Sputtered silicon nitride coatings for wear protection

Silicon nitride films were deposited by RF sputtering on 304 stainless steel substrates in a planar RF sputtering apparatus. The sputtering was performed from a Si3N4 target in a sputtering atmosphere of argon and nitrogen. The rate of deposition, the composition of the coatings, the surface microhardness and the adhesion of the coatings to the substrates were investigated as a function of the process parameters, such as: substrate target distance, fraction nitrogen in the sputtering atmosphere and sputtering pressure. Silicon rich coating was obtained for fraction nitrogen below 0.2. The rate of deposition decreases continuously with increasing fraction nitrogen and decreasing sputtering pressure. It was found that the adherence of the coatings improves with decreasing sputtering pressure, almost independently of their composition

Some properties of RF sputtered hafnium nitride coatings

Hafnium nitride coatings were deposited by reactive RF sputtering from a hafnium target in nitrogen and argon gas mixtures. The rate of deposition, composition, electrical resistivity and complex index of refraction were investigated as a function of target substrate distance and the fraction nitrogen, (fN2) in the sputtering atmosphere. The relative composition of the coatings is independent on fN2 for values above 0.1. The electric resistivity of the hafnium nitride films changes over 8 orders of magnitude when fN2 changes from 0.10 to 0.85. The index of refraction is almost constant at 2.8(1-0.3i) up to fN2 = 0.40 then decreases to 2.1(1 - 0.01i) for higher values of fN2

Fractional charge perspective on the band-gap in density-functional theory

The calculation of the band-gap by density-functional theory (DFT) methods is examined by considering the behavior of the energy as a function of number of electrons. It is found that the incorrect band-gap prediction with most approximate functionals originates mainly from errors in describing systems with fractional charges. Formulas for the energy derivatives with respect to number of electrons are derived which clarify the role of optimized effective potentials in prediction of the band-gap. Calculations with a recent functional that has much improved behavior for fractional charges give a good prediction of the energy gap and also $\epsilon_{{\rm homo}}\simeq-I$ for finite systems. Our results indicate it is possible, within DFT, to have a functional whose eigenvalues or derivatives accurately predict the band-gap

RF sputtered silicon and hafnium nitrides: Properties and adhesion to 440C stainless steel

Silicon nitride and hafnium nitride coatings were deposited by reactive RF sputtering on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. Depositions were at two background pressures, 8 and 20 mtorr, and at two different fractions (f) of nitrogen in argon, 0.25 and 0.60, for hafnium nitride and at f = 0.25 for silicon nitride. The coatings and the interface between the coating and substrates were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. A Knoop microhardness of 1650 + or - 100 kg/sq mm was measured for hafnium nitride and 3900 + or - 500 kg/sq mm for silicon nitride. The friction coefficients between a 440C rider and the coatings were measured under lubricated conditions. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C

Analisis Persebaran Polutan Karbon Monoksida dan Partikulat dari Kebakaran Hutan di Sumatera Selatan

Kebakaran hutan merupakan masalah serius yang dihadapi pada permasalahan pencemaran udara masa kini karena berperan sebagai sumber terbesar emisi CO. Wujud polutan dari kebakaran hutan pada umumnya dalam bentuk asap yang mengandung banyak partikulat. Sumatera Selatan memiliki kawasan hutan sebesar 4.222.484,9 ha. Besarnya luasan kawasan hutan di Sumatera Selatan berbanding lurus dengan besarnya potensi kebakaran hutan yang dapat terjadi. Jumlah titik api di Sumatera Selatan mengalami peningkatan sebesar 12% pada periode 2014-2015. Intesitas kebakaran hutan di Sumatera Selatan yang cukup tinggi memberikan perkiraan bahwa banyak dampak besar yang akan ditimbulkan. Gangguan kesetimbangan ekosistem, permasalahan kesehatan, sampai lumpuhnya aktivitas masyarakat adalah dampak yang diperkirakan akan timbul akibat kebakaran hutan. Selain itu, kebakaran hutan dapat menyebabkan gangguan terhadap wilayah lain yang jauh jaraknya dari area terbakar. Besarnya wilayah dan waktu jangkauan dampak dari kebakaran hutan sering tidak dapat diperkirakan karena terbatasnya informasi prediksi persebaran polutan dari kebakaran hutan. Suatu analisis persebaran polutan sangat diperlukan sebagai penyedia informasi prediksi dari besaran dampak yang ditimbulkan dari suatu area kebakaran hutan. Model persebaran ini dapat dijadikan sebagai acuan peringatan dini bagi daerah sekitar yang akan terkena dampak kebakaran hutan. Digunakan 2 jenis variabel penelitian yakni kecepatan angin dan jenis hutan. Data kecepatan angin yang digunakan adalah nilai rata-rata, maksimum, minimum dan modus dari data kecepatan angin periode 21 juli 2015 – 12 november 2015. Periode ini adalah periode penurunan kualitas udara kota Palembang akibat peristiwa kebakaran hutan sampai memasuki musim hujan. Jenis hutan yang dipakai sebagai variasi skenario, yaitu hutan alam primer dataran tinggi, hutan alam sekunder dataran rendah, hutan rakyat bambang lanang, hutan alam gambut sekunder. Pembagian jenis hutan ini berdasarkan data biomassa yang telah dihimpun sebelumnya pada tahun 2014. Jumlah total skenario yang disusun sebanyak 40 skenario sesuai variabel yang ditentukan. Analisis persebaran dan nilai konsentrasi dari polutan CO dan partikulat berdasarkan skenario yang disusun dengan menggunakan persamaan gauss plume. Validasi data menunjukkan bahwa hasil pemodelan dengan skenario kecepatan angin rata-rata yang paling mendekati nilai ISPU. Konsentrasi polutan yang sampai ke kota palembang dari sejumlah titik api kebakaran hutan adalah 2322,21 μg/m3 CO dan 245,62 μg/m3 PM10. Konsentrasi polutan yang sampai ke kota Palembang dari kebakaran hutan seluas 1 ha pada setiap titik api adalah 8,54 μg/m3 CO dan 0,9 μg/m3 PM10. Jarak terjaruh persebaran emisi CO dan PM10 sampai nilai ambang batas (10000 dan 150 ) telah terlewati adalah 120 km untuk emisi CO dan 200 km untuk emisi PM10

