Band 114, Heft 4-5

Commercial cotton gauze bandages are applied on wounds to prevent contact with dust and/or pathogens, while ensuring enough aeration for accelerated wound healing. More often than not, these bandages are used in conjunction with antiseptic (topical) agents to avoid any post-dressing infections. Additionally, healing medications need to be orally administered to accelerate the healing process and manage the pain. Mechanical debridement remains a problem upon removal of the wound dressing material which leads to delayed healing. In the present work, commercial bandages have been modified to have anti-microbial properties and the capability of localised drug delivery to minimise the local pain and post-dressing infections at a wound site. To achieve this diclofenac sodium (an anti-inflammatory drug) loaded biodegradable, polycaprolactone-based nanofibrous mat has been layered on top of a commercial cotton bandage whose surface has been modified with the coating of chitosan and zinc oxide nanoparticles. The chitosan coating over the cotton gauze bandage brings in the antibacterial properties, while the zinc oxide nanoparticles provide ultra-violet protection. The drug loaded nanofibrous mat releases diclofenac sodium under a simulated wound microenvironment. The article delineates the nanomaterials on cotton gauze bandages as an effective alternative to commonly used cotton gauze bandages for wound dressing applications.

Cobalt (Co) substituted brownmillerite KBiFe 2 O 5 (KBiFe 1.9 Co 0.1 O 5 : KBFCO) is synthesized by conventional solid-state reaction route. Rietveld refinement of X-ray diffraction data confirms the pure phase of KBFCO and crystallizes in monoclinic structure with P 2/ c space group. Surface morphology reveals that the grains are randomly distributed, and the average grain size varies in the range of 1–4 μm. The energy dispersive X-ray spectroscopy confirms that the chemical constituents of KBFCO are very close to the molar (1:1:2) ratio. The temperature (10–300 K) and frequency (500 Hz–1 MHz) dependent dielectric permittivity value decreases approximately 50% in the presence of the magnetic field (1.3 T). It confirms the signature of the magnetodielectric ( MD ) effect in the KBFCO sample. The magnetic field (±1.3 T) variation MD loop resembles the inverse-butterfly type behavior for the system. Both MD hysteresis and strength decrease with a decrease in temperature. A noticeable suppression in the dielectric relaxation is obtained by applying a 1.3 T magnetic field in the temperature range of 250 K–300 K. The measured MD effect is observed at a high frequency (30 kHz), suggesting the intrinsic effect is dominated in the probing temperature range. Observation of similar trends in magnetic field-dependent MD and magnetic loss ( ML ) loop rules out the existence of magnetoresistance origin MD effect. These results confirm that KBFCO has an excellent MD response even for a small applied field and holds great interest for future device applications.

9Cr-1W-0.06Ta reduced activation ferritic-martensitic (RAFM) steel has been investigated in normalized and tempered (N + T) condition and in thermo-mechanically treated (TMT) in austenitic and ferritic field conditions. RAFM steel in N + T condition has a tempered martensitic structure (body-centred tetragonal, bct). It is unstable and will transfer into a stable body-centered cubic (bcc) in the structure during a long period subjected to high temperatures. To make it stable structure, the steel was subjected to austenitization at 1423 K for 10 min, and then cooled in still air (≈−1 K s −1 ) to 973 K and this temperature was maintained for 2 h in furnace to fully convert austenite into ferritic phase then the steel was subjected to 25% reduction in thickness by hot rolling. Optical, scanning and transmission electron microscopic investigations have been carried out to assess the microstructural changes of the steel N + T and TMT conditions. Hardness, tensile and creep studies are carried out and the results were correlated with the microstructural studies. TMT processed steel resulted in coarser prior austenite grains and exhibited ferrite in phase with fine distribution of M 23 C 6 and MX precipitates whereas N + T condition is subjected to tempered martensitic structure with coarser M 23 C 6 and MX precipitates. Even though ferrite phase present in TMT processed steel it exhibits higher tensile and creep strengths due to the presence of high dislocations and finer distribution of precipitates than the N + T condition.

