Preparation and properties of high-energy-density aluminum/boroncontaining gelled fuels

Energetic nanofluid fuel has caught the attention of the field of aerospace liquid propellant for its high energy density(HED), but it suffers from the inevitable solid-liquid phase separation problem. To resolve this problem, herein we synthesized the high-Al-/B-containing(up to 30%(mass)) HED gelled fuels, with low-molecular-mass organic gellant Z, which show high net heat of combustion(NHOC), density, storage stability, and thixotropic properties. The characterizations indicate that the application of energetic particles to the gelled fuels obviously destroys their fibrous network structures but can provide the new particle-gellant gelation microstructures, resulting in the comparable stability between 1.0%(mass) Z/JP-10 + 30%(mass) Al or B and pure JP-10 gelled fuel. Moreover, the gelled fuels with high-content Al or B exhibit high shear-thinning property, recovery capability, and mechanical strength, which are favorable for their storage and utilization. Importantly, the prepared 1.0%(mass) Z/JP-10 + 30%(mass) B(or 1.0%(mass) Z/JP-10 + 30%(mass) Al) shows the density and NHOC 1.27 times(1.30) and 1.43 times(1.21)higher than pure JP-10, respectively. This work provides a facile and valid approach to the manufacturing of HED gelled fuels with high content of energetic particles for gel propellants.

A Comparative Study of Boron and Phosphorus Doping Effects in SiC: H Films Prepared by ECR-CVD

Hydrogenated silicon carbide films (SiC:H) were deposited using the electron cyclotron resonance chemical vapour deposition (ECR-CVD) technique from a mixture of methane, silane and hydrogen, and using diborane and phosphine as doping gases. The effects of changes in the microwave power on the deposition rate and optical bandgap were investigated, and variations in the photoand dark-conductivities and activation energy were studied in conjunction with film analysis using the Raman scattering technique. In the case of boron-doped samples, the conductivity increased rapidly to a maximum, followed by rapid reduction at high microwave power. The ratio of the photo- to dark-conductivity (σph/σd) peaked at microwave power of ~600 W. Under conditions of high microwave power, Raman scattering analysis showed evidence of the formation and increase in the silicon microcrystalline and diamond-like phases in the films, the former of which could account for the rapid increase and the latter the subsequent decrease in the conductivity.In the case of phosphorusdoped SiC:H samples, it was found that increase in the microwave power has the effect of enhancing the formation of the silicon microcrystalline phase in the films which occurred in correspondence to a rapid increase in the conductivity and reduction in the activation energy The conductivity increase stabilised in samples deposited at microwave power exceeding 500 W probably as a result of dopant saturation. Results from Raman scattering measurements also showed that phosphorus doping had the effect of enhancing the formation of the silicon microcrystals in the film whereas the presence of boron had the effect of preserving the amorphous structure.

Structural, electronic, and magnetic properties of boron cluster anions doped with aluminum:B_nAl^-(2 ≤ n ≤ 9)

The geometrical structures, relative stabilities, electronic and magnetic properties of small BnAl-（2〈n〈9）clusters are systematicalyy investigated by using the first-principles density functional theory. The results show that the A1 atom prefers to reside either on the outer-side or above the surface, but not in the centre of the clusters in all of the most stable BnAl-（2〈n〈9） isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters. All the results of the analysis for the fragmentation energies, the second-order difference of energies, and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B4A1- and B8A1- clusters each have a higher relative stability. Especially, the BsA1-cluster has the most enhanced chemical stability. Furthermore, both the local magnetic moments and the total magnetic moments display a pronounced oddeven oscillation with the number of boron atoms, and the magnetic effects arise mainly from the boron atoms except for the B7A1- and BgA1- clusters.

Reaction of boron to transition metal impurities and its effect on conductivity of aluminum

The effects of boron on electrical conductivity of aluminum and the action mechanism have been investigated. The results indicate that, by combining with the trace amounts of transition elements Ti, V and Zr to form two kinds of insoluble borides, boron can significantly improve the electrical conductivity of commercial aluminum. One of the borides contains 54.42% B, 13.70% Al and 23.39%(mole fraction) transition elements (including Ti, V, Zr and Fe) and is in the form of fine particles. The other one, in hexagonal shape, contains 78.59% B, 14.97% Al and 2.56%(mole fraction) transition elements (including Ti, V and Fe). Neither Cr nor Mn is found in these borides. The conversion of some transition metal impurities from solid solution state to the boride precipitates form leads to a decrease in electrical resistivity, and this decrease constitutes 86.2% of that can be achieved by complete removal of transition element impurities from aluminum melts.

