Effect of Atomization Parameters on Size and Morphology of Al-17Si Alloy Powder Produced by Free Fall Atomizer

Abstract: In the present work the effect of process parameters on the characteristics of Al-17Si alloy powder produced by gas atomization using a free fall nozzle of different apex angles. The axial gas velocity away from the nozzle exit is measured for different operating pressures. The alloy was melted to a superheat temperature of 100, 150 and 200°C and atomized by varying the gas flow rate and melt flow rate. The powder produced during gas atomization process generally exhibits a wide size distribution. ASTM standard sieve with vibratory shaker is used for powder analysis. The characterization of powder particles was accomplished by the parameters such as mass median, average size of powder particles; standard deviation and morphology of powder were studied by scanning electron microscopy. It is observed that decrease of apex angle results in axial velocity decreases in entire applied gas pressures range. Increase in apex angle results in decrease of gas jet length to metal stream collision, the median particle diameter of the powder increases resulting in decrease in particle irregularity. The median particle diameter of the powder has been shown to decrease almost linearly with increase in gas to melt flow (G/M) ratio. The sauter mean diameter variation, however, decreases slowly with increase in G/M ratio. Median particle diameter is significantly reduced with increase in the melt superheat

A Comparative Study on Microstructure and Tensile Properties of Spray Formed and Ascast Al-28Si-5Cu-4Fe and Al-28Si-5Cu-4Mg Alloys

In the present study, Al-28Si, Al-28Si-5Cu-4Fe and Al-28Si-5Cu-4Mg alloys were produced by spray forming and subsequently hot pressed for densification. The effect of alloy composition on the microstructure and mechanical behavior of spray-formed alloys were investigated. The microstructures consist of an equiaxed, nearly spheroidized grain morphology of α-Al matrix. The spray formed alloys exhibited sharply decreased segregation and increased metastable solid solubility and greater volume fraction of Si particles and intermetallic phases. Spray formed Al-28Si-5Cu-4Fe alloy contains Al 2 Cu, Al 5 FeSi along with Si. On the other hand, Al-28Si-5Cu-4Mg alloy showed Al 2 Cu, Al 48 Si 29 Mg 18 and Si. Hot pressing lead to a significant reduction of porosity and partial recrystallization of spray formed alloys. The room temperature tensile tests of spray formed hot pressed alloys showed significant increase in ultimate tensile strength compared to as cast alloys. Spray formed hot pressed Al-28Si-5Cu-4Fe alloy exhibited superior ultimate tensile strength and significant increase in elongation to fracture. This may be attributed to the presence of homogeneous distribution of fine Si particles, high content of short needle-like β-Al 5 FeSi intermetallic and precipitation strengthening phases

Microstructures and Mechanical properties of Spray deposited and Heat-treated Al-25Mg2 Si-2Cu alloy

The microstructural characteristics and  mechanical properties of Al–25Mg2Si-2Cu alloy were investigated. The alloy produced by spray atomization and deposition techniques followed by hot compression(HC) and age hardening(AGH) at 180ºC for 2h and 2h  intervals after the solution heat treatment. The microstructure features of as cast, spray deposited (SD),hot compressed and heat-treated alloys were studied. the results show the microstructure of spray-deposited alloy mainly comprised of a uniform distribution of   intermettalics   ?-Mg2Si phase, ?- Al2Cu and Q phase in Al-matrix. Eliminating the porosity of deposit and fragmentation of the ? And Q phases is the main features during hot compression. After solution treating and age hardening, the microstructure found to be comprised of mainly Mg2Si phase in a fine spherical form. Large quantity of ?- Al2Cu phase and Q Phase less than 50 nm in size uniformly distributed in the Al- matrix during aging. These fine ? particles combined with the ? can significantly increase the tensile strength and hardness of the alloy. In the peak-aged condition is because of high concentration of Mg2Si and Al2Cu metastable phases. The microstructural features of alloys been investigated through Optical (OM) and Scanning electron microscopy (SEM) and analyses of phases were carried out using Energy dispersive X-ray( EDS).The improvement in the tensile and hardness properties of studied alloys was investigated by tensile test and  micro- hardness.Keywords: Al-Mg2Si alloy, Spray deposition, Age hardening, Microstructure, Mechanical properties, Micro hardness

