Showing papers in "China Powder Science and Technology in 2005"

An Improved Algorithm of Classical Mie Scattering Calculation

Abstract: The calculation of the classical Mie theory is very important for particle size analysis. In the work, an improved algorithm of Mie scattering calculation is presented. By re-constructing the Mie scattering coefficients, a parameter is found to control the convergence and the precision of the Mie calculation. The related parameters are calculated by means of the proper downward or upward recurrences respectively, which are proved to be very fast and stable. Numerical calculation shows that the algorithm is efficient, reliable and robust in an extremely wide range of particle size and refractive index.

Analysis on Impact of Yellow River Water and Sediment Regulating Experiment on Change of Grain Size

Abstract: During 2002～2004, the Yellow River Conservancy Commission carried out 3 times of water and sediment regulations based on different regulation mode and different spatial scale. Through analysing the time and spatial change of grain size of suspended sediment and bed sediment in the Xiaolangdi reservoir and the lower Yellow River channel during the experiments, the paper shows that discharging fine sediment and keeping coarse sediment siltedi n Xiaolangdi reservoir benefitsr egulatings iltationi nr eservoira reaa nd the transportation of fine sediment discharged out of the reservoir to the Bohai sea and the average of medium particle diameter of suspended sediment in the lower Yellow River is coarser and coarser along the channel. The experiment has achieved the goal of all-around scouring of the river channel.

Ultra-fine Dry Powder Fire Extinguishant

Abstract: The types, characteristics,performances of dry chemicals are briefly introduced firstly. The burn mechanism,common dry chemicals and its fire extinguishing principle are disscussed. The relations between fire extinguish- ing performance and particle size of dry powder are studied, It is found that fire extinguishing performance increases sharply as decreasing the particle size of dry powder.The performances、advances in development and production、 advantages and prospectives of ultra-fine dry powder fire extinguishant are discussed, and the performances and application prospective of the nano- powder dry chemicals are analysed.

Low Speed,High Efficiency Dense Phase Pneumatic Conveying

Abstract: The low speed,high efficiency dense phase pneumatic conveying equipments can solve the difficulties of the breakage of the materials,the blockage and abrasion of the pipelines and reduce the consumption of gas.The several definitions of dense phase pneumatic conveying and phase-figure of conveying,the influence of flowing mode,the relevant judgments and the factors influencing the pneumatic conveying are reviewed.The appearance of the blockage during the conveying and the abrasion of the pipeline are introduced.Some methods of measurement and autocontrol are mentioned.

Surface Modifying and Applied Research of Aluminum Hydroxide

Abstract: The effect of surface modifying on properties of PVC/Al(OH)3 system was investigated The mechanism of flame-retardance and reinforce- ment of ultra-fine and active Al(OH)3 was analyzed by means of TGA and SEM The results show that the surface modifying can evidently improve the over-all properties of PVC/Al(OH)3 system

Key Technology of Fluidized Bed Counter-jet Mill and Its Progress

Abstract: The working principle and advantages of fluidized bed counter-jet mill were introduced.The recents research of key technology of fluidized bed mill,such as nozzle,comminution,classification,were reviewed.It's shown that the best working state of fluidized commter-jet mill can be achieved by improving on and optimizing key parts and the quality and quantity of products can be improued.

Inversion of Refractive Index in Particle Sizing by Multi-spectral Light Extinction Method

Abstract: The genetic algorithm (GA) is employed to inverse the refractive index of a particulate system The particle size distribution is provided to be known in advance Compared with other traditional optimization methods, GA's results approach the global optimum solution instead of locals ones The effect of GA is influenced a lot by the number of wavelength used for inversion as well as the dispersity of the particulate system More information of the transmission spectrum is known and the better the particles are dispersed, the higher precision of the results can be achieved Besides, since the monotonicity of extinction coefficient-refractive index curve for submicron level particles is more obvious than that for micrometer level ones, the extent of the multimodal distribution will be weakened and the inversion algorithm is more resistant to the measurement errors, which makes the inversion results more reliable

Technology of Recovery and Reutilization of Waste Printed Circuit Board

Abstract: This paper summarized the dangerous of waste PCB (printed circuited boards) and the necessity of the recovery and reutilization of waste PCB. The methods, which used to treat the waste PCB are listed, include chemical method and physical method. The technique flow of the physical method, which the most popular and environmental friend method being compared. At last the author give their opinion about the development trend and the focus on the recovery and utilization of waste PCB.

Rheological Characteristics of Nanocomposite-based Magnetorheological Suspension

Abstract: The magnetic field-induced shear stress(Δτ)and the response time (Δt) for a nanocomposite-based magnetorheological (MR) suspension were determined as functions of magnetic field strength (H), shear rate (γ) and temperature (T). The results showed that Δt had almost independence of H, γ and 71 The MR suspension responded to external magnetic field a little lower at "switching off" than at "switching on" . Δτ increased with the increase of H, a maximum of Δτ occurred with increasing γ ,and Δτ slowly decreased with T. The quantity relationship among them fitted in with the equation of Δτ=kHH+( kγ1- kγ2γ) γ -ktτT very well, where kH=28.32,kγ1=2.85,kγ2=0.0013, kt=3.8 . Using this equation can characterize well the properties for the MR suspensions, which is the basis of designing MR intelligent devices.

Research Progress on High-temperature Protection Coatings

Abstract: The high temperature protection coatings play an important role for preventing high temperature oxidation and hot corrosion from aircraft turbine engine and prolonging the time life of engine. Electron beam physical vapor deposition (EB-PVD) and air plasma spray (APS) deposition are now the two most important methods prepared for high temperature coatings. Progress on high temperature coatings, particularly several new- protection coatings is reviewed, together with a discussion of current limitations and future opportunities.

Development and Application of Nano-particles Coating

Abstract: The present researches in nano-particles coatings were reviewedSome important attributes of nano-particles such as optical,electromagnetic,mechanical hydromechanical property and their application in the coating were discussedThe deficiencies of nano-particles coating such as aggregating,characterizing and standards etcwere demonstratedIt is pointed out that the improvement of the nano-coatings and can be used widely would be a new task for industry of coating

Comparing with Air Control Modes in Dense Phase Pneumatic Conveying

Abstract: The main properties of the pressure regulators were introduced such as regulating range,pressure character:stic and flow character:stic.The choice and ragulation of the pressure regulator for pneumatic conveying was discussed.The air control modes in dense phase pneumatic conveying were analyzed,and their advantages and disadvantages were discussed in detail.Pressure regulator and pressure regulator-LAVAL air control modes were emphasized.Adjustable LAVAL pipe air control is a developmental direction for pneumatic conveying.

Application of Dynamic Light Scattering in Particle Measurements

Abstract: Dynamic light scattering(DLS) is one of the most popular methods used to determine the size of particles. The applications of DLS are introduced in detail, which include the measurements of particle sizing, rotational diffusion coefficient, dielectric constant, conductivity, the effect of environmental changes on particle's size and the confirmation of the crystallization conditions. A farther discussion of its developments and applications is given.The dificiency of dynamic light scattering is suggested. The following research topics such as overcoming the background noise,improving the quality of light source and building the intellectual algorithm,are pointed out.