Materials based on carbon nanotubes hold great promise for a variety of applications relevant to space exploration and the aerospace industry. Materials used for these applications will be subject to hostile environments including increased levels of high-energy particulate radiation. The type, energy range and fluence of the radiation will depend on the environment of the space mission. While it is not feasible to conduct an exhaustive study of the effects of space radiation on the earth's surface, ground-based experiments can be designed to simulate expected radiation environments using sources representing components of the relevant radiation environments. In this paper we present a compilation of results on materials based on singlewalled carbon nanotubes (SWNT) emphasizing nano-composites with raw (non-functionalized) and with 2–5% functionalized SWNTs in a polyethylene matrix. Materials such as these are promising candidates for multi-functional materials with good structural and radiation shielding characteristics. The radiation sources discussed here are relevant to the upper atmosphere (high energy neutrons), low earth orbit (medium energy protons) and interplanetary space (high energy protons and heavy ions). The samples are characterized before and after radiation with Raman spectroscopy which gives information on the structure of the SWNT and state of sidewall functionalization. Based on results from the SWNT papers (“buckypapers”) and the composites made from functionalized and non-functionalized SWNT, our data indicates that structural integrity and any sidewall functionalization of the SWNT in the nano-composite are radiation tolerant to radiation fluences commensurate with expected exposures on long-term spaceflight. More importantly, we find that the chemistry and material science of the processes used to produce the pristine and functionalized SWNT can affect the radiation characteristics of the nano-composites.

Thin film silicon material has an extensive application in cooling satellite instrumentation under cryogenic environment. The performance and reliability of the cooling system heavily depends on mechanical behavior of the thin films. In this paper, we built an experimental setup and used compressive gas to actuate a silicon thin film under both room temperature and cryogenic temperature. The elastic modulus was derived from the film's deflection using laser Michelson interferometer. Stress distribution was obtained using Micro Raman spectroscopy. It was found that Young's modulus derived from the deflection increases with decreasing temperature. Compressive stress concentrated at edge centers of the film and tensile stress occurred at the center. There is a good match between the theoretical predications and experimental observations.

In view of the potential use of amorphous magnets as radiation-resistant materials, we performed a comparative study between laser and particle beam induced effects in amorphous alloy systems. We irradiated Fe81B13.5 Si3.5C2, Fe40Ni38Mo4B18, Fe66Co18B15Si1 and Fe72.6Cr22Al4.8Si0.3Y0.3 with pulsed laser radiation as well as with high (W=7 MeV) and low energy (W=30 and 50 keV) electrons and with 2.8 MeV alpha particles. The irradiation effects in these systems were investigated using several complementary techniques: transmission and conversion electron Mössbauer spectroscopy, magnetometry and electron microscopy. We were able to deduce details of the mechanism of magnetic texture formation and of the amorphous-to-crystalline phase transformations in the studied amorphous alloys.

In the microelectronics industry, Sn is often electroplated as a protective layer on Cu conductors. Pure Sn layers on Cu develop whiskers that can cause component failures and have even been implicated in the loss of several satellites. Alloying Sn with Pb suppresses whisker formation, but the push towards Pb-free processing will make this unacceptable in the future. To understand the driving forces and mechanisms of whisker formation on pure Sn, we are measuring the kinetics of stress evolution and intermetallic formation in Sn/Cu layers. By using thin films of Sn and Cu, we can monitor the stress evolution in real time using wafer-curvature based techniques. Preliminary results of stress evolution in vapor-deposited films are presented showing the evolution of tensile stress in the Cu layers and compressive stress in the Sn layers.

Carbon-based materials including microcrystalline diamond, nanocrystalline diamond, and carbon nanotubes films were prepared by microwave plasma-assisted chemical vapor deposition (MWCVD) technique. While the former were submitted to gamma radiation doses of 1, 5, and 20 Mrad, the latter to low energy electron beam of 30 keV or to 30 GeV/cm2) to study the radiation-induced structural transformation. The characterizations were performed prior to and after irradiation using Raman spectroscopy, scanning electron microscopy, and X-ray diffraction, techniques. Microcrystalline diamond showed a dramatic modification in the structural properties only after a cumulative dose of 26 Mrad (2 Grad/cm2), while nanocrystalline carbon showed a relatively small but systematic transformation with increasing gamma radiation dose. The results indicate that nanocrystalline carbon tends to reach a state of saturation when submitted to 26 Mrad doses of gamma radiation, suggesting the possibility of fabricating radiation buffer materials that would undergo internal sp3 ⇔ sp2 inter-conversion while absorbing ionizing radiation without changing their average microstructure and protecting the device/material underneath. Single- and multi-walled nanotubes exhibited structural modifications after 5.5–8 hrs of continuous exposure to electron beam. The variation in the characteristic X-ray peaks for multi-walled and single-walled corresponding to intertube spacing and the high frequency Raman band around 1580 cm−1 (G band) are reflected in their corresponding spectra. The results indicate that there is an increase in the intertube spacing for multi-walled nanotubes due to electron irradiation. While single-wall nanotubes tends to ‘collapse’ after > 8 hours of exposure forming multi-wall nanotubes analyzed using scanning electron microscopy and Raman spectroscopy. These C materials can be employed for preventing space radiation from reaching sensitive materials and electronic devices at least for short term experiments and entitled them as ‘space radiation shields’.

