Different Amounts Of Al2O3 Research Articles

Effect of Al2O3 and ZrO2 Filler Material on the Microstructural, Thermal and Dielectric Properties of Borosilicate Glass-Ceramics

Various glass-ceramics are widely used or considered for use as components of microelectronic materials due to their promising properties. In this study, borosilicate glass was prepared using the powder metallurgical route and then mixed with different amounts of Al2O3 and ZrO2 filler materials. Glass-ceramics are produced by high-energy ball milling and conventional sintering process under Ar or air. In this study, the effects of different filler materials and different atmospheres on the microstructural, thermal and dielectric properties were investigated. The data showed that ZrO2 filler material led to better results than Al2O3 under identical working conditions and similar composite structures. ZrO2 filler material significantly enhanced the densification process of glass-ceramics (100% relative density) and led to a thermal conductivity of 2.904 W/K.m, a dielectric constant of 3.97 (at 5 MHz) and a dielectric loss of 0.0340 (at 5 MHz) for the glass with 30 wt.% ZrO2 sample. This paper suggests that prepared borosilicate glass-ceramics have strong sinterability, high thermal conductivity, and low dielectric constants, making them promising candidates for microelectronic devices.

Effect of Al2O3 on the Structural Properties of Water-Quenched Copper Slag Related to Pozzolanic Activity

Water-quenched copper slag (WCS) modified with alumina (Al2O3) has been proven as a cement substitute; however, the effect of Al2O3 on structural properties of WCS related to pozzolanic activity has not been well investigated. The structural properties and the pozzolanic activity of WCS with different amounts of Al2O3 are characterized by X-ray diffraction, differential scanning calorimetry, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and the uniaxial compressive strength test. The results show that only amorphous exists in copper slag, and the stability of amorphous first increases and then decreases with the increase in the alumina content. The addition of alumina significantly improves the pozzolanic activity of WCS at 7 and 28 days, but it has little effect on the pozzolanic activity of WCS when the slag’s curing age is 3 days. The results also show the increase in the non-bridging oxygen content, the decrease in the degree of polymerization, and the transition from Q2 and Q4 to Q3 with the increase of alumina content. Moreover, the addition of aluminum will convert Si-O-Si into Si-O-Al. These experimental results show that the addition of alumina can improve the pozzolanic activity of WCS, which can be used to partially replace cement.

A general strategy towards improving the strength and thermal shock resistance of glass-ceramics through microstructure regulation

Glass-ceramics are usually obtained through controlled crystallization. In this work, we propose a new strategy to add an appropriate amount of oxide particles to the parent glass to improve the performance of glass-ceramics. Different amounts of Al2O3 or/and CeO2 particles were added into a SiO2-Al2O3-ZnO-CaO-ZrO2-TiO2 based glass, and crystallization behavior, fracture strength, and thermal shock behavior were systematically evaluated. The results indicate that with the addition of Al2O3 or/and CeO2 particles of moderate amount, the unfavorable needle-like ZrSiO4, Zn2SiO4, and CaTiSiO5 crystals were largely inhibited when annealed at 900 °C. Accordingly, fracture strength is maintained high after heating at high temperatures. The thermal shock resistance is also enhanced drastically. The additive Al2O3 is thermodynamically favorable to react with the glass, forming particulate ZnAl2O4 instead of precipitating the needle-like crystals of Zn2SiO4 and CaTiSiO5; while CeO2 will combine with ZrO2 to form a solid solution and promote the precipitation of primary crystal CaZrTi2O7 that will not transform to ZrSiO4 with prolonging thermal exposure.

Evaluation of the influence of Al2O3 nanoparticles on the thermal stability and optical and electrochemical properties of PANI-derived matrix reinforced conducting polymer composites

A novel PANI-derived@Al2O3 hybrid has been fabricated using different amounts of Al2O3 via the polymerization of 2-chloroaniline with ammonium persulfate as the oxidant. The resulting samples were fully characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infra-red (FT-IR) and UV–vis spectroscopy, which show that the polymerization reaction occurred. Importantly, this work provides a helpful way of setting the optical properties of resulting nanocomposites by adjusting the quantity of nanoparticles; the band gap values of poly (2ClAni)@Al2O3 increases upon increasing the Al2O3 content. This was attributed to the rearrangement that occurs in the polymer matrix upon the addition of the nanoparticles. The electrochemical properties of the resulting hybrid materials were investigated using cyclic voltammetry.

