Filler Inclusions Research Articles

Effects of locally-gradient Co-doping on the electron properties of Bi2Te2.1Se0.9+0.33wt.% Co composite

Interconnected effects of the locally-gradient Co-doping and electron scattering by filler inclusions has been for the first time observed in thermoelectric Bi2Te2.1Se0.9 + 0.33 wt.% Co composite, prepared via spark plasma sintering (SPS) of matrix and filler powders at temperatures TS=573, 598, 623, 648, 673 and 698 K and at the same time t = 2.5 min. During SPS-process, initial Co inclusions, randomly distributed inside the Bi2Te2.1Se0.9 matrix, act as electron doping sources. High-temperature diffusion embedding of Co atoms in the Bi2Te2.9Se0.1 structure results in increasing electron concentration. This diffusion process corresponds to diffusion from limited doping sources, which are spatially separated inside the Bi2Te2.9Se0.1 matrix. Separate filler inclusion is each such source. Concentration profiles of Co distribution were applied to extract a diffusion coefficient, DCo, of Co atoms inside Bi2Te2.9Se0.1. The DCo increases with TS in accordance with Arrhenius law. Owing to locally-gradient distribution of doping Co atoms, the Co-doping is locally-gradient doping. Initial inclusions, consisting of only Co atoms, are gradually transforming into the “core Co@shell CoTe2” inclusions. This transformation is related to diffusion of Co atoms that is accompanied by subsequent solid-state Co+2Te→CoTe2 reaction. Room-temperature weighted mobility of electrons increases with growing TS. This behavior of mobility can be originated from electron scattering by magnetic moments of the Co cores.

Utilization of wollastonite, jarosite, and their blends for the sustainable development of concrete paver block mixes containing reclaimed asphalt pavement aggregates.

While several research studies considered the utilization of reclaimed asphalt pavement (RAP) aggregates for asphalt and concrete pavements, very few attempted its possible utilization for precast concrete applications like concrete paver blocks (CPBs). Moreover, few attempts made in the recent past to improve the strength properties of RAP inclusive concrete mixes by incorporating certain supplementary cementitious materials (SCMs) have reported an insignificant or marginal effect. The present study attempts to comprehensively investigate the utilization potential of some locally and abundantly available materials having suitable physicochemical properties to improve the performance of a zero-slump CPB mix containing 50% RAP aggregates. The studied filler materials, namely, wollastonite (naturally occurring calcium metasilicate mineral) and jarosite (hazardous zinc industry waste), were used to replace 5-15% and 10-20% by volume of Portland cement in the 50% RAP CPB mix. Apart from their individual effects, the efficacy of wollastonite-jarosite blends was also investigated. Considering the lack of indoor storage facilities and economic aspects of CPBs, the influence of water spray curing regime on the performance of the RAP CPB mixes was studied and compared to that of continuous water curing regime. Inclusion of the considered fillers was found to statistically and significantly enhance the flexural strength, tensile splitting strength, and abrasion resistance of the 50% RAP CPB mix; however, the compressive strength (in most cases), permeable voids, water absorption, and water permeability properties showed an insignificant improvement. Results of thermogravimetric analysis confirmed the occurrence of pozzolanic reactivity, and microstructure analysis revealed improvements in packing of concrete matrix and ITZ with filler inclusion qualitatively substantiating the improvements in strength and durability characteristics. The toxicity characteristics of heavy metals that may leach from the hazardous jarosite-based RAP CPB mixes were found to be within permissible limits. Based on the performance requirements specified by IS, IRC, and ASTM standards, all the RAP CPB mixes with filler inclusions fulfilled the acceptance criteria for heavy traffic applications, and water spray curing can enact as an alternate method for curing these mixes. However, to avail maximum performance benefits, it is recommended to use 5% wollastonite, 15% jarosite, and a combination of 10% wollastonite and 10% jarosite as a Portland cement substitute to produce sustainable eco-friendly RAP CPB mixes.

