scholarly journals The Influence of Thermal Dilution on the Microstructure Evolution of Some Combustion-Synthesized Refractory Ceramic Composites

Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 59
Author(s):  
Sofiya Aydinyan ◽  
Suren Kharatyan ◽  
Irina Hussainova
Keyword(s):  
Combustion Temperature ◽  
Heterogeneous Media ◽  
Combustion Process ◽  
Combustion Products ◽  
Ceramic Composites ◽  
High Yield ◽  
High Temperature Synthesis ◽  
High Level ◽  
Refractory Ceramics ◽  
Thermal Dilution

Modeling the self-sustained high-temperature synthesis (SHS) reaction via thermal dilution and transformation of the reaction heterogeneous media into a moderate exothermic one has unlimited potential for designing inorganic powders of a certain morphology beneficial for advanced consolidation. Thermal/inert dilution of the high-exothermic mixtures leads to the fluent decrease of both the combustion temperature and velocity, thus allowing to tailor the thermal regime of the combustion process, therewith contributing to high yield of reaction and governing the microstructural features of the combustion products. In the current review, we shed on light on the possibilities of this effective strategy to control the thermal behavior of the SHS process for the preparation of applicable powder precursors for the subsequent successful sintering. Since the SHS process of some refractory ceramics (MoSi2, TiB2, TiC, etc.) involves a relatively violent reaction rate and high combustion temperature, achieving a high level of microstructure control in these systems is often challenging. The challenge was tackled with a thermal dilution approach, attaining considerable enhancement in the homogeneity among phases with an increase of diluent content along with microstructure refinement.

Study on Preparation of Ti Powder by Self-Propagating High-Temperature Synthesis (SHS) with Magnesiothermit Reductive Process

2008 ◽  
Vol 575-578 ◽  
pp. 1086-1092
Author(s):  
Peng Lin Zhang ◽  
Tian Dong Xia ◽  
Guo Dong Zhang ◽  
Li Jing Yan
Keyword(s):  
Reaction Rate ◽  
Combustion Temperature ◽  
Combustion Process ◽  
Green Compact ◽  
Reaction Products ◽  
Technological Parameters ◽  
Solid Reaction ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Ti Powder

The combustion process of Mg-TiO2 system was preliminarily investigated from three aspects of thermodynamics, reaction kinetics and the technological parameters. The result indicates that the adiabatic temperature of Mg-TiO2 system is between 2060K and 2140K because the major existent modalities of TiO2 is the rutile and anatase, this meets the empirical criterion that the SHS reaction will be self-sustaining; The solid-solid reaction occurs at about 767K; Ti powders can be produced only when the ratio between Mg and TiO2 arrives at 2.9:1; The higher the vacuum, the more complete the reaction; The combustion temperature arrives at its peak when the pressure of green compact arrives at 250MPa; the velocity of the combustion wave increases with the augmentation of the pressure of green compact. So the proper control of the technological parameters can change the reaction temperature, reaction rate and the components of reaction products.

Self-propagating high-temperature synthesis of nano-sized titanium carbide powder

2002 ◽  
Vol 17 (11) ◽  
pp. 2859-2864 ◽  
Author(s):  
H. H. Nersisyan ◽  
J. H. Lee ◽  
C. W. Won
Keyword(s):  
Sodium Chloride ◽  
Titanium Carbide ◽  
Combustion Temperature ◽  
Combustion Process ◽  
Carbide Powder ◽  
Primary Carbide ◽  
Temperature Synthesis ◽  
Ultrafine Structure ◽  
High Temperature Synthesis ◽  
Carbon System

The combustion process of a titanium–carbon system with sodium chloride as an inert diluent was investigated. The combustion laws and microstructure of final products according to diluent content were obtained. It was shown that sodium chloride not only decreases combustion temperature but also makes effective protective shells around primary carbide crystals and keeps this ultrafine structure up to the end of combustion. As a result, nano-sized titanium carbide powders were successfully obtained.

scholarly journals Modelling of the formulated solid rocket propellant characteristics

