RuO2 single crystals were obtained by evaporation of PbO from Pb2Ru2O6.5 at high temperatures and were verified as good standards for WDS analysis. They were used for the investigation of phase equilibria and the extent of solid solubility in the RuO2–TiO2 system by WDS quantitative microanalysis. The solid solubility at 1350 °C was determined to be 16.5% TiO2 in RuO2 and 13.5% RuO2 in TiO2.

The effects of mechanical milling (MM) on the phase transformation of graphite carbon were investigated using high resolution electron microscopy (HREM), x-ray diffraction, and differential thermal analysis (DTA). Amorphization of graphite as a result of prolonged high-energy ball milling was directly observed with HREM. The exothermic peak in the DTA trace of the ∼200 h ball-milled sample indicated a crystallization onset temperature of about 670 °C and crystallization activation energy of 234 kJ/mole.

Copper sulfide (CuS) powder precipitated from a chemical bath containing Cu(II) chloride and thiourea and annealed in air at 150 °C for 1 h was dispersed in a poly(acrylic acid) aqueous solution (with additional water or propylene glycol as a dispersive agent) and cast on glass slides. Upon evaporation of the solvent, coatings of ∼50 μm in thickness of a CuS-poly(acrylic acid) composite are formed. Measurement of sheet resistance (R□) indicates a percolation threshold of electrical conduction at a weight fraction [wf is wt. % of CuS to poly(acrylic acid) + CuS] of about 40%; the composite undergoes a transition from insulator (R□ ∼ 1013 Ω) to conductive state (R□ ∼ 102 Ω). The morphology and thermal stability of the composite depend on the choice of the dispersive agent for the CuS powder; smoother and thermally stable (up to a temperature of 250 °C) coatings are obtained when propylene glycol is used. The results on x-ray diffraction, thermogravimetric analysis, and Fourier transform infrared spectroscopy studies are given to indicate the structure and bonding mechanisms and their dependence on temperature and dispersive agents.

Silicon carbide fiber (SCS-6) reinforced-reaction-formed silicon carbide matrix composites were fabricated using a reaction-forming process. Silicon-2 at. % niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bimodal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon, and silicon. Fiber pushout tests on these composites determined a debond stress of ∼67 MPa and a frictional stress of ∼60 MPa. A typical four-point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pullout.

The influence of applied stress on the measurement of hardness and elastic modulus using nanoindentation methods has been experimentally investigated using special specimens of aluminum alloy 8009 to which controlled stresses could be applied by bending. When analyzed according to standard methods, the nanoindentation data reveal changes in hardness with stress similar to those observed in conventional hardness tests. However, the same analysis shows that the elastic modulus changes with stress by as much as 10%, thus suggesting that the analysis procedure is somehow deficient. Comparison of the real indentation contact areas measured optically to those determined from the nanoindentation data shows that the apparent stress dependence of the modulus results from an underestimation of the contact area by the nanoindentation analysis procedures.

The finite element method has been used to study the behavior of aluminum alloy 8009 during elastic-plastic indentation to establish how the indentation process is influenced by applied or residual stress. The study was motivated by the experiments of the preceding paper which show that nanoindentation data analysis procedures underestimate indentation contact areas and therefore overestimate hardness and elastic modulus in stressed specimens. The NIKE2D finite element code was used to simulate indentation contact by a rigid, conical indenter in a cylindrical specimen to which biaxial stresses were applied as boundary conditions. Indentation load-displacement curves were generated and analyzed according to standard methods for determining hardness and elastic modulus. The simulations show that the properties measured in this way are inaccurate because pileup is not accounted for in the contact area determination. When the proper contact area is used, the hardness and elastic modulus are not significantly affected by the applied stress.

The relationship between microtexture and crystallinity of highly crystallized graphites with the residual resistivity ratio ρ300K/ρ4.2K of 3.45–5.50 was investigated. The graphite crystals studied were kish graphite (KG), highly oriented pyrolytic graphite (HOPG), and highly crystallized graphite films prepared from carbonized aromatic polyimide films. The study was made by the observations of an electron channeling pattern and electron channeling contrast image (ECI) under scanning electron microscope and the measurements of x-ray diffraction, magnetoresistance, and Hall coefficient. The values of the mean free path of the carriers λ, which approximates the mean crystal grain size, were estimated to be 2.6–6.1 μm from the magnetoresistance at 4.2 K for the highly crystallized graphites. The values of the average crystal grain diameter D in the basal plane evaluated from ECI were several hundred microns or more for KG, 60 μm for HOPG, and 6 and 12 μm for the graphite films. The difference between the values of λ and D for each crystallized graphite was discussed in relation to other results obtained.