Applications

A brief review is given about the development of rubber isostatic pressing (RIP) of powders for magnets and other materials that includes: principles of RIP; RIP apparatuses; recent progress; and advantages of RIP. As the recent progress, a new filling technique, ‘air tapping (AT) and grid separation (GS)’, is presented.

Bubble nucleation in weakly supersaturated solutions of carbon dioxide—such as champagne, sparkling wines and carbonated beers—is well understood. Bubbles grow and detach from nucleation sites: gas pockets trapped within hollow cellulose fibres. This mechanism appears not to be active in stout beers that are supersaturated solutions of nitrogen and carbon dioxide. In their canned forms these beers require additional technology (widgets) to release the bubbles which will form the head of the beer.

Applying RIP (Rubber Isostatic Pressing) to the ferrite sintered magnets, the following have been developed: (1) Ferrite sintered magnets having energy product as high as 5.12 MGOe (2) RIP setup for arc-segment magnets

Abstract BACKGROUND: The powder reaction moulding process uses a reactive monomer as carrier and binder for the moulding of metal or ceramic powders. De-binding is achieved using thermal depolymerisation which is followed by sintering to give the finished component. Binder can be recovered for re-use. RESULTS: Moulding compounds, with various powder volume fractions, have been prepared using stainless steel, silicon nitride and alumina with n-butyl cyanoacrylate as binder, and the stability of the compounds established.

A method of injection moulding or extruding an article is disclosed in which a ceramic and/or metallic powder is dispersed in a carrier to form a flowable composition. The carrier is preferably a monomeric cyanoacrylate which is reversibly polymerisable so as to yield a solid polymer, which in turn is capable of undergoing a thermally activated depolymerisation reaction so as to yield the monomeric species. The composition is injected into a mould or extruded through a die and the carrier polymerised in the mould or die.

New sintered Nd-Fe-B near net-shape magnets with a high remanent polarization of 1.47 T, a coercivity HcJ of 9.6 kA/cm (12 kOe) and a maximum energy density of 420 kJ/m3 (53 MGOe) can be manufactured by rubber isostatic pressing. The optimization of the remanent polarization by an improved alignment process of the powder particles results in a decrease of the coercivity by 0.4 kA/cm per 1 % ∆fφ for alignment coefficients fφ in the range 96 to 98 %. For alignment coefficients between 98 to 99 % the decrease of the coercivity even increases to about –1 kA/cm per % 1 ∆fφ.

Near-IR reflectance spectroscopy has been used to study the curing of ethyl cyanoacrylate adhesive on polished dental glass and microscope slide substrates. The effects of changing the glue film thickness and the type of substrate on the curing rate have been investigated whilst maintaining a constant humidity. The FTIR spectral data has been used to calculate and plot the extents of cure versus time for various film thicknesses.

Glass ionomer cement (GIC) has been successfully used in dental field for more than 40 years. Despite numerous advantages of GIC, low bond strength and slow setting rate limited conventional GICs for use only at low stress-bearing areas. To improve bond strength to tooth, two kinds of cyanoacrylates such as ethyl 2-cyanoacrylate (EC) and allyl 2-cyanoacrylate (AC) were added in a commercial GIC. Changes in setting time of cyanoacrylate-modified GICs (CMGICs) according to the concentration of cyanoacrylates and/or p-toluene sulfonic acid (TSA) was investigated using a rheometer.

Polymer electronics plays more and more important role nowadays, especially in flexible electronics. The progress is also reflected in packaging materials and technologies. Metallic solders are replaced by electrically conductive adhesives based on polymer’s matrix. Very high volume production also requires new methods of adhesive deposition. The ink-jet printing technology seems to be very promising for bumps making in Flip- Chip type interconnections. Unfortunately, the technology is only in its infancy.

The present work demonstrates feasibility of an inkjettable, isotropically electrically conductive adhesive in the form of a silver loaded resin with a 2-step curing mechanism. In the first step, the adhesive is dispensed (jetted) and precured leaving a “dry” surface. The second step consists of assembly and final curing. The 2-step cure system is based on a Acrylate-Epoxy-Resin matrix with very low viscosity, i.e., 3 mPas of newtonian properties. Spheroidal silver particles of high purity and a compatible organic coating have been loaded at 70% by weight.