Effect of trace boron on grain refinement of commercially pure aluminum by Al-5Ti-1B

The effect of boron content on grain refinement of commercially pure aluminum by Al-5Ti-1B was quantitatively assessed.When the boron content is less than 0.03 wt.%,the refining performance of Al-5Ti-1B gradually is weakened as the boron content increases,which is attributed to the reaction of boron with the Al_(3)Ti interlayer on TiB_(2)and the consumption of solute Ti.On the contrary,when the boron content exceeds 0.03 wt.%,the refining performance of Al-5Ti-1B gradually recovers with increasing boron content,which is related to the formation of primary AlB_(2)particles that provide additional nucleant substrates.

Study on Processing Conditions of Aluminum Matrix Composites Reinforced with Boron Carbide Particles

Different pre-heating of boron carbide particles for reinforcement and different processing conditions were studied in this work. Being one of the most cost-effective industrial methods, conventional melt stir-casting route was utilized.Result showed that the boron carbide particles distributed well for a suitable pre-heating temperature and processed in air.No reaction product was found at the A1-B4C interfaces at the resolution limit of SEM used in that way.

Flow characteristics of aluminum coated boron steel in hot press forming

The flow characteristics of aluminum coated boron steel in hot press forming were investigated.Furthermore,the effects of aluminum coated layer on press forming were analyzed during deep drawing.The results show that aluminum coated boron steel exhibits a high sensitivity on temperature and strain rate.Aluminum coating layer appears in surface flaking in a temperature range of 700-800 ℃,but smooth surface is formed above 900 ℃.

Boron nitride microribbons strengthened and toughened alumina composite ceramics with excellent mechanical,dielectric,and thermal conductivity properties

Aluminum oxide(Al_(2)O_(3))ceramics have been widely utilized as circuit substrates owing to their exceptional performance.In this study,boron nitride microribbon(BNMR)/Al_(2)O_(3)composite ceramics are prepared using spark plasma sintering(SPS).This study examines the effect of varying the amount of toughened phase BNMR on the density,mechanical properties,dielectric constant,and thermal conductivity of BNMR/Al_(2)O_(3)composite ceramics while also exploring the mechanisms behind the toughening and increased thermal conductivity of the fabricated ceramics.The results showed that for a BNMR content of 5 wt%,BNMR/Al_(2)O_(3)composite ceramics displayed more enhanced characteristics than pure Al_(2)O_(3)ceramics.In particular,the relative density,hardness,fracture toughness,and bending strength were 99.95%±0.025%,34.11±1.5 GPa,5.42±0.21 MPa·m^(1/2),and 375±2.5 MPa,respectively.These values represent increases of 0.76%,70%,35%,and 25%,respectively,compared with the corresponding values for pure Al_(2)O_(3)ceramics.Furthermore,during the SPS process,BNMRs are subjected to high temperatures and pressures,resulting in the bending and deformation of the Al_(2)O_(3)matrix;this leads to the formation of special thermal pathways within it.The dielectric constant of the composite ceramics decreased by 25.6%,whereas the thermal conductivity increased by 45.6%compared with that of the pure Al_(2)O_(3)ceramics.The results of this study provide valuable insights into ways of enhancing the performance of Al_(2)O_(3)-based ceramic substrates by incorporating novel BNMRs as a second phase.These improvements are significant for potential applications in circuit substrates and related fields that require high-performance materials with improved mechanical properties and thermal conductivities.

