Tesis sobre el tema "Electrically conductive thermoplastic composites"

Les matériaux polymères conducteurs électriques font partie des matériaux polymères fonctionnels à haute valeur ajoutée pour de multiples applications émergentes, en particulier dans le domaine de l’électronique souple. De nombreuses applications industrielles intéressantes existent comme le chauffage par effet Joule ou l’isolation/blindage électromagnétique. A l’heure actuelle, cette dynamique s’étend au secteur de la plasturgie via les technologies émergentes de la fabrication additive et de la plastronique. Cependant, de nombreux verrous concernant les polymères conducteurs actuellement disponibles doivent être levés. Récemment, le PEDOT a permis d’atteindre des niveaux de conductivité électrique proche des métaux (env. 5000 S/cm). Cependant, le PEDOT est un polymère infusible et ne peut donc pas être mis en œuvre facilement par les techniques conventionnelles de l’industrie de la plasturgie. Pour contourner cet inconvénient, la stratégie mise en œuvre a été d’utiliser le PEDOT comme charge conductrice organique en le dispersant dans une matrice thermoplastique par extrusion pour obtenir des composites thermoplastiques conducteurs
Electrically conductive polymer materials are among the functional polymer materials with high added value for many emerging applications, particularly in the field of flexible electronics. There are many interesting industrial applications, such as Joule heating and electromagnetic insulation/shielding. This dynamic is now being extended to the plastics processing sector via the emerging technologies of additive manufacturing and plastronics. However, there are still a number of obstacles to be overcome when it comes to the conductive polymers currently available. Recently, PEDOT has made it possible to achieve electrical conductivity levels close to those of metals (around 5000 S/cm). However, PEDOT is an infusible polymer and cannot therefore be processed easily using conventional techniques in the plastics processing industry. To overcome this drawback, the strategy implemented was to use PEDOT as an organic conductive filler by dispersing it in a thermoplastic matrix using extrusion to obtain conductive thermoplastic composites

The electronics industry is shifting its emphasis from reducing transistor size and operational frequency to increasing device integration, reducing form factor and increasing the interface of electronics with their surroundings. This new emphasis has created increased demands on the electronic package. To accomplish the goals to increase device integration and interfaces will undoubtedly require new materials with increased functionality both electrically and mechanically. This thesis focuses on developing new interconnect and printable conductive materials capable of providing power, ground and signal transmission with enhanced electrical performance and mechanical flexibility and robustness. More specifically, we develop: 1.) A new understanding of the conduction mechanism in electrically conductive composites (ECC). 2.) Develop highly conductive stretchable silicone ECC (S-ECC) via in-situ nanoparticle formation and sintering. 3.) Fabricate and test stretchable radio frequency devices based on S-ECC. 4.) Develop techniques and processes necessary to fabricate a stretchable package for stretchable electronic and radio frequency devices. In this thesis we provide convincing evidence that conduction in ECC occurs predominantly through secondary charge transport mechanism (tunneling, hopping). Furthermore, we develop a stretchable silicone-based ECC which, through the incorporation of a special additive, can form and sinter nanoparticles on the surface of the metallic conductive fillers. This sintering process decreases the contact resistance and enhances conductivity of the composite. The conductive composite developed has the best reported conductivity, stretchability and reliability. Using this S-ECC we fabricate a stretchable microstrip line with good performance up to 6 GHz and a stretchable antenna with good return loss and bandwidth. The work presented provides a foundation to create high performance stretchable electronic packages and radio frequency devices for curvilinear spaces. Future development of these technologies will enable the fabrication of ultra-low stress large area interconnects, reconfigurable antennas and other electronic and RF devices where the ability to flex and stretch provides additional functionality impossible using conventional rigid electronics.

The electrical and mechanical properties of electrically conductive fiber composites were measured and related to composite microstructure. Samples were manufactured by compression molding, extrusion, and injection molding to determine the effect of processing method on fiber length and orientation. A strong correlation between the processing-induced fiber-phase microstructure and the measured properties is found. The results are highly dependent on the type of conductive fiber. Computer-generated flow-field models are able to illustrate the thermal and flow processes which affect microstructure. A simple orientation model gives good qualitative agreement with experimental observations in injection molded composites.
Two models for predicting volume resistivity are proposed. One model assumes that the fibers are aligned end-to-end, and the effect of fiber orientation and concentration is obtained. The results agree qualitatively with experimental data, and give a lower bound or resistivity. More realistic fiber-fiber contacts are considered in the second model. The resistivity is expressed in terms of the area of contact, and orientation, length, and concentration of the fibers. Model predictions are in excellent agreement with experimental results.

The central topic of this thesis was the design and development of a bi-functional thermoplastic polyurethane (TPU) composite, which is halogen-free bio-based flame retardant (UL94-V0) with an electrical resistivity ≤ 1000 Ω.cm and a filler load that does not exceed 25 wt.%. In order to reach this goal, the experimental activities were divided into the following tasks: (a) materials pre-selection, (b) design of experiment (DOE), (c) materials compounding, (d) specimens preparation (injection moulding), and (e) materials characterization (electrical resistivity tests, flammability tests, and microstructure analysis). In other words, the main tasks were identifying the ingredients (in a first stage) and defining the optimal proportions of additives (in a second stage) capable of simultaneously conferring to the polymer of interest the most desirable values of flame retardancy (as high as possible) and electrical resistivity (as low as possible); followed by the material preparation (third stage) and the material characterization (forth stage). The materials (flame retardants and electrically conductive additives) used in the development of this novel formulation were pre-selected mainly based on bibliographical studies. Then, the experimental activities and the analysis of the test results allowed to identify positive and negative effects among the components of the formulation such as synergistic effects among flame retardants on the improvement of the fire resistant performance. The obtained final formulation accomplished the desired target values of flame retardancy (V0 compliant) and electrical resistivity (≤1000 Ω.cm). It was compared to commercial products from the companies RTP, BASF and LUBRIZOL, which are used in the same field of application. The material developed during this work showed a lower electrical resistivity than these commercially available products while being bio-based and V0 (UL-94 test) at the same time. In addition, an innovative online acquisition apparatus for monitoring the surface growth of flame retardant protective layers was designed and developed during this thesis, which provided a deep insight of the dynamic behaviour of a phosphorous-based flame retarded material. The measurement of the surface protective layer growth rate provided a better understanding of the behaviour of the flame retardant systems, correlating the speed of the chemical reaction with the performances of the material.

