组元配比对球磨固态燃烧式反应和扩散型反应的影响

采用搅拌式高能球磨机研究了不同铝含量的Al/CuO球磨固态燃烧反应和Al-Cu及Al-Cu-Al2O3扩散型反应。结果表明：理想配比的Al/CuO的反应孕育期最短,偏离这一配比,孕育期延长,反应由整体燃烧式逐渐过渡到渐进燃烧式完成;球磨强度扩大以燃烧式进行的组元配比范围;当铝含量超过理想配比中的比例,随Al含量增加,反应由单一的还原反应向还原＋合成复合反应模式转化,反应产物为平衡组织,依次为Cu Al2O3、CuoAl4 Al2O3、CuAl2 Al2O3、Al(Cu) Al2O3;而球磨Al-Cu和Al-Cu-Al2O3体系的反应以扩散方式进行,产物是非平衡组织。     

Effect of swirl flow on an atmospheric inductively coupled plasma supersonic jet

Recently supersonic jets extracted from atmospheric inductively coupled plasmas (ICP) have attracted a lot of attention. Usually atmospheric ICP generators have employed swirl flow injection in order to stabilize the plasma. However the effect of the swirl flow injection on the performance of atmospheric ICP generators has not been understood enough. This work found that the injection of the swirl flow deteriorates the performance. First we conducted the total enthalpy measurement based on the sonic flow method and evaluated the averaged specific enthalpy. Then laser absorption spectroscopy was employed in order to measure the temperature and the velocity of the extracted supersonic jet. The both measurements observed that the specific enthalpy of the jets decreased with the increase in the swirl flow fraction. This would be because the swirl flow affected the shape and the position of the plasma significantly.     

MHD 3D free convective flow of nanofluid over an exponentially stretching sheet with chemical reaction

This paper deals with a problem where the effect of variable magnetic field and chemical reaction on free convective flow of an electrically conducting incompressible water based nanofluid over an exponentially stretching sheet has been investigated. In the present study, Buongiorno model associated with Brownian motion and thermophoretic diffusion is employed to describe the heat transfer enhancement of nanofluids. Some suitable similarity transformations reduced the governing boundary layer non-linear partial differential equations into a set of ordinary non-linear differential equations. The transformed equations are then solved numerically using fourth order Runga-Kutta method along with Shooting technique. The major outcomes of the present study is that the magnetic field impedes the fluid motion while thermal as well as mass buoyancy forces accelerate it, the thermophoretic diffusion enhances dimensionless fluid temperature as well as concentration leading to thicker thermal and concentration boundary layers. On the other hand, concentration exponent, Brownian motion parameter and chemical reaction parameter exhibit reverse trend on temperature and concentration. In addition, the presence of magnetic field under the influence of thermal as well as mass buoyancies supports to reduce the rate of heat transfer as well as wall shear stress while the first order chemical reaction develops a thinner concentration boundary layer.     

Effect of liquid and air swirl strength and relative rotational direction on the instability of an annular liquid sheet

Summary Instability of a swirling annular liquid sheet in swirling inner and outer air streams has been investigated by a temporal linear stability analysis. The effects of the swirling and axial motion of the liquid and the air streams, as well as the effects of relative inner and outer air swirl orientation with respect to the liquid swirl direction on the instability have been investigated. Results show that for a non-swirling liquid sheet axial inner air stream is more effective than axial outer air stream in enhancing the sheet instability. This is opposite of a swirling liquid sheet where axial outer air is more effective in promoting sheet instability compared to axially moving inner air stream. The liquid swirl has a destabilizing effect at the outer interface but has a stabilizing effect at the inner interface. At high liquid swirl Weber number, the outer air (with axial and swirl velocity components) is more effective in enhancing sheet instability compared to the inner air (with axial and swirl velocity components). To understand the effect of air swirl orientation with respect to liquid swirl direction, four possible combinations with both swirling air streams with respect to the liquid swirl direction have been considered. Results show that at high liquid swirl Weber number a combination of counter-rotating-inner air stream and co-rotating-outer air stream has the largest most unstable wave number. However, at low liquid swirl, co-inner/counter-outer combination has the largest most unstable wave number. The combination of inner and the outer air stream co-rotating with the liquid has the highest growth rate. In many combustion applications, the liquid sheet is injected in high pressure environment where the effect of high ambient pressure results in increased aerodynamic interaction due to high air density. Hence the effect of high ambient pressure is studied in terms of the dimensionless parameter of air-to-liquid density ratio. Results show significantly higher disturbance growth rates at high air pressure. However, the qualitative sheet stability behavior is similar to that at atmospheric pressure.     

