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A review is presented of efforts to develop and demonstrate pyrolytic graphite coated throat inserts in solid propellant rocket nozzles. Discussion of modification attempts such as SiC, HfC and ZrC additions and chemically graded coatings is included. Selected test results on thermal expansion and erosion rates are provided., Presented at the AIAA/SAE Joint Propulsion Specialist Conference (9th) held in Las Vegas, NV in Nov 1973. Paper No. AIAA-73-1260.

The dc resistance of synthetic silver-silicon monoxide superlattice structures has been measured as a function of temperature in the range from 77K to 300K. A new type of switching was discovered in which the electrical resistance changes abruptly from the room temperature value to a lower value at some threshold temperature. When the temperature is increased again, the sample switches at a high threshold temperature to a resistance value larger than the room temperature value, this higher value was found not to be stable; it decayed to the room temperature value within several hours. The identity period of the samples investigated ranged from about 20A to 300A. Each switching sample could be repeatedly and reproducibly cycled many times., Master's thesis.

The investigation consisted of two parts. In part one, a High Rate Physical Vapor Deposition Process was developed for the deposition of metals, alloys, compounds and dispersion strengthened alloys. The relationship between the deposition temperature, the microstructure and the mechanical properties was studied. The materials resulting from this process were shown to have properties very similar to true engineering materials. These deposition techniques have been developed to the stage where they can be applied to the production of self-supporting shapes or coatings for engineering applications. The second part of this investigation was concerned with the study of the oxidation mechanism of Ni3Al containing yttrium., See also report dated Sep 1973, AD768794.

Values of the optical constants, n and k (n bar = n - i k), of vacuum deposited thin films of silicon monoxide over the range 1.0 to 50.0 microns, obtained from Attenuated Total Reflectance (ATR) are computed with a simple rigorous method. The ATR element used is a commercial one. A analysis is also presented of the calculation of n and k from transmission measurements showing consistency with ATR measurements for a liquid sample. A double beam ATR system is described for making precise measurements at a variable angle of incidence of the reflectivity using only one hemicylindrical reflectance element. The cell has two compartments for sample and reference beam respectively. The beam has a wedge shape with the focal line parallel to the cylinder axis and the optical elements are all standard mirrors.

The article studies the dependence of the high-voltage photovoltaic effect (HVPVE) and piezoeffect on the state of the thin CdTe film crystalline structures. The properties of the macro- and microstructure of thin CdTe films with different polarities of the HVPVE are established. The change of sign of the H V P V E is not connected with the change in the polarity of the piezoeffect., Trans. of Lietuvos Fizikos Rinkinya (USSR) v10 n2 p271-277 1970.

In this work elastic constants of some infrared window materials were calculated from ultrasonic measurements using a pulse overlap technique. Velocity measurements were determined in various directions in CVD zinc selenide and in hot forged KCl alloy windows. These measurements permitted the determination of Young's Modulus, the shear modulus, the bulk modulus, and Poisson's Ratio. Some anisotropy was found in the elastic properties of these fabricated or 'as-grown' infrared windows. For example, in the case of the chemically vapor deposited ZnSe which exhibits a small amount of elastic anisotropy, the elastic properties were found to be isotropic in all directions normal to the growth direction. The modulus values observed for directions in the plane of the zinc selenide window were found to change by approximately two percent when measured in directions parallel to the plate growth direction. The experimental results obtained were, in some cases, compared with various calculation approximations which yield polycrystalline elasticity parameters from single crystal data.

This report presents the Results and status of work after the third six month period of this program which consists of three separate tasks including the following: Optoelectronic materials and components; Minilaser development, diode pumps, KTN modulator program, coupling from laser to wave guide, feed materials for crystal growth; Superconducting Transition metal alloys; Development of surfaces and tunneling barriers for Al5 substrates; Chemical synthesis using high temperature lithium vapor species. Initiation of program involving the Synthesis of polymers and diamond-like materials; problem of purification and separation of the novel polylithium compounds., See also report dated 30 Jun 74, AD-782 573.

