Ultrasonic-assisted Deposition Research Articles

Effect of ultrasonic parameters on microstructure and mechanical properties of non-contact ultrasonic-assisted laser metal deposition of Fe-based powder

In order to study the effects of ultrasonic parameters on the microstructure and mechanical properties of non-contact ultrasonic assisted laser deposition, Fe-based powder was deposited on 42CrMoA steels with different ultrasonic amplitudes (UA) and excitation distances (d). The results show that the ultrasonic-assisted laser metal deposition (LMD) of Fe-based powder increases depth and width of the deposition layers. Due to the cavitation effect of ultrasonic, it effectively refines the grains and promotes the columnar to equiaxed transition (CET) of grains at the interface. When d = 50 mm, the grain size greater than 8 μm accounts for only 3.1 %, but the ultrasonic vibrations haven’t changed the phase type of the structures. With ultrasonic-assisted, the cracks generated in the deposition layer can be effectively inhibited and the mechanical properties can be improved. When d = 80 mm and UA = 30 μm, the average microhardness of the deposition layer reaches 772.9 HV, which is 95.8 HV higher than that without ultrasonic-assisted deposition. When UA = 40 μm, the tensile strength is 1237.9 MPa, which is increased by 26.8 % compared to without ultrasonic-assisted deposition. Compared to without ultrasonic-assisted, the friction coefficient of deposition layers is significantly decreased by 25.5 % with the application of UA = 30 μm.

Carbon Nanotube Coated Fibrous Tubes for Highly Stretchable Strain Sensors Having High Linearity.

Strain sensors are currently limited by an inability to operate over large deformations or to exhibit linear responses to strain. Producing strain sensors meeting these criteria remains a particularly difficult challenge. In this work, the fabrication of a highly flexible strain sensor based on electrospun thermoplastic polyurethane (TPU) fibrous tubes comprising wavy and oriented fibers coated with carboxylated multiwall carbon nanotubes (CNTs) is described. By combining spraying and ultrasonic-assisted deposition, the number of CNTs deposited on the electrospun TPU fibrous tube could reach 12 wt%, which can potentially lead to the formation of an excellent conductive network with high conductivity of 0.01 S/cm. The as-prepared strain sensors exhibited a wide strain sensing range of 0–760% and importantly high linearity over the whole sensing range while maintaining high sensitivity with a GF of 57. Moreover, the strain sensors were capable of detecting a low strain (2%) and achieved a fast response time whilst retaining a high level of durability. The TPU/CNTs fibrous tube-based strain sensors were found capable of accurately monitoring both large and small human body motions. Additionally, the strain sensors exhibited rapid response time, (e.g., 45 ms) combined with reliable long-term stability and durability when subjected to 60 min of water washing. The strain sensors developed in this research had the ability to detect large and subtle human motions, (e.g., bending of the finger, wrist, and knee, and swallowing). Consequently, this work provides an effective method for designing and manufacturing high-performance fiber-based wearable strain sensors, which offer wide strain sensing ranges and high linearity over broad working strain ranges.

Ultrasonic-Assisted Deposition Method for Creating Conductive Wrinkles on PDMS Surfaces

Harnessing surface wrinkle surfaces in various functional devices has been a hot topic. However, rapidly creating wrinkled surfaces on elastomers of arbitrary shape (especially curved surfaces) is still a great challenge. In this work, an ultrasonic-assisted deposition method has been proposed to achieve nanomodification of the robust layer (e.g., carbon nanotubes (CNTs)) with a labyrinth wrinkle pattern on polydimethylsiloxane (PDMS) fiber, sheet, and porous sponge. It is found that the swelling effect of the dispersion and the ultrasonic treatment play vital roles in the surface wrinkling. As a demonstration, the conductive wrinkled CNTs@PDMS fibers were assembled as stretchable strain sensors. The initial conductivity and the strain-sensing performances could be well tuned by simply adjusting the ultrasonic treatment time. The wrinkled CNTs@PDMS fiber strain sensor exhibited remarkable stretchability (ca. 300%) and good sensitivity, which can be applied in various human motion detection, voice recognition, and air-flow monitoring. It is also expected that the facile ultrasonic-assisted deposition method for surface wrinkling can be extended to fabricate various smart devices with promoted performances.

