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The purpose of this white paper is to provide an overview to the NRC Decadal Survey Mars and Ocean Worlds Sub-Panels on thermal protection system (TPS) technologies required for future Mars and Titan exploration missions. It considers the capability of heritage TPS technology used by previous Mars and Titan missions. A prime conclusion is that there are important advances regarding the availability of forebody TPS therefore, we recommend that NASA invest in a cross-cutting technology program that focuses on development and sustainment of relevant TPS materials, entry systems, test facilities, design tools, and flight instrumentation.

The purpose of this white paper is to provide an overview to the NRC Decadal Survey Inner Planets Sub–Panel on key technologies required for future Venus exploration missions. It covers both heritage technologies and identifies new technologies to enable future missions in all three mission classes. The technologies will focus on mission enabling and enhancing capabilities for in situ missions, because most orbiter related sub–systems are considered heritage technologies. This white paper draws heavily on the recently completed Venus Flagship Mission study that identified key technologies required to implement its Design Reference Mission and other important mission options. The highest priority technologies and capabilities for the Venus Flagship Design Reference mission consist of: surface sample acquisition and handling; mechanical implementation of a rotating pressure vessel; a rugged–terrain landing system; and a large scale environmental test chamber to test these technologies under relevant Venus–like conditions. Other longer–term Venus Flagship Mission options will require additional new capabilities, namely a Venus–specific Radioisotope Power System; active refrigeration, high temperature electronics and advanced thermal insulation. The white paper will also argue for a technology development program, since without it future Venus missions might not be achievable.

On September 12th, 2018, a sounding rocket flight test was conducted on a mechanically-deployed atmospheric entry system known as the Adaptable Deployable Entry and Placement Technology (ADEPT). The purpose of the Sounding Rocket One (SR-1) test was to gather critical flight data for evaluating the vehicle's in-space deployment performance and supersonic stability. This flight test was a major milestone in a technology development campaign for Nano-ADEPT: the application of ADEPT for small secondary payloads. The test was conducted above White Sands Missile Range, New Mexico on a SpaceLoft XL rocket manufactured by UP Aerospace. This paper describes the system components, hardware development campaign, test execution, and test conclusions.

NASA’s Entry, Descent and Landing Architecture Study uses a trajectory simulation framework to evaluate various technologies and concepts of operations for human scale EDL at Mars. The study results inform agency technology investments. This paper summarizes the design assumptions and analysis of two deployable entry concepts performed in Phase 2 of the study. The entry concepts include a rigid deployable called the Adaptable Deployable Entry Placement Technology and an inflatable concept called the Hypersonic Inflatable Aerodynamic Decelerator. This paper describes the concept operations of these vehicles to deliver a 20-metric ton payload to the surface of Mars. Details of vehicle design and flight performance are summarized along with results of analysis on the aft body heating and its effect on the payload. Finally, recommended technology investments based on the results are presented.

The Adaptive Deployable Entry and Placement Technology (ADEPT) is being considered as an entry, descent and landing (EDL) system to enable Human Mars class missions. ADEPT is a mechanically deployable decelerator that makes use of a 3 d woven carbon fabric as both heat shield and primary structure. The Human Mars Mission design study is focused, in part, on assessing the viability of ADEPT and identifying technical challenges, operational constraints, and critical risk mitigation activities. Study inputs included definition of the ground rules and assumptions, associated mission timelines and high level functional requirements. These inputs enabled the clarification of the concept of operations along with the design constraints and environments. Subsystem trades, mass sizing and integrated flight performance assessments enabled determination of a feasible mission architecture. Key outputs from the design study include a parametric mass model, driving requirements, key performance parameters and critical risks. These findings enable us to determine strategies for technical maturation and risk mitigation that can be assessed against resource and programmatic constraints to aid in advanced planning for human exploration of Mars.

