Reducing nitric oxide into nitrogen via a radio-frequency discharge

NO/N(2)/O(2)/H(2)O mixtures are usually converted into HNO(3) and/or NO(2) using different discharge approaches. In this study, a radio-frequency discharge was successfully used to reduce NO mainly into N(2) at a low pressure (4kPa). The influences of experimental parameters, including carrier gas, inlet concentration of NO, O(2), steam, and applied power, are discussed. At least 95.7% of the total N atoms converted from NO into N(2). Other traces of byproducts were N(2)O and HNO(2), but neither HNO(3) nor NO(2) were detected. In addition, conversion of NO apparently increased with elevated applied power or decreased inlet concentration of O(2), reaching 92.8% and 74.2% for the NO/N(2)/O(2) (2%) and NO/N(2)/O(2) (6%)/H(2)O (10%) mixtures, respectively, at 120W. In addition, from the optical emission spectra, a large amount of N(2) (first positive band and second positive band) and NO (gamma system) were observed, and the important reactions for NO removal and N(2) formation are proposed.     

碳纳米管改性对环氧树脂复合材料热学和电学性能的影响

分别采用混酸(浓H2SO4和浓HNOs)、浓HNOs、浓NaOH及浓H2SO4/H2O2对碳纳米管(CNTs)在室温下进行表面处理,通过FTIR、SEM、DSC和TGA研究了各改性方法对CNTs/环氧树脂(EP)复合材料热性能和电性能的影响.结果表明,混酸处理使CNTs在EP中的分散性、EP的玻璃化温度和热分解温度都显著提高,其它3种方法也有这种作用,相比较而言,H2SO4/H2O2和HNO3的改性作用稍差,而NaOH的最差.4种处理方法都使复合材料的导电性能、介电常数以及介电损耗显著下降,其中混酸处理使上述性能下降的程度最高,其次为H2SO4/H2O2处理,NaOH处理和HNO3处理对电性能影响较小.     

Fe3O4纳米粒子修饰碳纳米管的制备及其磁学性能（英文）

通过FeCl2.4H2O和FeCl3.6H2O混合共沉淀,合成平均粒径为6 nm和10 nm的Fe3O4纳米粒子。然后将两种Fe3O4纳米粒子分别与经HNO3氧化处理的多壁碳纳米管(MWCNTs)置于乙醇水溶液(水和乙醇的体积比为1∶1)中,在超声波作用下制备Fe3O4/MWCNT复合材料。用高分辨透射电子显微镜、X-射线光电子能谱、振动样品磁强计、X射线衍射仪、热重分析仪对所制备的Fe3O4/MWCNT复合材料进行表征。结果表明:由6 nm和10 nm Fe3O4纳米粒子所制备的Fe3O4/MWCNT复合材料中,Fe3O4的质量分数分别为26.65%和29.3%,相应的磁饱和强度分别为16.5 emug-1和7.5 emug-1。     

Photochemical removal of NO(2) by using 172-nm Xe(2) excimer lamp in N(2) or air at atmospheric pressure

Photochemical removal of NO(2) in N(2) or air (5-20% O(2)) mixtures was studied by using 172-nm Xe(2) excimer lamps to develop a new simple photochemical aftertreatment technique of NO(2) in air at atmospheric pressure without using any catalysts. When a high power lamp (300 mW/cm(2)) was used, the conversion of NO(2) (200-1000 ppm) to N(2) and O(2) in N(2) was >93% after 1 min irradiation, whereas that to N(2)O(5), HNO(3), N(2), and O(2) in air (10% O(2)) was 100% after 5s irradiation in a batch system. In a flow system, about 92% of NO(2) (200 ppm) in N(2) was converted to N(2) and O(2), whereas NO(2) (200-400 ppm) in air (20% O(2)) could be completely converted to N(2)O(5), HNO(3), N(2), and O(2) at a flow rate of 1l/min. It was found that NO could also be decomposed to N(2) and O(2) under 172-nm irradiation, though the removal rate is slower than that of NO(2) by a factor of 3.8. A simple model analysis assuming a consecutive reaction NO(2)-->NO-->N+O indicated that 86% of NO(2) is decomposed directly into N+O(2) and the rest is dissociated into NO+O under 172-nm irradiation. These results led us to conclude that the present technique is a new promising catalyst-free photochemical aftertreatment method of NO(2) in N(2) and air in a flow system.     

