Microstructure,optical and magnetic properties of Zr-doped SnO synthesized by the hydrothermal method

Sn_1?xZr_xO was successfully synthesized by the one-step hydrothermal method. X-ray diffraction and Raman patterns reveal that the lattice distortion of SnO occurs with an increase in Zr concentration, and Zr ions are located at the substituted (Zr_Sn) and interstitial (Zr_i) sites successively. Scanning electron microscope and transmission electron microscope images showed that Zr concentration does not affect the well-crystalline nature of Sn_1?xZr_xO. However, the system's morphology changes from three-dimensional flowerlike to two-dimensional sheetlike. Furthermore, X-ray photoelectron spectroscopy and Raman spectra indicate that there are inherent oxygen vacancies (V_O) in pure SnO lattice. UV–Visible absorption spectra show that the optical bandgap first decreases and then increases with Zr doping, which is explained by the sp–d exchange interactions in the case of Zr_Sn and the Burstein–Moss effect in the case of Zr_i. Additionally, Sn_1?xZr_xO samples exhibit room temperature ferromagnetism (RTFM), and the magnetic variation couples with the variation of the relative intensity of the Raman vibration modes. From the experimental results and the first-principles calculations, it can be seen that V_O and the exchange interaction between Zr 4d and O 2p states are accountable for the RTFM of Sn_1?xZr_xO. Meanwhile, the lattice distortion and the Zr–O–Zr super-exchange interaction caused by excessive doping could decrease FM.     

Microstructure,optical and magnetic properties of TiO2/CuO nanocomposites synthesized by a two-step method

TiO₂/CuO composites in different ratios were prepared via a two-step method. X-ray diffraction and transmission electron microscopy results indicated that part of Cu²⁺ substituted Ti⁴⁺ in the TiO₂ lattice in the composite, leading to Cu²⁺-substituted sites in the TiO₂ lattice as well as Cu²⁺ species located in the CuO lattice. Scanning electron microscopy revealed a morphology change in the sample from a three-dimensional structure to a two-dimensional structure while forming an interface between TiO₂ and CuO. X-ray photoelectron spectroscopy and Raman spectra showed that there are oxygen vacancies (V_O) and Ti³⁺ in the lattice. UV–vis absorption spectra exhibited a widening of the absorption range and a decrease in the bandgap with increasing amount of CuO in the TiO₂/CuO composites. Additionally, the composites exhibited room-temperature ferromagnetism (RTFM), as can be explained by the indirect double-exchange model, which is related to V_O and the exchange interaction between the 3d orbitals of Ti³⁺ and Ti⁴⁺ at the interface.     

Synthesis, characterization, and magnetic properties of monodisperse CeO2 nanospheres prepared by PVP-assisted hydrothermal method

ABSTRACT: Ferromagnetism was observed at room-temperature in monodisperse CeO2 nanospheres synthesized by hydrothermal treatment of Ce(NO3)3.6H2O using polyvinylpyrrolidone (PVP) as a surfactant. The structure and morphology of the products were characterized by; X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FE-SEM). The optical properties of the nanospheres were determined using ultraviolet and visible spectroscopy (UV-Vis) and photoluminescence (PL). The valence states of Ce ions were also determined using X-ray absorption near edge spectroscopy (XANES). The XRD results indicated that the synthesized samples had a cubic structure with a crystallite size in the range of ~ 9-19 nm. FE-SEM micrographs showed that the samples had a spherical morphology with a particle size in the range of ~ 100-250 nm. The samples also showed a strong UV absorption and room temperature photoluminescence. The emission might be due to charge transfer transitions from the 4f band to the valence band of the oxide. The magnetic properties of the samples were studied by Vibrating Sample Magnetometer (VSM). The samples exhibited room temperature ferromagnetism (RT-FM) with a small magnetization of ~ 0.0026-0.016 emu/g at 10 kOe. Our results indicate that oxygen vacancies could be involved in the ferromagnetic exchange and the possible mechanism of formation was discussed based on the experimental results.     

