Baseline design of a sorption-based Joule-Thomson cooler chain for the METIS instrument in the E-ELT

METIS, the Mid-Infrared E-ELT Imager and Spectrograph, is one of the proposed instruments in E-ELT (European Extremely Large Telescope). Its infrared detectors require multiple operating temperatures below 77 K. Therefore, active coolers have to be deployed to provide sub-liquid-nitrogen (sub-LN2) temperature cooling. However, the sensitive imaging optical detecting system also demands very low levels of vibration. Thus, the University of Twente proposed a vibration-free cooling technique based on physical sorption. In this paper, we describe the baseline design of such a sorption-based Joule-Thomson cooler chain for the METIS instrument, that is able to deliver cooling powers of 0.4 W at 8 K, 1.1 W at 25 K and 1.4 W at 40 K from a 70-K heat sinking. This design is based on working fluid selection, cascading cooler stages and operating parameter optimization. Also, the performance of the resulting cooler design is analyzed.     

Comparative study of the carbon nanofilm and nanodots grown by plasma-enhanced hot filament chemical vapor deposition

Carbon nanofilm and nanodots were grown by plasma-enhanced hot filament chemical vapor deposition using methane, hydrogen and nitrogen as the reactive gases. The results of field emission scanning electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy indicate that the amorphous carbon nanofilm and nanodots are formed without and with nitrogen, respectively. The formation of carbon nanofilm and nanodots is the consequence of different sputtering-etching effects. The photoluminescence (PL) of carbon nanofilm and nanodots was studied in a SPEX 1403 Ramalog system using a 325 nm He–Cd laser as an excitation source and the PL spectra show the PL bands centered at about 411 and 513 nm for the carbon nanofilm and 405 and 504 nm for the carbon nanodots. Simultaneously, the PL results also indicate that the intensity of PL bands of carbon nanofilm is lower than that of carbon nanodots. The generation of different PL bands was interpreted by the transition mechanism. The difference in the intensity of PL bands is related to the size of carbon nanodots. The electron field emission (EFE) characteristics of carbon nanofilm and nanodots were investigated in a high-vacuum system. The results show that Fowler–Nordhelm curves are composed of two or three straight lines and the carbon nanofilm can emit a high current density, which originate from the diversification of carbon nanodots. The difference in the EFE results of carbon nanofilm and nanodots is associated to the size and number of carbon nanodots. These results can enrich our knowledge about carbon-based nanomaterials and are important to fabricate the carbon-based solid nanodevices in the field of optoelectronics.     

Color-Tunable Polymeric Long-Persistent Luminescence Based on Polyphosphazenes

Organic long-persistent luminescence (OLPL) materials have attracted wide attention on account of their fascinating luminescence properties, presenting application prospects in the fields of bioimaging, information security, displays, anti-counterfeiting, and so on. Some effective strategies have been developed to promote the intersystem crossing (ISC) of the excited singlet state to triplet state and limit nonradiative transition, and thus OLPL materials with long lifetime (more than 1s) and high quantum yield have been explored. However, OLPL materials with dynamic and excitation-dependent characteristics are rarely reported. In this work, two novel polyphosphazene derivatives containing carbazolyl units are designed and synthesized successfully, and then they are doped into poly(vinyl alcohol) (PVA) films to achieve polymeric long-persistent luminescence (PLPL). Unexpectedly, excitation-dependent PLPL (ED-PLPL) is obtained under ambient conditions (in air at room temperature), and the persistent luminescence color can be changed from blue to green upon varying the excitation wavelength. At the same time, a dynamic cycle of ED-PLPL is realized based on the formation and destruction of hydrogen bonding interactions between the PVA chains and polyphosphazene phosphor. This work provides a new strategy for the design of color-tunable polymeric luminescent materials under ambient conditions.     

Experimental investigation on CO2 absorption in Sulfinol-M based Fe3O4 and MWCNT nanofluids

In recent years, absorption of carbon dioxide using nanofluids has increasingly gained attentions due to its unique advantages. In this study, the absorption of carbon dioxide using Sulfinol-M based nanofluids were investigated. Functionalized MWCNTs and Fe₃O₄ nanoparticles were dispersed in the absorbent in order to study their effects on absorption rate and equilibrium amount of absorption using a high pressure vessel equipped with a magnetic stirrer. The effects of different parameters including nanoparticle type, nanoparticle concentration in Sulfinol-M and initial pressure of CO₂ in gas phase were investigated. The obtained results revealed that the presence of both nanoparticles in the based solvent can enhance the rate of absorption and also the equilibrium solubility to a maximum amount of 46.7% and 23.2%, respectively. MWCNT shows better effects and it increases the solubility up to 7.3% more than Fe₃O₄ nanoparticle under the same condition. In addition, the possible mechanisms regarding mass transfer augmentation and equilibrium solubility enhancement are discussed.     

