Duplex and superduplex stainless steels: microstructure and properties evolution by surface modification processes

The paper presents an overview of diffusion surface treatments, especially nitriding processes, applied to duplex and superduplex stainless steels in the last five years. Research has been done mainly to investigate different nitriding processes in order to optimize parameters for the most appropriate procedure. The scope has been to improve mechanical and wear resistance without prejudice to the corrosion properties of the duplex and superduplex stainless steels. Our investigation also aimed to understand the effect of the nitriding layer on the precipitation of secondary phases after any heating step.Peer ReviewedPostprint (published version

Surface-functionalised materials for microplastic removal

Microplastic (MP) pollution is a matter of great concern attracting increasing attention due to its adverse effects on the environment. Different technologies and methodologies have been developed to remove these pollutants. Herein, we focus on a promising environmental solution that involves surface modification to change the wettability properties of MPs or solid materials by conferring superhydrophobicity and superoleophilicity to increase the selectivity for MP separation. Both processes can be used to selectively separate MPs because of the changes in the wettable properties of the MP or by changing the oil used in the case of superhydrophobic surfaces. We show two distinct methods based on changing the wettability properties of surfaces that could lead to innovative and environmental applications. We also discuss some of the challenges that need to be overcome

Estudio del comportamiento del acero inoxidable dúplex y superdúplex después de deformación plástica severa