Electrically conductive polymer composites, i.e. polymers filled with conductive fillers, may display a broad range of electrical properties. A rational design of fillers, filler surface chemistry and filler loading can tune the electrical properties of the composites to meet the requirements of specific applications. In this dissertation, two studies were discussed. In the first study, highly conductive composites with electrical conductivity close to that of pure metals were developed as environmentally-friendly alternatives to tin/lead solder in electronic packaging. Conventional conductive composites with silver fillers have an electrical conductivity 1~2 orders of magnitude lower than that of pure, even at filler loadings as high as 80-90 wt.%. It is found that the low conductivity of the polymer composites mainly results from the thin layer of insulating lubricant on commercial silver flakes. In this work, by modifying the functional groups in polymer backbones, the lubricant layer on silver could be chemically reduced in-situ to generate silver nanoparticles. Furthermore, these nanoparticles could sinter to form metallurgical bonds during the curing of the polymer matrix. This resulted in a significant electrical conductivity enhancement up to 10 times, without sacrificing the processability of the composite or adding extraneous steps. This method was also applied to develop highly flexible/stretchable conductors as building block for flexible/stretchable electronics. In the second study, a moderately conductive carbon/polymer composite was developed for use in sensors to monitor the thermal aging of insulation components in nuclear power plants. During thermal aging, the polymer matrix of this composite shrank while the carbon fillers remained intact, leading to a slight increase in filler loading and a substantial decrease in the resistivity of the sensors. The resistivity change was used to correlate with the aging time and to predict the need for maintenance of the insulation component according to Arrhenius’ equation. This aging sensor realized real-time, non-destructive monitoring capability for the aging of the target insulation component for the first time.

Recent advances in manufacturing of multifunctional materials have provided opportunities to develop structures that possess superior mechanical properties with other concurrent capabilities such as sensing, self-healing, electromagnetic and heat functionality. The idea is to fabricate components that can integrate multiple capabilities in order to develop lighter and more efficient structures. In this regard, due to their combined structural and electrical functionalities, electrically conductive carbon fiber reinforced polymer (CFRP) matrix composites have been used in a wide variety of applications in most of which they are exposed to unwanted impact-like mechanical loads. Experimental data have suggested that the application of an electromagnetic field at the moment of the impact can significantly reduce the damage in CFRP composites. However, the observations still need to be investigated carefully for practical applications. Furthermore, as the nature of the interactions between the electro-magneto-thermo-mechanical fields is very complicated, no analytical solutions can be found in the literature for the problem. In the present thesis, the effects of coupling between the electromagnetic and mechanical fields in electrically conductive anisotropic composite plates are studied. In particular, carbon fiber polymer matrix (CFRP) composites subjected to an impact-like mechanical load, pulsed electric current, and immersed in the magnetic field of constant magnitude are considered. The analysis is based on simultaneous solving of the system of nonlinear partial differential equations, including equations of motion and Maxwell's equations. Physics-based hypotheses for electro-magneto-mechanical coupling in transversely isotropic composite plates and dimension reduction solution procedures for the nonlinear system of the governing equations have been used to reduce the three-dimensional system to a two-dimensional (2D) form. A numerical solution procedure for the resulting 2D nonlinear mixed system of hyperbolic and parabolic partial differential equations has been developed, which consists of a sequential application of time and spatial integrations and quasilinearization. Extensive computational analysis of the response of the CFRP composite plates subjected to concurrent applications of different electromagnetic and mechanical loads has been conducted. The results of this work verify the results of the previous experimental studies on the subject and yield some suggestions for the characteristics of the electromagnetic load to create an optimum impact response of the composite.

