibers with volume fractions ranging from 0%, 1.5%, 3%, 5% and 6%, the study optimizes the mix design for enhanced workability and mechanical properties. The findings reveal that, although the addition of steel fibers had a negative effect on the flowability, the cohesion is significantly improved, providing a basis for a significant improvement in the mechanical properties. The optimal fiber content is identified at 5%, achieving the highest compressive strength of 71.7 MPa, split tensile strength of 8.2 MPa, and flexural strength of 12.8 MPa at 28 d. However, further increases in fiber content beyond 5% lead to a deceleration in compressive and splitting tensile strength improvement and a 27.5% drop in flexural strength at 28 d. The study also emphasizes the good dispersion within the concrete, which helps to enhance its ductility and crack resistance, to some extent.

Preparation and Application of CO2-Resistant Latex in Shale Reservoir Cementing

With the application of CO2 fracturing, CO2 huff and puff, CO2 flooding, and other stimulation technologies in shale reservoirs, a large amount of CO2 remained in the formation, which also lead to the serious corrosion problem of CO2 in shale reservoirs. In order to solve the harm caused by CO2 corrosion, it is necessary to curb CO2 corrosion from the cementing cement ring to ensure the long-term stable exploitation of shale oil. Therefore, a new latex was created using liquid polybutadiene, styrene, 2-acrylamide-2-methylpropanesulfonic acid, and maleic anhydride to increase the cement ring’s resistance to CO2 corrosion. The latex’s structure and characteristics were then confirmed using infrared, particle size analyzer, thermogravimetric analysis, and transmission electron microscopy. The major size distribution of latex is between 160 and 220 nm, with a solid content of 32.2% and an apparent viscosity of 36.8 mPa·s. And it had good physical properties and stability. Latex can effectively improve the properties of cement slurry and cement composite. When the amount of latex was 8%, the fluidity index of cement slurry was 0.76, the consistency index was 0.5363, the free liquid content was only 0.1%, and the water loss was reduced to 108 mL. At the same time, latex has a certain retarding ability. With 8% latex, the cement slurry has a specific retarding ability, is 0.76 and 0.5363, has a free liquid content of just 0.1%, and reduces water loss to 108 mL. Moreover, latex had certain retarding properties. The compressive strength and flexural strength of the latex cement composite were increased by 13.47% and 33.64% compared with the blank cement composite. A long-term CO2 corrosion experiment also showed that latex significantly increased the cement composite’s resilience to corrosion, lowering the blank cement composite’s growth rate of permeability from 46.88% to 19.41% and its compressive strength drop rate from 27.39% to 11.74%. Through the use of XRD and SEM, the latex’s anti-corrosion mechanism, hydration products, and microstructure were examined. In addition to forming a continuous network structure with the hydrated calcium silicate and other gels, the latex can form a latex film to attach and fill the hydration products. This slows down the rate of CO2 corrosion of the hydration products, enhancing the cement composite’s resistance to corrosion. CO2-resistant toughened latex can effectively solve the CO2 corrosion problem of the cementing cement ring in shale reservoirs.

Impact of in-process cooling and tool rotation speed on the mechanical and microstructural characteristics of friction stir processed AA2024

Despite significant grain size refinement, friction stir processing (FSP) of heat-treatable aluminum alloys is found to degrade the alloys of strength and hardness qualities. The drop in strength brought on by coarsening or the dissolution of the strengthening precipitate(s) could not be made up for by the improvement in strength brought about by the refinement of grain size following FSP. In order to get around this, the current work looks into a practical method of heat rejection from the FSP zone in addition to grain size refinement during FSP of AA2024 to regulate the precipitate evolution. Under natural cooling, air cooling, and CO2 cooling conditions, friction stir processing (FSP) was used to change the microstructure of Solutionized AA2024 at three distinct rotation speeds of 750, 1180, and 1500 rpm (fixed traverse speed of 50 mm/min). The microstructural evolution (through optical microscopy and SEM) and mechanical properties of FSP samples under different conditions of rotation speed and cooling and their differences were mainly discussed. All the FSP samples have a higher Vickers hardness than the base metal (minimum variation of 16.79% and maximum variation of 41.05%). The maximum hardness, yield strength, tensile strength, and elongation have been obtained under air cooling conditions and a rotation speed of 1180 rpm, which is a result of the simultaneous and effective effect of grain boundary strengthening and precipitation hardening.

