Lead free Piezoceramic materials for sensors and actuators
Piezoelectric materials are a class of functional materials which have a unique ability to couple electrical and mechanical energy, that is, development of an electrical voltage in response to mechanical stress or mechanically strained in response to applied voltage. It has been widely used to fabricate actuators, sensors, ultra sound transducers, and fuel injectors. One of the most commonly used piezoelectrics is the lead zirconate titanate (PZT) ceramics because of its superior piezoelectric properties (d33 ∼ 300–550 pC/N). However, due to the toxicity of lead oxide there is an increasing demand to replace these lead based piezoceramics with efficient lead free alternatives. An effort to increase the piezolectric charge coefficient of lead-free piezoceramic has resulted in BCZT ceramics with high piezoelectric charge coefficient (d33) ∼ 673 pC/N, large electromechanical coupling coefficient kp ∼ 59%, a high strain, Smax, of ∼0.157%, and a large piezoelectric voltage constant, (g33) ∼ 13 mV m/N.
Magnetostrictive materials for sensors
Owing to its superior strain sensitivity (dλ/dH) cobalt ferrite (CFO) has long been identified as a potential material for various magnetoelastic stress sensing applications such as power steering systems in automotive industries. Our research effort is centered around substitution of CFO lattice with various metal ions of varying valency, ionic size, and oxidation state. Apart from metal substitution our research also includes variation in processing techniques in presence and absence of magnetic field. We have achieved maximum magnetostriction of ~425 ppm. A remarkable increase in dλ/dH was observed compared to pure CFO ~5.5 vs. 0.8 ×
Nanomaterials and Nanobiomaterials for anticancer drug delivery system
Mesoporous silica based magnetic nanocarriers are getting increasing attention in targeted drug delivery due to its biocompatibility, high surface area, and high porosity. A primary aim of magnetic nanocarrier based drug delivery system is to develop a platform that effectively reduces systemic toxicity of drugs while retaining their pharmacological activity. Magnetic nanocarrier based drug delivery systems offer several advantages over the administration of molecular free drugs viz. specific targeting ability, enhanced permeability and retentivity (EPR), controlled drug release, improved solubility and stability of drugs, low toxicity to normal cell, low clearance, long circulation time etc., which contribute to enhanced tumor cell death. Our efforts mainly include integration of ferrite based nanoparticles into mesoporous SiO2 and polymeric systems to develop efficient nanocarriers. The magnetic ferrites we use have high saturation magnetization, high Curie temperature, superparamagnetic nature, chemical stability, low coercivity and biodegradability.
Chemical Mechanical Planarization (CMP) of Semiconductor Wafers for micro- and Opto-Electronic Devices
In an effort to produce defect-free planarization of semiconductor wafer surfaces for micro and opto-electronic devices, we are developing abrasive free and abrasive based CMP technologies to investigate the validity of the diverse nature of the experimental models. We are currently working on GaN/ AlGaN/ AlN and single crystal SiC wafer surfaces. We have achieved ultra-smooth surfaces with rms roughness of ~3 to 5 Å over a scan area of 5µm x 5µm.
BZT Ceramics for Microwave Window Sections in Fusion Reactor
Since the existing RF window material (Al2O3) in fusion reactor possesses very low dielectric loss, quality factor, thermal conductivity and high relative dielectric constant, developing an efficient alternative ceramic material is the primary objective of this research, Barium zinc tantalate, Ba(Zn1/3Ta2/3) O3 (BZT) ceramics with properties suitable for the required application is being investigated. The main properties required for this application include high density (to act as a vacuum barrier), low loss tangent (to have minimal loss) and high dielectric constant (to enable it reducing the window dimensions). Our research has resulted in novel microwave dielectric ceramics with maximum Quality factor (Qxf) of 1,20,000 GHz, high dielectric constant (~30), high thermal conductivity and very low temperature coefficient of thermal expansion.