Al2O3 Particle Size Research Articles

Moderation of Al dust explosions by micro- and nano-sized Al2O3powder

Adding solid inertants to combustible dust is one measure to prevent and mitigate dust explosions. Al2O3 at four particle size distributions was used to determine the minimum ignition energy (MIE) and maximum explosion pressure (Pmax) of aluminum dust and thus examine the effect of particle size on the inerting efficiency. It was interesting to observe that nano-sized Al2O3 powder showed excellent promise as a solid inertant, having inerting efficacy superior to that of micro-sized Al2O3. In addition to thermal inhibition, nano Al2O3 contributed to explosion moderation by binding Al particles together forming larger-sized aggregates that reduce dispersion in the dust clouds, and thus alleviate explosion hazards. Ignition sensitivity increased when micro-sized Al2O3 was admixed at 5 or 10% with 1000–1500 g/m3 Al mixtures, an effect apparently caused by a 20% decrease in effective particle size distribution brought on by the Al2O3 addition. Generally, increasing the amount of admixed Al2O3 increased MIE and decreased Pmax of Al dust clouds, and decreasing the particle size of Al2O3 resulted in better inerting performance on moderating both the likelihood of the ignition and the consequence of the explosion.

Coagulation of the Ionized Combustion Products in a Dust Flame of Aluminum Particles

The addition-agent effect of atoms of alkali metals (K, Na, Li, and Cs) and halogens (Cl and I) introduced into the combustion zone of a dust flame of aluminum particles on the average size of Al2O3 nanoparticles is studied. A physical model of coagulation of a monodisperse aerosol is proposed. The model takes into account the formation of a complex plasma consisting of positive and negative ions, electrons, neutral gas molecules, and suspended particles of the condensed phase in the combustion zone. The effect of the forces of Coulomb repulsion of unipolarly charged Al2O3 particles as well as their possible attraction by ion wind on the constant of the coagulation rate is also taken into account. It is shown that at low ion concentrations in the plasma, the coagulation rate is determined by the Coulomb repulsion of the particles, and at ion concentrations greater than 1020 m−3 the coagulation rate is determined by the attraction of the particles by the ion wind. The results of calculations of the dependence of the average Al2O3 particle size on the concentration of the additives are in a good quantitative agreement with the experimental data. The combined effect of the additives and the equilibrium products of aluminum oxide (AlO, Al, and Al2O) evaporation on the concentration of positive and negative gas ions, electrons, and Al2O3 particle size in the condensation zone is analyzed. The peculiarities of the influence of the additives of electronegative gases (Cl and I atoms) on the coagulation rate of a thermally ionized aerosol and on the particle size of Al2O3 are considered.

In–situ synthesis of an Al composite reinforced with multi–scale Al12Mo, (Al, Zr, Si) and Al2O3 particles through a multi–stage reaction

Heterogeneous strengthening effect has been a more and more attractive theory for designing metal matrix composites in recent years. In this paper, a new multiphase reinforced Al composite (Al12Mo+(Al,Zr,Si)+Al2O3)/Al has been prepared through a multi–stage reaction of Al–10ZrO2–5MoSi2 alloy on the basis of Al–10ZrO2, i.e. (ZrAl3+Al2O3)/Al composite, by introducing MoSi2. The strengthening phases, including micro–sized Al12Mo, sub–micron (Al,Zr,Si) and nano–sized Al2O3, are in–situ synthesized, performing attractive strengthening effect. The in–situ synthesized sub–micron (Al,Zr,Si) and nano–sized Al2O3 particles exhibit a net–work distribution, while micron Al12Mo particles act as the node of particle network. Compared with Al–10ZrO2, the Al–10ZrO2–5MoSi2 composite exhibits improved tensile strength at both room temperature (25 °C) and elevated temperature (350 °C). The reaction mechanism and phase evolution procedure have been discussed. This work can be referred in designing new multifarious particles reinforced composites to achieve promotion at material properties.

