Strength Coefficient Research Articles

Performance Evaluation of Hybrid PSO-BPNN-AdaBoost and PSO-BPNN-XGBoost Models for Rockburst Prediction with Imbalanced Datasets

The rockburst hazard is a primary geological disaster endangering the environment in underground engineering. Due to the complexity of the rockburst mechanism, traditional methods are insufficient to predict the rockburst hazard objectively, especially when dealing with an imbalanced dataset. To address this issue, the hybrid models of PSO-BPNN-AdaBoost and PSO-BPNN-XGBoost were developed to predict rockburst hazards in this study. First, a rockburst dataset with 266 cases was constructed, containing six indicators: the maximum tangential stress, uniaxial compressive strength, uniaxial tensile strength, elastic deformation energy index, tangential stress index, and brittleness coefficient of strength. Then, the original dataset was oversampled using the synthetic minority oversampling technique (SMOTE) for dataset balancing. Subsequently, the PSO-BPNN-AdaBoost and PSO-BPNN-XGBoost models were constructed and evaluated to have the best accuracies of 0.901 and 0.851, respectively. Finally, the developed models were applied to predict the rockburst hazard in the Daxaingling Tunnel, the Cangling Tunnel, and the Zhongnanshan Tunnel shaft. The results indicate that the obtained rockburst hazard levels are consistent with engineering records, and the developed PSO-BPNN-AdaBoost and PSO-BPNN-XGBoost models are reliable for rockburst prediction.

Blast response of rectangular graded foam sandwich plate with fiber-metal laminate face-sheets

In this paper, the dynamic response of a fully clamped rectangular graded foam sandwich plate (GFSP) with fiber-metal laminate (FML) face-sheets under impulse loading is studied analytically and numerically. Due to the fibers having intricate layups, there are various difficulties in developing an analytical model that can accurately analyze the structural properties of fiber layups. In this work, the bound and membrane mode solutions for the blast response of a rectangular GFSP with FML face-sheets are obtained on the basis of the modified rigid-plastic model by introducing the number of fiber layups, metal volume fraction, composite density coefficient, and composite strength coefficient. In addition, finite element analysis is performed using ABAQUS/Explicit software. Analytical predictions agree very well with numerical results. The effects of metal volume fraction, composite coefficients of density and strength, thickness and average yield strength of the graded foam, and gradient property of the foam on the blast response of GFSP with FML face-sheets are discussed. It is demonstrated that the proposed analytical model can be efficient in predicting the blast response of rectangular GFSP with FML face-sheets.

Residual displacement ground-motion model

Residual displacement (RD), indicative of permanent post-earthquake deformation resulting from nonlinear structural response, plays an important role in assessing structural integrity and seismic safety. This study introduces a ground-motion model (GMM) for predicting RDs in inelastic single-degree-of-freedom systems, utilizing a large database of recorded ground motions. The RD GMM adopts key input parameters including 5%-damped elastic pseudo-spectral acceleration (PSA) over periods from 0.01 to 4.0 s, yield strength coefficient (Cy), earthquake magnitude (M), and closest distance to the fault rupture plane (Rrup). Levels of inelasticity are accounted for by employing the yield strength reduction factor, denoted as (PSA/g)/Cy. The results indicate that while M and Rrup significantly affect RDs, site class and significant duration have relatively less influence. RD GMM coefficients and unconditional standard deviations of the model are provided for specific Cy values across a period range of 0.01–4.0 s. The analyses indicate relatively large standard deviations in the GMM due to inherent variability in residual displacement, highlighting the importance of understanding and accounting for this variability in seismic design and performance assessment. Validation against a multi-degree-of-freedom bridge residual drifts demonstrates the effectiveness of the model in predicting the distribution of residual drifts.

