Issue 6


9th Anniversary of Advanced Materials Letters: Progress and Opportunities

Ashutosh Tiwari

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 366-368
DOI: 10.5185/amlett.2019.1006

I am delighted to share the journey of Advanced Materials Letters (AML), which started its journey in June 2010 holding the hands of International Association of Advanced Materials (IAAM, www.iaamonline.org) with the motto of “Advancements of materials to global excellence”. The time was the starting of 2010 and we were discussing about our upcoming footsteps for the advancement of materials research for empowering the society. Certainly, during the meeting, the core team of IAAM decided to publish an open access journal in the field advanced materials so that the materials’ community should get the latest highlights in advanced materials without any subscription and without any processing fee. We are very much thankful to VBRI Press for providing their platform for this noble initiative. The journey of the remarkable growth and impact of AML begins with its subject area of materials science and technology, also reflected by its unique and popular website http://www.vbripress.com/aml/. After a worthy journey of over 8 years, AML is now going to celebrate its 9 th anniversary in 2019, so as the founder Editor of AML, I am feeling very gratified to highlight the progress, milestones and future opportunities.

Coating - A potent method to enhance electrochemical performance of Li(NixMnyCoz)O2 cathodes for Li-ion batteries

Leon Shaw; Maziar Ashuri

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 369-380
DOI: 10.5185/amlett.2019.2256

Layered lithium nickel manganese cobalt oxides, Li(NixMnyCoz)O2 where x + y + z = 1 (NMCs), have been studied extensively due to their higher capacity, less toxicity and lower cost compared to LiCoO2. However, widespread market penetration of NMCs as cathodes for Li-ion batteries (LIBs) is impeded by their poor capacity retention and low rate capability. Coatings provide an effective solution to these problems. This article focuses on review of the recent advancements in coatings of NMCs from the mechanism viewpoint. This is the first time that coatings on NMCs are reviewed based on their functionalities and mechanisms through which the electrochemical properties and performance of NMCs have been improved. To provide a comprehensive understanding of the functions and mechanisms offered by coatings, the following functions and mechanisms are reviewed individually: (i) scavenging HF in the electrolyte, (ii) scavenging water molecules in the electrolyte and thus suppressing HF propagation during charge/discharge cycles, (iii) serving as a buffer layer to minimize HF attack on NMCs and suppress side reactions between NMCs and the electrolyte, (iv) hindering phase transitions and impeding loss of lattice oxygen, (v) preventing microcracks in NMC particles to keep participation of most NMC material in lithiation/de-lithiation, and (vi) enhancing the rate capability of NMC cathodes. Finally, the personal perspectives on outlook are offered with an aim to stimulate further discussion and ideas on the rational design of coatings for durable and high-performance NMC cathodes for the next generation LIBs in the near future.

Analysis of machined electron beam treated Ti6Al4V-ELI implant surfaces

Miroslav Piska; Katrin Buckova

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 381-385
DOI: 10.5185/amlett.2019.2229

This work contributes to the problem of individual replacements of human joints by applying new types of implants and materials, made using modern additive technologies (melting of metal powders by laser and electron beam). The main attention is paid to the method called Electron Beam Melting used with the ARCAM Q10plus machine. Analyses of the sintered Ti6Al4V - ELI alloy samples were made from the point of view of production precision and quality after sintering in different technological modes and the surface quality reached after turning and tumbling, including measurement of other physical quantities. The results confirm an important effect of sample inclination in the chamber when building on the precision of the shape and quality of the surface. The tensile strengths were high (up to 1,012 MPa) and statistically consistent. Furthermore, the material exhibited high resistance to machining, expressed in terms of force loading and specific cutting forces, measured for a range of feed per rotation 0.05-0.40mm, cutting speed 48 m/min, depth of cut 1.0 mm and use of coated cemented carbides, in dry cutting conditions. Nevertheless, high quality after machining can be reached. The quality can be improved more by two-steps tumbling technology so finally, a glossy surfaces (Ra< 0.036 um) with high material ratios (Abbot-Firestone curves) and convenient tribological properties were found. Ongoing research is focused on studies of milling and belt grinding technology and fatigue properties in tensile R 0.1 mode of loading.