Features of the Microstructure and Thermoelectric Properties of Bi2Te2.7Se0.3 + Fe Composites with Core–Shell Filler Inclusions

Features of the Microstructure and Thermoelectric Properties of Bi2Te2.7Se0.3 + Fe Composites with Core–Shell Filler Inclusions

Rheological and physicochemical characteristics of asphalt mastics incorporating lime kiln dust and dolomite powder as sustainable fillers

The filler-bitumen interaction mechanism is one of the most essential phases for comprehending the asphalt mixture's performance. However, despite numerous studies, in-depth knowledge of filler-bitumen reciprocity at a microscale level is yet to be ascertained. The goal of this research is to gain a better understanding of the filler-bitumen microscale interaction in terms of the synergy and coaction between the physicochemical and rheological performance of mastics due to filler inclusions. The rheological properties of two sustainable mastics, dolomite powder (DP) and lime kiln dust (LKD), together with a neat PEN 60/70 binder, were analysed based on a temperature sweep at elevated temperature conditions. Meanwhile, frequency sweep and multiple stress creep recovery (MSCR) tests were also conducted at pavement serviceability temperature using the dynamic shear rheometer (DSR). Physicochemical tests using a scanning electron microscope (SEM) and energy dispersive X-rays (EDX) were conducted to analyse the impact of parameters such as particle shape, grain size, texture, and chemical compositions. The DSR test results showcased how the incorporation of fillers in asphalt binder considerably improved the performance of the binder in terms of rutting and fatigue. Likewise, its strain and non-recoverable compliance parameters were substantially reduced at higher filler and binder concentrations. Physical filler attributes of low rigden voids (R.V), high fineness modulus (FM), and high specific surface area (SSA) led to greater interfacial stiffness and elasticity in LKD mastics compared to DP mastics at different loading frequencies and temperature levels. The SEM/EDX results also indicated that the elemental calcium and carbon composition of each filler component, together with its grain morphology, strongly influenced its rheological performance.

Атомно-силовая микроскопия растянутых резин

Atomic force microscopy (AFM) is a powerful tool for studying the structural-mechanical proper-ties of polymers and polymer composites. Modern AFM methods provide not only a 3D-image of the surface but also its physical and mechanical properties. Elastomeric vulcanizates and their composites are widely used in tire industry. In this work, unfilled and filled (5, 30, 50 wt. parts of carbon black) rubbers in the tensile state, including open cracks, were investigated by the method of rapid nanoindentation. The defects in the stretched polymer matrix in the vicinity of the inclu-sions are shown. A binder oriented along the axis of deformation in the gaps between the filler inclusions forms strand-like structures. The stress-strain state of the stretched polymer is heterogene-ous. The stiffness of the polymer in the strands exceeds that of the surrounding matrix, i.e., the strands take the main load. At the same time, weakly loaded matrix areas shielded from load by filler inclusions are present in the material. Adjacent filler aggregates retain their relative position during stretching, and the strands appear in the filler-free areas. In the notch made in the stretched rubber, the polymer is in a critically stretched state – a slightest increase in stretching will lead to further crack propagation. In this case, an overstretched area up to 10 m wide having local defects and strands appears along the axis of the crack. The stiffness of the matrix in this region is hun-dreds of times greater than in the initial material, which indicates deformations many times greater than macroscopic ones.

Effect of locally-gradient Ni@NiTe2 inclusions on the Seebeck coefficient of Bi2Te3 + xNi composites

The Bi2Te3 + xNi composites with x = 0.00, 0.50, 0.85, 1.00, 1.25 and 1.50 wt% were prepared by spark plasma sintering method. Owing to high-temperature diffuse redistribution of matrix and filler atoms, filler inclusions in Bi2Te3 matrix are forming as locally-gradient Ni@NiTe2 inclusions. Since electrical conductivity of Ni is much higher as compared to that for Bi2Te3, the composites are electrically-inhomogeneous semiconductors. With increasing x, fraction of NiTe2 shell increases, and fraction of Ni core decreases, although all the composites with different x were sintered at the same temperature. This feature is originated from local overheating of the filler inclusions due to flowing pulse electrical current through the electrically-inhomogeneous medium. Diffusion coefficient of Ni inside Bi2Te3, estimated from analysis of Ni concentration profiles near the Ni@NiTe2 inclusions, enhances with increasing x. By using energy activation of the diffusion, local overheating temperatures of the filler inclusions were extracted. The x-dependent changes in electron concentration of the composites are related to competition of increasing in number of the filler inclusions and decreasing in fraction of Ni cores inside the inclusions. Effect of the filler content on the Seebeck coefficient of the composites was analysed by the Pisarenko relationship, plotted for simple parabolic band model. Magnetic electron scattering by ferromagnetic Ni cores in the Ni@NiTe2 inclusions can contribute to the Seebeck coefficient via relevant changes in scattering factor.

