. Interaksi Permukaan Serbuk . KristalografiTopik 5 dan 6

Pertemuan 4x sebelum ini mengenai partikel adalah dasar untuk memahami SERBUK

Interaksi Fisika terjadi antar partikel yang menyusun serbuk

Sifat dasar serbuk ditentukan oleh sifat partikel yang menyusunnya

Serbuk juga disusun oleh beberapa material yang saling berinteraksi secara fisika

Apa yg harus dianalisis pada Serbuk ?

Interaksi fisika antar material Ini manfaatnya untuk Farmasi(Finishing and Polishing covered previouslyProtection and Stabilization)

I. Conversion CoatingsBy chemical reactionBy Polymer interactionBy Metal complexation

Cemical ReactionOxidationmany are tightly adhering leading to passivation and hardening of surfaceAl2O3Chromium in Stainless steel rapidly corrodes to passivate the surface

Contoh Phosphate CoatingImmersion in a Zn-P bath with Phosphoric acid causes growth of a crystalline zinc phosphate layerIron, Zinc or Manganese Phosphate layer formedTypically applied to C-steel, low alloy steel and cast ironsSometimes applied to Zinc, Cadmium, Aluminum and TinTypically very thin ~ 2.5 mm

Contoh-Metal CoatingCansImmersion in a chromic acid bath (pH ~ 1.8) with other chemicals to coat surfaceKnown carcinogen chemicals used, so alternatives are currently under researchMolybdate chemicals currently best subsititute for aluminum coatingsVery good to minimize atmospheric corrosionMany household goods screws, hinges (yellow brown appearance)Typically very thin < 2.5 mm

II. Thermal Treatments

Thermal Treatments Weld Overlay coatingsTypically used to improve wear resistance by creating a hard surface over a tough bulk bodyHard FacingWeld buildup of parts alloy composition controls final propertiesExamples cutting tools, rock drills, cutting bladesCladding of material for corrosion resistanceThermal sprayingMolten particle deposition a stream of molten metal particles are deposited on the substrate surfaceMajor difference from hard facing is that the surface of the substrate is not subjected to welding. Instead it just undergoes a bonding process with the molten particles.

III. Metal CoatingsElectroplatingElectroless CoatingsMetallizing of Plastics and Ceramics

Metal Coatings - ElectroplatingUsed to increase wear and corrosion resistanceElectrochemical process used to create a thin coating bonding to substrateProcess is slow so coating thickness can be closely controlled (10-500 mm)ApplicationsTin and Zinc are deposited on steel for further working

Metal Coatings Metallizing of Plastics and CeramicsPoor adhesion is the major challenge (As in all coating processes, however it is more challenging in this case.)ApplicationsDecorative (plumbing fixtures, automotive parts), reflectivity (headlights), electrical conduction (electronic touchpads), and EMF shielding

Organic CoatingsEnamelsForm film primarily by solvent evaporation30 % Volatile Organic Content (VOC)Lacquers solvent evaporationWater-base paints water evaporation : ResinPowder Coating superior more detail to follow

Powder CoatingFully formulated paint ground into a fine powderPowder is sprayed onto part, retained by static electricityHeat cured onto partCan virtually eliminate VOCs

SummaryDont overlook coatings importance to overall product performanceCoating technology is very specialized get a couple of expert opinions before committing

Dasar-dasar Kristalografi

Kristal dan Kristalografi ?Kristalografi: Ilmu yang merupakan cabang dari mineralogi mempelajari struktur material dalam tingkat atomik (penentuan, klasifikasi dan penafsiran struktur geometri zat padat khususnya kristal).

Kristal: zat padat dengan struktur mikroskopiknya ditandai secara khusus oleh pengulangan 3 dimensi secara periodik dari motif yang tersusun dari atom.

Kajian keteraturan dan ketidakteraturan atom dalam struktur zat padat merupakan pembahasan utama dari kristalografi.

Point-point Penting

Pengukuran bentuk kristalin polihedral, TEORI SIMETRI kristal dan periodisitas struktur mikroskopiknya (simetri translasi) berkembang selama abad ke XVIII dan XIX.

Teori ini telah dibuktikan pertama kali melalui penelitian fundamental dengan difraksi sinar-X oleh Von Laue, Friedrich dan Knipping (1912).

Teori lain adalah TRANSLASI

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