Al2O3 Plates Research Articles

Advanced manufacturing of high conductive graphene coatings on polyethylene terephthalate substrate through laser-induced processes and thermal optimization

Graphene holds immense promise for applications in sensors due to its exceptional properties such as large carrier mobility and high electrical and thermal conductivities. Nevertheless, the manufacture of high conductive graphene films onto flexible substrates remains a formidable challenge. This paper presented a novel method for the precise incorporation of high conductive graphene coatings onto polyethylene terephthalate (PET) through the back transfer of laser-reduced graphene oxide (LRGO) from Al2O3 ceramic to PET. A record-low sheet resistance for LRGO so far, approximately 12 Ω/sq. was achieved, meantime exhibiting 5B level adhesion performance with PET substrate. The sheet resistance of the transferred LRGO was measured and demonstrated to be adjustable by manipulating laser power, scanning speed, and hatch distance. The analysis of reduction of graphene oxide (GO) involved a comprehensive examination of alterations in topography image, chemical bond content, C/O atomic ratio, and ID/IG intensity ratio. These observations provided insights into the factors contributing to the decrease of sheet resistance within LRGO. The adoption of a continuous gigahertz (GHz) femtosecond laser as the light source, coupled with the incorporation of thermally conductive Al2O3 plate as a heat sink, facilitated the manufacturing processes including reduction and transfer of GO. The manufacture of graphene coatings with high electrical conductivity on PET in a versatile and cost-effective manner, presents significant potential for diverse applications, particularly in conductive-coatings-based sensors.

Numerical study on the optimized thickness of layer configuration against the 7.62 APM2 projectile

This study aimed to select suitable materials and optimize the thickness of these materials so that they could prevent the perforation of 7.62-mm AP bullets at 830 m/s impact velocity. A numerical method is used to analyze the impact on layered configurations of Al2O3 and Al 7075-T651 to fulfill this aim. In order to optimize the thickness of the armor, normal impact and angular impact conditions were considered. Initially, a 20-mm Al2O3 front plate with a 20-mm Al 7075-T651 back plate is analyzed for layered configuration. Back plate thickness is reduced in steps to 10 mm such that no plastic deformation is observed on the rear side of the target. For further optimization of weight, the thickness of the Al2O3 plate is reduced to 18 mm. The weight of this configuration is 1.77 kg, and the areal density is 97.22 kg/m2. This configuration is analyzed for target orientations such as 80°, 70°, and 60°. In this analysis, the projectile deformed in a mushroom shape for 90° and 80° target orientations, while for 70° and 60° target orientations, the projectile experienced more damage on the shank part. The most effective configuration with the highest degree of ballistic performance is a layered combination of the 18-mm Al2O3 front plate and 10-mm Al 7075-T651 back plate at 70° target orientation.

Atomic-Layer-Deposition Derived Pt subnano Clusters on the (110) Facet of Hexagonal Al2O3 Plates: Efficient for Formic Acid Decomposition and Water Gas Shift

The Pt subnano clusters dispersed on the (110) facet of regularly shaped hexagonal Al2O3 plates were fabricated via an atomic layer deposition approach. The resulting material contains Pt loading as low as 0.07 wt %; the interfacial structure exhibits nearly full CO conversion for water gas shift reaction at 210 °C, and the turnover frequency (TOF) of CO is as high as 2.1 s–1, outperforming most of the systems reported. The same interfacial structure was also found to be highly active for catalytic decomposition of formic acid (FA), with full FA conversion (with little CO product) and the TOF being 1.02 s–1. Further characterizations together with density functional theory simulations elucidate that the superior catalytic performances are attributed to the unique interfacial structure and the synergism between the small Pt clusters and the Al2O3 (110) substrate, leading to lower energy barriers for the *COOH intermediate formation over the ultrafine Pt ensembles and the hydroxylation over the Al2O3 (110) substrate close to the Pt entities. Both are favorable for the evolution of *COOH intermediate and the reaction between *COOH and neighbor OH species. The current study provides insights into the effectiveness in generating high-performance catalytic material for clean energy production and modulation through precise control of the metal entity dimension and the oxide substrate engineering to achieve specific facet exposure.