Investigation of alumina nanoparticles role on the critical flux and performance of polyvinyl chloride membrane in a submerged membrane system for the removal of humic acid

In this work, the polyvinyl chloride/alumina (PVC/Al2O3) ultrafiltration (UF) nanocomposite membranes were prepared with different amounts of Al2O3 within a range of 0–2 wt.%. Neat PVC and optimum nanocomposite membranes were evaluated in a submerged membrane system for the removal of humic acid (HA). The Fourier transform infrared (FTIR) spectroscopy confirmed the presence of hydroxyl group (OH) on the surface of the PVC nanocomposite membrane. Results revealed that the nanocomposite membrane with 1.5 wt.% of Al2O3 nanoparticles has the highest value in porosity and hydrophilicity when compared to other samples. The results obtained from the field emission scanning electron microscopy (FE-SEM) images showed that as Al2O3 was added to the membrane structure, more pores and larger pores were formed on the membrane surface. A higher critical flux was obtained by the PVC/Al2O3 (1.5 wt.%) nanocomposite membrane due to change in the surface characteristics. Antifouling analysis under subcritical conditions for neat PVC membrane showed that the main portion of the total fouling ratio was irreversible fouling ratio (IFR), while the nanocomposite membrane with 1.5 wt.% of Al2O3 nanoparticles significantly decreased IFR. Finally, the nanocomposite membrane had a higher HA rejection than the neat PVC membrane.

New insights into the role of Al2O3 nano-supplements in mechanical performance of PMMA and PMMA/HA bone cements using nanoindentation and nanoscratch measurements

ABSTRACT This work was performed to investigate the mechanical and tribological properties of polymethyl methacrylate (PMMA)-based bone cement strengthened by nano-alumina (Al2O3) and nano-hydroxyapatite (HA) particles. Seven cement groups with different amounts of Al2O3 (3 and 5 wt. %) and HA (5 and 10 wt. %) nano-particles were prepared and the nanoindentation and nanoscratch tests were employed to obtain the results. Substantial improvement/reduction in mechanical properties was observed for the addition of 3 wt. % of Al2O3 /5 wt. % of Al2O3 plus 10 wt. % of HA into the PMMA matrix. The additives had almost no obvious effects on the friction of PMMA (~0.3). This research revealed that only the specific weight percent of Al2O3 (here 3 wt. %), compared to other PMMA/Al2O3 and PMMA/HA/Al2O3 cement nanocomposites, had great potential as an added component in PMMA bone cement to provide a significant increase in the mechanical properties of the cement.

Effect and Mechanism of Alumina on the Morphology and Mechanical Properties of Calcium Ferrite

Al2O3 greatly influences the formation of complex calcium ferrite, which is the main binder and iron-bearing phase in sinter. Experiments were carried out in air at 1200 °C with different amounts of Al2O3 mixed with CaO·Fe2O3 (calcium ferrite). The samples contained two phases: CaFe2O4 and Ca3.18Fe15.38Al1.34O28 (CFA). The results showed that the morphology of the complex calcium ferrite was massive (w(Al2O3) = 0 pct), columnar and plate-like (w(Al2O3) = 0.5 and 1 pct), and acicular and plate-like (w(Al2O3) = 2, 3, and 5 pct). A small amount of Al2O3 solid solution in CaFe2O4 increased the preferred orientation of the crystal. The gradual increase in Al2O3 in the sintered samples caused the complex calcium ferrite composition to be closer to that of silico-ferrite of calcium and aluminum (acicular SFCA-I). When Al2O3 dissolved into calcium ferrite, complex calcium ferrite was formed, which increased the hardness of the sample. The fracture toughness of the sample increased with increasing Al2O3 content from 0 to 2 pct, possibly due to a decrease in grain size. When the Al2O3 content exceeded 3 pct, Al2O3 dissolved into calcium ferrite and decreased the fracture toughness of the sample.

