Volume 10, Issue 7, July 2019


Smart Healthcare pulls up Clouds for Virtual Medicine

Ashutosh Tiwari

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 440-440
DOI: 10.5185/amlett.2019.1007

The field of medicine and healthcare services is one of those rare industries that are yet relatively unknown to the world of technology and cloud computing. It would not be wrong to say that the world of medicine has always been an ocean of paper trails, fax machines and hard copies. Due to these physical records and paper trails, the medical industry and healthcare services have always restricted to access privacy barriers and isolated data for each patient.For many years now, the industry has been screaming for a better system. There is no doubt about that healthcare services and medicine industry holds a number of flaws in terms of smart functioning.

Selecting the correct electromagnetic inspection technology 

Thomas W. Krause; P. Ross Underhill

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 441-448
DOI: 10.5185/amlett.2019.2262

Eddy current (EC) technology for inspection of conducting materials is a potential solution when conditions preclude the application of other methods. Such conditions include presence of sound absorbing coatings, unavailability of a couplant, multiple conducting layers with air gaps, limited access or near surface cladding. However, the choice of a particular EC technology may not be clear due to sources of electromagnetic interference, choice of probe design, target configuration or even available equipment. In addition, the choice of EC based technologies is extensive, including conventional EC, low frequency EC, remote field EC and pulsed EC. Each of these technologies has its own challenges and limitations, which need to be considered prior to a commitment to system development. Probe choice becomes a function of the particular technique that has been selected and may include ferrite core sensing coils, GMRs or eddy current coil array. Finally, EC signal analysis methods need to be selected based on effects of potentially multiple varying parameters. This paper examines the potential of electromagnetic inspection technology, discussing its limitations, effects of common essential parameters and analysis methodologies. Examples of recent technology applications are given and the benefits and limitations of various technologies are compared and discussed.

Influence of railway-track grinding on the track material condition and tribological behaviour

Eckart Uhlmann; Mykola Bobyr; Yuriy Borodiy; Pavlo Lypovka; Pavel Protsenko; Janis Thalau

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 449-454
DOI: 10.5185/amlett.2019.2234

As societies have a rising demand regarding mobility as well as an increasing ecological awareness, the energy efficiency, noise emissions and availability of transportation in urban environments become essential for growing cities. In this context, the role of rail-bound traffic in urban environments as well as in intercity-connections is of rising importance. To guarantee travelling comfort and safety, shorter downtimes as well as power efficiency, the condition of the railway network is subject to rising quality requirements. Therefore, the maintenance, repair and overhaul as well as the material quality of railway-tracks is faced with new challenges. An important part of track maintenance is track grinding. To ensure an economically reasonable track life cycle and to prolong the time period between repair tasks, grinding processes should not induce damage such as cracks and hardening. On the other side, high productivity of track grinding, which tends to induce damage, is crucial to reduce disruptions and delays from repair. Research work presented in this paper aims at reducing the lack of knowledge concerning interactions between the track grinding parameters, grinding tool specifications and the topology of the track’s surface and damage of the track’s sub surface. Industrial track grinding processes were tested under laboratory conditions with a variation of the grinding wheel circumferential speed and depth of cut. Afterwards the ground tracks specimens were evaluated with regard to the achieved surface roughness as well as the micro-hardening, induced cracks and residual stresses in the sub surface zone. Furthermore, the influence of different external factors such as environmental conditions on the results of track grinding is analysed by evaluating the influence of the track’s initial temperature on the process results. As a result, the main influencing factors on the surface quality and the sub surface damage in track grinding were identified and their influence on the tribological behaviour of the ground tracks in contact with an opposing steel disc was analysed. Based on these considerations, recommendations on eligible track grinding strategies, which lead to highly productive yet low-damage track repair, are derived.