This report deals largely with the characterization of films (ZnSe, ZnS, As2S3 and ThF4) on high power laser window substrates (BaF2 and ZnSe). Thus far attenuated total internal reflection spectra have been taken of As2S3 on BaF2; and calorimetric measurements for film absorption studies have been developed and applied to As2S3 on BaF2. A literature search has been undertaken to determine liquid coolants for high power windows but no promising candidates were found. A literature search of the mechanical, physical and chemical properties of films was made. Adhesion measurements have begun using pull tests and peeling tests, as well as microhardness measurements using a small diamond indenter in conjunction with the scanning electron beam microscope.

Potassium chloride surfaces have been produced on reactive atmosphere processed (RAP) KCl using HCl etching which show an order of magnitude improvement in KCl surface damage resistance. Surface damage level approaches the bulk level in some KCl samples. An inverse dependence of 10.6 micrometer optical absorption on film deposition rate is reported for germanium films, beta of approximately 10/cm is reported for the best films. Ion beam sputtering of ThF4 using pure argon ion beams results in films deficient in fluorine having high optical absorption at 10.6 micrometers. Reactive sputtering in argon- fluorine gas mixtures may be required for producing stoichiometric fluoride films. Rutherford backscattering for chemical analysis of films and window surface structure promises to be a new powerful technique for such studies, using moderate beam energies of 180 KeV H(+) and 280 KeV H(++)., See also semiannual technical rept. no. 1, AD777888.

This document reports the results of a 12-month contract to evaluate candidate refractory and insulator materials for use as the inlet duct liner, rotor, and nozzle exit, of a hot gas thrust vector control system. The purpose of this investigation was to define materials that would provide a minimum weight valve design. Materials were compared for erosion resistance when subjected to the particle-laden hot gas environment from a solid propellant motor firing approximating that expected in an advanced interceptor control system application. The best materials selected through design, analysis and test were chemically vapor deposited tungsten for the valve rotor and nozzle and rubber modified silica phenolic for the inlet duct liner. (Author), See also Volume 1, AD-530 168L.

Chemical vapor deposition investigations were undertaken to determine the feasibility of coating refractory metals and alloys onto the inside bores of gun barrels. Coatings of tungsten, molybdenum, vanadium, rhenium, and tantalum as well as tungsten alloys were attempted. Process parameters, compositions, and properties of the coatings were determined. Elemental tungsten depositions were initially used to establish the process parameters for subsequent work on tungsten alloy coatings. Ta-10W alloy was plated successfully on the steel substrate at 750 C and 1 atmosphere pressure. The coatings obtained were uniform and adherent. Properties of the alloy coating, Ta-10W, are such that this coating is especially applicable for a high temperature coating for fun barrels. (Author)

Measurement of the rate of oxidation and creep rate in air of chemically vapor deposited Si3N4 at around 1500C are reported. Attempts to prepare pure, dense Si3N4 bodies by hot pressing powder at ultra-high pressures were unsuccessful. Resistance heaters made of dense, sintered SiC were tested and found to have in-use lifetimes very much longer than those of commercially available heaters tested in the same way. Microscopic examination of the structures developed during the initial stage sintering of SiC doped with C and B indicates that these dopants inhibit surface diffusion until densification begins at around 1500C. Bodies of B4C having about 94% of theoretical density were made by using conventional sintering processes and doping the powder with either SiC or Be4C.

A major goal has been to understand the electronic properties of rutile and to permit investigation of its feasibility as a semiconductor device material. In addition, from a more fundamental standpoint, rutile is an excellent model system for the study of wide gap semiconductors in general. The following studies are reported: Impurity thermodynamics, Defect thermodynamics, Effects of internal fields on diffusion and distribution of ions, ESR measurements and miscellaneous projects, Results of crystal growth program-- Problems encountered in developing chemical vapor technique, Summary of major achievements of the crystal growth program, Plans for future research on growth of TiO2 crystal by chemical vapor transport.