[spa] Los diferentes grados de aceros inoxidables dúplex (DSS) se caracterizan por sus atractivas propiedades de resistencia mecánica y resistencia a la corrosión, debido a su microestructura equilibrada de ferrita (δ) y austenita (γ). Sin embargo, son susceptibles a la precipitación de fases secundarias cuando no se controlan los procesos de fabricación y/o de procesado durante su instalación. La formación de estas fases, particularmente fase sigma (σ) enriquecida en Cr y Mo y nitruros/carburos metálicos (Cr2N, M23C6), se produce en el rango de temperaturas de entre 600ºC y 900ºC a lo largo de un periodo de tiempo. Son particularmente investigadas ya que pueden perjudicar las propiedades mecánicas y la resistencia a la corrosión del material, dependiendo de su cantidad en la microestructura del material. A diferencia de los procesos convencionales que se llevan acabo para la obtención de estos aceros, el proceso de deformación plástica severa (SPD) - torsión a alta presión (HPT) ofrece la posibilidad de aportar propiedades mecánicas extraordinarias al material a consecuencia de la nanoestructuración obtenida, manteniendo hasta cierto modo sus dimensiones iniciales. La obtención de una microestructura de grano ultrafino o nanoestructura conlleva cambios internos desde el punto de vista termodinámico, un aumento de la energía interna debido al incremento de límites de grano. Por consiguiente, la precipitación de las fases secundarias se vería afectado en cierto modo. Por otro lado, la aportación de elementos intersticiales desde la superficie hacia el interior del material, por el proceso de difusión, mediante métodos termoquímicos como la nitruración o cementación, se aplican generalmente para mejorar las propiedades tribologías de los materiales bajo estudio. Sin embargo, desde el punto de vista termodinámico, la introducción de los elementos de C y/o N por difusión, puede tener influencia sobre la formación de las fases secundarias. Estos elementos son los principales para la formación de fases intermetálicas como carburos y/o nitruros metálicos. Por consiguiente, la precipitación en general en la microestructura resulta ser afectada y es oportuno determinar las consecuencias de estas modificaciones. En la presente tesis se propone el estudio y análisis microestructural del acero inoxidable dúplex UNS S32205 y superdúplex UNS S32750 después de ser deformados por torsión a alta presión. Se realiza una comparativa entre el material recocido y el material deformado para ver la influencia del proceso mecánico sobre la evolución de la precipitación de fases. Además, se analiza la microestructura tratada termoquímicamente mediante el proceso de nitruración y el de carburación con el fin mismo objetivo. La caracterización de las distintas fases se realiza mediante la utilización del microscopio electrónico de barrido (Scanning Electron Microscope – SEM), así como la disfracción de electrones retrodispersados (Electron Basckscatter Diffraction – EBSD) para determinar la distribución de las fases y su orientación cristalina. Además, mediante la microscopia electrónica de transmisión (Transmission Electron Microscope – TEM) y la técnica de difracción de electrones por precesión (Precession Electron Diffraction – PED) se realiza una mejor interpretación de las fases secundarias debido a la mayor resolución e información cristalográfica obtenida por los equipos. Se utiliza el sistema automático de medida de la orientación cristalina (Automatic Crystal Orientation Measurements – ACOM) tras observar la limitación de la técnica EBSD para la determinación de la distribución y orientación cristalina de fases en las muestras nanoestructuradas, siendo deformadas por HPT. La mejora de las propiedades mecánicas se determina mediante ensayos de microdureza y la influencia de la precipitación se analiza en el comportamiento general a la corrosión. Los resultados muestran que la precipitación de las fases secundarias tanto en el acero inoxidable dúplex como en el superdúplex es básicamente de la fase sigma (σ) y de nitruros de cromo (Cr2N), observada tras un tratamiento isotérmico posterior a la deformación plástica severa. El aumento de la deformación por cizallamiento provoca una nanoestructura y tras el tratamiento isotérmico, las fases secundarias aumentan considerablemente su cantidad, sobretodo en el acero inoxidable superdúplex. Esto contribuye al aumento en la dureza del material debido al fenómeno de envejecimiento por deformación, en comparación al mismo material sin haber sido deformado por HPT. En ambos casos se considera que la precipitación es una transformación invariante, donde la fase sigma es un producto de una fase inicial en estado sólido con distinta estructura cristalina. El comportamiento a la corrosión general del acero inoxidable dúplex y superdúplex no empeora excesivamente, y muestra una pasivación estable debido a la nanoestructuración de los materiales. La nitruración y cementación como procesos termoquímicos influyen considerablemente en el aumento de la precipitación de fase sigma, sin alterar significativamente el comportamiento a la corrosión.[eng] Duplex stainless steels (DSS) are characterized by their attractive properties of mechanical strength and corrosion resistance, due to the balanced microstructure of ferrite (δ) and austenite (γ). However, they are susceptible to secondary phase precipitation during uncontrolled manufacturing processes or heat treatments. The formation of these phases, particularly sigma (σ) phase, enriched in Cr and Mo, and intermetallic nitrides/carbides (Cr2N, M23C6), occurs in the range of 600ºC and 900ºC during different time. They are particularly investigated since they can decrease the mechanical properties and corrosion resistance of the material, depending on their amount in the microstructure. Unlike the conventional processes that are carried out to obtain these steels, severe plastic deformation process (SPD) by high-pressure torsion (HPT) provides extraordinary mechanical properties to the material due the obtained nanostructure, maintaining to a certain point its initial dimensions. Obtaining an ultra-fine grain microstructure or nanostructure entails internal changes from the thermodynamic point of view, an increase in internal energy due to the increments of grain boundaries. Consequently, the precipitation of the secondary phases would be altered. On the other hand, the introduction of interstitial elements from the surface to the inner part of the material by diffusion, mainly by thermochemical methods, such as nitriding or carburizing, can influence the formation of the undesirable phases. Consequently, the precipitation in the microstructure is affected and it is opportune to determine the influences of these modifications. The current thesis proposes the study and microstructural analysis of duplex stainless steel UNS S32205 and superduplex stainless steel UNS S32750 after being deformed by high-pressure torsion. A comparison between the annealed materials and the deformed materials is carried out to see the influence of the mechanical process on the evolution of secondary phase precipitation. The characterization of the different phases has been realized by using Scanning Electron Microscope - SEM, as well as the Electron Basckscatter Diffraction – EBSD technique to determine the distribution of the phases and their crystalline orientation. In addition, Transmission Electron Microscope - TEM and the Precession Electron Diffraction - PED technique as a high-resolution techniques have been used for a better interpretation of the secondary phases. The use of the Automatic Crystal Orientation Measurements – ACOM method has been required after observing the limitation of EBSD for the distribution and crystalline orientation determination of the nanostructured samples, being deformed by HPT. The improvement in mechanical properties has been determined by microhardness tests and the influence of the secondary phases has been analysed on the general corrosion behaviour of the materials. The results showes that the precipitation in both duplex and superduplex stainless steel is basically of sigma phase (σ) and of chromium nitrides (Cr2N), observed after an isothermal treatment after the severe plastic deformation. The increase in shear deformation causes a nanostructure and after an isothermal treatment, the secondary phases increase considerably in quantity, especially in the superduplex stainless steel. This contributes to the increase in the hardness of the material due to the phenomenon of aging by deformation, compared to the same material without having been deformed by HPT. In both cases, precipitation is considered as an invariant transformation, where sigma phase is a product of a solid- state initial phase with different crystalline structure. The general corrosion behaviour of both stainless steels is not deteriorated and it shows stable passivation due to the nanostructuring of the materials. Nitriding and carburizing as thermochemical processes considerably influence the increase in sigma phase precipitation, without significantly altering the corrosion behaviour

