Filler Fraction Research Articles

Cyanate Ester/TiO2 Composites for High‐Temperature and Miniaturized Microwave Substrate Applications

High‐temperature‐withstanding TiO2‐reinforced cyanate ester composites are developed by mechanical stirring, followed by curing at elevated temperatures. The uniform dispersion of the filler is confirmed using scanning electron microscopy and electron dispersive spectroscopy. All composites, up to a filler fraction of 30 vol%, exhibit a density of more than 90% while it reduces significantly after that. A high relative permittivity of 7.6 and a low loss tangent of 0.0112 are observed for the optimally filled 30 vol%. The addition of the filler further improves the temperature‐withstanding capability of the cyanate ester matrix. Moreover, a high thermal conductivity of 0.543 W mK−1, improved hardness of 24.88 HV, ultimate tensile strength of 11.68 MPa, and a low coefficient of thermal expansion of 36.44 ppm °C−1 are also shown by the optimally filled sample. A moisture absorption of 0.072 vol% observed for the optimal filled sample comes within the limit for microwave substrate applications. Thus, the developed composites are suitable candidates for high‐temperature microwave electronic applications.

Polyisoprene grafted white carbon black reinforced polyisobutylene‐based pressure‐sensitive adhesives: Comprehensive enhancement of adhesive performances

AbstractNowadays, inorganic fillers are widely used to enhance pressure‐sensitive adhesives (PSAs), but inorganic fillers have problems with poor compatibility and agglomeration. Furthermore, these types of PSAs usually have an antagonistic effect: as the shear performance improves, the initial tack decreases. This severely limits the application of PSAs. Herein, white carbon black (WCB) grafted with polyisoprene (PI) was prepared and used to enhance polyisobutylene‐based PSAs, and the optimal reaction conditions of grafting were explored. The shear and peel strength of PSAs all increase with the increase of the mass fraction of fillers. When the filler content is less than 10 wt%, the initial tack of PSAs increases. When the filler content exceeds 10 wt%, the initial viscosity of PSAs decreases, but it is still far higher than that of the unmodified WCB‐reinforced PSAs system. In addition, the rheological performances of PSAs were tested, further exploring the role of particle grafting in PSAs.Highlights PSAs reinforced with white carbon black grafted with polyisoprene were prepared. The optimal conditions for modified white carbon black have been determined. The grafting fillers have improved all the performance of PSAs. The grafting of fillers significantly reduces the antagonistic effect of PSAs. Rheology was used to explore the effect of filler grafting in the PSAs.

Design and preparation of composite bipolar plates with synergistic conductive networks of graphite and metal foam

Graphite composite bipolar plate (BP) have limited conductivity, which makes them less than ideal for extensive application in proton exchange membrane fuel cell (PEMFC). In traditional graphite composite BP, the construction process of the conductive network is entirely random. To enhance conductivity, it is typically necessary to increase the content of conductive fillers or incorporate high aspect ratio carbon nanomaterials to optimize the density of the conductive network. In this work, we manufactured a highly conductive composite bipolar plate with synergistic conductive networks of graphite and metal foam (MF). With a synergistic conductive network, the ASR of CuG80-20ppi decreased to 7.7 mΩ cm2. Additionally, thermal conductivity increased to 24.76 W/(m·K), and in-plane conductivity reached 294.1 S/cm at 80 wt% mass fractions of conductive filler, using 20 ppi copper foam as the metallic conductive network. CuG80-20ppi exhibited a flexural strength of 52.2 MPa. G80 and CuG80-20ppi have the 80 wt% conductive filler and are molded into BP with parallel flow fields. CuG80-20ppi enhances the current density of PEMFC by 0.132 W/cm2 and reduces the ohmic impedance by 5.25%. Therefore, the findings of this study offer valuable insights for the enhancement of composite BP conductivity, while simultaneously ensuring the stability and continuity of the synergistic conductive network. A novel approach is presented to enhance the electrical conductivity of graphite composite bipolar plate (BP) for proton exchange membrane fuel cells (PEMFCs). By embedding metal foam as a supplementary conductive network within the graphite matrix, a synergistic conductive architecture is achieved. This innovation significantly reduces the area specific resistance (ASR) to 7.7 mΩ cm2 and boosts thermal conductivity to 24.76 W/(m·K). The resulting CuG80-20ppi BP, with 80 wt% conductive filler, exhibits improved mechanical strength and conductivity, contributing to a 0.132 W/cm2 increase in PEMFC current density and a 5.25% reduction in ohmic impedance. This work highlights the potential of metal foam integration to enhance BP conductivity and PEMFC performance.

