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The primary objective of this research is to make nanocomposites with the incorporation of thermally stable silicate nanolayers in the polymer matrix. Several functionalized imidazolium clays, functionalized anionic clays, and silylated apophylites were synthesized and characterized by XRD and TGA. Thermal studies of functionalized clay have shown that the onset decomposition temperature of imidazolium functionalized clay (>325 deg C), alpha amino napthononate exchanged layered double hydroxide (NLDH) (approx. 300 deg C), and covalently silylated apophyllite (approx. 420 deg C) can exceed the onset temperature of conventional organoclays (approx. 260 deg C). Chemorheological measurements of 2 wt% organoclay filled epoxy have shown that the processing window is pretty wide after the addition of the organic layered-silicate to epoxy resin. The thermal stability of epoxy seems to be influenced by the addition of clay and diluent used in the epoxy system. In many cases, higher char yield for nanocomposites was observed suggesting clay is serving as catalyst and acting as barrier in the decomposition of the epoxy matrix. We also studied the thermal stability of tetra functional epoxy nanocomposite and a consistent small improvement in the onset temperature of the nanocomposite was noticed.

Polymorphism often occurs in energetic materials. Differences in the forms range from conformational changes in the molecule from one system to another, to conformational equivalents packing in different manners. These differences, whether drastic or subtle, can lead to substantial alterations in stability and performance. The authors recently reported on the crystal structures of five polymorphs of picryl bromide (a common energetic precursor): the previously identified alpha and beta forms, and three new forms, the gamma, delta, and epsilon forms. A new type of interaction has been identified between the nitro groups and pi-electrons of neighboring phenyl rings. Accurate estimation of the properties of new energetic materials can substantially reduce the development cost of new materials by focusing expensive scale-up and testing on only the most promising candidates. The characterization of this new force involved in crystal packing should greatly improve calculations of packing energy and thus improve predictions of explosive yield.

Considerable research has been conducted in improving the performance characteristics of nanocomposites, relatively few attempts have been made to address the thermal stability of nanocomposite. This research is focused on the preparation of the layered organosilicates with higher thermal stability, which can be used to make high- temperature polymer nanocomposites. Two approaches to formulate layered organosilicates nanocomposites with higher thermal stability were studied. In the first approach, apophyllite, a pure, natural and commercially-available layered silicate, was treated with 7-octenyltrichlorosilane in order to chemically graft the functional pendent organic group containing a C""C bond. The characterization from Fourier transform infrared (FTIR) spectroscopy, wide-angle x-ray diffraction (WAXD) and thermal gravimetric analysis (TGA) supports that the organic pendant group was successfully covalently grafted in the layered-silicate backbone, and the layered organosilicate is high thermally stable (decomposition temperature: 430 degrees C). In addition, vinyl ester nanocomposites were formulated and mechanical properties evaluated. In the second approach, a pure, natural and commercially-available layered silicate, was treated with synthesizied imidazolium salts. The nanodispersion of imidazolium treated clay in an epoxy matrix was evaluated qualitatively by X-ray diffraction (XRD), transmission electronic microscopy (TEM), confocal laser microscopy, and laser induced fluorescence spectroscopy. Results from the four complimentary techniques enable the characterization of the clay platelets over several length scales ranging from the micrometer to the nanometer scale. Mechanical property evaluation of the nanocomposites are underway., Prepared in cooperation with Univ., of Dayton Research Inst., Dayton, OH.

In recent years, the area of nanocomposites has received considerable attention with the expectation that nanotechnology can leas to lighter, better materials for engineering applications. For example, the attractiveness of polymer-clay nanocomposites resides in the potential of adding infinitesimally small clay platelets, to improve mechanical, thermal, barrier, and flame-retardant properties without increasing the specific gravity or reducing the transparency of the nanocomposite relative to the base material. One of the major roadblocks in the wider use of nanoclay platelets in thermoset and thermoplastic polymeric materials has been the poor dispersion of polar clay into a non-polar polymer matrix. It is believed that consistent improvements in strength and modulus of clay loaded polymeric system can be achieved by minimizing clay aggregation, promoting the formation of chemical bonds between polymer and clay and achieving exfoliation of clay. The other major problem that the nanocomposite community faces is the reduction in fracture toughness and failure strain of the nanocomposites due to the addition of clay.