The Adaptable, Deployable Entry and Placement Technology (ADEPT) architecture represents a novel approach for entry vehicle design utilizing a high performance carbon-fabric to serve as the primary drag surface of the mechanically deployed decelerator. The ADEPT project team is advancing this decelerator technology via systems-level testing at the one-meter diameter (nano-ADEPT) scale. A subsonic aeroloads test (May 2015) and an arc-jet aeroheating test (Sept 2015) have already been completed. The initial system-level development of the nano-ADEPT architecture will culminate in the launch of a 0.7 meter deployed diameter ADEPT sounding rocket flight experiment named, SR-1. Launch is planned for August 2017. The test will utilize the NASA Flight Opportunities Program sounding rocket platform provided by UP Aerospace to launch SR-1 to an apogee over 100 km and achieve re-entry conditions with a peak velocity near Mach 3. The SR-1 flight experiment will demonstrate most of the primary end-to-end mission stages including: launch in a stowed configuration, separation and deployment in exo-atmospheric conditions, and passive ballistic re-entry of a 70-degree half-angle faceted cone geometry. ADEPT SR-1 will determine supersonic through transonic aerodynamic stability of the unique ADEPT blunt body shape with an open-back entry vehicle configuration.

Thermal protection system materials for the Mars Science Laboratory mission were tested in the NASA Ames 60 MW arcjet in a shear environment. Shear tests were performed on candidate ablative heat shield materials in wedge and swept cylinder test fixtures. In portions of the expected flight environment, the proposed main heat shield material, known as SLA-561V, recessed orders of magnitude faster than predicted. An alternate main heat shield material, known as phenolic impregnated carbon ablator, behaved reasonably well in all regions of the flight envelope investigated here. However, the measured recession rate of the phenolic impregnated carbon ablator was on average 50% greater than the predicted recession by the fully implicit ablation and thermal response code, and in some cases the measured recession was as much as 150% greater (uncertainties included). Phenolic impregnated carbon ablator’s higher recession rate than predicted (in shear) resulted in adding thickness margin to the flight heat shield d...

Due to the enormous challenges of fabricating long horizontally aligned carbon nanotube (HACNT) bundle interconnects, there exists little research on characterization of long HACNT interconnects. In this paper, taking advantage of our unique HACNT fabrication process outlined in the companion paper, the electrical and self-heating characterization of long HACNT bundles are reported. Negative temperature coefficients of resistance for both per unit length resistance and metal-CNT contact resistance are confirmed from measurements. This first report on the electrical and thermal characterization fills the wide gap between CNT interconnect modeling efforts and corresponding experimental efforts by providing many important extracted parameters that are critical in various modeling and analyses.

Although horizontally-aligned carbon nanotube (HACNT) interconnects are the most common scenarios that have been modeled and analyzed in theoretical research, fabrication of HACNT test structures has remained an enigma until now. Through addressing several fabrication challenges, this paper reports a novel process that enables fabrication of high-density, long (over hundred microns), and thick (up to micrometer) HACNT interconnects. Furthermore, horizontal CNT-based 2-D Manhattan structure is demonstrated by properly designing the catalyst and flattening process. These structures are crucial for building angled interconnects and on-chip passive devices. In addition, to address the contact issue between metal and thick HACNT bundles, a multistep lithography combined with specifically designed metal deposition technique is performed to ensure full contact configuration. Using such a process, test structures with arrays of various sizes of HACNT bundle interconnects are fabricated. The process developed in this paper provides an important platform for future research and technology development of CNT-based interconnects and passive elements.

A wind tunnel test of the Adaptable Deployable Entry and Placement Technology (ADEPT) was conducted in April 2015 at the US Army's 7×10 Foot Wind Tunnel located at NASA Ames Research Center. Key geometric features of the fabric test article were a 0.7 m deployed base diameter, a 70° half-angle forebody cone angle, eight ribs, and a nose-to-base radius ratio of 0.7. The primary objective of this wind tunnel test was to obtain static deflected shape and pressure distributions while varying pretension at dynamic pressures and angles of attack relevant to entry conditions at Earth, Mars, and Venus. Other objectives included obtaining aerodynamic force and moment data and determining the presence and magnitude of any dynamic aeroelastic behavior (buzz/flutter) in the fabric trailing edge. All instrumentation systems worked as planned and a rich data set was obtained. This paper describes the test articles, instrumentation systems, data products, and test results. Four notable conclusions are drawn. First, test data support adopting a pre-tension lower bound of 10 lbf/in for Nano-ADEPT mission applications. Second, test results indicate that the fabric conditioning process needs to be reevaluated. Third, no flutter/buzz of the fabric was observed for any test condition and should also not occur at hypersonic speeds. Fourth, translating one of the gores caused ADEPT to generate lift without the need for a center of gravity offset. At hypersonic speeds, the lift generated by actuating ADEPT gores could be used for vehicle control.