A novel water‐based mechanochemical approach for surface modification of graphene platelets and their epoxy nanocomposites

AbstractGraphene (nano) platelets (GPs) are cost‐effective and possess high structural integrity, but their limited surface functional groups hinder their compatibility with polymers. In this study, an eco‐friendly, water‐based mechanochemical approach was developed to modify GPs with polyacrylamide (PAM), creating PAM graphene platelets (PAM‐GPs) with a grafting ratio of approximately 15%. The platelet was measured to be a few nanometers in thickness, and the grafted PAM provides abundant functional groups, including amide groups, which enhance compatibility with polymers. A typical polymer, bisphenol‐A epoxy, was compounded with PAM‐GPs, resulting in a high degree of exfoliation and dispersion of PAM‐GPs within the matrix. The resulting epoxy/PAM‐GP composites exhibited significantly improved mechanical properties, including an 18% increase in Young's modulus and a substantial enhancement in fracture toughness, with a 71% increase at a low filler fraction of 0.5 wt%. These improvements are attributed to the effective interfacial interaction between the PAM‐GPs and the epoxy matrix, facilitated by the grafted functional groups. This study highlights the potential of PAM‐GPs as toughening fillers for epoxy composites, emphasizing their applicability in enhancing the durability and performance of structural components in industrial applications.Highlights Polyacrylamide (PAM)‐modified graphene platelets by a water‐based approach. A strong interface promoted exfoliation and dispersion of platelets. PAM‐modified platelets improved epoxy modulus and toughness. Fractographic analysis unveils toughening mechanisms.

Elaboration and Experimental Characterizations of Copper-Filled Polyamide Micro-Composites for Tribological Applications

Polyamide 66 (PA66) has been used for dynamic bearing applications due to its good wear and abrasion resistance, hardness, and rigidity. PA66/copper micro-composites were studied with respect to micro-mechanical, tribological, and structural properties. A mixing step followed by injection molding was used to develop the different composites: PA66+5 wt.% Cu, PA66+10 wt.% Cu, and PA66+15 wt.% Cu. The morphological aspects of the composites were studied using scanning electron microscopy and microtomography. Good dispersion and adhesion of Cu particles across the matrix were also seen. DSC analysis showed a slight improvement in the % of crystallinity and thermal characteristics of the composites, particularly with 5 wt.% filler. Additional crystallization enhanced the tensile performance of the composites, including the modulus, elongation at break, and tensile strength. Nanoindentation tests also indicated an increase in indentation hardness and elastic modulus as a function of the filler fraction. A pin-on-disk tribometer was used to study the friction and wear properties of neat PA66 and copper-filled PA66 composites. It was found that the composite with 5 weight percent copper had the best wear resistance. A progressive decrease in the friction coefficient was also seen. Copper filler increases hardness and may effectively reduce the temperature at contact interfaces during rotating cycles.

INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG AND MWCNT-REINFORCED EPOXY HYBRID NANOCOMPOSITES: A SUSTAINABLE APPROACH FOR ENVIRONMENTAL PRESERVATION

