Development of a lightweight space debris shield using high strength fibers

In order to protect space structure against space debris impacts, it is indispensable to develop a shield with high strength materials. A high strength fiber is one of potential materials from a viewpoint of strength, lightweight, and flexibility. The purpose of this study was to develop a new lightweight shield composed of high strength fibers against medium size debris impacts. We developed four kinds of shields using Vectran fibers, and hypervelocity impact tests were carried out by a railgun accelerator. The experimental results showed that the developed shield could stop the polycarbonate projectile with 13 mm in diameter, 1 gram in weight, and 6.9 km/sec in velocity. Adoption of the high strength fiber in the bumper materials may reinforce the protection capability and reduce the weight drastically.     

Development of bumper shield using low density materials

In order to avoid critical accidents due to space debris, this paper proposes an extra bumper shield called an inflatable bumper. It consists of aluminum (Al2024-T3), high strength fiber Vectran and inflatable polyurethane. Because of this inflatability, it is compactly stored during its transportation. And after the installation outside of the space structures, this bumper is then inflated by the effect of expandable polyurethane. This method saves the amount of the transportation and the involved cost. In this paper the experiments, using several polyurethane's with different areal density, have been conducted, compared and evaluated from the viewpoints of the penetrated areal density, the total thickness penetrated, and mass distribution of the fragments captured inside the shield. As the results of the experiments, it is found that the protection ability of the proposed structure depends on the areal density of polyurethane layers and the optimum areal density is 0.525kg/m². And by using polyurethane between Vectran layers, this expandable structure captures the fragments of the secondary debris, which might cause a secondary impact on the space structure.     

Successive entrapping of red and yellow quinoid chalcones from aqueous extracts of dyer's saffron florets: a newly established and practically approved technique

Summary A setup for successive entrapping of red and yellow quinoid chalcone pigments was assembled. The device consists of four parts: a unit for the extraction of the pigments, a unit for their transfer to the column, a unit for entrapping the columns and a unit for releasing the trapped substances. The device enables us to extract the naturally occurring oxygen-labile, pH-sensitive and UV-fragile pigments on an economically approved scale.

---

Schrittweises Freimachen von roten und gelben chinolden Chalkonen aus wäßrigen Extrakten von Safranblütenfarben; eine neue entwickelte und geprüfte Technik

Zusammenfassung Es wurde ein Plan fur das schrittweise Freimachen von roten und gelben chinoiden Pigmenten entwickelt. Die Arbeitsweise besteht aus vier Schritten. zuerst in der Extraktion der Pigmente, dann deren Überführung in die Säule, daraufhin das Freimachen aus der Säule und schließlich das Freisetzen der abgeschiedenen Stoffe. Dieses Vorgehen ermöglicht, die pH-, 02- und UV-empfindlichen Stoffe ökonomisch und gezielt zu gewinnen.

     

Effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile using dialkylmagnesium as catalyst

An attempt was made to clarify the effect of addition of organoaluminum and organoboron compounds in the stereospecific polymerization of acrylonitrile (AN) initiated by dialkylmagnesium (R₂Mg) above 100°C. The triad isotacticity (i.e. the content of mm (m: meso)) as well as the viscosity-average molecular weight (M?_v) of polyacrylonitrile (PAN) increased when trialkylaluminum (R₃Al) and trialkylboron (R₃B) were used as additives. Diisobutylaluminum hydride [(i-C₄H₉)₂AlH] was found to be the best additive. in the stereospecific polymerization of AN, giving PAN with higher (mm) content (0.63), higher M?_v value (5.2 × 10⁴), and a yield approximately double that obtained using (n-C₆H₁₃)₂Mg alone. When the (n-C₆H₁₃)₂Mg/(i-C₄H₉)₂AlH system was used, the yield, (mm), and M?_v of PAN increased with polymerization temperature (T_p); maximum values of yield, (mm), and M?_v were obtained at c. 130°C. The optimum amount of additives was approximately equimolar to R₂Mg as initiator. The ¹³C chemical shift of α-carbon in R₂Mg at 90°C shifted by mixing with R₃Al and R₃B, respectively, indicating the existence of interaction between R₂Mg and the additives. The main role of the additives is considered to be suppression of the self-association of R₂Mg by strong interaction with R₂Mg.     

