Metal Composite Systems Research Articles

Growth of magnetic metals on carbon microspheres with synergetic dissipation abilities to broaden microwave absorption

• Facile electrostatic assembly approach for preparation of core-shell C/magnetic metal composite microspheres. • Excellent microwave absorption performance including a maximum reflection loss value of −54.1 dB and a broad effective absorption bandwidth of 6.7 GHz. • Profound magnetic coupling effect and magnetic-dielectric synergy mechanism for enhancing microwave absorption performance. Microwave absorption (MA) materials have been captured extensive attentions due to the serious electromagnetic (EM) pollution. Numerous interests focus on the MA performances of core-shell structural composites with magnetic constituents as cores and dielectric constituents as shells, which inevitably suppressed the magnetic coupling causing the decrease of magnetic loss to some extent. Herein, the core-shell structural carbon (C) microsphere/magnetic metal composites were fabricated through the combination of an electrostatic assembly approach and subsequent in-situ reduction reaction. The complex permittivity and permeability of core-shell C@magnetic metal composite system can be effective adjusted by the constituent and microstructure of shells. Thanks to the distinct magnetic coupling from the subtle designed structures and the promotion of the magnetic-dielectric synergy, the C@magnetic metal composite exhibited enhanced MA properties. The optimal reflection loss (RL) of C@Ni composite was -54.1 dB with a thickness of 3.4 mm, meanwhile the effective absorbing band could reach over 5.5 GHz at only a 1.8 mm thickness. Broad absorption bandwidth with RL below -10 dB could achieve 6.0 GHz and 6.7 GHz for C@Co and C@NiCo composites with a thin 2.1 mm thickness, respectively. Our exciting findings might lead a guide on the novel structure design for the functional core-shell structural composites used for microwave absorption. Graphical Abstract .

Modeling anisotropic fracture in a metal-fiber reinforced composite system

Hybrid structures consisting of metal and composites can be applied to specific requirements of different applications. The computational modeling of composites is quite complex compared to homogeneous and isotropic materials like metals because of the heterogeneity introduced due to the presence of different phases such as matrix, fiber and matrix-fiber interface, and anisotropy due to the fiber alignment. The crack propagation in a composite material depends on a combination of various damage modes, namely, fiber pull-out, matrix cracking, delamination. The strength and stiffness of the composite depend on the mechanical and fracture properties of the individual phases, and the fiber inclination. The metal-composite interface is modeled using the cohesive zone approach. A nonlocal diffused approach is proposed to model the anisotropic failure in composites reinforced with unidirectional and woven fibers and the interaction of the crack with the interface. Parametric studies are conducted to understand the role of fiber orientation and interface fracture properties of the system. The proposed model is illustrated through numerical examples to understand various failure mechanisms in a metal-composite system.

Theoretical studies of a metal composite based on a monolayer of pyrolyzed polyacrylonitrile containing paired metal atoms Cu—Co, Ni—Co, Ni—Cu, Ni—Fe and an amorphizing silicon additive

An urgent problem of radio engineering and radioelectronics nowadays is the synthesis of composite materials with preset parameters that can be used as electronics engineering materials. Of special interest are MW range wide-band electromagnetic radiation absorbers. Special attention is paid to materials on the basis of ferromagnetic metals that are capable of effectively absorbing and reflecting incident waves and having a clear nanostructure. Development of nanocapsulated metals will allow controlling the parameters of newly designed materials. This is achieved with the use of polymer matrices, e.g. pyrolyzed polyacrylonitrile (PPAN). This work is a theoretical study of a PPAN monolayer model containing pairs of transition metal atoms iron, nickel and cobalt which possess ferromagnetic properties, in Fe–Co, Ni–Co and Fe–Ni combinations, with silicon amorphizing admixture. We studied the geometrical structure of the metal composite systems which are modeled as PPAN molecular clusters the centers of which are voided of six matrix material atoms, the resultant defects (the so-called pores) being filled with pairs of the metal atoms being studied. The metal containing monolayer proved to be distorted in comparison with the initially planar PPAN monolayer. We plotted single-electron spectra of the composite nanosystems and characterized their band gaps. The presence of metal atoms reduces the band gap of a metal composite as compared with pure PPAN. We determined the charges of the metals and found electron density transfer from metal atoms to their adjacent PPAN monolayer atoms. We calculated the average bond energy of the test metal composite systems and proved them to be stable. The studies involved the use of the density functional theory (DFT) method with the B3LYP functional and the 6-31G(d) basis.

