Potential of Suspension Spraying for Development of Dense WC-12Co Coatings

Thermally sprayed WC-Co coatings provide excellent wear resistance and corrosion protection under heavy loads, but their application usually involves additional grinding and polishing steps, which can be 3-4 times costlier than the spraying process itself. There is thus the motivation to develop a process that produces smooth, near-net-shape carbide coatings. This contribution is an investigation of WC-12Co coatings obtained by suspension HVOF spraying. Significant work was devoted to the development and characterization of water-based hardmetal suspensions synthesized from commercially available WC and Co powders. The suspensions produced were sprayed using the HVOF process, and the resulting coatings were evaluated based on microstructure, hardness, and phase composition.

Suspension Spraying Tip: High Molecular Weight Solvent

In suspension spraying, the two most frequently used solvents are water and ethanol. In this study, we test a potential alternative, a high-molecular weight solvent. Two organic solvents are compared: ethanol (serving as a benchmark, suspension formulated at 10 wt.% solid load) and di-propylene glycol methyl ether (two suspensions at 10 wt.% and 20 wt.%). Submicron alpha-alumina powder is used as a model material to formulate the suspensions. It is shown that ethanol- and ether-based-feedstock coatings are fully comparable in terms of their microstructure, porosity content, surface roughness, and hardness. However, the ether-based coatings exhibit slightly higher levels of α-Al2O3 phase than their ethanol-based counterpart (17 wt.% vs. 6 wt.%). The use of 20 wt.% solid load in the ether solvent leads to a twofold increase in the deposition rate while, as opposed to ethanol, successfully retaining a dense microstructure. Ether also costs less than ethanol and is safer to handle.

Metode inokulasi buatan untuk menguji infeksi Peronosclerospora maydis penyebab penyakit bulai tanaman jagung

Keberadaan penyakit bulai akibat Peronosclerospora maydis pada tanaman jagung mampu menyebabkan kehilangan hasil hingga 100%. Pengendalian penyakit bulai dengan menggunakan varietas tahan dinilai cukup efektif. Di dalam pengembangan varietas tahan, seleksi ketahanan calon varietas baru harus dilakukan dan hal ini akan melibatkan inokulasi buatan. Tujuan dari penelitian ini adalah untuk mendapatkan metode inokulasi buatan Peronosclerospora maydis yang efektif pada tanaman jagung pada skala rumah kaca. Penelitian dilaksanakan di Laboratorium Bioteknologi Proteksi Tanaman dan rumah kaca Departemen Hama dan Penyakit Tumbuhan, Fakultas Pertanian, Universitas Padjadjaran pada bulan Oktober hingga Desember 2018. Bahan tanaman yang diinokulasikan berupa kecambah dan bibit tanaman jagung. Metode inokulasi buatan yang diujikan terdiri atas: (1) Sisip daun terinfeksi bulai pada kecambah (SD), (2) Semprot suspensi konidia pada kecambah (SI), (3) Sisip daun bergejala bulai + semprot suspensi konidia pada kecambah (SS), (4) Rendam kecambah pada suspensi konidia (RS), (5) Semprot suspensi konidia pada bibit (SB), dan dua perlakuan tanpa inokulasi (kontrol). Dari hasil percobaan metode sisip daun (SD) menyebabkan 83,3% tanaman jagung terinfeksi bulai dan dinilai sebagai metode inokulasi buatan yang efisien.Kata kunci: bulai, jagung, inokulasi buatan, Peronosclerospora maydis. ABSTRACTDowny mildew disease caused by Peronosclerospora maydis in maize plants can cause yield loss up to 100%. Disease management of downy mildew by using resistant varieties is considered quite effective. One of the steps to develop resistant varieties is resistance testing of the new variety candidates that involve artificial inoculation. The purpose of this study was to obtain an effective artificial inoculation method of Peronosclerospora maydis in maize plants in greenhouse. The research was conducted at the Laboratory of Biotechnology of Plant Protection and Glasshouse Department of Plant Pests and Diseases, Agriculture Faculty, Universitas Padjadjaran from October to December 2018. The plant materials used for inoculation were sprout and seedling of maize plant. The artificial inoculation methods tested were (1) infected leaf insertion among the sprouts (SD), (2) conidia suspension spraying on the sprouts (SI), (3) infected leaf insertion + conidia suspension spraying on the sprouts (SS), (4) sprout soaking in conidia suspension (RS), (5) conidia suspension spraying on the seedling (SB), and two treatments without inoculation (controls). The result showed that the insertion of infected leaves among the sprouts (SD) treatment resulted in 83.3% of infected maize plants by the downy mildew and was considered as the most efficient inoculation method.

Preparation of metallic monolithic Pt/FeCrAl fiber catalyst by suspension spraying for VOCs combustion

The catalyst was prepared by surface thermal treatment and spraying, and exhibited activity for the combustion of VOCs to CO2 and H2O.

Anode-supported BaZr0.8Y0.2O3−δ membranes by tape casting and suspension spraying

Dense BaZr[Formula: see text]Y[Formula: see text]O[Formula: see text] (BZY) proton-conducting electrolyte membranes are successfully fabricated on NiO–BaZr[Formula: see text]Ce[Formula: see text]Y[Formula: see text]O[Formula: see text](NiO–BZCY) using tape casting combined with suspension spraying technique. The NiO–BZCY anode substrates were prepared by the tape-casting method and the BZY electrolyte membranes were prepared on the NiO-BZCY anodes by suspension spraying. The thermal decomposition of the anode green tape prepared by tape casting was investigated by thermogravimetry-differential thermal analysis while the phase structure and the morphology of the anode/electrolyte bi-layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). No obvious reaction was found between NiO and BZCY in anode substrates and gas-tight BZY membranes were achieved after co-sintering at 1450[Formula: see text]C. With Sm[Formula: see text]Sr[Formula: see text]CoO[Formula: see text]–Ce[Formula: see text]Sm[Formula: see text]O[Formula: see text](SSC–SDC) as the composite cathode, a maximum power density of 121 mW cm[Formula: see text] was obtained at 650[Formula: see text]C for the single cell with 23 [Formula: see text]m thick BZY electrolyte. Resistances of the tested cell were investigated under open circuit conditions at different operating temperatures by impedance spectroscopy.

Nanoindentation Evaluation of Suspension Thermal Sprayed Nanocomposite WC-Co Coatings

The aim of this paper is to evaluate the microstructural and nanohardness characteristics of tungsten carbide-cobalt (WC-Co) cermet coatings deposited by liquid suspension spraying. Commercially available WC-Co coating powder was milled and water based suspension was produced as feedstock for the thermal spray coating process. Microstructural evaluations of WC-Co cermet coatings included XRD (X-Ray Diffraction) and SEM (Scanning Electron Microscopy). Post spraying nanomechanical evaluations were conducted using a Berkovich nanoindenter. Results indicated relatively higher modulus but lower hardness of suspension coatings. The load displacement curves during nanoindentation were characteristic of the complex coating microstructure showing signs of microcracking and pile-up.

Diagnostics of Hybrid Water/Argon Thermal Plasma Jet with Water, Ethanol and Their Mixture Injection to Plasma

A plasma torch with the water/argon stabilization of an arc is characterized by extremely hot and high velocity plasma together with the relatively low flow rate of plasma, therefore, the torch might be properly used for plasma suspension spraying. Enthalpy probe and emission spectroscopy measurements were carried out at constant arc power with the combination of the injection of water, ethanol or their mixture to the plasma jet to diagnose the changes in temperature, heat flux and other characteristics.