Issue 9


Drug Delivery & Tissue Engineering Conference

Ashutosh Tiwari

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 883-883
DOI: 10.5185/amlett.2017/9001

International Association of Advanced Materials (IAAM, www.iaamonline.org) is pleased to announce Drug Delivery & Tissue Engineering Conference 2018, Singapore with collaboration of VBRI Press AB, Sweden (www.vbripress.com). The conference is dedicated on the technology and systems in the drug delivery, different routes and methods of administration, nanomedicine, peptide, gene and protein delivery, pharmaceutical devices and their developments, and major challenges in drug delivery research and markets.

Novel metal-carbon nanomaterials: A review on covetics

Mete Bakir; Iwona Jasiuk

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 884-890
DOI: 10.5185/amlett.2017.1598

Covetics are a novel class of metal-carbon nanomaterials. The covetics are fabricated using a conventional induction furnace wherein an electric current is applied into an activated carbon infused molten metal medium. In situ generated arc discharge induces a chemical conversion reaction where the amorphous carbon attains a crystalline structure and forms covalent bonding with host metal matrix. Such fabrication approach also promotes higher carbon solubility in the molten metal than that in traditional metal-carbon alloys. Nanoscale structure analyses revealed single-phase carbon-metal lattice morphologies in the covetics. The covetics have also been shown to possess improved thermos-physical properties as compared to their parent metals. We herein present a review of the literature on the covetics. First, we introduce the covetic materials, and then provide a brief overview on metal-carbon nanocomposites. Then, we summarize experimental results on covetics. Finally, we discuss characterization challenges and future directions in the covetics research. 

Phase selective growth of Ge nanocrystalline films by ionized cluster beam deposition technique and photo-oxidation study                           

S. Mukherjee; A. Pradhan; T. Maitra; A. Nayak; S. Bhunia

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 891-896
DOI: 10.5185/amlett.2017.1462

In this paper, we report the possibility of phase-selective growth of Ge nanocrystals by changing the kinetic energy of the clusters in an ionised cluster beam deposition system. Typically, the films are of mixed phase of normal cubic and high energy tetragonal structures, the relative proportion of which could be controlled by controlling the ionisation and applied accelerating potential as has been confirmed from Raman spectroscopic study. The films deposited using neutral clusters showed higher yield of the tetragonal phase with nanocrystallites of diameter ~7 nm as evidenced from HRTEM data. The optical bandgap of the nanocrystals were observed to be blue shifted upto 1.75 eV compared to the bulk Ge attributing to the presence of Ge tetragonal ST-12 phase and the resulted quantum confinement effect inside the nanocrystals. The tetragonal-rich films were further studied by controlled photo-oxidation to tune their optical band gap. A visible photoluminescence due to excitonic transitions have been observed from the as-grown Ge film enriched in tetragonal phase with average crystallite size ~7 nm. The photoluminescence peak was further blue shifted after the course of photo-oxidation due to reduced nanocrystallite size. 

Mechanical properties and microstructure of magnesium alloy Mg22Gd processed by severe plastic deformation

Miloš Janeček; Peter Minárik; Tomáš Krajňák; Kristína Bartha; Josef Straskuy; Jakub Cizek

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 897-904
DOI: 10.5185/amlett.2017.1582

Mg22Gd alloy was processed by high pressure torsion (HPT) at room temperature and the pressure of 2 GPa. A series of specimens with different number of rotations N (N = 0-15) was prepared from the initial coarse grained as cast material. Mechanical properties were investigated by microhardness mapping. The microhardness was found to increase with increasing strain imposed by HPT and tend to saturate at about HV = 145. The microstructure (phase morphology and composition, etc.) evolution with strain was investigated by scanning electron microscopy and EDS. High Gd content in the alloy resulted in the precipitation of stable Mg5Gd phase. This phase exhibited apparently higher hardness than the magnesium matrix. During straining the phase was continuously fragmented and only tiny particles were found in heavily strained material. Electron back scatter diffraction (EBSD) and automated crystallographic orientation mapping in transmission electron (ACOM-TEM) were employed to characterize the fragmentation of the grain structure. HPT was found to result in strong grain refinement by the factor of approximately 1000. The dislocation density was determined by positron annihilation spectroscopy. Significant twinning was found in the initial stages of HPT straining. At high strains twin formation was suppressed and only dislocation storage in the material occurs.