Freeze-thaw resistance and deterioration mechanism of alkali-activated filling grouts prepared from full industrial solid wastes for tunnels

To promote the application of the proposed alkali-activated grout (AAG) prepared from full solid wastes in cold-zone tunnel projects located at high altitudes and latitudes, it is imperative to fully recognise its endurance to the repeated freezing and thawing in specific service scenarios. For this purpose, two groups of representative AAG were selected as subjects for this study, and a typical OPC-based grout was chosen as the control group. Freeze-thaw cycle tests were carried out on grout samples after 28 days of standard curing using the slow-freeze method to simulate the harsh service environment in cold regions. The deterioration impact of freeze-thaw cycling on the grout samples were evaluated by monitoring the changes in visual appearance, mass loss, mechanical strength, and damage coefficient after 20, 40, 60 and 80 freeze-thaw cycles. Furthermore, the deterioration mechanism of various grout samples under the action of freeze-thaw cycling was revealed by multi-technique characterization methods including X-ray diffraction (XRD), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP). The results show that at the same number of freeze-thaw cycles, the surface deterioration, mass loss and strength damage of AAG were obviously better than that of the OPC-based grout, suggesting that AAG exhibited greater resistance to freezing and thawing than the OPC-based grout. The mass loss ratio increased with the increase of the number of freeze-thaw cycles, following a roughly power function pattern. The deterioration in the flexural strength of grout samples caused by freeze-thaw cycles was more severe than the deterioration in their compressive strength. The gel products of AAG were mainly C-A-S-H and N-A-S-H, which showed stronger resistance to freeze-thaw damage than the gel products of the OPC-based grout, C-S-H and portlandite. Compared with the OPC-based grout, AAG samples possessed a denser microstructure with lower porosity and a smaller proportion of large-sized harmful pores, which was not favourable for the pore water holding and migration of during freeze-thaw cycling and the development of osmotic and frost heave stresses, thus providing better resistance to freezing and thawing. A variety of macroscopic characterisations and microstructural tests have demonstrated the good durability of AAG against the freeze-thaw cycles, which can serve as a scientific foundation for its future engineering uses.

Effect of episodic pre-failure cyclic loading on whole-life geotechnical properties of soft clays

Changes in soil properties due to loading and consolidation during the life of infrastructure affect the soil response to future events. This concept is encapsulated in the whole-life geotechnical design approach which accounts for the evolution of properties such as strength, stiffness and consolidation coefficient, to improve forecasts of system response through and beyond the design life. This paper explores the changing properties of a soft clay from episodes of pre-failure cyclic loading and consolidation through a series of stress-controlled cyclic direct simple shear (DSS) tests. The scenario is relevant to offshore applications where infrastructure is subject to cyclic seasonal loading, and is particularly relevant to floating offshore wind anchoring systems as these are located in deeper water, farther from shore where soft clays are common. The results quantify the effect of cyclic stress amplitude, number of cycles per packet, and number of consolidation intervals, on the clay properties. The results show increases in undrained strength by up to 70%, stiffness by up to 50% and consolidation coefficient by a factor of up to 30, highlighting the importance of accounting for whole-life effects for reliable and efficient geotechnical design.

Study on the removal behavior of constituent phases of SiCp/Al composites by ultrasonic vibration-assisted milling

SiCp/Al composites are widely used in aerospace, optical devices, electronic devices and other fields due to their excellent properties such as wear resistance, high specific strength and low thermal expansion coefficient. Due to the difference between the constituent phases of SiCp/Al composites and the high hardness of SiC particles, conventional milling (CM) leads to problems such as poor processing quality and severe tool wear. Ultrasonic vibration-assisted milling (UVAM) can achieve high-quality cutting of SiCp/Al composites. However, the relationship between constituent phases (SiC particles, Al matrix) and tool under ultrasonic vibration is complex and the research depth is insufficient. This paper focuses on the study of the interaction between the constituent phase of SiCp/Al composites and the tool in UVAM. The formation process of residual cutting zone and material removal mechanism in ultrasonic machining were analyzed, and the influence of ultrasonic vibration on the removal mechanism of SiCp/Al composites was explored from the aspects of tool cutting speed and tool kinetic energy. A three-dimensional micro-cutting model of SiCp/Al composite multi-particles was established, and the interaction between constituent phases and tool during cutting under different ultrasonic amplitude conditions was analyzed by finite element method and combined with a series of experiments. The results show that the introduced ultrasonic vibration increases the kinetic energy of the tool and improves the tool's ability to damage SiC particles and Al matrix. Compared with CM, UVAM significantly reduces surface pits, scratches, and SiC particle crushing defects, and the surface roughness Sa is reduced by 32.33 %. Tool wear is relieved, and the wear of the back tool face is reduced by 22.31 % at most. At the same time, the resultant milling force is also decreased 32.76 %. In short, the research in this paper is of great significance to improving the high-quality processing of SiCp/Al composites.