炭表面改性对负载型TiO_2/活性炭复合光催化剂性能的影响

采用HNO3、H2O2和O3对商品活性炭进行表面改性处理,考察了改性处理对活性炭表面基团、负载TiO2以及所形成的TiO2/活性炭复合光催化剂性能的影响。利用傅里叶红外光谱(IR)、X射线光电子能谱(XPS)、扫描电镜(SEM)及氮气吸附等手段对材料进行了表征。结果表明,3种改性方法均可有效提高活性炭载体表面的含氧官能团数量,但是对活性炭的比表面积和孔容影响不大;H2O2和O3对活性炭载体改性后可以提高对钛前驱体的吸附性能,HNO3改性有利于TiO2颗粒在活性炭表面的分散。使用改性后的活性炭作为载体制备的TiO2/活性炭光催化降解甲基橙的性能均高于未改性的TiO2/活性炭催化剂,其中以HNO3改性后的TiO2/活性炭活性最高。     

插层化合物在膨化过程中的热分解动力学

采用红外傅立叶变换光谱仪与热重分析仪联动装置在线检测HNO3-CH3COOH—GIC、H2SO4-GIC及H2SO4-CH3COOH—GIC等插层石墨的相变及热分解过程，同时通过快速扫描得到相应时间段内分解产物的红外光谱，并运用Kissinger—Ozawa原理计算了几种典型膨化反应的动力学参数。研究结果揭示了膨化过程的热分解机理，当升温速率在20℃／min～80℃／min范围时，由实验数据计算出膨化反应表观活化能不大于120kJ／mol。     

Measurement of the Refractive Indices of H(2)SO(4)-HNO(3)-H(2)O Solutions to Stratospheric Temperatures

Refractive indices of various H(2)SO(4)-H(2)O, HNO(3)-H(2)O, and H(2)SO(4)-HNO(3)-H(2)O solutions were measured at four wavelengths in the visible (351.0, 533.5, 632.9, and 782.6 nm) over a temperature range from 30 to -60 degrees C. The temperature dependence has been determined for the first time to the authors' knowledge. This dependence is of importance for applications to atmospheric aerosols at low temperatures. In particular, it is shown that (1) the molar refractivity of the solutions is independent of temperature, whereas the temperature dependence of the refractive index arises solely through the temperature dependence of the solution's mass density, (2) the molar refractivities of H(2)SO(4) and HNO(3) in a ternary solution may be calculated as the weighted sum of the molar refractivities of two binary solutions evaluated at a concentration that corresponds to the total acid concentration, and (3) the H(2)O molar refractivity in the solutions may be taken equal to that of pure water. Although the data for the ternary system have been used for this model verification, data for binary H(2)SO(4)-H(2)O and HNO(3)-H(2)O solutions were used to improve the accuracy of the modeled refractive indices to better than 0.0017% or 0.15% for concentrations of 5-70 wt.% and wavelengths from the near ultraviolet to the near infrared (0.25-2 mum).     

Effect of air in the thermal decomposition of 50 mass% hydroxylamine/water

This paper presents experimental measurements of 50 mass% hydroxylamine (HA)/water thermal decomposition in air and vacuum environments using an automatic pressure tracking adiabatic calorimeter (APTAC). Overall kinetics, onset temperatures, non-condensable pressures, times to maximum rate, heat and pressure rates versus temperature, and mixture vapor pressures for the experiments in vacuum were similar when compared to the corresponding data for HA decomposition in air. Determined was an overall activation energy of 119+/-8 kJ/mol (29+/-2 kcal/mol), which is low compared to 257 kJ/mol (61.3 kcal/mol) required to break the H(2)N-OH bond reported in the literature. The availability of oxygen from air did not affect detected runaway decomposition products, which were H(2), N(2), N(2)O, NO, and NH(3), for samples run in vacuum or with air above the sample. A delta H(rxn) of -117 kJ/mol (28 kcal/mol) was estimated for the HA decomposition reaction under runaway conditions.     

