Mass Fraction Of Al2O3 Research Articles

Effect of Al Content on the Isomerization Performance of Solid Superacid Pd–S2O82−/ZrO2 –Al2O3

The effect of Al content on the performance of the Pd–S2O82−/ZrO2–Al2O3 solid superacid catalyst was studied using n-pentane isomerization as a probe reaction. The catalysts were also characterized by X-ray diffraction (XRD), Fourier transform Infrared (FTIR), specific surface area measurements (BET), thermogravimetry–differential thermal analysis (TG–DTA), H2-temperature programmed reduction (TPR) and NH3 temperature-programmed desorption (NH3-TPD). The Pd–S2O82−/ZrO2–Al2O3 catalyst made from Al2O3 mass fraction of 2.5% exhibited the best performance and its catalytic activity increased by 44.0% compared with Pd–S2O82−/ZrO2. The isopentane yield reached 64.3% at a temperature of 238°C, a reaction pressure of 2.0MPa, a space velocity of 1.0h−1 and a H2/n-pentane molar ratio of 4.0. No obvious catalyst deactivation was observed within 100h.

A Thermodynamic Model for Evaluation of Mass Action Concentrations of La2O3-Al2O3-CaF2-CaO-MgO Slags for Electroslag Remelting Based on the Ion and Molecule Coexistence Theory

AbstractAccording to the ion and molecule coexistence theory (IMCT) for molten slags and corresponding phase diagrams, a thermodynamic model for the evaluation of mass action concentrations (designated by Ni for structure unit i) for La2O3-Al2O3, La2O3-Al2O3-CaF2, La2O3-Al2O3-CaF2-CaO, La2O3-Al2O3-CaF2-MgO and La2O3-Al2O3-CaF2-CaO-MgO slag systems for electroslag remelting (ESR) has been formulated. The influencing factors for the mass action concentration of La2O3, such as mass fraction of Al2O3, CaF2, CaO and MgO and temperature, were investigated. The results show that when the mole fraction of La2O3 is at 0.495, the mass action concentration of La2O3 · Al2O3 achieves its maximum value 0.946 in the La2O3-Al2O3 binary slag. In a composition area of La2O3: 10wt% ∼ 45wt%, Al2O3: 0wt% ∼ 50wt% and CaF2: 20wt% ∼ 70wt% of the La2O3-Al2O3-CaF2 ternary slag at 1873 K, the results show that the calculated values of NLa2O3 are in good agreement with the reported measured values of aLa2O3. The iso-curves of NLa2O3 is also drawn from the calculated results, which reveals that the mass action concentration of La2O3 decreases with the increasing of the Al2O3 and CaF2 content, and Al2O3 is stronger than CaF2 in decreasing the mass action concentration of La2O3. However, in La2O3-Al2O3-CaF2-CaO, La2O3-Al2O3-CaF2-MgO and La2O3-Al2O3-CaF2-CaO-MgO slag systems, the mass action concentration of La2O3 increases with the increasing of the MgO and CaO content, and CaO is stronger than MgO in increasing the mass action concentration of La2O3. In addition, the mass action concentration of La2O3 increases with the increasing temperature at the composition of 30wt%La2O3, 10wt%Al2O3, 40wt%CaF2, 10wt%MgO and 10wt%CaO.

Microstructure and mechanical properties of extruded Al/Al2O3 composites fabricated by stir-casting process

A novel two step mixing method including injection of particles into the melt by inert gas and stirring was used to prepare aluminum matrix composites (AMCs) reinforced with Al2O3 particles. Different mass fractions of micro alumina particles were injected into the melt under stirring speed of 300 r/min. Then the samples were extruded with ratios of 1.77 or 1.56. The microstructure observation showed that application of the injection and extrusion processes led to a uniform distribution of particles in the matrix. The density measurements showed that the porosity in the composites increased with increasing the mass fraction of Al2O3 and stirring speed and decreased by extrusion process. Hardness, yield and ultimate tensile strengths of the extruded composites increased with increasing the particle mass fraction to 7%, while for the composites without extrusion they increased with particle mass fraction to 5%.

Comparison of Conductivity of Al<sub>2</sub>O<sub>3</sub> Nanofluids between Experiments and Maxwell Model

The thermal properties of nano-fluids are affected by many factors. The effect of the diameter, mass fraction and volume fraction of Al2O3 in water on the thermal conductivity was measured by the method of hotwire. The diameter of nano-particle of Al2O3 was 10nm, 20nm, 50nm, 100nm and 500nm respectively. The mass fraction of Al2O3 in water was 10%, 12%, 15% and 20%. The results show that the diameter of the particle plays a critical role on thermal properties of the base fluid. And for the mass fraction, it will increase the thermal conductivity of the base fluid. When the size is more than 100nm, the coefficient of thermal conductivity is increased rapidly. Compared with the results calculated by the Maxwell model, the conductivity of the nanofulid with a diameter less than 10nm is consistent with the model’s result. And with the increasing of the diameter o f the nanoparticle, the deviation of the conductivity will also increase compared with the model’s results.