Micromechanical Fatigue Modelling of the Size Effect in Micro-Scale 316L Stainless Steel Specimens

E. Donnelly; F. M. Weafer; T. Connolley; P.E. McHugh; M. S. Bruzzi

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 455-459
DOI: 10.5185/amlett.2019.9812

For many years, computational modelling and simulation studies have been used by developers to advance device design and have been reported in regulatory medical device submissions. However, cardiovascular stent materials in such computational models are typically assumed to behave as a continuum. This approach assumes that bulk material properties apply to the micro-sized structure, i.e. material behavior is scale independent. However, as size is reduced, mechanical size effects arise as the grain size to specimen width ratio drops below a critical value. These size effects cause material behavior to deviate significantly from bulk material behavior. If such a deviation in material behavior is to be captured within computational models, it is necessary to represent the crystalline structure of a metal and to capture the anisotropic behavior of individual grains within these models. This paper describes the development of such a modelling methodology to investigate the phenomenon of strain localization within grains of a 316L stainless steel specimen under fatigue loading conditions.

Functionalization of Graphene and Reduced Graphene Oxide in Different Matrices

E. Celasco; M. Sangermano

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 460-464
DOI: 10.5185/amlett.2019.2201

Graphene (G) presents a huge variety of intriguing properties, as extraordinary electronic transport characteristics. G, thanks to its low chemical reactivity, can also be used as an active support for catalytic nanoparticles. Some possible graphene application could be: its employment in active material in electronic devices such as sensors, batteries, supercapacitors, hydrogen storage systems or as fillers to produce multifunctional nanocomposite polymeric materials. In more detail we would like to examine: different approach of reduction and functionalization of in situ reduced graphene oxide obtaining an enhancement of thermal conductivity and an resistivity decrease. Surface modification and functionalization of rGO to improve its dispersion in organic solvent and also polymeric matrix. Copyright © VBRI Press.

Effect of parasitic polytypes on ballistic electron transport in chemical vapor deposition grown 6H-SiC epitaxial layers

Ilan Shalish

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 465-469
DOI: 10.5185/amlett.2019.2193

Growth of epitaxial layers is required for most of today’s devices. Epilayer growth is commonly carried out under conditions less optimal than those of bulk growth. In materials having multiple stable polytypes, such as SiC, it may facilitate concurrent nucleation of undesired polytypes. Using ballistic electron emission spectroscopy, we have repeatedly encountered a spectral feature in chemical vapor deposition (CVD) grown 6H-SiC layers that was absent in spectra of bulk material. This feature is suggested to belong to 4H-SiC inclusions. The presence of a concurrent Schottky barrier in our CVD epilayers coincides with an observation of a lower Fermi level pinning position compared with bulk material. Copyright © VBRI Press.

Photomemristive heterostructures based on two-dimensional crystals

Gennady N. Panin; Olesya O. Kapitanova

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 470-475
DOI: 10.5185/amlett.2019.2212

The unique electronic and optical properties of recently discovered two-dimensional (2D) crystals, such as graphene, graphene oxide, molybdenum disulphide etc., demonstrate their enormous potential in creating ultrahigh density electronics for image recognition systems and information storage. Synapse-like memristive heterostructures are considered as a new type of electronic switches with extremely low power consumption and footprint that can be used to overcome the limit of current CMOS technology. Memristors with a floating photogate, called photomemristors, based on graphene and MoS2, are considered. Photocatalytic oxidation of graphene is considered as an effective method for creating memristive heterostructures with photoresistive switching for non-volatile electronic memory of ultrahigh density for the formation of self-assembled nanoscale memristive elements interfacing with neural networks. 2D photomemristors with a floating photogate exhibit multiple states that can be monitored over a wide range of electromagnetic radiation and can be used in neurohybrid systems for image processing and pattern recognition, as well as for selective manipulation of neurons by light. Copyright © VBRI Press.

