氮中二氧化硫标准气体定值方法的研究

介绍用脉冲荧光分析仪对氮中二氧化硫标准气体定值的分析方法,对方法的精密度、准确度及定值的不确定度进行了考察。该方法的定值结果与重量法的配制值相一致。用该法对荷兰国家计量院制备的氮中二氧化硫标准气体进行比对试验,取得了良好的等效性。     

A New Model for the Genesis of Natural Gases--Multi-source Overlap, Multi-stage Continuity, Type Controlled by Main Source and Nomenclature by Main Stage (Ⅰ)--Multi-source Overlap and Type Controlled by Main Source

Based on the geochemical studies of natural gases in the past ten years in China, the authors have proposed a new model for their genesis--multi-source overlap, multi-stage continuity, main source-controlling type and nomenclature by the main stage.Multi-source refers to a diversity of material sources involved in the formation of natural gases, including abiogenic and biogenic material sources. In regard to biogenic sources, either oil-generating or coal-generating organic matter would produce gaseous hydrocarbon reservoirs of commercial importance. Generally, natural gases originating from these sources can overlap to form gas reservoirs. Under specific circumstances mantle-source abiogenic gases could overlap biogenic gases to form gas reservoirs. In nature, natural gases predominated by gaseous hydrocarbons may be formed from a single end-member source. However, multi-source overlap is more typical of the genesis of natural gases.     

Novel correlations between the critical constants of the noble gases

For any particular fluid, the set of three critical constants (CC) – pressure P_c, temperature T_c and molar volume V_c – has a central importance in defining the physical behaviour of the fluid in the gas and liquid states. However, little attention seems to have been paid in the past to the relations between the CC of different substances. In the present paper, some simple and apparently novel relations have been found between the three CC for the set of four noble gases: Ne, Ar, Kr, Xe. Defining the critical quotient Q_c ≡ RT_c/P_c (where R is the Gas Constant) the correlations may be summarised by the dual equation: (V_c/cm³ mol⁻¹) = 27 + 0.31 (T_c/K) = 3.3 + 0.280 (Q_c/cm³ mol⁻¹), which describes the CC data for the quartet Ne–Xe with an average uncertainty of 0.5%. Regarding the other two noble gases, the two isotopes of the lightest member, ³He and ⁴He, show the deviations from these relations that are expected from quantal effects and their low molar masses; while for the heaviest member, Rn, the correlations enable a value of 145(5) cm³ mol⁻¹ to be estimated for V_c that is not otherwise well defined in the literature. By contrast, and contrary to the general assumption, the second lightest member, Ne, apparently does not show appreciable quantal effects in the area, so that Ne–Xe may be considered together as a group. These correlations are compared with the behaviour of a selection of polyatomic fluids; in these comparisons, the NG dual correlation equation provides a reference line defining the presumed simplest behaviour. This and related areas show a “Residual Volume Effect”, in that extrapolating the equivalent temperature and energy parameters to zero for the state of zero-mass point particles, referred to here as the hypothetical element zeronium (Ze), the system in each case still has a finite intercept; this intercept amounts to essentially 34% of the average volume for the present quartet Ne–Xe, rather than the zero volume expected for this condition.     

Mass Spectrometric Observation of Doubly Charged Alkaline‐Earth Argon Ions

Doubly charged diatomic ions MAr²⁺ where M=Mg, Ca, Sr or Ba have been observed by mass spectrometry with an inductively coupled plasma ion source. Abundance ratios are quite high, 0.1 % for MgAr²⁺, 0.4 % for CaAr²⁺, 0.2 % for SrAr²⁺ and 0.1 % for BaAr²⁺ relative to the corresponding doubly charged atomic ions M²⁺. It is assumed that these molecular ions are formed through reactions of the doubly charged metal ions with neutral argon atoms within the ion source. Bond dissociation energies (D₀) were calculated and agree well with previously published values. The abundance ratios MAr⁺/M⁺ and MAr²⁺/M²⁺ generally follow the predicted bond dissociation energies with the exception of MgAr²⁺. Mg²⁺ should form the strongest bond with Ar [D₀ (MgAr²⁺)=124 to 130 kJ mol^?1] but its relative abundance is similar to that of the weakest bound BaAr²⁺ (D₀=34 to 42 kJ mol^?1). The relative abundances of the various MAr²⁺ ions are higher than those expected from an argon plasma at T=6000 K, indicating that collisions during ion extraction reduce the abundance of the MAr²⁺ ions relative to the composition in the source. The corresponding singly charged MAr⁺ ions are also observed but occur at about three orders of magnitude lower intensity than MAr²⁺.     