O objetivo deste estudo foi o desenvolvimento de compósitos poliméricos flexíveis e altamente condutores elétricos preparados por moldagem por compressão e por fabricação de filamentos fundidos (FFF) para possíveis aplicações como materiais piezoresistivos ou piezoelétricos para sensores de compressão. Compósitos baseados em misturas de poli(fluoreto de vinilideno)/poliuretano termoplástico (PVDF/TPU) como matriz e contendo várias frações de negro de fumo-polipirrol (CB-PPy) como aditivo condutor foram preparados. Diversas técnicas de caracterização foram realizadas para avaliar as propriedades mecânicas, térmicas, químicas e elétricas, morfologia e printabilidade dos materiais investigados. Primeiro, blendas de PVDF/TPU com diferentes composições foram produzidas por mistura por fusão seguida de moldagem por compressão. Os resultados mostraram que a flexibilidade desejada para os materiais foi melhorada com a adição de TPU aos compósitos de PVDF. As imagens SEM evidenciaram a obtenção de uma blenda co-contínua com 50/50 vol% de PVDF/TPU. As blendas compostas de PVDF/TPU 38/62 vol% e a blenda co-contínua de PVDF/TPU 50/50 vol% foram selecionadas como matrizes para a preparação de compósitos moldados por compressão e impressos em 3D a fim de alcançar uma ótima combinação entre condutividade, propriedades mecânicas e printabilidade. Várias quantidades de negro de fumo-polipirrol, de 0 a 15%, foram adicionadas às blendas selecionadas para aumentar a condutividade elétrica dos compósitos e possivelmente atuar como agente nucleante para a fase cristalina do PVDF a fim de aumentar sua resposta piezoelétrica. A adição de CB-PPy aumentou a condutividade elétrica de todos os compósitos. No entanto, a condutividade elétrica dos compósitos baseados em blendas co-contínuas PVDF/TPU 50/50 vol% foi maior do que as encontradas para os compósitos de PVDF/TPU 38/62 vol% com mesma concentração de aditivo. De fato, o limiar de percolação elétrico dos compósitos com blenda co-contínua foi de 2%, enquanto o limiar de percolação elétrico dos compósitos compostos da blenda não contínua foi de 5%. Com relação às propriedades mecânicas, a incorporação do aditivo condutor nas blendas resultou em materiais mais rígidos com maior módulo de elasticidade, menor alongamento na ruptura e maior módulo de armazenamento. O módulo de armazenamento (G') e a viscosidade complexa (η*) dos compósitos aumentaram com a adição de CB-PPy. O limiar de percolação reológico foi de 3% para PVDF/TPU/CB-PPy 38/62 vol% e 1% para PVDF/TPU/CB-PPy 50/50 vol%, indicando que uma quantidade maior de carga poderia comprometer a processabilidade dos compósitos. A adição de CB-PPy também resultou na redução dos valores de Tg e Tm dos compósitos devido à redução da mobilidade das cadeias poliméricas. Com base na condutividade elétrica e no comportamento mecânico dos compósitos, três composições diferentes foram selecionadas para a extrusão de filamentos para serem posteriormente utilizados no processo de impressão 3D. No geral, as peças impressas em 3D apresentaram propriedades mecânicas e elétricas inferiores devido à presença de vazios, defeitos e camadas sobrepostas que podem dificultar o fluxo de elétrons. Os valores de condutividade elétrica dos compósitos impressos em 3D de PVDF/TPU/CB-PPy 38/62 vol% contendo 5% e 6% de CB-PPy são de uma a sete ordens de grandeza menores do que os encontrados para os compósitos com a mesma composição moldados por compressão. Mesmo que o valor da condutividade elétrica para o compósito PVDF/TPU 38/62 vol% com 6% de CB-PPy moldado por compressão foi de 1,94x10-1 S•m-1, o compósito impresso em 3D com a mesma composição mostrou um valor muito baixo de condutividade elétrica de 6,01x10-8 S•m-1. Por outro lado, o compósito co-contínuo de PVDF/TPU 50/50 vol% com 10% de aditivo impresso em 3D apresentou um alto valor de condutividade elétrica de 4,14×100 S•m-1 mesmo após o processo de impressão. Além disso, as respostas piezoresistivas dos compósitos foram investigadas. Para os compósitos PVDF/TPU/CB-PPy 38/62 vol%, as amostras moldadas por compressão e impressas em 3D com 5% e 6% de CB-PPy exibiram boa resposta piezoresistiva. No entanto, apenas os compósitos com 6% de aditivo apresentaram valores elevados de sensibilidade e gauge factor, atuação em ampla faixa de pressão e respostas piezoresistivas reprodutíveis durante a aplicação de 100 ciclos de compressão/descompressão para ambos os métodos de fabricação. Por outro lado, para os compósitos co-contínuos de PVDF/TPU/CB-PPy apenas a amostra moldada por compressão com 5% de CB-PPy apresentou respostas piezorresistivas boas e reprodutíveis. A cristalinidade e o teor de fase β do PVDF foram investigados para os compósitos. Embora o grau de cristalinidade das amostras tenha diminuído com a adição de CB-PPy, a porcentagem de fase β no PVDF aumentou. O coeficiente piezoelétrico d33 das amostras aumentou com a porcentagem de fase β. A adição de 6% ou mais de CB-PPy foi necessária para aumentar significativamente o coeficiente piezoelétrico (d33) dos compósitos. O conteúdo de fase β e as respostas piezoelétricas do PVDF foram menores para as amostras preparadas por FFF. Por fim, como pesquisa colateral, a eficiência de blindagem contra interferência eletromagnética (EMI-SE) foi medida para todos os compósitos. Compósitos com maior condutividade elétrica apresentaram melhor blindagem da radiação eletromagnética. Além disso, os compósitos baseados na blenda co-contínua apresentaram maior eficiência de blindagem contra EMI do que os compósitos de PVDF/TPU 38/62 vol%. O principal mecanismo de blindagem foi a absorção para todos os compósitos. As amostras preparadas por FFF apresentaram respostas de EMI-SE menores quando comparadas às amostras moldadas por compressão.
The aim of this study was the development of flexible and highly electrically conductive polymer composites via compression molding and fused filament fabrication for possible applications as piezoresistive or piezoelectric materials for pressure sensors. Composites based on blends of poly(vinylidene fluoride)/thermoplastic polyurethane (PVDF/TPU) as matrix and containing various fractions of carbon black-polypyrrole (CB-PPy) as conductive filler were prepared. Several characterization techniques were performed in order to evaluate the mechanical, thermal, chemical and electrical properties, morphology and printability of the investigated materials. First, PVDF/TPU blends with different compositions were prepared by melt compounding followed by compression molding. The results showed that the flexibility aimed for the final materials was improved with the addition of TPU to PVDF composites. SEM images evidenced the achievement of a co-continuous blend comprising 50/50 vol% of PVDF/TPU. The blends composed of PVDF/TPU 38/62 vol% and the co-continuous blend of PVDF/TPU 50/50 vol% were selected as matrices for the preparation of compression molded and 3D printed composites in order to achieve an optimal compromise between electrical conductivity, mechanical properties and printability. Various amounts of carbon black-polypyrrole, from 0 up to 15%, were added to the selected blends in order to rise the electrical conductivity of the composites and to possible act as nucleating filler for the β crystalline phase of PVDF in order to increase its piezoelectric response. The addition of CB-PPy increased the electrical conductivity of all composites. However, the electrical conductivity of composites based on PVDF/TPU 50/50 vol% co-continuous blends was higher than those found for PVDF/TPU 38/62 vol% composites at the same filler content. Indeed, the electrical percolation threshold of the conductive co-continuous composite blends was 2%, while the electrical percolation threshold of the composites with the nonco-continuous composite blends was 5%. With respect to the mechanical properties, the incorporation of the filler into the blends leaded to more rigid materials with higher elastic modulus, lower elongation at break and higher storage modulus. The storage modulus (G’) and complex viscosity (η*) of the composites increased with the addition of CB-PPy. The rheological percolation threshold was found to be 3% for PVDF/TPU/CB-PPy 38/62 vol% and 1% for PVDF/TPU/CB-PPy 50/50 vol%, indicating that higher amount of filler could compromise the processability of the composites. The addition of CB-PPy also resulted in a reduction on the Tg and Tm values of the composites due to the reduction of the mobility of the polymeric chains. Based on the electrical conductivity and mechanical behavior of the composites, three different compositions were selected for the extrusion of filaments to be used in a 3D printing process. Overall, the 3D printed parts presented lower mechanical and electrical properties because of the presence of voids, defects and overlapping layers that can hinder the flow of electrons. The electrical conductivity values of PVDF/TPU/CB-PPy 38/62 vol% composites containing 5% and 6 wt% of CB-PPy 3D printed samples are one to seven orders of magnitude lower than those found for compression molded composites with the same composition. Even if the electrical conductivity value for PVDF/TPU 38/62 vol% compression molded composite with 6% of CB-PPy was as high as 1.94x10-1 S•m-1, the 3D printed composite with same composition showed a very low electrical conductivity of 6.01x10-8 S•m-1. On the other hand, the 3D printed co-continuous composite PVDF/TPU 50/50 vol% with 10% of filler displayed a high value of electrical conductivity of 4.14×100 S•m-1 even after the printing process. Moreover, the piezoresistive responses of the composites were investigated. For PVDF/TPU/CB-PPy 38/62 vol% composites, the compression molded and 3D printed samples with 5% and 6% of CB-PPy exhibited good piezoresistive response. However, only the composites with 6% displayed high sensitivity and gauge factor values, large pressure range and reproducible piezoresistive responses under 100 cycles for both methods. On the other hand, for PVDF/TPU/CB-PPy co-continuous composites only the compression molded sample with 5% of CB-PPy presented good and reproducible piezoresistive responses. The crystallinity and β phase content of PVDF were investigated for the composites. Althought the degree of crystallinity of the samples decreased with the addition of CB-PPy, the percentage of β phase in PVDF was increased. The piezoelectric coefficient d33 of the samples increased with the percentage of β phase. The addition of 6% or more of CB-PPy was necessary to increase significatively the piezoelectric coefficient (d33) of the composites. The β phase content and piezoelectric responses of PVDF were lower for samples prepared by FFF. Finally, as a collateral research, the electromagnetic interference shielding effectiveness (EMI-SE) were measured for all composites. Composites with higher electrical conductivity showed better shielding of the electromagnetic radiation. In addition, composites based on the co-continuous blend displayed higher EMI shielding efficiency than 38/62 vol% composites. The main mechanism of shielding was absorption for all composites. Specimens prepared by FFF displayed diminished EMI-SE responses when compared to compression molded samples.
Lo scopo di questo studio è lo sviluppo di compositi polimerici flessibili e ad elevata conducibilità elettrica tramite stampaggio a compressione e manifattura additiva (fused filament fabrication) per possibili applicazioni come materiali piezoresistivi o piezoelettrici in sensori di pressione. In particolare, sono stati preparati compositi a base di miscele di poli(vinilidene fluoruro)/poliuretano termoplastico (PVDF/TPU) come matrice e contenenti varie frazioni di nerofumo-polipirrolo (CB-PPy) come riempitivo conduttivo. Sono state utilizzate diverse tecniche di caratterizzazione al fine di valutare le proprietà meccaniche, termiche, chimiche ed elettriche, la morfologia e la stampabilità dei materiali ottenuti. In primo luogo, miscele PVDF/TPU con diverse composizioni sono state preparate mediante mescolatura allo stato fuso seguita da stampaggio a compressione. I risultati hanno mostrato che la flessibilità del PVDF viene notevolemente migliorata dall’aggiunta di TPU. Le immagini SEM hanno evidenziato il raggiungimento di una miscela co-continua per una composizione 50/50% in volume di PVDF/TPU. Le miscele composte da PVDF/TPU 38/62 vol% e la miscela co-continua di PVDF/TPU 50/50 vol% sono state selezionate come matrici per la preparazione di compositi per stampaggio a compressione e manifattura additiva al fine di ottenere un compromesso ottimale tra conducibilità, proprietà meccaniche e stampabilità. Alle miscele selezionate sono state aggiunte varie quantità di nerofumo-polipirrolo, dallo 0 al 15%, per aumentare la conducibilità elettrica dei compositi ed eventualmente fungere da additivo nucleante per la fase β cristallina del PVDF al fine di aumentarne la risposta piezoelettrica. L'aggiunta di CB-PPy ha aumentato la conduttività elettrica di tutti i compositi. Tuttavia, la conduttività elettrica dei compositi basati su miscele co-continue di PVDF/TPU 50/50% in volume era superiore a quella trovata per compositi PVDF/TPU 38/62% in volume con lo stesso contenuto di riempitivo. Infatti, la soglia di percolazione elettrica delle miscele conduttive era del 2%, mentre la soglia di percolazione elettrica dei compositi con miscele composite non continue era del 5%. Per quanto riguarda le proprietà meccaniche, l'incorporazione del riempitivo nelle mescole ha portato a materiali più rigidi con modulo elastico più elevato, allungamento a rottura inferiore e modulo conservativo più elevato. Il modulo conservativo (G') e la viscosità complessa (η*) dei compositi sono aumentate con l'aggiunta di CB-PPy. La soglia di percolazione reologica è risultata essere del 3% per PVDF/TPU/CB-PPy 38/62 vol% e dell'1% per PVDF/TPU/CB-PPy 50/50 vol%, indicando che una maggiore quantità di riempitivo potrebbe compromettere la processabilità dei compositi. L'aggiunta di CB-PPy ha comportato anche una riduzione dei valori di Tg e Tm dei compositi a causa della riduzione della mobilità delle catene polimeriche. Sulla base della conduttività elettrica e del comportamento meccanico dei compositi, sono state selezionate tre diverse composizioni per l'estrusione di filamenti da utilizzare in un processo di stampa 3D. Nel complesso, le parti stampate in 3D presentavano proprietà meccaniche ed elettriche inferiori a causa della presenza di vuoti, difetti e strati sovrapposti che possono ostacolare il flusso di elettroni. I valori di conducibilità elettrica dei compositi PVDF/TPU/CB-PPy 38/62 vol% contenenti il 5% e il 6% di CB-PPy di campioni stampati in 3D sono da uno a sette ordini di grandezza inferiori a quelli trovati per i compositi stampati a compressione con la stessa composizione. Anche se il valore di conducibilità elettrica per il composito stampato a compressione PVDF/TPU 38/62 vol% con il 6% di CB-PPy era pari a 1,94x10-1 S•m-1, il composito stampato in 3D con la stessa composizione ha mostrato un valore molto basso di conducibilità elettrica, pari a 6,01x10-8 S•m-1. D'altra parte, il composito PVDF/TPU 50/50 vol% stampato in 3D con il 10% di riempitivo ha mostrato un elevato valore di conducibilità elettrica, pari a 4,14 × 100 S•m-1, anche dopo il processo di stampa. Inoltre, sono state studiate le risposte piezoresistive dei compositi. Per i compositi PVDF/TPU/CB-PPy 38/62 vol%, i campioni stampati a compressione e stampati in 3D con il 5% e il 6% di CB-PPy hanno mostrato una buona risposta piezoresistiva. Tuttavia, solo i compositi con il 6% hanno mostrato valori di sensibilità e gauge factor elevati, ampio intervallo di pressione e risposte piezoresistive riproducibili in 100 cicli per entrambi i metodi. D'altra parte, per i compositi co-continui PVDF/TPU/CB-PPy solo il campione stampato a compressione con il 5% di CB-PPy ha presentato risposte piezoresistive adeguate e riproducibili. La cristallinità e il contenuto di fase β del PVDF sono stati studiati per i compositi. Sebbene il grado di cristallinità dei campioni diminuisca con l'aggiunta di CB-PPy, la percentuale di fase β in PVDF risulta aumentata. Il coefficiente piezoelettrico d33 dei campioni aumenta anch’esso con la percentuale di fase β. L'aggiunta del 6% o più di CB-PPy è stata necessaria per aumentare significativamente il coefficiente piezoelettrico (d33) dei compositi. Il contenuto di fase β e le risposte piezoelettriche del PVDF sono inferiori per i campioni ottenuti mediante stampa 3D. Infine, come ricerca collaterale, è stata misurata l'efficacia della schermatura contro le interferenze elettromagnetiche (EMI-SE) per tutti i compositi. I compositi con una maggiore conduttività elettrica hanno mostrato una migliore schermatura della radiazione elettromagnetica. Inoltre, i compositi basati sulla miscela co-continua hanno mostrato un'efficienza di schermatura EMI maggiore rispetto ai compositi a 38/62% in volume. Per tutti i compositi, il principale meccanismo di schermatura è l'assorbimento. I campioni preparati mediante manifattura additiva hanno mostrato risposte EMI-SE inferiori rispetto ai campioni stampati a compressione.