Austenite stainless steel 316L was developed to improve corrosion resistance and is widely used in automobile components, thermal power plants, and pressure vessels due to their superior toughness and intergranular corrosion resistance. The austenite stainless steel 316L has a low carbon content of 0.03%, which helps in minimizing harmful carbide precipitation during welding. The joint strength of welded joints is poor unless proper care is taken. As a result, an attempt was made to use an activated Tungsten Inert Gas (A-TIG) welding procedure to improve the joint strength of butt welded joints of austenitic stainless steel 316L. The process parameters such as current, the volume of flow, and filler diameter were chosen in the study and generated an L 9 design matrix using MINI Tab software. The welded joints were prepared as per the design matrix using the activated flux of aluminum oxide nano powder as per the combination of process parameters. The mechanical tests such as tensile strength, hardness, and impact strength were evaluated and microstructural evaluation of welded joints was also assessed. The input parameters were optimized for better tensile strength of joints using Taguchi S / N analysis. It is found from the optimization that the highest ultimate tensile strength of 690.40 MPa was obtained at a current of 90 A, shielding gas flow of 13 l min –1 , and filler material diameter of 2.5 mm. The model was also validated by conducting experiments.

In this research work, the three-point flexural performance of carbon and/or glass inter-ply hybrid epoxy composite by altering the hybrid ratio and stacking position was studied. These materials were tested at various temperatures (30 °C, 50 °C, 70 °C and 110 °C). The test results of hybrid composites results were compared with neat glass/epoxy and carbon/epoxy composites. The stacking position of carbon fibers in hybrid composite plays a vital role while doing a flexural test. Incorporation of two stiffer carbon fibers in glass/epoxy composite i.e., C 2 G 3 and C 1 G 3 C 1 , resulted in a remarkable increment in the case of flexural strength. All composites exhibited ductile behavior at 110 °C. The fractured surfaces revealed the failure mechanism of the composites.

In this work, we report on the electrodeposition of CuInSe 2 (CIS) thin films with In 2 Se 3 rich surface by a single step deposition technique. It was observed that the In-content deposited in CIS can be improved by the addition of sodium dodecyl sulfate as a surfactant. The presence of an In–Se rich layer was confirmed by electrochemical, compositional and Raman spectroscopy analysis. The photo-electrochemical properties of the as-deposited CuInSe 2 thin films were found to be enhanced due to the presence of In–Se rich superficial layer. The presence of an In–Se layer over CIS may act as a p-n homo-junction which may be attributed as the primary reason for the improvement in the PEC properties.

Cold-rolled non-oriented (CRNO) electrical steels find a wide variety of applications in the core of electrical machines due to low core loss and high magnetic permeability. Stringent market conditions not only require CRNO steel with superior magnetic properties but also demand excellent surface conditions. CRNO steel is cold rolled to 0.5 mm in reversing mill. High hot rolled input thickness (>2.6 mm) increases the number of passes during cold rolling and adversely affects the mill productivity. It also results in surface defects such as buckling and coil break. The flow stress of this steel varies differently compared to conventional rolled steel. Thus, it becomes difficult to optimize the reduction schedule and hence safe hot rolling practice is adopted to restrict roll force within permissible limit resulting in higher thickness. A hot compression test was carried out in a Gleeble–3500 to evaluate the flow stress behaviour of this steel and a deformation map was developed to optimize the hot rolling window. The input from the hot compression test and deformation map was used to develop a mill setup model to accurately predict the roll force and optimize the reduction schedule of CRNO steel in the finishing stands of HSM. The final thickness of hot-rolled coils during industrial trials with an optimized reduction schedule was found to be in the range of 2.4–2.6 mm compared to 2.7–3.0 mm during conventional rolling. These coils were further cold rolled and finished in 4–5 passes compared to 6–7 passes with conventional rolling. Reduction in the number of passes has resulted in increased productivity during cold rolling as well as improved surface finish.