Bottom-up design of hydrogels through click-chemistry modification of magnetic nanoparticles

Ilaria Meazzini; Massimo Bonini; Francesca Ridi; Piero Baglioni

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 386-390
DOI: 10.5185/amlett.2018.2214

The paper describes a modular approach based on click chemistry for the surface modification of magnetic oxide nanoparticles and their covalent inclusion within chemical hydrogels. As a proof of concept, we prepared cobalt ferrite nanoparticles and we modified their surfaces through the reaction with molecules bearing a carboxylic function and, alternatively, either an azide or an alkyne moiety. In the second step, the modified nanoparticles were reacted through a Huisgen 1,3-dipolar cycloaddition with a molecule bearing an unsaturated function and either an alkyne or an azide moiety, respectively. Finally, the particles were successfully copolymerized with acrylamide and N,N'-methylenebisacrylamide to obtain a magnetically responsive hydrogel. This approach could be easily extended towards any type of inorganic oxide nanoparticles and their inclusion within any radically co-polymerized hydrogel. 

Visualization of mechanical loads with semiconductor nanocrystals 

Martin Moebius; Joerg Martin; Melinda Hartwig; Ricardo Decker; Lothar Kroll; Reinhard R. Baumann; Thomas Otto

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 391-394
DOI: 10.5185/amlett.2019.2221

Fibre-reinforced plastics offer excellent mechanical properties at low weight. Hence, such materials are ideally suited to reduce energy consumption and CO2 emission, e.g. in aircraft and automotive engineering, shipbuilding or in the field of renewable energies. However, in contrast to e.g. metals, lightweight structures are sensitive to mechanical loads exceeding a certain approved range. In order to detect mechanical overloads at an early stage and to avoid consequential failures in lightweight structures, we recently proposed a novel concept of a thin-film sensor for visualization of mechanical loads by using photoluminescence quenching of quantum dots. Here, we present results according to the optimization of the ionization efficiency of the cadmium selenide quantum dots by using poly(N-vinylkarbazol)(PVK) as charge transport material with favorable energy levels. Measurements of the photoluminescence intensity and electrical power confirm an increase of efficiency with almost the same photoluminescence drop compared to N,N,N′,N′-Tetrakis(3-methylphenyl)-3,3′-dimethyl-benzidine (HMTPD), most likely by the higher valence band offset between quantum dots and PVK. Furthermore, an integration of a layer stack with connected ceramic piezoelectric transducer demonstrates the successful use of the sensor system for mechanical load detection in lightweight structures. 

Room temperature growth of ultra porous hot-wire deposited tantalum pentoxide

Giorgos Papadimitropoulos; Maria Vasilopoulou; Nikos Vourdas; Dimitris N. Kouvatsos; Kostas Giannakopoulos; Stella Kennou; Dimitris Davazoglou

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 395-399
DOI: 10.5185/amlett.2019.2283

Tantalum pentoxide films were deposited on Si substrates at room temperature, by heating metallic filaments at temperatures below 600 o C, at a pressure of 1 Torr in O2 environment. This deposition method can be applied for all metallic oxides having higher vapor pressure than the corresponding metal. These (hwTa2O5) films were composed by amorphous material (as revealed by XRD measurements) and were found to be highly transparent within the range 350-1000 nm. Spectroscopic ellipsometry measurements have shown that the real part of the refractive index (n) of hwTa2O5 films depends on the deposition time and has a value below 1.5. As shown by scanning electron microscopy (TEM) measurements, these grains were composed by others with dimensions near 5 nm and with voids between them. The above microscopy measurements explain the high porosity of hwTa2O5 films. Moreover, hwTa2O5 films were also characterized by XPS and UPS measurements and the stoichiometric composition of the deposited films was determined.