Electroconductive composites are modern materials that are commonly used in many industries such as the construction industry among others. For example these materials can be useful as sensors for monitoring changes in constructions. The aim of this thesis is the research of electrically conductive silicate composite based on secondary raw materials. The design of this composite is based on the development of its own mixtures and experimental verification of the effect of the structure. The introduction part consists of a detailed analysis of 15 materials. Samples of the 5 fine and 2 coarse electrically conductive fillers were tested. Composite with filler Condufit C4 was selected as representative for type of fine fillers. Composite with filler Supragraphite C300 was selected as representative for type of coarse fillers. The selection of the composites was based on the impedance of the fabricated composites with these fillers. Subsequently, the individual components of the primary mixture were substituted. The cement was replaced by high-temperature fly ash in the amount of 20, 30, and 40 %, the aggregate of a similar fraction was replaced by steel sawdust, and the primary electrically conductive fillers were replaced by secondary ones in the amount of 30 and 50 %. All proposed replacements reduced the impedance of the composite. The most effective replacement for impedance reduction was replacement with waste graphite (up to 92 % reduction), which also slightly improved the mechanical properties of the composite. The result of this thesis is an optimized electrically conductive composite based on secondary raw materials with a fine type of filler with 30 % replacement by waste graphite "odpad vysavač"which achieves an impedance of 5 ohms. The partial goal of this thesis is a verification of the influence of moisture on the impedance of composites. Results are significantly affected by moisture when using the coarse type of filler, when using the fine type are not.