This experimental investigation explores the mechanical and tribological characteristics of cupola slag (CS) and multiwall carbon nanotubes (MWCNTs) reinforced hybrid nanofiller epoxy composites. Cupola slag is an industrial by-product that is generated during the melting of cast iron. The disposal of slag residues in landfills results in environmental pollution. In the context of environmental preserving as well developing new engineering composites material from waste to resource. MWCNTs possess an excellent strength-to-weight ratio, high stiffness, and thermal properties. The mechanical and tribological characteristics of the hybrid nanocomposites comprising epoxy were examined by varying the weight fraction of fillers composed of CS and MWCNTs. The experimental results indicated that the ECSM3 hybrid nanocomposites have superior tensile strength and the flexural modulus improved by 92 % and 78 % respectively when compared with epoxy. Similarly, the tribology performance of the ECSM3 exhibited improved specific wear resistance of 97 %, 106 % and 88 % on the dry-sliding loads of 10 N, 20 N and 30N, respectively. A morphological analysis was carried out on fractured and worn surfaces of the specimen to understand the homogeneous dispersion and matrix-interlocking mechanism between the hybrid nanofillers and the epoxy matrix. The integration of CS alongside MWCNTs for the fabrication of epoxy hybrid nanocomposites represents a stride towards sustainable and eco-friendly technology in the production of multifunctional composite materials for diverse engineering applications.

Optimizing Energy Storage Performance in Polymer Dielectrics through Dual Strategies: Constructing “Peaked” Barrieras and Enhancing Carrier Scattering

AbstractDielectric capacitors play a pivotal role in the advancement of electric power systems and emerging energy technologies. However, the deterioration of dielectric performance in energy storage materials at elevated temperatures represents a significant challenge. In this study, organic electron‐scattering agents into polyetherimide (PEI) are introduced, creating a “peaked barrier” to impede charge carrier transport. By doping PEI with an ultralow volume fraction (0.8%) of the organic molecule filler 4‐(dimethylamino)phenylboronic acid (4‐NB), the electron‐repelling nature of 4‐NB is leveraged in order to regulate charge carrier injection and transport in a synergistic manner. Consequently, the discharged energy density of the PEI composite material increases to 7.93 J cm−3 (720 kV mm−1) at 30 °C. At 150 °C, the discharged energy density increases to 5.21 J cm−3 (580 kV mm−1). In both cases, the charge and discharge efficiencies are maintained at 90%. It is noteworthy that the prepared PEI composite material also exhibits excellent charge dissipation characteristics, maintaining stable charge and discharge efficiency even after 50 000 charge–discharge cycles. In summary, the study's design concept systematically optimizes the processes of charge carrier injection, transport, and dissipation. This approach offers a novel perspective for the development of dielectrics that are suitable for long‐term energy storage.

A comparative study on the mechanical and antibacterial properties of BPA-free dental resin composites

ObjectiveThe commonly used base monomer utilized in resinous commercial dental restorative products is bis-GMA which is derived from bisphenol-A (BPA) - a well-known compound which may disrupt endocrine functions. To address concerns about its leaching into the oral environment and to optimize the quality of dental composites, a BPA-free alternative base monomer, fluorinated urethane dimethacrylate (FUDMA), was designed by modifying a UDMA monomer system. MethodsNine groups of composites were prepared by mixing the base monomers and TEGDMA in a ratio of 70/30 wt% to which were added silanized glass particles (mean diameter: 0.7 µm) in 3 different volume fractions (40, 45, and 50 vol%). Bis-GMA and UDMA base monomers were used as control groups in the same ratios. Various properties including degree of conversion (DC), flexural strength (FS) and flexural modulus (FM), water sorption (WS), solubility (SL), surface hardness and roughness, and initial adhesion property against S.mutans were investigated. One-way analysis of variance followed by Bonferroni test at α = 0.05 was used to analyze the results. ResultsA significant difference in FS between FUDMA-based composite with 40 vol% filler (120.3 ± 10.4 MPa) and Bis-GMA-based composite with the same filler fraction (105.8 ± 10.0 MPa) was observed but there was no significant difference among other groups. The UDMA based group exhibited the highest WS (1.3 ± 0.3 %). Bis-GMA showed greater initial bacterial adhesion but was not statistically different from the other groups (p = 0.082). SignificanceFUDMA-based resin composites exhibit comparable mechanical and bacterial adhesion properties compared with Bis-GMA and UDMA-based composites. The FUDMA composites show positive outcomes indicating they could be used as substitute composites to Bis-GMA-based composites.

Novel Resin-Based Antibacterial Root Surface Coating Material to Combat Dental Caries.

