Study on the Effects of Powder-Liquid Ratio and Cement Ratio on Mechanical Properties and Microscopic Characteristics of Polymer-Cement Composite

This paper is about a study on the mechanical properties of a new polymer-cement composite (PCC) in constant elongation, tension, and shear. The study explored the effects of powder-liquid ratio and cement ratio on the mechanical properties of PCC through detecting the strength, deformation, and energy consumption of specimens under different powder-liquid ratios and cement ratios. In addition, scanning electron microscope and mercury injection apparatus were used for an in-depth analysis on the micromorphology and pore structure features of PCC under different powder-liquid ratios and cement ratios to explore the influence of powder-liquid ratio and cement ratio of the micromechanical properties of PCC. The results showed that, with the increase of powder-liquid ratio and cement ratio, the constant elongation adhesion strength of PCC decreased, and, at a high powder-liquid ratio (0.55) or a high cement ratio (0.5), the constant elongation adhesion strength of PCC completely disappeared. Meanwhile, with the increase of powder-liquid ratio and cement ratio, the tensile shear strength of PCC increased, while the deformation capacity of PCC decreased. The optimal ranges of powder-liquid ratio and cement ratio for PCC were 0.35–0.4 and 0.3-0.4, respectively. Furthermore, the increased powder-liquid ratio and cement ratio made the total pore volume decreased and pore structure refined, which improved the compactness of PCC, thus influencing the performance of PCC macroscopically. An achievement for the study is a flexible composite material, which was formulated with the polymer film as continuous base phase, as well as the inorganic composition and cement hydrates as dispersion phase. The material can effectively improve the economy and practicability of cementation of fissures for airfield pavement.

Nanoscale Functional Additives Application in the Low Temperature Greases

Due to the fact that the application of AW and EP additives in low-temperature greases may lead to worse high-temperature and anti-corrosion characteristics as well as additional burden on the environment due to the content of aggressive components, in this paper, the possibility of replacing these additives with NFA, which do not have these disadvantages, was investigated. The analysis of nanosized particles being used as functional additives in greases was carried out. The morphology of the following nanoparticles was studied: montmorillonite K 10, silica, calcium car-bonate and borate, halloysite, and molybdenum disulfide incorporated in halloysite tubes. The effect of nanostructured components on the physicochemical characteristics and anti-wear and anti-scuffing properties of complex lithium, polyurea, and polymer greases were studied. Maximal improvement of anti-wear and anti-scuffing characteristics of cLi-greases was reached when using silica and calcium borate. Maximal improvement of anti-scuffing properties of PU-lubricant was reached when using calcium carbonate and the two-component NFA based on halloysite, for anti-wear properties when adding silicon dioxide and halloysite. When the concentrations of silicon dioxide and calcium carbonate was increased from 1 to 3 wt.%, there was a decrease in yield stress of the structural frame of the PU-lubricant and its colloidal stability was worse. The increase of the concentration of calcium carbonate and borate nanoparticles in the studied range led to a significant improvement of the anti-wear and anti-scuffing characteristics of the PU grease, respectively. The greases properties’ dependence from the nanostructured functional additives’ introduction method and their concentration were investigated. Nanoparticles were added into the test lubricants before and after the thermo-mechanical dispersion stage. The addition of silicon dioxide and calcium carbonate NFA after the heat treatment stage led to worsening of the characteristics of the plastic material, and the increase of their concentration from 1 to 3 wt.% formed a harder structure of Li-grease. On the contrary, the addition of calcium borate NFA is recommended after the thermomechanical dispersion. The choice of nanoparticles and the method of their addition to the lubricants of various types was carried out according to the results of the previous stage of the research. Along with the analysis of the physicochemical characteristics and anti-wear and anti-scuffing properties of the lubricants, the structure of the dispersion phase of nanomodified lubricants were studied.

The Influence of Substituents in Phosphazene Catalyst-Flame Retardant on the Thermochemistry of Benzoxazine Curing

This work is devoted to the influence of phosphazene modifiers with different substituents on the curing process, thermal properties and flammability of benzoxazine resin. Novel catalysts with m-toluidine substituents were introduced. The catalytic activity of studied phosphazene compounds decreased in the row: hexachlorocyclotriphosphazene (HCP) > tetra m-toluidine substituted phosphazene PN-mt (4) > hexa m-toluidine substituted phosphazene PN-mt (6) > hexaphenoxycyclotriphosphazene (HPP), where HPP is totally inactive. Two types of catalysis: basic and acid were proposed. A brief study of resulting properties of polybenzoxazines was presented. The addition of any studied modifier caused the decrease of glass transition temperature and thermal stability of polymers. The morphology of cured compositions was characterized by matrix-dispersion phase structure. All phosphazene containing polybenzoxazines demonstrated the improved flame resistance.