Dynamic response of spring valve subjected to underwater pressure pulse

Spring-loaded valves are widely used to protect sealed containers filled with liquid against sudden excessive overpressure; however, the unstable vibration of a valve spool under dynamic loading may lead to safety incidents. This study aims to investigate the nonlinear vibration processes of a valve spool subjected to an underwater pressure pulse. To achieve this objective, the spring-loaded valve was simplified to an air-back mass spring with a constraint boundary (AMSCB). A modified split Hopkinson pressure bar (SHPB) was adopted to generate a controllable pressure pulse to establish the relationship between the specific impulse and the discharged water mass. Following the experimental verification, the influences of the pressure pulse parameters and dimensionless time on the motion characteristics of the mass block and flow rate were studied based on finite element (FE) simulations. Five motion modes were identified according to the number of collisions with the constraint boundary and changes in movement direction: (i) no collision, (ii) single collision, (iii) chatter, (iv) single collision with direction change, (v) multiple collisions. Moreover, a theoretical model for predicting the movement of a mass block was developed and validated against numerical results. The classification phase diagram of the motion mode is presented in a two-dimensional plane composed of specific strength coefficient ϕ and fluid-structure interaction coefficient ψ, and the influence of the geometrical parameters of the AMSCB on the classification boundary of motion modes is presented. The results indicate that, when subjected to underwater pressure pulse loading, the mass block repeatedly collides with the constraint boundary and undergoes non-periodic motion. With higher loading pressure amplitude and duration, the mass block is more likely to collide with the back boundary, leading to a transition in movement modes from mode (i), mode (ii), mode (iv) to mode (v). Increasing the stiffness coefficient and areal density will increase the threshold of ϕ and ψ for the transition from mode (i) to mode (v), while the maximum allowable displacement has little effect on the classification boundaries. These research findings are valuable for analysing the motion response of mass spring with various constraint boundaries under dynamic loading, and for guiding the design of spring-loaded valves.

A New Approach to Characterize Superplastic Materials from Free-Forming Test and Inverse Analysis

For about 60 years, the aerospace industry has been strongly interested in superplastic forming processes to produce extremely light and complex-shaped components. Superplastic characteristics are found in lightweight metallic materials such as titanium-based, aluminum-based, and, more recently, magnesium-based alloys. Since the high ductility exhibited by superplastic materials is two orders of magnitude higher than that of conventional materials, complex-shaped components can be obtained. If made with conventional materials, they require expensive assembly operations. The behaviour of superplastic materials is summarized by a constitutive equation commonly obtained via tensile testing that subjects the tested material to a one-dimensional stress state. On the contrary, free-forming tests allows us to test the material by subjecting it to a stress state similar to that determined during a real superplastic-forming process. The aim of this work is to define the characteristic parameters of superplastic materials by free-forming tests. The behaviour of superplastic materials is commonly modelled using a power law which puts the material into a stress-to-strain-rate relationship. This law needs to identify two parameters characterizing superplastic materials: the strain rate sensitivity index and the strength coefficient. In this work, a new procedure is presented that implies the two material parameters vary with strain. It allows for a reduction in the number of constants needed to determine the material constitutive equation, thus requiring low simulation time compared to models that adopt the multiple-objective optimization based on genetic algorithms (GAs). It is more suitable to be used in the industrial field. Furthermore, the proposed procedure is compared with a conventional procedure which is also based on the inverse analysis carried out through the use of a finite element analysis. The results of the conventional procedure, based on the inverse analysis, which is conducted through the use of a finite element analysis, are used to calculate the material constants, and are compared with those coming from the procedure proposed in this work. The proposed procedure appears equally simple and gives more accurate results compared to the conventional procedure. In fact, the maximum percentage error, regarding the prediction of the forming times of a free-forming process, was reduced from 20% to 8%. The development of the proposed procedure, as well as the comparison of the results with a conventional procedure, required the development of an experimental activity. This activity consists of free-forming tests conducted at a constant pressure (the pressures employed vary from 0.2 to 0.4 MPa), at a temperature of 753 K, and on circular sheets (thickness 1.0 mm and radius 40 mm) in superplastic magnesium alloy AZ31.