Effect of fabrication parameters on grinding performances of electroplated Ni-B-diamond tools with D150-diamond particles

Electroplated Ni-B-diamond tools with D-150 diamond particles were fabricated and their tool life performances from slot grinding Al2O3 plates were evaluated. Electroplated diamond tools with high diamond particle density were prepared from martensitic stainless steel (AISI 440C) rods, using three sequential electroplating processes, namely Ni-undercoating, Ni-diamond co-electrodeposition, and Ni-B strengthening electroplating. Fabricating parameters of electroplated diamond tools, including the Ni-undercoating thickness, the choice between Ni-diamond and Ni-B-diamond co-electrodeposition, the diamond-coverage percentage, and the post-process annealing temperature, were studied to acquire the determinants of electroplated diamond tool with high grinding performance. Experimental results showed that the grinding performance of an electroplated diamond tool depends strongly on the Ni-undercoating thickness. The highest grinding performance can be achieved from the 400 °C-annealed electroplated diamond tool with Ni-undercoat thickness of 90 μm and diamond-coverage percentage of 80 %. Due to the cracking found along the interface between the Ni-undercoating and Ni-B deposit, Ni-B-diamond co-electrodeposition process is ill-suited for electroplated diamond tool fabrications. Diamond particles should extrude from the tool surface to cut and remove Al2O3 chips formed during grinding. Diamond-coverage should be more than 50 % to avoid low grinding performances due to the low bonding strength of diamonds.

Active Control of Boundary Lubrication of Ceramic Tribo-Pairs in Sodium Dodecyl Sulfate Aqueous Solutions

The objective of the study is to actively control friction between engineering ceramics in underwater applications. By designing a proper electrode system and applying an external electric field, the active control of friction between Al2O3 plate and ZrO2 ball in sodium dodecyl sulfate (SDS) aqueous solutions has been realized, which is different from the previous studies of potential-controlled boundary lubrication where at least one part of tribo-pairs is a conductor. Reversible change of friction coefficient has been observed in the range from 0.12 to 0.35. An indirect electric field-assisted adsorption/desorption model has been proposed to explain the observed phenomena. The addition of inorganic salts containing counterions to the SDS solution or increasing the concentration of SDS can shorten the response time of friction to the variation of the applied electric field by facilitating the formation of SDS micelles. This opens a new way to realize the active control of friction for insulative tribo-pairs without corrosion.

Practical Application Study of Highly Active CO2 Methanation Catalysts Prepared Using the Polygonal Barrel-Sputtering Method: Immobilization of Catalyst Particles

This study investigated immobilization (without binders and high-temperature heating) of highly active CO2 methanation catalyst particles, prepared by the polygonal barrel-sputtering method, onto porous Al2O3 plates. The catalyst particles were fixed uniformly and firmly on the plates and retained their high CO2 methanation performance.

Investigation of high temperature behavior of AlSi10Mg produced by selective laser melting

Among additive manufacturing (AM) processes, Selective Laser Melting (SLM) is the most diffused layer by layer method for manufacturing 3D components. It is based on local melting, induced by a laser scanning, on a powder bed; the limited dimensions of the liquid pool provoke rapid cooling rates which can be associated to significantly finer microstructure than the one obtained by a conventional casting process. Moreover, being the remelting of pre-existing pools, it is of relevant interest to investigate the wettability and the reactivity at high temperature of alloys produced by SLM. In the panorama of alloys for AM, the AlSiMg system is one of the most used, as it belongs to wide family of the Al–Si alloys, extensively used for conventional casting and die-casting technologies, and it offers good weldability. Therefore, the present work has the goal of investigating the high temperature behavior of the SLMed AlSiMg parts. Wettability tests on Al2O3 plates were performed considering two different atmospheres (vacuum and Argon) and the contact angle results compared; surface morphology together with the microstructures and the chemical composition variations were analyzed.

