Current Materials Science - Volume 18, Issue 4, 2025

The study systematically investigates the influence of annealing temperatures, ranging from 500°C to 900°C with 100°C increments, on the microstructural characteristics of cobalt ferrite (CoFe2O4) nanoparticles.

The nanoparticles, with sizes between 7-18 nm, were synthesized using the co-precipitation method. X-ray diffraction (XRD) analysis reveals that higher annealing temperatures correspond to noticeable increases in crystallite size, lattice parameter, unit cell volume, and interatomic distances within both octahedral and tetrahedral sites. Concurrently, a substantial decrease is observed in the average theoretical X-ray density, dislocation density, and microstructural strain. This investigation elucidates the underlying physical and chemical processes driving these transformations. To explore and quantify the intricate relationships between annealing temperature and various microstructural attributes of CoFe2O4 nanoparticles, Pearson’s correlation coefficient (r) serves as a robust statistical tool. The study establishes significant associations and elucidates the strength and direction of these correlations.

Regression analysis yields highly robust correlations (Adjusted R-Squared > 0.99) between microstructural features and annealing temperature. These correlations provide valuable predictive insights into microstructural characteristics, offering substantial support for optimizing CoFe2O4 nanoparticle applications across a temperature range spanning from 500°C to 900°C.

This research contributes to the scientific understanding of materials engineering and offers practical guidance for applications requiring precise control over nanoparticle properties.

The main goal of the current research was to investigate the influence of a wall-bounded medium on the settling behaviour of flexible planktonic particles. The particles are permeable and immersed in a Newtonian, incompressible, and viscous fluid.

This study employed the Immersed Boundary Method to analyze the interaction between the fluid and the flexible planktonic particles.

The research findings revealed a notable correlation between the terminal (fall) velocity of the particles and distance amongst the confining walls, referred to as the “wall gap.” Specifically, as the wall gap increased, the terminal velocity of the particle also increased. Additionally, the study demonstrated that the degree of distortion experienced by the flexible planktonic particles increased with the expansion of the wall gap.

In conclusion, the distance between the confining walls plays a significant role in determining the terminal velocity of the flexible planktonic particles during settling. This study highlights the importance of considering the wall gap as a crucial factor when examining the behaviour of these particles in a wall-bounded medium.

Herein, we prepared Zinc oxide (ZnO) and silver (Ag) doped ZnO nanoparticles (NPs) using a simple, fast, effective and economic co-precipitation method. The superior characteristics in the nanoscale range of ZnO encourage us to work on the ZnO NPs. Also, Ag has long been employed for its antibacterial qualities.

The samples were synthesized by chemical-co-precipitation method. X-ray diffraction (XRD) results indicate a hexagonal wurtzite structure of ZnO NPs and an additional peak corresponding to the metallic Ag phase in the Ag-ZnO sample. The EDAX elemental mapping confirms the uniform distribution of Ag in ZnO NPs. Photoluminescence (PL) spectroscopy investigates electronic structure and defects in NPs.

According to the PL study, the strong photoluminescence NBE observed at 393 nm, indicating the high crystalline quality of the material and broad blue-green emission at 467 nm and green-yellow emission at 560 nm were attributed to the Zn interstitial and oxygen vacancy defects present in ZnO NPs. Measurements from cyclic voltammetry (CV) demonstrate approximately symmetric peaks related to anodic and cathodic behaviours of the NPs based electrode. For ZnO sample, the anodic peak was found at 0.49 V and cathodic at 0.29 V, whereas, for Ag-ZnO sample, the anodic peak was at 0.59 V, and the cathodic peak was present at 0.19 V, respectively. The separation between cathodic and anodic peaks enhanced with Ag-doping in ZnO, which could be associated with the variations in the transfer of electrons at the interface between the working electrode and the solution, confirming an increase in the reaction activity of Ag-ZnO NPs.

The results indicate that Ag-doped ZnO NPs may be an efficient catalyst for waste water treatment and photocatalytic applications.

Ca-Mg nanoferrites of composition Ca0.5Mg0.5Fe2O4 were synthesized by wet chemical citrate precursor approach.

The prepared nanoparticles were characterized by an “X-ray diffractometer, Scanning electron microscopy, Diffused reflectance spectroscopy, and Impedance analyzer”. In the XRD pattern, the most intense reflection was observed from the (311) peak that corresponds to the cubic spinel phase of the prepared ferrite.

The average size of all crystallites was calculated to be 19 nm. The sample's porosity was found to be 61%. In the SEM micrograph, uniformity in the size of the particles was detected with some agglomeration. The calculated energy band gap (1.91eV) reveals the semiconducting nature of the prepared material.

The high value of the real part of the dielectric constant (290) and the low value of loss tangent (0.17) reveals that the synthesized material can be useful in magnetic cores, microwave components, and other high-frequency applications.