Investigation of the performance and life cycle assessment of alkali-activated sintered sludge-slag-based permeable concrete

As urbanization continues to accelerate, the application of permeable concrete is becoming an increasingly prevalent practice. Nevertheless, the carbon dioxide emission issue associated with traditional permeable concrete cannot be overlooked. In this study, alkali-activated sintered sludge and slag were employed as raw materials to prepare alkali-activated sintered sludge-slag-based permeable concrete. The effects of sludge calcination temperature, sludge content, and binder-to-aggregate ratio on the compressive strength, porosity, and permeability coefficient of the permeable concrete were investigated through the implementation of one-way experiments. The formation mechanism of permeable concrete materials was analyzed using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and a carbon emission assessment was performed. The findings indicated that an increase in sludge content resulted in a notable decline in the 28-day compressive strength, accompanied by a reduction in the Ca/Si ratio of the C-A-S-H hydration products, from 1.08 to 0.35. Conversely, the carbon emission assessment demonstrated that abiotic losses declined markedly with an increase in sludge content, effectively mitigating the carbon emission burden associated with construction materials.

Enhancing hydration resistance and mechanical properties of dolomite refractory through ZnO nanoparticle incorporation

AbstractThe study aims to enhance the hydration resistance of dolomite refractory by investigating the influence of ZnO nanoparticles on their physical and mechanical properties. Four samples with varying ZnO concentrations (0, 0.5, 1, and 2 wt%) were prepared. The main identified phases were magnesia (MgO) and lime (CaO). The microstructure of the dolomite refractory shown irregularly shaped grains dispersed within a matrix phase, with an increase in ZnO nanoparticles, leading to larger and more abundant grains. The incorporation of ZnO nanoparticles resulted in improved density, hydration resistance, and cold compressive strength, attributed to a reduction in porosity. The sample containing 2 wt% ZnO nanoparticles displayed the highest cold compressive strength and thermal expansion coefficient compared to the pure sample. The addition of ZnO enhanced the dolomite's compressive strength by approximately 46%. These findings suggest that ZnO nanoparticles can enhance the properties of dolomite refractory, particularly in terms of hydration resistance.

Evaluating the effect of A- and B-site cobalt doping on the structural, morphological, dielectric, and non-ohmic properties of CaCu3Ti4O12 ceramics prepared by the hydrothermal method