Joining of Metal to Ceramic Plate Using Super-Spread Wetting

Ceramic-metal composites with novel performance are desirable materials; however, differences in their properties result in difficulties in joining. In this study, the joining of metal to ceramic is investigated. We recently succeeded in causing super-spread wetting on the surface fine crevice structures of metal surfaces produced by both laser irradiation and reduction-sintering of oxide powders. In this work, joining copper onto an Al2O3 plate was achieved by taking advantage of super-spread wetting. Fe2O3 powder was first sintered under reducing conditions to produce a microstructure which can cause super-spread wetting of liquid metal on an Al2O3 plate. A powder-based surface fine crevice structure of metallic iron with high porosity was well-formed due to the bonding of the reduced metallic iron particles. This structure was joined on an Al2O3 plate with no cracking by the formation of an FeAl2O4 layer buffering the mismatch gap between the thermal expansion coefficients of iron and Al2O3. We successfully achieved metalizing of the Al2O3 surface with copper without interfacial cracks using super-spread wetting of liquid copper through the sintered metallic iron layer on the Al2O3 plate. Then, laser irradiation was conducted on the surface of the copper-metalized Al2O3 plate. A laser-irradiated surface fine crevice structure was successfully created on the copper-metalized Al2O3 plate. Moreover, it was confirmed that the super-spread wetting of liquid tin occurred on the laser-irradiated surface fine crevice structure, finally accomplishing the joining of a copper block and the copper-metalized Al2O3.

Fabrication and evaluation of electroplated diamond grinding rods strengthened with Cr-C deposit

Cr-C-Ni-diamond composite deposits with synthetic diamond particles of 50 μm in average size were electroplated onto a medium-carbon steel rod to fabricate electroplated diamond grinding rods. To make an electroplated Cr-C-Ni-diamond grinding rod with a high diamond density, three sequential electroplating processes were proposed, including Ni undercoating, Ni-diamond co-electroplating, and Cr-C strengthen-electroplating. The Cr-C strengthening deposit was prepared in an eco-friendly Cr3+-based plating bath. A composite Cr-C-Ni-diamond deposit with multi-layered diamond particles could be prepared on the steel rod substrate by repeating the proposed three sequential electroplating processes. After electroplating, some of the prepared grinding rods were annealed at 500 °C for 30 min to increase the hardness of Cr-C deposit. As-plated and annealed electroplated Cr-C-Ni-diamond grinding rods with one- and two-layered diamond particles were used to grind slots in Al2O3 plates in a depth of 5 mm to evaluate their grinding-life performances. Based on the results of grinding tests, the ground length of an electroplated Cr-C-Ni-diamond grinding rod was significantly increased after annealing at 500 °C for 30 min, and the length was further extended by electroplating two layers of Cr-Cs-Ni-diamond composite deposit. A relatively long ground length of 1320 mm was achieved from the 500 °C-annealed electroplated diamond grinding rod with two-layered diamonds, but only 30 mm from the as-plated one. It was evidenced that an anneal-hardened Cr-C deposit can serve as a competent strengthening layer in the electroplated diamond tool.

Formation of Al by Metallothermic Reduction of Al2O3 by Ti at High Temperature

This work reports a simple way of producing metallic Al as a product of the metallothermic reduction of Al2O3 by metallic Ti at 1600 °C. A porous carbon template (derived from rattan) was used here to capture the Al released from the interfacial reactions, being an easy way to quantify the amount of Al released. For the process, the carbon template was placed between a pair of Ti foils in contact with Al2O3 plates. Phase composition analysis revealed that Ti3Al and TiO were formed on the surface of Ti foils, while the rattan-derived carbon template was converted to Al4C3. After the process, almost all Ti foil was consumed and a mass loss of more than 10% was observed in the Al2O3 plates. The carbon trap could be any other reactive system that, during processing at high temperatures one could use the released aluminum to form in situ other compounds.