We have successfully prepared a challenging and wonderful material, reduced graphene oxide (RGO)/graphene with improved quality from high pure graphite (HPG) efficiently by planetary ball milling process followed by arc plasma treatment under hydrogen atmosphere. Graphene oxides (GO) have been synthesized with varying degrees of oxidation via the planetary ball milling route by milling HPG between 3 – 8 h. The lowest C/O ratio (0.965) was observed for the 8 h ball milled sample. The as-prepared GOs were taken for only five min of arc plasma treatment under a hydrogen atmosphere. As the typical GO (prepared by 8 h ball milling) underwent a reduction by plasma treatment for producing a typical RGO sample, it was found that the C/O ratio increased from 0.965 in GO to 14.86 in RGO. RGO shows a hexagonal structure with well-defined crystallinity. Bi-layered and transparent types of structures were found in the RGO sample. The typical plasma treated RGO sample (prepared from 8 h ball milled GO sample) exhibits extraordinary BET surface area and electrical conductivity values of 1230.0 m 2  g −1 and 4.587 × 10 3 S cm −1 , respectively, compared to those of HPG.

This article briefly discusses the role of interphase in the elastic moduli of unidirectional fiber-reinforced polymer composite materials. For this unidirectional glass fiber was chosen as reinforcement, and epoxy was selected as the matrix. A hexagonally packed representative volume element is used for the micromechanical analysis. Experimental validation was initially used to verify the accuracy of the established equations of the rule of mixing, Composite Cylinder Assemblage, Chamis, Halpin and Tsai, and Puck. The Chamis equation was found to be the most reasonable. Then the finite element approach in which interphase has been included was used to estimate the elastic moduli. The finite element model without interphase and the experimental result were taken as a reference. The influence of interface ratio and property of interphase on the homogenised elastic properties of the unidirectional fiber-reinforced polymer composites is analysed. A micromechanics plugin in Abaqus software was used to estimate the density and Young’s modulus of the unidirectional fiber-reinforced polymer composites. The interphase properties are varied, having 6.25%, 12.5%, 25% and 50% influence of the fiber phase and the remaining influence of the matrix phase with interface ratios of 0.1, 0.2 and 0.3. The interface ratio of 0.3, having 6.25% fiber phase influence, gave the most reasonable moduli values (with an error <10%) compared to the mean experimental moduli. The study showed interface ratio and interphase properties to critically influence the overall elastic property of the unidirectional fiber-reinforced polymer composites.

We report detailed studies of the dielectric, impedance, and magnetodielectric properties of sol–gel synthesized (1− x )Bi 5 Ti 3 FeO 15 –( x )Bi 2 Fe 4 O 9 , x = 0.1 composites. The Rietveld refinement of X-ray diffraction data confirms the presence of mixed phases Bi 5 Ti 3 FeO 15 ( A 2 1 am ) and Bi 2 Fe 4 O 9 ( Pbam ) with the orthorhombic crystal structure. The average grain size of the sample is calculated from scanning electron microscopy and found to be 0.74 µm and 0.80 µm for BTFO and BFO samples, respectively. The room temperature dielectric behavior of the prepared composite is demonstrated over a frequency range (10 2  Hz to 10 6  Hz) and at different fixed magnetic fields (0 T to 1.3 T). The decreasing trend of dielectric dispersion and loss signifies the presence of negative magnetodielectric and magneto-loss in the composite. Frequency-dependent magnetoresistance through impedance spectroscopy has been carried out to analyze the origin of the observed MD effect. The magnetic field-dependent MD and ML exhibit maximum coupling of about −0.19% and −0.36% at 50 kHz, respectively. The obtained MD response in this composite is due to the grain (capacitive) effect. These results establish a relation between the electric and magnetic order in the composites and extend their application in the field of magnetic memory and sensor devices.