Superhydrophobic PDMS coated 304 stainless-steel mesh for the removal of HDPE microplastics

The use of microplastics is a global issue that affects the environment, the economy and human health. Here we describe a superhydrophobic 304 stainless steel obtained by combining chemical etching and PDMS modification. Among other techniques, field emission scanning electron microscopy (FE-SEM) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) were used to identify the hierarchical structure as well as the chemical composition of the surface. The stainless-steel mesh was superhydrophobic (159°) and superoleophilic (0°). The coating presented high stability against abrasion of SiC abrasive paper as well as in the presence of different pH values in acidic or alkaline conditions. In addition, taking advantage of the coating's wetting properties, we show that the superhydrophobic surface can also be used to remove high-density polyethylene microplastics from water. A surface mechanism promoting the removal or microplastics is also proposed, considering the surface properties of the solid pollutants as well as the wetting properties of the superhydrophobic coating

Superhydrophobic and nanostructured CuFeCo powder alloy for the capture of microplastics

A superhydrophobic CuFeCo powder alloy, obtained by combining high-energy ball milling (HEBM) and liquid phase deposition (LPD), was used to remove high-density polyethylene fibres from water. After 48 h of HEBM, CuFeCo solid solution powder with ferromagnetic properties was obtained. High-resolution transmission electron microscopy showed a crystallite size of 20 nm, confirming its nanostructure. The metallic CuFeCo powder surface was functionalised with dodecanoic acid to confer superhydrophobicity (water contact angle = 162 ± 1°) and superoleophilicity (oil contact angle ~ 0°). Taking advantage of its superwettable properties, superhydrophobic CuFeCo particles were used to capture microplastics (270 μm < size < 1240 μm), which is an innovative application of superhydrophobic materials. This study demonstrates an innovative way of using superhydrophobic materials in environmental applications such as the removal of solid pollutants like microplastics

Superhydrophobic 304 Stainless Steel Mesh for the Removal of High-Density Polyethylene Microplastics

Microplastics are a global issue that affects the environment, economy, as well as human health. Herein, we present a superhydrophobic 304 stainless steel mesh obtained by chemical etching followed by a liquid-phase deposition of lauric acid that can be used for microplastic removal. Field emission scanning electron microscopy (FE-SEM) and high-resolution X-ray photoelectron spectroscopy (HR-XPS), among other techniques, were used to identify the hierarchical structure and chemical composition of the surface. They revealed that iron laurate decreased the surface free energy. The 304 stainless steel mesh was superhydrophobic (169°) and superoleophilic (0°). Taking advantage of these wetting properties, we showed an innovative use of these superhydrophobic surfaces in the removal of microplastics. Additionally, we analyzed the removal efficiency from a surface and colloidal point of view that allowed us to explain and clarify why microplastics can also be removed by their wetting properties. The loss of a double electrostatic cloud between the microplastics and the predominance of van der Waals interactions in the organic phase promote the removal of these persistent pollutants from water

Effect of the nanostructuring by high-pressure torsion process on the secondary phase precipitation in UNS S32750 Superduplex stainless steel

In this work, the precipitation and the morphology of secondary phases after severe plastic deformation (SPD) processing followed by an isothermal treatment was investigated. High-pressure torsion (HPT) was the SPD process carried out on superduplex 2507 (UNS S32750) stainless steel material under P = 6 GPa at room temperature. At this high strain levels (ε up to 170) samples have shown grain size decrease and strained microstructure with high dislocation density and nanostructure features. After a short isothermal treatment at 830 °C, the sigma phase and chromium nitrides were revealed as the main secondary phases identified by scanning and transmission electron microscopy and element analysis by energy dispersive spectroscopy. Scanning precession electron diffraction and automated crystal orientation mapping have been carried out in order to confirm the precipitation of the secondary phases. In fact, the results provide evidence that the precipitation of chromium nitrides seems to be the preferred nucleation site for sigma phase at higher deformation strain, in addition to the intergranular precipitation of sigma. Both the sigma phases nucleated integranularly and besides chromium nitrides are randomly orientated