Root caries caused by cariogenic bacteria are a burden on a large number of individuals worldwide, especially the elderly. Applying a protective coating to exposed root surfaces has the potential to inhibit the development of caries, thus preserving natural teeth. This study aimed to develop a novel antibacterial coating to combat root caries and evaluate its effectiveness using the antibacterial monomer dimethylaminohexadecyl methacrylate (DMAHDM). DMAHDM was synthesized and incorporated into a resin consisting of 55.8% urethane dimethacrylate (UDMA) and 44.2% TEG-DVBE (UV) at a 10% mass fraction of glass filler. Multiple concentrations of DMAHDM were tested for their impact on the resin's mechanical and physical properties. S. mutans biofilms grown on resin disks were analyzed for antibacterial efficacy. Cytotoxicity was assessed against human gingival fibroblasts (HGFs). The results showed an 8-log reduction in colony-forming units (CFUs) against S. mutans biofilm (mean ± sd; n = 6) (p < 0.05) when 5% DMAHDM was incorporated into the UV resin. There was a 90% reduction in metabolic activity and lactic acid production. A low level of cytotoxicity against HGF was observed without compromising the physical and mechanical properties of the resin. This coating material demonstrated promising physical properties, potent antibacterial effects, and low toxicity, suggesting its potential to protect exposed roots from caries in various dental procedures and among elderly individuals with gingival recession.

DETERMINATION OF PHYSICAL AND MECHANICAL PROPERTIES OF POLYETHYLENE AND POLYMER NANOCOMPOSITES USING THE METHODS OF MOLECULAR DYNAMICS

Today, molecular dynamics (MD) simulation become an effective method for investigating and predicting the physical and mechanical properties (PMP) of materials at the atomic scale. In this work, initial configurations of molecular systems of pure polyethylene (PE) and carbon nanotube-reinforced nanocomposites (PE-CNT) are created and described by the united atom model and Dreiding force field. Equilibration of the initial configurations of molecular models carried out using NVT and NPT ensembles in LAMMPS. Simulated complex of PMP of PE and PE-CNT includes elastic modulus, Poisson's ratio, bulk modulus, shear modulus, yield strength, mass isobaric heat capacity, and coefficient of linear thermal expansion (CLTE). The results verification of the PE molecular model showed the obtained MD simulation data either coincide with available literature data or are close to them. The results justify the use of the same algorithms to obtaine reliable data on the PMP of PE-CNT. Comparing the complex PMP of molecular models of pure PE and PE-CNT, it was established the elastic modulus of PE-CNT α=1.4 % increases by 10.4% at 300 K and by 29.3% at 320 K. The yield strength of PE-CNT α=1.4 % also increases by 33.2 % at a strain rate of 109 s−1 and a temperature of 300 K compared to PE. Meanwhile, mass isobaric heat capacity and CLTE decrease with increasing temperature: mass isobaric heat capacity decreases by 1.3 % at 300 K and by 4.4 % at 320 K; CLTE decreases by 20.2 % at 300 K and by 22.6 % at 320 K. Nonlinear two-parameter dependencies of the PMP of PE-CNT obtained in the temperature range (280–320) K and the volume fraction of fillers (0–1.5) %. These results allow to develop of new composite materials without conducting sufficiently complex and time-consuming numerical experiments based on MD simulation. The obtained data on the complex PMP are necessary for modeling the thermo-elastic-plastic state of products made of PE-CNT under operational conditions in a continuum approximation.

Influence of Silica Nanoparticles on the Physical Properties of Random Polypropylene

Influence of Silica Nanoparticles on the Physical Properties of Random Polypropylene

Role of Nanotitania Ceramic Particulate Filler on Mechanical and Wear Behaviour of Dental Composite