This dissertation deals with the study of electric and dielectric properties of composite structures on the base of alkali-activated aluminosilicates with admixtures of various carbon particles. These materials fabricated from alkali-activated blast furnace slag, quarz sand, natrium water glass as alkali activator, water, dispersant and small amount of carbon admixture (carbon black, graphite powder, carbon fibers or carbon nanotubes) to increase electric conductivity may be used for example to construction of snow-melting, deicing and self-monitoring systems. Their current-voltage characteristics and impedance spectra were used for determination of electric and dielectric properties of these structures. The equivalent circuits were used for evaluation of impedance spectra. The results were correlated with thermal properties of these structures.

Polymer electrolyte membrane fuel cells (PEMFCs) have the potential to play a major role as energy generators for transportation and portable applications. One of the current barriers to their commercialization is the cost of the components and manufacturing, specifically the bipolar plates. One approach to preparing PEMFCs for commercialization is to develop new bipolar plate materials, related to mass production of fuel cells. Thermoplastic/carbon filler composites with low filler loading have a major advantage in that they can be produced by a conventional low-cost injection molding technique. In addition, the materials used are inexpensive, easy to shape, and lightweight. An optimal bipolar plate must possess high surface and bulk electronic conductivity, sufficient mechanical integrity, low permeability, and corrosion resistance. However, it is difficult to achieve high electrical conductivity from a low-cost thermoplastic composite with low conductive filler loading. Concerns over electrical conductivity improvement and the injection processability of composites have brought forth the idea of producing a polypropylene/three-carbon-filler composite for bipolar plate application. The thesis addresses the development of synergistic effects of filler combinations, investigating composite conductive materials and using composite bipolar plate testing in PEMFCs. One significant effect of conductive network formation is the synergetic effects of different carbon filler sizes, shapes, and multiple filler ratios on the electrical conductivity of bipolar plate materials. A polypropylene resin combined with low-cost conductive fillers (graphite, conductive carbon black, and carbon fibers with 55 wt% of filler loading) compose the main composite for all investigations in this research. Numerous composite formulations, based on single-, two-, and three-filler systems, have been created to investigate the characteristics and synergistic effects of multiple fillers on composite conductivity. Electrical conductivity measurements corresponding to PEMFC performance and processing characteristics were investigated. Experimental work also involved other ex-situ testing for the physical requirements of commercial bipolar plates. All combinations of fillers were found to have a significant synergistic effect that increased the composite electrical conductivity. Carbon black was found to have the highest influence on the increase of electrical conductivity compared to the other fillers. The use of conjugated conducting polymers such as polypyrrole (PPy) to help the composite blends gain desirable conductivities was also studied. Electrical conductivity was significantly improved conductivity by enriching the conducting paths on the interfaces between fillers and the PP matrix with PPy. The conductive network was found to have a linkage of carbon fibers following the respective size distributions of fibers. The combination of Fortafil and Asbury carbon fiber mixture ameliorated the structure of conductive paths, especially in the through-plane direction. However, using small fibers such as carbon nanofibers did not significantly improve in electrical conductivity. The useful characteristics of an individual filler and filler supportive functions were combined to create a novel formula that significantly improved electrical conductivity. Other properties, such as mechanical and rheological ones, demonstrate the potential to use the composites in bipolar plate applications. This research contributes a direction for further improvement of marketable thermoplastic bipolar plate composite materials.

