Organic–inorganic hybrid gate dielectrics for low-voltage pentacene organic thin film transistors

Organic thin film transistors (OTFTs) for low-voltage operation have been realized with very thin organic–inorganic hybrid gate dielectrics. Organic–inorganic hybrid thin films have good electrical properties, including high dielectric strength and low leakage current density down to 40 nm thickness. In addition, organic–inorganic hybrid thin films have smooth and hydrophobic surface. OTFTs with 40-nm-thick organic–inorganic hybrid dielectrics are operating within −5 V and exhibit a mobility of 0.3 cm²/(V s), a threshold voltage of −2.6 V, and a small subthreshold swing of 0.43 V/decade. In addition, OTFTs with 40-nm-thick organic–inorganic hybrid dielectrics have low hysteresis.     

High speed TIG–MAG hybrid arc welding of mild steel plate

A TIG–MAG hybrid arc welding process was proposed to achieve high speed welding. The influences of hybrid arc welding parameters on welding speed and weld appearance were studied through orthogonal experiment and the microstructures and mechanical properties of weld were tested and compared with that of the conventional MAG weld. The TIG–MAG hybrid arc welding speed could reach up to 3.5 m/min for bead-on-plate welding of 2.5 mm thick mild steel plate under the condition of high quality of weld appearance and 4.5 m/min for butt welding of 2 mm thick mild steel plate, respectively. The mechanical properties of hybrid arc weld were not lower than that of the conventional MAG weld. The assistant TIG arc could effectively stabilize the MAG welding current and MAG arc voltage in high speed TIG–MAG hybrid arc welding process. The stable hybridization obtained by balance between TIG and MAG welding current and proper wire-electrode distance was a key factor to stabilize the welding process.     

Experimental investigation for optimizing the fabrication of a sapphire capillary using femtosecond laser machining and diamond tool micromilling

Sapphire capillaries manufactured with high efficiency and precision are needed for use in laser–plasma accelerators. A hybrid manufacturing process combining femtosecond laser machining and diamond tool micromilling was applied. By using a femtosecond laser mounted on a 5-axis machine, a capillary with a groove width of 630 µm and length of 90 mm was fabricated on a sapphire plate within 5 h. The surface roughness of the bottom of the cylinder groove was finished to 7.1 nm in Sa by milling with a polycrystalline diamond end mill.     

A new hybrid electrochemical-mechanical process (PEMEC) for polishing complex and rough parts

A new polishing process for metallic parts has been developed by simultaneously coupling drag finishing and electrochemical polishing. This new hybrid process, called PEMEC, enables an improvement in the surface roughness within some minutes, and at the same time, preserves the shape of the edges. This hybrid process is based on a synergistic effect between abrasive and chemical mechanisms. It has confirmed its suitability to be applied on complex and rough surfaces produced by additive manufacturing SLM parts.     

Cold metal transfer joining aluminum alloys-to-galvanized mild steel

The cold metal transfer (CMT) welding–brazing process provides a potential method to join dissimilar metals. In this research, various 1 mm thick aluminum alloys were joined to 1 mm thick mild steel (Q235) by the CMT welding technology. It was found that it is feasible to join aluminum alloys-to-galvanized mild steel using the cold metal transfer method. The optimum process variables for weldability of aluminum-galvanized steel of dimension 200 mm × 50 mm × 1 mm could be obtained with a wire of Al4043, 100% argon shielding gas, a welding voltage range of 12–14 V, a deviation distance range of 2–3.5 mm, a welding speed range of 6–8 mm/s and a wire-feed speed range of 4–6 m/min. The joint strength depended primarily on the thickness of the intermetallics and softening of the Al heat-affected-zone. By properly controlling the heat input (100–200 J/mm), the degradation of the HAZ property and thickness of the intermetallic reaction layer can be minimized, and consequently produced a hybrid aluminum-to-steel joint which had comparable strength to that of CMT weld-brazed Al-to-Al joint.     

Characterization of surface texture generate multi-process manufacture

In recent years, surfaces are being engineered to make their surface texture more suitable to their function. Most of the “engineered surfaces” are manufactured by more than one manufacturing process which results in a texture that is based on the combined processes. In order to characterize the surface texture generated by multi-process manufacture, various methods have been developed. In this paper, the existing methods that are based on the technique of linearization of the bearing area curve are reviewed and a segmented regression model for the surfaces generated by multi-process manufacture is presented. The parameters of this model can be used to control the manufacturing processes or to verify the suitability of the surface for the intended function.     

