High Frequency Dielectric Behavior of Rare Earth Substituted Sr-M Hexaferrite

S. Bindra Narang,Anterpreet Singh,Kulwant Singh 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.5

Strontium hexaferrites of a structural formula Sr1-xRExFe12O19, where RE=La3+, Nd3+ and Sm3+ with (x=0 to 0.30) were prepared by a standard ceramic technique. The lattice constants, density, porosity, dielectric constant and dielectric loss tangent were studied on a series of rare earth substituted strontium hexaferrites. The dielectric constant and dielectric loss tangent were measured in the frequency range of 0.3 GHz to 3.0 GHz at room temperature. The dielectric constant decreased with increasing frequency for all the three series. This behavior of dielectric properties with frequency has been explained with the Maxwell-Wagner type interfacial polarization in agreement with the Koops phenomenological theory. The substitution of rare earth ions into SrFe12O19 increases the value of the dielectric constant. This increase in dielectric constant could be due to the electronic exchange between Fe2+ ↔ Fe3+ and results in a local displacement determining the polarization of the ferrites. For these ferrite samples the Curie temperature decreases as rare earth ions substitution increases. Strontium hexaferrites of a structural formula Sr1-xRExFe12O19, where RE=La3+, Nd3+ and Sm3+ with (x=0 to 0.30) were prepared by a standard ceramic technique. The lattice constants, density, porosity, dielectric constant and dielectric loss tangent were studied on a series of rare earth substituted strontium hexaferrites. The dielectric constant and dielectric loss tangent were measured in the frequency range of 0.3 GHz to 3.0 GHz at room temperature. The dielectric constant decreased with increasing frequency for all the three series. This behavior of dielectric properties with frequency has been explained with the Maxwell-Wagner type interfacial polarization in agreement with the Koops phenomenological theory. The substitution of rare earth ions into SrFe12O19 increases the value of the dielectric constant. This increase in dielectric constant could be due to the electronic exchange between Fe2+ ↔ Fe3+ and results in a local displacement determining the polarization of the ferrites. For these ferrite samples the Curie temperature decreases as rare earth ions substitution increases.

Microwave dielectric properties of M-Type barium, calcium and strontium hexaferrite substituted with Co and Ti

Sukhleen Bindra Narang,I.S. Hudiara 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.2

Suitable ferrite components are designed for use in systems like radar, satellite uplinks, industrial heaters or dryers and nuclear systems which employ high power microwaves. Ferrites are also used as microwave absorbers. Radar absorbing paint made from ferrites can be used to coat military aircraft for stealth operation. In this study, some hexaferrites have been synthesized and characterized for their possible use at high frequencies. Three series of M type hexagonal ferrites having the general formula MeFe12O19 in which Me was Ba2+, Sr2+ or Ca2+ and Fe3+ ions were replaced partly by Co2+Ti4+ ions were chosen for synthesis and study. The microwave dielectric constants of these hexaferrites has been measured in the X band of the microwave frequency range after successively increasing the amount of substituted ions in the ferrites. The variation of Complex Permittivity of these hexaferrites with change in composition as well as change in frequency has been measured in this frequency range. Important inferences have been drawn using theoretical concepts.

Synthesis and microwave characterization of Bi- substituted barium lanthanum titanate

S. Bindra Narang,Shalini Bahel,Dalveer Kaur 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.5

Bi-substituted barium lanthanum titanates with the general formula Ba4(La(1-z)Biz)9.33Ti18O54 where z = 0.0 to 0.2 in steps of 0.05 were synthesized by a conventional mixed oxide route. The composition and morphology were determined using scanning electron microscopy (SEM) and X-ray powder diffraction analysis (XRD). Two dielectric performance parameters, namely dielectric constant and loss tangent were measured with varying microwave frequency in the range 0.3 to 3 GHz at room temperature. It was observed that the dielectric constant and loss tangent both increased initially for z ≤ 0.10 and then decreased. The best properties were obtained for z = 0.20 with a dielectric constant of 91.4 and loss tangent of 0.004. This could be a promising microwave material with a high dielectric constant and low loss. Bi-substituted barium lanthanum titanates with the general formula Ba4(La(1-z)Biz)9.33Ti18O54 where z = 0.0 to 0.2 in steps of 0.05 were synthesized by a conventional mixed oxide route. The composition and morphology were determined using scanning electron microscopy (SEM) and X-ray powder diffraction analysis (XRD). Two dielectric performance parameters, namely dielectric constant and loss tangent were measured with varying microwave frequency in the range 0.3 to 3 GHz at room temperature. It was observed that the dielectric constant and loss tangent both increased initially for z ≤ 0.10 and then decreased. The best properties were obtained for z = 0.20 with a dielectric constant of 91.4 and loss tangent of 0.004. This could be a promising microwave material with a high dielectric constant and low loss.