Theoretical study of metal composite based on pyrolyzed polyacrylonitrile monolayer containing Fe-Co, Ni-Co and Fe-Ni metal atom pairs and silicon amorphizing admixture

An urgent problem of radio engineering and radioelectronics nowadays is the synthesis of composite materials with preset parameters that can be used as electronics engineering materials. Of special interest are MW range wide-band electromagnetic radiation absorbers. Special attention is paid to materials on the basis of ferromagnetic metals that are capable of effectively absorbing and reflecting incident waves and having a clear nanostructure. Development of nanocapsulated metals will allow controlling the parameters of newly designed materials. This is achieved with the use of polymer matrices, e.g. pyrolyzed polyacrylonitrile (PPAN). This work is a theoretical study of a PPAN monolayer model containing pairs of transition metal atoms iron, nickel and cobalt which possess ferromagnetic properties, in Fe-Co, Ni-Co and Fe-Ni combinations, with silicon amorphizing admixture. We studied the geometrical structure of the metal composite systems which are modeled as PPAN molecular clusters the centers of which are voided of six matrix material atoms, the resultant defects (the so-called pores) being filled with pairs of the metal atoms being studied. The metal containing monolayer proved to be distorted in comparison with the initially planar PPAN monolayer. We plotted single-electron spectra of the composite nanosystems and characterized their band gaps. The presence of metal atoms reduces the band gap of a metal composite as compared with pure PPAN. We determined the charges of the metals and found electron density transfer from metal atoms to their adjacent PPAN monolayer atoms. We calculated the average bond energy of the test metal composite systems and proved them to be stable. The studies involved the use of the density functional theory (DFT) method with the B3LYP functional and the 6-31G(d) basis.

PH tunable anionic and cationic heavy metal reduction coupled adsorption by thiol cross-linked composite: Physicochemical interpretations and fixed-bed column mathematical model study

Over the past, extensive works executed to treat anionic and cationic heavy metal ions from wastewater. Although very few adsorbents were developed to adsorb anionic and cationic heavy metal ions from the same system. In this study, we explored the pH tunable complete reduction plus adsorption mechanism of Pb2+ and Cr2O72− by dithiocarbamate-based composite. The pH study recommended that; adsorption of Pb2+ occurred at pH 5.5, besides Cr2O72− reduction coupled adsorption executed at pH 3. Furthermore, quick adsorption occurred within 60 min with adsorption capacities of 228.69 and 219.75 mg g−1 for Pb2+ and Cr2O72−, respectively. Adsorption isotherm well described by the Redlich-Peterson model, also adsorption processes were fitted by pseudo-second-order kinetics model. Interestingly, characteristic techniques, a physical monolayer model and thermodynamic models were applied to the experimental results to further understand the adsorption mechanisms. The results indicated that the physical model with two types of interaction energies was more appropriate to interpret the adsorption mechanism. Based on the physical model, three thermodynamic functions were calculated and interpreted to attribute new macroscopic interpretations at the molecular level of the adsorption systems. Inspiringly, the metal-composite system highly effective for 5 regeneration cycles and fixed-bed column could decontaminate 17.2 L of ~10 mg L−1 Pb2+ and 7.3 L of ~10 mg L−1 Cr2O72− to the EPA’s wastewater discharge limit by 5 g of CSC@SDBC with the yielding of 400 and 346 mL of eluent, respectively. Theoretically, a liter of CSC@SDBC column may efficiently adsorb 145,646 mg of Pb2+ and 57,518 mg of Cr2O72− from industrial effluent, these were calculated from the Bohart-Adams model. These collective batch and fixed-bed systems were cost-effective and environmentally tolerable techniques to remove anionic and cationic heavy metal ions from industrial wastewater.

