Detonation nanodiamonds as UV radiation filter

The attenuation of ultraviolet radiation (UVR) by detonation nanodiamonds (DND) can be significant, depending on the concentration, composition of DND surface, size of DND particles and content of nitrogen defects in DND. The ability of DND to attenuate efficiently UVA (320–400 nm), UVB (290–320 nm) and UVC (190–290) radiation via absorption and scattering makes them attractive broad-spectrum UV-protecting agents. The studied DND exhibited red photoluminescence presumably due to the nitrogen-vacancy centers.     

Where and when are nanodiamonds formed under explosion?

The formation of nano-sized diamonds during the detonation of a TNT/RDX explosive with 50/50 composition was investigated experimentally in situ by means of small-angle X-ray scattering using synchrotron radiation with nanosecond time resolution. No nanodiamonds were observed immediately after the detonation front, as only the nucleation of nanodiamonds takes place at this moment. The increase in small-angle X-ray scattering which was observed during 2 μs was the cause of the dynamic growth of nanodiamonds. The inclusion of a very thin shell around the explosive causes a significant increase in this time, because the kinetic of nanodiamonds growth was changed.

In another set of experiments, the nanodiamonds were artificially introduced into different explosives before explosion. The nanodiamonds were not destroyed in RDX immediately after the detonation front, but burned in an oxidants with some delay. In TNT, the nanodiamonds were not destroyed at all.     

PREPARATION AND TESTING OF CARBON/SILICALITE-1 COMPOSITE MEMBRANES

Methods for preparation of carbon/silicalite-1 composite membranes have been developed. First, silicalite-1 membranes were prepared by in-situ hydrothermal synthesis on both porous alumina and metal disks. Preparation of the carbon/silicalite-1 composite membranes was accomplished by polymerizing furfuryl alcohol on the surface of the silicalite-1 membrane, followed by carbonizing the polymer layer in an inert atmosphere at 773 K. The pure silicalite-1 membrane showed no selectivity for single gases, indicating the presence of intercrystalline diffusion and viscous flow as the dominant transport mechanism. The carbon/zeolite composite membrane exhibited ideal selectivities for He/N₂, CO₂/N₂, and N₂/CH₄ of 11.99, 17.12, and 3.58 at room temperature. No permeation of n-butane and i-butane for the composite membrane was detected up to temperatures of 453 K, indicating that the pore size for the composite membrane was approximately 0.4 nm. By carefully oxidizing the carbon layer in air at 623 K, the pore size of the composite membrane was adjusted such that n-butane permeation could be detected. No permeation of i-butane was apparent, suggesting that the pore size of the composite membrane had been enlarged to approximately 0.5 nm. Further oxidation of the carbon layer produced a finite n-/i-C₄H₄ ideal selectivity, indicating that the pore size of the membrane was now larger than 0.55 nm. Therefore, selective oxidation of the carbon layer can be used to control the pore size of the composite membrane.     

SYNTHESIS OF MAGNETIC BEADS FOR BIO-SEPARATION USING THE SOLUTION METHOD

A modified solution process is used to produce super-paramagnetic nanocomposite particles containing functional groups for adsorption application. The powder is produced in a spray tower. The feed is a polymer solution containing two fractions of different particles: magnetite (14 nm) and polymer ion exchanger (150 nm). The spray-magnetic beads are submitted to different characterization methods: confocal laser scanning microscopy (CLSM), small-angle X-ray scattering (SAXS), and alternating gradient magnetometry (AGM). The characterization clearly proves the super-paramagnetic properties at room temperature of the composite particles, even at a high filling degree of 30 wt.%. The evaluation of the protein binding capacity of the composite material shows excellent values, which are comparable to other ion exchange resins. Compared to the conventional methods, the solution process has a high potential in scale-up. Thus a potential application of magnetic separation technology in technical scale is possible.     

Binder removal and microstructure with burnout conditions in BaTiO3 based Ni-MLCCs

The burnout conditions in multilayer ceramic capacitors (MLCCs) have been investigated to optimize the binder removal condition and to control the microstructure during the burnout process. MLCCs showed a delamination for the heating rate of 7 °C/min at 200 °C, and 6 °C/min at 250 °C and 300 °C in the ambient atmosphere. The heating rate affected the pore size distribution and mean pore size, showing the smaller and larger mean pore size in the reducing and at higher temperature, respectively. The cumulative pore surface area was dependent on the burnout temperature rather than the heating rate. The minimum pore surface area could be obtained at 300 °C with the heating rate of 3 °C/min, in which the pores were connected to be an open structure. The atmosphere and temperature affected the burnout microstructure related to the binder removal without the effect of the heating rate.     