Processing, dielectric behavior and conductivity of some complex tungsten-bronze dielectric ceramics

Sukhleen Bindra Narang,Dalveer Kaur,Kulwant S. Thind 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.1

Ceramic samples of a complex structural formula Ba6-3xR8+2xTi18O54, where R is a rare-earth oxide and R=Sm, Nd and Gd and x=0.2-0.7 were prepared by a high temperature solid-state reaction technique. The dielectric properties (i.e. dielectric constant (ε'), dielectric loss (ε'') and Q-factor) have been measured on the sintered disks with respect to the frequency in the range 0.3 GHz-3.0 GHz at room temperature. The dielectric properties of the synthesized samples have been found out to be a function of the wt.% of rare-earth oxides used. Dielectric conductivity (σ) was derived from the dielectric constant and loss tangent data in the same frequency range. Conductivity calculations were carried out based on this derived formula. The capacitance values have been calculated knowing the geometrical dimensions of the samples synthesized.

Structural and microwave dielectric properties of Ba6-3xGd8+2xTi18O54 solid-solutions

S.Bindra Narang,Dalveer Kaur,Kulwant Singh Thind 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.5

Ba6-3xGd8+2xTi18O54 (x = 0.0, 0.2 ≤ x ≤ 0.7) composites have been synthesized by employing a solid-state reactive sintering technique and studied from the point of view of microwave dielectric materials. In this series, formation of solid solutions was found, which was deduced from the linear change of the lattice parameters of the unit cells. Unit-cell parameters (Å) have been obtained with the help of the X-Ray powder diffraction (XRD) technique. Multi-phase microstructures have been observed for all the compositions using Scanning electron microscopy (SEM). We found good quality microwave materials which show a high dielectric constant (ε') of 70 and a low loss tangent (tanδ) of 0.006336 at 3 GHz. A minimum value of the A.C. dielectric conductivity (σa.c.) was 2.32E-12 mho/cm at 0.8 GHz. Ba6-3xGd8+2xTi18O54 (x = 0.0, 0.2 ≤ x ≤ 0.7) composites have been synthesized by employing a solid-state reactive sintering technique and studied from the point of view of microwave dielectric materials. In this series, formation of solid solutions was found, which was deduced from the linear change of the lattice parameters of the unit cells. Unit-cell parameters (Å) have been obtained with the help of the X-Ray powder diffraction (XRD) technique. Multi-phase microstructures have been observed for all the compositions using Scanning electron microscopy (SEM). We found good quality microwave materials which show a high dielectric constant (ε') of 70 and a low loss tangent (tanδ) of 0.006336 at 3 GHz. A minimum value of the A.C. dielectric conductivity (σa.c.) was 2.32E-12 mho/cm at 0.8 GHz.

You Dissolved My Beauty Slowly…Slowly

Nyamat BINDRA 이화여자대학교 아시아여성학센터 2016 이화여자대학교 아시아여성학센터 학술대회자료집 Vol.2016 No.1

In this paper, I present primary interviews complied overview of the pain, trauma, and challenges faced by the acid attack survivors. I have interviewed 20 survivors- male and female from across India and given them 1 voice! The paper looks at their current mindset, reasons of attack with a gender lens and their life before- loss of freedom to dress as desired and lack of self-esteem. I throw light on the current acids attack laws and regulations with a comparison to Bangladesh and special mention on the recent rule by the Delhi Government for providing free medical treatment to survivors. The paper will primarily throw light on what is in theory and ground realities. The way forward will stress on what the survivors want and an appeal for the international community to put pressure on India and the world to stress on mandatory psychological counseling, free education, jobs as per their qualifications and speedy justice. I have also interviewed 20 pharmacy shops, road side vendors and small clinics who sell acid even though there is a ban in India.