Characterizations of PMMA-based polymer electrolyte membranes with Al2O3

Abstract Poly(methyl methacrylate) (PMMA)-based polymer electrolyte membranes are prepared through the solution cast method, with PMMA:ethylene carbonate (EC):LiCF3SO3:Al2O3 weight ratio of 55.13:18.34:24.5:2. The effect of Al2O3 filler grain sizes of 50 nm and 10 μm on the polymer electrolytes was studied in this work. From the Cole-Cole plot obtained through electrochemical impedance spectroscopy, the highest ionic conductivity for 50-nm Al2O3 in the PMMA-LiCF3SO3-EC-Al2O3 sample was measured as 1.52 × 10−4 S/cm at room temperature. The bonding formation among the host polymer and other additives in the polymer electrolytes has been studied using Fourier transform infrared spectroscopy. A strong occurrence of CH3 stretching mode has proven that nano size Al2O3 results in a much stronger bonding effect with the host polymer. The particle sizes were calculated by applying the Debye-Scherrer equation from the X-ray diffraction results. This work considers the effect of instrument broadening to further improve the accuracy of particle broadening for particle size calculation. The average particle size of nano size Al2O3 in the PMMA sample is calculated as 2.9693 nm. Moreover, a higher amorphousity level obtained from nano size filler polymer electrolyte of 98.5% computed from differential scanning calorimetry thermograms had also explained the achievement of high ionic conductivity in this work.

Effects of Sintering and Compress on Porosity, Mechanical Properties and Conductivity of Cu-Al<sub>2</sub>O<sub>3</sub> Composite Materials Fabricated by Mechano-Chemical Method

Nano Al2O3 dispersion - strengthened Cu-matrix composite materials were fabricated by mechano-chemical method. The method carries out at room temperature by mechanical milling in the attritor in 16h hours using the mixtures of CuO, Al and Cu powder ingredients, and then the mixtures were cold pressed into cylindrical samples and sintered at various temperatures (from 700°C to 900°C) and time (from 1 to 3 hours) in argon atmosphere. The XRD pattern and EDS results revealed that Al2O3 phases were formed and dispersed into Cu-matrix during mechano-chemical process. The Al peak disapeared at the end of mechano-chemical process and the final obtained products were Cu-Al2O3 composite materials with Al2O3 content of 3-10% volume. The SEM and EDS results also showed that the particle sizes of Al2O3 were in about (50÷100)nm and uniformly dispersed within the C-matrix. The porosity of materials strongly depends on pressure compress, sintering time and temperature. It decreases with increasing of these parameters and reaches about 5%. The porosity and Al2O3 content affected on mechanical properties of materials, such as micro-hardness and compress strength, due to the dispersion of nano-Al2O3 into Cu-matrix. The conductivity of materials decreases with increasing porosity and Al2O3 content.

Resin Matrix Brake Materials Reinforced by Nano-Al2O3 for Mining Equipment

To verify the effect of Al2O3 particle content and size as an abrasive on resin matrix friction materials for mining equipment, the tribological performance of friction materials was studied by using a blockon- ring tribotester over a wide range of applied load and sliding speed. The testing conditions simulated brake conditions of mining equipment. The antiwear property of nano-Al2O3 was superior to that of micro- Al2O3 for friction materials. The friction coefficients of specimens increased with the increase of nano-Al2O3 content. The wear rates decreased with increasing nano-Al2O3 content. The wear rates of specimens containing nano-Al2O3 was about 2–8 times lower than that of specimen with micro-Al2O3. The specimen with 10.5 vol% nano-Al2O3 showed the best tribological properties. The wear mechanism of specimens with nano-Al2O3 was abrasive wear and plastic deformation.

Effect of La2O3 on the in-situ reaction products in Al–CuO–Ti–C system

The Aluminum Matrix Composites were manufactured by in situ reactive near liquidus cast of La2O3 powder, aluminum powder, CuO powder, Ti powder, graphite powder with 6063 aluminum alloy as the matrix using the contact reaction method. The x-ray Diffraction, Differential Scanning Calorimeter, Scanning Electron Microscope and Energy Dispersive Spectroscopy were utilized to study the phase evolution and observe the morphology and distribution of the in situ products. The effect of La2O3 on the in situ reaction products in Al–CuO–Ti–C system was investigated. The results manifest that the microstructure of the in situ reaction products in the Al–CuO–Ti–C system is composed of needle-like and lath-like Al3Ti phase, nearly globular-like Al2O3 and granular-like TiC. The microstructure of the in situ reaction products in the Al–CuO–Ti–C-La2O3 system is composed of blocky-like and short rod-like Ti2Al20La phase, globular-like Al2O3 and granular-like TiC. By comparing the two systems, the addition of La2O3 eliminates the needle-like Al3Ti phase of 120 μm and the agglomerated lath-like Al3Ti phase of 50 μm, forms the blocky-like and short rod-like Ti2Al20La of under 20 μm. At the same time, it improves the agglomeration phenomenon of TiC and Al2O3 particles, making them more diffusely distributed in the matrix. The size of TiC and Al2O3 particles reduces from 1 μm to 0.5 μm and 5 μm to 1 μm, respectively.

