Keywords : composite

Dielectric Properties of Cu based Polymeric Composites in X-band of Microwave Frequency

Azizurrahaman Ansari

Advanced Materials Letters, 2019, Volume 10, Issue 10, Pages 737-740
DOI: 10.5185/amlett.2019.0034

In this work, the microwave dielectric properties of Cu and PEO based composite sheets are studied in the X-band. The desired composites sheets (thickness ~ 250 μm) are prepared via solution casting method, one of the best methods for sheet preparation. Various characterization techniques including the X-ray diffraction and Scanning Electron Microscopy are used to analyze the presence and uniform dispersion of Cu particles into polyethylene oxide (PEO) matrix. Vector Network Analyzer is employed to obtain the scattering parameters (S21/S11), which are then used to extract the dielectric permittivity of the samples using cavity perturbation technique in the X-band of microwave frequency. The real and imaginary parts (dielectric constant and dielectric loss) of the complex permittivity of synthesized composite sheets are found to be increased with the addition of copper contents (10, 20, and 30 wt %). This enhancement of the dielectric properties in the X-band of microwave frequency may be attributed to the interfacial polarization mechanism. Copyright © VBRI Press.

Functionalized Nano Carbon for excellent Microwave Absorption at GHz Frequency

Avanish Kumar Srivastava; Bhumika Samaria; Smita Soni; Anuj Shukla; Umesh Kumar

Advanced Materials Letters, 2019, Volume 10, Issue 9, Pages 637-642
DOI: 10.5185/amlett.2019.0027

In the present study, nano carbon (NC) was chemically functionalized by refluxing in nitric acid for 6 h to form acid functionalized NC (FNC). TEM, XRD, FTIR, Raman, N2 BET surface area and dc electrical conductivity characterizations confirm the functionalization and formation of surface oxygen functional groups, which in turn increase the hydrophilicity of FNC, thus rendering them solution processable. The basic framework of NC did not get change as confirmed from different characterization techniques. FNC were dispersed in an epoxy matrix by a solution blending method with different FNC loading levels (5, 7.0, 10, 12& 15 wt %). The FNC/epoxy composites were studied for electromagnetic properties in 8-12 GHz. Electromagnetic properties such as real and imaginary part of dielectric permittivity found increasing with increase of FNC loading. Reflection loss result of 10wt % of FNC composite shows RL >10 dB from 9.5 to12.0 GHz (absorption bandwidth~ 2.5 GHz) and effective absorption bandwidth (RL> 5dB) ~ 7 GHz (8-15 GHz).  As a kind of potential microwave absorption material, the FNC composites are light weight and show excellent microwave absorbing ability. Copyright © VBRI Press.

Metal oxide (V2O5) incorporated fly ash based geopolymer for better sustainable engineering composites

Muhammad Akbar Malik; Manas Sarkar; Moumita Maiti; Shilang Xu

Advanced Materials Letters, 2019, Volume 10, Issue 5, Pages 346-350
DOI: 10.5185/amlett.2019.2174

During the coal-burning process, fly ash is produced as a by-product and disposal of this vast waste material is becoming challenge in the current environmental scenario. In the present work, metal oxide V2O5 with different weights (3% and 5%) of fly ash was utilized in presence of alkaline activators to lower the mullitization temperature below to 1000  o C for the development of new concrete approaches. The building composites were made by using sintered fly ash and alkaline activators at ambient temperature. The micro structural analysis (XRD, FESEM, EDX) of the composites reveals the formation of needle like nano sized mullite at 1000  o C. The durability and mechanical strengths tests including, compressive strength, flexural strength, split tensile strength, chloride ion permeability, water absorption and ultrasonic pulse velocity were conducted on the composites specimens. The experimental tests confirm the better strength and enhanced durability properties of the newly formed building composites. The study suggested a new methodology to utilize the waste material fly ash with vanadium oxide as an alternative cementitious materials for advanced durable building composites.

Inherent species characteristic influence and growth performance assessment for mycelium composite applications

Mitchell Jones; Tien Huynh; Sabu John

Advanced Materials Letters, 2018, Volume 9, Issue 1, Pages 71-80
DOI: 10.5185/amlett.2018.1977

Composite materials produced using mycelial growth attract commercial and academic interest due to their economic, environmentally sustainable and green manufacturing process. However, their manufacture via slow biological growth affects the larger scale production viability of these materials, which must compete with rapidly producible synthetic materials. Hyphal characteristics vary significantly by species, which is the most influential growth performance factor in conjunction with environmental conditions and chemical nutrition. This study assessed the effect of potential growth predictors such as hyphal type, pathogenicity, taxonomic and association based classification systems on hyphal extension rate and growth density for commonly used and non-traditional species. It provides a simple, low-cost process for screening species by growth performance prior to more application-dependent mechanical evaluation. This facilitates more efficient and accurate species selection for composite manufacturing applications. Trimitic and dimitic species containing skeletal hyphae exhibited higher hyphal extension rates than species containing generative-binding or purely generative hyphae but no other parameters investigated in this study were good predictors for growth performance with significant species-specific variation present instead. However, the methodology used to test growth performance did prove effective and could be used on a case by case basis for growth screening in mycelium composite applications.