Influence of the temperature conditions of the graphene oxide synthesis on graphene oxide – induced fluorescence quenching of ssDNA 

T. E. Timofeeva; G. N. Aleksandrov; A. V. Kuznethov; N. R. Maksimova; S. A. Smagulova

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 905-909
DOI: 10.5185/amlett.2017.1589

Graphene oxide (GO) is the high-biocompatible, good aqueous dispersible and low-cost material. Fluorescence quenching and adsorption capacity of GO, different affinity of single-stranded and double-stranded DNA molecules to GO are used to design GO-based fluorescent sensors to detect complementary single stranded DNA. In this work, in the framework of the development of graphene oxide-based test systems for the diagnosis of point mutations in DNA, we study fluorescence quenching efficiency of GO. The graphene oxides were prepared by the modified Hummers method at different synthesis conditions and were characterized. During the study, it was found that the reaction temperature is the most dominant parameter to control GO properties. GO suspension synthesized at 75 0 C of the reaction mixture showed the most high fluorescence quenching efficiency. Basing on XPS O1s, FT- IR spectra analysis, on data of the fluorescence emission spectra of dye-labeled DNA in the presence of various concentrations of GO it is found the effect of  oxygen  functional  groups  such  as  carboxyl,  phenol,  carbonyl,  and  epoxy on the efficiency of fluorescence quenching by GO. These results will be useful for in-depth studies of oligonucleotides and GO interaction and opens new opportunities for sensitive detection of biorecognition events.

Effect of hafnium addition on wear resistance of zinc-aluminum 5 alloy: A three-dimensional presentation  

Adnan I. O. Zaid; Ahmad O. Mostafa

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 910-915
DOI: 10.5185/amlett.2017.1662

ZAMAK 5 alloy is known to solidify in a large grain dendritic structure, which negatively affects its mechanical properties and surface quality. It is therefore of prime importance to reduce its grain size in order to overcome these drawbacks. In this paper, the effect of addition of hafnium (Hf) on the microstructural and mechanical characteristics of ZAMAK 5 alloy has been investigated. An amount of 0.10 wt.% Hf was introduced to the starting alloy using the well-established microalloying technique. The microstructural examination revealed that addition of Hf transformed the large grained dendrites into fine grains, which turned to increase its hardness number by 2.5% and slightly enhance its both yield and fracture stresses. The wear resistance was determined using a pin-on-disc test at different loads, speeds and time periods and the mass loss results of both alloys, before and after Hf addition, were compared with each other. The results indicated that ZAMAK 5 possesses better performance against wear at minimum speed, load and time (23.4m/min., 5N and 15min). Whereas, the Hf-containing alloy showed 42% improved performance against wear at severe experimental conditions of 153.5 m/min., 20N and 60min. The cumulative mass loss results were presented by three dimensional graphs in terms of speed, time and load, which indicated that the mass loss is a function of the three parameters. However, the graphs did not specify the most influential factor on the wear behaviour of both alloys. Full factorial design of experiments was used to identify the effect of parametric interaction on the cumulative mass loss of tested specimens and accordingly the speed was considered to be the main factor. The grain refined alloy is recommended to work under reduced speed and load conditions for prolonged service life. 

Two-dimensional NiTe nanosheets anchored on three-dimensional nickel foam as high-performance catalyst for electrochemical water oxidation 

Yibing Li; Chuan Zhao

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 916-921
DOI: 10.5185/amlett.2017.1669

Development of efficient and affordable electrocatalysts towards water oxidation is important for the large-scale production of hydrogen. Herein, for the first time, we report a two-dimensional (2D) ultrathin NiTe nanosheets as a highly effective catalyst for electrochemical oxygen evolution reaction (OER) via a facile one-pot in-situ hydrothermal approach by using three-dimensional (3D) nickel foam (NF) as both catalyst support and source of nickel. The morphology, electrochemical active surface area (ECSA) and the catalytic activity can be easily engineered by the reaction conditions. The prepared 2D NiTe ultrathin nanosheets have large number of exposed active sites and 3D hierarchical porous structure, which offer superior activity for water oxidation. The electrode only needs an overpotential of 410 mV to afford an extraordinarily high current density of 300 mA cm - 2 and exhibits excellent long-term water catalysis durability. This facile approach for preparation of highly active ultrathin NiTe catalyst is novel and applicable to a wide range of functional materials for various applications including catalysis, energy conversion and energy storage. 