Evolution of cube-on-face texture in Fe-1%Si steel induced by physical contact during the phase transformation from γ to α

When any sample is heat treated, it is normally placed on a supporting material. Normally, such physical contact is not expected to affect the microstructure evolution of the sample. In this study, however, the physical contact between Fe-1%Si sheet and the Al2O3 plate was found to have a strong effect on the evolution of a cube-on-face texture during heat treatment, producing as much as 76.0% when determined by the orientation within {100} ±15°. The similar result was obtained for the tungsten and quartz plates. The results provide a promising method to produce the high efficiency Si steel with a cube-on-face texture.

Wetting mechanism and bending property of Cu/Al2O3 laminated composites with pretreated CuO interlayer

Addition of oxygen in the interface between Cu and Al2O3 can significantly improve the wettability. In the present work, Cu/Al2O3 laminated composites were fabricated by bonding Cu foils with CuO-coated Al2O3 plates. Before bonding, the coated Al2O3 plates were pretreated at different temperature in the air. The effect of pretreated temperature on the interfacial microstructure, wettability and bending property were investigated. Phase composition in the interface after wetting test was characterized according to the thermodynamics of Cu–O system. The wetting mechanism and bending failure mode of Cu/Al2O3 laminated composites were also analyzed. Pretreated temperature significantly influences the wettability and bending strength of the composites. The contact angle decreased to about 22° when the pretreated temperature equal to 1100 °C. Continuous CuAlO2 in the interlayer is beneficial to the wettability between Cu melt and Al2O3, while other phases such as Cu2O and CuAl2O4 would increase the contact angle. Crack formation and propagation are the main failure mode of Cu/Al2O3 laminated composites during bending test. Different from the wettability, Cu/Al2O3 laminated composites fabricated with pretreated temperature at 1050 °C show the highest bending strength, although the contact angle is not the lowest on this condition. The reason is illustrated through analyzing the bending failure mode.

Round‐robin exercise on the three‐ and four‐point flexural strength of thin ceramic plates for power modules

AbstractRound‐robin exercises on three‐ and four‐point flexural tests were successfully conducted to evaluate the fracture strength of Si3N4, Al2O3, and AlN thin plates for power modules. A 0.64 mm × 12 mm × 40 mm test specimen was loaded in three‐point flexure with a major span of 30 mm or was loaded in four‐point flexure with a major/minor span of 30/10 mm. For a 0.32 mm × 12 mm × 20 mm test specimen, both major and minor spans were halved. All test specimens were loaded in a fully articulated fixture provided by the test organizer. Reasonable consistencies in the resultant flexural strength were obtained between laboratories, indicating our new test condition for three‐ and four‐point bending of thin ceramic plates is satisfactory for reliable measurement of the flexural strength.

Porous Al2O3 plates prepared by combing foaming and gel-tape casting methods for efficient collection of oil from water

Absorbent materials are considered as the most effective way of dealing with oil spill accidents and the increasing industrial oily wastewater leakages. However, poor recycling ability and low efficiency limit their application. This paper presents a fabrication approach of porous Al2O3 plates (PAP), which combines foaming and gel-tape-casting methods. The plates, which had high bending strength (4.5 ± 0.2 MPa) and oil permeation (4.4 × 105 L·m−2·h−1·bar−1), absorbed various kinds of oils rapidly, with space utilization >98%, while the absorbed oil was readily collected by simply being poured out or gas blown. Furthermore, the plate markedly maintained its high separation efficiency, mechanical strength, and hydrophobic properties after 1000 absorption-blowing cycles, as well as after treatment in several harsh environments. The results suggest that this fast and simple ceramic plate preparation approach can be proposed for practical applications in technologies of collecting oils and organic solvents from water.