Sturdy memristive switching characteristics of flexible 2D SnO prepared by liquid-to-solid exfoliation

Monolayer-thick two-dimensional (2D) tin monoxide (SnO) was synthesized by facile liquid-to-solid exfoliation. The SnO monolayer nanosheet displayed a 2D multidomain texture, where the nanoscale 2D SnO crystallites (~7 nm in average) were laterally dispersed in the form of the nano-network. Owing to the series-and-shunt filament networks formed along the lateral domain walls, the Ag/SnO/Ag lateral memristor exhibited the sturdy memristive switching characteristics (i.e., high on/off ratio ~ 10³, data retention up to 1200 s, reliable endurance upon 100-times write/erase operations, and stable durability against the 50-times continuous bending stresses). These advocate that the liquid-to-solid exfoliated 2D SnO monolayer holds promise for future flexible nanoelectronics.     

Impact of reactive precursors on the sintering of tin monoxide

The thermodynamic stability limits of Sn(II) under ambient conditions imposes constraints on the densification of divalent tin based oxides. In the case of tin monoxide (SnO), a low temperature (≤ 300 °C) electric field assisted processing route (Cool-SPS) affords densification up to 90 % of theoretical density. This is demonstrated for both conventional SnO and reactive tin(II) oxyhydroxide [Sn₆O₄(OH)₄] precursor powders. The choice of starting precursor impacts both the optimized processing parameters and the resulting ceramic microstructure. Characterizations of phase content and stability have been performed on both the precursor powders and resulting ceramics. Preliminary electrochemical property measurements are presented and their connection to observed microstructures and choice of initial precursor is discussed.     

Synthesis and magnetic properties of ceramic MgO porous film

Ordered porous MgO films with pore diameters in the 15–28 nm range have been prepared on porous anodic alumina substrates at 573 K in a fixed O₂ pressure of 1.4 × 10⁻⁴ mbar using DC-reactive magnetron sputtering. X-ray diffraction and scanning probe microscope observations have revealed that homogeneous MgO ceramics with face-centered cubic structure are formed with a highly ordered nanopore array arranged in a close packed hexagonal pattern. The results of magnetic measurements have shown that the porous MgO ceramics possess remarkable room temperature ferromagnetism and the maximum saturation magnetization along the out-of-plane direction was as high as 78 emu/cm³. Experimental and theoretical results suggest that oxygen vacancies and the unique porous structure of the films are responsible for the high magnetization. These results provide new insights into magnetic ordering in undoped dilute ferromagnetic semiconductor oxides and may be useful in the development of MgO-based spintronics devices and novel multifunctional materials.     

有机物原位包裹Co微米球的溶剂热制备

以醋酸钴为钴源,乙二醇为溶剂,氢氧化钠为添加剂,三嵌段共聚物P123为表面活性剂,采用溶剂热法一步制备了有机物包裹的Co微米颗粒。通过表征测试发现,有机物包裹的Co微米颗粒为球状,粒径均匀,尺寸约5 μm左右。通过热重以及磁性能测试发现,所制备的有机物包裹Co微米颗粒在450 ℃以内热稳定性良好;饱和磁感应强度高达169 emu/g,矫顽力低至50 Oe,剩磁在10 emu/g以内,软磁性能良好。本研究中以常用溶剂水、乙醇为参照组进行了对比实验,并对样品进行了表征和性能测试。此外,本研究进一步探讨了表面活性剂P123对样品结构及性能的影响。     

Densification of thermodynamically unstable tin monoxide using cold sintering process

SnO is a thermodynamically unstable phase and undergoes thermal decomposition into SnO₂ and Sn at a relatively low temperature when heating under ambient conditions. With the cold sintering process (CSP), SnO can be densified up to 89% of theoretical density within 100 min by applying uniaxial pressure of 350 MPa and transient liquid phase. 15-fold BET specific surface area reduction is observed between the ball-milled powder and the cold-sintered pellet, indicating experimental evidence of sintering. The temperature profiles of 70–265 °C show densification while maintaining the phase purity. Water and 2 M acetic acid solution are studied as transient liquid phases which promotes dissolution-precipitation on the particle surface and induces crystalline texture. Electrical properties of the cold sintered bulk, notably electrical conductivity and Seebeck coefficient, are measured as a function of temperature.     