CaCu3Ti4O12 (CCTO), CaCu3-xCoxTi4O12 (CCCxTO) and CaCu3Ti4-xCoxO12 (CCTCxO) ceramics with x = 0.1 were synthesized by the hydrothermal process at 200 °C for 24 h. The influence of cobalt substitution on the copper and titanium sites in CaCu3Ti4O12 on the structural, morphological, and physical properties was investigated. It was shown through the analysis of X-ray diffractograms of CCTO, CCCxTO, and CCTCxO compounds that they crystallized in a pure perovskite structure without the presence of secondary phases. The refinement of the spectra using the Rietveld method showed an efficient formation of the crystalline phase of the cubic structure (Im3¯), which remains unchanged, with an increase in the unit cell due to the substitution of Co2+/Co3+ in the Cu2+ and Ti4+ sites of the CCTO ceramic. Raman spectroscopy was used as a complementary characterization method to XRD in order to detect vibrational bands and highlight any changes in the crystal lattice. SEM results showed that cobalt insertion increased the average grain size. The dielectric properties were studied by complex impedance spectroscopy in a frequency range from 1 kHz to 1 MHz at different temperatures, where the insertion of cobalt in the Cu2+ and Ti4+ sites has a significant effect on the permittivity value (εr) and dielectric losses (tanδ). The non-ohmic characteristics showed that the change in grain size due to cobalt incorporation is beneficial to improving the breakdown strength (Eb) and nonlinear coefficient (α), which can be attributed to the grain boundary properties of the Internal Barrier Layer Capacitor (IBLC) model and the behavior of the Schottky barrier.

Reversible Schiff-base chemistry enables thermosetting smart composites with versatile properties

Fibre-reinforced polymer composites have become indispensable structural materials in modern life and global industry due to their superior specific properties and improved energy efficiency. However, the irreversibility of commercially available thermoset matrices, characterized by covalent cross-linking, poses challenges to both the recyclability and the enhancement of functionality. Herein, inspired by living tissues, we demonstrated recyclable, reprocessing, self-growing, and thermally/water modulated carbon fibre reinforced polyimine composites at low processing temperatures (≤110 °C, without any catalyst), realizing the intelligent composites. The tensile strength and average friction coefficients of our composites were 129.1 MPa and 0.52, respectively. Moreover, the chemical welding and self-growing mechanism of our system were deeply explored. The process enabled the recovery of clean and intact carbon fibres. We aim for this work to further deepen the understanding of dynamic polyimine networks with semi-aromatic skeleton, and facilitate the preparation of smart, adaptive and pluripotent composites.

Post-fire residual mechanical properties of Q460GJ steel under different pre-tensile stresses

Previous studies on the post-fire mechanical properties of steel were conducted with unstressed state, without considering the influence of pre-stress which subjected to structures in reality. In this article, the post-fire residual mechanical properties of Q460GJ steel under different pre-tensile stresses were studied. The stress-strain curve, elastic modulus, yield strength, ultimate strength and fracture elongation of Q460GJ steel after different elevated temperatures heating are analyzed in detail. The experimental results are compared with that of Q460 steel and S460 steel in the existing literatures. At last, the predictive equations of post-fire mechanical properties of Q460GJ steel under different pre-tensile stresses are established. Q460GJ steel still maintains good ductility after elevated temperature heating, which increases the possibility of reuse of Q460GJ steel element after fire. The Q460GJ steel has better post-fire ductility than that of Q460 and S460 steels. The predictive equations for the post-fire residual mechanical properties for Q460GJ steel under different pre-tensile stresses were proposed. The variation coefficients of yield strength for Q460GJ steel under different pre-tensile stresses after 20 min different elevated temperatures heating were within 0.065. The findings should have a great significance to providing theoretical support for design of reusing or restoring steel building after fire.

Post-Fire Stability Bearing Capacity of I-Shaped Aluminum Alloy Members Under Axial Compression

Compared to steel structures, aluminum alloy structures are more susceptible to fire damage. Accurately evaluating the residual bearing capacity of fire-damaged aluminum alloy members is crucial for effective post-disaster management. Therefore, this paper investigates the post-fire bearing capacity of I-shaped aluminum alloy members under axial compression. First, a post-fire test on 16 I-shaped aluminum alloy members under axial compression was carried out. The test results indicate that all specimens fail by the minor axis flexural buckling, and the bearing capacity of the specimens decreases with the increase of the slenderness ratio. Moreover, a trilinear relationship is found between bearing capacity and post-fire temperatures. Second, finite element (FE) models are established using ABAQUS and validated against the test results. Subsequently, numerical analysis is carried out, considering various aluminum alloy brands, post-fire temperatures, slenderness ratios, initial geometrical imperfections, and cross-section dimensions. Through the statistical regression technology and the introduction of strength and stability-bearing capacity reduction coefficients, the formulae for estimating the post-fire stability-bearing capacity of I-shaped aluminum alloy members under axial compression are derived. Finally, the proposed formulae are verified to be accurate through error analysis.

