A Study on the Action of Ozone and on the Thermal Stability of Nanodiamond

Ultradisperse detonation diamond (UDD), a nanodiamond having particle size around 4 nm has been treated with ozone in an aqueous slurry. The reaction kinetics appeared to be relatively slow and long ozonation times were needed in order to functionalize the surface of a special nanodiamond sample with a very low degree of oxidation and foreign groups. The resulting ozonated nanodiamond has been studied by FT-IR and electronic spectroscopy. It has been shown that the ozonation of cyclohexane and adamantane can be taken as a model reaction for the ozonation of diamond. Together with ketonic groups of various nature formed on the surface of nanodiamond, the ozonation leads also to the formation of simple molecules like for instance HCOOH and HCHO which remain in the water solution and which have been detected by HPLC analysis using a diode-array detector. The thermal stability of the nanodiamond sample has been studied by thermogravimetric analysis (TGA-DTG) combined with differential thermal analysis (DTA) both under inert atmosphere and in air flow. The studies on thermal stability have been conducted in comparison to a sample of bulk diamond. It appears that the behavior of nanodiamond is completely different than the bulk diamond sample. For instance, under inert atmosphere and at 900°C the weight loss undergone by the nanodiamond is 11.5% while it is negligible in the case of bulk diamond under the same conditions. Similarly, in air flow the nanodiamond burns abruptly above 450°C while bulk diamond starts to burn only above 850°C. These differences have been explained in terms of different particle size and surface functionalization.     

金属掺杂对碳纳米纤维结构及导电性能的研究

以DMF为溶剂,利用静电纺丝法制备了PAN/Ni(OAc)_2、PAN/Co(OAc)_2和PAN/Cu(OAc)_2复合纳米纤维,在250℃对复合纳米纤维进行预氧化处理,然后在800℃下进行碳化处理得到碳基复合纳米纤维。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电镜(TEM)和比表面与孔径分析仪(ASAP 2020)等对复合纳米纤维表面形貌和结构进行了表征,用四探针测试仪测试碳基复合纳米纤维的电导率。研究结果表明:高温处理后C/Co、C/Ni和C/Cu复合纳米纤维的直径比前驱体复合纳米纤维有所下降,部分纤维发生断裂,金属Co、Ni和Cu较均匀地分散在碳纤维内部。碳基复合纤维的比表面积和孔体积大大增加,分别为597m~2·g~(-1)和0.297cm~3·g~(-1),C/Cu复合纳米纤维的导电率最高可达8.75S/m。     

A Study on the Action of Ozone and on the Thermal Stability of Nanodiamond

Abstract

Ultradisperse detonation diamond (UDD), a nanodiamond having particle size around 4 nm has been treated with ozone in an aqueous slurry. The reaction kinetics appeared to be relatively slow and long ozonation times were needed in order to functionalize the surface of a special nanodiamond sample with a very low degree of oxidation and foreign groups. The resulting ozonated nanodiamond has been studied by FT‐IR and electronic spectroscopy. It has been shown that the ozonation of cyclohexane and adamantane can be taken as a model reaction for the ozonation of diamond. Together with ketonic groups of various nature formed on the surface of nanodiamond, the ozonation leads also to the formation of simple molecules like for instance HCOOH and HCHO which remain in the water solution and which have been detected by HPLC analysis using a diode‐array detector. The thermal stability of the nanodiamond sample has been studied by thermogravimetric analysis (TGA‐DTG) combined with differential thermal analysis (DTA) both under inert atmosphere and in air flow. The studies on thermal stability have been conducted in comparison to a sample of bulk diamond. It appears that the behavior of nanodiamond is completely different than the bulk diamond sample. For instance, under inert atmosphere and at 900°C the weight loss undergone by the nanodiamond is 11.5% while it is negligible in the case of bulk diamond under the same conditions. Similarly, in air flow the nanodiamond burns abruptly above 450°C while bulk diamond starts to burn only above 850°C. These differences have been explained in terms of different particle size and surface functionalization.     