Influence of Al2O3 particle size on properties of thermoplastic starch–TiO2–Al2O3 composites

Thermoplastic starch (TPS), an inexpensive, renewable, widely available and biodegradable biopolymer, has been promoted as a promising alternative to synthetic polymers based on fossil resources. However, it exhibits weak mechanical properties and high moisture uptake. Reinforcing fillers have been used to improve the properties of thermoplastic starch. This work studies the effects of Al2O3 particle size on dielectric, thermal, physical, mechanical and morphological properties of thermoplastic starch–TiO2–Al2O3 composites at the fixed TPS:TiO2:Al2O3 weight ratio 97:2:1. The Al2O3 particle sizes tested were 0.05 μm, 1 μm and 5 μm. Dielectric, thermal, mechanical and morphological properties were determined. With increasing Al2O3 particle size, slight increases were observed in contact angle, hardness and thermal stability, while dielectric constant, dissipation factor and glass transition temperature decreased. However, the Al2O3 particle size did not significantly affect tensile properties. Scanning electron microscopy was used to investigate the morphology in the composites. In summary, the incorporation of TiO2 and Al2O3 in thermoplastic starch could extend its potential in flexible films, compost bags and packaging applications.

Development of Accident-Tolerant FeCrAl Steels Containing Al2O3 Particles by Means of Internal Al Oxidation

FeCrAl ferritic steels containing dispersed Al2O3 particles instead of Y2O3 or Ce2O3 particles were developed for accident-tolerant fuel cladding in light-water reactors. Forcible addition of only oxygen through mechanical alloying can create Al2O3 particles by precipitation during annealing above 973 K. The oxygen content was controlled to use oxidation of internal aluminum to form Al2O3 particles and increase the number density of Al2O3 particles with an average diameter of around 40 nm. The size and number density of Al2O3 particles are significantly affected by lattice misfit, and thus interfacial energy between Al2O3 particles and the matrix, and by aluminum solubility into the ferrite matrix. The estimated Al2O3 particle strengthening stress is consistent with measured tensile stress at 973 K. Both stresses are slightly improved with increasing oxygen content, but are half the level of that in steel strengthened by Ce2O3 and CeAlO3 particles.

200 MeV proton irradiation of the oxide-dispersion-strengthened copper alloy (GlidCop-Al15)

In search to identify extremely stable materials to perform the collimation function of the 7-TeV proton beam halo at the Large Hadron Collider (LHC), oxide dispersion strengthened (DS) copper alloys were explored. These internally oxidized copper alloys known as GlidCop are also leading candidates for high heat flux applications in fusion reactors and as divertor and first wall structure in ITER. These considerations have led to an extensive body of research on neutron-induced changes in the microstructure and physio-mechanical properties. This study focused primarily on the damage induced by 200 MeV protons on as wrought and cold-worked GlidCop Al15 DS copper ally selected as a candidate material of the LHC beam collimation structure to damage levels up to ∼10 displacements-per-atom (dpa) and irradiation temperatures up to ∼600 °C. For reference, low dose spallation neutron damage at sub-zero irradiation temperature was included in the study. Proton irradiation effects on dimensional stability, mechanical behavior, electrical resistivity and X-ray diffraction-based microstructural changes are presented in the paper. GlidCop Al15 exhibited excellent thermal stability and superior to pure Cu resistance to conductivity loss. Proton irradiation-induced hardening and embrittlement at distinct irradiation temperature regimes were shown to follow similar trends to what was reported under neutron exposure to even higher dpa damage. At Tirr ∼600 ± 20 °C the cold-worked DS copper alloy exhibited softening accompanied by elongation reduction while at Tirr ∼200 ± 10 °C the as-wrought experienced hardening with elongation increase. High resolution X-ray diffraction revealed that even low-dose neutron irradiation has a strong influence on the size and distribution of dispersed Al2O3 particles.