镁氢化和镁镍共晶反应对氢化燃烧合成产物储氢性能的影响

通过改变氢化燃烧合成Mg2Ni中镁氢化反应的保温时间,以及镁镍合成反应温度和合成保温时间,来研究镁氢化反应、镁镍燃烧合成反应对产物Mg2Ni储氢性能的影响。实验结果表明,镁氢化反应保温120min时,产物的首次吸氢动力学性能变差;合成温度的提高有利于吸氢量的提高（合成温度850K时,吸氢量最大可达3．36wt％）;保温时间的延长对于产物吸氢量的影响随合成温度的差异而表现不同。     

The Use of a Laser Doppler Anemometer to Investigate Vortex Structures in Highly Turbulent Swirl Flow When There Are Predominant Fluctuations

The modeling and experimental investigation of large-scale vortex structures at the exit of a model burner of a low-emission combustion chamber when there is artificial generation of air flow-rate fluctuations are considered. A method for the diagnostics of vortex structures is developed using a two-component laser Doppler anemometer, which enables vortex structures in the jet mixing zone to be distinguished. The intensity of the swirling of the flow is calculated. A simplified rapid method of vortex-structure diagnostics is proposed, which significantly reduces the time of the experiment and the number of measurements required.     

反应温度对碳纳米管的影响

本文利用化学气相沉积( CVD)法,以乙烯为碳源气体,二茂铁为催化剂,在二氧化硅上制备出一系列碳纳米管,并通过拉曼光谱和扫描电子显微镜( SEM)对其形貌、结构和组分进行表征,分析反应温度对碳纳米管的影响.研究发现:当反应温度为860℃时,有均匀的碳纳米管薄膜生成,其管径和长度分别达到104 nm和95 μm,同时结构缺陷少,非碳管杂质较少,纯度较高.     

Effect of reaction conditions on silanisation of sepiolite nanoparticles

The study provides insights into the silanisation process of sepiolite nanoparticles. The nanoparticles were modified applying acidic and basic silanisation methods using Methacryloxypropyltrimethoxysilane (γ-MPS) as coupling agent. The silanisation reaction was performed in the following conditions: (1) acidic ethanol–water solution with a pH of 5 and (2) basic cyclohexane with a pH of 9. The influence of the conditions on the surface chemistry of modified particles was then investigated. To characterise the surface of sepiolite nanoparticles, analytical methods such as Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, X-Ray diffraction (XRD), scanning electron microscopy (SEM), and zeta potential analyses were applied. In addition, the colloidal stability of the modified nanoparticles was studied using a separation analysis. According to XRD and SEM, the basal interlayer distance of pristine sepiolite is not altered by silanisation process. TGA reveals that the grafting percentage of organosilane synthesised by basic method is approximately two times of that of acidic method. The silane coverage on the surface of the sepiolite and the per cent of hydroxyl groups covalently bound to γ-MPS were calculated. Separation analysis indicates decline in dispersion stability of the modified nanoparticles in ethanol due to increment of their hydrophobicity.     

温度对固相聚合反应盐酸掺杂聚苯胺的影响

利用固相聚合反应法制备了盐酸掺杂聚苯胺,并以红外光谱(FT-IR),电子扫描显微镜(SEM)、X射线衍射(XRD)、循环伏安(cyclic voltametry)等测试,对聚苯胺进行了表征。结果表明,固相反应法合成的聚苯胺颗粒要比液相法合成的聚笨胺颗粒相对小,并表现出良好的结晶性,而低温(0℃)固相聚合反应法制备的盐酸掺杂聚苯胺要比室温固相聚合反应法制备的聚苯胺颗粒分布均匀,晶化率好,还具有良好的电导率。循环伏安测试表明,固相反应法合成的聚苯胺有较好的电化学活性。     