Establishment of structure-property linkages using a Bayesian model selection method: Application to a dual-phase metallic composite system

We investigate the viability of establishing low-cost surrogate structure-property (S–P) linkages by introducing a Bayesian model selection method to extend the Materials Knowledge Systems (MKS) homogenization framework, which employs the n-point spatial correlation function, principal component analysis, and regression techniques. In particular, we place emphasis not only on choosing the important structural features but also on interpreting their implications for the property under consideration. First, the yield strengths of synthetic microstructures with various morphological characteristics are estimated by physics-based crystal plasticity simulation. Then, the dimension-reduced microstructural features are revealed by a combination of 2-point spatial correlations and principal component analysis. The Bayesian model selection method is further applied to establish a microstructure-to-yield-strength surrogate model. Finally, the model is validated with an independent dataset and its constituent features are interpreted with a morphology reconstruction based on a Monte Carlo algorithm. The method is found to be capable of interpreting the key microstructural features as well as modeling the mechanical response of a dual-phase metallic composite in consideration of the diverse microstructural factors.

Design of an Impedance-Graded Metallic Composite System as a Protective Mechanism for Concrete Structures

Protecting concrete structures from high energetic dynamic events such as blasts and impact is a major concern, in both civil- and military-related applications. Most conventional techniques fail to counter the unpredictable nature of dynamic loads, as well as the complex response of structures due to stress wave propagation. Hence, this paper explores the possibility of using a functionally graded—according to impedance—metallic composite system as a protective mechanism to a concrete structure. An analytical framework was developed using matlab, based on elastic and shock wave propagation theories, especially incorporating multiple interactions within the composite system, as well as reflections of free surfaces. A numerical analysis was carried out using the advanced finite element code LS-DYNA. The main objective of this paper was to compare the performance of the composite system against the conventional monolithic system.

An Innovative Approach of Using Continuous Impedance-Graded Metallic Composite System for Attenuation of Stress Waves

This paper presents an innovative approach of stress attenuation through a continuous impedance-graded material system for high strain-rate events. High energetic dynamic events such as blasts and impact could cause stress waves—in the form of elastic, plastic, and shock—to propagate in a solid material. An impedance-graded composite is created by arranging different metallic alloys in the reducing order of their impedance through the system. Impedance, which is the product of volumetric mass density and wave velocity, is chosen as the function as it plays a governing role in elastic, plastic, and shock waves. An analytical framework to quantify the stress wave propagation through an impedance-graded multimaterial system is developed based on the principles of shock and elastic wave theories. The numerical simulations carried out using nonlinear finite element code, LS-DYNA, were able to capture and quantify the elastic, plastic, and shock waves and their reflections at different interfaces. It was identified that the final transmitted stress wave, which could comprise elastic, plastic, and shock waves, as well as the reflected tensile elastic wave at each material interface, needs to be controlled in order to develop a robust multimaterial system.

Establishment of Structure-Property Linkages Using a Bayesian Model Selection Method: Application to A Dual-Phase Metallic Composite System

Abstract We investigate the viability of establishing low-cost surrogate structure-property (S–P) linkages by introducing a Bayesian model selection method to extend the Materials Knowledge Systems (MKS) homogenization framework, which employs the n-point spatial correlation function, principal component analysis, and regression techniques. In particular, we place emphasis not only on choosing the important structural features but also on interpreting their implications for the property under consideration. First, the yield strengths of synthetic microstructures with various morphological characteristics are estimated by physics-based crystal plasticity simulation. Then, the dimension-reduced microstructural features are revealed by a combination of 2-point spatial correlations and principal component analysis. The Bayesian model selection method is further applied to establish a microstructure-to-yield-strength surrogate model. Finally, the model is validated with an independent dataset and its constituent features are interpreted with a morphology reconstruction based on a Monte Carlo algorithm. The method is found to be capable of interpreting the key microstructural features as well as modeling the mechanical response of a dual-phase metallic composite in consideration of the diverse microstructural factors.