Architecture - behaviour - properties relationship in Star-shaped MPA-PMMA and MPA-PS hyper-branched copolymers

Gabriel Ríos Valer; Gisela Díaz; Juan M Giussi; Marcelo Ceolín

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 476-483
DOI: 10.5185/amlett.2019.2224

The molecular architecture of polymers is a crucial feature in the moment of think the relationship between properties and applications. The same polymer can present important differences according to its architecture and leads to different possible applications. In this paper, we describe the well preparation of hyperbranched copolymers based on bis (Hydroxyl-Methyl) propionic acid polyester (MPA). The co-monomers introduced via atom transfer radical polymerization were methyl methacrylate (MMA) and styrene (St). In order to study the effect of confinement, linear PMMA and PSt have been prepared, and moreover different levels of branching of each polymer were prepared. The synthesised star PMPA-PMMA and PMPA-PSt copolymers have been characterized and identified by infrared spectroscopy and nuclear magnetic resonance spectroscopy. Thermal transitions in solid state were studied using differential scanning calorimetry, and the thermal stability was evaluated by thermogravimetric analysis. Finally, solution properties have been evaluated thought Dynamic Light Scattering. Our results, obtained by a meticulous and systematic comparative study, showed a clear tendency between architectural level and thermal properties. Moreover, properties in solution revealed interesting response due to the modification of solvent nature.Copyright © VBRI Press.

Graphene and doped graphene: A comparative DFT study

Jyoti Tyagi; Lekha Sharma; Rita Kakkar

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 484-490
DOI: 10.5185/amlett.2019.2168

Two different models, ovalene (C32H14) and circumcoronene (C54H18) and their respective doped models (C31XH14, C53XH18 where X = B, Al, N, P, Fe, Ni and Pt) have been considered for DFT calculations at the GGA-PBE/DNP level. The two models are compared on the basis of various calculated structural parameters and electronic properties. Electronic density of states (DOS) spectra are also plotted to see the changes in the electronic properties on increasing the size. No major changes are observed in the structural and electronic properties as one move from the smaller model to the higher one. It is found that doping maintains the planarity of the surface but induces comparatively large changes in the bond lengths around the doped atom, weakening the bonds. Copyright © VBRI Press.

Ag2CO3 / Magnetic reduced graphene oxide nanocomposite as advanced visible light photocatalytic hybrid materials for efficient degradation of azo dye

Mohamed A. Elsayed; Hesham R. Tantawy; Amr A. Nada; Mohamed E. Elmowafy

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 491-498
DOI: 10.5185/amlett.2019.2189

Due to intrinsic properties of graphene-like high electrical conductivity and large surface area, these properties make it an attractive matrix for composites. In this work, reduced graphene oxide (RG)/Fe3O4 (M)/Ag2CO3 (S) hybrid nano-composite (MRGS) has been effectively produced by coprecipitation techniques. The prepared composites were investigated by powder X-ray diffraction (XRD), Fourier transforms infrared spectra (FT-IR), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra (UV-vis/DRS), Raman and vibrating sample magnetometer (VSM). The prepared MRGS nano-composite shows significant enhancement in the degradation rate of Tartrazine dye (TZ) compared to commercial photo-catalyst such as TiO2. Meanwhile, the visible light absorption of the MRGS nano-composite is progressively refining with the increase of the percentage of Ag2CO3 on the surface of (RG). The obtained MRGS 75 photo-catalyst shows the best photo-catalytic activity for TZ under visible light irradiation. The close contact between Ag2CO3 and RG in the composite leads to accelerating the charge transfer on Ag2CO3 to RG and thus enhancing the photocatalytic activity. Additionally, the prepared composite displays superb separability and significant stability. Copyright © VBRI Press.