博士
逢甲大學
紡織工程所
95
The main purpose of the research is to prevent the interferences and dangers from electrostatic discharge and electromagnetic interference and also reduce the hazards caused by electromagnetic radiation. Enhance, the Cu/SS/PA6 rotor twisted conductive yarn (RTCY) using for loop, weft (woven fabric only) and warp yarn and the Cu/PPs and SS/PPs rotor twisted conductive cords (RTCC) using for weft-inlaid yarn were fabricated by a Rotor Twister. The results indicated that the better shielding effectiveness and molding outcome of CWKF reinforced composite are fabricated with the parameters for rotor speed of 8000 rpm and weft-inlaid two ends of Cu/PPs and SS/PPs RTCC. Furthermore, the optimum parameters in spinning process were performed again in the two-step spinning method combined with Ring spinning frame and Rotor Twister; and it produced a series of conductive hybrid yarn and cord: NiCu/SS/PP Ring-RTCY using for loop yarn; NiCu/SS/Carbon/PP and NiCu/SS/Kevlar/PP Ring-RTCY using for warp yarn; NiCu/SS/Carbon/PPs and NiCu/SS/Kevlar/PPs Ring-RTCC using for weft-inlaid yarn. The conductive woven fabrics were fabricated with various intervals between Cu/SS/PA6 RTCY via a semi-automatic loom and the conductive co-woven-knitted fabrics (Conductive CWKF) were fabricated with the various (Ring) RTCY and (Ring) RTCC. Then ,the composites were fabricated with 4 or 6 layers of CWKF via the hand-lamination. The thickness of 1- 3 mm for thermoplastic composites reinforced by conductive interlaced woven fabrics or thermoplastic composites reinforced by conductive co-woven-knitted fabrics, were fabricated and cooling naturally at room temperature. The influences of interval between RTCY and laminations on the electromagnetic shielding effectiveness (EMSE), tensile strength and elongation were investigated in this dissertation. Besides, the effects of yarn density and materials in warp and weft directions, content of metal fiber, content of reinforcement fiber, laminating angles, laminations, and thickness on the electromagnetic shielding effectiveness (EMSE) for various measurement system and electromagnetic wave in near/far field, surface resistivity, electrostatic discharge decay (ESD), tensile strength, elongation, storage modulus, loss modulus and loss tangent, tanδ. When the NiCu wire, Kevlar filaments, Carbon filaments are not utilized yet, the optimum shielding effectiveness of CWKF reinforced composite are fabricated with the parameters for the loop yarn of Cu/SS/PA6 RTCY-8k, weft-inlaid two ends of Cu/PPs and SS/PPs RTCC, laminated for 6 layers of CWKF in a thickness of 3 mm. The EMSE of above parameters is about 50 dB in the range of 300 – 1500 MHz and it is around 45 dB in the range of 1.5 – 8.5 GHz. As the NiCu wire, Kevlar filaments, Carbon filaments are utilized in the spinning process, the optimum shielding effectiveness of CWKF reinforced composite are fabricated with the parameters for the loop yarn of NiCu/SS/PP Ring-RTCY, weft-inlaid two ends of NiCu/SS/Carbon/PPs Ring-RTCC, laminated for 4 layers of CWKF in a thickness of 3 mm. The EMSE of above parameters is about 70 dB in the range of 300 – 1500 MHz and it is around 90 dB in the range of 1.5 – 8.5 GHz. The conductive thermoplastic composites fabricated in this dissertation can be utilized for the anti-impact, electromagnetic shielding materials and conductive parts in vehicles and the housing for computers, electronic instruments, scientific appliances. Keywords : copper wire, nickel coated copper wire, stainless steel wire, rotor twister, ring spinning frame, woven fabric, co-woven-knitted fabric, thermoplastic composite, electromagnetic shielding effectiveness (EMSE), electrostatic discharge decay (ESD), tensile strength, elongation

Numerous alternative energy sources are being researched for sustainable energy applications, but their overall benefit is still too costly for them to be considered viable. Commonly produced temperature gradients created by the environment, or are man-made, can be converted into useful energy by using thermoelectric materials. Inorganic semiconductors are the most commonly used thermoelectric materials, but have raised concerns due to toxicity issues, rarity of heavy elements used, and high fabrication temperatures. These concerns have led research efforts into electrically conductive polymer composites prepared in ambient conditions from aqueous solutions. By combining polymer latex with carbon nanotubes (CNT), electrical conductivity can resemble metals while thermal conductivity remains similar to polymers. Using different CNT stabilizers for these fully organic composites can tailor the thermoelectric properties and harvest thermal gradients from previously inconceivable places (e.g., body heat converted into a voltage). A semiconducting CNT stabilizer, meso-tetra(4-carboxyphenyl) porphine (TCPP), was used to investigate the influence stabilizers have on composite thermoelectric properties. As TCPP was compared to a similar system containing an insulating stabilizer, sodium deoxycholate (DOC), the multi-walled carbon nanotube (MWNT)-filled composites showed a 5x increase in the Seebeck coefficient (S). TCPP did not have a distinct effect on the electrical conductivity (σ), demonstrating the tailorability of S with this molecule. An intrinsically conductive polymer, poly(3,4-ethylenedioxythiophene) :poly(styrene sulfonate) (PEDOT:PSS), was used to stabilize highly conductive double-walled carbon nanotubes (DWNT) and demonstrate the promise of fully organic composites as thermoelectric materials. This combination of CNT and stabilizer produced metallic electrical conductivity (200,000 S m-1) and power factors (S2σ) within an order of magnitude of commonly used semiconductors (~400 μW m-1 K-2). Electrical conductivity was doubled by stabilizing single-walled carbon nanotubes (SWNT) with PEDOT:PSS in a thin film without the insulating polymer latex. To further demonstrate the tailorability of polymer composites, a dual stabilizer approach using semiconducting and intrinsically conductive stabilizers was used. This approach effectively provided the high electrical conductivity from PEDOT:PSS and the enhanced Seebeck coefficients of TCPP. By using multiple stabilizers for CNTs within the same composite, power factors among the highest reported for fully organic composites are achieved (~500 μW m-1 K-2). These water-based, flexible composites are becoming real competition as their conversion efficiencies, when normalized by density, are similar to commonly used semiconductors.

