Effect of the Melt Pool Boundary Network on the Anisotropic Mechanical Properties of Selective Laser Melted 304L

Anisotropic mechanical properties are a well-known issue in selective laser melted parts. The microstructure produced by selective laser melting (SLM) is directional, including the solidified melt pool structures and grains. This work investigates the melt pool boundary’s effects on 304L stainless steel’s compressive properties. 304L stainless steel solid cylinders were built using a pulse laser SLM machine in four directions using three hatch angle rotations: 0°, 67°, and 105°. The twelve samples were compression tested, and the results were analyzed. Numerical models were also created with the different hatch angles and directions. The melt pool boundary network (MPBN) in each build was tracked using the model across multiple planes. Results showed that both the hatch angle and build orientation influenced the concentration of melt pool boundaries present in the manufactured samples. A weak negative correlation of compressive strength to the melt pool boundaries’ concentration was also observed, indicating that the melt pool boundary concentration negatively affected the material’s strength. Local anisotropic plastic deformation was also observed in some of the compressed samples. In those samples, it was observed that directions that plastically deformed more also contained higher concentration of the melt pool boundaries.

The Effect of Alkalization on Carboxymethil Cellulose Synthesis from Stem and Peel Cellulose of Banana

BACKGROUND: North Sumatra is one of the regions in Indonesia that produce bananas. Banana stems and peels contain cellulose and it can be isolated in nanofiber form. Carboxymethylcellulose is a cellulose derivative that undergoes an alkalization and etherification process AIM: This research was conducted to evaluate the alkalization effect on synthesis of carboxymethyl cellulose from stem and peel cellulose of banana. METHODS: Stem and peel of banana was extracted with NaOH 17.5% and the extract was synthesized to carboxymethyl cellulose (CMC). The synthesis of CMC was beginning with alkalization process in variation of NaOH concentration and the reaction was then etherificated with sodium monochloroacetate. CMC was characterized by FTIR and DS values ​​were determined. RESULTS: FTIR spectra of synthesized CMC had different pattern compared to cellulose. It showed that an etherification reaction had been occurred in the cellulose compound. Spectra of CMC with variation in alkali concentration was not much different from one another. The synthesized CMC from stem and peel cellulose of banana had different degree of substitution (DS) values ​​due to variate concentration of NaOH in alkalization. CONCLUSION: Alkalization on CMC synthesis affects the DS value of synthesized CMC. The increase DS value is proportional to the rise in NaOH concentration even though there is a boundary concentration to obtain the optimum DS value.

Relaxation Behavior of Zr Substituted CaCu3Ti4O12 Ceramics

The dielectric properties of Zr substituted CaCu3Ti4O12ceramics have been investigated in detail. Grain size decreases with Zr content increasing. The hetero-electrical microstructures of prepared samples have been confirmed by the impedance spectra. The dielectric loss has been improved by Zr doping because of the enhancement of grain boundary resistivity. A Debye-like boundary relaxation behavior has been observed in the temperature range of 220-600K. As Zr content increases, the relaxation time increases due to the higher grain boundary concentration. This work has provided an additional proof for the origin of giant dielectric response in CaCu3Ti4O12ceramics.