A viable process for multilevel interconnects was developed. Silicon dioxide sputtered at a substrate temperature of 200 C controlled by gallium heat sinking to a heater block, at argon pressure of 5 millitorr, and at a power density of 14 watts/sq. in. was demonstrated to have appropriate etching characteristics and to be virtually free of pinholes. Pure aluminum and 4% copper in aluminum were shown to be compatible with the silicon dioxide process and to give good level-to-level electrical contact at feedthroughs sputter cleaned just prior to the metal deposition. Beryllium oxide was deposited by rf sputtering from a beryllium oxide target and by reactive rf sputtering from a beryllium target using oxygen-argon mixtures. In both cases stress levels in the films deposited were very high, producing pronounced bowing of substrates. Layers on the order of 2 micrometers thick shattered silicon substrates 5 centimeters in diameter and 325 micrometers thick. Reactively sputtered films deposited at about 3000A/hr. while films rf sputtered from a beryllium oxide target deposited at a rate of about 6500A/hr for 500 watts into a 3.5 inch diameter target.

Carbon ribbon from Kapton 6H6 film was produced. The pro-perties of carbon ribbon pyrolyzed at temperatures from 900^C to 1250^C were improved substantially by low rates of pyrolysis and a high degree of stretch during pyrolysis. Tensile strengths to 186,000 psi and moduli to 24.3 million psi were obtained. (Author, modified-PL)

Volume 3 describes the development of a process for coating large diameter rocket nozzle throat inserts with pyrolytic graphite. Inserts with throat diameters of 7.0, 10.6, 12.45 and 13.0 inches were fabricated., See also Volume 1, AD907191.

The initial work of Yim and Stofko demonstrated that good quality epitaxial films of ZnS and ZnSe could be achieved by chemical vapor phase deposition (CVD). The purpose of this work is to conduct further exploratory research using CVD aimed at elucidating optimum growth and doping conditions with the goal of producing controlled dopant characteristics. Results on dopants such as Cu, Ga, and Al are presented. It is found that in order to achieve routinely a low resistivity (rho < one ohm-cm) of n-type ZnSe film, the gallium-to-zinc ratio has to be about 25%. Such a result has never been previously obtained in open-tube vapor-phase-epitaxy. These films were grown on highly-insulating ZnSe substrates, p+-GaAs, and p-GaAs substrates. Preliminary results on graded heterostructures of InAs(1-x)P(x) for lightemitting or detector applications are also discussed. (Modified author abstract)

3-D preforms, supplied by AMMRC, with center-to-center spacings of 0.125, 0.040, and 0.030 in. using Thornel 50 and rigidized with phenolic resin furfuryl alcohol resin and pitch were den-sified by the differential pressure chemical vapor deposition process. The highest density achieved was 1.56 gm/cc. Models were machined for each of nine billets and supplied to AMMRC for testing at AFML's 50 mw facility. (Author-PL)

The report describes progress made toward the synthesis of GaN thin films from chemical vapor deposition using the organometallic source triethylgallium monammine (Ga(C2H5)3.NH3). Work is reported on reflection electron diffraction and transmission electron diffraction measurements, along with preliminary scanning electron microscopy results. Problems related to oxygen contamination are discussed and their influence on Hall effect measurements are presented. Also discussed is the problem of reactant decomposition. (Author), See also report dated 1973, AD-755 237.

Phase 2-Tasks 3 and 4 - Non-linear (elastic-plastic) thermostructural analyses were performed for seven PG/SiC codeposited inserts subjected to actual solid rocket test environments. A failure criteria for multiaxial stress fields and orthotropic material strengths was identified and used to predict failure of success of the inserts. A comparison of analytical predictions and actual test results in good correlation. Hence, a baseline was established from which a rational approach to designing codeposited inserts can be developed in the future. (Author)