Closed-loop control of product properties in metal forming: A review and prospectus

Metal forming processes today operate with astounding productivity, repeatably creating precise parts in high volumes out of the stock sheet and bar products of the upstream metals industries. This achievement has come through decades of development of ever stiffer and more precise tooling used in fast-acting tightly controlled equipment, and yet in the wider context of manufacturing, metal forming processes seem to be less effective: tooling costs are high, and can only be justified by large batch production; the parts made by metal forming are usually not as required for assembly, and must be processed in further downstream machining operations; current processes do not respond well to process disturbances such as tool wear or unanticipated variation in material properties; twenty years of laboratory development of new flexible forming processes has led to little industrial take-up, due to a lack of precision. The missing ingredient in forming which gives rise to these problems is the absence of effective closed-loop control of product properties. The normal practice for blacksmiths and craft workers in former times – using their personal senses to adjust processing in response to evolving conditions – has been forgotten in the pursuit of process rigidity. This paper therefore aims to motivate a new wave of interest in applying closed-loop control of product properties to metal forming processes. A novel framework is developed to show metal forming processes at the heart of an outer control loop, and existing applications are reviewed. Surveys of sensors, actuators and modelling techniques reveal a rich seam of opportunities for new developments, and the paper concludes with some suggestions about near term opportunities for applying closed-loop control of properties to metal forming processes.     

Printing of uniform PZT thin films for MEMS applications

A flexible manufacturing method for the deposition of lead zirconate titanate (PZT) thin films based on ink jet printing has been developed and used to fabricate a first functioning piezoelectric micromachined transducer by printing. The performance of the printed PZT based transducer was fit to established models to determine piezoelectric coupling and dielectric properties. The piezoelectric coefficient, d₃₁, for printed PZT was between −75 pC/N and −95 pC/N. The relative permittivity was 750–890 and the dielectric loss tangent was 2.4–2.8%. This process enables digital deposition of printed devices with the key properties within the range required for high performance piezoelectric MEMS.     

Preparation of W–Cu nano-composite powder using a freeze-drying technique

W–Cu composite materials have been widely used in heat sink apparatus and as electronic packaging materials. The preparation of the materials, especially the synthesis of W–Cu nanopowder, is a subject much more researches on. This paper focuses on the synthesis of W–Cu composite nanopowder using the freeze-drying technique, an environment-friendly and advanced technique for powder manufacturing. The process involved mixing ammonium metatungstate with CuSO₄·5H₂O as preliminary liquid solution and the use of liquid nitrogen as a cryogenic media; W–5Cu, W–10Cu and W–20Cu composite nanopowders were obtained after vacuum drying and following thermal decomposition reduction. X-ray diffraction, infrared spectroscopy and field emission scanning electron microscopy were used to characterize these nanopowders. The results showed that the freeze-drying precursor was the amorphous matter containing tungstate, sulfate, crystal water and ammonia. Copper appeared at 200 °C, tungsten and β-tungsten could not be obtained until 500 °C, and pure tungsten was found above 700 °C, which meant that the whole reduction process was completed. Crystallized W–Cu composite nanopowder, with particle sizes of 10–20 nm, was produced via a two-stage reduction: 400 °C for 2 h and then 700 °C for 2 h.     

Machining performance on hybrid process of abrasive jet machining and electrical discharge machining

To develop a hybrid process of abrasive jet machining (AJM) and electrical discharge machining (EDM),the effects of the hybrid process parameters on machining performance were comprehensively investigated to confirm the benefits of this hybrid process.The appropriate abrasives delivered by high speed gas media were incorporated with an EDM in gas system to construct the hybrid process of AJM and EDM,and then the high speed abrasives could impinge on the machined surface to remove the recast layer caused by EDM process to increase the efficiency of material removal and reduce the surface roughness.In this study,the benefits of the hybrid process were determined as the machining performance of hybrid process was compared with that of the EDM in gas system.The main process parameters were varied to explore their effects on material removal rate,surface roughness and surface integrities.The experimental results show that the hybrid process of AJM and EDM can enhance the machining efficiency and improve the surface quality.Consequently,the developed hybrid process can fit the requirements of modern manufacturing applications.