Wear behavior of secondary processed spray formed Al-28Si-5Cu-4Mg alloy

In the present study Al-28Si-5Cu-4Mg alloy has been spray formed and hot pressed for densification. Hot pressing refined the microstructure and reduced the porosity in the spray formed alloy from 10 to 1%. The microstructure of spray formed and hot pressed alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary and eutectic Si with fine needles of Q-Al 12 Si 7 Mg 4 Fe intermetallics and Chinese script like θ- Al 2 Cu precipitates in α-Al matrix. The size of Si particles ranged from 3–10 µm. In contrast the microstructure of as-cast alloy consisted of coarse primary and eutectic Si, long needles of Q-Al-Si-Mg-Cu-Fe phase and bright grey θ-Al 2 Cu phase in the α-Al matrix. The size of primary Si varied from 30–250 µm. The spray formed and hot pressed alloy exhibited a higher hardness compared to the as-cast alloy. The wear behavior of both the alloys, under dry sliding conditions, showed an increase in the wear rate with an increase in the load. However, the spray formed and hot pressed alloy exhibited maximum wear resistance and minimum coefficient of friction, while as-cast alloy exhibited minimum wear resistance and maximum coefficient of friction over the entire range of applied load. The high wear resistance and high hardness of spray formed and hot pressed alloy are explained in the light of its microstructural modifications induced during spray forming and subsequent hot pressing and also the topographical features of worn surfaces and morphology of debris particles

Effect of Cu and Mg on the wear properties of spray formed Al -22Si alloy

In the present study, the effect of Cu and Mg on the wear behavior of spray formed Al-22Si alloy has been investigated and the same has been compared with that of its counterpart as-cast alloy. Al-22Si and Al–22Si–4Cu–1.7Mg alloys prepared by spray deposition process were hot pressed to reduce the porosity. The microstructures were examined by optical and scanning electron microscopes. The microstructure of spray formed Al-22Si alloy is fine and homogeneous and primary silicon phase distributed in the aluminum matrix evenly are fine and faceted having a mean size of 12 µm. The microstructure of spray formed Al–22Si–4Cu–1.7Mg alloy exhibited equiaxed grain morphology with fine and uniform distribution of both primary and eutectic Si with fine Q-Al-Si-Mg-Cu phase and θ-Al 2 Cu precipitates dispersed evenly in α- Al matrix. In contrast the microstructure of as-cast Al–22Si alloy consisted of coarse plates of primary Si of size 350 µm and eutectic Si needles. The as-cast Al–22Si–4Cu–1.7Mg alloy consisted of coarse primary Si with Chinese script like θ-Al 2 Cu precipitates and needles of Q-Al- Si-Mg-Cu phase in α-Al matrix. The wear study of both as-cast and spray formed and hot pressed alloys under an applied load of 10 to 50 N and sliding velocity of 0.4 to1.5 ms -1 indicated two distinct regimes of mild and severe wear. In both the regimes, the spray-formed and hot pressed alloys consistently indicated a low wear rate compared to that of as-cast alloys. The high wear resistance of spray formed and hot pressed Al–22Si and Al–22Si–4Cu–1.7Mg alloys were explained in the light of their microstructural modifications induced during spray forming and subsequent hot pressing

Microstructural and Hardness of Spray Deposited Al-30Mg 2 Si-2Cu Alloy in Solutionized and Aged Conditions