Determination of Boron Trifluoride in Boron Trifluoride Complex by Fluoride Ion Selective Electrode

A method was proposed to determine boron trifluoride in boron trifluoride complex using fluoride ion selective electrode(ISE). Hydroxide was chosen to mask aluminum for the determination of 0.01—0.1 mol/L of fluoride. The simulation indicated that the permissible aluminum masked at a certain p H value was limited and hardly related to F-concentration and boric acid. It is better to control p H value below 11.5 and the aluminum concentration within 0.025 mol/L to minimize the interference of hydroxide to the fluoride ISE. The decomposition conditions of boron trifluoride by aluminum chloride were investigated. It is found that the F-detection ratio will approach 1.0 if the Al/F molar ratio is 0.3—0.7 and aluminum concentration is no more than 0.02 mol/L when heated at 80 ℃ for 10 min. In one word, hydroxide is quite fit to mask aluminum for samples which contain high content of fluoride and aluminum and the BF3 content can be successfully determined by this method.

Preparation of quasi-isotropic thermal conductive composites by interconnecting spherical alumina and 2D boron nitride flakes

Achieving thermal management composite material with isotropic thermal dissipation property by using an environmentally friendly and efficient method is one of the most challenging techniques as a traditional approach tending to form a horizontally arranged network within the polymer matrix or the preparation steps which are unduly cumbersome.What presented here is a closestack thermally conductive three-dimensional(3D)hybrid network structure prepared by a simple and green strategy that intercalating the modified aluminum oxide(m-Al_(2)O_(3))spheres of different sizes into the modified two-dimensional(2D)boron nitride(m-h-BN)flakes.An effective 3D network is created by the multi-dimensional fillers through volume exclusion and synergistic effects.The m-h-BN flakes facilitate in-plane heat transfer,while the variously sized m-Al_(2)O_(3)spheres insert into the gaps between adjacent m-h-BN flakes,which is conducive to the heat transfer in the out-of-plane direction.Additionally,strong interactions between the m-Al_(2)O_(3)and m-h-BN promote the effective heat flux inside the 3D hybrid network structure.The 3D hybrid composite displays favorable quasi-isotropic heat dissipation property(through-plane thermal conductivity of 2.2 W·m^(-1)·K^(-1)and in-plane thermal conductivity of 11.6 W·m^(-1)·K^(-1))in comparison with the single-filler composites.Furthermore,the hybrid-filler composite has excellent mechanical properties and thermal stability.The efficient heat dissipation capacity of the hybrid composite is further confirmed by a finite element simulation,which indicates that the sphere-flake hybrid structure possesses a higher thermal conductivity and faster thermal response performance than the single-filler system.The composite material has great potential in meeting the needs of emerging and advancing power systems.

Re-recognition of the Effects of Phosphorus and Boron on the γ’’ and γ’ Phases in IN718 Alloy

The effects of P and B on the matrix strength and precipitations of γ’ and γ’’ phases in the grain interior were re-recognized in this study. The combination addition of P and B markedly accelerated the precipitations of γ’ and γ’’ phases and strengthened the matrix of IN718 alloy when air-cooled from high temperature, while made no difference when waterquenched from high temperature. The effect of single addition of P on the precipitations of γ’’ and γ’ phases was the same with that of the combination addition of P and B, while the single addition of B had no effect on the precipitations of the two phases. Therefore, it was P rather than B which accelerated the precipitations of γ’ and γ’’ phases. P could take part in the precipitations of γ’ and γ’’ phases, which was revealed by electrochemical extraction and quantitative analysis of chemical composition. It also revealed that P atoms were dissolved in the c matrix to a relatively high degree at the temperature that γ’ and γ’’ phases began to precipitate, and consequently the precipitations of γ’ and γ’’ phases were accelerated. The first-principle calculation indicated that P decreased the formation enthalpies of γ’ and γ’’ phases when it occupied the Ni lattice sites in the two phases, which explained the effect of P on the γ’ and γ’’ phases.

Involvement of Antioxidative Defense System in Rice Seedlings Exposed to Aluminum Toxicity and Phosphorus Deficiency

Plants growing in acid soils may suffer both phosphorus （P） deficiency and aluminum （Al） toxicity.Hydroponic experiments were undertaken to assess the single and combination effects of Al toxicity and low P stress on seedling growth,chlorophyll and proline contents,antioxidative response and lipid peroxidation of two rice genotypes （Yongyou 8 and Xiushui 132） differing in Al tolerance.Al toxicity and P deficiency both inhibited rice seedling growth.The development of toxic symptoms was characterized by reduced chlorophyll content,increased proline and malondialdehyde contents in both roots and leaves,and increased peroxidase and superoxide dismutase activities in roots,but decreased in leaves.The stress condition induced more severe growth inhibition and oxidative stress in Yongyou 8,and Xiushui 132 showed higher tolerance to both Al toxicity and P deficiency.P deficiency aggravated Al toxicity to plant growth and induced more severe lipid peroxidation.