Nanodiamonds as modifier of ethylene-1-octene copolymer structure and properties

The structure and stretching behavior of low density (0.86 g/cm³) ethylene-1-octene copolymer (EOC) modified with 0.015–1.44 vol.% (0.05–5 wt.%) of nanodiamonds (ND) particles were studied. Analysis of the structure of the EOC and nanocomposites by DSC, wide and small angle X-ray techniques revealed three phase structure in isotropic samples. In addition to the amorphous phase, there are two ordered phases: orthorhombic crystallites and hexagonal mesophase. ND particles display quite uniform distribution in EOC matrix up to 1.44 vol.%. The average size of ND particles is similar according to SAXS and WAXS data. It was found that introduction of ND particles into EOC matrix leads to the formation of the perfect orthorhombic phase crystallites, increases the rate of crystallization and crystallinity, resulting in increase in strength and Young modulus.     

THE EFFECT OF PRECIPITATION PARAMETERS ON PREPARATION OF LITHIUM FLUORIDE (LIF) NANO-POWDER

Lithium fluoride powder (LiF) is a white powder with a density of 2.64 gr/cm³ and a melting point of 848°C. This powder has several applications such as flux, glaze, soldering, and aluminum melting process, but one of the most important uses of this powder is its application in dosimetry. The commercial powders currently used for this purpose have average sizes of 5 to 10 micrometers; the objective of this research is to produce LiF powder with nano-metric particle size. In this study, the reaction of LiOH + HF → LiF + H₂O has been selected from among several reactions that were able to produce LiF powder, and some precipitation parameters such as temperature, time, agitation type, and supersaturation degree have been controlled. The morphology, phase analysis, and particle size distribution of the resulting powders were analyzed by SEM, XRD, and LPSA. Finally, lithium fluoride nano-powder was synthesized at a temperature of 25°C, pH about 2-3, reaction time less than 1 s, and agitation by ultrasonic bath.     

应急处理推进剂N_2O_4泄漏的粉体制备及试验研究

为了应急处理液体推进剂N2O4泄漏液,采用CaO水解-正丁醇共沸蒸馏法制备出粒径均匀的多孔性纳米球型Ca(OH)2粉体,粒径为200~300nm,孔径8~15nm,比表面积为63m2/g。将粉体装入压力瓶中形成移动的装置,通过挤压使粉体喷射与泄漏物发生物理吸附和酸碱中和反应。结果表明,粉体对泄漏液N2O4挥发的NO2气体去除率可达90%以上。粉体主要通过吸附、吸收、浸润、界面化学反应等作用捕获挥发气体,覆盖泄漏液,避免其进一步挥发和扩散。     

Preparation of Silica Nanostructured Spheres by Sol Spray Drying

Silica nanostructured spheres were obtained by spray drying of silica sol prepared in situ. Their morphologies were significantly affected by the aggregation of the primary particles in the sol. They had the mode of the pore sizes which was about the same order as Laser Particle Size Analyzer (LPA) diameter. Increasing the mixing ratio of the larger particles (20 nm) to smaller ones (7 nm) decreased the Brunauer, Emmett and Teller (BET) specific surface area, as expected. Pore volume decreased with the pore size distribution broadened and the mean pore diameter was not affected by the increase, due to the decrease in aggregation of the primary particles. Either the increase in the drying temperature and use of ethanol as a cosolvent made the agglomerates hollower, the larger of which with thinner shell transformed to doughnut type agglomerates, due to the structural and hydrodynamic instabilities.     

PRODUCTION OF HYDROCORTISONE MICRO- AND NANO-PARTICLES USING SUPERCRITICAL ANTI-SOLVENT WITH ENHANCED MASS TRANSFER

Supercritical anti-solvent precipitation with enhanced mass transfer (SAS-EM) is used for the formation of particles of hydrocortisone (HC), an anti-inflammatory drug. This technique is similar to the supercritical anti-solvent process but uses a reflecting horn surface that vibrates at 20 kHz frequency, which enhances the mass transfer of the solvent to supercritical fluid anti-solvent, reducing the growth of the particles. Controllable sizes and morphologies of HC particles are obtained using the SAS-EM process. At a power supply of 0 watts (to ultrasonic transducer), HC fibers of an average length of ∼81 μm and an average diameter of ∼6 μm are obtained. Upon increasing the power supply to 120 watts, which enhances mass transfer, particles of average size as low as 180 nm are obtained. Intermediate particle size and morphology are easily obtained by adjusting the power supply to the desired intermediate value. The obtained powder is free of impurities and is mostly amorphous.     