We present an ac dielectrophoretic (DEP) technique for single-cell trapping using embedded carbon nanofiber (CNF) nanoelectrode arrays (NEAs). NEAs fabricated by inlaying vertically aligned carbon nanofibers in SiO 2 matrix are applied as "points-and-lid" DEP devices in aqueous solution. The miniaturization of the electrode size provides a highly focused electrical field with the gradient enhanced by orders of magnitude. This generates extremely large positive DEP forces near the electrode surface and traps small bioparticles against strong hydrodynamic forces. This technology promises new capabilities to perform novel cell biology experiments at the nanoscale. We anticipate that the bottom-up approach of such nano-DEP devices allows the integration of millions of nanolectrodes deterministically in lab-on-a-chip devices and will be generally useful for manipulating submicron particles.

We present temperature-dependent electrical characteristics of vertically aligned carbon nanofiber (CNF) arrays for on-chip interconnect applications. The study consists of three parts. First, the electron transport mechanisms in these structures are investigated using I-V measurements over a broad temperature range (4.4 K to 350 K). The measured resistivity in CNF arrays is modeled based on known graphite two-dimensional hopping electron conduction mechanism. The model is used because of the disordered graphite structure observed during high-resolution scanning transmission electron microscopy (STEM) of the CNF and CNF-metal interface. Second, electrical reliability measurements are performed at different temperatures to demonstrate the robust nature of CNFs for interconnect applications. Finally, some guidance in catalyst material selection is presented to improve the nanostructure of CNFs, making the morphology similar to multiwall nanotubes.

Developing biomaterial constructs that closely mimic the natural tissue microenvironment with its complex chemical and physical cues is essential for improving the function and reliability of implantable devices, especially those that require direct neural-electrical interfaces. Here we demonstrate that free-standing vertically aligned carbon nanofiber (VACNF) arrays can be used as a multifunctional 3-D brush-like nanoengineered matrix that interpenetrates the neuronal network of PC12 cells. We found that PC12 neuron cells cultured on VACNF substrates can form extended neural network upon proper chemical and biochemical modifications. The soft 3-D VACNF architecture provides a new platform to fine-tune the topographical, mechanical, chemical, and electrical cues at subcellular nanoscale. This new biomaterial platform can be used for both fundamental studies of material-cell interactions and the development of chronically stable implantable neural devices. Micropatterned multiplex VACNF arrays can be selectively controlled by electrical and electrochemical methods to provide localized stimulation with extraordinary spatiotemporal resolution. Further development of this technology may potentially result in a highly multiplex closed-loop system with multifunctions for neuromodulation and neuroprostheses.

A dc plasma enhanced chemical vapor deposition process is used to obtain vertically aligned carbon nanofibers (CNFs) from palladium catalysts using an ammonia–acetylene process gas mixture. Transmission electron microscopy is used to elucidate the microstructure of the as-grown fibers revealing different growth anomalies such as a new secondary growth phenomenon which we term hybrid tip growth. Also included in our analysis are conventional tip growth derived structures. In a few instances, the conventional tip growth derived structures possess elongated catalyst particles that impart small cone angles to the carbon nanofiber microstructure. Detailed microchemical analysis reveals that hybrid tip grown CNFs using thick Pd films are partially filled with Pd. Analysis of these growth phenomenon and implications for potential use as on-chip interconnects are discussed.

Small spacecraft have emerged in recent years from a niche academic pursuit to a platform for governments and corporations to perform scientific and commercial ventures in space at much lower cost. Simultaneously, the field of Entry, Descent, and Landing (EDL) is rapidly maturing a number of technologies geared toward delivering ever-larger payloads to destinations across our solar system, with the culminating event being safe transport of human beings to the surface of Mars. One of these technologies for landing large payloads, known as the Adaptable, Deployable Entry and Placement Technology (ADEPT), uses a mechanical skeleton to deploy a revolutionary carbon fabric system that serves as both heat shield and primary structure during atmospheric entry. This paper explores the application of a Nano-ADEPT entry system for delivery of very small payloads (< 5 kg) to locations of interest in an effort to leverage low-cost platforms to rapidly mature the technology while simultaneously delivering high-value science. It is shown that secondary payload missions to Mars as well as entry from low Earth orbit are feasible. Secondary payload missions to Venus at small scale present a greater challenge and may only be feasible if the system can be designed with exceptionally low mass. The technology maturation strategy for Nano-ADEPT is described. Four test campaigns underway at the time of writing are discussed in detail, including deployment testing, wind tunnel testing, system-level arc jet testing, and a sounding rocket flight test. To conclude, a mission opportunity is described to demonstrate Nano-ADEPT from the International Space Station.