磁性多孔尖晶石铁氧体制备及催化臭氧性能

为了提高臭氧氧化水中难降解有机物性能,采用溶胶–凝胶法合成了磁性多孔尖晶石铁氧体NiFe2O4和MnFe2O4.通过SEM、XRD、VSM和XPS对其性能进行表征,对催化剂不同存在条件下催化臭氧降解水中邻苯二甲酸二丁酯(DBP)的效果、催化臭氧化机理及催化剂的稳定性进行了探讨.结果表明:两种催化剂均为磁性、多孔状、尖晶石结构铁氧体,NiFe2O4和MnFe2O4对催化臭氧化DBP具有良好的强化能力,比单独臭氧化体系对DBP去除率可分别提高54%和47%,NiFe2O4催化臭氧化能力强于MnFe2O4.两种催化剂催化臭氧降解DBP的反应均遵循羟基自由基机理,反应过程中水中金属离子溶出均低于0.06 mg/L,结构稳定,易于回收处理.     

Influence of the contacts and firing process on the properties of thick film resistors on alumina and dielectrics

This paper describes the behaviour of thick film ruthenium resistors when printed and fired onto standard 96% alumina substrates and onto alumina substrates covered with a dielectric film during long-term thermal ageing. It was observed that the behaviour of the resistors on alumina and dielectric depends upon the firing process of the resistors and the kind of terminations. An analysis of the effects of thermal ageing was made as well as some SEM observations of diffusion processes between the resistor and its terminations.     

Experimental study on the influence of the shape of the cross-section and the rebar arrangement on the fracture of LRC beams

The experimental program reported in this paper was planned to investigate the sensitivity of lightly reinforced concrete beams to the shape of the cross-section and to the rebar arrangement. Twenty-four micro-concrete reinforced beams were tested; these were rectangular and T beams reinforced with one, two or three rebars aligned horizontally or vertically. The concrete mechanical properties were all obtained from independent tests. Likewise, experimental errors due to material heterogeneity or incorrect set-up of the tests were minimized to ensure a high level of control during the execution of the program. The experimental results exhibit maximum load shape effect, i.e. the maximum load does not vary as no-tension hypothesis indicates. Beams in which rebars are aligned horizontally show a secondary load peak after cover cracking, while a vertical arrangement of the rebars provokes more energy dissipation and ductility in the post-peak response.     

Further Studies on the Chromatic Adaptation of the Eye and Its Effects on the Appearance of Colours

The study of the effect of chromatic adaptation on the appearance of colours is furthered by the application of the binocular matching technique to seven illuminants radiating in different regions of the spectrum. The invariants are calculated and their distribution is discussed.     

不同因素对钼及钼合金塑脆性能影响的研究

钼及其合金具有很好的高温强度和抗腐蚀性等优异性能,广泛应用于众多高科技领域.综述了C、N、O杂质元素、掺杂元素和稀土氧化物、常规的K、Si、Al、Ca、Mg、Fe等元素以及织构等因素对钼及钼合金塑脆性能的影响,总结了提高钼合金塑性的基本方法和规律.同时指出钼及钼合金今后研究的重点是提高合金的横向塑性,以使其得到更广泛的应用.     

Studies on the durability of natural fibres and the effect of corroded fibres on the strength of mortar

This paper presents the results of the variation in chemical composition and tensile strength of coir, sisal, jute and Hibiscus cannabinus fibres, when they are subjected to alternate wetting and drying and continuous immersion for 60 days in three mediums (water, saturated lime and sodium hydroxide). Compressive and flexural strengths of cement mortar (1:3) specimens reinforced with dry and corroded fibres were determined after 28 days of normal curing. From the results it is observed that there is substantial reduction in the salient chemical composition of all the four fibres, after exposure in the various mediums. Coir fibres are found to retain higher percentages of their initial strength than all other fibres, after the specified period of exposure in the various mediums. The compressive and flexural strengths of all natural fibre reinforced mortar specimens using corroded fibres are less than the strength of the reference mortar (i.e. without fibres) and fibre reinforced mortar specimens reinforced with dry natural fibres.     