GAS PERMEANCE BEHAVIOR AT ELEVATED TEMPERATURE IN MESOPOROUS ANODIC OXIDIZED ALUMINA SYNTHESIZED BY PULSE-SEQUENTIAL VOLTAGE METHOD

Mesoporous anodic oxidized alumina (MAOA) capillary tubes with and without a barrier layer have been synthesized by applying a pulse-sequential voltage. The single gas permeances at an elevated temperature and the thermal and hydrothermal stabilities of MAOA were investigated. A highly oriented radial mesopore channel with pore sizes from 40 to 4 nm was formed in the MAOA tubes. Micropores with sizes from 0.4 to 0.8 nm were formed in the barrier layer. The H₂ permeance of MAOA with a barrier layer (barrier type) was approximately 540 times lower than that of MAOA without a barrier layer (block type) at 773 K. The H₂/N₂ permselectivity of the barrier type in the temperature range from 333 to 673 K was 3.4; those of the barrier type at 773 and 823 K were 4.4 and 11, respectively. On the other hand, the H₂/N₂ permselectivities of the block type were from 3.1 to 3.6 in the temperature range from 333 to 773 K. The H₂ permeance and the H₂/N₂ permselectivity of the amorphous silica membrane on the block type were 1.1 × 10^-7 mol/m² · s · Pa and 40 at 773 K, respectively. MAOA synthesized by the pulse-sequential voltage method can be applied to the mesoporous support of the gas separation membrane at elevated temperatures.     

EFFECT OF ZEOLITE CRYSTALLITE SIZE ON Pt/KL CATALYSTS USED FOR THE AROMATIZATION OF n-OCTANE

The effects of varying zeolite crystallite size in n-octane aromatization over Pt/KL have been studied on a series of catalysts. Various KL zeolites were synthesized via microwave-hydrothermal treatment, which allows for good control of crystallite morphology. Zeolites with different crystallite sizes were prepared by varying aging time (17-24 h), amount of barium (0-445 ppm), and seeding (0-8 wt%). The results showed that higher aging time resulted in smaller zeolite crystallite size, whereas the addition of barium resulted in larger crystallite size. Moreover, the addition of seeding reduced the crystallite size from 1.47 to 0.94 μm. Pt supported on different zeolite catalysts (Pt/KL) was prepared by vapor phase impregnation (VPI). The fresh catalysts were characterized by DRIFTS of adsorbed CO and volumetric hydrogen chemisorption. The results indicated that Pt clusters are well dispersed inside the zeolite channel in all the catalysts prepared. The aromatization of n-octane was tested on the different catalysts at 500°C and atmospheric pressure. It was found that the catalytic activity of all catalysts dropped rapidly after about 200 min on stream due to coke plugging inside the pore of the KL zeolite. It was also observed that less ethylbenzene (EB) and o-xylene (OX) were obtained as the conversion increased because both EB and OX are converted to smaller molecules such as benzene, toluene, etc., by secondary hydrogenolysis. Furthermore, the EB/OX ratio increases with zeolite crystallite size due to an enhanced preferential conversion of the larger OX molecules compared to the narrower EB as their path through the pores is restricted.     

粉煤灰-水泥浆体的孔体积分形维数及其与孔结构和强度的关系

采用压汞法对不同龄期粉煤灰-水泥浆体的孔分形结构进行了实验研究，测定了复合浆体孔体积分形维数，探讨了孔体积分形维数与孔隙率，孔表面积、平均孔径、孔分布及宏观力学性能的关系。实验结果表明：粉煤灰-水泥浆体的孔结构具有明显的分形特征，孔体积分形维数在3．3～3．5之间；孔体积分形维数越大，浆体的孔径越小、孔隙率越低，孔表面积越大，小于20nm的微孔越多，大于100nm的大孔越少，而且复合体系的抗压及抗折强度也越高。     

混凝土孔结构及其分形维数与氯离子扩散性能的关系

氯离子扩散系数是研究海洋环境下混凝土结构耐久性的重要参数之一。通过开展不同水胶比混凝土的压汞试验和盐雾扩散试验,研究了混凝土内部孔隙率、孔径分布及临界孔径对氯离子扩散系数的影响规律。结合Menger海绵体模型,建立孔体积分形维数与氯离子扩散系数的关系。结果表明:孔隙率和临界孔径与无量纲化氯离子扩散系数的相关性很高,可作为反映混凝土氯离子扩散性能的重要参数;通过数学分析计算得到的孔表面分形维数分布在2.56~3.86之间,孔体积分形维数分布在2.85~2.98之间;基于压汞法和分形理论计算得到的孔体积分形维数可以作为评价氯离子扩散系数的指标,在孔径小于10 nm、10～100 nm、100～1 000 nm以及大于1 000 nm四类区间,氯离子扩散系数随孔体积分形维数的增加而下降。     