An Al–30Mg 2 Si- 2Cu alloy was produced by spray casting and the secondary processing such as hot compression and heat treatment were carried out. The coarsening behavior, distribution and size of the Mg 2 Si precipitates, the influence of subsequent heat treatment on the microstructure were investigated Uniform distribution of Mg 2 Si was achieved by spray casting. The hardness tests were conducted on spray deposited, secondary processed and heat treated alloys. The results indicate that spray casting has strong influence on microstructure and hardness of the material. The microstructural refinement of the alloy was enhanced during hot compression. The alloying with copper lead to further increase in strength by age hardening due to precipitation Al 2 Cu phase. A significant improvement in hardness was observed after hot compression and heat treatment

Plume detection and emission estimate for biomass burning plumes from TROPOMI carbon monoxide observations using APE v1.1

This paper presents the automated plume detection and emission estimation algorithm (APE), developed to detect CO plumes from isolated biomass burning events and to quantify the corresponding CO emission rate. APE uses the CO product of the Tropospheric Monitoring Instrument (TROPOMI) on board the Copernicus Sentinel-5 Precursor (S5P) satellite, launched in 2017, and collocated active fire data from the Visible Infrared Imaging Radiometer Suite (VIIRS), the latter flying 3 min ahead of S5P. After identifying appropriate fire events using VIIRS data, an automated plume detection algorithm based on traditional image processing algorithms selects plumes for further data interpretation. The approach is based on thresholds optimized for data over the United States in September 2020. Subsequently, the CO emission rate is estimated using the cross-sectional flux method, which requires horizontal wind fields at the plume height. Three different plume heights were considered, and the ECMWF Reanalysis v5 (ERA5) data were used to compute emissions. A varying plume height in the downwind direction based on three-dimensional Lagrangian simulation was considered appropriate. APE is verified for observations over Australia and Siberia. For all fire sources identified by VIIRS, only 16 % of the data corresponded to clear-sky TROPOMI CO data with plume signature. Furthermore, the quality filters of APE resulted in emission estimations for 26 % of the TROPOMI CO data with plume signatures. Visual filtering of the APE's output showed a true-positive confidence level of 97.7 %. Finally, we provide an estimate of the emission uncertainties. The greatest contribution of error comes from the uncertainty in Global Fire Assimilation System (GFAS) injection height that leads to emission errors &lt;100 %, followed by systematic errors in the ERA5 wind data. The assumption of constant emission during plume formation and spatial under-sampling of CO column concentration by TROPOMI yields an error of &lt;20 %. The randomized errors from the ensemble ERA5 wind data are found to be less than 20 % for 97 % of the cases.</p

Data quality monitoring and performance metrics of a prospective, population-based observational study of maternal and newborn health in low resource settings