Modeling and analysis of temperature distribution in the multilayer metal composite structures in grinding

The article covers a mathematical model of a temperature distribution in the three-layer metal composite structures when grinding their working layers. The computer program TEMSS, created on the basis of thermal models, allows calculation of all the characteristics of the temperature distribution in the layers of the metal composite structure, depending on the system structure, material properties of its layers, grinding and machining conditions, and duration. The work establishes the adequacy of the developed mathematical model of the temperature distribution when grinding the metal composite systems. The article covers the analysis of standard metal composite systems with Loctite, Chester molecular, and Devcon polymers on the basis of the temperature distribution model, revealing the influence of lamination on the nature of the temperature distribution. Critical temperatures are defined that determine the occurrence of thermal grinding defects in the metal composite system, including their dependencies on processing conditions and the system structure. Thus, it is found that when grinding a working steel layer of the composite system using the standard grinding conditions recommended in the reference handbooks for steel workpieces, the temperature in the working and polymer-composite layers, as a rule, exceeds the threshold values for these materials.

Copper (II) Fluoride Cathodes in High Energy Primary Lithium Cells

QinetiQ has evaluated the performance of copper (II) fluoride (CuF2) in high energy density primary lithium cells. With a high density of 4.2 g/cm3, a theoretical initial voltage of 3.5 V vs. Li and a capacity of 528 mAh/g CuF2 appears competitive to well-known manganese dioxide, MnO2 (3.0 V, 308 mAh/g) and carbon mono fluoride, CFx (3.0 V, 864 mAh/g) making it attractive for further evaluation as a lithium cell cathode material. The aim of this work was to compare practical cell performance, including energy density and heat generation, at equivalent discharge rate or the same current per gram of active material for CuF2 and CFx pouch cells of equivalent format and volume. Heat generation is inherent to the reaction between CFx and lithium metal. Transition metal fluoride systems are also expected to inherently generate heat. Direct observation of heat generated during a cell discharge has not been reported for metal fluoride based cathodes to date. Initial studies focussed upon capacity and rate performance using a PTFE binder in Swagelok cells, where 507 mAh/g (96% of theoretical capacity) over an average voltage of 2.47 V was achieved at C/140 rate dropping to 70% at C/20, as shown in Fig. 1. The two stages in voltage profile seem related to formation of CuF followed by reduction to Cu. The conversion reaction is slower for this stage resulting in the sloped voltage profile observed. Composite ink formulation studies were conducted and down selection of binders appropriate to CuF2 led to the scale up and testing of coated electrodes, initial “Swagelok cells” and then in a multilayer pouch cell of 5.5 Ah theoretical capacity; the first reported for this cathode material. A higher specific current of 43 mA/g was applied in order to better observe any thermal effects in both materials. At this relatively high current and rate C/11.5 the CuF2 cell delivered 38% of theoretical capacity and remained 5°C cooler than the CFx cell (8.3 Ah) discharged at the same specific current or C/20 to the point of 2.0 V after which significant increase in heat was observed down to the 1.7 V cut off value (Fig. 2). The concept of using a mixed conducting matrices system, MCM’s [1] was explored with interest in improving CuF2 cathode performance and reducing the active material costs. The MCM’s typically metal oxides or sulphides, act as both ionic and electronic conductors and have been claimed to exhibit performance advantages over using carbon based conductive matrices alone. Composites of CuF2 with molybdenum trioxide MoO3 and with MnO2 were compared to previous results of pure CuF2 in “Swagelok cells”. Both showed some evidence of a synergistic effect manifesting as changes in discharge voltage profile. Further work would include investigation of these systems at higher rates and evaluation of the heat generated by these mixed metal composite systems in multilayer cells.

Mechanical modeling based on numerical homogenization of an Al2O3/Al composite manufactured via binder jet printing

The present research work takes advantage of a recently published numerical homogenization implementation in MATLAB to find the elasticity tensor of a ceramic–metallic composite (CMC) system to be compared to an experimental data. Numerical homogenization is an efficient way to determine effective macroscopic properties of a composite material. This technique represents an effective means to model a two-phase composite. In this work, an extension of a previously published numeric homogenization code was investigated in order to model the compressive elastic modulus of the ceramic–metallic composites. The extension to the numerical code makes use of physical micrograph images to accurately describe the phase distribution of the composite. Multiple micrographs were taken from each sample, to subsequently better represent the actual microstructure of the composite as a whole. The composites were created using a binder jet 3D printing technology, where a ceramic precursor material was initially assembled, followed by a molten metal infiltration process. It was found that the studied numerical homogenization yielded an elastic modulus approximately 11.5% lower than the experimental data, suggesting a reliable modeling technique for predicting the elastic tensor of CMCs.