Effect of transient pinning on stability of drops sitting on an inclined plane

We report on new instabilities of the quasi-static equilibrium of water drops pinned by a hydrophobic inclined substrate. The contact line of a statically pinned drop exhibits three transitions of partial depinning: depinning of the advancing and receding parts of the contact line and depinning of the entire contact line leading to the drop's translational motion. We find a region of parameters where the classical Macdougall-Ockrent-Frenkel approach fails to estimate the critical volume of the statically pinned inclined drop

Lattice dynamics and vibrational spectra of the orthorhombic, tetragonal and cubic phases of methylammonium lead iodide

The hybrid halide perovskite CH3NH3PbI3 exhibits a complex structural behaviour, with successive transitions between orthorhombic, tetragonal and cubic polymorphs at ca. 165 K and 327 K. Herein we report first-principles lattice dynamics (phonon spectrum) for each phase of CH3NH3PbI3. The equilibrium structures compare well to solutions of temperature-dependent powder neutron diffraction. By following the normal modes we calculate infrared and Raman intensities of the vibrations, and compare them to the measurement of a single crystal where the Raman laser is controlled to avoid degradation of the sample. Despite a clear separation in energy between low frequency modes associated with the inorganic PbI3 network and high-frequency modes of the organic CH3NH3+ cation, significant coupling between them is found, which emphasises the interplay between molecular orientation and the corner-sharing octahedral networks in the structural transformations. Soft modes are found at the boundary of the Brillouin zone of the cubic phase, consistent with displacive instabilities and anharmonicity involving tilting of the PbI6 octahedra around room temperature.Comment: 9 pages, 4 figure

Posttransplant lymphoproliferative disorders in neuronal xenotransplanted macaques

Posttransplant lymphoproliferative disorders (PTLDs) are a heterogeneous group of lymphoid proliferations that occur in the setting of depressed T-cell function due to immunosuppressive therapy used following solid organ transplantation, hematopoietic stem cell transplantation, and also xenotransplantation. In the present study, 28 immunosuppressed parkinsonian Macaca fascicularis were intracerebrally injected with wild-type or CTLA4-Ig transgenic porcine xenografts to identify a suitable strategy to enable long-term cell survival, maturation, and differentiation. Nine of 28 (32%) immunosuppressed primates developed masses compatible with PTLD, located mainly in the gastrointestinal tract and/or nasal cavity. The masses were classified as monomorphic PTLD according to the World Health Organization classification. Immunohistochemistry and polymerase chain reaction (PCR) analyses revealed that the PTLDs were associated with macaca lymphocryptovirus as confirmed by double-labeling immunohistochemistry for CD20 and Epstein-Barr nuclear antigen 2 (EBNA-2), where the viral protein was located within the CD20+ neoplastic B cells. In sera from 3 distinct phases of the experimental life of the primates, testing by quantitative PCR revealed a progression of the viral load that paralleled the PTLD progression and no evidence of zoonotic transmission of porcine lymphotropic herpesvirus through xenoneuronal grafts. These data suggest that monitoring the variation of macaca lymphocryptovirus DNA in primates could be used as a possible early diagnostic tool for PTLD progression, allowing preemptive treatment such as immunosuppression therapy reduction