Dielectric and magnetic properties of BiFeO3 ceramics prepared by hydrothermal synthesis

Single-phase BiFeO₃ powders were prepared at a temperature of 200 °C by a hydrothermal synthesis. BiFeO₃ ceramics were prepared with the powders by a conventional ceramic process. The BiFeO₃ ceramics with no impurity phase were prepared at the sintering temperature of 650–800 °C. The dense microstructure was observed in the BiFeO₃ ceramics sintered at a temperature of 700 °C and higher. BiFeO₃ ceramics show linear M–H curves in low H, which are antiferromagnetic behaviors. The dielectric dispersion was observed at the frequency range of 10 kHz to 1 MHz in the BiFeO₃ ceramic sintered at 700 °C or lower. The dielectric constant and loss of the BiFeO₃ ceramics sintered at 750 °C or higher were about 85 and 0.4 at 100 kHz, respectively.     

Synthesis and magnetic properties of Zr doped ZnO Nanoparticles

Zr doped ZnO nanoparticles are prepared by the sol-gel method with post-annealing. X-ray diffraction results show that all samples are the typical hexagonal wurtzite structure without any other new phase, as well as the Zr atoms have successfully entered into the ZnO lattices instead of forming other lattices. Magnetic measurements indicate that all the doping samples show room temperature ferromagnetism and the pure ZnO is paramagneism. The results of Raman and X-ray photoelectron spectroscopy indicate that there are a lot of oxygen vacancies in the samples by doping element of Zr. It is considered that the observed ferromagnetism is related to the doping induced oxygen vacancies.     

Size dependence of the magnetic properties of Ni nanoparticles prepared by thermal decomposition method

By means of thermal decomposition, we prepared single-phase spherical Ni nanoparticles (23 to 114 nm in diameter) that are face-centered cubic in structure. The magnetic properties of the Ni nanoparticles were experimentally as well as theoretically investigated as a function of particle size. By means of thermogravimetric/differential thermal analysis, the Curie temperature T_C of the 23-, 45-, 80-, and 114-nm Ni particles was found to be 335°C, 346°C, 351°C, and 354°C, respectively. Based on the size-and-shape dependence model of cohesive energy, a theoretical model is proposed to explain the size dependence of T_C. The measurement of magnetic hysteresis loop reveals that the saturation magnetization M_S and remanent magnetization increase and the coercivity decreases monotonously with increasing particle size, indicating a distinct size effect. By adopting a simplified theoretical model, we obtained M_S values that are in good agreement with the experimental ones. Furthermore, with increase of surface-to-volume ratio of Ni nanoparticles due to decrease of particle size, there is increase of the percentage of magnetically inactive layer.     

水热法制备的Ce-ZnO结构表征及其光催化性能研究

采用水热法制备不同摩尔比的稀土元素Ce掺杂Zn O光催化纳米材料Ce-Zn O,用红外(FTIR)光谱、X射线衍射(XRD)、紫外-可见光谱(UV-Vis)、光致发光(PL)等对其进行表征;研究了不同Ce掺杂量的Ce-Zn O对亚甲基蓝溶液(MB)光催化性能的影响。结果表明,Ce掺杂量2%时,Zn O的表面状态得到明显改善,生成更多的羟基自由基;同时增加光生电子空穴对的浓度,显著提高Zn O的光催化性能;经过2 h紫外汞灯照射,其降解率达到93.68%;且经过5次循环使用后,2%Ce-Zn O的降解率依旧能达到85%以上,具有良好的光催化性能和循环稳定性。     

Study of the oxygen vacancy influence on magnetic properties of Fe- and Co-doped SnO2 diluted alloys