Low–temperature fabrication of HfAlO alloy dielectric using atomic–layer deposition and its application in a low–power device

This paper presents a systematic study of HfAlO alloy films, which were prepared by doping HfO2 with different amounts of Al using atomic layer deposition at low growth temperature (150 °C). The chemical constituents of the various HfAlO films were determined by X–ray photoelectron spectroscopy. Carrier transport through the HfAlO layer presented a good fit with the Poole–Frenkel emission and Fowler–Nordheim tunnelling mechanisms in different voltage ranges. Barrier heights (conduction band offset) between the HfAlO films and Si substrate, which were derived from the Fowler–Nordheim fittings, increased with increasing Al content in the alloy films, and the leakage current was suppressed well owing to the higher barrier. The 10 nm HfAlO dielectric layer, which was grown by the repeated deposition of 1 cycle each of HfO2 and Al2O3 (defined as H1A1), showed a high gate capacitance of 723 nF/cm2, a high breakdown voltage of 8.0 V, a small leakage current, and a smooth surface. HfAlO films doped with different amounts of Al2O3 in HfO2 were employed to study their effects on the operation of amorphous indium–gallium–zinc oxide (a–IGZO) thin–film transistors (TFTs). The a–IGZO TFTs based on the H1A1 gate dielectric showed desirable properties including a high Ion/off ratio of 1.7 × 107, a small subthreshold swing of 176 mV/decade, and low operating voltage of 2.0 V.

Ag diffusion inhibition and enhanced flexural strength in low temperature co-fired CaO-Al2O3-B2O3-SiO2 glasses

This work explores Ag diffusion mechanism and mechanical strength in low-k 35 wt% CaO-33 wt% Al2O3-15 wt% B2O3-17 wt% SiO2 glasses with different amounts of Al2O3 (0–30 wt%) and SiO2 (0–8 wt%) ceramic-filler additions using low temperature co-firing with Ag electrode. The 8 wt% Al2O3-added specimen displays the highest flexural strength of ∼268 Mpa due to higher densification and less pores, which could be attributed to well wetting at boundaries between glasses and Al2O3 ceramics. The crystalline SiO2-ceramic-added glasses can effectively inhibit diffusion of Ag ions with a higher diffusion activation energy of 391 kJ/mol in the 8 wt% SiO2-ceramic-added specimen. A model of Ag diffusion inhibition is proposed based on percolation clusters of broken bonds for SiO2-added CaO-Al2O3-B2O3-SiO2 glasses. We propose that percolation clusters of broken bonds were increased in the SiO2-ceramic-added glass matrix at T > Tg and clusters of oxygen ions can trap Ag ions to form Ag-O bonds to reduce thermal diffusion of Ag ions. The Al2O3 and SiO2 co-added CaO-Al2O3-B2O3-SiO2 glasses can be considered as a candidate for low temperature co-fired microwave dielectric ceramic substrate.

Nano Al2O3 Oranının Ni-Co Matrisli Nano Kompozit Kaplamaların Tribolojik Özelliklerine Etkisi

Due to the micro-electrical mechanical system (MEMS) and Nano-electrical mechanical system (MEMS) usage potential, Ni-Co based nanocomposite coatings have been remarkable. Especially, they are promises to solve tribological problem of MEMS and NEMS system. Therefore, Ni-Co alloy and Ni-Co/ Al2O3 composite coatings were prepared from a modified Watt's type electrolyte by Direct Current (DC) with 7A/dm2 current density and four different amounts of Al2O3 added to electrolyte concentration. Effect of amount of Al2O3 in the Ni-Co matrix on mechanical and physical properties were investigated. Produced composite coating layers structure were characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical properties were determined with Vickers microhardness test method. Tribological properties was carried out with reciprocating pin on disk system. As a result of investigation and characterization best mechanical and tribological properties were achieved with 1 g/l Al2O3 addition into electrolyte and at PRC current type.