Faktor Risiko Indeks Massa Tubuh (Imt), Usia Menarche, Paritas Dan Kontrasepsi Hormonal Terhadap Osteoarthritis Genu Pada Pasien Wanita Rumah Sakit Universitas Airlangga

Latar Belakang : Osteoarthritis (OA) merupakan penyakit degeneratif yang berkaitan dengan kartilago sendi dan pada umumnya terjadi di sendi lutut. Osteoarthritis (OA) banyak menyerang wanita daripada pria,hal ini dikarenakan oleh hormon estrogen. Riskesdas mencatat prevalensi terjadinya penyakit sendi di Jawa Timur sebesar 26,9%. Osteoarthritis (OA) menyebabkan Years of Life Disability pada wanita. Penelitian ini bertujuan untuk mencari hubungan Indeks Massa Tubuh (IMT), usia menarche, paritas dan pengguanan kontrasepsi hormonal terhadap Osteoarthritis (OA) genu di Rumah Sakit Universitas Airlangga Surabaya. Metode : Penelitian ini merupakan penelitian observasional analitik dengan pendekatan kasus kontrol (case control). Metode yang digunakan dalam penelitian ini adalah wawancara singkat dengan menggunakan kuesioner sebagai panduan wawancara. Jumlah sampel penelitian diambil dengan cara perhitungan rumus. Sampel yang dibutuhkan sebanyak 42 dari kelompok kasus atau Osteoarthritis(OA) dan 42 dari kelompok kontrol atau non-Osteoarthritis. Hasil : Karakterisitik kelompok kasus adalah usia 56-60 tahun (62,1%), Indeks Massa Tubuh 23-24,9 (58,7%), usia menarche 12-13 tahun (53,6%), paritas pada kelompok multipara (52,6%), penggunaan kontrasepsi hormonal pada kelompok dengan riwayat penggunaan pil (62,3%) mayoritas menggunakan pil kombinasi (60,5%) dengan durasi penggunaan rata-rata >1 tahun (56,8%). Kesimpulan :Adanya hubungan antara Indeks Massa Tubuh (IMT) dan Jenis penggunaan kontrasepsi hormonal terhadap Osteoarthrirtis (OA) genu pada pasien wanita di Rumah Sakit Universitas Airlangga Surabaya

Pengembangan Komik sebagai Media Layanan Informasi tentang Bahaya Narkoba untuk Siswa Kelas VII SMP Negeri 10 Probolinggo.

ABSTRAK   Febriyanti, Syella Alisiya. 2011. Pengembangan Komik sebagai Media Layanan Informasi tentang Bahaya Narkoba untuk Siswa Kelas VII SMP Negeri 10 Probolinggo. Skripsi, Jurusan Bimbingan Konseling dan Psikologi, Fakultas Ilmu Pendidikan, Universitas Negeri Malang. Pembimbing: (I) Dr. Blasius Boli Lasan, M.Pd., (II) Dra.Ella Faridati Zen, M.Pd.   Kata Kunci: komik, layanan informasi, bahaya narkoba.   Pencegahan penyalahgunaan narkoba di kalangan siswa Sekolah Menengah Pertama (SMP) dapat dilakukan dengan memberikan informasi tentang bahaya narkoba. Salah satu media yang dapat digunakan adalah komik. Komik sudah tidak asing lagi di kalangan siswa SMP karena siswa sudah terbiasa membaca komik dan sudah memahami komik. Oleh karena itu dilakukan penelitian dan pengembangan yang dapat mempermudah konselor dalam memberikan bimbingan informasi. Penelitian dan pengembangan yang dilaksanakan bertujuan untuk menghasilkan komik sebagai media layanan informasi tentang bahaya narkoba untuk siswa SMP. Penelitian ini merupakan penelitian pengembangan komik sebagai layanan informasi tentang bahaya narkoba yang mengadaptasi langkah-langkah pengembangan dari Borg and Gall (1983). Subyek uji coba adalah ahli bimbingan dan konseling, ahli media, dan calon pengguna produk. Data dikumpulkan menggunakan format penilaian ahli dan calon pengguna produk. Data kuantitatif dianalisis dengan analisis rerata, dan data kualitatif dianalisis dengan analisis deskriptif. Produk pengembangan ini telah dinilai oleh ahli dan calon pengguna produk. Secara kuantitatif, hasil penilaian keseluruhan dari para ahli dan calon pengguna produk untuk spesifikasi produk aspek ketepatan memperoleh nilai rerata 3,28; aspek kegunaan 3,25; aspek keterlaksanaan 3,08 dan kemenarikan 3,4.  Dengan demikian menurut para ahli dan calon pengguna produk, untuk spesifikasi produk dapat di interpretasikan sangat tepat, sangat berguna, sangat terlaksana dan sangat menarik serta dapat digunakan sebagai media pemberian informasi bahaya narkoba bagi siswa SMP. Berdasarkan hasil penilaian ahli dan calon pengguna produk, dapat disimpulkan produk yang dihasilkan dari pengembangan ini yang berupa komik sebagai layanan informasi tentang bahaya narkoba untuk siswa SMP dapat diterima (acceptable) secara teoritis. Hasil penilaian oleh uji kelompok kecil hasil pretest-posttest memperoleh nilai rata-rata keseluruhan 7,2 dan 8,7 yang berarti tingkat perubahan atau kemajuan siswa sangat tinggi setelah diberikan informasi bahaya narkoba. Dari hasil tersebut dapat disimpulkan bahwa komik sebagai layanan informasi tentang bahaya narkoba berterima secara praktis. Berdasarkan hasil penelitian tersebut, maka saran yang diberikan adalah konselor harus memahami prosedur dan materi bimbingan sehingga proses bimbingan dapat berjalan secara efektif dan siswa dapat mencapai tujuan bimbingan yang dikehendaki.  Saran bagi pengembang selanjutnya adalah hendaknya dilakukan uji lapangan utama dan dilakukan penelitian untuk mengetahui efektivitas komik sebagai layanan informasi tentang bahaya narkoba untuk siswa.

