Effect of high cobalt concentration on hopping motion in cobalt manganese spinel oxide (CoxMn3–xO4,x≥ 2.3)

Hopping motions in cobalt manganese spinel oxides with high cobalt concentration (CoxMn3−xO4, 2.3 ≤ x ≤ 2.7) are investigated in order to clarify the origin of unusual electrical behaviors as negative temperature coefficient (NTC) thermistors. Based on the resistance versus temperature (R−T) characteristics, hopping conduction mechanisms in MCO compounds (x = 2.3 and 2.5) are attributed to variable range hopping (VRH) motion with a parabolic distribution of the density of states (DOS) near the Fermi level. However, when Co content increases up to 2.7, transition in the hopping motion occurs from VRH to the nearest neighboring hopping (NNH) motion, which can be responsible for a huge increase of the resistance accompanied by decrease of the factor of thermal sensitivity (B value) in MCO compounds (x = 2.7). Also, hopping distance and activation energies for MCO (x = 2.3 and 2.5) compounds following VRH conduction are calculated as a function of temperature, indicating that higher B value observed in MCO (x = 2.5) compound is due to the larger hopping distance compared to that of MCO (x = 2.3) compound

Quasi-intrinsic colossal permittivity in Nb and In co-doped rutile TiO2 nanoceramics synthesized through a oxalate chemical-solution route combined with spark plasma sintering

Nb and In co-doped rutile TiO2 nanoceramics (n-NITO) were successfully synthesized through a chemical-solution route combined with a low temperature spark plasma sintering (SPS) technique. The particle morphology and the microstructure of n-NITO compounds were nanometric in size. Various techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG)/differential thermal analysis (DTA), Fourier transform infrared (FTIR), and Raman spectroscopy were used for the structural and compositional characterization of the synthesized compound. The results indicated that the as-synthesized n-NITO oxalate as well as sintered ceramic have a co-doped single phase of titanyl oxalate and rutile TiO2, respectively. Broadband impedance spectroscopy revealed that novel colossal permittivity (CP) was achieved in n-NITO ceramics exhibiting excellent temperaturefrequency stable CP (up to 104) as well as low dielectric loss (B5%). Most importantly, detailed impedance data analyses of n-NITO compared to microcrystalline NITO (m-NITO) demonstrated that the origin of CP in NITO bulk nanoceramics might be related with the pinned electrons in defect clusters and not to extrinsic interfacial effects

Hopping Conduction in (Ni,Co,Mn)O₄ Prepared by Different Synthetic Routes: Conventional and Spark Plasma Sintering

(Ni,Co,Mn)O₄ (NMC) oxides were prepared by conventional sintering (CS) and spark plasma sintering (SPS) using micro and nanopowders. Small hopping polaron theory was used in order to investigate effect of processing routes on electrical properties of NMC oxides as negative temperature coefficient (NTC) thermistors. Also, X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques were utilized to analyze compositional and structural effects on the electrical properties of NMC compounds. Hopping conduction in NMC prepared by SPS and CS using nanopowder occurs via variable range hopping (VRH) mechanism, however conduction in NMC prepared by CS using micropowder follows nearest neighboring hopping (NNH) mode. Hopping distance and activation energy for the VRH mode were calculated using corresponding physical model

Production of nanoparticles from natural hydroxylapatite by laser ablation

Laser ablation of solids in liquids technique has been used to obtain colloidal nanoparticles from biological hydroxylapatite using pulsed as well as a continuous wave (CW) laser. Transmission electron microscopy (TEM) measurements revealed the formation of spherical particles with size distribution ranging from few nanometers to hundred nanometers and irregular submicronic particles. High resolution TEM showed that particles obtained by the use of pulsed laser were crystalline, while those obtained by the use of CW laser were amorphous. The shape and size of particles are consistent with the explosive ejection as formation mechanism

Recovery of Ni-Co-Mn Oxides from End-of-Life Lithium-Ion Batteries for the Application of a Negative Temperature Coefficient Sensor

This study demonstrates the current advancements in battery management systems (BMSs), emphasizing the need for precise temperature monitoring within battery packs to enhance safety and performance through efficient thermal management. The increased demand for lithium-ion batteries (LIBs) has driven the development of temperature sensors with improved accuracy and stability. In particular, Ni-Co-Mn-based spinel oxides are commonly used due to their stable negative temperature coefficient (NTC) behavior. However, challenges arise in manufacturing due to the high cost and uncertain supply of critical cathode components (e.g., Co, Ni, and Mn) for LIBs. This research focuses on developing spinel-type (Ni0.6Co0.4Mn2)O4 using recycled Ni-Co-Mn oxides obtained from end-of-life (EOL) LIBs, demonstrating temperature resistance behavior suitable for temperature sensing. The oxides are prepared through hydrometallurgy, oxalate synthesis, and post-heat treatment. Successful integration into spinel-type NTC thermistors suggests broader applications in various industrial fields. A systematic investigation into the synthesis and characterization of recovered Ni-Co-Mn oxides from EOL LIB cathode materials (Li(Ni0.33Co0.33Mn0.33)O2) is presented for NTC thermistor application. Thermogravimetric analysis-derivative thermogravimetry (TGA-DTG) identifies the optimal post-heat treatment temperature. The X-ray diffraction (XRD) patterns confirm a cubic spinel structure of the Ni-Co-Mn oxides, supported by scanning electron microscope (SEM) images showing a uniform microstructure. Also, energy dispersive X-ray spectroscopy (EDS) mapping confirms homogeneous element distribution. Recovered oxide pellets from the sintering process exhibit a single spinel structure, with X-ray photoelectron spectroscopy (XPS) analysis revealing changes in the valence states for Ni and Mn. Resistivity measurements demonstrate semiconductive behavior, which shows a B value (3376.92 K) suitable for NTC thermistor applications. This study contributes valuable insights to black powder recycling from EOL LIBs and its potential in temperature-sensitive electronic devices