The compatibility study is an important aspect before pre-formulation of the energetic composites. Any sort of the incompatibility between the ingredients of the energetic composites greatly affects the safety and functionality of the energetic composites. Therefore, to develope safer energetic composites, the compatibility between the different ingredients of the energetic formulations and their thermal decomposition kinetics is important study as it is directly linked with the safety and functionality of the energetic composites.

The compatibility of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) with different polyester-based polyurethanes (PUs) were studied by using vacuum stability tester (VST) and differential scanning calorimetry (DSC) methods as outlined by North Atlantic Treaty Organisation Standardisation Agreement (STANAG 4147). The mixture of RDX with polyester-based PUs was cured with MDI (4,4’-methylene diphenyl diisocyanate), IPDI (isophorone diisocyanate) and TMDI (2,2,4-trimethylhexamethylene diisocyanate) as curatives to get polyester-based PUs. The VST measurements were carried out at isothermal temperature of 100°C for 40 h. For kinetic study, all the samples were subjected to heat from 25-600°C at different heating rates under flow rate of nitrogen gas of 40 mL/min.

The VST results revealed that energetic RDX was compatible with all polyester-based PUs and was chemically stable. The thermal decomposition behaviour was studied by employing thermogravimetric analysis (TGA) and DSC. The DSC results indicated that peak temperature difference (Tp) between pure RDX and binary mixture of RDX and polyester-based PUs i.e., RDX/PE/MDI, RDX/PE/IPDI and RDX/PE/TMDI were found to be greater than 4°C indicating that RDX was not compatible with all types polyester-based PUs. The thermal stability in terms of Tmax values of RDX/PE/MDI, RDX/PE/IPDI and RDX/PE/TMDI was found to be significantly reduced as compared to pure RDX. The activation energy obtained by the Kissinger method for RDX/PE/MDI, RDX/PE/IPDI and RDX/PE/TMDI samples was found to be 220.2, 271.5 and 210.4 kJ/mol, respectively. The experimental results showed that the values are comparable and in good agreement with the values obtained by Ozawa method.

This study provides useful information for selecting polyester -based PUs as polymeric binder for the preparation of RDX-based energetic composites.

In this paper, we explore the world of flexible patch antennas, specifically focusing on their horizontal V-folding percentages. The folding of these antennas plays a crucial role in the realm of wireless communication.

Our V-folding antenna is ingeniously crafted for seamless communication with objects featuring sharp curves. What sets our study apart is the exploration of the effects of V-folding percentages on the current distribution, a novel approach. We closely monitored the surface current distribution of the V-folded antenna, considering the percentage-wise impact along with the influence of the ground plane. Delving deeper, we scrutinized changes in ground plane size and drew comparisons between a standard ground and a resized one in the context of the V-folded patch antenna.

The resized ground plane outshone its normal counterpart, exhibiting superior performance. With the normal ground, the FPA operated at 1.42 GHz and 4.485 GHz. Post-resizing the ground, it showcased commendable stability in retaining the V-folding frequency shift.

Crafting the antenna's structure was a meticulous process accomplished through the use of CST Microwave Studio software, and we validated our design using a vector network analyzer.

A series of nickel doped cobalt (NixCo1-xFe2O4, x=0.0 to 1.0) were successfully synthesized using green synthesized process.

Tensile strain of all positive slope samples observed from the W-H (Williamson Hall) plot. It was discovered that as Ni-substitution increased, the dielectric constant (є’) increased from 148.07 to 243.62. Conversely, when the amount of Ni-substitution increases, the dielectric loss (tan δ from 0.23 to 0.05), imaginary part (є” from 98.81 to 17.87), and ac conductivity (σac from 1.62 to 0.15) all decreases at 1MHz frequency.

This demonstrates that when Ni-substitution increases, energy losses at high frequencies decrease. Dielectric constant and ac conductivity, of all samples act in accordance with Koop's theory, the Maxwell-Wagner polarization procedure, and electron hopping.

This makes them suitable materials for high-frequency applications.

Hydroxyl-Terminated Polybutadiene (HTPB)-based energetic compositions have been developed for enhanced blast energetic composite, composite rocket propellant formulations, metal cutting, demolition, welding and explosive reactive armour in civil and military applications. The types and choice of curing agents are crucial in enhancing the mechanical and structural integrity of the binder. To understand the stability and safety of energetic composites for potential applications, it is necessary to understand the thermal decomposition kinetics and thermodynamic parameters clearly.

The main objective is to study the decomposition kinetic and thermodynamic parameters of energetic composites cured by different curing agents.

A series of energetic composites based on HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane) and HTPB-based binder system cured with various curing agents were prepared by the cast cured method. The curatives, namely MDI (4,4’-methylene diphenyl diisocyanate), IPDI (isophorone diisocyanate), TDI (toluene dissocyanate) and TMDI (2,2,4-trimethylhexamethylene diisocyanate) were used. The thermal analysis method was employed to investigate the thermal decomposition characteristics, which are closely associated with the thermal stability and safety considerations during handling, processing, and storage. The kinetic parameters for thermal decomposition reactions were studied by employing the Flynn-Wall-Ozawa method. The thermodynamic parameters of the activation enthalpy, activation Gibbs energy free and activation entropy of all energetic composites were also determined by the theory of activated complex.