We propose a novel technique for characterizing interfacial structures in vertically aligned carbon nanofibers (CNFs) utilizing scanning transmission electron microscopy (STEM). In this technique, vertically aligned CNFs are selectively grown using plasma-enhanced chemical vapor deposition (PECVD), on a substrate comprising a narrow strip (width ∼100 nm) formed by focused ion beam. Using STEM, we obtain images of nanostructures of CNFs having diameters as small as 10 nm, while focusing on the interfacial region near the nanofiber base. Stacked graphite sheets parallel to the substrate are observed near the base of these CNFs.

Electrical properties of plasma-enhanced chemical vapor deposited carbon nanofibers (CNFs) are characterized with measurements over a broad temperature range (4-300 K). Temperature-dependent measurements of CNF via resistivity reveal a behavior resembling the mixture of graphite a-axis and c-axis transport mechanisms. For the first time, temperature-dependent characteristics of CNFs are measured and modeled based on previously developed models for electron conduction in graphite. Reliability measurements are performed to demonstrate the robust electrical and thermal properties of CNF vias for next-generation on-chip-interconnect designs.

It has been suggested that CNTs and carbon nanofibers CNFs can be used as thermal interface materials to enhance contact thermal conductance for electronic packaging applications. Several groups have reported mixed experimental results from no improvements to large improvements in the thermal contact conductance due to the CNTs and CNFs 8‐12. These mixed results can be caused by the difference in surface coverage and perpendicular alignment of the CNTs or CNFs. Moreover, the results can be affected by two other factors. First, the CNTs and CNFs grown using different methods possess different defect densities and different intrinsic thermal conductivities. Secondly, the contact thermal resistance of the nanometer scale point and line contacts between a CNT or CNF and a planar surface can be high due to enhanced phonon-boundary scattering at the nanocontacts. We have used a microfabricated device to measure the thermal resistance of an individual CNF from a vertically aligned CNF film for applications as thermal interface materials. The measurement was conducted before and after a platinum Pt layer was deposited on the contacts between the CNF and the microdevice so as to investigate the thermal contact resistance between the CNF and a planar surface. The contact resistance was reduced by the platinum coating for about 9‐13% of the total thermal resistance of the nanofiber sample before the Pt coating. At temperature 300 K, the obtained axial thermal conductivity of the carbon nanofibers was about three times smaller than that of graphite fibers grown by pyrolysis of natural gas prior to high-temperature heat treatment.

The rapid development in nanomaterials and nanotechnologies has provided many new opportunities for electroanalysis. We review our recent results on the fabrication and electroanalytical applications of nanoelectrode arrays based on vertically aligned multi-walled carbon nanotubes (MWCNTs). A bottom-up approach is demonstrated, which is compatible with Si microfabrication processes. MWCNTs are encapsulated in SiO2 matrix leaving only the very end exposed to form inlaid nanoelectrode arrays. The electrical and electrochemical properties have been characterized, showing well-defined quasireversible nanoelectrode behavior. Ultrasensitive detection of small redox molecules in bulk solutions as well as immobilized at the MWCNT ends is demonstrated. A label-free affinity-based DNA sensor has shown extremely high sensitivity approaching that of fluorescence techniques. This platform can be integrated with microelectronics and microfluidics for fully automated microchips.

Nanoengineered materials have emerged as efficient thermal interface materials in a variety of thermal management applications. For example, integrated circuits (IC) are subject to tight thermal budgets to maintain acceptable reliability standards. This letter presents thermal contact resistance measurement results and analyses for copper gap-filled carbon nanofiber−copper composite arrays. Experimental results demonstrate the efficient interfacial thermal conduction of these structures. Using copper as a gap-fill material for improving lateral heat spreading and mechanical stability is discussed.