Seven 1.7-inch throat diameter rocket nozzles were test fired in the HIPPO high pressure facilities at Edwards Air Force Base using three different solid propellants. Three 1.0-inch and two 2.0-inch throat diameter rocket nozzles were test fired at Atlantic Research Corporation using three different gel propellants. All of the throat inserts and most of the entrance sections were coated with PG/SiC. The erosion rates of all of the coated inserts tested in this program are plotted in Figures 49 and 50 as functions of pressure with temperature and level of gas oxidizing species indicated. No delaminations occurred. Some cracking of the inserts occurred but this did not interfere with the attainment of erosion data. (Modified author abstract)

Research was conducted on electrooptic materials. Single crystals of Bi4Ti3O12 are grown in the correct platy habit and optimization of the growth condition is studied. The new ferroelastic materials isopropyl ammonium chloroplatinate and isopropyl ammonium chlorostannate have been grown as quite good quality crystals and many properties have been measured. The main effort has gone into preparation of coatings on crystals and glasses and their characterization. RF sputtering has been shown to be a tremendously versatile tool for the preparation of both crystalline and noncrystalline layers of many compositions. By controlling process parameters in the sputtering chamber, composition and valence state in the sputtered layers can be controlled. Glass surface coatings and glass surface strengthening have been prepared by CVD, microwave plasma, and ion exchange techniques.

In order to better prepare coatings for infrared laser windows, a program has been initiated to thoroughly study the science and technology of the deposition of inorganic elements and compounds as thin films. Deposition techniques include sputtering, PVD, and CVD; characterization techniques include ellipsometry, SEM, x-ray emission analysis, IR and Raman spectroscopy, ISS, AES, SIMS, and strain measurements. Extensive theoretical calculations by Loomis have shown that effective coatings with the requisite optical properties can be prepared using two-layer films of the appropriate materials and thicknesses. Germanium can be used as the first layer on KCl, ZnSe and CdTe window materials, the second layer can be chosen (theoretically) from a number of other materials. Since this laboratory has extensive experience in the controlled deposition of germanium films, efforts are being concentrated on using this material as the first layer film. (Modified author abstract)

The study of glasses has been important historically because of their great technological usefulness. One class of these materials, amorphous semiconductors, has evoked a great deal of interest during the past few years. The report is intended to provide an overview of the field, its present standing, and its promise. The fundamental structural and electronic properties and the present level of understanding of these properties is of primary concern. However, much of the progress in solid state physics has traditionally been motivated by technological considerations. Therefore, the principal aspects of the physics underlying the more important amorphous semiconductor devices are discussed, as well as the technological setting in which this new field finds itself., Report of the Ad Hoc Committee on the Fundamentals of Amorphous Semiconductors.

Progress is described in a program intended to clarify the nature of mass transport in MgO through (1) growth of crystals of improved perfection and purity, (2) measurement of cation self-diffusion rates over a wide range of temperatures, and (3) extension of diffusion measurements as close as possible to the melting point of the material. Crystals of MgO2 cm in diameter and 2 mm in thickness are routinely and reproducibly grown epitaxially on MgO substrates by means of chemical vapor transport with HCl at 1000 C. Measurements of Ni(2+) diffusion in MgO have been extended to 2460C (0.88 T(M)) in an attempt to reveal intrinsic transport. The measurements extend by 70% the temperature range over which transport data for MgO are now available, but fail to reveal a change in transport mechanism. Mg26 self-diffusion in MgO in the temperature range 1600- 2250C was studied. The results are interpreted as extrinsic diffusion and are not in accord with limited data in the literature for diffusion of the radioisotope Mg28. Neither of the present diffusion studies has revealed a significant difference between transport in moderate purity crystals and crystals of the best quality which are commercially available.

Presented at IVth All-Union Conference on Crystal Orowth. Tsakhkadsore Armenian SSR. 16-23 Sep 1972.

