Soil Chemical Analysis

A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

Perspective on the Development of Lead-free Piezoceramics

Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

Single-phased ferroelectromagnet BiFeO3 ceramics with high resistivity were synthesized by a rapid liquid phase sintering technique. Saturated ferroelectric hysteresis loops were observed at room temperature in the ceramics sintered at 880 °C for 450 s. The spontaneous polarization, remnant polarization, and the coercive field are 8.9 μC/cm2, 4.0 μC/cm2, and 39 kV/cm, respectively, under an applied field of 100 kV/cm. It is proposed that the formation of Fe2+ and an oxygen deficiency leading to the higher leakage can be greatly suppressed by the very high heating rate, short sintering period, and liquid phase sintering technique. The latter was also found effective in increasing the density of the ceramics. The sintering technique developed in this work is expected to be useful in synthesizing other ceramics from multivalent or volatile starting materials.

Room-temperature saturated ferroelectric polarization in BiFeO3 ceramics synthesized by rapid liquid phase sintering

Novel gas sensors with high sensing properties, simultaneously operating at room temperature are considerably more attractive owing to their low power consumption, high security and long-term stability. Till date, zinc oxide (ZnO) as semiconducting metal oxide is considered as the promising resistive-type gas sensing material, but elevated operating temperature becomes the bottleneck of its extensive applications in the field of real-time gas monitoring, especially in flammable and explosive gas atmosphere. In this respect, worldwide efforts have been devoted to reducing the operating temperature by means of multiple methods In this communication, room-temperature gas sensing properties of ZnO based gas sensors are comprehensively reviewed. Much more attention is particularly paid to the effective strategies that create room-temperature gas sensing of ZnO based gas sensors, mainly including surface modification, additive doping and light activation. Finally, some perspectives for future investigation on room-temperature gas-sensing materials are discussed as well.

Room-temperature gas sensing of ZnO-based gas sensor: A review

In this article, we report the synthesis techniques of ZnO nanoparticles (NPs) in open air atmosphere by pulse laser ablation (PLA) method using solid ZnO polycrystalline palette followed by fabrication of formaldehyde (HCHO) sensor. The crystalline phase and morphology of the obtained ZnO NPs were studied by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The XRD patterns showed that the NPs were polycrystalline structure with good crystallinity. The FESEM images revealed that the NPs were spherical in shape and loosely agglomerated. The average diameter of the NPs was in the range of 30–43 nm. Moreover, the ZnO NPs-based sensor exhibited excellent formaldehyde sensing performance at a temperature of 350 °C. The sensor exhibited a gas response of about 5.2 toward 300 ppm formaldehyde with 25 s response and 12 s recovery time. Furthermore, the ZnO NPs-based sensor exhibited excellent reliability and reproducibility to formaldehyde. On the other hand, the sensor showed high sensitivity of about 0.2% ppm $^{-{1}}$ to formaldehyde with a 50 ppm lower detection limit. In addition, the sensor showed an excellent linear relationship ( ${R} ^{{2}} = {0.7948}$ ) between the response and the concentration of formaldehyde in the range of 50–400 ppm. This work demonstrates that PLA in open air is a rapid and cost-effective method for synthesizing metal oxide NPs for gas-sensing applications without the need for wet chemical routes.

Fabrication of Fast and Reliable Pulse Laser-Ablated ZnO Nanoparticles-Based Formaldehyde Sensor

Newborn leopard cubs are totally dependent on their dam for first few weeks of life. Therefore, care of orphaned newborn cubs is an exacting task and success depends on a thorough observation and careful adoption of hygienic measures. Three orphaned leopard cubs (two females and one male) 2-3 days old were brought to the veterinary clinic in Dantewada (Chhattisgarh). Cubs weighed 340g (male) and 320 and 280g (2 female cubs). Their eyes were closed and appeared dehydrated. Body temperatures were recorded as normal (320 C). They were 2-3 days old as their eyes were closed and opened after 7-8 days. On clinical examination, no physical injury and congenital defects were detected. These cubs were kept in a well cleaned room with proper ventilation besides, entry to the room was restricted. Umbilicus was disinfected with povidone iodine to avoid any naval infection. Lytren’s warmed oral electrolyte, glucose* solution was given to them as a first meal (Benshaul, 1962)