Low loss dielectric ceramics for microwave applications: a review

S. Bindra Narang,Shalini Bahel 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.3

Microwave dielectric ceramics have been used for a wide range of applications from wireless communication (including mobile communication, ultra high speed local area networks, intelligent transport system, satellite communication) to consumer electronic products. The need for portable, light weight and multifunctional electronic components has forced scientists to search for new advanced microwave materials. During the past 25 years, a large number of dielectric materials have been developed and the properties of existing materials have been improved. However, the data on these very useful materials are scattered. The main purpose of this review is to bring together the data of low loss microwave dielectric ceramics and classify them according to their applications. This should be of immense help to researchers and technologists all over the world.

Electrical and magnetic properties of rare earth substituted strontium hexaferrites

Anterpreet Singh,S. Bindra Narang,Kulwant Singh Thind,O.P. Pandey,R.K. Kotnala 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.2

Samples of strontium ferrite (Sr-M) with different molar substitution concentrations of lanthanum, neodymium and samarium ions were prepared by a standard ceramic processing technique. AC conductivity, dielectric constant and dielectric loss tangent measurements were carried out in the frequency range of 20 Hz to 1MHz. The experimental results indicate that AC electrical conductivity increases with increasing frequency. The increase in AC conductivity with frequency can be explained on the basis of Koops model, whereas the dielectric constant and dielectric loss tangent variations have been explained with a Maxwell-Wagner type interfacial polarization in agreement with the Koops phenomenological theory. The effects of rare earth substitution on the magnetic properties such as the saturation magnetization moment (Ms), coercive field (Hc), remenance (Mr),and Curie temperature Tc (K) have been investigated. It is found that the values of the magnetization moment (Ms), and remenance (Mr) decrease with increasing rare earth ions substitution for all the series. The reason for the decrease may be both the magnetic dilution and spin canting, which promote reduction of superexchange interactions. The enhancement of Hc values may be due to higher magnetocrystalline anisotropy, where Fe2+ ion anisotropy on the 2a site could be dominant in all hexaferrites series.

Direct Laser Deposition‑Additive Manufacturing of Ti–15Mo Alloy: Effect of Build Orientation Induced Surface Topography on Corrosion and Bioactivity

Tarun Bhardwaj,Mukul Shukla,Nisheeth K. Prasad,C. P. Paul,K. S. Bindra 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.7

In this study, the direct laser deposition-additive manufacturing (DLD-AM) process is employed to fabricate Ti–15Mobiomedical alloy along two build directions. The aim is to analyse the effect of induced surface topography on corrosionand in-vitro bioactivity, motivated towards ultimate reduction in post-fabrication surface modifications. The effectof surface roughness on corrosion resistance is analysed in-vitro in simulated body fluid (SBF) by electrochemical study. Owing to higher surface roughness in the vertical build samples (Ra = 52.70 ± 11.40 μm) than the horizontal build samples(Ra = 27.10 ± 4.17 μm), upto 75% higher corrosion resistance is found for horizontally built samples. The double passivebarrier layer formed in horizontal build higher surface finish samples results in lower corrosion. Further, wettability testconfirms that both the build orientations exhibit a hydrophilic surface nature, leading to improved cell attachment. SEM–EDSanalysis establishes the in-vitro apatite formation on immersion in SBF, for both build orientation samples. This study leadsto understand the role of build orientation induced surface topography for production of minimal post-surface treatmentTi–15Mo bio-implants by the DLD-AM process.

Hiccups in neurocritical care

Vanitha Rajagopalan,Deep Sengupta,Keshav Goyal,Surya Kumar Dube,Ashish Bindra,Shweta Kedia 대한신경집중치료학회 2021 대한신경집중치료학회지 Vol.14 No.1

Hiccups are usually self-limiting and benign but can be distressing when they become persistent or intractable and produce significant morbidity. In the intubated patients in neurocritical care, persistent hiccups may cause respiratory alkalosis and are also associated with an increased incidence of ventilator-associated pneumonia. Several pharmacological and nonpharmacological strategies have been devised for the treatment of persistent and intractable hiccups. The evidence to support or declare any intervention as harmful is scarce. In this review, we have presented the pathophysiology and workup, and a stepwise management protocol for intractable hiccups.