Cold forging is extensively applied to produce components such as shafts, axles, gears, crankshafts and couplings for automobiles. EN 24 and EN 353 steels possess relatively lower carbon content and have great commercial importance, particularly in the automotive sector. While EN 24 is a preferred choice for shafts, EN 353 is largely used in manufacturing gears and pinions. Apart from improving the mechanical properties of steel, heat treatment makes the steel softer, which reduces excessive forming loads during the cold forging process. The objective of this work is to assess the effect of spheroidization annealing on the fatigue characteristics of both EN 24 and EN 353 steels. Specimens prepared from the chosen materials with and without heat treatment were subjected to low cycle fatigue tests and the fractography images were studied. The investigations revealed that (i) the extent of spheroidization was improved with extended holding time during the heating cycle, (ii) EN 24 steel became softer after spheroidization and had the fatigue life almost doubled, and (iii) For EN 353 steel, the spheroidization resulted in a 50% increase in the fatigue life.

Varied morphologies of crystalline copper oxide nanoparticles were synthesized using one step chemical bath deposition under microwave heating of prepared growth solution at 1200 W microwave power for a very short duration of 2–8 min. The structure and crystallinity of the as grown copper oxide nanoparticles were studied by wide angle X-ray diffractometer analysis. The particle size values obtained from Scherrer’s relation and the Williamson–Hall plot methods are in the 16–18 nm range. The approximate size of as grown copper oxide nanoparticles evaluated from field emission scanning electron microscopic images are in the range of approximately 15–20 nm. The presence of copper and oxygen was verified by energy dispersive X-ray spectroscopy analysis. Their weight % and atomic % exhibits the rich amount of development of copper oxide nanoparticles in a 1:1 stoichiometric ratio. The optical properties of as grown copper oxide nanoparticles were examined by assessing absorption spectra of the sample in ultraviolet–visible range. The significant peak of absorption spectra is seen near 340 nm wavelength which explains the mono-dispersion behaviour of nanoparticles. Evaluation of Urbach energy of copper oxide nanoparticles reveals that the nanomaterial has microstructural lattice disorder. These characterizations of as synthesized copper oxide nanoparticles explain the feasibility and potential of such nanomaterial to be incorporated in a wide range of utilities.

In this study, polyvinylidene fluoride (PVDF) thick films with thickness ∼180 µm were synthesized by solution casting. X-ray diffraction study established the co-existence of both α and β-phases. Raman spectroscopy of the synthesized PVDF thick films corroborated the existence of α and β-phases in 0.71:1 ratio. Surface micrographs of PVDF thick films showed dense microstructure with grain size ∼10 µm. Additionally, the room temperature values of dielectric constant and dielectric loss at 100 kHz were measured to be ∼20 and 0.33, respectively. Furthermore, ferroelectric behavior of PVDF thick films was confirmed by the polarization versus electric field ( P–E ) hysteresis loop study. A leakage current density of 1.55 × 10 −5  A cm −2 at an applied electric field of 500 kV cm −1 was obtained in PVDF thick films.

Electrochemical corona discharge micromachining (µ-ECDM) is a newly advented, advanced hybrid machining process capable of machining non-conducting and conducting materials. In this article, Polymethyl methacrylate (PMMA), a non-conducting material, often used in microfluidic applications, is machined to generate microchannels. The process parameters chosen for machining are voltage, duty factor, and concentration. The process parameters are chosen at three levels, and their effect on machining characteristics such as material removal rate and surface roughness are detailed in this paper. Optimization is carried out for individual response using the signal to noise ratio optimization technique for maximizing material removal rate and minimizing surface roughness.

The constitutive relationship between stress and strain for titanium alloy Ti6Al4V has been investigated using tensile tests at four different temperatures that is room temperature, 200 °C, 400 °C, and 550 °C. Detail observations on the variation of nature of flow curves in the work hardening regime have been reported at different test temperatures. At room temperature and 550 °C, the flow curves are found to be linear in nature and follow the Hollomon relationship. The flow curves at 200 and 400 °C exhibit non-linear nature and demonstrate Ludwigson relationship. The various constant parameters of above relationships influence the overall strength and ductility of the alloy at different temperatures. The alloy shows presence of premature plastic instability or inflection points in the early period of flow curves and displays a fast decrease in work hardening rate at room temperature and 550 °C, which in turn results in lower values of strain to fracture.