New insight into minimal architecture based carbon nanotubes anode with improved mechanical properties for Li-ion battery

Satish Teotia; B.P. Singh; Anisha Chaudhary; Indu Elizabeth; Anchal Srivastava; Saroj Kumari; S. R. Dhakate; S. Gopukumar; R. B. Mathur

Advanced Materials Letters, 2017, Volume 8, Issue 11, Pages 1038-1045
DOI: 10.5185/amlett.2017.1692

The quick advancement of flexible energy storage gadgets has persuaded individuals to look for reliable electrodes with high mechanical flexibility and remarkable electrochemical performance. In the present study, we demonstrate a simple and scalable process to fabricate a flexible, light-weight, free-standing polyvinylidene fluoride-multiwalled carbon nanotubes (PVDF-MWCNT) composite paper, which can be specifically utilized as a flexible anode for lithium ion batteries (LIBs). The excellent binding of MWCNT with PVDF matrix, developed by a straightforward vacuum filtration process, provides sufficient structural integrity to the composite paper. The breaking strength of the PVDF-MWCNT composite paper so formed is found to be 3.5 MPa with strain to failure of 11.25%. The composite paper so developed shows a good cycle reversible charge capacity when used as anode in a standard Li-ion battery. The PVDF-MWCNT composite paper provides a novel pathway to large scale fabrication of flexible electrodes which can be used without conducting support of copper sheet. 

Composite BME-AuNPs: Chemopreventive effect on skin carcinoma and inhibition on leukemia blood cancer cells

Ramesh Gunti; Gangappa Dharmapuri; Sumanjoshi Doddapaneni; Chander Amgoth

Advanced Materials Letters, 2017, Volume 8, Issue 11, Pages 1057-1064
DOI: 10.5185/amlett.2017.1733

Herein, the chemopreventive effect of oral and topical administration of composite of alcoholic plant extracts of Butea monosperma (Lam.) Taub. (BME) leaves and gold nanoparticles (Au NPs) have been investigated. The tumor growth has been initiated by the 7, 12-dimethyl benz (a) anthracene (DMBA) and skin tumorigenesis in male Swiss albino mice were promoted by the 12-O-tetradecanoylphorbol-13-acetate (TPA). However, malignant feature of the skin tumors were treated with composite of (BME-Au NPs) to reduce the tumor incidence, tumor burden, tumor yield, cumulative number of tumors, tumor size, mass, and volume, respectively. Furthermore, studies were extended to treat CML (chronic myeloid leukemia) K562 (blood cancer) cells with the combination of DMBA/TPA-(BME-Au NPs) and it show greater (~80%) cellular inhibition on cancer cells. Compare to BME alone the composite of (BME-Au NPs) shows significant effect on skin carcinoma and as well on cancer cells. 

Preparation of partially acetylated chitin nanofiber/polyethylene composite film

Keisho Iimori; Ryo Endo; Kazuya Yamamoto; Jun-ichi Kadokawa

Advanced Materials Letters, 2017, Volume 8, Issue 4, Pages 362-367
DOI: 10.5185/amlett.2017.1451

Chitin is widely distributed in nature and an important renewable resource. However, it has been difficult to provide a wide variety of material applications from chitin, due to poor solubility and processability. In this study, we performed surface modification of self-assembled chitin nanofibers (CNFs) by acetylation and their composite fabrication with a commodity plastic, low density polyethylene (LDPE). The self-assembled CNF dispersion with DMF was first prepared by regeneration from a chitin ion gel with an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), using methanol, followed by exchange of a dispersion medium according to the previously reported method by us. Surface acetylation of the product was then performed by reaction of acetic anhydride in the dispersion to obtain partially acetylated CNFs, which formed a film by isolation. The composites of the film with LDPE with the different weight ratios were fabricated by pressing at 170 o C at 0.1 MPa. The SEM measurements of the products observed the morphologies that LDPE interpenetrated from surfaces into cross-sections of the partially acetylated CNF films with increasing the LDPE ratios. The tensile testing of the composite films indicated reinforcing effect of LDPE present in the composites.