Effect of One Step Solid State Reaction Route on the Semiconductor Behavior of the Spinel (NI, Co, and Mn)O₄ to Be Used as Temperature Sensor

Achieving carbon neutrality is important to solve environmental problems and thus requires decarbonizing manufacturing processes to reduce greenhouse gas emissions. The firing of ceramics, including calcination and sintering, is a typical fossil fuels-driven manufacturing process that requires large power consumption. Although the firing process in manufacturing ceramics cannot be eliminated, an effective firing strategy to reduce processing steps can be a choice to lower power consumption. Herein, we suggest a one-step solid solution reaction (SSR) route to manufacture (Ni, Co, and Mn)O4 (NMC) electroceramics for their application in temperature sensors with negative temperature coefficient (NTC). Additionally, the effect of the one-step SSR route on the electrical properties of the NMC is investigated. Similar to the NMC prepared using the two-step SSR route, spinel structures with dense microstructure are observed in the NMC prepared via the one-step SSR route. Based on the experimental results, the one-step SSR route can be considered as one of the effective processing techniques with less power consumption to manufacture electroceramics

Estudio comparativo de métodos de detección del virus del rizado del tomate Nueva Delhi (Tomato leaf curl New Delhi virus, ToLCNDV) en Mallorca

[spa] Los virus que afectan a vegetales causan consecuencias económicas debido a que su infección produce el debilitamiento de la planta, disminuyendo así la calidad y el rendimiento de los cultivos. Los virus emergentes son los más agresivos en cuanto a los daños que producen en los cultivos, debido al desconocimiento o falta de información para controlarlos adecuadamente y evitar así, su propagación. ToLCNDV (Tomato Leaf Curl New Delhi virus) fue detectado por primera vez en India el año 1995, en el cultivo de tomate. Es un virus que pertenece a la familia Geminiviridae y al género Begomovirus, que se caracteriza por ser uno de los fitopatógenos más severos que afectan a los cultivos hortícolas, presentando un único vector conocido, Bemisia tabaci. ToLCNDV se encuentra principalmente en Asia y Europa. En España se detectaron las primeras infecciones en el año 2012, afectando en su mayoría a Solanáceas y Cucurbitáceas. Los síntomas más evidentes de ToLCNDV, como norma general, son la aparición de mosaicos, hojas enrolladas, nervios hinchados y retraso en el crecimiento de la planta, que pueden causar su debilitamiento, pero también puede llegar a producir la muerte de la misma. El manejo de la enfermedad es uno de los grandes desafíos que se tienen actualmente, debido a que los virus en general no son fáciles de tratar, más bien hay que evitar su aparición, ya sea controlando a su vector, adquiriendo buenas prácticas agrícolas, o mediante el empleo de variedades resistentes, donde esta última opción está siendo estudiada para el caso de ToLCNDV. Actualmente existen diferentes técnicas de detección para muchos de los virus existentes. En este trabajo se estudiaron diversas maneras para detectar ToLCNDV. Para ello, primero se hizo una detección sintomática en campo en muestras de calabacín de la variedad Amalthe, Chenopodium sp. y una muestra de tomate de ensalada; luego se hizo una detección mediante la técnica serológica en laboratorio DAS- ELISA y por último se empleó el análisis molecular mediante PCR, bajo dos métodos de extracción de ADN, el primero DNeasy® Plant Mini Kit (250) de la casa comercial QIAGEN y el segundo método de extracción, E.Z.N.A® HP Plant DNA Mini Kit de la casa comercial OMEGA. En este trabajo de fin de grado se ha estudiado principalmente el cultivo de calabacín, ya que se sabe que tiene una alta incidencia de infección y grandes pérdidas económicas en este tipo de hortaliza, además se estudió también, una posible infección del virus en la vegetación auxiliar Chenopodium sp., evaluando diferentes métodos de detección de su ADN viral, con el objetivo de determinar cuál es el método más sensible y eficaz a la hora de analizar las muestras vegetales en laboratorio, para facilitar su detección y reconocimiento tanto en Mallorca como en el resto de España

Low-volume return premium in the Korean stock market

We propose a new mechanism with which we explain an exceptional phenomenon in the Korean stock market, wherein the post-event return of an abnormally low-volume stock is larger than that of an abnormally high-volume stock, in contrast to what happens in other major stock markets. This mechanism is a combination of two market characteristics: one is the mean-reversion of trading volume; the other is the dominance of stocks with a positive correlation between return and change in trading volume. Using evidence from the Korean stock market, we show that the return generated by this mechanism has a highly concentrated distribution with a negative average and that the value has a scale higher than that of positive returns generated by other factors. We conclude that our suggested mechanism can explain the low-volume return premium in the Korean stock market. This finding presents a new way to explain how trading volume change affects future returns.N