Nanocomposites are a relatively new class of materials obtained by dispersing montmorillonite clay in a polymer matrix. Evidences from literature suggest that clay platelet dispersion during nanocomposite preparation and clay-matrix adhesion are major technical issues that need to be addressed in order to achieve the desired property enhancements in polymer-clay hybrid nanocomposites. We have studied the interaction of the organically functionalized clay with the epoxy resin by including along the chain structure functional groups that will facilitate interaction with the resin. Through conventional routes, functional molecules have been synthesized and deposited on to the clay surface. Both the functionalized and nonfunctionalized clay has been analyzed using thermal gravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR). The exfoliation of nanoclay platelets in amine cured epoxy system has been studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM)., Pub in: Materials Research Society Symposium Proceedings, Volume 703. Prepared in collaboration with the National Institute of Standards and Technology, Polymer Division, Gaithersburg, MD. This article is from ADA401575 Nanophase and Nanocomposite Materials IV held in Boston, Massachusetts on November 26-29, 2001

The Scanning Probe Microscope at Howard University is functional. The SPM is a centerpiece in the laboratory of Professor Huber. The AFM is used in the performance of the grant DAAD19-99-1-0282 for the testing and fabrication of nanostructured thermoelectric materials and devices based in Bi and Bi-Sb alloys. These materials are sought for thermoelectric applications at around 100 K, such as detector coolers and cryogen shields. The report itemizes other grants and proposal based on the AFM and purchase details. The report also describes activities such as training of students, a new course being developed and offered. The report also presents research results: Optical Microscopy and electric Force Characterization of a Bi nanowire, AFM and living cells (with Dr. Palmer a co-investigator in the original proposal), and the research in Bi nanowires. Finally, the report presents a list of collaborators involved in making the instrument into a true research facility., Original contains color plates: All DTIC reproductions will be in black and white.

Characterization of heterogeneous phases in polymers and hydrophilic regions in coatings have been the subject of AFOSR funded research project. Although hydrophilic regions occupy only a small fraction of the coating film volume. the hydrophilic regions control the corrosion protection performance of a polymer coating. At present the progress in the characterization of hydrophilic regions in coatings is very limited because of the lack of suitable analytical technique that can provide nanoscale lateral information. We mapped mechanical and chemical heterogeneities in model polymer coating compounds and characterized degradation susceptible regions in commercial coatings at nanoscale level. Nanoindentation procedure in combination with TMAFM was used to identify soft and hard regions in a heterogeneous model coating compound. To map chemically heterogeneous regions in model systems. we developed AFM/chemical modification approach. An effort was made to relate the microstructure of polymer coating film to the changes that occur to film upon environmental exposure and relate the changes to the chemistry of degraded compound. The material leached out from the coating during immersion was characterized. The leached material was mostly unreacted starting monomers and oligomers. They probably represent the degradation-susceptible regions (hydrophilic regions) of coating film. With the use of an atomic force microscope (AFM). which provides nanometer spatial resolution and angstrom depth resolution, we recently observed the progression of pathway formation in polyester and acrylic-polyurethane coatings, common protective materials for industrial, automobile, and aerospace applications. FTIR results in combination with AFM results (pit formation) support the observation that the extent of degradation of polyurethane coating film is much larger for samples exposed to UV at high relative humidities compared to no UV and high relative humidity.

This is the final report of a project for investigating laser (assisted) methods of growing nitrile thin films. We have grown thin films of AlN and SiN by laser ablation from powders. We have also developed an efficient method for laser assisted CVD of aluminum, or aluminum containing films from trimethylalaminum.

This report describes our efforts to develop anti-cyanide drugs using simple, water soluble metalloporphyrin molecules. Vanadium (4), chromium (3) molybdenum (5), manganese (3), iron (3), nickel (2), copper (2), silver (3), zinc, indium (3), aluminum, platinum (2), palladium (2), and gold (3) porphyrins had no affinity for cyanide at ph7.2. In vitro work showed cobalt (3), rhodium (3), and ruthenium (2) porphyrins bind cyanide in both the di- and trivalent states, from kinetic, equilibrium and electrochemical studies. Nickel (2) central N-alkyl porphyrins liberate nickel to complex with cyanide and are otherwise stable to nickel loss. sterically hindered porphyrins in the iron (III) form rapidly complex cyanide. The LD-50s of thirteen porphyrins and phthalocyanines are in the 100-600 mg/kg range in rats. None of the cobalt, iron, rhodium or silver porphyrins or phthalocyanines protect mice in a prophylactic fashion against 2 LD-50s of cyanide.