Microstructural effects on the rotating bending fatigue behavior of Ti–6Al–4V produced via laser powder bed fusion with novel heat treatments

The rotating bending fatigue (RBF) behavior (fully reversed, R = −1) of additively manufactured (AM) Ti–6Al–4V alloy produced via laser powder bed fusion (PBF-L) was investigated with respect to different microstructures achieved through novel heat treatments. The investigation herein seeks to elucidate the effect of microstructure by controlling variables that can affect fatigue behavior in Ti–6Al–4V, such as chemistry, porosity, and surface roughness. In order to control these variables, different hot isostatic pressing (HIP) treatments at 800 °C, 920 °C, and 1050 °C with a 920 °C temper were applied to three sets of Ti–6Al–4V cylinders that originated from the same PBF-L build, such that there were 30 tests per condition. After HIP treatment, the specimens were machined and tested. The highest runout stress was achieved after sub-β transus HIP at 800 °C for 2 h at 200 MPa of pressure. A significant drop in fatigue strength was attributed to large prior-β grains and grain boundary α resulting from super-β transus HIP treated specimens. For the sub-β transus HIP specimens, differences in fatigue strength were attributed to α lath thickness, relative dislocation density, and dislocation boundary strengthening.

Effects of interlaminar modification on mechanical, thermal conductivity and ablative performance of C/C composites doped with high thermal conductivity graphite film

C/C composites modified with high thermal conductivity graphite film (C/C-HTCGF) were prepared by resin impregnation‑carbonization and chemical vapor infiltration. Effects of interlaminar HTCGF modification on microstructure, mechanical, thermal conductivity (TC) and ablative properties were investigated. The findings demonstrate that the interlaminar HTCGF modification not only affects the flexural and compressive strength, but also results in the pseudoplastic behavior for the composites. After 3000 °C graphitization, the flexural and compressive strength drop from 109.81 and 142.4 MPa to 88.49 and 60.5 MPa, respectively, which can be attributed to the increased defects (cracks and pores) and degraded carbon fibers' strength in the composites. Meanwhile, the TC of the composites increases from 56.929 to 160.569 W/ (m·K) and 12.452 to 38.839 W/(m·K) in both transverse direction and thickness direction due to the increased graphitization degree. Moreover, the enhanced TC after graphitization declines the maximum surface temperature (110 °C) during ablation.

Application of Novel Ruthenium (II) Polypyridyl Complexes as Robust DNA Probes, Optical Material and Antimicrobials-An Experimental and DFT Approach.

The nature of the interaction of DNA with heteroleptic Ruthenium (II) Polypyridyl complexes of the type [Ru (A)2TPIP]2+, where TPIP = 2-(1-p-tolyl-1H pyrazol-4 -yl)-1H-imidazo [4, 5-f[1. 10] phenanthroline and A = 1,10 phenanthroline (1),4,4'-dimethyl-1,10-ortho Phenanthroline (2),2,2' - bipyridine(3) and 4, 4' dimethyl 2, 2'- bipyridine (4), has been investigated by experimentaland molecular docking approaches. The order of the DNA binding affinities of the synthesised complexes is 1 > 2 > 3 > 4. The findings imply that the unsubstitutedcomplex has a better affinity to bind with DNA than the substituted (dmp and dmb) emphasizing the significance of the auxiliary ligand. Additionally, as the medium's ionic strength drops, the DNA/Ru ratio rises, or when water is displaced by glycerol, the intercalation of complexes into DNA increases. DFT calculations at the B3LYP/LANL2MBlevel was used for molecular geometry (Ground State) and electronic characteristic calculations. The HOMO-LUMO gap of the Ru [II]complex is less than the intercalator and hence kinetically labile. Among the complexes, the bpy complex has shown utmost non-linear optical properties (α = -153.9099 10-24esuand β = 3.8498 10-30esu). The docking study shows the significance of the Metal-intercalator's shorter length may increase DNA binding affinity. This study divulges that the Ruthenium (II) polypyridyl complexes bind to DNA preponderantly by intercalation supporting Viscosity studies. All the complexes have a considerable attraction for guanine. The standarddiskdiffusion method reveals that complexes (1,2,3 and 4) have good antibacterial activity.