Comparison of Three Aluminum Coagulants for Phosphorus Removal

That phosphorus has been removed more from water in purification process can result in higher grade of biological stability of the effluent tap water, especially for the water plant when using surface water source. This study conducted the experiments of phosphorus removal by three coagulants including aluminum chloride, aluminum sulfate and poly aluminum chloride. The results indicated that the poly aluminum chloride is the preferred one that could remove phosphorus up to 80%, followed by aluminum chloride and aluminum sulfate. The lowest proportion of aluminum quality to phosphorus quality is 63 as using poly aluminum chloride, followed by aluminum chloride and aluminum sulfate. It is suggested that the poly aluminum chloride should be the best option to remove phosphorus in water plant.

Reactive Stream Stabilization for Minimizing Transport of Phosphorus and Nitrogen from Agricultural Landscapes

A reactive stream stabilization (RS2) system based on aluminum as the adsorbent and garden mulch as the organic matter source was designed to minimize release of agricultural nonpoint source pollutants and installed along the bank of the Little Bogue Creek, MS in 2008. The scope of this research was to design, install and assess the performance of a field scale RS2 structure based on results from previous lab scale studies. Concentrations of alum and total organic carbon (TOC) in the RS2 test barrier and surrounding area were measured to evaluate design parameters of RS2 and the removal effectiveness was examined from soils and monitoring wells that were sampled in 2009. The mean concentration of Al from the reactive barrier was 2.1 mg/g and organic matter from the monitoring wells was 4.7 mg/L, values significantly greater than the surrounding area (p < 0.05). Soil Mehlich-3 P and total phosphorus (TP) were decreased by 55% and 30%, and 40% of the TN and 51% of the nitrate in the ground water were removed through the RS2. The design objectives have been satisfied with the installed RS2 system and the initial sampling data shows effective nutrient removal.

Ab Initio Study of Aluminum-Phosphorus Co-doped Graphene

In the present work it is studied the phosphorus-aluminum co-doping effect on the electronic and structural graphene properties using ab initio calculations in the framework of DFT （density functional theory）. The doping of graphene with substituent heteroatoms can modify the band structures as well as the electron transfer, improving the electronic performance that could enhance the sensing ability in gas sensor devices. The incorporation of heteroatoms in the graphene monolayer alters the unit cell. The alteration degree depends on the dopant concentration. Furthermore, the electronic properties were modified by opening the gap up to 0.61 eV produced by the combination of phosphorus and aluminum as dopants. The dopant concentration can be controlled, which causes different degrees of semiconductor behavior on the co-doped graphene.

氮化硼颗粒增强铝基复合材料研究进展

铝基复合材料作为一种轻质高强度材料具有广泛的应用前景。本文综述了当前氮化硼纳米颗粒增强铝基复合材料的研究进展,通过液相法和固相法的分类详细介绍了搅拌铸造、超声辅助铸造、选择性激光熔化(SLM)、热挤压等制备氮化硼纳米颗粒增强铝基复合材料的方法,总结了所制备复合材料的力学性能和功能特性。最后指出了不同制备方法存在的问题,并且对氮化硼纳米颗粒增强铝基复合材料的未来进行了展望。