Optimization of acid hydrolysis process for the preparation cellulose nanofibrils

Melina E. Bracone; Leandro N. Luduena; Vera A. Alvarez

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 499-507
DOI: 10.5185/amlett.2019.2182

Cellulose nanofibrils can be obtained from microcrystalline cellulose by acid hydrolysis processes. Under optimum hydrolysis conditions is possible to obtain cellulose nanofibers with high surface/volume ratio, high aspect ratio (length to diameter), high crystallinity and improved thermal stability. All these parameters then determine their effectiveness as reinforcement in a polymer matrix. In this work, cellulose nanofibrils were obtained from commercial microcellulose supplied by Aldrich. The acid hydrolysis synthesis was optimized studying the effect of reaction time and temperature and acid solution concentration. The optimized parameters were selected so as to obtain fibers with high crystallinity, high aspect ratio with diameter in nanoscale and high thermal stability. The morphology and size (length and diameter) of the fibers was analyzed by Field Emission Scanning Electron Microscopy (FESEM), the chemical structure by Fourier Transform Infrared Spectroscopy (FTIR), thermal stability by Thermogravimetric Analysis (TGA) and crystallinity by X-ray Diffraction (XRD). Copyright © VBRI Press.

Alginate/k-carrageenan and alginate/gelatin composite hydrogel beads for controlled drug release of curcumin

Sayeesh PM; Reshma Joy; Nibisha Pradeep; Franklin John; Jinu George

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 508-514
DOI: 10.5185/amlett.2019.2149

Hydrogel beads based on natural polymers like alginate, κ-Carrageenan, and gelatin represent an efficient scaffold for controlled hydrophobic drug delivery. We report herein the development and characterization different formulations of hydrogel systems based on the above-mentioned polymers having adequate properties as drug delivery matrices. Different combinations of alginate/κ-Carrageenan and alginate/gelatin hydrogel beads were developed and drug release properties were compared using curcumin as a model drug. Alginate/κ-Carrageenan hydrogel beads with 50:50 weight ratio exhibited higher swelling and better drug release percentage than compared to other beads. Antibacterial activity of curcumin released from hydrogel beads against B. cereus was established by disc assay. Encapsulation efficiency and drug release behaviour of different formulations of alginate/κ-Carrageenan and alginate/gelatin indicates that the polymer blends synthesized possess considerable potential in pharmaceutical and medicinal applications. Copyright © VBRI Press.

Study of microstructure and mechanical properties of friction stir welded ferrite-martensite DP700 steel

Mahdi Mahmoudiniya; Leo A.I. Kestens; Shahram Kheirandish; Amir Hossein Kokabi

Advanced Materials Letters, 2019, Volume 10, Issue 7, Pages 515-518
DOI: 10.5185/amlett.2019.2211

In the present study, a 2 mm thick ferrite-martensite dual phase steel was subjected to friction stir welding. The welding was conducted by a tungsten carbide tool at a constant rotational speed of 800 rpm and various feed rates of 50, 100 and 150 mm/min. The microstructural features of friction stir welded joints were characterized by field emission - scanning electron microscopy as well as by transmission electron microscopy. The relationship between microstructure and tensile properties of the joints was investigated. Results showed that the stir zone of the welds consisted of bainite packets, exhibiting a different morphology compared to the ferrite phase and to the martensite phase. Microstructural examination of the heat affected zone showed that there is a softened region in the heat affected zone in all joints, irrespective of the welding speed. Decomposition of the martensite phase during tempering of the initial martensite of the base material was responsible for the observed hardness reduction. The decrease of the hardness in the softened zone was 28 ± 3, 21 ± 2.5 and 15 ± 3.2 HV for welding speeds of 50, 100 and 150 mm/min, respectively; whereby the base material exhibited a hardness of 275 ± 3 HV. The lower softening corresponded to the higher welding speed, i.e., under conditions whereby heat input to the weld was minimum. The tensile test results showed that the ultimate tensile strength of all welded joints is lower than the base metal and failure takes place in the softened region of the joints. The increment of welding speed increased the strength of the joint so that the weld conducted at the highest welding speed (150 mm/min) showed the highest tensile strength of 687 MPa, i.e. 95% of the strength of the base metal (723 MPa). Copyright © VBRI Press.