Microstructure and microwave dielectric properties of Al2O3 added Li2ZnTi3O8 ceramics

Recently, the rapid development of advanced communication systems increasingly strongly demands high-performance microwave dielectric ceramics in microwave circuits. Among them, Li2ZnTi3O8 ceramics have been one of the most widely investigated species, due to its high quality factor, moderate firing conditions and low cost. However, the dielectric constants of the already reported Li2ZnTi3O8 ceramics are fixed in a narrow range, limiting their wider applications. To adjust the dielectric constant of the Li2ZnTi3O8 based ceramics, in this work Li2ZnTi3O8 ceramics added with different amounts of Al2O3 (0–8 wt%) were prepared by conventional solid-state reaction. The microstructure and microwave dielectric properties of the samples were investigated. Due to the addition of Al2O3, the sintering temperature of the ceramics would be increased somewhat. Some Al3+ ions could substitute for Ti4+ ions in Li2ZnTi3O8, and the added Al2O3 would react with ZnO to produce a ZnAl2O4 phase accompanying with the formation of TiO2 phase, which would inhibit the growth of Li2ZnTi3O8 grains. The dielectric constant of the finally obtained ceramics would be reduced from 26.2 to 17.9, although the quality factors of the obtained ceramics would decrease somewhat and the temperature coefficient of resonant frequency would deviate further from zero.

Microstructure and properties of mullite-based porous ceramics produced from coal fly ash with added Al2O3

Using coal fly ash slurry samples supplemented with different amounts of Al2O3, we fabricated mullite-based porous ceramics via a dipping-polymer-replica approach, which is a popular method suitable for industrial application. The microstructure, phase composition, and compressive strength of the sintered samples were investigated. Mullite was identified in all of the prepared materials by X-ray diffraction analysis. The microstructure and compressive strength were strongly influenced by the content of Al2O3. As the Al/Si mole ratio in the starting materials was increased from 0.84 to 2.40, the amount of amorphous phases in the sintered microstructure decreased and the compressive strength of the sintered samples increased. A further increase in the Al2O3 content resulted in a decrease in the compressive strength of the sintered samples. The mullite-based porous ceramic with an Al/Si molar ratio of 2.40 exhibited the highest compressive strength and the greatest shrinkage among the investigated samples prepared using coal fly ash as the main starting material.

Effect of Al2O3 + 4SiO2 Additives on Sintering Behavior and Thermal Shock Resistance of MgO-Based Ceramics

In order to improve the sinterability and thermal shock resistance of ceramic based on MgO magnesium oxide of micron grain size composition is used as the main starting raw material with additions of nano-Al2O3 and nano-SiO2. Ceramic based on MgO is prepared by adding different amounts of Al2O3 and SiO2 to MgO in a molar ratio 1:4. The mixture is molded and sintered in an air atmosphere. Ceramic phase composition and microstructure are studied in an x-ray diffractometer and a scanning electron microscope. The effect of adding different amounts of Al2O3 + 4SiO2 on sinterability and thermal shock resistance of MgO base ceramic is studied. Addition of Al2O3 + 4SiO2 has a favorable effect on test ceramic sinterability and thermal shock resistance. During reaction of solid substances there is formation of magnesia-alumina-spinel and forsterite that leads to retardation of periclase phase grain migration. The degree of specimen compaction is improved and this has a favorable effect on sinterability of ceramic based on MgO. The degree of compaction increases as there is an increase in sintering temperature in the range 1400 to 1500°C. In addition, specimen thermal shock resistance is improved due to connection between microcracks. As a result of adding Al2O3 in an amount up to 30 wt.% + SiO2 in an amount up to 45 wt.% MgO sinterability and thermal shock resistance are improved.