Cu-NiO Nano-composite Formation Through Reactive Milling: Reaction Mechanism

Yasaman Kolvandi; Mohammad Aghagholizadeh; Saeed Sheibani

Advanced Materials Letters, 2017, Volume 8, Issue 1, Pages 82-87
DOI: 10.5185/amlett.2017.6864

In this paper, the possibility of production of Cu matrix nano-composite powder containing 10, 37 and 54 wt.% NiO using mechano-chemical reduction of different copper oxides (CuO and Cu2O) was studied. Structural evolutions were characterized by X-ray diffraction. Also, the microstructure was characterized by scanning electron microscopy and transmission electron microscopy. Particular attention has been paid to the reaction mechanism and kinetics using differential scanning calorimetry. It was found that the reactions completed gradually between 5 to 22h of milling. Formation of Cu2O and Cu(Ni) solid solution, as intermediate phases, were observed during the reaction. It was found that, the initial excess Cu delayed reduction reaction and decreased the final crystallite size up to 18nm. Microstructural results showed that relatively large nano-composite agglomerates powder composed of uniform dispersion of NiO nano-particles in nano-crystalline Cu matrix were obtained. Kinetic study revealed that CuO reduction to Cu through two-steps reaction with lower activation energies in each step had higher rate, compared to one-step reduction of Cu2O. 

Designing Of LDPE/fly Ash/ Expanded Graphite Sheet For Electrostatic Charge Dissipation Application

Anuj Gulati; Narayan Agarwal;Sundeep K. Dhawan; Swati Varshney

Advanced Materials Letters, 2016, Volume 7, Issue 5, Pages 360-365
DOI: 10.5185/amlett.2016.5841

The paper aims to explore the utilization of industrial waste fly ash as a filler material into low density polyethylene (LDPE) polymer matrix with / without expanded graphite to optimize the electrostatic charge dissipative (ESD) properties as injection molded sheets. Homogeneous mixing of composite mixture has been carried out in a single screw extruder via melt blending and designed to sheet form by using an injection molding machine. The mechanical and thermal properties of the composite sheet depend on the formulation of composite material. The presence of fly ash particles and fly ash/ expanded graphite in the polymer system allows the composite sheet to acquire good mechanical and electrostatic charge dissipative properties. Static voltage decay rate and decay value measurement were carried out for LDPE and LDPE/fly ash/expanded graphite composite sheet. LDPE/fly ash/expanded graphite composite sheet having high percentage of expanded graphite showed good electrostatic charge dissipative properties. Further, structural analysis, surface morphology, thermal stability and mechanical properties have been explored by XRD, SEM, TGA and tensile testing. 

Thermal Conductivities Of Silica Aerogel Composite Insulating Material

Ehsan Rezaei; Jafarsadegh Moghaddas

Advanced Materials Letters, 2016, Volume 7, Issue 4, Pages 296-301
DOI: 10.5185/amlett.2016.6178

Silica aerogels have interesting physical properties such as hydrophobicity and low thermal conductivity are advantageous for a wide variety of actual applications, such as super thermal insulators. Poor mechanical properties prevented to use silica aerogel directly. In this study, nano silica aerogel and its composite with cotton were synthesized using a water glass precursor by ambient pressure drying method .To modify silica aerogel use trimethyl chlorosilane (TMCS) diluted in n-hexane (1:5 volume ratio). By adding TMCS, –OR groups in silica aerogel structure replaced –OH and silica aerogel became hydrophobic. Thermal conductivity and hydrophobicity of synthesized samples were measured by needle probe method and contact angle meter respectively. Pure silica aerogel contact angel is 166 o and it shows silica aerogel is super hydrophobic. Silica aerogel added to cotton structure in 20 %, 40 %, 60 % and 80 % wt. Silica aerogel particles attached cotton fibers and changed hydrophobicity properties. Contact angels of composites are 115°, 120°, 128° and 129° respectively. Cotton is hydrophilic and its ability to absorb moisture causes decreasing contact angel in composites. Silica aerogel and cotton thermal conductivities are 0.0134 Wm-1K-1and 0.0308 Wm-1K-1respectively. Having low thermal conductivity, pure silica aerogel is known as super thermal. Thermal conductivity of composites was measured 0.0251, 0.0227, 0.0216 and 0.0171 Wm-1K-1 respectively. By increasing silica aerogel ratio, thermal conductivity decreased. In silica aerogel- cotton composite improved structural strength and the thermal conductivity and hydrophobicity were acceptable. 

