低温下活性炭吸附分离Kr和Xe

研究了低温下活性炭吸附分离Kr和Xe的方法。Kr和Xe混合气在-78 ℃活性炭吸附柱上进行富集,根据Kr、Xe在活性炭柱上脱附条件的差异实现了Kr和Xe的分离。结果表明,Kr和Xe的回收率均大于90%,Kr样品中Xe的去污系数达10⁴以上,Xe样品中Kr的去污系数达10³以上。     

甲醛改性多壁碳纳米管吸附铀的性能研究

对纯化后的多壁碳纳米管（MWCNTs）采用甲醛进行羟甲基化改性,研究了改性后的MWCNTs对铀的吸附性能,考察了介质酸度、温度、超声时间、溶液初始浓度以及改性MWCNTs加入量对铀的吸附量和吸附率的影响。结果表明,改性MWCNTs在水溶液中的分散性良好,在pH为2.0～7.0范围内,改性MWCNTs对铀的吸附量和吸附率随pH增大而升高。铀的吸附量随初始浓度的增大而升高,铀初始浓度为50 μg/mL时,吸附量达46.44 mg/g,对铀的吸附率达90%以上。温度、超声时间和离子强度对其吸附量影响不大。吸附反应符合Langmuir和Freundlich方程,最大理论吸附容量为55.87 mg/g。     

低温活性炭降氡技术研究

地下低本底实验室在创造低放射性本底实验环境方面有着很大的降氡需求,为此本文研发了一种原理性活性炭降氡装置,以筛选出的KC-6型活性炭为研究对象,使用连续进气法,在-50~25℃温度范围内测量了活性炭对氡的动力学吸附系数。实验结果表明,在该温度范围内,活性炭的动力学吸附系数与绝对温度呈指数关系,降低活性炭的温度能显著提高活性炭对氡的吸附性能,在-48℃的温度条件下,活性炭的动力学吸附系数达171.4L/g,较室温条件下增加了20倍以上。依据本实验获得的实验数据,计算出KC-6型活性炭的吸附热Q=(20.5±1.7)kJ/mol。     

Plasma-Chemical Synthesis of Nanosized Powders-Nitrides,Carbides,Oxides,Carbon Nanotubes and Fullerenes

In this article the plasma-chemical synthesis of nanosized powders(nitrides,carbides,oxides,carbon nanotubes and fullerenes) is reviewed.Nanosized powders-nitrides,carbides,oxides,carbon nanotubes and fullerenes have been successfully produced using different techniques,technological apparatuses and conditions for their plasma-chemical synthesis.     

偕胺肟基改性碳纳米管对铀的吸附性能研究

对多壁碳纳米管（MWNTs）进行偕胺肟基改性,采用透射电子显微镜（TEM）和傅里叶变换红外光谱仪（FTIR）进行表征,研究了改性前后MWNTs在不同条件下对铀的吸附性能。结果表明,在pH=2～8的范围内,未改性的碳纳米管（raw-MWNTs）与偕胺肟基改性碳纳米管（AO-MWNTs）对铀的吸附容量均是先增大后降低,pH值为5时达到最大。随着铀初始浓度的增大,raw-MWNTs和AO-MWNTs对铀的吸附容量逐渐升高。当铀初始浓度为10 mg/L时,AO-MWNTs对铀振荡吸附30 min后达到平衡,吸附容量可达18.93 mg/g,而raw-MWNTs对铀振荡吸附60 min后趋于稳定,吸附容量可达9.59 mg/g。AO-MWNTs对铀的吸附符合Langmuir和Freundlich模型,最大理论吸附容量为106.38 mg/g。     

多晶硅薄膜等离子体增强化学气相沉积低温制备工艺

采用电子回旋共振等离子增强化学气相沉积(ECR-PECvD)方法,以SiH4和H2为气源,在普通玻璃衬底上沉积多晶硅薄膜.利用XRD、Raman光谱和TEM研究了衬底温度、氢气流量和微波功率对多晶硅薄膜结构的影响.结果表明,制得的多晶硅薄膜多以(220)取向择优生长,少数条件下会呈现(111)择优取向.当衬底温度为300℃、H2流速为25 mL/min、微波功率为600 W时,多晶硅薄膜结晶状态最好,且呈最佳的(220)取向.     

