Synergistic effect of La and Co co-doping on room-temperature ferromagnetism enhancement of TiO2 nanoparticles

The synergistic influence of lanthanum and cobalt co-doping on room temperature ferromagnetism (RTFM) of TiO₂ system is investigated. A series of Ti_0.97?xCo_0.03La_xO₂ nanoparticles were prepared and their structures and properties were systematically studied with X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, UV–vis spectrophotometer, Raman spectra and magnetic measurement techniques, respectively. Detailed experimental characterizations indicate that the as-prepared La and Co co-doped samples exhibit single anatase phase, and all the samples exhibit strong visible photoluminescence associated with oxygen vacancies and a clear ferromagnetic hysteresis loop, both of which were dramatically enhanced with La and Co co-doping, and the maximum saturation magnetization (M_s) reaches 1.38 emu/g at the La content of 6 mol%. It is speculated that oxygen vacancies modulated by ionic La play an important role in the enhanced RTFM, which can be attributed to the bound magnetic polarons (BMPs) formed via ferromagnetic coupling between two neighboring Co²⁺ ions mediated by oxygen vacancy (F⁺ center). Our results present an alternative method to obtain high performance RTFM.     

Fabrication of dense nano-laminated tungsten carbide materials doped with Cr3C2/VC through two-step sintering

This work investigates the critical roles of two-step sintering (TSS) and laminated structure on the sintering behavior and mechanical properties of functionally graded WC-TiC-Al₂O₃ nanostructured composite materials doped with Cr₃C₂/VC. Results show that excellent mechanical properties are achieved for tailored TSS conditions with a hardness of 27.91?±?2.3?GPa and a flexural strength of 1423.3?±?23.5?MPa. The desirable mechanical properties are attributed to the suppressed grain growth without densification deterioration. TSS is more effective in facilitating the favorable dispersion of secondary phase toughening nano-particulates in a WC matrix than conventional sintering (CS). Cr₃C₂/VC dopant plays an important role in maximizing and shifting the temperature range of the kinetic window for WC-Al₂O₃ composites. Al₂O₃ crack deflection, transgranular Al₂O₃, microcracking, WC crack bridging and plate-like WC crack deflection are the major toughening mechanisms. Residual surface compressive stress induced by the graded structure is also an appreciated contribution to the improvement of mechanical properties.     

Elimination of boron and lithium coexisting in geothermal water by adsorption-membrane filtration hybrid process

Direct release of geothermal waters to the environment may cause some damages to some plants because they contain toxic species such as boron, arsenic, fluoride etc. along with valuable minerals including lithium. In this study, a hybrid process combining adsorption and membrane filtration was used to separate boron and lithium simultaneously from geothermal water. According to the results obtained, separation efficiencies for lithium and boron from geothermal water were 100% and 83% using boron selective ion exchange resin Dowex XUS-43594.00 and lithium selective λ-MnO₂ adsorbent, respectively. The kinetic data of lithium and boron adsorption have been evaluated using pseudo-first order and pseudo-second-order kinetic models.     

In situ synthesis of ZrB2–MoSi2 platelet composites: Reactive hot pressing process,microstructure and mechanical properties

Using elemental Zr, B, Mo and Si as raw materials, partially textured ZrB₂–MoSi₂ composites with in situ platelet ZrB₂ grains were fabricated by reactive hot pressing. Synthesized by a combustion reaction, the in situ formed ZrB₂ phase had unique characteristics to grow up to platelet grains, on the surroundings of Mo–Si–B ternary liquid phase at high temperature. Mechanical properties were dependent on grain size and aspect ratio of the ZrB₂ platelets. The rotation and realignment of the platelet ZrB₂ grains under hot pressing led to a partially textured microstructure, which showed anisotropic mechanical properties on different directions of the as-sintered samples. A roadmap of the reaction process, microstructure evolution and texture formation was given to describe the preparation of partially textured ZrB₂–MoSi₂ composites by reactive hot pressing.     

ABS阻燃与抑烟性的研究

对ABS树脂的阻燃、抑烟性等性能进行了研究和探讨。实验结果表明,采用共混、添加复合阻燃剂、抑烟剂的方法可以有效地获得阻燃、抑烟性及其他性能皆优的ABS树脂体系。     

Kinetics of the peracetic acid decomposition: Part II: pH effect and alkaline hydrolysis

The effect of pH on the decomposition of peracetic acid in an aqueous solution was studied. It was found that three potential reactions, namely i) the spontaneous decomposition, ii) the hydrolysis and iii) the transition metal catalysed decomposition, are responsible for the consumption of peracetic acid. The spontaneous decomposition reaches its maximum at pH 8.2, while both the hydrolysis and metal ion catalysed decomposition increase as the pH increases. At pH 10.5 and higher, the hydrolysis becomes dominant when the metal ion catalysed decomposition is minimized by the addition of DTMPA. The kinetics of the peracetic acid hydrolysis was developed, which can very well predict the development of peracetic acid and hydrogen peroxide during the decomposition reaction.     