Microstructure and Properties of Electroless Ni-P/Si3N4 Nanocomposite Coatings Deposited on the AW-7075 Aluminum Alloy

The article presents the results of mechanical and tribological tests of Ni-P/Si3N4 nanocomposite coatings deposited on the AW-7075 aluminum alloy using the chemical reduction method. The influence of the chemical composition on the Vickers microhardness determined by the DSI method was examined. The nanocomposite layers were made of Si3N4 silicon nitride in a polydisperse powder with a particle size ranging from 20 to 25 nm. The influence of the content of the dispersion layer material on the adhesion to the substrate was analyzed. The abrasive wear was tested and determined in the reciprocating motion using the “ball-on-flat” method. The surface topography was examined by the contact method with the use of a profilometer. Based on the obtained test results, it was found that the Ni-P/Si3N4 layers produced in the bath with the Si3N4 nanoparticle content in the amount of 2 g/dm3 are more resistant to wear and show greater adhesion than the Ni-P/Si3N4 layers deposited in the bath with 5 g/dm3 of the dispersion phase. NiP/Si3N4 layers provide protection against abrasive wear under various loads and environmental conditions.

Investigation of the Rheokinetic Properties and Penetration Depth of Aluminosilicate Adhesive in Pine Wood

Practical work and is devoted to the study of the rheological and deformative properties of Geofip aluminosilicate glue, obtained on the basis of an alkaline aluminosilicate binder composition Na2O Al2O3×6SiO2×20H2O, modified with 5% Cr2O3, when gluing wooden trusses in the field. The rheological and deformative properties of an aluminosilicate adhesive based on an alkaline aluminosilicate binder composition of Na2O×Al2O3×6SiO2×20H2O modified with 5% Cr2O3 have been investigated. It is noted that the dynamic viscosity of the adhesive slurry in the speed range from 0.1 to 0.8 RPM varies from 147600 to 144600 cP, and the average plastic viscosity in the same speed range is 87.39 cP. It was found that at shear rates from 0.021 to 0.168 1/s, an increase in shear force from 31 to 242.9 dyne/cm2 is observed due to the stabilization and uniformity of the dispersion phase particle distribution in the dispersion medium of the adhesive. It is shown that the aluminosilicate adhesive at a surface tension value of 88.1 mN/m is characterized by coefficients of wetting (s = 0.648) and fluidity (f = -62.02 mN/m), which ensures the uniformity of its application to the pine substrate. The average thickness of the adhesive layer was 1.25 mm, and the average depth of penetration of the aluminosilicate adhesive into the wood substrate, respectively, 0.12 mm. The destruction of the adhesive seam occurred at shear stresses of 515 MPa. The relative shear deformations were 162.5×10-5 mm.

Effect of Nano-Y2O3 Content on Microstructure and Mechanical Properties of Fe18Cr Films Fabricated by RF Magnetron Sputtering

In this work, FeCr-based films with different Y2O3 contents were fabricated using radio frequency (RF) magnetron sputtering. The effects of Y2O3 content on their microstructure and mechanical properties were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma emission spectrometer (ICP) and a nanoindenter. It was found that the Y2O3-doped FeCr films exhibited a nanocomposite structure with nanosized Y2O3 particles uniformly distributed into a FeCr matrix. With the increase of Y2O3 content from 0 to 1.97 wt.%, the average grain size of the FeCr films decreased from 12.65 nm to 7.34 nm, demonstrating a grain refining effect of Y2O3. Furthermore, the hardness of the Y2O3-doped FeCr films showed an increasing trend with Y2O3 concentration, owing to the synergetic effect of dispersion strengthening and grain refinement strengthening. This work provides a beneficial guidance on the development and research of composite materials of nanocrystalline metal with a rare earth oxide dispersion phase.

Microstructure Evolution of Al-Zn-Mg-Cu Alloy with Erbium during Homogenization

The microstructure evolution of Al-Zn-Mg-Cu alloy with erbium was studied by optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) during homogenization process. The results showed that there were serious component segregation in the as-cast structure of the alloy, mainly composed of T(AlZnMgCu) , S(Al2CuMg) and a small amount of Al8Cu4Er and Al7Cu2Fe. The overheating temperature of the alloy was 482.5 °C. After homogenized at 470 °C for 24 h, the dissolution of T(AlZnMgCu) phase and S(Al2CuMg) phase reached to a balance, but the residual Al8Cu4Er phase could not be dissolved completely. Compared with single-stage homogenization, Al3(Er,Zr) dispersion phase with smaller grain size and more uniform distribution can be obtained after two stage homogenization process of 400 °C for 8 h followed by 470 °C for 24 h. By comparing the residue of non-equilibrium eutectic phase, two-stage homogenization is the best.