黏结剂含量对含铝炸药燃烧能量的影响

利用小型密闭燃烧装置分别测试了两种黏结剂含量的RDX基和HMX基含铝炸药燃烧产生的准静态压力,得到4种含铝炸药燃烧能量的关系。利用气相色谱仪检测出部分气相燃烧产物的含量,通过化学计算探讨了4种含铝炸药的铝粉反应率,并用扫描电镜和能谱(EDS)对4种炸药的微观形貌和表面元素进行表征。结果表明,含铝炸药中黏结剂含量增加会使炸药与铝粉颗粒的表面包覆层变厚,更加阻碍铝粉在燃烧初期的吸热,从而在一定程度上导致铝粉反应率减小,并降低炸药燃烧总能量。     

Effect of temperature schedule on the particle size of barium titanate during solid-state reaction

Nano-sized BaTiO₃ particles were synthesized by a solid-state reaction in air using a 2-step heat treatment process. The dependence of the particle size and tetragonality (=c/a) on the temperature schedule was investigated. The temperature was held for 10 h at an intermediate temperature before heating to the target temperature of 1000°C for 1 h. Although more heat was consumed, the powders synthesized by the 2-step heat treatment method showed a much smaller particle size with higher tetragonality than those produced by direct heating. For example, the mean particle size was <100 nm at a holding temperature ranging from 500-700 °C, while it was 246 nm for direct heating to the same target temperature of 1000 °C. This was explained by the enhanced nucleation rate during temperature holding stage based on the TG/DTA and high temperature XRD results.     

涡流板制冷特性的实验研究

引进集成整合的观念,研制成新的制冷装置（即涡流板）,并利用涡流板制冷实验系统,以压缩空气为介质,对涡流板的制冷特性进行实验研究,获得了涡流板的制冷性能参数与入口气流参数及冷流比之间的关系。研究结果表明：涡流板同单管涡流管相比具有相同的制冷,洼能,为涡流板进一步研究奠定了基础。     

Effect of the geometric parameters on a flexible fiber motion in a tangentially injected divergent swirling tube flow

A particle-level simulation method is employed to study the effects of some geometric parameters, such as the injector diameter, the injection angle and position on fiber motions in a 3D compressible decaying swirling flow in a divergent tube. The flexibility of the fiber is defined by the bending and twisting displacements. The fiber-wall collision and compressible effects are considered here. The fiber with different complex configurations moves as spiral orbit with stream-wise direction. With the increase in the injector diameter, the deformation degree of the fiber increases. For a larger injector diameter, the fiber appears to be closed coil loops or asymmetric S-loopturn. The larger the injection angle is, the earlier the fiber starts to swirl and the larger the number of ‘turn’ is. The complex coiled configurations with entanglement can be observed under small injection angle. Especially, a ‘zigzag’ configuration is formed for larger injection angle and injection position.     

纳米硫化锌的制备及助燃性能

以NaCl,HOCH2CH2OH和（CHa）2CHOH为分散剂,用固相法在室温合成了纳米硫化锌,用紫外吸收光谱,红外光谱和氮气吸附等方法对纳米硫化锌粉体的结构,组成,平均粒径和比表面积等进行了表征,研究了分散剂和温度等因素对纳米硫化锌粉体的性能以及纳米硫化锌对重油-煤-水三元混合流体燃烧性能的影响．结果表明：加入适量的分散剂和表面活性剂,在室温用固相法能够制备出分散性好的单一立方相纳米硫化锌．在其紫外吸收光谱中纳米硫化锌吸收峰蓝移,并具有红外透明性．纳米硫化锌作为助燃剂添加到重油-煤-水三元混合流体燃料燃中,能够明显提高重油-煤-水三元混合流体的燃烧性能.     

Effect of size of copper nanoparticles on its catalytic behaviour in Ullman reaction

The condensation of iodobenzene to biphenyl is an industrially important reaction due to its significant role in organic synthesis as drug intermediates. The reaction takes place in the presence of copper powder as catalyst. We have shown in this paper that the size of the copper nanoparticles as well as its exposed surface area is responsible for the yield of chemical reaction. The uncapped copper powder showed a 43% conversion of iodobenzene to biphenyl in 5 h under our experimental conditions. Same amount of copper nanoparticles (size, ∼66 nm diameter) prepared by citrate capping showed 88% conversion of iodobenzene to biphenyl, which increased to about 95% when 8 nm diameter capped copper nanoparticles are used. Surprisingly, 5 nm size copper nanoparticles showed no change in the yield of about 95%.     