Mechanical, magnetic, and transport properties of arbitrary inhomogeneous composites are investigated by a Bruggeman-type mean-field approach. The theory yields materials parameters as functions of the volume fractions, geometries, and materials constants of the phases. Each system is described by a single response parameter g, which is equal to the percolation threshold of the composite. For macroscopic systems, the approach yields very simple expressions, but nanoscale and multiferroic effects yield relatively complicated corrections to g. In the respective cases, the parameter g depends on the length scale of the composite and has the character of a combination of magnetic, electric, and mechanical degrees of freedom.

The effect of the radiation component of the space environment on polyimide films is reviewed. Experimental data obtained by electron spin resonance and dynamical mechanical analysis proved that the ionizing radiation generates free radicals with a long lifetime through a dominant chain scission mechanism. The radiation-induced shift of the glass transition of polyimide towards lower values confirms the decrease of the average molecular mass of the polymer during irradiation. The importance of polyimide for space exploration is critically analyzed.

Vibrational spectroscopies and in particular Raman spectroscopy are known to be among the most useful tools to characterize and control the properties of carbon materials. This is because of the possibility to detect and study the carbon bonding state and because of the strong correlation between shape and width of the vibrational signals and the structure of the amorphous network. The aim of this work is to present some experiments in which the formation and evolution of carbon films obtained by energetic particle irradiation of solid targets or by deposition of carbonaceous species onto suitable surfaces, are controlled and studied by these methods. Particular attention will be given to pure amorphous carbon films and carbon based binary alloys.

We have performed molecular dynamics simulation of displacement events on silicon and carbon sublattices in silicon carbide for displacement doses ranging from 0.005 to 0.5 displacements per atom. Our results indicate that the displacement threshold energy is about 21 eV for C and 35 eV for Si, and amorphization can occur by accumulation of displacement damage regardless of whether Si or C is displaced. In addition, we have simulated defect production in high-energy cascades as a function of the primary knock-on atom energy and observed features that are different from the case of damage accumulation in Si. These systematic studies shed light on the phenomenon of non-ionizing energy loss that is relevant to understanding space radiation effects in semiconductor devices.

Contaminating films on spacecraft sensitive materials surfaces in many cases consist primarily of products resulting from the interaction of atomic oxygen with silicones. Necessity of a drastic reduction of the outgassing of volatiles and the following contamination has thus become a challenging problem. The effective surface conversion of space related organosilicone materials to oxide-based protective sub-surface layers under ground-based OpenAir™ plasma pre-treatment has been researched. Oxygen plasma asher testing and complementary surface analysis techniques have been used to assess the surface composition, bounding states and atomic oxygen resistance of the treated materials. It was shown that the application of this approach may essentially simplify the technological development to reduce or prevent contamination caused by silicone-coated space materials and structures.

Main areas of Skobeltsyn Institute of Nuclear Physics Moscow State University activities in study of space environment effect on materials are following: effect of space radiation on spacecraft materials and equipment elements, spacecraft charging in space plasma in various orbits, influence of atomic oxygen flux on materials in LEO, surface erosion and destruction under impact of micrometeoroids and small particles of space debris.

The methods of computer and laboratory modeling used are described. Results of the researches are presented, as far as some experiments onboard the MIR station and ISS are described. Principle problems for contemporary and future research are proposed for discussion. Principle problems for contemporary and future research are proposed for discussion.

While spacecrafts experience temperatures from -120 to 110°C on the orbit, their surface reaches extremely high temperatures, well above 1000 °C, during descent into the atmosphere due to aerodynamic heating. Sophisticated insulation systems are designed for thermal protection. One of the steps in designing a protection system is experimental temperature measurements.

Neutron flux induces point defects formation and accumulation in diamond and SiC single crystals, which causes overall lattice expansion. During thermal annealing this process is reversed, so the annealing temperature and time result in the “reduced” lattice parameter (measured by X-Ray diffraction), which allows determining the maximum temperature, if the exposure time is known. This paper describes the use of irradiated single crystal high temperature sensors for measuring temperatures in thermal protection systems during spacecraft descent, as well as other space applications. These additional applications include measuring the furnace temperature during single crystal growth in space at zero gravity, and measuring the rocket combustion chamber turbo pump temperature.