Substrate integrated circular cavity resonator filled with nano-fibrillated cellulose for humidity detection

Majid Ndoye; Benoit Bideau; Aina Heritiana Rasolomboahanginjatovo; Éric Loranger; Dominic Deslandes; Frédéric Domingue

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 400-404
DOI: 10.5185/amlett.2019.1927

In this work, a novel microwave sensor fully based on Substrate Integrated Waveguide (SIW) technology filled with nano-fibrillated cellulose for humidity detection is presented for the very first time. The proposed structure consists of a circular SIW cavity resonator perturbed by the inclusion of nano-fibrillated cellulose inside the cavity. Due to the presence of humidity, the relative permittivity of the eco-friendly dielectric, which is known as a humidity sensitive material, changes, leading to a shift of the resonance frequency of the Substrate Integrate Cavity Circular Resonator (SICCR). The proposed humidity sensor structure operates between 4.28 to 4.32 GHz and exhibits a frequency shift of around 20 MHz for relative humidity in the range of 11.7% to 91% RH. The proposed sensing device operates with very low-cost sustainable and renewable material, is simple to manufacture, co-integrates with existing microwave planar circuits and has the advantage of demonstrating high sensitivity performance.

Oxygen vacancy filament-based resistive switching in Hf0.5Zr0.5O2 thin films for non-volatile memory

Mark Kracklauer; Fabian Ambriz-Vargas; Gitanjali Kolhatkar; Bernhard Huber; Christina Schindler; Andreas Ruediger

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 405-409
DOI: 10.5185/amlett.2019.2225

The continued evolution of electronic devices relies on the development of new semiconductor memory technology. Given the high compatibility of the Hf0.5Zr0.5O2 thin films with the CMOS technology, we investigate the charge transport mechanisms that occur in a relative thick Hf0.5Zr0.5O2 thin film (4 to 6 nm-thick) when subjected to electrical stresses. To that end we fabricate Hf0.5Zr0.5O2 heterostructures with a Pt tip as the top electrode and TiN and Pt as bottom electrode by radio-frequency magnetron sputtering. After analyzing the surface morphology of the as-received and as-deposited films by atomic force microscopy, the transfer of the desired chemical stoichiometry from the sputtering target to the substrate surface is studied by Raman spectroscopy. The ferroelectricity of the Hf0.5Zr0.5O2 thin films is confirmed by piezoresponse force microscopy measurements, and a retention of 22 h is obtained, attesting to the non-volatility of the samples. Nano-scale electrical measurements reveal the presence of resistive switching, where the low resistance state (ON state) in both Pt-tip/Hf0.5Zr0.5O2/TiN and Pt-tip/Hf0.5Zr0.5O2/Pt heterostructures can be created by the formation of a conductive filament based on oxygen vacancies.

Innovative silicon compatible materials for light emitting devices  

Adriana Scarangella; Riccardo Reitano; Francesco Priolo; Maria Miritello

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 410-416
DOI: 10.5185/amlett.2019.2276

The paper reports the potentialities of innovative silicon compatible materials for light emitting devices. In particular thin films of Er doped yttrium oxide have been synthesized by a technique totally compatible with ULSI processes. Through the structural characterization, we will verify the high stability of the film and the good dopant dissolution. Moreover, by the investigation of the optical properties, we will demonstrate that the use of this compound is effective to introduce more than 10 21 Er/cm 3 in optically active state, value that cannot be reached in other Si compatible materials. The influence of Er content on the optical properties will be described in details. Moreover, we will propose the introduction of a proper sensitizer for Er, bismuth, in the same thin film. In particular, we will show that the (Er+Bi) co-doped yttrium oxide is a perfect host to overcome another important drawback of Er doped materials that is its low absorption cross section. The influence of Bi and Er contents on optical properties will be extensively discussed along the paper. Through the optimization of ratio between Bi and Er concentrations, high energy transfer efficiency will be reached with simultaneously a consistent increase of the effective Er cross section. A factor of more than three orders of magnitude have been obtained with respect to the direct excitation of Er.