Nanotitania is a well-acceptable material in biomedical applications due to its excellent biocompatibility. However, its other performances in terms of physical properties, mechanical properties and specific wear rate have been the keen interest of researchers. The study aims to modify dental composite formulation by adding nanotitania filler in different mass fractions and study to investigate its influence on physical and mechanical properties. A conventional monomer matrix consisting of Bisphenol A-Glycidyl methacrylate (BisGMA), Urethane dimethacrylate (UDMA), Triethylene glycol dimethacrylate (TEGDMA), Camphor Quinone (CO), Ethyl-4-dimethylaminobenzoate (EDMAB) was first added and modified with varying nanotitania filler fractions (0,0.5,1,1.5 wt. %). The performance of newly formulated composites was investigated in four major parameters like apparent porosity, hardness, compressive strength and specific wear rate. All tests are performed as per ISO4049 standard which are requirements for fabrication, characterization, direct/indirect restoration of dental composite, inlays, onlays, veneers, crowns and bridges. Specific wear rate was estimated using pin on disk tribometer under constant load of 20N. Due to its extremely hard and brittle nature, the micro-hardness and compressive strength of resin composite on adding 0.5 wt.-% of nanotitania filler fraction (DC0.5TiO2) were increased by 68% and 16% respectively. Using a pin on disc tribometer, a wear assessment has been performed and it was found that under constant wear parameters and distilled water environmental conditions, the specific wear rate was decreased by 26 % on adding 0.5 wt.-% mass fraction of nanotitania. Nanotitania indicated excellent performance based on mechanical and wear properties and hence, it can be suggested to use nanotitania as a novel filler of dental composite for the replacement of other non-biocompatible ceramic filler.

Influence of axial pressure on the Payne effect of natural rubber vulcanizates

Rubber nanocomposites are key materials for aircraft or automobile tires, which are often subjected to the combined effect of pressure and shear during service. However, the effect of pressure on their strain softening under large amplitude oscillatory shear is not yet clarified. Herein a strain-controlled rotational rheometer is used to investigate the influence of axial pressure on the Payne effect of vulcanized natural rubber composites. Under high axial pressure, the Payne effect of rubber vulcanizates is remarkably suppressed, mainly attributed to the increasing intermolecular local friction hindering wall slip and nonlinear stretching of the rubber network. Furthermore, low temperature, high frequency and high filler fraction may weaken the suppression behavior. The investigation may reveal the role of axial pressure in the strain softening of vulcanized rubber.

Viscosity of Mono‐ and Polydisperse Mixtures of Photopolymer and Rigid Spheres for Manufacturing of Engineered Composite Materials Using Vat Photopolymerization

Vat photopolymerization (VP) additive manufacturing involves selectively curing low‐viscosity photopolymers via exposure to ultraviolet light in a layer‐wise fashion. Dispersing filler materials in the photopolymer enables tailored end‐use properties, but also increases the viscosity and the timescale associated with interparticle network structural recovery postshear. These rheological properties influence self‐leveling and recoating of the liquid photopolymer mixture during VP. Herein, viscosity of photopolymer and rigid spherical glass microparticles (filler) is experimentally determined as a function of filler fraction, filler size distribution (mono‐ and polydisperse), shear rate, and temperature, which are important VP process parameters. Employing existing viscosity models for mono‐ and polydisperse polymer mixtures demonstrates that particle–particle interactions and the formation of nonspherical clusters of particles strongly affect the viscosity of both monodisperse and polydisperse mixtures with particle volume fractions &gt; 0.05 due to agglomeration/deagglomeration of clusters at elevated shear rates. Consequently, unmodified viscosity models, which assume uniformly dispersed, rigid, spherical particles, are applicable only for mixtures with particle volume fractions &lt; 0.05. It is shown that modifying model parameters such as the fluidity limit and intrinsic viscosity, which explicitly account for nonspherical clusters of particles, improves agreement between viscosity models and experiments, in particular when using a fractal approach.

Design and performance study of ultra-high temperature CaMnO3/polysilylaryl-enyne absorbing material

This work describes the preparation and properties of a novel category of thermosetting microwave absorbing composite materials. The composites were prepared by a simple solution casting process, employing high temperature resistant polysilylaryl-enyne (abbreviated as PSAE) resin as matrix and perovskite CaMnO3 (abbreviated as CMO) ceramic filler as absorbent filler. The microstructure, electromagnetic, wave absorbing and thermal properties of the CMO-PSAE composites were all examined. The results showed that the increasing fraction of CaMnO3 filler not only densified the microstructure of the composites, but also greatly improved their temperature resistance, thermal conductivity and wave absorption properties. The CMO-PSAE composite doped with 50 vol% CaMnO3 ceramic filler showed the strongest ability to absorb electromagnetic waves, with an effective absorption bandwidth (EAB) of 4.16 GHz and a minimum reflection loss is −53.01 dB. Besides, the thermal conductivity of the composite reached 1.106 W/(m·K). Furthermore, this composite material has exceptional thermal resistance, with the highest Td5 reaching 650 °C. Composites with varying doping levels can be used for specific performance needs in practical scenarios. Thus, such novel CMO-PSAE composites exhibit potential applications in the electromagnetic countermeasure field under high-temperature environments.