Transition-metal (TM)-doped diluted magnetic oxides (DMOs) have attracted attention from both experimental and theoretical points of view due to their potential use in spintronics towards new nanostructured devices and new technologies. In the present work, we study the magnetic properties of Sn_0.96TM_0.04O₂ and Sn_0.96TM_0.04O_1.98(V_O)_0.02, where TM = Fe and Co, focusing in particular in the role played by the presence of O vacancies nearby the TM. The calculated total energy as a function of the total magnetic moment per cell shows a magnetic metastability, corresponding to a ground state, respectively, with 2 and 1 μ_B/cell, for Fe and Co. Two metastable states, with 0 and 4 μ_B/cell were found for Fe, and a single value, 3 μ_B/cell, for Co. The spin-crossover energies (E_S) were calculated. The values are E_S^0/2 = 107 meV and E_S^4/2 = 25 meV for Fe. For Co, E_S^3/1 = 36 meV. By creating O vacancies close to the TM site, we show that the metastablity and E_S change. For iron, a new state appears, and the state with zero magnetic moment disappears. The ground state is 4 μ_B/cell instead of 2 μ_B/cell, and the energy E_S^2/4 is 30 meV. For cobalt, the ground state is then found with 3 μ_B/cell and the metastable state with 1 μ_B/cell. The spin-crossover energy E_S^1/3 is 21 meV. Our results suggest that these materials may be used in devices for spintronic applications that require different magnetization states.     

Tunable optical,electronic and magnetic properties of semiconductor nanoparticles induced by magnetic and nonmagnetic dopants: A comparative experimental and theoretical study

While combining semiconductor and magnetic properties at the nanoscale provides dilute magnetic semiconductor (DMS) nanomaterials with a wide range of applications in next-generation electronic devices, tuning DMS properties still presents a challenge. Here, the synthesis of pure ZnO and transition metal (TM)-doped ZnO nanoparticles (NPs) with different magnetic (Fe and Co) and nonmagnetic (Mn) dopant concentrations (ranging from 2% to 10%) is reported using a co-precipitation method. Introducing the TM-dopants into ZnO NPs with 35?nm wurtzite structure causes crystallite and mean NP sizes to decrease, as characterized by X-ray diffraction and field-emission scanning electron microscopic analyses. Room-temperature magnetic measurements indicate coexistence of paramagnetic and ferromagnetic phases with tunability in the resulting TM-doped NPs. The maximum ferromagnetic coercivity and saturation magnetization are found to be 89?Oe and 0.074?emu/g for 10% Fe-doped ZnO NPs. UV–visible spectra showed a blue shift with increasing the dopant concentration, being in agreement with increasing trend in band gap energy calculated from band structure and density of state of TM-doped ZnO nanocrystal systems.     

Effect of annealing temperature on structural and magnetic properties of Co2TiO4 ceramics prepared by sol-gel method

In this paper, polycrystalline Co₂TiO₄ ceramics have been synthesized using a sol-gel process followed by annealing at different temperatures. The lattice size and the average grain size of the samples increases with rise in annealing temperature. The temperature-dependent inverse paramagnetic susceptibilities recorded under zero-field-cooling condition have been fitted according to the Néel's expression for ferrimagnets. Subsequently, the molecular field constants and the corresponding exchange constants have been calculated. The fitting result shows that the magnetic interaction in the system becomes weaker as the annealing temperature rises. In addition, negative magnetization is observed during field-cooling process. The higher annealing temperature is beneficial to the growth of tetrahedral sublattice, leading to a decrease on compensation temperature. Furthermore, magnetization hysteresis loops for all the samples demonstrate the crucial role of grain size on the magnetic properties.     

Fuel properties and combustion performance of hydrochars prepared by hydrothermal carbonization of different recycling paper mill wastes

The incineration of high-moisture solid residues generated at the recycling paper mills represents an energetically unfavourable method of resource utilization. Alternatively, hydrothermal pre-treatment is considered. In this study, low-value paper sludges from three different recycling streams were hydrothermally carbonized at 205, 225, and 245°C for 3 h. The raw feedstocks and derived hydrochars were analyzed for energy properties, chemical characteristics, surface morphology, functional groups, and combustion performance employing energy densification and mass yield quantification, scanning electron microscopy, elemental analyzer, Fourier-transform infrared spectroscopy, and thermogravimetry. The increase in reaction temperature was reported to cause a decrease in mass yield and an increase in energy densification and calorific values corresponding to 5.98%–49.35% and 10.10%–58.51% for raw fibre rejects and final sludge-derived hydrochar, respectively. Hydrothermal carbonization (HTC) had a non-significant influence on the energy densification of primary clarifier sludge-derived hydrochar. Higher reaction temperatures favoured the rate of dehydration and decarboxylation, leading to hydrochars with lower H/C and O/C ratios, thereby enhancing the overall fuel properties. The low-nitrogen and low-sulphur fuels obtained validated the effectiveness of HTC treatment to produce high-quality cleaner solid fuel. The burnout temperature was mostly reduced with an increase in HTC temperature. At HTC-205 and 225°C, the ignition temperature and the combustion performance increased as a result of the HTC reaction mechanisms. HTC effectively recovered hydrochar with increased carbon content, improved energy densification, and good combustion adequacy. Hydrochar derived from recycling mills may play a role in the energy sector as a substitute for coal or in co-combustion at coal-fired power plants.     