Determination of chromium in urine by stable isotope dilution gas chromatography/mass spectrometry using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent

An isotope dilution gas chromatography/mass spectrometry method using lithium bis(trifluoroethyl)dithiocarbamate as a chelating agent is described for the determination of chromium in urine. A wet digestion procedure with HNO3-H2O2 is used for oxidizing the organic matter associated with urine samples. The isotope ratios are measured by selected ion monitoring in a general-purpose mass spectrometer using a 10-m fused silica capillary column. Memory effect, in sequential analyses of samples with different isotope ratios, was evaluated by preparing a series of synthetic mixtures and was found to be negligible. The accuracy of the method was verified by quantitation of chromium in the NIST freeze-dried urine reference material, SRM-2670, with a recommended chromium concentration of 13 micrograms/L in the normal level and certified chromium concentration of 85 +/- 6 micrograms/L in the elevated level.     

N2O removal in N2 or air by ArF excimer laser photolysis at atmospheric pressure

A photochemical process is proposed as a new efficient N(2)O removal technique in N(2) or air at atmospheric pressure and room temperature without using any catalysts. N(2)O diluted in N(2) or air was decomposed into N(2), O(2), and NO by using a 193 nm ArF excimer laser. The maximum conversion of N(2)O in N(2)O/N(2) or N(2)O/N(2)/O(2) mixtures was 93% at a laser power of 136 mJ, a repetition frequency of 5 Hz, and an irradiation time of 30 min. The formation ratios of N(2):O(2):NO in N(2)O/N(2) and N(2)O/N(2)/O(2) mixtures were 64:31:5.1% and 60:27:13%, respectively. The decomposition mechanism of N(2)O under 193 nm photolysis was discussed by comparing experimental data with calculated model using known photochemical and gas kinetic data.     

Morphological modification of MWCNT functionalized with HNO3/H2SO4 mixtures

The acidic oxidation with HNO3/H2SO4 mixtures is widely reported as an effective method to functionalize multi-walled carbon nanotubes (MWCNT). Although effective, a bad control of the oxidation conditions frequently cause serious modifications of carbon nanotube network, limiting further potential applications. Investigations about the effect of functionalization operating conditions on the morphological, chemical and chemical-physical properties of MWCNT can be useful for a proper setting of oxidation reactions of MWCNT according to their specific applications. In this work the effect of HNO3/H2SO4 ratio on the morphological and chemical-physical properties and on the degree of functionalization of MWCNT was investigated. Electron microscopy, thermogravimetric, X-ray diffraction, titration and water dispersion analyses clearly revealed that the increase of the amount of concentrated sulphuric acid in the HNO3/H2SO4 mixture lead to an increase of the amount of functional groups on the MWCNT surface but also to an increase of structural damage in terms of tube cutting and generation of additional defects in the graphitic network of pristine     

2,6-二氨基-3,5-二硝基吡嗪-1-氧化物的热安全特性分析

采用差示扫描量热仪(DSC)对2,6-二氨基-3,5-二硝基吡嗪-1-氧化物(LLM-105)进行线性升温实验,分析其热分解特性。通过Kissinger和Friedman模型对DSC曲线进行动力学计算,并结合热平衡方程计算其绝热诱导期(TMRad)及自加速分解温度(θ_sad)。结果表明:LLM-105的初始分解温度、最高分解温度、分解完成温度均随着升温速率的增加而向高温方向移动,平均分解热为718.7 J/g。通过Kissinger模型计算得到的表观活化能为358.2 kJ/mol;而通过Friedman模型的计算曲线可知,LLM-105在不同反应阶段中具有不同反应。当绝热诱导期为2.0、4.0、8.0 h时,对应温度分别为296.8、290.7、284.7 ℃。当质量分别取5.0、15.0、25.0、50.0 kg时,自加速分解温度分别为267.0、265.0、262.0、259.0 ℃。随着包装质量的增加,分解放出的热量交换到周围环境中的难度就会越大,安全性也进一步降低。因此,在储存LLM-105时,必须控制一定的药品尺寸及良好的通风条件,以保证其储存安全。     