This program was undertaken to contribute to improvement in the life of rapid fire machine gun barrels by manufacturing composite barrels by lining steel barrels with a refractory carbide material. The liner was applied by chemical vapor deposition of the coating on the barrel inside diameter. Two systems, low and high temperature, were used for the depositions. Both yielded high quality titanium carbonitride liners which had good adherence and controlled thickness. Controlled firing tests showed that the performance of barrels lined by the low temperature method was less satisfactory than that of standard chromium plated barrels. Post-firing analysis indicated that the substrate metallurgical condition allowed the steel to soften at operational temperatures and caused early failure of the barrels. The liner itself appeared relatively unchanged during the tests. The performance of barrels lined by the higher temperature method was comparable to that of standard barrels. It was concluded that although the titanium carbonitride liner material offered surface protection, base materials with improved high temperature capability will also be required to achieve longer lifetimes for barrels.

The report contains a fundamental study of the nucleation and film growth mechanisms in heteroepitaxial semiconductor thin films, and applies the results to the preparation of improved thin films and thin-film devices on insulating substrates. The program involves both theoretical and experimental investigations. The emphasis is on chemical vapor deposition (CVD) techniques.

Supersedes AD072796.

This report discusses a number of organic coatings(Parylene, Teflon and Polyimide) APPLIED BY VAPOR DEPOSITION IN ELECTRONIC COMPONENTS. (AH-PL).

The vapor phase deposition of hafnia and zirconia on graphite substrates by decomposition of the isopropyl and tertiary butyl alkoxides was in vestigated. The infrared spectra of the isopropoxides-zirconium and hafnium were obtained. Thorium isopropoxide infrared data were also obtained and the spectra compared with titanium and aluminum isopropoxides. The tertiary but oxides show more promise for coating applications because of their higher vapor pressures. The vapor pressures and decomposition temperatures of the zirconium and hafnium butoxides were studied. Preliminary data on the oxidation re sistance to 1000 C of various grades of graphite coated by this method are reported. The results indicate a potential route to more protective refractory coatings than currently available., Report on Refractory Inorganic Nonmetallic Materials.

The object of this project is to establish a reliable supply of high quality magnetic bubble materials to support the device work of various Department of Defense agencies. This work encompasses bulk, non-magnetic garnet crystal growth (for use as substrates), substrate polishing and preparation, liquid phase epitaxial growth of high performance magnetic garnet film compositions, chemical vapor deposition of Ga-YIG films, and the investigation of arc-plasma spraying as a technique for preparing magnetic bubble garnet films. Characterization data are given for materials delivered during this phase.

The paper describes an experiment in precipitation of molybdenum from gaseous phase in an attempt to determine the factors which affect the orientation of chemical vapor deposited coatings. In the experiment, high- temperature pyrolysis of molybdenum pentochloride was used. Application of the coating was accomplished at three fixed temperatures of the base: 1120, 1300, and 1430C. Two types of bases were used: rolled molybdenum, foil and tablets. X-ray analysis of the coatings was performed. Change in the temperature of the base and change in pressure of the gaseous phase were found to affect the coating process. Texture of the base was found not to have a dominant effect on texture of the coating., Edited machine trans. of Metallurgiya i Metallovedenie Chistykh Metallov (USSR) n8 p5-13 1969, by Francis T. Russell.

It is shown that the morphology, and crystal perfection of single crystals of molybdenum and tungsten obtained by vapor deposition using the thermal decomposition of halides, depends on the supersaturation. The crystals were examined by metallographic investigations and X-rays to determine position, extension, and kind of the disturbances. At lower supersaturations with a given equilibrium form face, disturbances appears regularly in layers and within defined crystallographic positions, which depend on the growth direction in different planes., Unedited rough draft trans. of Journal of Crystal Growth (Netherlands) v9 n1 p228-237 1971.