BACKGROUND: To describe quantitative data quality monitoring and performance metrics adopted by the Global Network´s (GN) Maternal Newborn Health Registry (MNHR), a maternal and perinatal population-based registry (MPPBR) based in low and middle income countries (LMICs). METHODS: Ongoing prospective, population-based data on all pregnancy outcomes within defined geographical locations participating in the GN have been collected since 2008. Data quality metrics were defined and are implemented at the cluster, site and the central level to ensure data quality. Quantitative performance metrics are described for data collected between 2010 and 2013. RESULTS: Delivery outcome rates over 95% illustrate that all sites are successful in following patients from pregnancy through delivery. Examples of specific performance metric reports illustrate how both the metrics and reporting process are used to identify cluster-level and site-level quality issues and illustrate how those metrics track over time. Other summary reports (e.g. the increasing proportion of measured birth weight compared to estimated and missing birth weight) illustrate how a site has improved quality over time. CONCLUSION: High quality MPPBRs such as the MNHR provide key information on pregnancy outcomes to local and international health officials where civil registration systems are lacking. The MNHR has measures in place to monitor data collection procedures and improve the quality of data collected. Sites have increasingly achieved acceptable values of performance metrics over time, indicating improvements in data quality, but the quality control program must continue to evolve to optimize the use of the MNHR to assess the impact of community interventions in research protocols in pregnancy and perinatal health.Fil: Goudar, Shivaprasad S.. KLE University. Jawaharlal Nehru Medical College; IndiaFil: Stolka, Kristen B.. Research Triangle Institute International; Estados UnidosFil: Koso Thomas, Marion. Eunice Kennedy Shriver National Institute of Child Health and Human Development; Estados UnidosFil: Honnungar, Narayan V.. KLE University. Jawaharlal Nehru Medical College; IndiaFil: Mastiholi, Shivanand C.. KLE University. Jawaharlal Nehru Medical College; IndiaFil: Ramadurg, Umesh Y.. S. Nijalingappa Medical College; IndiaFil: Dhaded, Sangappa M.. KLE University. Jawaharlal Nehru Medical College; IndiaFil: Pasha, Omrana. Aga Khan University; PakistánFil: Patel, Archana. Indira Gandhi Government Medical College and Lata Medical Research Foundation; IndiaFil: Esamai, Fabian. University School of Medicine; KeniaFil: Chomba, Elwyn. University of Zambia; ZambiaFil: Garces, Ana. Universidad de San Carlos; GuatemalaFil: Althabe, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Efectividad Clínica y Sanitaria; ArgentinaFil: Carlo, Waldemar A.. University of Alabama at Birmingahm; Estados UnidosFil: Goldenberg, Robert L.. Columbia University; Estados UnidosFil: Hibberd, Patricia L.. Massachusetts General Hospital for Children; Estados UnidosFil: Liechty, Edward A.. Indiana University; Estados UnidosFil: Krebs, Nancy F.. University of Colorado School of Medicine; Estados UnidosFil: Hambidge, Michael K.. University of Colorado School of Medicine; Estados UnidosFil: Moore, Janet L.. Research Triangle Institute International; Estados UnidosFil: Wallace, Dennis D.. Research Triangle Institute International; Estados UnidosFil: Derman, Richard J. Christiana Care Health Services; Estados UnidosFil: Bhalachandra, Kodkany S.. KLE University. Jawaharlal Nehru Medical College; IndiaFil: Bose, Carl L.. University of North Carolina; Estados Unido

Pentastatin-1, a collagen IV derived 20-mer peptide, suppresses tumor growth in a small cell lung cancer xenograft model

<p>Abstract</p> <p>Background</p> <p>Angiogenesis is the formation of neovasculature from a pre-existing vascular network. Progression of solid tumors including lung cancer is angiogenesis-dependent. We previously introduced a bioinformatics-based methodology to identify endogenous anti-angiogenic peptide sequences, and validated these predictions <it>in vitro </it>in human umbilical vein endothelial cell (HUVEC) proliferation and migration assays.</p> <p>Methods</p> <p>One family of peptides with high activity is derived from the α-fibrils of type IV collagen. Based on the results from the <it>in vitro </it>screening, we have evaluated the ability of a 20 amino acid peptide derived from the α5 fibril of type IV collagen, pentastatin-1, to suppress vessel growth in an angioreactor-based directed <it>in vivo </it>angiogenesis assay (DIVAA). In addition, pentastatin-1 suppressed tumor growth with intraperitoneal peptide administration in a small cell lung cancer (SCLC) xenograft model in nude mice using the NCI-H82 human cancer cell line.</p> <p>Results</p> <p>Pentastatin-1 decreased the invasion of vessels into angioreactors <it>in vivo </it>in a dose dependent manner. The peptide also decreased the rate of tumor growth and microvascular density <it>in vivo </it>in a small cell lung cancer xenograft model.</p> <p>Conclusions</p> <p>The peptide treatment significantly decreased the invasion of microvessels in angioreactors and the rate of tumor growth in the xenograft model, indicating potential treatment for angiogenesis-dependent disease, and for translational development as a therapeutic agent for lung cancer.</p