Vertically-aligned Zn2SnO4–Fe3O4 core-shell microsphere-based thermal interface material with high thermal conductivity

In this study, we successfully fabricated vertically aligned Zn2SnO4 (ZTO)-Fe3O4 core-shell microsphere (MS)-based thermal interface material (TIM) formed by an external magnetic field. The thermal conductivity of the randomly distributed ZTO-Fe3O4 core-shell/PDMS-based TIMs was enhanced with increasing loading fraction of fillers and TIM with 25 vol % fillers 2.5 times effectively reduced GPU temperature compared to bare PDMS sample. Moreover, the vertically-aligned 25 vol% ZTO-Fe3O4 core-shell filler embedded TIM additionally reduced temperature by 5.1 % and 24.1 % compared to randomly dispersed ZTO-Fe3O4 MS TIMs and bare PDMS, respectively. Experimental results showed that the ZTO-Fe3O4 TIMs can be used as high thermal conductivity TIM filler, and vertically aligned core-shell filler can maximize thermal conductivity by forming an effective thermal path from bottom to top. The theoretical analysis results obtained using COMSOL Multiphysics 5.6 simulation corresponded well with experimental ones. Our suggested vertically aligned ZTO-Fe3O4 core-shell-based TIM can provide an effective heat dissipation path for advanced semiconductor devices with a wide range of applications.

Transient Response of Macroscopic Deformation of Magnetoactive Elastomeric Cylinders in Uniform Magnetic Fields.

Significant deformations of bodies made from compliant magnetoactive elastomers (MAE) in magnetic fields make these materials promising for applications in magnetically controlled actuators for soft robotics. Reported experimental research in this context was devoted to the behaviour in the quasi-static magnetic field, but the transient dynamics are of great practical importance. This paper presents an experimental study of the transient response of apparent longitudinal and transverse strains of a family of isotropic and anisotropic MAE cylinders with six different aspect ratios in time-varying uniform magnetic fields. The time dependence of the magnetic field has a trapezoidal form, where the rate of both legs is varied between 52 and 757 kA/(s·m) and the maximum magnetic field takes three values between 153 and 505 kA/m. It is proposed to introduce four characteristic times: two for the delay of the transient response during increasing and decreasing magnetic field, as well as two for rise and fall times. To facilitate the comparison between different magnetic field rates, these characteristic times are further normalized on the rise time of the magnetic field ramp. The dependence of the normalized characteristic times on the aspect ratio, the magnetic field slew rate, maximum magnetic field values, initial internal structure (isotropic versus anisotropic specimens) and weight fraction of the soft-magnetic filler are obtained and discussed in detail. The normalized magnetostrictive hysteresis loop is introduced, and used to explain why the normalized delay times vary with changing experimental parameters.

Improvement of Microwave Dielectric Properties by Impact of Sodium Ion Doping in Complex Oxides for Polymer Composites