We report the analysis of a plasma enhanced chemical vapor deposition process for carbon nanofiber growth. A direct current (dc) plasma is employed with a mixture of acetylene and ammonia. Residual gas analysis is performed on the downstream plasma effluent to determine degrees of precursor dissociation and high molecular weight species formation. Results are correlated to growth quality obtained in the plasma as a function of dc voltage∕power, gas mixture, and pressure. Behaviors in plasma chemistry are understood through application of a zero-dimensional model.

We report an innovative approach that combines nanopatterning and nanomaterials synthesis with traditional silicon micromachining technologies for large-scale fabrication of carbon nanotube (CNT) probe tips for atomic force microscopy imaging applications. Our batch fabrication process has produced 244 CNT probe tips per 4-in. wafer with control over the CNT location, diameter, length, orientation, and crystalline morphology. CNT probe tips with diameters ranging between 40 and 80 nm and lengths between 2 and 6 μm are found to be functional probe tips with no need for shortening. This reliable and true bottom-up wafer scale integration and fabrication process provides a new class of high performance nanoprobes. Preliminary AFM imaging results show that the CNT probe tips are strong, wear-resistant, and capable of high-resolution and critical-dimension imaging.

In this paper, we examine mechanisms of electron transport across the metal-carbon nanotube (CNT) interface for two different types of multiwall carbon nanotube (MWNT) architectures, horizontal or side-contacted MWNTs and vertical or end-contacted MWNTs. Horizontally aligned nanotube growth and electrical characteristics are examined with respect to their potential applications in silicon-based technologies. Recent advances in the synthesis techniques of vertical MWNTs have also enhanced the possibility for a manufacturable solution incorporating this novel material as on-chip interconnects or vias as copper interconnect feature sizes are scaled into the sub-100-nm regime. A vertical MWNT architecture is presented that may be suitable for integration into silicon-based technologies. The growth method for this architecture and its effect on electrical characteristics are examined. Through simulations, dc measurements, and comparison of our results with previous studies, we explain why high contact resistance is observed in metal-CNT-metal systems.

The growth of carbon nanofibres (CNF) by plasma enhanced chemical vapour deposition (PECVD) and the integration of CNFs into devices are studied using high throughput methodology. A growth compatibility chip containing candidate metal contact underlayers and transition metal catalyst layers are used to explore growth activity from various pairings of these two layers. In addition, catalyst density microarray chips (CDMCs) where each chip consists of catalyst patterns with various feature sizes and densities were used to investigate CNF growth and integration. The CDMCs were used to efficiently explore CNF growth conditions as well as subsequent downstream integration and testing for applications in ultrasensitive biosensing and field emission. The methodology described here is widely applicable as a general approach for optimizing the bottom-up growth and integration of nanostructures.

The application of high throughput methodology in the discovery of catalyst formulations and novel nanomaterials is expected to impact a wide range of applications. Carbon nanomaterials such as nanotubes, nanofibers, and diamond-like carbon are promising candidate materials for use in a wide variety of electrical, optical and mechanical applications. Therefore, the application of combinatorial methodologies to the discovery and optimization of carbon nanomaterials and catalyst formulations to produce them will accelerate the advancement of nanoscale science and technology. Here, we present an overview of the various combinatorial methodologies employed in the search for carbon nanotubes and related structures. It is hoped that continued innovations in high throughput methodology, especially for nanomaterials development, would be adapted to the many challenges facing nanotechnology.

We report the detection of DNA PCR amplicons using an ultrasensitive label-free electronic technique based on multiwalled carbon nanotube (MWNT) nanoelectrode arrays embedded in an SiO(2) matrix. Specific PCR amplicons are reliably detected using electrochemical (EC) methods through allele-specific oligonucleotide hybridization. The inherent guanine bases in the DNA amplicon target of [Formula: see text] bases serve as signal moieties with the aid of Ru(bpy)(3)(2+) mediators, providing an amplified anodic current associated with the oxidation of guanine groups at the nanoelectrode surface. The reduced size and density of the nanoelectrode array provided by MWNTs dramatically improves the sensitivity of EC detection. In addition, the abundant guanine bases in target DNA produce a large signal. Less than [Formula: see text] target amplicons can be detected on a microspot, approaching the sensitivity limit of conventional laser-based fluorescence techniques. This method also eliminates the labelling requirement and makes the measurements much simpler. This platform can be employed for developing highly automated electronic chips with multiplex nanoelectrode arrays for quick DNA analysis.