2021 ◽  
Vol 6 (2) ◽  
pp. 061-073
Author(s):  
Oyedeko K.F.K ◽  
Egwenu S. O.
Keyword(s):  
Mathematical Model ◽  
Combustion Temperature ◽  
Specific Impulse ◽  
Combustion Process ◽  
General Rule ◽  
Combustion Products ◽  
Potassium Nitrate ◽  
Chamber Pressure ◽  
Performance Parameters ◽  
Solid Rocket

This study is a mathematical model to obtain the characteristics performance of magnesium metal (powder) and carbon on a potassium nitrate-sucrose (KNSU) solid propellant formulation. Characterization of propellant is, as a general rule, important to determine its performance before it can be suitable for use for a rocket flight or any mission. Method of ballistic load cell evaluation was used to validate results and a mathematical model using the combustion exhaust products was solved to obtain the characteristics performance parameters of the propellant. The carbon constituent which acts as an opacifier and coolant was kept constant at 2% in order to arrest some of the heat during the combustion process and helped to lower the combustion temperature, because high combustion temperature could lead to combustion chamber rupture or failure. The effect of addition of magnesium which was optimized for 3% in the formulation contributed significantly in improving the overall performance of the propellant. The utilization of magnesium in KNSU propellant provided higher values parameters and better performance compared to when not included. This was confirmed with the model equations. The propellant combustion products equation was used to model and obtain the characteristics performance parameters. This gave propellant specific impulse (122.9s), combustion temperature (1821K), heat ratio (1.1592), molecular weight (36.89g/mole), propellant density (1912.5kg/m3) and characteristics velocity (1000m/s) result while maintaining the same chamber pressure.

scholarly journals Effect of magnesium metal in the characteristics performance of a sucrose-based solid rocket propellant

2021 ◽  
Vol 6 (2) ◽  
pp. 051-060
Author(s):  
Oyedeko K.F.K ◽  
Egwenu S. O
Keyword(s):  
Air Pollution ◽  
Magnesium Oxide ◽  
Combustion Temperature ◽  
Specific Impulse ◽  
Research Work ◽  
Combustion Process ◽  
Combustion Products ◽  
Potassium Nitrate ◽  
Magnesium Metal ◽  
Propellant Performance

This research work aimed at investigating the effects of magnesium metal (powder) and carbon on a potassium nitrate-sucrose (KNSU) solid propellant formulation. Characterization of propellant is very important to determine its performance before it can be suitable for use for a rocket flight or any mission. Ballistic loadcell method was used. The ballistic load cell instrumentation measured the thrust generated by the propellant, the propellant burn time and the exit temperature of the burning hot propellant gases. The carbon constituent which acts as an opacifier and coolant was kept constant at 2% in order to arrest some of the heat during the combustion process and helped to lower the combustion temperature, because high combustion temperature could lead to combustion chamber rupture or failure. Also, carbon was not increased beyond 2%, so as not to make the propellant excessively smoky because of presence of magnesium oxide and other solids in the combustion products that can cause air pollution, and could be harmful to human lives and the environment. The propellant specific impulse (117.9s), combustion temperature (1818K), heat ratio (1.1508), propellant molecular weight (38.88g/mole), propellant density (1874.6kg/m3), characteristics velocity (997.2m/s) and burn rate (0.00906m/s) were obtained. The effect of addition of magnesium which was optimized for 3% in the formulation contributed significantly in improving the overall performance of the propellant as parameters such as the specific impulse, chamber temperature, characteristics velocity and heat ratio were found to have higher values as compare to the KNSU propellant when magnesium was not present in the formulation. Basically, higher values of these parameters suggest better propellant performance. Also, in this case, when carbon was increased beyond 2%, the propellant was excessively smoky because of presence of magnesium oxide and other solids in the combustion products that can cause air pollution, and could be harmful to human lives and the environment.

scholarly journals Effects of Catalysts on Emissions of Pollutants from Combustion Processes of Liquid Fuels