Dissertação de mestrado em Bioengenharia
As the era of the nanomaterials draws near, the electrically conductive polymeric materials have been receiving increasing attention towards the development of diverse applications in electronics, sensors and actuators. Among these materials, the intrinsic conductive polymers (ICPs) stand out, namely polypyrrole (PPy), an inexpensive and highly conductive ICP (up to 500 S.m-1) of facile synthesis, environmentally stability and biocompatibility. By its turn, bacterial cellulose (BC), a biopolymer with highly versatile characteristics, namely chemical purity (0% pectins and hemicelluloses), high crystallinity (95%), low density (1.25 g cm-3), high surface area (37 m2g-1) as well as excellent mechanical properties (Young’s modulus of approx. 15-35 GPa) and low-cost production, have also been drawing a lot of attention. With a combination of these material’s promising characteristics in sight, the aim of this work was to obtain electrically conductive BC-PPy composites via in situ polymerization. This was achieved by using wet chemical polymerization method. Never-dried and freeze-dried BC thin films were used as the templates for monomer deposition and polymerization. Additionally, an adaptation of the chemical vapour deposition synthesis method was also implemented and tested. The effect of freezedrying towards the conductivity of the composites was also assessed as it showed promise attending to some published results where the composites are freeze-dried. Electrically conductive BC-PPy composites exhibiting tailor-made conductivity, which varied depending on the synthesis method selected, were obtained. These conductivities vary between the ranges of 3x10-5 and 5x10-5 S.m-1 (CVD) and 3-140 S.m-1 (WCP), depending on processing method. Additionally, the composites were characterized, alongside the BC and PPy, using a different set of analytical techniques such as conductivity assays, tensile testing, thermogravimetric analyses (TGA), Fourier transform infrared spectroscopy by attenuated reflectance (FTIR-ATR), X-ray diffraction crystallography (XRD) and scanning electron microscopy (SEM). This characterization lead to the conclusion that the BC fibres not only were completely coated by a PPy layer but that a chemical interaction between them also exist.
Dada a crescente popularidade dos nanomateriais, os materiais poliméricos electricamente condutores sido alvo de atenção crescente no contexto do desenvolvimento de diversas aplicações no ramo da electrónica, dos sensores e actuadores. Destes materiais, destacam-se os polímeros intrinsecamente condutores (PIC), nomeadamente o polipirrol (PPy), um PIC low cost, altamente condutor (≤500 Sm- 1), de síntese fácil, e altamente estável no ambiente bem como biocompatível. A celulose bacteriana (CB), um biopolímero com características altamente versáteis, nomeadamente a sua pureza química (0% pectinas e hemiceluloses), elevada cristalinidade (95%), baixa densidade (1,25 g.cm-3), grande área superficial (37 m2.g -1), bem como excelentes propriedades mecânicas (módulo de Young de ~15-35 GPa) e produção de baixo custo, também tem demonstrado uma crescente popularidade. Com a combinação das características promissoras destes materiais em vista, este trabalho visou obter compósitos electricamente conductores de CB-PPy via polimerização in situ. Para este fim, para além do método tradicional de polimerização química em solução (PQS), uma adaptação desta técnica foi testada, tendo-se usado BC liofilizada alternativamente à hidratada. Paralelamente, também foi testada adaptação do método de síntese por deposição química de vapor (DQV). O efeito da liofilização na condutividade dos compósitos também foi avaliado, visto que se revelou promissor dado alguns resultados encontrados na literatura em que há liofilização dos compósitos. Foram obtidos compósitos porosos e não-porosos de BC-PPy com conductividade tailor-made, i.e., variável (3x10-5 a 5x10-5 S.m-1 (DQV) e 3-140 S.m-1 (PQS)) consoante o método de síntese utilizado. Finalmente, os compósitos foram caracterizados, conjuntamente com a CB e o PPy, usando um conjunto de diferentes de técnicas analíticas tais como ensaios de condutividade elétrica, ensaios mecânicos, análise termogravimétrica, espectroscopia de infravermelho por reflectância atenuada, cristalografia por diffracção de raios-X e microscopia eletrônica de varrimento. Esta caracterização permitiu concluir que ocorre o revestimento total das fibras de CB pelo PPy, bem como existe uma interacção química entre a CB e o PPy.

No
Shape memory polymers with surface micropatterns have seen rising demand for high value applications such as adjustable adherence surfaces, dynamic micro-geometries for cell culture studies and switchable information carriers. Recently, microinjection molding has emerged as an efficient way to manufacture devices which contain surface micro-features using a wide range of polymers with high accuracy. In this study, shape memory polyurethane-carbon nanotube composites were prepared by twin-screw melt extrusion and subsequently processed using microinjection molding to obtain components with surface micropatterns. Then an electro-activated surface micropattern tuning system was developed which could recover the original micropatterned surface of the components after a thermal deformation by applying a current which heats the component using resistive heating. In order to optimize the technique, three key areas were investigated in this work: conductivity of the microinjection molded microparts, the retention of shape memory micropatterns on the surface of microparts during annealing treatment, and the macroscopic area shrinkage of microparts after thermal treatment. It has been found that the electrical conductivity of microinjection molded parts is relatively low due to the high shear rates prevalent in the process. An annealing treatment improves the electrical conductivity by several orders of magnitude, but can be detrimental to the dimensional stability of the micropatterns, which depends significantly on the micro-injection molding parameters, especially the mold temperature. Increasing the mold temperature, melt temperature, injection speed and injection pressure result in better retention of the micropattern and improved dimension stability during annealing treatment. This work demonstrates the potential of electro-activated surface micropattern control for microinjection molded electrically conductive shape memory polymer composites, which could be a promising technology for a range of application areas including electro-adjustable adherence, information storage, and anti-counterfeiting technology.

碩士
淡江大學
化學工程與材料工程學系碩士班
94
In this study, we aimed at blending varies polyethylene(PE) and polypropylene(PP) with carbon black(CB) by melt mixing to manufacture electrically conductive polymer composites. We used the surface resistance meter to measured surface resistance coefficient, and scanning electron microscopy(SEM) to investigate the morphology of polymer composites and the dispersion of carbon black in the polymer matrix. Thermal degradation behavior and dynamics mechanical properties of polymer composites were analyzed by thermal gravimetric analysis(TGA) and dynamics mechanical analysis(DMA), the degree of crystallization and melt temperature(Tm) of the blends were observed by differential scanning calorimetry(DSC). The results indicated in PE/PP/CB composites, the CB was dispersed in PE, and the existence of PP helps CB dispersed in PE and the formation of CB conductive networks. CB networks will improves thermal stability and mechanical properties of polymer composites. The rheological properties were measured by plate-plate rheometer.