Efficient Coating Method via Matching Rough Surface of Stainless Steel with Al2O3 Particles

An efficient method of coating alumina (Al2O3) on stainless steel has been investigated by matching the rough surface of the substrate with different sizes of Al2O3 particles. An empirical correlation was established based upon the data of a controllable and measured pore size of the substrate surface by varying etching conditions. The correlation agreed fairly well with experimental results (deviations of ±20%). The Al2O3 coatings prepared by powders with average particle size of 324 nm had an optimal adhesion performance, and the minimum of coating weight loss on the inner surface of tubule after ultrasonic vibration was 1.7 wt %. The developed method of Al2O3 coating has potential prospects for the preparation of monolithic catalyst support.

PHYSICO-CHEMICAL AND TOXICOLOGICAL BEHAVIOUR OF Al2O3 NANOPARTICLES IN FINE PARTICULATE MATTER

The booming production and application of nanoparticles have raised great concern over its effect on environment, due to their increasing release in the environmental systems via intentional or unintentional activities, where their possible physicochemical and toxicological behavior remain unknown. The nanoparticles are released into the different environmental systems like air, soils and waters. However, their interaction with air matrices has been rarely investigated. For this reason, the changes of main physicochemical properties of Al2O3 nanoparticles in the presence of fine particulate matter were examined, as well as their toxicity towards gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) using colony counting method was assessed in the presence of fine particulate matter. E. coli and B. subtilis were the most strongly affected species by the Al2O3 nanoparticles under the influence of fine particulate media. Furthermore, the main physicochemical properties (particle size, zeta potential, and surface chemistry) were changed with the exposure of the fine particulate matter. Sulfone groups were detached and nitro groups were attached on nanoparticles surface according to FTIR analysis. Particle size of Al2O3 was decreased with the correlation of zeta potentials. This is one of the rare study to evaluate the effect of fine particulate media on Al2O3 nanoparticles with the respect of the physicochemical properties and toxicity of Al2O3.

Influence of aging, varying particle size & volume fraction of Al2O3 particles on the hardness and wear behavior of Al 7150 alloy composite produced by hot uniaxial compaction method

The influence of aging, particle size and volume fraction (5, 10, 20 & 25%) of alumina particulates on the hardness & wear behavior of Al 7150 alloy composites produced by hot uniaxial compaction method was investigated. The as-received Al2O3 particulates were first mechanically ball milled for durations of 45, 180, 360, 420 and 580 min to reduce its particle size. The milled alumina particles of 165 nm, 65 nm, 45 nm, 27 nm and 21 nm were later independently blended with the Al 7150 alloy powders to produce five sets of cylindrical specimens using a punch-die setup. The compaction pressure was 500 MPa with a holding time of 3 h, at a temperature of 400 °C. The Vickers microhardness tests revealed an improvement in the hardness with the increase in the volume % of the reinforcement and decreasing particulate size. The Age hardenability of the composites was also investigated by first solutionizing the composite samples followed by aging at 3 h (T4-underage), 24 h (T6-peak age) & 96 h (T7-overage). The wear behavior of the samples was studied by comparing the wear rate of the un-reinforced alloy and non-heat treated (reinforced) Al 7150 alloy composite samples with T6 heat treated composite specimens using a pin on disc wear testing machine under different load and sliding distance conditions. The test specimens were characterized using XRD, FESEM and EDS analysis. Apart from the effect of particle size and volume fraction of Al2O3 reinforcement, the precipitation hardening which occurred during aging, influenced the microhardness and wear behavior of the composite samples.

Effect of Ni content and Al2O3 particle size on the thermal and mechanical properties of Al2O3/Ni composites prepared by spark plasma sintering

Alumina-nickel composites were prepared by carrying out spark plasma sintering (SPS) of nano-sized and micro-sized Al2O3 particles with 15–45 wt% Ni powders. The powder materials were sintered at a temperature of 1400 °C under a constant uniaxial pressure of 50 MPa. FESEM micrographs of the products showed uniformly dispersed nickel inclusions in both matrices at intergranular positions. Presence of Al2O3 as the major phase along with Ni as the minor phase was confirmed using XRD analysis. Thermal and mechanical properties of the nano- and micro-sized Al2O3/Ni composites were investigated. The thermal conductivity of nano-sized alumina composites was seen to increase with the increase in nickel content, however, an opposite trend was observed for micro-sized alumina-based composites. Moreover, thermal conductivities of all the composites decreased with increase in temperature. The composites also showed high hardness and fracture toughness values of up to 19.6 GPa and 4.71 MPa ∗ m1/2, respectively, and relative density values, between 79 and 99%, that decreased with increasing Ni content. Furthermore, the nano-sized Al2O3/Ni composites showed thermal and mechanical properties superior to those of the micro-sized Al2O3/Ni composites.