Relationship between the physicochemical and electrostatic charge characteristics of filler materials on the morphological and adhesive Pull-Off tensile strength of asphalt mastics

• This paper assesses the viability of using mineral fillers from industrial by-products. • Lime kiln dust and dolomite powder were studied and compared to cement powder. • Changes in asphalt binder phases occur as a result of asphalt-filler interactions. • The pH conditions dictate mastics adhesive tendencies due to electrostatic ionic exchange. • Thus, impacting pull-off strengths within asphalt-aggregate interfaces. The influence of filler particle mineralogy, pH and electrostatic charge on the adhesive tensile strength and morphological structure of asphalt mastic composites were assessed in this study. Three different fillers i.e., dolomite powder (DP), lime kiln dust (LKD), and ordinary Portland cement (OPC) together with a conventional PEN 60/70 binder were used for the asphalt mastic preparation. The mastics were mixed at dosages of (0.4, 0.8, and 1.2) filler to binder concentration (F/B) by volume as per the dust to binder specifications of Superpave mix designs. OPC mastic was utilised as the control mastic sample for all conducted tests, while the DP and LKD mastics were tested as sustainable alternatives to the OPC. The impact of filler inclusions in asphalt liquid phases was investigated via optical microscope assessments. Similarly, physicochemical tests of the elemental and mineralogical composition of each filler were accounted for using x-ray diffraction tests. The surface charge characteristics of each test filler was analysed relative to its mastic pH conditions through the application of zeta potential tests. Adhesive pull-off tensile strengths of the mastics on granite and limestone interfaces were also assessed for both dry and moisture conditions. The incorporation of fillers in asphalt binders highlighted the effect of filler reactivity and inert tendency on binders’ morphological phase modification wherein the OPC and LKD were reactive with the asphaltene while the DP was less reactive and inert. Results obtained from both the x-ray diffraction and zeta potential tests also infer the calcium based OPC and LKD to exhibit better surface ionic attraction compatibility with the PEN 60/70 binder than the DP at high F/B. Meanwhile, the relationship between the filler surface charge and mastic pH condition was observed to be significant and reliant upon the mastics adhesive pull-off tensile characteristics.

Features of the Transport Properties of Thermoelectric Nanocomposites Based on a Matrix from BiSbTe1.5Se1.5 Medium-Entropy Alloy and Carbon-Nanotube Filler

For the first time, thermoelectric nanocomposites consisting of a BiSbTe1.5Se1.5 medium-entropy alloy (nanocomposite matrix) and “Taunit-M”, CNT carbon nanotubes (nanocomposite filler)are obtained. All BiSbTe1.5Se1.5 + xCNT nanocomposites with different filler contents (x = 0, 0.05, 0.1, 0.5, 1.0, 1.5, and 2.0 wt %), obtained by spark plasma sintering of the initial powders of the matrix material and filler, consist of micron-sized filler inclusions formed from clusters of nanotubes. The inclusions themselves are randomly distributed within the polycrystalline matrix. In the temperature range of 290–500 K, the transport properties (electrical resistivity and total thermal conductivity, including the electronic and phonon contributions, as well as the contribution of bipolar thermal conductivity) of the nanocomposites with various filler contents are studied. It is established that the introduction of CNTs into the matrix leads to a qualitative change in the type of electrical conductivity from “metallic” (electrical resistance increases with temperature), characteristic of the nanocomposite matrix, to “semiconductor” (resistance decreases with temperature), characteristic of nanocomposites. The observed “semiconductor” behavior of the electrical conductivity is characteristic of electrically inhomogeneous systems, in which current transfer is determined by the movement of electrons through the interfaces between the inhomogeneities. For all nanocomposites with different filler contents, the temperature dependences of the total thermal conductivity are qualitatively similar. At low temperatures, they are determined by the phonon contribution; at high temperatures, by the bipolar-thermal-conductivity contribution; the electronic contribution manifests itself at all temperatures, but it gradually decreases with increasing x. The minimum thermal conductivity is observed for the nanocomposite with x = 0.5 at % CNT.

