Keywords : carbon nanotube

Investigating the Machinability of Metallic Matrix Composites Reinforced by Carbon Nanotubes: A Review

Robiul Islam Rubel; Md. Hasan Ali; Md. Abu Jafor; Sk. Suzauddin Yusuf

Advanced Materials Letters, 2019, Volume 10, Issue 11, Pages 786-792
DOI: 10.5185/amlett.2019.0025

The modern manufacturing technology tends to innovate different materials with simultaneous low density in weight, porosity, high toughness, corrosion resistance, thermal and electrical properties etc. Metallic matrix-based carbon nanotubes composites (CNTs) are a relatively new material concept. The CNT reinforced composite materials harvest the dual benefit of alloying metals with high mechanical properties of CNTs. Besides, the materials being innovated must have good forming or machining characteristics. However, no machining data or machining model are yet available for these newly developed composites. In this work, the mechanical machining of metal-matrix/CNTs composites has studied to review the available data and better understanding the material removal behaviour. The work also concludes on the suggestive machining techniques adopted that will not affect the structural deformation, mechanical, thermal, electrical properties as well as must not alter the mechanical characteristics of the machined surface. The present study will assist in optimizing the manufacturing composites with desirable mechanical properties in future CNT reinforced composite developments. Copyright © VBRI Press.

Spinel NiCo2O4 and single walled carbon nanotube nanocomposites for high performance supercapacitor application  

Surjit Sahoo; Chandra Sekhar Rout

Advanced Materials Letters, 2017, Volume 8, Issue 8, Pages 847-851
DOI: 10.5185/amlett.2017.1539

In the present work, we report the hydrothermal synthesis of NiCo2O4/Single walled carbon nanotubes (SWNTs) nanocomposites for supercapacitor applications. The SWNTs provided the conductive network and favored the growth of NiCo2O4 nanoparticles on its surface to facilitate the collection and transportation of electrons during the electrochemical charge storage performance. Due to the improved conductivity and higher surface area of the NiCo2O4/SWNTs nanocomposites as compared to pure NiCo2O4 nanorods, it exhibited a specific capacitance of 1623 F/g and 1098 F/g at 1mV/s scan rate and 1A/g current density. Obtained energy density and power density of the NiCo2O4/SWNTs nanocomposites were 56.19 Wh/Kg and 9.824 kW/kg respectively. These results demonstrated that the nanocomposites could be a promising candidate for future high performance energy storage devices. 

Three-dimensional nanocomposites of graphene/carbon nanotube matrix-embedded Si nanoparticles for superior lithium ion batteries

Dafang He; Lixian Li; Fengjuan Bai; Chenyang Zha; Liming Shen; Harold H. Kung; Ningzhong Bao

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 206-211
DOI: 10.5185/amlett.2017.7038

A unique hierarchically nanostructured composite of Si nanoparticles (Si NPs) embedded in a three-dimensional (3D) carbon nanotube (CNT)/graphene sheet (GS) matrix (Si@CNT/GS) is fabricated by freeze-drying and thermal reduction. In this novel nanostructured composite, since the intertwined elastic CNTs effectively disperse the Si NP anode material and provide extra physical connections between Si NPs and the surrounding 3D conductive matrix, the interconnected 3D CNT/GS matrix can serve to buffer the volume change of the Si NPs during cycling while simultaneously enhance the electrical conductivity of the overall electrode. As a result, Si@CNT/GS nanocomposite exhibits a high reversible capacity of 1362 mAh·g -1 at 500 mA·g -1 over 500 cycles, and an excellent rate capability of 504 mAh·g -1 at 8400 mA·g -1 , considerably improving the battery performance compared with those electrodes made from Si@graphene nanocomposites, thus exhibiting great potential as an anode composite structure for lithium storage. Copyright © 2017 VBRI Press.

