Industrial crystallization, hardness

The ultra-micro-hardness of inorganic and organic salts has been measured for 15 substances. These are products usually produced in industrial crystallization. The hardness-force-dependency was examined and data are compared to those from literature. In the case of potassium nitrate a strong direction dependency of the hardness was observed. Also effects of impurities in the crystal lattice were analysed. In the end an attempt has been introduced to calculate the hardness of crystals from a physical model. 

ULRICH KRUSE Hardness of Salts Used in Industrial Crystallization... 

The pharmaceutical industry has been required by regulatory authorities to take a strong interest in polymorphism and solvatomorphism once it was realized that the nature of the structure adopted by a given compound upon crystallization would then exert a profound effect on the solid-state properties of that system. For a given material, the heat capacity, conductivity, volume, density, viscosity, surface tension, diffusivity, crystal hardness, crystal shape and color, refractive index, electrolytic conductivity, melting or sublimation properties, latent heat of fusion, heat of solution, solubility, dissolution rate, enthalpy of transitions, phase diagrams, stability, hygroscopicity, and rates of reactions, were all affected by the nature of the crystal structure. 

In the confectionery industry, com symps are used extensively in nearly every type of confection, ranging from hard candy to marshmallows. In hard candies, which are essentially soHd solutions of nearly pure carbohydrates, com symp contributes resistance to heat discoloration, prevents sucrose crystallization, and controls hygroscopicity, viscosity, texture, and sweetness. Maltose symps, high conversion symps, and acid-converted symps (36 and 42 DE) are used for this appHcation. 

The crystallization kinetics defines the open time of the bond. For automated industrial processes, a fast crystallizing backbone, such as hexamethylene adipate, is often highly desirable. Once the bond line cools, crystallization can occur in less than 2 min. Thus, minimal time is needed to hold or clamp the substrates until fixturing strength is achieved. For specialty or non-automated processes, the PUD backbone might be based on a polyester polyol with slow crystallization kinetics. This gives the adhesive end user additional open time, after the adhesive has been activated, in which to make the bond. The crystallization kinetics for various waterborne dispersions were determined by Dormish and Witowski by following the Shore hardness. Open times of up to 40 min were measured [60]. 

At present the iron-based alloys diffusion saturation by nitrogen is widely used in industry for the increase of strength, hardness, corrosion resistance of metal production. Inexhaustible and unrealized potentialities of nitriding are opened when applying it in combination with cold working [1-3], It is connected with one of important factors, which affects diffusion processes and phase formation and determines surface layer structure, mechanical and corrosion properties, like crystal defects and stresses [4, 5], The topical question in this direction is clarification of mechanisms of interstitial atoms diffusion and phase formation in cold worked iron and iron-based alloys under nitriding. 

Phosphonates are surface-active chelants and are widely used in industry for scale and corrosion control, and in cleaning agents, dispersants, and other applications. The annual sales of phosphonates in the U S A amount to over two billion dollars per year [8]. Phosphonates inhibit calcium scale formation by interfering with the crystal structure of calcium salts, making the crystals softer so that they are more easily removed by washing - the threshold effect [9]. A key application is controlling scale particularly in hard-to-reach places such as laundry and dishwashing machines. 

Hardness determination methods find wide uses in basic research on the mechanical properties of minerals and their deformation. In the face of the rapid development of industrial uses of natural minerals, as well as manmade, in monocrystal or grain form or as polymineral materials, there is a definite need for more comprehensive crystallomechanical investigations. Apart from the above aspects, hardness determination should furnish valuable information on the genesis of minerals. These authors consider that it would well serve the purpose to examine the mechanical properties of all minerals so as to obtain their allround crystallomechanical characterization and to investigate into their anisotropy and relationship to the structure and composition of minerals. By determining the typomorphism of the mechanical parameters of minerals and its involvement in the conditions of their formation, and also by investigating the specificity of occurrence of deformations in minerals under natural conditions and of the deformative mechanism, it should be possible to develop a general theory of mechanical properties of crystals. 

An interesting example of a mineral featuring remarkable hardness anisotropy and considerable hardness scatter is silicon carbide, SiC, widely used in electronic, electrical engineering and machining industries. It can crystallize in two polymorphous varieties, namely cubic / -SiC and hexag-... 

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