Study on Properties of Epoxy Resin /Al<sub>2</sub>O<sub>3</sub> Composites

An epoxy resin/Al2O3 composite was prepared via a new type of process.The effects of Al2O3 content on the mechanical properties and thermal conductivity of the composite were investigated.It shows that the thermal conductivity of the epoxy resin/Al2O3 composite aggrandizes with the addition of aluminum oxide.As the content of Al2O3 is 30%,the thermal conductivity coefficient reaches 0.46W/m·K. Al2O3 particles can hinder the propagation of flaw or make crack change direction.and lead to generate scales flake and islands peak shape on the fracture surface when The thetensile fracture surfaces tested under the liquid nitrogen temperatures(77k). When the mass fraction of Al2O3 is 20%, the mechanics properties of the composite is better

Wear performance of alumina-reinforced copper–matrix composites prepared by powder metallurgy

Copper–alumina composite materials with improved electrical conductivity and tribological properties were developed. The copper–alumina composite materials were prepared by powder metallurgy using nano-Cu/Al2O3 powder. The powders were deoxidized from CuO/Al2O3 powder synthesized by coprecipitation using NH4HCO3 as precipitator and CuSO4 + NH4Al(SO4)2 as maternal solution. The wear test against 440C stainless steel was performed at room temperature using a ball-on-flat configuration with 300 µm amplitude at various normal loads ranging from 0.1 N to 1 N. The effects of load and mass fraction of Al2O3 on the friction coefficient and wear loss were investigated. Results showed that the wear loss first decreased and then increased with an increase in the mass proportion of Al2O3 from 1% to 5%. Minimum wear loss was found at 2% proportion, in which the electrical conductivity was 82% of the International Annealed Copper Standard. The friction coefficient of the copper increased slightly with an increase in load. By contrast, it first increased and then decreased for the copper–alumina composite materials. The wear loss of the copper–alumina composite materials is always lower than that of copper. The highest relative wearability is 3.13, indicating better wear resistance. The wear mechanism of copper is oxidation wear, whereas that for the copper–alumina composite materials is adhesive wear.

The mechanical alloying mechanism of various Fe2O3–Al–Fe systems

The mixed powders of in situ Al2O3 particles and Fe (Al) solid solution were prepared via self-propagating combustion reaction initiated by mechanical alloying (MA), and the MA mechanism of several Fe2O3–Al–Fe systems with different Al2O3 mass fractions were studied. The adiabatic temperature (Tad) of each system was calculated to estimate whether the self-propagating combustion reaction could be initiated in theory. The microstructure of the mixed powders was investigated by SEM, EDS and TEM. The phase analysis was evaluated by XRD, and the Fe lattice parameter was calculated from the XRD patterns. The results showed that with the addition of Fe during the MA process, the activation period was prolonged and the sharp increase of temperature occurred, and when the Al2O3 mass fraction was decreased to 10.94%, the self-propagating combustion reaction could not occur in theory and practice. When there was no added Fe, the final product was homogeneous Fe (Al) solid solution.

PW based phase change nanocomposites containing γ-Al2O3

Phase change nanocomposites were prepared by dispersing γ-Al2O3 nanoparticles into melting paraffin wax (PW). Intensive sonication was used to make well dispersed and homogeneous composites. Differential scanning calorimetric (DSC) and transient short-hot-wire (SHW) method were employed to measure the thermal properties of the composites. The composites decreased the latent heat thermal energy storage capacity, Ls, and melting point, Tm, compared with those of the PW. Interestingly, the composites with low mass fraction of the nanoparticles, have higher latent heat capacity than the calculated latent heat capacity value. The thermal conductivity of the nanocomposites was enhanced and increased with the mass fraction of Al2O3 in both liquid state and solid state.

Evaluated Material Properties for a Sintered alpha‐Alumina

Results of a data evaluation exercise are presented for a particular specification of sintered alpha‐alumina (mass fraction of Al2O3, ≥0.995; relative density (rho/rhotheoretical), ≥0.98; and nominal grain size, 5 μm). A comprehensive set of material property data is established based on published physical, mechanical, and thermal properties of alumina specimens that conform to the constraints of the material specification. The criteria imposed on the properties are that the values should be derived from independent experimental studies, that the values for physically related properties should be mutually self‐consistent, and that the sets of values should be compatible with established material property relations. The properties assessed in this manner include crystallography, thermal expansion, density, sound velocity, elastic modulus, shear modulus, Poisson's ratio, bulk modulus, compressive strength, flexural strength, Weibull characteristic strength, Weibull modulus, tensile strength, hardness, fracture toughness, creep rate, creep rate stress exponent, creep activation energy, friction coefficient, wear coefficient, melting point, specific heat, thermal conductivity, and thermal diffusivity.