A combined hot filament/direct current (dc) plasma approach to chemical vapor deposition of carbon nanofibers (CNFs) using an acetylene/ammonia feedstock has been explored. As a part of the study, the impact of filament usage and substrate holder design has been examined by scanning electron microscopy imaging of deposition products and monitoring of downstream products by residual gas analysis (RGA). It is demonstrated that the filament wire is important primarily in the pretreatment of the substrate, improving CNF growth quality. However, the filament has a more minor impact when combined with the dc plasma, increasing growth rate but reducing growth quality. The substrate holder is modified by introducing a graphite spacer into the electrode. By varying the size of the spacer, the effective surface area of the cathode is modified, allowing control over the power input to the reactor while holding the voltage constant. This allows for some independent control of physicochemical processes that are typically inseparable in plasma processing, including gas phase chemistry, substrate heating and etching by ion bombardment, and growth alignment effects due to the electric field. This work demonstrates how separating these processes allows for better control over the desired growth product.

With their interesting electrical, structural, and physical properties, carbon nanotubes (CNTs) are envisioned to impact future nanoelectronics, nanosensors, and nanophotonics. Current research and development efforts in the growth of CNTs rely on the time-consuming one-parameter-at-a-time approach, whereby marginal variations in growth conditions from run-to-run experiments could result in substantially different outcomes. Here we report a highly efficient combinatorial approach to study the effects of catalysts and underlying metals for the generation of a comprehensive discovery library of CNTs. Shadow masking and sequential ion-beam deposition are used to construct an ensemble of catalysts and underlying metals on a generic addressable platform, whereby upon chemical vapor deposition, the CNT library can be assayed efficiently and conveniently to reveal a host of interesting phenomena. The approach could, in principle, be adapted and used for combinatorial investigations of other nanostructures.

In this report, we show controlled in-situ doping of a single crystalline metal oxide nanowire, using indium-doped tin oxide (In−SnO2) as an example, during a heteroepitaxial growth process. Highly regular and high-density arrays of In−SnO2 nanowires, which demonstrate three- and four-fold growth symmetry, are obtained directly on optical sapphire substrates. Similar synthesis strategies, involving careful selection of desired growth conditions and smart manipulation of favorable thermodynamic properties, could be extended to production of various doped metal oxide nanowires.

Carbon nanotubes (CNTs), due to their unique electronic and extraordinary mechanical properties, have been receiving much attention for a wide variety of applications. Recently, plasma enhanced chemical vapour deposition (PECVD) has emerged as a key growth technique to produce vertically-aligned nanotubes. This paper reviews various plasma sources currently used in CNT growth, catalyst preparation and growth results. Since the technology is in its early stages, there is a general lack of understanding of growth mechanisms, the role of the plasma itself, and the identity of key species responsible for growth. This review is aimed at the low temperature plasma research community that has successfully addressed such issues, through plasma and surface diagnostics and modelling, in semiconductor processing and diamond thin film growth.

A nanoelectrode array based on vertically aligned multiwalled carbon nanotubes (MWNTs) embedded in SiO2 is used for ultrasensitive DNA detection. Characteristic electrochemical behaviors are observed for measuring bulk and surface-immobilized redox species. Sensitivity is dramatically improved by lowering the nanotube density. Oligonucleotide probes are selectively functionalized to the open ends of nanotubes. The hybridization of subattomole DNA targets can be detected by combining such electrodes with Ru(bpy)32+ mediated guanine oxidation.

Single-wall carbon nanotube (SWNT)/poly(methyl methacrylate) (PMMA) composites were fabricated and exposed to ionizing radiation for a total dose of 5.9 Mrads. Neat nanotube paper and pure PMMA were also exposed for comparison, and nonirradiated samples served as controls. A concentration of 0.26 wt% SWNT increased the glass transition temperature (Tg), the Vickers hardness number, and modulus of the matrix. Irradiation of the composite did not significantly change the Tg, the Vickers hardness number, or the modulus; however, the real and imaginary parts of the complex permittivity increased after irradiation. The dielectric properties were found to be more labile to radiation effects than mechanical properties.