Revisiting the fabrication of superhydrophobic aluminum surfaces and their use as soft substrates for droplet manipulation

Superhydrophobic aluminum (Al) surfaces are desired in many applications and have been widely studied, but some fundamental issues in their fabrication are not yet fully understood. In this study, commonly used HCl solution and organic acid/sulfur reagents were employed for clarifying the phenomena in etching and composition modification. An unstable layer was revealed after HCl etching, which was removable with water flushing, and this layer, consisting of scattered AlCl3/Al2O3 particles surrounded by Al2O3 plates with cracks, caused changes in surface appearance from bright to dark. A complete change in surface color corresponded to sufficient etching, and hence, this visible phenomenon could be used to confirm the shortest etching time for achieving desirable superhydrophobicity. Composition modification with dodecanethiol and myristic acid also modified the microstructure through a slight etching mechanism and a synergistic effect was found with the use of their mixture, which led to the finest grains and most abundant carbon chains on the final surfaces. Consequently, the best superhydrophobicity was revealed in static and dynamic experiments with droplets. Finally, using the advantage of flexibility, a superhydrophobic Al sheet was demonstrated to be suitable for subjecting droplets to controlled rolling and coalescence, which could be meaningful for many droplet-related studies.

Evolution of Cube-on-Face Texture in Fe-1%Si Steel Induced by Physical Contact During the Phase Transformation from <i>Γ</i> to <i>Α</i>

When any sample is heat treated, it is normally placed on a supporting material. Such physical contact is not expected to affect the microstructure evolution of the sample. In this study, however, the physical contact between Fe-1%Si sheet and the Al2O3 plate was found to have a strong effect on the evolution of a cube-on-face texture during heat treatment, producing as much as 76.0% when determined by the orientation within {100} ±15o. The similar result was obtained for the tungsten and quartz plates. The results provide a promising method to produce the high efficiency Si steel with a cube-on-face texture.

EFFECT OF COATING TIME ON ELECTROCHEMICAL DEPOSITION OF MOLYBDENUM OXIDES THIN FILM ON THE SURFACE OF ANODIZED ALUMINUM PLATE FOR ULTRACAPACITOR ELECTRODE MATERIAL

In this work, effect of coating time on the structural, compositional and morphological properties of MoO3-coated Al2O3 plate for application as an electrode material for ultracapacitor was investigated. The 1[Formula: see text]cm [Formula: see text] 1[Formula: see text]cm aluminum plate was anodized by an electrochemical plating technique at 12[Formula: see text]V for 20 and 30[Formula: see text]min, respectively. MoO3 film was then coated on anodized aluminum plate over a range of coating time (2–10[Formula: see text]min, in intervals of 4[Formula: see text]min) at an applied voltage of 6[Formula: see text]V with constant electric current of 1[Formula: see text]A. X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) were employed in the characterization of the MoO3/Al2O3 plate obtained. The SEM results obtained indicated that the coating time significantly affected the roughness and the surface area of the samples. The EDX analysis revealed the chemical composition element of Mo, O and Al and the result from XPS confirmed the existence of MoO3.

Structural and Fluorine Plasma Etching Behavior of Sputter-Deposition Yttrium Fluoride Film.

Yttrium fluoride (YF3) films were grown on sapphire substrate by a radio frequency magnetron using a commercial ceramic target in a vacuum chamber. The structure, composition, and plasma etching behavior of the films were systematically investigated. The YF3 film was deposited at a working pressure of 5 mTorr and an RF power of 150 W. The substrate-heating temperature was increased from 400 to 700 °C in increments of 100 °C. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction results confirmed an orthorhombic YF3 structure was obtained at a substrate temperature of 700 °C for 2 h. X-ray photoelectron spectroscopy revealed a strongly fluorinated bond (Y–F bond) on the etched surface of the YF3 films. HRTEM analysis also revealed that the YF3 films became yttrium-oxyfluorinated after exposure to fluorocarbon plasma. The etching depth was three times lower on YF3 film than on Al2O3 plate. These results showed that the YF3 films have excellent erosion resistance properties compared to Al2O3 plates.