无铅SAC0307焊料润湿性与漫流性集成测试

为节省测试时间并降低测试成本,通过测量SAC0307焊料对铜管的润湿力、爬升高度及焊料对铜片的润湿力和铺展率,建立润湿性和漫流性的对应关系,集成测试获得焊料对铜片的润湿性能和铺展能力。结果表明,松香助焊剂作用下焊料对铜片的润湿力为铜管的1.1倍,丁二酸助焊剂作用下焊料对铜片的润湿力是铜管的1.3倍,松香和丁二酸两种助焊剂作用下焊料在铜管内爬升高度与铜片上铺展率的关系都为指数关系。     

The effect of substrate surface roughness on the nucleation of cubic boron nitride films

Boron nitride (BN) films have been deposited on silicon (Si) substrates with a root-mean-square surface roughness between 0.2 and 170 nm using mass-selected ion beam deposition (MSIBD). Mechanical scratching by either diamond or alumina powders with different powder sizes was used for substrate pretreatment. The effect of substrate surface roughness on the subsequent growth of BN films at different ion energies (75–500 eV) was investigated by Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and transmission electron microscopy (TEM). For rough substrates the surface morphology of the BN films changes from a granular structure at low ion energies to a flat and featureless surface at 500 eV ion energy. In the latter case grooves and valleys are first filled up with amorphous BN before turbostratic BN (t-BN) is formed. Eventually c-BN nucleates on the t-BN interfacial layer. The c-BN nucleation threshold energy of about 125 eV remains unchanged. Surface-like growth processes dominate at low ion energy, leading to the granular morphology. The observations are explained by ion impact on inclined micro-surfaces, leading to reduced projected ion ranges and enhanced sputtering and re-deposition into surface grooves and valleys.     

Preparation and particle size characterization of Cu nanopartides prepared by anodic arc plasma

Copper nanoparticles were successfully prepared in large scale by means of anodic arc discharging plasma method in inert atmosphere. The particle size, specific surface area, crystal structure, and morphology of the samples were characterized by X-ray diffraction （XRD）, BET equation, transmission electron microscopy （TEM）, and the corresponding selected area electron diffraction （SAED）. The experimental results indicate that the crystal structure of the samples is fcc structure the same as that of the bulk materials. The specific surface area is 11 m^2/g, the particle size distribution is 30 to 90 nm, and the average particle size is about 67 nm obtained from TEM and confirmed from XRD and BET results. The nanoparticles with uniform size, high purity, narrow size distribution and spherical shape can be prepared by this convenient and effective method.     

炮钢表面电弧离子镀TiAlN薄膜的摩擦磨损性能

为了提高PCrNi3Mo钢的耐磨性,利用电弧离子镀技术在其表面沉积了Ti_(0.7)Al_(0.3)N和Ti0.5Al0.5N薄膜,分析了沉积态和磨损态薄膜膜层的微观结构和形貌.结果表明,两种薄膜膜层均属于晶粒细小的柱状晶结构.Ti_(0.7)Al_(0.3)N和Ti0.5Al0.5N薄膜的硬度分别比PCrNi3Mo钢提高了4.75和4.22倍,而弹性模量分别比PCrNi3Mo钢提高了88%和84%.Ti_(0.7)Al_(0.3)N薄膜的稳定摩擦系数较小,两种薄膜具有显著的减摩耐磨作用.PCrNi3Mo钢的磨损机理主要为严重粘着磨损,而两种薄膜的磨损机理属于轻微粘着磨损.Ti0.5Al0.5N薄膜因脆性断裂局部产生了更大面积的剥落区,低硬度的PCrNi3Mo钢基体对膜层的支撑力变小是导致薄膜局部发生开裂破坏的主要原因.     

Effect of orientation and presence of hydride on the fatigue crack growth behavior of Zr–2.5 wt% Nb

Fatigue crack growth (fcg) behavior of cold-worked and stress relieved Zr–2.5 Nb was studied in the longitudinal (with and without hydrides) and transverse direction at ambient temperature and load ratio of 0.1 using compact tension samples. Fatigue loading in the transverse direction (distribution of both hard and soft grains) showed facet formation on the fracture surface and the highest ΔK_th whereas loading in the longitudinal direction (distribution of primarily soft grains) showed no facet formation and a lower ΔK_th. Hydrided Zr–2.5 Nb loaded in the transverse direction showed large facets with the lowest ΔK_th. Texture influenced fcg at low ΔK but not at higher ΔK.     

Hot shearing processes: Correlation of numerical simulation with real wear phenomena

Metal sheet shearing is a necessary procedure for dimensional control during steel forming. Due to extreme operating conditions, shearing blades suffer from severe wear and need frequent repair, causing high maintenance costs. In order to increase the lifetime of cutting blades, FEM simulation of the metal shearing process was performed, implementing a hybrid friction coefficient based on data obtained from a newly developed forming tribometer. A good correlation was found between the shape of the sheared work piece as predicted by the FEM model and as found in the real application. Finally, a relationship is proposed between stress and temperature distributions as calculated by the simulation and shearing blade areas most affected by wear.