混炼法制备的NBR/HMMT纳米复合材料的结构与性能研究

通过混炼法实现了NBR在本体状态下对有机改性蒙脱土的插层复合。XRD分析表明该复合材料中蒙脱土层间距从1.2nm扩大到4.8nm，TEM研究表明HMMT以1－10nm薄片分散在橡胶基体中。该体系表现出优良物理机械性能。     

马尾松基磁性水热炭的制备及其吸附性能

磁性水热炭兼具水热炭的吸附性能和磁性材料可回收的优点,是一种具有广阔应用前景的水处理吸附材料。目前,磁性水热炭一般采用两步法制备,工艺较为复杂。为此,本文以马尾松锯末为原料,以FeSO₄作为磁化剂,NaOH作为活化剂,1,2-丙二醇作为还原剂,开发一步法制备磁性水热炭技术。考察了反应温度、反应时间对磁性水热炭产率和结构的影响,采用XRD、SEM、BET、VSM等对产品进行表征,并将磁性水热炭用于去除水中Cu²⁺离子。结果表明：随着反应温度的升高和反应时间的增加,磁性水热炭的产率逐渐降低,但比表面积增加,磁性增强。在水热反应温度为240℃、反应时间为8h的条件下,制备的马尾松基磁性水热炭具有良好的吸附性能和磁性,磁性水热炭对Cu²⁺吸附量为9.58mg/g,最大饱和磁化强度3.74emu/g,具有较好的应用潜力。     

Structure and performance of hydrogenated natural rubber prepared by the latex method

Hydrogenated natural rubber (HNR) with different degrees of hydrogenation was prepared by the latex method. The hydrazine hydrate/hydrogen peroxide/boric acid catalytic system could result in the hydrogenation of natural rubber (NR) under the latex state. The NR without hydrogenation contained around 13% of gel, when the hydrogenation degree reached 66.9%, the gel content was 34.4%. The decomposition temperature of HNR kept on increasing, which was all higher than that of NR and the glass transition temperature increased slightly. The cross-linking density of vulcanised rubber rose along with the increasing degree of hydrogenation, the NR cross-linking density was 0.114 mmol cm^?3, when the hydrogenation degree was 34.6%, 42.7% and 66.9%, the cross-linking density was 0.182, 185 and 221 mmol cm^?3, respectively. This further proved decreasing flexibility of the HNR after hydrogenation and weakening crystallisation of HNR along with increasing degree of hydrogenation.     

Analysis of structural,optical and magnetic properties of Fe/Co co-doped ZnO nanocrystals

In this paper, the structural, optical and magnetic properties of pure ZnO and Fe/Co co-doped ZnO nanoparticles are presented. Rietveld refinement of XRD pattern revealed the single phase wurtzite structure for prepared samples. FTIR study confirmed the formation of tetrahedral coordination between zinc and oxygen ions. SEM and TEM techniques were used to examine the morphology of samples. The absorption spectra showed the decrease in optical energy band gap with Fe/Co co-doping in ZnO. PL spectra demonstrated five peaks correspond to the ultraviolet region, violet, violet-blue, blue-green and green in the visible region. Emission peak in the UV region is attributed to near band-edge excitonic emission. Other four emission peaks in PL spectra are related to different defect states. M-H curve showed room temperature ferromagnetic (RTFM) behaviour of doped ZnO sample. This paper enhances the understanding of structural, optical and magnetic properties of Fe/Co co-doped ZnO nanocrystals for application in spintronics, solar cells, and ceramics.