The reported research examines the effect of 5–70 nm SiO2 nanoparticles on the mechani-cal properties of nanocement materials. The strength development of portland cement with nano-SiO2 and superplasticizing admixture is investigated. Experimental results demonstrate an in-crease in the compressive strength of mortars with SiO2nanoparticles. The distribution of nano-SiO2 particles within the cement paste plays an essential role and governs the overall perfor-mance of these products. Therefore, the addition of a superplasticizer is proposed to facilitate the distribution of nano-SiO2 particles. The application of effective superplasticizer and high-speed dispergation are found to be very effective dispersion techniques that improve the strength of su-perplasticized portland cement mortars, reaching up to 63.9 MPa and 95.9 MPa after aging dur-ing 1 and 28 days, respectively. These values compare favorably with the observed compressive strengths of reference portland cement mortars of 53.3 MPa and 86.1 MPa. It is concluded that the effective dispersion of nanoparticles is essential to obtain the composite materials with im-proved performance.

In this work the synthesis and mechanical characterization of a polymer matrix composite is reported. An epoxy resin is used as matrix with addition of starch and coconut fibers as reinforcement. Vickers hardness and impact tests are used for mechanical characterization. Starch is used to promote degradability of the polymer matrix with clear benefits for the environment. Natural fibers have been used for reinforcing the composite materials. Natural fibers have several advantages such as price, low density and relatively high mechanical properties, they are also biodegradable and non abrasive In this investigation, the composite material samples are fabricated with epoxy resin, 5, 10, 15 wt % of starch and 5, 10 wt % of coconut fibers with the help of silicon molds which have the dimensions and geometry according to ASTM Standards for make Impact and Vickers hardness tests. The obtained results show that increases in the amount of coconut fibers cause an enhancement of the mechanical properties of the material, due to a good adhesion between the polymeric matrix and the natural fibers.

The synthesis, mechanical and magnetic properties of bulk composite Fe72B19.2Si4.8M4 (M=Cr, Zr) alloys obtained by a copper mould injection casting technique under a protective helium atmosphere are reported and discussed. The resultant microstructure of the composite alloys consists of crystalline Fe92Si8 and Fe2B phases embedded in a glassy matrix. The values of microhardness (Hv) show maxima for the alloy containing Cr with 10.24±0.95 GPa. The maximum value of saturation magnetization average (μ0Ms) is 1.25±0.02 T for Cr-containing alloy. The Curie temperatures (Tc) of amorphous phases are higher than 390 K for both alloys. However, the bulk composite alloys presents values for crystallization temperature (Tx) of 1289±10 K and 1140±10 K for Cr and Zr-containing alloys, respectively. These results are interpreted on the basis of the interplay between the crystalline and amorphous phases.

X ray diffraction (XRD) is the common technique for texture analysis by means of pole figure (PF) measurement. PF reflects the grains orientation distribution but contains no information about grain microstructure. The reflected intensity can be affected by the extinction phenomenon that reduces the pole density (PD). The parameters of extinction are related to the crystal microstructure. The parameter of the primary extinction is connected with domain size and parameter of the secondary extinction is related to the angle of domains disorientation that depends on dislocation density in domain boundary. An original XRD method is proposed for correction of PD, considering extinction phenomenon, and separation of the extinction parameters in the case of textured aluminum. The problem is solved under some assumptions. In the present work cold rolled nickel with and without annealing at 600 °C is investigated. The validity of the proposed assumptions for Ni is evaluated in terms of the extinction length. The corrected PD in the maximum of PF and the parameters of the primary and secondary extinction are calculated using the first order reflection for Cu Kα- and Co Kα- radiations and the second order reflection for one of the used wavelengths. Both in cold rolled sample without annealing and in the annealed sample the primary and secondary extinctions are present simultaneously. According to the obtained parameters of extinction the microstructure of textured nickel is evaluated and their modification at the annealing process is demonstrated.

Composite particles destined to build plasma sprayed coatings, are prepared by the mechanofusion process (MF). These particles consist of a stainless steel core particle coated by finer particles of alumina. Changes induced by the MF process are monitored by SEM, DRX, and laser granulometry, revealing that the dry particle coating process is governed by agglomeration and rolling phenomena. Simultaneously, the MF performance is controlled by the operating parameters such as the compression gap, the mass ratio of host to guest particle, and the powder input rate. The mechanical energy input leads to a nearly rounded shape of the final composite particles; however, no formation of new phases or components decomposition is detected by XRD analysis. The resulting composite powder features optimal characteristics, concerning particle shape and phases distribution, to be plasma sprayed in air.

This work deals with rotating bending fatigue tests on aluminum alloy 6061-T6, under loading condition close to the elastic limit of the material. Results have been obtained for three types of specimens: without artificial pitting, specimens with one artificial pitting hole and specimens with two neighboring artificial pitting holes. Results show that fatigue endurance is reduced in the case of one pitting hole and considerably for two neighboring pitting holes. In order to explain this behavior, numerical analysis by FE are carried out to determine the stress concentrations for the three types of specimens. It is found that the stress concentration for two neighboring pitting holes is an exponential function of the separation between the two holes, under uniaxial loading. The probability to find two or more neighboring pitting holes in real industrial materials, such as cast iron, corroded or pitting metallic alloys is high; then, the stress concentration for two or more neighboring pitting holes needs to be considered for the fatigue prediction life under fatigue loading and corrosion attack applications.

The goal in this study is to synthesize a Ruddleden-Poper La-Ni phase (La4Ni3O10) using a polymeric route. This material exhibits mixed ionic and electronic conduction (MIEC) properties and can be used as cathode material in the manufacture of Solid Oxide Fuel Cells (SOFC). In addition, an easy and inexpensive synthesis method is presented The polymeric precursors are prepared following the Castillo method using optimized the complexation ratios (HMTA/metallic salts) from 1 to 6. The obtained powders are characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) in order to determine the processing conditions for formation of the crystalline phase. Experiments performed using complexation ratios of 5 and 6 do not show coagulation. However, the solution prepared using a complexation ratio of 5, is transformed into a gel after few days. Gels produced from solutions prepared with complexation ratios from 2 to 5 were heated at 800, 900 and 1000°C to obtain solid materials. These powders are characterized by TGS, DSC and XRD and it is found that the temperature needed to obtain crystalline La4Ni3O10 was 1000°C.

The synthesis of Al2O3-based functional materials having 10 vol. % of fine aluminum or titanium and aluminum-disperse or titanium-dispersed nitride hardened-particles has been explored. Two experimental steps have been set for the synthesis; specifically, sintering of Al2O3-aluminum or Al2O3-titanium powders which were thoroughly mixed under high energy ball-milling, pressureless-sintered at 1400°C during 1 h in argon atmosphere and then for the second step it was induced formation of aluminum nitride or titanium nitride at 500°C during different times (24, 72 and 120 h) by a nitriding process via immersion in ammoniac salts. SEM analyses of the microstructures obtained in nitride bodies were performed in order to know the effect of the ammoniac salts used as nitrating on the microstructure of aluminum or titanium for each studied functional material. It was observed that an aluminum nitride or titanium nitride layer growth from the surface into the bulk and reaches different depth as the nitriding time of the functional material was increased. The use of aluminum or titanium significantly enhanced density level and hardness of the functional materials.