Graphene micromesh for transparent conductive films application 

Ryousuke Ishikawa; Hiroki Nishida; Hiro Fukushima; Sho Watanabe; Sohei Yamazaki; Gilgu Oh; Nozomu Tsuboi

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 417-420
DOI: 10.5185/amlett.2019.2238

In order to improve the properties of the graphene transparent conductive film, we developed a process of O2 plasma patterning graphene using a metal mesh as an etching mask. The CVD growth conditions of high-quality multilayer graphene samples consisting of 400 layers or more were found using Ni foil, and the R sheet = 3.4 ± 0.6 Ω/sq. was achieved. The best performance of graphene micromesh based transparent conductive films so far was R sheet = 22.2 Ω/sq. at T = 47.1 ± 1.9 %. According to theoretical calculations based on the combined resistance of the two-dimensional resistance lattice circuit, a combined resistance of 46.8 Ω can be realized at T = 90%.

Applications of nano-scale Cirrus DopantTM to improve existing coatings

See Leng Tay; Chris Goode; Wei Gao

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 421-424
DOI: 10.5185/amlett.2019.2219

The use of ceramic nano-powders to create composite coatings is well known but is neither simple to industrialize nor environmentally friendly. Patented Cirrus Dopant™ technology from Cirrus Materials Science offers the performance advantages of nano-composite coatings without the implementation and process drawbacks. Cirrus Dopant™ technology is applicable to commercial baths for a large variety of electrolytic and electroless deposited coatings including Ni, Ni-P, Ni-B, Co-P, Au, Ag, Sn, and Zn-Ni. Successful application of the technology simply requires optimization of a specialized Dopant™ to the bath. This paper discusses the process and results for nano-doping commercially important coating baths.

Chitin nanofibrils in renewable materials for packaging and personal care applications

Maria-Beatrice Coltelli; Vito Gigante; Luca Panariello; Laura Aliotta; Pierfrancesco Morganti; Serena Danti; Patrizia Cinelli; Andrea Lazzeri

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 425-430
DOI: 10.5185/amlett.2019.2250

Chitin nano-fibrils, obtained by waste sea food (for example exoskeletons of crustaceous), are available as water diluted nano-suspensions. Hence, their dispersion at the nanoscale in a molten polyester matrix is considered an issue, because diluted liquids cannot be usually added easily in most common extruders. In the present paper the use of poly(ethylene glycol) (PEG) of different molecular weight was investigated to prepare solid pre-composites useful to disperse chitin nanofibrils in poly(lactic acid) (PLA) by extrusion. The tensile properties of injection moulded specimens were determined and insights were also provided regarding the thermal characteristics of chitin nanofibril-reinforced nanocomposites. This study allowed the identification of a process leading to transparent PLA-based nanocomposites suitable to be exploited in packaging and personal care applications, where the intrinsic anti-microbial and tissue regenerative properties of chitin nanofibrils can be greatly useful.

Synthesis of AgNPs embedded double network nanocomposite hydrogels having high swelling and anti-bacterial characteristics

Akansha Dixit; Nand Kumar; Dibyendu S. Bag; Kavita Agarwal; Dhirendra K. Sharma; N. Eswara Prasad

Advanced Materials Letters, 2019, Volume 10, Issue 6, Pages 431-439
DOI: 10.5185/amlett.2019.2258

Silver nanoparticles (AgNPs) embedded double network (DN) nanocomposite hydrogels [of P(AM-co-HEMA) as second network and PVA-Borax as first network] were synthesized by in-situ reduction of silver nitrate using citric acid in presence of the fully swollen high strength DN hydrogels. The AgNPs embedded DN nanocomposites hydrogels (Ag-DNG) were characterized by FTIR, XRD and TEM analyses. Such Ag-DNG hydrogels were studied for their degree of swelling and swelling kinetics. They were also evaluated for their anti-bacterial characteristics using a Gram negative (Escherichia coli) and a Gram positive (Bacillus subtilis) bacteria. The XRD analysis revealed the presence of AgNPs in the DN nanocomposite hydrogels. The AgNPs were observed to be 20-50 nm in diameter as observed by TEM analysis. The degree of swelling of Ag-DNG hydrogels was lower than that of the virgin DN hydrogel which was because of the space of pores of the DN hydrogels occupied by AgNPs. The virgin DN hydrogels did not exhibit any antimicrobial property, whereas Ag-DNG hydrogels exhibited a significant amount of antibacterial activity towards gram positive and gram negative bacteria. Such AgNPs incorporated high strength DN nanocomposite hydrogels may find potential biomedical application.