Broadband wide angular response microwave absorbing dielectric resonator array structure

Omar H. AL-Zoubi

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 922-926
DOI: 10.5185/amlett.2017.1594

In this article, we report a new method for enhancing microwave absorbing material properties by using dielectric resonator arrays structure. The proposed structure is an array of circular cylinder dielectric resonators (CDR) that are composed of microwave absorbing (MA) material. The performance of the proposed structure is studied using numerical electromagnetic methods. The results show that an MA martial performance can be significantly enhanced if constructed in the form of CDR arrays compared with similar thickness flat sheet of counterpart MA material. The band width, thickness, angular response, and absorption strength are significantly enhanced by implementing the introduced method. A well deigned CDR array with height of 4 mm can achieve ~ 13 GH 10-dB bandwidth, with ~45-degree angular response. The introduced MA structures exhibits the wide angular response, up to 45 degrees, for both TE and TM polarizations.

Assessing the linear and planer micro-structural defects in SnO2 Nanoparticles through high resolution transmission electron microscopy (HRTEM)

Shrabani Mondal; Rashmi Madhuri; Prashant K. Sharma

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 927-931
DOI: 10.5185/amlett.2017.1741

This letter assesses the origin of linear and planer micro-structural defects in SnO2 nanoparticles through high resolution transmission electron microscopy (HRTEM). For the purpose, SnO2 nanoparticles of size 5-15 nm are synthesized by chemical co-precipitation followed by calcinations. In the low temperature (200°C and 400°C) calcinations range no significant evidence of micro-structural defect are observed. Whereas, SnO2 nanoparticles calcined at 600°C shows better crystallinity with multiple 1-D linear defects along with 2-D planer defects. Contribution of size and strain effect causing such circumstances is illustrated in detail. Influence of these micro-structural defects on the luminescence properties of SnO2 nanoparticles is also elaborated in detail.

A comparative investigation of mechanical and tribological properties of multilayered CVD-diamond coatings: effect of boron doping

Kaleem Ahmad Najar; Nazir Ahmad Sheikh; M. A. Shah

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 932-938
DOI: 10.5185/amlett.2017.6959

In the present work, smooth boron-doped (BD) and undoped multilayered diamond coating systems (MDCS) with top layer nanocrystallinity were deposited on chemically etched cemented tungsten carbide (WC-6%Co) substrates, using hot filament chemical vapour deposition (HFCVD) technique. Both coatings were accomplished by combining the alternate thin films of microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) with a transition layer (TL) of ~1μm thick, using predetermined process parameters during the deposition process. The effects of boron doping on the residual stresses (σ), hardness (H) and coefficient of friction (COF) of MDCS were analyzed using Raman spectroscopy, Berkovich Nanoindenter and Micro-tribometer, respectively. The comparison has been documented between BD-MDCS with undoped one, under same input operating conditions and within same atmospheric conditions. The frictional characteristics were studied under the application of increasing normal load when sliding against smooth alumina (Al2O3) ceramic counter ball for the total duration of 20 min, within dry sliding conditions. The average values of COF of undoped-MDCS and BD-MDCS decrease from ~0.30 – 0.27 and ~0.28 – 0.25, respectively under the application of 1 – 10 N loads. Also, the average values of indentation depths for undoped-MDCS and BD-MDCS were ~65 nm and ~70 nm, with average hardness values in the range of ~65 – 80 GPa and ~55 – 75 GPa, respectively. Therefore, depositing smooth, adhesive and thick BD-multilayered diamond coatings on cemented tungsten carbide components would certainly enable its many useful future applications in mechanical industry. 

Synthesis of AlN particles by chemical route for thermal interface material

Jongbin Ahn; Youngkook Kim; Junggoo Lee; Dongsoo Kim

Advanced Materials Letters, 2017, Volume 8, Issue 9, Pages 939-943
DOI: 10.5185/amlett.2017.1666

Aluminum urea chloride complex was easily synthesized by microwave irradiation from mixed solution and it was used as a precursor for further process. The complexes have proved that urea molecules constructed a coordination sphere around the aluminum atom and formed a stable structure with microwave irradiation. Molar ratio between urea and aluminum chloride was an important factor for the synthesis of AlN particles. After microwave irradiation to the solution with molar ratio (urea/Aluminum chloride) above 6, AlN particles without Al2O3 were formed from aluminum urea chloride by heat treatment at 1000 in nitrogen atmosphere. AlN particles with low oxygen content of 0.85 wt% were successfully synthesized at 1700 under N2 atmosphere in the molar ratio of 6.