We report on the electrochemical study of three carbon nanotube ensemble electrodes: single-walled nanotube paper, as-produced multiwalled nanotube towers, and heat-treated multiwalled nanotube towers. Cyclic voltammetry was used in 0.10 M KCl containing 5.0 mM K4Fe(CN)6 to obtain information on both the capacitive background and electron transfer rate from the faradaic reaction of the redox species. The capacitance gives insight into the effective surface area (including both the exterior surface and the interior surface within the film) as well as the “pseudocapacitance” due to faradaic reactions of surface bonded oxides. We found that a large portion of the carbon nanotube surface of the as-produced multiwalled nanotube tower electrode was blocked by amorphous carbon. It can be largely removed by prolonged heat treatment. Among the three types of samples, the single-walled nanotube paper electrode presented the largest volume specific capacitance, consistent with its highest carbon nanotube packing de...

Multiwalled carbon nanotubes (MWCNTs) have been grown on various substrates by thermal chemical vapor deposition using multilayered metal catalysts. Ion beam sputtering is used to deposit various metal layers sequentially. Underlayers of Al (2−20 nm) are shown to influence the growth characteristics with Fe or Ni used as active catalysts. The as-sputtered catalyst surface, characterized using atomic force and scanning tunneling microscopies, consists of nanometer scale (

High-throughput methods are utilized in the discovery and optimization of heterogeneous catalyst formulations that promote single-walled carbon nanotube (SWNT) synthesis. Catalyst compositions, substrates, and reaction conditions are varied to efficiently investigate SWNT growth by chemical vapor deposition (CVD). A robotic microarray printer is employed to print libraries of the liquid-based catalyst precursors onto various substrates. After CVD, the catalyst arrays are qualitatively screened for yield via electron microscopy. More comprehensive characterization of candidate catalysts is further investigated with confocal Raman spectroscopy (CRS). Detailed CRS mapping reveals information concerning the printed catalyst and nanotube homogeneity in the microarrays. This powerful characterization approach allows for the high-throughput screening of nanotube type, diameter distribution, and purity within the microarrays. The methodology described has enabled the efficient exploration of synthesis parameters,...

We have functionalized single walled carbon nanotubes (SWNTs) with atomic hydrogen generated in a cold plasma. A band at 2924 cm-1 (3.4 μm), characteristic of the C−H stretching mode, is observed using Fourier transform infrared spectroscopy. Additional confirmation of functionalization is provided by irradiating with atomic deuterium. A band in the region 1940 cm-1 (5.2 μm) to 2450 cm-1 (4.1 μm) corresponding to the C−D stretching mode is confirmed and another weak band in the region 1050 cm-1 (9.5 μm) to 1300 cm-1 (7.7 μm) corresponding to C−D bending mode is also seen. Our approach using a glow discharge provides a clean gas-phase process to functionalize SWNTs for further application development.

Ion beam sputtering has been used for the sequential deposition of metal multilayers on various substrates to control the density of single-walled carbon nanotubes (SWNTs) synthesized by chemical vapor deposition. Underlayers (10–20 nm) of Al and Ir were found to activate the substrates for SWNT growth with Fe as active catalyst. Adding Mo as co-catalyst gives increased production of SWNTs and the density can be controlled by varying the thickness of the different metal layers. High-resolution transmission electron microscopy and Raman scattering are used to characterize the SWNTs.

Carbon nanotube (CNT) exhibits extraordinary mechanical and unique electronic properties and offers significant potential for structural, sensor, and nanoelectronics applications. An overview of CNT, growth methods, properties and applications is provided. Single-wall, and multi-wall CNTs have been grown by chemical vapor deposition. Catalyst development and optimization has been accomplished using combinatorial optimization methods. CNT has also been grown from the tips of silicon cantilevers for use in atomic force microscopy.