The Influence of Al<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub> Additions on the Sintering Behavior of Partial Reaction Bonding Silicon Nitride

To compare the influence of Al2O3 and TiO2 on the sintering behavior of partial reaction bonding silicon nitride (RBSN) and post densification behavior, different amounts of Al2O3 or TiO2 have been added into Si-Si3N4-Y2O3 system. The results indicated that a high amount of Al2O3 addition inhibited the reaction bonding process, a lower nitridation degree was obtained, while TiO2 has limited influence on nitridation, only slightly decreased nitration degree with increasing TiO2 addition. After post sintered at 1800 °C, a density ranging from 2.31 to 3.09g/cm3 were obtained with additions of Al2O3 and TiO2, much larger than the one without them. The linear shrinkage of post-sintered samples was strongly promoted with high Al2O3 content, but it was irrelevant with the amount of TiO2. The highest bending strength of 523MPa can be obtained with addition of 6wt% Al2O3. TiO2 transformed into TiN which located at grain boundary interfaces, restraining the grain growth of β-Si3N4 and leading to an inferior flexural strength after post sintered at 1800 °C.

A comparative study on the structural aspects of sodium borosilicate glasses and barium borosilicate glasses: Effect of Al2O3 addition

Sodium borosilicate and barium borosilicate glasses containing different amounts of Al2O3 were prepared by conventional melt-quench method and their structural information was obtained by 29Si, 11B and 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) technique. By employing the Dell and Bray model, different types of boron and silicon structural units present in the glass have been identified. The relative concentrations of BO3 and BO4− structural units evaluated from the 11B MAS NMR patterns match (within experimental errors) with that predicted by Dell and Bray model. Al3+ ion exists only as AlO4− structural units with Si-O-Al type of linkages in the glass. Higher glass transition temperature of barium borosilicate glass compared to sodium borosilicate glass has been attributed to the formation of relatively more connected BO4– structural units at the expense of less connected BO3 structural units in the former glass.

A Study of the Heat Transfer Behavior of Mold Fluxes with Different Amounts of Al2O3

The element Al in molten aluminum containing steel reacts with the liquid mold flux and thus be transferred into the mold flux during the continuous casting process. Additionally, the increase in alumina in a mold flux changes its performance significantly. Thus, in this paper, the heat transfer properties of mold fluxes with the Al2O3 content ranging from 7 to 40 wt. % were studied with the Infrared Emitter Technique (IET). Results found that heat flux at the final steady state decreased from 423 kW·m−2 to 372 kW·m−2 with the increase in Al2O3 content from 7% to 30%, but it increased to 383 kW·m−2 when the Al2O3 content was further increased to 40%. Both crystalline layer thickness and crystalline fraction first increased, then decreased with the further addition of A2O3 content. Moreover, it indicated that the heat transfer process inside the mold was dominated by both a crystallization of mold flux and the resulting interfacial thermal resistance. Further, the Rint increased from 9.2 × 10−4 m2·kW−1 to 11.0 × 10−4 m2·kW−1 and then to 16.0 × 10−4 m2·kW−1 when the addition of Al2O3 content increased from 7% to 20% and then to 30%, respectively; however, it decreased to 13.6 × 10−4 m2·kW−1 when the Al2O3 content reached 40%.

AlON phase formation in hot-pressing sintering Al2O3/AlN composites and their oxidation behavior

Samples with various ratios of AlN/Al2O3 were fabricated via vacuum hot-pressing at 1700 °C under an applied pressure of 30 MPa for 90 min using Y2O3 as a sintering aid. The densification process, microstructural development, and formation of AlON phase from Al2O3 and AlN were investigated. Al2O3 additive can improve the physical and mechanical properties, and purification of the grain boundaries. AlON are almost formed completely when the content of Al2O3 is 80 vol%. The effects of composition, microstructure, and exposure time at 1400 °C on the oxidation behavior of AlN samples with different amounts of Al2O3 were investigated. The sample with 80 vol% alumina has the best oxidation resistance.