Mechanical and electronic properties of ultrathin nanodiamonds under uniaxial compressions

Mechanical and electronic properties of ultrathin hydrogenated nanodiamonds (with diameters from 0.71 nm to 1.4 nm) under uniaxial compression have been investigated by means of density functional theory calculations. The computed Young's moduli of nanodiamonds are lower than the bulk value and increase with size, which can be fitted to an empirical function of diameter. Similar to the bulk diamond, the HOMO–LUMO gaps of nanodiamond reduces under uniaxial strain, implying tunable electronic properties via mechanical deformations.     

高活性微米多孔铝粉的制备与表征

为得到具有高活性多孔铝粉和氢化铝共存的混合体系,在常压下采用格氏试剂法对普通铝粉进行活化,通过半固相反应得到高活性微米多孔铝粉,用红外光谱、X射线衍射、扫描电子显微镜、静态氮吸附等方法对样品进行了表征,通过氧化还原滴定法测试了微米多孔铝粉的活性。结果表明,制备所得样品的主要成分是铝粉,同时还有部分AlH3;样品具有多孔结构,粒径多数分布在30μm左右,不仅具有孔径在2~10nm之间的中孔,还存在孔径分布在1nm以下的部分微孔结构;总孔体积为普通铝粉的5~7倍,比表面积为普通铝粉的2~3倍,样品平均活性含量达到92.83%。这种含有AlH3的高活性微米多孔铝粉混合体系在含能材料领域有很大的应用价值。     

Preparation of phenolic-based carbon foam with controllable pore structure and high compressive strength

Phenolic-based carbon foams with controllable pore structure and high compressive strength were prepared by foaming of resin solution under the pressure of 4 MPa and then carbonizing. Results showed that the average pore size of carbon foam ranging from 20 to 180 nm can be controlled by changing the resin concentration. The nanometer pore structure resulted in significant improvement of compressive strength and thermal insulation properties of the carbon foams. Carbon foam with bulk density of 0.73 g/cm³, average pore size of 20 nm, compressive strength of 98.3 MPa and thermal conductivity of 0.24 W/mK was obtained.     

Properties and microstructure of sintered incinerator bottom ash

The fraction of incinerator bottom ash with a particle size less than 8 mm produced at a commercial municipal solid waste incinerator was wet milled, dried, compacted and sintered at a range of temperatures to form ceramic materials. The effects of milled ash particle size distribution, powder compaction pressure and sintering temperature were investigated, and the materials formed characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermal analysis (TG/DTA). The main minerals present in the milled ash were quartz (SiO₂) and calcite (CaCO₃). Sintered densities of materials produced from ash milled to 95% less than 27 μm increased from 1.38 to 2.63 g/cm³ on increasing the sintering temperature from 1020 to 1080 °C. Firing above 1080 °C caused a rapid decrease in density and sample expansion. The principal crystalline phase present in the high-density material was diopside (CaMgSi₂O₆). This work shows that a significant fraction of incinerator bottom ash can be processed to form sintered materials with properties controlled by ash particle size distribution and sintering conditions.     

双峰孔分布Al_2O_3载体的研究

采用两种不同孔径分布的拟薄水铝石干胶粉,制备呈明显双峰孔分布的Al2O3载体。考察原料粉体、孔结构调节剂种类和用量以及焙烧温度等对Al2O3载体的孔分布的影响,并采用N2物理吸附法和高压压汞法分析载体孔结构。结果表明,两种干胶粉按质量1∶1混合时,能改变单一粉体的堆积状态,制得载体兼具单一原料制备载体时的孔分布,孔容达到最大,为1.58 cm3·g-1,且孔径分布集中在(10~100)nm和300 nm以上;加入不同孔结构调节剂后,对载体孔径分布调节作用相似,孔径分布更为集中;添加质量分数5%尿素后,(10~100)nm孔径分布达到62.1%;载体的比表面积随尿素含量增加依次降低,适量添加调节剂可制得所需最佳孔径分布;载体在约920℃焙烧时,晶型为γ相和δ相的混合相。