Microhardness Of Ribbons Research Articles

Towards better understanding of the influence of process parameters in roll compaction/dry granulation on throughput, ribbon microhardness and granule failure load

A key quality attribute for solid oral dosage forms is their hardness and ability to withstand breaking or grinding. If the product is to be manufactured continuously, it can be of interest to monitor the hardness of the material at different stages of manufacturing. Using the controlled process parameters of roll compaction/dry granulation specific compaction force, roll speed and gap width, hardness of the resulting ribbons and granules can be predicted. For the first time, in this study two yield variables (corrected torque of the granulation unit and throughput of material) are used to predict the granules failure load. The increase in granule hardness was monitored in-line when the specific compaction force was increased during the compaction process. This opens the way for in-line control of material hardness, and its use for feedback and feedforward control loops for future continuous manufacturing processes.

MCC–mannitol mixtures after roll compaction/dry granulation: percolation thresholds for ribbon microhardness and granule size distribution

In roll compaction, the specific compaction force, the gap width and the roll speed are the most important settings as they have a high impact in the products obtained. However the mechanical properties of the mixture being compacted are also critical. For this reason, a multilevel full factorial design including these parameters as factors plus three repetitions of the center point was performed for microcrystalline cellulose, mannitol and five binary mixtures (15, 30, 50, 70 and 85% MCC). These two reference excipients were chosen in order to investigate the plastic/brittle behavior of mixtures for the roll compaction process. These materials were roll compacted in a 3-W-Polygran® 250/50/3 (Gerteis) and the ribbons obtained were collected and milled into granules which were characterized regarding granule size distribution. After statistical evaluation, it was found that the most critical factors affecting the D10, D50, D90 and the fines fraction from the granules were the gap width and the specific compaction force, as well as the proportion of MCC together with its quadratic effect and the interaction between force and proportion of MCC. The microhardness of the ribbons from the center point as well as the D10, D50, D90 and the fines fraction from the granules produced at these same conditions were characterized. In all the cases, the proportion of MCC, i.e. the composition of the mixture, showed also an important effect on these properties measured. In this sense, the percolation theory was applied in order to study further the importance of the plastic/brittle ratio by calculating the percolation threshold or the limit over which the behavior of the system changes. This resulted in values of 34% for the HU (expression of microhardness), 27% and 28% for the D10 and fines, respectively (percolation of MCC) and 84% and 85% for the D50 and D90, respectively (percolation of mannitol).

Solidification Structure Characteristics and Mechanical Properties of (Ag-Cu<sub>28</sub>)-25Sn Alloy Ribbons Prepared by Melt Spinning Method

To obtain novel intermediate temperature alloy solders with melting temperature of 400~600°C, (Ag-Cu28)-25Sn alloy ribbons were prepared by high frequency induction melting and melt spinning at different quenching linear speed. The effect of the development of solidification structure on melting properties and microhardness of the ribbons were investigated. The XRD results show that the as-prepared alloy ribbons have the same phase composition as the master alloy, which consists of Ag4Sn and Cu3Sn. With the quenching linear speed increasing, the solidification structures are refined and change from dendritic crystals to uniform granular crystals. As the quenching linear speed increases up to 32.25m/s, the grain size of the alloy ribbon has a distribution ranging from submicron to about 2μm. The DSC results indicate that the melting properties of alloy ribbons strongly depend on the solidification structure, and the melting temperature of alloy ribbons decreases with the quenching linear speed increasing. The lowest liquidus points of the alloy ribbon prepared at linear speed of 32.25m/s are located at 473.6°C and 524.7°C, respectively. The refined solidification structure notably increases the microhardness of the alloy ribbons, and the largest hardness value of 396HV is obtained for the alloy ribbon prepared at linear speed of 32.25m/s, which increases 27.0% compared with the master alloy.