Size effect modellings of axial compressive failure of RC columns at low temperatures

This paper applied a thermal-mechanical sequential coupled mesoscopic simulation method to explore the axial compression performance and the corresponding size effect of Reinforced Concrete Columns confined by Stirrups (i.e., RCCS) at low temperatures, with considering the interaction between concrete meso-components and steel bars as well as the low-temperature effect of mechanical parameters. Based on the heat conduction analysis, the axial compression mechanical failure behavior of RCCS with four structural sizes (i.e., 267 × 267 × 801, 400 × 400 × 1200, 600 × 600 × 1800 and 800 × 800 × 2400 mm) and two stirrup ratios (i.e., 1.26% and 2.89%) at different temperatures (i.e., T = 20, −30, −60 and −90°C) was subsequently simulated. The effects of temperature, structural size and volume stirrup ratio on axial compression properties were quantitatively discussed. The results showed that the peak strength of RCCS increased with the decreasing temperature, and the smaller-sized RCCS showed a stronger effect of low-temperature enhancement. Both the residual strength and displacement ductility coefficient decreased with the decreasing temperature. The peak strength, residual strength and displacement ductility coefficient of RCCS decreased with the increasing structural size, showing obvious size effects. The size effect on peak strength increased with the decreasing temperature, (the maximum increase was nearly 140%), but the size effect on displacement ductility coefficient decreased (the maximum decrease was nearly 70%). The peak strength, residual strength and ductility were enhanced with the increasing volume stirrup ratio, which was helpful to reduce the influence of size effect. Finally, an improved size effect theoretical model was proposed, which can effectively predict the axial compressive strength of RCCS with different structural sizes and stirrup ratios at room and low temperatures. The present research results can provide reference for the large-scale engineering application of RCCS in low-temperature environments.

MPFEM investigation on densification and mechanical structures during ferrous powder compaction

Metal powder compaction is a crucial process in powder metallurgy, significantly affecting the final properties of compacts. However, the quantitative characteristics of multi-scale mechanical structures and the microscopic densification behavior, taking into account the influence of friction conditions, remain unclear. This study utilises a two-dimensional multi-particle finite element method to analyse the ferrous powder compaction. The evolution of powder densification, powder deformation and multi-scale mechanical behaviour under different friction coefficient conditions are analyzed quantitatively and qualitatively. Results reveal that powder densification occurs in distinct stages, with lower friction coefficients promoting greater powder densification, as observed from relative density and coordination number. Additionally, as the axial strain increases, plastic strain gradually rises whilst roundness decreases. Higher friction coefficients are associated with higher equivalent plastic strain but lower powder roundness. The Von Mises stress exhibits different stages of increase with the increment of axial strain. Powders with lower friction coefficients exhibit lower levels of Von Mises stress. As axial strain increases, the number, length, strength and direction coefficient of force chains undergo different evolution processes. Force chains exhibit longer length, fewer numbers, lower strength and lower direction coefficients at lower friction coefficients.

Effects of Mixture Proportions and Molding Method on the Performance of Pervious Recycled Aggregate Concrete.

