Different Degrees Of Agglomeration Research Articles

Agglomeration of 3 mol% Y–TZP powders sythesized by hydrothermal treatment

Mechanical mixtures of zirconia gel and crystalline Y 2O 3 (3 mol%) have been hydrothermally treated at 110°C for 7 days in the presence of different mineralizer solutions. Taking the K 2CO 3/KOH molar ratio constant and equal 3, the total concentration of the mineralizer solutions was changed between 0.25 and 3.0 M. Predominant tetragonal (T) ZrO 2, characterized by different crystal size and different degree of agglomeration resulted by changing the concentration of mineralizer solution. The crystallization rate of Y-TPZ based powders, as well as the texture of the corresponding sintered products, are discussed in terms of concentration of the mineralizer solutions.

FORMATION AND MICROSTRUCTURE OF SiO2-TiO2-ZrO2 GELS

Gels were formed in the SiO2-TiO2-ZrO2 system. All of them were amorphous by XRD analysis, even though opaque gels were formed in the compositions range more than 80mol% TiO2 and 60mol% ZrO2, and transparent gels were formed in the rest compositions. Morphology of these particles were observed by SEM. It was found that the opaque gels consisted of spherical particles and the transparent gels consisted of bulk matrix. The opaque gels containing spherical particles were of different degree of agglomeration depending on the compositions. The compositional homogeneity of the particles was confirmed by EDX. It was found that sub micron spherical particles formed during gelation process were aggregated or packed together to form micro-sized spherical particles. Gels were heat treated at 200, 400 and 600°C for 1 hour to study the crystallization behavior.

Electron microscopy of nanocrystalline BaTiO 3

The microstructure of nanocrystalline BaTiO 3 prepared by microemulsion or sol-gel techniques is compared by means of transmission electron microscopy. After microemulsion a completely crystalline structure with a narrow size distribution is found. A log-normal distribution (statistical variance s = 1.66) observed for sol-gel-prepared crystallites after crystallization (T a = 873K) is compared with other synthesis routes. The microemulsion or sol-gel techniques were found to differ significantly with respect to crystallite growth which is related to the different degrees of agglomeration.

Preparation and sintering behaviour of YBaCuO thick films prepared by tape casting

Abstract A composition of cyclic hydrocarbon as solvent, an acrylic binder and a plasticizer was used for tape casting of superconducting YBa2Cu3O7-δ. A small-particle-size superconducting powders, ≈ 1μm, with two different degree of agglomeration were added to adequate amount of the organic mixture for obtaining slips. Thick films of several thickness were prepared. The sintering was performed in the 920–940°C temperature range. The organic compounds were burnout at 500°C. High density values were obtained for tape fired at 940°C. SEM analysis revealed a rather homogeneous microstructure for samples made from the weak agglomerated powders. Tc and Jc at 77K were measured on Ag-electroded samples.

Fire‐retarding polypropylene with magnesium hydroxide

AbstractFour types of magnesium hydroxide with different particle and crystallite sizes and different degrees of agglomeration were added at amounts up to 60% by weight to polypropylene to obtain a series of composites. The burning characteristics, tensile yield strength, flexural modulus, notched Izod impact strength, and melt flow index of the resulting composites were measured. Magnesium hydroxide coated with sodium stearate was found to give an increased melt flow index and impact strength to the composites as compared to values obtained with uncoated magnesium hydroxide. Incorporation of not less than about 57% by weight of magnesium hydroxide made the composite nonflammable, but at the same time considerably reduced its impact, flexural, and tensile yield strengths. As the amount of magnesium hydroxide filler was increased, the tensile yield strength and flexural strength of the composite proportionally decreased while the flexural modulus increased. The impact strength reached a maximum value when the amount of incorporation was 30% by weight. The lower the degree of agglomeration of the magnesium hydroxide filler and the greater the crystallite size within the range to about 2μm, the better were the mechanical properties of the composite.