Bacterial cellulose/polyaniline (BC/PANi) nanocomposites have been lately receiving attention by the scientific community towards the development of electronic applications. The current work aims to determine the most suitable BC modification method to obtain an effective drug delivery membrane through electric stimulus. Thus, the BC/PANi nanocomposites were synthesized through the employment of different BC matrixes (drained, freeze dried and regenerated), as well as through different polymerization methods (in situ and ex situ). Prior to modification, the effects of both drying methods (freeze drying and oven drying), and regeneration process on BC structure were studied. By freeze drying BC, the fibril network is preserved, leading to a more porous material. On the other hand, regenerated BC presented a compact surface due to the incapacity to reorganize into fibrils during the regeneration process. This way, freeze dried BC should be more suited for modification. To obtain a highly conductive nanocomposite, the in situ polymerization on drained BC should be employed. The introduction of PANi onto BC obstructed the pores, which led into a more compact and rougher material. Also, a decrease in the thermal stability, as well as a decrease in the BC crystallinity was observed. The nanocomposites were drug loaded with sodium sulfacetamide to evaluate the antimicrobial activity. It was observed that without electrical stimulus, only drug loaded drained in situ BC/PANi nanocomposite presented an inhibitory effect onto the Escherichia coli (E. coli) growth (13%). By applying electric stimulus onto this membrane, the inhibition in E. coli growth is further evidenced (20%). This way, in situ polymerization of aniline on drained BC presented to be an effective method to create a highly conductive membrane for drug release through electrical stimulus.
Os nanocompósitos de celulose bacteriana/polianilina (CB / PANi) têm recebido nos últimos tempos um grande interesse por parte da comunidade científica para o desenvolvimento de aplicações eletrónicas. Este trabalho tem como objetivo determinar o método de modificação mais adequado da CB para a obtenção de uma membrana eficaz na libertação de fármacos através de estímulo elétrico. Assim sendo, os nanocompósitos CB/PANi foram sintetizados utilizando diferentes matrizes de CB (drenada, liofilizada e regenerada) bem como através de diferentes métodos de polimerização (in situ e ex situ). Antes da modificação, foram estudados os efeitos tanto do método de secagem (liofilização e secagem no forno) como também o processo de regeneração na estrutura da CB. O processo liofilização levou à preservação da estrutura tridimensional, obtendo assim um material mais poroso. Por outro lado, a CB regenerada apresentou uma superfície compacta devido à incapacidade de reorganizar-se em fibrilas durante o processo de regeneração. Desta forma, a CB liofilizada aparenta ser a matriz mais adequada para modificação. Contudo, relativamente aos diferentes nanocompósitos obtidos, para se obter uma membrana com elevada condutividade, o método mais adequado é a polimerização in situ na CB drenada. A introdução de PANi na CB obstruiu os poros, levando à formação de um material mais compacto e rugoso. Também foi observado uma diminuição na estabilidade térmica bem como uma diminuição na cristalinidade da CB. A sulfacetamida de sódio foi incorporada nos nanocompósitos para avaliar a atividade antimicrobiana onde, sem estímulo elétrico, apenas o nanocompósito in situ com CB drenada apresentou um efeito inibitório sobre o crescimento de Escherichia coli (E. coli) (13%). Através da aplicação de estímulo elétrico sobre esta membrana, a inibição no crescimento de E. coli é potenciado (20%). Assim sendo, a polimerização in situ da anilina numa membrana drenada mostrou ser eficaz na libertação do fármaco por estímulo elétrico.

碩士
國立中正大學
化學工程研究所
106
There are three topics in this study. The first research is about carbon nanotubes and styrene-isoprene-styrene block copolymer, making a conductive film by simple ways, it’s applied to electromagnetic shielding. Both increasing the carbon nanotubes loading or the thickness lead to the improvement of electromagnetic interference shielding effectiveness (EMI SE). The best EMI SE we had measured is 23.6 dB from 18 wt% SIS/CNT and its resistivity is 2.26×10-3 Ω-m. In another part, we improved the process of the first research. After comparing some organic solvent, we chose ethyl acetate. We filled SIS/CNT in an aerosol spray can, and it would be a potential product which is low cost and environmentally friendly. Moreover, we tested the proportion of ethanol and acetic acid to reduce the cost. 　　The second research is about preparing a spirally structured sensor by using graphene and SIS. We made low loading (0.5 wt%) to high loading (30 wt%), and its resistivity could change in six order of magnitude. Sticking on human’s face, it can be sensed small motion by blinking, changing expression and smiling. Sticking on human’s throat, it can be sensed by swallowing and pronouncing, even you don’t really pronounce still can be sensed. 　　In the third research, we investigated different mechanical strength and electrical properties of styrenic thermoplastic elastomers (TPE-s). We also compared those properties that mixing CNT to the elastomer. The elastomer which we experimented includes SIS, styrene-butadiene-styrene block copolymer (SBS) and styrene-ethylene-butylene-styrene block copolymer (SEBS). We applied these composite materials to sense pronouncing and finger bending. Keywords : carbon nanotube, styrenic block copolymer, electromagnetic interference shielding, graphene, sensor.

博士
國立臺灣大學
化學工程學研究所
103
This thesis study contains two parts. The first part is carbon-coated silicon nano-composites as negative electrodes for lithium-ion batteries. The second part is electrically conductive adhesives (ECAs) containing Ag-plated graphite particles. An effective method to produce carbon-coated silicon nano-composites as a high-capacity anode material for rechargeable lithium-ion batteries has been investigated. Initially, silicon particles mixed in different carbon precursor solutions via ultrasonication were prepared by thermal treatment in inert gas at elevated temperature (600 - 1000 oC) to form a homogeneous carbon-coated layer onto the surface of the silicon nanoparticles. The effects of the processing temperature, the duration of thermal treatment, silicon particle size, and the mass ratio of carbon precursor to silicon were investigated in detail. All of these parameters significantly influence the cyclic charge/discharge performance of the carbon-coated Si nanocomposites. Carbon-coated Si nano-composites by using honey as carbon precursor in Argon gas at 1000 oC showed the better cycling performance, with a capacity loss of less than 0.42 % per cycle and retaining a specific capacity of 2355 mAh/g beyond 51 cycles, which is much better than the graphite anode. Furthermore, the capacity fading and lithiation mechanisms of silicon and carbon-coated silicon particles also been measured and studied by cycling tests. The dimensional stability of the Si nanoparticles provided by the carbon nano-coating enhances the electric contact of silicon particles and it seems to be the leading reason for this better improved electrochemical performance. Besides, the conductivities of electrically conductive adhesives (ECAs) containing silver-coated graphite particles by self-activated deposition has been investigated. A novel silver self-activated electroless deposition on graphite designed as conductive filler were employed, and a uniform silver coating with minimal agglomeration on graphite surface was obtained. Furthermore, the electrical resistivity of electrical conductive adhesives containing silver-plated graphite powders have also been investigated in this study. The best result of the electrical resistivity of epoxy-based conductive adhesives obtained is 5.16 × 10-4 Ω-cm for 60 wt% of silver-plated graphite powders. The weight percentage of silver in this epoxy-based adhesive is reduced to 56.6 wt%, which is much less than that of the regular silver conductive adhesives.