Field Emission Image Analysis: Precise Determination Of Emission Site Density And Other Parameters

Rajkumar Patra; Anjali Singh; V. D. Vankar; S. Ghosh

Advanced Materials Letters, 2016, Volume 7, Issue 10, Pages 771-776
DOI: 10.5185/amlett.2016.6368

We report a simple and detailed simulation based analysis of an experimental field emission (FE) image captured on a phosphor coated indium tin oxide (ITO)/glass plate due to the electron emission from a multiwalled carbon nanotube (MWCNT) film. Emission intensity versus effective emissive area, number of CNTs present in the film contributing emission process and number density of MWCNTs at high field (during FE process) along with other FE parameters viz. turn on field, threshold field are determined, which agrees well with experimental results. Over estimation of calculated value over experimental results is realized with creation of new emission sites at high electric field due to combined effect of divergence of electron within electrode because of electron-air molecule collision, assumption of evenly placement of emitters during calculation, damages and/or tear-off of emitters at high electric field, contribution of adsorbates of MWCNT walls and the energy loss due to absorption of phosphor atom. This analysis renders a unique way to analyze field emission data and supports the theoretical formulation to evaluate the best possible values of FE parameters.

 Facile Growth Of Carbon Nanaotube Electrode From Electroplated Ni Catalyst For Supercapacitor

Visittapong Yordsri; Winadda Wongwiriyapan; Chanchana Thanachayanont

Advanced Materials Letters, 2015, Volume 6, Issue 6, Pages 501-504
DOI: 10.5185/amlett.2015.SMS6

A facile growth of carbon nanotubes (CNTs) was facilitated by the use of direct-current plating technique for catalyst preparation. Ni nanoparticles (NPs) were deposited on Cu foil at different applied voltages of 1.0, 1.5 and 2.0 V. The Ni-deposited foil was subsequently used as catalyst for CNTs synthesis by chemical vapour deposition (CVD) method. CVD was carried out at 800 ºC using ethanol as carbon source. A voltage of 1.5 V was the optimum condition to deposit uniform Ni NPs that had a narrow size distribution of 55±3 nm, which in turn, yielded synthesized CNTs with a uniform diameter of approximately 60±5 nm with graphitic layers parallel to the CNTs axis. On the other hand, electroplated Ni at 1.0 V produced CNTs with graphitic layers at an angle to the CNTs axis, while electroplated Ni at 2.0 V produced curly CNTs with a wide distribution of diameters. These results show that Ni NPs size distribution could be controlled by electroplated voltage. Our observation was that Ni NPs with a narrow distribution of sizes and a uniform diameter is a key to uniform CNT synthesis. Furthermore, the synthesized CNTs electrode shows a faradic pseudo capacitance property, which can be attributed to the existence of oxidized Ni NPs. These results propose that the synthesized CNTs are promising materials for future super capacitor application. The optimization of ratio of Ni NPs and CNTs may improve the supercapacitors performance.  

Geometrical Shape Dependence Field Emission From Patterned Carbon Nanotube Array: A Simulation Based Study

Rajkumar Patra; Himani Sharma; Swati Singh; S. Ghosh; V. D. Vankar

Advanced Materials Letters, 2014, Volume 5, Issue 10, Pages 573-577
DOI: 10.5185/amlett.2014.5578

Designing an efficient field emission source requires theoretical optimization of electron emitters’ geometrical distribution over the surface for its best performance in terms of current density. Seven and nineteen bundles of CNT arrays arranged in different models are analysed in detail using a computational theory in CST studio suite software based on the particle tracking mode. A three dimensional model has been employed to calculate FE properties with high accuracy. Simulations were carried out for a particular number of CNTs of constant height and radius located at fixed distances from each other and arranged in different geometrical patterns. Among all patterns, rectangular arrangement of CNTs is found to produce the maximum current. The edge effect and screening effect are incorporated in calculating total emission current and are found to diminish the contribution of inner rings 10% or less than that of maximum contribution. These findings can be employed as guideline to fabricate pattered CNT structures experimentally for industry applications. 