硼对铝胁迫下杉木生长、生理和光合特性的影响

为了研究硼对铝胁迫下杉木生长、生理和光合特性的影响,揭示硼介导的杉木耐铝调控机制,为进一步利用养分管理手段减轻杉木铝毒害提供参考,以3月龄幼苗为材料,共设置4个处理,对照(CK)、缺硼(-B)、缺硼加铝(-B+Al)和加硼加铝(+B+Al),分析不同处理间杉木生长、叶片光合和抗性生理指标的差异。结果表明:(1)与CK相比,胁迫处理均能显著抑制苗高生长,苗高降幅介于31.83%~55.56%之间,而且铝胁迫下,加硼(+B+Al)能显著缓解缺硼(-B+Al)引起的苗高生长、叶片丙二醛(MDA)、过氧化氢(H_(2)O_(2))和光合色素含量下降;与-B+Al处理相比,+B+Al处理的苗高、MDA、H_(2)O_(2)、叶绿素和类胡萝卜素含量分别增加48.02%、24.18%、16.39%、17.16%和17.78%。(2)与CK相比,不同胁迫处理显著提高叶片超氧化物歧化酶、过氧化物酶、过氧化氢酶和抗坏血酸过氧化物酶活性,其活性大小均表现为:+B+Al>-B+Al>-B>CK,增幅分别介于17.10%~128.87%、15.19%~152.10%、37.39%~412.11%和44.07%~271.66%之间。(3)杉木叶片净光合速率、水分利用效率、最大荧光、可变荧光、PSⅡ潜在光化学活性、PSⅡ最大光化学效率、光化学淬灭系数和实际最大量子产额在不同胁迫处理下较CK均出现不同程度下降,降幅分别介于51.06%~59.50%、2.43%~16.71%、7.07%~20.45%、7.80%~29.93%、27.16%~54.07%、2.53%~13.53%、4.66%~12.61%和4.25%~13.77%之间,而且-B+Al处理的降幅显著大于+B+Al处理。可见在铝胁迫下,与缺硼相比,外源加硼处理通过提高叶片抗氧化酶活性,降低叶片H_(2)O_(2)和MDA的积累,减轻H_(2)O_(2)诱导的叶片氧化损伤和光合色素的下降,提高叶片光合效率和光能利用率,促进碳同化产物合成,从而缓解铝胁迫引起的对生长的抑制。

Processing of nanostructured metallic matrix composites by a modified accumulative roll bonding method with structural and mechanical considerations

Particulate reinforced metallic matrix composites have attracted considerable attention due to their lightweight, high strength, high specific modulus, and good wear resistance. A1/B4C composite strips were produced in this work by a modified accumulative roll bonding process where the strips were rotated 90° around the normal direction between successive passes. Transmission electron microscopy and X-ray diffraction analyses reveal the development of nanostructures in the Al matrix after seven passes. It is found that the B4C reinforcement distribution in the matrix is improved by progression of the process. Additionally, the tensile yield strength and elongation of the processed materials are increased with the increase of passes.

高频感应燃烧红外吸收光谱法测定碳化硼增强铝基复合材料中碳

碳化硼增强铝基复合材料是一种新型的核电站乏燃料储存框架材料,准确测定其中的碳含量有利于从源头上指导复合材料的质量控制。通过对样品称样量、助熔剂种类、用量及加入顺序等关键参数考察,确定了最佳工作条件:样品量为0.025~0.050 g,助熔剂组合为0.4 g铁+0.2 g锡+1.5 g钨。采用合金钢、生铁和高碳铬铁标准样品校准碳硫分析仪,建立了高频感应燃烧红外吸收光谱法测定碳化硼增强铝基复合材料中碳含量的分析方法。通过对试样测定的精密度和加标回收率实验验证,证明方法用于碳化硼增强铝基复合材料中碳含量的分析切实可行。方法在含量为0.006%~9%线性良好,实际样品中碳测定结果的精密度(RSD,n=6)为0.50%~1.3%,加标回收率为93.0%~100%。方法满足碳化硼增强铝基复合材料中碳含量的快速准确检测需求。

表面负载金属纳米粒子的氮化物陶瓷导热填料的制备与表征

采用直接混合加热法制备氮化物陶瓷复合导热填料,这是一种可以批量生产,并且不使用溶剂、对环境友好的制备方法。通过扫描电镜、X射线衍射仪、TCI导热仪研究不同金属纳米粒子(镍、钴和银)在氮化物(氮化铝、氮化硼)上的负载情况以及负载量,并考察了复合陶瓷导热填料对聚乙烯醇基复合导热膜导热性能的影响。结果表明,金属纳米粒子成功负载到氮化物上而不改变氮化物的晶体结构。且负载金属粒子的尺寸随乙酸盐含量的增加而增大。另外,负载金属粒子的陶瓷导热填料能有效提高聚乙烯醇基复合导热膜导热能力,Ag/AlN-0.05导热膜的导热率能达到0.752 W/(m·K)。