Evaporation induced electricity generation in freestanding and flexible carbon-based hybrid film

Energy harvesting from ambient environment attracts widespread interest for its great potential in green and sustainable development. Very recently, evaporation, a ubiquitous process existing in nature was demonstrated as a reliable process, which can convert low-grade thermal energy in environment into electricity. Evaporation-driven water flow within a piece of carbon black sheet or printed porous carbon film could generate sustainable direct-current electricity with open-circuit voltage ( V oc) up to 1 V, and with lifetime over hundreds of hours. However, both the flame-deposited carbon black sheets and all-printed porous carbon films need to be deposited or printed on rigid substrates (e.g., silica glass and Al2O3 plate) in the previous work, which has deceased the effective evaporation area and occupied excessive space, thus limiting the application of this new energy harvesting strategy as a practical power source. In this work, we present the fabrication of a flexible and freestanding carbon nanoparticles/glass fiber hybrid film (CNGF) for electricity generation via evaporation-driven water flow within it. The CNGF hybrid film has a structure of reinforced concrete, thus exhibits good flexibility and mechanical properties. The carbon film with the size of 1 cm × 4.5 cm × 0.13 mm and glassfiber/carbon nanoparticle mass ratio of 0.6, has a max tensile stress of 4.9 MPa. The electrical resistance of the carbon film keeps nearly unchanged after 10000 bends at a max bending angle of 90°, indicating its excellent flexibility. Without the limit of rigid substrates, the double-side evaporation enables higher water flow rate through the film. The freestanding carbon film thus has higher electrical power output than the carbon films reported before. A device with the size of 1 cm × 4.5 cm × 0.13 mm generates an open-circuit voltage of ~1 V and current of ~ 0.86 μA under ambient condition. The hybrid carbon film can also be easily scaled-up. We demonstrated a carbon film with the maximum width of 40 cm, which has an output current of ~28 μA. Furthermore, the excellent flexibility allows the film to be rolled up to save space, even with a high power output. To demonstrate the application of carbon film, we successfully degraded methylene blue (MB) by using our device as power source. Given the simple fabrication, robust mechanical property, high electricity output, such a freestanding and flexible carbon-based hybrid film shows great potential in environmental energies harvesting for green and sustainable development.

Tunneling anomalous Hall effect in nanogranular CoFe-B-Al-O films near the metal-insulator transition

We present results of experimental studies of structural, magneto-transport and magnetic properties of CoFe-B-Al-O films deposited onto a glass ceramic substrate by the ion-beam sputtering of the target composed of Co40Fe40B20 and Al2O3 plates. The system consists on the strained crystalline CoFe metallic nanogranules with the size 2-5 nm which are embedded into the B-Al-O oxide insulating matrix. Our investigations are focused on the anomalous Hall effect (AHE) resistivity Rh and longitudinal resistivity R at T=5-200 K on the metallic side of metal-insulator transition in samples with the metal content x=49-56 at.%, that nominally corresponds to (Co40Fe40B20)x(Al2O3)100-x in the formula approximation. The conductivity at T > 15 K follows the lnT behavior that matches a strong tunnel coupling between nanogranules. It is shown that the scaling power-laws between AHE resistivity and longitudinal resistivity strongly differ, if temperature T or metal content x are variable parameters: Rh(T)~R(T)^0.4-0.5 obtained from the temperature variation of R and Rh at fixed x, while Rh(x)/x~R(x)^0.24, obtained from measurements at the fixed low temperature region (10-40 K) for samples with different x. We qualitatively describe our experimental data in the frame of phenomenological model of two sources of AHE e.m.f. arising from metallic nanogranules and insulating tunneling regions, respectively, at that the tunneling AHE (TAHE) source is strongly shunted due to generation of local circular Hall currents. We consider our experimental results as the first experimental proof of the TAHE manifestation.