Precise isosbestic points of water have been measured in the OH stretching region of the Raman spectrum. Measurements were carried out between 3 and 85 C and for several orientations.

This paper reports on a study of the photochemistry of cyano and dicyanoacetylene at 193 nm. In particular, those photolysis channel have been characterized which lead to the production of excited state fragments and CN in the ground state. In addition to the direct production of CN and C2H, there is a second channel leading to C3N and H atoms. The results also show that at high laser intensity the HC3N dissociates by two photon photolysis and that the C3N undergoes secondary photolysis. Keywords: Photodissociation, cyanoacetylenes, Photochemistry.

The investigative work has involved analysis and interpretation of the features seen from the diamond films supplied by various workers mentioned in A, above. From the various diamond films, three general types of peaks were seen. These correspond to peak frequencies of 1330/cm (a very sharp peak), ca. 1350/cm (a very broad peak), and ca. 1600/cm (a broad and sometimes structured contour). To understand these three classes of peaks we obtained Raman spectra from bulk crystalline diamond, from various graphites, and from a wide range of amorphous carbons. The data and tentative interpretation are presented below.

A significant amount of the first years work on this contract (ca. 50%)involved service work to characterize and evaluate diamond films supplied by other SDIO/IST contractors. The investigative work has involved analysis and interpretation of the features seen from the diamond films supplied by various workers mentioned.

The extent of cyanide uptake by various molecules at pH 7.4 was monitored with a cyanide specific electrode. Low molecular weight aliphatic aldehydes scavenged cyanide best, followed by aromatic aldehydes with electron withdrawing functions. Palladium(II) complexes rapidly bound four moles of cyanide, gold(III) species bound three, while platinum(II, IV) and trivalent rhodium and ruthenium complexes were less reactive. A ruthenium porphyrin complexed two cyanides in both the +2 and +3 oxidation states. A nickel(II) schiff-base adduct took up four moles of cyanide through a dissociative process. Nickel(II) cyclams rapidly bound one cyanide, and three more at later times. Keywords: Metalloporphyrins, Cyanohydrins, Ketones, Metal complexes, Antidotes.

The purpose of this project was to identify and develop prophylactic anti-cyanide agents including metal complexes, alkylidines, metalloporphyrins and aldehyde and ketone cyanohydrin formers. The screen involved pre- administration of drugs to mice at 15 and 60 minutes, followed by 2 lethal dose- 50s of potassium cyanide. Out of forty-three drugs, only nickel (II) chloride, cobalt(II)-chloride and 2-carboxybenzaldehyde survived the screen. The affinity of lower oxidation states of cyanocobalt(III)porphyrins and metal(ethylenediaminetetraacetic acid) adducts for cyanide was probed, and complexes that selectively release a cyanide specific metal upon demand were investigated. Keywords: Cyanide, Cyanide scavengers, Porphyrins, Metalloporphyrins, Cobalt, Cyanohydrins, Aldehydes, Ketones, Metal complexes, Nickel.

Raman spectra have been obtained from fused silica optical fibers under high reversible torsion. These results are compared to Raman results from fused silica, irreversibly compacted to 90 kbar. An interpretation is presented which suggests a negative correlation between the mean Si-O-Si bridging angle and the mean Si-O distance, plus a negative correlation between the mean Si-O-Si bridging angle and the mean tilt angle between Si04 tetrahedra.

Laboratory experiments are described that provide fundamental information about photochemical processes in comets. The yield of cometary radicals such as CN, OH, etc. can be determined as a function of photolyzing wavelength. Quantum state distributions of the internal energy of the cometary radicals can also be measured as a function of wavelength permitting one to define the recoil velocity of the fragments. This type of information supplies the data needed for more elaborate models to interpret the data being obtained on comets.