2014 ◽  
Vol 13 (2) ◽  
pp. 5-17
Author(s):  
Agnieszka Bok ◽  
Joanna Guziałowska-Tic ◽  
Wilhelm Jan Tic
Keyword(s):  
Combustion Process ◽  
Combustion Products ◽  
Organometallic Complexes ◽  
Liquid Fuels ◽  
Motor Fuels ◽  
Harmful Emissions ◽  
Fuel Oils ◽  
Sulphur Oxides ◽  
Dynamic Growth ◽  
Combustion Processes

Abstract The dynamic growth of the use of non-renewable fuels for energy purposes results in demand for catalysts to improve their combustion process. The paper describes catalysts used mainly in the processes of combustion of motor fuels and fuel oils. These catalysts make it possible to raise the efficiency of oxidation processes simultanously reducing the emission of pollutants. The key to success is the selection of catalyst compounds that will reduce harmful emissions of combustion products into the atmosphere. Catalysts are introduced into the combustion zone in form of solutions miscible with fuel or with air supplied to the combustion process. The following compounds soluble in fuel are inclused in the composition of the described catalysts: organometallic complexes, manganese compounds, salts originated from organic acids, ferrocen and its derivatives and sodium chloride and magnesium chloride responsible for burning the soot (chlorides). The priority is to minimize emissions of volatile organic compounds, nitrogen oxides, sulphur oxides, and carbon monoxide, as well as particulate matter.

scholarly journals Multi-curie production of gallium-68 on a biomedical cyclotron and automated radiolabelling of PSMA-11 and DOTATATE

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Helge Thisgaard ◽  
Joel Kumlin ◽  
Niels Langkjær ◽  
Jansen Chua ◽  
Brian Hook ◽  
...  
Keyword(s):  
Radiochemical Purity ◽  
High Yield ◽  
Clinical Use ◽  
Automated Production ◽  
Automated Method ◽  
Gallium 68 ◽  
High Yields ◽  
High Level ◽  
Mev Protons ◽  
Very High

Abstract Background With increasing clinical demand for gallium-68, commercial germanium-68/gallium-68 ([68Ge]Ge/[68Ga]Ga) generators are incapable of supplying sufficient amounts of the short-lived daughter isotope. In this study, we demonstrate a high-yield, automated method for producing multi-Curie levels of [68Ga]GaCl3 from solid zinc-68 targets and subsequent labelling to produce clinical-grade [68Ga]Ga-PSMA-11 and [68Ga]Ga-DOTATATE. Results Enriched zinc-68 targets were irradiated at up to 80 µA with 13 MeV protons for 120 min; repeatedly producing up to 194 GBq (5.24 Ci) of purified gallium-68 in the form of [68Ga]GaCl3 at the end of purification (EOP) from an expected > 370 GBq (> 10 Ci) at end of bombardment. A fully automated dissolution/separation process was completed in 35 min. Isolated product was analysed according to the Ph. Eur. monograph for accelerator produced [68Ga]GaCl3 and found to comply with all specifications. In every instance, the radiochemical purity exceeded 99.9% and importantly, the radionuclidic purity was sufficient to allow for a shelf-life of up to 7 h based on this metric alone. Fully automated production of up to 72.2 GBq [68Ga]Ga-PSMA-11 was performed, providing a product with high radiochemical purity (> 98.2%) and very high apparent molar activities of up to 722 MBq/nmol. Further, manual radiolabelling of up to 3.2 GBq DOTATATE was performed in high yields (> 95%) and with apparent molar activities (9–25 MBq/nmol) sufficient for clinical use. Conclusions We have developed a high-yielding, automated method for the production of very high amounts of [68Ga]GaCl3, sufficient to supply proximal radiopharmacies. The reported method led to record-high purified gallium-68 activities (194 GBq at end of purification) and subsequent labelling of PSMA-11 and DOTATATE. The process was highly automated from irradiation through to formulation of the product, and as such comprised a high level of radiation protection. The quality control results obtained for both [68Ga]GaCl3 for radiolabelling and [68Ga]Ga-PSMA-11 are promising for clinical use.