Peramalan Indeks Harga Saham Hang Seng (HSI) Berdasarkan Down Jones Industrial Average (DJIA) dengan Menggunakan Metode Fungsi Transfer

Permasalahan yang dihadapi oleh investor dalam dunia industri saham berkaitan dengan pengambilan keputusan yang dikaitkan dengan ketidakpastian faktor - faktor internal, eksternal, dan global. Salah satu indikator yang digunakan sebagai pegangan oleh para investor adalah indeks harga saham salah satunya Indeks Harga Saham Hang Seng. Pergerakan Indeks Harga Saham Hang Seng dipengaruhi oleh Down Jones Industrial Average (DJIA). Pada penelitian ini dapat menggunakan metode fungsi transfer untuk peramalan Indeks Harga Saham Hang Seng. Pola pergerakan pada harga penutupan Indeks Harga Saham Hang Seng pada tanggal 17 Maret 2020 sampai 31 Maret 2021 cenderung fluktuatif. Model fungsi transfer untuk peramalan Indeks Harga Saham Hang Seng (HSI) dengan orde nilai (b,r,s) adalah (1,0,0), sehingga model yang terbentuk adalah dan didapatkan hasil peramalan Indeks Harga Saham Hang Seng waktu ke t sama dengan 0,259 nilai Down Jones Industrial Average (DJIA) waktu (t-1). Nilai ramalan tertinggi sebesar $31150,27 terjadi pada tanggal 30 April 2021 dan harga terendah sebesar$ 30180,72 yang terjadi pada tanggal 1 April 2021. Akurasi untuk model fungsi transfer berdasarkan nilai MAPE sebesar 6,74. ================================================================================================= The investor problems in the stock industry are relation to make decision of the uncertainty of internal, external, and global factors. One of the indicators used as a guide by investors is the stock price index, which is the Hang Seng Stock Price Index. The movement of the Hang Seng Stock Price Index can be influenced by the Down Jones Industrial Average (DJIA). In this study, we use the transfer function method for forecasting the Hang Seng Stock Price Index (HSI). The movement pattern on the closing price of the Hang Seng Stock Price Index on March 17, 2020 to March 31, 2021 tends to fluctuate. Forecasting the HSI on DJIA by using transfer function method with the orde value of (b,r,s) is (1,0,0) so that the model is and HSI forecast at time t is 0,259 DJIA at time (t-1). The forecasting results have the highest price of $31150,27 in April 30, 2021 and the lowest price of$ 30180,72 on April 1, 2021. The accuracy for the transfer function model using MAPE is 6,7