Mechanical and anticorrosion properties of furan/epoxy‐based basalt fiber‐reinforced composites

A furan/epoxy blend applicable to composite manufacture was studied and corresponding basalt fiber‐reinforced composites were prepared. The processability, mechanical properties, and reasons for the improved mechanical properties of this blend were investigated by rheology machine, mechanical testing machine, and scanning electron microscopy. With excellent processability, furan/epoxy was suitable for manufacturing composites. Furan/epoxy with the ratio of 5/5 showed the best properties, and the impact strength, flexural strength and flexural modulus were 15.43 kJ/m², 102.81 MPa, and 3209.40 MPa, respectively. The river‐like fracture surface of the furan/epoxy system was well consistent with the mechanical properties. The mechanical and anti‐corrosive properties of basalt fiber‐reinforced furan/epoxy composites were also studied. The mechanical properties of composites changed the same as those of furan/epoxy matrix did. Furan resin effectively improved the anti‐acid but not anti‐alkali property of composites, probably because furan could be cured in acidic condition and basalt fiber was resistant to acid and alkali. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44799.     

Composition and characteristics of primary combustion products of boron-based propellants

Primary combustion products of boron-based propellants are incomplete combustion products that are emitted from the gas generator of a solid ducted rocket. Studying the composition of primary combustion products provides valuable information about the primary combustion process and also helps to better understand the secondary combustion process. The particle size of the primary combustion products is analyzed by a laser particle size analyzer. The qualitative analysis of the sample composition is performed by using x-ray diffraction, x-ray photoelectron spectroscopy, and thermogravimetry–differential scanning calorimetry experiments. Based on these results, an integrated quantitative analysis of the sample composition is conducted. The quantitative analysis methods include tube furnace heating, ion chromatography, infrared spectroscopy, and inductively coupled plasma chromatography. In addition, scanning electron microscopy and energy dispersive spectrometry are also used to analyze the micro-morphology and distribution of different components in the sample. The primary combustion products mainly contain B, C, B _m C _n , H₃BO₃, B₂O₃, BN, Mg, MgCl₂, and NH₄Cl. B _m C _n (22–24%), H₃BO₃ (20%), and B (16.8%) are the three major components, while B _m C _n , B, and C (9.8–11.8%) are the three combustible components present in the highest amounts. The oxidant NH₄ClO₄ is completely consumed during the primary combustion, while the metal additive Mg does not show much reactivity. The micro-morphology and distribution of B _m C _n , H₃BO₃ (or B₂O₃), B, Mg, and C in the sample are investigated. Some components in the primary combustion products are found to be agglomerated, while some components are dispersed. Large particles in the sample mainly include B and Mg, while B _m C _n , H₃BO₃ (or B₂O₃), and C particles are small. In general, the combustion completeness of the primary combustion products is rather low. Therefore, better understanding and controlling of the secondary combustion process is very important to improve the performance of B-based propellants.     

Structure and conductivity of carbon materials produced from coal pitch with carbon additives

Attention focuses on the structure and electrical conductivity of carbon materials obtained by the carbonization of coal pitch in the presence of additives (nanotubes, graphite foam, and graphite), at temperatures up to 900°C. In some cases, ultrasonic mixing is used on introducing the additives to the pitch. Ultrasonic mixing is found to change the properties of the pitch and affect the properties of the carbon material produced. In particular, the proportion of carbon with an ordered structure is increased; the electrical conductivity at temperatures below 40 K is increased; and the energy barrier E _g between individual crystallites is reduced almost fourfold. At higher temperatures, the electrical conductivity is practically unchanged. Adding nanotubes to the pitch reduces the content of ordered carbon structures in the carbon material produced and lowers its electrical conductivity. Adding graphite foam and graphite to the pitch increases the order and electrical conductivity of the carbon material produced and lowers the energy barrier E _g between individual crystallites in the samples. The electrical conductivity of all the carbon materials below 16 K is described by the characteristic formula for fluctuation-induced tunneling conduction. This indicates that contacts between individual crystallites are mainly responsible for the electrical conductivity.     

Experimental study of the relationship between separation performance and lengths of vortex finder of a novel de-foulant hydrocyclone with continuous underflow and reflux function

To solve the blockage and defer the fouling of sewage heat exchanger, a novel de-foulant hydrocyclone with continuous underflow and reflux function was proposed. Experimental results demonstrated that the novel hydrocyclone had a remarkable behavior on separating the sand (75–250 μm) and foulant (<4 mm). The continuous underflow and reflux function could significantly improve the separation efficiency by relieving the particle re-entrainment and eliminating the air core without increasing energy consumption (<17 kPa) and split ratio (<10%) considerably. Besides, the range of optimum vortex finder length was proportional to the particle density.