708 A NEW DIAGNOSTIC PARADIGM FOR LARYNGOPHARYNGEAL REFLUX DISEASE: CORRELATION OF IMPEDANCE-PH MONITORING AND DIGITAL REFLUX SCINTIGRAPHY RESULTS

2021 ◽  
Vol 34 (Supplement_1) ◽  
Author(s):  
Jin-soo Park ◽  
Oleksandr Khoma ◽  
Hans Van Der Wall ◽  
Gregory Falk
Keyword(s):  
Laryngopharyngeal Reflux ◽  
Ph Monitoring ◽  
Acid Reflux ◽  
High Rate ◽  
High Yield ◽  
Time Activity ◽  
Proximal Esophagus ◽  
Laryngopharyngeal Reflux Disease ◽  
High Level ◽  
No Gold Standard

Abstract   No gold-standard investigation exists for laryngopharyngeal reflux (LPR). Multichannel intraluminal impedance (MII)-pH testing has uncertain utility in LPR. Meanwhile, reflux scintigraphy allows immediate and delayed visualisation of tracer reflux in the esophagus, pharynx, and lungs. The present study aimed to correlate MII-pH and scintigraphic reflux results in patients with primary LPR. Methods Consecutive patients with LPR underwent MII-pH and scintigraphic reflux studies. Abnormal values for MII-pH results were defined from existing literature. MII-pH and scintigraphic data were correlated. Results 105 patients with LPR (31 males (29.5%), median age 60 years (range: 20–87)) were studied. Scintigraphic reflux was seen in the pharynx in 94 (90.4%), and in the proximal esophagus in 94 (90.4%). Delayed scintigraphic contamination of the pharynx was seen in 101 patients (96.2%) and in the lungs of 56 patients (53.3%). Abnormal reflux was seen in the distal esophagus in 12.4%, proximal esophagus in 25.7%, and in the pharynx in 82.9%. Patients with poor scintigraphic clearance had higher Demeester scores (p = 0.043), more proximal reflux episodes (p = 0.046), more distal acid reflux episodes (p = 0.023), and longer bolus clearance times (p = 0.002). Conclusion Reflux scintigraphy has a high yield in LPR patients. Scintigraphic time-activity curves correlated with validated MII-pH results. A high rate of pulmonary microaspiration was found in LPR patients. This study demonstrated a high level of pharyngeal contamination by scintigraphy and MII-pH, which supports the use of digital reflux scintigraphy in diagnosing LPR.

SPECTRAL DIAGNOSTICS OF THE HYDROCARBON FUEL COMBUSTION PROCESS

2021 ◽  
pp. 12-17
Author(s):  
M. A. Vaganov
Keyword(s):  
Combustion Process ◽  
Hydrocarbon Fuel ◽  
Combustion Products ◽  
Combustible Mixture ◽  
Fuel Combustion ◽  
Propane Combustion ◽  
Gaseous Hydrocarbon ◽  
Spectral Bands ◽  
Air Supply ◽  
Spectral Diagnostics

It is proposed to use the methods of applied optical spectroscopy to solve the problem of control and diagnostics of gaseous hydrocarbon fuel combustion in this work. The results of an experimental study of spectroscopic informative parameters characterizing the propane combustion process are presented for three modes: combustion of pure propane without air supply, stoichiometric combustion and combustion with a change in the amount of supplied air relative to stoichiometric combustion. As a result of the experiment, it was found that the most intense bands in the emission spectrum of the flame arising from the combustion of propane correspond to the spectral bands of radicals of combustion products: OH, CH, and C2. While the intensities of various systems of bands in the flame spectrum depend significantly on the composition of the combustible mixture.

scholarly journals Monitoring the effects of exposure to lead and cadmium in working and living environment through standard biochemical blood parameters and liver endonucleases activity

2011 ◽  
Vol 65 (4) ◽  
pp. 403-409 ◽  
Author(s):  
Ruzica Nikolic ◽  
Jasmina Jovanovic ◽  
Gordana Kocic ◽  
Tatjana Cvetkovic ◽  
Svetlana Stojanovic ◽  
...  
Keyword(s):  
Liver Enzymes ◽  
Harmful Effect ◽  
Toxic Metal ◽  
Combustion Products ◽  
Blood Parameters ◽  
Living Environment ◽  
The Body ◽  
Lead Contamination ◽  
Lead And Cadmium ◽  
High Level