Mechanical Properties and Nanocrystallization Behavior of Al-Ni-La Alloys

Rapidly solidified Al89Ni6La5 ribbons were obtained by induction melting and ejecting the melt onto a rotating Cu wheel in an Ar atmosphere. The ribbons were investigated by differential scanning calorimetry (DSC), X-ray diffractometry (XRD), transmission electron microscopy (TEM), microindentation, and nanoindentation techniques. The XRD and TEM studies revealed that the ribbon was fully amorphous; however, DSC did not show any glass transition. The alloy undergoes two stages of crystallization. The growth of fcc-Al is responsible for the first stage, and precipitation of Al3Ni and Al11La3 is responsible for the second stage of crystallization. Microhardness of ribbons in the as-melt-spun, partially, and fully devitrified conditions was examined and subsequently correlated with evolved microstructure. Significant improvement in hardness was observed, with the progress of primary nanocrystallization, due to the effective barrier to shear band by a hard La-rich shell around the fcc-Al nanocrystals and enrichment of the remaining amorphous matrix by the solute elements. The pile up of materials in the form of semicircular shear bands was observed around all the indentations. During nanoindentation, it was observed that hardness and modulus values were initially increased and then decreased. The reasons for such observation were also discussed.

Nanostructured Al 86Gd 6Ni 6Co 2 bulk alloy produced by twist extrusion of amorphous melt-spun ribbons

Amorphous Al 86Gd 6Ni 6Co 2 ribbons produced by melt-spinning were consolidated using twist extrusion (TE). Transition of the amorphous alloy ribbon into the crystalline state at 5 K/min occurs via three stages in the temperature range from 473 to 673 K. Formation of fcc Al nanocrystals is the dominant process in the first and second stages, which leads to increasing microhardness of ribbons from 360 to 620 kgf/mm 2. From one to five TE passes were performed on chopped ribbon in several experimental runs at temperatures between 458 and 573 K and applied pressures between 1150 and 1700 MPa. Full consolidation of the ribbons was achieved at TE temperatures ≥523 K. The maximum microhardness (550 kgf/mm 2) was reached in bulk materials consolidated at 513 K with a nanocomposite microstructure consisting of about 57 vol.% of Al-crystals with a size of about 13 nm embedded in the residual amorphous phase. Extrusion at 573 K resulted in full crystallization of the amorphous phase via precipitation of equilibrium intermetallics and lowering of the microhardness to 380 kgf/mm 2.

How do roll compaction/dry granulation affect the tableting behaviour of inorganic materials? Microhardness of ribbons and mercury porosimetry measurements of tablets.

The effect of roll compaction/dry granulation on the ribbon and tablet properties produced using different magnesium carbonates was evaluated. The ribbon microhardness and the pore size distribution of tablets were used as evaluation factors. Increasing the specific compaction force resulted in higher microhardness for ribbons prepared with all four magnesium carbonates accompanied with decreased part of fine. Consequently, the corresponding produced tablets displayed a lower tensile strength. A possible correlation between the particle shape, surface area and the resulting pore structure of tablets produced with the four different types of magnesium carbonate was observed. The tensile strength of tablets prepared using granules was lower than tensile strength of tablets produced using starting materials. The partial loss of compactibility resulted in a demand of low loads during roll compaction. However, the impact of changes in the material properties during the roll compaction depended greatly on the type of magnesium carbonate, the specific compaction force and the tableting pressure applied.

Microstructure and thermal stability of a rapidly solidified Al-4Er alloy

The effect of the rapid-solidification melt-spinning process on an Al-4Er alloy has been studied. Compared to the normally solidified master alloy, rapid-solidification processing promotes the formation of a eutectic suppressed, relatively refined microstructure. Varying relative proportions of microstructures occupy the ribbon longitudinal transverse cross section: the featureless zone at the contact surface, the columnar zone in the middle and the equiaxed grains zone with degenerated dendrites at the free surface. The presence of a finely dispersed, coherent Al3Er secondary equilibrium phase in the contact is evident. Ribbon microhardness remains fairly stable up to 200 ° C and at further elevated temperatures retains higher mean values than the master alloy.