Aluminium (Al) and its constituent alloys has been consistently favoured as a promising material for industrial applications. In conventional casting technique of Al alloys, alloying elements are amalgamated in molten pool of Al melt followed by manual skimming. In contrast, batch type manufacturing includes intrinsic mixing and casting discontinuity, which negatively impacts the flexibility and cost-effectiveness of the process, resulting in a decline in the overall efficacy of the process. In the present study, a novel continuous casting processing route has been used to make Al–Cu binary alloys of different compositions. The newly designed technique makes use of a novel mechanical force convection technology, as well as bottom feeding of the molten metal and alloying element throughout the manufacturing process. The bottom feeding along with rotational swirl ensures better amalgamation of alloying element. Feed rates of Al melt and Al–Cu master alloy were mathematically modelled to obtain the desired alloy composition. The microstructural characterization of the developed alloys exhibit Al–Cu intermetallic phase invariably distributed throughout the sample, which concludes a better performing processing route to prepare Al–Cu binary alloys.

Aluminium–tin (Al–Sn) immiscible alloys for bearing materials are difficult to cast by the conventional direct chill casting method. At higher concentrations, Sn accumulates at the bottom of the as-cast solid due to a significant density difference in Al and Sn. In the present investigation, Al–Sn alloys were fabricated by the direct chill (DC) casting method under the influence of mechanical forced convection (MFC). A computer-based simulation approach has been implemented to study the effect of MFC device position and impeller speed on melt flow and solidification. Optimized parameters were experimentally validated and the quality of as-cast ingots was evaluated. Hence, this optimization approach can be used to produce better quality Al–Sn bearing materials with uniformly distributed Sn phase in Al-matrix by the direct chill casting route.

Polymeric barrier coatings are one of the most sought-after methods for protecting metallic parts from corrosion and for ensuring a glossy appearance. In this work, pure polyester barrier coating was applied on a steel substrate using a microwave-assisted curing process with an experimental design based on L9 Taguchi orthogonal array. It included three key factors, viz. voltage, powder output from the spray gun and microwave power with three levels of each. The heat required for curing was achieved through electromagnetic-thermal energy conversion with the aid of a graphite susceptor. A multi-physics numerical study was carried out to identify the magnitude of temperature attained at different levels of microwave power and irradiation time. This was used to build the microwave curing set-up. The impact of parametric variation of the microwave-assisted process on the gloss was quantified. In addition, an assessment of dry film thickness, corrosion resistance, and impact strength was performed. Taguchi analysis reveals that out of three factors used, microwave power has the most significant impact on the gloss units. The desired level of impact strength was achieved for all samples, with the exception of the one coated with the factor combination of the least levels. Corrosion resistance for specimens was measured to be 240 h using a standard salt spray test. Specimen prepared with larger power input showed lesser blistering. The results substantiate the feasibility of a microwave-assisted process route for the industrial coating process.

The present work encompasses synthesis and fabrication of short rattan fiber (1–3 mm) reinforced epoxy composite with enhanced mechanical properties. Acrylic acid has been considered as surfactant for surface modification of rattan fiber to enhance adhesion with thermosetting polymer such as epoxy. Calculation of various mechanical properties has been performed and analysed with different weight percentage of fiber matrix composition. Micrographs were studied using scanning electron microscopy. The acrylic acid treated composite shows better tensile, flexural and impact strength at 45.5 MPa, 121.89 MPa and 39.45 J m −1 , respectively. Regression analysis reveals that the composite with 18% fiber content (optimum weight percentage) exhibits better mechanical properties. The results suggest that rattan fibers provide a natural and sustainable choice for reinforcing composites in a wide range of technical applications where synthetic fibres are currently utilized.

