Materials & Coatings

Exfoliated Graphite Nano-Reinforcements With Surface Modifications to Improve Dispersability

Exfoliated graphite nanoflakes are a potential low-cost source of nano-reinforcement for making polymer composites with unique properties. The chemical nature of the graphitic surface leads to a low-surface energy as produced. This makes the nanoflakes difficult to disperse in polymer resins and makes it difficult to make high-quality composites. To improve nanoflake dispersability in various polymers, two surface treatments were selected to modify the chemical structure of the graphite nanoflakes.

Posted in: Briefs, TSP, Materials, Fabrication, Composite materials, Graphite, Nanomaterials, Resins
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MicroGel® for Passivation of Pigment Degradation

MicroGel® is a unique, highly porous xero-gel silica formed using sol-gel techniques. The starting materials used are designed per guidance from molecular dynamic calculations, and are made up of mixed alkali silicates rather than normally used single alkali silicates that are gelled with appropriate mineral acid at controlled temperature and time.

Posted in: Briefs, TSP, Materials, Fabrication, Composite materials, Materials properties, Silicon alloys
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Producing Synthetic Agglutinates in Simulated Lunar Regolith

Method helps in the study of Lunar material.

A method was developed of synthesizing agglutinates as components of simulated Lunar regolith. The method is needed for further development of Lunar-exploration capabilities because natural Lunar regolith contains agglutinates that contribute significantly to its mechanical and thermophysical properties. Agglutinates are particles that, in the Lunar case, are aggregates of smaller regolith particles (mineral grains, glasses, and even older agglutinates) bonded together by vesicular, flow-banded glass.

Posted in: Briefs, Materials, Soils, Glass, Materials identification, Test procedures
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Modeling of Failure for Analysis of Triaxial Braided Carbon Fiber Composites

Better understanding of triaxial braided composites will lead to improved aerospace and automotive structures.

In the development of advanced aircraft-engine fan cases and containment systems, composite materials are beginning to be used due to their low weight and high strength. The design of these structures must include the capability of withstanding impact loads from a released fan blade. Relatively complex triaxially braided fiber architectures have been found to yield the best performance for the fan cases. To properly work with and design these structures, robust analytical tools are required that can be used in the design process.

Posted in: Briefs, TSP, Materials, CAD, CAM, and CAE, Failure modes and effects analysis, Composite materials, Fibers, Fans, Jet engines
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Selective Functionalization of Carbon Nanotubes: Part II

Different species are deposited at different distances.

An alternative method of low-temperature plasma functionalization of carbon nanotubes provides for the simultaneous attachment of molecular groups of multiple (typically two or three) different species or different mixtures of species to carbon nanotubes at different locations within the same apparatus. This method is based on similar principles, and involves the use of mostly the same basic apparatus, as those of the methods described in “Low-Temperature Plasma Functionalization of Carbon Nanotubes” (ARC-14661-1), NASA Tech Briefs, Vol. 28, No. 5 (May 2004), page 45.

Posted in: Briefs, Materials, Joining, Gases, Materials properties, Nanomaterials
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Catalyst for Carbon Monoxide Oxidation

This catalyst forms carbon dioxide in a high-powered, pulsed CO2 laser.

In many applications, it is highly desirable to operate a CO2 laser in a sealed condition, for in an open system the laser requires a continuous flow of laser gas to remove the dissociation products that occur in the discharge zone of the laser, in order to maintain a stable power output. This adds to the operating cost of the laser, and in airborne or space applications, it also adds to the weight penalty of the laser. In a sealed CO2 laser, a small amount of CO2 gas is decomposed in the electrical discharge zone into corresponding quantities of CO and O2. As the laser continues to operate, the concentration of CO2 decreases, while the concentrations of CO and O2 correspondingly increase. The increasing concentration of O2 reduces laser power, because O2 scavenges electrons in the electrical discharge, thereby causing arcing in the electric discharge and a loss of the energetic electrons required to boost CO2 molecules to lasing energy levels. As a result, laser power decreases rapidly.

Posted in: Briefs, TSP, Materials, Lasers, Carbon monoxide, Catalysts
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Titanium Hydroxide — a Volatile Species at High Temperature

Titanium hydroxide, TiO(OH)2 (g), has been identified as the primary reaction product of TiO2    (s) + H2O (g) at high temperatures (1,200–1,400 °C) through the use of the transpiration technique. This technique is a well-established method used to measure equilibrium pressures at 1 atm. Reactive O2 /H2O mixtures of gases flow over the sample, and react to form volatile Ti hydroxides. The collected reaction gas condensate is analyzed to determine the vapor and dissociation pressures. From the amount of condensate and its relation to the partial pressures of the reactive gases, the identity of the volatile hydroxide can be determined. From the relation of product pressure to temperature, thermodynamic enthalpy and entropy of formation can be calculated.

Posted in: Briefs, TSP, Materials, Water, Oxygen, Titanium, Test procedures
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Zinc-Doped Tricalcium Phosphate Ceramic for Surgical Implants

This material exhibits an osteogenesis-promoting effect without toxicity, making it suitable as a surgical implant.

A ceramic body consisting of the phases of tricalcium phosphate and/or hydroxyapatite provides biocompatibility with hard tissues. When such a ceramic body is implanted in a bone, direct connection is formed between the bone and the ceramic body without intervention of any fibrous connective tissues. This zinc-containing or zinc-doped ceramic material mainly consists of tricalcium phosphate and is suitable as a ceramic material for biomedical use. In particular, the material provides surgical implant materials for hard tissue consisting of zinc-doped tricalcium phosphate to promote bone formation by releasing zinc in the body.

Posted in: Briefs, MDB, Briefs, Coatings & Adhesives, Materials, Bio-Medical, Implants & Prosthetics, Medical, Prostheses and implants, Biomaterials, Calcium, Ceramics, Materials properties, Zinc alloys
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Neuroprosthetics and Solutions for Restoring Sensorimotor Functions

A new class of prosthetic devices looks, feels, and functions like natural limbs.

Advances in body armor and life-saving technology have increased survival rates of severely injured military personnel. Unfortunately, the survivors of improvised explosive devices are often left with amputations and/or spinal cord injuries. The increase in amputations and paralysis among military personnel requires significant advances in prosthetics and functional electrical stimulation (FES) systems so that the soldiers can return to the field or to productive civilian lives.

Posted in: Briefs, MDB, TSP, Briefs, TSP, Coatings & Adhesives, Materials, Bio-Medical, Implants & Prosthetics, Medical
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Biotic-Abiotic Interface Between the Body and an Artificial Limb

A modified titanium construct and specially machined surface increase adherence of tissue to a prosthetic limb.

Because of its high mechanical properties, chemical stability, and biocompatibility, titanium is a commonly used material in dental and orthopedic applications. Its excellent biocompatibility allows titanium implants to be directly anchored to bone, or osseo-integrated. The conventional prosthetic replacement in amputees is a stump-socket design, which transfers forces through the prosthetic to an external contact point on the patient. Such a design results in non-uniform distribution of pressure, and can lead to pain, infection, and necrosis of the soft tissues at the point of contact.

Posted in: MDB, Briefs, TSP, Coatings & Adhesives, Materials, Bio-Medical, Implants & Prosthetics, Medical, Prostheses and implants, Materials properties, Titanium, Biomechanics
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