The high-strength and ductile hypo-, hyper- and eutectic Ti-Fe alloys were formed in the shape of the arc-melted ingots with the dimensions of about 25–40 mm in diameter and 10–15 mm in height. The structure of the samples consists of cubic Pm 3 m TiFe and BCC Im 3 m β-Ti supersaturated solid solution phase. The arc-melted hypereutectic Ti65Fe35 alloy has a dispersed structure consisting of the primary TiFe phase and submicron-size eutectic structure. This alloy exhibits excellent mechanical properties: a Young's modulus of 149 GPa, a high mechanical fracture strength of 2.2 GPa, a 0.2 % yield strength of 1.8 GPa and 6.7 % ductility. The hard round-shaped intermetallic TiFe phase and the supersaturated β-Ti solid solution result in a high strength of the Ti65Fe35 alloy which in addition has much higher ductility compared to that of the nanostructured or glassy alloys. The reasons for the high ductility of the hypereutectic alloy are discussed.

We had studied the effects of hyperthermal (5.1eV) atomic oxygen (AO) on the structural characteristics of the silica layer and Si/SiOx interface formed by the oxidation of Si-single crystal by a variety of microcharacterization techniques. A laser detonation source was used to produce atomic oxygen with 5.1eV kinetic energy. High Resolution Transmission Electron Microscopy (HRTEM) and Selected Area Electron Diffraction (SAED) demonstrated that the silica layer formed on Si(100) by atomic oxygen is thicker, more homogeneous, and less amorphous, compared to the oxide layer created by molecular oxygen (MO). High spatial resolution Electron Energy Loss Spectroscopy (EELS) study confirmed that the Si/SiOx interface created by atomic oxygen is abrupt containing no suboxides as opposed to the broad interface with transitional states formed by molecular oxygen. SAED technique was used to observe sharper diffraction rings present in the diffraction pattern of Si(100) oxidized by reactive atomic oxygen as opposed to the diffused haloes present in the diffraction pattern of Si(100) oxidized by molecular oxygen. Radial Distribution Function (RDF) analyses were performed on the SAED patterns of Si(100) oxidized in atomic and molecular oxygen, indicating that a more ordered oxide is formed by atomic oxygen. Initial Fluctuation Electron Microscopy (FEM) results confirmed an increased medium range ordering in SiOx formed by atomic oxygen when compared to the non-regular arrangement present in the amorphous oxide formed by the oxidation of Si(100) in molecular oxygen.

We describe two new beamlines for radiation effects research at the Indiana University Cyclotron Facility. Protons with energies up to 205 MeV are available. One of the beamlines offers momentum selected beams at energies as low as 52 MeV.

This work applies different thermal analysis methods to polymer based materials degradation, studying the degradation process itself and evaluating the degree of material damage as a consequence of chemical degradation by thermal or radiation effects. On the one hand, thermal degradation in varied atmospheres is investigated by means of thermogravimetric analysis (TGA) in dynamic experiments. The authors find that the evolution of the sample mass follows a mixture of logistics models, and these can fit an overall TGA curve. The fitting parameters have important physical meaning related to the kinetics of the different processes involved and to the relative amount of each component in the sample. The method itself entails separating overlapping processes. Other improvements made by the authors are related to reducing the noise and smoothing the TGA and differential scanning calorimetry (DSC) data, particularly when estimating TGA derivatives through logistic regression.

Analyzing many materials by means of TGA results in more or less complex traces that do not allow a simple parametric fit like the one described above. Although it reproduces asymptoticity at the beginning and end of the reaction, there are times when many processes overlap, resulting in a complex trace that would need a high number of logistic components to be adequately fitted. However, it is possible to use a local polynomial regression model instead. This is also applicable to DSC traces, whose shapes are totally different from those found in TGA. The authors propose a model based on a nonparametric estimation, where the fit's suitability very much depends on the bandwidth selection, especially where derivatives are concerned. The proposed model gives a satisfactory fitting. It smoothes noise and always provides reliable values, different from those obtained by other methods strongly dependent on user choice.

On the other hand, to evaluate the degree of damage by thermal analysis methods, dynamic mechanical analysis (DMA) is applied to polyamides. The glass transition temperature is measured before and after exposure to varying doses of proton radiation, emulating the space environment. Other examples show how exposure over long periods at moderately elevated temperatures results in reduction of some mechanical properties. Additionally, the effect of different nanofillers on styrene-isoprene-styrene block copolymers is evaluated by DMA. A shift in the glass transition temperature seems to be dependent on nanofiller content. The degradation of some materials suitable for space applications, such as polyethylene and polyamide, are also briefly reviewed.

