Magnetic and humidity sensing properties of nanostructured Cu[x]Co[1-x]Fe2O4 synthesized by auto combustion technique

Magnetic nanomaterials (23-43 nm) of Cu$_x$Co$_{1-x}$Fe$_2$O$_4$\ (x = 0.0, 0.5 and 1.0) were synthesized by auto combustion method. The crystallite sizes of these materials were calculated from X-ray diffraction peaks. The band observed in Fourier transform infrared spectrum near 575 cm$^{-1}$ in these samples confirm the presence of ferrite phase. Conductivity measurement shows the thermal hysteresis and demonstrates the knee points at 475$^o$C, 525$^o$C and 500$^o$C for copper ferrite, cobalt ferrite and copper-cobalt mixed ferrite respectively. The hystersis M-H loops for these materials were traced using the Vibrating Sample Magnetometer (VSM) and indicate a significant increase in the saturation magnetization (M$_s$) and remanence (M$_r$) due to the substitution of Cu$^{2+}$ ions in cobalt ferrite, while the intrinsic coercivity (H$_c$) was decreasing. Among these ferrites, copper ferrite exhibits highest sensitivity for humidity.Comment: 12 pages, 7 figure

Bottom-Up and Top-Down Approaches for MgO

In this chapter, we present an overview of synthesis of MgO nanoparticles and thin films by using top-down and bottom-up approaches. The bottom-up approaches are generally utilized to grow nanoparticles by the methods that involve chemical reactions. Sometimes, methods based on these reactions are also able to grow thin films. The top-down approaches are preferred for growing thin films where bulk material is used for depositions. The methods, which are frequently used, are radio frequency sputtering, pulsed lased deposition, and molecular beam epitaxy and e-beam evaporation. Sometimes, methods like mechanical milling and high energy ball milling are used to grow nanoparticles

Achieving tolerant CO₂ electro-reduction catalyst in real water matrix

In order to achieve practical application of electrochemical CO₂ conversion technologies, the development of durable catalyst in real water matrix is essential because the use of catalysts only showing high performance within a well-refined environment cannot guarantee their feasibility in realistic conditions. Here, we report a design strategy for a catalyst, which shows excellent tolerance to deactivation factors, using a carbon-based material under more practical condition implemented by real tap water. Screening analyses on various components in tap water elucidated that the impurity group, which can be deposited on the catalyst surface and impede the active sites, such as copper, zinc, and especially iron are the main factors responsible for deactivation. Based on these findings, the structural modified nitrogen-doped carbon nanotube (denoted as ball mill N-CNT) was adopted as a catalyst design to secure durability. Consequently, the ball mill N-CNT revealed tolerance to the disclosed deactivation factors and showed stable performance during unprecedented long-time of 120 h in tap water media

On the optical properties of Ag^{+15} ion-beam irradiated TiO_{2} and SnO_{2} thin films

The effects of 200-MeV Ag^{+15} ion irradiation on the optical properties of TiO_{2} and SnO_{2} thin films prepared by using the RF magnetron sputtering technique were investigated. These films were characterized by using UV-vis spectroscopy, and with increasing irradiation fluence, the transmittance for the TiO_{2} films was observed to increase systematically while that for SnO_{2} was observed to decrease. Absorption spectra of the irradiated samples showed minor changes in the indirect bandgap from 3.44 to 3.59 eV with increasing irradiation fluence for TiO_{2} while significant changes in the direct bandgap from 3.92 to 3.6 eV were observed for SnO_{2}. The observed modifications in the optical properties of both the TiO_{2} and the SnO_{2} systems with irradiation can be attributed to controlled structural disorder/defects in the system.Comment: 6 pages, ICAMD-201

Direct and real-time observation of hole transport dynamics in anatase TiO2 using X-ray free-electron laser

Carrier dynamics affects photocatalytic systems, but direct and real-time observations in an element-specific and energy-level-specific manner are challenging. In this study, we demonstrate that the dynamics of photo-generated holes in metal oxides can be directly probed by using femtosecond X-ray absorption spectroscopy at an X-ray free-electron laser. We identify the energy level and life time of holes with a long life time (230 pico-seconds) in nano-crystal materials. We also observe that trapped holes show an energy distribution in the bandgap region with a formation time of 0.3 pico-seconds and a decay time of 8.0 pico-seconds at room temperature. We corroborate the dynamics of the electrons by using X-ray absorption spectroscopy at the metal L-edges in a consistent explanation with that of the holes

d° Ferromagnetism of Magnesium Oxide

Magnetism without d-orbital electrons seems to be unrealistic; however, recent observations of magnetism in non-magnetic oxides, such as ZnO, HfO2, and MgO, have opened new avenues in the field of magnetism. Magnetism exhibited by these oxides is known as d° ferromagnetism, as these oxides either have completely filled or unfilled d-/f-orbitals. This magnetism is believed to occur due to polarization induced by p-orbitals. Magnetic polarization in these oxides arises due to vacancies, the excitation of trapped spin in the triplet state. The presence of vacancies at the surface and subsurface also affects the magnetic behavior of these oxides. In the present review, origins of magnetism in magnesium oxide are discussed to obtain understanding of d° ferromagnetism

Countermeasures against large-scale reflection DDoS attacks using exploit IoT devices

With the of utilizing IoT devices increasing recently, such devices are being infected with malicious codes and being used to carry out DDoS attacks. In particular, there have been cases of large-scale DDoS reflex attacks of 100GB or more using IoT devices such as wireless sharing devices, CCTVs and smart cars. There is a vulnerability that is being exploited for attacks through Simple Service Discovery Protocol (SSDP) to search for IoT devices. This study examines different types of IoT devices used in DDoS attacks, and conducts experiments in which reflection DDoS attacks are carried out on IoT devices in order to measure the attack threat levels. This study also suggests methods that IoT service operators can employ to remove IoT device vulnerabilities, as well as effective countermeasures that Internet service operators can apply to address reflection DDoS attacks that exploit IoT devices