Effects of doping Al2O3/2SiO2 on the structure and properties of magnesium matrix ceramic

To improve the sintering properties and the thermal shock resistance of magnesium matrix ceramic, this work used micron-sized MgO as the main raw material and nano-Al2O3 and SiO2 as additives. Magnesium matrix ceramic was doped with different amounts of Al2O3 and SiO2 (Al2O3 and SiO2 at a molar ratio of 1:2) and sintered under standard atmospheric conditions. The effect of Al2O3/2SiO2 doping amounts on sintering properties, thermal shock resistance, phase composition, and microstructure of composite ceramic materials were investivigated. The results suggested that introducing Al2O3/2SiO2 could improve the sintering properties of magnesium matrix ceramic. The grain boundary migration of its periclase phase could be hindered by the magnesium aluminate spinel and forsterite formed by solid reaction including Al2O3, SiO2 addition, and the MgO itself. Furthermore, according to the mechanism of thermal expansion mismatching, with increasing Al2O3/2SiO2 addition, thermal shock times increased significantly, the number of ceramic internal micro-cracks increased after the thermal shock and the material fracture surface energy was improved. It is found that the way of transgranular combining intergranular fractures can decrease the stress concentration at the crack tips and hinder crack propagation. The secondary phase particles deflected matrix internal micro-cracks and the crack propagation path length thus increased, residual stress field were subjected to interference and energy dissipation mechanisms improved. Meanwhile, thermal shock times for the material were enhanced and the degree of densification increased with increasing sintering temperature.

Tribology of NiCrAlY+Al2O3 composite coatings by plasma spraying with hybrid feeding of dry powder+suspension

NiCrAlY layers containing different amounts of Al2O3 (0, 3, 6, 12, 18wt%) were deposited onto stainless steel substrates by a “hybrid” plasma spray process whereby the NiCrAlY powder was fed in dry form whilst fine Al2O3 powder, dispersed in ethanol, was injected through a suspension feeding system.The Al2O3 reinforcement, consisting of fine, rounded particles interspersed within larger NiCrAlY lamellae, only causes marginal changes in hardness, due to the limited particles-matrix cohesion. Nonetheless, at room temperature, ball-on-disk dry sliding wear rates against sintered Al2O3 counterparts decrease from ≈5×10−4mm3/(Nm) for pure NiCrAlY to ≈5×10−6mm3/(Nm) with 18wt% Al2O3 addition. Pure NiCrAlY indeed suffers adhesive wear, whereas, on the composite coatings, the pull-out of some Al2O3 particles triggers the formation of a tribo-layer of smeared oxide fragments, which mediates the contact with the counterbody.At 400°C and at 700°C, all wear rates are levelled to ≈8×10−5mm3/(Nm) and ≈2×10−5mm3/(Nm), respectively. An oxide layer grows on the NiCrAlY matrix upon high-temperature exposure, resulting in a tribo-oxidation wear mechanism, which makes the addition of Al2O3 irrelevant. At 700°C, coatings are further strengthened by partial healing of interlamellar defects and by fine-grained β-NiAl precipitating within the metal matrix.

Comprehensive study of Mn–Fe–Al oxygen-carriers for chemical-looping with oxygen uncoupling (CLOU)

The reactivity and attrition resistance of Mn–Fe oxygen carriers with addition of Al2O3 as support have been investigated. Spray-dried oxygen-carrier particles with Mn:Fe molar ratios of 80:20 and 33:67 were prepared using different amounts of Al2O3. Each material was calcined for 4h at 950°C, 1100°C or 1200°C. The oxygen carriers were studied in a batch fluidized bed reactor to investigate their reactivity with wood char, CH4, syngas and also their oxygen release in N2. In order to measure the mechanical stability of the different materials, the attrition resistance was measured in a jet-cup apparatus. Addition of Al2O3 to materials with a Mn:Fe molar ratio of 80:20 was not advantageous. Generally oxidation of these materials was problematic. The Al2O3 supported materials with a Mn:Fe molar ratio of 80:20 calcined at 950°C and 1100°C showed poor attrition resistance and were highly fragmented or turned to dust, whereas those calcined at 1200°C showed high attrition resistance but poor gas conversion.Materials with a Mn:Fe molar ratio of 33:67 supported with Al2O3 generally showed better attrition resistance. Also their oxidation with 5vol% of oxygen was possible at temperatures higher than 850°C. Furthermore, some of these materials showed good reactivity with methane, syngas and char. Low attrition, good reactivity and CLOU properties in combination with potentially low raw materials costs, make these materials interesting for CLC.