防雪栅与路基间距对路基积雪分布影响规律的数值模拟研究

防雪栅是目前道路风吹雪灾害地区主要的防护设施,该研究结合数值模拟和现场实测方法,研究防雪栅与路基的布置间距对路基周围积雪分布的影响规律,进而分析积雪堆积机理。结果表明:数值模拟结果与现场实测结果有很好的对应关系,验证了结果的正确性;随着路堤与防雪栅间距的增大,路堤两个坡脚处的风速减小区范围均呈先增大后减小的趋势。路堤表面各部分的剪切速度均呈先增大后减小又增大的趋势,透风率为60%的防雪栅与路堤的最不利组合间距为16.67倍的防雪栅高度;随着路堑与防雪栅间距的增大,路堑内部积雪不易消除,因此防雪栅对路堑的挡雪效果不佳;运用剪切速度能够清晰地判断路基表面的积雪堆积与侵蚀,建议在风吹雪灾害频发地区修建铁路前可先采用该方法对工程表面的积雪堆积与侵蚀进行预判断,可合理确定工程中防雪栅布置的位置。     

沉淀剂对纳米CeO_2粒径及Zeta电位的影响研究

采用不同沉淀剂制备纳米CeO2.用FE-SEM、XRD、IR、马尔文动态激光散射纳米粒度及Zeta电位仪等对纳米CeO2的微观尺寸和形貌,以及Zeta电位进行了表征.结果表明:CeO2呈球形,尺寸均小于100nm且和所选用的沉淀剂有关.随着所采用沉淀荆pH值的增加,纳米CeO2的O-Ce键合强度增强,制备的CeO2试样的Zeta-pH曲线依次下移,等电点依次左移.同时,团聚粒径减小,分布集中.     

基于图谱理论的图像聚类数的确定及应用?

针对现有图像识别中聚类数的确定算法存在的精度问题,本文研究了用谱图理论来确定图像聚类数的方法,即图像中赋权图的 Laplace 矩阵的零特征值和图像聚类数之间的关系.通过从理想状况、分块状况到一般状况的赋权图的普拉斯矩阵的讨论,运用矩阵论知识推证了若图像的赋权图的 Laplace 如上三种情形,则图像的聚类数是其对应赋权图的 Laplace 矩阵零特征值的重数.实例分析讨论了赋权图参数,发现参数位于0.4至0.6时能获得高的估计精度.同时采用我们的方法得到的聚类数,比利用图谱中权矩阵1特征值的重数的方法精度更高.     

Au and Au---Zn contacts on p-GaSb and the characteristics of the interfaces

We analyse the specific contact resistance _C and the interfacial microstructural characteristics (by Auger electron spectroscopy and X-ray diffraction) of Au and AuZn contacts on p-GaSb. The experiments showed that _C hardly depends on the inclusion of Zn in the metallic film or on the annealing processes, at least for the carrier concentrations available (p 1.6 × 10¹⁷ cm⁻³). However, the dependence of _C on the acceptor concentration leads us to conclude that field emission is the principal conduction mechanism. The efficacy of an Ar glow discharge in considerably reducing the oxide present at the GaSb substrate is demonstrated. We also show that rapid thermal annealing produces much thinner interface-reacted layers than does the conventional (resistive) heat treatment.     

Influence of Enhancers on the Physicochemical Properties and on the Release of Suppositories of Clomipramine Hydrochloride

Abstract

The clomipramine hydrochloride shows a low rectal bioavailability (28 p. cent). The suppositories were manufactured with a semi-synthetic glyceride as the excipient: Suppocire NAI 10.

Two groups of enhancers could be distinguished in vitro:

Sodium salicylate at 0.1 p. cent, Sodium dioctylsulfosuccinate at 0.5 p. cent, Sodium laurylsulphate, 0.1 p. cent, Polyoxyethylene 2,3 lauryl ether at 1 and 2 p. cent, which didn't induce any influence on the clomipramine HCl dissolution time.

Sodium salicylate at 0.5, 1, 5, 10 percent, Polysorbate 20 at 0.5 p. cent, Polysorbate 80 at 0.5 and 2.0 p. cent, which induced a decrease of the clomipramine HCl release rate.

Some ex vivo assays were carried out, using a rat rectal mucosa. In these conditions, Polyoxyethylene 2.3 lauryl ether 1 p. cent and Polysorbate 80 at 2 p. cent induced an increase of the clomipramine HCl absorption. (9.80 p. cent to 16.25 p. cent)

These experiments showed in one hand that it was impossible to choose one or several enhancers among the assayed ones, using only the measure of the physicochemical properties of the suppositories containing an active materials as soluble as the clomipramine HCl, in the other hand the ex vivo assays could be useful to study the optimization of the formula by the use of several enhancers.