Self-assembled InAsSb/InGaAs quantum dots are candidates for optical detectors and emitters in the 2–5 micron band with a wide range of applications for atmospheric chemistry studies. It is known that while the energy band gap of unstrained bulk InAs1−xSbx is smallest for x=0.62, the biaxial strain for bulk InAs1−xSbx grown on In0.53Ga0.47As shifts the energy gap to higher energies and the smallest band gap is reached for x=0.51. The aim of the present study is to examine how the electronic confinement in the quantum dots modifies these simple considerations. We have calculated the electronic structure of lens shaped InAs1−xSbx quantum dots with diameter 37 nm and height 4 nm embedded in a In0.53Ga0.47As matrix of thickness 7 nm and lattice matched to an InP buffer. The relaxed atomic positions were determined by minimizing the elastic energy obtained from a valence force field description of the inter-atomic interaction. The electronic structure was calculated with an empirical tight binding approach. For Sb concentrations larger than x=0.5, it is found that the InSb/ In0.53Ga0.47As heterostructure becomes type II leading to no electron confined in the dot. It is also found that the energy gap decreases with increasing Sb content in contradiction with previous experimental results. A possible explanation is a significant variation is quantum dot size with Sb content.

The degradation of PMMA-CNT thin film composites was examined, using electron beam radiation as a function of CNTs concentration. The findings show that the addition of CNT fillers can significantly reinforce composites against the irradiation induced degradation of PMMA, in which polymer free radicals are mainly responsible for the progress of the degradation. The results show that CNT networks are able to effectively disperse irradiated electrons through the matrix. The saturation of reinforcement effects was observed at a concentration of CNTs of approximately 0.5 wt%. This concentration was interpreted in terms of the critical concentration needed for percolation of the CNTs network, and this was further verified by sheet resistivity measurements. Free radical interactions with CNTs were also investigated by accelerated electron beam radiation and thermogravimetric analysis. CNTs were able to inhibit the free radical proliferation during a degradation process and to reduce the extent of degradation of the composites.

This paper deals with the aerothemodynamic analysis of an advanced concept of hot structure to be investigated in the Expert flight test programme.

Three-dimensional fluid dynamic computations have been carried out at the flight conditions of the reference Expert trajectory to evaluate the aerothermodynamic field and the thermal loads on the winglet. The physical model includes viscous effects, real gas properties, non equilibrium chemical reactions and surface catalytic effects. The unsteady aerothermal analysis has been carried out considering different thermal boundary conditions (adiabatic wall or thermal coupling with the capsule metallic skin).

The results are discussed with particular attention to the temperature distributions in the Ultra High Temperature Ceramics (UHTC) and in the structural support.

Kapton polyimide (PI) is widely used on the exterior of spacecraft as a thermal insulator. Atomic oxygen (AO) in lower earth orbit (LEO) causes severe degradation in Kapton resulting in reduced spacecraft lifetimes. One solution is to coat the polymer surface with SiO2 since this coating is known to impart remarkable oxidation resistance. Imperfections in the SiO2 application process and micrometeoroid / debris impact in orbit damage the SiO2 coating, leading to erosion of Kapton.

A self passivating, self healing silica layer protecting underlying Kapton upon exposure to AO may result from the nanodispersion of silicon and oxygen within the polymer matrix. Polyhedral oligomeric silsesquioxane (POSS) is composed of an inorganic cage structure with a 2:3 Si:O ratio surrounded by tailorable organic groups and is a possible delivery system for nanodispersed silica. A POSS dianiline was copolymerized with pyromellitic dianhydride and 4, 4′-oxydianiline resulting in POSS Kapton Polyimide. The glass transition temperature (Tg) of 5 to 25 weight % POSS Polyimide was determined to be slightly lower, 5 – 10 %, than that of unmodified polyimides (414 °C). Furthermore the room temperature modulus of polyimide is unaffected by POSS, and the modulus at temperatures greater than the Tg of the polyimide is doubled by the incorporation of 20 wt % POSS.

To simulate LEO conditions, POSS PI films underwent exposure to a hyperthermal O-atom beam. Surface analysis of exposed and unexposed films conducted with X-ray photoelectron spectroscopy, atomic force microscopy, and surface profilometry support the formation of a SiO2 self healing passivation layer upon AO exposure. This is exemplified by erosion rates of 10 and 20 weight % POSS PI samples which were 3.7 and 0.98 percent, respectively, of the erosion rate for Kapton H at a fluence of 8.5 × 1020 O atoms cm-2. This data corresponds to an erosion yield for 10 wt % POSS PI of 4.8 % of Kapton H. In a separate exposure, at a fluence of 7.33 × 1020 O atoms cm-2, 25 wt % POSS Polyimide showed the erosion yield of about 1.1 % of that of Kapton H. Also, recently at a lower fluence of 2.03 × 1020 O atoms cm-2, in going from 20 to 25 wt % POSS PI the erosion was decreased by a factor of 2 with an erosion yield too minor to be measured for 25 wt % POSS PI.