Hybrid materials for electromagnetic shielding: A review

AbstractExtensive development in electronics and allied sectors has led to unseen pollution termed electromagnetic interference (EMI). Motivated by its after‐effects, the fabrication of efficient EMI shielding has become a major area of research. This review presents a detailed analysis of very recent trends in various hybrid materials based on polymers, cement, concrete, paints, and so on with diverse filler inclusions for electromagnetic shielding applications. This paper also focuses on the origin and effects of electromagnetic (EM) radiation, the shielding mechanism, and the suitability of the hybrids, various fabrication techniques, characterization; and so on. Fiber‐reinforced polymer composites, metal films, microfilms, inks, paints, multiple laminated composites, foams, aerogel‐based polymer composites, textiles, and so on are discussed. Newly developed materials like MXene, borophene, semiconducting filler‐based hybrid materials are also covered. Finally, an attempt is made, to sum up, the major challenges faced in the design and development of polymer materials for EMI shielding applications.

Hybrid nanocomposites of elastomeric polyurethane containing halloysite nanotubes and POSS nanoparticles: tensile, hardness, damping and abrasion performance

AbstractThermoplastic polyurethane (TPU) matrix was reinforced with polyhedral oligomeric silsesquioxane (POSS) and halloysite nanotubes (HNT), both separately and combined. Composite samples were fabricated using a melt-compounding method. Characterization of the composites obtained was performed via tensile and hardness tests, melt-flow index measurements (MFI), abrasion tests, dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) to investigate the mechanical performance, flow behaviour, tribological characteristics, thermo-mechanical response and morphological properties. The greatest tensile strength value was obtained for the smallest HNT content. Further addition of HNT resulted in agglomerations for both POSS and HNT particles. The shore hardness of TPU was enhanced by filler inclusions. The TPU/POSS composites displayed significant improvement in terms of abrasion resistance compared to TPU at lower loading levels. The DMA study showed that composites containing 0.5% POSS and 1.0% HNT displayed the greatest storage modulus. The glass-transition temperature of TPU shifted to smaller values with the addition of both nanoparticles. The HNT inclusions increased the MFI value of TPU because of their large aspect ratio. Homogeneous mixing of nanoparticles in the TPU matrix was confirmed by a SEM study of the composites. Their dispersion decreased as the concentrations of POSS and HNT increased. An adjuvant effect of POSS with HNT was achieved in their hybrid composites.

A Study on the Influence of the Chemical Nature of Fillers on Rheological and Fatigue Behavior of Bitumen Emulsion Mastic.

Cold Bitumen Emulsion (CBE) mixture technologies have been recently developed to lower pavement construction temperatures to reduce environmental costs and control gas emissions. Due to its poor early mechanical strength, active fillers (i.e., cement) have been used to obtain high early stiffness in order to have the potential for timely construction of the next layer. There is, however, a lack of understanding about the impact of active fillers on the viscoelastic behavior and fatigue damage resistance of CBE mastics. This study, therefore, aims to identify the influence of active fillers on the rheological properties and the resulting fatigue behavior of CBE mastic, supported by chemical analysis for the filler-bitumen emulsion. For this aim, bitumen emulsion was mixed separately with seven fillers/blended fillers to prepare the CBE mastics. Various experiments, including continuous pH monitoring tests (chemical reactivity of filler-bitumen emulsion), Strain Sweep (SS) tests, Temperature-Frequency Sweep (TFS) tests, Time Sweep (TS) tests, and Linear Amplitude Sweep (LAS) tests were conducted on the CBE binder and the prepared mastics. Results show that the rheological performance and the fatigue damage resistance depend not only on the filler inclusions but also on filler type and chemistry. On this basis, the rise in complex shear modulus and the decrease in the viscous component is associated with a significant enhancement in fatigue performance for specific fillers.