Enhanced high-temperature ductility without strength drop in a lean Co Ni-based superalloy

The conventional Ni-based IN738LC superalloy series are typically hardened by a fine distribution of closely spaced fine and coarse Ni3(Al, Ti)-type L12 ordered γ' precipitates, which is formed by solid-state nucleation and growth in the disordered γ matrix. However, outstanding high-temperature mechanical performance requires a high amount (∼9 wt%) of Co, which is the alloy's most expensive adding element. Here, we report a compositionally modified IN738LC alloy with a 50% reduction in Co content and a 20% increase in comparatively cheaper Mo content. This compositional modification caused more γ' precipitates with uniform distribution than those in the conventional counterpart subjected to the same heat treatments. The modified superalloy showed a twofold increase in high-temperature (750 °C) tensile elongation while maintaining the conventional one's strength (∼1.1 GPa) at the temperature. This remarkable ductility gain, while no loss in strength, was predominantly attributed to a transition in the high-temperature deformation mechanism, i.e., from multiple intersecting slip bands-indued stress localization for the conventional IN738LC alloy to unidirectional microtwins for the modified IN738LC material. More Mo and less Co contents could drive more coherent γ' precipitates in the annealed state and the high density of microtwins in the deformed state, resulting in stress delocalization and enhanced ductility at comparable strength. The findings of this study have significant implications for the development of cost-effective, strong, and ductile superalloys for high-temperature applications.

Fabrication and Physico-mechanical Characterization of Short Natural/Synthetic Fiber–Reinforced Hybrid Composites: Effects of Biodegradation and Chemical Aging

The main goal of this study was to develop eco-friendly and low-cost multiple short natural fiber-reinforced hybrid composites with the hybridization of comparatively high-strength glass fibers. The hybrid composites were fabricated via hand lay-up by using short jute, silk, water hyacinth, and glass fibers for the reinforcements and unsaturated polyester resin for the thermoset polymer matrix. The reinforcing fibers were randomly oriented, and five types of hybrid composites were fabricated with different types of fiber content (wt.%). The performance of the manufactured hybrid composites was assessed by tensile, flexural, and impact testing, as well as water uptake (%). It was revealed that composites with high glass fiber content (wt.%) exhibited optimum mechanical performance in most cases, while poor moisture resistance performance was exhibited for the hybrid composites containing higher natural fibers (wt.%). The hybrid composite samples were also aged in soil medium (biodegradation) for 25 days and different chemical solutions (alkaline, acidic, and salt) for 10 days. After biodegradation, the drop of tensile strength (TS) and tensile modulus (TM) was revealed to be approximately 38–61 and 58–72%, respectively. On the other hand, after chemical aging, the drop of TS and TM was exhibited to be approximately 49–76% and 51–65%, respectively, for alkali solution aging; 42–75% and 29–76%, respectively, for acid solution aging; and 43–59% and 51–65%, respectively, for salt solution aging.

Advanced Solid Geopolymer Formulations for Refractory Applications.

Cement, as a construction material, has low thermal resistance, inherent fire resistance, and is incombustible up to a certain degree. However, the loss of its mechanical performance and spalling are its primary issues, and it thus cannot retain its performance in refractory applications. The present study explores the performance of geopolymer formulations that have excellent fire resistance properties for potential refractory applications. This study is unique, as it investigates advanced solid geopolymer formulations that need only water to activate and bind. Various solid geopolymer formulations with fly ash as a precursor; potassium hydroxide and potassium silicate as activators; and mullite and alumina as refractory aggregates were studied for their compressive strength at up to 1100 °C and compared with their two-part conventional liquid alkaline geopolymer counterparts. Advanced solid geopolymer formulations with mullite and alumina as refractory aggregates had mechanical strength values of 84 MPa and 64 MPa post-1100 °C exposure and were further exposed to ten thermal cycles of 1100 °C to study their fatigue resistance and post-exposure compressive strengths. The geopolymer sample with mullite as a refractory aggregate yielded 115.2 MPa compressive strength after the fourth cycle of exposure. This sample was also studied for its temperature distribution upon direct flame exposure. All the geopolymer formulations displayed a drop in compressive strength at 600 °C due to viscous sintering and then a rise in strength at 1100 °C due to phase transformation. X-ray diffraction studies revealed that the formation of crystalline phases such as leucite, sanidine, and annite were responsible for the superior strengths at 1100 °C for the alumina- and mullite-based geopolymer formulations.