Electron backscattered diffraction analysis of friction stir processed nanocomposites produced via spark plasma sintering.

In the present study, Spark Plasma Sintered (SPSed) aluminium matrix composites were severely deformed through Friction stir processing (FSP). Pure aluminium powders and bimodal sized Al2 O3 particles (80 nm and 25 μm) were firstly mixed by ball milling and then consolidated by spark plasma sintering. The effect of the heat input as well the bimodal particle size of the alumina on the materials' microstructure and texture development was evaluated by electron back scattered diffraction (EBSD) analysis. The EBSD analysis clearly showed that the SPSed nanocomposites possessed bimodal aluminium matrix grain structure as well as a crystallography characterised by random texture. In addition, microstructural examination revealed that the partial recrystallisation occurred during SPS for all the nanocomposites. Also, it is revealed that the Zener pinning effect of Al2 O3 nanoparticles retarded recrystallised grain growth following recrystallisation during FSP and then leading to grain refinement of the aluminium. The results revealed that the heat generated during FSP has a remarkable effect on the grain distribution as well as on the crystallographic orientation. Also, a mixture of {112} <110> shear elements and an ideal strong B/B¯ component were observed. The microstructural changes, occurred during FSP in the stir zone region for Al-Al2 O3 nanocomposites, were attributed to both the discontinuous along with the continuous recrystallisation (DDRX/CDRX). It should be pointed out that with increasing the heat input, recrystallised grains portion increased.

Nanosize Effect of Al2O3 in Ag/Al2O3 Catalyst for the Selective Catalytic Oxidation of Ammonia

Ammonia (NH3) has potentially harmful effects on human health and has recently been found to be an important factor in the formation of haze; thus, its emission control is urgent, especially during haze pollution periods. In this work, two kinds of Ag/Al2O3 catalysts with different Al2O3 particle sizes (micro-Al2O3 and nano-Al2O3) were prepared and tested for the selective catalytic oxidation of ammonia (NH3-SCO). It was shown that Ag/nano-Al2O3 was much more active than Ag/micro-Al2O3 for NH3-SCO in the low-temperature range. The results of characterization by BET, TEM, NH3-TPD, XRD, H2-TPR, UV–vis, and XAFS revealed that Ag/nano-Al2O3 possesses much smaller Ag particles and more metallic Ag species (AgNPs) and also contains abundant acid sites, which facilitate the adsorption and dissociation of NH3, therefore resulting in much higher NH3-SCO activity. In addition, on the basis of in situ DRIFTS, kinetic measurements, and DFT calculation results, we discovered that the NH3-SCO reaction over Ag/nano-Al2O...

Evolution of phase composition and microstructure of commercial Al2O3 gel in different heat treatment condition

Evolutions of phase composition and microstructure of commercial Al2O3 gel in different heat treatment conditions (temperature, atmosphere and additives) were investigated. There was almost no effect of atmosphere and carbon additive on phase evolution of Al2O3 gel during heating, γ-Al2O3 formed at 800 °C, γ-Al2O3 and minor θ-Al2O3 co-existed at 1000 °C, and single phase of ɑ-Al2O3 occurred at heating temperature ≥1200 °C. Atmosphere and carbon had great effects on morphology and crystal size of Al2O3 particles. Crystal size of spherical-shape Al2O3 particles was 10–20 nm after heating at 800–1000 °C in air, afterwards, they rapidly grew into micro or macro scale when temperature was above 1200 °C, and sintering phenomena of worm-like Al2O3 particles were observed. In the presence of carbon, spherical-shape Al2O3 particles grew slightly from 10 to 20 nm to 50–60 nm with the temperature increasing from 800 °C to 1500 °C in reducing atmosphere, carbon inclusions in Al2O3 grain boundaries triggered a steric hindrance of Al2O3 particles growth. Al2O3 gel had a high reactive ability and could react with microsilica to form nano mullite crystals at relatively lower temperature.