The Raman spectrum from pure silica optical fibers has been analyzed into a set of Gaussian components. Each component used is related to an observed feature of the spectrum, and a residual of about 1% resulted without the use of additional components. Both single- and multi-phonon peaks were fitted. These Gaussian components have analog in the infrared absorption spectrum, and hence they are of value in studying the fundamental and overtone infrared absorption of silica, as well as the infrared OH overtone and combination spectra. (Author)

The Raman work during the 81-86 contract period involved B2O3 glasses and melts, optical fiber work on SiO2 involving high tensile stress and high torsional forces, reversibly and irreversibly compacted fused silica (1,7), ZrF4-based glasses and melts (13, 16), BeF2 glass (15), silica aerogel (12), heat treated silica aerogel (14), silica glass (6), overtone spectra from OH in silica glass (2), and molten silica (17). We will begin by describing the B2O3 Raman work. Borates, Zirconium fluorides, Beryllium fluorides. (mjm)

Raman measurements of the rate of OH uptake in silicone-clad pure fused silica optical filters (530 ppm initial OH), immersed in water at room temperature, were accomplished with and without tensile stress by determining the integrated intensity of the OH-stretching contour at approx. 3690 per cm. Up to tensile stresses of 1.56 GPa (15.6 kbar), no significant changes in the rate of OH uptake, relative to the uptake rate for an unstressed fiber, were observed. For diffusion through silicone rubber, a 14% increase in the overall Raman OH signal from the fused silica occurred in 200 h. This 14% increase means that a large increase in the OH concentration occurred within a few microns from the surface of the 200 micron diameter fiber, because diffusion of water is very slow in fused silica at room temperature. (Author), Presented at the Annual Meeting of the American Ceramic Society (83rd), 6 May 81, Washington, DC. Prepared in cooperation with Coppin State Coll., Baltimore, MD. Dept. of Chemistry.

A plot of E-sq - (E-bar) sq (T,V,N) vs temperature from -30 C to 150 c was found to be so nearly perfectly linear that small negative deviations near -30 C suggested error in C sub v rather than a failure of the linearity. An empirical equation was derived to describe C sub v. Other properties of supercooled water were discussed.

Both metal ion complexes and unsaturated organic compounds are being explored as potential in vivo anti-cyanide drugs. Certain water soluble metalloporphyrins containing cobalt (III), silver (II), chromium (II), rhodium (III), palladium (II), or iron (III), and cobalt (II), and (III) sulfonated phthalocyanines have been shown to rapidly complex cyanide at physiological pH. Detailed kinetic work indicates than both cyanide and HCN are reactants. A number of five, six and seven membered ring systems with activated double bonds known as alkylidenes have been shown to complex cyanide. Kinetic work indicates a rate law first order in each reactant, then a following cyanide independent rearrangement, forming a low molecular weight covalently bound cyanide species, with the loss of water and carbon dioxide. Twenty such drugs have been synthesized. Keywords: Antidotes; Therapy.

A new component has been found near 2050/cm in the Raman spectrum or liquid water. This component refers to the two-phonon combination nu sub 2 + nu sub L(where 2 refers to intramolecular bending and L to libration), but the nu sub 2 and nu sub L fundamental involved in this two-phonon component arise from water molecules hydrogen bonded to three rather than to four nearest neighbors. The nu sub 2 bending fundamental from three bonded water molecules was also uncovered. The new Raman data are in excellent agreement with published infrared data and theoretical calculations. Keywords: Water; Raman spectroscopy; Isosbestic point.

Raman studies of vitreous B2O3 have been conducted between 8 and 700K, and as a function of hydrostatic pressure (about 8 kbar) at room temperature. The low temperature Raman spectra exhibit two broad bands at 50/cm and 137/cm. From the temperature dependence of the 50/cm band, it has been concluded that the vibrational density of states in the low frequency region (30w300/cm) is better described when the Raman coupling coefficient C sub b varies as w. A shift in frequency of the Raman spectra as a function of temperature is attributed to a structural change near the glass transition. Near the glass transition temperature, the boroxol rings break up thereby leading to a more open structure. Above the melting point, i.e. when the viscosity is low, a regrouping of atoms occurs which results in a low density random network structure of BO3 triangles.