Impurity Effects on Transistor Behavior at Low Temperature

Unusual low temperature behavior has been observed in NPN silicon transistors when gallium is employed as the base dopant. The current gain exhibits a pronounced "hump" near 76°K in these devices, which enables them to be studied and utilized at this low temperature. Near the hump temperature, the tolerance of the gallium doped devices to fast neutrons is observed to be approximately a factor of five greater than at room temperature. The peak in transistor gain at low temperature has been explained in terms of the change in emitter injection efficiency with temperature as a result of the different rates of carrier freeze-out in the base and emitter regions. In the model proposed, the increased radiation tolerance results from a decrease in the recombination in the emitter space charge region at low temperatures.     

微量氙低温分凝条件的优化

利用自行研制的FNQ-01型气体分凝器实验平台研究了不同条件组合对微量氙收集效率的影响,通过正交法设计优化了稀有气体氙分凝取样条件,选出最佳条件为原料气中氙的体积分数为1.046×10^-3,冷凝温度-198 ℃,原料气进气流速0.3 L/min,分凝器收集压力55 kPa,蒸发温度-50 ℃。在此条件下,Xe的平均收集效率为73％。此外,还研究了不同进气方式对氙收集效率和分凝的影响。     

AlNi纳米合金薄膜低温电阻率的特性研究

通过磁控溅射制备了AlNi纳米合金薄膜,并利用自制的直排四探针低温测量系统测量了薄膜电阻率随温度(8~300K)的变化规律。结果表明:由于电子-声子和电子-磁子相互作用,纯Al和Ni纳米晶薄膜的电阻率分别呈现出正的电阻率温度系数,且电子-磁子散射对电阻率的贡献主要体现在高温区(80~300K),在低温区(40K)电子-晶界/表面散射对电阻率的贡献占主导地位。Ni原子掺入量的增加,诱导了纳米晶薄膜无序程度的增强,从而使Al1-xNix纳米合金薄膜逐渐由晶体的金属特性过渡到半导体特性,导致其呈现出负的电阻率温度系数。由于增强的电子极化效应,Al1-xNix纳米合金薄膜电阻率与温度的关系并不完全遵循半导体的热激发导电模型。     

低能氦等离子体低温条件下钨材料的表面形貌

为研究氦等离子体在钨表面造成的表面纳米结构,利用荷兰基础能源研究所Pilot-PSI直线等离子体发生装置在673 K温度下,对钨材料进行了低能（40 eV）高束流强度（4×10²³ m^-2•s^-1）氦等离子体辐照。实验结果表明,辐照后钨材料表面出现了多种不同形态的纳米结构,表面纳米结构和晶粒的表面法向之间存在明显关联。在表面法向为［111］的晶粒表面出现三角形的纳米结构,在［110］取向的晶粒表面出现条带状的纳米结构,而在［001］取向的晶粒表面没有明显的结构出现。晶粒表面的纳米结构尺寸在50 nm左右,高度起伏在5 nm以下。另外,氦等离子体辐照会造成晶界处的高度差,在25 nm左右。分析推测氦等离子体辐照造成的晶粒表面和晶界的形貌可能是由近表面的气泡所导致的。     

Na125I在碳纳米管中的填充

碳纳米管(CNTs)在经纯化、开口处理后，用Na^125I示踪，研究NaI溶液对CNTs的填充、洗涤以及它们从碳纳米管中的释放情况；用HREM、SEM、EDS对CNTs的填充情况进行了表征。结果显示CNTs管腔内有NaI填充并且在溶液中会缓慢释放出来。因此放射性核素示踪技术可以应用于CNTs的填充、释放等行为的研究。     

Study of Coincidence Doppler Broadening in Carbon Nanotubes

Coincidence Doppler broadening measurements of positron annihilation for multi- walled carbon nanotubes, double-walled carbon nanotubes, single-walled carbon nanotubes and graphite were performed. The ratio curves of the Doppler broadening for these samples to silicon were obtained. It is shown that there are distinct peaks at the position of 10×10-3 m0c for both carbon nanotubes and graphite, however the amplitudes of the peaks are not the same. We have the opinion that these peaks arise from the annihilation of positron with the 2s and 2p electron of carbon element.     

Synthesis of Crystalline Carbon Nitride Thin Films by Pulsed Arc Discharge at Atmospheric Pressure

The preparation of crystalline C3N4 films was investigated using pulsed arc discharge from mixed methanol and ammonia water at atmospheric pressure. The X-ray diffraction （XRD） patterns of the films prepared at a substrate temperature of 450℃ suggested that the film was composed of α-C3N4 and fl-C3N4 crystallites. Raman spectra exhibited distinct peaks which are in good agreement with those predicted theoretically for C3N4 crystallites.     