Effects of 316SS addition on the properties of the coatings based on Al2O3 applied by plasma spraying

Ceramic plasma-sprayed coatings are successfully used for prolonging the service life of industrial components where high wear and corrosion resistance are required. In this work, various types of coatings based on alumina were deposited by atmospheric plasma spraying on 304 L austenitic stainless steel substrate. These coatings were used in further tribological studies. For the atmospheric plasma spraying applications, spraying parameter choices such as carrier gases, plasma enthalpy, current intensity, spraying distance, and particles granulometry are the key issues. Two kinds of Al2O3 particle sizes 2–12 µm (Amperit) and 15–45 µm (Norton) were used to prepare pure and composite coatings. The spraying distance was varied from 90 mm to 120 mm. Microstructure characterization performed by scanning electron microscopy showed that the Amperit powders projected at a distance of 90 mm provided better cohesion and a more dense microstructure. However, the choice of the spraying distance of 120 mm was defined to manufacture composite structures, which allowed more stability in the plasma jet and enabled large metal particles to be mixed with ceramics. To develop hard and wear-resistant coatings, alumina and 316SS were mixed with different addition rates by volume (Al2O3–5 vol.%316SS and Al2O3–25 vol.%316SS) and fed through a single injection port. Composite coatings include porosity and unmolten particles in a lamellar microstructure. The addition of 316SS powder led to the formation of typical layered structure due to the effect of viscosity and different densities of the two particles. These coatings were investigated by different tests to evaluate microhardness, cohesion, and fracture values of such materials. Despite the significant decrease in the microhardness values, the 316SS particle addition demonstrates an improvement in the toughness and crack resistance.

Production and Mechanical Testing of Aluminium Alloy Based Hybrid Metal Matrix Composite

The present work aims for uniformly dispersing Aluminium Oxide (Al2O3) and Graphite (Gr) particulates in an Aluminium Alloy Matrix to produce a hybrid composite and then to carry out the investigation and analysis of mechanical properties of developed composite. The particle size of Al2O3 and Gr were less than 45 microns. The stir casting technique is utilized to produce the hybrid composite having 2% Al2O3 with 0.5%, 1% Gr and 4% Al2O3 with 0.5%, 1% Gr. The composites were studied for density changes due to reinforcements, hardness, tensile strength and wear behaviour in Non-Heat Treated (NHT) conditions. The tests were done at the laboratory conditions as per ASTM guidelines. The Pin-On-Disc machine is used to test the sliding wear behaviour under dry conditions. The measured density is found to be decreasing as the reinforcement quantity is increased. The as cast Al alloy was found to be having highest hardness and the composites with increasing Gr exhibited lower hardness. The composite tensile strength is observed to be decreased in comparison to base alloy due to the presence of Gr but composite having highest quantity of Gr showed superior wear resistance which is mainly because the Gr particulates provide an inherent lubricating properties to composite. The composites developed in the present work can be used in the automobile and aerospace parts that are light in weight and require self-lubricating properties to enhance the wear resistance.

Effect of micro alumina particles additions on the interfacial behavior and mechanical properties of Sn-9Zn-1Al2O3 nanoparticles on low temperature wetting and soldering of 6061 aluminum alloys

The effects of micro Al2O3 particles additions on microstructures and thermal and mechanical properties of the Sn-9Zn-1Al2O3 nanoparticles on low temperature wetting and soldering of 6061 aluminum alloys are investigated in this study. The results show that the melting temperature of the alloys firstly slightly decreases and then slightly increases with the increase in the micro Al2O3 particles concentration, while the pasty ranges of the alloys are simultaneously increased. The spreading coefficient of Sn-9Zn-1Al2O3-0.25microAl2O3 is about 13.75%, and is increased to about 41.5% of Sn-9Zn-1Al2O3-0.75microAl2O3. Both the surface diffusion, rapid adsorption and phase flow contribute to the formation of precursor film. When micro Al2O3 is added to the composite solder alloys, acicular Sn-Zn eutectic structures are smaller in size from acicular to acicular or circular spot. The strengthening mechanisms with bimodal size Al2O3 particles are on account of grain refinement and load transfer effect of bimodal sized Al2O3. The strength induced by particles is a very important part, which it can account for 21% of the total tensile strength of the solder.