Study on Preparation Process and Properties of High Hydrogen Content Concrete for Neutron Shielding

A series of concrete samples with high hydrogen content were prepared by pressing process with aluminum hydroxide, boron carbide and aluminate cement as raw materials. the mechanical performance of the shielding material was examined by flexural strength tester and compression strength tester. Thermogravimetric analyzer was used to test the weight loss performance of the shielding material, hydrated cement and Al(OH)3. The thermal stability of the concrete at working temperature were investigated by bake the samples at 210°C for 90 hours and at 300°C for 5 hours. The shielding performance against neutron from 241Am-Be source were examined by neutron penetration tests. The test results show that the mechanical properties of the shielding material decrease with the increase of the content of aluminum hydroxide, the compression strength of the shielding material reached above 10MPa. The decomposition temperature of conc is 220°C, the weight loss curve tends to be plateau after baking at 210°C for 20 hours. Most of the crystal water lost after holding at 300°C for 5 hours, but the dimensions of the samples show no obvious change. The shielding performance of the material against neutron from 241Am-Be source is comparable to that of lead-boron polyethylene.

Kinetic Study on Microwave Magnetizing Roast of Fe2O3 Powders

In this paper, the reaction kinetic mechanism of Fe2O3 powder containing carbon was studied by microwave magnetizing roast. Based on the temperature-rise curve and weight loss curve of Fe2O3 powder by microwave magnetizing roast, the kinetic parameters of Fe2O3 powder microwave magnetizing roast were calculated by non-isothermal methods. The controlling steps of different temperature-rising periods in microwave magnetizing roast process of Fe2O3 powder were calculated by the Achar-Brindley-Sharp-Wendworth method. The results indicated that the controlling step of microwave magnetizing roast was phase boundary reaction control of contracted cylinder in 250~450°C, and it was three-dimensional diffusion control of spherical symmetry in 450~650°C. The results showed that the starting temperature of reduction roasting of Fe2O3 powder was 250°C, which was lower than that under electrical heating, thereby, it proved in theory that microwave heating can enhance reaction rate.

Determination of Char-CO2 Gasification Rate through Reaction Product

This paper presents gasification kinetic parameters generated for Japanese lignite coal char reacting with carbon dioxide and the method for obtaining them. The experiments were conducted in a PTGA at atmospheric pressure within a temperature range of 1148K-1223K, and a mass spectrometer (MS) is coupled with PTGA to obtain the concentrations of product gas. The experiments were carried out with isothermal method, and kinetic parameters were determined through the analysis of the weight changes of coal char and the concentrations of products respectively. The effect of CO2 partial pressure on reaction rate was analyzed by nth order rate equation. It was found that the activation energy of char-CO2 reaction obtained from weight loss curve and product concentrations were 187.9kJ/mol and 187.0kJ/mol respectively, and the reaction order n were 0.24 and 0.222, proving MS a feasible method for kinetics research. Through the comparison, the method to obtain the kinetic data by concentrations of gas products was determined, and a more clear understanding of the gasification process was established.

Pyrolysis Characteristics of Rice Husk Using TG-DTG Analysis

The rice husk from China has been non-isothermally pyrolysed on thermogravimetric analyzer(TGA). The analyses were performed at different heating rates (20, 40, 60, 80, 100°C/min) up to 900°C with nitrogen as purge gas. The weight loss curve showed that the main pyrolysis of rice husk took place in the range of 200~500°C. On the basis of experiment data, a pyrolysis kinetic model was proposed. The kinetic parameters of activation energy(E) and frequency factor(A) were obtained by the Direct Arrhenius Plot Method. There was no clear relationship between activation energy and heating rate.

Pyrolysis Characteristics of Oil Sands

Three oil sand samples from Indonesia have been non-isothermally pyrolysed on thermogravimetric analyzer (TGA). The analyses were performed at different heating rates (5, 15 and 25oC/min) up to 850oC with nitrogen as purge gas. The weight loss curve shows that the main pyrolysis of oil sand takes place in the range of 200~600oC. On the basis of experimental data, a pyrolysis kinetic model was proposed. The kinetic parameters of activation energy (E) and frequency factor (A) were obtained by Integral Method. There is no clear relationship between activation energy and heating rate.

Kinetic Model of Spherical Sponge Iron Reduced by Hydrogen

Spherical sponge iron (SSI) with high activity and intension could be prepared through direct reduction by hydrogen. To optimize the reduction technology, kinetic model of SSI reduction was established. The total reaction rate changing with reduction index R was deduced which describing the total reaction rate with effective diffusion coefficient De and chemical reaction rate constant k. According to the weight loss curve of SSI reduction, De and k were calculated. The total reactive rate increased with the increasing of temperature because both De and k increased with the increasing of reaction temperature. Compared De with k, it concluded that SSI reduced by hydrogen was controlled by the chemical reaction, combination of the chemical reaction and the internal diffusion, the internal diffusion when the temperature was lower than T3, from T3 to T4, over T5, respectively.

Analysis on Reductive Kinetics of SSI Reduced by Hydrogen

Spherical sponge iron (SSI) with high activity and intension could be prepared through direct reduction by hydrogen. To optimize the reduction technology, reductive kinetics of SSI was analyzed on the basement of unreacted core model. In the light of the single reaction surface theory, the ratio of internal diffusion resistance fI and chemical reaction resistance fR was calculated according to the weight loss curve of SSI reduction. Under different temperature, both fI and fR increased with the reaction time, especially the radium of unreacted core was small after a period of reaction time. Compared the ratio of fI and fR, it concluded that SSI reduced by hydrogen was controlled by the chemical reaction, combination of chemical reaction and the internal diffusion, the internal diffusion under the temperature being lower than T3, from T3 to T4, more than T5, respectively.

Research on TG-DTG Analysis and Combustion Kinetics Characteristic of Biomass Fly Ash and Ash

The fly ash and ash of different biomass power plants are selected as research objects, of which the combustion characteristics are studied. At the heating rates of 50°C/min, at the final reaction temperature of 900°C, and under the condition of air as carrier gas, weight loss curve and weight loss rate curve are analyzed respectively. TG, DTG curves of fly ash and ash from different power plant are gained, different combustion conditions are studied, and combustion kinetic equations of different biomass fly ash and ash are established, kinetics parameters are obtained by the Coats-Redfern method. Besides, combustion condition and reburning feasibility of different biomass fly ash and ash are analyzed, which provide a theoretical support for biomass power plant operation, such as improving their fuel burn rate.

Estimation of Curing Profile's Parameters for Flip Chip Packaging Using DSC and TGA

This paper presents the method to estimate curing profile's parameters for curing process of Moisture Resistance Cyanate Ester (MRCE) based underfill used in Flip Chip Ceramic Ball Grid Array (FC-CBGA). The two steps curing profile was found to eliminate voids formation in underfill during curing process. The important parameters in two steps curing profile such as first fixed temperature and duration of second temperature rise were estimated by superimposed of cure initiation curve and weight percentage loss curve of underfill epoxy material. Differential Scanning Calorimeter (DSC) analysis was carried out to characterize the cure kinetics reaction of underfill epoxy and produced the cure initiation curve. Thermal Gravimetric Analysis (TGA) was performed to characterize the weight loss of underfill and produced the weight loss curve. It was estimated that the first fixed temperature and duration of second temperature rise for two steps curing profile were 100 oC and 60-80 minutes respectively. The simulation experiment was conducted to verify the profile and no voids formation observed along this curing process.