High Stability Field Emission From Zinc Oxide Coated Multiwalled Carbon Nanotube Films

Rajkumar Patra; Santanu Ghosh; Himani Sharma; Vasant D. Vankar

Advanced Materials Letters, 2013, Volume 4, Issue 11, Pages 849-855
DOI: 10.5185/amlett.2013.4465

A comparative study of electron field emission (FE) property of pristine mutiwalled carbon nanotubes (p-CNTs), zinc (Zn) coated CNTs (Zn-CNT), zinc oxide (ZnO) coated CNTs (ZnO-CNT) is reported. CNTs were synthesized on p-type Si (100) by microwave plasma enhanced chemical vapor deposition (MPECVD) method and the sample was divided into three parts. On two of these parts, a thin layer (~ 4nm) of Zn film was deposited. One of these (Zn-CNT) was kept for analysis and the other one was annealed in oxygen (O2) atmosphere at 520° C for 60 minutes to get ZnO coated CNT film (ZnO-CNT). Scanning electron microscope (SEM) analysis confirmed CNT formation as well as Zn and ZnO coating on the top of p-CNT films. Further, energy-dispersive X-ray spectroscopy (EDX) results confirmed the presence of zinc and oxygen in these two samples. A detailed field emission study performed in these films give following results: (i) lowest turn-on field (electric field required to produce 10 μA/cm 2 current density) and threshold fields (electric field required to produce 100 μA/cm 2 current density) for pristine sample (3.3 V/μm and 5.1 V/μm respectively), followed by ZnO-CNT sample (3.7 V/μm and 6.3 V/μm respectively); (ii) highest temporal stability in current density versus field (J-E characteristics) in ZnO-CNT film as compared to other two, (iii) highest field enhancement factor in ZnO-CNT films as compared to other two. The FE results are correlated with microstructures of the samples as revealed by micro-Raman spectroscopy and transmission electron microscopy (TEM) studies.

Solvent Tuned PANI-CNT Composites As advanced Electrode Materials For Supercapacitor application

Ashok K. Sharma; Yashpal Sharma; Rajesh Malhotra; J.K. Sharma

Advanced Materials Letters, 2012, Volume 3, Issue 2, Pages 82-86
DOI: 10.5185/amlett.2012.1315

Composites of polyaniline and multiwalled carbon nanotube were prepared by in- situ chemical oxidative polymerization of the aniline monomer in 1M HCl and 1M HCl with 20% ethanol as solvent. The PANI-CNT composites were characterized by FTIR and XRD method. The surface morphology characterization of the composites was done by using scanning electron microscopy (SEM). Electrochemical behavior of prepared PANI-CNT composites was investigated by means of cyclic voltammetry. Specific capacitance of PANI-CNT composite using 0.02M aniline in 1M HCl (20% ethanol) and 1M HCl was 597.82 and 484.49 F/g respectively at scan rate of 2mV/s in 1M H2SO4.

Machining characteristics of nanocomposites

K.S. Umashankar; K.V. Gangadharan; Vijay Desai; B. Shivamurthy

Advanced Materials Letters, 2011, Volume 2, Issue 3, Pages 222-226
DOI: 10.5185/amlett.2011.1209

Nanocomposites were prepared with Al/Al-Si alloys (LM 6 and LM 25) as matrix and multi-wall carbon nanotube (MWNT) of 0.25, 0.5, 0.75, 1.0 and 1.5 wt. % as reinforcement through powder metallurgy (PM) followed by sintering and hot extrusion techniques. Fabricated nanocomposites were machined on a Panther 1530/1650 lathe by using tungsten carbide tool. Recurrence quantification analysis (RQA) was used to study the machining characteristics by using cutting force signal stability. Highest value of determinism (DET-one of the RQA parameter) was observed for 0.5 wt.% MWNT reinforced Al and Al-Si nanocomposites. This attributes better machining characteristic due uniformity of the signals. Also it is observed better mechanical properties at 0.5 wt.% reinforced nanocomposite and further reinforcement deteriorate the machinability and mechanical properties.