Mechanochemical decomposition of PVC by using La2O3 as additive

A polyvinyl chloride (PVC, [CH2CHCl]n) sample was ground with one of the following oxide samples, lanthanum oxide (La2O3) and calcium oxide (CaO), as a reference, to investigate its mechanochemical (MC) decomposition. According to the XRD patterns for the ground products, peaks of lanthanum oxy-chloride, LaOCl which is water insoluble, were observed to appear in the patterns of the mixture samples at a molar ratio of (PVC: La2O3 = 1:2) and (1:4), after 20 min grinding, while the patterns of the ground PVC-CaO mixtures show the formation of CaOHCl, which is water soluble, in the products after 2 h grinding. TG patterns taken for the PVC-La2O3 mixtures ground for different periods of time do not indicate significant weight loss in the range from 200 to 300 degrees C, and this suggests that La2O3 is more effective additive than CaO in the MC decomposition for PVC. FT-IR patterns for organic phases in the ground mixture show the reduction of CCl bindings in the PVC structure. The MC reaction between PVC and La2O3 is accompanied by the formation of C-O single bonds, to form LaOCl, which is insoluble in water at ambient condition. This is the reason why the yield of Cl extracted by the water leaching reaches only less than 50%, while it reaches almost 100% in the yield of Cl from the PVC-CaO mixture ground for 2 h or more.     

单分子层复合微粉研究

研究了CeO₂/γ-Al₂O₃单分子层复合微粉的制备机理.研究结果说明,CeO₂可以在γ-Al₂O₃表面形成单层分散相,可以通过浸渍、焙烧的方法制备CeO₂/γ-Al₂O₃单分子层复合微粉;CeO₂起始物的种类对其单层分散阈值(最大单层分散容量)有影响,以硝酸亚铈为起始物的CeO₂/γ-Al₂O₃复合微粉的CeO₂单层分散阈值为0.042gCeO₂/g(γ-Al₂O₃),而以醋酸亚铈为起始物的CeO₂单层分散阈值则为0.10gCeO₂/g(γ-Al₂O₃).     

Preparation and photocatalytic activity of iron oxide-loaded potassium titanate layered compounds

Iron oxide-loaded hydrous potassium tetratitanate (K0.3Ti4O7.3(OH)1.7) compounds consisting of 1.48 wt% (sample 'B'), 1.87 wt% (sample 'C') and 5.60 wt% (sample 'D') of iron oxide were synthesized by suspending the K0.3Ti4O7.3(OH)1.7 (sample 'A') in Fe2(SO4)3 solution for 24 h, followed by washing several times with deionized water and then dried at 120 degrees C for 24 h. The K0.3Ti4O7.3(OH)1.7 was synthesized by refluxing the K2Ti4O9 x 2H2O in 1 M HNO3 solution. Band-gap energies of the K0.3Ti4O7.3(OH)1.7 and the iron oxide-loaded samples are 3.12 +/- 0.6 eV and 2.23 +/- 0.09 eV, respectively. Photooxidation activity towards methylene blue decomposition under fluorescence irradiation was found to decrease as follow: sample 'B' > sample 'C' > Sample 'A' > sample 'D' > commercial Fe2O3-Blank. The photoactivity under sunlight irradiation was found to decrease as follow: sample 'B' > sample 'A' > Sample 'C' > sample 'D' > commercial Fe2O3-Blank.     

