Hole-doped high entropy ferrites: Structure and charge compensation mechanisms in (Gd0.2La0.2Nd0.2Sm0.2Y0.2)1−xCaxFeO3

High entropy oxides (HEOs) can be defined as single-phase oxide solid solutions with five or more cations in near equiatomic proportion occupying a given cation sub-lattice. The compositional flexibility while retaining the phase purity can be considered one of the major strengths of this materials class. Taking advantage of this aspect, here we explore the extent to which an aliovalent hole dopant can be incorporated into a perovskite-HEO system. Nine systems, (Gd_0.2La_0.2Nd_0.2Sm_0.2Y_0.2)_1−xCa_xFeO₃, with varying amount of Ca content (x = 0–.5) are synthesized using nebulized spray pyrolysis. Single-phase orthorhombic (Pbnm) structure can be retained up to 20% of Ca doping. Beyond 20% of Ca, a secondary rhombohedral (R-3c) phase emerges. The ⁵⁷Fe Mössbauer spectra indicate that charge compensation occurs only via oxygen vacancy formation in the single-phase systems containing up to 15% of Ca. In addition, partial transition from Fe³⁺ to Fe⁴⁺ occurs in the 20% Ca-doped case. Room temperature Mössbauer spectroscopy further reflects the coexistence of multiple magnetic phases in crystallographic single-phase (Gd_0.2La_0.2Nd_0.2Sm_0.2Y_0.2)_1−xCa_xFeO₃, which is supported by magnetometry measurements. These initial results show the potential of charge doping to tune structural–magneto–electronic properties in compositionally complex HEOs, warranting further research in this direction.     

Real geo-time-based secured access computation model for e-Health systems

Role Back Access Control model (RBAC) allows devices to access cloud services after authentication of requests. However, it does not give priority in Big Data to devices located in certain geolocations. Regarding the crisis in a specific region, RBAC did not provide a facility to give priority access to such geolocations. In this paper, we planned to incorporate Location Time- (GEOTime) based condition alongside Priority Attribute role-based access control model (PARBAC), so requesters can be allowed/prevented from access based on their location and time. The priority concept helped to improve the performance of the existing access model. TIME-PARBAC also ensures service priorities based on geographical condition. For this purpose, the session is encrypted using a secret key. The secret key is created by mapping location, time, speed, acceleration and other information into a unique number, that is, K(Unique_Value) = location, time, speed, accelerator, other information. Spatial entities are used to model objects, user position, and geographically bounded roles. The role is activated based on the position and attributes of the user. To enhance usability and flexibility, we designed a role schema to include the name of the role and the type of role associated with the logical position and the rest of the PARBAC model proposed using official documentation available on the website for Azure internet of things (IoT) Cloud. The implementation results utilizing a health use case signified the importance of geology, time, priority and attribute parameters with supporting features to improve the flexibility of the existing access control model in the IoT Cloud.     

Experimental Investigation and Analysis on Borosilicate Glass Using Electrochemical Discharge Machining Process

Silicon - Electrochemical discharge machining process (ECDM) is a non-traditional machining process which has widely used in medical, electronics and aerospace industry. This paper discuss about...     

Green Synthesis-Mediated Silver Nanoparticles Based Biocomposite Films for Wound Healing Application

Journal of Inorganic and Organometallic Polymers and Materials - Wound care is a clinical challenge due to the susceptibility of the wound to multidrug-resistant bacterial infections. We report a...     

Effect of Tool Geometry on the Machining Characteristics amid SiC Powder Mixed Electric Discharge Drilling of Hybrid Metal Matrix Composite

Silicon - The manufacturing of hybrid metal matrix composites (HMMCs) combines two or more reinforcing materials exhibiting distinct properties, with a steady metal matrix phase. Such combinations...     

Machinability and surface morphology investigations of multiwall carbon nanotube reinforced aluminium 7075 metal matrix composite during electrical discharge machining: A grey relational approach

Multiwall carbon nanotube buttressed aluminium 7075 metal matrix composite was synthesized through an amended liquid metallurgy method, which consisted semisolid stirring, ultrasonic treatment and squeeze casting. Aim was to investigate its machinability and surface morphology during electrical discharge machining. Variable machining factors were peak current, pulse-on time and gap voltage, whereas the responses under investigation were electrode wear rate, material removal rate and average surface roughness. Results revealed electrode wear rate, material wear rate and average surface roughness increased on increasing peak current and pulse-on time, but all these responses behaved inversely with the increase of gap voltage. Average surface roughness reduced by around 44 % on reducing the peak current from 10 A to 4 A and increasing gap voltage from 55 V to 80 V at constant pulse-on time of 300 μs; however, it increased by around 25 % on reducing the gap voltage from 80 V to 55 V and increasing the pulse-on time from 100 μs to 300 μs at constant peak current of 10 A. Significance of the process parameters were verified, regression models were developed and morphology of the machined surfaces was studied. Finally, multiple response optimization was conducted following grey relational approach.     

Impact of Drain Underlap and High Bandgap Strip on Cylindrical Gate All Around Tunnel FET and its Influence on Analog/RF Performance

Silicon - This paper comprises of design and analysis of novel gate all around (GAA) cylindrical tunnel field effect transistor (TFET) using technology computer aided designing (TCAD) tool. The...     

Kinetic study of Hg(II)-promoted substitution of cyanide from hexacyanoferrate(II) in an anionic surfactant medium by 2,2′-bipyridine

The kinetic investigation of Hg(II)-promoted reaction between [Fe(CN)₆]⁴⁻ and 2,2′-bipyridine (Bipy) has been performed in anionic sodium dodecyl sulfate (SDS) micellar medium by recording the surge in absorbance at 400 nm, corresponding to ultimate reaction product [Fe(CN)₄ Bipy]²⁻ using UV–visible spectrophotometer. Pseudo-first-order condition has been used to examine the progress of reaction as a function of temperature, [Fe(CN)₆⁴⁻], ionic strength, [SDS], pH, [Hg²⁺], and [Bipy] by changing one parameter at a time. The results exhibit that [Hg²⁺], [SDS], and pH are the decisive parameter showing maximum reaction rate at 1.5 × 10⁻⁴ mol dm⁻³, 6.0 × 10⁻³ mol dm⁻³, and 3.8, respectively. [Fe(CN)₆]⁴⁻ does not show any appreciable effect on the critical micellar concentration (CMC) of SDS as the polar head of SDS and [Fe(CN)₆]⁴⁻ both are negatively charged. Variable order kinetics was observed for [Fe(CN)₆]⁴⁻ and Bipy in their examined concentration range. The reverse response observed in the reaction rate with [KNO₃] shows a negative salt effect. The K⁺ provided by K₄[Fe(CN)₆] and KNO₃ decreases the repulsion between the negatively charged heads of the surfactant molecules thereby decreasing the CMC of SDS. The negative value for the entropy of activation also supports the interchange dissociative (I_d) mechanism recommended by us.