Synthesis of highly isotactic (mm > 0.70) polyacrylonitrile by anionic polymerization using diethylberyllium as a main initiator

An attempt was made to synthesize steroregular polyacrylonitrile (PAN) with a high triad isotacticity (i.e. the content of mm (m, meso)) exceeding 0.70 by the anionic polymerization method. In the stereospecific polymerization of acrylonitrile (AN) initiated by diethylberyllium (Et₂Be) in xylene at 130°C, the (mm) content as well as the viscosity-average molecular weight (MÞ_v) of PAN increased by addition of diisobutylaluminum hydride (i-C₄H₉)₂AlH) as an additive to the polymerization system. Maximum (mm) content, attained in the molar ratio region of (i-C₄H₉)₂AlH/Et₂Be > 1.0, was about 0.73. The stereospecific polymerization of AN was also initiated using a mixture of Et₂Be and di-n-hexylamagnesium ((Et₂Be/(n-C₆H₁₃)₂ Mg system), where both Et₂Be and (n-C₆H₁₃)₂ Mg can induce the stereospecific polymerization of AN at 130°C. The (mm) content of the PAN sample prepared using the Et₂Be/(n-C₆H₁₃)₂ Mg system ((mm) = 0.64) was higher than that of PAN samples synthesized using Et₂Be alone ((mm) = 0.56) and (n-C₆H₁₃)₂Mg alone ((mm) = 0.51) under the same conditions except initiator. A significant difference in ¹³C chemical shifts of α-carbons between Et₂Be (1.35 ppm) and (n-C₆H₁₃)₂Mg (10.72 ppm) dissolved in hydrocarbon solvent at 110°C leads us to the conclusion that when Et₂Be induces the stereospecific polymerization in the Et₂Be/(n-C₆H₁₃)₂Mg system as initiator, the main role of (n-C₆H₁₃)₂Mg is considered to be the suppression of the association of Et₂Be (active site) itself.     

High strain rate superplasticity of a 25 Wt Pct Cr-7 Wt Pct Ni-3 Wt Pct Mo-0.14 Wt Pct N duplex stainless steel

Effects of prior thermomechanical treatments on the superplasticity of a 25 wt pct Cr-7 wt pct Ni-3 wt pct Mo-0.14 wt pct N δ/γ duplex stainless steel have been studied by means of hot tensile testing with constant crosshead speeds. The objective is to increase the strain rate suitable for superplasticity. The strain rate is found to be markedly increased by a special prior treatment,i.e., solution treatment at temperatures in the δ single-phase region with subsequent heavy cold-rolling. In hot tensile tests at 1273 K, elongations greater than 1000 and 300 pct were observed at initial strain rates (έ) of 10⁻³ to 10⁻¹ s⁻¹ and 1 x 10⁰ s⁻¹, respectively. The results for strain rates 〈10⁻¹ s⁻¹ can be explained in terms of a structural superplastic effect due to grain refinement. In the case of έ 〉 10⁻¹ s⁻¹, transformation superplastic effects due to γ-phase precipitation from the σ-ferrite matrix are also important, especially in the early stages of deformation. In the equiaxedδ/γ microduplex structures during stable superplastic deformation, there exists a mixture of two different structures,i.e., dislocated and recovered/ recrystallized δ grains with a homogeneous dispersion of dislocation-free γ particles. This result shows that dynamic recrystallization ofδ grains occurs locally and intermittently due to the dispersion of relatively hardγ particles. The apparent average grain growth rate during deformation is small compared to static grain growth, because grain refinement due to dynamic recrystallization reduces the superplasticity-enhanced grain growth.     

Phoswich detectors combining doubly or triply ZnS(Ag), NE102A, BGO and/or NaI(Tl) scintillators for simultaneous counting of α, β and γ rays

Phoswich detectors for simultaneous counting of α, β and γ rays have been developed: ZnS(Ag)/Au Mylar/NE102A, ZnS(Ag)/Au Mylar/BGO and ZnS(Ag)/NaI(Tl) for α and β(γ) rays and ZnS(Ag)/Au Mylar/NE102A/BGO and ZnS(Ag)/NE102A/NaI(Tl) for α, β and γ rays. They were prepared by coupling a ZnS(Ag) film scintillator for α counting with a scintillator(s) for β and γ counting having different rise time. In order to adjust each component of pulse height within a given dynamic range, a sheet of Au-coated Mylar (Au Mylar) was used, if necessary, as an optical ND filter for lowering transmittance of scintillation of the ZnS(Ag). Characteristics of these phoswiches were examined by a technique of pulse-shape discrimination. Excellent discrimination among the radiations was attained and small tailings from each other peak were obtained for the prepared phoswiches.     

Trimethylamine-sensing mechanism of TiO2-based sensors 2. Effects of catalytic activity of TiO2-based specimens on their trimethylamine-sensing properties

The effects of metal additives on the catalytic of TiO₂ for trimethylamine (TMA) oxidation have been investigated in relation to their TMA-sensing properties. The catalytic activity is more or less enhanced by adding a small amount of Ru, In or Au, the behaviour being in good agreement with the fact that these metals are effective in promoting the TMA sensitivity. In contrast, it is found that too great an enhancement in the catalytic activity induced by the addition of Pd, Pt or Rh results in deterioration of the sensitivity. Referring to the relationship between the catalytic activity and the TMA-sensing property, a possible mechanism is discussed.