Heavy metals as pollutants in the working and living environment are a serious health and environmental problem because they are toxic, non-biodegradable, accumulate in living systems and have a long half-life in soil. Sources of lead contamination are combustion products in the chemical industry and metallurgy, industrial waste water, landfills, traffic etc. Lead enters into the body via the food chain and drinking water. In the body lead is deposited in the liver, kidneys, brain and mineral tissues. Excretion of lead causes damage to the epithelial cells of certain organs. High level exposure to cadmium is usually the result of environmental pollution by human activities. Exposure to cadmium can lead to acute and chronic tissue damage of various organs, including liver and kidneys in humans and in animals. In this paper we analyzed the effects of lead and cadmium exposure, in working and living environment, on the model system of experimental animals, particularly the activity of certain liver enzymes, acid and alkaline DNase, and standard biochemical blood parameters. The study showed that lead and cadmium significantly affect the protein content, red blood cells, hemoglobin and hematocrit, and the activity of liver enzymes. This harmful effect of this toxic metal can be reduced by the supplements.

scholarly journals Energy-saving biomass stove

2014 ◽  
Vol 6 (2) ◽  
pp. 115-119
Author(s):  
Tri Hoang
Keyword(s):  
Energy Saving ◽  
Rice Husk ◽  
Flue Gas ◽  
Particle Concentration ◽  
Combustion Process ◽  
Combustion Products ◽  
Raw Material ◽  
Gas Emission ◽  
Biomass Stove ◽  
Residual Oxygen

This paper introduces an energy-saving biomass stove. The principle of energy-saving biomass stove is gasification. It is a chemical process, transforms solid fuel into a gas mixture, called (CO + H2 + CH4) gas. Emission lines in the stove chimneys typically remain high temperatures around 90° to 120°C. The composition of the flue gas consists of combustion products of rice husk which are mainly CO2, CO, N2. A little volatile in the rice husk, which could not burn completely, residual oxygen and dust will fly in airflow. The amount of dust in the outlet gas is a combination of un-burnt amount of impurity and firewood, usually occupied impurity rate of 1 % by weight of dry husk. Outlet dust of rice husk furnace has a normal size from 500μm to 0.1 micron and a particle concentration ranges from 200-500 mg/m3. Gas emissions is created when using energy-saving stove and they will be used as the main raw material in combustion process Therefore the CO2 emission into the environment when using the stove will be reduced up to 95% of a commonly used stove. Bài báo giới thiệu một bếp tiết kiệm dùng năng lượng sinh khối. Bếp tiết kiệm năng lượng thực hiện nguyên lý khí hóa sinh khối. Đó là một quá trình hóa học, chuyển hóa các loại nhiên liệu dạng rắn thành một dạng hỗn hợp khí đốt, gọi là khí Gas (CO + H2 + CH4). Dòng khí thải ra ở ống khói của bếp thông thường có nhiệt độ vẫn còn cao khoảng 90° ~ 120°C. Thành phần của khói thải bao gồm các sản phẩm cháy của trấu, chủ yếu là các khí CO2, CO, N2, một ít các chất bốc trong trấu không kịp cháy hết, oxy dư và tro bụi bay theo dòng khí. Lượng bụi tro có trong khói thải chính là một phần của lượng không cháy hết và lượng tạp chất không cháy có trong củi, lượng tạp chất này thường chiếm tỷ lệ 1% trọng lượng trấu khô. Bụi trong khói thải lò đốt trấu thông thường có kích thước hạt từ 500μm tới 0,1μm, nồng độ dao động trong khoảng từ 200-500 mg/m3. Lượng khí thải được sinh ra khi sử dụng bếp tiết kiệm năng lượng, sẽ được dùng làm nguyên liệu đốt cháy chính của quá trình đó. Do đó lượng khí CO2 thải ra môi trường khi sử dụng bếp tiết kiệm sẽ được giảm xuống 95 % so với sử dụng bếp thường.

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