http://www.zoosprint.org/ZooPrintJournal/2003/March/1058.pdf

Relationship of age with body weight in orphaned leopard cubs

In this work, the MoS2 functionalized AlGaN/GaN high-electron mobility transistor (HEMT) was utilized for the first time to detect toxic mercury (Hg2+) ions under ultraviolet (UV) illumination. The AlGaN/GaN HEMT was fabricated on the sapphire substrate, and corresponding structural and electrical properties were investigated. Subsequently, the optimization of MoS2 concentration for device functionalization was carried out by performing sensing analysis of Hg2+ ions on three devices, and it was observed that the 20 mg/mL concentration of MoS2 is optimum for the detection of Hg2+ ions. Furthermore, the detection of Hg2+ ions was performed under UV exposure, where the developed sensor showed much-improved sensitivity of $548.07~\mu \text{A}$ /ppb compared with normal light. The comparative analysis indicates the increase of three orders of magnitude in sensitivity under UV irradiation, and it is the highest sensitivity ever observed by the AlGaN/GaN HEMT sensor for Hg2+ ion detection. Moreover, the sensor also exhibits the limit of detection (LoD) of 6.14 parts per trillion (ppt) that is much lower than the World Health Organization (WHO) standard limit for Hg2+ ions in drinking water. Due to the photoexcitation process, the generation of electron–hole pairs provides more binding sites on the MoS2 surface, which results in the ultrasensitive detection of the Hg2+ ions at trace and ultratrace levels.

Ultrasensitive Detection of Mercury Ions Under UV Illumination of MoS 2 Functionalized AlGaN/GaN Transistor

Based on soil samples collected from 814 geo-coded sites in the rainfed croplands, irrigated croplands, rangelands and protected forests within the Shekhawati region of Thar Desert, Rajasthan, India, a spatial analysis of the distribution pattern of organic carbon (OC) and macronutrients i.e., available phosphorus (P) and available potassium (K) and micronutrients viz., DTPA extractable zinc (Zn), copper (Cu), iron (Fe) and manganese (Mn) was carried out in GIS environment. It revealed that OC is deficient almost throughout the region, while P is deficient in large parts of the dune-covered west. Among others, K, Cu and Mn are adequately supplied in most areas, but Zn and Fe are inadequate in large parts. Irrigated croplands are better endowed than other land uses in respect of OC, P, Zn and Cu; forests in respect of K and Fe, and rainfed croplands in respect of Mn. The distribution pattern of the organic C and nutrients appears to be controlled by both natural and anthropogenic processes. Among the natural processes, fluvial processes appear to control the distribution in the hills and plains in the wetter east, while aeolian processes appear to control the distribution in the drier dune-covered west. Anthropogenic processes, especially through land use decisions and fertilizers input in irrigated tracts, have also influenced the sufficiency or otherwise of the soil nutrients.

Spatial variability of available soil nutrients in the Shekhawati region of Thar Desert, India.

In this study, filamentary discharges have been investigated at 1.5 mm dielectric-dielectric electrode gap of a coaxial dielectric barrier discharge (DBD) quartz tube filled with nitrogen gas. Different types of discharge patterns have been established in the tube using alternating field (35-45 kHz). Electrical characteristics of the discharge have been investigated, which mainly depend on gas pressure, applied frequency and voltage amplitude. The on set of the discharge current occurs earlier at higher operating voltage due to the increased value of E/n, where E is the electric field and n is the neutral gas density. The observed phenomenon occurs due to increase in rate of voltage rise time. At higher voltage, increase in net current increases the chances of electron impact. Analysis of the voltage versus charge plot (lissajous figure) supports the theory of capacitances of a double barrier discharge. The energy consumed per cycle of the DBD source measured using lissajous figure is few milli joules. Energy consumption per cycle is the key parameter for evaluating the efficiency of the device.

/pdf/study-of-filamentary-behaviour-in-coaxial-dielectric-barrier-wnz4rfkqwe.pdf

Mahesh Kumar

Papers

Fabrication of Fast and Reliable Pulse Laser-Ablated ZnO Nanoparticles-Based Formaldehyde Sensor

Relationship of age with body weight in orphaned leopard cubs

Ultrasensitive Detection of Mercury Ions Under UV Illumination of MoS 2 Functionalized AlGaN/GaN Transistor

Spatial variability of available soil nutrients in the Shekhawati region of Thar Desert, India.

Study of filamentary behaviour in coaxial dielectric barrier discharge lamp