A cost-effective and facile synthesis method is developed for hybrid aerogels using recycled cellulose fiber concentration of 1–4 wt.% and methoxytrimethylsilane (MTMS). The developed hybrid aerogel was modified with surface hydroxyl groups to achieve superhydrophobic behavior with a contact angle as high as 163.4°. This excellent three-dimensional reticular structure with various cellulose concentrations provides a thermal conductivity of 0.039–0.041 W m −1  K −1 . However, the thermal degradation of the hybrid aerogels exhibits a superior improvement with minimum weight loss. A comparatively good sound absorption coefficient of 0.392–0.504 was achieved with the inclusion of cellulose fiber concentration from 1 to 4 wt.% in comparison with silica aerogels (0.303–0.512). The experimental results also show an increase in compressive Young’s modulus of hybrid aerogels up to 96%, with an increase in cellulose concentration. This work delivers a facile approach to developing hybrid aerogels with an industrial application to replace polymer-based insulations.

Evolution of structural and magnetic properties in a nickel/chromium (Ni/Cr) multilayer, as a function of different annealing temperatures was investigated. The Ni/Cr multilayer of nominal structure [Cr (50 Å)/Ni (50 Å)] ×10 /Cr (30 Å) was grown on a Si substrate by radio frequency ion beam sputtering at room temperature. X-ray diffraction, X-ray reflectometry, atomic force microscopy and crossectional scanning electron microscopy were employed for the complete structural characterization of the multilayer whereas superconducting quantum interference device vibration sample magnetometer was used for the bulk magnetisation study. The effect of in-situ and ex-situ annealing on overall structural property of the multilayer also reported in present work. From in-situ X-ray reflectometry (50–400 °C), 300 °C was detected as the optimum temperature for improved structural properties of the Ni/Cr multilayer. Initiation of alloying in the multilayer sample was noticed at 350 °C. The multilayer found to exhibit polycrystalline nature observed by X-ray diffraction. Total thickness of the multilayer system was confirmed by crossectional scanning electron microscopy and in well agreement with X-ray reflectivity results. The Ni/Cr sample found to exhibit soft ferromagnetic behaviour after annealing at 300 °C and 400 °C. However the net magnetic moment reduced upon annealing at higher temperature (400 °C).

Lately, coated steel sheets have replaced bare steel in the automotive sectors due to their corrosion protection. Among them, zinc-coated high strength interstitial free (HIF) steel is widely used due to its durability, formability, good surface finish, impact resistance, and corrosion resistance. However, joining galvannealed (GA) steel using conventional fusion welding processes is challenging as it results in porosity and potentially harmful fumes. To overcome these challenges, this work uses a pulse MIG (metal inert gas) brazing technique to join the HIF-GA steel sheet with a lap joint configuration utilizing Cu-Si base filler wire (CuSi3Mn1) in an argon atmosphere. The study aims to evaluate the effect of heat input on bead geometry and Zn degradation in MIG brazed joints by adjusting the current from 40 to 60 A and brazing speed from 400 to 500 mm min −1 . It is observed that the heat input is inversely proportional to the wetting angle and directly proportional to the bead width, leg length, and cross-sectional area. Heat input influences Zn degradation on both the front (at the toe) and back sides of the lap joint. The corrosion behavior of joints is studied using an electrochemical test (in 3.5% NaCl solution) and a salt spray test (in 5% NaCl solution). Further, the Zn degradation is analyzed with EDS line scanning to understand the corrosion resistance of the MIG brazed joints. A potentiostatic polarization study is also conducted to determine the corrosion rate using a Tafel plot. It is found that the lowest corrosion rate in base metal (BM) increased from 0.88 to 12.26 mm year −1 with the increase in heat input from 61 to 113 J mm −1 .

In the present study, aluminum matrix was reinforced with SiC and TiO 2 powders to synthesize Al–SiC–TiO 2 hybrid composites by using a powder metallurgy route. The influence of variation in TiO 2 content is thoroughly evaluated over the microstructure and mechanical properties. The uniform distribution and growth in the interfacial bonding between the matrix phase and reinforcement particles were confirmed from the overall scanning electron micrographs. Further, the measured hardness and density values significantly increased with the increase in TiO 2 content. In addition to that, the compressive strength had increased up to 5 wt.% of TiO 2 . However, at higher content of TiO 2 , a decreasing trend is found due to the excess cluster formation.