The thermogravimetric results show that the thermal stability is almost similar for all composites cured with the different types of curing agents. The average activation energy of the energetic composites cured with IPDI, MDI, TMDI and TDI was 207.5, 237.3, 243.3 and 187.6 kJ/mol, respectively. The thermodynamic parameters for the thermal decomposition process show that they are generally thermodynamically stable and non-spontaneous. Scanning Electron Microscope (SEM) micrographs of all the samples clearly indicate that HMX crystals are well embedded in the polymer matrices.

The thermal stability of all energetic composites is almost constant. The activation energy of the prepared energetic composites is significantly varied with varying the type of curing agents in the HTPB-based binder system. The thermodynamic parameters indicate that composites possess superior stability and thermal safety. The SEM micrographs indicate that HMX crystals of prepared composites are embedded in the polymer matrix.

The rationality of the mixing process specified in the “Technical Guideline for Construction of Direct-to-Plant SBS Modified Bituminous Pavement” needs further verification.

To study the dynamic modification effect during the mixing process of SBS-T and the optimal mixing process.

SBS-T-modified asphalt under different mixing processes was collected in this paper, and the microscopic images were obtained by using fluorescence microscopy. Then qualitative and quantitative analysis were conducted on the dynamic modification effect. The pavement performances of SBS-T modified asphalt mixture under different mixing processes were studied using the high-temperature rutting, low-temperature bending, and immersion Marshall tests.

An increase in temperature is beneficial for SBS-T to reach a rapid melting state. The fluorescence microscopic area reaches its maximum at a mixing temperature of 180°C, a mixing time of 60s~75 s without asphalt, and a mixing time of 120 seconds with asphalt.

The mixing process of SBS-T modified asphalt mixture is as follows: modifier content of 6%~7.5%, mixing temperature of 170°C~180°C, mixing time of 60s~75 s without asphalt, and mixing time of 120 s with asphalt.

Localized corrosion in welds has always been a very common and difficult problem in many industrial fields. Preferential corrosion usually occurs in the weld zones with irregular shapes of metal welds due to the welding process.

To address the challenge of monitoring corrosion behavior at the weld zone in real-time, a novel Ag/AgCl flexible array, arranged in a 4×8 electrode configuration, has been developed. This array is employed for in situ monitoring of the corrosion process in Q235 steel welded joints (including single butt welds, double butt welds, and fillet welds) immersed in a 0.01 mol/L NaCl solution with a pH of 9. The measurement is conducted using a custom-made array electrode signal test system.

The results demonstrate that the prepared electrode exhibits a highly responsive behavior to chlorine ions from 0.001 to 0.1 mol/L concentration and maintains excellent stability during 4000 s. The weld zone shows higher corrosion activity and trends to generate pitting corrosion for all three welded joints in the first 15 min. With the increase of time, micro pitting corrosion dissolves and expands to macro point corrosion in the next 30 min.

The flexible reference array electrode proves to be a powerful tool for the in situ monitoring of carbon steel corrosion, offering a comprehensive depiction of the steel's corrosion status over time. Such insights are crucial for making accurate corrosion predictions and conducting service life evaluations of steel structures.

The production process of Portland cement (OPC) consumes energy and releases carbon dioxide, which affects the environment. It has been found that geopolymer cementing material is a better substitute for it. The strength effect of fiber on geopolymer materials is the basis of the application of fiber geopolymer concrete in structural beams, slabs, and other components.

Geopolymer concrete was prepared with fly ash, slag, and water glass as the main raw materials, and the effects of fiber type, quality, and blending method on the compressive properties and elastic modulus of geopolymer concrete were compared to explore the working mechanism of fiber-reinforced geopolymer concrete.

Through experimental research, the results showed that in 0.2% flocculent lignin fibers, when the mass ratio of carbon fibers was increased, the strength of the geopolymer concrete decreased. Due to the increased mass ratio of wavy steel fibers, comprising 0.2% flocculent lignin fibers, the strength enhancement effect was not apparent. Moreover, with regard to enhancing the modulus of elasticity of geopolymer concrete, blending fibers exerted the most significant effect. The fiber was added to geopolymer concrete to form a three-dimensional supporting frame system. When cracks occurred under the action of force, the development of cracks was limited due to the fibers, and the bonding slip delayed the propagation of cracks. The composite fiber could make full use of the advantages of each material and improve the strength of geopolymer concrete.

The compressive properties of geopolymer concrete could be enhanced by blending single-fiber or mix-fibers, and the effect of mix-fibers was more optimal than that of others. The above research results provide a theoretical reference for the design of geopolymer concrete and a theoretical basis for the application of fiber geopolymer concrete in structural beams, slabs, and other components.