304Cu抗菌不锈钢盐酸基酸洗工艺的研究

为了明确盐酸基酸洗液对含Cu抗菌不锈钢表面氧化层的酸洗行为,采用正交试验法研究以盐酸为基础,Fe~(3+)、H_2O_2和HNO_3为氧化剂的304Cu抗菌不锈钢酸洗工艺.并运用扫描电镜、透射电镜及电化学等手段分析经最佳配方酸洗后试样的表面形貌、成分及酸洗机理.结果表明:最佳酸洗工艺配方为HCl(36%~38%)120 ml/L、H_2O_2(30%)80 ml/L、FeCl_3·6H_2O 20g/L、HNO_310 ml/L,酸洗温度30℃,酸洗时间15 min.经该配方酸洗后材料表面平整度和光亮度较好,具有抗菌性能的点状ε-Cu相在基体上弥散分布.材料经酸洗去除氧化层后,仍具有足够含量的抗菌元素Cu存在.酸洗脱除氧化层过程由电荷传递过程控制,该酸洗液对不锈钢具有孔蚀诱导性,酸洗时间不宜过长.     

Preparation of MoO3/MoS2/TiO2 composites for catalytic degradation of methylene blue

Metastable hexagonal MoO3 microrods were grown from bulk MoS2 and used as support materials for MoS2 and TiO2 nanoparticles. The hybrid composites that consisted of MoO3, MoS2, and TiO2 were prepared at a low temperature using the one-step synthesis method. The crystallinity and morphology of the MoO3/MoS2/TiO2 composites that were prepared using HNO3 and titanium tetraisopropoxide were compared with those of the MoO3/MoS2 composites that were prepared without titanium tetraisopropoxide. Titanium isopropoxide facilitated the formation of the MoO3 microrods from the oxidation of the bulk MoS2. The desired MoO3/MoS2/TiO2 composites were obtained using 0.5 g of bulk MoS2, 3-4 ml of HNO3, and 0.367 ml of titanium tetraisopropoxide. The MoO3/MoS2/TiO2 composites that were treated with ultrasonic waves showed rapid degradation of the methylene blue solution (2 x 10(-4) M) in the dark and good photocatalytic ability under ultraviolet light irradiation. The decomposition of methylene blue depended on the composition of the composite.     

N2O5/HNO3体系硝解三(N-乙酰基)六氢化均三嗪制备RDX

采用乙腈和三聚甲醛为原料、浓硫酸为催化剂合成三(N-乙酰基)六氢化均三嗪(TRAT),再以N2O5/HNO3为硝解剂合成黑索今(RDX)。实验表明:当摩尔比n(N2O5):n(HNO3):n(TRAT)=60:6:1,硝解温度50℃,反应时间为1h时,RDX的最高产率可达87.4%。产品通过红外光谱、核磁共振进行了表征,并对副产物进行了研究,副产物通过质谱验证。     

Complete CO oxidation over Cu2O nanoparticles supported on silica gel

We find that nearly monodisperse copper oxide nanoparticles prepared via the thermal decomposition of a Cu(I) precursor exhibit exceptional activity toward CO oxidation in CO/O2/N2 mixtures. Greater than 99.5% conversion of CO to CO2 could be achieved at temperatures less than 250 degrees C for over 12 h. In addition, the phase diagram and pathway for CO oxidation on Cu2O (100) is computed by ab initio methods and found to be in qualitative agreement with the experimental findings.     

Possibility of methane decomposition in a gas discharge

The possibility of using a gas discharge such as a corona discharge or a barrier discharge for decomposition of methane in different gaseous mixtures is investigated theoretically. The effect of preheating of the gas to a temperature of 1200 K on the degree of methane conversion in the discharge is studied. A kinetic model that describes the processes of methane decomposition and oxidation in CH₄/CO₂, CH₄/H₂O, and CH₄/O₂ mixtures is developed. The effect of the discharge parameters and gas additives on the efficiency of methane decomposition is investigated. The optimum temperature of the mixture, particle lifetime, and initial concentration of oxygen for the production of hydrogen molecules are found. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 6, pp. 1016–1023, November–December, 1998.