The treatment of carbon fiber surfaces by oxidation, vapor deposition, and solution- reduction is described. The surfaces of treated and untreated fibers are characterized by various techniques. The solution-reduction treatments were the most effective, producing carbon/epoxy composite shear strengths up to 12,000 psi. The method is extremely fast, requiring less than one minute of residence time. This approach has commercial significance when compared with currently used oxidation treatments requiring several hours. (P.S.-PL)

X-ray analysis of vapor deposited molybdenum shows that either (111) or (100) preferred orientations can be obtained. Further work indicates that precise control of impurities is needed before reproducible results can be obtained. Cathodes having (111) orientations were produced using vapor deposition techniques. Methods of polish ing cathode surfaces were studied. X-ray studies show that heat treatment is adequate to restore the preferred orientation at a mechanically pol ished surface. The reproducibility of performance of test diodes was established by comparison of currea with data from previous work. Con struction of an emission electron microscope for cathode work function distribution studies is in progress. Preliminary work has been done with an electron mirror microscope.

Thin gold films were vapor deposited on nickel, nickel-chromium, and nickel rhenium surfaces to be used for lubrication purposes. The durability of the film was determined by friction characteristics. Durability and strong bonding (adhesion) between the film and the substrate are essential when thin films are used as lubricants. Two methods of substrate preparation for vapor deposition were investigated: (1) mechanical polishing and (2) electron bombardment. Friction experiments were conducted with a hemispherical niobium rider sliding on the deposited gold film on a rotating disk. Results of this investigation indicated that the film endurance life during friction experiments was increased when the substrate was electron bombarded and thermally etched prior to vapor deposition on the etched surface at an elevated temperature of 800 deg F. A diffusion-type interface was believed to be formed between the film and the substrate.

Investigations were performed in an effort to extend the state-of-the-art of GaAsP light emitters and emitter arrays. This effort included a materials study aimed at providing usable GaAsP capable of yielding high quantum and power efficiency at the desired wavelength. The effort also consisted of a study of processing and fabrication techniques to take full advantage of the material capabilities. Device quality slices GaAs(1-x)P(x) material have been prepared by chemical vapor epitaxial deposition with values of x ranging from 0.01 to 0.18. Both selenium and sulfur have been successfully used as a dopant. Hemispherical shaped junction light emitters were fabricated from this material with a quantum efficiency as high as 6.6%. Emission wavelengths from 7800A to 8600A were demonstrated. At the present time, the problem of device degradation has been found to be the main area in which further effort is reqiured. (Author)

The shear moduli of boron filaments were determined by a dynamic torsion-pendulum method and a static torque-twist method. A detailed description of the equipment and techniques involved in the two experimental methods is included. Similar vapor deposition processes were used by two different manufacturers to produce the boron filaments used in the study.

The patent application concerns a thin film infrared photovoltaic detector and a technique for making a discrete detector and imaging arrays from polycrystalline semiconducting InSb films deposited on amorphous insulating substrates. The film is oxidized to provide an oxide layer over which semitransparent nickel counter-electrodes are then evaporated through a suitable aperture mask followed by a thick aluminum evaporation over the nickel in the region near the edge of the semiconductor to form a continuous metallic bridge between the active area and the area to which a lead is to be attached.

Supersedes AD-022 340.

As a part of a liquid propellant positive expulsion program an investigation was made of a process for forming a rollonet within a propellant tank after the tank is fully assembled. The process used the chemical vapor deposition of aluminum, by thermal decomposition of aluminum alkyl, on the heated interior of the tank walls to form the rollonet. Details of experimental equipment, procedures and processes, and test results are discussed. The results of detailed material evaluation on samples of deposited aluminum are presented in photomicrographs, tabulated physical properties data, and X-ray examination photos. (Author)

Research and development activities relating to the chemical vapor deposition of beryllium oxide are described. The program centered about the supporting research and engineering effort required to scale-up the vapor deposition process. Studies covered in this report period include: optimization of fluidized bed sublimation apparatus; analysis and characterization of beryllium basic formate sublimation; design, construction, and testing of prototype vapor deposition equipment. The theoretical and empirical studies in support of these activities are reported. (Author)

Electromagnetic compatibility of GaAs oscillators as a function both of contacting procedures and of active region thickness was investigated by evaluation of their output spectra. Twenty-three devices were measured for spectral output. (Author)