A Compact Ionic Polymer Metal Composite (IPMC) System with Inductive Sensor for Closed Loop Feedback

Ionic polymer metal composite (IPMC), of which a low actuating voltage (<5 V), high power efficiency and biocompatibility makes it a proven candidate for low power devices. However, due to its inherent nonlinear behaviour and time-variance, feedback control, as well as reliable sensing means, are required for accurate operations. This paper presents an IPMC actuator implemented with an inductive sensor to enhance the reliability and compactness of the overall device. A practical, low cost and importantly, compact inductive sensor fabricated on a printed circuit board (PCB) is proposed here. Target material selections and coil design considerations are discussed. It is experimentally determined that the inductive sensor has comparable performance to a laser sensor. Based on a proportional-integral-derivative (PID) control results the inductive sensor has demonstrated to be an alternative to a laser sensor allowing devices using IPMC actuators to be compact.

Stress Analysis of a Three-Layer Metal Composite System of Bearing Assemblies During Grinding

A mathematical model of the stress state of a three-layer metal composite system caused by cutting forces during grinding the working layer of the system is elaborated. The implementation of the model by using the finite-element method made it possible to assess the effect of structure of the system, the deformation properties of layer materials, and grinding conditions on the distribution and level of normal and tangential stresses in layers, which determine the load-carrying capacity of the system. The results of an analysis of stress fields can serve as a basis for determining the grinding conditions ensuring retention of the load-carrying capacity of the metal composite system.

A simple post modification method for novel porous superabsorbent p(acrylamide) hydrogels and their H2 production

Poly(Acrylamide) (AAm) hydrogels were synthesized in bulk and reacted with NH2OH.HCl to develop a new functional group to confer high swelling, porosity and high metal ion binding abilities. The chemically-modified hydrogels, denoted as amidoximated poly(Acrylamide) (amid-p(AAm)) showed increased water swelling ability of up to 16-fold. The chemical modification induced structural changes were examined by FT-IR spectroscopy, water and pH swelling experiments, optical microscope images, titration studies, and even TG analysis. The amid-p(AAm) hydrogels were used as template for absorption of Co(II) and Ni(II) ions from their aqueous solutions and treated with aqueous NaBH4 for in situ metal nanoparticle preparation of the corresponding ions within the amid-p(AAm) matrices. The amid-p(AAm)-M (M:Co or Ni) composites were then used as catalyst in the hydrolysis of NaBH4 for H2 generation, and their catalytic performances were investigated. Various parameters for the hydrolysis of NaBH4 such as functionality of polymer matrices, the types of metal nanoparticles, metal catalyst amounts within hydrogel matrices, and temperature were investigated. Considerably low activation energy in comparison to similar studies in the literature were calculated for NaBH4 hydrolysis by amid-p(AAm)-Co metal composite systems: Ea = 17.26 ± 0.06.