Neon‐Bearing Ammonium Metal Formates: Formation and Behaviour under Pressure

The incorporation of noble gas atoms, in particular neon, into the pores of network structures is very challenging due to the weak interactions they experience with the network solid. Using high‐pressure single‐crystal X‐ray diffraction, we demonstrate that neon atoms enter into the extended network of ammonium metal formates, thus forming compounds Ne_x[NH₄][M(HCOO)₃]. This phenomenon modifies the compressional and structural behaviours of the ammonium metal formates under pressure. The neon atoms can be clearly localised within the centre of [M(HCOO)₃]₅ cages and the total saturation of this site is achieved after ～1.5 GPa. We find that by using argon as the pressure‐transmitting medium, the inclusion inside [NH₄][M(HCOO)₃] is inhibited due to the larger size of the argon. This study illustrates the size selectivity of [NH₄][M(HCOO)₃] compounds between neon and argon insertion under pressure, and the effect of inclusion on the high‐pressure behaviour of neon‐bearing ammonium metal formates.     

Development toward a double focusing isotopic separator for noble gas isotope enrichment

A double focusing sector field mass filter used in Nier–Johnson geometry has been built in order to perform Kr isotope enrichment for ⁸¹Kr and ⁸⁵Kr isotopes. The principle consists in implanting Kr⁺ ions accelerated at 7 keV in Al foils after separation using the magnetic sector. A specific ion source has been designed capable of generating high Kr⁺ ion beams (>0.5 μA) to transfer into the collecting Al foils in 3 to 5 h significant fractions of large Kr samples (10¹⁵ to 10¹⁶ atoms) initially introduced in the instrument. Implanted Kr isotopes can be further selectively released from the Al foil by surface ablation using an infrared laser beam. Implantation yields and enrichment factors are measured using a conventional mass spectrometer. Copyright © 2016 John Wiley & Sons, Ltd.     

Head-on collision of normal shock waves in dusty gases

The head-on collision of normal shock waves in dusty gases has been investigated numerically, using the modified random-choice method. The results concerning the various flow field properties as well as the waves configuration were compared with those of a pure gas case.     

防污染的自消应力高纯度气体低温换热器的设计

该设计解决了低温工程与低温技术等领域所使用的高纯度气体介质换热的要求,具有显著的经济效益和社会效益。其换热器是由四个管壳式热交换器串联组合而成,壳体呈窄矩形,换热管采用U形换热管,四个管壳式热交换器呈方阵置放在低温换热器筒体内。低温换热器采用的材料是0Cr18N i9/304,该种材料的透气性小、耐磨损、抗腐蚀能力强和性能稳定,防止了气体被污染。另外在低温下,考虑了材料的热胀冷缩所产生的应力,使应力能够自行消除,提高了它的密封性能,最终使低温换热器密封性能好,防止了气体被污染,保证了气体的高纯度。     

Electro-photo modulation of the fermi level in WSe2/graphene van der Waals heterojunction

We report an electro-photo double modulation of the fermi level in a WSe₂/graphene heterojunction. The heterojunction exhibits high I_ON/I_OFF ratio (~10³) in transfer characteristic in dark and distinct rectification behavior in output characteristic under light illumination, respectively. Time-dependent photoresponse reveals that the heterojunction has a considerable potential in the application of photodetection. Interestingly, an exotic current peak is observed in transfer characteristic under light illumination. This novel behavior is attributed to the tunable fermi level at the WSe₂/graphene heterojunction by electro-photo double modulation. The results may be helpful to develop tunable photovoltaic optoelectronics based on van der Waals heterojunctions.