Development and characterization of biocomposite films using banana pseudostem, cassava starch and poly(vinyl alcohol): A sustainable packaging alternative

To meet the need for sustainable packaging, we introduce a novel biocomposite film consisting of banana pseudostem, cassava starch, and poly(vinyl alcohol). We aimed to evaluate the optimal biocomposite film composition, which is characteristic for packaging materials. Using the solvent casting method, we produced biocomposite films with varying proportions (10–40 % w/w) of the lignocellulosic component from both Sour and Ash Plantain banana pseudostems. The resulting biocomposite films were characterized for mechanical, chemical, thermal, water absorption, gas permeability, and morphological properties. At the 25 % lignocellulosic level, a notable drop (P < 0.05) in tensile strength and elongation was observed, while water absorption increased, and gas permeability decreased. Fourier Transform Infrared Spectroscopy analysis revealed insights into the structural attributes of lignocellulosic composites. Thermogravimetric analysis indicated an onset temperature of 120 °C for thermal degradation, confirming the biocomposite's thermal stability. A fundamental discovery emerged with the optimal composition at a 30 % pseudostem powder inclusion, offering an exceptional balance of tensile strength, elongation at break, water absorption, and gas permeability. This breakthrough holds significant implications for eco-friendly biocomposite films, particularly in food packaging. Future work may be undertaken to further explore banana pseudostems' potential in creating biocomposite films with advanced functionalities and their broader applications, including characterizations.

Comparative evaluation of two cetylpyridinium chloride-based mouthwashes on the mechanical properties and strength loss of elastomeric chains used in dentistry: An vitro study

ObjectivesEvaluate the strength degradation of polymeric ligature chains after their immersion in cetylpyridinium chloride-based mouthwashes. Methods240 elastomeric samples from four different manufacturers (Rocky Mountain®, Ormco®, Morelli® and Dentaurum®) in two types of configurations (with and without intermodular links) and divided in 3 groups (distilled water, Vitis CPC Protect® and PERIO·AID® 0.05%) at 5 follow-up periods (0–24 h, 7–14 -21 days) were immersed twice a day for 60 s, following the manufacturers' protocols. A universal traction machine was used to perform the measurements and a post hoc multiple comparisons were based on the Bonferroni test and extended to a 3-way ANOVA test (α = 0.05). ResultsThere was a drop in strength up to 35.9% at 24 h. After a week, the short chains (52%) degraded less than the long ones (57.3%) with significant differences (p < 0.001) and the same pattern was observed until 21 days (p < 0.001). At 24 h, the degradation of the chains exposed in distilled water was 25.8%, in VITIS CPC Protect® 28.6% and in PERIO· AID® 0.05%, 27% with significant differences (p < 0.001). At 21 days, the VITIS CPC Protect® group obtained a much greater loss of strength, being this drop statistically significant (p < 0.001). The chains from Ormco® and RMO® experienced the least loss of force when immersed in the control group or PERIO AID® 0 0.05% (48% and 51%), while Dentaurum's in VITIS CPC Protect® lost more than 75%. ConclusionsThe orthodontic elastomeric chains suffer a sharp drop in strength during the first days of treatment. When comparing the mouthwashes, there were statistically significant differences in terms of strength degradation. Clinical significanceBased on the results, some types of chains, such as the ones without intermodular links from Ormco® showed better properties throughout the study. When immersed in PERIO·AID®0.05%, all showed significantly better results over time. Thus, PERIO·AID®0.05% can be recommended as a complementary oral hygiene element in dental treatments when elastomeric chains are used.