Modelling of Electrical Conductivity of a Silver Plasma at Low Temperature

During the working of electrical fuses, inside the fuse element the silver ribbon first begins to melt, to vaporize and then a fuse arc appears between the two separated parts of the element. Second, the electrodes are struck and the burn-back phenomenon takes place. Usually,the silver ribbon is enclosed inside a cavity filled with silica sand. During the vaporization of the fuse element, one can consider that the volume is fixed so that the pressure increase appears to reach pressures higher than atmospheric pressure. Thus, in this paper two pressures, 1 atm and 10 atm, are considered. The electrical field inside the plasma can reach high values since the distance between the cathode surface and the anode surface varies with time. That is to say from zero cm to one cm order. So we consider various electrical fields: 10~2V/m, 10~3V/m, 5×10~3V/m,10~4V/m at atmospheric pressure and 10~5V/m at a pressure of 10 atm. This study is made in heavy species temperature range from 2,400 K to 10,000 K. To study the plasma created inside the electric fuse, we first need to determine some characteristics in order to justify some hypotheses.That is to say: are the classical approximations of the thermal plasmas physics justified? In other words: plasma frequency, the ideality of the plasma, the Debye-Hückel approximation and the drift velocity versus thermal velocity. These characteristics and assumptions are discussed and commented on in this paper. Then, an evaluation of non-thermal equilibrium versus considered electrical fields is given. Finally, considering the high mobility of electrons, we evaluate the electrical conductivities.     

Zr-Sn-Nb薄片合金高温低周疲劳行为

采用Zr-Sn-Nb合金薄片漏斗试样,完成了室温和500℃高温下的低周疲劳试验,提出基于漏斗根部节点轴向应变的疲劳损伤等效假设。根据有限元分析,建立了Zr-Sn-Nb合金室温和高温下薄片漏斗试样测试应变到漏斗根部轴向应变的转换模型。结合低周疲劳试验结果,建立了在室温和500℃高温条件下用于估算Zr-Sn-Nb合金疲劳寿命的Manson-Conffin模型。结果表明:Zr-Sn-Nb合金具有循环稳定性;高温严重影响了Zr-Sn-Nb合金低应变幅下的疲劳寿命,随着应变幅的增加,温度影响趋弱。     

Calculational Study of Time-Dependent Neutron Spectra in Ice at Low Temperature

Calculations on the time-dependent neutron spectra in an ice block are reported for the temperature range of 86–16 K.

Three models for the lattice vibrational frequency distributions were applied to calculate scattering kernels. Calculated spectra were compared with measured spectra. It was found that the calculation with the Debye model agrees well with the experiment.

From the present analysis, it was suggested that the Debye temperature θ_D of the low temperature ice can be expressed as θ_D = 208 + 0.3T ₀ where T ₀ is the medium temperature.     

51Cr示踪法研究UDP-Gal在血小板储存中的作用

用^51Cr示踪法对尿嘧啶二磷酸半乳糖(UDP—Gal)在4℃低温储存兔血小板中的保护作用进行了研究。结果显示在血小板中加入UDP—Gal进行储存，回输体内后在肝脏中的破坏率明显减少．寿命延长。表明UDP—Ga对低温储存的血小板具有良好的保护作用。     

用碳纳米管从硝酸溶液中回收镅

研究了用碳纳米管从放射性废硝酸溶液中进行镅的回收。在浓硝酸溶液中,碳纳米管对镅的吸附率小于1％;随着硝酸浓度的降低,镅的吸附率迅速升高,当溶液的pH值大于5时,碳纳米管对镅的吸附率达到99.95％以上。用1．5mol／L硝酸进行解吸,一次解吸能够从碳纳米管回收99％以上的镅。     

Oxidation Degradation of Aqueous Carbofuran Induced by Low Temperature Plasma

The oxidative degradation of aqueous carbofuran, a heavily used toxic carbamate insecticide by low temperature plasma, was investigated. The results show that the treatment efficiency increases with the increase in initial concentration. Raising the treatment temperature and changing the pH value can result in enhanced degradation of carbofuran in solution. The results also show that low temperature plasma treatment can effectively remove chemical oxygen demand （COD） of carbofuran in the solution.     

活性炭纤维在低温下对Kr的静态吸附

研究了粘胶基活性炭纤维(Viscose-based ACF,VACF)、沥青基活性炭纤维(Pitch-based ACF,PACF)和颗粒活性炭(Grain activated carbon,GAC)在201K时对Kr的静态吸附等温线和吸附速度,并与同样条件下VACF对Xe的吸附进行了比较。结果表明：在201K条件下,VACF对Kr,Xe具有基本相同的平衡吸附容量,但VACF对Kr的吸附速度要大于对Xe的吸附速度。