On the Role of Solid Lubricant Fillers in the Tribological, Micromechanical, and Morphological Properties of PA66 Composites

Abstract To achieve thermoplastics-based composites with high tribological performances, molybdenum disulfide (MoS2) and graphite (Gr) were incorporated separately to a polyamide 66 (PA66) matrix. Two different development methodologies of composites were used. The morphological features and the micro-mechanical properties of composites were investigated to stress the influence of the filler surface treatment and its dispersion. The friction coefficient was evaluated using a ball on a flat micro-tribometer. The wear mechanisms were also characterized. The best tribological performance was exhibited by 10 wt% of graphite. The surface treatment of the filler inclusions by 3-aminopropyltriethoxysilane (AMPTES) showed an improvement in the morphological aspects of adhesion at the filler/matrix interface.

Identification of primary and secondary filler structures in a polymer matrix by atomic force microscopy images analysis methods

Segmentation algorithms have been developed to study the surface of filled rubbers using atomic force microscopy (AFM) images. The analysis reveals two types of segments in the material: micropellets (large, dense inclusions of a insufficiently ground filler) and aggregates (small primary filler inclusions). The proposed approach allows us to find the minimum size of a representative area, starting from the filler distribution can be treated as homogeneous (mesoscale). Secondary structures (clusters) created by aggregates are identified and their fractal parameters are calculated. The validity of the approach for the analysis of rubbers filled with carbon black is demonstrated. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

Elastic behavior of silica/poly(dimethylsiloxane) nanocomposites: nano-size effects

Elastomeric materials require the incorporation of reinforcing fillers in order to improve their mechanical properties. The enhancement of properties is very much dependent on the size and any surface modification of the reinforcing agent. It is widely accepted that the reinforcement effects are primarily due to molecular interactions of the polymeric matrix and the filler inclusions and it involves both chemical and physical interactions. Herein, we have incorporated silica nano fillers (Stober silica) into poly (dimethylsiloxane) (PDMS) elastomeric networks. The mechanical and swelling properties of the networks were investigated as a function of filler sizes (50, 130, and 170 nm), volume fraction of the filler inclusions, and surface treatment of the particles by were analyzed to give the Mooney-Rivlin constants 2C1 and 2C2. These properties were found to be dependent on the size of the nano inclusions. Thus, a nano size phenomenon had been discerned and was one of the highlights of this investigation. This phenomenon was largely attributed to the high specific surface area of the nano fillers used that leads to significant increase in the interfacial interactions. Also, and as would be expected, the properties of the polymeric networks filled with unmodified particles were different than those obtained for the polymeric networks filled with surface-modified particles. This has been primarily attributed to changes in the surface properties, and as would be expected, the elastic properties of the networks were thus shown to be strongly dependent on type and concentration.

Dielectric behavior of Silica/Poly(dimethylsiloxane) nanocomposites. nano size effects

The enhancement of properties of elastomeric composite materials is very much dependent on the size and the surface modification of the reinforcing filler inclusions. It is well accepted that the reinforcement effects are primarily due to molecular interactions of the polymeric matrix and the filler inclusions and it involves both chemical and physical interactions.In the present study, we have incorporated silica nano fillers (Stober silica) into poly(dimethylsiloxane) (PDMS) elastomeric networks. The dielectric properties of the networks were investigated as a function of filler nano filler size, volume fraction, and surface treatment by hexamethyldisilazane. The broad-spectrum dielectric properties (in particular, the dielectric constant, the dielectric loss, and tan δ) were characterized. These properties were found to be dependent on the size of the nano inclusions; thus, the results clearly showed a nano size phenomenon that was a highlight of the present research. Certainly, that can be largely attributed to the high specific surface area of the nano fillers, which significantly leads to a pronounced increase in interfacial interactions. Also, and as would be expected, the dielectric properties of the polymeric networks filled with unmodified particles were different from those for the polymeric networks filled with surface-modified particles. Again, this is mainly attributed to changes in the surface properties. The expected dependence of properties of the nanocomposite networks on the nature of the filler and its concentration has thus been demonstrated.