The use of pervious concrete pavement systems with recycled aggregates is a sustainable and innovative solution to major urbanization challenges such as repurposing construction waste, alleviating urban waterlogging, and reducing heat-island effects. This study aims to investigate the effects of mixture proportions and molding methods on the performance of pervious recycled aggregate concrete (PRAC). To this end, the coarse aggregate size (4.75~9.5 mm, 9.5~16 mm, and 16~19 mm), the molding method (layered insertion-tamping and vibration molding with vibration times of 5 s, 10 s, or 15 s, respectively), and the replacement rate of recycled coarse aggregate (RCA) (0%, 30%, 50%, and 100%, respectively) are considered. The results reveal that the addition of RCA to permeable concrete weakens its permeability. However, the compressive strength of PRAC reaches its maximum value when the RCA replacement rate is 50%. A larger aggregate particle size (16~19 mm) enhances the compressive strength of PRAC, yet decreases the permeability of PRAC. By using vibration molding to fabricate PRAC, an extension to the vibration duration increases the compressive strength, yet concurrently decreases the permeability. Based on the compressive strength and permeability coefficient of PRAC, the optimal mixture proportions and molding method are suggested.

Interfacial assembly of nanocellulose microgels enhances thermal insulation of Pickering foam

Nanocellulose has attracted extensive attention in the preparation of thermal insulation materials because of its high Young's modulus, high strength and low thermal expansion coefficient. In this study, nanocellulose microgels prepared by self-assembly of 2,2,6,6-Tetramethylpiperidoxyl oxidized nanocellulose (TOCNC) and Nisin were used as particle stabilizers, and acrylated epoxidized soybean oil (AESO) was used as oil phase to prepare Pickering emulsion, which was cured by heating to obtain biomass-based Pickering thermal insulation foam. Pickering foams prepared based on microgels with different Nisin contents have significant differences in thermal insulation performance. The results show that the addition of microgel particles can improve the thermal stability, increase the roughness of pore wall and reduce the thermal conductivity of AESO polymer foam. Among them, the Pickering foam prepared by microgel containing 0.06 wt% Nisin has the best thermal insulation performance and rougher pore wall surface, and its thermal conductivity is 0.040 W/(m·K), which is obviously lower than that of the foam prepared by TOCNC (0.083 W/(m·K)). Based on the structural design of nanocellulose microgel particles, this work innovatively realized the assembly of microgels at the oil-water interface and the regulation of thermal insulation performance through Pickering technology, and developed a biomass-based foam with improved thermal insulation effect, which provides a new idea for expanding the advanced application of nanocellulose in the field of thermal insulation materials.

Fabrication and characterization of novel glass-ionomer cement prepared from oyster shells

Glass ionomer cement (GIC) is one of the most widely used restorative materials for temporary fillings and reconstructions in dentistry, but it has relatively poor mechanical properties that make its use limited, especially in places subject to high pressure. Thus, to extend the applicability of GIC, samples based on SiO2, P2O5, Al2O3, CaF2, and NaF were prepared with the addition of calcium oxide CaO extracted from natural sources (oyster shells) in different ratios of 0, 5, 10, 15, 20, and 25% wt. The suggested glass samples were evaluated, and their physical and mechanical properties were compared. XRD, SEM, and FTIR were performed on the samples. 24 specimens were prepared for each test in order to assess the mechanical properties as per the specific requirements. The tests included measuring bending strength, elastic modulus, adjusted direct tensile strength, absorption, water solubility, and diffusion coefficients after the specimens were stored in distilled water for 60 days. All calculations were carried out in accordance with standard procedures. The findings indicated a slight improvement in the bending resistance of the recommended GIC. Glass modified with 20% by weight of calcium oxide was the best among the ratios in terms of the results obtained and compared to the traditional commercial type. The malleable strength of the sample was 54.121 MPa, while the flexural modulus increased, the tensile strength reached 10.154 MPa, and the solubility was 25.87 µg/mm3 after storage for 60 days. These indicate that the developed material is suitable for use as a dental restoration material when compared to international commercial cement specifications.

Development of Interpenetrating Phase Structure AZ91/Al2O3 Composites with High Stiffness, Superior Strength and Low Thermal Expansion Coefficient

Development of Interpenetrating Phase Structure AZ91/Al2O3 Composites with High Stiffness, Superior Strength and Low Thermal Expansion Coefficient