This article presents our recent work in the controlled synthesis of multiwalled (MWNT) and single-walled nanotubes (SWNT) with ordered architectures. The general synthesis approach involves chemical vapor deposition using rationally designed catalyst and substrates. The results include self-oriented MWNTs, individual SWNTs grown from controlled surface sites, and structures of suspended SWNTs along well-defined directions. The chemically derived nanotube architectures have opened up new possibilities in fundamental characterization and potential applications of nanotube materials. Systematic electron transport measurements are carried out to elucidate the electrical properties of various classes of SWNTs and to explore the physics in one-dimensional systems. High-performance electrical devices based on individual SWNTs are enabled by combining synthesis and microfabrication approaches.

Eine einfache Modifizierung der Losungsmittelbedingungen ermoglicht einen leichten Zugang zu supramolekularen Fulleren-Nanostrukturen. Das hier gezeigte Fullerenderivat liefert bei der Selbstorganisation entweder Nanostabe oder Vesikel. Die Nanostabe sind langer als 70 μm und haben je nach Gegenion Durchmesser von 10–250 nm. Durch Ultraschallbehandlung erhalt man dagegen Vesikel mit einem Durchmesser von 10–70 nm und einer Wandstarke von 3–6 nm, aber keine Nanostabe.

High-resolution imaging of soft and weakly adsorbed biomolecules on surfaces within buffer solutions presents a big challenge in research. Here we demonstrate that a single carbon nanotube could be used as a tip for probing biomolecules in solution using atomic force microscopy (AFM). Combining the unique properties of carbon nanotube tips with the newly developed magnetically driven oscillating AFM technique, we were able to obtain molecular-level, high-resolution images of DNA molecules adsorbed on the mica surface in solution. The length and the buckling force of the single nanotube tip can be derived directly from the force-distance curve. These measurements indicate that the nanotube tip is quite resilient, and it can quickly recover to its full length after repeatedly being crashed on the surface with excess force. The well-defined tip geometry provides extraordinary resolution in AFM imaging. The application of carbon nanotubes as AFM tips could lead to breakthroughs in biological studies.

The synthesis of bulk amounts of high quality single-walled carbon nanotubes (SWNTs) is accomplished by optimizing the chemical compositions and textural properties of the catalyst material used in the chemical vapor deposition (CVD) of methane. A series of catalysts are derived by systematically varying the catalytic metal compounds and support materials. The optimized catalysts consist of Fe/Mo bimetallic species supported on a novel silica−alumina multicomponent material. The high SWNT yielding catalyst exhibits high surface-area and large mesopore volume at elevated temperatures. Gram quantities of SWNT materials have been synthesized in ∼0.5 h using the optimized catalyst material. The nanotube material consists of individual and bundled SWNTs that are free of defects and amorphous carbon coating. This work represents a step forward toward obtaining kilogram scale perfect SWNT materials via simple CVD routes.

Recent progress1,2,3 in the synthesis of high-quality single-walled carbon nanotubes4 (SWNTs) has enabled the measurement of their physical and materials properties5,6,7,8. The idea that nanotubes might be integrated with conventional microstructures to obtain new types of nanoscale devices, however, requires an ability to synthesize, isolate, manipulate and connect individual nanotubes. Here we describe a strategy for making high-quality individual SWNTs on silicon wafers patterned with micrometre-scale islands of catalytic material. We synthesize SWNTs by chemical vapour deposition of methane on the patterned substrates. Many of the synthesized nanotubes are perfect, individual SWNTs with diameters of 1–3 nm and lengths of up to tens of micrometres. The nanotubes are rooted in the islands, and are easily located, characterized and manipulated with the scanning electron microscope and atomic force microscope. Some of the SWNTs bridge two metallic islands, offering the prospect of using this approach to develop ultrafine electrical interconnects and other devices.

We report the synthesis of high-quality single-walled carbon nanotubes SWNT by chemical vapor deposition CVD of methane at 10008C on supported Fe O catalysts. The type of catalyst support is found to control the formation of individual 23 or bundled SWNTs. Catalysts supported on crystalline alumina nanoparticles produce abundant individual SWNTs and small bundles. Catalysts supported by amorphous silica particles produce only SWNT bundles. Studies of the ends of SWNTs lead to an understanding of their growth mechanism. Also, we present the results of methane CVD on supported NiO, CoO and NiOrCoO catalysts. q 1998 Published by Elsevier Science B.V. All rights reserved.