안드로이드 스마트폰 기반의 원격 IPMC 제어시스템 구현

최근 의료 및 생체공학 분야의 액추에이터(actuator)와 센서 및 연료전지로 활용할 수 있는 새로운 재료인 IPMC(Ionic Polymer Metal Composite)에 대한 관심이 높아지고 있다. 이러한 IPMC의 특징은 센서(sensor)와 액추에이터(actuator)의 성질을 동시에 가지는 있는 특이한 성질을 가진 복합재료로서 IPMC에 전압을 가하면 움직임이 생기며, IPMC에 움직임이 발생하면 IPMC 내부에 전압이 충전되는 성질이 있어 모션 센서나 힘 센서로도 활용할 수 있다. 본 논문에서는 이러한 IPMC에 대한 몇 가지 특성을 파악하고 IT 기술인 스마트폰의 연계하여 원격지에서 IPMC의 동작을 제어할 수 있도록 시스템을 구성하였다. 또한, 스마트폰을 기반으로 하여 영상정보를 전송하여 모니터링 하도록 하였다. IPMC의 동작제어는 스마트폰의 블루투스를 이용하여 동작명령을 전송하도록 시스템을 구현하였다. 본 논문의 실험 및 구현으로부터 IPMC 물성에 대한 정확한 분석은 부족하지만 향후 IPMC의 활용에 있어서 IT 기술과의 융합을 통하여 센서, 액추에이터, 연료전지 등과 같은 분야에 적극 활용할 수 있음을 확인할 수 있었다. Recently, Ionic Polymer Metal Composite (IPMC) systems receive great attention in the fields of the medical and biomedical Engineering because of several merits in terms of new actuators and sensors and fuel cell materials. When the voltage is excited to IPMC system, it moves. Conversely, if there are any movement on the IPMC, the IPMC has charge voltage by the internal properties. Therefore the IPMC can be used as a motion sensor or force sensor. In this paper, we identify characteristics of the IPMC and control its movements from remote locations by the smart-phone system based on visual information for monitoring. Additionally, control of movements of the IPMC is realized by transmit motion commands using the smart-phone system with the blue-tooth communication. Unfortunately, there are some deficiencies to perfectly attain physical properties of the IPMC systems from our experiments in this paper. However, in its utilization point of view, we demonstrate that the IPMC has some potentials as new sensors, actuators, and fuel cells.

Multiscale modeling of metal-composite interfaces in titanium-graphite fiber metal laminates part II: Continuum scale

This study presents a multiscale numerical framework designed to predict the nonlinear constitutive behavior of metal-composite interfaces in titanium-graphite fiber metal laminates. Molecular-level property predictions derived in a separate analysis are used to parameterize a finite element model of the interface by means of a traction-separation constitutive law. Additional continuum-level energy dissipation and progressive failure phenomena are implemented into commercial finite element software through a user-defined material subroutine. Results obtained from this multiscale interface model are compared against experimental measurements of titanium-graphite fiber metal laminates in a short-beam shear loading configuration. The model predictive accuracy and its application to other bonded metal-composite systems are subsequently discussed.

Drawing behaviour of metal–composite sandwich structures

The drawing behaviour of metal–composite sandwich structures is investigated as a function of the constituent material properties and the process variables of blank preheat temperature and blank-holder force. Materials include three grades of aluminium alloy as the skin layer material and two types of reinforced polypropylene composite as the core layer material. Blank-holder force has a significant effect on the failure mode of the metal–composite system with lower forces resulting in wrinkling as the dominate mode and higher forces resulting in splitting and fracture. Increasing preheat temperature decreases the failure in the composite core however it will increase the severity of wrinkling in the outer flange and sidewall.

A Mathematical Model of Formation of the Structure of Composite Films by the Cut-Off Method

We substantiate the possibility of obtaining metal composite films with a prescribed composition by the method of cut-off of the sedimentation space over a horizontally located cathode. We present a calculation scheme and derive a formula which enables us to control the composition of the disperse phase in a composite electrolytic film by the cut-off time. The results obtained open up new possibilities for forming the structure and, consequently, the properties of metal composite thin-film systems.

Tribological investigation of 2009 Al-20 vol.% SiC p/17-4 PH Part II: counterpart performance

A statistical model for steady-state sliding wear of the metal counterpart in metal-composite systems has been extended to include composite reinforcement size and size distribution. It has been shown that the wear rate of the metal counterpart under conditions where MMC wear is characterized by plastic deformation (microplowing) is controlled by the ratio between the mean of particulate radius squared and the square mean particulate radius, E(r 2) E(r 2) , a descriptor of the particulate size and distribution. Under these instances, e.g. for 4, 10 and 13 μm particulate discontinuously reinforced aluminum (DRA)/17-4 PH tribosystems, the modified statistical model permits accurate prediction of the wear performance of the unreinforced counterpart. However, when MMC wear involves reinforcement cracking and delamination, the model overestimates the wear rate of the counterpart, i.e. in the 29 μm AlSiC p/17-4 PH tribosystems.