Metal-free SiOC/g-C3N4 heterojunction composites with efficient visible-light photocatalytic H2 production

Photocatalytic water splitting to product hydrogen (H2) is a desired route to utilize solar energy into chemical energy. At present, most photocatalysts for H2generation contains metallic elements with high-cost, confined reserves, and environmentallyunfriendly. The exploitation of metal-free and efficient photocatalysts becomesparticularlyimportant. Herein, a new metal-free g-C3N4-based heterojunction composites were facilely produced via the ultrasonic assisted deposition and subsequent calcination from g-C3N4 layers embedded with SiOC with prominent conductivity and large surface area. Systematic investigates suggested that the SiOC/g-C3N4 heterojunctions exhibited eminently meliorated photocatalytic H2 production efficiency. The optimum H2 production rate (1020 μmol h−1 g−1) of the SiOC/g-C3N4 photocatalyst is 3.2 and 25.5 folds that of g-C3N4 and SiOC, respectively. The boosted photocatalytic activity primarily originates from the increased absorptivity of light, the markedly expedited charge migration and the impeded recombination of charge carriers. This study offers a new perspective for the scientific contrive and fabrication of high-quality heterojunction photocatalysts for solar energy utilization.

Optical properties of InP/ZnS quantum dots deposited into nanoporous anodic alumina

Spectral characteristics of InP/ZnS core/shell colloidal quantum dots of two different sizes (QD-1 and QD-2) were investigated. Absorption and luminescence spectra were analyzed for a series of solutions with a concentration range from 0.04 to 40 g/l. Energies of the optical transitions are evaluated. The obtained values of 2.60 eV (QD-1) and 2.38 eV (QD-2) correspond to the InP first excitonic transitions while 4.06 (QD-2) and 4.70 eV (QD-1, QD-2) are assumed to be caused by the ZnS shell absorption. Structures based on nanoporous anodic aluminum oxide (AAO) with the QDs were synthesized via an electrochemical oxidation and ultrasonic-assisted deposition. Chromaticity coordinates and correlated color temperatures for all phosphors under study were calculated. The fabrication possibilities of InP/ZnS@AAO nanostructures with tunable emission color (including the border of white region) were shown.

Highly sensitive carbon nanotubes–SnO2 nanocomposite sensor for acetone detection in diabetes mellitus breath

Multiwall carbon nanotubes (MWCNTs)/SnO2 nanocomposites were synthesized by ultrasonic-assisted deposition–precipitation method and used for detection of acetone in the same range of concentrations as in diabetes mellitus breath. The nanocomposite samples were characterized by BET, FE-SEM, XRD and TEM. MWCNTs with an average size of about 60nm are coated with and uniformly dispersed in 5–10nm SnO2 nanoparticles matrix. To diagnose diabetes, the sensors responses to ppm concentrations of acetone were measured in a flow system at various temperatures and 85% relative humidity. Addition of MWCNTs dramatically enhances the sensors response to acetone. Moreover, the sensors response to ethanol, as an interfering species with acetone in human breath, was also measured. Breath humidity increases the conductivity of the sensing materials and therefore, lowers the sensors response to acetone.

Highly sensitive and selective sensors to volatile organic compounds using MWCNTs/SnO2

Multiwall carbon nanotubes (MWCNTs)/SnO2 gas sensors were fabricated using ultrasonic-assisted deposition–precipitation method and used for detection of ethanol, acetaldehyde, acetone, toluene and trichloroethylene (TCE) VOCs at various temperatures. The MWCNTs/SnO2 samples were characterized by BET specific surface area measurement, FE-SEM and XRD. The sensors responses to 300ppm of VOCs were measured in a flow system at various temperatures in the range of 100–350°C. MWCNTs are coated with SnO2 nanoparticles and embedded into the SnO2 matrix. The sensors’ responses dramatically increase by adding 0.05 and 0.10wt% MWCNTs to SnO2. Response enhancements up to 2.4, 4.4, 5.3, and 3.6 times are observed for ethanol, acetaldehyde, acetone and toluene, respectively. The 0.05wt% MWCNTs/SnO2 sensor shows significant responses to sub-ppm levels of acetaldehyde and acetone, as the diabetes diagnostic gas in breath. Moreover, significant enhancement of the sensors selectivity to ethanol, acetaldehyde and acetone with respect to TCE and toluene are observed by addition of the MWCNTs.

Improvement of copper plating adhesion on silane modified PET film by ultrasonic-assisted electroless deposition

Copper thin film on silane modified poly(ethylene terephthalate) (PET) substrate was fabricated by ultrasonic-assisted electroless deposition. The composition and topography of copper plating PET films were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. Peel adhesion strength, as high as 16.7 N/cm, was achieved for the planting copper layer to the modified PET substrate with ultrasonic-assisted deposition; however, a relative low value as 11.9 N/cm was obtained for the sample without ultrasonic vibration by the same measurement. The electrical conductivity of Cu film was changed from 7.9 × 10 4 to 2.1 × 10 5 S/cm by using ultrasonic technique. Ultrasonic operation has the significant merits of fast deposition and formation of good membranes for electroless deposition of Cu on PET film.