The research presented in this study focuses on the dielectric properties of complex oxide-filled epoxy, polyurethane, and silicone rubber composites. Specifically, we investigated various compositions of (1-x) CaWO4-xNa2WO4 (x = 0, 0.2, 0.4), in addition to Na0.5Bi0.5Mo0.5W0.5O4 and Bi2Mo0.5W0.5O6. These complex oxide materials were meticulously synthesized through a solid-state reaction, and their distinct phases were confirmed via rigorous X-ray diffraction (XRD) characterization. We then proceeded to create the composites by manually blending these complex oxides with epoxy, polyurethane, and silicone rubber matrices. The central focus of the study was to examine the impact of varying volume fractions of the complex oxide fillers on the dielectric properties of the composites in the frequency range of 4 – 8 GHz.Our observations revealed a direct correlation between the content of the complex oxide filler and the dielectric properties, including the dielectric constant and dielectric loss. Specifically, the addition of 10 % by volume fraction of (1-x) CaWO4-xNa2WO4 (x = 0, 0.4), Na0.5Bi0.5Mo0.5W0.5O4, or Bi2Mo0.5W0.5O6 fillers to the respective polymer matrices led to a significant enhancement in both the dielectric constant and the loss tangent. Promising results were particularly evident in three composite formulations: the 10 % 0.4Na2WO4-0.6CaWO4/silicone rubber composite demonstrated a dielectric constant (εr) of 2.02 ´ 102 and a loss tangent (tanδ) of -4.07 ´ 10-1 at 7.1 GHz; the 10 % Na0.5Bi0.5Mo0.5W0.5O4/epoxy composite exhibited a dielectric constant of 1.37 ´ 102 and a loss tangent of -6.43 ´ 10-1 at 7.22 GHz; and the 10 % Bi2W0.5Mo0.5O6/polyurethane composite displayed favorable properties with a dielectric constant (ϵr) of 8.37x101 and a loss tangent (tanδ) of -3.4 ´ 10-1 at 7.12 GHz.These results suggest the suitability of these composite materials for a wide range of microwave technology applications, including wireless communication, radar systems, and various microwave devices.

Effect of silicon carbide particles on the mechanical, thermal and structural properties of recycled high-density polyethylene

In this research work, recycled high-density polyethylene (rHDPE)/silicon carbide (SiC) composites were produced by melt compounding followed by injection moulding technique. It has been revealed from the mechanical properties that the addition of SiC increases the hardness, density, flexural strength of the composite and tensile strength of the composite. The impact strength at 15 wt-% SiC composite gives the best results. From the thermal analysis, it was observed that the addition of SiC in rHDPE increases the melting point and total enthalpy of crystallisation. The residual value of rHDPE composites increases with the rise in filler loading which enhances the thermal stability of the composites. Melt flow index (MFI) decreases with the increased in silicon carbide. The heat deflection temperature (HDT) increased with the loading of filler content. The contact angle analysis revealed the hydrophilic nature of the composite. MFI reduced with the incorporation of filler content. The SEM images concluded the agglomeration of the composite at higher filler fractions. These results confirm the possibility of using rHDPE/SiC composite to produce various parts for household commodities and structural applications.

Rock-physics model of a gas hydrate reservoir with mixed occurrence states

Seismic interpretation of gas hydrates requires the assistance of rock physics. Changes in gas hydrate saturation can alter the elastic properties of formations, and this relationship can be considerably influenced by the occurrence state of gas hydrates. Pore-filling, load-bearing, and cementing types are three single gas hydrate occurrence states commonly considered in rock-physics investigations. However, many gas hydrate-bearing formations are observed to have mixed occurrence states, and their rock-physics properties do not fully conform to models of single occurrence states. We develop a generalized rock-physics model for gas hydrate-bearing formations with three mixed occurrence states observed in the field or laboratory experiments: coexisting pore-filling-type and matrix-forming-type gas hydrates (case 1); pore-filling type when [Formula: see text] (gas hydrate saturation) &lt; [Formula: see text] (critical saturation) and pore-filling + matrix-forming type when [Formula: see text] (case 2); and matrix-forming type when [Formula: see text] and matrix-forming + pore-filling type when [Formula: see text] (case 3). Instead of initial porosity, the apparent porosity (the volume fraction of an effective pore filler) [Formula: see text] represents the influence of occurrence states on the pore space. These three mixed occurrence states can be modeled using a unified workflow, in which the volume fractions of various gas hydrate types are expressed in general forms in terms of the apparent porosity. In addition, the model considers the effect of a pore filler on shear modulus. The developed model is validated through calibration with real well-log data and published experimental data corresponding to five gas hydrate-bearing formations. The model effectively interprets the influences of gas hydrate saturation and occurrence state on these formations. Thus, the generalized model provides a theoretical basis for the analysis of sensitive elastic parameters and quantitative interpretation for gas hydrate reservoirs.