Numerical simulation of soot formation in pulverized coal combustion with detailed chemical reaction mechanism

A two-dimensional unsteady numerical simulation with a detailed chemical reaction mechanism that considers 158 species and 1804 reactions is applied to pulverized coal combustion in a mixing layer and the soot formation behavior is investigated in detail. The computational conditions and ignition process are the same as those in our previous work (Muto et al., 2017). The results show that the peak of the mass density of the soot is distributed in the region where the gas temperature is higher than the unburned gas temperature of the mixture of volatile matter and air (1300–1400?K) and lower than the flame temperature (2000?K $～$). This is due to the fact that soot formation from the precursors (C₂H₂ and C₆H₆) is enhanced as the gas temperature increases, whereas the quantities of the precursors and the produced soot are reduced due to oxidation at the higher gas temperature condition that exists close to the flame. The peak value of the mass density of the soot is also distributed in the region between the peak values of the gas temperature and the probability density function of the number of coal particles.     

Effect of calcining temperature on particle size of hydroxyapatite synthesized by solid-state reaction at room temperature

Using diammonium phosphate, calcium nitrate tetrahydrate and sodium bicarbonate as raw materials, hydroxyapatite (HAP) was facilely synthesized by solid-state reaction at room temperature. The crystallinity, phase, morphology and particle size of the products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry/differential thermal analysis (TG–DTA) and particle size analyzer. The influence of calcining temperature on the crystallinity and composition of HAP phase was also investigated.     

Effect of aggregates on the diffusion properties and microstructure of cement with slurried silica fume based materials

Diffusivity of cement-based materials is an important factor regarding durability and the service life prediction of concrete structures. The present research focuses on investigating the influence of aggregates on tritiated water diffusivity of cement-based materials containing slurried silica fume. Effective diffusion coefficients of mortars with several sand volume fractions varying from 0 to 65% were determined by through-out diffusion tests. Microstructure was examined by scanning electron microscopy associated to energy dispersive spectrometry analysis, thermogravimetric analysis, water and mercury porosimetry, and BET adsorption analysis. It was found that large agglomerated particles of silica fume observed in cement paste and mortar with a low sand content (here 10%), reduce pozzolanic reactivity and thus affect the effectiveness of silica fume on the materials sustainability parameters. The clusters present in these formulations are mainly due to the interaction of silica fume with calcium hydroxide of the mixing solution and not to the initial state of the slurry, which was well stirred and whose particles size were checked before use. However, the presence of high content of aggregates (more than 30% of sand volume fraction) during mortar's mixing improves the dispersion of slurried silica fume particles and helps to ‘shear’ and break up agglomerates of silica fume providing a better homogenization of the material and improving the microstructural and diffusivity parameters. The addition of superplastizer in mortars with more than 50% sand content may also participate in dispersing silica fume.     

尿素对以硝酸铝和葡萄糖为原料合成氮化铝粉末反应过程中相变及反应速率的影响

以硝酸铝(Al(NO3)3·9H2O)和葡萄糖(C6H12O6·H2O)为原料,利用碳热还原法制备氮化铝粉末,研究了尿素对前驱物的制备及前驱物氮化反应的影响,研究发现添加尿素合成的前驱物和未添加尿素合成的前驱物在氮化反应过程中相变和反应速率存在较大差异。在没有添加尿素合成的前驱物的氮化反应过程中,出现了γ-Al2O3、α-Al2O3、AlON和AIN相,该前驱物的反应速率慢,完全氮化需要在1600℃下才能完成。对于添加尿素合成的前驱物而言,在其氮化反应过程中仅出现了γ-Al2O3和AIN相,没有α-Al2O3和AlON的生成,AIN直接由γ-Al2O3氮化生成,该前驱物的氮化反应速率快,氮化反应温度低,在1400℃下即可实现完全氮化。分析讨论了两种前驱物的氮化反应速率不同的主要原因,并利用XRD、SEM等分析方法对粉末进行了表征。     

Al-TiO2-C-Ti-Fe体系的燃烧模式研究

采用与计算机相连的快速图像采集系统对Al-TiO2-C-Ti-Fe体系的燃烧模式进行研究。结果表明，燃烧波蔓延模式随着Fe含量的增中即绝热温度的降低，由稳定的平面燃烧逐渐转化为非稳定的多点波动燃烧，然而随着Fe含量进一步增加，燃烧模式又转化为稳定的平面燃烧。