Integrated Raman intensities of bands between 0-900 per cm have been obtained for molten B203 from 288-906 C. Emphasis was placed on the highly depolarized low-frequency contour (adjoining the exciting line) which is intense, broad, skewed to high frequencies, and displays a weak, broad, shoulder centered between 100-150 per cm. The total integrated contour intensity from 0-300 as well as the peak intensity, obey the one-phonon Bose-Einstein (B.-E.) relation within 6%. The integrated intensity of the polarized 800 per cm boroxol ring (B306) line, however, decreases with temperature rise, in quantitative agreement with previous work, J. Chem. Phys., 72, 113 (1980), and correction using neutron scattering results yields a enthalpy H value of 5.0 kcal/mole ring rupture. The low-frequency contour probably involves nonsymmetric collective modes of very large assemblies, cages, or rings, as well as librations of B306 groups (100-150 per cm), and the fact that the B.-E. distribution is obeyed at temperatures for which B306 ring rupture is important indicates that such large temporal aggregates are involved that whether B03 triangles or B306 rings are present may be nearly irrelevant., Prepared in cooperation with National Bureau of Standards, Washington, DC. Center for Materials Science.

The ArF laser photodissociation of C2N2, C1CN and BrCN have been studied in a pulsed beam. Comparisons are made between these results and the radical product distirbutions measured in an effusive beam. Comparisons are also made between the effects of cooling by expansion in argon and expansion in methane. The later is known to more effectively cool vibrational modes in the parent molecule. (Author)

Simian virus 40 DNA was irradiated by a high intensity ArF excimer laser. Analysis by gel electrophoresis, neutral sucrose gradient analysis, and alkaline sucrose gradient analysis showed that the laser irradiation leads to breaking of the sugar phosphate backbone in a sequential manner at random sites. The causitive process is either attack by laser generated free radicals or two photon direct scission. (Author), Prepared in cooperation with University of the District of Columbia, Washington. Dept. of Biology and Schools of Medicine and Dentistry, Washington, DC. Dept. of Biochemistry.

Raman data for ice VII to 30 GPa and x-ray lattice parameters to 36 GPa, all at room temperature, are presented and discussed. Both the Raman OH-stretching peak frequency (delta cap Nu) and the edge distance of the body-centered cubic unit cell (a) decrease at a decreasing rate with pressure rate. The OH peak frequency is found to be virtually linear in the nearest-neighbor 0-0 distance (r00) between about 2.5 and 2.9 A. However, the data can also be fitted with a slight cubic dependence, which when extrapolated, gives rise to a minimum in delta cap Nu at r00 = 2.35 plus or minus 0.06 A. This is close to the value of 2.4 A found for the symmetric O-H-O units in other materials. (Author)

Surface Raman scattering using a spinning technique was investigated for solid NaBO3.4H2O and NaBO3.H2O as well as for electron bombarded peroxyborates heated for various times and at temperatures form 110-180 deg C, and for solid Na2O2 and BaO2. The Raman spectra indicate that the breakdown of peroxy groups is accompanied by the formation of trapped molecular O2. Quantitative Raman intensity data were also obtained as functions of heating time at 115 deg C for the 1556 cm-1 line from O2 and for the 890 and 705 cm-1 lines whose intensities scale with the peroxy concentration. These intensity data were treated by logistics theory, and they were found to be consistent with a second-order auto-catalyzed forward reaction dependent on the product of the peroxy and 02 concentrations, plus a first-order reverse reaction dependent only on the 02 concentration.

The nascent quantum state distributions of CN (X2 Sigma(+)) fragments produced in the dissociation of ClCN and BrCN by photolysis at 193nm, in an effusive beam have been measured. The rotational distribution of the fragments is highly excited. The results show that the excited electronic state which dissociates is bent. A simple parameterization is shown to fit the results. This parameterization is based on a classical model which has dynamical implications. (Author)

Two silver azide crystals (body centered tetrogonal) were studied. In addition, data were taken on one of these with the cavity in the magnetic field of a fixed magnet. The magnetic field strength, 1.25 kilogauss, was measured by use of a gauss meter. The position of the cavity was such that the axis of the cylindrical cavity was midway between the pole pieces and normal to the magnetic field. A comparison of the nature of the dispersion curves for silver azide and that of alpha-lead azide shows that they are quite different, even though silver and alpha-lead azides are members of the same crystalline system (orthorhombic). Silver azide yields a curve which is very similar to those of potassium and thallium azides.