Application of two phase model to linear dynamic rheology of filled polymer melts

The linear dynamic rheology for a series of filled polymer melts is investigated to take account for the respective contributions of the bulky polymer phase away from the filler inclusions and the “filler phase” composed of filler particles coated with polymer layer. Time-concentration superposition principles are introduced to the linear viscoelasticities of both the bulky polymer phase and the “filler phase”. The result highlights the importance of the polymer dynamics to both the “filler phase” and the composite melt. Polymer mediated filler jamming towards glass formation is revealed for the “filler phase”, which accounts for origin of the fluid-to-solid transition upon filling.

Linear viscoelasticity of polymer melts filled with nano-sized fillers

The linear dynamic rheology of polymer melts filled with nano-sized fillers is investigated in relation to a proposed two phase model. A common principle is disclosed for nanofilled polymers exhibiting either fluid- or solid-like behaviors with increasing filler volume fraction. The bulky polymer phase far away from the filler inclusions in the nanocomposites behaves the same as in the unfilled case while its contribution to the composite modulus is enlarged due to strain amplification effect. The filler forms aggregates together with polymer chains absorbed on the filler surface, which is termed as the “filler phase” in the proposed model. The dynamics of the “filler phase” slow down with increasing filler concentration. The applicability of the proposed two phase model is discussed in relation to the well-known structural inhomogeneity of nanofilled polymers as well as the strain amplification and the filler clustering effects.

Dielectric Behavior of Silica/Polyacrylamide Nanocomposites

Polyacrylamide (PAAM) nano silica inclusions composites were prepared having different ratios of nano silica. The silica inclusions were either modified or unmodified. The nanocomposite films were characterized by transmission electron microscope (TEM) and infrared spectroscopy (IR). The dielectric behavior of the composites had been investigated as a function of the concentration of the nano silica inclusions. The results show that the dielectric constant and dielectric loss of the nanocomposites are smaller than those obtained for the neat polymer. As the concentration of the surface-modified nano silica inclusions increases, the dielectric constant decreases. This behavior may be attributed to the successful interaction between the polymer and the surface of the nano silica inclusions. As would be expected, the results thus obtained are a clear manifestation of the role of surface treatment of the filler inclusions and subsequently the role played by the interface on the properties of the composites.

Monte Carlo simulations on the effects of nanoparticles on chain deformations and reinforcement in amorphous polyethylene networks

Reinforcing effects in an amorphous polyethylene matrix were estimated for spherical filler particles arranged either on a cubic lattice or randomly in space. Attention was first focused on the effects of the type of arrangement of the particles on the microscopic properties of the polymer chains. Specifically, Monte Carlo rotational isomeric state (MC-RIS) simulations were carried out to predict the effects of the volumes excluded by the filler particles on the configurational distribution functions of the chains, and from these distributions the elastomeric properties of the composites. The calculations were carried out for a range of particle sizes and particle volume fractions. As expected, filler inclusions are found to increase the non-Gaussian behavior of the chains. The results were compared with those from small-angle neutron scattering (SANS) experiments. In the case of arrangement on a cubic lattice, chains dimensions were always found to decrease. In the randomly-dispersed filler arrangements, there were significant increases in chain dimensions relative to the unfilled system in some instances, and the changes were in excellent agreement with the SANS results. The present simulations thus give further encouragement to interpretations of chain deformations in filled systems in terms of volume exclusion effects from the nanoparticle inclusions, including their dispersions and arrangements within polymer matrices.

A Model for Polymer Composite Wear Behavior Including Preferential Load Support and Surface Accumulation of Filler Particulates

A rule-of-mixtures model is developed for the time-dependent wear and friction behavior of polymer matrix materials containing particulate filler inclusions, based upon the specific wear rates of filler and matrix materials. The model accounts for the accumulation of wear-resistant filler particles within the near-surface region of the composite as sliding proceeds. Account is also made for preferential support of the normal load by filler particles at the sliding surface. Though particle/matrix interfacial shear stress and particle aspect ratio do affect initial transient behavior, wear rate, and friction are independent of preferential load support under steady-state conditions. The model indicates that steady-state composite wear rate can be most affected by the specific wear resistance of the filler particles, as well as the volume fraction filling of particles into the polymer matrix.