Frequency And Temperature Dependent Impedance Study In 50% BaTiO3- 50% La0.7Sr0.3MnO3 Nanocomposite

Momin Hossain Khan;Sudipta Pal

Advanced Materials Letters, 2014, Volume 5, Issue 7, Pages 384-388
DOI: 10.5185/amlett.2014.05552

We report the impedance spectroscopy (IS) behavior of the ferroelectric- ferromagnetic (50% BaTi O3-50% La0.7Sr0.3MnO3) nano-composite prepared by sol-gel method. Frequency and temperature dependence of the complex impedance and conductivity has been measured over the temperature range 310 K-430 K. A distribution of relaxation times and decentralization of the semicircle has been observed from the Cole–Cole plots of real and imaginary parts of the complex impedance. Non-Debye type relaxation has been observed in the investigated composite system. An equivalent circuit has been constructed to describe the IS. Interestingly, a typical universal dielectric response in the frequency-dependent conductivity at different temperature has been found. The frequency dependent ac conductivity at different temperature indicates that the conduction process is thermally activated. The activation energy has been obtained from the Arrhenius fitting. The obtained dc conductivity showed that the system undergoes a positive temperature coefficient resistance (PTCR) to negative temperature coefficient resistance (NTCR) near 350 K. The results would help to understand deeply the relaxation process in these types of materials.

Preparation and Studies on (1-x) BiFeO3–x Li0.5Fe2.5O4 (x=0.25 And 0.5) multiferroic nano-composites 

Samar Layek; Soumen Kumar Bag;H.C. Verma

Advanced Materials Letters, 2013, Volume 4, Issue 1, Pages 26-30
DOI: 10.5185/amlett.2013.icnano.289

Multiferroic nano-composite (1-x) BiFeO3–x Li0.5Fe2.5O4 (x=0.25 and 0.5) have been successfully synthesized by mixing the two phases, prepared independently by two different methods followed by annealing at 600 0C. Existence of the two phases in the composite is confirmed by x-ray diffraction pattern. Average particle size is calculated to be about 45 nm for both of these phases. The saturation magnetization, remnant magnetization and coercive field increases linearly with increasing ferromagnetic phase (Li0.5Fe2.5O4) as investigated by VSM measurement. Local magnetic behaviors have been investigated by 57Fe Mössbauer spectroscopic studies. Large dielectric constant of the order of 10 3 -10 4 has been observed in these composites.

Preparation, Characterization And Application Studies Of Inorganic-organic Novel Polymer Composite

Vivek Singh Chauhan; M. Yunus; Nalini Sankararamakrishnan

Advanced Materials Letters, 2010, Volume 1, Issue 3, Pages 225-231
DOI: 10.5185/amlett.2010.6135

A novel iron doped chitosan coated activated alumna (IDCA) derivative was prepared and spectroscopic studies including FTIR, Elemental analysis (EA), XRD, and SEM were used for its characterization. Thermodynamic behavior of the adsorbent was evaluated by Thermogravimetric Analysis (TGA) and Differential Scanning calorimetry (DSC) analysis. The pore size distribution and nitrogen adsorption isotherm revealed the existence of micro porous structure. The applicability of the adsorbent towards the removal of arsenite and arsenate has been demonstrated.

Adsorption Behavior of Potato Starch-silica Nanobiocomposite

Vandana Singha; Sadanand Pandeya;Rashmi Sanghib; Somit Kumar Singha

Advanced Materials Letters, 2010, Volume 1, Issue 1, Pages 40-47
DOI: 10.5185/amlett.2010.4107

In continuation to our recent study on the synthesis and characterization of starch-silica nanocomposite, in the present study the nanocomposite has been evaluated for the removal of Cd(II) from the aqueous solution. The conditions for the sorption have been optimized and kinetic and thermodynamic studies were performed to understand the adsorption behaviour of the composite. Though the cadmium sorption by the nanocomposite takes place in wide pH range, pH 7.5 was found most favorable and at this pH the adsorption equlibrium data were modeled using the Langmuir and Freundlich isotherms at 10°C, 20°C, 30°C and 40°C. At all the temperatures, the data fitted more satisfactorily to Langmuir isotherm indicating unilayer adsorption. Based on Langmuir model, Qmax was calculated to be 769.23 mg/g. The adsorption showed pseudo second order kinetics with a rate constant of 5.65 × 10 -5 g mg -1 min -1 (at 100 mg/L initial Cd(II) concentration) indicating chemisorption. The thermodynamic study revealed the endothermic and spontaneous nature of the adsorption. Effect of electrolyte on the adsorption was also studied. The nanocomposite was sucessfully recycled for six consecutive adsorption-desorption cycles with only a marginal loss in its efficiency indicating its high reusability. The composite was found to be a highly stable photoluminescent Cd(II) adsorbent which may be suitable for sensor applications in detecting the metal ions both in vivo and vitro as the material is natural polymer based.