BeO Utilization in Reactors for the Improvement of Extreme Reactor Environments - A Review

Ceramic material is one of the essential materials used in reactors. Beryllium oxide ceramics have good high-temperature radiation stability, high density, high strength, and thermal conductivity at high temperatures, and the price of beryllium oxide is relatively moderate. This makes it more suitable for use as a reflector, moderator, and dispersion phase fuel matrix in a reactor. In recent years, beryllium oxide has attracted widespread attention due to its high hardness, high resistivity, high thermal conductivity, high melting point, and high radiation resistance. Because of its excellent mechanical properties, beryllium oxide materials also have a long history in the field of nuclear energy. Reactor extreme environments have become a significant challenge for optimizing reactor operation and safety performance. The utilization of beryllium oxide can significantly alleviate extreme reactor environments. According to research, the coupling of beryllium oxide material can effectively improve nuclear fuels' thermal conductivity, such as uranium dioxide. Beryllium oxide also has good radiation resistance and neutron scattering properties, which increases its applications in nuclear energy. The article comprehensively reviews the BeO utilization approaches in reactors to improve extreme reactor environments for current reactor operation and future reactor design optimization.

Modulation Instability Analysis of a Nonautonomous (3+1)-Dimensional Coupled Nonlinear Schrödinger Equation

We investigate the modulation instability (MI) analysis of a nonautonomous (3+1)-dimensional coupled nonlinear Schrödinger (NLS) equation with time-dependent dispersion and phase modulation coefficients. By employing standard linear stability analysis, we obtain an explicit expression for the MI gain as a function of dispersion, phase modulation, perturbation wave numbers and an initial incidence power. The nonautonomous coupled NLS equation is found to be modulationally unstable for the same sign of dispersion and phase modulation coefficients. This equation is modulationally stable for zero dispersion and or phase modulation coefficients. But non-zero dispersion coefficient, it is modulationally stable/unstable on distinct bandwidth of wave numbers. The trigonometric, exponential, algebraic function of time and constant have been chosen as test functions for dispersion and phase modulation to find the effect on the MI analysis. The effect of focusing and defocusing medium on the MI analysis has also been investigated. The MI bandwidth in the focusing medium is found to be larger than defocusing medium. It is found that the modulation instability of the equation can be managed by proper choice of the dispersion and phase modulation parameters.

The influence of base oil type on the rheological properties of ecological lubricating greases

The article presents the results of research on the influence the type of base oil in lubricating compositions has on the rheological parameters of selected lubricants. Vegetable, mineral, and synthetic dispersion phases were used to produce lubricating greases. The modified amorphous silica was used as the dispersed phase. However, as a modifying additive was used a substance containing the antioxidants, corrosion inhibitors, and EP/AW additives. The experiments on rheological properties were carried out using a Physica MCR 101 rotational rheometer (manufactured by Anton Paar), equipped with a diffusion air bearing and connected to a pneumatic supply – an oil-free Jun-Air compressor and air drying block. The device is equipped with a Peltier system for temperature control in the range of –20°C to 200°C and an external thermostatic VISCOTHERM V2 system, working in the temperature range of –20°C to 200°C. The rheometer control and measurement data analysis were performed using Rheoplus software. The tests were carried out using a cone-plate measuring system with a shear rate range of 0.01–100 s-1 at 20°C for lubricating compositions prepared on various oil bases. To evaluate the value of rheological parameters, the results of tests of the dependence between shear stress and shear rate (flow curves) were used. For the theoretical determined on the flow curves, the following rheological models were used: Bingham, Herschel–Bulkley, Casson, and Tscheuschner. The values of the shear stress (yield point) in depending on the type of dispersion phase has changed. This proves that the use of a base oil with the appropriate functional properties does not weaken, but reinforces the spatial structure of a lubricating grease. It has an important meaning when selecting construction parameters when designing a central lubrication system with grease made from a vegetable oil base (Abyssinian oil). The rheological properties of the lubricating grease are influenced by the type of base oil and thickener, any additives in the grease, the production technology of the grease, and the conditions in which it is used. The tests revealed an important influence of the base oil on the rheological parameters that describe the behaviour of lubricating compositions subjected to stresses and strains in a lubricating system.